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Sample records for strong adsorption sites

  1. Xenon capture on silver-loaded zeolites: characterization of very strong adsorption sites

    International Nuclear Information System (INIS)

    Daniel, Cecile; Elbaraoui, Adnane; Aguado, Sonia; Schuurman, Yves; Farrusseng, David; Springuel-Huet, Marie-Anne; Nossov, Andrei; Fontaine, Jean-Pierre; Topin, Sylvain; Taffary, Thomas; Deliere, Ludovic

    2013-01-01

    The number and strength of adsorption sites for Xe in silver-modified zeolites are estimated from isotherm measurements at various temperatures over a broad range of pressure (from 1 ppm to atmospheric pressure). Fully and partially exchanged silver zeolites were synthesized starting from Na-ZSM-5(25), Na-ZSM-5(40), Na-Beta, NaX, and NaY. We have discovered that silver-modified zeolites may present one or two distinct adsorption sites depending on the nature of the material and silver loadings. The strongest adsorption sites are characterized by isosteric heat of adsorption in the order of -40 to -50 kJ.mol -1 . For Pentasil-type zeolites, we observe a linear 2:1 correlation between the total amount of silver and the number of strong sites. The highest concentration of strong sites is found for fully silver exchanged ZSM-5 (5.7 * 10 -4 mol/g), which presents the largest silver content for Pentasil-type zeolite. The equilibrium constant of Ag-ZSM-5 at low pressure is about 50 times larger than that of AgX. Qualitative correlations were established between Xe adsorption isotherms and Xe NMR signals. We show that Xe NMR could be used as a quantitative method for the characterization of the strength and of the number of strong Xe adsorption sites on silver-exchanged zeolites. The numbers of strong adsorption sites responsible for the Xe adsorption at 10-1000 ppm can be determined by the length of the plateau observed at low Xe uptake. In practice, our findings give guidelines for the discovery and optimization of silver-loaded zeolites for the capture of Xe at ppm levels. It appears that the amount of silver is a key parameter. Silver-modified ZSM-5 shows adsorption capacities 2-3 orders of magnitude larger than currently applied adsorbents for atmospheric Xe capture. (authors)

  2. Strong Selective Adsorption of Polymers.

    Science.gov (United States)

    Ge, Ting; Rubinstein, Michael

    2015-06-09

    A scaling theory is developed for selective adsorption of polymers induced by the strong binding between specific monomers and complementary surface adsorption sites. By "selective" we mean specific attraction between a subset of all monomers, called "sticky", and a subset of surface sites, called "adsorption sites". We demonstrate that, in addition to the expected dependence on the polymer volume fraction ϕ bulk in the bulk solution, selective adsorption strongly depends on the ratio between two characteristic length scales, the root-mean-square distance l between neighboring sticky monomers along the polymer, and the average distance d between neighboring surface adsorption sites. The role of the ratio l / d arises from the fact that a polymer needs to deform to enable the spatial commensurability between its sticky monomers and the surface adsorption sites for selective adsorption. We study strong selective adsorption of both telechelic polymers with two end monomers being sticky and multisticker polymers with many sticky monomers between sticky ends. For telechelic polymers, we identify four adsorption regimes at l / d 1, we expect that the adsorption layer at exponentially low ϕ bulk consists of separated unstretched loops, while as ϕ bulk increases the layer crosses over to a brush of extended loops with a second layer of weakly overlapping tails. For multisticker chains, in the limit of exponentially low ϕ bulk , adsorbed polymers are well separated from each other. As l / d increases, the conformation of an individual polymer changes from a single-end-adsorbed "mushroom" to a random walk of loops. For high ϕ bulk , adsorbed polymers at small l / d are mushrooms that cover all the adsorption sites. At sufficiently large l / d , adsorbed multisticker polymers strongly overlap. We anticipate the formation of a self-similar carpet and with increasing l / d a two-layer structure with a brush of loops covered by a self-similar carpet. As l / d exceeds the

  3. Strong adsorption of chlorotetracycline on magnetite nanoparticles

    International Nuclear Information System (INIS)

    Zhang, Di; Niu, Hongyun; Zhang, Xiaole; Meng, Zhaofu; Cai, Yaqi

    2011-01-01

    Highlights: → Fe 3 O 4 MNPs selectively adsorb CTC through chelation between CTC and Fe atoms. → Fe 3 O 4 MNPs remain high adsorption ability to CTC in environmental water samples. → Fe 3 O 4 MNPs sorbed with CTC are easily collected from water under a magnetic field. → The collected Fe 3 O 4 MNPs are regenerated by treatment with H 2 O 2 or calcination. - Abstract: In this work, environmentally friendly magnetite nanoparticles (Fe 3 O 4 MNPs) were used to adsorb chlorotetracycline (CTC) from aqueous media. Fe 3 O 4 MNPs exhibit ultrahigh adsorption ability to this widely used antibiotic. The adsorption behavior of CTC on Fe 3 O 4 MNPs fitted the pseudo-second-order kinetics model, and the adsorption equilibrium was achieved within 10 h. The maximum Langmuir adsorption capacity of CTC on Fe 3 O 4 (476 mg g -1 ) was obtained at pH 6.5. Thermodynamic parameters calculated from the adsorption data at different temperature showed that the adsorption reaction was endothermic and spontaneous. Low concentration of NaCl and foreign divalent cations hardly affected the adsorption. Negative effect of coexisting humic acid (HA) on CTC adsorption was also observed when the concentration of HA was lower than 20 mg L -1 . But high concentration of HA (>20 mg L -1 ) increased the CTC adsorption on Fe 3 O 4 MNPs. The matrix effect of several environmental water samples on CTC adsorption was not evident. Fe 3 O 4 MNPs were regenerated by treatment with H 2 O 2 or calcination at 400 o C in N 2 atmosphere after separation from water solution by an external magnet. This research provided a high efficient and reusable adsorbent to remove CTC selectively from aqueous media.

  4. Interplay between strong correlation and adsorption distances: Co on Cu(001)

    Science.gov (United States)

    Bahlke, Marc Philipp; Karolak, Michael; Herrmann, Carmen

    2018-01-01

    Adsorbed transition metal atoms can have partially filled d or f shells due to strong on-site Coulomb interaction. Capturing all effects originating from electron correlation in such strongly correlated systems is a challenge for electronic structure methods. It requires a sufficiently accurate description of the atomistic structure (in particular bond distances and angles), which is usually obtained from first-principles Kohn-Sham density functional theory (DFT), which due to the approximate nature of the exchange-correlation functional may provide an unreliable description of strongly correlated systems. To elucidate the consequences of this popular procedure, we apply a combination of DFT with the Anderson impurity model (AIM), as well as DFT + U for a calculation of the potential energy surface along the Co/Cu(001) adsorption coordinate, and compare the results with those obtained from DFT. The adsorption minimum is shifted towards larger distances by applying DFT+AIM, or the much cheaper DFT +U method, compared to the corresponding spin-polarized DFT results, by a magnitude comparable to variations between different approximate exchange-correlation functionals (0.08 to 0.12 Å). This shift originates from an increasing correlation energy at larger adsorption distances, which can be traced back to the Co 3 dx y and 3 dz2 orbitals being more correlated as the adsorption distance is increased. We can show that such considerations are important, as they may strongly affect electronic properties such as the Kondo temperature.

  5. How strong is the edge effect in the adsorption of anticancer drugs on a graphene cluster?

    Science.gov (United States)

    Rungnim, Chompoonut; Chanajaree, Rungroj; Rungrotmongkol, Thanyada; Hannongbua, Supot; Kungwan, Nawee; Wolschann, Peter; Karpfen, Alfred; Parasuk, Vudhichai

    2016-04-01

    The adsorption of nucleobase-analog anticancer drugs (fluorouracil, thioguanine, and mercaptopurine) on a graphene flake (C54H18) was investigated by shifting the site at which adsorption occurs from one end of the sheet to the other end. The counterpoise-corrected M06-2X/cc-pVDZ binding energies revealed that the binding stability decreases in the sequence thioguanine > mercaptopurine > fluorouracil. We found that adsorption near the middle of the sheet is more favorable than adsorption near the edge due to the edge effect. This edge effect is stronger for the adsorption of thioguanine or mercaptopurine than for fluorouracil adsorption. However, the edge effect reduces the binding energy of the drug to the flake by only a small amount, <5 kcal/mol, depending on the adsorption site and the alignment of the drug at this site.

  6. [Adsorption of heavy metals on the surface of birnessite relationship with its Mn average oxidation state and adsorption sites].

    Science.gov (United States)

    Wang, Yan; Tan, Wen-Feng; Feng, Xiong-Han; Qiu, Guo-Hong; Liu, Fan

    2011-10-01

    Adsorption characteristics of mineral surface for heavy metal ions are largely determined by the type and amount of surface adsorption sites. However, the effects of substructure variance in manganese oxide on the adsorption sites and adsorption characteristics remain unclear. Adsorption experiments and powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) were combined to examine the adsorption characteristics of Pb2+, Cu2+, Zn2+ and Cd2+ sequestration by birnessites with different Mn average oxidation state (AOS), and the Mn AOS dependent adsorption sites and adsorption characteristics. The results show that the maximum adsorption capacity of Pb2+, Cu2+, Zn2+ and Cd2+ increased with increasing birnessite Mn AOS. The adsorption capacity followed the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. The observations suggest that there exist two sites on the surface of birnessite, i. e., high-binding-energy site (HBE site) and low-binding-energy site (LBE site). With the increase of Mn AOS for birnessites, the amount of HBE sites for heavy metal ions adsorption remarkably increased. On the other hand, variation in the amount of LBE sites was insignificant. The amount of LBE sites is much more than those of HBE sites on the surface of birnessite with low Mn AOS. Nevertheless, both amounts on the surface of birnessite with high Mn AOS are very close to each other. Therefore, the heavy metal ions adsorption capacity on birnessite is largely determined by the amount of HBE sites. On birnessite surface, adsorption of Cu2+, Zn2+, and Cd2+ mostly occurred at HBE sites. In comparison with Zn2+ and Cd2+, more Cu2+ adsorbed on the LBW sites. Pb2+ adsorption maybe occupy at both LBE sites and HBE sites simultaneously.

  7. Dispersion of Co/CNTs via strong electrostatic adsorption method: Thermal treatment effect

    Energy Technology Data Exchange (ETDEWEB)

    Akbarzadeh, Omid, E-mail: omid.akbarzadeh63@gmail.com; Abdullah, Bawadi, E-mail: bawadi-abdullah@petronas.com.my; Subbarao, Duvvuri, E-mail: duvvuri-subbarao@petronas.com.my [Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Zabidi, Noor Asmawati Mohd, E-mail: noorasmawati-mzabidi@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

    2015-07-22

    The effect of different thermal treatment temperature on the structure of multi-walled carbon nanotubes (MWCNTs) and Co particle dispersion on CNTs support is studied using Strong electrostatic adsorption (SEA) method. The samples tested by N{sub 2}-adsorption, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). N{sub 2}-adsorption results showed BET surface area increased using thermal treatment and TEM images showed that increasing the thermal treatment temperature lead to flaky CNTs and defects introduced on the outer surface and Co particle dispersion increased.

  8. Strong and weak adsorption of CO{sub 2} on PuO{sub 2} (1 1 0) surfaces from first principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Yu, H.L. [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Deng, X.D. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Li, G.; Lai, X.C. [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China); Meng, D.Q., E-mail: yuhuilong2002@126.com [Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, Mianyang 621907 (China)

    2014-10-15

    Highlights: • The CO{sub 2} adsorption on PuO{sub 2} (1 1 0) surface was studied by GGA + U. • Both weak and strong adsorptions exist between CO{sub 2} and the PuO{sub 2} (1 1 0) surface. • Electrostatic interactions were involved in the weak interactions. • Covalent bonding was developed in the strong adsorptions. - Abstract: The CO{sub 2} adsorption on plutonium dioxide (PuO{sub 2}) (1 1 0) surface was studied using projector-augmented wave (PAW) method based on density-functional theory corrected for onsite Coulombic interactions (GGA + U). It is found that CO{sub 2} has several different adsorption features on PuO{sub 2} (1 1 0) surface. Both weak and strong adsorptions exist between CO{sub 2} and the PuO{sub 2} (1 1 0) surface. Further investigation of partial density of states (PDOS) and charge density difference on two typical absorption sites reveal that electrostatic interactions were involved in the weak interactions, while covalent bonding was developed in the strong adsorptions.

  9. Quantitative imaging of cation adsorption site densities in undisturbed soil

    Science.gov (United States)

    Keck, Hannes; Strobel, Bjarne W.; Gustafsson, Jon-Petter; Koestel, John

    2017-04-01

    The vast majority of present soil system models assume a homogeneous distribution and accessibility of cation adsorption sites (CAS) within soil structural units like e.g. soil horizons. This is however in conflict with several recent studies finding that CAS in soils are not uniformly but patchily distributed at and below the cm-scale. It is likely that the small-scale distribution of CAS has significant impact on the performance of these models. However, systematic approaches to map CAS densities in undisturbed soil with 3-D resolution that could lead to respective model improvements are still lacking. We therefore investigated the 3-D distribution of the CAS in undisturbed soils using X-ray scanning and barium ions as a contrast agent. We appraised the validity of the approach by comparing X-ray image-derived cation exchange coefficients (CEC) with ones obtained using the ammonium acetate method. In the process, we evaluated whether there were larger CAS concentrations at aggregate and biopore boundaries as it is often hypothesized. We sampled eight small soil cores (approx. 10 ccm) from different locations with contrasting soil texture and organic matter contents. The samples were first saturated with a potassium chloride solution (0.1 mol per liter), whereupon a 3-D X-ray image was taken. Then, the potassium chloride solution was flushed out with a barium chloride solution (0.3 mol per liter) with barium replacing the potassium from the CAS due to its larger exchange affinity. After X-ray images as well as electrical conductivity in the effluent indicated that the entire sample had been saturated with the barium chloride, the sample was again rinsed using the potassium chloride solution. When the rinsing was complete a final 3-D X-ray image was acquired. The difference images between final and initial 3-D X-ray images were interpreted as depicting the adsorbed barium as the density of barium exceeds the one of potassium by more than 2 times. The X-ray image

  10. Effect of strong acids on red mud structural and fluoride adsorption properties.

    Science.gov (United States)

    Liang, Wentao; Couperthwaite, Sara J; Kaur, Gurkiran; Yan, Cheng; Johnstone, Dean W; Millar, Graeme J

    2014-06-01

    The removal of fluoride using red mud has been improved by acidifying red mud with hydrochloric, nitric and sulphuric acid. The acidification of red mud causes sodalite and cancrinite phases to dissociate, confirmed by the release of sodium and aluminium into solution as well as the disappearance of sodalite bands and peaks in infrared and X-ray diffraction data. The dissolution of these mineral phases increases the amount of available iron and aluminium oxide/hydroxide sites that are accessible for the adsorption of fluoride. However, concentrated acids have a negative effect on adsorption due to the dissolution of these iron and aluminium oxide/hydroxide sites. The removal of fluoride is dependent on the charge of iron and aluminium oxide/hydroxides on the surface of red mud. Acidifying red mud with hydrochloric, nitric and sulphuric acid resulted in surface sites of the form ≡SOH2(+) and ≡SOH. Optimum removal is obtained when the majority of surface sites are in the form ≡SOH2(+) as the substitution of a fluoride ion does not cause a significant increase in pH. This investigation shows the importance of having a low and consistent pH for the removal of fluoride from aqueous solutions using red mud. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Endangerment of cultural heritage sites by strong rain

    Science.gov (United States)

    Krauß, Thomas; Fischer, Peter

    2017-09-01

    Due to climate change extreme weather conditions become more and more frequent in the last years. Especially in Germany nearly every year a large flood event happens. Most of these events are caused by strong rain. There are at most two causes for these floodings: The first is locally strong rain in the area of damage, the second happens at damage sites located near confluxes and strong rain in the upper stream areas of the joining rivers. The amount of damage is often strongly correlated with unreasonable designation of new construction in such endangered regions. Our presented study is based on an earlier project together with a German insurance company. In this project we analyzed correlations of geographical settings with the insurance data of flood damages over ten years. The result of this study was a strong relation of the terrain with the amount and the probability of damages. Further investigations allow us to derive a system for estimating potential endangerment due to strong rain just from suitable digital terrain models (DTMs). In the presented study we apply this method to different types of cultural heritage (CH) sites in Germany and other parts of the world to detect which type of CH sites were build with potential endangerment of strong rain events in mind and which ones are prone to such events.

  12. A supramolecular strategy for self-mobile adsorption sites in affinity membrane.

    Science.gov (United States)

    Lin, Ligang; Dong, Meimei; Liu, Chunyu; Wei, Chenjie; Wang, Yuanyuan; Sun, Hui; Ye, Hui

    2014-09-01

    Disclosed here is the design of a novel supramolecular membrane with self-mobile adsorption sites for biomolecules purification. In the 3D micropore channels of membrane matrix, the ligands are conjugated onto the cyclic compounds in polyrotaxanes for protein adsorption. During membrane filtration, the adsorption sites can rotate and/or slide along the axial chain, which results in the enhanced adsorption capacity. The excellent performance of supra-molecular membrane is related with the dynamic working manner of adsorption sites, which plays a crucial role on avoiding spatial mismatching and short-circuit effect. The supra-molecular strategy described here has general suggestions for the "sites" involved technologies such as catalysis, adsorption, and sensors, which is of broad interest. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Wrinkles and Folds of Activated Graphene Nanosheets as Fast and Efficient Adsorptive Sites for Hydrophobic Organic Contaminants.

    Science.gov (United States)

    Wang, Jun; Chen, Baoliang; Xing, Baoshan

    2016-04-05

    To create more wrinkles and folds as available adsorption sites, graphene nanosheets (GNS) were thermally treated with KOH for morphological alteration. The surface structures and properties of the activated graphene nanosheets (AGN) were characterized by BET-N2, SEM, TEM, Raman, XRD, XPS, and FTIR. After KOH etching, the highly crystal structure was altered, self-aggregation of graphene layers were evidently relieved, and more single to few layer graphene nanosheets were created with wrinkles and folds. Also both specific surface area and micropore volume of AGN increased relative to GNS. The adsorption of AGN toward p-nitrotoluene, naphthalene and phenanthrene were greatly enhanced in comparison with GNS, and gradually promoted with increasing degree of KOH etching. Adsorption rate of organic contaminants on AGN was very fast and efficient, whereas small molecules showed higher adsorption rates due to the more porous surface of graphene. In addition to π-π interaction, the high affinities of p-nitrotoluene to AGN are suggested from strong electron charge transfer interactions between nitro groups on p-nitrotoluene and defect sites of AGN. A positively linear correlation between organic molecule uptake and the micropore volume of AGN indicated that pore-filling mechanism may play an important role in adsorption. Morphological wrinkles and folds of graphene nanosheets can be regulated to enhance the adsorption capability and kinetics for efficient pollutant removal and to selectively preconcentrate adsorbates with different sizes for detection.

  14. Radiochemical study of Re/W adsorption behavior on a strongly basic anion exchange resin

    International Nuclear Information System (INIS)

    Gott, Matthew D.; Missouri Univ., Columbia, MO; Ballard, Beau D.; Redman, Lindsay N.

    2014-01-01

    Rhenium-186g is a radionuclide with a high potential for therapeutic applications. It emits therapeutic β - particles accompanied by low energy γ-rays, which allows for in-vivo tracking of the radiolabeled compound and dosimetry estimates. The current reactor production pathway 185 Re(n,γ) 186g Re produces low specific activity 186g Re, thereby limiting its therapeutic application. Work is underway to develop an accelerator-based, charged particle induced production method for high specific activity 186g Re from targets of enriched 186 W. To optimize the chemical 186g Re recovery method, batch studies have been performed to characterize the adsorption behavior of Re and W on a strongly basic anion exchange resin. An in-depth physicochemical profile was developed for the interaction of Re with resin material, which showed the reaction to be endothermic and spontaneous. Basic (NaOH) and acidic (HNO 3 ) matrices were used to determine the equilibrium distribution coefficients for Re and W. The resin exhibits the best affinity for Re at slightly basic conditions and little affinity above moderately acidic concentrations. Tungsten has low affinity for the resin above moderately basic concentrations. A study was performed to examine the effect of W concentration on Re adsorption, which showed that even a high ionic WO 4 2- strength of up to 1.9 mol kg -1 does not significantly compromise ReO 4 - retention on the resin. (orig.)

  15. Surface complexation modeling of uranyl adsorption on corrensite from the Waste Isolation Pilot Plant Site

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang-Won; Leckie, J.O. [Stanford Univ., CA (United States); Siegel, M.D. [Sandia National Labs., Albuquerque, NM (United States)

    1995-09-01

    Corrensite is the dominant clay mineral in the Culebra Dolomite at the Waste Isolation Pilot Plant. The surface characteristics of corrensite, a mixed chlorite/smectite clay mineral, have been studied. Zeta potential measurements and titration experiments suggest that the corrensite surface contains a mixture of permanent charge sites on the basal plane and SiOH and AlOH sites with a net pH-dependent charge at the edge of the clay platelets. Triple-layer model parameters were determined by the double extrapolation technique for use in chemical speciation calculations of adsorption reactions using the computer program HYDRAQL. Batch adsorption studies showed that corrensite is an effective adsorbent for uranyl. The pH-dependent adsorption behavior indicates that adsorption occurs at the edge sites. Adsorption studies were also conducted in the presence of competing cations and complexing ligands. The cations did not affect uranyl adsorption in the range studied. This observation lends support to the hypothesis that uranyl adsorption occurs at the edge sites. Uranyl adsorption was significantly hindered by carbonate. It is proposed that the formation of carbonate uranyl complexes inhibits uranyl adsorption and that only the carbonate-free species adsorb to the corrensite surface. The presence of the organic complexing agents EDTA and oxine also inhibits uranyl sorption.

  16. Surface complexation modeling of uranyl adsorption on corrensite from the Waste Isolation Pilot Plant Site

    International Nuclear Information System (INIS)

    Park, Sang-Won; Leckie, J.O.; Siegel, M.D.

    1995-09-01

    Corrensite is the dominant clay mineral in the Culebra Dolomite at the Waste Isolation Pilot Plant. The surface characteristics of corrensite, a mixed chlorite/smectite clay mineral, have been studied. Zeta potential measurements and titration experiments suggest that the corrensite surface contains a mixture of permanent charge sites on the basal plane and SiOH and AlOH sites with a net pH-dependent charge at the edge of the clay platelets. Triple-layer model parameters were determined by the double extrapolation technique for use in chemical speciation calculations of adsorption reactions using the computer program HYDRAQL. Batch adsorption studies showed that corrensite is an effective adsorbent for uranyl. The pH-dependent adsorption behavior indicates that adsorption occurs at the edge sites. Adsorption studies were also conducted in the presence of competing cations and complexing ligands. The cations did not affect uranyl adsorption in the range studied. This observation lends support to the hypothesis that uranyl adsorption occurs at the edge sites. Uranyl adsorption was significantly hindered by carbonate. It is proposed that the formation of carbonate uranyl complexes inhibits uranyl adsorption and that only the carbonate-free species adsorb to the corrensite surface. The presence of the organic complexing agents EDTA and oxine also inhibits uranyl sorption

  17. Radiochemical study of Re/W adsorption behavior on a strongly basic anion exchange resin

    Energy Technology Data Exchange (ETDEWEB)

    Gott, Matthew D. [Los Alamos National Laboratory, Los Alamos, NM (United States). Chemistry Div.; Missouri Univ., Columbia, MO (United States). Dept. of Chemistry; Ballard, Beau D.; Redman, Lindsay N. [Los Alamos National Laboratory, Los Alamos, NM (United States). Chemistry Div.; and others

    2014-07-01

    Rhenium-186g is a radionuclide with a high potential for therapeutic applications. It emits therapeutic β{sup -} particles accompanied by low energy γ-rays, which allows for in-vivo tracking of the radiolabeled compound and dosimetry estimates. The current reactor production pathway {sup 185}Re(n,γ){sup 186g}Re produces low specific activity {sup 186g}Re, thereby limiting its therapeutic application. Work is underway to develop an accelerator-based, charged particle induced production method for high specific activity {sup 186g}Re from targets of enriched {sup 186}W. To optimize the chemical {sup 186g}Re recovery method, batch studies have been performed to characterize the adsorption behavior of Re and W on a strongly basic anion exchange resin. An in-depth physicochemical profile was developed for the interaction of Re with resin material, which showed the reaction to be endothermic and spontaneous. Basic (NaOH) and acidic (HNO{sub 3}) matrices were used to determine the equilibrium distribution coefficients for Re and W. The resin exhibits the best affinity for Re at slightly basic conditions and little affinity above moderately acidic concentrations. Tungsten has low affinity for the resin above moderately basic concentrations. A study was performed to examine the effect of W concentration on Re adsorption, which showed that even a high ionic WO{sub 4}{sup 2-} strength of up to 1.9 mol kg{sup -1} does not significantly compromise ReO{sub 4}{sup -} retention on the resin. (orig.)

  18. Position-Dependent Dynamics Explain Pore-Averaged Diffusion in Strongly Attractive Adsorptive Systems.

    Science.gov (United States)

    Krekelberg, William P; Siderius, Daniel W; Shen, Vincent K; Truskett, Thomas M; Errington, Jeffrey R

    2017-12-12

    Using molecular simulations, we investigate the relationship between the pore-averaged and position-dependent self-diffusivity of a fluid adsorbed in a strongly attractive pore as a function of loading. Previous work (Krekelberg, W. P.; Siderius, D. W.; Shen, V. K.; Truskett, T. M.; Errington, J. R. Connection between thermodynamics and dynamics of simple fluids in highly attractive pores. Langmuir 2013, 29, 14527-14535, doi: 10.1021/la4037327) established that pore-averaged self-diffusivity in the multilayer adsorption regime, where the fluid exhibits a dense film at the pore surface and a lower density interior pore region, is nearly constant as a function of loading. Here we show that this puzzling behavior can be understood in terms of how loading affects the fraction of particles that reside in the film and interior pore regions as well as their distinct dynamics. Specifically, the insensitivity of pore-averaged diffusivity to loading arises from the approximate cancellation of two factors: an increase in the fraction of particles in the higher diffusivity interior pore region with loading and a corresponding decrease in the particle diffusivity in that region. We also find that the position-dependent self-diffusivities scale with the position-dependent density. We present a model for predicting the pore-average self-diffusivity based on the position-dependent self-diffusivity, which captures the unusual characteristics of pore-averaged self-diffusivity in strongly attractive pores over several orders of magnitude.

  19. Fluoride adsorption on goethite in relation to different types of surface sites

    NARCIS (Netherlands)

    Hiemstra, T.; Riemsdijk, van W.H.

    2000-01-01

    Metal (hydr)oxides have different types of surface groups. Fluoride ions have been used as a probe to assess the number of surface sites. We have studied the F− adsorption on goethite by measuring the F− and H interaction and F− adsorption isotherms. Fluoride ions exchange against singly coordinated

  20. Study of Adsorption Property of Ga(III) onto Strongly Basic Resin for Ga Extraction from Bayer Liquor

    Science.gov (United States)

    Zhao, Zhuo; Yang, Yongxiang; Lu, Hao; Hua, Zhongsheng; Ma, Xiaoling

    Ion-exchange is the main technology used in industry for gallium recovery from Bayer liquor, the largest gallium production resource. However, the co-extraction of vanadium and the degradation of resins are the major issues. Further investigations related to fundamental theory are needed. This paper reports the study of the adsorption properties of a strongly basic resin having a combination of one =NOH group and another active group -NH2 for Ga(III) extraction. The influence of operational conditions such as contact time, initial Ga(III) concentration and temperature on Ga(III) adsorption were extensively investigated. The results revealed that the resin has high adsorption capacity and Ga(III) selectivity. The optimal adsorption condition was obtained at temperatures of 40-50°C and contact time of 40-60 min. The Ga(III) adsorption data on the resin fit well with the pseudo second-order kinetics. Langmuir and Freundlich models were used to describe Ga(III) adsorption isotherms on the resin.

  1. Adsorption of arsenic by iron rich precipitates from two coal mine drainage sites on the West Coast of New Zealand

    International Nuclear Information System (INIS)

    Rait, R.; Trumm, D.; Pope, J.; Craw, D.; Newman, N.; MacKenzie, H.

    2010-01-01

    Dissolved As can be strongly adsorbed to fine grained Fe(III) minerals such as hydroxides, oxyhydroxides and hydroxysulphates. Therefore precipitates that form during neutralisation or treatment of acid mine drainage have potential to be useful for treatment of As-contaminated water because acid mine drainage is often Fe rich. We tested the adsorption properties of Fe(III) rich precipitates from two West Coast coal mines with As-contaminated water from an historic gold ore processing site near Reefton. Precipitates were collected from distinctly different settings, an active acid mine drainage treatment plant at Stockton mine and the neutralisation/oxidation zone of acid mine drainage discharge at the abandoned Blackball Coal Mine. The two mine sites produce precipitates with different compositions and mineralogy. Arsenic adsorption onto precipitates from each site was determined in batch and column tests under laboratory conditions. Batch experiments indicate As adsorption occurs rapidly during the first 5 h and reaches equilibrium after 24 h. At equilibrium, and for a dosing ratio of 50 g of precipitate per litre of water, As concentrations decreased from 99 mg/L to 0.0080 mg/L with precipitates from Stockton and to 0.0017 mg/L with precipitates from Blackball. Arsenic adsorption capacity is up to 12 mg/g on precipitates from Stockton sludge and 74 mg/g on precipitates from Blackball. The Blackball precipitate adsorbs more As than precipitates from Stockton which is probably due to the higher Fe oxide content but pH and surface structure could also play a role. The column experiment confirmed that adsorption of As from a continuous waste stream onto these precipitates is possible, and that passive remediation using this waste product mixed with gravel to enhance permeability could be a viable approach at As-contaminated mine sites. (author). 56 refs., 10 figs., 6 tabs.

  2. Adsorption site of ammonia on copper-exchanged Y-type zeolite under coexisting water vapor. Temperature-programed desorption and infrared adsorption spectra

    Energy Technology Data Exchange (ETDEWEB)

    Kasaoka, S.; Sasaoka, E.; Shiraga, T.; Ono, Y.

    1978-03-01

    Sodium Y zeolites were copper-exchanged with cupric nitrate in water, in aqueous ammonia, and in aqueous ammonia/ammonium chloride, and calcined at 500/sup 0/C. Temperature-programed desorption and IR spectroscopy showed three types of adsorption sites for 0.1-1.0% ammonia gas from nitrogen containing 0-12% water vapor: physisorption, adsorption as tetraamminocopper(II) on copper(II) sites (type 2 site), and adsorption as ammonium ion on hydroxyl sites (type 3 site). Adsorption on type 2 sites occurred only at high ammonia concentration; desorption occurred around 175/sup 0/C. Type 3 sites consisted of Cu(OH)/sup +/ and Al(OH)/sup +/, adsorbed ammonia from low concentrations, and at temperatures above 200/sup 0/C, were probably the active sites for the reduction of nitric oxide by ammonia.

  3. Site competition on metal surfaces: an electron spectroscopic study of sequential adsorption on W(110)

    International Nuclear Information System (INIS)

    Steinkilberg, M.; Menzel, D.

    1977-01-01

    Using UPS and XPS, the sequential adsorption of hydrogen + carbon monoxide, and of hydrogen + oxygen, on W(110) has been studied at room temperature. Adsorption of CO on a H-covered surface is rapid and leads to total displacement of hydrogen. The resulting CO layer however, is different from that formed on the clean surface under identical conditions, in that it consists of a higher percentage of virgin CO, while considerably more β-CO forms on the clean surface. Oxygen does not adsorb on a H-covered surface, nor displace hydrogen. It is concluded that hydrogen most probably occupies the same sites utilized by dissociative adsorption of CO and oxygen, while virgin CO can also occupy different sites; its adsorption can thus lead to interactional weakening of the H-surface bond. (Auth.)

  4. NH{sub 3} adsorption on the Lewis and Bronsted acid sites of MoO{sub 3} (0 1 0) surface: A cluster DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Zhifeng [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); College of Material Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Fan, Junyan [Foundation Department, Shanxi Police Academy, No. 27 Second Section of Old Jinci Road, Taiyuan 030021, Shanxi (China); Zuo, Zhijun [Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Li, Zhe, E-mail: lizhe@tyut.edu.cn [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Zhang, Jinshan [College of Material Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China)

    2014-01-01

    The adsorption of NH{sub 3} on the Lewis and Bronsted acid sites of MoO{sub 3} (0 1 0) surface has been investigated based on the density functional theory (DFT) method using the clusters models. The calculated results indicate that NH{sub 3} could strongly adsorb on both the Lewis and Bronsted acid sites in the form of NH{sub 3} species and NH{sub 4}{sup +} respectively, whereas the adsorption on the Lewis acid site is found to be more favorable energetically than that on the Bronsted acid site. For the Lewis acid site Mulliken population analysis shows a donation of lone pairs from NH{sub 3} to the surface and activation of N–H bond. The overlaps of N-s, N-p and Mo-d orbitals suggest the strong interaction between N and Mo atoms. For the Bronsted acid site N–H bond is also activated by the formation of NH{sub 4}{sup +} species. The hybridizations between H and O atoms as well as N and H atoms are the major reasons for strong chemical adsorption of NH{sub 3} and the existence of NH{sub 4}{sup +} species, which partly attributed to the presence of N–H… O hydrogen bonds. Furthermore, the formation of a second Lewis acid site at adjacent or diagonal site results in slight changes of adsorption stability, structural changes and charge redistributions, suggesting its small influence on NH{sub 3} adsorption.

  5. Removal of Chromium by Using of Adsorption onto Strong Base Anion Resin: Study of Equilibrium and Kinetic

    Directory of Open Access Journals (Sweden)

    Mehdi Shirzad Siboni

    2011-10-01

    Full Text Available Chromium is one of the heavy metals that is found in industrial effluents and is very toxic for human and environment. In this work the removal of hexavalent chromium by using of adsorption onto strongly basic anion was investigated. Various parameters such as pH, initial hexavalent chromium concentration, contact time and resin dosage were studied. Experimental data were expressed by Langmiur and Freundlich isotherm Pseudo-first order, Pseudo-second order and modified Pseudo-first order kinetic models. The results showed chromium removal was increased by increase of contact time and resin dosage, while decreased by increase of pH and initial hexavalent chromium concentration. At contact time equal 120 min, resin dosage 0.2 g/100 ml and initial hexavalent chromium concentration of 30 mg/l, by increasing pH from 3 to 11, removal efficiency was decreased from 93.56 % to 69.12 %. In addition, by increasing contact time from 5 min to 120 min, removal efficiency was increased from 39.51 % to 94.41 %. The results also showed hexavalent chromium sorption follows Langmiur isotherm model. Pseudo second order models best describe chromium removal by using of adsorption onto strongly basic anion resin. The results revealed that removal of hexavalent chromium from aqueous solution by using of adsorption onto stringly basic onion resins can be done quick and effective.

  6. Adsorption

    Directory of Open Access Journals (Sweden)

    Sushmita Banerjee

    2017-05-01

    Full Text Available Application of saw dust for the removal of an anionic dye, tartrazine, from aqueous solutions has been investigated. The experiments were carried out in batch mode. Effect of the parameters such as pH, initial dye concentration and temperature on the removal of the dye was studied. Equilibrium was achieved in 70 min. Maximum adsorption of dye was achieved at pH 3. Removal percent was found to be dependent on the initial concentration of dye solution, and maximum removal was found to be 97% at 1 mg/L of tartrazine. The removal increases from 71% to 97% when the initial concentration of dye solution decreases from 15 mg/L to 1 mg/L. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The (Langmuir adsorption capacity of the adsorbent is found to be 4.71 mg/g at 318 K. Kinetic modeling of the process of removal was carried out and the process of removal was found to follow a pseudo second order model and the value of rate constant for adsorption process was calculated as 2.7 × 10−3 g mg−1 min−1 at 318 K. The thermodynamic parameters such as change in free energy (ΔG°, enthalpy (ΔH° and entropy (ΔS° were determined and the negative values of ΔG° indicated that the process of removal was spontaneous at all values of temperatures. Further, the values of ΔH° indicated the endothermic nature of the process of removal.

  7. Goethite surface reactivity: III. Unifying arsenate adsorption behavior through a variable crystal face - Site density model

    Science.gov (United States)

    Salazar-Camacho, Carlos; Villalobos, Mario

    2010-04-01

    We developed a model that describes quantitatively the arsenate adsorption behavior for any goethite preparation as a function of pH and ionic strength, by using one basic surface arsenate stoichiometry, with two affinity constants. The model combines a face distribution-crystallographic site density model for goethite with tenets of the Triple Layer and CD-MUSIC surface complexation models, and is self-consistent with its adsorption behavior towards protons, electrolytes, and other ions investigated previously. Five different systems of published arsenate adsorption data were used to calibrate the model spanning a wide range of chemical conditions, which included adsorption isotherms at different pH values, and adsorption pH-edges at different As(V) loadings, both at different ionic strengths and background electrolytes. Four additional goethite-arsenate systems reported with limited characterization and adsorption data were accurately described by the model developed. The adsorption reaction proposed is: lbond2 FeOH +lbond2 SOH +AsO43-+H→lbond2 FeOAsO3[2-]…SOH+HO where lbond2 SOH is an adjacent surface site to lbond2 FeOH; with log K = 21.6 ± 0.7 when lbond2 SOH is another lbond2 FeOH, and log K = 18.75 ± 0.9, when lbond2 SOH is lbond2 Fe 2OH. An additional small contribution of a protonated complex was required to describe data at low pH and very high arsenate loadings. The model considered goethites above 80 m 2/g as ideally composed of 70% face (1 0 1) and 30% face (0 0 1), resulting in a site density for lbond2 FeOH and for lbond2 Fe 3OH of 3.125/nm 2 each. Below 80 m 2/g surface capacity increases progressively with decreasing area, which was modeled by considering a progressively increasing proportion of faces (0 1 0)/(1 0 1), because face (0 1 0) shows a much higher site density of lbond2 FeOH groups. Computation of the specific proportion of faces, and thus of the site densities for the three types of crystallographic surface groups present in

  8. Spectroscopic link between adsorption site occupation and local surface chemical reactivity

    DEFF Research Database (Denmark)

    Baraldi, A.; Lizzit, S.; Comelli, G.

    2004-01-01

    rules, from which adsorption sites are directly determined. Theoretical calculations rationalize the results for transition metal surfaces in terms of the energy shift of the d-band center of mass and this proves that adsorbate-induced SCL shifts provide a spectroscopic measure of local surface...

  9. On-site Destruction of Radioactive Oily Wastes Using Adsorption Coupled with Electrochemical Regeneration - 12221

    Energy Technology Data Exchange (ETDEWEB)

    Brown, N.W. [Arvia Technology Ltd, Daresbury Innovation Centre, Daresbury, WA4 4FS (United Kingdom); Wickenden, D.A. [Magnox Ltd, Berkeley Centre, Gloucestershire, GL13 9PB (United Kingdom); Roberts, E.P.L. [School of Chemical Engineering, University of Manchester, Manchester, M60 1QD (United Kingdom)

    2012-07-01

    Arvia{sup R}, working with Magnox Ltd, has developed the technology of adsorption coupled with electrochemical regeneration for the degradation of orphan radioactive oil wastes. The process results in the complete destruction of the organic phase where the radioactivity is transferred to liquid and solid secondary wastes that can then be processed using existing authorised on-site waste-treatment facilities.. Following on from successful laboratory and pilot scale trials, a full scale, site based demonstrator unit was commissioned at the Magnox Trawsfynydd decommissioning site to destroy 10 l of LLW and ILW radioactive oils. Over 99% of the emulsified oil was removed and destroyed with the majority of activity (80 - 90%) being transferred to the aqueous phase. Secondary wastes were disposed of via existing routes with the majority being disposed of via the sites active effluent treatment plant. The regeneration energy required to destroy a litre of oil was 42.5 kWh/l oil. This on-site treatment approach eliminates the risks and cost associated with transporting the active waste oils off site for incineration or other treatment. The Arvia{sup R} process of adsorption coupled with electrochemical regeneration has successfully demonstrated the removal and destruction of LLW and ILW radioactive oils on a nuclear site. Over 99.9% of the emulsified oil was removed, with the majority of the radioactive species transferred to the aqueous, supernate, phase (typically 80 - 90 %). The exception to this is Cs-137 which appears to be more evenly distributed, with 43% associated with the liquid phase and 33 % with the Nyex, the remainder associated with the electrode bed. The situation with Plutonium may be similar, but this requires confirmation, hence further work is underway to understand the full nature of the electrode bed radioactive burden and its distribution within the body of the electrodes. - Tritium gaseous discharges were negligible; hence no off-gas treatment

  10. High-resolution insight into the competitive adsorption of heavy metals on natural sediment by site energy distribution.

    Science.gov (United States)

    Huang, Limin; Jin, Qiang; Tandon, Puja; Li, Aimin; Shan, Aidang; Du, Jiajie

    2018-04-01

    Investigating competitive adsorption on river/lake sediments is valuable for understanding the fate and transport of heavy metals. Most studies have studied the adsorption isotherms of competitive heavy metals, which mainly comparing the adsorption information on the same concentration. However, intrinsically, the concentration of each heavy metal on competitive adsorption sites is different, while the adsorption energy is identical. Thus, this paper introduced the site energy distribution theory to increase insight into the competitive adsorption of heavy metals (Cu, Cd and Zn). The site energy distributions of each metal with and without other coexisting heavy metals were obtained. It illustrated that site energy distributions provide much more information than adsorption isotherms through screening of the full energy range. The results showed the superior heavy metal in each site energy area and the influence of competitive metals on the site energy distribution of target heavy metal. Site energy distributions can further help in determining the competitive sites and ratios of coexisting metals. In particular, in the high-energy area, which has great environmental significance, the ratios of heavy metals in the competitive adsorption sites obtained for various competitive systems were as follows: slightly more than 3:1 (Cu-Cd), slightly less than 3:1 (Cu-Zn), slightly more than 1:1 (Cd-Zn), and nearly 7:2:2 (Cu-Cd-Zn). The results from this study are helpful to deeply understand competitive adsorption of heavy metals (Cu, Cd, Zn) on sediment. Therefore, this study was effective in presenting a general pattern for future reference in competitive adsorption studies on sediments. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Quantitative imaging of the 3-D distribution of cation adsorption sites in undisturbed soil

    Science.gov (United States)

    Keck, Hannes; Strobel, Bjarne W.; Petter Gustafsson, Jon; Koestel, John

    2017-10-01

    Several studies have shown that the distribution of cation adsorption sites (CASs) is patchy at a millimetre to centimetre scale. Often, larger concentrations of CASs in biopores or aggregate coatings have been reported in the literature. This heterogeneity has implications on the accessibility of CASs and may influence the performance of soil system models that assume a spatially homogeneous distribution of CASs. In this study, we present a new method to quantify the abundance and 3-D distribution of CASs in undisturbed soil that allows for investigating CAS densities with distance to the soil macropores. We used X-ray imaging with Ba2+ as a contrast agent. Ba2+ has a high adsorption affinity to CASs and is widely used as an index cation to measure the cation exchange capacity (CEC). Eight soil cores (approx. 10 cm3) were sampled from three locations with contrasting texture and organic matter contents. The CASs of our samples were saturated with Ba2+ in the laboratory using BaCl2 (0.3 mol L-1). Afterwards, KCl (0.1 mol L-1) was used to rinse out Ba2+ ions that were not bound to CASs. Before and after this process the samples were scanned using an industrial X-ray scanner. Ba2+ bound to CASs was then visualized in 3-D by the difference image technique. The resulting difference images were interpreted as depicting the Ba2+ bound to CASs only. The X-ray image-derived CEC correlated significantly with results of the commonly used ammonium acetate method to determine CEC in well-mixed samples. The CEC of organic-matter-rich samples seemed to be systematically overestimated and in the case of the clay-rich samples with less organic matter the CEC seemed to be systematically underestimated. The results showed that the distribution of the CASs varied spatially within most of our samples down to a millimetre scale. There was no systematic relation between the location of CASs and the soil macropore structure. We are convinced that the approach proposed here will strongly

  12. Studies on the adsorption behaviour of heavy rare earths with a strong cation exchanger DOWEX 50W-2X8

    International Nuclear Information System (INIS)

    Vijayalakshmi, R.; Singh, D.K.; Anitha, M.; Kotekar, M.K.; Dasgupta, K.; Singh, H.

    2014-01-01

    Rare earths have been a very fascinating area of research since long due to its wide applicability's in many field including superconductors, lasers, phosphors, medical, electronics, magnet, optics etc. Separation of rare earths is a challenging task and over the years many separation schemes based on solvent extraction, ion exchange, membrane etc have been developed and deployed. In the present work, we have investigated the adsorption behavior of heavy rare earths from a crude concentrate analyzing ∼ 80% Y 2 O 3 , ∼12% Dy 2 O 3 , ∼4% Er 2 O 3 etc., with a strong cationic exchanger namely Dowex 50W-2X8 in order to separate them in pure form. To start with, Y was selected as a representative of heavy rare earths and the conditions were optimized in batch experiments and later were applied to the feed solution containing Dy, Er, Ho etc. in a column study. Effects of experimental variables such as contact time, pH, weight of resin, concentration of the feed metal, temperature, desorption agents, on adsorption of Y was studied

  13. Strong adsorption characteristics of a novel overoxidized poly(3,4-ethylenedioxythiophene) film and application for dopamine sensing

    International Nuclear Information System (INIS)

    Lin, Jia-Min; Su, Ya-Ling; Chang, Wei-Ting; Su, Wan-Yu; Cheng, Shu-Hua

    2014-01-01

    Highlights: • A novel overoxidized poly(3,4-ethylenedioxythiophene) film is obtained. • The film structure favors the adsorption of dopamine. • The sensor is able to detect dopamine in the presence of ascorbic acid (1000X). - Abstract: An overoxidized poly(3,4-ethylenedioxythiophene) film-modified screen-printed carbon electrodes (SPCE/PEDOT ox ) was prepared and characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle techniques. The obtained film is a porous structure with highly abundant oxygen functionality. The SPCE/PEDOT ox could adsorb cations strongly and perform catalytic oxidation of biomolecules. The potential-induced adsorption of dopamine was observed for SPCE/PEDOT ox . A simple medium-exchange procedure was developed for the selective determination of dopamine by the use of the dopamine-adsorbed electrode. Under optimal differential pulse voltammetry (DPV), the proposed assay can be employed in the determination of submicromolar concentration of dopamine without the coexisting interferences of ascorbic acid (1000-fold) and uric acid (10-fold)

  14. Hierarchically porous, ultra-strong reduced graphene oxide-cellulose nanocrystal sponges for exceptional adsorption of water contaminants

    DEFF Research Database (Denmark)

    Yousefi, Nariman; Wong, Kerwin K.W.; Hosseinidoust, Zeinab

    2018-01-01

    Self-assembly of graphene oxide (GO) nanosheets into porous 3D sponges is a promising approach to exploit their capacity to adsorb contaminants while facilitating the recovery of the nanosheets from treated water. Yet, forming mechanically robust sponges with suitable adsorption properties presents...... a significant challenge. Ultra-strong and highly porous 3D sponges are formed using GO, vitamin C (VC), and cellulose nanocrystals (CNCs) - natural nanorods isolated from wood pulp. CNCs provide a robust scaffold for the partially reduced GO (rGO) nanosheets resulting in an exceptionally stiff nanohybrid....... The concentration of VC as a reducing agent plays a critical role in tailoring the pore architecture of the sponges. By using excess amounts of VC, a unique hierarchical pore structure is achieved, where VC grains act as soft templates for forming millimeter-sized pores, the walls of which are also porous...

  15. Exact results for the behavior of the thermodynamic Casimir force in a model with a strong adsorption

    Science.gov (United States)

    Dantchev, Daniel M.; Vassilev, Vassil M.; Djondjorov, Peter A.

    2016-09-01

    When massless excitations are limited or modified by the presence of material bodies one observes a force acting between them generally called Casimir force. Such excitations are present in any fluid system close to its true bulk critical point. We derive exact analytical results for both the temperature and external ordering field behavior of the thermodynamic Casimir force within the mean-field Ginzburg-Landau Ising type model of a simple fluid or binary liquid mixture. We investigate the case when under a film geometry the boundaries of the system exhibit strong adsorption onto one of the phases (components) of the system. We present analytical and numerical results for the (temperature-field) relief map of the force in both the critical region of the film close to its finite-size or bulk critical points as well as in the capillary condensation regime below but close to the finite-size critical point.

  16. The nature of cationic adsorption sites in alkaline zeolites-single, dual and multiple cation sites

    Czech Academy of Sciences Publication Activity Database

    Nachtigall, P.; Delgado, M. R.; Nachtigallová, Dana; Arean, C. O.

    2012-01-01

    Roč. 14, č. 5 (2012), s. 1552-1569 ISSN 1463-9076 R&D Projects: GA ČR GA203/09/0143 Institutional research plan: CEZ:AV0Z40550506 Keywords : exchanged ZSM-5 zeolites * carbon-monoxide adsorption * low-temperature CO * solid-state NMR * high-silica zeolites Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.829, year: 2012

  17. Transient biouptake flux and accumulation by micro-organisms: The case of two types of sites with Langmuir adsorption

    NARCIS (Netherlands)

    Galceran, J.; Monne, J.; Puy, J.; Leeuwen, van H.P.

    2006-01-01

    The uptake of a chemical species by an aquatic microorganism is modelled considering two kinds of sites where Langmuirian adsorption is followed by first order internalisation kinetics. Simpler models, such as only one internalisation route (while most of the adsorption takes place on

  18. Factors influencing U(VI adsorption onto soil from a candidate very low level radioactive waste disposal site in China

    Directory of Open Access Journals (Sweden)

    Zuo Rui

    2016-01-01

    Full Text Available The properties of soil at disposal sites are very important for geological disposal of very low level radioactive waste in terms of U(VI. In this study, soil from a candidate very low level radioactive waste disposal site in China was evaluated for its capacity on uranium sorption. Specifically, the equilibrium time, initial concentration, soil particle, pH, temperature, and carbonate were evaluated. The results indicated that after 15-20 days of sorption, the Kd value fluctuated and stabilized at 355-360 mL/g. The adsorptive capacity of uranium was increased as the initial uranium concentration increased, while it decreased as the soil particle size increased. The pH value played an important role in the U(VI sorption onto soil, especially under alkaline conditions, and had a great effect on the sorption capacity of soil for uranium. Moreover, the presence of carbonate decreased the sorption of U(VI onto soil because of the role of the strong complexation of carbonate with U(VI in the groundwater. Overall, this study assessed the behavior of U(VI sorption onto natural soil, which would be an important factor in the geological barrier of the repository, has contribution on mastering the characteristic of the adsorption of uranium in the particular soil media for the process of very low level radioactive waste disposal.

  19. Molecular studies of Cs adsorption sites in inorganic layered materials: the influence of solution concentration.

    Science.gov (United States)

    Sato, Kiminori; Hunger, Michael

    2017-07-19

    Radioactive Cs released into a soil environment migrates along with groundwater in a manner dependent on Cs concentration. Data on the variation of Cs adsorption as a function of solution concentration are an essential prerequisite to successful decontamination work in Fukushima. To aid the ongoing decontamination work, the adsorption of Cs in aqueous solution across a wide Cs + molarity range is studied for the case of saponite clay as adsorbent, an inorganic layered material that is an abundant mineral in the soil environment. The local molecular structures, i.e. nanosheet surfaces, nanosheet edges, and oncoming hexagonal cavities, participating in Cs adsorption are qualitatively highlighted by means of a recently developed analytical method using data from a conventional elution test, 133 Cs magic-angle-spinning nuclear magnetic resonance (MAS NMR), and the radiocesium interception potential (RIP) [K. Sato, et al., J. Phys. Chem. C, 2016, 120, 1270]. The concentrations of nanosheet edges amount to between 100 and 400 mmol kg -1 , which are not substantially different from those of the nanosheet surfaces, generally regarded as the main decontamination sites. This unambiguously implies that the nanosheet edges should be targeted as the molecular sites for decontaminating radioactive Cs, in addition to the nanosheet surfaces.

  20. Topographic gradient based site characterization in India complemented by strong ground-motion spectral attributes

    KAUST Repository

    Nath, Sankar Kumar; Thingbaijam, Kiran Kumar; Adhikari, M. D.; Nayak, Avinash; Devaraj, N.; Ghosh, Soumalya K.; Mahajan, Arun K.

    2013-01-01

    We appraise topographic-gradient approach for site classification that employs correlations between 30. m column averaged shear-wave velocity and topographic gradients. Assessments based on site classifications reported from cities across India indicate that the approach is reasonably viable at regional level. Additionally, we experiment three techniques for site classification based on strong ground-motion recordings, namely Horizontal-to-Vertical Spectral Ratio (HVSR), Response Spectra Shape (RSS), and Horizontal-to-Vertical Response Spectral Ratio (HVRSR) at the strong motion stations located across the Himalayas and northeast India. Statistical tests on the results indicate that these three techniques broadly differentiate soil and rock sites while RSS and HVRSR yield better signatures. The results also support the implemented site classification in the light of strong ground-motion spectral attributes observed in different parts of the globe. © 2013 Elsevier Ltd.

  1. Topographic gradient based site characterization in India complemented by strong ground-motion spectral attributes

    KAUST Repository

    Nath, Sankar Kumar

    2013-12-01

    We appraise topographic-gradient approach for site classification that employs correlations between 30. m column averaged shear-wave velocity and topographic gradients. Assessments based on site classifications reported from cities across India indicate that the approach is reasonably viable at regional level. Additionally, we experiment three techniques for site classification based on strong ground-motion recordings, namely Horizontal-to-Vertical Spectral Ratio (HVSR), Response Spectra Shape (RSS), and Horizontal-to-Vertical Response Spectral Ratio (HVRSR) at the strong motion stations located across the Himalayas and northeast India. Statistical tests on the results indicate that these three techniques broadly differentiate soil and rock sites while RSS and HVRSR yield better signatures. The results also support the implemented site classification in the light of strong ground-motion spectral attributes observed in different parts of the globe. © 2013 Elsevier Ltd.

  2. Determination of deuterium adsorption site on palladium(1 0 0) using low energy ion recoil spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kambali, I. [Department of Physics, University of Newcastle, Callaghan (Australia); O' Connor, D.J. [Department of Physics, University of Newcastle, Callaghan (Australia)], E-mail: john.oconnor@newcastle.edu.au; Gladys, M.J. [Department of Physics, University of Newcastle, Callaghan (Australia); Karolewski, M.A. [Department of Chemistry, University of Brunei Darussalam, Gadong BE1410 (Brunei Darussalam)

    2008-05-15

    Ion beam analysis has been recently applied to study the adsorption phenomena of some adsorbates on metal surfaces. In this paper, surface recoils created by low energy Ne{sup +} ions are employed to study the adsorption site of deuterium (D) atoms on Pd(1 0 0). This technique is extremely surface sensitive with the capacity for atomic layer depth resolution. From azimuthal angle observations of Pd(1 0 0) specimen, it was found that at room temperature, D was adsorbed in the fourfold hollow site of Pd(1 0 0) at a height of 0.25 {+-} 0.05 A above the surface. The adsorbate remains in the hollow site at all temperatures to 383 K though the vertical height above the surface is found to depend on coverage and for the first time evidence is found of a transition to a p(2 x 2) structure for the adsorbate. There is no evidence of D sitting in the Pd(1 0 0) subsurface at room and higher temperatures.

  3. A cluster DFT study of NH{sub 3} and NO adsorption on the (MoO{sub 2}){sup 2+}/HZSM-5 surface: Lewis versus Brønsted acid sites

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Zhifeng [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); College of Material Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Zuo, Zhijun [Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Li, Zhe, E-mail: lizhe@tyut.edu.cn [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Zhang, Jinshan [College of Material Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China)

    2014-12-01

    Graphical abstract: - Highlights: • NH{sub 3} adsorption is found to be more favorable energetically than NO adsorption on both Lewis and Brønsted acid sites. • Lewis and Brønsted acid sites are competitive energetically for NH{sub 3} adsorption. • Reduced-state Mo{sup 5+} is suggested to play a key role in adsorption and activation of NO{sub x} together with the adsorbed NH{sub 4}{sup +}. - Abstract: A systematic DFT study was carried out to investigate NH{sub 3} and NO adsorption on both Lewis and Brønsted acid sites of (MoO{sub 2}){sup 2+}/HZSM-5 catalyst by using cluster models. The adsorption energy results indicate that NH{sub 3} could strongly adsorb on both Lewis and Brønsted acid sites in the form of coordinated NH{sub 3} and NH{sub 4}{sup +}, respectively, whereas NO represents poorer adsorption ability. It is also found that Lewis and Brønsted acid sites are competitive energetically for NH{sub 3} adsorption. According to the difference in the proposed mechanisms for NH{sub 3} adsorption on different acid sites, particular attention has been focused on the first dissociation of coordinated NH{sub 3} for Lewis acid site and the effect of Mo site on the introduction of NO for Brønsted acid site. For the coordinated NH{sub 3} on Lewis acid site, the more electron donation from NH{sub 3} is, the greater its adsorption stability is and the higher active its H atoms are. In addition, DOS results show that stability of the H atoms is enhanced by interacting with framework oxygen and especially the H atoms chemical-bonded with framework oxygen. For the NH{sub 4}{sup +} on Brønsted acid site, reduced-state Mo{sup 5+} holds stronger reducibility and oxidizability than terminal oxygen, which is suggested to play a key role in adsorption and activation of NO{sub x} together with the adsorbed NH{sub 4}{sup +}.

  4. Generation of highly stable and active strong base sites on organized nano-porous alumina by calcium oxide

    Science.gov (United States)

    Tarlani, Aliakbar; Zarabadi, Mir Pouyan

    2013-02-01

    In a new approach, strong basic sites has been successfully prepared by loading of calcium nitrate (Ca) on organized nano-porous alumina (ONPA). The prepared CaONPAs were characterized by low-angle X-ray diffraction (XRD), N2 adsorption-desorption isotherms (Brunauer-Emmett-Teller (BET)-Barret-Joyner-Halenda (BJH)), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Measuring of the amount of the basic sites and the basicity was carried out by titration method, temperature-programmed desorption (TPD-CO2) and Hammett indicators. Resistance of the basic sites was also tested by washing with water. N2 sorption measurements showed that supporting of the calcium nitrate on ONPA can lead to the bimodal porosity at lower loading. BET surface area of the bare ONPA was 212 m2/g which decreased to 111 m2/g for the 25% of loading of Ca (25CaONPA). The results pointed out that CaONPA samples have basicity between 18.4 < H_ < 22 for 15 and 25% of loadings and well-preserved of the basicity after washing with water especially for 5 and 15% samples. Also no crystalline phase of CaO was observed for 25CaONPA which was calcined at 600 °C.

  5. Probing adsorption sites of carbon dioxide in metal organic framework of [Zn(bdc)(dpds)]n: A molecular simulation study

    Science.gov (United States)

    Lu, Shih-I.; Liao, Jian-Min; Huang, Xiao-Zhuang; Lin, Chia-Hsun; Ke, Szu-Yu; Wang, Chih-Chieh

    2017-11-01

    We used force-field based grand-canonical Monte Carlo simulation method and density functional theory to study adsorption characteristics of carbon dioxide (CO2) molecules in a metal-organic framework (MOF) compound, [Zn(bdc)(dpds)]n. The studied MOF include a metal ion (Zn(II)), an anion organic linker (dianion of benzene dicarboxylicacid, bdc2-) and a neutral organic linker (4,4‧-dipyridyldisulfide, dpds). Results from calculated adsorption isotherms and enthalpies of adsorption agree with the experimental data. The interactions between the adsorbed CO2 and the organic linkers were examined in simulations. Calculated results show available absorption sites are surrounded by two dpds ligands in which an S-S bond as an N-N‧ spacer connect two pyridines. In contrast, the bdc2- ligand does not give a significant contribution to the substantial adsorption amount even though it contains the carboxylate group that provides available bonding site to CO2.

  6. Attenuation relations of strong motion in Japan using site classification based on predominant period

    International Nuclear Information System (INIS)

    Toshimasa Takahashi; Akihiro Asano; Hidenobu Okada; Kojiro Irikura; Zhao, J.X.; Zhang Jian; Thio, H.K.; Somerville, P.G.; Yasuhiro Fukushima; Yoshimitsu Fukushima

    2005-01-01

    A spectral acceleration attenuation model for Japan is presented. The data set includes a very large number of strong ground motion records up to the end of 2003. Site class terms, instead of individual site correction terms, are used based on a recent study on site classification for strong motion recording stations in Japan. By using site class terms, tectonic source type effects are identified and accounted in the present model. Effects of faulting mechanism for crustal earthquakes are also accounted for. For crustal and interface earthquakes, a simple form of attenuation model is able to capture the main strong motion characteristics and achieves unbiased estimates. For subduction slab events, a simple distance modification factor is employed to achieve plausible and unbiased prediction. Effects of source depth, tectonic source type, and faulting mechanism for crustal earthquakes are significant. (authors)

  7. Shear-wave velocity compilation for Northridge strong-motion recording sites

    Science.gov (United States)

    Borcherdt, Roger D.; Fumal, Thomas E.

    2002-01-01

    Borehole and other geotechnical information collected at the strong-motion recording sites of the Northridge earthquake of January 17, 1994 provide an important new basis for the characterization of local site conditions. These geotechnical data, when combined with analysis of strong-motion recordings, provide an empirical basis to evaluate site coefficients used in current versions of US building codes. Shear-wave-velocity estimates to a depth of 30 meters are derived for 176 strong-motion recording sites. The estimates are based on borehole shear-velocity logs, physical property logs, correlations with physical properties and digital geologic maps. Surface-wave velocity measurements and standard penetration data are compiled as additional constraints. These data as compiled from a variety of databases are presented via GIS maps and corresponding tables to facilitate use by other investigators.

  8. Site classification of Indian strong motion network using response spectra ratios

    Science.gov (United States)

    Chopra, Sumer; Kumar, Vikas; Choudhury, Pallabee; Yadav, R. B. S.

    2018-03-01

    In the present study, we tried to classify the Indian strong motion sites spread all over Himalaya and adjoining region, located on varied geological formations, based on response spectral ratio. A total of 90 sites were classified based on 395 strong motion records from 94 earthquakes recorded at these sites. The magnitude of these earthquakes are between 2.3 and 7.7 and the hypocentral distance for most of the cases is less than 50 km. The predominant period obtained from response spectral ratios is used to classify these sites. It was found that the shape and predominant peaks of the spectra at these sites match with those in Japan, Italy, Iran, and at some of the sites in Europe and the same classification scheme can be applied to Indian strong motion network. We found that the earlier schemes based on description of near-surface geology, geomorphology, and topography were not able to capture the effect of sediment thickness. The sites are classified into seven classes (CL-I to CL-VII) with varying predominant periods and ranges as proposed by Alessandro et al. (Bull Seismol Soc Am 102:680-695 2012). The effect of magnitudes and hypocentral distances on the shape and predominant peaks were also studied and found to be very small. The classification scheme is robust and cost-effective and can be used in region-specific attenuation relationships for accounting local site effect.

  9. Predicting Multicomponent Adsorption Isotherms in Open-Metal Site Materials Using Force Field Calculations Based on Energy Decomposed Density Functional Theory

    NARCIS (Netherlands)

    Heinen, J.; Burtch, N.; Walton, K.; Fonseca Guerra, C.; Dubbeldam, D.

    2016-01-01

    For the design of adsorptive-separation units, knowledge is required of the multicomponent adsorption behavior. Ideal adsorbed solution theory (IAST) breaks down for olefin adsorption in open-metal site (OMS) materials due to non-ideal donor–acceptor interactions. Using a

  10. The genealogy of sequences containing multiple sites subject to strong selection in a subdivided population.

    Science.gov (United States)

    Nordborg, Magnus; Innan, Hideki

    2003-03-01

    A stochastic model for the genealogy of a sample of recombining sequences containing one or more sites subject to selection in a subdivided population is described. Selection is incorporated by dividing the population into allelic classes and then conditioning on the past sizes of these classes. The past allele frequencies at the selected sites are thus treated as parameters rather than as random variables. The purpose of the model is not to investigate the dynamics of selection, but to investigate effects of linkage to the selected sites on the genealogy of the surrounding chromosomal region. This approach is useful for modeling strong selection, when it is natural to parameterize the past allele frequencies at the selected sites. Several models of strong balancing selection are used as examples, and the effects on the pattern of neutral polymorphism in the chromosomal region are discussed. We focus in particular on the statistical power to detect balancing selection when it is present.

  11. Identifying the Tunneling Site in Strong-Field Ionization of H_{2}^{+}.

    Science.gov (United States)

    Liu, Kunlong; Barth, Ingo

    2017-12-15

    The tunneling site of the electron in a molecule exposed to a strong laser field determines the initial position of the ionizing electron and, as a result, has a large impact on the subsequent ultrafast electron dynamics on the polyatomic Coulomb potential. Here, the tunneling site of the electron of H_{2}^{+} ionized by a strong circularly polarized (CP) laser pulse is studied by numerically solving the time-dependent Schrödinger equation. We show that the electron removed from the down-field site is directly driven away by the CP field and the lateral photoelectron momentum distribution (LPMD) exhibits a Gaussian-like distribution, whereas the corresponding LPMD of the electron removed from the up-field site differs from the Gaussian shape due to the Coulomb focusing and scattering by the down-field core. Our current study presents the direct evidence clarifying a long-standing controversy over the tunneling site in H_{2}^{+} and raises the important role of the tunneling site in strong-field molecular ionization.

  12. The correlation of adsorption behavior between ciprofloxacin hydrochloride and the active sites of Fe-doped MCM-41

    Science.gov (United States)

    Wu, Ying; Tang, Yiming; Li, Laisheng; Liu, Peihong; Li, Xukai; Chen, Weirui; Xue, Ying

    2018-02-01

    Fe-MCM-41s with various molar ratios of silicon to iron (20, 40, 80 and 160) were prepared to investigate adsorption properties of ciprofloxacin hydrochloride (CPX) in aqueous solutions. Fe-MCM-41s were characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption/desorption isotherms and infrared spectroscopy (FT-IR). Effects of silicon–iron ratio, adsorbent dosage, pH and temperature were conducted to explore the adsorption mechanism of CPX on Fe-MCM-41. The results showed that the introduction of iron facilitated the absorption quantity for CPX from 20.04 to 83.33 mg g-1 at 120 min of reaction time, which was mainly attributed to surface complexation. The promotion of hydrophobic effect, electrostatic interactions and π-π electron donor–acceptor interaction also played coordinate roles in the adsorption process. The experimental kinetic data followed both the pseudo-second-order and intra-particle diffusion models, while the adsorption isotherm data fit well to Freundlich model at high temperature. Thermodynamic study showed that the adsorption was spontaneous. Under the effect of electrostatic interaction, pH of the solution strongly affected CPX adsorption. Five representative metal cations (Ca, Cu, Ni, Pb and Cd) were chosen to study the effects on CPX adsorption and their complexation. The inhibiting effect of metal cations on CPX adsorption was sequenced in the order of Cu > Ni > Pb > Cd > Ca, which followed the same order as the complexation stability constants between CPX and cations. The Fe-MCM-41 adsorbent possessed excellent reusability for 4 cycles use, suggesting a potential applicability of Fe-MCM-41 to remove CPX in water.

  13. Surface complexation modeling of U(VI) adsorption by aquifer sediments from a former mill tailings site at Rifle, Colorado

    Science.gov (United States)

    Hyun, S.P.; Fox, P.M.; Davis, J.A.; Campbell, K.M.; Hayes, K.F.; Long, P.E.

    2009-01-01

    A study of U(VI) adsorption by aquifer sediment samples from a former uranium mill tailings site at Rifle, Colorado, was conducted under oxic conditions as a function of pH, U(VI), Ca, and dissolved carbonate concentration. Batch adsorption experiments were performed using tailings site at Naturita, Colorado, indicated that possible calcite nonequilibrium of dissolved calcium concentration should be evaluated. The modeling results also illustrate the importance of the range of data used in deriving the best fit model parameters. ?? 2009 American Chemical Society.

  14. On sulfur core level binding energies in thiol self-assembly and alternative adsorption sites: An experimental and theoretical study

    International Nuclear Information System (INIS)

    Jia, Juanjuan; Kara, Abdelkader; Pasquali, Luca; Bendounan, Azzedine; Sirotti, Fausto; Esaulov, Vladimir A.

    2015-01-01

    Characteristic core level binding energies (CLBEs) are regularly used to infer the modes of molecular adsorption: orientation, organization, and dissociation processes. Here, we focus on a largely debated situation regarding CLBEs in the case of chalcogen atom bearing molecules. For a thiol, this concerns the case when the CLBE of a thiolate sulfur at an adsorption site can be interpreted alternatively as due to atomic adsorption of a S atom, resulting from dissociation. Results of an investigation of the characteristics of thiol self-assembled monolayers (SAMs) obtained by vacuum evaporative adsorption are presented along with core level binding energy calculations. Thiol ended SAMs of 1,4-benzenedimethanethiol (BDMT) obtained by evaporation on Au display an unconventional CLBE structure at about 161.25 eV, which is close to a known CLBE of a S atom on Au. Adsorption and CLBE calculations for sulfur atoms and BDMT molecules are reported and allow delineating trends as a function of chemisorption on hollow, bridge, and atop sites and including the presence of adatoms. These calculations suggest that the 161.25 eV peak is due to an alternative adsorption site, which could be associated to an atop configuration. Therefore, this may be an alternative interpretation, different from the one involving the adsorption of atomic sulfur resulting from the dissociation process of the S–C bond. Calculated differences in S(2p) CLBEs for free BDMT molecules, SH group sulfur on top of the SAM, and disulfide are also reported to clarify possible errors in assignments

  15. On sulfur core level binding energies in thiol self-assembly and alternative adsorption sites: An experimental and theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Juanjuan [Institut des Sciences Moléculaires d’Orsay, Université-Paris Sud, 91405 Orsay (France); CNRS, UMR 8214, Institut des Sciences Moléculaires d’Orsay, Orsay ISMO, Bâtiment 351, Université Paris Sud, 91405 Orsay (France); Kara, Abdelkader, E-mail: abdelkader.kara@ucf.edu, E-mail: vladimir.esaulov@u-psud.fr [Department of Physics, University of Central Florida, Orlando, Florida 32816 (United States); Pasquali, Luca [Dipartimento di Ingegneria “E. Ferrari,” Università di Modena e Reggio Emilia, Via Vignolese 905, 41125 Modena (Italy); IOM-CNR, s.s. 14, Km. 163.5 in AREA Science Park, 34149 Basovizza, Trieste (Italy); Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park 2006 (South Africa); Bendounan, Azzedine; Sirotti, Fausto [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex (France); Esaulov, Vladimir A., E-mail: abdelkader.kara@ucf.edu, E-mail: vladimir.esaulov@u-psud.fr [Institut des Sciences Moléculaires d’Orsay, Université-Paris Sud, 91405 Orsay (France); CNRS, UMR 8214, Institut des Sciences Moléculaires d’Orsay, Orsay ISMO, Bâtiment 351, Université Paris Sud, 91405 Orsay (France); IOM-CNR, s.s. 14, Km. 163.5 in AREA Science Park, 34149 Basovizza, Trieste (Italy)

    2015-09-14

    Characteristic core level binding energies (CLBEs) are regularly used to infer the modes of molecular adsorption: orientation, organization, and dissociation processes. Here, we focus on a largely debated situation regarding CLBEs in the case of chalcogen atom bearing molecules. For a thiol, this concerns the case when the CLBE of a thiolate sulfur at an adsorption site can be interpreted alternatively as due to atomic adsorption of a S atom, resulting from dissociation. Results of an investigation of the characteristics of thiol self-assembled monolayers (SAMs) obtained by vacuum evaporative adsorption are presented along with core level binding energy calculations. Thiol ended SAMs of 1,4-benzenedimethanethiol (BDMT) obtained by evaporation on Au display an unconventional CLBE structure at about 161.25 eV, which is close to a known CLBE of a S atom on Au. Adsorption and CLBE calculations for sulfur atoms and BDMT molecules are reported and allow delineating trends as a function of chemisorption on hollow, bridge, and atop sites and including the presence of adatoms. These calculations suggest that the 161.25 eV peak is due to an alternative adsorption site, which could be associated to an atop configuration. Therefore, this may be an alternative interpretation, different from the one involving the adsorption of atomic sulfur resulting from the dissociation process of the S–C bond. Calculated differences in S(2p) CLBEs for free BDMT molecules, SH group sulfur on top of the SAM, and disulfide are also reported to clarify possible errors in assignments.

  16. Kinetics of Cation and Oxyanion Adsorption and Desorption on Ferrihydrite: Roles of Ferrihydrite Binding Sites and a Unified Model

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Lei [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry; Shi, Zhenqing [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry; Lu, Yang [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry; Dohnalkova, Alice C. [Environmental; Lin, Zhang [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry; Dang, Zhi [School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People’s Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry

    2017-08-29

    Understanding the kinetics of toxic ion reactions with ferrihydrite is crucial for predicting the dynamic behavior of contaminants in soil environments. In this study, the kinetics of As(V), Cr(VI), Cu, and Pb adsorption and desorption on ferrihydrite were investigated with a combination of laboratory macroscopic experiments, microscopic investigation and mechanistic modeling. The rates of As(V), Cr(VI), Cu, and Pb adsorption and desorption on ferrihydrite, as systematically studied using a stirred-flow method, was highly dependent on the reaction pH and metal concentrations and varied significantly among four metals. Spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) showed, at sub-nano scales, all four metals were distributed within the ferrihydrite particle aggregates homogeneously after adsorption reactions, with no evidence of surface diffusion-controlled processes. Based on experimental results, we developed a unifying kinetics model for both cation and oxyanion adsorption/desorption on ferrihydrite based on the mechanistic-based equilibrium model CD-MUSIC. Overall, the model described the kinetic results well, and we quantitatively demonstrated how the equilibrium properties of the cation and oxyanion binding to various ferrihydrite sites affected the adsorption and desorption rates. Our results provided a unifying quantitative modeling method for the kinetics of both cation and oxyanion adsorption/desorption on iron minerals.

  17. Studies on entrained DNPPA separation by charcoal adsorption from aqueous solutions generated during uranium recovery from strong phosphoric acid

    International Nuclear Information System (INIS)

    Singh, D.K.; Vijayalakshmi, R.; Singh, H.

    2010-01-01

    During the separation of metal ions by solvent extraction technique in hydrometallurgical operations, organic solvents either get entrained or dissolved in various types of aqueous streams, which need to be separated out to prevent environmental pollution and solvent loss. Generally entrained solvents are separated on plant scale by parallel plate separators or by froth floatation cells, while the dissolved solvents are recovered either by organic diluent wash or by charcoal adsorption. A novel process has been developed to recover uranium from merchant grade phosphoric acid (MGA) employing synergistic mixture of DNPPA (di-nonyl phenyl phosphoric acid ) and TOPO (tri-n-octyl phosphine oxide) dissolved in petrofin. After recovery of uranium, MGA has to be returned to the host company for the production of fertilizer. This MGA has to be free from any contamination due to DNPPA and TOPO. Separation of DNPPA and TOPO from MGA by diluent wash method has been reported. There is no information available in literature for the separation of DNPPA and TOPO from such aqueous streams by carbon adsorption. The present investigation describes the methodology based on charcoal adsorption study (batch and continuous column operation) to separate DNPPA from MGA. Three different types of charcoal namely coconut shell based, coal based and pelletized charcoal were evaluated for DNPPA separation from MGA containing 100 mg/L DNPPA. It was found that the % DNPPA adsorptions in single contact (0.5g C/50 ml) were 57, 34 and 10 in coconut shell, coal based and pelletised charcoal respectively. Based on the results, the coconut shell based charcoal was selected for further study. Adsorption of DNPPA by coconut shell based charcoal was investigated by carrying out the experiments with 50 ml MGA containing 770 mg/L DNPPA by adding 1 to 7 g charcoal respectively in separate beakers

  18. The Correlation of Adsorption Behavior between Ciprofloxacin Hydrochloride and the Active Sites of Fe-doped MCM-41

    Directory of Open Access Journals (Sweden)

    Ying Wu

    2018-02-01

    Full Text Available HIGHLIGHTSFe incorporation significantly accelerated the adsorption of CPX on MCM-41.Fe leaching can be ignored when pH was higher than 4.0.pH played an important role in CPX adsorption on Fe-MCM-41.Co-effect of CPX and metal cations on Fe-MCM-41 was investigated.Fe-MCM-41s with various molar ratios of silicon to iron (20, 40, 80, and 160 were prepared to investigate adsorption properties of ciprofloxacin hydrochloride (CPX in aqueous solutions. Fe-MCM-41s were characterized by transmission electron microscope (TEM, X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, nitrogen adsorption/desorption isotherms, and infrared spectroscopy (FT-IR. Effects of silicon-iron ratio, adsorbent dosage, pH, and temperature were conducted to explore the adsorption mechanism of CPX on Fe-MCM-41. The results showed that the introduction of iron facilitated the absorption quantity for CPX from 20.04 to 83.33 mg g−1 at 120 min of reaction time, which was mainly attributed to surface complexation. The promotion of hydrophobic effect, electrostatic interactions, and π-π electron donor-acceptor interaction also played coordinate roles in the adsorption process. The experimental kinetic data followed both the pseudo-second-order and intra-particle diffusion models, while the adsorption isotherm data fit well to Freundlich model at high temperature. Thermodynamic study showed that the adsorption was spontaneous. Under the effect of electrostatic interaction, pH of the solution strongly affected CPX adsorption. Five representative metal cations (Ca, Cu, Ni, Pb, and Cd were chosen to study the effects on CPX adsorption and their complexation. The inhibiting effect of metal cations on CPX adsorption was sequenced in the order of Cu > Ni > Pb > Cd > Ca, which followed the same order as the complexation stability constants between CPX and cations. The Fe-MCM-41 adsorbent possessed excellent reusability for 4 cycles use, suggesting a potential applicability of

  19. A three-site Langmuir adsorption model to elucidate the temperature, pressure, and support dependence of the hydrogen coverage on supported Pt particles

    NARCIS (Netherlands)

    Ji, Y.; Koot, V.; van der Eerden, A.M.J.; Weckhuysen, B.M.; Koningsberger, D.C.; Ramaker, D.E.

    2007-01-01

    The three-site adsorption model, previously developed to describe H adsorption on small Pt particles, was used to gain insight into dependence of hydrogen coverage on temperature, pressure, and support ionicity. The three sites, in order of decreasing PtH bond strength, involve H in an atop, a

  20. Strong Earthquake Motion Estimates for Three Sites on the U.C. Riverside Campus; TOPICAL

    International Nuclear Information System (INIS)

    Archuleta, R.; Elgamal, A.; Heuze, F.; Lai, T.; Lavalle, D.; Lawrence, B.; Liu, P.C.; Matesic, L.; Park, S.; Riemar, M.; Steidl, J.; Vucetic, M.; Wagoner, J.; Yang, Z.

    2000-01-01

    The approach of the Campus Earthquake Program (CEP) is to combine the substantial expertise that exists within the UC system in geology, seismology, and geotechnical engineering, to estimate the earthquake strong motion exposure of UC facilities. These estimates draw upon recent advances in hazard assessment, seismic wave propagation modeling in rocks and soils, and dynamic soil testing. The UC campuses currently chosen for application of our integrated methodology are Riverside, San Diego, and Santa Barbara. The procedure starts with the identification of possible earthquake sources in the region and the determination of the most critical fault(s) related to earthquake exposure of the campus. Combined geological, geophysical, and geotechnical studies are then conducted to characterize each campus with specific focus on the location of particular target buildings of special interest to the campus administrators. We drill and geophysically log deep boreholes next to the target structure, to provide direct in-situ measurements of subsurface material properties, and to install uphole and downhole 3-component seismic sensors capable of recording both weak and strong motions. The boreholes provide access below the soil layers, to deeper materials that have relatively high seismic shear-wave velocities. Analyses of conjugate downhole and uphole records provide a basis for optimizing the representation of the low-strain response of the sites. Earthquake rupture scenarios of identified causative faults are combined with the earthquake records and with nonlinear soil models to provide site-specific estimates of strong motions at the selected target locations. The predicted ground motions are shared with the UC consultants, so that they can be used as input to the dynamic analysis of the buildings. Thus, for each campus targeted by the CEP project, the strong motion studies consist of two phases, Phase 1-initial source and site characterization, drilling, geophysical logging

  1. Hydrogen adsorption strength and sites in the metal organic framework MOF5: Comparing experiment and model calculations

    Science.gov (United States)

    Mulder, F. M.; Dingemans, T. J.; Schimmel, H. G.; Ramirez-Cuesta, A. J.; Kearley, G. J.

    2008-07-01

    Hydrogen adsorption in porous, high surface area, and stable metal organic frameworks (MOF's) appears a novel route towards hydrogen storage materials [N.L. Rosi, J. Eckert, M. Eddaoudi, D.T. Vodak, J. Kim, M. O'Keeffe, O.M. Yaghi, Science 300 (2003) 1127; J.L.C. Rowsell, A.R. Millward, K. Sung Park, O.M. Yaghi, J. Am. Chem. Soc. 126 (2004) 5666; G. Ferey, M. Latroche, C. Serre, F. Millange, T. Loiseau, A. Percheron-Guegan, Chem. Commun. (2003) 2976; T. Loiseau, C. Serre, C. Huguenard, G. Fink, F. Taulelle, M. Henry, T. Bataille, G. Férey, Chem. Eur. J. 10 (2004) 1373]. A prerequisite for such materials is sufficient adsorption interaction strength for hydrogen adsorbed on the adsorption sites of the material because this facilitates successful operation under moderate temperature and pressure conditions. Here we report detailed information on the geometry of the hydrogen adsorption sites, based on the analysis of inelastic neutron spectroscopy (INS). The adsorption energies for the metal organic framework MOF5 equal about 800 K for part of the different sites, which is significantly higher than for nanoporous carbon materials (˜550 K) [H.G. Schimmel, G.J. Kearley, M.G. Nijkamp, C.T. Visser, K.P. de Jong, F.M. Mulder, Chem. Eur. J. 9 (2003) 4764], and is in agreement with what is found in first principles calculations [T. Sagara, J. Klassen, E. Ganz, J. Chem. Phys. 121 (2004) 12543; F.M. Mulder, T.J. Dingemans, M. Wagemaker, G.J. Kearley, Chem. Phys. 317 (2005) 113]. Assignments of the INS spectra is realized using comparison with independently published model calculations [F.M. Mulder, T.J. Dingemans, M. Wagemaker, G.J. Kearley, Chem. Phys. 317 (2005) 113] and structural data [T. Yildirim, M.R. Hartman, Phys. Rev. Lett. 95 (2005) 215504].

  2. Earthquake Strong Ground Motion Scenario at the 2008 Olympic Games Sites, Beijing, China

    Science.gov (United States)

    Liu, L.; Rohrbach, E. A.; Chen, Q.; Chen, Y.

    2006-12-01

    Historic earthquake record indicates mediate to strong earthquakes have been frequently hit greater Beijing metropolitan area where is going to host the 2008 summer Olympic Games. For the readiness preparation of emergency response to the earthquake shaking for a mega event in a mega city like Beijing in summer 2008, this paper tries to construct the strong ground motion scenario at a number of gymnasium sites for the 2008 Olympic Games. During the last 500 years (the Ming and Qing Dynasties) in which the historic earthquake record are thorough and complete, there are at least 12 earthquake events with the maximum intensity of VI or greater occurred within 100 km radius centered at the Tiananmen Square, the center of Beijing City. Numerical simulation of the seismic wave propagation and surface strong ground motion is carried out by the pseudospectral time domain methods with viscoelastic material properties. To improve the modeling efficiency and accuracy, a multi-scale approach is adapted: the seismic wave propagation originated from an earthquake rupture source is first simulated by a model with larger physical domain with coarser grids. Then the wavefield at a given plane is taken as the source input for the small-scale, fine grid model for the strong ground motion study at the sites. The earthquake source rupture scenario is based on two particular historic earthquake events: One is the Great 1679 Sanhe-Pinggu Earthquake (M~8, Maximum Intensity XI at the epicenter and Intensity VIII in city center)) whose epicenter is about 60 km ENE of the city center. The other one is the 1730 Haidian Earthquake (M~6, Maximum Intensity IX at the epicenter and Intensity VIII in city center) with the epicentral distance less than 20 km away from the city center in the NW Haidian District. The exist of the thick Tertiary-Quaternary sediments (maximum thickness ~ 2 km) in Beijing area plays a critical role on estimating the surface ground motion at the Olympic Games sites, which

  3. Influence of porous texture and surface chemistry on the CO₂ adsorption capacity of porous carbons: acidic and basic site interactions.

    Science.gov (United States)

    Sánchez-Sánchez, Angela; Suárez-García, Fabián; Martínez-Alonso, Amelia; Tascón, Juan M D

    2014-12-10

    Doped porous carbons exhibiting highly developed porosity and rich surface chemistry have been prepared and subsequently applied to clarify the influence of both factors on carbon dioxide capture. Nanocasting was selected as synthetic route, in which a polyaramide precursor (3-aminobenzoic acid) was thermally polymerized inside the porosity of an SBA-15 template in the presence of different H3PO4 concentrations. The surface chemistry and the porous texture of the carbons could be easily modulated by varying the H3PO4 concentration and carbonization temperature. Porous texture was found to be the determinant factor on carbon dioxide adsorption at 0 °C, while surface chemistry played an important role at higher adsorption temperatures. We proved that nitrogen functionalities acted as basic sites and oxygen and phosphorus groups as acidic ones toward adsorption of CO2 molecules. Among the nitrogen functional groups, pyrrolic groups exhibited the highest influence, while the positive effect of pyridinic and quaternary functionalities was smaller. Finally, some of these N-doped carbons exhibit CO2 heats of adsorption higher than 42 kJ/mol, which make them excellent candidates for CO2 capture.

  4. Carbon monoxide adsorption on low-silica zeolites: from single to dual and to multiple cation sites.

    Science.gov (United States)

    Otero Areán, C; Rodríguez Delgado, M; López Bauçà, C; Vrbka, L; Nachtigall, P

    2007-09-07

    Infrared spectra of CO adsorbed on the Al-rich Na-A zeolite were analysed by using a combined theoretical and experimental approach, showing that such spectra cannot be interpreted by assigning each IR band to CO interacting with a specific type of single cation site. This concept, which usually works well for high-silica zeolites, should not be uncritically extended to Al-rich zeolites that are crowded with cations in configurations which lead to preferential formation of CO adsorption complexes involving more than one cation site.

  5. Proceedings of the DOE/Yucca Mountain Site Characterization Project Radionuclde Adsorption Workshop at Los Alamos National Laboratory, September 11--12, 1990

    International Nuclear Information System (INIS)

    Canepa, J.A.

    1992-08-01

    Los Alamos National Laboratory hosted a workshop on radionuclide adsorption for the Department of Energy (DOE)/Yucca Mountain Site Characterization Project on September 11 and 12, 1990. The purpose of the workshop was to respond to a recommendation by the Nuclear Waste Technical Review Board that the DOE organize a radionuclide adsorption workshop to be attended by the DOE and its contractors involved in the measurement and modeling of such adsorption. The workshop would have two general purposes: (a) to determine the applicability of available radionuclide adsorption data on tuff and models for predicting such adsorption under existing and postclosure conditions at Yucca Mountain and (b) to establish what additional radionuclide adsorption research and model development are needed. Individual projects are processed separately for the databases

  6. Binding energy and preferred adsorption sites of CO on gold and silver-gold cluster cations: adsorption kinetics and quantum chemical calculations.

    Science.gov (United States)

    Neumaier, Marco; Weigend, Florian; Hampe, Oliver; Kappes, Manfred M

    2008-01-01

    We revisit the reactivity of trapped pure gold (Au(n)+, n cations (Ag(m)Au(n)+, m + n carbon monoxide as studied in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The experimental results are discussed in terms of ab initio computations which provide a comprehensive picture of the chemical binding behaviour (like binding energy, adsorption sites, associated vibrational frequencies) of CO to the noble metal as a function of cluster size and composition. Starting from results for pure gold cluster cations for which an overall decrease of CO binding energy with increasing cluster size was experimentally observed--from about 1.09 +/- 0.1 eV (for n = 6) to below 0.65 +/- 0.1 eV (for n > 26) we demonstrate that metal--CO bond energies correlate with the total electron density and with the energy of the lowest unoccupied molecular orbital (LUMO) on the bare metal cluster cation as obtained by density functional theory (DFT) computations. This is a consequence of the predominantly sigma-donating character of the CO-M bond. Further support for this concept is found by contrasting the predictions of binding energies to the experimental results for small alloy cluster cations (Ag(m)Au(n)+, 4 < m + n < 7) as a function of composition. Here, binding energy drops with increasing silver content, while CO still binds always in a head-on fashion to a gold atom. Finally we show how the CO stretch frequency of Ag(m)Au(n)CO+ may be used to identify possible adsorption sites and pre-screen favorable isomers.

  7. Nonlinear Site Response Validation Studies Using KIK-net Strong Motion Data

    Science.gov (United States)

    Asimaki, D.; Shi, J.

    2014-12-01

    Earthquake simulations are nowadays producing realistic ground motion time-series in the range of engineering design applications. Of particular significance to engineers are simulations of near-field motions and large magnitude events, for which observations are scarce. With the engineering community slowly adopting the use of simulated ground motions, site response models need to be re-evaluated in terms of their capabilities and limitations to 'translate' the simulated time-series from rock surface output to structural analyses input. In this talk, we evaluate three one-dimensional site response models: linear viscoelastic, equivalent linear and nonlinear. We evaluate the performance of the models by comparing predictions to observations at 30 downhole stations of the Japanese network KIK-Net that have recorded several strong events, including the 2011 Tohoku earthquake. Velocity profiles are used as the only input to all models, while additional parameters such as quality factor, density and nonlinear dynamic soil properties are estimated from empirical correlations. We quantify the differences of ground surface predictions and observations in terms of both seismological and engineering intensity measures, including bias ratios of peak ground response and visual comparisons of elastic spectra, and inelastic to elastic deformation ratio for multiple ductility ratios. We observe that PGV/Vs,30 — as measure of strain— is a better predictor of site nonlinearity than PGA, and that incremental nonlinear analyses are necessary to produce reliable estimates of high-frequency ground motion components at soft sites. We finally discuss the implications of our findings on the parameterization of nonlinear amplification factors in GMPEs, and on the extensive use of equivalent linear analyses in probabilistic seismic hazard procedures.

  8. Site-specific strong ground motion prediction using 2.5-D modelling

    Science.gov (United States)

    Narayan, J. P.

    2001-08-01

    An algorithm was developed using the 2.5-D elastodynamic wave equation, based on the displacement-stress relation. One of the most significant advantages of the 2.5-D simulation is that the 3-D radiation pattern can be generated using double-couple point shear-dislocation sources in the 2-D numerical grid. A parsimonious staggered grid scheme was adopted instead of the standard staggered grid scheme, since this is the only scheme suitable for computing the dislocation. This new 2.5-D numerical modelling avoids the extensive computational cost of 3-D modelling. The significance of this exercise is that it makes it possible to simulate the strong ground motion (SGM), taking into account the energy released, 3-D radiation pattern, path effects and local site conditions at any location around the epicentre. The slowness vector (py) was used in the supersonic region for each layer, so that all the components of the inertia coefficient are positive. The double-couple point shear-dislocation source was implemented in the numerical grid using the moment tensor components as the body-force couples. The moment per unit volume was used in both the 3-D and 2.5-D modelling. A good agreement in the 3-D and 2.5-D responses for different grid sizes was obtained when the moment per unit volume was further reduced by a factor equal to the finite-difference grid size in the case of the 2.5-D modelling. The components of the radiation pattern were computed in the xz-plane using 3-D and 2.5-D algorithms for various focal mechanisms, and the results were in good agreement. A comparative study of the amplitude behaviour of the 3-D and 2.5-D wavefronts in a layered medium reveals the spatial and temporal damped nature of the 2.5-D elastodynamic wave equation. 3-D and 2.5-D simulated responses at a site using a different strike direction reveal that strong ground motion (SGM) can be predicted just by rotating the strike of the fault counter-clockwise by the same amount as the azimuth of

  9. Source, propagation and site effects: impact on mapping strong ground motion in Bucharest area

    International Nuclear Information System (INIS)

    Radulian, R.; Kuznetsov, I.; Panza, G.F.

    2004-01-01

    Achievements in the framework of the NATO SfP project 972266 focused on the impact of Vrancea earthquakes on the security of Bucharest urban area are presented. The problem of Bucharest city security to Vrancea earthquakes is discussed in terms of numerical modelling of seismic motion and intermediate term earthquake prediction. A hybrid numerical scheme developed by Faeh et al. (1990; 1993) for frequencies up to 1 Hz is applied for the realistic modelling of the seismic ground motion in Bucharest. The method combines the modal summation for the 1D bedrock model and the finite differences for the 2D local structure model. All the factors controlling the ground motion at the site are considered: source, propagation and site effects, respectively. The input data includes the recent records provided by the digital accelerometer network developed within the Romanian-German CRC461 cooperation programme and CALIXTO'99, VRANCEA'99, VRANCEA2001 experiments. The numerical simulation proves to be a powerful tool in mapping the strong ground motion for realistic structures, reproducing acceptably from engineering point of view the observations. A new model of the Vrancea earthquake scaling is obtained and implications for the determination of the seismic motion parameters are analyzed. The role of the focal mechanism and attenuation properties upon the amplitude and spectral content of the ground motion are outlined. CN algorithm is applied for predicting Vrancea earthquakes. Finally, implications for the disaster management strategy are discussed. (authors)

  10. Conductance of Sidewall-Functionalized Carbon Nanotubes: Universal Dependence on Adsorption Sites

    DEFF Research Database (Denmark)

    García-Lastra, J.M.; Thygesen, Kristian Sommer; Strange, Mikkel

    2008-01-01

    We use density functional theory to study the effect of molecular adsorbates on the conductance of metallic carbon nanotubes (CNT). The five molecules considered (NO2, NH2, H, COOH, OH) lead to very similar scattering of the electrons. The adsorption of a single molecule suppresses one of the two...

  11. Soot particles at an elevated site in eastern China during the passage of a strong cyclone

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Hongya [State Key Laboratory of Coal Resources and Safe Mining, School of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083 (China); Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502 (Japan); Shao, Longyi [State Key Laboratory of Coal Resources and Safe Mining, School of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083 (China); Zhang, Daizhou, E-mail: dzzhang@pu-kumamoto.ac.jp [Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502 (Japan)

    2012-07-15

    Atmospheric particles larger than 0.2 {mu}m were collected at the top of Mt. Tai (36.25 Degree-Sign N, 117.10 Degree-Sign E, 1534 m a.s.l.) in eastern China in May 2008 during the passage of a strong cyclone. The particles were analyzed with electron microscopes and characterized by morphology, equivalent diameter and elemental composition. Soot particles with coating (coated soot particles) and those without apparent coating (naked soot particles) were predominant in the diameter range smaller than 0.6 {mu}m in all samples. The number-size distribution of the relative abundance of naked soot particles in the prefrontal air was similar to that in the postfrontal air and their size modes were around 0.2-0.3 {mu}m. However, the distribution of inclusions of coated soot particles showed a mode in the range of 0.1-0.3 {mu}m. The coating degree of coated soot particles, which was defined by the ratio of the diameter of inclusion to the diameter of particle body, showed a mode around 0.5 with the range of 0.3-0.6. These results indicate that the status of soot particles in the prefrontal and postfrontal air was similar although air pollution levels were dramatically different. In addition, the relative abundance of accumulation mode particles increased with the decrease of soot particles after the front passage. - Highlights: Black-Right-Pointing-Pointer Particles at an elevated site in eastern China in a strong cyclone were studied. Black-Right-Pointing-Pointer Aged status of soot particles in the prefrontal and postfrontal air was similar. Black-Right-Pointing-Pointer Soot particles in elevated layers could be considered as aged ones.

  12. A comparative study of surface waves inversion techniques at strong motion recording sites in Greece

    Science.gov (United States)

    Panagiotis C. Pelekis,; Savvaidis, Alexandros; Kayen, Robert E.; Vlachakis, Vasileios S.; Athanasopoulos, George A.

    2015-01-01

    Surface wave method was used for the estimation of Vs vs depth profile at 10 strong motion stations in Greece. The dispersion data were obtained by SASW method, utilizing a pair of electromechanical harmonic-wave source (shakers) or a random source (drop weight). In this study, three inversion techniques were used a) a recently proposed Simplified Inversion Method (SIM), b) an inversion technique based on a neighborhood algorithm (NA) which allows the incorporation of a priori information regarding the subsurface structure parameters, and c) Occam's inversion algorithm. For each site constant value of Poisson's ratio was assumed (ν=0.4) since the objective of the current study is the comparison of the three inversion schemes regardless the uncertainties resulting due to the lack of geotechnical data. A penalty function was introduced to quantify the deviations of the derived Vs profiles. The Vs models are compared as of Vs(z), Vs30 and EC8 soil category, in order to show the insignificance of the existing variations. The comparison results showed that the average variation of SIM profiles is 9% and 4.9% comparing with NA and Occam's profiles respectively whilst the average difference of Vs30 values obtained from SIM is 7.4% and 5.0% compared with NA and Occam's.

  13. Surface wave site characterization at 27 locations near Boston, Massachusetts, including 2 strong-motion stations

    Science.gov (United States)

    Thompson, Eric M.; Carkin, Bradley A.; Baise, Laurie G.; Kayen, Robert E.

    2014-01-01

    The geotechnical properties of the soils in and around Boston, Massachusetts, have been extensively studied. This is partly due to the importance of the Boston Blue Clay and the extent of landfill in the Boston area. Although New England is not a region that is typically associated with seismic hazards, there have been several historical earthquakes that have caused significant ground shaking (for example, see Street and Lacroix, 1979; Ebel, 1996; Ebel, 2006). The possibility of strong ground shaking, along with heightened vulnerability from unreinforced masonry buildings, motivates further investigation of seismic hazards throughout New England. Important studies that are pertinent to seismic hazards in New England include source-parameter studies (Somerville and others, 1987; Boore and others, 2010), wave-propagation studies (Frankel, 1991; Viegas and others, 2010), empirical ground-motion prediction equations (GMPE) for computing ground-motion intensity (Tavakoli and Pezeshk, 2005; Atkinson and Boore, 2006), site-response studies (Hayles and others, 2001; Ebel and Kim, 2006), and liquefaction studies (Brankman and Baise, 2008). The shear-wave velocity (VS) profiles collected for this report are pertinent to the GMPE, site response, and liquefaction aspects of seismic hazards in the greater Boston area. Besides the application of these data for the Boston region, the data may be applicable throughout New England, through correlations with geologic units (similar to Ebel and Kim, 2006) or correlations with topographic slope (Wald and Allen, 2007), because few VS measurements are available in stable tectonic regions.Ebel and Hart (2001) used felt earthquake reports to infer amplification patterns throughout the greater Boston region and noted spatial correspondence with the dominant period and amplification factors obtained from ambient noise (horizontal-to-vertical ratios) by Kummer (1998). Britton (2003) compiled geotechnical borings in the area and produced a

  14. Detailed site effect estimation in the presence of strong velocity reversals within a small-aperture strong-motion array in Iceland

    KAUST Repository

    Rahpeyma, Sahar

    2016-08-11

    The rock site characterization for earthquake engineering applications in Iceland is common due to the easily exposed older bedrock and more recent volcanic lava rock. The corresponding site amplification is generally assumed to be low but has not been comprehensively quantified, especially for volcanic rock. The earthquake strong-motion of the Mw6.3 Ölfus earthquake on 29 May 2008 and 1705 of its aftershocks recorded on the first small-aperture strong-motion array (ICEARRAY I) in Iceland showed consistent and significant variations in ground motion amplitudes over short distances (<2 km) in an urban area located mostly on lava rock. This study analyses the aftershock recordings to quantify the local site effects using the Horizontal to Vertical Spectral Ratio (HVSR) and Standard Spectral Ratio (SSR) methods. Additionally, microseismic data has been collected at array stations and analyzed using the HVSR method. The results between the methods are consistent and show that while the amplification levels remain relatively low, the predominant frequency varies systematically between stations and is found to correlate with the geological units. In particular, for stations on lava rock the underlying geologic structure is characterized by repeated lava-soil stratigraphy characterized by reversals in the shear wave velocity with depth. As a result, standard modeling of HVSR using vertically incident body waves does not apply. Instead, modeling the soil structure as a two-degree-of-freedom dynamic system is found to capture the observed predominant frequencies of site amplification. The results have important implications for earthquake resistant design of structures on rock sites characterized by velocity reversals. © 2016 Elsevier Ltd

  15. Surface sites on carbon-supported Ru, Co and Ni nanoparticles as determined by microcalorimetry of CO adsorption

    International Nuclear Information System (INIS)

    Cerro-Alarcon, M.; Maroto-Valiente, A.; Rodriguez-Ramos, I.; Guerrero-Ruiz, A.

    2005-01-01

    The adsorption of CO on carbon-supported metal (Ru, Co and Ni) catalysts was studied by microcalorimetry. A correlation of the results thus obtained with those reported for monocrystals or with other studies available in the scientific literature for supported metal catalysts, including infrared spectroscopy data, enables the determination of the type of exposed crystalline planes and/or of the different types of CO adsorbed species. The results obtained suggest that the energetic distribution of the surface sites depends on the carbon support material and on the applied reduction treatment. In this way, the use of a high surface area graphite (clean of surface oxygen groups) leads to an electron density enrichment on the small metal particles (Ru) and, in general, to a higher heterogeneity of the active surface sites. The elimination of surface oxygen functional groups (with the reduction treatment at the higher temperature) of the carbon molecular sieve support leads to changes in the surface structure of the metal particles and, consequently, to higher CO adsorption heats, particularly for Ru and Co

  16. Effects of NH4+, K+, Mg2+, and Ca2+ on the Cesium Adsorption/Desorption in Binding Sites of Vermiculitized Biotite.

    Science.gov (United States)

    Yin, Xiangbiao; Wang, Xinpeng; Wu, Hao; Takahashi, Hideharu; Inaba, Yusuke; Ohnuki, Toshihiko; Takeshita, Kenji

    2017-12-05

    The reversibility of cesium adsorption in contaminated soil is largely dependent on its interaction with micaceous minerals, which may be greatly influenced by various cations. Herein, we systematically investigated the effects of NH 4 + , K + , Mg 2+ , and Ca 2+ on the adsorption/desorption of Cs + into different binding sites of vermiculitized biotite (VB). Original VB was initially saturated by NH 4 + , K + , or Mg 2+ ; we then evaluated the adsorption of Cs + on three treated VBs, and the desorption by extraction with NH 4 + , K + , Mg 2+ , or Ca 2+ was further evaluated. Our structural analysis and Cs + extractability determinations showed that NH 4 + and K + both collapsed the interlayers of VB, resulting in the dominant adsorption of Cs + to external surface sites on which Cs + was readily extracted by NH 4 + , K + , Mg 2+ , or Ca 2+ irrespective of their species, whereas Mg 2+ maintained the VB with expanded interlayers, leading to the overwhelming adsorption of Cs + in collapsed interlayer sites on which the Cs + desorption was difficult and varied significantly by the cations used in extraction. The order of Cs + extraction ability from the collapsed interlayers was K + ≫ Mg 2+ ≈ Ca 2+ ≫ NH 4 + . These results could provide important insights into Cs migration in soil and its decontamination for soil remediation.

  17. ENHANCING EFFECTIVENESS OF EMSP PROJECTS THROUGH STRONG CONNECTIONS TO SITE PROBLEMS

    International Nuclear Information System (INIS)

    Josephson, Gary B.; Hale, Donna

    2003-01-01

    The Environmental Management Science Program (EMSP) funds basic science research that will lead to reduced remediation cost, schedule, technical uncertainties, and risk for DOE's environmental clean up. The Tanks Focus Area (TFA) has partnered with EMSP to accomplish those same objectives for DOE's largest and most expensive remediation effort - to retrieve and immobilize the highly radioactive wastes that are our nation's chief nuclear defense program legacy. TFA has been tasked to facilitate success of the EMSP investment. The key for EMSP projects to contribute to this remediation effort is communication. First, the scientist needs to understand much more about how his scientific results would be used than he could ever learn from the original EMSP solicitation or by reading the referenced DOE needs statements. Second, the scientist's results must be communicated to the site problem holders in a usable form and in a timely manner such that important information gaps can still be filled by the EMSP project. Research results can be used in a variety of ways besides deployment of new hardware or a new process. When results are USED the site problem holders become 'users'. The important aspect that research results are to be used is captured in the TFA lexicon for their clients, the DOE sites--'USERS'. The best method observed, so far, to accomplish the indispensable communication necessary for success is through direct contact between EMSP researchers and TFA/site problem holders, person to person. The observation that direct contact is the best medium for exchange of complex information may seem inanely obvious. However, it is not the normal procedure in the more academic world of the fundamental scientists, where publishing of results in a peer-reviewed journal completes the transmittal of scientific results. Direct communication between EMSP researchers and site users doesn't occur naturally. TFA actively bridges this gap between science and technology

  18. In vitro transcription in the presence of DNA oligonucleotides can generate strong anomalous initiation sites.

    Science.gov (United States)

    Chow, C W; Clark, M P; Rinaldo, J E; Chalkley, R

    1996-03-01

    In the present study, we have explored an unexpected observation in transcription initiation that is mediated by single-stranded oligonucleotides. Initially, our goal was to understand the function of different upstream regulatory elements/initiation sites in the rat xanthine dehydrogenase/oxidase (XDH/XO) promoter. We performed in vitro transcription with HeLa nuclear extracts in the presence of different double-stranded oligonucleotides against upstream elements as competitors. A new and unusual transcription initiation site was detected by primer extension. This new initiation site maps to the downstream region of the corresponding competitor. Subsequent analyses have indicated that the induction of a new transcription initiation site is anomalous which is due to the presence of a small amount of single-stranded oligonucleotide in the competitor. We found that this anomalous initiation site is insensitive to the orientation of the promoter and requires only a small amount of single-stranded oligonucleotide (< 2-fold molar excess relative to template). We surmise that a complementary interaction between the single-stranded oligonucleotide and transiently denatured promoter template may be responsible for this sequence-specific transcription initiation artifact. To study the regulation of transcription initiation by in vitro transcription approaches, we propose that one should probe the effect of removing transacting factors by adding an excess of a cognate oligonucleotide which does not bear exact sequence identity to the template.

  19. Mutations at the Qo-Site of the Cytochrome bc1 Complex Strongly Affect Oxygen Binding

    DEFF Research Database (Denmark)

    Husen, Peter; Solov'yov, Ilia A

    2017-01-01

    The homodimeric bc1 protein complex is embedded in membranes of mitochondria and photosynthetic bacteria, where it transports protons across the membrane to maintain an electrostatic potential used to drive ATP synthesis as part of the respiratory or photosynthetic pathways. The reaction cycle...... at the Qo-sites, and, moreover, different behavior of the two monomers of the bc1 complex is observed. The conformational differences at the Qo-sites of the two monomers are studied in detail and discussed. The anionic form of semiquinone was identified as leading to the greatest opportunity for side...

  20. Crystal Structures, Surface Stability, and Water Adsorption Energies of La-Bastnäsite via Density Functional Theory and Experimental Studies

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, Sriram Goverapet [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Shivaramaiah, Radha [Univ. of California, Davis, CA (United States); Kent, Paul R. C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Stack, Andrew G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Navrotsky, Alexandra [Univ. of California, Davis, CA (United States); Riman, Richard [State Univ. of New Jersey, Piscataway, NJ (United States); Anderko, Andre [OLI Systems, Inc., Cedar Knolls, NJ (United States); Bryantsev, Vyacheslav S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-07-11

    Bastnasite is a fluoro-carbonate mineral that is the largest source of rare earth elements such as Y, La and Ce. With increasing demand for REE in many emerging technologies, there is an urgent need for improving the efficiency of ore beneficiation by froth flotation. In order to design improved flotation agents that can selectively bind to the mineral surface, a fundamental understanding of the bulk and surface properties of bastnasite is essential. Density functional theory calculations using the PBEsol exchange correlation functional and the DFT-D3 dispersion correction reveal that the most stable form of La bastnsite is isomorphic to the structure of Ce bastnasite belonging to the P2c space group, while the Inorganic Crystal Structure Database structure in the P2m space group is ca. 11.3 kJ/mol higher in energy per LaFCO3 formula unit. We report powder X-ray diffraction measurements on synthetic of La bastnasite to support these theoretical findings. Six different surfaces are studied by DFT, namely [100], [0001], [101], [102], [104] and [112]. Among these, the [100] surface is the most stable with a surface energy of 0.73 J/m2 in vacuum and 0.45 J/m2 in aqueous solution. We predicted the shape of a La bastnasite nanoparticle via thermodynamic Wulff construction to be a hexagonal prism with [100] and [0001] facets, chiseled at its ends by the [101] and [102] facets. The average surface energy of the nanoparticle in the gas phase is estimated to be 0.86 J/m2, in good agreement with a value of 1.11 J/m2 measured by calorimetry. The calculated adsorption energy of a water molecule varies widely with the surface plane and specific adsorption sites on a given surface. Moreover, the first layer of water molecules is predicted to adsorb strongly on the La-bastnasite surface, in agreement with water adsorption calorimetry experiments. Our work provides an important step towards a detailed atomistic understanding of

  1. Enhancing Effectiveness of EMSP Projects Through Strong Connections to Site Problems

    International Nuclear Information System (INIS)

    Guillen, D. P.; Josephson, G. B.

    2002-01-01

    The Environmental Management Science Program (EMSP) funds basic science research that will lead to reduced remediation cost, schedule, technical uncertainties, and risk for DOE's environmental clean up. The Tanks Focus Area (TFA) has partnered with EMSP to accomplish those same objectives for DOE's largest and most expensive remediation effort--to retrieve and immobilize the highly radioactive wastes that are our nation's chief nuclear defense program legacy. TFA has been tasked to facilitate success of the EMSP investment. The key for EMSP projects to contribute to this remediation effort is communication. First, scientists need to understand much more about how their scientific results would be used than they could ever learn from the original EMSP solicitation or by reading the referenced DOE needs statements. Second, the scientists' results must be communicated to the site problem holders in a usable form and in a timely manner such that important information gaps can still be filled by the EMSP project. Research results can be used in a variety of ways besides deployment of new hardware or a new process. When results are USED the site problem holders become ''users''. The important aspect that research results are to be used is captured in the TFA lexicon for their clients, the DOE sites--''users''. This paper will show, through several examples, significant contributions EMSP scientists have made to solving DOE's high-level waste challenges through direct and enhanced communication with TFA and site users

  2. Strong Ligand-Protein Interactions Derived from Diffuse Ligand Interactions with Loose Binding Sites.

    Science.gov (United States)

    Marsh, Lorraine

    2015-01-01

    Many systems in biology rely on binding of ligands to target proteins in a single high-affinity conformation with a favorable ΔG. Alternatively, interactions of ligands with protein regions that allow diffuse binding, distributed over multiple sites and conformations, can exhibit favorable ΔG because of their higher entropy. Diffuse binding may be biologically important for multidrug transporters and carrier proteins. A fine-grained computational method for numerical integration of total binding ΔG arising from diffuse regional interaction of a ligand in multiple conformations using a Markov Chain Monte Carlo (MCMC) approach is presented. This method yields a metric that quantifies the influence on overall ligand affinity of ligand binding to multiple, distinct sites within a protein binding region. This metric is essentially a measure of dispersion in equilibrium ligand binding and depends on both the number of potential sites of interaction and the distribution of their individual predicted affinities. Analysis of test cases indicates that, for some ligand/protein pairs involving transporters and carrier proteins, diffuse binding contributes greatly to total affinity, whereas in other cases the influence is modest. This approach may be useful for studying situations where "nonspecific" interactions contribute to biological function.

  3. Estimation of 1-D velocity models beneath strong-motion observation sites in the Kathmandu Valley using strong-motion records from moderate-sized earthquakes

    Science.gov (United States)

    Bijukchhen, Subeg M.; Takai, Nobuo; Shigefuji, Michiko; Ichiyanagi, Masayoshi; Sasatani, Tsutomu; Sugimura, Yokito

    2017-07-01

    The Himalayan collision zone experiences many seismic activities with large earthquakes occurring at certain time intervals. The damming of the proto-Bagmati River as a result of rapid mountain-building processes created a lake in the Kathmandu Valley that eventually dried out, leaving thick unconsolidated lacustrine deposits. Previous studies have shown that the sediments are 600 m thick in the center. A location in a seismically active region, and the possible amplification of seismic waves due to thick sediments, have made Kathmandu Valley seismically vulnerable. It has suffered devastation due to earthquakes several times in the past. The development of the Kathmandu Valley into the largest urban agglomerate in Nepal has exposed a large population to seismic hazards. This vulnerability was apparent during the Gorkha Earthquake (Mw7.8) on April 25, 2015, when the main shock and ensuing aftershocks claimed more than 1700 lives and nearly 13% of buildings inside the valley were completely damaged. Preparing safe and up-to-date building codes to reduce seismic risk requires a thorough study of ground motion amplification. Characterizing subsurface velocity structure is a step toward achieving that goal. We used the records from an array of strong-motion accelerometers installed by Hokkaido University and Tribhuvan University to construct 1-D velocity models of station sites by forward modeling of low-frequency S-waves. Filtered records (0.1-0.5 Hz) from one of the accelerometers installed at a rock site during a moderate-sized (mb4.9) earthquake on August 30, 2013, and three moderate-sized (Mw5.1, Mw5.1, and Mw5.5) aftershocks of the 2015 Gorkha Earthquake were used as input motion for modeling of low-frequency S-waves. We consulted available geological maps, cross-sections, and borehole data as the basis for initial models for the sediment sites. This study shows that the basin has an undulating topography and sediment sites have deposits of varying thicknesses

  4. Seismic velocity site characterization of 10 Arizona strong-motion recording stations by spectral analysis of surface wave dispersion

    Science.gov (United States)

    Kayen, Robert E.; Carkin, Brad A.; Corbett, Skye C.

    2017-10-19

    Vertical one-dimensional shear wave velocity (VS) profiles are presented for strong-motion sites in Arizona for a suite of stations surrounding the Palo Verde Nuclear Generating Station. The purpose of the study is to determine the detailed site velocity profile, the average velocity in the upper 30 meters of the profile (VS30), the average velocity for the entire profile (VSZ), and the National Earthquake Hazards Reduction Program (NEHRP) site classification. The VS profiles are estimated using a non-invasive continuous-sine-wave method for gathering the dispersion characteristics of surface waves. Shear wave velocity profiles were inverted from the averaged dispersion curves using three independent methods for comparison, and the root-mean-square combined coefficient of variation (COV) of the dispersion and inversion calculations are estimated for each site.

  5. Strong lithium polysulfide chemisorption on electroactive sites of nitrogen-doped carbon composites for high-performance lithium-sulfur battery cathodes.

    Science.gov (United States)

    Song, Jiangxuan; Gordin, Mikhail L; Xu, Terrence; Chen, Shuru; Yu, Zhaoxin; Sohn, Hiesang; Lu, Jun; Ren, Yang; Duan, Yuhua; Wang, Donghai

    2015-03-27

    Despite the high theoretical capacity of lithium-sulfur batteries, their practical applications are severely hindered by a fast capacity decay, stemming from the dissolution and diffusion of lithium polysulfides in the electrolyte. A novel functional carbon composite (carbon-nanotube-interpenetrated mesoporous nitrogen-doped carbon spheres, MNCS/CNT), which can strongly adsorb lithium polysulfides, is now reported to act as a sulfur host. The nitrogen functional groups of this composite enable the effective trapping of lithium polysulfides on electroactive sites within the cathode, leading to a much improved electrochemical performance (1200 mAh g(-1) after 200 cycles). The enhancement in adsorption can be attributed to the chemical bonding of lithium ions by nitrogen functional groups in the MNCS/CNT framework. Furthermore, the micrometer-sized spherical structure of the material yields a high areal capacity (ca. 6 mAh cm(-2)) with a high sulfur loading of approximately 5 mg cm(-2), which is ideal for practical applications of the lithium-sulfur batteries. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Comparison of reactivity on step and terrace sites of Pd (3 3 2) surface for the dissociative adsorption of hydrogen: A quantum chemical molecular dynamics study

    International Nuclear Information System (INIS)

    Ahmed, Farouq; Nagumo, Ryo; Miura, Ryuji; Ai, Suzuki; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Miyamoto, Akira

    2011-01-01

    The notion of 'active sites' is fundamental to heterogeneous catalysis. However, the exact nature of the active sites, and hence the mechanism by which they act, are still largely a matter of speculation. In this study, we have presented a systematic quantum chemical molecular dynamics (QCMD) calculations for the interaction of hydrogen on different step and terrace sites of the Pd (3 3 2) surface. Finally the dissociative adsorption of hydrogen on step and terrace as well as the influence of surface hydrogen vacancy for the dissociative adsorption of hydrogen has been investigated through QCMD. This is a state-of-the-art method for calculating the interaction of atoms and molecules with metal surfaces. It is found that fully hydrogen covered (saturated) step sites can dissociate hydrogen moderately and that a monovacancy surface is suitable for significant dissociative adsorption of hydrogen. However in terrace site of the surface we have found that dissociation of hydrogen takes place only on Pd sites where the metal atom is not bound to any pre-adsorbed hydrogen atoms. Furthermore, from the molecular dynamics and electronic structure calculations, we identify a number of consequences for the interpretation and modeling of diffusion experiments demonstrating the coverage and directional dependence of atomic hydrogen diffusion on stepped palladium surface.

  7. Let the Weakest Link Go! Empirical Explorations on the Relative Importance of Weak and Strong Ties on Social Networking Sites

    OpenAIRE

    Nicole C. Krämer; Leonie Rösner; Sabrina C. Eimler; Stephan Winter; German Neubaum

    2014-01-01

    Theoretical approaches as well as empirical results in the area of social capital accumulation on social networking sites suggest that weak ties/bridging versus strong ties/bonding social capital should be distinguished and that while bonding social capital is connected to emotional support, bridging social capital entails the provision of information. Additionally, recent studies imply the notion that weak ties/bridging social capital are gaining increasing importance in today’s social media...

  8. Metabolic and Target-Site Mechanisms Combine to Confer Strong DDT Resistance in Anopheles gambiae

    Science.gov (United States)

    Mitchell, Sara N.; Rigden, Daniel J.; Dowd, Andrew J.; Lu, Fang; Wilding, Craig S.; Weetman, David; Dadzie, Samuel; Jenkins, Adam M.; Regna, Kimberly; Boko, Pelagie; Djogbenou, Luc; Muskavitch, Marc A. T.; Ranson, Hilary; Paine, Mark J. I.; Mayans, Olga; Donnelly, Martin J.

    2014-01-01

    The development of resistance to insecticides has become a classic exemplar of evolution occurring within human time scales. In this study we demonstrate how resistance to DDT in the major African malaria vector Anopheles gambiae is a result of both target-site resistance mechanisms that have introgressed between incipient species (the M- and S-molecular forms) and allelic variants in a DDT-detoxifying enzyme. Sequencing of the detoxification enzyme, Gste2, from DDT resistant and susceptible strains of An. gambiae, revealed a non-synonymous polymorphism (I114T), proximal to the DDT binding domain, which segregated with strain phenotype. Recombinant protein expression and DDT metabolism analysis revealed that the proteins from the susceptible strain lost activity at higher DDT concentrations, characteristic of substrate inhibition. The effect of I114T on GSTE2 protein structure was explored through X-ray crystallography. The amino acid exchange in the DDT-resistant strain introduced a hydroxyl group nearby the hydrophobic DDT-binding region. The exchange does not result in structural alterations but is predicted to facilitate local dynamics and enzyme activity. Expression of both wild-type and 114T alleles the allele in Drosophila conferred an increase in DDT tolerance. The 114T mutation was significantly associated with DDT resistance in wild caught M-form populations and acts in concert with target-site mutations in the voltage gated sodium channel (Vgsc-1575Y and Vgsc-1014F) to confer extreme levels of DDT resistance in wild caught An. gambiae. PMID:24675797

  9. Periodic DFT study of acidic trace atmospheric gas molecule adsorption on Ca- and Fe-doped MgO(001) surface basic sites.

    Science.gov (United States)

    Baltrusaitis, Jonas; Hatch, Courtney; Orlando, Roberto

    2012-08-02

    The electronic properties of undoped and Ca- or Fe-doped MgO(001) surfaces, as well as their propensity toward atmospheric acidic gas (CO2, SO2, and NO2) uptake was investigated with an emphasis on gas adsorption on the basic MgO oxygen surface sites, O(surf), using periodic density functional theory (DFT) calculations. Adsorption energy calculations show that MgO doping will provide stronger interactions of the adsorbate with the O(surf) sites than the undoped MgO for a given adsorbate molecule. Charge transfer from the iron atom in Fe-doped MgO(001) to NO2 was shown to increase the binding interaction between adsorbate by an order of magnitude, when compared to that of undoped and Ca-doped MgO(001) surfaces. Secondary binding interactions of adsorbate oxygen atoms were observed with surface magnesium sites at distances close to those of the Mg-O bond within the crystal. These interactions may serve as a preliminary step for adsorption and facilitate further adsorbate transformations into other binding configurations. Impacts on global atmospheric chemistry are discussed as these adsorption phenomena can affect atmospheric gas budgets via altered partitioning and retention on mineral aerosol surfaces.

  10. Let the Weakest Link Go! Empirical Explorations on the Relative Importance of Weak and Strong Ties on Social Networking Sites

    Directory of Open Access Journals (Sweden)

    Nicole C. Krämer

    2014-12-01

    Full Text Available Theoretical approaches as well as empirical results in the area of social capital accumulation on social networking sites suggest that weak ties/bridging versus strong ties/bonding social capital should be distinguished and that while bonding social capital is connected to emotional support, bridging social capital entails the provision of information. Additionally, recent studies imply the notion that weak ties/bridging social capital are gaining increasing importance in today’s social media environments. By means of a survey (N = 317 we challenged these presuppositions by assessing the social support functions that are ascribed to three different types of contacts from participants’ network (weak, medium, or strong tie. In contrast to theoretical assumptions, we do not find that weak ties are experienced to supply informational support whereas strong ties first and foremost provide emotional support. Instead we find that within social networking sites, strong ties are perceived to provide both emotional and informational support and weak ties are perceived as less important than recent literature assumes.

  11. Monovalent Strep-Tactin for strong and site-specific tethering in nanospectroscopy.

    Science.gov (United States)

    Baumann, Fabian; Bauer, Magnus S; Milles, Lukas F; Alexandrovich, Alexander; Gaub, Hermann E; Pippig, Diana A

    2016-01-01

    Strep-Tactin, an engineered form of streptavidin, binds avidly to the genetically encoded peptide Strep-tag II in a manner comparable to streptavidin binding to biotin. These interactions have been used in protein purification and detection applications. However, in single-molecule studies, for example using atomic force microscopy-based single-molecule force spectroscopy (AFM-SMFS), the tetravalency of these systems impedes the measurement of monodispersed data. Here, we introduce a monovalent form of Strep-Tactin that harbours a unique binding site for Strep-tag II and a single cysteine that allows Strep-Tactin to specifically attach to the atomic force microscope cantilever and form a consistent pulling geometry to obtain homogeneous rupture data. Using AFM-SMFS, the mechanical properties of the interaction between Strep-tag II and monovalent Strep-Tactin were characterized. Rupture forces comparable to biotin:streptavidin unbinding were observed. Using titin kinase and green fluorescent protein, we show that monovalent Strep-Tactin is generally applicable to protein unfolding experiments. We expect monovalent Strep-Tactin to be a reliable anchoring tool for a range of single-molecule studies.

  12. Strain selection, biomass to biofuel conversion, and resource colocation have strong impacts on the economic performance of algae cultivation sites

    Directory of Open Access Journals (Sweden)

    Erik R. Venteris

    2014-09-01

    Full Text Available Decisions involving strain selection, biomass to biofuel technology, and the location of cultivation facilities can strongly influence the economic viability of an algae-based biofuel enterprise. We summarize our past results in a new analysis to explore the relative economic impact of these design choices. Our growth model is used to predict average biomass production for two saline strains (Nannocloropsis salina, Arthrospira sp., one fresh to brackish strain (Chlorella sp., DOE strain 1412, and one freshwater strain (order Sphaeropleales. Biomass to biofuel conversion is compared between lipid extraction (LE and hydrothermal liquefaction (HTL technologies. National-scale models of water, CO2 (as flue gas, land acquisition, site leveling, construction of connecting roads, and transport of HTL oil to existing refineries are used in conjunction with estimates of fuel value (from HTL to prioritize and select from 88,692 unit farms (UF, 405 ha in pond area, a number sufficient to produce 136E+9 L yr-1 of renewable diesel (36 billion gallons yr-1. Strain selection and choice of conversion technology have large economic impacts, with differences between combinations of strains and biomass to biofuel technologies being up to $10 million dollars yr-1 UF-1. Results based on the most productive strain, HTL-based fuel conversion, and resource costs show that the economic potential between geographic locations within the selection can differ by up to $4 million yr-1 UF-1, with 1.8 BGY of production possible from the most cost-effective sites. The local spatial variability in site rank is extreme, with very high and low sites within 10s of km of each other. Colocation with flue gas sources has a strong influence on rank, but the most costly resource component varies from site to site. The highest rank UFs are located predominantly in Florida and Texas, but most states south of 37°N latitude contain promising locations.

  13. Using a Full Complex Site Transfer Function to Estimate Strong Ground Motion in Port-au-Prince (Haiti).

    Science.gov (United States)

    ST Fleur, S.; Courboulex, F.; Bertrand, E.; Mercier De Lepinay, B. F.; Hough, S. E.; Boisson, D.; Momplaisir, R.

    2017-12-01

    To assess the possible impact of a future earthquake in the urban area of Port-au-Prince (Haiti), we have implemented a simulation approach for complex ground motions produced by an earthquake. To this end, we have integrated local site effect in the prediction of strong ground motions in Port-au-Prince using the complex transfer functions method, which takes into account amplitude changes as well as phase changes. This technique is particularly suitable for basins where a conventional 1D digital approach proves inadequate, as is the case in Port-au-Prince. To do this, we use the results of the Standard Spectral Ratio (SSR) approach of St Fleur et al. (2016) to estimate the amplitude of the response of the site to a nearby rock site. Then, we determine the phase difference between sites, interpreted as changes in the phase of the signal related to local site conditions, using the signals of the 2010 earthquake aftershocks records. Finally, the accelerogram of the simulated earthquake is obtain using the technique of the inverse Fourier transform. The results of this study showed that the strongest soil motions are expected in neighborhoods of downtown Port-au-Prince and adjacent hills. In addition, this simulation method by complex transfer functions was validated by comparison with recorded actual data. Our simulated response spectra reproduce very well both the amplitude and the shape of the response spectra of recorded earthquakes. This new approach allowed to reproduce the lengthening of the signal that could be generated by surface waves at certain stations in the city of Port-au-Prince. However, two points of vigilance must be considered: (1) a good signal-to-noise ratio is necessary to obtain a robust estimate of the site-reference phase shift (ratio at least equal to 10); (2) unless the amplitude and phase changes are measured on strong motion records, this technique does not take non-linear effects into account.

  14. Predicting Multicomponent Adsorption Isotherms in Open-Metal Site Materials Using Force Field Calculations Based on Energy Decomposed Density Functional Theory.

    Science.gov (United States)

    Heinen, Jurn; Burtch, Nicholas C; Walton, Krista S; Fonseca Guerra, Célia; Dubbeldam, David

    2016-12-12

    For the design of adsorptive-separation units, knowledge is required of the multicomponent adsorption behavior. Ideal adsorbed solution theory (IAST) breaks down for olefin adsorption in open-metal site (OMS) materials due to non-ideal donor-acceptor interactions. Using a density-function-theory-based energy decomposition scheme, we develop a physically justifiable classical force field that incorporates the missing orbital interactions using an appropriate functional form. Our first-principles derived force field shows greatly improved quantitative agreement with the inflection points, initial uptake, saturation capacity, and enthalpies of adsorption obtained from our in-house adsorption experiments. While IAST fails to make accurate predictions, our improved force field model is able to correctly predict the multicomponent behavior. Our approach is also transferable to other OMS structures, allowing the accurate study of their separation performances for olefins/paraffins and further mixtures involving complex donor-acceptor interactions. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Deep subsurface structure modeling and site amplification factor estimation in Niigata plain for broadband strong motion prediction

    International Nuclear Information System (INIS)

    Sato, Hiroaki

    2009-01-01

    This report addresses a methodology of deep subsurface structure modeling in Niigata plain, Japan to estimate site amplification factor in the broadband frequency range for broadband strong motion prediction. In order to investigate deep S-wave velocity structures, we conduct microtremor array measurements at nine sites in Niigata plain, which are important to estimate both long- and short-period ground motion. The estimated depths of the top of the basement layer agree well with those of the Green tuff formation as well as the Bouguer anomaly distribution. Dispersion characteristics derived from the observed long-period ground motion records are well explained by the theoretical dispersion curves of Love wave group velocities calculated from the estimated subsurface structures. These results demonstrate the deep subsurface structures from microtremor array measurements make it possible to estimate long-period ground motions in Niigata plain. Moreover an applicability of microtremor array exploration for inclined basement structure like a folding structure is shown from the two dimensional finite difference numerical simulations. The short-period site amplification factors in Niigata plain are empirically estimated by the spectral inversion analysis from S-wave parts of strong motion data. The resultant characteristics of site amplification are relative large in the frequency range of about 1.5-5 Hz, and decay significantly with the frequency increasing over about 5 Hz. However, these features can't be explained by the calculations from the deep subsurface structures. The estimation of site amplification factors in the frequency range of about 1.5-5 Hz are improved by introducing a shallow detailed structure down to GL-20m depth at a site. We also propose to consider random fluctuation in a modeling of deep S-wave velocity structure for broadband site amplification factor estimation. The Site amplification in the frequency range higher than about 5 Hz are filtered

  16. Detailed site effect estimation in the presence of strong velocity reversals within a small-aperture strong-motion array in Iceland

    KAUST Repository

    Rahpeyma, Sahar; Halldorsson, Benedikt; Olivera, Christian; Green, Russell A.; Jonsson, Sigurjon

    2016-01-01

    The rock site characterization for earthquake engineering applications in Iceland is common due to the easily exposed older bedrock and more recent volcanic lava rock. The corresponding site amplification is generally assumed to be low but has

  17. Adsorption of zinc(II) on hydrous iron oxides

    International Nuclear Information System (INIS)

    Music, S.; Ristic, M.

    1992-01-01

    The adsorption of Zn 2+ ions on amorphous Fe(OH 3 ) and α-Fe 2 O 3 , as a function of pH, has been investigated. In the pH region corresponding to the formation of positively charged Zn-hydroxy complexes, an abrupt increase in adsorption was observed. The influence of EDTA and glycine on the adsorption of Zn 2+ by α-Fe 2 O 3 has also been investigated. Strong suppression of the adsorption of Zn 2+ was observed for high [EDTA or Gly]/[Zn 2+ ] concentration ratios. The results of the adsorption of Zn 2+ in the presence of an organic ligand were explained by the formation of Zn-EDTA or Zn-glycine complexes and also by the occupation of adsorption sites by the free organic ligand. (author) 26 refs.; 6 figs

  18. Strain selection, biomass to biofuel conversion, and resource colocation have strong impacts on the economic performance of algae cultivation sites

    Energy Technology Data Exchange (ETDEWEB)

    Venteris, Erik R.; Wigmosta, Mark S.; Coleman, Andre M.; Skaggs, Richard

    2014-09-16

    Decisions involving strain selection, biomass to biofuel technology, and the location of cultivation facilities can strongly influence the economic viability of an algae-based biofuel enterprise. In this contribution we summarize our past results in a new analysis to explore the relative economic impact of these design choices. We present strain-specific growth model results from two saline strains (Nannocloropsis salina, Arthrospira sp.), a fresh to brackish strain (Chlorella sp., DOE strain 1412), and a freshwater strain of the order Sphaeropleales. Biomass to biofuel conversion is compared between lipid extraction (LE) and hydrothermal liquefaction (HTL) technologies. National-scale models of water, CO2 (as flue gas), land acquisition, site leveling, construction of connecting roads, and transport of HTL oil to existing refineries are used in conjunction with estimates of fuel value (from HTL) to prioritize and select from 88,692 unit farms (UF, 405 ha in pond area), a number sufficient to produce 136E+9 L yr-1 of renewable diesel (36 billion gallons yr-1, BGY). Strain selection and choice of conversion technology have large economic impacts, with differences between combinations of strains and biomass to biofuel technologies being up to $10 million dollars yr-1 UF-1. Results based on the most productive species, HTL-based fuel conversion, and resource costs show that the economic potential between geographic locations within the selection can differ by up to $4 million yr-1 UF-1, with 2.0 BGY of production possible from the most cost-effective sites. The local spatial variability in site rank is extreme, with very high and low rank sites within 10s of km of each other. Colocation with flue gas sources has a strong influence on site rank, but the most costly resource component varies from site to site. The highest rank sites are located predominantly in Florida and Texas, but most states south of 37°N latitude contain promising locations. Keywords: algae

  19. SISMA (Site of Italian Strong Motion Accelerograms): a Web-Database of Ground Motion Recordings for Engineering Applications

    International Nuclear Information System (INIS)

    Scasserra, Giuseppe; Lanzo, Giuseppe; D'Elia, Beniamino; Stewart, Jonathan P.

    2008-01-01

    The paper describes a new website called SISMA, i.e. Site of Italian Strong Motion Accelerograms, which is an Internet portal intended to provide natural records for use in engineering applications for dynamic analyses of structural and geotechnical systems. SISMA contains 247 three-component corrected motions recorded at 101 stations from 89 earthquakes that occurred in Italy in the period 1972-2002. The database of strong motion accelerograms was developed in the framework of a joint project between Sapienza University of Rome and University of California at Los Angeles (USA) and is described elsewhere. Acceleration histories and pseudo-acceleration response spectra (5% damping) are available for download from the website. Recordings can be located using simple search parameters related to seismic source and the recording station (e.g., magnitude, V s30 , etc) as well as ground motion characteristics (e.g. peak ground acceleration, peak ground velocity, peak ground displacement, Arias intensity, etc.)

  20. Strain Selection, Biomass to Biofuel Conversion, and Resource Colocation have Strong Impacts on the Economic Performance of Algae Cultivation Sites

    Energy Technology Data Exchange (ETDEWEB)

    Venteris, Erik R., E-mail: erik.venteris@pnl.gov; Wigmosta, Mark S.; Coleman, Andre M.; Skaggs, Richard L. [Pacific Northwest National Laboratory, Richland, WA (United States)

    2014-09-16

    Decisions involving strain selection, biomass to biofuel technology, and the location of cultivation facilities can strongly influence the economic viability of an algae-based biofuel enterprise. We summarize our past results in a new analysis to explore the relative economic impact of these design choices. Our growth model is used to predict average biomass production for two saline strains (Nannochloropsis salina and Arthrospira sp.), one fresh to brackish strain (Chlorella sp., DOE strain 1412), and one freshwater strain (order Sphaeropleales). Biomass to biofuel conversion is compared between lipid extraction and hydrothermal liquefaction (HTL) technologies. National-scale models of water, CO{sub 2} (as flue gas), land acquisition, site leveling, construction of connecting roads, and transport of HTL oil to existing refineries are used in conjunction with estimates of fuel value (from HTL) to prioritize and select from 88,692 unit farms (UF, 405 ha in pond area), a number sufficient to produce 136E + 9 L year{sup −1} of renewable diesel [36 billion gallons year{sup −1} (BGY)]. Strain selection and choice of conversion technology have large economic impacts, with differences between combinations of strains and biomass to biofuel technologies being up to $10 million year{sup −1} UF{sup −1}. Results based on the most productive strain, HTL-based fuel conversion, and resource costs show that the economic potential between geographic locations within the selection can differ by up to 4 million year{sup −1} UF{sup −1}, with 1.8 BGY of production possible from the most cost-effective sites. The local spatial variability in site rank is extreme, with very high and low sites within 10 kms of each other. Colocation with flue gas sources has a strong influence on rank, but the most costly resource component varies from site to site. The highest rank UFs are located predominantly in Florida and Texas, but most states south of 37°N latitude contain promising

  1. A first-principles study of oxygen adsorption on Ir(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Hengjiao, E-mail: gaohengjiao@163.com; Xiong, Yuqing, E-mail: xiongyq@hotmail.com; Liu, Xiaoli, E-mail: shantianzi@126.com; Zhao, Dongcai, E-mail: zhaodongc@163.com; Feng, Yudong, E-mail: yudong_feng@sina.com; Wang, Lanxi, E-mail: wanglanxi@live.com; Wang, Jinxiao, E-mail: coldwind716@gmail.com

    2016-12-15

    Highlights: • Adsorption of oxygen on Ir(111) surface was studied by density functional theory. • The most stable adsorption site was determined by adsorption energy calculation. • Adsorption of oxygen at bridge and top site on Ir surface was the most stable ones. • Interaction of O 2p and Ir 5d orbits is relatively strong and formed hybridization. - Abstract: In order to understand deposition mechanism of iridium thin film by atomic layer deposition, the adsorption of oxygen on Ir(111) surface was studied by use of density functional theory and a periodical slab model. By calculating the adsorption energy and structure of oxygen at four adsorption sites (top, bridge, fcc-hollow and hcp-hollow) on Ir(111) surface, the most stable adsorption site was determined. On this basis, the banding mechanism of O and Ir atoms was studied by density of states of oxygen and iridium atoms. Oxygen adsorbed at hcp(parallel) site on Ir(111) surface was the most stable one according to the adsorption energy calculation results. Orbital charge analysis indicate that charge transferred from 5p and 5d orbit to 2p orbit of adsorbed O atoms, and 6s orbit of iridium atoms. Meanwhile, density of state study indicated that adsorption of oxygen on Ir(111) surface is mainly due to the interaction between 2p orbit of O atoms and 5d orbit of iridium atoms.

  2. The role of the anionic and cationic pt sites in the adsorption site preference of water and ethanol on defected Pt4/Pt(111) substrates: A density functional theory investigation within the D3 van der waals corrections

    Science.gov (United States)

    Seminovski, Yohanna; Amaral, Rafael C.; Tereshchuk, Polina; Da Silva, Juarez L. F.

    2018-01-01

    Platinum (Pt) atoms in the bulk face-centered cubic structure have neutral charge because they are equivalent by symmetry, however, in clean Pt surfaces, the effective charge on Pt atoms can turn slightly negative (anionic) or positive (cationic) while increasing substantially in magnitude for defected (low-coordinated) Pt sites. The effective charge affect the adsorption properties of molecular species on Pt surfaces and it can compete in importance with the coupling of the substrate-molecule electronic states. Although several studies have been reported due to the importance of Pt for catalysis, our understanding of the role played by low-coordinated sites is still limited. Here, we employ density functional theory within the Perdew-Burke-Ernzerhof exchange-correlation functional and the D3 van der Waals (vdW) correction to investigate the role of the cationic and anionic Pt sites on the adsorption properties of ethanol and water on defected Pt4/Pt(111) substrates. Four substrates were carefully selected, namely, two two-dimensional (2D) Pt4 configurations (2D-strand and 2D-island) and two tri-dimensional (3D) Pt4 (3D-fcc and 3D-hcp), to understand the role of coordination, effective charge, and coupling of the electronic states in the adsorption properties. From the Bader charge analysis, we identified the cationic and anionic sites among the Pt atoms exposed to the vacuum region in the Pt4/Pt(111) substrates. We found that ethanol and water bind via the anionic O atoms to the low-coordinated defected Pt sites of the substrates, where the angle PtOH is nearly 100° for most configurations. In the 3D-fcc or 3D-hcp defected configurations, the lowest-coordinated Pt atoms are anionic, hence, those Pt sites are not preferable for the adsorption of O atoms. The charge transfer from water and ethanol to the Pt substrates has similar magnitude for all cases, which implies similar Coulomb contribution to the adsorption energy. Moreover, we found a correlation of the

  3. Adsorption and separation of CO{sub 2} on Fe(II)-MOF-74: Effect of the open metal coordination site

    Energy Technology Data Exchange (ETDEWEB)

    Lou, Wolong; Yang, Jiangfeng; Li, Libo; Li, Jinping, E-mail: Jpli211@hotmail.com

    2014-05-01

    We describe the successful synthesis of Fe{sub 2}(dobdc) (dobdc{sup 4−}=2, 5-dioxido-1, 4-benzenedicarboxylate), which has an open metal coordination site Fe(II), and investigate the adsorption properties of three important molecules CO{sub 2}, CH{sub 4} and N{sub 2} on Fe{sub 2}(dobdc) and an oxidized analog, Fe{sub 2}(O{sub 2})(dobdc). We found that CO{sub 2} adsorption isotherm of Fe{sub 2}(dobdc) at 10 bar was very different from Fe{sub 2}(O{sub 2})(dobdc), with the capacities of 144.5 cm{sup 3} g{sup −1} and 98.1 cm{sup 3} g{sup −1}, respectively. The adsorption capacities for CH{sub 4} were 75.8 cm{sup 3} g{sup −1} and 36.8 cm{sup 3} g{sup −1}, respectively, at 10 bar in these materials. Using ideal adsorbed solution theory (IAST), we obtain the adsorption selectivity for CO{sub 2} using equimolar mixtures of CO{sub 2}/CH{sub 4} and CO{sub 2}/N{sub 2} with Fe{sub 2}(dobdc) and Fe{sub 2}(O{sub 2})(dobdc) as a function of pressure. Fe{sub 2}(dobdc) has a higher, more stable separation factor. - Graphical abstract: The selectivity of CO{sub 2}/CH{sub 4} mixture (50%/50%) on Fe{sub 2}(dobdc) and Fe{sub 2}(O{sub 2})(dobdc). - Highlights: • We explored the contrastive adsorption of CO{sub 2}, CH{sub 4}, and N{sub 2} in Fe{sub 2}(dobdc) and Fe{sub 2}(O{sub 2})(dobdc) for the first time. • Through IAST, we obtain the adsorption selectivity for CO{sub 2} from the equimolar mixture of CO{sub 2}/CH{sub 4} and CO{sub 2}/N{sub 2} for Fe{sub 2}(dobdc) and Fe{sub 2}(O{sub 2})(dobdc). • We determined that the open coordination site of Fe(II) is the main reason for different adsorption performances.

  4. A ChIP-Seq benchmark shows that sequence conservation mainly improves detection of strong transcription factor binding sites.

    Directory of Open Access Journals (Sweden)

    Tony Håndstad

    Full Text Available BACKGROUND: Transcription factors are important controllers of gene expression and mapping transcription factor binding sites (TFBS is key to inferring transcription factor regulatory networks. Several methods for predicting TFBS exist, but there are no standard genome-wide datasets on which to assess the performance of these prediction methods. Also, it is believed that information about sequence conservation across different genomes can generally improve accuracy of motif-based predictors, but it is not clear under what circumstances use of conservation is most beneficial. RESULTS: Here we use published ChIP-seq data and an improved peak detection method to create comprehensive benchmark datasets for prediction methods which use known descriptors or binding motifs to detect TFBS in genomic sequences. We use this benchmark to assess the performance of five different prediction methods and find that the methods that use information about sequence conservation generally perform better than simpler motif-scanning methods. The difference is greater on high-affinity peaks and when using short and information-poor motifs. However, if the motifs are specific and information-rich, we find that simple motif-scanning methods can perform better than conservation-based methods. CONCLUSIONS: Our benchmark provides a comprehensive test that can be used to rank the relative performance of transcription factor binding site prediction methods. Moreover, our results show that, contrary to previous reports, sequence conservation is better suited for predicting strong than weak transcription factor binding sites.

  5. Construction of iron-polymer-graphene nanocomposites with low nonspecific adsorption and strong quenching ability for competitive immunofluorescent detection of biomarkers in GM crops.

    Science.gov (United States)

    Yin, Kaifei; Liu, Anran; Shangguan, Li; Mi, Li; Liu, Xu; Liu, Yuanjian; Zhao, Yuewu; Li, Ying; Wei, Wei; Zhang, Yuanjian; Liu, Songqin

    2017-04-15

    We developed a new immunofluorescent biosensor by utilizing a novel nanobody (Nb) and iron-polymer-graphene nanocomposites for sensitive detection of 5-enolpyruvylshikimate-3-phosphate synthase from Agrobacdterium tumefaciens strain CP4 (CP4-EPSPS), which considered as biomarkers of genetically modified (GM) crops. Specifically, we prepared iron doped polyacrylic hydrazide modified reduced graphene nanocomposites (Fe@RGO/PAH) by in-situ polymerization approach and subsequent a one-pot reaction with hydrazine. The resulting Fe@RGO/PAH nanocomposites displayed low nonspecific adsorption to analytes (11% quenching caused by nonspecific adsorption) due to electrostatic, energetic and steric effect of the nanocomposites. After Nb immobilizing, the as-prepared Fe@RGO/PAH/Nbs showed good selectivity and high quenching ability (92% quenching) in the presence of antigen (Ag) and polyethylene glycol (PEG) modified CdTe QDs (Ag/QDs@PEG), which is a nearly 4 fold than that of the unmodified GO in same condition. The high quenching ability of Fe@RGO/PAH/Nbs can be used for detection of CP4-EPSPS based on competitive immunoassay with a linearly proportional concentration range of 5-100ng/mL and a detection limit of 0.34ng/mL. The good stability, reproducibility and specificity of the resulting immunofluorescent biosensor are demonstrated and might open a new window for investigation of fluorescent sensing with numerous multifunctional graphene based materials. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Strong cooperative effect of oppositely charged surfactant mixtures on their adsorption and packing at the air-water interface and interfacial water structure.

    Science.gov (United States)

    Nguyen, Khoi T; Nguyen, Tuan D; Nguyen, Anh V

    2014-06-24

    Remarkable adsorption enhancement and packing of dilute mixtures of water-soluble oppositely-charged surfactants, sodium dodecyl sulfate (SDS) and dodecyl amine hydrochloride (DAH), at the air-water interface were observed by using sum frequency generation spectroscopy and tensiometry. The interfacial water structure was also observed to be significantly influenced by the SDS-DAH mixtures, differently from the synergy of the single surfactants. Most strikingly, the obtained spectroscopic evidence suggests that the interfacial hydrophobic alkyl chains of the binary mixtures assemble differently from those of single surfactants. This study highlights the significance of the cooperative interaction between the headgroups of oppositely charged binary surfactant systems and subsequently provides some insightful observations about the molecular structure of the air-aqueous interfacial water molecules and, more importantly, about the packing nature of the surfactant hydrophobic chains of dilute SDS-DAH mixtures of concentration below 1% of the CMC.

  7. Preferential adsorption of NH3 gas molecules on MWCNT defect sites probed using in situ Raman spectroscopy

    CSIR Research Space (South Africa)

    Chimowa, George

    2017-06-01

    Full Text Available The preferential adsorption of NH(sub3) gas molecules on multi-walled carbon nanotubes (MWCNTs) was studied using in situ Raman spectroscopy. It was observed that the full widths at half maximum of the G band and the intensity ratio I(sub2D...

  8. Theoretical investigation of site-specific characteristics of CO adsorption complexes in the Li+-FER zeolite

    Czech Academy of Sciences Publication Activity Database

    Nachtigall, Petr; Bulánek, R.

    2006-01-01

    Roč. 307, č. 1 (2006), s. 118-127 ISSN 0926-860X R&D Projects: GA MŠk(CZ) LC512 Institutional research plan: CEZ:AV0Z40550506 Keywords : adsorption * spectroscopy * DFT Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.630, year: 2006

  9. Density functional theory study of elemental mercury adsorption on boron doped graphene surface decorated by transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Jungsuttiwong, Siriporn, E-mail: siriporn.j@ubu.ac.th [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Wongnongwa, Yutthana [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Namuangruk, Supawadee [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathum Thani 12120 (Thailand); Kungwan, Nawee [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Promarak, Vinich [Department of Material Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21210 (Thailand); Kunaseth, Manaschai, E-mail: manaschai@nanotec.or.th [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathum Thani 12120 (Thailand)

    2016-01-30

    Graphical abstract: Decoration of Pd{sub 4}-A (square planar) on B-doped graphene significantly promotes Hg{sup 0} adsorption, a single site of Pd{sub 4} cluster on BDG could strongly adsorb up to six Hg atoms. - Highlights: • Transition metal atom and cluster binds strongly on B-doped graphene surface. • Decoration of transition metal on B-doped graphene significantly promotes Hg{sup 0} adsorption. • Adsorption strength of Hg{sup 0} atom on metal decorated B-doped graphene: Pd > Pt > Ru > W > Cu. • One site decorated Pd4 cluster adsorbed Hg{sup 0} strongly up to six atoms.

  10. Site blocking in silver-exchanged zeolite Y by carbon monoxide and ethene using xenon adsorption and 129Xe NMR spectroscopy

    Science.gov (United States)

    Boddenberg, B.; Watermann, J.

    1993-03-01

    The adsorption isotherms and 129Xe NMR chemical shifts of xenon in the zeolites NaY, AgY, and in AgY preloaded with ≈ 1 molecule/supercage ethene and carbon monoxide were measured at 25°C. The experimental data reveal the blocking of the silver-cation sites for xenon by the preadsorbed molecules. Ethene and CO are found to block the previously postulated two types of silver-cation species in the supercages of AgY in a different way.

  11. Combined Theoretical and Experimental Investigation of CO Adsorption on Coordinatively Unsaturated Sites in CuBTC MOF

    Czech Academy of Sciences Publication Activity Database

    Rubeš, M.; Grajciar, L.; Bludský, Ota; Wiersum, A. D.; Llewellyn, P. L.; Nachtigall, P.

    2012-01-01

    Roč. 13, č. 2 (2012), s. 488-495 ISSN 1439-4235 R&D Projects: GA MŠk LC512 Grant - others:GA MŠk(CZ) 7E09111; 7th framework programme(XE) 228862 Institutional research plan: CEZ:AV0Z40550506 Keywords : ab initio calculations * adsorption * density functional calculations * metal-organic frameworks * microcalorimetry Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.349, year: 2012

  12. Carbon monoxide adsorption on low-silica zeolites-from single to dual and to multiple cation sites

    Czech Academy of Sciences Publication Activity Database

    Otero Areán, C.; Rodríguez Delgado, M.; López Bauca, C.; Vrbka, Luboš; Nachtigall, Petr

    2007-01-01

    Roč. 9, č. 33 (2007), s. 4657-4661 ISSN 1463-9076 R&D Projects: GA MŠk LC512; GA ČR GA203/06/0324 Grant - others:UIB(ES) MAT2005-05350 Institutional research plan: CEZ:AV0Z40550506 Keywords : zeolite * adsorption * DFT Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.343, year: 2007

  13. The Importance of Surface-Binding Site towards Starch-Adsorptivity Level in α-Amylase: A Review on Structural Point of View

    Directory of Open Access Journals (Sweden)

    Umi Baroroh

    2017-01-01

    Full Text Available Starch is a polymeric carbohydrate composed of glucose. As a source of energy, starch can be degraded by various amylolytic enzymes, including α-amylase. In a large-scale industry, starch processing cost is still expensive due to the requirement of high temperature during the gelatinization step. Therefore, α-amylase with raw starch digesting ability could decrease the energy cost by avoiding the high gelatinization temperature. It is known that the carbohydrate-binding module (CBM and the surface-binding site (SBS of α-amylase could facilitate the substrate binding to the enzyme’s active site to enhance the starch digestion. These sites are a noncatalytic module, which could interact with a lengthy substrate such as insoluble starch. The major interaction between these sites and the substrate is the CH/pi-stacking interaction with the glucose ring. Several mutation studies on the Halothermothrix orenii, SusG Bacteroides thetaiotamicron, Barley, Aspergillus niger, and Saccharomycopsis fibuligera α-amylases have revealed that the stacking interaction through the aromatic residues at the SBS is essential to the starch adsorption. In this review, the SBS in various α-amylases is also presented. Therefore, based on the structural point of view, SBS is suggested as an essential site in α-amylase to increase its catalytic activity, especially towards the insoluble starch.

  14. Adsorption of selenium by amorphous iron oxyhydroxide and manganese dioxide

    Science.gov (United States)

    Balistrieri, L.S.; Chao, T.T.

    1990-01-01

    This work compares and models the adsorption of selenium and other anions on a neutral to alkaline surface (amorphous iron oxyhydroxide) and an acidic surface (manganese dioxide). Selenium adsorption on these oxides is examined as a function of pH, particle concentration, oxidation state, and competing anion concentration in order to assess how these factors might influence the mobility of selenium in the environment. The data indicate that 1. 1) amorphous iron oxyhydroxide has a greater affinity for selenium than manganese dioxide, 2. 2) selenite [Se(IV)] adsorption increases with decreasing pH and increasing particle concentration and is stronger than selenate [Se(VI)] adsorption on both oxides, and 3. 3) selenate does not adsorb on manganese dioxide. The relative affinity of selenate and selenite for the oxides and the lack of adsorption of selenate on a strongly acidic surface suggests that selenate forms outer-sphere complexes while selenite forms inner-sphere complexes with the surfaces. The data also indicate that the competition sequence of other anions with respect to selenite adsorption at pH 7.0 is phosphate > silicate > molybdate > fluoride > sulfate on amorphous iron oxyhydroxide and molybdate ??? phosphate > silicate > fluoride > sulfate on manganese dioxide. The adsorption of phosphate, molybdate, and silicate on these oxides as a function of pH indicates that the competition sequences reflect the relative affinities of these anions for the surfaces. The Triple Layer surface complexation model is used to provide a quantitative description of these observations and to assess the importance of surface site heterogeneity on anion adsorption. The modeling results suggest that selenite forms binuclear, innersphere complexes with amorphous iron oxyhydroxide and monodentate, inner-sphere complexes with manganese dioxide and that selenate forms outer-sphere, monodentate complexes with amorphous iron oxyhydroxide. The heterogeneity of the oxide surface sites

  15. New developments for localized adsorption

    International Nuclear Information System (INIS)

    Boudh-hir, M.E.

    1989-02-01

    Using the diagrammatic expansion, new developments for localized adsorption are found. It is proved that the correlations in the system, in the absence of the attractive site potential, and the periodicity of the sites play a fundamental role in the adsorption phenomena. 14 refs, 2 figs, 2 tabs

  16. Structure sensitivity in adsorption

    DEFF Research Database (Denmark)

    Hammer, Bjørk; Nielsen, Ole Holm; Nørskov, Jens Kehlet

    1997-01-01

    The structure sensitivity of CO adsorption on different flat, stepped, kinked and reconstructed Pt surfaces is studied using large-scale density-functional calculations. We find an extremely strong structure sensitivity in the adsorption energy with variations up to 1 eV (or 100%) from one...... structure to the next. We propose a model to explain this behavior, and use it to discuss more generally the origin of structure sensitivity in heterogeneous catalysis....

  17. Facile Assembly of 3D Porous Reduced Graphene Oxide/Ultrathin MnO2 Nanosheets-S Aerogels as Efficient Polysulfide Adsorption Sites for High-Performance Lithium-Sulfur Batteries.

    Science.gov (United States)

    Zhao, Xiaojun; Wang, Hui; Zhai, Gaohong; Wang, Gang

    2017-05-23

    Rechargeable lithium-sulfur (Li-S) batteries are receiving much attention due to their high specific capacity, low cost, and environmental friendliness. Nonetheless, fast capacity decay and low specific capacity still limit their practical implementation. Herein, we report a facile strategy to overcome these challenges by the design and fabrication of 3D porous reduced graphene oxide/ultrathin MnO 2 nanosheets-S aerogel (rGM-SA) composites for Li-S batteries. By a simple solvothermal reaction process, nanosized S atoms are homogeneously decorated into the 3D scaffold formed by reduced graphene oxide (rGO) and MnO 2 nanosheets, which can form the homogeneous rGM-SA composites. In this porous network architecture, rGO serves as an electron and ion transfer pathway, a physical adsorption site for polysulfides, and provides structural stability. The ultrathin MnO 2 nanosheets provide strong binding sites for trapping polysulfide intermediates. The 3D porous rGO/MnO 2 architecture enables rapid ion transport and buffers volume expansion of sulfur during discharge. The rGM-SA composites can be directly used as lithium-sulfur battery cathodes without using binder and conductive additive. As a result of this multifunctional arrangement, the rGM-SA composites exhibit high and stable-specific capacities over 200 cycles and excellent high-rate performances. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. A semi-empirical analysis of strong-motion peaks in terms of seismic source, propagation path, and local site conditions

    Science.gov (United States)

    Kamiyama, M.; Orourke, M. J.; Flores-Berrones, R.

    1992-09-01

    A new type of semi-empirical expression for scaling strong-motion peaks in terms of seismic source, propagation path, and local site conditions is derived. Peak acceleration, peak velocity, and peak displacement are analyzed in a similar fashion because they are interrelated. However, emphasis is placed on the peak velocity which is a key ground motion parameter for lifeline earthquake engineering studies. With the help of seismic source theories, the semi-empirical model is derived using strong motions obtained in Japan. In the derivation, statistical considerations are used in the selection of the model itself and the model parameters. Earthquake magnitude M and hypocentral distance r are selected as independent variables and the dummy variables are introduced to identify the amplification factor due to individual local site conditions. The resulting semi-empirical expressions for the peak acceleration, velocity, and displacement are then compared with strong-motion data observed during three earthquakes in the U.S. and Mexico.

  19. Site classification for National Strong Motion Observation Network System (NSMONS) stations in China using an empirical H/V spectral ratio method

    Science.gov (United States)

    Ji, Kun; Ren, Yefei; Wen, Ruizhi

    2017-10-01

    Reliable site classification of the stations of the China National Strong Motion Observation Network System (NSMONS) has not yet been assigned because of lacking borehole data. This study used an empirical horizontal-to-vertical (H/V) spectral ratio (hereafter, HVSR) site classification method to overcome this problem. First, according to their borehole data, stations selected from KiK-net in Japan were individually assigned a site class (CL-I, CL-II, or CL-III), which is defined in the Chinese seismic code. Then, the mean HVSR curve for each site class was computed using strong motion recordings captured during the period 1996-2012. These curves were compared with those proposed by Zhao et al. (2006a) for four types of site classes (SC-I, SC-II, SC-III, and SC-IV) defined in the Japanese seismic code (JRA, 1980). It was found that an approximate range of the predominant period Tg could be identified by the predominant peak of the HVSR curve for the CL-I and SC-I sites, CL-II and SC-II sites, and CL-III and SC-III + SC-IV sites. Second, an empirical site classification method was proposed based on comprehensive consideration of peak period, amplitude, and shape of the HVSR curve. The selected stations from KiK-net were classified using the proposed method. The results showed that the success rates of the proposed method in identifying CL-I, CL-II, and CL-III sites were 63%, 64%, and 58% respectively. Finally, the HVSRs of 178 NSMONS stations were computed based on recordings from 2007 to 2015 and the sites classified using the proposed method. The mean HVSR curves were re-calculated for three site classes and compared with those from KiK-net data. It was found that both the peak period and the amplitude were similar for the mean HVSR curves derived from NSMONS classification results and KiK-net borehole data, implying the effectiveness of the proposed method in identifying different site classes. The classification results have good agreement with site classes

  20. Simultaneous fluorescence light-up and selective multicolor nucleobase recognition based on sequence-dependent strong binding of berberine to DNA abasic site.

    Science.gov (United States)

    Wu, Fei; Shao, Yong; Ma, Kun; Cui, Qinghua; Liu, Guiying; Xu, Shujuan

    2012-04-28

    Label-free DNA nucleobase recognition by fluorescent small molecules has received much attention due to its simplicity in mutation identification and drug screening. However, sequence-dependent fluorescence light-up nucleobase recognition and multicolor emission with individual emission energy for individual nucleobases have been seldom realized. Herein, an abasic site (AP site) in a DNA duplex was employed as a binding field for berberine, one of isoquinoline alkaloids. Unlike weak binding of berberine to the fully matched DNAs without the AP site, strong binding of berberine to the AP site occurs and the berberine's fluorescence light-up behaviors are highly dependent on the target nucleobases opposite the AP site in which the targets thymine and cytosine produce dual emission bands, while the targets guanine and adenine only give a single emission band. Furthermore, more intense emissions are observed for the target pyrimidines than purines. The flanking bases of the AP site also produce some modifications of the berberine's emission behavior. The binding selectivity of berberine at the AP site is also confirmed by measurements of fluorescence resonance energy transfer, excited-state lifetime, DNA melting and fluorescence quenching by ferrocyanide and sodium chloride. It is expected that the target pyrimidines cause berberine to be stacked well within DNA base pairs near the AP site, which results in a strong resonance coupling of the electronic transitions to the particular vibration mode to produce the dual emissions. The fluorescent signal-on and emission energy-modulated sensing for nucleobases based on this fluorophore is substantially advantageous over the previously used fluorophores. We expect that this approach will be developed as a practical device for differentiating pyrimidines from purines by positioning an AP site toward a target that is available for readout by this alkaloid probe. This journal is © The Royal Society of Chemistry 2012

  1. Shear-wave velocity characterization of the USGS Hawaiian strong-motion network on the Island of Hawaii and development of an NEHRP site-class map

    Science.gov (United States)

    Wong, Ivan G.; Stokoe, Kenneth; Cox, Brady R.; Yuan, Jiabei; Knudsen, Keith L.; Terra, Fabia; Okubo, Paul G.; Lin, Yin-Cheng

    2011-01-01

    To assess the level and nature of ground shaking in Hawaii for the purposes of earthquake hazard mitigation and seismic design, empirical ground-motion prediction models are desired. To develop such empirical relationships, knowledge of the subsurface site conditions beneath strong-motion stations is critical. Thus, as a first step to develop ground-motion prediction models for Hawaii, spectral-analysis-of-surface-waves (SASW) profiling was performed at the 22 free-field U.S. Geological Survey (USGS) strong-motion sites on the Big Island to obtain shear-wave velocity (VS) data. Nineteen of these stations recorded the 2006 Kiholo Bay moment magnitude (M) 6.7 earthquake, and 17 stations recorded the triggered M 6.0 Mahukona earthquake. VS profiling was performed to reach depths of more than 100 ft. Most of the USGS stations are situated on sites underlain by basalt, based on surficial geologic maps. However, the sites have varying degrees of weathering and soil development. The remaining strong-motion stations are located on alluvium or volcanic ash. VS30 (average VS in the top 30 m) values for the stations on basalt ranged from 906 to 1908 ft/s [National Earthquake Hazards Reduction Program (NEHRP) site classes C and D], because most sites were covered with soil of variable thickness. Based on these data, an NEHRP site-class map was developed for the Big Island. These new VS data will be a significant input into an update of the USGS statewide hazard maps and to the operation of ShakeMap on the island of Hawaii.

  2. Oxygen adsorption on the Al9Co2(001) surface: first-principles and STM study

    International Nuclear Information System (INIS)

    Villaseca, S Alarcón; Loli, L N Serkovic; Ledieu, J; Fournée, V; Dubois, J-M; Gaudry, É; Gille, P

    2013-01-01

    Atomic oxygen adsorption on a pure aluminum terminated Al 9 Co 2 (001) surface is studied by first-principle calculations coupled with STM measurements. Relative adsorption energies of oxygen atoms have been calculated on different surface sites along with the associated STM images. The local electronic structure of the most favourable adsorption site is described. The preferential adsorption site is identified as a ‘bridge’ type site between the cluster entities exposed at the (001) surface termination. The Al–O bonding between the adsorbate and the substrate presents a covalent character, with s–p hybridization occurring between the states of the adsorbed oxygen atom and the aluminum atoms of the surface. The simulated STM image of the preferential adsorption site is in agreement with experimental observations. This work shows that oxygen adsorption generates important atomic relaxations of the topmost surface layer and that sub-surface cobalt atoms strongly influence the values of the adsorption energies. The calculated Al–O distances are in agreement with those reported in Al 2 O and Al 2 O 3 oxides and for oxygen adsorption on Al(111). (paper)

  3. Adsorption site and structure determination of c(2x2) N{sub 2}/Ni(100) using angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Moler, E.J.; Kellar, S.A.; Huff, W.R.A. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The authors have determined the atomic spatial structure of c(2x2) N2Ni(100) with Angle-Resolved Photoemission Extended Fine Structure (ARPEFS) from the nitrogen 1s core level using monochromatized x-rays from beamline 6.1 at SSRL and beamline 9.3.2 at the ALS. The chemically shifted N 1s peak intensities were summed together to obtain ARPEFS curves for both nitrogen atoms in the molecule. They used a new, highly-optimized program based on the Rehr-Albers scattering matrix formalism to find the adsorption site and to quantitatively determine the bond-lengths. The nitrogen molecule stands upright at an atop site, with a N-Ni bond length of 2.25(1) {angstrom}, a N-N bond length of 1.10(7) {angstrom}, and a first layer Ni-Ni spacing of 1.76(4) {angstrom}. The shake-up peak shows an identical ARPEFS diffraction pattern, confirming its intrinsic nature and supporting a previous use of this feature to decompose the peak into contributions from the chemically inequivalent nitrogen atoms. Comparison to a previously published theoretical treatment of N-N-Ni and experimental structures of analogous adsorbate systems demonstrates the importance of adsorbate-adsorbate interactions in weakly chemisorbed systems.

  4. P-EXAFS investigations of Zn uptake by montmorillonite. The strong and weak sites concept in the 2SPNE SC/CE sorption model

    International Nuclear Information System (INIS)

    Daehn, R.; Baeyens, B.; Bradbury, M.H.

    2012-01-01

    Document available in extended abstract form only. The sorption of radioactive elements on the immobile components in the near- and far-fields of a deep geological radioactive waste repository is a significant process in retarding their aqueous phase transport and an important component in safety assessment studies. The development of robust and well-founded mechanistic sorption models to predict the uptake of radionuclides under different geochemical conditions would enhance the justification and defensibility of the sorption values used in safety studies and thereby represent a considerable contribution to the scientific basis for radioactive waste disposal. The 2 site proto-lysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) sorption model has been used over the past decade or so to quantitatively describe the uptake of metals with oxidation states from II to VI on 2:1 clay minerals; montmorillonite and illite (Bradbury and Baeyens, 1997). One of the main features in this model is that there are two broad categories of amphoteric edge sorption sites; the so called strong (≡SSOH) and weak (≡SW1OH) sites. Because of their different sorption characteristics, it was expected that the coordination environments of the surface complexes on the two site types would be different. Although the 2SPNE SC/CE model uses different mechanistic uptake processes to describe sorption, it can only be described as a 'quasi mechanistic' model because the exact nature of the surface binding sites and surface complexes is not known. In order to check the 'strong site / weak site' sorption sites hypothesis in the 2SPNE SC/CE sorption model, it was essential to perform polarised extended X-ray absorption fine structure (P-EXAFS) measurements on an uptake system, in which it was possible to obtain good spectra particularly at the low metal loadings (∼2 mmol kg-1 or less) corresponding to occupancies dominated by strong sites. The Zn-montmorillonite system

  5. New particle formation in the presence of a strong biomass burning episode at a downwind rural site in PRD, China

    Directory of Open Access Journals (Sweden)

    Z. B. Wang

    2013-02-01

    Full Text Available In order to characterise the features of particle pollution in the Pearl River Delta (PRD region, a 1-month intensive campaign was conducted at the rural supersite (Kaiping in the autumn of 2008. In total, 12 new particle formation (NPF events are identified out of 30 campaign days. The results show that in the case of higher source and sink values, the result of the competition between source and sink is more likely the key limiting factor to determine the observation of NPF events at Kaiping. One episode with consecutive NPF events in the presence of strong biomass burning plume was observed between 10 and 15 November. The elevation of particle volume concentration (6.1 µm3/cm3/day is due to the coaction by the local biomass burning and secondary transformation. Organics and sulphates are the major components in PM1, accounting for 42 and 35% of the mass concentration, respectively. In this study, a rough estimation is applied to quantify the contributions of diverse sources to the particle number concentration. On average, the primary emission and secondary formation provide 28 and 72% of particle number concentration and 21 and 79% of mass concentration, respectively.

  6. New particle formation in the presence of a strong biomass burning episode at a downwind rural site in PRD, China

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z. B.; Hu, M.; Yue, D. L.; Yang, Q.; Zhang, Y. H. [State Key Joint Lab. of Environmental Simulation and Pollution Control, Coll. of Environmental Sciences and Engineering, Peking Univ., Beijing (China)], e-mail: minhu@pku.edu.cn; He, L. Y.; Huang, X. F. [Key Lab. for Urban Habitat Environmental Science and Technology, School of Environment and Energy, Peking Univ. Shenzhen Graduate School, Shenzhen (China); Zheng, J. [Dept. of Atmospheric Science, Texas AandM Univ., College Station, Texas (United States); Zhang, R. Y. [State Key Joint Lab. of Environmental Simulation and Pollution Control, Coll. of Environmental Sciences and Engineering, Peking Univ., Beijing (China); Department of Atmospheric Science, Texas AandM Univ., College Station, Texas (United States))

    2013-09-15

    In order to characterise the features of particle pollution in the Pearl River Delta (PRD) region, a 1-month intensive campaign was conducted at the rural supersite (Kaiping) in the autumn of 2008. In total, 12 new particle formation (NPF) events are identified out of 30 campaign days. The results show that in the case of higher source and sink values, the result of the competition between source and sink is more likely the key limiting factor to determine the observation of NPF events at Kaiping. One episode with consecutive NPF events in the presence of strong biomass burning plume was observed between 10 and 15 November. The elevation of particle volume concentration (6.1 mm{sup 3}/cm{sup 3}/day) is due to the coaction by the local biomass burning and secondary transformation. Organics and sulphates are the major components in PM{sub 1}, accounting for 42% and 35% of the mass concentration, respectively. In this study, a rough estimation is applied to quantify the contributions of diverse sources to the particle number concentration. On average, the primary emission and secondary formation provide 28 and 72% of particle number concentration and 21% and 79% of mass concentration, respectively.

  7. Copper adsorption in tropical oxisols

    Directory of Open Access Journals (Sweden)

    Silveira Maria Lucia Azevedo

    2003-01-01

    Full Text Available Cu adsorption, at concentrations between 0 to 800 mg L-1, was evaluated in surface and subsurface samples of three Brazilian soils: a heavy clayey-textured Rhodic Hapludalf (RH, a heavy clayey-textured Anionic ''Rhodic'' Acrudox (RA and a medium-textured Anionic ''Xanthic'' Acrudox (XA. After adsorption, two consecutive extractions were performed to the samples which received 100 mg L-1 copper. Surface samples adsorbed higher amounts of Cu than the subsurface, and exhibited lower Cu removed after the extractions, reinforcing the influence of the organic matter in the reactions. Cu adsorption was significant in the subsurface horizons of the Oxisols, despite the positive balance of charge, demonstrating the existence of mechanisms for specific adsorption, mainly related to the predominance of iron and aluminum oxides in the mineral fractions. In these samples, Cu was easily removed from the adsorption sites. RH demonstrated a higher capacity for the Cu adsorption in both horizons.

  8. Start-up of an UASB-septic tank for community on-site treatment of strong domestic sewage.

    Science.gov (United States)

    Al-Shayah, Mohammad; Mahmoud, Nidal

    2008-11-01

    Two community on-site UASB-septic tanks were operated in parallel over a six months period under two different hydraulic retention times (HRT) of 2 days for R1 and 4 days for R2 at mean sewage temperature of 24 degrees C. The sewage was characterised by a high COD(tot) concentration of 1189 mg/L, with a large fraction of COD(sus), viz. 54%. The achieved removal efficiencies in R1 and R2 for COD(tot), COD(sus), BOD5 and TSS were "56%, 87%, 59% and 81%" and "58%, 90%, 60% and 82%" for both systems, respectively. R2 achieved a marginal but significant (p<0.05) better removal efficiencies of those parameters as compared to R1. The COD(col) and COD(dis) removals in R1 and R2 were respectively 31% and 20%, and 34% and 22%. The sludge accumulation was very low suggesting that the desludging frequency will be of several years. Accordingly, the reactor can be adequately designed at 2 days HRT.

  9. Strong-motion characteristics and source process during the Suruga Bay earthquake in 2009 through observed records on rock sites

    International Nuclear Information System (INIS)

    Shiba, Yoshiaki; Sato, Hiroaki; Kuriyama, Masayuki

    2010-01-01

    On 11 August 2009, a moderate earthquake of M 6.5 occurred in the Suruga Bay region, south of Shizuoka prefecture. During this event, JMA Seismic Intensity reached 6 lower in several cities around the hypocenter, and at Hamaoka nuclear power plant of Chubu Electric Power reactors were automatically shutdown due to large ground motions. Though the epicenter is located at the eastern edge of source area for the assumed great Tokai earthquake of M 8, this event is classified into the intra-plate (intra-slab) earthquake, due to its focal depth lower than that of the plate boundary and fault geometry supposed from the moment tensor solution. Dense strong-motion observation network has been deployed mainly on the rock outcrops by our institute around the source area, and the waveform data of the main shock and several aftershocks were obtained at 13 stations within 100 km from the hypocenter. The observed peak ground motions and velocity response spectral amplitudes are both obviously larger than the empirical attenuation relations derived from the inland and plate-boundary earthquake data, which displays the characteristics of the intra-slab earthquake faulting. Estimated acceleration source spectra of the main shock also exhibit the short period level about 1.7 times larger than the average of those for past events, and it corresponds with the additional term in the attenuation curve of the peak ground acceleration for the intra-plate earthquake. Detailed source process of the main shock is inferred using the inversion technique. The initial source model is assumed to be composed of two distinct fault planes according to the minute aftershock distribution. Estimated source model shows that large slip occurred near the hypocenter and at the boundary region between two fault planes where the rupture transfers from primary to secondary fault. Furthermore the broadband source inversion using velocity motions in the frequency up to 5 Hz demonstrates the high effective

  10. Physical and Chemical Aerosol Properties At An Urban and A Rural Site During An Episode of Strong Photochemical Activity During Escompte

    Science.gov (United States)

    van Dingenen, R.; Putaud, J. P.; dell'Acqua, A.; Martins-Dos Santos, S.; Viidanoja, J.; Raes, F.

    During the ESCOMPTE campaign (10 June to 14 July, 2001), JRC mobile laboratories for aerosol physical and chemical measurements were deployed at two ground-based sites: Vallon Dol, located at the Northern edge of the Marseille agglomeration and Vi- non, a rural site about 80 km North-East of Marseille. Both sites were equipped with on-line instrumentation for number size distributions in the diameter size range 6nm to 10µm (10 minute time resolution), equivalent black carbon (15 minute time reso- lution), major anions and cations (15 minute time resolution). Time-integrated filter sampling at each site with a time resolution of 6-12 hours was performed with 2 sets of virtual impactors, separating the fine and coarse aerosol fraction. One set, loaded with quartz filters, was analyzed off-line using the `evolved gas analysis` technique for organic and elemental carbon. The second set, loaded with paper filters, was analyzed for dust (by ashing) and ionic composition. On top of the common instrumentation, the urban site was additionally performing on-line PM10 measurements (TEOM with sample equilibration system, 10 minute time resolution) and, during intensive obser- vation periods (IOP), size-segregated sampling with a 8 stage low-pressure Berner im- pactor (6-12 hours time resolution). In this presentation we will focus on data obtained during the second IOP (20-6 to 26-6). During this episode, the sea-breeze transported Marseille pollution plume was clearly observed at the Vinon rural site. Comparison of the aerosol properties at both sites will allow to evaluate the processes that contribute to the (trans)formation of particulate matter in the particular conditions of a marine air mass, mixed with local pollution and undergoing strong photochemical processes during in-land transport.

  11. The influence of carrier gas flow rate in inverse gas chromatography on the estimation of water vapor adsorption on Nylon-6 micro fiber

    OpenAIRE

    丸井, 正樹; 山本, 直子; 牛腸, ヒロミ; マルイ, マサキ; ヤマモト, ナオコ; ゴチョウ, ヒロミ; MASAKI, MARUI; NAOKO, YAMAMOTO; HIROMI, GOCHO

    2002-01-01

    The adsorption behaviors of water vapor on Nylon-6 micro fiber are measured at 90℃ with inverse gas chromatography, of which the carrier gas flow rates are 10~40ml/min. The values of retention volume decrease when the peak area is on the increase. lt indicates that Nylon-6 micro fiber has strong adsorption of water vapor at low vapor pressure. The adsorption isotherm as a whole is found to be of BET II type with certain number of adsorption sites. The gas flow rate has no effect on the estima...

  12. Computational study of ethanol adsorption and reaction over rutile TiO2 (110) surfaces

    KAUST Repository

    Muir, J. N.

    2012-01-01

    Studies of the modes of adsorption and the associated changes in electronic structures of renewable organic compounds are needed in order to understand the fundamentals behind surface reactions of catalysts for future energies. Using planewave density functional theory (DFT) calculations, the adsorption of ethanol on perfect and O-defected TiO 2 rutile (110) surfaces was examined. On both surfaces the dissociative adsorption mode on five-fold coordinated Ti cations (Ti 4+ 5c) was found to be more favourable than the molecular adsorption mode. On the stoichiometric surface E ads was found to be equal to 0.85 eV for the ethoxide mode and equal to 0.76 eV for the molecular mode. These energies slightly increased when adsorption occurred on the Ti 4+ 5c closest to the O-defected site. However, both considerably increased when adsorption occurred at the removed bridging surface O; interacting with Ti 3+ cations. In this case the dissociative adsorption becomes strongly favoured (E ads = 1.28 eV for molecular adsorption and 2.27 eV for dissociative adsorption). Geometry and electronic structures of adsorbed ethanol were analysed in detail on the stoichiometric surface. Ethanol does not undergo major changes in its structure upon adsorption with its C-O bond rotating nearly freely on the surface. Bonding to surface Ti atoms is a σ type transfer from the O2p of the ethanol-ethoxide species. Both ethanol and ethoxide present potential hole traps on O lone pairs. Charge density and work function analyses also suggest charge transfer from the adsorbate to the surface, in which the dissociative adsorptions show a larger charge transfer than the molecular adsorption mode. This journal is © 2012 the Owner Societies.

  13. Numerical evaluation of Cs adsorption in PB column by extended Langmuir formula and one-dimensional adsorption model

    International Nuclear Information System (INIS)

    Hiroshi Ogawa; Akiko Kitajima; Hisashi Tanaka; Tohru Kawamoto

    2015-01-01

    Adsorption property of granulated Prussian blue adsorbent on radioactive cesium was evaluated for efficient decontamination in Fukushima area. The adsorbent was found to show an inflective adsorption isotherm, which was expressed by extended Langmuir formula with three adsorption sites. Adsorption speeds of each site were evaluated by time-dependent batch experiment. The simulation using derived parameters and one-dimensional adsorption model successfully reproduced the experimental data of cesium decontamination by small and large columns. (author)

  14. Growth-induced strong pinning sites in laser ablated YBa2Cu3O7-δ films with a non-random distribution

    International Nuclear Information System (INIS)

    Huijbregtse, J.M.; Klaassen, F.C.; Geest, R.C.F. van der; Dam, B.; Griessen, R.

    1999-01-01

    Recently, the authors showed that natural linear defects are the origin of the high critical currents in laser ablated YGBa 2 Cu 3 O 7-δ films. Combining wet-chemical etching and Atomic Force Microscopy, they find that these dislocations are created by island coalescence during growth. Consequently, the defect density can be reproducibly varied by manipulating the density of growth islands, which in turn depends on the substrate temperature. Interestingly, the radial defect distribution function approaches zero at small distances, indicating short range order. Therefore, they are now able to study vortex matter in films with a tailored non-random distribution of natural strong pinning sites

  15. Rare gases adsorption and separation on silver doped adsorbent

    International Nuclear Information System (INIS)

    Deliere, Ludovic

    2015-01-01

    The Comprehensive Nuclear-Test-Ban Treaty (CTBT) implements means for detecting nuclear tests in an International Monitoring System (IMS). The Commissariat a l'Energie Atomique et aux Energies Alternatives (CEA) has developed in the mid-90's, the SPALAX system (Systeme de Prelevement d'Air en Ligne avec l'Analyse des radioXenons). Xenon analysis, including radioactive isotopes from the fission reaction during the explosion, requires the development of highly efficient process for xenon concentration. In this work, the adsorption and diffusion phenomena of noble gases are studied in silver exchanged ZSM-5 zeolite. The 'experience/Monte Carlo simulation' coupling is used to determine the essential thermodynamic data on the adsorption of noble gases and to characterize the adsorption sites. The presence of a strong adsorption site, identified as silver nanoparticles and intervening at low concentration of noble gases (including xenon and radon) in some silver exchanged zeolites, achieves adsorption and selectivity performance to date unrivaled. These results allow considering their use in many critical applications in the field of capture and separation of rare gases: rare gas industrial production, reprocessing of spent fuel from gas, radon in air pollution control. (author) [fr

  16. Adsorption isotherm special study. Final report

    International Nuclear Information System (INIS)

    1993-05-01

    The study was designed to identify methods to determine adsorption applicable to Uranium Mill Tailings Remedial Action (UMTRA) Project sites, and to determine how changes in aquifer conditions affect metal adsorption, resulting retardation factors, and estimated contaminant migration rates. EPA and ASTM procedures were used to estimate sediment sorption of U, As, and Mo under varying groundwater geochemical conditions. Aquifer matrix materials from three distinct locations at the DOE UMTRA Project site in Rifle, CO, were used as the adsorbents under different pH conditions; these conditions stimulated geochemical environments under the tailings, near the tailings, and downgradient from the tailings. Grain size, total surface area, bulk and clay mineralogy, and petrography of the sediments were characterized. U and Mo yielded linear isotherms, while As had nonlinear ones. U and Mo were adsorbed strongly on sediments acidified to levels similar to tailings leachate. Changes in pH had much less effect on As adsorption. Mo was adsorbed very little at pH 7-7.3, U was weakly sorbed, and As was moderately sorbed. Velocities were estimated for metal transport at different pHs. Results show that the aquifer materials must be characterized to estimate metal transport velocities in aquifers and to develop groundwater restoration strategies for the UMTRA project

  17. On the Adsorption of DNA Origami Nanostructures in Nanohole Arrays.

    Science.gov (United States)

    Brassat, Katharina; Ramakrishnan, Saminathan; Bürger, Julius; Hanke, Marcel; Doostdar, Mahnaz; Lindner, Jörg K N; Grundmeier, Guido; Keller, Adrian

    2018-05-22

    DNA origami nanostructures are versatile substrates for the controlled arrangement of molecular capture sites with nanometer precision and thus have many promising applications in single-molecule bioanalysis. Here, we investigate the adsorption of DNA origami nanostructures in nanohole arrays which represent an important class of biosensors and may benefit from the incorporation of DNA origami-based molecular probes. Nanoholes with well-defined diameter that enable the adsorption of single DNA origami triangles are fabricated in Au films on Si wafers by nanosphere lithography. The efficiency of directed DNA origami adsorption on the exposed SiO 2 areas at the bottoms of the nanoholes is evaluated in dependence of various parameters, i.e., Mg 2+ and DNA origami concentrations, buffer strength, adsorption time, and nanohole diameter. We observe that the buffer strength has a surprisingly strong effect on DNA origami adsorption in the nanoholes and that multiple DNA origami triangles with 120 nm edge length can adsorb in nanoholes as small as 120 nm in diameter. We attribute the latter observation to the low lateral mobility of once adsorbed DNA origami on the SiO 2 surface, in combination with parasitic adsorption to the Au film. Although parasitic adsorption can be suppressed by modifying the Au film with a hydrophobic self-assembled monolayer, the limited surface mobility of the adsorbed DNA origami still leads to poor localization accuracy in the nanoholes and results in many DNA origami crossing the boundary to the Au film even under optimized conditions. We discuss possible ways to minimize this effect by varying the composition of the adsorption buffer, employing different fabrication conditions, or using other substrate materials for nanohole array fabrication.

  18. Sorption of BTX mixtures to contaminated and uncontaminated site soils

    International Nuclear Information System (INIS)

    Uchrin, C.G.; Koshy, K.; Wojtenko, I.

    1995-01-01

    Both adsorption and desorption studies are being performed examining benzene, toluene, and meta-xylene (BTX) as single components, binary mixtures, and trinary mixture onto both existing contaminated soils as well as some uncontaminated reference soils. The contaminated soils were obtained from an oil refinery site and another industrial site in New Jersey. The oil refinery site soil did not exhibit significant amounts of either benzene, toluene or xylene but was contaminated with other compounds while the other industrial site soil was contaminated with toluene among other compounds. The organic carbon content of the soils ranged from 0.14 to 2.91 percent. Preliminary adsorption studies showed BTX to strongly sorb to these soils. The adsorption studies onto the reference soils also demonstrated the effect of organic matter on adsorption. Sequential batch desorption studies show the BTX to desorb quickly, reaching equilibrium within 48 hours. Long-term uptake and release were not noted with these soil/contaminant systems

  19. Adsorption of carbon monoxide on Ag(I)-ZSM-5 zeolite: An ab initio density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Qiu Zhenzhen [College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China); Yu Yangxin, E-mail: yangxyu@mail.tsinghua.edu.cn [Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China); Mi Jianguo [College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

    2012-10-01

    Highlights: Black-Right-Pointing-Pointer Significant difference in adsorption energy is found for CO adsorbed on different Ag{sup +}-exchange sites. Black-Right-Pointing-Pointer Energetically stable sites in Ag-ZSM-5 are found. Black-Right-Pointing-Pointer Introduction of the two Al atoms to the site of Ag-ZSM-5 results in a reduction of CO adsorption energy. Black-Right-Pointing-Pointer Comparison of CO adsorption energy on the corresponding charge-exchange sites of Ag-ZSM-5 and Cu-ZSM-5 is made. - Abstract: Adsorption of carbon monoxide on different Ag{sup +}-exchange sites of Ag-ZSM-5 zeolite has been investigated using density functional theory. The coordination and local geometry of the Ag{sup +} ion in Ag-ZSM-5 as well as adsorption structures and energies of CO adsorbed on these sites are explored extensively. The structure of Ag{sup +}-exchange sites, location of the Al atom on the T site, and number of the Al atoms contained in the sites are considered in the theoretical calculations. The calculated results show that the Ag-O coordination number of two is strongly preferred before and after CO adsorption. The Ag-O bond lengths are in a broad range of 2.2-2.9 Angstrom-Sign , and the Ag-C bond lengths for CO adsorbed on Ag-ZSM-5 zeolite are calculated to be 2.0-2.2 Angstrom-Sign . Both Ag-O and Ag-C bond lengths for CO-Ag-ZSM-5 complex are longer than those for CO-Cu-ZSM-5 complex. The calculated adsorption energy of CO adsorbed on the I2 sites is between 28.5 and 29.6 kcal/mol, and that on the Z5, Z6, M5 and M6 sites containing one Al atom on the T position is between 11.3 and 18.9 kcal/mol whereas the calculated adsorption energy of CO adsorbed on the M7 site containing one Al atom is 19.9 kcal/mol. The introduction of the two Al atoms to the Ag{sup +}-exchange site results in a reduction of CO adsorption energy. In general, the adsorption energy of CO on Ag-ZSM-5 is lower than that on Cu-ZSM-5. The predicted coordination of the Ag{sup +} ion, bond lengths

  20. Hydrogen sulfide adsorption on activated carbon fiber. Tests on Parisian subway; Elimination du sulfure d'hydrogene par adsorption sur tissu de charbon actif. Essais sur site RATP

    Energy Technology Data Exchange (ETDEWEB)

    Bouzaza, A.; Marsteau, St.; Laplanche, A. [Ecole Nationale Superieure de Chimie, Lab. Chimie des Nuissances et Genie de l' Environnement - CNGE, 35 - Rennes (France); Garrot, B. [RATP, Dept. Environnement et Securite-Domaines d' Expertises de l' Environnement-Entite Qualite de l' Air, 75 - Paris (France)

    2003-06-01

    Hydrogen sulfide has an unpleasant odor and may cause damage to the electrical materials of the Parisian subway. The activated carbon has some intrinsic catalytic activity, so the removal of hydrogen sulfide is due to an adsorption-oxidation process. In a laboratory scale, some kinetic parameters were acquired, which allowed us to build up two dynamic reactors. These continuous reactors, equipped with activated carbon fibers, were tested on the Madeleine station of the Parisian subway. The feasibility of the elimination of H{sub 2}S by continuous adsorption-oxidation was confirmed. The relative humidity of the gas phase was found to play an important role in the performance of the elimination. The durability of the pilot tested was compatible with an industrial exploitation of the process. (authors)

  1. Theoretical insights into acetylene adsorption on nanoporous gold surfaces: Role of residual silver

    Science.gov (United States)

    Luo, Yafei; Chen, Zhongzhu; Xu, Zhigang; Yang, Donglin; Zhang, Jin; Tang, Dianyong

    2018-03-01

    Unveiling the acetylene adsorption is crucial for designing novel and highly active catalyst for the semihydrogenation of alkyne. In order to achieve this goal, we have studied C2H2 adsorption on the various nanoporous gold models in detail, including the Au(100), Au(111) and Au(321) slab models. The calculated results indicate that the C atoms of C2H2 experience rehybridization from sp toward sp2/sp3 when the adsorption occurs on bridge and hollow sites, which can be illustrated via the projected density of state (PDOS) and crystal orbital Hamilton population (COHP). Meanwhile, the formation of σ(Ausbnd C) bond is beneficial for facilitating acetylene adsorption and the kink Au atom plays an important role for the C2H2 adsorption. In addition, for C2H2 adsorption on the Ag doped nanoporous gold, the configurations strongly depend on the position of superficial unsubstituted Au atoms. Further, the inversely relationship has been found between the adsorption energies and number of the Ag substituents, demonstrating that the superficial Ag substituents are harmful for C2H2 adsorption and activation.

  2. Efficient adsorptive removal of Congo red from aqueous solution by synthesized zeolitic imidazolate framework-8

    Directory of Open Access Journals (Sweden)

    Canlan Jiang

    2016-10-01

    Full Text Available Dyes exposure in aquatic environment creates risks to human health and biota due to their intrinsic toxic mutagenic and carcinogenic characteristics. In this work, a metal-organic frameworks materials, zeolitic imidazolate framework-8 (ZIF-8, was synthesized through hydrothermal reaction for the adsorptive removal of harmful Congo red (CR from aqueous solution. Results showed that the maximum adsorption capacity of CR onto ZIF-8 was ultrahigh as 1250 mg g−1. Adsorption behaviors can be successfully fitted by the pseudo-second order kinetic model and the Langmuir isotherm equation. Solution conditions (pH condition and the co-exist anions may influent the adsorption behaviors. The adsorption performance at various temperatures indicated the process was a spontaneous and endothermic adsorption reaction. The enhanced adsorption capacity was determined due to large surface area of ZIF-8 and the strong interactions between surface groups of ZIF-8 and CR molecules including the electrostatic interaction between external active sites Zn−OH on ZIF-8 -and −SO3 or –N=N– sites in CR molecule, and the π–π interaction.

  3. The effect of high ionic strength on neptunium (V) adsorption to a halophilic bacterium

    Science.gov (United States)

    Ams, David A.; Swanson, Juliet S.; Szymanowski, Jennifer E. S.; Fein, Jeremy B.; Richmann, Michael; Reed, Donald T.

    2013-06-01

    The mobility of neptunium (V) in subsurface high ionic strength aqueous systems may be strongly influenced by adsorption to the cell wall of the halophilic bacteria Chromohalobacter sp. This study is the first to evaluate the adsorption of neptunium (V) to the surface of a halophilic bacterium as a function of pH from approximately 2 to 10 and at ionic strengths of 2 and 4 M. This is also the first study to evaluate the effects of carbonate complexation with neptunium (V) on adsorption to whole bacterial cells under high pH conditions. A thermodynamically-based surface complexation model was adapted to describe experimental adsorption data under high ionic strength conditions where traditional corrections for aqueous ion activity are invalid. Adsorption of neptunium (V) was rapid and reversible under the conditions of the study. Adsorption was significant over the entire pH range evaluated for both ionic strength conditions and was shown to be dependent on the speciation of the sites on the bacterial surface and neptunium (V) in solution. Adsorption behavior was controlled by the relatively strong electrostatic attraction of the positively charged neptunyl ion to the negatively charged bacterial surface at pH below circum-neutral. At pH above circum-neutral, the adsorption behavior was controlled by the presence of negatively charged neptunium (V) carbonate complexes resulting in decreased adsorption, although adsorption was still significant due to the adsorption of negatively charged neptunyl-carbonate species. Adsorption in 4 M NaClO4 was enhanced relative to adsorption in 2 M NaClO4 over the majority of the pH range evaluated, likely due to the effect of increasing aqueous ion activity at high ionic strength. The protonation/deprotonation characteristics of the cell wall of Chromohalobacter sp. were evaluated by potentiometric titrations in 2 and 4 M NaClO4. Bacterial titration results indicated that Chromohalobacter sp. exhibits similar proton buffering

  4. Adsorption behaviors of thiophene, benzene, and cyclohexene on FAU zeolites: Comparison of CeY obtained by liquid-, and solid-state ion exchange

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Yucai [College of Chemistry and Chemical Engineering, China University of Petroleum (East China), Qingdao 266555, Shandong (China); Key Laboratory of Petrochemical Catalytic Science and Technology, Liaoning Province, Liaoning Shihua University, Fushun 113001, Liaoning (China); Mo, Zhousheng; Yu, Wenguang; Dong, Shiwei; Duan, Linhai [College of Chemistry and Chemical Engineering, China University of Petroleum (East China), Qingdao 266555, Shandong (China); Gao, Xionghou, E-mail: gaoxionghou@petrochina.com.cn [Petrochemical Research Institute, PetroChina Company Limited, 9 Dongzhimen North Street, Dongcheng District, Beijing 100007 (China); Song, Lijuan, E-mail: lsong56@263.net [College of Chemistry and Chemical Engineering, China University of Petroleum (East China), Qingdao 266555, Shandong (China); Key Laboratory of Petrochemical Catalytic Science and Technology, Liaoning Province, Liaoning Shihua University, Fushun 113001, Liaoning (China)

    2014-02-15

    Cerium containing Y zeolites were prepared by liquid- (L-CeY) and solid- (S-CeY) state ion exchange from NaY and HY, respectively. The structural and textural properties were characterized by XRD and N{sub 2} adsorption, and acidity properties were characterized by NH{sub 3} temperature-programmed desorption (NH{sub 3}-TPD) and in situ FTIR spectrum of chemisorbed pyridine (in situ Py-FTIR). Furthermore, the single component adsorption and multi-component competitive adsorption behavior of thiophene, benzene and cyclohexene on those zeolites have also been studied by using vapor adsorption isotherms, solution adsorption breakthrough curves, thermogravimetry and derivative thermogravimetry (TG/DTG), frequency response (FR) and in situ FTIR techniques. The results indicate that the primary adsorption mode of benzene is simply micropore filling process, but the nature of effect of aromatics on selective adsorption of thiophene is competitive adsorption. The strong chemical adsorptions and protonization reactions of thiophene and cyclohexene occur upon the Brönsted acid sites of the HY and L-CeY zeolites, and the preferable acid catalytic protonization reactions of olefins hinder the further adsorption of sulfur compounds.

  5. Limited mobility of dioxins near San Jacinto super fund site (waste pit) in the Houston Ship Channel, Texas due to strong sediment sorption.

    Science.gov (United States)

    Louchouarn, Patrick; Seward, Shaya M; Cornelissen, Gerard; Arp, Hans Peter H; Yeager, Kevin M; Brinkmeyer, Robin; Santschi, Peter H

    2018-02-20

    Sediments from a waste pit in Houston Ship Channel (HSC) were characterized using a number of molecular markers of natural organic matter fractions (e.g., pyrogenic carbon residues, PAHs, lignins), in addition to dioxins, in order to test the hypothesis that the dispersal and mobility of dioxins from the waste pit in the San Jacinto River is minimal. Station SG-6, sampled at the site of the submerged waste pit, had the highest dioxin/furan concentrations reported for the Houston Ship Channel/Galveston Bay (HSC/GB) system (10,000-46,000 pg/g), which translated into some of the highest reported World Health Organization Toxic Equivalents (TEQs: 2000-11,000 pg/g) in HSC sediments. Using a multi-tracer approach, this study confirmed our hypothesis that sludges from chlorinated pulps are a very likely source of dioxins/furans to this pit. However, this material also contained large quantities of additional hydrophobic organic contaminants (PAHs) and pyrogenic markers (soot-BC, levoglucosan), pointing to the co-occurrence of petroleum hydrocarbons and combustion byproducts. Comparison of dioxin/furan signatures in the waste pit with those from sediments of the HSC and a control site suggests that the remobilization of contaminated particles did not occur beyond the close vicinity of the pit itself. The dioxins/furans in sediments outside the waste pit within the HSC are rather from other diffuse inputs, entering the sedimentary environment through the air and water, and which are comprised of a mixture of industrial and municipal sources. Fingerprinting of waste pit dioxins indicates that their composition is typical of pulp and paper sources. Measured pore water concentrations were 1 order of magnitude lower than estimated values, calculated from a multiphase sorption model, indicating low mobility of dioxins within the waste pit. This is likely accomplished by co-occurring and strong sorbing pyrogenic and petrogenic residues in the waste pit, which tend to keep

  6. Theoretical insights into the uranyl adsorption behavior on vanadium carbide MXene

    Science.gov (United States)

    Zhang, Yu-Juan; Zhou, Zhang-Jian; Lan, Jian-Hui; Ge, Chang-Chun; Chai, Zhi-Fang; Zhang, Peihong; Shi, Wei-Qun

    2017-12-01

    Remediation of the contamination by long-lived actinide wastes is extremely important but also challenging. Adsorption based techniques have attracted much research attention for their potential as low-cost and effective methods to reduce the radioactive waste from solution. In this work, we have investigated the adsorption behavior of uranyl species [with the general form UO2(L1)x(L2)y(L3)z, where L1, L2 and L3 stand for ligands H2O, OH and CO3, respectively] on hydroxylated vanadium carbide V2C(OH)2 MXene nanosheets using density functional theory based simulation methods We find that all studied uranyl species can stably bond to hydroxylated MXene with binding energies ranging from -3.3 to -4.6 eV, suggesting that MXenes could be effective adsorbers for uranyl ions. The strong adsorption is achieved by forming two Usbnd O bonds with the hydroxylated Mxene. In addition, the axial oxygen atoms from the uranyl ions form hydrogen bonds with the hydroxylated V2C, further strengthening the adsorption. We have also investigated the effects of F termination on the uranyl adsorption properties of V2C nanosheets. Usbnd F bonds are in general weaker than Usbnd O bonds on the adsorption site, suggesting that F terminated Mexne is less favorable for uranyl adsorption applications.

  7. First principles study of NH3 molecular adsorption on LiH (100) surfaces

    International Nuclear Information System (INIS)

    Lu Xiaoxia; Chen Yuhong; Dong Xiao

    2012-01-01

    The adsorption of NH 3 on LiH (100) crystal surfaces was studied by first principles method. The preferred adsorption sites, adsorption energy, dissociation energy and electronic structure of the LiH (100)/NH 3 systems were calculated separately. It is found that chemical adsorption happened mainly when NH 3 molecules are on the LiH (100) crystal surfaces. When NH 3 is adsorbed on the Li top site, NH 2 is formed on the LiH (100) crystal surfaces after loss of H atom, the calculated adsorption energy, 0.511 eV, belongs to strong chemical adsorption, then the interaction is strongest. The interaction between NH 2 and the neighboring Li, H are ionic. The covalent bonds are formed between N and H atoms in NH 2 . One H 2 molecule is formed by another H atom in NH 3 and H atom from LiH (100) crystal sur- faces. The covalent bonds are formed between H and H atoms in H 2 . (authors)

  8. Seismic Intensity Map Triggered by Observed Strong Motion Records Considering Site Amplification and its service based on Geo-spatial International Standard

    International Nuclear Information System (INIS)

    Matsuoka, Masashi

    2014-01-01

    Instrumental seismic intensity measurement is carried out at approximately 4,200 points in Japan, but the correct values at points without seismometers cannot always be provided because seismic motion depends on geologic and geomorphologic features. Quick provision of accurate information on seismic intensity distribution over wide areas is required for disaster mitigation. To estimate seismic intensity at specific points, it is important to prepare ground amplification characteristics for local areas beforehand and use an interpolation algorithm. The QuiQuake system (quick estimation system for earthquake maps triggered by using observation records from K-NET and KiK-net that have been released by the National Research Institute for Earth Science and Disaster Prevention), which uses these, was developed; it can be started up automatically using seismograms and can immediately display a seismic intensity distribution map. The calculation results are sent to IAEA and JNES in the form of strong motion evaluation maps with a mesh size of 250 x 250 m. These maps are also sent to the general public via social networking web sites. (author)

  9. An unsaturated metal site-promoted approach to construct strongly coupled noble metal/HNb3O8 nanosheets for efficient thermo/photo-catalytic reduction.

    Science.gov (United States)

    Shen, Lijuan; Xia, Yuzhou; Lin, Sen; Liang, Shijing; Wu, Ling

    2017-10-05

    Creating two-dimensional (2D) crystal-metal heterostructures with an ultrathin thickness has spurred increasing research endeavors in catalysis because of its fascinating opportunities in tuning the electronic state at the surface and enhancing the chemical reactivity. Here we report a novel and facile Nb 4+ -assisted strategy for the in situ growth of highly dispersed Pd nanoparticles (NPs) on monolayer HNb 3 O 8 nanosheets (HNb 3 O 8 NS) constituting a 2D Pd/HNb 3 O 8 NS heterostructure composite without using extra reducing agents and stabilizing agents. The Pd NP formation is directed via a redox reaction between an oxidative Pd salt precursor (H 2 PdCl 4 ) and reductive unsaturated surface metal (Nb 4+ ) sites induced by light irradiation on monolayer HNb 3 O 8 NS. The periodic arrangement of metal Nb nodes on HNb 3 O 8 NS leads to a homogeneous distribution of Pd NPs. Density functional theory (DFT) calculations reveal that the direct redox reaction between the Nb 4+ and Pd 2+ ions leads to a strong chemical interaction between the formed Pd metal NPs and the monolayer HNb 3 O 8 support. Consequently, the as-obtained Pd/HNb 3 O 8 composite serves as a highly efficient bifunctional catalyst in both heterogeneous thermocatalytic and photocatalytic selective reduction of aromatic nitro compounds in water under ambient conditions. The achieved high activity originates from the unique 2D nanosheet configuration and in situ Pd incorporation, which leads to a large active surface area, strong metal-support interaction and enhanced charge transport capability. Moreover, this facile Nb 4+ -assisted synthetic route has demonstrated to be general, which can be applied to load other metals such as Au and Pt on monolayer HNb 3 O 8 NS. It is anticipated that this work can extend the facile preparation of noble metal/nanosheet 2D heterostructures, as well as promote the simultaneous capture of duple renewable thermal and photon energy sources to drive an energy efficient

  10. Competitive adsorption-desorption reactions of two hazardous heavy metals in contaminated soils.

    Science.gov (United States)

    Davari, Masoud; Rahnemaie, Rasoul; Homaee, Mehdi

    2015-09-01

    Investigating the interactions of heavy metals is imperative for sustaining environment and human health. Among those, Cd is toxic for organisms at any concentration. While Ni acts as a micronutrient at very low concentration but is hazardous toxic above certain threshold value. In this study, the chemical adsorption and desorption reactions of Ni and Cd in contaminated soils were investigated in both single and binary ion systems. Both Ni and Cd experimental data demonstrated Langmuir type adsorption. In the competitive systems, an antagonistic effect was observed, implying that both ions compete for same type of adsorption sites. Adverse effect of Cd on Ni adsorption was slightly stronger than that of opposite system, consistent with adsorption isotherms in single ion systems. Variation in ionic strength indicated that Ca, a much weaker adsorbate, could also compete with Cd and Ni for adsorption on soil particles. Desorption data indicated that Cd and Ni are adsorbed very tightly such that after four successive desorption steps, less than 0.5 % of initially adsorbed ions released into the soil solution. This implies that Ca, at concentration in equilibrium with calcite mineral, cannot adequately compete with and replace adsorbed Ni and Cd ions. This adsorption behavior was led to considerable hysteresis between adsorption and desorption in both single and binary ion systems. In the binary ion systems, desorption of Cd and Ni was increased by increase in both equilibrium concentration of adsorbed ion and concentration of competitor ion. The overall results obtained in this research indicate that Cd and Ni are strongly adsorbed in calcareous soil and Ca, the major dissolved ion, insignificantly influences metal ions adsorption. Consequently, the contaminated soils by Ni and Cd can simultaneously be remediated by environmentally oriented technologies such as phytoremediation.

  11. Adsorption of phenolic compound by aged-refuse

    Energy Technology Data Exchange (ETDEWEB)

    Chai Xiaoli [State Key Laboratory of Pollution Control and Resource Reuse, School of Enviromental Science and Engineering, Tongji University, Siping Road 1239, Shanghai 200092 (China)]. E-mail: xlchai@mail.tongji.edu.cn; Zhao Youcai [State Key Laboratory of Pollution Control and Resource Reuse, School of Enviromental Science and Engineering, Tongji University, Siping Road 1239, Shanghai 200092 (China)

    2006-09-01

    The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic.

  12. Adsorption of phenolic compound by aged-refuse

    International Nuclear Information System (INIS)

    Chai Xiaoli; Zhao Youcai

    2006-01-01

    The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic

  13. Detailed characterization and preliminary adsorption model for materials for an intermediate-scale reactive-transport experiment

    International Nuclear Information System (INIS)

    Ward, D.B.; Bryan, C.R.

    1994-01-01

    An experiment involving migration of fluid and tracers (Li, Br, Ni) through a 6-m-high x 3-m-dia caisson Wedron 510 sand, is being carried out for Yucca Mountain Site Characterization Project. Sand's surface chemistry of the sand was studied and a preliminary surface-complexation model of Ni adsorption formulated for transport calculations. XPS and leaching suggest that surface of the quartz sand is partially covered by thin layers of Fe-oxyhydroxide and Ca-Mg carbonate and by flakes of kaolinite. Ni adsorption by the sand is strongly pH-dependent, showing no adsorption at pH 5 and near-total adsorption at pH 7. Location of adsorption edge is independent of ionic strength and dissolved Ni concentration; it is shifted to slightly lower pH with higher pCO2 and to slightly higher pH by competition with Li. Diminished adsorption at alkiline pH with higher pCO2 implies formation of dissolved Ni-carbonato complexes. Ni adsorption edges for goethite and quartz, two components of the sand were also measured. Ni adsorption on pure quartz is only moderately pH-dependent and differs in shape and location from that of the sand, whereas Ni adsorption by goethite is strongly pH-dependent. A triple-layer surface-complexation model developed for goethite provides a good fit to the Ni-adsorption curve of the sand. Based on this model, the apparent surface area of the Fe-oxyhydroxide coating is estimated to be 560 m 2 /g, compatible with its occurrence as amorphous Fe-oxyhydroxide. Potentiometric titrations on sand also differ from pure quartz and suggest that effective surface area of sand may be much greater than that measured by N 2 -BET gas adsorption. Attempts to model the adsorption of bulk sand in terms of properties of pure end member components suggest that much of the sand surface is inert. Although the exact Ni adsorption mechanisms remain ambiguous, this preliminary adsorption model provides an initial set of parameters that can be used in transport calculations

  14. Thorough removal of inorganic and organic mercury from aqueous solutions by adsorption on Lemna minor powder

    Energy Technology Data Exchange (ETDEWEB)

    Li Shunxing, E-mail: lishunxing@fjzs.edu.cn [Department of Chemistry, Zhangzhou Normal University, Zhangzhou 363000 (China); Fujian Province University Key Laboratory of Analytical Science, Zhangzhou Normal University, Zhangzhou (China); Zheng Fengying; Huang Yang [Department of Chemistry, Zhangzhou Normal University, Zhangzhou 363000 (China); Fujian Province University Key Laboratory of Analytical Science, Zhangzhou Normal University, Zhangzhou (China); Ni Jiancong [Department of Chemistry, Zhangzhou Normal University, Zhangzhou 363000 (China)

    2011-02-15

    The adsorption ability of duckweed (Lemna minor) powders for removing inorganic and organic mercury (methyl and ethyl mercury) has been studied using cold vapour atomic absorption spectrometry. The optimal adsorption conditions were: (a) the pH value of the solution 7.0 for inorganic and ethyl mercury, 9.0 for methyl mercury, and (b) equilibrium adsorption time 10, 20, and 40 min for inorganic mercury, methyl mercury, and ethyl mercury, respectively. After adsorption by L. minor powder for 40 min, when the initial concentrations of inorganic and organic mercury were under 12.0 {mu}g L{sup -1} and 50.0 {mu}g L{sup -1}, respectively, the residual concentrations of mercury could meet the criterion of drinking water (1.0 {mu}g L{sup -1}) and the permitted discharge limit of wastewater (10.0 {mu}g L{sup -1}) set by China and USEPA, respectively. Thorough removal of both inorganic and organic mercury from aqueous solutions was reported for the first time. The significant adsorption sites were C-O-P and phosphate groups by the surface electrostatic interactions with aqueous inorganic and organic mercury cations, and then the selective adsorption was resulted from the strong chelating interaction between amine groups and mercury on the surface of L. minor cells.

  15. Thorough removal of inorganic and organic mercury from aqueous solutions by adsorption on Lemna minor powder

    International Nuclear Information System (INIS)

    Li Shunxing; Zheng Fengying; Huang Yang; Ni Jiancong

    2011-01-01

    The adsorption ability of duckweed (Lemna minor) powders for removing inorganic and organic mercury (methyl and ethyl mercury) has been studied using cold vapour atomic absorption spectrometry. The optimal adsorption conditions were: (a) the pH value of the solution 7.0 for inorganic and ethyl mercury, 9.0 for methyl mercury, and (b) equilibrium adsorption time 10, 20, and 40 min for inorganic mercury, methyl mercury, and ethyl mercury, respectively. After adsorption by L. minor powder for 40 min, when the initial concentrations of inorganic and organic mercury were under 12.0 μg L -1 and 50.0 μg L -1 , respectively, the residual concentrations of mercury could meet the criterion of drinking water (1.0 μg L -1 ) and the permitted discharge limit of wastewater (10.0 μg L -1 ) set by China and USEPA, respectively. Thorough removal of both inorganic and organic mercury from aqueous solutions was reported for the first time. The significant adsorption sites were C-O-P and phosphate groups by the surface electrostatic interactions with aqueous inorganic and organic mercury cations, and then the selective adsorption was resulted from the strong chelating interaction between amine groups and mercury on the surface of L. minor cells.

  16. Physisorption and desorption of H2, HD and D2 on amorphous solid water ice. Effect on mixing isotopologue on statistical population of adsorption sites.

    Science.gov (United States)

    Amiaud, Lionel; Fillion, Jean-Hugues; Dulieu, François; Momeni, Anouchah; Lemaire, Jean-Louis

    2015-11-28

    We study the adsorption and desorption of three isotopologues of molecular hydrogen mixed on 10 ML of porous amorphous water ice (ASW) deposited at 10 K. Thermally programmed desorption (TPD) of H2, D2 and HD adsorbed at 10 K have been performed with different mixings. Various coverages of H2, HD and D2 have been explored and a model taking into account all species adsorbed on the surface is presented in detail. The model we propose allows to extract the parameters required to fully reproduce the desorption of H2, HD and D2 for various coverages and mixtures in the sub-monolayer regime. The model is based on a statistical description of the process in a grand-canonical ensemble where adsorbed molecules are described following a Fermi-Dirac distribution.

  17. Adsorption studies on Pt(111)

    International Nuclear Information System (INIS)

    Hopster, H.

    1977-06-01

    The adsorption of O 2 , CO, and C 2 H 2 as well as the CO oxidation on Pt(111) were studied by high-resolution electron spectroscopy. Using a platinum monocrystal sample with a contonuous stage density, the adhesion coefficient for O 2 and the reaction probability for CO were determined as a function of stage density and oxygen cover by measuring the oxygen cover and its time behaviour. The study of vibrations of adsorbed CO showed that CO is bound in linear form on two different adsorption sites. The adsorption of acetylene was studied at 140 K and 300 K. The frequencies of the C-H stretching and flexural vibrations as well as the C-C-H bonding angle were determined. (orig./GSC) [de

  18. Adsorption and desorption for dynamics transport of hexavalent chromium Cr(Ⅵ) in soil column

    Science.gov (United States)

    Tong, J.

    2017-12-01

    Batch experiments have been carried out to study the adsorption of heavy metals in soils, and the migration and transformation of hexavalent chromium Cr(Ⅵ) in the soil of a vegetable base were studied by dynamic adsorption and desorption soil column experiments. The aim of this study was to investigate the effect of initial concentration and pH value on the adsorption process of Cr(Ⅵ). Breakthrough curve were used to evaluate the capacity of Cr(Ⅵ) adsorption in soil columns. The results show that the higher the initial concentration, the worse the adsorption capacity of Cr(Ⅵ). The adsorption of Cr(Ⅵ) was strongly sensitive to pH value. The capacity of Cr(Ⅵ) adsorption is maximized at very low pH value. This may be due to changes in pH that cause a series of complex reactions in Cr(Ⅵ). In a strongly acidic environment, the reaction of Cr(Ⅵ) with hydrogen ions is accompanied by the formation of Cr3+, which reacts with the soil free iron-aluminum oxide to produce hydroxide in the soil. The results of the desorption experiments indicate that Cr(Ⅵ) is more likely to leach from this soil, but if the eluent is strong acid solution, the leaching process will be slow and persistent. The program CXTFIT was used to fit the breakthrough curve to estimate parameters. The results of the calculation of the dispersion coefficient (D) can be obtained by this program. The two-site model fit the breakthrough curve data of Cr(Ⅵ) well, and the parameters calculated by CXTFIT can be used to explain the behavior of Cr(Ⅵ) migration and transformation in soil columns. When pH=2, the retardation factor (R) reach at 79.71 while the value of the R is generally around 10 in other experiments. The partitioning coefficient β shows that more than half of the adsorption sites are rate-limited in this adsorption process and non-equilibrium effects the Cr(Ⅵ) transport process in this soil.

  19. A DFT study on benzene adsorption over tungsten sulfides: surface model and adsorption geometries

    NARCIS (Netherlands)

    Koide, R.; Hensen, E.J.M.; Paul, J.F.; Cristol, S.; Payen, E.; Nakamura, H.; Santen, van R.A.

    2007-01-01

    Benzene adsorption on a WS2(100) surface was studied by ab initio periodic DFT computations. Benzene adsorption is facile on the bridge site of the bare W edge via ¿2 or ¿3 coordination. Taking into account the stable configuration at the W edge under typical hydrotreating reaction conditions (623

  20. <strong>Mini-project>

    DEFF Research Database (Denmark)

    Katajainen, Jyrki

    2008-01-01

    In this project the goal is to develop the safe * family of containers for the CPH STL. The containers to be developed should be safer and more reliable than any of the existing implementations. A special focus should be put on strong exception safety since none of the existing prototypes available...

  1. Hydrogen adsorption on and solubility in graphites

    International Nuclear Information System (INIS)

    Kanashenko, S.L.; Wampler, W.R.

    1996-01-01

    The experimental data on adsorption and solubility of hydrogen isotopes in graphite over a wide range of temperatures and pressures are reviewed. Langmuir adsorption isotherms are proposed for the hydrogen-graphite interaction. The entropy and enthalpy of adsorption are estimated, allowing for effects of relaxation of dangling sp 2 bonds. Three kinds of traps are proposed: edge carbon atoms of interstitial loops with an adsorption enthalpy relative to H 2 gas of -4.4 eV/H 2 (unrelaxed, Trap 1), edge carbon atoms at grain surfaces with an adsorption enthalpy of -2.3 eV/H 2 (relaxed, Trap 2), and basal plane adsorption sites with an enthalpy of +2.43 eV/H 2 (Trap 3). The adsorption capacity of different types of graphite depends on the concentration of traps which depends on the crystalline microstructure of the material. The number of potential sites for the 'true solubility' (Trap 3) is assumed to be about one site per carbon atom in all types of graphite, but the endothermic character of this solubility leads to a negligible H inventory compared to the concentration of hydrogen in type 1 and type 2 traps for temperatures and gas pressures used in the experiments. Irradiation with neutrons or carbon atoms increases the concentration of type 1 and type 2 traps from about 20 and 200 appm respectively for unirradiated (POCO AXF-5Q) graphite to about 1500 and 5000 appm, respectively, at damage levels above 1 dpa. (orig.)

  2. Experimental investigation of H2/D2 isotope separation by cryo-adsorption in metal-organic frameworks

    International Nuclear Information System (INIS)

    Teufel, Julia Sonja

    2012-01-01

    Light-gas isotopes differ in their adsorption behavior under cryogenic conditions in nanoporous materials due to their difference in zero-point energy. However, the applicability of these cryo-effects for the separation of isotope mixtures is still lacking an experimental proof. The current work describes the first experimentally obtained H 2 /D 2 selectivity values of nanoporous materials measured by applying isotope mixtures in low-temperature thermal desorption spectroscopy (TDS). The dissertation contains the following key points: 1) A proof of the experimental method, i.e. it is shown that TDS leads to reasonable selectivity values. 2) A series of small-pore MFU-4 derivatives (MOFs) is shown to separate isotope mixtures by quantum sieving, i.e. by the difference in the adsorption kinetics. The influence of the pore size on the selectivity is studied systematically for this series. 3) Two MOFs with pores much larger than the kinetic diameter of H 2 do not exhibit kinetic quantum sieving. However, if the MOFs are exposed to an isotope mixture, deuterium adsorbs preferentially at the adsorption sites with high heats of adsorption. According to the experimental results, these strong adsorption sites can be every selective for deuterium. On the basis of the experimentally obtained selectivity values, technical implementations for H 2 /D 2 light-gas isotope separation by cryo-adsorption are described.

  3. REMOVAL OF U(VI) IN MULTI-COMPONENT SYSTEMS BY ADSORPTION USING ACTIVATED CARBON DERIVED FROM RICE STRAW

    International Nuclear Information System (INIS)

    YAKOUT, S.M.; RIZK, M.A.

    2008-01-01

    The use of low cost activated carbon derived from rice straw has been investigated as a replacement for the current expensive methods for radionuclides removal from wastewater. The adsorption studies were carried out in multi-component systems. The effects of common cations and anions on uranium uptake were investigated. Different cations under investigation showed marginal effect on the adsorption of uranium, except in case of iron ion where the adsorption was significantly depressed by the addition of Fe ion (R % was 20%). Coexistence of iron ions at high levels may compete strongly for the adsorption sites with uranium ions resulting in a substantial reduction of uranium removal. The prepared activated carbon showed good selectivity in uranium extraction even in the presence of large concentrations (100 ppm) of anionic complexing agents and common electrolyte species.The simultaneous presence of both U(VI) / Th(IV) reduced sorption through competition for sorption sites on carbon surface. It is concluded that multi-species adsorption can be significantly affected by adsorbate interactions. Understanding these interactions needs great attention in adsorption study in the future

  4. Application of modified multiwall carbon nanotubes as a sorbent for zirconium (IV) adsorption from aqueous solution

    International Nuclear Information System (INIS)

    Yavari, R.; Davarkhah, R.

    2013-01-01

    Modified multiwall carbon nanotubes (MWCNTs) by nitric acid solution were used to investigate the adsorption behavior of zirconium from aqueous solution. Pristine and oxidized MWCNTs were characterized using nitrogen adsorption/desorption isotherm, Boehm's titration method, thermogravimetry analysis, transmission electron microscopy and Fourier transform infrared spectroscopy. The results showed that the surface properties of MWCNTs such as specific surface area, total pore volume, functional groups and the total number of acidic and basic sites were improved after oxidation. These improvements are responsible for their hydrophobic properties and consequently an easy dispersion in water and suitable active sites for more adsorption of zirconium. The adsorption of Zr(IV) as a function of initial concentration of zirconium, contact time, MWCNTs dosage, HCl and HNO 3 concentration and also ionic strength was investigated using a batch technique under ambient conditions. The experimental results indicated that sorption of Zr(IV) was strongly influenced by zirconium concentrations, oxidized MWCNTs content and acid pH values. The calculated correlation coefficient of the linear regressions values showed that Langmuir model fits the adsorption equilibrium data better than the Freundlich model. Kinetic data of sorption indicated that equilibrium was achieved within 60 min and the adsorption process can be described by the pseudo second-order reaction rate model. Based on the experimental results, surface complexation is the major mechanism for adsorption of Zr(IV) onto MWCNTs. Also, Study on the desorption process of zirconium showed that the complete recovery can be obtained using nitric or hydrochloric acids of 4 M. (author)

  5. Strong interactions

    International Nuclear Information System (INIS)

    Froissart, Marcel

    1976-01-01

    Strong interactions are introduced by their more obvious aspect: nuclear forces. In hadron family, the nucleon octet, OMEGA - decuplet, and quark triply are successively considered. Pion wave having been put at the origin of nuclear forces, low energy phenomena are described, the force being explained as an exchange of structure corresponding to a Regge trajectory in a variable rotating state instead of the exchange of a well defined particle. At high energies the concepts of pomeron, parton and stratons are introduced, pionization and fragmentation are briefly differentiated [fr

  6. Understanding the adsorptive and photoactivity properties of Ag-graphene oxide nanocomposites.

    Science.gov (United States)

    Martínez-Orozco, R D; Rosu, H C; Lee, Soo-Wohn; Rodríguez-González, V

    2013-12-15

    Nanocomposites of graphene oxide (GO) and silver nanoparticles (AgNPs) were synthetized using a practical photochemical silver functionalization. Their photocatalytic activities were evaluated with two dyes, Rhodamine B and Indigo Carmine, under visible-light irradiation. The prepared nanocomposites were characterized by HRTEM, FESEM, XRD, Raman, FTIR and UV-vis absorption spectroscopy. These nanocomposites present new defect domains of sp(3) type in combination with several graphitic functional groups that act as nucleation sites for anchoring AgNPs, while the sp(2)-sp(3) edge defects domains of GO generate the photoactivity. Furthermore, their photocatalytic performances are governed by their large adsorption capacity, and strong interaction with dye chromophores. A comprehensive photocatalytic way underlying the importance of adsorption is suggested to explain the low visible-light responsive photoactivity of the AgNPs-GO nanocomposites and the possible binding-site saturation. Then, the usage of H2SO4 allows the production of ionic species and helps to confirm the strong adsorption of both dyes. The ability to synthesize AgNPs-GO nanocomposites with extensive adsorptive capacity is certainly of interest for the efficient removal of hazardous materials. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Arsenic Adsorption Equilibrium Concentration and Adsorption Rate of Activated Carbon Coated with Ferric-Aluminum Hydroxides

    Science.gov (United States)

    Zhang, M.; Sugita, H.; Oguma, T.; Hara, J.; Takahashi, S.

    2015-12-01

    In some areas of developing countries, ground or well water contaminated with arsenic has been reluctantly used as drinking water. It is highly desirable that effective and inexpensive arsenic removal agents should be developed and provided to reduce the potential health risk. Previous studies demonstrated that activated carbon coated with ferric-aluminum hydroxides (Fe-Al-C) has high adsorptive potential for removal of arsenic. In this study, a series of experiments using Fe-Al-C were carried to discuss adsorption equilibrium time, adsorption equilibrium concentration and adsorption rate of arsenic for Fe-Al-C. Fe-Al-C used in this study was provided by Astec Co., Ltd. Powder reagent of disodium hydrogen arsenate heptahydrate was dissolved into ion-exchanged water. The solution was then further diluted with ion-exchanged water to be 1 and 10 mg/L as arsenic concentration. The pH of the solution was adjusted to be around 7 by adding HCl and/or NaOH. The solution was used as artificial arsenic contaminated water in two types of experiments (arsenic adsorption equilibrium and arsenic adsorption rate tests). The results of the arsenic equilibrium tests were showed that a time period of about 3 days to reach apparent adsorption equilibrium for arsenic. The apparent adsorption equilibrium concentration and adsorbed amount of arsenic on Fe-Al-C adsorbent could be estimated by application of various adsorption isotherms, but the distribution coefficient of arsenic between solid and liquid varies with experimental conditions such as initial concentration of arsenic and addition concentration of adsorbent. An adsorption rate equation that takes into account the reduction in the number of effective adsorption sites on the adsorbent caused by the arsenic adsorption reaction was derived based on the data obtained from the arsenic adsorption rate tests.

  8. First-principles study of the alkali earth metal atoms adsorption on graphene

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Minglei [School of Mechanical Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Tang, Wencheng, E-mail: 101000185@seu.edu.cn [School of Mechanical Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Ren, Qingqiang [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, Hunan (China); Wang, Sake [Department of Physics, Southeast University, Nanjing 210096, Jiangsu (China); JinYu [School of Materials Science and Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Jiangsu Key Laboratory of Advanced Metallic Materials, Southeast University, Nanjing 211189, Jiangsu (China); Du, Yanhui [School of Mechanical Engineering, Southeast University, Nanjing 211189, Jiangsu (China); Zhang, Yajun [Department of Engineering Mechanics, School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027, Zhejiang (China)

    2015-11-30

    Graphical abstract: - Highlights: • The adsorption of Be and Mg adatoms on graphene is physisorption. • Ca, Sr, and Ba adatoms bond ionically to graphene and the most stable adsorption site for them is hollow site. • The zero band gap semiconductor graphene becomes metallic and magnetic after the adsorption of Ca, Sr, and Ba adatoms. - Abstract: Geometries, electronic structures, and magnetic properties for alkali earth metal atoms absorbed graphene have been studied by first-principle calculations. For Be and Mg atoms, the interactions between the adatom and graphene are weak van der Waals interactions. In comparison, Ca, Sr and Ba atoms adsorption on graphene exhibits strong ionic bonding with graphene. We found that these atoms bond to graphene at the hollow site with a significant binding energy and large electron transfer. It is intriguing that these adatoms may induce important changes in both the electronic and magnetic properties of graphene. Semimetal graphene becomes metallic and magnetic due to n-type doping. Detailed analysis shows that the s orbitals of these adatoms should be responsible for the arising of the magnetic moment. We believe that our results are suitable for experimental exploration and useful for graphene-based nanoelectronic and data storage.

  9. Adsorption and migration of single metal atoms on the calcite (10.4) surface

    International Nuclear Information System (INIS)

    Pinto, H; Haapasilta, V; Lokhandwala, M; Foster, Adam S; Öberg, S

    2017-01-01

    Transition metal atoms are one of the key ingredients in the formation of functional 2D metal organic coordination networks. Additionally, the co-deposition of metal atoms can play an important role in anchoring the molecular structures to the surface at room temperature. To gain control of such processes requires the understanding of adsorption and diffusion properties of the different transition metals on the target surface. Here, we used density functional theory to investigate the adsorption of 3 d (Ti, Cr, Fe, Ni, Cu), 4 d (Zr, Nb, Mo, Pd, Ag) and 5 d (Hf, W, Ir, Pt, Au) transition metal adatoms on the insulating calcite (10.4) surface. We identified the most stable adsorption sites and calculated binding energies and corresponding ground state structures. We find that the preferential adsorption sites are the Ca–Ca bridge sites. Apart from the Cr, Mo, Cu, Ag and Au all the studied metals bind strongly to the calcite surface. The calculated migration barriers for the representative Ag and Fe atoms indicates that the metal adatoms are mobile on the calcite surface at room temperature. Bader analysis suggests that there is no significant charge transfer between the metal adatoms and the calcite surface. (paper)

  10. First-principles study of the alkali earth metal atoms adsorption on graphene

    International Nuclear Information System (INIS)

    Sun, Minglei; Tang, Wencheng; Ren, Qingqiang; Wang, Sake; JinYu; Du, Yanhui; Zhang, Yajun

    2015-01-01

    Graphical abstract: - Highlights: • The adsorption of Be and Mg adatoms on graphene is physisorption. • Ca, Sr, and Ba adatoms bond ionically to graphene and the most stable adsorption site for them is hollow site. • The zero band gap semiconductor graphene becomes metallic and magnetic after the adsorption of Ca, Sr, and Ba adatoms. - Abstract: Geometries, electronic structures, and magnetic properties for alkali earth metal atoms absorbed graphene have been studied by first-principle calculations. For Be and Mg atoms, the interactions between the adatom and graphene are weak van der Waals interactions. In comparison, Ca, Sr and Ba atoms adsorption on graphene exhibits strong ionic bonding with graphene. We found that these atoms bond to graphene at the hollow site with a significant binding energy and large electron transfer. It is intriguing that these adatoms may induce important changes in both the electronic and magnetic properties of graphene. Semimetal graphene becomes metallic and magnetic due to n-type doping. Detailed analysis shows that the s orbitals of these adatoms should be responsible for the arising of the magnetic moment. We believe that our results are suitable for experimental exploration and useful for graphene-based nanoelectronic and data storage.

  11. Theoretical evaluation on selective adsorption characteristics of alkali metal-based sorbents for gaseous oxidized mercury.

    Science.gov (United States)

    Tang, Hongjian; Duan, Yufeng; Zhu, Chun; Cai, Tianyi; Li, Chunfeng; Cai, Liang

    2017-10-01

    Alkali metal-based sorbents are potential for oxidized mercury (Hg 2+ ) selective adsorption but show hardly effect to elemental mercury (Hg 0 ) in flue gas. Density functional theory (DFT) was employed to investigate the Hg 0 and HgCl 2 adsorption mechanism over alkali metal-based sorbents, including calcium oxide (CaO), magnesium oxide (MgO), potassium chloride (KCl) and sodium chloride (NaCl). Hg 0 was found to weakly interact with CaO (001), MgO (001), KCl (001) and NaCl (001) surfaces while HgCl 2 was effectively adsorbed on top-O and top-Cl sites. Charge transfer and bond population were calculated to discuss the covalency and ionicity of HgCl 2 bonding with the adsorption sites. The partial density of states (PDOS) analysis manifests that HgCl 2 strongly interacts with surface sites through the orbital hybridizations between Hg and top O or Cl. Frontier molecular orbital (FMO) energy and Mulliken electronegativity are introduced as the quantitative criteria to evaluate the reactivity of mercury species and alkali metal-based sorbents. HgCl 2 is identified as a Lewis acid and more reactive than Hg 0 . The Lewis basicity of the four alkali metal-based sorbents is predicted as the increasing order: NaCl < MgO < KCl < CaO, in consistence with the trend of HgCl 2 adsorption energies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Site response variation due to the existence of near-field cracks based on strong motion records in the Shi-Wen river valley, southern Taiwan

    Science.gov (United States)

    Wu, Chi-Shin; Yu, Teng-To; Peng, Wen-Fei; Yeh, Yeoin-Tein; Lin, Sih-Siao

    2014-10-01

    Site effect analysis has been applied to investigate soil classification, alluvium depth, and fracture detection, although the majority of previous studies have typically focused only on the response of large-scale single structures. In contrast, we investigated the site effect for small-scale cracks using a case study in southern Taiwan to provide a means of monitoring slope stability or foundation integrity in situ using only an accelerometer. We adopted both the reference site and horizontal-to-vertical spectral ratio methods. We obtained seismographs associated with the typhoon-related development of a crack set (52 m long, 5 m deep) in a steep slope and compared the resonance frequency between two conditions (with and without cracks). Moreover, we divided the seismic waves into P, S, and coda waves and examined the seismic source effect. Our results demonstrate that frequencies of 14.5-17.5 Hz are most sensitive to these cracks, particularly for the E-W component of the P-waves, which coincides with the crack’s strike. Peak ground acceleration, which is controlled by seismic moment and attenuated distance, is another important factor determining the resonance results. Our results demonstrate that the ratio of temporal seismic waves can be used to detect the existence of nearby subsurface cracks.

  13. Site response variation due to the existence of near-field cracks based on strong motion records in the Shi-Wen river valley, southern Taiwan

    International Nuclear Information System (INIS)

    Wu, Chi-Shin; Yu, Teng-To; Peng, Wen-Fei; Yeh, Yeoin-Tein; Lin, Sih-Siao

    2014-01-01

    Site effect analysis has been applied to investigate soil classification, alluvium depth, and fracture detection, although the majority of previous studies have typically focused only on the response of large-scale single structures. In contrast, we investigated the site effect for small-scale cracks using a case study in southern Taiwan to provide a means of monitoring slope stability or foundation integrity in situ using only an accelerometer. We adopted both the reference site and horizontal-to-vertical spectral ratio methods. We obtained seismographs associated with the typhoon-related development of a crack set (52 m long, 5 m deep) in a steep slope and compared the resonance frequency between two conditions (with and without cracks). Moreover, we divided the seismic waves into P, S, and coda waves and examined the seismic source effect. Our results demonstrate that frequencies of 14.5−17.5 Hz are most sensitive to these cracks, particularly for the E−W component of the P-waves, which coincides with the crack’s strike. Peak ground acceleration, which is controlled by seismic moment and attenuated distance, is another important factor determining the resonance results. Our results demonstrate that the ratio of temporal seismic waves can be used to detect the existence of nearby subsurface cracks. (paper)

  14. Adsorption and dissociation of H2S on Mo(1 0 0) surface by first-principles study

    International Nuclear Information System (INIS)

    Luo, Haijun; Cai, Jianqiu; Tao, Xiangming; Tan, Mingqiu

    2014-01-01

    Density-functional theory calculations had been used to investigate the adsorption and dissociation of H 2 S on Mo(1 0 0) surface. Adsorption mechanisms of H 2 S, HS, S and H on the Mo(1 0 0) surface were analyzed. H 2 S was found to be adsorbed at bridge, hollow and top sites with adsorption energies of −1.25, −1.03 and −0.92 eV, respectively. HS was strongly chemically absorbed at hollow, bridge and top sites with adsorption energies of −4.51, −4.08 and −3.45 eV, respectively, and sulfur and hydrogen preferred to be absorbed at hollow and bridge sites, respectively. In addition, potential energy profiles of H 2 S dissociation on Mo(1 0 0) had been constructed by a climbing image nudged elastic band method. Four possible dissociation pathways of the first H 2 S dehydrogenation were examined with reaction barriers of 0.28, 0.37, 0.075, and 0.21 eV, respectively, while the energy barrier to break the S-H bond of HS with or without hydrogen co-adsorption was almost the same low. This work showed that the decomposition of H 2 S on the molybdenum surface was kinetically and thermodynamically facile. Local densities of electronic states were further used to characterize the interaction between H 2 S and substrate.

  15. Decrease in zinc adsorption onto soil in the presence of EPS-rich and EPS-poor Pseudomonas aureofaciens.

    Science.gov (United States)

    Drozdova, O Yu; Pokrovsky, O S; Lapitskiy, S A; Shirokova, L S; González, A G; Demin, V V

    2014-12-01

    from heavy-metal adsorption. The removal efficiency of heavy metals in an abiotic organic-rich soil system should therefore be significantly higher than that in the presence of bacteria. This effect can be explained by the shielding of strongly bound metal sites on the organic-rich soil particles by inert bacterial exopolysaccharides. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Ground characteristics at observation site of strong motion in Hachinohe Inst. Tech. Hachinohe, Aomori; Hachinohe Kodai konai ni secchishita kyoshin kansokuten no jiban tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Sakajiri, N [Hachinohe Institute of Technology, Aomori (Japan)

    1997-10-22

    Discussions were given on ground structures in the city of Hachinohe and vibration characteristics of the grounds during earthquakes. In order to identify ground structures and vibration characteristics thereof in the city of Hachinohe, strong motion seismographs were installed in five locations of the city and in the Tohoku University. At the Hachinohe Institute of Technology, strong motion seismographs were installed underground (-65 m) and on the ground, where S-wave logging experiments were performed using the plank hammering method. The records therefrom were used to estimate Q values, and the Q values were used to compare the computed ground amplification characteristics with the spectral ratio of seismic waves in and on the ground. The analysis has conducted the Q value estimation on each bed from a depth greater than 4 m, whereas relatively reasonable values were derived only from sections from 4 m to 13 m, and other sections showed no stable values. According to the result of observations derived from the seismographs installed in and on the ground, the maximum amplitude of the ground surface seismograph was found about five times greater than that of underground in the NS components, about eight times in the EW components, and about six times in vertical movements. The result indicates that the amplitude is obviously affected greatly by the characteristics of the ground. 4 refs., 8 figs., 1 tab.

  17. Site-specific glycoprofiling of N-linked glycopeptides using MALDI-TOF MS: strong correlation between signal strength and glycoform quantities

    DEFF Research Database (Denmark)

    Thaysen-Andersen, Morten; Mysling, Simon; Højrup, Peter

    2009-01-01

    Site-specific glycoprofiling of N-linked glycopeptides using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is an emerging technique, but its quantitative accuracy lacks documentation. Thus, a systematic study of widely different glycopeptides was perf......Site-specific glycoprofiling of N-linked glycopeptides using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is an emerging technique, but its quantitative accuracy lacks documentation. Thus, a systematic study of widely different glycopeptides...... was performed to determine the relationship between the relative abundances of the individual glycoforms and the MALDI-TOF MS signal strength. Glycopeptides derived from glycoproteins containing neutral glycans (ribonuclease B, IgG, and ovalbumin) were initially profiled and yielded excellent and reproducible...... quantitation (correlation coefficient r = 0.9958, n = 5) when evaluated against a normal phase HPLC 2-AB glycan profile. Similarly, precise quantitation was observed for various forms of N-glycans (free, permethylated, and fluorescence-labeled) using MS. In addition, three different sialoglycopeptides from...

  18. Catalysis on singly dispersed bimetallic sites

    Science.gov (United States)

    Zhang, Shiran; Nguyen, Luan; Liang, Jin-Xia; Shan, Junjun; Liu, Jingyue; Frenkel, Anatoly I.; Patlolla, Anitha; Huang, Weixin; Li, Jun; Tao, Franklin

    2015-08-01

    A catalytic site typically consists of one or more atoms of a catalyst surface that arrange into a configuration offering a specific electronic structure for adsorbing or dissociating reactant molecules. The catalytic activity of adjacent bimetallic sites of metallic nanoparticles has been studied previously. An isolated bimetallic site supported on a non-metallic surface could exhibit a distinctly different catalytic performance owing to the cationic state of the singly dispersed bimetallic site and the minimized choices of binding configurations of a reactant molecule compared with continuously packed bimetallic sites. Here we report that isolated Rh1Co3 bimetallic sites exhibit a distinctly different catalytic performance in reduction of nitric oxide with carbon monoxide at low temperature, resulting from strong adsorption of two nitric oxide molecules and a nitrous oxide intermediate on Rh1Co3 sites and following a low-barrier pathway dissociation to dinitrogen and an oxygen atom. This observation suggests a method to develop catalysts with high selectivity.

  19. Adsorption of gaseous pollutants on activated carbon filters. Modelling of the coupled exchanges of heat and mass; Adsorption de polluants gazeux sur des filtres de charbon actif. Modelisation des echanges couples de matiere et de chaleur

    Energy Technology Data Exchange (ETDEWEB)

    Fiani, E.

    2000-01-27

    The aim of this work is to remove gasoline and odorous molecules vapors. Thermodynamics and kinetics studies have been carried out; they concern the fixation of representative gases on activated carbons. Hydrogen sulfide and n-butane are chosen to represent the odorous molecules. Different activated carbons are considered: only the adsorbent impregnated by KOH has satisfying performance. The adsorption of hydrocarbons on a granulated activated carbon is studied on four original devices specifically perfected for this work: gravimetry, calorimetry, thermal measurements and gaseous phase chromatography. The gravimetric measurements are coupled to thermal measurements inside the granulates. Strong temperature variations have then been observed inside a granulate during the adsorption. These experimental results have been taken into account to adapt the classical Langmuir kinetic model. This new model allows to predict all the curves: setting / internal temperature variation for the adsorption of the hydrocarbons alone. The competitive nature of the adsorption sites allows then to explain qualitatively the adsorption of binary mixtures of hydrocarbons. At last, the classical Langmuir model allows to explain correctly the thermodynamic results, for the hydrocarbons alone or in binary mixture. The proposed modelling allows then to treat both on a kinetic and thermodynamic way the case of a non isothermal adsorption at the scale of an activated carbon granulate and to predict the phenomena at the filter scale. (O.M.)

  20. Adsorption of aqueous Zn(II) species on synthetic zeolites

    International Nuclear Information System (INIS)

    Badillo-Almaraz, Veronica; Trocellier, Patrick; Davila-Rangel, Ignacio

    2003-01-01

    To supply a good quality drinkable water tends to become a strategic task in both developed and under development countries in the world due to the number of potential contamination sources. One of the major problems is derived from the presence of heavy toxic metals like zinc or lead resulting from industrial activities. Zeolites are known as very efficient mineral substrates for fixing aqueous ionic species through their wide range of channels present in the crystalline structure and due to their strong surface reactivity. MicroPIXE coupled with microRBS (3.05 MeV 4 He + ions) have been used to quantify the incorporation of zinc within two commercial zeolites containing alkali elements (zeolite X and clinoptilolite) in the concentration range of: 0.0002-0.05 M at neutral pH. At the beginning of the interaction between zeolite and Zn(II) solution, the adsorption process exhibits a direct proportionality between the content of zinc fixed on the mineral substrate and the aqueous concentration up to 0.01 M. Beyond this point a saturation effect seems to occur, indicating the strong decrease of available adsorption sites. Sodium or potassium ions are probably exchanged with Zn(II) ions during this process. The compared behaviour of the two zeolites is then discussed in terms of kinetic effects based on ionic radius values. A co-adsorption test carried on with a 50-50% Zn(II) 0.001 M-Pb(II) 0.001 M solution shows that lead does not occupy the same sites as zinc because the content of zinc fixed on the zeolite sample exactly corresponds to the result obtained with a pure 0.001 M Zn(II) solution. All these data clearly showed that zeolite surface reactivity is greatly influenced by the mineral cage-like structure and particularly the presence of pockets, spaces and channels

  1. Adsorption behavior of Am(III) on granite

    International Nuclear Information System (INIS)

    Zhang Yingjie; Feng Xiaogui; Liang Junfu; Chen Jing; Su Rui; Wang Ju; Liu Chunli

    2009-01-01

    The adsorption behavior of Am(III) on granite (sampled from drilling well BS01 at Beishan (BS) area--a potential candidate site for China's high-level radioactive waste repository, the granite sample's depth about 300 m) was studied in BS03 well groundwater by a batch technique at (25±1) degree C. The influences of pH, sulphate ion, total carbonate ion, humic acid, and concentration of the Am(III) on the adsorption behavior were also studied, and the possible adsorption mechanism was discussed. Experimental results show that the adsorption distribution rate of Am(III) on granite increases with increasing pH of aqueous phase. The chemical composition of the groundwater is the main factor which influences the species of Am(III) and adsorption behavior. The adsorption mechanism of Am(III) on granite is surface complexation. The adsorption isotherm of Am(III) on granite can be described by Freundlich's equation. (authors)

  2. Hydrogen adsorption on bimetallic PdAu(111) surface alloys

    DEFF Research Database (Denmark)

    Takehiro, Naoki; Liu, Ping; Bergbreiter, Andreas

    2014-01-01

    The adsorption of hydrogen on structurally well defined PdAu-Pd(111) monolayer surface alloys was investigated in a combined experimental and theoretical study, aiming at a quantitative understanding of the adsorption and desorption properties of individual PdAu nanostructures. Combining...... the structural information obtained by high resolution scanning tunneling microscopy (STM), in particular on the abundance of specific adsorption ensembles at different Pd surface concentrations, with information on the adsorption properties derived from temperature programmed desorption (TPD) spectroscopy...... and high resolution electron energy loss spectroscopy (HREELS) provides conclusions on the minimum ensemble size for dissociative adsorption of hydrogen and on the adsorption energies on different sites active for adsorption. Density functional theory (DFT) based calculations give detailed insight...

  3. Experimental and numerical study of the stability of phyllosilicates in a strong thermal gradient. Test in the geothermal site of Soultz-sous-Forets

    International Nuclear Information System (INIS)

    Baldeyrou-Bailly, A.

    2003-01-01

    Thermodynamic data of hydrated phyllosilicates, in particular clay minerals are not well known. The stability fields of these minerals are not well determined; following some authors they even do not exist. We have developed an experimental approach, in which a sequence of local equilibrium states between a fluid and minerals take place in a closed gold cell along a strong thermal gradient. The experiments were conducted in the chemical systems: Mg-Al-Si-H 2 O (MASH), K-Al-Si-H 2 O (KASH), and K-Mg-Al-Si-H 2 O (KMASH). The sequences of crystallization observed along the thermal gradient are the same if one exchanges the position of the cells containing the initial reacting materials with respect to the thermal gradient end-members. The crystallization sequences correspond to local equilibrium states. Following the temperature increase (from 200 to 350 C) one observes the following sequences: di-octahedral smectite? tri-octahedral smectite; kaolinite? donbassite? tri-octahedral chlorite; smectite? illite? muscovite; or even kaolinite? illite + smectite? donbassite; commonly observed in hydrothermal systems. They allow to develop a thermodynamic model for hydrated phyllosilicates, taking into account their hydration state as a function of temperature. This model shows the stability fields of clay minerals between 200 and 350 C.The chemical and mineralogical dynamics showed in these experimental systems has been applied to predict the possible dissolutions and/or precipitations which may take place between the circulated hot fluid and the geothermal granitic reservoir in the geothermal system at Soultz-sous-Forets. These processes may affect the duration of the geothermal reservoir, as a function of evolution in the morphology of the porosity. Our experimental approach shows that feldspars and smectites are forming the major part of the total volume of silicates which may precipitate in addition to carbonates already described in previous studies. (author)

  4. Immunity of the Fe-N-C catalysts to electrolyte adsorption: phosphate but not perchloric anions

    DEFF Research Database (Denmark)

    Hu, Yang; Jensen, Jens Oluf; Pan, Chao

    2018-01-01

    often carried out, like for Pt-based catalysts, in dilute perchloric acid by assuming its non-adsorbing nature on the active sites. The assumption is however not true. In this work, a typical Fe-N-C catalyst was first synthesized by high-pressure pyrolysis in the presence of carbon support...... and thoroughly characterized in terms of morphology, structure and active site distribution. The subsequent electrochemical characterization of the catalyst shows strong adsorption and poisoning effect of, in addition to the known Cl-, perchloric anions on the oxygen reduction reaction (ORR) activity...

  5. Weakly-bound adsorption states and low-temperature adsorption kinetiks of oxygen on tungsten (100) and (110) faces

    International Nuclear Information System (INIS)

    Zhukov, V.V.; Osovskij, V.D.; Ptushnikov, Yu.G.; Sukretnyj, V.G.; Chujkov, B.A.

    1986-01-01

    A molecular beam technique with an effusion source operating at T=200 K is used to study the adsorption interaction of oxygen with W(100) and (110) faces in the range of the simple temperatures from 5 to 340 K. Three weakly-bound adsorption states of oxygen are detected corresponding to adsorption in the second, third and forth monolayer. These states are characterized by adsorption energies of 0.13, 0.08 and 0.07 eV and desorption temperatures of 45, 27 and 25 K, respectively. The kinetics of filling of these states is almost similar for both faces, whereas the adsorption kinetics in the first monolayer is essentially different. A dissociative nature of adsorption at T >or approx. 5 K and a jump migration mechanism of the admolecules in the precursor state to the stationary adsorption sites are suggested

  6. A first principles kinetic Monte Carlo investigation of the adsorption and mobility of gadolinium on the (100) surface of tungsten

    International Nuclear Information System (INIS)

    Samin, Adib J.; Zhang, Jinsuo

    2017-01-01

    An accurate characterization of lanthanide adsorption and mobility on tungsten surfaces is important for pyroprocessing. In the present study, the adsorption and diffusion of gadolinium on the (100) surface of tungsten was investigated. It was found that the hollow sites were the most energetically favorable for the adsorption. It was further observed that a magnetic moment was induced following the adsorption of gadolinium on the tungsten surface and that the system with adsorbed hollow sites had the largest magnetization. A pathway for the surface diffusion of gadolinium was determined to occur by hopping between the nearest neighbor hollow sites via the bridge site and the activation energy for the hop was calculated to be 0.75 eV. The surface diffusion process was further assessed using two distinct kinetic Monte Carlo models; one that accounted for lateral adsorbate interactions up to the second nearest neighbor and one that did not account for such interatomic interactions in the adlayer. When the lateral interactions were included in the simulations, the diffusivity was observed to have a strong dependence on coverage (for the coverage values being studied). The effects of lateral interactions were further observed in a one-dimensional simulation of the diffusion equation where the asymmetry in the surface coverage profile upon its approach to a steady state distribution was clear in comparison with the simulations which did not account for those interactions.

  7. A first principles kinetic Monte Carlo investigation of the adsorption and mobility of gadolinium on the (100) surface of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Samin, Adib J., E-mail: samin.2@osu.edu; Zhang, Jinsuo

    2017-05-15

    An accurate characterization of lanthanide adsorption and mobility on tungsten surfaces is important for pyroprocessing. In the present study, the adsorption and diffusion of gadolinium on the (100) surface of tungsten was investigated. It was found that the hollow sites were the most energetically favorable for the adsorption. It was further observed that a magnetic moment was induced following the adsorption of gadolinium on the tungsten surface and that the system with adsorbed hollow sites had the largest magnetization. A pathway for the surface diffusion of gadolinium was determined to occur by hopping between the nearest neighbor hollow sites via the bridge site and the activation energy for the hop was calculated to be 0.75 eV. The surface diffusion process was further assessed using two distinct kinetic Monte Carlo models; one that accounted for lateral adsorbate interactions up to the second nearest neighbor and one that did not account for such interatomic interactions in the adlayer. When the lateral interactions were included in the simulations, the diffusivity was observed to have a strong dependence on coverage (for the coverage values being studied). The effects of lateral interactions were further observed in a one-dimensional simulation of the diffusion equation where the asymmetry in the surface coverage profile upon its approach to a steady state distribution was clear in comparison with the simulations which did not account for those interactions.

  8. Investigation of fluorine adsorption on nitrogen doped MgAl_2O_4 surface by first-principles

    International Nuclear Information System (INIS)

    Lv, Xiaojun; Xu, Zhenming; Li, Jie; Chen, Jiangan; Liu, Qingsheng

    2016-01-01

    Graphical abstract: First-principles calculations indicate that MgAl_2O_4 surface is fluorine-loving, but hydrophobic. N doped MgAl_2O_4 (100) surface structure shows the highest fluorine adsorption performance and fluorine atom is more preferentially adsorbed on the Mg-Al bridge site. The fluorine adsorption intensity follow this order: N doped MgAl_2O_4 (100) > Al_2O_3 (0001) > MgAl_2O_4 (100) > MgO (100). N doped MgAl_2O_4 is a promising candidate for fluorine removal. - Highlights: • MgAl_2O_4 surface is fluorine-loving, not hydrophilic. • Fluorine preferentially adsorbs on the Mg-Al bridge site. • Adsorption intensity follow this order: N doped MgAl_2O_4 > Al_2O_3 > MgAl_2O_4 > MgO. • Excellent adsorption performance attributes to electron compensation of N atom. • Nitrogen doped MgAl_2O_4 is a promising candidate for fluorine removal. - Abstract: The nature of fluorine adsorption on pure and N doped MgAl_2O_4 surface has been investigated by first-principles calculations based on the density functional theory. Calculated results indicate that MgAl_2O_4 surface is fluorine-loving, not hydrophilic. Nitrogen doped MgAl_2O_4 (100) surface shows the highest fluorine adsorption performance and fluorine atom preferentially adsorbs on the Mg-Al bridge site. The fluorine adsorption intensity follow this order: Nitrogen doped MgAl_2O_4 (100) > Al_2O_3 (0001) > MgAl_2O_4 (100) > MgO (100). In-depth PDOS analysis suggested that 2p orbitals of F atom strongly hybridized with 3s- and 3p-orbitals of Al atom contribute to its high adsorption intensity. According to the analysis of Hirshfeld charge, the excellent fluorine adsorption performance of nitrogen doped MgAl_2O_4 attributes to the electron compensation effect of nitrogen atom and strong electrostatic interactions. All these evidences demonstrate a fact nitrogen doped MgAl_2O_4 is a promising candidate for fluorine removal.

  9. Interfacial adsorption of insulin - Conformational changes and reversibility of adsorption

    NARCIS (Netherlands)

    Mollmann, SH; Jorgensen, L; Bukrinsky, JT; Elofsson, U; Norde, W; Frokjaer, S

    The adsorption of human insulin to Teflon particles was studied with respect to conformational changes and the reversibility of adsorption was examined by total internal reflection fluorescence (TIRF). Adsorption isotherms for the adsorption of human insulin indicated high affinity adsorption, even

  10. Lithium Mediated Benzene Adsorption on Graphene and Graphene Nanoribbons

    OpenAIRE

    Krepel, Dana; Hod, Oded

    2013-01-01

    The anchoring of benzene molecules on lithium adsorption sites at the surface of graphene and nanoribbons thereof are investigated. The effects of adsorbate densities, specific adsorption locations, and spin states on the structural stability and electronic properties of the underlying graphene derivatives are revealed. At sufficiently high densities, bare lithium adsorption turns armchair graphene nanoribbons metallic and their zigzag counterparts half-metallic due to charge transfer from th...

  11. Random and cooperative sequential adsorption

    Science.gov (United States)

    Evans, J. W.

    1993-10-01

    Irreversible random sequential adsorption (RSA) on lattices, and continuum "car parking" analogues, have long received attention as models for reactions on polymer chains, chemisorption on single-crystal surfaces, adsorption in colloidal systems, and solid state transformations. Cooperative generalizations of these models (CSA) are sometimes more appropriate, and can exhibit richer kinetics and spatial structure, e.g., autocatalysis and clustering. The distribution of filled or transformed sites in RSA and CSA is not described by an equilibrium Gibbs measure. This is the case even for the saturation "jammed" state of models where the lattice or space cannot fill completely. However exact analysis is often possible in one dimension, and a variety of powerful analytic methods have been developed for higher dimensional models. Here we review the detailed understanding of asymptotic kinetics, spatial correlations, percolative structure, etc., which is emerging for these far-from-equilibrium processes.

  12. Gas-phase formaldehyde adsorption isotherm studies on activated carbon: correlations of adsorption capacity to surface functional group density.

    Science.gov (United States)

    Carter, Ellison M; Katz, Lynn E; Speitel, Gerald E; Ramirez, David

    2011-08-01

    Formaldehyde (HCHO) adsorption isotherms were developed for the first time on three activated carbons representing one activated carbon fiber (ACF) cloth, one all-purpose granular activated carbon (GAC), and one GAC commercially promoted for gas-phase HCHO removal. The three activated carbons were evaluated for HCHO removal in the low-ppm(v) range and for water vapor adsorption from relative pressures of 0.1-0.9 at 26 °C where, according to the IUPAC isotherm classification system, the adsorption isotherms observed exhibited Type V behavior. A Type V adsorption isotherm model recently proposed by Qi and LeVan (Q-L) was selected to model the observed adsorption behavior because it reduces to a finite, nonzero limit at low partial pressures and it describes the entire range of adsorption considered in this study. The Q-L model was applied to a polar organic adsorbate to fit HCHO adsorption isotherms for the three activated carbons. The physical and chemical characteristics of the activated carbon surfaces were characterized using nitrogen adsorption isotherms, X-ray photoelectron spectroscopy (XPS), and Boehm titrations. At low concentrations, HCHO adsorption capacity was most strongly related to the density of basic surface functional groups (SFGs), while water vapor adsorption was most strongly influenced by the density of acidic SFGs.

  13. Studies on adsorption capacity of clay-Sargassum sp biosorbent for Cr (VI) removal in wastewater from electroplating industry

    Science.gov (United States)

    Aprianti, Tine; Aprilyanti, Selvia; Apriani, Rachmawati; Sisnayati

    2017-11-01

    Various raw biosorbents have been studied for pollutant treatment of heavy metals contained in wastewater. In this study, clay and brown seaweed, Sargassum sp, are used for hexavalent chromium [Cr (VI)] biosorption. The adsorption capacity is adequately improved by combining clay and Sargassum sp as the adsorbent agent. Ion exchange of metal ions has shown strong coordination cross-linkage due to organic functional hydroxyl groups (OH-) contained in brown seaweed that provide sites to capture and bind the metal ions. Clay is known as an inexpensive adsorbent due to its wide availability besides its large specific surface area. Combining clay and Sargassum sp as biosorbent resulting better adsorption, the adsorption capacity reaches most favorable results of 99.39% at Sargassum: clay ratio of 40:60 on contact time 10 h. This study has proven that composit biosorbent used has succeeded in reducing hexavalent chromium pollutant in wastewater.

  14. Bio-oil hydrodeoxygenation catalysts produced using strong electrostatic adsorption

    Science.gov (United States)

    We synthesized hydrothermally stable metal catalysts with controlled particle size and distribution, with the goal of determining which catalyst(s) can selectively catalyze the production of aromatics from bio-oil (from pyrolysis of biomass). Both precious and base transition metal catalysts (Ru, Pt...

  15. Gallium adsorption on (0001) GaN surfaces

    International Nuclear Information System (INIS)

    Adelmann, Christoph; Brault, Julien; Mula, Guido; Daudin, Bruno; Lymperakis, Liverios; Neugebauer, Joerg

    2003-01-01

    We study the adsorption behavior of Ga on (0001) GaN surfaces combining experimental specular reflection high-energy electron diffraction with theoretical investigations in the framework of a kinetic model for adsorption and ab initio calculations of energy parameters. Based on the experimental results we find that for substrate temperatures and Ga fluxes typically used in molecular-beam epitaxy of GaN, finite equilibrium Ga surface coverages can be obtained. The measurement of a Ga/GaN adsorption isotherm allows the quantification of the equilibrium Ga surface coverage as a function of the impinging Ga flux. In particular, we show that a large range of Ga fluxes exists, where 2.5±0.2 monolayers (in terms of the GaN surface site density) of Ga are adsorbed on the GaN surface. We further demonstrate that the structure of this adsorbed Ga film is in good agreement with the laterally contracted Ga bilayer model predicted to be most stable for strongly Ga-rich surfaces [Northrup et al., Phys. Rev. B 61, 9932 (2000)]. For lower Ga fluxes, a discontinuous transition to Ga monolayer equilibrium coverage is found, followed by a continuous decrease towards zero coverage; for higher Ga fluxes, Ga droplet formation is found, similar to what has been observed during Ga-rich GaN growth. The boundary fluxes limiting the region of 2.5 monolayers equilibrium Ga adsorption have been measured as a function of the GaN substrate temperature giving rise to a Ga/GaN adsorption phase diagram. The temperature dependence is discussed within an ab initio based growth model for adsorption taking into account the nucleation of Ga clusters. This model consistently explains recent contradictory results of the activation energy describing the critical Ga flux for the onset of Ga droplet formation during Ga-rich GaN growth [Heying et al., J. Appl. Phys. 88, 1855 (2000); Adelmann et al., J. Appl. Phys. 91, 9638 (2002).

  16. Adsorption. What else?

    OpenAIRE

    Rodrigues, Alirio E.

    2012-01-01

    [EN] Chemical Engineering today combines Molecular and Materials Engineerig and Process and Product Engineering (ChE=M2P2). Cyclic adsorptive processes (Simulated Moving Bed –SMB and Pressure Swing Adsorption-PSA) will be discussed for “old” and “new” applications making use of “old” and “new” (MOFs) adsorbent materials. After revisiting my memory as PhD student and the First Brazilian Adsorption meeting I will review the basic concepts involved in adsorption processes and then...

  17. Relationship between the adsorption species of cesium and radiocesium interception potential in soils and minerals: an EXAFS study

    International Nuclear Information System (INIS)

    Fan, Qiaohui; Yamaguchi, Noriko; Tanaka, Masato; Tsukada, Hirofumi; Takahashi, Yoshio

    2014-01-01

    This study examined the radiocesium (RCs) interception potential (RIP), cation exchange capacity (CEC), total organic carbon (TOC) content, and adsorption species in soils and minerals by using extended X-ray absorption fine structure (EXAFS) spectroscopy. The RIP related to Cs + adsorption by frayed-edge site (FES) has often been used to measure the mobility and bioavailability of RCs in the environment. This study found that the presence of organic matter (OM) can reduce RIP to a certain extent. The adsorption amount (=Q T ) in soil was obviously correlated to RIP at a small [Cs + ] region, whereas a linear relationship between Q T and CEC was observed at a large [Cs + ] region. Both the inner-sphere (IS) and outer-sphere (OS) complexes of Cs + were observed through EXAFS at a molecular scale. The linear correlation between log (RIP/CEC) and the ratio of the coordination number (CN) of IS (=CN IS ) and OS (=CN OS ) complexes noted as CN IS /(CN IS + CN OS ) suggested that the ratio of CN is very sensitive to Cs + adsorption species with variable RIP and CEC. The adsorption species of Cs + in soil was mainly dependent on the clay mineral content of soil. RIP was affected not only by FES but also by other strong adsorption sites, such as the interlayers and cavities identified as the IS complex in EXAFS analysis. Findings indicated that the EXAFS approach is a powerful and efficient tool to explore the behavior of Cs + in a given environment. - Highlights: • The relationship of Cs + species on soils and minerals and RIP was firstly clarified in this study. • Coordination number of Cs + was very sensitive to Cs + adsorption species with variable RIP and CEC. • This finding can be used as a basis for understanding of Cs + behavior in nature

  18. Adsorption of Arsenite onto Kemiron in a batch system

    African Journals Online (AJOL)

    doti

    This study investigated the effect of pH and coexisting ions on As(III) adsorption using batch experiment and discovered that pH strongly influenced As(III) adsorption. However, differences ... contamination by such heavy metals as arsenic (As). Arsenite ..... and then transition through point of zero charge (PZC) and then into ...

  19. Adsorption and Desorption of Cesium in Clay Minerals: Effects of Natural Organic Matter and pH

    Science.gov (United States)

    Yoon, Hongkyu; Ilgen, Anastasia; Mills, Melissa; Lee, Moo; Seol, Jeung Gun; Cho, Nam Chan; Kang, Hyungyu

    2017-04-01

    Cesium (Cs) released into the environment (e.g., Fukushima accident) poses significant environmental concerns and remediation challenges. A majority of Cs in the environment have remained within the surface soils due to the strong adsorption affinity of Cs towards clay minerals. Different clay minerals have different bonding sites, resulting in various adsorption mechanisms at nanometer scale. For example, the illite commonly has a basal spacing of 1.0 nm, but becomes wider to 1.4 nm once other cations exchange with K in the interlayer site. Cs adsorbs into these expanded wedged zone strongly, which can control its mobility in the environment. In addition, natural organic matter (NOM) in the surface soils can interact with clay minerals, which can modify the mechanisms of Cs adsorption on the clay minerals by blocking specific adsorption sites and/or providing Cs adsorption sites on NOM surface. In this work, three representative clay minerals (illite, vermiculite, montmorillonite) and humic acid (HA) are used to systematically investigate the adsorption and desorption behavior of Cs. We performed batch adsorption experiments over a range of Cs concentrations on three clay minerals with and without HA, followed by sequential desorption batch testing. We tested desorption efficiency as a function of initial adsorbed Cs concentration, HA content, sodium concentration, and pH. The sequential extraction results are compared to the structural changes in clay minerals, measured using extended X-ray absorption fine structure spectroscopy (EXAFS) and aberration-corrected (scanning) transmission electron microscopy (TEM) - energy dispersive X-ray spectroscopy (EDX). Hence, this work aims to identify the mechanisms of Cs fixation at the nanometer (or atomic-) scale as a function of the clay mineral properties (e.g. expandability, permanent surface charge) and varying organic matter content at different pH values and to enhance our atomic-scale mechanistic understanding of

  20. [Adsorption kinetics and mechanism of lead (II) on polyamine-functionalized mesoporous activated carbon].

    Science.gov (United States)

    Li, Kun-Quan; Wang, Yan-Jin; Yang, Mei-Rong; Zhu, Zhi-Qiang; Zheng, Zheng

    2014-08-01

    Bagasse mesoporous carbon was prepared by microwave assisted H3 PO4 activation. Amido and imido groups were modified with ethanediamine on the channels' surface of mesoporous carbon through nitric oxidation and amide reaction. The influence of Pb(II) concentration, adsorption time on Pb(II) adsorption on the ethanediamine-modified mesoporous carbon (AC-EDA) was investigated. The adsorption kinetics and mechanism were also discussed. The results showed that AC-EDA had a great performance for Pb(II) adsorption, and more than 70% of Pb(II) was adsorbed in 5 minutes. The adsorption amount of Pb(II) on the carbon increased with the increase of solution pH in acidic conditions. It was found that AC-EDA had different binding energies on different adsorption sites for Pb(II) separation. The Pb(II) adsorption process on AC-EDA was controlled by intra-particle diffusion in the first 3 min, and then film diffusion played the important pole on the adsorption. The adsorption amount increased with the increase of temperature, indicating the adsorption was an endothermic reaction. The high adsorption energy (> 11 kJ x mol(-1)) implied that the) adsorption was a chemical adsorption. The XPS of AC-EDA before and after Pb(II) adsorption showed that the polyamine group was involved in the adsorption, and should be a main factor of the high efficient adsorption.

  1. Propylene/propane mixture adsorption on faujasite sorbents

    NARCIS (Netherlands)

    Van Miltenburg, A.; Gascon, J.; Zhu, W.; Kapteijn, F.; Moulijn, J.A.

    2008-01-01

    The adsorption of propylene and propane on zeolite NaX with and without a saturated (36 wt%) amount of CuCl have been investigated. The single component adsorption isotherms could be well described with a Dual-Site Langmuir model. The dispersion of CuCl results in a decrease of the maximum

  2. A Simple Adsorption Experiment

    Science.gov (United States)

    Guirado, Gonzalo; Ayllon, Jose A.

    2011-01-01

    The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent…

  3. Adsorption of palladium ions by modified carbons from rice husks

    International Nuclear Information System (INIS)

    Mostafa, M.R.

    1994-01-01

    Steam activated carbon of high surface area does not show palladium ions adsorption. Treatment of this carbon with HF acid increases to a great extent the gas adsorption capacity expressed as nitrogen surface area as well as the adsorption capacity of palladium ions from aqueous solution. HHB was loaded in different amounts on to these carbons. The acid sites represent the active fraction of the surface on which the adsorption palladium ions proceed. The uptake of palladium ions by HHB treated carbons is related to the total number of HHB molecules loaded on the carbon surface. (author)

  4. Adsorption-induced step formation

    DEFF Research Database (Denmark)

    Thostrup, P.; Christoffersen, Ebbe; Lorensen, Henrik Qvist

    2001-01-01

    Through an interplay between density functional calculations, Monte Carlo simulations and scanning tunneling microscopy experiments, we show that an intermediate coverage of CO on the Pt(110) surface gives rise to a new rough equilibrium structure with more than 50% step atoms. CO is shown to bind...... so strongly to low-coordinated Pt atoms that it can break Pt-Pt bonds and spontaneously form steps on the surface. It is argued that adsorption-induced step formation may be a general effect, in particular at high gas pressures and temperatures....

  5. Adsorption of H2S molecule on TiO2/Au nanocomposites: A density functional theory study

    Directory of Open Access Journals (Sweden)

    Amirali Abbasi

    2017-01-01

    Full Text Available The adsorption of hydrogen sulfide molecule on undoped and N-doped TiO2/Au nanocomposites was investigated by density functional theory (DFT calculations. The results showed that the adsorption energies of H2S on the nanocomposites follow the order of 2N doped (Ti site>N-doped (Ti site>Undoped (Ti site. The structural properties including bond lengths, angles and adsorption energies and electronic properties in view of the projected density of states (PDOSs and molecular orbitals (MOs were analyzed in detail. The results indicated that the interaction between H2S molecule and N-doped TiO2/Au nanocomposite is stronger than that between H2S and undoped nanocomposite, suggesting that N-doping helps to strengthen the interaction of H2S with TiO2/Au nanocomposite. Mulliken population analysis was conducted to analyze the charge transfer between the nanocomposite and H2S molecule. Although H2S molecule has no significant interaction with undoped nanocomposite, it tends to be strongly adsorbed on the N-doped nanocomposite. The results also suggest that the two doped nitrogen atoms in TiO2 greatly strengthen the adsorption process, being a helpful procedure to help in the design and development of improved sensor devices for H2S detection.

  6. Communication: Thermodynamic analysis of critical conditions of polymer adsorption

    International Nuclear Information System (INIS)

    Cimino, R.; Neimark, A. V.; Rasmussen, C. J.

    2013-01-01

    Polymer adsorption to solid surfaces is a ubiquitous phenomenon, which has attracted long-lasting attention. Dependent on the competition between the polymer-solid adsorption and polymer-solvent solvation interactions, a chain may assume either 3d solvated conformation when adsorption is weak or 2d adsorbed conformation when adsorption is strong. The transition between these conformations occurring upon variation of adsorption strength is quite sharp, and in the limit of “infinite” chain length, can be treated as a critical phenomenon. We suggest a novel thermodynamic definition of the critical conditions of polymer adsorption from the equality of incremental chemical potentials of adsorbed and free chains. We show with the example of freely jointed Lennard-Jones chains tethered to an adsorbing surface that this new definition provides a link between thermodynamic and geometrical features of adsorbed chains and is in line with classical scaling relationships for the fraction of adsorbed monomers, chain radii of gyration, and free energy

  7. Communication: Thermodynamic analysis of critical conditions of polymer adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Cimino, R.; Neimark, A. V., E-mail: aneimark@rutgers.edu [Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854 (United States); Rasmussen, C. J. [DuPont Central Research and Development, Corporate Center for Analytical Sciences, Macromolecular Characterization, Route 141 and Henry Clay, Wilmington, Delaware 19803 (United States)

    2013-11-28

    Polymer adsorption to solid surfaces is a ubiquitous phenomenon, which has attracted long-lasting attention. Dependent on the competition between the polymer-solid adsorption and polymer-solvent solvation interactions, a chain may assume either 3d solvated conformation when adsorption is weak or 2d adsorbed conformation when adsorption is strong. The transition between these conformations occurring upon variation of adsorption strength is quite sharp, and in the limit of “infinite” chain length, can be treated as a critical phenomenon. We suggest a novel thermodynamic definition of the critical conditions of polymer adsorption from the equality of incremental chemical potentials of adsorbed and free chains. We show with the example of freely jointed Lennard-Jones chains tethered to an adsorbing surface that this new definition provides a link between thermodynamic and geometrical features of adsorbed chains and is in line with classical scaling relationships for the fraction of adsorbed monomers, chain radii of gyration, and free energy.

  8. Radioactive nuclide adsorption

    International Nuclear Information System (INIS)

    Fukushima, Kimichika.

    1982-01-01

    Purpose: To improve the efficiency of a radioactive nuclide adsorption device by applying a nickel plating on a nickel plate to render the surface active. Constitution: A capturing device for radioactive nuclide such as manganese 54, cobalt 60, 58 and the like is disposed to the inside of a pipeway provided on the upper portion of fuel assemblies through which liquid sodium as the coolant for LMFBR type reactor is passed. The device comprises a cylindrical adsorption body and spacers. The adsorption body is made of nickel and applied with a nickel plating on the surface thereof. The surface of the adsorption body is unevened to result in disturbance in the coolant and thereby improve the adsorptive efficiency. (Kawakami, Y.)

  9. Irreversible adsorption of particles on heterogeneous surfaces.

    Science.gov (United States)

    Adamczyk, Zbigniew; Jaszczółt, Katarzyna; Michna, Aneta; Siwek, Barbara; Szyk-Warszyńska, Lilianna; Zembala, Maria

    2005-12-30

    Methods of theoretical and experimental evaluation of irreversible adsorption of particles, e.g., colloids and globular proteins at heterogeneous surfaces were reviewed. The theoretical models were based on the generalized random sequential adsorption (RSA) approach. Within the scope of these models, localized adsorption of particles occurring as a result of short-ranged attractive interactions with discrete adsorption sites was analyzed. Monte-Carlo type simulations performed according to this model enabled one to determine the initial flux, adsorption kinetics, jamming coverage and the structure of the particle monolayer as a function of the site coverage and the particle/site size ratio, denoted by lambda. It was revealed that the initial flux increased significantly with the site coverage theta(s) and the lambda parameter. This behavior was quantitatively interpreted in terms of the scaled particle theory. It also was demonstrated that particle adsorption kinetics and the jamming coverage increased significantly, at fixed site coverage, when the lambda parameter increased. Practically, for alpha = lambda2theta(s) > 1 the jamming coverage at the heterogeneous surfaces attained the value pertinent to continuous surfaces. The results obtained prove unequivocally that spherically shaped sites were more efficient in binding particles in comparison with disk-shaped sites. It also was predicted that for particle size ratio lambda charge. Particle deposition occurred under diffusion-controlled transport conditions and their coverage was evaluated by direct particle counting using the optical and electron microscopy. Adsorption kinetics was quantitatively interpreted in terms of numerical solutions of the governing diffusion equation with the non-linear boundary condition derived from Monte-Carlo simulations. It was proven that for site coverage as low as a few percent the initial flux at heterogeneous surfaces attained the maximum value pertinent to homogeneous

  10. Interaction of Freshwater Diatom with Gold Nanoparticles: Adsorption, Assimilation, and Stabilization by Cell Exometabolites

    Directory of Open Access Journals (Sweden)

    Aridane G. González

    2018-03-01

    Full Text Available The rising concern about the potential toxicity of synthetic gold nanoparticles (AuNPs in aquatic environments requires a rigorous estimation of physico-chemical parameters of reactions between AuNPs and major freshwater microorganisms. This study addresses the interaction of 10-nm size, positively charged AuNPs with periphytic freshwater diatoms (Eolimna minima. The adsorption experiments on viable cells were performed in 10 mM NaCl and 5 mM NaCl + 5 mM NaHCO3 solution at a variable pH (3–10, at an AuNPs concentration from 1 µg/L to 10,000 µg/L, and an exposure time from a few minutes to 55 days. Three types of experiments, adsorption as a function of time (kinetics, pH-dependent adsorption edge, and constant-pH “Langmuirian” type isotherms, were conducted. In addition, long-term interactions (days to weeks of live diatoms (under light and in the darkness were performed. The adsorption was maximal at a pH from 3 to 6 and sizably decreased at a pH of 6 to 10. Results of adsorption experiments were modeled using a second order kinetic model, a Linear Programming Model, Freundlich isotherm, and a ligand binding equation for one site competition. The adsorption of AuNPs(+ most likely occurred on negatively-charged surface sites of diatom cell walls such as carboxylates or phosphorylates, similar to previously studied metal cations. Under light exposure, the AuNPs were stabilized in aqueous solution in the presence of live cells, probably due to the production of exometabolites by diatoms. The adsorbed amount of AuNPs decreased after several days of reaction, suggesting some AuNPs desorption. In the darkness, the adsorption and assimilation were stronger than under light. Overall, the behavior of positively charged AuNPs at the diatom–aqueous solution interface is similar to that of metal cations, but the affinity of aqueous AuNPs to cell exometabolites is higher, which leads to the stabilization of nanoparticles in solution in the

  11. Influence of alternative cations distribution in AgxLi96-x-LSX on dehydration kinetics and its selective adsorption performance for N2 and O2

    Science.gov (United States)

    Panezai, Hamida; Sun, Jihong; Jin, Xiaoqi

    2016-12-01

    Adsorption characteristics of pure gases N2 and O2 on various silver exchanged low silica X-type (AgxLi96-x-LSX) zeolites were investigated. The equilibrium adsorption isotherms of N2 and O2 were measured at 273 and 298 K. Textual and structural properties of parent and resultant AgxLi96-x-LSX were characterized by XRD, BET surface area, and SEM techniques. Kinetics of their thermal dehydration were studied by exploiting thermogravimetric and differential data (TG-DTG) obtained at three heating rates (5, 10 and 15 K) using two model-free (Kissinger and Flynn-Wall-Ozawa) and one model fitting (Coats-Redfern) methods. Forty one mechanism functions were used to evaluate kinetic triplet (activation energy, frequency factor, and most probable mechanism/model) for different stages of dehydration. Results revealed that the impact of very small content of silver on the adsorption of N2 is pronounced and attributed to weak chemical bonds formed between N2 and Ag+ clusters due to strong adsorption of N2 at low pressure, whereas O2 adsorption is affected to a negligible extent. In addition, the N2/O2 adsorption selectivity shows unexpected low values for Ag87.08Li7.94Na0.98-LSX with higher Ag+ content (91.00 %), which might be due to low crystalline water content as well as Ag+ clusters located at SIII sites. N2 adsorption strongly depends on temperature as higher adsorption occurs at low temperature 273 K as compared to 298 K.

  12. Adsorption of glyphosate in chilean soils and its relationship with unoccupied phosphate binding sites Adsorção de glifosato em solos chilenos e sua relação com sítios de adsorção disponíveis para adsorção de fosfato

    Directory of Open Access Journals (Sweden)

    Marcelo Kogan

    2003-04-01

    Full Text Available The objective of this work was to investigate glyphosate adsorption by soils and its relationship with unoccupied binding sites for phosphate adsorption. Soil samples of three Chilean soils series - Valdivia (Andisol, Clarillo (Inceptisol and Chicureo (Vertisol - were incubated with different herbicide concentrations. Glyphosate remaining in solution was determined by adjusting a HPLC method with a UV detector. Experimental maximum adsorption capacity were 15,000, 14,300 and 4,700 mg g¹ for Valdivia, Clarillo, and Chicureo soils, respectively. Linear, Freundlich, and Langmuir models were used to describe glyphosate adsorption. Isotherms describing glyphosate adsorption differed among soils. Maximum adjusted adsorption capacity with the Langmuir model was 231,884, 17,874 and 5,670 mg g-1 for Valdivia, Clarillo, and Chicureo soils, respectively. Glyphosate adsorption on the Valdivia soil showed a linear behavior at the range of concentrations used and none of the adjusted models became asymptotic. The high glyphosate adsorption capacity of the Valdivia soil was probably a result of its high exchangeable Al, extractable Fe, and alophan and imogolite clay type. Adsorption was very much related to phosphate dynamics in the Valdivia soil, which showed the larger unoccupied phosphate binding sites. However relationship between unoccupied phosphate binding sites and glyphosate adsorption in the other two soils (Clarillo and Chicureo was not clear.O objetivo deste trabalho foi investigar a adsorção de glifosato em solos e sua relação com os sítios disponíveis para adsorção de fosfato. Amostras de três solos chilenos - Valdivia (Andisol, Clarillo (Inceptisol e Chicureo (Vertisol - foram incubadas com diferentes concentrações do herbicida. O glifosato remanescente na solução foi determinado pelo método de HPLC com detector de UV modificado. A capacidade de adsorção máxima experimental foi de 15.000, 14.300 e 4.700 mg g-1 para os solos de

  13. Optimization and Control of Pressure Swing Adsorption Processes Under Uncertainty

    KAUST Repository

    Khajuria, Harish; Pistikopoulos, Efstratios N.

    2012-01-01

    The real-time periodic performance of a pressure swing adsorption (PSA) system strongly depends on the choice of key decision variables and operational considerations such as processing steps and column pressure temporal profiles, making its design

  14. Capability of defective graphene-supported Pd{sub 13} and Ag{sub 13} particles for mercury adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Meeprasert, Jittima; Junkaew, Anchalee; Rungnim, Chompoonut; Kunaseth, Manaschai [National Nanotechnology Center, NSTDA, 111 Thailand Science Park, Klong Luang, Pathum Thani 12120 Thailand (Thailand); Kungwan, Nawee [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Promarak, Vinich [School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Wangchan, Rayong 21210 (Thailand); Namuangruk, Supawadee, E-mail: supawadee@nanotec.or.th [National Nanotechnology Center, NSTDA, 111 Thailand Science Park, Klong Luang, Pathum Thani 12120 Thailand (Thailand)

    2016-02-28

    Graphical abstract: Defective graphene (DG) supported Ag{sub 13} and Pd{sub 13} nanoparticles acts as sorbents for elementary mercury (Hg{sup 0}) adsorption. Hg is inert to DG surface, but it moderately adsorbs on deposited Ag{sub 13}-DG and strongly adsorbs on deposited Pd{sub 13}-DG. - Highlights: • Pd{sub 13}-DG composite has highest stability. • Pd{sub 13}-DG composite is the most reactive sorbent for Hg{sup 0} adsorption. • Hg{sup 0} adsorption abilities of Pd-DG composites are relatively higher than those of Ag-DG composites. • The d-band center of deposited metal is an adsorption descriptor of composite models. - Abstract: Reactivity of single-vacancy defective graphene (DG) and DG-supported Pd{sub n} and Ag{sub n} (n = 1, 13) for mercury (Hg{sup 0}) adsorption has been studied using density functional theory calculation. The results show that Pd{sub n} binds defective site of DG much stronger than the Ag{sub n}, while metal nanocluster binds DG stronger than single metal atom. Metal clustering affects the adsorption ability of Pd composite while that of Ag is comparatively less. The binding strength of −8.49 eV was found for Pd{sub 13} binding on DG surface, indicating its high stability. Analyses of structure, energy, partial density of states, and d-band center (ε{sub d}) revealed that the adsorbed metal atom or cluster enhances the reactivity of DG toward Hg adsorption. In addition, the Hg adsorption ability of M{sub n}-DG composite is found to be related to the ε{sub d} of the deposited M{sub n}, in which the closer ε{sub d} of M{sub n} to the Fermi level correspond to the higher adsorption strength of Hg on M{sub n}-DG composite. The order of Hg adsorption strength on M{sub n}-DG composite are as follows: Pd{sub 13} (−1.68 eV) >> Ag{sub 13} (−0.67 eV) ∼ Ag{sub 1} (−0.69 eV) > Pd{sub 1} (−0.62 eV). Pd{sub 13}-DG composite is therefore more efficient sorbent for Hg{sup 0} removal in terms of high stability and high adsorption

  15. Adsorption of trace elements of radionuclides on hydrous iron oxides

    International Nuclear Information System (INIS)

    Music, S.; Ristic, M.

    1988-01-01

    Factors that influence the adsorption of trace elements or radionuclides on hydrous iron oxides were investigated. The adsorption of monovalent cations (Cs + , Rb + ) on hydrous iron oxides is not strongly pH-dependent and it can be regarded as nonspecific. On the other hand, the adsorption of Ag + , divalent cations (Zn 2+ , Cd 2+ , Mn 2+ , Sr 2+ ) or trivalent cations (Cr 3+ , La 3+ , Ce 3+ , Eu 3+ , Gd 3+ , Er 3+ , Yb 3+ ) is strongly pH-dependent. The regularities of the adsorption of these cations on hydrous iron oxides are discussed. The differences in the adsorption behaviour of some divalent and trivalent cations are also explained. Freshly precipitated iron(III) hydroxide can be used for the decontamination of radionuclides from low-level waste solutions. However, the efficacy of decontamination depends on the oxidation state and the chemical properties of radionuclides. (author) 40 refs.; 9 figs

  16. Enhanced fluoride adsorption using Al (III) modified calcium hydroxyapatite

    International Nuclear Information System (INIS)

    Nie, Yulun; Hu, Chun; Kong, Chuipeng

    2012-01-01

    Highlights: ► Al modified hydroxyapatite possessed a higher defluoridation capacity of 32.57 mg/g. ► Hydroxyl groups on the surface of Al-HAP was the adsorption sites for F − removal. ► Enhanced F − removal over Al-HAP was attributed to the modification with aluminum. - Abstract: Aluminum-modified hydroxyapatite (Al-HAP) was prepared and characterized using XRD and BET analyses. Al-HAP possessed higher defluoridation capacity (DC) of 32.57 mgF − /g than unmodified hydroxyapatite (HAP) which showed a DC of 16.38 mgF − /g. The effect of Al/Ca atomic ratio in Al-HAP, solution pH and co-existing anions was further studied. The results indicated that the adsorption data could be well described by the Langmuir isotherm model and the adsorption kinetic followed the pseudo-second-order model. The pH changes during the adsorption process suggested that the -OH on the surface of Al-HAP was the adsorption sites. The more adsorption sites were formed on Al modified HAP, which possessed abundant surface hydroxyl groups, resulting in higher efficiency of F − removal. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated in order to understand the nature of adsorption process. The results revealed that the adsorption reaction was a spontaneous and endothermic process.

  17. Study on Shale Adsorption Equation Based on Monolayer Adsorption, Multilayer Adsorption, and Capillary Condensation

    Directory of Open Access Journals (Sweden)

    Qing Chen

    2017-01-01

    Full Text Available Shale gas is an effective gas resource all over the world. The evaluation of pore structure plays a critical role in exploring shale gas efficiently. Nitrogen adsorption experiment is one of the significant approaches to analyze pore size structure of shale. Shale is extremely heterogeneous due to component diversity and structure complexity. Therefore, adsorption isotherms for homogeneous adsorbents and empirical isotherms may not apply to shale. The shape of adsorption-desorption curve indicates that nitrogen adsorption on shale includes monolayer adsorption, multilayer adsorption, and capillary condensation. Usually, Langmuir isotherm is a monolayer adsorption model for ideal interfaces; BET (Brunauer, Emmett, Teller adsorption isotherm is a multilayer adsorption model based on specific assumptions; Freundlich isotherm is an empirical equation widely applied in liquid phase adsorption. In this study, a new nitrogen adsorption isotherm is applied to simultaneously depict monolayer adsorption, multilayer adsorption, and capillary condensation, which provides more real and accurate representation of nitrogen adsorption on shale. In addition, parameters are discussed in relation to heat of adsorption which is relevant to the shape of the adsorption isotherm curve. The curve fitting results indicate that our new nitrogen adsorption isotherm can appropriately describe the whole process of nitrogen adsorption on shale.

  18. O{sub 2} adsorption and dissociation on the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) tri-metallic nanoparticles: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Sha; Yang, Yongpeng; Huang, Shiping, E-mail: huangsp@mail.buct.edu.cn

    2017-07-15

    Highlights: • O{sub 2} adsorption and dissociation on Pd{sub 13-n}Ni{sub n}@Pt{sub 42} NPs are performed by DFT. • Adsorption energies of O{sub 2} and O are strongly affected by the coordination number. • Adsorption energy and d-band center displays the opposite change tendency. • Ni{sub 13}@Pt{sub 42} is the most active catalyst among Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) NPs. - Abstract: Density functional theory calculations are performed to investigate O{sub 2} adsorption and dissociation on the icosahedral Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) tri-metallic nanoparticles. The parallel adsorption of O{sub 2} on Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) is stronger than the vertical adsorption. The adsorption of O{sub 2} on the bridge site (B1) is favorable in the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) nanoparticles, while the adsorption of O atom on the hollow site (H1) is preferred. The adsorption energies of O{sub 2} and O are strongly affected by the coordination number. Low coordination site shows strong adsorption of O{sub 2} and O on the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) nanoparticles. The adsorption energies of O{sub 2} and O atoms are found to be correlated well with the d-band center of surface Pt. For the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and13) nanoparticles catalysts, the ORR activity follows the order of Ni{sub 13}@Pt{sub 42} > Pd{sub 13}@Pt{sub 42} > Pd{sub 12}Ni{sub 1}@Pt{sub 42} > Pd{sub 1}Ni{sub 12}@Pt{sub 42}, illustrating that the Ni{sub 13}@Pt{sub 42} is the strongest ORR activity among the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and13) nanoparticles catalysts. Our results have important significance to understand the mechanism of O{sub 2} dissociation on the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) tri-metallic nanoparticles.

  19. Chemical characterization, leach, and adsorption studies of solidified low-level wastes

    International Nuclear Information System (INIS)

    Walter, M.B.; Serne, R.J.; Jones, T.L.; McLaurine, S.B.

    1986-12-01

    Laboratory and field leaching experiments are beig conducted by Pacific Northwest Laboratory (PNL) to investigate the performance of solidified low-level nuclear waste in a typical, arid, near-surface disposal site. Under PNL's Special Waste Form Lysimeters-Arid Program, a field test facility was constructed to monitor the leaching of commercial solidified waste. Laboratory experiments were conducted to investigate the leaching and adsorption characteristics of the waste forms in contact with soil. Liquid radioactive wastes solidified in cement, vinyl ester-styrene, and bitumen were obtained from commercial boiling water and pressurized water reactors, and buried in a field leaching facility on the Hanford site in southeastern Washington State. Batch leaching, soil column adsorption, and soil/waste form column experiments were conducted in the laboratory, using small-scale cement waste forms and Hanford site ground water. The purpose of these experiments is to evaluate the ability of laboratory leaching tests to predict leaching under actual field conditions and to determine which mechanisms (i.e., diffusion, solubility, adsorption) actually control the concentration of radionuclides in the soil surrounding the waste form. Chemical and radionuclide analyses performed on samples collected from the field and laboratory experiments indicate strong adsorption of /sup 134,137/Cs and 85 Sr onto the Hanford site sediment. Small amounts of 60 Co are leached from the waste forms as very mobile species. Some 60 Co migrated through the soil at the same rate as water. Chemical constituents present in the reactor waste streams also found at elevated levels in the field and laboratory leachates include sodium, sulfate, magnesium, and nitrate. Plausible solid phases that could be controlling some of the chemical and radionuclide concentrations in the leachate were identified using the MINTEQ geochemical computer code

  20. On the adsorption/reaction of acetone on pure and sulfate-modified zirconias.

    Science.gov (United States)

    Crocellà, Valentina; Cerrato, Giuseppina; Morterra, Claudio

    2013-08-28

    In situ FTIR spectroscopy was employed to investigate some aspects of the ambient temperature (actually, IR-beam temperature) adsorption of acetone on various pure and sulfate-doped zirconia specimens. Acetone uptake yields, on all examined systems and to a variable extent, different types of specific molecular adsorption, depending on the kind/population of available surface sites: relatively weak H-bonding interaction(s) with surface hydroxyls, medium-strong coordinative interaction with Lewis acidic sites, and strong H-bonding interaction with Brønsted acidic centres. Moreover acetone, readily and abundantly adsorbed in molecular form, is able to undergo the aldol condensation reaction (yielding, as the main reaction product, adsorbed mesityl oxide) only if the adsorbing material possesses some specific surface features. The occurrence/non-occurrence of the acetone self-condensation reaction is discussed, and leads to conclusions concerning the sites that catalyze the condensation reaction that do not agree with either of two conflicting interpretations present in the literature of acetone uptake/reaction on, mainly, zeolitic systems. In particular, what turns out to be actually necessary for the acetone aldol condensation reaction to occur on the examined zirconia systems is the presence of coordinatively unsaturated O(2-) surface sites of basicity sufficient to lead to the extraction of a proton from one of the CH3 groups of adsorbed acetone.

  1. Adsorption of 2,4-Dichlorophenoxyacetic Acid onto Volcanic Ash Soils:

    Directory of Open Access Journals (Sweden)

    Ei Ei Mon

    2009-01-01

    Full Text Available The quantification of the linear adsorption coefficient (Kd for soils plays a vital role to predict fate and transport of pesticides in the soil-water environment. In this study, we measured Kd values for 2,4-Dichlorophenoxyacetic acid (2,4-D adsorption onto Japanese volcanic ash soils with different amount of soil organic matter (SOM in batch experiments under different pH conditions. All measurements followed well both linear and Freundlich adsorption isotherms. Strong correlations were found between measured Kd values and pH as well as SOM. The 2,4-D adsorption increased with decreasing pH and with increasing SOM. Based on the data, a predictive Kd equation for volcanic ash soils, log (Kd = 2.04 - 0.37 pH + 0.91 log (SOM, was obtained by the multiple regression analysis. The predictive Kd equation was tested against measured 2,4-D sorption data for other volcanic ash soils and normal mineral soils from literature. The proposed Kd equation well predicted Kd values for other volcanic ash soils and slightly over- or under-predicted Kd values for normal mineral soils. The proposed Kd equation performed well against volcanic ash soils from different sites and countries, and is therefore recommended for predicting Kd values at different pH and SOM conditions for volcanic ash soils when calculating and predicting 2,4-D mobility and fate in soil and groundwater.

  2. Suitability of adsorption isotherms for predicting the retention capacity of active slag filters removing phosphorus from wastewater.

    Science.gov (United States)

    Pratt, C; Shilton, A

    2009-01-01

    Active slag filters are an emerging technology for removing phosphorus (P) from wastewater. A number of researchers have suggested that adsorption isotherms are a useful tool for predicting P retention capacity. However, to date the appropriateness of using isotherms for slag filter design remains unverified due to the absence of benchmark data from a full-scale, field filter operated to exhaustion. This investigation compared the isotherm-predicted P retention capacity of a melter slag with the P adsorption capacity determined from a full-scale, melter slag filter which had reached exhaustion after five years of successfully removing P from waste stabilization pond effluent. Results from the standard laboratory batch test showed that P adsorption correlated more strongly with the Freundlich Isotherm (R(2)=0.97, Pretention capacity of 0.014 gP/kg slag; markedly lower than the 1.23 gP/kg slag adsorbed by the field filter. Clearly, the result generated by the isotherm bears no resemblance to actual field capacity. Scanning electron microscopy analysis revealed porous, reactive secondary minerals on the slag granule surfaces from the field filter which were likely created by weathering. This slow weathering effect, which generates substantial new adsorption sites, is not accounted for by adsorption isotherms rendering them ineffective in slag filter design.

  3. Modelling phosphate adsorption to the soil: Application of the non-ideal competitive adsorption model

    International Nuclear Information System (INIS)

    Abou Nohra, Joumana S.; Madramootoo, Chandra A.; Hendershot, William H.

    2007-01-01

    Phosphorus (P) transport in subsurface runoff has increased despite the limited mobility of P in soils. This study investigated the ability of the non-ideal competitive adsorption (NICA) model to describe phosphate (PO 4 ) adsorption for soils in southern Quebec (Canada). We measured the surface charge and PO 4 adsorption capacity for 11 agricultural soils. Using the experimental data and a nonlinear fitting function, we derived the NICA model parameters. We found that the NICA model described accurately the surface charge of these soils with a mean R 2 > 0.99, and described the adsorption data with a mean R 2 = 0.96. We also found that the variable surface charge was distributed over the two binding sites with the low pH sites demonstrating a stronger binding energy for hydroxyl and PO 4 ions. We established that the NICA model is able to describe P adsorption for the soils considered in this study. - The NICA model accurately described the adsorption of phosphate to some southern Quebec soils

  4. Kinetics of adsorption and uptake of Cu2+ by Chlorella vulgaris: influence of pH, temperature, culture age, and cations.

    Science.gov (United States)

    Mehta, S K; Singh, Alpana; Gaur, J P

    2002-03-01

    Adsorption and uptake of Cu2+ by Chlorella vulgaris were distinguished by extracting the surface-bound Cu2+ with EDTA. The uptake of Cu2+ followed Michaelis Menten kinetics. The maximum rate of Cu2+ uptake (0.362fmolcell(-1) h(-1)) was obtained at pH 6.0. The rate of Cu2+ uptake was greater for cultures in the exponential phase of growth, and increased with a rise in temperature from 6 to 25 degrees C, thus pointing towards an active mechanism. The maximum number of Cu2+ binding sites was 3.245 fmol cell(-1) at pH 4.5. Adsorption of Cu2+ was strongly pH-dependent thereby indicating that the number and nature of metal binding sites on the cell surface change with changing chemistry of the solution. Unlike uptake, the adsorption remained unaffected by small changes in temperature. Older cultures displayed a higher Cu2+ adsorption capacity than the exponentially growing ones thus suggesting generation of new and/or additional Cu2+ binding sites on older cells of C. vulgaris. By pH titration, the cation-exchange capacity of Chlorella, measured in terms of H+/ Na+ exchange, was about 17 fmol cell(-1) at pH 10.5. Negligible cation exchange capacity at and below pH 5.0 indicated that ion exchange was not the sole mechanism of Cu2+ adsorption by Chlorella. The uptake and adsorption of Cu2+ were inhibited by 100 microM of various cations including other heavy metal ions. The general concept that cations competitively inhibit accumulation of metals in living organisms does not hold for C. vulgaris. Non-competitive, uncompetitive and mixed inhibition of Cu2+ uptake and adsorption by various cations were more common than competitive inhibition.

  5. adsorption, eosin, humic, peat

    OpenAIRE

    anshar, andi muhammad

    2015-01-01

    Eosin is one of the dyes commonly used in the industry and has the potential to cause pollution of the water environment. The Eosin pollution treatment methods used in this study was the adsorption method using humin fraction obtained from the peat land comes from Kalimantan. From the research data showed that the adsorption of eosin in humin result of washing with HCl / HF optimum at pH 4 and a contact time of 60 minutes with the adsorption-order rate was 8,4 x 10-3 min-1

  6. Competitive Protein Adsorption - Multilayer Adsorption and Surface Induced Protein Aggregation

    DEFF Research Database (Denmark)

    Holmberg, Maria; Hou, Xiaolin

    2009-01-01

    In this study, competitive adsorption of albumin and IgG (immunoglobulin G) from human serum solutions and protein mixtures onto polymer surfaces is studied by means of radioactive labeling. By using two different radiolabels (125I and 131I), albumin and IgG adsorption to polymer surfaces...... is monitored simultaneously and the influence from the presence of other human serum proteins on albumin and IgG adsorption, as well as their mutual influence during adsorption processes, is investigated. Exploring protein adsorption by combining analysis of competitive adsorption from complex solutions...... of high concentration with investigation of single protein adsorption and interdependent adsorption between two specific proteins enables us to map protein adsorption sequences during competitive protein adsorption. Our study shows that proteins can adsorb in a multilayer fashion onto the polymer surfaces...

  7. Effects of heavy metal adsorption on silicene

    KAUST Repository

    Kaloni, Thaneshwor P.

    2014-06-02

    Based on first-principles calculations, we study the effects of heavy metal atoms (Au, Hg, Tl, and Pb) adsorbed on silicene. We find that the hollow site is energetically favorable in each case. We particulary address the question how the adsorption modifies the band structure in the vicinity of the Fermi energy. Our results demonstrate that the heavy metal adatoms result in substantial energy gaps and band splittings in the silicene sheet as long as the binding is strong, which, however, is not always the case. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) Carbon nanotube flexible sponge was manufactured as high performance electromagnetic shielding material. Chemical vapour deposition (CVD) synthesized sponges with extreme light weight show an electromagnetic shielding above 20 dB and a specific electromagnetic shielding as high as 1100 dB cm3g-1 in the whole 1-18 GHz range. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Ab initio modeling of Al adsorption on CaF2 surfaces

    International Nuclear Information System (INIS)

    Barzilai, S.; Argaman, N.; Froumin, N.; Fuks, D.; Frage, N.

    2008-01-01

    Ab initio simulations of the adsorption of Al atoms on CaF 2 (0 0 1) and (1 1 1) surfaces have been performed for supercells with 7 different atomic configurations, using density functional theory. For (1 1 1) surfaces, a repulsive interaction was observed for most configurations, while a weak attraction was obtained when the Al atom was placed above F atoms. For the Ca-terminated (0 0 1) surface, the adsorption energy was about 5 times larger, whereas for the F-terminated (0 0 1) surface it was about 20 times greater. The comparative analysis indicates that the (0 0 1) surfaces are reactive and have a strong Al adatom bonding (chemisorption), especially for the F-terminated substrate. On the contrary, the (1 1 1) plane may be considered as non-reactive (physisorption), having a weak bonding of the Al adatom above the F site

  9. Nicotine adsorption on single wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Girao, Eduardo C. [Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, Campus do Pici, 60455-900 Fortaleza, Ceara (Brazil); Fagan, Solange B.; Zanella, Ivana [Area de Ciencias Tecnologicas, Centro Universitario Franciscano - UNIFRA, 97010-032 Santa Maria, RS (Brazil); Filho, Antonio G. Souza, E-mail: agsf@fisica.ufc.br [Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, Campus do Pici, 60455-900 Fortaleza, Ceara (Brazil)

    2010-12-15

    This work reports a theoretical study of nicotine molecules interacting with single wall carbon nanotubes (SWCNTs) through ab initio calculations within the framework of density functional theory (DFT). Different adsorption sites for nicotine on the surface of pristine and defective (8,0) SWCNTs were analyzed and the total energy curves, as a function of molecular position relative to the SWCNT surface, were evaluated. The nicotine adsorption process is found to be energetically favorable and the molecule-nanotube interaction is intermediated by the tri-coordinated nitrogen atom from the nicotine. It is also predicted the possibility of a chemical bonding between nicotine and SWCNT through the di-coordinated nitrogen.

  10. Application of the IAS theory combining to a three compartments description of natural organic matter to the adsorption of atrazine or diuron on activated carbon.

    Science.gov (United States)

    Baudu, M; Raveau, D; Guibaud, G

    2004-07-01

    The study of natural organic matter (NOM) adsorption on an activated carbon showed that equilibrium cannot be described according to a simple model such as a Freundlich isotherm and confirms the need for a closer description of the organic matter to simulate the competitive adsorption with micropollutants. A representation of the organic matter in three fractions is chosen: non-adsorbable, weak and strong adsorbable. The Ideal Adsorbed Solution Theory (IAST) can, under restrictive conditions, be used to effectively predict the competition between the pesticides and the organic matter. Therefore, it was noted that the model simulated with good precision the competition between atrazine or diuron and natural organic matter in aqueous solution for two activated carbons (A and B). The same parameters for the modeling of organic matter adsorption (Freudlich constants for two absorbable fractions) are used with the two pesticides. However, IAST does not allow correct modeling of pesticide adsorption onto two other (C and D) activated carbons in solution in natural water to be described. IAS theory does not reveal competition between diuron and NOM and pore blockage mechanism by the NOM is proposed as the major effect for the adsorption capacity reduction. However, the difference observed between the two pesticides could be due to in addition to the pore blockage effect, a particular phenomenon with the diuron, especially with D activated carbon. We can suppose specific interactions between the diuron and the adsorbed organic matter and a competition between adsorption sites of NOM and activated carbon surface.

  11. Hybrid adsorptive membrane reactor

    Science.gov (United States)

    Tsotsis, Theodore T [Huntington Beach, CA; Sahimi, Muhammad [Altadena, CA; Fayyaz-Najafi, Babak [Richmond, CA; Harale, Aadesh [Los Angeles, CA; Park, Byoung-Gi [Yeosu, KR; Liu, Paul K. T. [Lafayette Hill, PA

    2011-03-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  12. Co adsorption in kaolinite

    International Nuclear Information System (INIS)

    Souza, Eliel S.; Silva, Paulo S.C.

    2017-01-01

    Adsorption of metal ions in clay minerals has been used as an alternative to water and effluents treatment. Kaolinite is a clay mineral that presents low specific surface area and exchange ion capacity. Nevertheless, structural modifications can be achieved by means of acid or thermal activation. In this paper, it was studied the surface area of kaolinite/bentonite, kaolinite/activated carbon mixtures, thermal activated kaolinite and thermal activated kaolinite/activated carbon mixture. The mixture of kaolinite/activated carbon was tested for pH, contact time, interfering ions and initial concentration effects in the cobalt adsorption. Results showed that the optimized parameters are pH 6 and contact time of 30 min. Chromium acted as a competitive ion, zinc does not appear to have affected adsorption while iron seems to have favored it. Langmuir and Freundlich isotherms indicated that the adsorption of Co in the mixture of kaolinite/activated carbon is a spontaneous process. (author)

  13. Co adsorption in kaolinite

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Eliel S.; Silva, Paulo S.C., E-mail: eliel201019@hotmail.com, E-mail: pscsilva@ipen.br [Instituto de Pesquisas Energética s e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

    2017-07-01

    Adsorption of metal ions in clay minerals has been used as an alternative to water and effluents treatment. Kaolinite is a clay mineral that presents low specific surface area and exchange ion capacity. Nevertheless, structural modifications can be achieved by means of acid or thermal activation. In this paper, it was studied the surface area of kaolinite/bentonite, kaolinite/activated carbon mixtures, thermal activated kaolinite and thermal activated kaolinite/activated carbon mixture. The mixture of kaolinite/activated carbon was tested for pH, contact time, interfering ions and initial concentration effects in the cobalt adsorption. Results showed that the optimized parameters are pH 6 and contact time of 30 min. Chromium acted as a competitive ion, zinc does not appear to have affected adsorption while iron seems to have favored it. Langmuir and Freundlich isotherms indicated that the adsorption of Co in the mixture of kaolinite/activated carbon is a spontaneous process. (author)

  14. Macromolecule simulation and CH{sub 4} adsorption mechanism of coal vitrinite

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Song, E-mail: songyu10094488@126.com [School of Resources and Earth Science, China University of Mining & Technology, Xuzhou 221116 (China); Key Laboratory of Coal bed Methane Resource & Reservoir Formation Process, Ministry of Education, Xuzhou 221008 (China); Yan-ming, Zhu; Wu, Li [School of Resources and Earth Science, China University of Mining & Technology, Xuzhou 221116 (China); Key Laboratory of Coal bed Methane Resource & Reservoir Formation Process, Ministry of Education, Xuzhou 221008 (China)

    2017-02-28

    around [−C=O] and [C−O-C] whereas is rather dispersed about [-COOH] and [CH{sub 3}]. Simulation and experiment data are both in strong agreement with the Langmuir and D-A isothermal adsorption model and the D-A model fit better than Langmuir model. Preferential adsorption sites and orientations in vitrinite are identical to those of graphite/graphene. However, the energy of the most preferential location is much lower than that of graphite/graphene. CH{sub 4} is more easily absorbed on the surface of vitrinite. Adsorbability varies considerably at different adsorption locations and sites on the surface of vitrinite. Crystal parameter of vitrinite is a = b = c = 15.8 Å and majority of its micropores are blow 15.8 Å, indicating that the vitrinite have the optimum adsorption aperture. It can explain its higher observed adsorption capacities for CH{sub 4} compared with graphite/graphene.

  15. Adsorption mechanism of microcrystalline cellulose as green adsorbent for the removal of cationic methylene blue dye

    International Nuclear Information System (INIS)

    Tan, K.B.; Salamatinia, B.

    2016-01-01

    The adsorption mechanism of pure cellulose is yet to be explored. Thus, in this study, the adsorption mechanism of Microcrystalline Cellulose (MCC), a polysaccharide which is renewable, low cost and non-toxic, was studied on the adsorption of model dye Methylene blue (MB). It was found that the main adsorption mechanism of MB on MCC was due to the electrostatic attraction between the positively charged MB dye and negatively charged MCC. Thus, physical adsorption was the dominant effect, since electrostatic attraction is categorized as physical adsorption. This was verified by Dubinin-Radushkevich isotherm, whereby mean free energy adsorption value was found to be less than 8 kJ/mol. The values of Gibbs free energy for thermodynamics studies were found to be within the range of -20 kJ/mol and 0 kJ/mol, which also indicated physical adsorption. It was due to the electrostatic attraction as adsorption mechanism of this adsorption process which resulted rapid adsorption of MB dye. It was found that equilibrium dye concentration was achieved between 1-3 minutes, depending on the adsorption temperature. The rapid adsorption, as compared to a lot of materials, showed the potential of MCC as the future of green adsorbent. The adsorption of Methylene Blue on MCC fitted well in Langmuir Isotherm, with R2 values of higher than 0.99, while fitted moderately in Freundlich Isotherm, with R2 values between 0.9224 and 0.9223. Comparatively, the adsorption of MB on MCC fitted best Langmuir Isotherm as compared to Freundlich Isotherm which monolayer adsorption occurred at the homogenous surface of MCC. This also indicated adsorbed MB molecules do not interact with each other at neighboring adsorption sites. The maximum adsorption capacity calculated from Langmuir Isotherm was found to be 4.95 mg/g. Despite the potential of MCC as green adsorbent, the challenge of low adsorption capacity has to be addressed in the future. (author)

  16. Adsorption behavior and electronic properties of Pdn (n ≤ 10) clusters on silicon carbide nanotubes: a first-principles study

    International Nuclear Information System (INIS)

    Wang Jianguang; Ma Li; Wang Guanghou

    2013-01-01

    First-principles calculations have been carried out to investigate the adsorption of Pd n (n ≤ 10) clusters on the single-walled (8, 0) and (5, 5) SiC nanotubes (SiCNTs). We find that the Pd n clusters can be stably adsorbed on the outer surfaces of both SiCNTs through an exothermic adsorption process. The adsorption energies of the Pd n clusters on the (8, 0) SiCNT are generally larger than those of clusters on the (5, 5) SiCNT. The number of bonds between the Pd n clusters and the SiCNTs increases with increasing cluster size. The Pd atoms adjacent to the SiCNTs adsorb preferentially on the bridge sites over an axial Si–C bond. The adsorption leads to elongation of the Pd–Pd bond lengths and structural reconstruction for the Pd n clusters. Moreover, the adsorbed Pd n clusters show two-layered structures at the cluster size n ≥ 4. We also find that the adsorbed Pd n clusters induce some impurity states within the band gap of the pristine SiCNTs and the strong pd hybridization near the Fermi level, thereby reducing the band gap. The charge transfer from the SiCNTs to the Pd atoms that occurs is observed for all the systems considered. Due to the strong interactions between the Pd n clusters and the SiCNTs, most adsorbed Pd n clusters exhibit zero magnetic moment. (paper)

  17. Adsorption characteristics of brilliant green dye on kaolin

    International Nuclear Information System (INIS)

    Nandi, B.K.; Goswami, A.; Purkait, M.K.

    2009-01-01

    Experimental investigations were carried out to adsorb toxic brilliant green dye from aqueous medium using kaolin as an adsorbent. Characterization of kaolin is done by measuring: (i) particle size distribution using particle size analyzer, (ii) BET surface area using BET surface analyzer, and (iii) structural analysis using X-ray diffractometer. The effects of initial dye concentration, contact time, kaolin dose, stirring speed, pH and temperature were studied for the adsorption of brilliant green in batch mode. Adsorption experiments indicate that the extent of adsorption is strongly dependent on pH of solution. Free energy of adsorption (ΔG 0 ), enthalpy (ΔH 0 ) and entropy (ΔS 0 ) changes are calculated to know the nature of adsorption. The calculated values of ΔG 0 at 299 K and 323 K indicate that the adsorption process is spontaneous. The estimated values of ΔH 0 and ΔS 0 both show the negative sign, which indicate that the adsorption process is exothermic and the dye molecules are organized on the kaolin surface in less randomly fashion than in solution. The adsorption kinetic has been described by first-order, pseudo-second-order and intra-particle-diffusion models. It was observed that the rate of dye adsorption follows pseudo-second-order model for the dye concentration range studied in the present case. Standard adsorption isotherms were used to fit the experimental equilibrium data. It was found that the adsorption of brilliant green on kaolin follows the Langmuir adsorption isotherm

  18. A review on adsorption refrigeration technology and adsorption deterioration in physical adsorption systems

    Energy Technology Data Exchange (ETDEWEB)

    Wang, D.C.; Li, Y.H. [College of Electromechanical Engineering, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Laboratory of Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Li, D.; Zhang, J.P. [College of Electromechanical Engineering, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Xia, Y.Z. [Laboratory of Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China)

    2010-01-15

    As one kind of environmentally friendly refrigeration, the adsorption refrigeration has attracted many attentions in resent decades. This paper introduces the researches of adsorption refrigeration systems with the commonly used working pairs, advanced adsorption cycles, heat and mass transfer enhancement and attempts of adsorption refrigeration applications. Poor heat and mass transfer problem is a bottleneck to prevent the improvements of the adsorption refrigeration technique. Two ways to enhance the heat and mass transfer are discussed in this paper. The adsorption deterioration of adsorbent, another obstacle to physical adsorption refrigeration applications, is also pointed out. And the possible reasons and the possible methods are analyzed. (author)

  19. Investigation of fluorine adsorption on nitrogen doped MgAl{sub 2}O{sub 4} surface by first-principles

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Xiaojun; Xu, Zhenming [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Li, Jie, E-mail: 15216105346@163.com [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Chen, Jiangan [Faculty of Resource and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou 341000 (China); Liu, Qingsheng [Faculty of Metallurgical and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000 (China)

    2016-07-15

    Graphical abstract: First-principles calculations indicate that MgAl{sub 2}O{sub 4} surface is fluorine-loving, but hydrophobic. N doped MgAl{sub 2}O{sub 4} (100) surface structure shows the highest fluorine adsorption performance and fluorine atom is more preferentially adsorbed on the Mg-Al bridge site. The fluorine adsorption intensity follow this order: N doped MgAl{sub 2}O{sub 4} (100) > Al{sub 2}O{sub 3} (0001) > MgAl{sub 2}O{sub 4} (100) > MgO (100). N doped MgAl{sub 2}O{sub 4} is a promising candidate for fluorine removal. - Highlights: • MgAl{sub 2}O{sub 4} surface is fluorine-loving, not hydrophilic. • Fluorine preferentially adsorbs on the Mg-Al bridge site. • Adsorption intensity follow this order: N doped MgAl{sub 2}O{sub 4} > Al{sub 2}O{sub 3} > MgAl{sub 2}O{sub 4} > MgO. • Excellent adsorption performance attributes to electron compensation of N atom. • Nitrogen doped MgAl{sub 2}O{sub 4} is a promising candidate for fluorine removal. - Abstract: The nature of fluorine adsorption on pure and N doped MgAl{sub 2}O{sub 4} surface has been investigated by first-principles calculations based on the density functional theory. Calculated results indicate that MgAl{sub 2}O{sub 4} surface is fluorine-loving, not hydrophilic. Nitrogen doped MgAl{sub 2}O{sub 4} (100) surface shows the highest fluorine adsorption performance and fluorine atom preferentially adsorbs on the Mg-Al bridge site. The fluorine adsorption intensity follow this order: Nitrogen doped MgAl{sub 2}O{sub 4} (100) > Al{sub 2}O{sub 3} (0001) > MgAl{sub 2}O{sub 4} (100) > MgO (100). In-depth PDOS analysis suggested that 2p orbitals of F atom strongly hybridized with 3s- and 3p-orbitals of Al atom contribute to its high adsorption intensity. According to the analysis of Hirshfeld charge, the excellent fluorine adsorption performance of nitrogen doped MgAl{sub 2}O{sub 4} attributes to the electron compensation effect of nitrogen atom and strong electrostatic interactions. All these

  20. Bovine serum albumin adsorption on functionalized porous silicon surfaces

    Science.gov (United States)

    Tay, Li-Lin; Rowell, Nelson L.; Lockwood, David J.; Boukherroub, Rabah

    2004-10-01

    The large surface area within porous Si (pSi) and its strong room temperature photoluminescence (PL) make it an ideal host for biological sensors. In particular, the development of pSi-based optical sensors for DNA, enzyme and other biochemical molecules have become of great interest. Here, we demonstrate that the in-situ monitoring of the pSi PL behaviour can be used as a positive identification of bovine serum albumin (BSA) protein adsorption inside the porous matrix. Electrochemically prepared pSi films were first functionalized with undecylenic acid to produce an organic monolayer covalently attached to the porous silicon surfaces. The acid terminal group also provided favourable BSA binding sites on the pSi matrix sidewalls. In-situ PL spectra showed a gradual red shift (up to 12 meV) in the PL peak energy due to the protein incorporation into the porous matrix. The PL then exhibited a continuous blue shift after saturation of the protein molecules in the pores. This blue shift of the PL peak frequency and a steady increase in the PL intensity is evidence of surface oxidation. Comparing the specular reflectance obtained by Fourier transform infrared spectroscopy (FTIR) before and after BSA incubation confirmed the adsorption of protein in the pSi matrix.

  1. Coverage-dependent adsorption thermodynamics of oxygen on ZnO(0001)

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ming; Seebauer, Edmund G., E-mail: eseebaue@illinois.edu

    2017-03-01

    Highlights: • Adsorption enthalpy and entropy of oxygen on Zn-term ZnO(0001) were measured by photoreflectance. • These parameters are large in magnitude and vary nonmonotonically with coverage. • Many kinds of sites, chemical species and reconstructions contribute to this behavior. • Entropic and enthalpic contributions to the free energy are comparable near room temperature. - Abstract: The equilibrium behavior of oxygen adsorbed on metal oxide surfaces such as ZnO(0001) often affects their behavior in applications such as gas sensing. The present work attempts to bridge this distinct gap to applications from an alternate perspective by employing the optical technique of photoreflectance (PR) to measure the enthalpy ΔH{sub ads} and entropy ΔS{sub ads} of oxygen adsorption as a function of coverage on Zn-terminated ZnO(0001). The large and strongly coverage-dependent parameters, stemming from a multiplicity of sites, chemical species and reconstructions, lead to a nonmonotonic coverage variation in both ΔH{sub ads} and ΔS{sub ads}. The entropic contribution to the free energy is comparable to the enthalpic contribution even near room temperature, so that temperature effects on oxygen adsorption may be uncommonly large.

  2. Laboratory study on the adsorption of Mn(2+) on suspended and deposited amorphous Al(OH)(3) in drinking water distribution systems.

    Science.gov (United States)

    Wang, Wendong; Zhang, Xiaoni; Wang, Hongping; Wang, Xiaochang; Zhou, Lichuan; Liu, Rui; Liang, Yuting

    2012-09-01

    Manganese (II) is commonly present in drinking water. This paper mainly focuses on the adsorption of manganese on suspended and deposited amorphous Al(OH)(3) solids. The effects of water flow rate and water quality parameters, including solution pH and the concentrations of Mn(2+), humic acid, and co-existing cations on adsorption were investigated. It was found that chemical adsorption mainly took place in drinking water with pHs above 7.5; suspended Al(OH)(3) showed strong adsorption capacity for Mn(2+). When the total Mn(2+) input was 3 mg/L, 1.0 g solid could accumulate approximately 24.0 mg of Mn(2+) at 15 °C. In drinking water with pHs below 7.5, because of H(+) inhibition, active reaction sites on amorphous Al(OH)(3) surface were much less. The adsorption of Mn(2+) on Al(OH)(3) changed gradually from chemical coordination to physical adsorption. In drinking water with high concentrations of Ca(2+), Mg(2+), Fe(3+), and HA, the removal of Mn(2+) was enhanced due to the effects of co-precipitation and adsorption. In solution with 1.0 mg/L HA, the residual concentration of Mn(2+) was below 0.005 mg/L, much lower than the limit value required by the Chinese Standard for Drinking Water Quality. Unlike suspended Al(OH)(3), deposited Al(OH)(3) had a much lower adsorption capacity of 0.85 mg/g, and the variation in flow rate and major water quality parameters had little effect on it. Improved managements of water age, pipe flushing and mechanical cleaning were suggested to control residual Mn(2+). Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Adsorption of uranium on halloysite

    International Nuclear Information System (INIS)

    Kilislioglu, A.; Bilgin, B.

    2002-01-01

    Adsorption of uranium (U(VI)) from aqueous solutions on halloysite type clay was studied as a function of amount of adsorbent, initial concentration and pH. The values of adsorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption was calculated as 5.91 kJ/mol from D-R adsorption isotherm. Lagergren and Bangham equation has been used for dynamic modelling of process and the rate constants of adsorption of uranium on halloysite type clay were calculated at 293, 313 and 333 K. In order to explain the mechanism of adsorption reaction, the rate constants were calculated at high and low uranium concentrations. Adsorption reaction was studied at 293, 303, 313, 323 and 333 K for halloysite type clay and also thermodynamic constants have been calculated. The results show that the adsorption reaction was endothermic and more spontaneous at high temperature. (orig.)

  4. Adsorption of uranium on halloysite

    Energy Technology Data Exchange (ETDEWEB)

    Kilislioglu, A.; Bilgin, B. [Istanbul Univ. (Turkey). Faculty of Engineering

    2002-07-01

    Adsorption of uranium (U(VI)) from aqueous solutions on halloysite type clay was studied as a function of amount of adsorbent, initial concentration and pH. The values of adsorption data were fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. The mean energy of adsorption was calculated as 5.91 kJ/mol from D-R adsorption isotherm. Lagergren and Bangham equation has been used for dynamic modelling of process and the rate constants of adsorption of uranium on halloysite type clay were calculated at 293, 313 and 333 K. In order to explain the mechanism of adsorption reaction, the rate constants were calculated at high and low uranium concentrations. Adsorption reaction was studied at 293, 303, 313, 323 and 333 K for halloysite type clay and also thermodynamic constants have been calculated. The results show that the adsorption reaction was endothermic and more spontaneous at high temperature. (orig.)

  5. Adsorption behavior of strontium on binary mineral mixtures of Montmorillonite and Kaolinite

    Energy Technology Data Exchange (ETDEWEB)

    Bascetin, Elvan [Cekmece Nuclear Research and Training Center, P.K.1 34149, Atatuerk Airport, Istanbul (Turkey); Atun, Guelten [Engineering Faculty, Chemistry Department, Istanbul University, 34850 Avcilar, Istanbul (Turkey)]. E-mail: gultena@istanbul.edu.tr

    2006-08-15

    The adsorption behavior of kaolinite and montmorillonite minerals and their mixtures in respect of Sr ion were studied by means of a batch method using {sup 90}Sr as a radio tracer. The effect of several parameters such as temperature, pH, Sr concentration and supporting electrolyte were investigated. Experimentally measured distribution coefficients showed a good agreement to within 98.5-99.7% with theoretically calculated values. The values of adsorption capacity of adsorbents and mean adsorption energy of adsorption were calculated by fitting the adsorption data to Dubinin-Radushkevich isotherm. The adsorption capacity of clay mixtures decreased as kaolinite fractions increased. The mean adsorption energy values of 8.0-9.5 kJ mol{sup -1} showed that adsorption was governed by ion exchange. The Freundlich parameters were used to characterize a site distribution function for binary exchange between Sr and Na.

  6. Adsorption behavior of strontium on binary mineral mixtures of Montmorillonite and Kaolinite

    International Nuclear Information System (INIS)

    Bascetin, Elvan; Atun, Guelten

    2006-01-01

    The adsorption behavior of kaolinite and montmorillonite minerals and their mixtures in respect of Sr ion were studied by means of a batch method using 90 Sr as a radio tracer. The effect of several parameters such as temperature, pH, Sr concentration and supporting electrolyte were investigated. Experimentally measured distribution coefficients showed a good agreement to within 98.5-99.7% with theoretically calculated values. The values of adsorption capacity of adsorbents and mean adsorption energy of adsorption were calculated by fitting the adsorption data to Dubinin-Radushkevich isotherm. The adsorption capacity of clay mixtures decreased as kaolinite fractions increased. The mean adsorption energy values of 8.0-9.5 kJ mol -1 showed that adsorption was governed by ion exchange. The Freundlich parameters were used to characterize a site distribution function for binary exchange between Sr and Na

  7. One-step polymer surface modification for minimizing drug, protein, and DNA adsorption in microanalytical systems

    DEFF Research Database (Denmark)

    Larsen, Esben Kjær Unmack; Larsen, Niels Bent

    2013-01-01

    The non-specific adsorption of dissolved analytes strongly reduces the sensitivity and reliability in polymer microanalytical systems. Here, a one-step aqueous phase procedure modifies polymer material surfaces to strongly reduce their non-specific adsorption of a broad range of organic analytes ...

  8. Atomic hydrogen and oxygen adsorptions in single-walled zigzag silicon nanotubes

    International Nuclear Information System (INIS)

    Chen, Haoliang; Ray, Asok K.

    2013-01-01

    Ab initio calculations have been performed to study the electronic and geometric structure properties of zigzag silicon nanotubes. Full geometry and spin optimizations have been performed without any symmetry constraints with an all electron 3-21G* basis set and the B3LYP hybrid functional. The largest zigzag SiNT studied here, (12, 0), has a binding energy per atom of 3.584 eV. Atomic hydrogen and oxygen adsorptions on (9, 0) and (10, 0) nanotubes have also been studied by optimizing the distances of the adatoms from both inside and outside the tube. The adatom is initially placed in four adsorption sites-parallel bridge (PB), zigzag bridge (ZB), hollow, and on-top site. The on-top site is the most preferred site for hydrogen atom adsorbed on (9, 0), with an adsorption energy of 3.0 eV and an optimized distance of 1.49 Å from the adatom to the nearest silicon atom. For oxygen adsorption on (9, 0), the most preferred site is the ZB site, with an adsorption energy of 5.987 eV and an optimized distance of 1.72 Å. For atomic hydrogen adsorption on (10, 0), the most preferred site is also the on-top site with an adsorption energy of 3.174 eV and an optimized distance of 1.49 Å. For adsorption of atomic oxygen on (10, 0), the most preferred site is PB site, with an adsorption energy of 6.306 eV and an optimized distance of 1.71 Å. The HOMO–LUMO gaps of (9, 0) after adsorptions of hydrogen and oxygen atoms decrease while the HOMO–LUMO gaps of (10, 0) increase after adsorption of hydrogen and oxygen

  9. Waved graphene: Unique structure for the adsorption of small molecules

    International Nuclear Information System (INIS)

    Pan, Hui

    2017-01-01

    We propose waved graphenes for the strong adsorption of molecules and investigate their potential applications. We find that the physical adsorption of molecules on waved graphene is greatly enhanced by compression. At optimal compression, the physical adsorption energies of H_2, N_2, NO, and CO are increased by 6–9 times, and that for O_2 is more than 2 times. We show that the energy for their chemical adsorption on waved graphene decreases dramatically with the increment of compression. The energy of dissociation of H_2 on flat graphene is 1.63 eV and reduced to 0.06 eV (96% reduction) on waved graphene at a compression of 50%, respectively. The energy for chemical adsorption of O_2 on waved graphenes is extremely reduced from 0.98 eV to −0.57 eV as with compression increasing from 0 to 50%, indicating the transition of endothermic chemical adsorption to exothermic. We further show that the electronic properties of waved graphenes are modified, leading to the change of electrical characters. We see that the waved graphenes may find applications in gas storage, sensor and catalyst because of enhanced physical and chemical adsorption and the induced change of electronic properties. - Highlights: • Adsorption of small molecules on waved graphene is greatly enhanced. • Strong physical adsorption in the trough of waved graphene can be achieved by tuning the curvature. • Chemical adsorption is on the crest of waved graphene. • Exothermic dissociation of H2 and O2 can be realized on waved graphene under high compression. • Wave graphene can be candidates as catalysts and gas storage/sensor.

  10. Waved graphene: Unique structure for the adsorption of small molecules

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Hui, E-mail: huipan@umac.mo

    2017-03-01

    We propose waved graphenes for the strong adsorption of molecules and investigate their potential applications. We find that the physical adsorption of molecules on waved graphene is greatly enhanced by compression. At optimal compression, the physical adsorption energies of H{sub 2}, N{sub 2}, NO, and CO are increased by 6–9 times, and that for O{sub 2} is more than 2 times. We show that the energy for their chemical adsorption on waved graphene decreases dramatically with the increment of compression. The energy of dissociation of H{sub 2} on flat graphene is 1.63 eV and reduced to 0.06 eV (96% reduction) on waved graphene at a compression of 50%, respectively. The energy for chemical adsorption of O{sub 2} on waved graphenes is extremely reduced from 0.98 eV to −0.57 eV as with compression increasing from 0 to 50%, indicating the transition of endothermic chemical adsorption to exothermic. We further show that the electronic properties of waved graphenes are modified, leading to the change of electrical characters. We see that the waved graphenes may find applications in gas storage, sensor and catalyst because of enhanced physical and chemical adsorption and the induced change of electronic properties. - Highlights: • Adsorption of small molecules on waved graphene is greatly enhanced. • Strong physical adsorption in the trough of waved graphene can be achieved by tuning the curvature. • Chemical adsorption is on the crest of waved graphene. • Exothermic dissociation of H2 and O2 can be realized on waved graphene under high compression. • Wave graphene can be candidates as catalysts and gas storage/sensor.

  11. Sub-ambient carbon dioxide adsorption properties of nitrogen doped graphene

    Energy Technology Data Exchange (ETDEWEB)

    Tamilarasan, P.; Ramaprabhu, Sundara, E-mail: ramp@iitm.ac.in [Alternative Energy and Nanotechnology Laboratory (AENL), Nano Functional Materials Technology Centre (NFMTC), Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)

    2015-04-14

    Carbon dioxide adsorption on carbon surface can be enhanced by doping the surface with heterogeneous atoms, which can increase local surface affinity. This study presents the carbon dioxide adsorption properties of nitrogen doped graphene at low pressures (<100 kPa). Graphene was exposed to nitrogen plasma, which dopes nitrogen atoms into carbon hexagonal lattice, mainly in pyridinic and pyrrolic forms. It is found that nitrogen doping significantly improves the CO{sub 2} adsorption capacity at all temperatures, due to the enrichment of local Lewis basic sites. In general, isotherm and thermodynamic parameters suggest that doped nitrogen sites have nearly same adsorption energy of surface defects and residual functional groups. The isosteric heat of adsorption remains in physisorption range, which falls with surface coverage, suggesting the distribution of magnitude of adsorption energy. The absolute values of isosteric heat and entropy of adsorption are slightly increased upon nitrogen doping.

  12. Simulating multi-component liquid phase adsorption systems: ethanol and residual sugar

    Energy Technology Data Exchange (ETDEWEB)

    Jones, R.; Tezel, F.H.; Thibault, J. [Department of Chemical and Biological Engineering, University of Ottawa (Canada)], email: Jules.Thibault@uottawa.ca

    2011-07-01

    A series of multi-component adsorption studies was performed to determine the relative advantages of producing ethanol which is to be blended with gasoline. These studies developed a model to describe the competition for adsorption sites between ethanol and sugar molecules on the surface of the adsorbent. Three competitive adsorption models established by batch systems were examined to evaluate the suitability of the experiment data across different ethanol and sugar concentrations and determine their isotherm parameters. Multi-component packed bed adsorption experiments were then performed. The results show that ethanol capacity was decreased only slightly from that obtained in single component adsorption studies. There is significant evidence to indicate that sugar displacement from adsorption sites occurs because adsorption of ethanol is preferred. So the capacity of sugars will be greatly reduced if there are appreciable ethanol concentrations.

  13. Adsorption of lead onto smectite from aqueous solution.

    Science.gov (United States)

    Mhamdi, M; Galai, H; Mnasri, N; Elaloui, E; Trabelsi-Ayadi, M

    2013-03-01

    The purpose of this research is to study the effect of a new method of adsorption using membrane filtration to determine the maximum amount of lead adsorbed by clay and investigate the behavior of the clay after adsorption of the said metal. Treatment of wastewater contaminated with heavy metals depends on the characteristics of the effluent, the amount of final discharge, the cost of treatment, and the compatibility of the treatment process. The process of adsorption of heavy metals by clays may be a simple, selective, and economically viable alternative to the conventional physical-chemical treatment. This is justified by the importance of the surface developed by this material, the presence of negative charges on the said surface, the possibility of ion exchange taking place, and its wide availability in nature. The removal of lead from wastewater was studied by using the adsorption technique and using clay as the adsorbent. A method was optimized for adsorption through a membrane approaching natural adsorption. This new method is simple, selective, and the lead adsorption time is about 3 days. The various properties of clay were determined. It was observed that the cation exchange capacity of the clay was 56 meq/100 g of hydrated clay for the raw sample and 82 meq/100 g for the purified sample. The total surface area determined by the methylene blue method was equal to 556 and 783 m(2)/g for the raw and purified samples, respectively. The adsorption kinetics depends on several parameters. The Pb(II) clay, obeys the Langmuir, Freundlich, and the Elovich adsorption isotherms with high regression coefficients. The use of this adsorbent notably decreases the cost of treatment. It was concluded that clay shows a strong adsorption capacity on Pb(II), the maximum interaction occurring with purified clay treated at high concentration of lead. It is proposed that this adsorption through a membrane be extended for the treatment of effluents containing other metals.

  14. Regenerative adsorption distillation system

    KAUST Repository

    Ng, Kim Choon

    2013-12-26

    There is provided a regenerative adsorption distillation system comprising a train of distillation effects in fluid communication with each other. The train of distillation effects comprises at least one intermediate effect between the first and last distillation effects of the train, each effect comprising a vessel and a condensing tube for flow of a fluid therein. The system further comprises a pair of adsorption-desorption beds in vapour communication with the last effect and at least one intermediate effect, wherein the beds contain an adsorbent that adsorbs vapour from the last effect and transmits desorbed vapour into at least one of the intermediate effect.

  15. Regenerative adsorption distillation system

    KAUST Repository

    Ng, Kim Choon; Thu, Kyaw; Amy, Gary; Chunggaze, Mohammed; Al-Ghasham, Tawfiq

    2013-01-01

    There is provided a regenerative adsorption distillation system comprising a train of distillation effects in fluid communication with each other. The train of distillation effects comprises at least one intermediate effect between the first and last distillation effects of the train, each effect comprising a vessel and a condensing tube for flow of a fluid therein. The system further comprises a pair of adsorption-desorption beds in vapour communication with the last effect and at least one intermediate effect, wherein the beds contain an adsorbent that adsorbs vapour from the last effect and transmits desorbed vapour into at least one of the intermediate effect.

  16. The adsorption coefficient (KOC) of chlorpyrifos in clay soil

    International Nuclear Information System (INIS)

    Halimah Muhamad; Nashriyah Mat; Tan Yew Ai; Ismail Sahid

    2005-01-01

    The purpose of this study was to determine the adsorption coefficient (KOC) of chlorpyrifos in clay soil by measuring the Freundlich adsorption coefficient (Kads(f)) and desorption coefficient (1/n value) of chlorpyrifos. It was found that the Freundlich adsorption coefficient (Kads(f)) and the linear regression (r2) of the Freundlich adsorption isotherm for chlorpyrifos in the clay soil were 52.6 L/kg and 0.5244, respectively. Adsorption equilibrium time was achieved within 24 hours for clay soil. This adsorption equilibrium time was used to determine the effect of concentration on adsorption. The adsorption coefficient (KOC) of clay soil was found to be 2783 L/kg with an initial concentration solution of 1 μg/g, soil-solution ratio (1:5) at 300 C when the equilibrium between the soil matrix and solution was 24 hours. The Kdes decreased over four repetitions of the desorption process. The chlorpyrifos residues may be strongly adsorbed onto the surface of clay. (Author)

  17. Adsorption of heavy metal ions by sawdust of deciduous trees

    International Nuclear Information System (INIS)

    Bozic, D.; Stankovic, V.; Gorgievski, M.; Bogdanovic, G.; Kovacevic, R.

    2009-01-01

    The adsorption of heavy metal ions from synthetic solutions was performed using sawdust of beech, linden and poplar trees. The adsorption depends on the process time, pH of the solution, type of ions, initial concentration of metals and the sawdust concentration in suspension. The kinetics of adsorption was relatively fast, reaching equilibrium for less than 20 min. The adsorption equilibrium follows Langmuir adsorption model. The ion exchange mechanism was confirmed assuming that the alkali-earth metals from the adsorbent are substituted by heavy metal ions and protons. On lowering the initial pH, the adsorption capacity decreased, achieving a zero value at a pH close to unity. The maximum adsorption capacity (7-8 mg g -1 of sawdust) was achieved at a pH between 3.5 and 5 for all the studied kinds of sawdust. The initial concentration of the adsorbate and the concentration of sawdust strongly affect the process. No influence of particles size was evidenced. A degree of adsorption higher than 80% can be achieved for Cu 2+ ions but it is very low for Fe 2+ ions, not exceeding 10%.

  18. Theoretical investigation of CO adsorption on Rhn (n = 3-13) clusters

    NARCIS (Netherlands)

    Shetty, S.G.; Strych, S.; Jansen, A.P.J.; Santen, van R.A.

    2009-01-01

    The adsorption of CO onto Rhn (n = 3–13) clusters has been investigated using the density functional approach. Stable active sites for CO adsorption such as top, bridge, and hollow have been identified on these clusters. Our results show that CO mostly prefers the bridge or top site, except on the

  19. Ozone adsorption on carbon nanoparticles

    Science.gov (United States)

    Chassard, Guillaume; Gosselin, Sylvie; Visez, Nicolas; Petitprez, Denis

    2014-05-01

    Carbonaceous particles produced by incomplete combustion or thermal decomposition of hydrocarbons are ubiquitous in the atmosphere. On these particles are adsorbed hundreds of chemical species. Those of great concern to health are polycyclic aromatic hydrocarbons (PAHs). During atmospheric transport, particulate PAHs react with gaseous oxidants. The induced chemical transformations may change toxicity and hygroscopicity of these potentially inhalable particles. The interaction between ozone and carbon particles has been extensively investigated in literature. However ozone adsorption and surface reaction mechanisms are still ambiguous. Some studies described a fast catalytic decomposition of ozone initiated by an atomic oxygen chemisorption followed by a molecular oxygen release [1-3]. Others suggested a reversible ozone adsorption according to Langmuir-type behaviour [4,5]. The aim of this present study is a better understanding of ozone interaction with carbon surfaces. An aerosol of carbon nanoparticles was generated by flowing synthetic air in a glass tube containing pure carbon (primary particles studied. Accordingly to literature, it has been observed that the number of gas-phase ozone molecules lost per unit particle surface area tends towards a plateau for high ozone concentration suggesting a reversible ozone adsorption according to a Langmuir mechanism. We calculated the initial reaction probability between O3 and carbon particles.An initial uptake coefficient of 1.10-4 was obtained. Similar experiments were realized by selecting the particles size with a differential mobility analyser. We observed a strong size-dependent increase in reactivity with the decrease of particles size. This result is relevant for the health issues. Indeed the smallest particles are most likely to penetrate deep into the lungs. Competitive reactions between ozone and other species like H2O or atomic oxygen were also considered. Oxygen atoms were generated by photolysis of O3

  20. Employment of the generalized adsorption model for the prediction of the solid-water distribution of radiocesium in the river-estuary-ocean system

    International Nuclear Information System (INIS)

    Fan, Qiaohui; Takahashi, Yoshio

    2017-01-01

    Since last century, a large amount of radiocesium (RCs) released from atomic weapon tests and nuclear accidents, such as in Chernobyl and Fukushima, was directly introduced into the environment through atmospheric transportation and deposition on land surface soil, discharged into river systems by erosion effects during rainfall, and finally released into the ocean. In this study, a generalized adsorption model (GAM) for Cs + was employed to estimate the solid-water distribution of Cs + in the river-estuary-ocean system. The results confirmed that the capacity of each adsorption site of river sediments, i.e., interlayer site, type II site, and planar site, can be precisely optimized through the adsorption isotherm of Cs + on the river sediments combined with the radiocesium interception potential (RIP) and cation exchange capacity (CEC). According to the GAM, the main contributor for Cs + adsorption is the frayed edge site rather than others due to the very low concentration of Cs + in the river-estuary-ocean system. The different solid-water distribution of Cs + in the river-estuary-ocean system was dominantly controlled by the salinity in the aqueous phase. Therefore, Cs + should be highly reactive with strong adsorptive character to particulate matter in the river system, whereas a conservative distribution must be dominant in ocean with much weaker affinity to particulate matter because of the high salinity. - Highlights: • A new method to extend the utility range of GAM from illite to natural samples. • GAM was adapted to quantitatively explore the transportation of radiocesium in river in rive-estuary-ocean system. • High reactivity in river water and conservative behavior in seawater were clarified.

  1. Physical adsorption and molecular dynamics

    International Nuclear Information System (INIS)

    Cohan, N.V.

    1981-01-01

    Some aspects of noble gases adsorption (except He) on graphite substracts are reviewed. Experimental results from this adsorption are analyzed and compared with molecular dynamics calculations. (L.C.) [pt

  2. Adsorption mechanism of acids and bases in reversed-phase liquid chromatography in weak buffered mobile phases designed for liquid chromatography/mass spectrometry.

    Science.gov (United States)

    Gritti, Fabrice; Guiochon, Georges

    2009-03-06

    The overloaded band profiles of five acido-basic compounds were measured, using weakly buffered mobile phases. Low buffer concentrations were selected to provide a better understanding of the band profiles recorded in LC/MS analyses, which are often carried out at low buffer concentrations. In this work, 10 microL samples of a 50 mM probe solution were injected into C(18)-bonded columns using a series of five buffered mobile phases at (SW)pH between 2 and 12. The retention times and the shapes of the bands were analyzed based on thermodynamic arguments. A new adsorption model that takes into account the simultaneous adsorption of the acidic and the basic species onto the endcapped adsorbent, predicts accurately the complex experimental profiles recorded. The adsorption mechanism of acido-basic compounds onto RPLC phases seems to be consistent with the following microscopic model. No matter whether the acid or the base is the neutral or the basic species, the neutral species adsorbs onto a large number of weak adsorption sites (their saturation capacity is several tens g/L and their equilibrium constant of the order of 0.1 L/g). In contrast, the ionic species adsorbs strongly onto fewer active sites (their saturation capacity is about 1g/L and their equilibrium constant of the order of a few L/g). From a microscopic point of view and in agreement with the adsorption isotherm of the compound measured by frontal analysis (FA) and with the results of Monte-Carlo calculations performed by Schure et al., the first type of adsorption sites are most likely located in between C(18)-bonded chains and the second type of adsorption sites are located deeper in contact with the silica surface. The injected concentration (50 mM) was too low to probe the weakest adsorption sites (saturation capacity of a few hundreds g/L with an equilibrium constant of one hundredth of L/g) that are located at the very interface between the C(18)-bonded layer and the bulk phase.

  3. A Density Functional Theory Study of the Adsorption of Benzene on Hematite (α-Fe2O3 Surfaces

    Directory of Open Access Journals (Sweden)

    Nelson Y. Dzade

    2014-02-01

    Full Text Available The reactivity of mineral surfaces in the fundamental processes of adsorption, dissolution or growth, and electron transfer is directly tied to their atomic structure. However, unraveling the relationship between the atomic surface structure and other physical and chemical properties of complex metal oxides is challenging due to the mixed ionic and covalent bonding that can occur in these minerals. Nonetheless, with the rapid increase in computer processing speed and memory, computer simulations using different theoretical techniques can now probe the nature of matter at both the atomic and sub-atomic levels and are rapidly becoming an effective and quantitatively accurate method for successfully predicting structures, properties and processes occurring at mineral surfaces. In this study, we have used Density Functional Theory calculations to study the adsorption of benzene on hematite (α-Fe2O3 surfaces. The strong electron correlation effects of the Fe 3d-electrons in α-Fe2O3 were described by a Hubbard-type on-site Coulomb repulsion (the DFT+U approach, which was found to provide an accurate description of the electronic and magnetic properties of hematite. For the adsorption of benzene on the hematite surfaces, we show that the adsorption geometries parallel to the surface are energetically more stable than the vertical ones. The benzene molecule interacts with the hematite surfaces through π-bonding in the parallel adsorption geometries and through weak hydrogen bonds in the vertical geometries. Van der Waals interactions are found to play a significant role in stabilizing the absorbed benzene molecule. Analyses of the electronic structures reveal that upon benzene adsorption, the conduction band edge of the surface atoms is shifted towards the valence bands, thereby considerably reducing the band gap and the magnetic moments of the surface Fe atoms.

  4. Adsorption and Gas Separation of Molecules by Carbon Nanohorns.

    Science.gov (United States)

    Gatica, Silvina M; Nekhai, Anton; Scrivener, Adam

    2016-05-19

    In this paper, we report the results of Monte Carlo simulations of the adsorption of neon, argon, methane and carbon dioxide in carbon nanohorns. We model the nanohorns as an array of carbon cones and obtained adsorption isotherms and isosteric heats. The main sites of adsorption are inside the cones and in the interstices between three cones. We also calculated the selectivity of carbon dioxide/methane, finding that nanohorns are a suitable substrate for gas separation. Our simulations are compared to available experimental data.

  5. Sulfate adsorption on goethite

    Energy Technology Data Exchange (ETDEWEB)

    Rietra, R P.J.J.; Hiemstra, T; Riemsdijk, W.H. van

    1999-10-15

    Recent spectroscopic work has suggested that only one surface species of sulfate is dominant on hematite. Sulfate is therefore a very suitable anion to test and develop adsorption models for variable charge minerals. The authors have studied sulfate adsorption on goethite covering a large range of sulfate concentrations, surface coverages, pH values, and electrolyte concentrations. Four different techniques were used to cover the entire range of conditions. For characterization at low sulfate concentrations, below the detection limit of sulfate with ICP-AES, the authors used proton-sulfate titrations at constant pH. Adsorption isotherms were studied for the intermediate sulfate concentration range. Acid-base titrations in sodium sulfate and electromobility were used for high sulfate concentrations. All the data can be modeled with one adsorbed species if it is assumed that the charge of adsorbed sulfate is spatially distributed in the interface. The charge distribution of sulfate follows directly from modeling the proton-sulfate adsorption stoichoimemtry sine this stoichiometry is independent of the intrinsic affinity constant of sulfate. The charge distribution can be related to the structure of the surface complex by use of the Pauling bond valence concept and is in accordance with the microscopic structure found by spectroscopy. The intrinsic affinity constant follows from the other measurements. Modeling of the proton-ion stoichoimetry with the commonly used 2-pK models, where adsorbed ions are treated as point charges, is possible only if at least two surface species for sulfate are used.

  6. Conformational changes of plasma fibronectin detected upon adsorption to solid substrates: A spin-label study

    International Nuclear Information System (INIS)

    Narasimhan, C.; Lai, Chingsan

    1989-01-01

    Changes in local environment of the free sulfhydryl groups in plasma fibronectin upon adsorption of the protein to polystyrene beads have been examined by electron spin resonance (ESR) spin-label spectroscopy. The two free sulfhydryl groups per subunit of plasma fibronectin were modified chemically with an [ 15 N, 2 H]maleimide spin-label. For soluble fibronectin, both free sulfhydryl groups shown to be in confined environments as evidenced from the labeled protein exhibiting a strongly immobilized ESR spectrum as described previously using [ 14 N, 1 H]maleimide spin-labels. When the labeled protein was adsorbed to the beads, half of the strongly immobilized component was found to convert into a weakly immobilized component, a result indicating that one of the two labeled sites becomes exposed and exhibits a fast tumbling motion. Experiments conducted using various spin-labeled fibronectin fragments suggest that the newly exposed labeled site is located between the DNA-binding and the cell-binding regions of the molecule. The data obtained indicate that, upon adsorption to polystyrene beads, plasma fibronectin undergoes a conformational change through which the buried free sulfhydryl group near the cell-binding region of the molecule is exposed. This observation may have important implications regarding the expression of cell adhesive properties of the fibronectin molecule

  7. Density functional theory study on the interactions of l-cysteine with graphene: adsorption stability and magnetism

    International Nuclear Information System (INIS)

    Luo, Huijuan; Li, Hejun; Fu, Qiangang; Chu, Yanhui; Cao, Xiaoyu; Sun, Can; Yuan, Xiaoyan; Liu, Lei

    2013-01-01

    Understanding the interactions between graphene and biomolecules is of fundamental relevance to the area of nanobiotechnology. Herein, we take l-cysteine as the probe biomolecule and investigate its adsorption on pristine graphene and B-, N-, Al-, Ni-, Ga-, Pd-doped graphene using density functional theory calculations. Three kinds of upright adsorption configurations, via unprotonated functional groups (–SH, –NH 2 , –COOH), are considered. The calculations reveal pristine graphene physically adsorbs l-cysteine. N-doped graphene shows physisorption towards the S-end and N-end l-cysteine, and chemisorption towards the O-end radical. Strong chemisorption, with site-specific preference, occurs on Al-, Ni-, Ga- and Pd-doped graphene, accompanied by severe structural changes. Spin polarization with an unusual mirror symmetry on Ni- and Pd-doped graphene is induced by chemisorption of unprotonated l-cysteine, except for O-end adsorption on Pd-doped graphene. The magnetization arises mainly from spin polarization of the C 2p z orbital, with a minor magnetism located on Ni or Pd. The influence of van der Waals forces is also evaluated. A thorough analysis of the adsorption stability and magnetism of these systems would be beneficial to facilitate applications in graphene-based biosensing, biomolecule immobilization, magnetic bio-separation and other fields in bionanotechnology. (paper)

  8. Effects of Post-Pyrolysis Air Oxidation of Biomass Chars on Adsorption of Neutral and Ionizable Compounds.

    Science.gov (United States)

    Xiao, Feng; Pignatello, Joseph J

    2016-06-21

    This study was conducted to understand the effects of thermal air oxidation of biomass chars experienced during formation or production on their adsorptive properties toward various compounds, including five neutral nonpolar and polar compounds and seven weak acids and bases (pKa = 3-5.2) selected from among industrial chemicals and the triazine and phenoxyacetic acid herbicide classes. Post-pyrolysis air oxidation (PPAO) at 400 °C of anoxically prepared wood and pecan shell chars for up to 40 min enhanced the mass-normalized adsorption at pH ∼ 7.4 of all test compounds, especially the weak acids and bases, by up to 100-fold. Both general and specific effects were identified. The general effect results from "reaming" of pores by the oxidative removal of pore wall matter and/or tarry deposits generated during the pyrolysis step. Reaming creates new surface area and enlarges nanopores, which helps relieve steric hindrance to adsorption. The specific effect results from creation of new acidic functionality that provides sites for the formation of very strong, charge-assisted hydrogen bonds (CAHB) with solutes having comparable pKa. The CAHB hypothesis was supported by competition experiments and the finding that weak acid anion adsorption increased with surface carboxyl content, despite electrostatic repulsion from the growing negative charge. The results provide insight into the effects of air oxidation on pollutant retention.

  9. Adsorption property of volatile molecules on ZnO nanowires ...

    Indian Academy of Sciences (India)

    2018-02-02

    Feb 2, 2018 ... 2Centre for Fire Explosive and Environment Safety, Defence Research and Development Organisation, Ministry ... present work, Zn site was chosen as an adsorption site for a ... Virtual NanoLab [18] software was utilized to construct the ..... In reality, there will be plenty of vapour molecules that interact over.

  10. Behaviors and kinetics of toluene adsorption-desorption on activated carbons with varying pore structure.

    Science.gov (United States)

    Yang, Xi; Yi, Honghong; Tang, Xiaolong; Zhao, Shunzheng; Yang, Zhongyu; Ma, Yueqiang; Feng, Tiecheng; Cui, Xiaoxu

    2018-05-01

    This work was undertaken to investigate the behaviors and kinetics of toluene adsorption and desorption on activated carbons with varying pore structure. Five kinds of activated carbon from different raw materials were selected. Adsorption isotherms and breakthrough curves for toluene were measured. Langmuir and Freundlich equations were fitted to the equilibrium data, and the Freundlich equation was more suitable for simulating toluene adsorption. The process consisted of monolayer, multilayer and partial active site adsorption types. The effect of the pore structure of the activated carbons on toluene adsorption capacity was investigated. The quasi-first-order model was more suitable for describing the process than the quasi-second-order model. The adsorption data was also modeled by the internal particle diffusion model and it was found that the adsorption process could be divided into three stages. In the external surface adsorption process, the rate depended on the specific surface area. During the particle diffusion stage, pore structure and volume were the main factors affecting adsorption rate. In the final equilibrium stage, the rate was determined by the ratio of meso- and macro-pores to total pore volume. The rate over the whole adsorption process was dominated by the toluene concentration. The desorption behavior of toluene on activated carbons was investigated, and the process was divided into heat and mass transfer parts corresponding to emission and diffusion mechanisms, respectively. Physical adsorption played the main role during the adsorption process. Copyright © 2017. Published by Elsevier B.V.

  11. Study of 63Ni adsorption on NKF-6 zeolite

    International Nuclear Information System (INIS)

    Zhang Hui; Yu Xianjin; Chen Lei; Jing Yongjie; Ge Zhiwei

    2010-01-01

    The adsorption of 63 Ni from aqueous solutions using NKF-6 zeolite was investigated by a batch technique under ambient conditions. The adsorption was investigated as a function of contact time, pH, ionic strength, foreign ions, humic substances (FA/HA) and temperature. The kinetic adsorption was well described by the pseudo-second-order rate equation. The adsorption of 63 Ni on NKF-6 zeolite was strongly dependent on pH and ionic strength, and the adsorption of 63 Ni increased with increasing NKF-6 zeolite content. At low pH values, the presence of FA enhanced the adsorption of 63 Ni on NKF-6 zeolite, but the presence of HA had no drastic effect. At high pH values, the presence of FA or HA decreased the adsorption of 63 Ni on NKF-6 zeolite. The adsorption isotherms were well represented by the Langmuir model. The thermodynamic parameters (i.e., ΔH 0 , ΔS 0 and ΔG 0 ) for the adsorption of 63 Ni were determined from the temperature dependent isotherms at 293.15, 313.15 and 333.15 o K, respectively, and the results indicate that the adsorption reaction was favored at high temperature. The results suggest that the adsorption process of 63 Ni on NKF-6 zeolite is spontaneous and endothermic. - Research highlights: → As an economical and efficient method, adsorption technique has been widely applied in the disposal of wastewaters. The study of 63 Ni on NKF-6 zeolite, especially the thermodynamic data of 63 Ni adsorption on NKF-6 zeolite and the effect of humic substances on 63 Ni uptake to humic-zeolite hybrids, is still scarce. In this paper, the sorption of 63 Ni on NKF-6 zeolite is studied as a function of various environmental conditions such as contact time, pH, ionic strength, foreign ions, humic substances and temperature. Based on the obtained experimental results, the adsorption mechanism of 63 Ni on NKF-6 zeolite is stated in detail. This study will have an important reference value in evaluating the physiochemical behavior of radionuclide 63 Ni.

  12. Adsorption of arsenic and phosphate onto the surface of calcite as revealed by batch experiments and surface complexation modelling

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt

    different calcite-equilibrated solutions that varied in pH, PCO2, ionic strength and activity of Ca2+, CO3 2- and HCO3 -. To avoid the precipitation of phosphate or arsenic-containing minerals the experiments were conducted using a short reaction time (generally 3 h) and a low concentration of phosphate...... adsorption affinity for calcite is greater as compared to arsenate and the phosphate sorption isotherms are more strongly curved. However, the amount of both arsenate and phosphate adsorbed varied with the solution composition in the same manner. In particular, adsorption increased as the CO3 2- activity...... decreased (at constant pH) and as pH increased (at constant CO3 2- activity). The dependency on the carbonate activity indicates competition for sorption sites between carbonate and arsenate/phosphate, whereas the pH dependency is likely a response to changes in arsenate and phosphate speciation...

  13. Spectroscopy, microscopy and theoretical study of NO adsorption on MoS2 and Co-Mo-S hydrotreating catalysts

    DEFF Research Database (Denmark)

    Topsøe, Nan-Yu; Tuxen, Anders Kyrme; Hinnemann, Berit

    2011-01-01

    nfrared (IR) spectroscopy using NO as a probe molecule has been one of the important methods for characterizing hydrotreating catalysts, since this technique provides information on the nature and quantity of active edge sites of these catalysts. However, due to the strong adsorption of NO, which......) calculations, we present new atomic-scale insight into the nature of NO adsorption on MoS2 and Co-Mo-S nanoclusters. The DFT calculations and STM experiments show that NO does not adsorb at fully sulfided MoS2 edges not containing hydrogen. However, typical sulfided catalysts will have hydrogen present...... NO as a probe molecule to obtain detailed atomic-scale information on hydrotreating catalysts and the origins of activity differences. (C) 2011 Published by Elsevier Inc....

  14. Neptunium (V) Adsorption to a Halophilic Bacterium Under High Ionic Strength Conditions: A Surface Complexation Modeling Approach

    Energy Technology Data Exchange (ETDEWEB)

    Ams, David A [Los Alamos National Laboratory

    2012-06-11

    Rationale for experimental design: Np(V) -- important as analog for Pu(V) and for HLW scenarios; High ionic strength -- relevant to salt-based repositories such as the WIPP; Halophilic microorganisms -- representative of high ionic strength environments. For the first time showed: Significant adsorbant to halophilic microorganisms over entire pH range under high ionic strength conditions; Strong influence of ionic strength with increasing adsorption with increasing ionic strength (in contrast to trends of previous low ionic strength studies); Effect of aqueous Np(V) and bacterial surface site speciation on adsorption; and Developed thermodynamic models that can be incorporated into geochemical speciation models to aid in the prediction of the fate and transport of Np(V) in more complex systems.

  15. Systematic investigations of peak deformations due to co-solvent adsorption in preparative supercritical fluid chromatography.

    Science.gov (United States)

    Glenne, Emelie; Leek, Hanna; Klarqvist, Magnus; Samuelsson, Jörgen; Fornstedt, Torgny

    2017-05-05

    Strangely shaped overloaded bands were recently reported using a standard supercritical fluid chromatographic system comprising a diol column as the stationary phase and carbon dioxide with methanol as the mobile phase. Some of these overloaded elution profiles appeared strongly deformed and even had "anti-Langmuirian" shapes although their solute compounds had "Langmuirian" adsorption. To obtain a more complete understanding of the generality of these effects, the investigation was expanded to cover also other common co-solvents, such as ethanol, 2-propanol, and acetonitrile, as well as various stationary phase materials, such as silica, and 2-ethylpyridine. From this expanded study it could be confirmed that the effects of deformed overloaded solute band shapes, due to co-solvent adsorption, is general phenomena in supercritical fluid chromatographic. It could also be concluded that these effects as well as previously observed "solvent effects" or "plug effects" are entirely due to competition between the solute and solvent molecules for the adsorption sites on the stationary phase surface. Finally, guidelines were given for how to evaluate the risk of deformations occurring for a given solvent-column combination, based simply on testing retention times of solutes and co-solvent. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Fundamentals of high pressure adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Y.P.; Zhou, L. [Tianjin University, Tianjin (China). High Pressure Adsorption Laboratory

    2009-12-15

    High-pressure adsorption attracts research interests following the world's attention to alternative fuels, and it exerts essential effect on the study of hydrogen/methane storage and the development of novel materials addressing to the storage. However, theoretical puzzles in high-pressure adsorption hindered the progress of application studies. Therefore, the present paper addresses the major theoretical problems that challenged researchers: i.e., how to model the isotherms with maximum observed in high-pressure adsorption; what is the adsorption mechanism at high pressures; how do we determine the quantity of absolute adsorption based on experimental data. Ideology and methods to tackle these problems are elucidated, which lead to new insights into the nature of high-pressure adsorption and progress in application studies, for example, in modeling multicomponent adsorption, hydrogen storage, natural gas storage, and coalbed methane enrichment, was achieved.

  17. Screening of active metals for reactive adsorption desulfurization adsorbent using density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lei; Zhao, Liang, E-mail: liangzhao@cup.edu.cn; Xu, Chunming; Wang, Yuxian; Gao, Jinsen

    2017-03-31

    Highlights: • Electronic characteristics determined adsorption characteristics of transition metals. • Cobalt has the similar adsorption ability of thiophene as nickel. • Adsorption capacity of Cr and Mo was extremely fierce, while Cu has the potential ability for adsorbing thiophene. • The preference adsorption site for thiophene was hollow site on all the seven surface. - Abstract: To explore characteristics of active metals for reactive adsorption desulfurization (RADS) technology, the adsorption of thiophene on M (100) (M = Cr, Mo, Co, Ni, Cu, Au, and Ag) surfaces was systematically studied by density functional theory with vdW correction (DFT + D3). We found that, in all case, the most stable molecular adsorption site was the hollow site and adsorptive capabilities of thiophene followed the order: Cr > Mo > Co ≈ Ni > Cu > Au ≈ Ag. By analyzing the nature of binding between thiophene and corresponding metals and the electronic structure of metals, the excessive activities of Cr and Mo were found to have a negative regeneration, the passive activities of Au and Ag were found to have an inactive adsorption for RADS adsorbent alone, while Ni and Co have appropriate characteristics as the active metals for RADS, followed by Cu.

  18. Traps for phosphorus adsorption

    International Nuclear Information System (INIS)

    Montoya, Nawer D; Villegas, Wilson E; Rodriguez, Lino M; Taborda, Nelson; Montes de C, Consuelo

    2001-01-01

    Several AL 2 O 3 supported oxides such as: NiO, CuO, Co 2 O 3 BaO, CeO 2 and ZnO were investigated for phosphorus adsorption. Zno/y-Al 2 O 3 exhibited the highest phosphorus adsorption capacity. However, since it diminishes the activity of to the reaction mixture it should be located upstream of the NoX catalyst, i.e. 0,3% Pd-H-MOR, in order to protect it against p poisoning. The treatment procedure with citric acid was effective for the removal of more than 70% phosphorus from the adsorbent, ZnO/y-Al 2 O 3

  19. Theoretical study of the adsorption of rhodium on a TiO{sub 2}(1 1 0)-1 Multiplication-Sign 1 surface

    Energy Technology Data Exchange (ETDEWEB)

    Mutombo, P., E-mail: mutombo@fzu.cz [Institute of Physics of Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 16253 Praha 6 (Czech Republic); Balazs, N. [Reaction Kinetics Laboratory, Institute of Nanochemistry and Catalysis, CRC of the Hungarian Academy of Sciences, University of Szeged, P.O. Box 168, H-6701 Szeged (Hungary); Majzik, Z. [Institute of Physics of Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 16253 Praha 6 (Czech Republic); Reaction Kinetics Laboratory, Institute of Nanochemistry and Catalysis, CRC of the Hungarian Academy of Sciences, University of Szeged, P.O. Box 168, H-6701 Szeged (Hungary); Berko, A. [Reaction Kinetics Laboratory, Institute of Nanochemistry and Catalysis, CRC of the Hungarian Academy of Sciences, University of Szeged, P.O. Box 168, H-6701 Szeged (Hungary); Chab, V. [Institute of Physics of Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 16253 Praha 6 (Czech Republic)

    2012-03-01

    Density functional theory (DFT) calculations were used to study the adsorption of rhodium on a TiO{sub 2}(1 1 0)-1 Multiplication-Sign 1 surface as a function of coverage. It was found that Rh atom prefers the hollow site between a bridging oxygen atom, a threefold oxygen atom and a fivefold coordinated Ti atom, regardless of the coverage used. DFT calculations also suggest that Rh-Rh interaction is attractive along the [0 0 1] direction, implying that the Rh 1D nanostructure should grow preferentially along this direction. Simulated Rh dimer clusters resemble strongly Pd dimers resolved in STM experiments suggesting that both metals occupy the same adsorption site at the TiO{sub 2}(1 1 0) surface.

  20. Theoretical study of the adsorption of rhodium on a TiO2(1 1 0)-1 × 1 surface

    International Nuclear Information System (INIS)

    Mutombo, P.; Balázs, N.; Majzik, Z.; Berkó, A.; Cháb, V.

    2012-01-01

    Density functional theory (DFT) calculations were used to study the adsorption of rhodium on a TiO 2 (1 1 0)-1 × 1 surface as a function of coverage. It was found that Rh atom prefers the hollow site between a bridging oxygen atom, a threefold oxygen atom and a fivefold coordinated Ti atom, regardless of the coverage used. DFT calculations also suggest that Rh-Rh interaction is attractive along the [0 0 1] direction, implying that the Rh 1D nanostructure should grow preferentially along this direction. Simulated Rh dimer clusters resemble strongly Pd dimers resolved in STM experiments suggesting that both metals occupy the same adsorption site at the TiO 2 (1 1 0) surface.

  1. Preparation of crosslinked poly (acryloyloxyethyltrimethyl ammonium chloride) microsphere and its adsorption and mechanism towards shikimic acid

    Energy Technology Data Exchange (ETDEWEB)

    Men, Jiying, E-mail: menjiying@nuc.edu.cn; Wang, Ruixin; Li, Huan; Li, Xinyan; Yang, Shanshan; Liu, Haisi; Gao, Baojiao

    2017-02-01

    Shikimic acid (SA) is a key raw material for the synthesis of the antiviral drug, but its extraction and separation from plants is still limited. Crosslinked poly (acryloyloxyethyltrimethyl ammonium chloride, DAC) microspheres were synthesized via inverse-phase suspension polymerization. In the synthesizing, N,N′-methylene bisacrylamide (MBA) was used as crosslinker, cyclohexane as dispersed medium and span-60 as dispersants, obtaining CPDAC gel microspheres. The effect of polymerization condition on balling performance and the characteristics of CPDAC were examined. The adsorption properties of CPDAC towards SA were mainly explored and the data of adsorption isotherm were analyzed by using Langmuir, Freundlich, Temkin, Sips and Toth models. Furthermore, the adsorption mechanism was analyzed in depth, and the adsorption thermodynamics was also investigated. The results show that in order to prepare CPDAC, water phase must be added dropwise to oil phase, and the volume ratio of oil-water is more than 2:1. The mean diameter of CPDAC decreases with increasing span-60 and accelerating agitating rate. The strong electrostatic interaction is formed between quaternary ammonium nitrogen of CPDAC and −COO{sup –} of SA. The adsorption kinetic data is fitted well with pseudo-first-order model. The adsorption ability is higher in aqueous water than ethanol, reaching 108 mg/g, and Toth model is more suitable for describing the actual adsorption process. The adsorption of CPDAC towards SA is dependent on the pH value of the medium. The adsorption process is exothermic, the adsorption amount decreases with the increase of temperature, and the process is driven by enthalpy. The adsorption amount decreases with the increase of salinity. The reusability of CPDAC towards SA can keep 86.1% at the sixth cycle. - Highlights: • CPDAC microspheres were synthesized via inverse-phase suspension polymerization. • SA was adsorbed strongly by strong electrostatic interaction.

  2. Diffusion Influenced Adsorption Kinetics.

    Science.gov (United States)

    Miura, Toshiaki; Seki, Kazuhiko

    2015-08-27

    When the kinetics of adsorption is influenced by the diffusive flow of solutes, the solute concentration at the surface is influenced by the surface coverage of solutes, which is given by the Langmuir-Hinshelwood adsorption equation. The diffusion equation with the boundary condition given by the Langmuir-Hinshelwood adsorption equation leads to the nonlinear integro-differential equation for the surface coverage. In this paper, we solved the nonlinear integro-differential equation using the Grünwald-Letnikov formula developed to solve fractional kinetics. Guided by the numerical results, analytical expressions for the upper and lower bounds of the exact numerical results were obtained. The upper and lower bounds were close to the exact numerical results in the diffusion- and reaction-controlled limits, respectively. We examined the validity of the two simple analytical expressions obtained in the diffusion-controlled limit. The results were generalized to include the effect of dispersive diffusion. We also investigated the effect of molecular rearrangement of anisotropic molecules on surface coverage.

  3. Density functional study of carbon monoxide adsorption on small cationic, neutral, and anionic aluminum nitride clusters

    Science.gov (United States)

    Guo, Ling

    CO adsorption on small cationic, neutral, and anionic (AlN)n (n = 1-6) clusters has been investigated using density functional theory in the generalized gradient approximation. Among various possible CO adsorption sites, an N on-top (onefold coordinated) site is found to be the most favorable one, irrespective of the charge state of the clusters. The adsorption energies of CO on the anionic (AlN)nCO (n = 2-4) clusters are greater than those on the neutral and cationic complexes. The adsorption energies on the cationic and neutral complexes reflect the odd-even oscillations, and the adsorption energies of CO on the cationic (AlN)nCO (n = 5, 6) clusters are greater than those on the neutral and anionic complexes. The adsorption energies for the different charge states decrease with increasing cluster size.

  4. The removal of heavy metals from aqueous solution by adsorption on weathered coal

    Energy Technology Data Exchange (ETDEWEB)

    Meena, A.K.; Gupta, M.D.; Mishra, G.K.; Rajagopal, C.; Nagar, P.N. [Central Research Institute (Ayurveda), Gwalior (India)

    2009-07-01

    The adsorption followed first-order kinetics. The results indicate the potential application of this method for effluent treatment in industries and also provide strong evidence to support the adsorption mechanism proposed. On the basis of experimental results, it can be inferred that the adsorbent weathered coal may be useful in developing an adsorptive technology for the removal of heavy metals. 25 refs., 8 figs., 4 tabs.

  5. Chirality in adsorption on solid surfaces.

    Science.gov (United States)

    Zaera, Francisco

    2017-12-07

    In the present review we survey the main advances made in recent years on the understanding of chemical chirality at solid surfaces. Chirality is an important topic, made particularly relevant by the homochiral nature of the biochemistry of life on Earth, and many chiral chemical reactions involve solid surfaces. Here we start our discussion with a description of surface chirality and of the different ways that chirality can be bestowed on solid surfaces. We then expand on the studies carried out to date to understand the adsorption of chiral compounds at a molecular level. We summarize the work published on the adsorption of pure enantiomers, of enantiomeric mixtures, and of prochiral molecules on chiral and achiral model surfaces, especially on well-defined metal single crystals but also on other flat substrates such as highly ordered pyrolytic graphite. Several phenomena are identified, including surface reconstruction and chiral imprinting upon adsorption of chiral agents, and the enhancement or suppression of enantioselectivity seen in some cases upon adsorption of enantiomixtures of chiral compounds. The possibility of enhancing the enantiopurity of adsorbed layers upon the addition of chiral seeds and the so-called "sergeants and soldiers" phenomenon are presented. Examples are provided where the chiral behavior has been associated with either thermodynamic or kinetic driving forces. Two main approaches to the creation of enantioselective surface sites are discussed, namely, via the formation of supramolecular chiral ensembles made out of small chiral adsorbates, and by adsorption of more complex chiral molecules capable of providing suitable chiral environments for reactants by themselves, via the formation of individual adsorbate:modifier adducts on the surface. Finally, a discussion is offered on the additional effects generated by the presence of the liquid phase often required in practical applications such as enantioselective crystallization, chiral

  6. Density functional theory studies of the adsorption of ethylene and oxygen on Pt(111) and Pt3Sn(111)

    DEFF Research Database (Denmark)

    Watwe, R.M.; Cortright, R.D.; Mavrikakis, Manos

    2001-01-01

    Density functional theory, employing periodic slab calculations, was used to investigate the interactions of ethylene and oxygen with Pt(111) and Pt3Sn(111). The predicted energetics and structures of adsorbed species on Pt(111) are in good agreement with experimental data. The binding energies...... more than adsorption on two-fold and one-fold sites. Oxygen atoms bond as strongly on Pt3Sn(111) as on Pt(111), and these atoms prefer to adsorb near Sn atoms on the surface. The addition of Sn to Pt(111) leads to a surface heterogeneity, wherein ethylidyne species prefer to adsorb away from Sn atoms...

  7. AIR SEPARATION BY PRESSURE SWING ADSORPTION USING SUPERIOR ADSORBENTS; FINAL

    International Nuclear Information System (INIS)

    Ralph T Yang

    2001-01-01

    Li-X zeolite (Si/Al= 1.0) is currently the best sorbent for use in the separation of air by adsorption processes. In particular, pressure swing adsorption (PSA) using zeolite sorbents is being increasingly used for air separation. Silver is also known to strongly affect the adsorptive properties of zeolites; and it is known that thermal vacuum dehydration of silver zeolites leads to the formation of silver clusters within the zeolite. In this work we have synthesized type X zeolites containing Ag and also varying mixtures of Li and Ag. In this project, we developed the Ag-containing zeolite as the best sorbent for air separation. We have also studied Co-ligand compounds as oxygen-selective sorbents. Syntheses, structural characterization and adsorption properties have been performed on all sorbents. The results are described in detail in 5 chapters

  8. Insight into the adsorption of chloramphenicol on a vermiculite surface

    Science.gov (United States)

    Tri, Nguyen Ngoc; Carvalho, A. J. P.; Dordio, A. V.; Nguyen, Minh Tho; Trung, Nguyen Tien

    2018-05-01

    Four stable configurations were found upon adsorption of the chloramphenicol on a period slab model of the vermiculite surface, using the PBE and C09-vdW functionals in a projector-augmented wave (PAW) method approach. The adsorption is a strong chemisorption process, characterized by an adsorption energy of -106.5 kcal mol-1 at the most stable configuration. Stability of configurations contributed mainly by Mg⋯O/Cl attractive electrostatic interactions and C/Osbnd H⋯O hydrogen bonds. It is remarkable that the vermiculite is found to be a solid material with good potential to be used for adsorption and consequent removal of this type of antibiotic drugs.

  9. AIR SEPARATION BY PRESSURE SWING ADSORPTION USING SUPERIOR ADSORBENTS

    Energy Technology Data Exchange (ETDEWEB)

    Ralph T. Yang

    2001-08-31

    Li-X zeolite (Si/Al = 1.0) is currently the best sorbent for use in the separation of air by adsorption processes. In particular, pressure swing adsorption (PSA) using zeolite sorbents is being increasingly used for air separation. Silver is also known to strongly affect the adsorptive properties of zeolites; and it is known that thermal vacuum dehydration of silver zeolites leads to the formation of silver clusters within the zeolite. In this work we have synthesized type X zeolites containing Ag and also varying mixtures of Li and Ag. In this project, we developed the Ag-containing zeolite as the best sorbent for air separation. We have also studied Co-ligand compounds as oxygen-selective sorbents. Syntheses, structural characterization and adsorption properties have been performed on all sorbents. The results are described in detail in 5 chapters.

  10. Mercury adsorption properties of sulfur-impregnated adsorbents

    Science.gov (United States)

    Hsi, N.-C.; Rood, M.J.; Rostam-Abadi, M.; Chen, S.; Chang, R.

    2002-01-01

    Carbonaceous and noncarbonaceous adsorbents were impregnated with elemental sulfur to evaluate the chemical and physical properties of the adsorbents and their equilibrium mercury adsorption capacities. Simulated coal combustion flue gas conditions were used to determine the equilibrium adsorption capacities for Hg0 and HgCl2 gases to better understand how to remove mercury from gas streams generated by coal-fired utility power plants. Sulfur was deposited onto the adsorbents by monolayer surface deposition or volume pore filling. Sulfur impregnation increased the total sulfur content and decreased the total and micropore surface areas and pore volumes for all of the adsorbents tested. Adsorbents with sufficient amounts of active adsorption sites and sufficient microporous structure had mercury adsorption capacities up to 4,509 ??g Hg/g adsorbent. Elemental sulfur, organic sulfur, and sulfate were formed on the adsorbents during sulfur impregnation. Correlations were established with R2>0.92 between the equilibrium Hg0/HgCl2 adsorption capacities and the mass concentrations of elemental and organic sulfur. This result indicates that elemental and organic sulfur are important active adsorption sites for Hg0 and HgCl2.

  11. Testing strong interaction theories

    International Nuclear Information System (INIS)

    Ellis, J.

    1979-01-01

    The author discusses possible tests of the current theories of the strong interaction, in particular, quantum chromodynamics. High energy e + e - interactions should provide an excellent means of studying the strong force. (W.D.L.)

  12. Contribution of Ash Content Related to Methane Adsorption Behaviors of Bituminous Coals

    Directory of Open Access Journals (Sweden)

    Yanyan Feng

    2014-01-01

    Full Text Available Methane adsorption isotherms on coals with varying ash contents were investigated. The textural properties were characterized by N2 adsorption/desorption isotherm at 77 K, and methane adsorption characteristics were measured at pressures up to 4.0 MPa at 298 K, 313 K, and 328 K, respectively. The Dubinin-Astakhov model and the Polanyi potential theory were employed to fit the experimental data. As a result, ash content correlated strongly to methane adsorption capacity. Over the ash range studied, 9.35% to 21.24%, the average increase in methane adsorption capacity was 0.021 mmol/g for each 1.0% rise in ash content. With the increasing ash content range of 21.24%~43.47%, a reduction in the maximum adsorption capacities of coals was observed. In addition, there was a positive correlation between the saturated adsorption capacity and the specific surface area and micropore volume of samples. Further, this study presented the heat of adsorption, the isosteric heat of adsorption, and the adsorbed phase specific heat capacity for methane adsorption on various coals. Employing the proposed thermodynamic approaches, the thermodynamic maps of the adsorption processes of coalbed methane were conducive to the understanding of the coal and gas simultaneous extraction.

  13. The adsorption behavior of functional particles modified by polyvinylimidazole for Cu(II) ion

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ruixin; Men, Jiying; Gao, Baojiao [School of Chemical Engineering and Environment, North University of China, Taiyuan (China)

    2012-03-15

    In this paper, a novel composite material the silica grafted by poly(N-vinyl imidazole) (PVI), i.e., PVI/SiO{sub 2}, was prepared using 3-methacryloxypropyl trimethoxysilane (MPS) as intermedia through the ''grafting from'' method. The adsorption behavior of metal ions by PVI/SiO{sub 2} was researched by both static and dynamic methods. Experimental results showed that PVI/SiO{sub 2} possessed very strong adsorption ability for metal ions. For different metal ions, PVI/SiO{sub 2} exhibited different adsorption abilities with the following order of adsorption capacity: Cu{sup 2+}> Cd{sup 2+}> Zn{sup 2+}. The adsorption material PVI/SiO{sub 2} was especially good at adsorbing Cu(II) ion and the saturated adsorption capacity could reach up to 49.2 mg/g. The empirical Freundlich isotherm was found to describe well the equilibrium adsorption data. Higher temperatures facilitated the adsorption process and thus increased the adsorption capacity. The pH and grafting amount of PVI had great influence on the adsorption amount. In addition, PVI/SiO{sub 2} particles had excellent eluting and regenerating property using diluted hydrochloric acid solution as eluent. The adsorption ability trended to steady during 10 cycles. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Ion adsorption properties of molybdenum (II) bromide

    International Nuclear Information System (INIS)

    Ganzerli-Valentini, M.T.; Meloni, S.; Caramella-Crespi, V.; Borroni, P.A.

    1976-01-01

    The adsorption of about 50 ions on molybdenum dibromide, (Mo 6 Br 8 )Br 4 .2H 2 O in nitric acid was investigated. The behaviour of the investigated elements on MDB in nitric acid, in the concentration range 10 -2 -8M is presented, where the distribution coefficients are given against the HNO 3 molarity. In some cases the elements were investigated in different oxidation states. Most of the elements are not adsorbed or poorly adsorbed, among these the stable anions, thus indicating that bromide ions substitution with other anions is not competitive. The preparation of the adsorber and its characterization is presented and discussed. Adsorption mechanism studies were carried out for some noble metals and chromium. Sorption cannot be ascribed to ion exchange mechanism but to formation of insoluble species, and to settlement of few ions into surface sorption sites or into a limited number of cavitites in the cluster crystal structure of the adsorber. (T.G.)

  15. Appearance of enhancement effect in adsorption of binary gas mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Sakano, T. [Ajinomoto General Foods, Inc., Tokyo (Japan); Tamon, H.; Okazaki, M. [Kyoto University, Kyoto (Japan)

    1997-10-20

    The properties of adsorbents and adsorbates contributing to the enhancement in adsorption of binary gas mixtures were experimentally investigated. It is found that adsorbent is required to maintain the phenolic hydroxyl group and the carbonyl group as acidic surface oxides on the carbon surface, and to have a microporous structure for the main adsorption sites. Each gas component is required to be chemisorbed on the phenolic hydroxyl group or the carbonyl group on the adsorbent, and that both components are adsorbed in the micropores together. From the characterization of adsorbents after adsorption-desorption runs, it is demonstrated that the adsorbates in the micropores exist at a higher density than in the bulk state through the promotion of micropore filling when adsorption enhancement appears. 17 refs., 7 figs., 5 tabs.

  16. Study of adsorption properties on lithium doped activated carbon materials

    International Nuclear Information System (INIS)

    Los, S.; Daclaux, L.; Letellier, M.; Azais, P.

    2005-01-01

    A volumetric method was applied to study an adsorption coefficient of hydrogen molecules in a gas phase on super activated carbon surface. The investigations were focused on getting the best possible materials for the energy storage. Several treatments on raw samples were used to improve adsorption properties. The biggest capacities were obtain after high temperature treatment at reduced atmosphere. The adsorption coefficient at 77 K and 2 MPa amounts to 3.158 wt.%. The charge transfer between lithium and carbon surface groups via the doping reaction enhanced the energy of adsorption. It was also found that is a gradual decrease in the adsorbed amount of H 2 molecules due to occupation active sites by lithium ions. (author)

  17. Water on TiO2 studied by work function change: adsorption in cycles

    International Nuclear Information System (INIS)

    Bundaleski, Nenad; Silva, Ana G; Jean-Shaw, Bobbie; Teodoro, Orlando; Moutinho, Augusto

    2013-01-01

    The nature of water adsorption on TiO 2 (110) rutile surface attracts a lot of attention for quite some time. In spite of the considerable experimental and theoretical efforts a lot of details remain unclear. We have been using work function study to follow the adsorption of water on TiO 2 at room temperature, and interpreted the results in terms of fast dissociative adsorption on bridging oxygen vacancies (BOV) and much slower non-dissociative adsorption on Ti 5f rows. Additionally, we concluded that water from Ti 5f rows efficiently desorbs at room temperature which is not the case for BOV adsorption sites. Here we propose a novel experimental approach which consists of monitoring in real-time the work function change during cycles of water adsorption. Since desorption at BOVs does not take place at room temperature, this method allows us to resolve the adsorption dynamics on the two adsorption sites. The first results changed our understanding of the phenomenon: we show that both, adsorption on BOVs and Ti 5f are both very fast. Additionally, slow exponential decay of the work function is observed, which is not directly related to water adsorption. The possible explanation of the third slow contribution could be related to the migration of hydrogen atoms along the bridging oxygen rows.

  18. Adsorption of emerging contaminant metformin using graphene oxide.

    Science.gov (United States)

    Zhu, Shuai; Liu, Yun-Guo; Liu, Shao-Bo; Zeng, Guang-Ming; Jiang, Lu-Hua; Tan, Xiao-Fei; Zhou, Lu; Zeng, Wei; Li, Ting-Ting; Yang, Chun-Ping

    2017-07-01

    The occurrence of emerging contaminants in our water resources poses potential threats to the livings. Due to the poor treatment in wastewater management, treatment technologies are needed to effectively remove these products for living organism safety. In this study, Graphene oxide (GO) was tested for the first time for its capacity to remove a kind of emerging wastewater contaminants, metformin. The research was conducted by using a series of systematic adsorption and kinetic experiments. The results indicated that GO could rapidly and efficiently reduce the concentration of metformin, which could provide a solution in handling this problem. The uptake of metformin on the graphene oxide was strongly dependent on temperature, pH, ionic strength, and background electrolyte. The adsorption kinetic experiments revealed that almost 80% removal of metformin was achieved within 20 min for all the doses studied, corresponding to the relatively high k 1 (0.232 min -1 ) and k 2 (0.007 g mg -1  min -1 ) values in the kinetic models. It indicated that the highest adsorption capacity in the investigated range (q m ) of GO for metformin was at pH 6.0 and 288 K. Thermodynamic study indicated that the adsorption was a spontaneous (ΔG 0  adsorption of metformin increased when the pH values changed from 4.0 to 6.0, and decreased adsorption were observed at pH 6.0-11.0. GO still exhibited excellent adsorption capacity after several desorption/adsorption cycles. Besides, both so-called π-π interactions and hydrogen bonds might be mainly responsible for the adsorption of metformin onto GO. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Cd(II) adsorption on various adsorbents obtained from charred biomaterials

    International Nuclear Information System (INIS)

    Li Zhenze; Katsumi, Takeshi; Imaizumi, Shigeyoshi; Tang Xiaowu; Inui, Toru

    2010-01-01

    Cadmium could cause severe toxicant impact to living beings and is especially mobile in the environment. Biomass is abundant and effective to adsorb heavy metals, but is easy to be decomposed biologically which affects the reliability of long-run application. Several biomasses were charred with and without additives at temperatures less than 200 deg. C in this study. The prepared adsorbents were further testified to remove Cd(II) from aqueous solution. Equilibrium and kinetic studies were performed in batch conditions. The effect of several experimental parameters on the cadmium adsorption kinetics namely: contact time, initial cadmium concentration, sorbent dose, initial pH of solution and ionic strength was evaluated. Kinetic study confirmed (1) the rapid adsorption of Cd(II) on GC within 10 min and (2) the following gradual intraparticle diffusion inwards the sorbent at neutral pH and outwards at strong acidic solution. The grass char (GC) was selected for further test according to its high adsorption capacity (115.8 mg g -1 ) and affinity (Langmuir type isotherm). The Cd(II) removal efficiency was increased with increasing solution pH while the highest achieved at sorbent dosage 10.0 g L -1 . The ionic strength affects the sorption of Cd(II) on GC to a limited extent whereas calcium resulted in larger competition to the sorption sites than potassium. Spectroscopic investigation revealed the adsorption mechanisms between Cd(II) and surface functional groups involving amine, carboxyl and iron oxide. The long-term stability of the pyrolyzed grass char and the potential application in engineering practices were discussed.

  20. Theoretical study on the gas adsorption capacity and selectivity of CPM-200-In/Mg and CPM-200-In/Mg-X (-X = -NH2, -OH, -N, -F).

    Science.gov (United States)

    Liu, Xiao-le; Chen, Guang-Hui; Wang, Xiu-Jun; Li, Peng; Song, Yi-Bing; Li, Rui-Yan

    2017-11-15

    The adsorption capacities of a heterometallic metal-organic framework (CPM-200-In/Mg) to VOCs (HCHO, C 2 H 4 , CH 4 , C 2 H 2 , C 3 H 8 , C 2 H 6 , C 2 H 3 Cl, C 2 H 2 Cl 2 , CH 2 Cl 2 and CHCl 3 ) and some inorganic gas molecules (HCN, SO 2 , NO, CO 2 , CO, H 2 S and NH 3 ), as well as its selectivity in ternary mixture systems of natural gas and post-combustion flue gas are theoretically explored at the grand canonical Monte Carlo (GCMC) and density functional theory (DFT) levels. It is shown that CPM-200-In/Mg is suitable for the adsorption of VOCs, particularly for HCHO (up to 0.39 g g -1 at 298 K and 1 bar), and the adsorption capacities of some inorganic gas molecules such as SO 2 , H 2 S and CO 2 match well with the sequence of their polarizability (SO 2 > H 2 S > CO 2 ). The large adsorption capacities of HCN and HCHO in the framework result from the strong interaction between adsorbates and metal centers, based on analyzing the radial distribution functions (RDF). Comparing C 2 H 4 and CH 4 molecules interacting with CPM-200-In/Mg by VDW interaction, we speculate that the high adsorption capacities of their chlorine derivatives in the framework could be due to the existence of halogen bonding or strong electrostatic and VDW interactions. It is found that the basic groups, including -NH 2 , -N and -OH, can effectively improve both the adsorption capacities and selectivity of CPM-200-In/Mg for harmful gases. Note that the adsorption capacity of CPM-200-In/Mg-NH 2 (site 2) (245 cm 3 g -1 ) for CO 2 exceeded that of MOF-74-Mg (228 cm 3 g -1 ) at 273 K and 1 bar and that for HCHO can reach 0.41 g g -1 , which is almost twice that of 438-MOF and nearly 45 times of that in active carbon. Moreover, for natural gas mixtures, the decarburization and desulfurization abilities of CPM-200-In/Mg-NH 2 (site 2) have exceeded those of the MOF-74 series, while for post-combustion flue gas mixtures, the desulfurization ability of CPM-200-In/Mg-NH 2 (site 2) is still

  1. Theoretical investigation of OCN− adsorption onto boron nitride nanotubes

    International Nuclear Information System (INIS)

    Soltani, Alireza; Ahmadian, Nasim; Amirazami, Abolfazl; Masoodi, Anis; Lemeski, E. Tazikeh; Moradi, Ali Varasteh

    2012-01-01

    Highlights: ► Adsorption behavior of OCN − on (6, 0) and (8, 0) BNNTs based on density functional theory. ► OCN − is strongly bound to BNNTs in corresponding configurations. ► The effect of the OCN − adsorption on the geometries and electronic properties of related BNNTs is investigated. ► BNNTs is suggested as superior sensor for OCN − comparing with CNTs. - Abstract: First-principles calculations based on density functional theory (DFT) method are used to investigate the adsorption properties of OCN − on H-capped zigzag and armchair single-walled BN nanotubes (BNNTs). The results indicate that OCN − is strongly bound to the outer surface of zigzag (6, 0) BNNTs in comparison with armchair (5, 5) BNNT. Binding energy and equilibrium distance corresponding to the most stable configuration are found to be −486.79 kJ mol −1 and 1.526 Å, respectively being typical for the chemisorptions. Energy gap, dipole moment, natural atomic orbital occupancies and global indices for most stable configuration are calculated. Furthermore, the effect of the OCN − adsorption on the geometries and electronic properties of related BNNT is also studied. The calculated density of states (DOS) reveals that there is a significant orbital hybridization between two species in adsorption process being an evidence of strong interaction. Therefore, one can conclude that BNNTs play an important role as suitable sensor.

  2. Adsorption of elemental mercury vapors from synthetic exhaust combustion gas onto HGR carbon.

    Science.gov (United States)

    Musmarra, D; Karatza, D; Lancia, A; Prisciandaro, M; Mazziotti di Celso, G

    2016-07-01

    An activated carbon commercially available named HGR, produced by Calgon-Carbon Group, was used to adsorbe metallic mercury. The work is part of a wider research activity by the same group focused on the removal of metallic and divalent mercury from combustion flue gas. With respect to previously published papers, this one is aimed at studying in depth thermodynamic equilibria of metallic mercury adsorption onto a commercial activated carbon. The innovativeness lies in the wider operative conditions explored (temperature and mercury concentrations) and in the evaluation of kinetic and thermodynamic data for a commercially available adsorbing material. In detail, experimental runs were carried out on a laboratory-scale plant, in which Hg° vapors were supplied in a nitrogen gas stream at different temperature and mercury concentration. The gas phase was flowed through a fixed bed of adsorbent material. Adsorbate loading curves for different Hg° concentrations together with adsorption isotherms were achieved as a function of temperature (120, 150, 200°C) and Hg° concentrations (1.0-7.0 mg/m(3)). Experimental runs demonstrated satisfying results of the adsorption process, while Langmuir parameters were evaluated with gas-solid equilibrium data. Especially, they confirmed that adsorption capacity is a favored process in case of lower temperature and they showed that the adsorption heat was -20 kJ/mol. Furthermore, a numerical integration of differential equations that model the adsorption process was proposed. Scanning electron microscopy (SEM) investigation was an useful tool to investigate about fresh and saturated carbon areas. The comparison between them allowed identification of surface sites where mercury is adsorbed; these spots correspond to carbon areas where sulfur concentration is greater. Mercury compounds can cause severe harm to human health and to the ecosystem. There are a lot of sources that emit mercury species to the atmosphere; the main ones are

  3. Study of Adsorption Mechanism of Congo Red on Graphene Oxide/PAMAM Nanocomposite

    Science.gov (United States)

    Rafi, Mohammad; Samiey, Babak; Cheng, Chil-Hung

    2018-01-01

    Graphene oxide/poly(amidoamine) (GO/PAMAM) nanocomposite adsorbed high quantities of congo red (CR) anionic dye in 0.1 M NaCl solution, with the maximum adsorption capacity of 198 mg·g−1. The kinetics and thermodynamics of adsorption were investigated to elucidate the effects of pH, temperature, shaking rate, ionic strength, and contact time. Kinetic data were analyzed by the KASRA model and the KASRA, ISO, and pore-diffusion equations. Adsorption adsorption isotherms were studied by the ARIAN model and the Henry, Langmuir, and Temkin equations. It was shown that adsorption sites of GO/PAMAM at experimental conditions were phenolic hydroxyl groups of GO sheets and terminal amine groups of PAMAM dendrimer. Analysis of kinetic data indicated that amine sites were located on the surface, and that hydroxyl sites were placed in the pores of adsorbent. CR molecules interacted with the adsorption sites via hydrogen bonds. The molecules were adsorbed firstly on the amine sites, and then on the internal hydroxyl sites. Adsorption kinetic parameters indicated that the interaction of CR to the –NH3+ sites was the rate-controlling step of adsorption of CR on this site and adsorption activation energies calculated for different parts of this step. On the other hand, kinetic parameters showed that the intraparticle diffusion was the rate-controlling step during the interaction of CR molecules to –OH sites and activation energy of this step was not calculable. Finally, the used GO/PAMAM was completely regenerated by using ethylenediamine. PMID:29587463

  4. Study of Adsorption Mechanism of Congo Red on Graphene Oxide/PAMAM Nanocomposite

    Directory of Open Access Journals (Sweden)

    Mohammad Rafi

    2018-03-01

    Full Text Available Graphene oxide/poly(amidoamine (GO/PAMAM nanocomposite adsorbed high quantities of congo red (CR anionic dye in 0.1 M NaCl solution, with the maximum adsorption capacity of 198 mg·g−1. The kinetics and thermodynamics of adsorption were investigated to elucidate the effects of pH, temperature, shaking rate, ionic strength, and contact time. Kinetic data were analyzed by the KASRA model and the KASRA, ISO, and pore-diffusion equations. Adsorption adsorption isotherms were studied by the ARIAN model and the Henry, Langmuir, and Temkin equations. It was shown that adsorption sites of GO/PAMAM at experimental conditions were phenolic hydroxyl groups of GO sheets and terminal amine groups of PAMAM dendrimer. Analysis of kinetic data indicated that amine sites were located on the surface, and that hydroxyl sites were placed in the pores of adsorbent. CR molecules interacted with the adsorption sites via hydrogen bonds. The molecules were adsorbed firstly on the amine sites, and then on the internal hydroxyl sites. Adsorption kinetic parameters indicated that the interaction of CR to the –NH3+ sites was the rate-controlling step of adsorption of CR on this site and adsorption activation energies calculated for different parts of this step. On the other hand, kinetic parameters showed that the intraparticle diffusion was the rate-controlling step during the interaction of CR molecules to –OH sites and activation energy of this step was not calculable. Finally, the used GO/PAMAM was completely regenerated by using ethylenediamine.

  5. Adsorption and collective paramagnetism

    CERN Document Server

    Selwood, Pierce W

    1962-01-01

    Adsorption and Collective Paramagnetism describes a novel method for studying chemisorption. The method is based on the change in the number of unpaired electrons in the adsorbent as chemisorption occurs. The method is applicable to almost all adsorbates, but it is restricted to ferromagnetic adsorbents such as nickel, which may be obtained in the form of very small particles, that is to say, to ferromagnetic adsorbents with a high specific surface. While almost all the data used illustratively have been published elsewhere this is the first complete review of the subject. The book is addresse

  6. Probing Gas Adsorption in Zeolites by Variable-Temperature IR Spectroscopy: An Overview of Current Research.

    Science.gov (United States)

    Garrone, Edoardo; Delgado, Montserrat R; Bonelli, Barbara; Arean, Carlos O

    2017-09-15

    The current state of the art in the application of variable-temperature IR (VTIR) spectroscopy to the study of (i) adsorption sites in zeolites, including dual cation sites; (ii) the structure of adsorption complexes and (iii) gas-solid interaction energy is reviewed. The main focus is placed on the potential use of zeolites for gas separation, purification and transport, but possible extension to the field of heterogeneous catalysis is also envisaged. A critical comparison with classical IR spectroscopy and adsorption calorimetry shows that the main merits of VTIR spectroscopy are (i) its ability to provide simultaneously the spectroscopic signature of the adsorption complex and the standard enthalpy change involved in the adsorption process; and (ii) the enhanced potential of VTIR to be site specific in favorable cases.

  7. Parameterization and evaluation of sulfate adsorption in a dynamic soil chemistry model

    International Nuclear Information System (INIS)

    Martinson, Liisa; Alveteg, Mattias; Warfvinge, Per

    2003-01-01

    Including sulfate adsorption improves the dynamic behavior of the SAFE model. - Sulfate adsorption was implemented in the dynamic, multi-layer soil chemistry model SAFE. The process is modeled by an isotherm in which sulfate adsorption is considered to be fully reversible and dependent on sulfate concentration as well as pH in soil solution. The isotherm was parameterized by a site-specific series of simple batch experiments at different pH (3.8-5.0) and sulfate concentration (10-260 μmol l -1 ) levels. Application of the model to the Lake Gaardsjoen roof covered site shows that including sulfate adsorption improves the dynamic behavior of the model and sulfate adsorption and desorption delay acidification and recovery of the soil. The modeled adsorbed pool of sulfate at the site reached a maximum level of 700 mmol/m 2 in the late 1980s, well in line with experimental data

  8. Adsorption of diclofenac and nimesulide on activated carbon: Statistical physics modeling and effect of adsorbate size

    Science.gov (United States)

    Sellaoui, Lotfi; Mechi, Nesrine; Lima, Éder Cláudio; Dotto, Guilherme Luiz; Ben Lamine, Abdelmottaleb

    2017-10-01

    Based on statistical physics elements, the equilibrium adsorption of diclofenac (DFC) and nimesulide (NM) on activated carbon was analyzed by a multilayer model with saturation. The paper aimed to describe experimentally and theoretically the adsorption process and study the effect of adsorbate size using the model parameters. From numerical simulation, the number of molecules per site showed that the adsorbate molecules (DFC and NM) were mostly anchored in both sides of the pore walls. The receptor sites density increase suggested that additional sites appeared during the process, to participate in DFC and NM adsorption. The description of the adsorption energy behavior indicated that the process was physisorption. Finally, by a model parameters correlation, the size effect of the adsorbate was deduced indicating that the molecule dimension has a negligible effect on the DFC and NM adsorption.

  9. Metal adsorption on monolayer blue phosphorene: A first principles study

    Science.gov (United States)

    Khan, Imran; Son, Jicheol; Hong, Jisang

    2018-01-01

    We investigated the electronic structure, adsorption energies, magnetic properties, dipole moment and work function of metal adatoms (Mg, Cr, Mo, Pd, Pt, and Au) adsorption on a blue phosphorene monolayer. For Mg, Pt and Au metals, the most stable state was found in hollow site while for Cr, Mo and Pd metals we found an adsorption in valley site. We suggest that the Pd and Pt atoms prefer 2D growth mode while the Mg, Cr, Mo and Au atoms prefer 3D island growth mode on monolayer phosphorene. The electronic band structures and magnetic properties were dependent on the doping site and dopant materials. For instance, the semiconducting features were preserved in Mg, Pd, Pt, and Au doped systems. However, the Cr and Mo doped systems displayed half-metallic band structures. The total magnetic moment of 4.05, 2.0 and 0.77 μB /impurity atom were obtained in Cr, Mo and Au doped systems whereas the Mg, Pd and Pt doped systems remained nonmagnetic. We also investigated the magnetic interaction between two transition metal impurities. We observed ferromagnetic coupling between two transition metal impurities in Cr and Mo doped systems while the Au doped system displayed almost degenerated magnetic state. For Mg, Cr, and Mo adsorptions, we found relatively large values of dipole moments compared to those in the Pd, Pt and Au adsorptions. This resulted in a significant suppression of the work function in Mg, Cr and Mo adsorptions. Overall, adsorption can tune the physical and magnetic properties of phosphorene monolayer.

  10. Study on Shale Adsorption Equation Based on Monolayer Adsorption, Multilayer Adsorption, and Capillary Condensation

    OpenAIRE

    Chen, Qing; Tian, Yuanyuan; Li, Peng; Yan, Changhui; Pang, Yu; Zheng, Li; Deng, Hucheng; Zhou, Wen; Meng, Xianghao

    2017-01-01

    Shale gas is an effective gas resource all over the world. The evaluation of pore structure plays a critical role in exploring shale gas efficiently. Nitrogen adsorption experiment is one of the significant approaches to analyze pore size structure of shale. Shale is extremely heterogeneous due to component diversity and structure complexity. Therefore, adsorption isotherms for homogeneous adsorbents and empirical isotherms may not apply to shale. The shape of adsorption-desorption curve indi...

  11. First-principles calculation of adsorption of shale gas on CaCO3 (100) surfaces.

    Science.gov (United States)

    Luo, Qiang; Pan, Yikun; Guo, Ping; Wang, Zhouhua; Wei, Na; Sun, Pengfei; Liu, Yuxiao

    2017-06-16

    To demonstrate the adsorption strength of shale gas to calcium carbonate in shale matrix, the adsorption of shale gas on CaCO3 (100) surfaces was studied using the first-principles method, which is based on the density functional theory (DFT). The structures and electronic properties of CH4, C2H6, CO2 and N2 molecules were calculated by the generalized gradient approximation (GGA), for a coverage of 1 monolayer (ML). Under the same conditions, the density of states (DOS) of CaCO3 (100) surfaces before and after the adsorption of shale gas molecules at high-symmetry adsorption sites were compared. The results showed that the adsorption energies of CH4, C2H6, CO2 and N2 on CaCO3 (100) surfaces were between 0.2683 eV and -0.7388 eV. When a CH4 molecule was adsorbed at a hollow site and its 2 hydrogen atoms were parallel to the long diagonal (H3) on the CaCO3 (100) surface, it had the most stable adsorption, and the adsorption energy was only -0.4160 eV. The change of adsorption energy of CH4 was no more than 0.0535 eV. Compared with the DOS distribution of CH4 before adsorption, it shifted to the left overall after adsorption. At the same time, the partial density of states (PDOS) curves of CaCO3 (100) surfaces before and after adsorption basically overlapped. This work showed that the adsorption effect of shale gas on calcium carbonate is very weak, and the adsorption is physisorption at the molecular level.

  12. Adsorption of ammonia on vanadium-antimony mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, Hernan; German, Estefania [Departamento e Instituto de Fisica del Sur, Universidad Nacional del Sur-CONICET, Avda. Alem 1253, (8000) Bahia Blanca (Argentina); Juan, Alfredo, E-mail: cajuan@uns.edu.ar [Departamento e Instituto de Fisica del Sur, Universidad Nacional del Sur-CONICET, Avda. Alem 1253, (8000) Bahia Blanca (Argentina); Irigoyen, Beatriz [Departamento de Ingenieria Quimica, Facultad de Ingenieria, Universidad de Buenos Aires, Pabellon de Industrias, Ciudad Universitaria, (1428) Ciudad Autonoma de Buenos Aires (Argentina)

    2012-02-01

    We analyzed the adsorption of ammonia (NH{sub 3}) on the VSbO{sub 4}(1 1 0) catalyst surface using density functional theory (DFT) calculations. We followed the evolution of the chemical bonds between different atoms of the resulting NH{sub 3}/VSbO{sub 4} system and the changes in the electronic structure of the catalyst. NH{sub 3} preferential adsorption geometries were analyzed through the crystal orbital overlap population (COOP) concept and the density of states (DOS) curves. The VSbO{sub 4}(1 1 0) surface exhibits Lewis and Bronsted acid sites on which the ammonia molecule can interact. On the Lewis acid site, NH{sub 3} adsorption resulted in the interaction between the N and a surface V-isolated cation. On Bronsted acid site, N interacted with a surface H coming from the chemical dissociation of water. The COOP analysis indicate that NH{sub 3} interaction on the VSbO{sub 4}(1 1 0) surface is weak. In addition, the DOS curves show more developed electronic interactions for NH{sub 3} adsorption on Lewis acid site than over Bronsted acid site.

  13. Oxygen adsorption on Pt(110)-(1x2): new high-coverage structures

    DEFF Research Database (Denmark)

    Helveg, Stig; Lorensen, Henrik Qvist; Horch, Sebastian

    1999-01-01

    From an interplay between scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations, a comprehensive picture is obtained for oxygen adsorption on the Pt(110)-(1 x 2) surface, from single isolated oxygen atoms chemisorbed in FCC sites along the platinum ridges...... adsorption and platinum lattice distortions. (C) 1999 Elsevier Science B.V. All rights reserved....

  14. Effect of pH to adsorption behavior of Pu on bentonite in aqueous environment

    International Nuclear Information System (INIS)

    Wang Xiaoqiang; Tuo Xianguo; Li Pingchuan; Leng Yangchun; Su Jilong; Yueping

    2013-01-01

    The effects of pH to the adsorption behavior of Pu in GMZ-bentonite, Lingshou Ca-bentonite, Na-bentonite and bleaching earth were tested by static adsorption experiments in aqueous environment. The results show that the adsorption equilibrium time of Pu is four days in GMZ-bentonite and 5-6 days in bleaching earth, Ca-bentonite and Na-bentonite. In aqueous environment, the adsorption capacity of bentonite to Pu increases with pH in water phase, and it is weak in acidic aqueous environment and strong in alkaline aqueous environment extremely. (authors)

  15. Adsorptive desulfurization with CPO-27/MOF-74: an experimental and computational investigation.

    Science.gov (United States)

    Van de Voorde, Ben; Hezinová, Markéta; Lannoeye, Jeroen; Vandekerkhove, Annelies; Marszalek, Bartosz; Gil, Barbara; Beurroies, Isabelle; Nachtigall, Petr; De Vos, Dirk

    2015-04-28

    By combining experimental adsorption isotherms, microcalorimetric data, infrared spectroscopy and quantum chemical calculations the adsorption behaviour of the CPO-27/MOF-74 series (Ni, Co, Mg, Cu, and Zn) in the desulfurization of fuels is evaluated. The results show a clear influence of the metal ion on the adsorption capacity and affinity for S-heterocyclic compounds, with CPO-27(Ni) being the best performing material both in terms of capacity and affinity. The microcalorimetric data and infrared spectroscopy confirm the high affinity of CPO-27(Ni) for thiophene and similar compounds, while the computational data reveal that the origin of this outstanding adsorption performance is the strong sulfur-metal interaction.

  16. Characteristics of Alcian-blue Dye Adsorption of Natural Biofilm Matrix

    Science.gov (United States)

    Kurniawan, A.; Yamamoto, T.; Sukandar; Guntur

    2018-01-01

    In this study, natural biofilm matrices formed on stones have been used for the adsorption of Alcian blue dye. Alcian blue is a member of polyvalent basic dyes that largely used from laboratory until industrial dying purposes. The adsorption of the dye onto the biofilm matrix has been carried out at different experimental conditions such as adsorption isotherm and kinetic of adsorption. The electric charge properties of biofilm matrix and its changes related to the adsorption of Alcian blue have been also investigated. Moreover, the results of Alcian blue adsorption to the biofilm were compared to those onto the acidic and neutral resin. The kinetics of adsorption result showed that the adsorption of the Alcian blue dye reached to a maximum adsorption amount within 60 minutes. The adsorption amount of Alcian blue to biofilm increased monotonously, and the maximum adsorption amount was greater compared to the resins. On the contrary, Alcian blue did not attach to the neutral resin having no electric charge. It seems that Alcian blue attached to the acidic resins due to electrostatic attractive force, and the same seems to be the case for adsorption of Alcian blue to biofilm. The adsorption of Alcian blue to the biofilm and acidic resins fitted to Langmuir type indicates that the binding of Alcian blue to the biofilm and acidic resins occurred in a monolayer like form. The maximum adsorption amount of Alcian blue on the biofilm (0.24 mmol/dry-g) was greater than those of acidic resin (0.025 mmol/dry-g). This indicates that the biofilm has many more sites for Alcian blue attachment than acidic resins. According to the result of this study, the biofilm matrix can be a good adsorbent for dye such as Alcian blue or other dyes that causing hazards in nature.

  17. Chemical Tuning of Adsorption Properties of Titanate Nanotubes

    Directory of Open Access Journals (Sweden)

    Anastasia V. Grigorieva

    2012-01-01

    Full Text Available A conventional hydrothermal method widely used for the preparation of titania-based nanotubes still generates many unsolved questions. One of them is definitely connected with the influence of a posthydrothermal treatment of titania nanotubes on their micromorphology, structure, and adsorption characteristics. Here, it was analyzed systematically by a group of methods including nitrogen adsorption and temperature-programmed desorption of ammonia and carbon dioxide. It is proved that adsorption characteristics and the surface state of titania nanotubes correlate with a sodium content, since sodium ions act as Lewis acid sites and shield Ti4+ acid sites of the nanotubes. To obey a balance between chemical and heat treatments of the nanotubes to design their functional properties has been suggested.

  18. Nitrogen adsorption on Fe(111), (100), and (110) surfaces

    DEFF Research Database (Denmark)

    Mortensen, Jens Jørgen; Ganduglia-Pirovano, Veronica; Hansen, Lars Bruno

    1999-01-01

    Adsorption energies and structures for N atoms on three low-index surfaces of Fe have been calculated using density functional theory (DFT) and the generalized gradient approximation (GGA). At low N coverage the adsorption energy on Fe(100) is found to be similar to 0.7 eV higher than on the (111......) and (110) surfaces - particularly the c(2 x 2)-N/Fe(100) structure with the N atoms in four-fold sites is very stable. We attribute the differences in adsorption energy to the lack of four-fold sites on the (111) and (110) surfaces, We suggest that at higher N coverages, islands with a structure similar...

  19. Sodium dodecyl sulfate-ethoxylated polyethylenimine adsorption at the air-water interface: how the nature of ethoxylation affects the pattern of adsorption.

    Science.gov (United States)

    Batchelor, Stephen N; Tucker, Ian; Petkov, Jordan T; Penfold, Jeffrey; Thomas, Robert K

    2014-08-19

    The strong interaction between ionic surfactants and polyelectrolytes of opposite charge results in enhanced surface adsorption at the air-water interface down to low surfactant concentrations and in some cases in the formation of ordered surface structures. A notable example which exhibits such properties is the mixture of polyethylenimine, PEI, and sodium dodecyl sulfate, SDS. However, the electrostatic interaction, around charge neutralization, between the surfactant and polymer often results in precipitation or coacervation. This can be mitigated for PEI-surfactant mixtures by ethoxylation of the PEI, but this can also result in a weaker surface interaction and a significant reduction in the adsorption. It is shown here that by localizing the ethoxylation of the PEI into discrete regions of the polymer precipitation upon the addition of SDS is suppressed, the strong surface interaction and enhanced adsorption of the polymer-surfactant mixture is retained. The adsorption of SDS in the presence of ethoxylated PEI is greatly enhanced at low SDS concentrations compared to the adsorption for pure SDS. The adsorption is equally pronounced at pH 7 and 10 and is largely independent of the degree of ethoxylation. Surface ordering, more than monolayer adsorption, is observed over a relatively narrow range of SDS concentrations and is most pronounced at pH 10 and for the polymers with the lower degree of ethoxylation. The results show that ethoxylated PEI's reported here provide a suitable route to enhanced surfactant adsorption while retaining favorable solution properties in which precipitation effects are minimized.

  20. First-principle study of Mg adsorption on Si(111) surfaces

    International Nuclear Information System (INIS)

    Min-Ju, Ying; Ping, Zhang; Xiao-Long, Du

    2009-01-01

    We have carried out first-principle calculations of Mg adsorption on Si(111) surfaces. Different adsorption sites and coverage effects have been considered. We found that the threefold hollow adsorption is energy-favoured in each coverage considered, while for the clean Si(111) surface of metallic feature, we found that 0.25 and 0.5 ML Mg adsorption leads to a semiconducting surface. The results for the electronic behaviour suggest a polarized covalent bonding between the Mg adatom and Si(111) surface. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  1. Synergetic effects in CO adsorption on Cu-Pd(111) alloys

    DEFF Research Database (Denmark)

    Lopez, Nuria; Nørskov, Jens Kehlet

    2001-01-01

    We present density functional calculations for the interaction of CO on different Cu-Pd(111) bulk and surface alloys. The modification of the adsorption properties with respect to hose of the adsorption on pure Cu(111) and Pd(111) is described in terms of changes in the adsorption sites...... and the change of the electronic structure occurring upon alloying. The presence of cooperative, synergetic. effects is found to be important specially for Cu-rich bulk alloys. In this case. a larger adsorption energy is found for the inactive component than for the pure inactive system. This activation induces...

  2. Plant residues: short term effect on sulphate, borate, zinc and copper adsorption by an acid oxisol

    Directory of Open Access Journals (Sweden)

    Dias Ana Cristi Basile

    2003-01-01

    Full Text Available Laboratory experiments were carried out to examine the effects of plant residues on Cu, Zn, B and S adsorption by an acidic oxisol. The plant residues were: black oats (Avena strigosa, oil seed radish(Raphanus sativus, velvet beans (Stizolobium cinereum, and pigeon pea (Cajanus cajan collected at flowering stage. Plant residues increased Cu and Zn adsorptions and decreased B and S adsorptions. The results indicated that for short term effect plant residues decreased the availabilities of Cu and Zn through metal organic complex reactions and increased availabilities of S and B through competition with organic anions by the adsorption sites on soil.

  3. Controlled swelling and adsorption properties of polyacrylate/montmorillonite composites

    Energy Technology Data Exchange (ETDEWEB)

    Natkanski, Piotr [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Kustrowski, Piotr, E-mail: kustrows@chemia.uj.edu.pl [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Bialas, Anna; Piwowarska, Zofia [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Michalik, Marek [Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, 30-063 Krakow (Poland)

    2012-10-15

    A series of novel polyacrylate/montmorillonite composites was synthesized by in situ polymerization in aqueous slurry of clay. Dissociated (obtained by adding ammonium or sodium hydroxide) and undissociated forms of acrylic acid were used as monomers in the hydrogel synthesis. The structure and composition of the samples were studied by powder X-ray diffraction, diffuse reflectance infra-red Fourier transform spectroscopy, thermogravimetry and elemental analysis. It has been found that the kind of monomer influences strongly the location of a polymer chain in the formed composite. Complete intercalation of hydrogel into the interlayer space of montmorillonite was observed for sodium polyacrylate, whereas polyacrylic acid and ammonium polyacrylate mainly occupied the outer surface of the clay. The position of hydrogel determined the swelling and adsorption properties of the studied composites. The important factor influencing the kinetics of Fe(III) cation adsorption was pH. The analysis of adsorption isotherms allowed to propose the mechanism of Fe(III) cation adsorption. Highlights: Black-Right-Pointing-Pointer Polyacrylate hydrogels can be introduced into the interlayers of clay. Black-Right-Pointing-Pointer The position of hydrogel in the composite depends on the polymer type. Black-Right-Pointing-Pointer Ammonium polyacrylate places outside the clay, sodium one is intercalated into it. Black-Right-Pointing-Pointer Swelling and adsorption capacities can be controlled by the polymer position. Black-Right-Pointing-Pointer High adsorption efficiency in Fe(III) removal was observed.

  4. Thermodynamics of adsorption of dithiocarbamates at the hanging mercury drop.

    Science.gov (United States)

    Giannakopoulos, Evangelos; Deligiannakis, Yiannis

    2007-02-27

    Two dimethyldithiocarbamate (DMDTC) pesticides, thiram and ziram, are adsorbed onto a Hg drop via an entropically driven process. The adsorption isotherms are described by the Frumkin equation. For both molecules, the adsorption is characterized by a nonlinear pseudosigmoid temperature dependence of the Gibbs free energy. For the temperature range of 273-313 K, DeltaGADS varies between -43.4 and -56.71 kJ/mol for thiram and -42.60 and -55.67 kJ/mol for ziram. This variation of DeltaGADS reveals that the adsorption strength is increased at higher temperatures. During the adsorption of either molecule, strong lateral interactions are developed between neighboring adsorbates, which are severely weakened as the temperature increases. A unified reaction scheme is suggested for both ziram and thiram that predicts the formation and adsorption of a surface complex, (DMDTC)2Hg. In the case of thiram, two DMDTC molecules are formed by the cleavage of the disulfide S-S bond near the Hg electrode. The thermodynamic and structural parameters reveal that there are two limiting thermodynamic regimes for the adsorbed (DMDTC)2Hg species that originate from two limiting adsorption conformations of the adsorbates on the Hg surface. A transition occurs between these two conformations at temperatures in the region of 285-295 K. This transition is accompanied by large entropic and enthalpic changes.

  5. Interaction between calcium and phosphate adsorption on goethite.

    Science.gov (United States)

    Rietra, R P; Hiemstra, T; van Riemsdijk, W H

    2001-08-15

    Quantitatively, little is known about the ion interaction processes that are responsible for the binding of phosphate in soil, water, and sediment, which determine the bioavailability and mobility of phosphate. Studies have shown that metal hydroxides are often responsible for the binding of PO4 in soils and sediments, but the binding behavior of PO4 in these systems often differs significantly from adsorption studies on metal hydroxides in laboratory. The interaction between PO4 and Ca adsorption was studied on goethite because Ca can influence the PO4 adsorption equilibria. Since adsorption interactions are very difficult to discriminate from precipitation reactions, conditions were chosen to prevent precipitation of Ca-PO4 solids. Adsorption experiments of PO4 and Ca, individually and in combination, show a strong interaction between adsorbed Ca and PO4 on goethite for conditions below the saturation index of apatite. It is shown that it is possible to predict the adsorption and interaction of PO4 and Ca on electrostatic arguments using the model parameter values derived from the single-ion systems and without invoking ternary complex formation or precipitation. The model enables the prediction of the Ca-PO4 interaction for environmentally relevant calcium and phosphate concentrations.

  6. Adsorption of gas molecules on graphene-like InN monolayer: A first-principle study

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xiang; Yang, Qun [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Optoelectronic Engineering, Chongqing University, 400044 Chongqing (China); Meng, Ruishen [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Tan, Chunjian [Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Optoelectronic Engineering, Chongqing University, 400044 Chongqing (China); Liang, Qiuhua [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Jiang, Junke [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Optoelectronic Engineering, Chongqing University, 400044 Chongqing (China); Ye, Huaiyu [Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Optoelectronic Engineering, Chongqing University, 400044 Chongqing (China); Chen, Xianping, E-mail: xianpingchen@cqu.edu.cn [Faculty of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, 541004 Guilin (China); Key Laboratory of Optoelectronic Technology & Systems, Education Ministry of China, Chongqing University and College of Optoelectronic Engineering, Chongqing University, 400044 Chongqing (China)

    2017-05-15

    Highlights: • A comprehensive adsorption mechanism of InN monolayer is theoretical studied to distinguish the physic/chemi-sorption. • Different adsorption sites for different gases are systematically discussed. • The influence (enhanced or weakened) of external electric field to InN-gas system is well investigated. • The influences of gas adsorption to the optical properties (work function and light adsorption ability) of InN monolayer are also researched. - Abstract: Using first-principles calculation within density functional theory (DFT), we study the gas (CO, NH{sub 3}, H{sub 2}S, NO{sub 2}, NO, SO{sub 2}) adsorption properties on the surface of single-layer indium nitride (InN). Four different adsorption sites (Bridge, In, N, Hollow) are chosen to explore the most sensitive adsorption site. On the basis of the adsorption energy, band gap and charge transfer, we find that the most energetic favourable site is changeable between In site and N site for different gases. Moreover, our results reveal that InN is sensitive to NH{sub 3}, SO{sub 2}, H{sub 2}S and NO{sub 2}, by a physisorption or a chemisorption nature. We also perform a perpendicular electric field to the system and find that the applied electric field has a significant effect for the adsorption process. Besides, we also observed the desorption effects on NH{sub 3} adsorbed at the hollow site of InN when the electric field applied. In addition, the optical properties of InN monolayer affected by different gases are also discussed. Most of the gas adsorptions will cause the inhibition of light adsorption while the others can reduce the work function or enhance the adsorption ability in visible region. Our theoretical results indicate that monolayer InN is a promising candidate for gas sensing applications.

  7. Adsorption behavior of NH3 and NO2 molecules on stanene and stanane nanosheets - A density functional theory study

    Science.gov (United States)

    Nagarajan, V.; Chandiramouli, R.

    2018-03-01

    Using density functional theory method, we investigate the adsorption properties of NH3 and NO2 molecules on stanene and stanane nanosheets. The adsorption of molecules is explored based on the charge transfer, energetics, energy band gap and average energy gap variation. Moreover, the optimal adsorption sites of NH3 and NO2 molecules are identified on stanene and stanane nanosheets. Besides, the state-of-the-art provides the key features for the development of chemi-resistive nanosensor based on stanene and stanane nanosheets upon adsorption of NH3 and NO2 molecules. Furthermore, the study shows that adsorption of NO2 molecules is more prominent rather than NH3 molecules.

  8. Non-Calorimetric Determination of the Adsorption Heat of Volatile Organic Compounds under Dynamic Conditions

    Directory of Open Access Journals (Sweden)

    Abdelhamid Korrir

    2015-04-01

    Full Text Available Avoiding strong chemical bonding, as indicated by lower heat of adsorption value, is among the selection criteria for Volatile Organic Compounds adsorbents. In this work, we highlight a non-calorimetric approach to estimating the energy of adsorption and desorption based on measurement of involved amounts, under dynamic conditions, with gaseous Fourier Transform Infrared spectroscopy. The collected data were used for obtaining adsorption heat values through the application of three different methods, namely, isosteric, temperature programmed desorption (TPD, and temperature-programmed adsorption equilibrium (TPAE. The resulting values were compared and discussed with the scope of turning determination of the heat of adsorption with non-calorimetric methods into a relevant decision making tool for designing cost-effective and safe operating of adsorption facilities.

  9. Abortion: Strong's counterexamples fail

    DEFF Research Database (Denmark)

    Di Nucci, Ezio

    2009-01-01

    This paper shows that the counterexamples proposed by Strong in 2008 in the Journal of Medical Ethics to Marquis's argument against abortion fail. Strong's basic idea is that there are cases--for example, terminally ill patients--where killing an adult human being is prima facie seriously morally...

  10. Strong Langmuir turbulence

    International Nuclear Information System (INIS)

    Goldman, M.V.

    1984-01-01

    After a brief discussion of beam-excited Langmuir turbulence in the solar wind, we explain the criteria for wave-particle, three-wave and strong turbulence interactions. We then present the results of a numerical integration of the Zakharov equations, which describe the strong turbulence saturation of a weak (low-density) high energy, bump-on-tail beam instability. (author)

  11. Adsorption properties of the SAPO-5 molecular sieve

    KAUST Repository

    Hu, Enping; Lai, Zhiping; Wang, Kean

    2010-01-01

    The adsorption properties of an aluminophosphate molecular sieve, SAPO-5, were measured for a number of gases and vapors, including N2, water, isopropanol, and xylenes. The data showed that SAPO-5 is quite hydrophobic and has a strong selectivity of o-xylene over its isomers m- and p-xylene. © 2010 American Chemical Society.

  12. Fluoride adsorption onto an acid treated lateritic mineral from Kenya ...

    African Journals Online (AJOL)

    1) from Kenya was studied by batch experiments. The effect of acid-treatment of adsorbent and change in temperature, mass of LM-1, pH and selected competing ions was evaluated. The adsorption process was strongly influenced by ...

  13. Hydrogen adsorption on palladium and palladium hydride at 1 bar

    DEFF Research Database (Denmark)

    Johansson, Martin; Skulason, Egill; Nielsen, Gunver

    2010-01-01

    strongly to Pd hydride than to Pd. The activation barrier for desorption at a H coverage of one mono layer is slightly lower on Pd hydride, whereas the activation energy for adsorption is similar on Pd and Pd hydride. It is concluded that the higher sticking probability on Pd hydride is most likely caused...

  14. Phosphorus adsorption pattern in selected cocoa growing soils in ...

    African Journals Online (AJOL)

    Application of phosphate fertilizer for the correction of P deficiency in soil is ideal in agricultural practices. Unfortunately, only a small fraction of applied P fertilizer is available for plant uptake due to fertilizer-soil interactions which leads to fixation of P. phosphorus adsorption isotherm and buffering capacity are strong tools ...

  15. Adsorption of charged macromolecules at a gold electrode

    NARCIS (Netherlands)

    Kleijn, J.M.; Barten, D.; Cohen Stuart, M.A.

    2004-01-01

    Using an optical reflectometer with impinging-jet system, the adsorption from aqueous solution onto gold of three charged macromolecules has been studied: the strong linear-chain polyelectrolyte polyvinyl pyridine (PVP +), the fifth-generation poly(propylene imine) dendrimer DAB-64, which has a

  16. Adsorption properties of the SAPO-5 molecular sieve

    KAUST Repository

    Hu, Enping

    2010-09-09

    The adsorption properties of an aluminophosphate molecular sieve, SAPO-5, were measured for a number of gases and vapors, including N2, water, isopropanol, and xylenes. The data showed that SAPO-5 is quite hydrophobic and has a strong selectivity of o-xylene over its isomers m- and p-xylene. © 2010 American Chemical Society.

  17. Adsorption thermal energy storage for cogeneration in industrial batch processes: Experiment, dynamic modeling and system analysis

    International Nuclear Information System (INIS)

    Schreiber, Heike; Graf, Stefan; Lanzerath, Franz; Bardow, André

    2015-01-01

    Adsorption thermal energy storage is investigated for heat supply with cogeneration in industrial batch processes. The feasibility of adsorption thermal energy storage is demonstrated with a lab-scale prototype. Based on these experiments, a dynamic model is developed and successfully calibrated to measurement data. Thereby, a reliable description of the dynamic behavior of the adsorption thermal energy storage unit is achieved. The model is used to study and benchmark the performance of adsorption thermal energy storage combined with cogeneration for batch process energy supply. As benchmark, we consider both a peak boiler and latent thermal energy storage based on a phase change material. Beer brewing is considered as an example of an industrial batch process. The study shows that adsorption thermal energy storage has the potential to increase energy efficiency significantly; primary energy consumption can be reduced by up to 25%. However, successful integration of adsorption thermal storage requires appropriate integration of low grade heat: Preferentially, low grade heat is available at times of discharging and in demand when charging the storage unit. Thus, adsorption thermal energy storage is most beneficial if applied to a batch process with heat demands on several temperature levels. - Highlights: • A highly efficient energy supply for industrial batch processes is presented. • Adsorption thermal energy storage (TES) is analyzed in experiment and simulation. • Adsorption TES can outperform both peak boilers and latent TES. • Performance of adsorption TES strongly depends on low grade heat temperature.

  18. Adsorption of Dyes in Studying the Surface Chemistry of Ultradispersed Diamond

    Science.gov (United States)

    Khokhlova, T. D.; Yunusova, G. R.; Lanin, S. N.

    2018-05-01

    The effect the surface chemistry of ultradispersed diamond (UDD) has on the adsorption of watersoluble dyes is considered. A comparison is made to adsorption on graphitized thermal carbon black (GTCB), which has a homogeneous and nonporous surface. The adsorption isotherms of dyes and the dependence of the adsorption on the pH of solutions are measured. It is found that UDD adsorbs acid (anionic) dyes—acid orange (AO) and acid anthraquinone blue (AAB)—but barely adsorbs a basic (cationic) dye, methylene blue (MB), because of the predominance of positively charged basic groups on the surface of UDD. The maximum adsorption of AO is much lower on UDD than on GTCB, while the maximum adsorption of AAB is similar for both surfaces. The adsorption of AO on UDD depends strongly on the pH of the solution, while the adsorption of AAB is independent of this parameter. It is suggested that the adsorption of AAB is determined not only by ionic and hydrophobic interactions but also by coordination interactions with impurity metal ions on a UDD surface. It is concluded that the adsorption of dyes characterizes the chemistry of a UDD surface with high sensitivity.

  19. Adsorption of ammonia at GaN(0001) surface in the mixed ammonia/hydrogen ambient - a summary of ab initio data

    International Nuclear Information System (INIS)

    Kempisty, Paweł; Krukowski, Stanisław

    2014-01-01

    Adsorption of ammonia at NH 3 /NH 2 /H-covered GaN(0001) surface was analyzed using results of ab initio calculations. The whole configuration space of partially NH 3 /NH 2 /H-covered GaN(0001) surface was divided into zones of differently pinned Fermi level: at the Ga broken bond state for dominantly bare surface (region I), at the valence band maximum (VBM) for NH 2 and H-covered surface (region II), and at the conduction band minimum (CBM) for NH 3 -covered surface (region III). The electron counting rule (ECR) extension was formulated for the case of adsorbed molecules. The extensive ab intio calculations show the validity of the ECR in case of all mixed H-NH 2 -NH 3 coverages for the determination of the borders between the three regions. The adsorption was analyzed using the recently identified dependence of the adsorption energy on the charge transfer at the surface. For region I ammonia adsorbs dissociatively, disintegrating into a H adatom and a HN 2 radical for a large fraction of vacant sites, while for region II adsorption of ammonia is molecular. The dissociative adsorption energy strongly depends on the Fermi level at the surface (pinned) and in the bulk (unpinned) while the molecular adsorption energy is determined by bonding to surface only, in accordance to the recently published theory. Adsorption of Ammonia in region III (Fermi level pinned at CBM) leads to an unstable configuration both molecular and dissociative, which is explained by the fact that broken Ga-bonds are doubly occupied by electrons. The adsorbing ammonia brings 8 electrons to the surface, necessitating the transfer of these two electrons from the Ga broken bond state to the Fermi level. This is an energetically costly process. Adsorption of ammonia at H-covered site leads to the creation of a NH 2 radical at the surface and escape of H 2 molecule. The process energy is close to 0.12 eV, thus not large, but the direct inverse process is not possible due to the escape of the

  20. Mathematical Model for Multicomponent Adsorption Equilibria Using Only Pure Component Data

    DEFF Research Database (Denmark)

    Marcussen, Lis

    2000-01-01

    A mathematical model for nonideal adsorption equilibria in multicomponent mixtures is developed. It is applied with good results for pure substances and for prediction of strongly nonideal multicomponent equilibria using only pure component data. The model accounts for adsorbent...

  1. Influence of adsorption thermodynamics on guest diffusivities in nanoporous crystalline materials

    NARCIS (Netherlands)

    Krishna, R.; van Baten, J.M.

    2013-01-01

    Published experimental data, underpinned by molecular simulations, are used to highlight the strong influence of adsorption thermodynamics on diffusivities of guest molecules inside ordered nanoporous crystalline materials such as zeolites, metal-organic frameworks (MOFs), and zeolitic imidazolate

  2. Adsorption and diffusion of fluorine on Cr-doped Ni(111) surface: Fluorine-induced initial corrosion of non-passivated Ni-based alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Cui-Lan, E-mail: rencuilan@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Han, Han [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Gong, Wen-Bin [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Shanghai 215123 (China); Wang, Cheng-Bin; Zhang, Wei [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800 (China); Cheng, Cheng [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Huai, Ping, E-mail: huaiping@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhu, Zhi-Yuan [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Key Laboratory of Interfacial Physics and Technology, Chinese Academy of Sciences, Shanghai 201800 (China)

    2016-09-15

    Adsorption and diffusion behaviors of fluorine on Cr-doped Ni(111) surface are investigated by using first-principles simulation. It shows that the Cr in the Cr-doped Ni(111) surface serve a trap site for fluorine with adsorption energy 3.52 eV, which is 1.04 eV higher than that on Ni(111) surface. Moreover, the Cr atom is pulled out the surface for 0.41 Å after the fluorine adsorption, much higher than that on Ni(111) surface. Further diffusion behaviors analysis confirms the conclusion because the fluorine diffusion from neighbored sites onto the Cr top site is an energy barrierless process. Detailed electronic structure analysis shows that a deeper hybrid state of F 2 p-Cr 3 d indicates a strong F−Cr interaction. The Ni−Cr bond is elongated and weakened due to the new formed F−Cr bonding. Our results help to understanding the basic fluorine-induced initial corrosion mechanism for Ni-based alloy in molten salt environment.

  3. Influences of salt concentration, loading and pH on strontium adsorption

    International Nuclear Information System (INIS)

    Atun, G.; Kaplan, Z.

    1996-01-01

    The adsorption of Sr on clay with contains zeolites and montmorillonite mixtures was investigated in solutions of NaCl by means of a batch technique. Sr retention was reduced with increasing NaCl concentration from 5*10 -4 to 5*10 -1 M. Distribution coefficients (K d ) linearly increased with pH in the acidic region but they were almost independent of pH in neutral and alkaline solutions. By fitting the data of the Dubinin-Radushkevich (D-R) isotherm, the mean energies of adsorption and adsorption capacities of Sr at different pH values were calculated. The results showed that the mode of adsorption below pH 4.5 is ion exchange, while above that value a multilayer adsorption occurs. Adsorption data were fitted to the Freundlich isotherm and from empirical Freundlich parameters a site distribution function was calculated. (author)

  4. Combined DFT and XPS investigation of iodine anions adsorption on the sulfur terminated (001) chalcopyrite surface

    Energy Technology Data Exchange (ETDEWEB)

    Li, Kui, E-mail: likui9606@stu.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Zhao, Yaolin, E-mail: zhaoyaolin@mail.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Zhang, Peng, E-mail: zp32@qq.com [Sino Shaanxi Nuclear Industry Group, Xi’an 710100 (China); He, Chaohui, E-mail: hechaohui@mail.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Deng, Jia, E-mail: djkokocase@stu.xjtu.edu.cn [School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Ding, Shujiang, E-mail: dingsj@mail.xjtu.edu.cn [Department of Applied Chemistry, School of Science, Xi’an Jiaotong University, Xi’an 710049 (China); Shi, Weiqun, E-mail: shiwq@ihep.ac.cn [Key Laboratory of Nuclear Radiation and Nuclear Energy Technology and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2016-12-30

    Highlights: • Metal surface sites of (001)-S surface of chalcopyrite show significant chemical affinity to iodide and iodate. • The energetically favorable active site is copper for iodide adsorption and iron for iodate adsorption, respectively. • Iodate undergoes a dissociative adsorption on the copper site of chalcopyrite surface. - Abstract: The adsorption of iodine anions (iodide and iodate) on the sulfur terminated (001) chalcopyrite surface has been systematically investigated combining first-principles calculations based on density functional theory (DFT) with X-ray photoelectron spectroscopy (XPS) measurements. Based on the total energy calculations and geometric optimization, the thermodynamically preferred site was copper atom for iodide adsorption and iron atom for iodate adsorption, respectively. In the case of Cu site mode, the iodate underwent a dissociative adsorption, where one I−O bond of iodate ion was broken and the dissociative oxygen atom adsorbed on the adjacent sulphur site. Projected density of states (PDOS) analysis further clarified the interaction mechanism between active sites of chalcopyrite surface and adsorbates. In addition, full-range XPS spectra qualitatively revealed the presence of iodine on chalcopyrite surface. High resolution XPS spectra of the I 3d peaks after adsorption verified the chemical environment of iodine. The binding energies of 618.8 eV and 623.5 eV for I 3d{sub 5/2} peaks unveiled that the adsorption of iodide and iodate ions on copper-iron sulfide minerals was the result of formation of low solubility metal iodides precipitate. Also two I 3d peaks with low intensity around 618 eV and 630 eV might be related to the inorganic reduction of iodate to iodide by reducing S{sup 2−} ion of chalcopyrite.

  5. Effects of humic acid on adsorption of actinide elements on rocks and others

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, Masakazu; Sato, Seichi; Ohashi, Hiroshi [Hokkaido Univ., Sapporo (Japan). Faculty of Engineering; Sakamoto, Yoshiaki; Nagao, Seiya; Onuki, Toshihiko; Senoo, Muneaki

    1996-01-01

    Since the transfer rates of radionuclides are reduced by their adsorption to rocks and soils, it is essential to elucidate the adsorption process for safety assessment of their geological disposal. In this study, adsorption of Np(V) to goethite, one of the widely distributed minerals was investigated as functions of pH and humic acid concentration. The surface charge density of goethite was determined and the zero charge point was 6.2 for synthesized and 6.4 for natural goethite. Since the point for humic acid was 4.5, adsorption sites for humic acid were reduced as the increase of negative charge density above pH6, resulting in a decrease in its adsorption rate. Np(V) adsorption to goethite was raised by the presence of humic acid in the range of 0-10ppm because the surface charge on the rock was shifted to negative by the adsorption of humic acid, resulting in easy adsorption of NpO{sub 2}{sup +}, which is stable in the condition below pH 9.5. On the other hand, humic acid adsorption was saturated at a concentration higher than 50 ppm, but its content in the solution would increase. Thus, it was thought that Np(V)-humic acid complex becomes more stable, resulting in the decrease in Np(V) adsorption rate. (M.N.)

  6. Adsorption of heavy metal from landfill leachate by wasted biosolids ...

    African Journals Online (AJOL)

    However, the concentration of Cd, Cu and Zn was not detected in the leachate but Fe was found to be in high concentration (184 mg/L) in raw leachate collected from a municipal landfill site. Therefore, the effects of biomass dosage, contact time, pH and agitation speed were observed for optimal adsorption of iron from ...

  7. Adsorption of SO{sub 2} on Li atoms deposited on MgO (1 0 0) surface: DFT calculations

    Energy Technology Data Exchange (ETDEWEB)

    Eid, Kh.M., E-mail: Kheid98@hotmail.com [Physics Department, Faculty of Education, Ain Shams University, Cairo 11757 (Egypt); Ammar, H.Y. [Department of Physics, Faculty of Science, Najran University, Najran 1988 (Saudi Arabia)

    2011-05-01

    The adsorption of sulfur dioxide molecule (SO{sub 2}) on Li atom deposited on the surfaces of metal oxide MgO (1 0 0) on both anionic and defect (F{sub s}-center) sites located on various geometrical defects (terrace, edge and corner) has been studied using density functional theory (DFT) in combination with embedded cluster model. The adsorption energy (E{sub ads}) of SO{sub 2} molecule (S-atom down as well as O-atom down) in different positions on both of O{sup -2} and F{sub s} sites is considered. The spin density (SD) distribution due to the presence of Li atom is discussed. The geometrical optimizations have been done for the additive materials and MgO substrate surfaces (terrace, edge and corner). The oxygen vacancy formation energies have been evaluated for MgO substrate surfaces. The ionization potential (IP) for defect free and defect containing of the MgO surfaces has been calculated. The adsorption properties of SO{sub 2} are analyzed in terms of the E{sub ads}, the electron donation (basicity), the elongation of S-O bond length and the atomic charges on adsorbed materials. The presence of the Li atom increases the catalytic effect of the anionic O{sup -2} site of MgO substrate surfaces (converted from physisorption to chemisorption). On the other hand, the presence of the Li atom decreases the catalytic effect of the F{sub s}-site of MgO substrate surfaces. Generally, the SO{sub 2} molecule is strongly adsorbed (chemisorption) on the MgO substrate surfaces containing F{sub s}-center.

  8. Adsorption of polycyclic aromatic hydrocarbons by graphene and graphene oxide nanosheets.

    Science.gov (United States)

    Wang, Jun; Chen, Zaiming; Chen, Baoliang

    2014-05-06

    The adsorption of naphthalene, phenanthrene, and pyrene onto graphene (GNS) and graphene oxide (GO) nanosheets was investigated to probe the potential adsorptive sites and molecular mechanisms. The microstructure and morphology of GNS and GO were characterized by elemental analysis, XPS, FTIR, Raman, SEM, and TEM. Graphene displayed high affinity to the polycyclic aromatic hydrocarbons (PAHs), whereas GO adsorption was significantly reduced after oxygen-containing groups were attached to GNS surfaces. An unexpected peak was found in the curve of adsorption coefficients (Kd) with the PAH equilibrium concentrations. The hydrophobic properties and molecular sizes of the PAHs affected the adsorption of G and GO. The high affinities of the PAHs to GNS are dominated by π-π interactions to the flat surface and the sieving effect of the powerful groove regions formed by wrinkles on GNS surfaces. In contrast, the adsorptive sites of GO changed to the carboxyl groups attaching to the edges of GO because the groove regions disappeared and the polar nanosheet surfaces limited the π-π interactions. The TEM and SEM images initially revealed that after loading with PAH, the conformation and aggregation of GNS and GO nanosheets dramatically changed, which explained the observations that the potential adsorption sites of GNS and GO were unusually altered during the adsorption process.

  9. Preparation and evaluation of molecularly imprinted polymer for selective recognition and adsorption of gossypol.

    Science.gov (United States)

    Zhi, Keke; Wang, Lulu; Zhang, Yagang; Zhang, Xuemin; Zhang, Letao; Liu, Li; Yao, Jun; Xiang, Wei

    2018-03-01

    Molecularly imprinted polymers (MIPs) were designed and prepared via bulk thermal polymerization with gossypol as the template molecule and dimethylaminoethyl methacrylate as the functional monomer. The morphology and microstructures of MIPs were characterized by scanning electron microscope and Brunauer-Emmett-Teller surface areas. Static adsorption tests were performed to evaluate adsorption behavior of gossypol by the MIPs. It was found that adsorption kinetics and adsorption isotherms data of MIPs for gossypol were fit well with the pseudo-second-order model and Freundlich model, respectively. Scatchard analysis showed that heterogeneous binding sites were formed in the MIPs, including lower-affinity binding sites with the maximum adsorption of 252 mg/g and higher-affinity binding sites with the maximum adsorption of 632 mg/g. Binding studies also revealed that MIPs had favorable selectivity towards gossypol compared with non-imprinted polymers. Furthermore, adsorption capacity of MIPs maintained above 90% after 5 regeneration cycles, indicating MIPs were recyclable and could be used multiple times. These results demonstrated that prepared MIPs could be a promising functional material for selective adsorption of gossypol. Copyright © 2017 John Wiley & Sons, Ltd.

  10. Simulation of the effects of phosphate on adsorption of arsenite and arsenate on ferrihydrite matrix using a geochemical equilibrium model

    International Nuclear Information System (INIS)

    Kassenga, G.R.

    2005-01-01

    Arsenic is of environmental concern because of its toxicity to plants, animals, and human beings. Iron oxides, including the poorly crystalline (amorphous) iron oxides, e.g., ferrihydrite, have a strong affinity for both arsenite and arsenate (the most toxic species of arsenic). In view of this, adsorption on ferrihydrite matrix is the main process of immobilization of arsenic in groundwater. The presence of phosphate in groundwater may however limit adsorption of arsenic on iron oxides due to competition for adsorption sites, resulting in higher aqueous concentrations in some environments. This paper analyses the effects of phosphate on aqueous concentration of arsenic at different pH using a geochemical equilibrium simulation model. It specifically focuses on arsenite and arsenate, the most toxic forms of arsenic. A general description of the occurrence of arsenic in the environment, its toxicity, and health hazards is first given. The paper discusses sources and geochemical processes that control arsenic mobility in aquifers. Adsorption and desorption reactions of arsenic on ferrihydrite and the factors that affect them are described. Modeling of adsorption/desorption processes is then discussed. Finally, the effects of phosphate on adsorption and desorption processes of arsenic on ferrihydrite as a function of pH are analyzed using PHREEQC Version 2, a computer program for simulating chemical reactions and transport processes in natural and polluted water. The model is applied in a case study formulated on the basis of a realistic hydrogeochemical setting to demonstrate how the use of arsenical pesticides and phosphate fertilizers may pose potential public health problems in areas where groundwater is used for domestic purposes. The modeling results have shown that aqueous concentration of arsenic increases with increasing phosphate-phosphorus concentration for pH values less than 10 assuming that ferrihydrite concentration and other hydrogeochemical conditions

  11. Adsorption Desalination: A Novel Method

    KAUST Repository

    Ng, Kim Choon

    2010-11-15

    The search for potable water for quenching global thirst remains a pressing concern throughout many regions of the world. The demand for new and sustainable sources and the associated technologies for producing fresh water are intrinsically linked to the solving of potable water availability and hitherto, innovative and energy efficient desalination methods seems to be the practical solutions. Quenching global thirst by adsorption desalination is a practical and inexpensive method of desalinating the saline and brackish water to produce fresh water for agriculture irrigation, industrial, and building applications. This chapter provides a general overview of the adsorption fundamentals in terms of adsorption isotherms, kinetics, and heat of adsorption. It is then being more focused on the principles of thermally driven adsorption desalination methods. The recent developments of adsorption desalination plants and the effect of operating conditions on the system performance in terms of specific daily water production and performance ratio are presented. Design of a large commercial adsorption desalination plant is also discussed herein.

  12. Strong intrinsic motivation

    OpenAIRE

    Dessi, Roberta; Rustichini, Aldo

    2015-01-01

    A large literature in psychology, and more recently in economics, has argued that monetary rewards can reduce intrinsic motivation. We investigate whether the negative impact persists when intrinsic motivation is strong, and test this hypothesis experimentally focusing on the motivation to undertake interesting and challenging tasks, informative about individual ability. We find that this type of task can generate strong intrinsic motivation, that is impervious to the effect of monetary incen...

  13. Bitcoin Meets Strong Consistency

    OpenAIRE

    Decker, Christian; Seidel, Jochen; Wattenhofer, Roger

    2014-01-01

    The Bitcoin system only provides eventual consistency. For everyday life, the time to confirm a Bitcoin transaction is prohibitively slow. In this paper we propose a new system, built on the Bitcoin blockchain, which enables strong consistency. Our system, PeerCensus, acts as a certification authority, manages peer identities in a peer-to-peer network, and ultimately enhances Bitcoin and similar systems with strong consistency. Our extensive analysis shows that PeerCensus is in a secure state...

  14. Strong gravity and supersymmetry

    International Nuclear Information System (INIS)

    Chamseddine, Ali H.; Salam, A.; Strathdee, J.

    1977-11-01

    A supersymmetric theory is constructed for a strong f plus a weak g graviton, together with their accompanying massive gravitinos, by gaugin the gradel 0Sp(2,2,1)x 0Sp(2,2,1) structure. The mixing term between f and g fields, which makes the strong graviton massive, can be introduced through a spontaneous symmetry-breaking mechanism implemented in this note by constructing a non-linear realization of the symmetry group

  15. Methyl Butanoate Adsorption on MoS2 Surface: A Density Functional Theory Investigation

    Directory of Open Access Journals (Sweden)

    Prabowo Wahyu Aji Eko

    2018-01-01

    Full Text Available Methyl butanoate is one of the compound which is obtained from triglyceride molecule. It has hydrocarbon components and hence may produce hydrocarbon through hydrodeoxygenation (HDO or decarbonylation (DCO processes. The first step to uncover the underlying mechanism of HDO or DCO is to find the active site of methyl butanoate adsorption over the catalyst. This study attempts to investigate the active site of methyl butanoate adsorption on MoS2 surface. Stable bonding configuration for methyl butanoate adsorption on MoS2 is investigated by using density functional theory (DFT. This investigation consists of geometry optimisation and adsorption energy calculations. The stable configuration of methyl butanoate adsorption on MoS2 surface is found to be on top of Mo atom in Mo-edge surface.

  16. First principles study of the adsorption of a NO molecule on N-doped anatase nanoparticles

    International Nuclear Information System (INIS)

    Liu Juan; Liu Qin; Fang Pengfei; Pan Chunxu; Xiao Wei

    2012-01-01

    The adsorption of a NO molecule on 72 atom N-doped TiO 2 nanoparticles has been studied by first principles calculations. Two types of adsorption are considered in the calculations. In one type of the adsorption, the NO molecule forms one bond with the particle, while in the other type of adsorption, the NO molecule forms two bonds with the particle. The second type of adsorption is more energetic favorable. The adsorption energies, bond lengths, density of the states (DOSs), and the difference of the charge density are calculated to investigate the adsorption. In the adsorption process, the unpaired electron of the NO molecule transfers to the empty state of the particle, making the Fermi levels lower. As a result, the electrons of the N-doped system occupy lower energy states, making the system energy lower than that of the undoped particle. Since the adsorption of a NO molecule on N-doped nanoparticles is stronger than that on undoped particles, N-doped particles can adsorb more NO molecules on their surfaces than the undoped particles do. Meanwhile, there are more adsorption sites on the N-doped particles, on which the adsorption energies are much higher than that of the undoped particle, some of them are even higher than the highest adsorption energy of the undoped particle. It suggests that N-doped particles are more active and they can adsorb more small toxic gas molecules in the air. So, the doping method can be used to remove NO molecules for the air pollution control through the surface adsorption strategy.

  17. Heavy metal ion adsorption behavior in nitrogen-doped magnetic carbon nanoparticles: Isotherms and kinetic study

    International Nuclear Information System (INIS)

    Shin, Keun-Young; Hong, Jin-Yong; Jang, Jyongsik

    2011-01-01

    Graphical abstract: Display Omitted Research highlights: → The monodisperse and multigram-scale N-MCNPs are fabricated by carbonization of polypyrrole as a carbon precursor. → The synthesized N-MCNPs provide an enhanced adsorption uptake for various heavy metal ions. → The N-MCNPs can be applied to the Langmuir model and pseudo-second-order kinetics. → The iron-impregnated N-MCNPs are reused up to 5 times with no loss of removal efficiency. - Abstract: To clarify the heavy metal adsorption mechanism of nitrogen-doped magnetic carbon nanoparticles (N-MCNPs), adsorption capacity was investigated from the adsorption isotherms, kinetics and thermodynamics points of view. The obtained results showed that the equilibrium adsorption behavior of Cr 3+ ion onto the N-MCNPs can be applied to the Langmuir model and pseudo-second-order kinetics. It indicated that the fabricated N-MCNPs had the homogenous surface for adsorption and all adsorption sites had equal adsorption energies. Furthermore, the adsorption onto N-MCNPs taken place through a chemical process involving the valence forces. According to the thermodynamics, the adsorption process is spontaneous and endothermic in nature which means that the adsorption capacity increases with increasing temperature due to the enhanced mobility of adsorbate molecules. The effects of the solution pH and the species of heavy metal ion on the adsorption uptake were also studied. The synthesized N-MCNPs exhibited an enhanced adsorption capacity for the heavy metal ions due to the high surface area and large amount of nitrogen contents.

  18. Surface and adsorptive properties of Moringa oleifera bark for removal of V(V) from aqueous solutions.

    Science.gov (United States)

    Mnisi, Robert Londi; Ndibewu, Peter Papoh

    2017-11-04

    The bark of Moringa oleifera, a cheap and readily available natural biopolymeric resource material, found to significantly reduce coliform load and turbidity in contaminated water is investigated in this paper. Its surface and adsorptive properties are investigated to explore its adsorptive potential in removing V(V) from aqueous solutions. Surface properties were investigated using FTIR, HRSEM/EDS, IC, and BET-N 2 adsorption techniques. Adsorptive properties were investigated by optimizing adsorption parameters such as pH, temperature, initial metal concentration, and adsorbent dosage, using V(V) as an adsorbate. The adsorption-desorption isotherms are typical of type II with a H3 hysteresis loop and is characteristic of a largely macroporous material. Bottle ink pores are observed, which can provide good accessibility of the active sites, even though the internal BET surface area is typically low (1.79 g/m 2 ). Solution pH significantly influences the adsorptive potential of the material. The low surface area negatively impacts on the adsorption capacity, but is compensated for by the exchangeable anions (Cl - , F - , PO 4 3- , NO 3 - , and SO 4 2- ) and cations (Ca 2+ , K + , Mg 2+ , and Al 3+ ) at the surface and the accessibility of the active sites. Adsorption isotherm modeling show that the surface is largely heterogeneous with complex multiple sites and adsorption is not limited to monolayer.

  19. Processes of H{sub 2} adsorption on Fe(1 1 0) surface: A density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Weiwei; Peng, Liang; Peng, Daoling [Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Gu, Feng Long, E-mail: gu@scnu.edu.cn [Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education, School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Liu, Jun [Material Design and Simulation Technology Co. Ltd., Room 1716, V-Faction, 10 Vanke, 2 Ring Road of North Section, Chengdu (China)

    2014-03-01

    Highlights: • The hydrogen coverages for H{sub 2} adsorption on Fe(1 1 0) surface ranging from 0.125 to 1.000 are prepared by using different surface supercells. • With the reduction of coverage, the average iron atomic energy is increased and the adsorption energy is decreased, leading to the system more stable; while coverage has little effect on the Fe(1 1 0) surface structure and the hydrogen adsorption process. • The most stable absorption site is found to be the on-top site. • DFT calculations show that it is a weak adsorption and the adsorption energy barriers under 4.4 kcal/mol. • The final state is H{sub 2} molecule dissociated into two hydrogen atoms interacting with surface iron atoms to form stable Fe-H bonds. - Abstract: Processes of H{sub 2} adsorption on Fe(1 1 0) surface have been studied by the density functional theory, properties such as surface structure, adsorption position, and adsorption energies are discussed as well. To investigate the atomic geometries and stability under different hydrogen coverages for this adsorption, the hydrogen coverages ranging from 0.125 to 1.000 are prepared by using different surface supercells. It is found that with the reduction of coverage, the average iron atomic energy and the adsorption energy are increased, leading to the system more stable; while coverage has little effect on the Fe(1 1 0) surface structure and the hydrogen adsorption process. The most stable absorption site is found to be the on-top site. Our calculations show that it is a weak adsorption and the adsorption energy barriers under 4.4 kcal/mol. The final state is H{sub 2} molecule dissociated into two hydrogen atoms and interacting with surface iron atoms to form stable Fe-H bonds.

  20. Adsorption facility and adsorption vessel for radioactive carbon dioxide

    International Nuclear Information System (INIS)

    Harashina, Heihachi; Miwa, Keiichi; Kobayashi, Takeo.

    1992-01-01

    If 14 CO 2 gas-containing gases to be adsorbed are pressurized and sent to a packaging adsorption means, CO 2 ingredient in the gases to be adsorbed is adsorbed or absorbed, and remaining gases are passed through and sent out to downstream. CO 2 adsorption or absorption of the packaging adsorption means is judged by monitoring the state of the remaining gases, and if it is normal, remaining gases are sent further to downstream and processed. If abnormality is found, a gas feedback system is operated, and CO 2 removing gas is sent again to the packaging adsorption means, in which CO 2 gases are adsorbed or absorbed again repeatingly. With such procedures, in a case where C 14 nuclides having a long half decay time are supplied in the form of 14 CO 2 gas, they are efficiently adsorbed or absorbed in the packaging system to improve removing and storing property of 14 C nuclides. (T.M.)

  1. Counterion adsorption and desorption rate of a charged macromolecule

    Science.gov (United States)

    Shi, Yu; Yang, Jingfa; Zhao, Jiang

    The rate constant of counterion adsorption to and desorption from a synthetic polyelectrolyte, polystyrene sulfonate (PSS-), is measured in aqueous solution by single molecule fluorescence spectroscopy. The results show that both adsorption and desorption rate of counterions have strong dependence on polymer concentration, salt concentration as well as the molecular weight of polyelectrolytes. The results clearly demonstrate that the contribution of electrostatic interaction and the translational entropy to the distribution of counterions of a polyelectrolyte molecule. The information is helpful to the understanding of polyelectrolyte physics. National Natural Science Foundation of China.

  2. Carbon nanomaterials for gas adsorption

    CERN Document Server

    Terranova, Maria Letizia

    2012-01-01

    Research in adsorption of gases by carbon nanomaterials has experienced considerable growth in recent years, with increasing interest for practical applications. Many research groups are now producing or using such materials for gas adsorption, storage, purification, and sensing. This book provides a selected overview of some of the most interesting scientific results regarding the outstanding properties of carbon nanomaterials for gas adsorption and of interest both for basic research and technological applications. Topics receiving special attention in this book include storage of H, purific

  3. Hydrogen purification by periodic adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Barg, Christian; Secchi, Argimiro R.; Trierweiler, Jorge O. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Dept. de Engenharia Quimica]. E-mail: cbarg@enq.ufrgs.br; arge@enq.ufrgs.br; jorge@enq.ufrgs.br

    2000-07-01

    The periodic adsorption processes have been widely used for industrial applications, mainly because it spends less energy than the usual gas separation processes, like the cryogenic distillation. The largest commercial application of periodic adsorption processes is the pressure swing adsorption (PSA) applied to hydrogen purification. Although its wide use in the chemical and petrochemical industry, there are no reports in the open literature about complete modeling studies of a complex commercial unit, with multiple adsorbents and multiple beds and several feed components. This study has as objective the modeling, optimization and dynamical analysis of an industrial PSA unit for hydrogen purification. (author)

  4. Molecular Level Investigation of CH 4 and CO 2 Adsorption in Hydrated Calcium–Montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Mal-Soon [Physical; McGrail, B. Peter [Physical; Rousseau, Roger [Physical; Glezakou, Vassiliki-Alexandra [Physical

    2017-11-17

    We have studied the mechanism of intercalation and methane adsorption from a H2O/CH4/CO2 mixture on a prototypical shale component, Ca-montmorillonite. We employed ab initio molecular dynamics simulations at 323 K and 90 bar to obtain molecular level information of adsorption energetics, speciation, and structural and thermodynamic properties. Interaction of CH4 with surface Lewis acidic sites (Ca2+, surface OH) results in large induced dipoles (~1 D) that lead to relatively strong adsorption energies that level off once a full CH4 layer is formed. Intercalated CH4, also exhibits induced dipoles at low hydration levels, when the interaction with Ca2+ cations are less hindered. CO2 displaces CH4 in the coordination sphere of the cations (in the interlayer) or in the surface, thereby driving CH4 extraction. Our simulations indicate that there is a Goldilocks pressure range (~60-100 bar) where scCO2 –facilitated CH4 extraction will be maximized.

  5. Protein Adsorption in Three Dimensions

    Science.gov (United States)

    Vogler, Erwin A.

    2011-01-01

    Recent experimental and theoretical work clarifying the physical chemistry of blood-protein adsorption from aqueous-buffer solution to various kinds of surfaces is reviewed and interpreted within the context of biomaterial applications, especially toward development of cardiovascular biomaterials. The importance of this subject in biomaterials surface science is emphasized by reducing the “protein-adsorption problem” to three core questions that require quantitative answer. An overview of the protein-adsorption literature identifies some of the sources of inconsistency among many investigators participating in more than five decades of focused research. A tutorial on the fundamental biophysical chemistry of protein adsorption sets the stage for a detailed discussion of the kinetics and thermodynamics of protein adsorption, including adsorption competition between two proteins for the same adsorbent immersed in a binary-protein mixture. Both kinetics and steady-state adsorption can be rationalized using a single interpretive paradigm asserting that protein molecules partition from solution into a three-dimensional (3D) interphase separating bulk solution from the physical-adsorbent surface. Adsorbed protein collects in one-or-more adsorbed layers, depending on protein size, solution concentration, and adsorbent surface energy (water wettability). The adsorption process begins with the hydration of an adsorbent surface brought into contact with an aqueous-protein solution. Surface hydration reactions instantaneously form a thin, pseudo-2D interface between the adsorbent and protein solution. Protein molecules rapidly diffuse into this newly-formed interface, creating a truly 3D interphase that inflates with arriving proteins and fills to capacity within milliseconds at mg/mL bulk-solution concentrations CB. This inflated interphase subsequently undergoes time-dependent (minutes-to-hours) decrease in volume VI by expulsion of either-or-both interphase water and

  6. Hydrogen adsorption in doped porous carbons

    International Nuclear Information System (INIS)

    L Balan; L Duclaux; S Los

    2005-01-01

    properties of doped microporous carbons (SWNTs and activated carbons). The raw nano-structured carbon materials are microporous activated carbons (BET specific surface area: 1600 m 2 /g), electric-arc closed-end single-walled carbon nano-tubes (SWNTs), and HiPCO SWNTs. They have been doped in the vapour phase by K, and Li (in order to obtain KC 7 , KC 10 , LiC 18 SWNTs and LiC 6 , LiC 18 , KC 24 activated carbons). The hydrogen adsorption-desorption isotherms of the doped activated carbons were obtained at room temperature and at 77 K, up to 3 MPa, by a volumetric method. The adsorption of D 2 was studied in situ on doped nano-tubes and nano-filaments by neutron diffraction on D1B experiment (ILL), at λ=2.52 Angstroms, as a function of temperature [300 - 20 K] and pressure. Simultaneously the adsorption isotherms were recorded in the range 0 - 0.1 MPa [13]. Doping of microporous carbon by Li or K leads to an increase in the energy of adsorption of H 2 or D 2 Molecules. Thus, the room temperature sorption capacities (al P≤3 MPa) can be higher than that of the raw materials after slight doping. However, the maximum H 2 (or D 2 ) storage measured at T ≤ 77 K is lower than the one of pristine Materials as the sites of adsorption are occupied by alkali ions inserted in the micropores [14]. The microporous adsorption sites of doped single-walled carbon nano-tubes, identified by neutron diffraction, are both the interstitial voids (in electric-arc or HiPCO tubes) in between the tubes and the central canals of the tubes (only in HiPCO tubes) [15]. We have also prepared nano-structured porous doped carbons by ball-milling carbon host materials with some dopant, such as alkali or alkaline earth metal. The new nano-porous carbons obtained by this method have been characterised and tested for their hydrogen-adsorption properties. References: [1]A. Chambers et al, J. Phys. Chem. B, 102, 4253,1998. [2]A. C. Dillon et al, Nature, 386, 377,1997. [3]J. Conard, Ann. Chim. Sci. Mat 26

  7. Hydrogen adsorption in doped porous carbons

    International Nuclear Information System (INIS)

    Balan, L.; Duchaux, L.; Los, S.

    2005-01-01

    properties of doped microporous carbons (SWNTs and activated carbons). The raw nano-structured carbon materials are microporous activated carbons (BET specific surface area: 1600 m 2 /g), electric-arc closed-end single-walled carbon nano-tubes (SWNTs), and HiPCO SWNTs. They have been doped in the vapor phase by K, and Li (in order to obtain KC 7 , KC 10 , LiC 18 SWNTs and LiC 6 , LiC 18 , KC 24 activated carbons). The hydrogen adsorption-desorption isotherms of the doped activated carbons were obtained at room temperature and at 77 K, up to 3 MPa, by a volumetric method. The adsorption of D 2 was studied in situ on doped nano-tubes and filaments by neutron diffraction on DIB experiment (ILL), at λ = 2.52 Angstroms, as a function of temperature [300-20 K] and pressure. Simultaneously the adsorption isotherms were recorded in the range 0-0.1 MPa [13]. Doping of microporous carbon by Li or K leads to an increase in the energy of adsorption of H 2 or D 2 molecules. Thus, the room temperature sorption capacities (at P≤3 MPa) can be higher than that of the raw materials after slight doping. However, the maximum H 2 (or D 2 ) storage measured at T≤ 77 K is lower than the one of pristine materials as the sites of adsorption are occupied by alkali ions inserted in the micropores [14]. The microporous adsorption sites of doped single-walled carbon nano-tubes, identified by neutron diffraction, are both the interstitial voids (in electric-arc or HiPCO tubes) in between the tubes and the central canals of the tubes (only in HiPCO tubes) [15]. We have also prepared nano-structured porous doped carbons by ball-milling carbon host materials with some dopant, such as alkali or alkaline earth metal. The new nano-porous carbons obtained by this method have been characterised and tested for their hydrogen-adsorption properties. [1] A. Chambers et al, J. Phys. Chem. B, 102, 4253, 1998; [2] A. C. Dillon et al, Nature, 386, 377, 1997; [3] J. Conard, Ann. Chim. Sci. Mat 26, 107, 2001; [4] A

  8. Aqueous complexation, precipitation, and adsorption reactions of cadmium in the geologic environment

    International Nuclear Information System (INIS)

    Zachara, J.M.; Rai, D.; Felmy, A.R.; Cowan, C.E.; Smith, S.C.; Moore, D.A.; Resch, C.T.

    1992-06-01

    This report contains new laboratory data and equilibrium constants for important solubility and adsorption reactions of Cd that occur in soil and groundwater and attenuate Cd migration. In addition, extensive interaction experiments with Cd and soils from electric utility sites are described. These experiments show the importance of precipitation and adsorption reactions in soil and demonstrate how such reactions can be modeled to predict Cd attenuation near utility sites

  9. Water adsorption on goethite: Application of multilayer adsorption models

    Science.gov (United States)

    Hatch, C. D.; Tumminello, R.; Meredith, R.

    2016-12-01

    Adsorbed water on the surface of atmospheric mineral dust has recently been shown to significantly affect the ability of mineral dust aerosol to act as cloud condensation nuclei. We have studied water adsorption as a function of relative humidity (RH) on goethite (α-FeO(OH)), a common component of atmospheric mineral dust. The goethite surface area and particle size was determined using BET analysis and with N2 as an adsorbate and scanning electron microscopy, respectively. Water adsorption on the sample was monitored using horizontal attenuated total reflectance Fourier transform infrared (HATR-FTIR) spectroscopy equipped with a flow cell. Water content was determined using Beer's law and the optical constants for bulk water. The results were analyzed using Type II adsorption isotherms to model multilayer adsorption, including BET (Brunauer, Emmet and Teller), FHH (Frenkel, Halsey and Hill) and Freundlich. BET fits to experimental data provide parameters of monolayer coverage, while the FHH and Freundlich isotherms provide insights into multilayer adsorption mechanisms. Results indicate that goethite contains 5% H2O by mass at 50% RH, which increases to 12% by mass at 90% RH. Adsorption parameters and experimental results will be presented.

  10. The effect of mixed HCl–KCl competitive adsorbate on Pt adsorption and catalytic properties of Pt–Sn/Al{sub 2}O{sub 3} catalysts in propane dehydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Zangeneh, Farnaz Tahriri, E-mail: tahriri_zangeneh@yahoo.com [Department of Chemistry, Science and Research Branch, Islamic Azad University, P.O. Box 14155-4933, Tehran (Iran, Islamic Republic of); Catalyst Research Group, Petrochemical Research and Technology Company, National Petrochemical Company, P.O. Box 14358-84711, Tehran (Iran, Islamic Republic of); Taeb, Abbas [Department of Chemistry, Science and Research Branch, Islamic Azad University, P.O. Box 14155-4933, Tehran (Iran, Islamic Republic of); Gholivand, Khodayar [Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran (Iran, Islamic Republic of); Sahebdelfar, Saeed [Catalyst Research Group, Petrochemical Research and Technology Company, National Petrochemical Company, P.O. Box 14358-84711, Tehran (Iran, Islamic Republic of)

    2015-12-01

    Highlights: • Impregnation is a critical step in preparation of Pt-based dehydrogenation catalysts. • A competitor ion could strongly influence the impregnation of Pt on alumina support. • The competitor type is much more effective than pH of impregnation solution. • HCl competitor can be partially replaced by KCl reducing acidic attack on support. • Adsorption parameters can be estimated by a simple equilibrium-based model. - Abstract: The effect of competitive adsorbate concentration and combination on the adsorption of H{sub 2}PtCl{sub 6} onto γ-Al{sub 2}O{sub 3} in the preparation and performance of PtSnK/γ-Al{sub 2}O{sub 3} catalyst for propane dehydrogenation was investigated. The catalysts were prepared by sequential impregnation of Sn and Pt precursors. The effect of competitor concentration on Pt adsorption was studied by using hydrochloric acid (0.1–0.3 M) and the effect of pH was studied by using KCl/HCl mixtures at constant (0.1 M) total chloride ion concentration. The catalysts were characterized by nitrogen adsorption/desorption, XRD, XRF, SEM and CO chemisorption. The catalytic performance tests were carried out in a fixed-bed quartz reactor under kinetic controlled condition for proper catalyst screening. It was found that the corrosive competitor HCl could be partially substituted with KCl without appreciable impact on catalyst performance with the advantage of lower acid attack on the support and reduced leaching of the deposited tin. A model based on initial concentration and uptake of the adsorbates was developed to obtain the adsorption parameters. Values of 890 μmol/g and 600 lit/mol were obtained for adsorption site concentration of the tin-impregnated support and equilibrium constant for Pt adsorption, respectively, for HCl concentration range of 0.1–0.3 M.

  11. MONTE CARLO SIMULATIONS OF THE ADSORPTION OF DIMERS ON STRUCTURED HETEROGENEOUS SURFACES

    Directory of Open Access Journals (Sweden)

    Abreu C.R.A.

    2001-01-01

    Full Text Available The effect of surface topography upon the adsorption of dimer molecules is analyzed by means of grand canonical ensemble Monte Carlo simulations. Heterogeneous surfaces were assumed to consist of a square lattice containing active sites with two different energies. These were distributed in three different configurations: a random distribution of isolated sites; a random distribution of grains with four high-energy sites; and a random distribution of grains with nine high-energy sites. For the random distribution of isolated sites, the results are in good agreement with the molecular simulations performed by Nitta et al. (1997. In general, the comparison with theoretical models shows that the Nitta et al. (1984 isotherm presents good predictions of dimer adsorption both on homogeneous and heterogeneous surfaces with sites having small differences in characteristic energies. The molecular simulation results also show that the energy topology of the solid surfaces plays an important role in the adsorption of dimers on solids with large differences in site energies. For these cases, the Nitta et al. model does not describe well the data on dimer adsorption on random heterogeneous surfaces (grains with one acid site, but does describe reasonably well the adsorption of dimers on more patchwise heterogeneous surfaces (grains with nine acid sites.

  12. Effects of chemical functional groups on elemental mercury adsorption on carbonaceous surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Liu Jing, E-mail: liujing27@mail.hust.edu.cn [State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074 (China); Cheney, Marcos A. [Department of Natural Sciences, University of Maryland Eastern Shore, Princess Anne, MD 21853 (United States); Wu Fan; Li Meng [State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2011-02-15

    A systematic theoretical study using density functional theory is performed to provide molecular-level understanding of the effects of chemical functional groups on mercury adsorption on carbonaceous surfaces. The zigzag and armchair edges were used in modeling the carbonaceous surfaces to simulate different adsorption sites. The edge atoms on the upper side of the models are unsaturated to simulate active sites. All calculations (optimizations, energies, and frequencies) were made at B3PW91 density functional theory level, using RCEP60VDZ basis set for mercury and 6-31G(d) pople basis set for other atoms. The results indicate that the embedding of halogen atom can increase the activity of its neighboring site which in turn increases the adsorption capacity of the carbonaceous surface for Hg{sup 0}. The adsorption belongs to chemisorptions, which is in good agreement with the experimental results. For the effects of oxygen functional groups, lactone, carbonyl and semiquinone favor Hg{sup 0} adsorption because they increase the neighboring site's activity for mercury adsorption. On the contrary, phenol and carboxyl functional groups show a physisorption of Hg{sup 0}, and reduce Hg capture. This result can explain the seemingly conflicting experimental results reported in the literature concerning the influence of oxygen functional groups on mercury adsorption on carbonaceous surface.

  13. Adsorption and Diffusion of Lithium and Sodium on Defective Rhenium Disulfide: A First Principles Study.

    Science.gov (United States)

    Mukherjee, Sankha; Banwait, Avinav; Grixti, Sean; Koratkar, Nikhil; Singh, Chandra Veer

    2018-02-14

    Single-layer rhenium disulfide (ReS 2 ) is a unique material with distinctive, anisotropic electronic, mechanical, and optical properties and has the potential to be used as an anode in alkali-metal-ion batteries. In this work, first principles calculations were performed to systematically evaluate the potential of monolayer pristine and defective ReS 2 as anodes in lithium (Li)- and sodium (Na)-ion batteries. Our calculations suggest that there are several potential adsorption sites for Li and Na on pristine ReS 2 , owing to its low-symmetry structure. Additionally, the adsorption of Li and Na over pristine ReS 2 is very strong with adsorption energies of -2.28 and -1.71 eV, respectively. Interestingly, the presence of point defects causes significantly stronger binding of the alkali-metal atoms with adsorption energies in the range -2.98 to -3.17 eV for Li and -2.66 to -2.92 eV for Na. Re single vacancy was found to be the strongest binding defect for Li adsorption, whereas S single vacancy was found to be the strongest for Na. The diffusion of these two alkali atoms over pristine ReS 2 is anisotropic, with an energy barrier of 0.33 eV for Li and 0.16 eV for Na. The energy barriers associated with escaping a double vacancy and single vacancy for Li atoms are significantly large at 0.60 eV for the double-vacancy case and 0.51 eV for the single-vacancy case. Similarly, for Na, they are 0.59 and 0.47 eV, respectively, which indicates slower migration and sluggish charging/discharging. However, the diffusion energy barrier over a Re single vacancy is found to be merely 0.42 eV for a Li atom and 0.28 eV for Na. Overall, S single and double vacancies can reduce the diffusion rate by 10 3 -10 5 times for Li and Na ions, respectively. These results suggest that monolayer ReS 2 with a Re single vacancy adsorbs Li and Na stronger than pristine ReS 2 , with negligible negotiation with the charging/discharging rate of the battery, and therefore they can be used as an anode

  14. Post-adsorption process of Yb phosphate nano-particle formation by Saccharomyces cerevisiae

    Science.gov (United States)

    Jiang, MingYu; Ohnuki, Toshihiko; Tanaka, Kazuya; Kozai, Naofumi; Kamiishi, Eigo; Utsunomiya, Satoshi

    2012-09-01

    In this study, we have investigated the post-adsorption process of ytterbium (Yb) phosphate nano-particle formation by Saccharomyces cerevisiae (yeast). The yeast grown in P-rich medium were exposed to 1.44 × 10-4 mol/L Yb(III) solution for 2-120 h, and 2 months at 25 ± 1 °C at an initial pH of 3, 4, or 5, respectively. Ytterbium concentrations in solutions decreased as a function of exposure time. Field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (FESEM), transmission electron microscopy (TEM), and synchrotron-based extended X-ray absorption fine structure (EXAFS) analyses revealed that nano-sized blocky Yb phosphate with an amorphous phase formed on the yeast cells surfaces in the solutions with Yb. These nano-sized precipitates that formed on the cell surfaces remained stable even after 2 months of exposure at 25 ± 1 °C around neutral pHs. The EXAFS data revealed that the chemical state of the accumulated Yb on the cell surfaces changed from the adsorption on both phosphate and carboxyl sites at 30 min to Yb phosphate precipitates at 5 days, indicating the Yb-phosphate precipitation as a major post-adsorption process. In addition, the precipitation of Yb phosphate occurred on cell surfaces during 7 days of exposure in Yb-free solution after 2 h of exposure (short-term Yb adsorption) in Yb solution. These results suggest that the released P from the inside of yeast cells reacted with adsorbed Yb on cell surfaces, resulting in the formation of Yb precipitates, even though no P was added to the exposure solution. In an abiotic system, the EXAFS data showed that the speciation of sorbed Yb on the reference materials, carboxymethyl cellulose and Ln resin, did not change even when the Yb was exposed to P solution, without forming Yb phosphate precipitates. This result strongly suggests that the cell surface of the yeast plays an important role in the Yb-phosphate precipitation process, not only as a carrier of the

  15. Theoretical study of heavy metal Cd, Cu, Hg, and Ni(II) adsorption on the kaolinite(0 0 1) surface

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jian, E-mail: zhaojian0209@aliyun.com [Institute of Applied Physics and Computational Mathematics, PO Box 8009, Beijing 100088 (China); State Key Laboratory of Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China); He, Man-Chao [State Key Laboratory of Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China)

    2014-10-30

    Highlights: • We investigated the adsorption of Cd, Cu, Hg, and Ni(II) on kaolinite(0 0 1) surface. • The adsorption capabilities of the kaolinite for HM atoms were Ni > Cu > Cd > Hg(II). • The adsorption energy increases with the coverage for Cd, Cu, and Hg(II) atoms. • The adsorption energy decreases with the coverage for Ni(II) atoms. - Abstract: Heavy metal pollution is currently of great concern because it has been recognized as a potential threat to air, water, and soil. Adsorption was one of the most popular methods for the removal of heavy metal. The adsorption of heavy metal Cd, Cu, Hg, and Ni(II) atoms on the hydroxylated (0 0 1) surface of kaolinite was investigated using density-functional theory within the generalized gradient approximation and a supercell approach. The coverage dependence of the adsorption structures and energetics were systematically studied for a wide range of coverage Θ [from 0.11 to 1.0 monolayers (ML)] and adsorption sites. The most stable among all possible adsorption sites for Cd(II) atom was the two-fold bridge site followed by the one-fold top site, and the top site was the most favorite adsorption site for Cu and Ni(II) atoms, while the three-fold hollow site was the most stable adsorption site for Hg(II) atom followed by the two-fold bridge site. The adsorption energy increases with the coverage for Cd, Cu, and Hg(II) atoms, thus indicating the higher stability of surface adsorption and a tendency to the formation of adsorbate islands (clusters) with increasing the coverage. However, the adsorption energy of Ni(II) atoms decreases when increasing the coverage. The adsorption capabilities of the kaolinite clay for the heavy metal atoms were in the order of Ni > Cu > Cd > Hg(II). The other properties of the Cd, Cu, Hg, and Ni(II)/kaolinite(0 0 1) system including the different charge distribution, the lattice relaxation, and the electronic density of states were also studied and discussed in detail.

  16. Theoretical study of heavy metal Cd, Cu, Hg, and Ni(II) adsorption on the kaolinite(0 0 1) surface

    International Nuclear Information System (INIS)

    Zhao, Jian; He, Man-Chao

    2014-01-01

    Highlights: • We investigated the adsorption of Cd, Cu, Hg, and Ni(II) on kaolinite(0 0 1) surface. • The adsorption capabilities of the kaolinite for HM atoms were Ni > Cu > Cd > Hg(II). • The adsorption energy increases with the coverage for Cd, Cu, and Hg(II) atoms. • The adsorption energy decreases with the coverage for Ni(II) atoms. - Abstract: Heavy metal pollution is currently of great concern because it has been recognized as a potential threat to air, water, and soil. Adsorption was one of the most popular methods for the removal of heavy metal. The adsorption of heavy metal Cd, Cu, Hg, and Ni(II) atoms on the hydroxylated (0 0 1) surface of kaolinite was investigated using density-functional theory within the generalized gradient approximation and a supercell approach. The coverage dependence of the adsorption structures and energetics were systematically studied for a wide range of coverage Θ [from 0.11 to 1.0 monolayers (ML)] and adsorption sites. The most stable among all possible adsorption sites for Cd(II) atom was the two-fold bridge site followed by the one-fold top site, and the top site was the most favorite adsorption site for Cu and Ni(II) atoms, while the three-fold hollow site was the most stable adsorption site for Hg(II) atom followed by the two-fold bridge site. The adsorption energy increases with the coverage for Cd, Cu, and Hg(II) atoms, thus indicating the higher stability of surface adsorption and a tendency to the formation of adsorbate islands (clusters) with increasing the coverage. However, the adsorption energy of Ni(II) atoms decreases when increasing the coverage. The adsorption capabilities of the kaolinite clay for the heavy metal atoms were in the order of Ni > Cu > Cd > Hg(II). The other properties of the Cd, Cu, Hg, and Ni(II)/kaolinite(0 0 1) system including the different charge distribution, the lattice relaxation, and the electronic density of states were also studied and discussed in detail

  17. Prediction of Pure Component Adsorption Equilibria Using an Adsorption Isotherm Equation Based on Vacancy Solution Theory

    DEFF Research Database (Denmark)

    Marcussen, Lis; Aasberg-Petersen, K.; Krøll, Annette Elisabeth

    2000-01-01

    An adsorption isotherm equation for nonideal pure component adsorption based on vacancy solution theory and the Non-Random-Two-Liquid (NRTL) equation is found to be useful for predicting pure component adsorption equilibria at a variety of conditions. The isotherm equation is evaluated successfully...... adsorption systems, spreading pressure and isosteric heat of adsorption are also calculated....

  18. Ultra Low Concentration Adsorption Equilibria

    National Research Council Canada - National Science Library

    Mahle, John J; Buettner, Leonard C; LeVan, M. D; Schindler, Bryan J

    2006-01-01

    .... Specifically this work focuses on novel experimental and modeling methods to characterize and predict at ultra-low chemical vapor concentrations the protection afforded by adsorption-based vapor filtration systems...

  19. Potential Theory of Multicomponent Adsorption

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Stenby, Erling Halfdan

    1998-01-01

    We developed a theory of multicomponent adsorption on the basis of the potential concept originally suggested by Polanyi. The mixture is considered as a heterogeneous substance segregated in the external field emitted by the adsorbent. The same standard equation of state, with no additional fitting...... parameters, is used for the segregated and for the bulk phases. With this approach, few parameters are needed to correlate pure component adsorption isotherms. These parameters may be used to predict adsorption equilibria of multicomponent mixtures without additional adjustment. A connection between...... the potential theory and the spreading pressure concept is established, and problems of the theory consistency are studied. Numerical algorithms are suggested for evaluation of the segregated state of the mixture in the potential field of adsorption forces. Comparison with experimental data shows good agreement...

  20. First-principles simulations of iron with nitrogen: from surface adsorption to bulk diffusion

    International Nuclear Information System (INIS)

    Wu, M H; Liu, X H; Gu, J F; Jin, Z H

    2013-01-01

    Adsorption, absorption and diffusion pathways of nitrogen are studied for ferromagnetic body-centered cubic iron via spin-polarized density functional theory in combination with the climbing image nudged elastic band method. The computed data suggest that, depending on the coverage of N atoms, N prefers to stay on particular surface sites. Once pinned down well below the surface, N prefers to move into octahedral interstices rather than tetrahedral interstices. However, the tetrahedral interstices are crucial because they act as transition states and yield the saddle point energies of the corresponding minimum energy pathways. In comparison with carbon, we found that nitrogen prefers a different pathway from the (1 0 0) surface to the subsurface due to its strong repulsive interaction with Fe ions. (paper)

  1. Adsorption kinetics of surfactants on activated carbon

    Science.gov (United States)

    Arnelli; Aditama, WP; Fikriani, Z.; Astuti, Y.

    2018-04-01

    A study on the adsorption of both cationic and anionic surfactants using activated carbon as well as the investigation of the adsorption isotherms and adsorption kinetics has been conducted. The results showed that the adsorption of sodium lauryl sulfate (SLS) by activated carbon was Langmuir’s adsorption isotherm while its adsorption kinetics showed pseudo-second order with an adsorption rate constant of 2.23 x 103 g mg-1 hour-1. Meanwhile, the adsorption of HDTMA-Br by activated carbon showed that the isotherm adsorption tended to follow Freundlich’s isotherm and was pseudo-second order with an adsorption rate constant of 89.39 g mg-1 hour-1.

  2. Adsorption of amylase enzyme on ultrafiltration membranes

    DEFF Research Database (Denmark)

    Beier, Søren; Enevoldsen, Ann Dorrit; Kontogeorgis, Georgios

    2007-01-01

    A method to measure the static adsorption on membrane surfaces has been developed and described. The static adsorption of an amylase-F has been measured on two different ultrafiltration membranes, both with a cut-off value of 10 kDa (a PES membrane and the ETNA10PP membrane, which is a surface......-modified PVDF membrane). The adsorption follows the Langmuir adsorption theory. Thus, the static adsorption consists of monolayer coverage. The static adsorption is expressed both as a permeability drop and an adsorption resistance. From the adsorption isotherms the maximum static permeability drops...... and the maximum static adsorption resistances are determined. The maximum static permeability drop for the hydrophobic PES membrane is 75 % and the maximum static adsorption resistance is 0.014 m2hbar/L. The maximum static permeability drop for the hydrophilic surface-modified PVDF membrane (ETNA10PP) is 23...

  3. Adsorption of metalorganic molecules on metal-semiconductor systems

    Energy Technology Data Exchange (ETDEWEB)

    Brand, Christian; Schmeidel, Jedrzej; Chen, Wei; Tegenkamp, Christoph; Pfnuer, Herbert [Institut fuer Festkoerperphysik, Leibniz Universitaet Hannover (Germany)

    2011-07-01

    The controlled implementation of single molecules in appropriate contact assemblies is the ultimate realization of an ultra-small device structure. Besides extremely high integration densities the functionalities of the devices are adjustable by chemical synthesis. However, the interaction of the molecule with its environment is decisive. The adsorption of ferrocene-1,1'-dithiol (FDT) on Ag-{radical}(3) reconstructions on nominally flat and vicinal Si(111) substrates has been studied. The FDT was chosen because of its large conductance and high structural flexibility with respect to rotation of the two cyclopentadienyl (Cp) rings. The reconstruction is a prototype of a highly conductive low dimensional electron gas on a technologically relevant substrate. The adsorption of intact molecules takes place predominantly at defect sites, e.g. vacancy and step structures. Submolecular resolution showing the Cp-ring structure was obtained at perfect terrace sites. Due to chemisorption of the S-atoms at hollow sites the molecule axis is oriented parallel to the substrate. The initial rotational flexibility is frozen and only tow different rotated configurations were found. The adsorption geometry is confirmed by VASP calculations. Recently, Ag reconstructions on Si(557) substrates have been used. The effect of the uniaxial step configuration towards the adsorption of the FDT molecules is discussed.

  4. Adsorption of antibiotics on microplastics.

    Science.gov (United States)

    Li, Jia; Zhang, Kaina; Zhang, Hua

    2018-06-01

    Microplastics and antibiotics are two classes of emerging contaminants with proposed negative impacts to aqueous ecosystems. Adsorption of antibiotics on microplastics may result in their long-range transport and may cause compound combination effects. In this study, we investigated the adsorption of 5 antibiotics [sulfadiazine (SDZ), amoxicillin (AMX), tetracycline (TC), ciprofloxacin (CIP), and trimethoprim (TMP)] on 5 types of microplastics [polyethylene (PE), polystyrene (PS), polypropylene (PP), polyamide (PA), and polyvinyl chloride (PVC)] in the freshwater and seawater systems. Scanning Electron Microscope (SEM) and X-ray diffractometer (XRD) analysis revealed that microplastics have different surface characterizes and various degrees of crystalline. Adsorption isotherms demonstrated that PA had the strongest adsorption capacity for antibiotics with distribution coefficient (K d ) values ranged from 7.36 ± 0.257 to 756 ± 48.0 L kg -1 in the freshwater system, which can be attributed to its porous structure and hydrogen bonding. Relatively low adsorption capacity was observed on other four microplastics. The adsorption amounts of 5 antibiotics on PS, PE, PP, and PVC decreased in the order of CIP > AMX > TMP > SDZ > TC with K f correlated positively with octanol-water partition coefficients (Log K ow ). Comparing to freshwater system, adsorption capacity in seawater decreased significantly and no adsorption was observed for CIP and AMX. Our results indicated that commonly observed polyamide particles can serve as a carrier of antibiotics in the aquatic environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. The pH-dependent adsorption of tributyltin to charcoals and soot

    International Nuclear Information System (INIS)

    Fang Liping; Borggaard, Ole K.; Marcussen, Helle; Holm, Peter E.; Bruun Hansen, Hans Christian

    2010-01-01

    Widespread use of tributyltin (TBT) poses a serious environmental problem. Adsorption by black carbon (BC) may strongly affect its behavior. The adsorption of TBT to well characterized soot and two charcoals with specific surface area in the range of 62-111 m 2 g -1 have been investigated with main focus on pH effects. The charcoals but not soot possess acidic functional groups. TBT adsorption reaches maximum at pH 6-7 for charcoals, and at pH > 6 for soot. Soot has between 1.5 and 15 times higher adsorption density (0.09-1.77 μmol m -2 ) than charcoals, but charcoals show up to 17 times higher sorption affinities than soot. TBT adsorption is successfully described by a new pH-dependent dual Langmuir model considering electrostatic and hydrophobic adsorption, and pH effects on TBT speciation and BC surface charge. It is inferred that strong sorption of the TBTOH species to BC may affect TBT toxicity. - Tributyltin adsorption to black carbon increases at increasing pH but charcoal exhibits electrostatic and hydrophobic adsorption, whereas soot only adsorbs hydrophobically.

  6. The pH-dependent adsorption of tributyltin to charcoals and soot

    Energy Technology Data Exchange (ETDEWEB)

    Fang Liping, E-mail: fang@life.ku.d [Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C (Denmark); Borggaard, Ole K.; Marcussen, Helle; Holm, Peter E.; Bruun Hansen, Hans Christian [Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C (Denmark)

    2010-12-15

    Widespread use of tributyltin (TBT) poses a serious environmental problem. Adsorption by black carbon (BC) may strongly affect its behavior. The adsorption of TBT to well characterized soot and two charcoals with specific surface area in the range of 62-111 m{sup 2} g{sup -1} have been investigated with main focus on pH effects. The charcoals but not soot possess acidic functional groups. TBT adsorption reaches maximum at pH 6-7 for charcoals, and at pH > 6 for soot. Soot has between 1.5 and 15 times higher adsorption density (0.09-1.77 {mu}mol m{sup -2}) than charcoals, but charcoals show up to 17 times higher sorption affinities than soot. TBT adsorption is successfully described by a new pH-dependent dual Langmuir model considering electrostatic and hydrophobic adsorption, and pH effects on TBT speciation and BC surface charge. It is inferred that strong sorption of the TBTOH species to BC may affect TBT toxicity. - Tributyltin adsorption to black carbon increases at increasing pH but charcoal exhibits electrostatic and hydrophobic adsorption, whereas soot only adsorbs hydrophobically.

  7. Powerful greenhouse gas nitrous oxide adsorption onto intrinsic and Pd doped Single walled carbon nanotube

    International Nuclear Information System (INIS)

    Yoosefian, Mehdi

    2017-01-01

    Highlights: • Investigation of the adsorption of Nitrous oxide on SWCNT and Pd/SWCNT. • Nitrous oxide adsorbed on Pd/SWCNT system demonstrates a strong adsorption. • The Pd/SWCNT is potential sensor for the Nitrous oxide gaseous molecule detection. - Abstract: Density functional studies on the adsorption behavior of nitrous oxide (N_2O) onto intrinsic carbon nanotube (CNT) and Pd-doped (5,5) single-walled carbon nanotube (Pd-CNT) have been reported. Introduction of Pd dopant facilitates in adsorption of N_2O on the otherwise inert nanotube as observed from the adsorption energies and global reactivity descriptor values. Among three adsorption features of N_2O onto CNT, the horizontal adsorption with E_a_d_s = −0.16 eV exhibits higher adsorption energy. On the other hand the Pd-CNT exhibit strong affinity toward gas molecule and would cause a huge increase in N_2O adsorption energies. Chemical and electronic properties of CNT and Pd-CNT in the absence and presence of N_2O were investigated. Adsorption of N_2O gas molecule would affect the electronic conductance of Pd-CNT that can serve as a signal of gas sensors and the increased energy gaps demonstrate the formation of more stable systems. The atoms in molecules (AIM) theory and the natural bond orbital (NBO) calculations were performed to get more details about the nature and charge transfers in intermolecular interactions within adsorption process. As a final point, the density of states (DOSs) calculations was achieved to confirm previous results. According to our results, intrinsic CNT cannot act as a suitable adsorbent while Pd-CNT can be introduced as novel detectable complex for designing high sensitive, fast response and high efficient carbon nanotube based gas sensor to detect N_2O gas as an air pollutant. Our results could provide helpful information for the design and fabrication of the N_2O sensors.

  8. Effect of aggregate structure on VOC gas adsorption onto volcanic ash soil.

    Science.gov (United States)

    Hamamoto, Shoichiro; Seki, Katsutoshi; Miyazaki, Tsuyoshi

    2009-07-15

    The understanding of the gaseous adsorption process and the parameters of volatile organic compounds such as organic solvents or fuels onto soils is very important in the analysis of the transport or fate of these chemicals in soils. Batch adsorption experiments with six different treatments were conducted to determine the adsorption of isohexane, a gaseous aliphatic, onto volcanic ash soil (Tachikawa loam). The measured gas adsorption coefficient for samples of Tachikawa loam used in the first three treatments, Control, AD (aggregate destroyed), and AD-OMR (aggregate destroyed and organic matter removed), implied that the aggregate structure of volcanic ash soil as well as organic matter strongly enhanced gas adsorption under the dry condition, whereas under the wet condition, the aggregate structure played an important role in gas adsorption regardless of the insolubility of isohexane. In the gas adsorption experiments for the last three treatments, soils were sieved in different sizes of mesh and were separated into three different aggregate or particle size fractions (2.0-1.0mm, 1.0-0.5mm, and less than 0.5mm). Tachikawa loam with a larger size fraction showed higher gas adsorption coefficient, suggesting the higher contributions of macroaggregates to isohexane gas adsorption under dry and wet conditions.

  9. Non-equilibrium dynamics of single polymer adsorption to solid surfaces

    International Nuclear Information System (INIS)

    Panja, Debabrata; Barkema, Gerard T; Kolomeisky, Anatoly B

    2009-01-01

    The adsorption of polymers to surfaces is crucial for understanding many fundamental processes in nature. Recent experimental studies indicate that the adsorption dynamics is dominated by non-equilibrium effects. We investigate the adsorption of a single polymer of length N to a planar solid surface in the absence of hydrodynamic interactions. We find that for weak adsorption energies the adsorption timescales ∼N (1+2ν)/(1+ν) , where ν is the Flory exponent for the polymer. We argue that in this regime the single chain adsorption is closely related to a field-driven polymer translocation through narrow pores. Surprisingly, for high adsorption energies the adsorption time becomes longer, as it scales as ∼N 1+ν , which is explained by strong stretching of the unadsorbed part of the polymer close to the adsorbing surface. These two dynamic regimes are separated by an energy scale that is characterized by non-equilibrium contributions during the adsorption process. (fast track communication)

  10. Adsorption of organic stormwater pollutants onto activated carbon from sewage sludge.

    Science.gov (United States)

    Björklund, Karin; Li, Loretta Y

    2017-07-15

    Adsorption filters have the potential to retain suspended pollutants physically, as well as attracting and chemically attaching dissolved compounds onto the adsorbent. This study investigated the adsorption of eight hydrophobic organic compounds (HOCs) frequently detected in stormwater - including four polycyclic aromatic hydrocarbons (PAHs), two phthalates and two alkylphenols - onto activated carbon produced from domestic sewage sludge. Adsorption was studied using batch tests. Kinetic studies indicated that bulk adsorption of HOCs occurred within 10 min. Sludge-based activated carbon (SBAC) was as efficient as tested commercial carbons for adsorbing HOCs; adsorption capacities ranged from 70 to 2800 μg/g (C initial  = 10-300 μg/L; 15 mg SBAC in 150 mL solution; 24 h contact time) for each HOC. In the batch tests, the adsorption capacity was generally negatively correlated to the compounds' hydrophobicity (log K ow ) and positively associated with decreasing molecule size, suggesting that molecular sieving limited adsorption. However, in repeated adsorption tests, where competition between HOCs was more likely to occur, adsorbed pollutant loads exhibited strong positive correlation with log K ow . Sewage sludge as a carbon source for activated carbon has great potential as a sustainable alternative for sludge waste management practices and production of a high-capacity adsorption material. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Adsorption of nicotine on different zeolite types, from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Stošić Dušan K.

    2007-01-01

    Full Text Available The plant alkaloid, nicotine, is a strongly toxic heterocyclic compound: the lethal dose for an adult human being (40-60 mg is importantly lower in comparison with the other known poisons such as arsenic or strychni­ne. Cigarettes represent "the most toxic and addictive form of nicotine". Besides the negative effects of nicotine on public health produced by self-administration, recently another potentially very dangerous effect has been recognized: because of its miscibility with water, nicotine can be found in industrial wastewaters, and consequently, in groundwater. Therefore, the problem of nicotine removal from aqueous solutions has became an interesting topic. In this work, the removal of nicotine has been probed by adsorption on solid materials. Adsorption of nicotine on different zeolites (clinoptilolite, ZSM-5 and β zeolite and on activated carbon was investigated from aqueous solutions, at 298 K. The obtained results are presented as adsorption isotherms: the amount of adsorbed nicotine as a function of equilibrium concentration. These data were obtained from the residual amount of nicotine in the aqueous phase, by the use of UV spectroscopy. The highest amounts of adsorbed nicotine was found for activated carbon and p zeolite (~ mmol·g-1. The attempt to modify the adsorption properties of ZSM-5 zeolite has been also done: ZSM-5 was modified by ion-exchange with VIII group metal (Cu2+ and Fe3+. In addition, the adsorption of nicotine on ZSM-5 zeolite with different Si/Al ratios has been done. It has been noticed that ion-exchange did not improve the adsorption possibilities, while the adsorption was importantly lower in the case of higher silicon content in ZMS-5 structure. 13C NMR spectra were collected for suspensions formed of solid adsorbent and aqueous solution of nicotine; in this way, the part of nicotine molecule which is most probably connected with the adsorbent was recognized.

  12. Adsorption refrigeration technology theory and application

    CERN Document Server

    Wang, Ruzhu; Wu, Jingyi

    2014-01-01

    Gives readers a detailed understanding of adsorption refrigeration technology, with a focus on practical applications and environmental concerns Systematically covering the technology of adsorption refrigeration, this book provides readers with a technical understanding of the topic as well as detailed information on the state-of-the-art from leading researchers in the field. Introducing readers to background on the development of adsorption refrigeration, the authors also cover the development of adsorbents, various thermodynamic theories, the design of adsorption systems and adsorption refri

  13. Gas adsorption capacity in an all carbon nanomaterial composed of carbon nanohorns and vertically aligned carbon nanotubes.

    Science.gov (United States)

    Puthusseri, Divya; Babu, Deepu J; Okeil, Sherif; Schneider, Jörg J

    2017-10-04

    Whereas vertically aligned carbon nanotubes (VACNTs) typically show a promising adsorption behavior at high pressures, carbon nanohorns (CNHs) exhibit superior gas adsorption properties in the low pressure regime due to their inherent microporosity. These adsorption characteristics are further enhanced when both materials are opened at their tips. The so prepared composite material allows one to investigate the effect of physical entrapment of CO 2 molecules within the specific adsorption sites of VACNTs composed of opened double walled carbon nanotubes (CNTs) and in specific adsorption sites created by spherically aggregated opened single walled carbon nanohorns. Combining 50 wt% of tip opened CNTs with tip opened CNHs increases the CO 2 adsorption capacity of this material by ∼24% at 30 bar and 298 K compared to opened CNHs alone.

  14. Strongly interacting Fermi gases

    Directory of Open Access Journals (Sweden)

    Bakr W.

    2013-08-01

    Full Text Available Strongly interacting gases of ultracold fermions have become an amazingly rich test-bed for many-body theories of fermionic matter. Here we present our recent experiments on these systems. Firstly, we discuss high-precision measurements on the thermodynamics of a strongly interacting Fermi gas across the superfluid transition. The onset of superfluidity is directly observed in the compressibility, the chemical potential, the entropy, and the heat capacity. Our measurements provide benchmarks for current many-body theories on strongly interacting fermions. Secondly, we have studied the evolution of fermion pairing from three to two dimensions in these gases, relating to the physics of layered superconductors. In the presence of p-wave interactions, Fermi gases are predicted to display toplogical superfluidity carrying Majorana edge states. Two possible avenues in this direction are discussed, our creation and direct observation of spin-orbit coupling in Fermi gases and the creation of fermionic molecules of 23Na 40K that will feature strong dipolar interactions in their absolute ground state.

  15. A strong comeback

    International Nuclear Information System (INIS)

    Marier, D.

    1992-01-01

    This article presents the results of a financial rankings survey which show a strong economic activity in the independent energy industry. The topics of the article include advisor turnover, overseas banks, and the increase in public offerings. The article identifies the top project finance investors for new projects and restructurings and rankings for lenders

  16. SeO{sub 2} adsorption on CaO surface: DFT study on the adsorption of a single SeO{sub 2} molecule

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Yaming; Zhuo, Yuqun; Lou, Yu; Zhu, Zhenwu [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Li, Liangliang [Key Laboratory of Advanced Materials, Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2017-08-15

    Highlights: • Adsorption mechanisms of SeO{sub 2} on CaO surface under O{sub 2} were firstly studied by DFT. • The adsorption energies, bond length and electron density maps were calculated. • The electronic structure changes upon adsorption were studied. - Abstract: Selenium is a hazardous element in coal. During coal combustion, most of the selenium will convert to SeO{sub 2} in the flue gas. Ca-based adsorbents, especially CaO, have been considered as a potential sorbent to adsorb SeO{sub 2} due to its low cost. In this paper, the adsorption mechanisms of single SeO{sub 2} on CaO surface were investigated by density functional theory (DFT) calculation. Both the physisorption and chemisorption structures were determined. It has been identified that the adsorption of SeO{sub 2} on CaO surface is primarily chemisorption, while physisorption takes effects at the initial stage of the process. Under O{sub 2} atmosphere, selenate is hard to form. Most of the adsorption products are selenite. Additionally, the electron density maps were obtained to reveal the surface active sites. The partial density of states (PDOS) was calculated for analyzing the electronic structural change of SeO{sub 2} and CaO surface during adsorption. The results provide fundamental information of the adsorption process, which could be meaningful for the development of new absorbents.

  17. The Frontier Between Adsorption and Precipitation of Polyacrylic Acid on Calcium Carbonate Frontière entre adsorption et précipitation de l'acide polyacrylique sur le carbonate de calcium

    Directory of Open Access Journals (Sweden)

    Cabane B.

    2006-12-01

    Full Text Available Adsorption of polymers on mineral surfaces allowing colloidal stability have widespread applications in industrial processes. The binding mechanism has been quite well described on oxide surfaces. Mainly in terms of hydrogen bonds and electrostatic interactions between charged sites and polymer segments. This phenomenon has been modelized and the influence of pH. Ionic strentgh, and molecular weight can be calculated or predicted. In the case of sparingly soluble substrates such as BaSO4, CaCO3 or CaSO4, several problems arise : the difficulty for the identification of surface sites and the interference of ions coming from the material's solubility. In the case of calcite, the solubility imposes dissolved calcium ions in solution which could complex the polyelectrolyte and reduce its solubility. For that purpose, we have measured the binding energy using microcalorimetry. Microcalorimetric measurements have shown that the adsorption enthalpy is weakly enclothermic: about + 2 kj/mol. Interestingly, this value is very closed to that of calcium complexation with PANa. It is suggested that the driving force for adsorption is the net gain in entropy of the system. The microcalorimetric adsorption isotherm does not show any evidence for a strongly exothermic interaction between positive edges and negative segment of the polyion. Practically, in most cases, adsorption of polymers is calculated from the decrease of its concentration in the solution after separation of the solid by centrifugation. This procedure does not discriminate therefore between real adsorption and phase separation. To answer the question, we have performed adsorption experiments using a dialysis membrane to separate the solid particles from the solution. It has been established that in some circumstances, depending on the relative amount of calcite, calcium ions and polyelectrolyte, precipitation takes place rather than adsorption. This is especially the case at low polymer

  18. Evaluation of pesticide adsorption in gas chromatographic injector and column

    Directory of Open Access Journals (Sweden)

    Gevany Paulino de Pinho

    2012-01-01

    Full Text Available Components in complex matrices can cause variations in chromatographic response during analysis of pesticides by gas chromatography. These variations are related to the competition between analytes and matrix components for adsorption sites in the chromatographic system. The capacity of the pesticides chlorpyrifos and deltamethrin to be adsorbed in the injector and chromatographic column was evaluated by constructing three isotherms and changing the column heating rate to 10 and 30 ºC min-1. By using ANCOVA to compare the slope of calibration graphs, results showed that the higher the injector temperature (310 ºC the lower the pesticide adsorption. Also, deltamethrin influenced the adsorption of chlorpyrifos on the column chromatographic.

  19. Adsorption of diuron and dichlobenil on multiwalled carbon nanotubes as affected by lead.

    Science.gov (United States)

    Chen, Guang-Cai; Shan, Xiao-Quan; Pei, Zhi-Guo; Wang, Huanhua; Zheng, Li-Rong; Zhang, Jing; Xie, Ya-Ning

    2011-04-15

    The effect of lead on the adsorption of diuron and dichlobenil on multiwalled carbon nanotubes (MWCNTs) was investigated to explore the possible application of MWCNTs for removal of both herbicides from contaminated water. The adsorption of diuron and dichlobenil on MWCNTs at pH 6 was nonlinear and fit the Polanyi-Manes model well. The adsorption of diuron and dichlobenil was closely correlated with specific surface areas and micropore volumes of MWCNTs. An increase in oxygen content of MWCNTs with same diameters and similar surface areas decreased the adsorption of diuron and dichlobenil, while increased the adsorption of lead. Micro-Fourier transform infrared spectroscopic study indicated that hydrogen bonding is a main mechanism responsible for the adsorption of diuron or dichlobenil onto MWCNTs-O. Oxygen containing groups, mainly carboxylic groups, significantly increased the adsorption of lead through the formations of outer-sphere and inner-sphere complexes, which are verified by X-ray absorption spectroscopic measurements. Oxygen containing groups and the presence of lead diminished the adsorption of diuron and dichlobenil. The suppression mechanisms of lead were ascribed to hydration and complexation of lead with carboxylic groups, which may occupy part of surface of MWCNTs-O. The large hydration shell of lead cations may intrude or shield hydrophobic and hydrophilic sites, resulting in a decreased adsorption of diuron and dichlobenil at the lead-complexed moieties. Copyright © 2011 Elsevier B.V. All rights reserved.

  20. Adsorption of Pb(II) present in aqueous solution on calcium, strontium and barium hydroxy apatites

    International Nuclear Information System (INIS)

    Vilchis G, J.

    2013-01-01

    Calcium, strontium and barium hydroxy apatites were successfully synthesized by chemical precipitation method, the obtained powders were characterized by the techniques of X-ray diffraction (XRD), scanning electron microscopy (Sem), semi-quantitative elemental analysis (EDS), infrared spectroscopy (IR), and N 2 physisorption studies, complementary to these analytical techniques, was determined the surface fractal dimension (Df), and the amount of surface active sites of the materials, in order to know application as ceramic for water remediation. The ability of Pb(II) ion adsorption present in aqueous solution on the hydroxy apatites synthesized by batch type experiments was studied as a function of contact time, concentration of the adsorbate and temperature. The maximum lead adsorption efficiencies obtained were 0.31, 0.32 and 0.26 mg/g for calcium, strontium and barium hydroxy apatites respectively, achieved an equilibrium time of 20 minutes in the three solid-liquid systems studied. Experimental data were adequately adjusted at the adsorption kinetic model pseudo-second order, for the three cases. Moreover, experimental data of the strontium and calcium hydroxy apatites were adjusted to the Langmuir adsorption isotherm, indicating that the adsorption was through a monolayer, whereas barium hydroxyapatite was adjusted to the Freundlich adsorption isotherm, indicating a multilayer adsorption. The thermodynamic parameters obtained during adsorption studies as a function of temperature showed physisorption, exothermic and spontaneous processes respectively. The results showed that the calcium hydroxyapatite, strontium and barium are an alternative for the Pb(II) ion adsorption present in wastewaters. (Author)

  1. Equilibrium, kinetic and thermodynamic studies of adsorption of Th(IV) from aqueous solution onto kaolin

    International Nuclear Information System (INIS)

    Hongxia Zhang; Zhiwei Niu; Zhi Liu; Zhaodong Wen; Weiping Li; Xiaoyun Wang; Wangsuo Wu

    2015-01-01

    The kinetics and thermodynamics of the adsorption of Th(IV) on the kaolin were studied by using batch method. In addition, the experimental data were studied by dynamic and thermodynamic models. The results showed that the adsorption capacity of the adsorbent increased with increasing temperature and solid liquid ratio, but decreased with increasing initial Th(IV) ion concentration, and the best fit was obtained for the pseudo-second-order kinetics model. The calculated activation energy for adsorption was about 45 kJ/mol, which indicated the adsorption process to be chemisorption. The adsorption isotherm data could be well described by the Langmuir as well as Dubinin-Radushkevich model. The mean free energy (E) of adsorption was calculated to be about 15 kJ/mol. The thermodynamic data calculated showed that the adsorption was spontaneous and enhanced at higher temperature. Considering kinetics and equilibrium studies, the adsorption on the sites was the rate-limiting step and that adsorption was mainly a chemisorption process through cation exchange. (author)

  2. Adsorption of SO2 on bituminous coal char and activated carbon fiber

    Science.gov (United States)

    DeBarr, Joseph A.; Lizzio, Anthony A.; Daley, Michael A.

    1997-01-01

    The SO2 adsorption behaviors of activated carbons produced from Illinois coal and of commercially prepared activated carbon fibers (ACFs) were compared. There was no relation between surface area of coal-based carbons and SO2 adsorption, whereas adsorption of SO2 on the series of ACFs was inversely proportional to N2 BET surface area. Higher surface area ACFs had wider pores and adsorbed less SO2; thus, pore size distribution is thought to play a significant role in SO2 adsorption for these materials. Oxidation with HNO3 and/or H2SO4, followed by heat treatment at 700−925°C to remove carbon−oxygen complexes, resulted in increased SO2 adsorption for both coal chars and ACFs. This behavior was explained by an increase in the available number of free sites, previously occupied by oxygen and now available for SO2 adsorption. The use of nitrogen-containing functional groups on ACFs of proper pore size shows promise for further increasing SO2 adsorption capacities. Knowledge of the relationship among the number of free sites, pore size, and surface chemistry on corresponding SO2 adsorption should lead to the development of more efficient adsorbents prepared from either coal or ACFs.

  3. Correlations and adsorption mechanisms of aromatic compounds on a high heat temperature treated bamboo biochar

    International Nuclear Information System (INIS)

    Yang, Kun; Yang, Jingjing; Jiang, Yuan; Wu, Wenhao; Lin, Daohui

    2016-01-01

    Adsorption of aromatic compounds, including polycyclic aromatic hydrocarbons, nitrobenzenes, phenols, and anilines, on a bamboo biochar produced at 700 °C (Ba700) was investigated with the mechanism discussion by isotherm fitting using the Polanyi-theory based Dubinin–Ashtakhov (DA) model. Correlations of adsorption capacity (Q 0 ) of organic compounds with their molecular sizes and melting points, as well as correlations of adsorption affinity (E) with their solvatochromic parameters (i.e., π* and α m ), on the biochar, were developed and indicating that adsorption is captured by the pore filling mechanism and derived from the hydrophobic effects of organic compounds and the forming of π-π electron donor-acceptor (EDA) interactions and hydrogen bonding interactions of organic molecules with surface sites of the biochar. The effects of organic molecular sizes and melting points on adsorption capacity are ascribed to the molecular sieving effect and the packing efficiency of the organic molecules in the biochar pores, respectively. These correlations can be used to quantitatively estimate the adsorption of organic compounds on biochars from their commonly physicochemical properties including solvatochromic parameters, melting points and molecular cross-sectional area. The prediction using these correlations is important for assessing the unknown adsorption behaviors of new organic compounds and also helpful to guide the surface modification of biochars and make targeted selection in the environmental applications of biochars as adsorbents. - Highlights: • Adsorption of organic chemicals on biochars are captured by pore filling mechanism. • Adsorption is derived from Van der Waals force, π-π EDA and H-bonding interactions. • Adsorption capacity is negatively correlated with organic molecular sizes/melting points. • Adsorption capacity is restricted by molecular sieving effect and packing efficiency. • Adsorption affinity has a LSER with chemical

  4. Adsorption of oxazole and isoxazole on BNNT surface: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Jasleen, E-mail: jasleen.chem@gmail.com; Singla, Preeti, E-mail: preetisingla21@gmail.com; Goel, Neetu, E-mail: neetugoel@pu.ac.in

    2015-02-15

    Highlights: • The adsorption of oxazole and isoxazole over (6,0) and (5,5) BNNTs is studied. • The adsorption energies and structural changes are inductive of covalent adsorption. • The solvent plays an important role in improving the adsorption properties. • The adsorption witnesses substantial changes in electronic properties of the BNNT. • The functionalization of the BNNTs open up their applicability as drug carrier. - Abstract: The adsorption behavior of oxazole and isoxazole heterocycles over the (6,0) zigzag and (5,5) armchair boron nitride nanotube (BNNT) has been studied within the formalism of density functional theory (DFT). The adsorption energies, the frontier molecular orbital (FMO) analysis and the structural changes at the adsorption site are indicative of covalent adsorption on the zigzag BNNT surface, while the adsorption is physical in nature on the armchair BNNT surface. The role of solvent in improving the adsorption properties over the BNNT surface is elucidated by reoptimizing the structures in aqueous phase. The solvation energy is indicative of remarkable increase in the solubility of BNNTs after adsorption of heterocyclic rings. The Density of states (DOS) Plots, natural bond orbital (NBO) analysis and the quantum molecular descriptors (QMD) are witness to the substantial changes in the electronic properties of the BNNT systems following the attachment of these heterocycles with the tube surface. The study envisages the functionalization of the BNNT as well as its applicability as carrier of the drugs containing heterocyclic rings oxazole and isoxazole with marked sensitivity to the type of adsorbate and the adsorbent.

  5. Long Term Sorption Diffusion Experiment (LTDE-SD). Supporting laboratory program - Sorption diffusion experiments and rock material characterisation. With supplement of adsorption studies on intact rock samples from the Forsmark and Laxemar site investigations

    Energy Technology Data Exchange (ETDEWEB)

    Widestrand, Henrik; Byegaard, Johan; Selnert, Eva; Skaalberg, Mats; Hoeglund, Susanne; Gustafsson, Erik (Geosigma AB, Uppsala (Sweden))

    2010-12-15

    The LTDE-SD experiment, (Long Term Sorption Diffusion Experiment) aims at increasing the scientific knowledge of sorption and diffusion under in situ conditions and to provide data for performance and safety assessment calculations. In this report, performance and results of laboratory sorption and diffusion experiments and porosity investigations using site-specific crushed and intact rock materials are presented, including a geological and mineralogical characterization of the samples. A synthetic groundwater and a part of the radionuclide tracer cocktail that was used for the in situ experiment were used also in the laboratory experiments. 13 radionuclide tracers were analysed in the laboratory experiments. The method descriptions from SKB Site Investigations were applied in order to enable comparisons with Site Investigations data. The water saturation porosity of 10 unaltered matrix rock samples from KA3065A02 and A03 is 0.26 +- 0.08% and two fracture material samples show porosities of 2.4% and 5.2% respectively. 14C-methylmethacrylate impregnation (the PMMA-method) show that the unaltered rock matrix porosity is relatively homogeneous with grain boundary porosity, while the porosity of fracture samples is heterogeneous and have increased porosity up to more than 10% in some parts. Through-diffusion experiments using tritiated water (H3HO) give a matrix diffusivity in the range from 2.7centre dot10-14 to 6.5centre dot10-14 m2/s in four samples from KA3065A02 and A03. The results of the porosity and diffusion measurements are coherent in ranges with earlier LTDE-SD measurements and are also in line with the SKB Site Investigations results. In the batch sorption experiments using crushed rock material, two matrix rock samples of Aevroe granodiorite, one red-stained altered Aevroe granodiorite sample and two chlorite-calcite dominated fracture samples were analysed for three different size fractions as a function of time up to 186 days contact time. The

  6. Macromolecule simulation and CH4 adsorption mechanism of coal vitrinite

    Science.gov (United States)

    Yu, Song; Yan-ming, Zhu; Wu, Li

    2017-02-01

    The microscopic mechanism of interactions between CH4 and coal macromolecules is of significant practical and theoretical importance in CBM development and methane storage. Under periodic boundary conditions, the optimal energy configuration of coal vitrinite, which has a higher torsion degree and tighter arrangement, can be determined by the calculation of molecular mechanics (MM) and molecular dynamics (MD), and annealing kinetics simulation based on ultimate analysis, 13C NMR, FT IR and HRTEM. Macromolecular stabilization is primarily due to the van der Waals energy and covalent bond energy, mainly consisting of bond torsion energy and bond angle energy. Using the optimal configuration as the adsorbent, GCMC simulation of vitrinite adsorption of CH4 is conducted. A saturated state is reached after absorbing 17 CH4s per coal vitrinite molecule. CH4 is preferentially adsorbed on the edge, and inclined to gathering around the branched chains of the inner vitrinite sites. Finally, the adsorption parameters are calculated through first principle DFT. The adsorbability order is as follows: aromatic structure> heteroatom rings > oxygen functional groups. The adsorption energy order is as follows: Top graphene. However, the energy of the most preferential location is much lower than that of graphite/graphene. CH4 is more easily absorbed on the surface of vitrinite. Adsorbability varies considerably at different adsorption locations and sites on the surface of vitrinite. Crystal parameter of vitrinite is a = b = c = 15.8 Å and majority of its micropores are blow 15.8 Å, indicating that the vitrinite have the optimum adsorption aperture. It can explain its higher observed adsorption capacities for CH4 compared with graphite/graphene.

  7. Investigation of the adsorption of amino acids on Pd(1 1 1): A density functional theory study

    International Nuclear Information System (INIS)

    James, Joanna N.; Han, Jeong Woo; Sholl, David S.

    2014-01-01

    Graphical abstract: - Highlights: • Density functional theory calculations have been performed to study the adsorption of glycine, alanine, norvaline, valine, proline, cysteine, and serine on Pd(1 1 1). • The common structural framework for the adsorption of most amino acids onto Pd(1 1 1) is in a tridentate fashion via a nitrogen atom and two oxygen atoms. • The shifts in vibrational frequencies associated with NHH and COO support the adsorption patterns of amino acids we examined. • The adsorption strength of amino acids depends on how much the molecules deform during the adsorption process. - Abstract: Density functional theory calculations have been used to study the adsorption of glycine, alanine, norvaline, valine, proline, cysteine, and serine on Pd(1 1 1). Most amino acids except cysteine adsorb onto the surface in a tridentate fashion through a nitrogen atom and both oxygen atoms. For cysteine, an additional bond is formed with the surface due to the strong affinity of the sulfur atom, resulting in a significantly larger adsorption energy. The adsorption patterns of amino acids we examined are supported by the shifts in vibrational frequencies associated with NHH and COO. The adsorption strength of amino acids depends on how much the molecules deform during the adsorption process. Understanding the adsorption of amino acids on Pd(1 1 1) provides fundamental information for future consideration of the interactions between their derivatives or more complicated biomolecules and metal surfaces

  8. Adsorption characteristics and polymerization of pyrrole on Y-zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Akihiko; Kitajima, Tsutomu; Tsutsumi, Kazuo

    1999-10-26

    Conductive polymers have attracted considerable interest from the viewpoint of their electrochemical aspects and have been investigated for application in novel devices such as solid electrolyte cells and molecular electronic devices. Adsorption characteristics and polymerization of pyrrole on Y-zeolites of different cation types (NaY, HY, and CuY) have been investigated in connection with adsorption behavior, in situ IR spectroscopy, and EPR spectroscopy. Adsorption of pyrrole on NaY is physisorption giving no significant changes in IR and EPR spectra. In the adsorption on HY and CuY, the formation of pyrrole oligomers or polymers is observed. Pyrrole oligomer formed on HY is a nonconjugated one, which gives no EPR signal. In the case of CuY, EPR signal assigned to polaron of polypyrrole was observed at g = 2.008 by the pyrrole adsorption. The relationship between the amount of the spin of g = 2.008 and the adsorbed amount of pyrrole was linear even at the number of pyrrole exceeding that of Cu{sub 2+}, which suggests that the polymerization giving conjugated polypyrrole would take place on Cu{sup 2+} sites and the polypyrrole of aromatic form would be oxidized to quinoid form to give polaron on CuY surface.

  9. Adsorption of gas molecules on armchair AlN nanoribbons with a dangling bond defect by using density functional theory

    International Nuclear Information System (INIS)

    Sun, Guodong; Zhao, Peng; Zhang, Wenxue; Li, Hui; He, Cheng

    2017-01-01

    In this paper, the adsorption of gas molecules (CO, NO, O_2, CO_2, and NO_2) on armchair aluminum nitride nanoribbons (AAlNNRs) with a dangling bond defect has been investigated by density functional theory. For all the studied systems, the adsorption geometries, adsorption energies, charge transfer, and electronic structures are discussed. The adsorption energies of O_2, NO_2, and CO_2 are -1.53, -2.24, and -2.88 eV, respectively, corresponding to strong chemisorption. While for CO and NO, the adsorptions are between weak chemisorption and strong physisorption. Moreover, the magnetic property of defective AAlNNR are sensitive to the adsorption of NO_2. Therefore, based on the obtained results, AAlNNRs with a dangling bond defect is promising for using in gas sensor devices to detect NO_2. - Highlights: • The adsorption properties of gas molecules on defective AAlNNRs are performed by DFT. • The adsorption of O_2, NO_2, and CO_2 on defective AAlNNRs are strong chemisorption. • The magnetic property of defective AAlNNRs are sensitive to the adsorption of NO_2. • The defective AAlNNRs is promising in gas sensor devices to detect and capture NO_2.

  10. Oxygen adsorption on the Al0.25Ga0.75N (0001) surface: A first-principles study

    Science.gov (United States)

    Fu, Jiaqi; Song, Tielei; Liang, Xixia; Zhao, Guojun

    2018-04-01

    To understand the interaction mechanism for the oxygen adsorption on AlGaN surface, herein, we built the possible models of oxygen adsorption on Al0.25Ga0.75N (0001) surface. For different oxygen coverage, three kinds of adsorption site are considered. Then the favorable adsorption sites are characterized by first principles calculation for (2 × 2) supercell of Al0.25Ga0.75N (0001) surface. On basis of the optimal adsorption structures, our calculated results show that all the adsorption processes are exothermic, indicating that the (0001) surface orientation is active towards the adsorption of oxygen. The doping of Al is advantage to the adsorption of O atom. Additionally, the adsorption energy decreases with reducing the oxygen coverage, and the relationship between them is approximately linear. Owing to the oxygen adsorption, the surface states in the fundamental band gap are significant reduced with respect to the free Al0.25Ga0.75N (0001) surface. Moreover, the optical properties on different oxygen coverage are also discussed.

  11. Adsorption and co-adsorption of graphene oxide and Ni(II) on iron oxides: A spectroscopic and microscopic investigation.

    Science.gov (United States)

    Sheng, Guodong; Huang, Chengcai; Chen, Guohe; Sheng, Jiang; Ren, Xuemei; Hu, Baowei; Ma, Jingyuan; Wang, Xiangke; Huang, Yuying; Alsaedi, Ahmed; Hayat, Tasawar

    2018-02-01

    Graphene oxide (GO) may strongly interact with toxic metal ions and mineral particles upon release into the soil environment. We evaluated the mutual effects between GO and Ni (Ni(II)) with regard to their adsorption and co-adsorption on two minerals (goethite and hematite) in aqueous phase. Results indicated that GO and Ni could mutually facilitate the adsorption of each other on both goethite and hematite over a wide pH range. Addition of Ni promoted GO co-adsorption mainly due to the increased positive charge of minerals and cation-π interactions, while the presence of GO enhanced Ni co-adsorption predominantly due to neutralization of positive charge and strong interaction with oxygen-containing functional groups on adsorbed GO. Increasing adsorption of GO and Ni on minerals as they coexist may thus reduce their mobility in soil. Extended X-ray absorption fine structure (EXAFS) spectroscopy data revealed that GO altered the microstructure of Ni on minerals, i.e., Ni formed edge-sharing surface species (at R Ni-Fe ∼3.2 Å) without GO, while a GO-bridging ternary surface complexes (at R Ni-C ∼2.49 Å and R Ni-Fe ∼4.23 Å) was formed with GO. These findings improved the understanding of potential fate and toxicity of GO as well as the partitioning processes of Ni ions in aquatic and soil environments. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Strong Electroweak Symmetry Breaking

    CERN Document Server

    Grinstein, Benjamin

    2011-01-01

    Models of spontaneous breaking of electroweak symmetry by a strong interaction do not have fine tuning/hierarchy problem. They are conceptually elegant and use the only mechanism of spontaneous breaking of a gauge symmetry that is known to occur in nature. The simplest model, minimal technicolor with extended technicolor interactions, is appealing because one can calculate by scaling up from QCD. But it is ruled out on many counts: inappropriately low quark and lepton masses (or excessive FCNC), bad electroweak data fits, light scalar and vector states, etc. However, nature may not choose the minimal model and then we are stuck: except possibly through lattice simulations, we are unable to compute and test the models. In the LHC era it therefore makes sense to abandon specific models (of strong EW breaking) and concentrate on generic features that may indicate discovery. The Technicolor Straw Man is not a model but a parametrized search strategy inspired by a remarkable generic feature of walking technicolor,...

  13. Adsorption properties of AlN on Si(111) surface: A density functional study

    Science.gov (United States)

    Yuan, Yinmei; Zuo, Ran; Mao, Keke; Tang, Binlong; Zhang, Zhou; Liu, Jun; Zhong, Tingting

    2018-04-01

    In the process of preparing GaN on Si substrate by MOCVD, an AlN buffer layer is very important. In this study, we conducted density functional theory calculations on the adsorption of AlN molecule on Si(111)-(2 × 2) surface, with the AlN molecule located horizontally or vertically above Si(111) surface at different adsorption sites. The calculations revealed that the lowest adsorption energy was at the N-top-Al-bridge site in the horizontal configuration, with the narrowest band gap, indicating that it was the most preferential adsorption growth status of AlN. In the vertical configurations, N adatom was more reactive and convenient to form bonds with the topmost Si atoms than Al adatom. When the N-end of the AlN molecule was located downward, the hollow site was the preferred adsorption site; when the Al-end was located downward, the bridge site was the most energetically favorable. Moreover, we investigated some electronic properties such as partial density of states, electron density difference, Mulliken populations, etc., revealing the microscale mechanism for AlN adsorption on Si(111) surface and providing theoretical support for adjusting the processing parameters during AlN or GaN production.

  14. Adsorption of binary gas mixtures in heterogeneous carbon predicted by density functional theory: on the formation of adsorption azeotropes.

    Science.gov (United States)

    Ritter, James A; Pan, Huanhua; Balbuena, Perla B

    2010-09-07

    Classical density functional theory (DFT) was used to predict the adsorption of nine different binary gas mixtures in a heterogeneous BPL activated carbon with a known pore size distribution (PSD) and in single, homogeneous, slit-shaped carbon pores of different sizes. By comparing the heterogeneous results with those obtained from the ideal adsorbed solution theory and with those obtained in the homogeneous carbon, it was determined that adsorption nonideality and adsorption azeotropes are caused by the coupled effects of differences in the molecular size of the components in a gas mixture and only slight differences in the pore sizes of a heterogeneous adsorbent. For many binary gas mixtures, selectivity was found to be a strong function of pore size. As the width of a homogeneous pore increases slightly, the selectivity for two different sized adsorbates may change from being greater than unity to less than unity. This change in selectivity can be accompanied by the formation of an adsorption azeotrope when this same binary mixture is adsorbed in a heterogeneous adsorbent with a PSD, like in BPL activated carbon. These results also showed that the selectivity exhibited by a heterogeneous adsorbent can be dominated by a small number of pores that are very selective toward one of the components in the gas mixture, leading to adsorption azeotrope formation in extreme cases.

  15. Plasmons in strong superconductors

    International Nuclear Information System (INIS)

    Baldo, M.; Ducoin, C.

    2011-01-01

    We present a study of the possible plasmon excitations that can occur in systems where strong superconductivity is present. In these systems the plasmon energy is comparable to or smaller than the pairing gap. As a prototype of these systems we consider the proton component of Neutron Star matter just below the crust when electron screening is not taken into account. For the realistic case we consider in detail the different aspects of the elementary excitations when the proton, electron components are considered within the Random-Phase Approximation generalized to the superfluid case, while the influence of the neutron component is considered only at qualitative level. Electron screening plays a major role in modifying the proton spectrum and spectral function. At the same time the electron plasmon is strongly modified and damped by the indirect coupling with the superfluid proton component, even at moderately low values of the gap. The excitation spectrum shows the interplay of the different components and their relevance for each excitation modes. The results are relevant for neutrino physics and thermodynamical processes in neutron stars. If electron screening is neglected, the spectral properties of the proton component show some resemblance with the physical situation in high-T c superconductors, and we briefly discuss similarities and differences in this connection. In a general prospect, the results of the study emphasize the role of Coulomb interaction in strong superconductors.

  16. Combined quantum chemistry and Monte Carlo simulation of competitive adsorption of O{sub 2} and OH on Pt surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Li, Rui, E-mail: ruililcu@gmail.com [Department of Chemistry, Liaocheng University, Liaocheng 252059 (China); Li, Haibo; Xu, Shuling [Department of Chemistry, Liaocheng University, Liaocheng 252059 (China); Liu, Jifeng, E-mail: liujifeng111@gmail.com [Key Laboratory of Food Nutrition and Safety, Ministry of Education of China, Tianjin University of Science and Technology, Tianjin 300457 (China)

    2017-07-15

    Highlights: • Competitive adsorption of O{sub 2} and OH on different Pt surfaces was theoretically studied. • The adsorption energies of O{sub 2} and OH depend on the Pt surfaces and the adsorption sites. • The order of O{sub 2} adsorption efficiency was characterized. - Abstract: To obtain a microscopic explanation on the difference of oxygen reduction reaction activity on different Pt low index surfaces, we simulated competitive adsorptions of O{sub 2} and OH on four Pt low index surfaces. Firstly, all possible chemical adsorption configurations of the O{sub 2} and OH molecules on the three surfaces were acquired through density functional theory. The distribution of these configurations on the different surfaces was collected from Monte Carlo simulations. Our results demonstrated that the adsorption energy order of O{sub 2} on different surfaces was (110)(1 × 2) > (110) > (100) > (111) and that the adsorption energy order of the OH molecules on Pt surfaces was the same. Considering the competitive adsorption of O{sub 2} and OH on Pt surfaces, the final O{sub 2} adsorption efficiencies order of three surfaces was (111) > (110) > (100) > (110)(1 × 2), which was consistent with the experimental activities of oxygen reduction. Our study provided theoretical references for previous experimental studies and had important significance for the understanding of oxygen adsorption on Pt surfaces.

  17. Entropy of adsorption of mixed surfactants from solutions onto the air/water interface

    Science.gov (United States)

    Chen, L.-W.; Chen, J.-H.; Zhou, N.-F.

    1995-01-01

    The partial molar entropy change for mixed surfactant molecules adsorbed from solution at the air/water interface has been investigated by surface thermodynamics based upon the experimental surface tension isotherms at various temperatures. Results for different surfactant mixtures of sodium dodecyl sulfate and sodium tetradecyl sulfate, decylpyridinium chloride and sodium alkylsulfonates have shown that the partial molar entropy changes for adsorption of the mixed surfactants were generally negative and decreased with increasing adsorption to a minimum near the maximum adsorption and then increased abruptly. The entropy decrease can be explained by the adsorption-orientation of surfactant molecules in the adsorbed monolayer and the abrupt entropy increase at the maximum adsorption is possible due to the strong repulsion between the adsorbed molecules.

  18. Kinetics Study of Gas Pollutant Adsorption and Thermal Desorption on Silica Gel

    Directory of Open Access Journals (Sweden)

    Rong A

    2017-06-01

    Full Text Available Silica gel is a typical porous desiccant material. Its adsorption performance for gaseous air pollutants was investigated to determine its potential contribution to reducing such pollutants. Three gaseous air pollutants, toluene, carbon dioxide, and methane, were investigated in this paper. A thermogravimetric analyzer was used to obtain the equilibrium adsorption capacity of gases on single silica gel particles. The silica gel adsorption capacity for toluene is much higher than that for carbon dioxide and methane. To understand gas pollutant thermal desorption from silica gel, the thermogravimetric analysis of toluene desorption was conducted with 609 ppm toluene vapor at 313 K, 323 K, and 333 K. The overall regeneration rate of silica gel was strongly dependent on temperature and the enthalpy of desorption. The gas pollutant adsorption performance and thermal desorption on silica gel material may be used to estimate the operating and design parameters for gas pollutant adsorption by desiccant wheels.

  19. A study on adsorption of Pb(II), Cr(Ш) and Cu(II) from aqueous ...

    African Journals Online (AJOL)

    Peanut husk has been used in this work for removing Pb(II), Cr(Ш) and Cu(II) from aqueous solution. Batch adsorption studies were carried out under different pH, initial concentration of metal ions, interfering metal ions, time and temperature. Adsorption was poor in strongly acidic solution but was improved in alkaline ...

  20. Modeling the effect of structural details of nonionic surfactant on micellization in solution and adsorption onto hydrophobic surfaces

    NARCIS (Netherlands)

    Jodar-Reyes, A.B.; Ortega-Vinuesa, J.L.; Martin-Rodriguez, A.; Leermakers, F.A.M.

    2002-01-01

    Applying the classical one-gradient self-consistent-field (SCF) theory for adsorption and/or association, we can show that the molecular architecture of nonionic surfactants influences strongly the micellization in solution and the adsorption on solid-liquid interfaces. This is illustrated by using

  1. New ends to the tale of tails: adsorption of comb polymers and the effect on colloid stability

    NARCIS (Netherlands)

    Charlaganov, M.; Kosovan, P.; Leermakers, F.A.M.

    2009-01-01

    In this paper we consider the classical problem of homopolymer adsorption at the solid–liquid interface and discuss its implications for colloidal stability. More specifically, our focus is on comb-like homopolymers in the strong adsorption limit. A self-consistent field analysis shows that for

  2. A biological oil adsorption filter

    Energy Technology Data Exchange (ETDEWEB)

    Pasila, A [University of Helsinki (Finland). Dept. of Agricultural Engineering and Household Technology

    2005-12-01

    A new oil adsorption method called adsorption filtration (AF) has been developed. It is a technology where by oil residues can be cleaned from water by running it through a simple filter made from freeze treated, dried, milled and then fragmented plant material. By choosing suitable plants and fragmentation sizes it is possible to produce filters, which pass water but adsorb oil. The aim of this study was to investigate the possibilities of manufacturing oil adsorbing filter materials from reed canary grass (Phalaris arundinacea), flax (Linum usitatissimum L.) or hemp fibre (Cannabis sativa L.). The oil (80 ml) was mixed with de-ionised water (200 ml) and this mixture was filtered through 10 or 20 g adsorption filters. Fine spring harvested hemp fibre (diameter less than 1 mm) and reed canary grass fragments adsorb 2-4 g of oil per gram of adsorption material compared to 1-3 g of water. Adsorption filtration is thus a novel way of gathering spilled oil in shallow coastal waters before the oil reaches the shore. (author)

  3. A biological oil adsorption filter

    International Nuclear Information System (INIS)

    Pasila, A.

    2005-01-01

    A new oil adsorption method called adsorption filtration (AF) has been developed. It is a technology where by oil residues can be cleaned from water by running it through a simple filter made from freeze treated, dried, milled and then fragmented plant material. By choosing suitable plants and fragmentation sizes it is possible to produce filters, which pass water but adsorb oil. The aim of this study was to investigate the possibilities of manufacturing oil adsorbing filter materials from reed canary grass (Phalaris arundinacea), flax (Linum usitatissimum L.) or hemp fibre (Cannabis sativa L.). The oil (80 ml) was mixed with de-ionised water (200 ml) and this mixture was filtered through 10 or 20 g adsorption filters. Fine spring harvested hemp fibre (diameter less than 1 mm) and reed canary grass fragments adsorb 2-4 g of oil per gram of adsorption material compared to 1-3 g of water. Adsorption filtration is thus a novel way of gathering spilled oil in shallow coastal waters before the oil reaches the shore. (author)

  4. Adsorption mechanism of BMP-7 on hydroxyapatite (001) surfaces

    International Nuclear Information System (INIS)

    Zhou, Hailong; Wu, Tao; Dong, Xiuli; Wang, Qi; Shen, Jiawei

    2007-01-01

    Many properties and functions of bone-related proteins perform through the interface with the hydroxyapatite. However, the mechanism of difference of proteins adsorbing behaviors caused by the variation of calcium and phosphate ions on hydroxyapatite is still unclear at atomic level. In this work, we investigated the site-selective adhesion and the adsorption mechanism of protein BMP-7 to the hydroxyapatite surfaces in aqueous media during adsorption and desorption processes. Molecular dynamics (MD) and steered molecular dynamics (SMD) simulations combined with trajectory analysis were employed to give insight into the underlying behaviors of BMP-7 binding. The results suggest that the adsorption sites could be divided into two categories: COO - and NH 2 /NH3+. For COO - , the adsorption phenomenon is driven by the electrostatic interaction formed between the negative charged carboxylate groups and the Ca1 cations on the hydroxyapatite surface. While for NH 2 /NH3+, the interaction is through the intermolecular H-bonds between the N-containing groups and the phosphate on the hydroxyapatite surface

  5. Radionuclide adsorption characteristics around coastal water

    International Nuclear Information System (INIS)

    Song, Young Il; Chung, Yang Geun; Hong, Sung Yul; Lee, Gab Bock

    1999-01-01

    The adsorption capacity of radionuclides onto suspended sediment was experimented on each of the coastal seawater sampled around the Kori and the Wolsung nuclear power plant. During the experiment the quantity and size fraction of suspended sediment were adjusted and the seawater and sediment chemistry is approximated to the expected field condition. Because the sorption capacity depends on the specific minerals, ocean chemistry and radionuclide involved, it is necessary to analyze sediment mineralogy. Clay mineral is dominant in seabed mineral and suspended sediment as the result of x-ray diffraction. Radionuclide sorbed to silty-clay mineral can be rather transported to ocean than scavenged to seabed because of low quantity and fine grained suspended sediment in the coast around the Kori and the Wolsung. The result of adsorption examinations shows that 139 Ce and 51 Cr and 110m Ag are strongly sorbed to suspended particle, while 137 Cs is less sorbed and 60 Co uptake is varied with experiment condition, which can be inferred from various biological factors. (author). 9 refs., 2 tabs., 7 figs

  6. Strongly intensive quantities

    International Nuclear Information System (INIS)

    Gorenstein, M. I.; Gazdzicki, M.

    2011-01-01

    Analysis of fluctuations of hadron production properties in collisions of relativistic particles profits from use of measurable intensive quantities which are independent of system size variations. The first family of such quantities was proposed in 1992; another is introduced in this paper. Furthermore we present a proof of independence of volume fluctuations for quantities from both families within the framework of the grand canonical ensemble. These quantities are referred to as strongly intensive ones. Influence of conservation laws and resonance decays is also discussed.

  7. Strong-coupling approximations

    International Nuclear Information System (INIS)

    Abbott, R.B.

    1984-03-01

    Standard path-integral techniques such as instanton calculations give good answers for weak-coupling problems, but become unreliable for strong-coupling. Here we consider a method of replacing the original potential by a suitably chosen harmonic oscillator potential. Physically this is motivated by the fact that potential barriers below the level of the ground-state energy of a quantum-mechanical system have little effect. Numerically, results are good, both for quantum-mechanical problems and for massive phi 4 field theory in 1 + 1 dimensions. 9 references, 6 figures

  8. A density functional study of carbon monoxide adsorption on small cationic, neutral, and anionic gold clusters

    Science.gov (United States)

    Wu, X.; Senapati, L.; Nayak, S. K.; Selloni, A.; Hajaligol, M.

    2002-08-01

    CO adsorption on small cationic, neutral, and anionic Aun (n=1-6) clusters has been investigated using density functional theory in the generalized gradient approximation. Among various possible CO adsorption sites, the on-top (one-fold coordinated) is found to be the most favorable one, irrespective of the charge state of the cluster. In addition, planar structures are preferred by both the bare and the CO-adsorbed clusters. The adsorption energies of CO on the cationic clusters are generally greater than those on the neutral and anionic complexes, and decrease with size. The adsorption energies on the anions, instead, increase with cluster size and reach a local maximum at Au5CO-, in agreement with recent experiment. The differences in adsorption energies for the different charge states decrease with increasing cluster size.

  9. Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

    Science.gov (United States)

    Tournassat, C.; Tinnacher, R. M.; Grangeon, S.; Davis, J. A.

    2018-01-01

    The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonite edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites ('spillover' effect). A series of U(VI) - Na-montmorillonite batch adsorption experiments was conducted as a function of pH, with variable U(VI), Ca, and dissolved carbonate concentrations. Based on the experimental data, a new type of surface complexation model (SCM) was developed for montmorillonite, that specifically accounts for the spillover effect using the edge surface speciation model by Tournassat et al. (2016a). The SCM allows for a prediction of U(VI) adsorption under varying chemical conditions with a minimum number of fitting parameters, not only for our own experimental results, but also for a number of published data sets. The model agreed well with many of these datasets without introducing a second site type or including the formation of ternary U(VI)-carbonato surface complexes. The model predictions were greatly impacted by utilizing analytical measurements of dissolved inorganic carbon (DIC) concentrations in individual sample solutions rather than assuming solution equilibration with a specific partial pressure of CO2, even when the gas phase was

  10. U(VI) adsorption on natural iron-coated sands: comparison of approaches for modeling adsorption on heterogeneous environmental materials

    International Nuclear Information System (INIS)

    Logue, Brian A.; Smith, Robert W.; Westall, John C.

    2004-01-01

    Adsorption of U(VI) on 6 samples of natural Fe-rich sands from Oyster, VA was studied over a range of U(VI) concentrations (0.1-100 μM), pH values (3-7.6), and dithionite-citrate-bicarbonate (DCB) extractable amounts of Fe (3.1-12.3 μmol/g). Four modeling approaches were applied to represent the U(VI) adsorption data. Model I was a two-site, diffuse double layer, surface complexation model based on data for synthetic ferrihydrite [Geochim. Cosmochim. Acta 58 (1994) 5465-5478]. Considering the magnitude of approximations necessary for application of the laboratory-based model to natural sands, Model I was surprisingly accurate, as determined by the goodness of fit parameter, χ 2 /N of 53.1-22.2. Model II was based on the reactions and diffuse double layer treatment of Model I, but was calibrated to a portion of U(VI) adsorption data for each sand, and then used to predict adsorption data for the same sand under different experimental conditions. Model II did not increase the accuracy of the predictions made with Model I, χ 2 /N of 42.4-27.6. Models III and IV were four-site affinity spectrum models, without an explicit electric double layer model or explicit surface hydrolysis reactions. Model III was based on a discrete log K spectrum approach, and Model IV was obtained from adjusting all surface stability constants and site concentrations for all surface sites. Models III and IV represented the U(VI) adsorption data with the greatest accuracy, χ 2 /N ranged from 13.8 to 4.4. Model I provides evidence supporting the practice of using pure phase thermodynamic reaction constants for describing the adsorption characteristics of environmentally important sorbents in certain simple cases. Yet, affinity spectrum approaches (Models III and IV) become increasingly important as more accurate interpolation of adsorption data is necessary, the sorbent becomes increasingly complex, or the range of experimental conditions expands

  11. Strongly disordered superconductors

    International Nuclear Information System (INIS)

    Muttalib, K.A.

    1982-01-01

    We examine some universal effects of strong non-magnetic disorder on the electron-phonon and electron-electron interactions in a superconductor. In particular we explicitly take into account the effect of slow diffusion of electrons in a disordered medium by working in an exact impurity eigenstate representation. We find that the normal diffusion of electrons characterized by a constant diffusion coefficient does not lead to any significant correction to the electron-phonon or the effective electron-electron interactions in a superconductor. We then consider sufficiently strong disorder where Anderson localization of electrons becomes important and determine the effect of localization on the electron-electron interactions. We find that due to localization, the diffusion of electrons becomes anomalous in the sense that the diffusion coefficient becomes scale dependent. This results in an increase in the effective electron-electron interaction with increasing disorder. We propose that this provides a natural explanation for the unusual sensitivity of the transition temperature T/sub c/ of the high T/sub c/ superconductors (T/sub c/ > 10 0 K) to damage effects

  12. Strong Coupling Holography

    CERN Document Server

    Dvali, Gia

    2009-01-01

    We show that whenever a 4-dimensional theory with N particle species emerges as a consistent low energy description of a 3-brane embedded in an asymptotically-flat (4+d)-dimensional space, the holographic scale of high-dimensional gravity sets the strong coupling scale of the 4D theory. This connection persists in the limit in which gravity can be consistently decoupled. We demonstrate this effect for orbifold planes, as well as for the solitonic branes and string theoretic D-branes. In all cases the emergence of a 4D strong coupling scale from bulk holography is a persistent phenomenon. The effect turns out to be insensitive even to such extreme deformations of the brane action that seemingly shield 4D theory from the bulk gravity effects. A well understood example of such deformation is given by large 4D Einstein term in the 3-brane action, which is known to suppress the strength of 5D gravity at short distances and change the 5D Newton's law into the four-dimensional one. Nevertheless, we observe that the ...

  13. Acoustic and adsorption properties of submerged wood

    Science.gov (United States)

    Hilde, Calvin Patrick

    Wood is a common material for the manufacture of many products. Submerged wood, in particular, is used in niche markets, such as the creation of musical instruments. An initial study performed on submerged wood from Ootsa Lake, British Columbia, provided results that showed that the wood was not suitable for musical instruments. This thesis re-examined the submerged wood samples. After allowing the wood to age unabated in a laboratory setting, the wood was retested under the hypothesis that the physical acoustic characteristics would improve. It was shown, however, that the acoustic properties became less adequate after being left to sit. The adsorption properties of the submerged wood were examined to show that the submerged wood had a larger accessible area of wood than that of control wood samples. This implied a lower amount of crystalline area within the submerged wood. From the combined adsorption and acoustic data for the submerged wood, relationships between the moisture content and speed of sound were created and combined with previous research to create a proposed model to describe how the speed of sound varies with temperature, moisture content and the moisture content corresponding to complete hydration of sorption sites within the wood.

  14. Adsorption Properties of MFM-400 and MFM-401 with CO2 and Hydrocarbons: Selectivity Derived from Directed Supramolecular Interactions.

    Science.gov (United States)

    Ibarra, Ilich A; Mace, Amber; Yang, Sihai; Sun, Junliang; Lee, Sukyung; Chang, Jong-San; Laaksonen, Aatto; Schröder, Martin; Zou, Xiaodong

    2016-08-01

    ([Sc2(OH)2(BPTC)]) (H4BPTC = biphenyl-3,3',5,5'-tetracarboxylic acid), MFM-400 (MFM = Manchester Framework Material, previously designated NOTT), and ([Sc(OH)(TDA)]) (H2TDA = thiophene-2,5-dicarboxylic acid), MFM-401, both show selective and reversible capture of CO2. In particular, MFM-400 exhibits a reasonably high CO2 uptake at low pressures and competitive CO2/N2 selectivity coupled to a moderate isosteric heat of adsorption (Qst) for CO2 (29.5 kJ mol(-1)) at zero coverage, thus affording a facile uptake-release process. Grand canonical Monte Carlo (GCMC) and density functional theory (DFT) computational analyses of CO2 uptake in both materials confirmed preferential adsorption sites consistent with the higher CO2 uptake observed experimentally for MFM-400 over MFM-401 at low pressures. For MFM-400, the Sc-OH group participates in moderate interactions with CO2 (Qst = 33.5 kJ mol(-1)), and these are complemented by weak hydrogen-bonding interactions (O···H-C = 3.10-3.22 Å) from four surrounding aromatic -CH groups. In the case of MFM-401, adsorption is provided by cooperative interactions of CO2 with the Sc-OH group and one C-H group. The binding energies obtained by DFT analysis for the adsorption sites for both materials correlate well with the observed moderate isosteric heats of adsorption for CO2. GCMC simulations for both materials confirmed higher uptake of EtOH compared with nonpolar vapors of toluene and cyclohexane. This is in good correlation with the experimental data, and DFT analysis confirmed the formation of a strong hydrogen bond between EtOH and the hydrogen atom of the hydroxyl group of the MFM-400 and MFM-401 framework (FW) with H-OEtOH···H-OFW distances of 1.77 and 1.75 Å, respectively. In addition, the accessible regeneration of MFM-400 and MFM-401 and release of CO2 potentially provide minimal economic and environmental penalties.

  15. Anti-site defected MoS2 sheet-based single electron transistor as a gas sensor

    Science.gov (United States)

    Sharma, Archana; Husain, Mushahid; Srivastava, Anurag; Khan, Mohd. Shahid

    2018-05-01

    To prevent harmful and poisonous CO gas molecules, catalysts are needed for converting them into benign substances. Density functional theory (DFT) calculations have been used to study the adsorption of CO and CO2 gas molecules on the surface of MoS2 monolayer with Mo atom embedded at S-vacancy site (MoS). The strong interaction between Mo metal with pristine MoS2 sheet suggests its strong binding nature. Doping Mo into MoS2 sheet enhances CO and CO2 adsorption strength. The sensing response of MoS-doped MoS2 system to CO and CO2 gas molecules is obtained in the single electron transistor (SET) environment by varying bias voltage. Doping reduces charging energy of the device which results in fast switching of the device from OFF to ON state.

  16. Adsorption of Hydrogen and Potassium on GaAs(110) Studied by Time-of-Flight Scattering and Recoiling Spectrometry

    International Nuclear Information System (INIS)

    Gayone, J.E.

    2000-01-01

    function of the exposure indicate that the initial strong decrease in the rate of unrelaxation is mainly a /consequence of the variation of the sticking coefficient. Below 100 L, most of the H atoms participate in the unrelaxation process. However, above 500 L, it is necessary to increase strongly the H coverage to produce small changes in the atomic structure of the surface. The measurements of the As and Ga direct recoils intensities change with the incident direction of the projectile in accordance with the crystallographic structure of the surface. On the other hand, the H recoil intensity is almost independent of the crystallographic sample orientation, indicating that an important fraction of the H atoms are not adsorbed in well ordered sites.Measurements as a function of the sample temperature show a continuous decrease of the H DR intensity for both low and high exposures. The combined results of forward recoiled atom and scattered projectile intensities suggest that an important fraction of the adsorbed H atoms is not bonded in a well ordered layer and may be forming molecules since the beginning of the adsorption process. The adsorption of K on GaAs(110) is mainly studied by DRS. The analysis of K direct recoil intensity indicates that at room temperature, the adsorption of K saturates at 0.5 ML, which corresponds to an atom density of ∼ 4.4x10 1 4 at/cm 2 . The adsorption process proceeds in two stages, which depend on the K coverage (Θ (K)). At low coverages, Θ (K)<0.1 ML, the K atoms are adsorbed exclusively on the [001] Ga rows and close to the sites of a new As layer, with a local crystallographic order. At high coverages the K atoms start to adsorb also along the As rows, although with a lower probability than on the Ga rows. At saturation, the K layer does not form an ordered structure. The dependence of the direct-recoil ion fractions on the K coverage is consistent with the structural information obtained from the analysis of the total recoiled

  17. Methane adsorption on the surface of a model of shale: A density functional theory study

    International Nuclear Information System (INIS)

    Zhu, Yuan-qiang; Su, Hong; Jing, Ya; Guo, Jianchun; Tang, Junlei

    2016-01-01

    Highlights: • The adsorption of methane on kerogen was investigated by DFT method with D3 dispersion correction. • Methane prefers to be adsorbed on the sites directly above the carbon atoms of the kerogen. • The interaction energy with BSSE corrections is around 14 kJ mol −1 . • RDG gradient isosurface depicted the van der Waals interactions between methane and kerogen. • The adsorption of methane on kerogen slightly depends upon the adsorption sites on kerogen as well as the orientations of methane. - Abstract: As a model of shale, one part of polycyclic aromatic ring was used to represent the kerogen surface with the structural heterogeneity. The adsorption mechanisms of methane on the surface of the kerogen were investigated by M06-2× functional with D3 dispersion correction. Nine stable adsorption sites and the orientations of methane (CH 4 ) on the surface of the kerogen were systematically considered. Information from different methods lead to the same conclusion that methane prefers to be adsorbed on the sites directly above the carbon atoms of the kerogen rather than above the center of the six-membered rings. The interactions between methane and the surface of the kerogen are the van der Waals interactions. The interaction energies with the basis set superposition error (BSSE) corrections are around 14 kJ mol −1 at the M06-2×-D3/Jun-cc-pVDZ level. The RDG scatter graphs and the RDG gradient isosurface further illustrate that the interactions between methane and the surface of the kerogen belong to the van der Waals interactions. The weak interactions indicate that the adsorption of methane on the surface of the kerogen is physical adsorption and it slightly depends upon the adsorption sites on kerogen as well as the orientations of methane. These results are helpful for the understanding of the microcosmic mechanism of methane–shale interactions and for the exploitation of shale gas.

  18. The Adsorption of Cd(II) on Manganese Oxide Investigated by Batch and Modeling Techniques.

    Science.gov (United States)

    Huang, Xiaoming; Chen, Tianhu; Zou, Xuehua; Zhu, Mulan; Chen, Dong; Pan, Min

    2017-09-28

    Manganese (Mn) oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II) on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II) concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R² > 0.999). The adsorption of Cd(II) on Mn oxide significantly decreased with increasing ionic strength at pH adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II) on Mn oxide at pH 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II) calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II) on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by ion exchange sites (X₂Cd) at low pH and inner-sphere surface complexation sites (SOCd⁺ and (SO)₂CdOH - species) at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water-mineral interface.

  19. The Adsorption of Cd(II on Manganese Oxide Investigated by Batch and Modeling Techniques

    Directory of Open Access Journals (Sweden)

    Xiaoming Huang

    2017-09-01

    Full Text Available Manganese (Mn oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R2 > 0.999. The adsorption of Cd(II on Mn oxide significantly decreased with increasing ionic strength at pH < 5.0, whereas Cd(II adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II on Mn oxide at pH < 5.0 and pH > 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II on Mn oxide can be satisfactorily simulated by ion exchange sites (X2Cd at low pH and inner-sphere surface complexation sites (SOCd+ and (SO2CdOH− species at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water–mineral interface.

  20. The Adsorption of Cd(II) on Manganese Oxide Investigated by Batch and Modeling Techniques

    Science.gov (United States)

    Huang, Xiaoming; Chen, Tianhu; Zou, Xuehua; Zhu, Mulan; Chen, Dong

    2017-01-01

    Manganese (Mn) oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II) on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II) concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R2 > 0.999). The adsorption of Cd(II) on Mn oxide significantly decreased with increasing ionic strength at pH adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II) on Mn oxide at pH 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II) calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II) on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by ion exchange sites (X2Cd) at low pH and inner-sphere surface complexation sites (SOCd+ and (SO)2CdOH− species) at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water–mineral interface. PMID:28956849

  1. Adsorption of alkali and alkaline-earth metal atoms on stanene: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Kadioglu, Yelda; Ersan, Fatih [Department of Physics, Adnan Menderes University, 09100 Aydın (Turkey); Gökoğlu, Gökhan [Department of Physics, Karabük University, 78050 Karabük (Turkey); Aktürk, Olcay Üzengi [Department of Electrical & Electronics Engineering, Adnan Menderes University, 09100 Aydın (Turkey); Nanotechnology Application and Research Center, Adnan Menderes University, 09100 Aydın (Turkey); Aktürk, Ethem, E-mail: ethem.akturk@adu.edu.tr [Department of Physics, Adnan Menderes University, 09100 Aydın (Turkey); Nanotechnology Application and Research Center, Adnan Menderes University, 09100 Aydın (Turkey)

    2016-09-01

    This paper presents a study on the adsorption of alkali and alkaline-earth metal atoms on single-layer stanene with different levels of coverage using first-principles plane wave calculations within spin-polarized density functional theory. The most favorable adsorption site for alkali atoms (Li, Na, K) were found to be the hollow site similar to other group IV single-layers, but the case of alkaline-earths on stanene is different from silicene and germanene. Whereas Mg and Ca are bound to stanene at hollow site, the bridge site is found to be energetically favorable for Be adatom. All adsorbed atoms are positively charged due to the charge transfer from adatom to stanene single-layer. The semimetallic bare stanene become metallic except for Be adsorption. The Beryllium adsorption give rise to non-magnetic semiconducting ground state. Our results illustrate that stanene has a reactive and functionalizable surface similar to graphene or silicene. - Highlights: • Alkali and alkaline-earth metal atoms form stronger bonds with stanene compared to other group IV monolayers. • Semi-metallic stanene becomes nonmagnetic metal for Li, Na, K, Mg, and Ca atoms adsorption. • Semi-metallic stanene becomes nonmagnetic semiconductor with 94 meV band gap for Be atom adsorption.

  2. Metal-polymer interfaces studied with adsorption microcalorimetry and photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bebensee, Fabian

    2010-06-21

    The interface formation between calcium and two different semiconducting, ?-conjugated polymers, namely poly(3-hexylthiophene) (P3HT) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-(1-cyanovilylene)phenylene] (CN-MEH-PPV), was investigated using adsorption microcalorimetry, low energy ion scattering spectroscopy (LEIS), atomic beam scattering and X-ray photoelectron spectroscopy. In addition to the interface formation on pristine, i.e., untreated polymer surfaces, the influence of electron irradiation prior to calcium deposition and the effect of dosing calcium at a low substrate temperature was studied. The reactive site for the interaction of calcium atoms impinging on a pristine P3HT surface appears to be the sulfur in the thiophene ring, as is concluded from a combination of XPS, adsorption calorimetry and theory results. The interaction, in fact, is strong enough that the sulfur atoms abstracted from the thiophene ring under formation of calcium sulfide with an overall reaction energy of this process of 405 kJ per mol. Quantitative evaluation of XPS data reveal that the depth up to which Ca atoms react with sulfur in the polymer is 3 nm, irrespective of increasing the amount of Ca dosed onto the substrate. A closed layer of Ca is only formed at a Ca coverage exceeding 11 ML, as suggested by LEIS. Irradiation of P3HT with electrons with a kinetic energy of 100 eV results in dehydrogenation of the hexyl side chains and formation of new C=C double bonds. This in turn results in a higher initial sticking probability of 0.63 for Ca, while no other significant changes could be observed: XPS indicates that the thiophene rings remain intact and the measured heat of adsorption is the same as observed for the deposition of Ca on pristine P3HT. Dosing Ca onto P3HT held at low temperature (130 K) is found to result in a very low saturation thickness of the reacted layer of approximately 0.3 nm. Upon warming the sample up to room temperature, the thickness of the reacted layer

  3. The effect of various cations and pH on the adsorption of U(VI) on Amberlite IR-118H resin

    International Nuclear Information System (INIS)

    Kilislioglu, Ayben

    2003-01-01

    The effects of various metal cations and pH on the adsorption of uranium(VI) on strongly acidic cation exchanger Amberlite IR-118H (AIR-118H) were studied. The metal cations suppress U(VI) adsorption differently depending on their ionic radii. Adsorption of U(VI) on AIR-118H peaks at pH 3.4, which was attributed to the occurrence of different forms of U(VI) at different pH values. The adsorption data were then processed using the Frumkin-Fowler-Guggenheim equation, and the standard free energy of adsorption was calculated

  4. Theoretical insight of adsorption cooling

    KAUST Repository

    Chakraborty, Anutosh

    2011-06-03

    This letter proposes and presents a thermodynamic formulation to calculate the energetic performances of an adsorption cooler as a function of pore widths and volumes of solid adsorbents. The simulated results in terms of the coefficient of performance are validated with experimental data. It is found from the present analysis that the performance of an adsorption cooling device is influenced mainly by the physical characteristics of solid adsorbents, and the characteristics energy between the adsorbent-adsorbate systems. The present study confirms that there exists a special type of silicagel having optimal physical characteristics that allows us to obtain the best performance.

  5. Theoretical insight of adsorption cooling

    KAUST Repository

    Chakraborty, Anutosh; Leong, Kai Choong; Thu, Kyaw; Saha, Bidyut Baran; Ng, Kim Choon

    2011-01-01

    This letter proposes and presents a thermodynamic formulation to calculate the energetic performances of an adsorption cooler as a function of pore widths and volumes of solid adsorbents. The simulated results in terms of the coefficient of performance are validated with experimental data. It is found from the present analysis that the performance of an adsorption cooling device is influenced mainly by the physical characteristics of solid adsorbents, and the characteristics energy between the adsorbent-adsorbate systems. The present study confirms that there exists a special type of silicagel having optimal physical characteristics that allows us to obtain the best performance.

  6. Potential Theory of Multicomponent Adsorption

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Stenby, Erling Halfdan

    1998-01-01

    We developed a theory of multicomponent adsorption on the basis of the potential concept originally suggested by Polanyi. The mixture is considered as a heterogeneous substance segregated in the external field emitted by the adsorbent. The same standard equation of state, with no additional fitting...... and high degree of predictability of the theory developed....... the potential theory and the spreading pressure concept is established, and problems of the theory consistency are studied. Numerical algorithms are suggested for evaluation of the segregated state of the mixture in the potential field of adsorption forces. Comparison with experimental data shows good agreement...

  7. The surface characteristics of hyperbranched polyamide modified corncob and its adsorption property for Cr(VI)

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Hai, E-mail: linhai@ces.ustb.edu.cn [School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory on Resource-oriented Treatment of Industrial Pollutants, Beijing 100083 (China); Han, Shaoke; Dong, Yingbo; He, Yinhai [School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Beijing Key Laboratory on Resource-oriented Treatment of Industrial Pollutants, Beijing 100083 (China)

    2017-08-01

    Highlights: • An anion adsorbent was synthesized by hyperbranched polyamide modified corncob (HPMC). • The surface characteristics of samples (RCC, HPMC, HPMC-Cr) were studied. • Langmuir isotherm provided more fit and maximum adsorption capacity was 131.6 mg/g. • The adsorption process was chemisorption, controlled by intra-particle diffusion and film diffusion. • Adsorption is fast, stable, spontaneous and endothermic. - Abstract: A low-cost anion adsorbent for Cr(VI) effectively removing was synthesized by hyperbranched polyamide modified corncob (HPMC). Samples were characterized by Brunauer–Emmett–Teller (BET) surface area analysis, field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy, Fourier transform infrared (FTIR) and zeta potential analysis. Kinetics, isotherms and thermodynamics studies of HPMC for Cr(VI) adsorption were investigated in batch static experiments, in the temperature range of 25–45 °C, pH = 2.0. Results showed that the adsorption was rapid and stable, with the uptake capacity higher than 80% after 30 min. Adsorption behavior and rate-controlling mechanisms were analyzed using three kinetic models (pseudo-first order, pseudo-second order, intra-particle kinetic model). Kinetic studies showed that the adsorption of HPMC to Cr(VI) relied the pseudo-second-order model, and controlled both by the intra-particle diffusion and film diffusion. Equilibrium data was tested by Langmuir and Freundlich adsorption isotherm models. Langmuir model was more suitable to indicate a homogeneous distribution of active sites on HPMC and monolayer adsorption. The maximum adsorption capacity from the Langmuir model, q{sub max}, was 131.6 mg/g at pH 2.0 and 45 °C for HPMC. Thermodynamic parameters revealed spontaneous and endothermic nature of the Cr(VI) adsorption onto HPMC.

  8. Adsorption of sulfonamides to demineralized pine wood biochars prepared under different thermochemical conditions

    International Nuclear Information System (INIS)

    Xie, Mengxing; Chen, Wei; Xu, Zhaoyi; Zheng, Shourong; Zhu, Dongqiang

    2014-01-01

    The main objective of this study was to understand the key factors and mechanisms controlling adsorption of sulfonamides to biochars. Batch adsorption experiments were performed for sulfamethoxazole and sulfapyridine to three pine-wood biochars prepared under different thermochemical conditions: pyrolysis at 400 °C (C400) and 500 °C (C500), and pyrolysis at 500 °C followed with hydrogenation (C500-H). For both sulfonamides, the adsorbent surface area-normalized adsorption was stronger to C500 than to C400. This is attributable to the enhanced π–π electron-donor–acceptor interaction with the carbon surface of C500 due to the higher degree of graphitization. Despite the relatively large difference in surface O-functionality content between C500 (12.2%) and C500-H (6.6%), the two biochars exhibited nearly identical adsorbent surface area-normalized adsorption, indicating negligible role of surface O-functionalities in the adsorption to these adsorbents. Effects of solution chemistry conditions (pH, Cu 2+ , and dissolved soil humic acid) on adsorption were examined. -- Highlights: • Adsorption to biochars is dominated by π–π electron-donor–acceptor (EDA) interaction. • Graphitic surfaces of biochars are predominant adsorption sites. • Surface O-functionalities of biochars play minor roles in adsorption. • Adsorption affinities are markedly affected by Cu ions and humic acids. -- Adsorption of sulfonamides to biochars is dominated by π–π electron-donor–acceptor (EDA) interaction with the graphitic surface

  9. Evaluation of ferrolysis in arsenate adsorption on the paddy soil derived from an Oxisol.

    Science.gov (United States)

    Jiang, Jun; Dai, Zhaoxia; Sun, Rui; Zhao, Zhenjie; Dong, Ying; Hong, Zhineng; Xu, Renkou

    2017-07-01

    Iron oxides are dominant effective adsorbents for arsenate in iron oxide-rich variable charge soils. Oxisol-derived paddy soils undergo intensive ferrolysis, which results in high leaching and transformation of iron oxides. However, little information is available concerning the effect of ferrolysis on arsenate adsorption by paddy soil and parent Oxisol. In the present study, we examined the arsenate affinity of soils using arsenate adsorption/desorption isotherms, zeta potential, adsorption kinetics, pH effect and phosphate competition experiments. Results showed that ferrolysis in an alternating flooding-drying Oxisol-derived paddy soil resulted in a significant decrease of free iron oxides and increase of amorphous iron oxides in the surface and subsurface layers. There were more reactive sites exposed on amorphous than on crystalline iron oxides. Therefore, disproportionate ratios of arsenate adsorption capacities and contents of free iron oxides were observed in the studied Oxisols compared with paddy soils. The Gibbs free energy values corroborated that both electrostatic and non-electrostatic adsorption mechanisms contributed to the arsenate adsorption by bulk soils, and the kinetic adsorption data further suggested that the rate-limiting step was chemisorption. The zeta potential of soil colloids decreased after arsenate was adsorbed on the surfaces, forming inner-sphere complexes and thus transferring their negative charges to the soil particle surfaces. The adsorption/desorption isotherms showed that non-electrostatic adsorption was the main mechanism responsible for arsenate binding to the Oxisol and derived paddy soils, representing 91.42-94.65% of the adsorption capacities. Further studies revealed that arsenate adsorption was greatly inhibited by increasing suspension pH and incorporation of phosphate. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Effect of Humid Aging on the Oxygen Adsorption in SnO₂ Gas Sensors.

    Science.gov (United States)

    Suematsu, Koichi; Ma, Nan; Watanabe, Ken; Yuasa, Masayoshi; Kida, Tetsuya; Shimanoe, Kengo

    2018-01-16

    To investigate the effect of aging at 580 °C in wet air (humid aging) on the oxygen adsorption on the surface of SnO₂ particles, the electric properties and the sensor response to hydrogen in dry and humid atmospheres for SnO₂ resistive-type gas sensors were evaluated. The electric resistance in dry and wet atmospheres at 350 °C was strongly increased by humid aging. From the results of oxygen partial pressure dependence of the electric resistance, the oxygen adsorption equilibrium constants ( K ₁; for O - adsorption, K ₂; for O 2- adsorption) were estimated on the basis of the theoretical model of oxygen adsorption. The K ₁ and K ₂ in dry and wet atmospheres at 350 °C were increased by humid aging at 580 °C, indicating an increase in the adsorption amount of both O - and O 2- . These results suggest that hydroxyl poisoning on the oxygen adsorption is suppressed by humid aging. The sensor response to hydrogen in dry and wet atmosphere at 350 °C was clearly improved by humid aging. Such an improvement of the sensor response seems to be caused by increasing the oxygen adsorption amount. Thus, the humid aging offers an effective way to improve the sensor response of SnO₂ resistive-type gas sensors in dry and wet atmospheres.

  11. Effect of Humid Aging on the Oxygen Adsorption in SnO2 Gas Sensors

    Directory of Open Access Journals (Sweden)

    Koichi Suematsu

    2018-01-01

    Full Text Available To investigate the effect of aging at 580 °C in wet air (humid aging on the oxygen adsorption on the surface of SnO2 particles, the electric properties and the sensor response to hydrogen in dry and humid atmospheres for SnO2 resistive-type gas sensors were evaluated. The electric resistance in dry and wet atmospheres at 350 °C was strongly increased by humid aging. From the results of oxygen partial pressure dependence of the electric resistance, the oxygen adsorption equilibrium constants (K1; for O− adsorption, K2; for O2− adsorption were estimated on the basis of the theoretical model of oxygen adsorption. The K1 and K2 in dry and wet atmospheres at 350 °C were increased by humid aging at 580 °C, indicating an increase in the adsorption amount of both O− and O2−. These results suggest that hydroxyl poisoning on the oxygen adsorption is suppressed by humid aging. The sensor response to hydrogen in dry and wet atmosphere at 350 °C was clearly improved by humid aging. Such an improvement of the sensor response seems to be caused by increasing the oxygen adsorption amount. Thus, the humid aging offers an effective way to improve the sensor response of SnO2 resistive-type gas sensors in dry and wet atmospheres.

  12. Inter-row Adsorption Configuration and Stability of Threonine Adsorbed on the Ge(100) Surfaces

    International Nuclear Information System (INIS)

    Lee, Myungjin; Park, Youngchan; Jeong, Hyuk; Lee, Hangil

    2013-01-01

    The adsorption structures of threonine on the Ge(100) surface were investigated using core-level photoemission spectroscopy (CLPES) in conjunction with density functional theory (DFT) calculations. CLPES measurements were performed to identify the experimentally preferred adsorption structure. The preferred structure indicated the relative reactivities of the carboxyl and hydroxymethyl groups as electron donors to the Ge(100) surface during adsorption. The core-level C 1s, N 1s, and O 1s CLPES spectra indicated that the carboxyl oxygen competed more strongly with the hydroxymethyl oxygen during the adsorption reaction. Three among six possible adsorption structures were identified as energetically favorable using DFT calculation methods that considered the inter- and intra-bonding configurations upon adsorption onto the Ge(100) surface. These structures were O-H dissociated N dative inter bonding, O-H dissociated N dative intra bonding, O-H dissociation bonding. One of the adsorption structures: O-H dissociated N dative inter bonding was predicted to be stable in light of the transition state energies. We thus confirmed that the most favorable adsorption structure is the O-H dissociated N dative-inter bonding structure using CLPES and DFT calculation

  13. Multifaceted adsorption of α-cyano-4-hydroxycinnamic acid on silver colloidal and island surfaces

    Science.gov (United States)

    Jung, Dawoon; Jeon, Kooknam; Yeo, Juhyun; Hussain, Shafqat; Pang, Yoonsoo

    2017-12-01

    The surface adsorption of organic nitrile compounds on the silver colloidal and island surfaces has been studied using surface-enhanced Raman scattering (SERS). α-Cyano-4-hydroxycinnamic acid (CHCA) with nitrile and carboxyl groups shows various surface adsorption on the silver surfaces. In acidic conditions, the surface adsorption of CHCA via the nitrile group with a more or less tilted geometry to the surface was found. When the solution pH increases, the carboxylate and nitrile groups of deprotonated CHCA participate in the surface adsorption, whereas the molecular plane of CHCA becomes more parallel to the surface. The ν(Ctbnd N) band in SERS of CHCA is the indicator of the surface adsorption geometry. The strongly red-shifted and broadened ν(Ctbnd N) band in SERS represents the surface adsorption via π-electrons of the Ctbnd N bond (side-on geometry; π-coordination). Nitriles adsorbed on the surface via the nonbonding electron pair of the nitrogen atom (end-on geometry; σ-coordination) often cause the blue-shifts and small band broadening in ν(Ctbnd N) in SERS. The surface adsorption geometry of organic nitriles based on many previous experimental results was further confirmed by the surface adsorption of CHCA on the silver island surfaces and dinitrile compounds on the silver colloidal surfaces.

  14. LIGO: The strong belief

    CERN Multimedia

    Antonella Del Rosso

    2016-01-01

    Twenty years of designing, building and testing a number of innovative technologies, with the strong belief that the endeavour would lead to a historic breakthrough. The Bulletin publishes an abstract of the Courier’s interview with Barry Barish, one of the founding fathers of LIGO.   The plots show the signals of gravitational waves detected by the twin LIGO observatories at Livingston, Louisiana, and Hanford, Washington. (Image: Caltech/MIT/LIGO Lab) On 11 February, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo collaborations published a historic paper in which they showed a gravitational signal emitted by the merger of two black holes. These results come after 20 years of hard work by a large collaboration of scientists operating the two LIGO observatories in the US. Barry Barish, Linde Professor of Physics, Emeritus at the California Institute of Technology and former Director of the Global Design Effort for the Internat...

  15. Strongly interacting Higgs bosons

    International Nuclear Information System (INIS)

    Appelquist, T.; Bernard, C.

    1980-01-01

    The sensitivity of present-energy weak interactions to a strongly interacting heavy-Higgs-boson sector is discussed. The gauged nonlinear sigma model, which is the limit of the linear model as the Higgs-boson mass goes to infinity, is used to organize and catalogue all possible heavy-Higgs-boson effects. As long as the SU(2)/sub L/ x SU(2)/sub R/ symmetry of the Higgs sector is preserved, these effects are found to be small, of the order of the square of the gauge coupling times logarithms (but not powers) of the Higgs-boson mass divided by the W mass. We work in the context of a simplified model with gauge group SU(2)/sub L/; the extension to SU(2)/sub L/ x U(1) is briefly discussed

  16. Fast gas adsorption measurements for complicated adsorption mechanisms

    NARCIS (Netherlands)

    Robens, E.; Poulis, J.A.; Massen, C.H.

    2000-01-01

    Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present paper, we discuss the applicability of this

  17. Adsorption characteristics of N-nitrosodimethylamine from aqueous solution on surface-modified activated carbons

    Energy Technology Data Exchange (ETDEWEB)

    Xiaodong, Dai [Chemistry and Chemical Engineering School, China University of Petroleum, Dongying 257061, Shandong (China); Institute for Sustainability and Innovation, Victoria University, Melbourne, VIC 8001 (Australia); Zou, Linda [SA Water Centre for Water Management and Reuse, University of South Australia, Adelaide, SA5095 (Australia); Zifeng, Yan [Chemistry and Chemical Engineering School, China University of Petroleum, Dongying 257061, Shandong (China); Millikan, Mary [Institute for Sustainability and Innovation, Victoria University, Melbourne, VIC 8001 (Australia)

    2009-08-30

    This study investigated the removal of N-nitrosodimethylamine (NDMA) by an adsorption mechanism using commercially available activated carbons and surface-modified activated carbons. The effects of the modification on the properties of the activated carbon were studied by N{sub 2} adsorption/desorption, Diffuse Reflectance Infrared Fourier Transmission (DRIFT) analysis and X-Ray Photoelectron Spectroscopy (XPS). Adsorption experiments revealed that the activated carbons demonstrated a greater capacity for NDMA adsorption capacity than can be achieved using zeolite. The equilibrium data was fitted to the Freundlich equation and it was found that the adsorption capacity was significantly influenced by the micropore size, relative pore volume and surface characteristics. Adsorption experiments were conducted using unmodified and modified activated carbons. The results indicated that the adsorption capacity of NDMA can be significantly improved by heat treatment and doping of TiO{sub 2} particles. This was because the surface treatments yielded more hydrophobic sites and fewer oxygen-containing surface functional groups, and consequently an increased capacity for NDMA adsorption.

  18. Adsorption characteristics of N-nitrosodimethylamine from aqueous solution on surface-modified activated carbons

    International Nuclear Information System (INIS)

    Dai Xiaodong; Zou, Linda; Yan Zifeng; Millikan, Mary

    2009-01-01

    This study investigated the removal of N-nitrosodimethylamine (NDMA) by an adsorption mechanism using commercially available activated carbons and surface-modified activated carbons. The effects of the modification on the properties of the activated carbon were studied by N 2 adsorption/desorption, Diffuse Reflectance Infrared Fourier Transmission (DRIFT) analysis and X-Ray Photoelectron Spectroscopy (XPS). Adsorption experiments revealed that the activated carbons demonstrated a greater capacity for NDMA adsorption capacity than can be achieved using zeolite. The equilibrium data was fitted to the Freundlich equation and it was found that the adsorption capacity was significantly influenced by the micropore size, relative pore volume and surface characteristics. Adsorption experiments were conducted using unmodified and modified activated carbons. The results indicated that the adsorption capacity of NDMA can be significantly improved by heat treatment and doping of TiO 2 particles. This was because the surface treatments yielded more hydrophobic sites and fewer oxygen-containing surface functional groups, and consequently an increased capacity for NDMA adsorption.

  19. Novel adsorptive ultrafiltration membranes derived from polyvinyltetrazole-co-polyacrylonitrile for Cu(II) ions removal

    KAUST Repository

    Kumar, Mahendra

    2016-05-04

    Novel adsorptive ultrafiltration membranes were manufactured from synthesized polyvinyltetrazole−co−polyacrylonitrile (PVT−co−PAN) by nonsolvent induced phase separation (NIPS). PVT−co−PAN with various degree of functionalization (DF) was synthesized via a [3+2] cycloaddition reaction at 60°C using a commercial PAN. PVT−co−PAN with varied DF was then explored to prepare adsorptive membranes. The membranes were characterized by surface zeta potential and static water contact angle measurements, scanning electron microscopy as well as atomic force microscopy (AFM) techniques. It was shown that PVT segments contributed to alter the pore size, charge and hydrophilic behavior of the membranes. The membranes became more negatively charged and hydrophilic after addition of PVT segments. The PVT segments in the membranes served as the major binding sites for adsorption of Cu(II) ions from aqueous solution. The maximum adsorption of Cu(II) ions by the membranes in static condition and in a continuous ultrafiltration of 10 ppm solution was attained at pH = 5. The adsorption data suggest that the Freundlich isotherm model describes well Cu(II) ions adsorption on the membranes from aqueous solution. The adsorption capacity obtained from the Freundlich isotherm model was 44.3 mg g−1; this value is higher than other membrane adsorption data reported in the literature. Overall, the membranes fabricated from PVT−co−PAN are attractive for efficient removal of heavy metal ions under the optimized conditions.

  20. Bovine serum albumin adsorption onto functionalized polystyrene lattices: A theoretical modeling approach and error analysis

    Science.gov (United States)

    Beragoui, Manel; Aguir, Chadlia; Khalfaoui, Mohamed; Enciso, Eduardo; Torralvo, Maria José; Duclaux, Laurent; Reinert, Laurence; Vayer, Marylène; Ben Lamine, Abdelmottaleb

    2015-03-01

    The present work involves the study of bovine serum albumin adsorption onto five functionalized polystyrene lattices. The adsorption measurements have been carried out using a quartz crystal microbalance. Poly(styrene-co-itaconic acid) was found to be an effective adsorbent for bovine serum albumin molecule adsorption. The experimental isotherm data were analyzed using theoretical models based on a statistical physics approach, namely monolayer, double layer with two successive energy levels, finite multilayer, and modified Brunauer-Emmet-Teller. The equilibrium data were then analyzed using five different non-linear error analysis methods and it was found that the finite multilayer model best describes the protein adsorption data. Surface characteristics, i.e., surface charge density and number density of surface carboxyl groups, were used to investigate their effect on the adsorption capacity. The combination of the results obtained from the number of adsorbed layers, the number of adsorbed molecules per site, and the thickness of the adsorbed bovine serum albumin layer allows us to predict that the adsorption of this protein molecule can also be distinguished by monolayer or multilayer adsorption with end-on, side-on, and overlap conformations. The magnitudes of the calculated adsorption energy indicate that bovine serum albumin molecules are physisorbed onto the adsorbent lattices.

  1. Novel adsorptive ultrafiltration membranes derived from polyvinyltetrazole-co-polyacrylonitrile for Cu(II) ions removal

    KAUST Repository

    Kumar, Mahendra; Shevate, Rahul; Hilke, Roland; Peinemann, Klaus-Viktor

    2016-01-01

    Novel adsorptive ultrafiltration membranes were manufactured from synthesized polyvinyltetrazole−co−polyacrylonitrile (PVT−co−PAN) by nonsolvent induced phase separation (NIPS). PVT−co−PAN with various degree of functionalization (DF) was synthesized via a [3+2] cycloaddition reaction at 60°C using a commercial PAN. PVT−co−PAN with varied DF was then explored to prepare adsorptive membranes. The membranes were characterized by surface zeta potential and static water contact angle measurements, scanning electron microscopy as well as atomic force microscopy (AFM) techniques. It was shown that PVT segments contributed to alter the pore size, charge and hydrophilic behavior of the membranes. The membranes became more negatively charged and hydrophilic after addition of PVT segments. The PVT segments in the membranes served as the major binding sites for adsorption of Cu(II) ions from aqueous solution. The maximum adsorption of Cu(II) ions by the membranes in static condition and in a continuous ultrafiltration of 10 ppm solution was attained at pH = 5. The adsorption data suggest that the Freundlich isotherm model describes well Cu(II) ions adsorption on the membranes from aqueous solution. The adsorption capacity obtained from the Freundlich isotherm model was 44.3 mg g−1; this value is higher than other membrane adsorption data reported in the literature. Overall, the membranes fabricated from PVT−co−PAN are attractive for efficient removal of heavy metal ions under the optimized conditions.

  2. Phosphate-mediated electrochemical adsorption of cisplatin on gold electrodes

    International Nuclear Information System (INIS)

    Kolodziej, Adam; Figueiredo, Marta C.; Koper, Marc T.M.; Fernandez-Trillo, Francisco; Rodriguez, Paramaconi

    2017-01-01

    Highlights: •The potential-dependent adsorption and deposition of cisplatin on polycrystalline gold electrode is mediated by the adsorption of phosphate anions on gold electrode. •Quantitative analysis suggests that the stoichiometry of the phosphate species and the cisplatin adsorbed was 1:1. •Upon reduction of the phosphate-mediated cisplatin adsorption, the platinum deposits are formed by 3D nanoclusters -- Abstract: This manuscript reports the potential-dependent adsorption and deposition of cisplatin on polycrystalline gold electrode. It was found that this process is mediated by the adsorption of phosphate anions on the gold electrode and that the maximum coverage of Pt adsorbed is given by the maximum coverage of phosphate adsorbed at a given potential. The interaction of cisplatin with the phosphate groups was confirmed by in situ FTIR spectroscopy under external reflexion configuration. Quantitative analysis suggests that the stoichiometry of the phosphate species and the cisplatin adsorbed was 1:1. Moreover, the relationship between the charge of the Pt deposited and the charge of the electrochemical surface area of the Pt deposited on the gold electrodes indicates that 3D nanoclusters of a few atoms of Pt were formed over the gold electrode upon the electrochemical reduction of the adsorbed cisplatin. The Pt nanoclusters formed under these conditions were later evaluated for the oxidation of a monolayer of carbon monoxide. The Pt nanoclusters showed a high overpotential for the oxidation of the carbon monoxide monolayer and the high oxidation overpotential was attributed to the absence of adsorption sites for OH species on the Pt clusters: only at potentials where the OH species are adsorbed at the edge between the Pt nanocluster and the gold support, the oxidation of the carbon monoxide on the Pt nanoparticles takes place.

  3. CONTAMINANT ADSORPTION AND OXIDATION VIA FENTON REACTION

    Science.gov (United States)

    A ground water treatment process is proposed involving two cgemical processes: adsorption and oxidation. Adsorption of an organic compound onto granulated activated carbon (GAC) containing iron conveniently results in immobilizing and concentrating contaminants from the ground w...

  4. Adsorption of selected emerging contaminants onto PAC and GAC: Equilibrium isotherms, kinetics, and effect of the water matrix.

    Science.gov (United States)

    Real, Francisco J; Benitez, F Javier; Acero, Juan L; Casas, Francisco

    2017-07-03

    The removal of three emerging contaminants (ECs) (amitriptyline hydrochloride (AH), methyl salicylate (MS) and 2-phenoxyethanol (PE)) dissolved in several water matrices by means of their adsorption onto powdered activated carbon (PAC) and granular activated carbon (GAC) has been investigated. When dissolved in ultrapure water, adsorption of the ECs followed the trend of AH > MS > PE, with a positive effect of the adsorbent dose. According to the analysis of the adsorption isotherms and adsorption kinetics, PAC showed strongly higher adsorption efficiency in both capacity and velocity of the adsorption, in agreement with its higher mesoporosity. Equilibrium isotherm data were fitted by Langmuir and Freundlich models. Pseudo-second order kinetics modeled very successfully the adsorption process. Finally, the effect of the presence of dissolved organic matter (DOM) in the water matrices (ultrapure water, surface water and two effluents from wastewater treatment plants) on the adsorption of the selected ECs onto PAC was established, as well as its performance on the removal of water quality parameters. Results show a negative effect of the DOM content on the adsorption efficiency. Over 50% of organic matter was removed with high PAC doses, revealing that adsorption onto PAC is an effective technology to remove both micro-pollutants and DOM from water matrices.

  5. Adsorption and activation of methane and methanol on Pt(100) surface: a density functional study

    International Nuclear Information System (INIS)

    Moussounda, P.S.

    2006-11-01

    The activation of methane (CH 4 ) and methanol (CH 3 OH) on Pt(100) surface has been investigated using density functional theory calculations based on plane-wave basis and pseudo-potential. We optimised CH 4 /Pt(100) system. The calculated adsorption energies over the top, bridge and hollow sites are small, weakly dependent on the molecular orientation. The nature of the CH 4 -Pt interaction was examined through the electronic structure changes. The adsorption of methyl (CH 3 ) and hydrogen (H) and the co-adsorption of CH 3 +H were also calculated. From these results, we examined the dissociation of CH 4 to CH 3 +H, and the activation energies found are in good agreement with the experimental and theoretical values. The activation of CH 3 OH/Pt(100) has been studied. All the sites have almost the same adsorption energy. The adsorption of oxygen (O) and the co-adsorption of CH 4 and O were also examined. In addition, the formation of CH 3 OH assuming a one-step mechanism step via the co-adsorption of CH 4 +O has been studied and the barrier height was found to be high. (authors)

  6. Reactive adsorption of SO2 on activated carbons with deposited iron nanoparticles.

    Science.gov (United States)

    Arcibar-Orozco, Javier A; Rangel-Mendez, J Rene; Bandosz, Teresa J

    2013-02-15

    The effect of iron particle size anchored on the surface of commercial activated carbon on the removal of SO(2) from a gas phase was studied. Nanosize iron particles were deposited using forced hydrolysis of FeCl(3) with or without H(3)PO(4) as a capping agent. Dynamic adsorption experiments were carried out on either dry or pre-humidified materials and the adsorption capacities were calculated. The surface of the initial and exhausted materials was extensively characterized by microscopic, porosity, thermogravimetric and surface chemistry. The results indicate that the SO(2) adsorption capacity increased two and half times after the prehumidification process owing to the formation of H(2)SO(4) in the porous system. Iron species enhance the SO(2) adsorption capacity only when very small nanoparticles are deposited on the pore walls as a thin layer. Large iron nanoparticles block the ultramicropores decreasing the accessibility of the active sites and consuming oxygen that rest adsorption centers for SO(2) molecules. Iron nanoparticles of about 3-4 nm provide highly dispersed adsorption sites for SO(2) molecules and thus increase the adsorption capacity of about 80%. Fe(2)(SO(4))(3) was detected on the surface of exhausted samples. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Theoretical study of adsorption of organic phosphines on transition metal surfaces

    Science.gov (United States)

    Lou, Shujie; Jiang, Hong

    2018-04-01

    The adsorption properties of organic phosphines on transition metal (TM) surfaces (Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) have been studied to explore the possibility of building novel heterogeneous chiral catalytic systems based on organic phosphines. Preferred adsorption sites, adsorption energies and surface electronic structures of a selected set of typical organic phosphines adsorbed on TM surfaces are calculated with density-functional theory to obtain a systematic understanding on the nature of adsorption interactions. All organic phosphines considered are found to chemically adsorb on these TM surfaces with the atop site as the most preferred one, and the TM-P bond is formed via the lone-pair electrons of the P atom and the directly contacted TM atom. These findings imply that it is indeed possible to build heterogeneous chiral catalytic systems based on organic phosphines adsorbed on TM surfaces, which, however, requires a careful design of molecular structure of organic phosphines.

  8. ADSORPTION MALACHITE GREEN ON NATURAL ZEOLITE

    OpenAIRE

    Eko Ariyanto

    2012-01-01

    A natural zeolite was employed as adsorbent for reducing of malachite green from aqueous solution. A batch system was applied to study the adsorption of malachite green in single system on natural zeolite. The adsorption studies indicate that malachite green in single component system follows the second-order kinetics and the adsorption is diffusion process with two stages for malachite green. Malachite green adsorption isotherm follows the Langmuir model.

  9. ADSORPTION MALACHITE GREEN ON NATURAL ZEOLITE

    Directory of Open Access Journals (Sweden)

    Eko Ariyanto