Competitive Adsorption between Nanoparticles and Surface Active Ions for the Oil-Water Interface.

Science.gov (United States)

Hua, Xiaoqing; Bevan, Michael A; Frechette, Joelle

2018-04-24

Nanoparticles (NPs) can add functionality (e.g., catalytic, optical, rheological) to an oil-water interface. Adsorption of ∼10 nm NPs can be reversible; however, the mechanisms for adsorption and its effects on surface pressure remain poorly understood. Here we demonstrate how the competitive reversible adsorption of NPs and surfactants at fluid interfaces can lead to independent control of both the adsorbed amount and surface pressure. In contrast to prior work, both species investigated (NPs and surfactants) interact reversibly with the interface and without the surface active species binding to NPs. Independent measurements of the adsorption and surface pressure isotherms allow determination of the equation of state (EOS) of the interface under conditions where the NPs and surfactants are both in dynamic equilibrium with the bulk phase. The adsorption and surface pressure measurements are performed with gold NPs of two different sizes (5 and 10 nm), at two pH values, and across a wide concentration range of surfactant (tetrapentylammonium, TPeA + ) and NPs. We show that free surface active ions compete with NPs for the interface and give rise to larger surface pressures upon the adsorption of NPs. Through a competitive adsorption model, we decouple the contributions of NPs wetting at the interface and their surface activity on the measured surface pressure. We also demonstrate reversible control of adsorbed amount via changes in the surfactant concentration or the aqueous phase pH.

Noncompetitive and Competitive Adsorption of Heavy Metals in Sulfur-Functionalized Ordered Mesoporous Carbon.

Science.gov (United States)

Saha, Dipendu; Barakat, Soukaina; Van Bramer, Scott E; Nelson, Karl A; Hensley, Dale K; Chen, Jihua

2016-12-14

In this work, sulfur-functionalized ordered mesoporous carbons were synthesized by activating the soft-templated mesoporous carbons with sulfur bearing salts that simultaneously enhanced the surface area and introduced sulfur functionalities onto the parent carbon surface. XPS analysis showed that sulfur content within the mesoporous carbons were between 8.2% and 12.9%. The sulfur functionalities include C-S, C═S, -COS, and SO x . SEM images confirmed the ordered mesoporosity within the material. The BET surface areas of the sulfur-functionalized ordered mesoporous carbons range from 837 to 2865 m 2 /g with total pore volume of 0.71-2.3 cm 3 /g. The carbon with highest sulfur functionality was examined for aqueous phase adsorption of mercury (as HgCl 2 ), lead (as Pb(NO 3 ) 2 ), cadmium (as CdCl 2 ), and nickel (as NiCl 2 ) ions in both noncompetitive and competitive mode. Under noncompetitive mode and at a pH greater than 7.0 the affinity of sulfur-functionalized carbons toward heavy metals were in the order of Hg > Pb > Cd > Ni. At lower pH, the adsorbent switched its affinity between Pb and Cd. In the noncompetitive mode, Hg and Pb adsorption showed a strong pH dependency whereas Cd and Ni adsorption did not demonstrate a significant influence of pH. The distribution coefficient for noncompetitive adsorption was in the range of 2448-4000 mL/g for Hg, 290-1990 mL/g for Pb, 550-560 mL/g for Cd, and 115-147 for Ni. The kinetics of adsorption suggested a pseudo-second-order model fits better than other models for all the metals. XPS analysis of metal-adsorption carbons suggested that 7-8% of the adsorbed Hg was converted to HgSO 4 , 14% and 2% of Pb was converted to PbSO 4 and PbS/PbO, respectively, and 5% Cd was converted to CdSO 4 . Ni was below the detection limit for XPS. Overall results suggested these carbon materials might be useful for the separation of heavy metals.

Competitive and Cooperative Effects during Nickel Adsorption to Iron Oxides in the Presence of Oxalate

Energy Technology Data Exchange (ETDEWEB)

Flynn, Elaine D. [Department of Earth and Planetary; Catalano, Jeffrey G. [Department of Earth and Planetary

2017-08-09

Iron oxides are ubiquitous in soils and sediments and play a critical role in the geochemical distribution of trace elements and heavy metals via adsorption and coprecipitation. The presence of organic acids may potentially alter how metals associate with iron oxide minerals through a series of cooperative or competitive processes: solution complexation, ternary surface complexation, and surface site competition. The macroscopic and molecular-scale effects of these processes were investigated for Ni adsorption to hematite and goethite at pH 7 in the presence of oxalate. The addition of this organic acid suppresses Ni uptake on both minerals. Aqueous speciation suggests that this is dominantly the result of oxalate complexing and solubilizing Ni. Comparison of the Ni surface coverage to the concentration of free (uncomplexed) Ni²⁺ in solution suggests that the oxalate also alters Ni adsorption affinity. EXAFS and ATR-FTIR spectroscopies indicate that these changes in binding affinity are due to the formation of Ni–oxalate ternary surface complexes. These observations demonstrate that competition between dissolved oxalate and the mineral surface for Ni overwhelms the enhancement in adsorption associated with ternary complexation. Oxalate thus largely enhances Ni mobility, thereby increasing micronutrient bioavailability and inhibiting contaminant sequestration.

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.

Adsorption of CO, CO2, H2, and H2O on titania surfaces with different oxidation states

International Nuclear Information System (INIS)

Raupp, G.B.; Dumesic, J.A.

1985-01-01

The adsorptive properties of titania surfaces with different oxidation states were proved by temperature-programmed desorption (TPD) of CO, H 2 , CO 2 , and H 2 O. Auger electron spectroscopy and X-ray photoelectron spectroscopy revealed that vacuum annealing an oxidized titanium foil at temperatures from 300 to 800 K was an effective means of systematically varying the average surface oxidation state from Ti 4+ to Ti 2+ . Carbon monoxide weakly adsorbed (desorption energy of 44-49 kJ x mol -1 ) in a carbonyl fashion on coordinatively unsaturated cation sites. Titania surfaces were inert with respect to H 2 adsorption and dissociation. Carbon dioxide adsorbed in a linear molecular fashion. Water adsorbed both molecularly and dissociatively. Results are discussed in terms of the role of titania oxidation state in CO hydrogenation over titania-supported metal catalysts. 74 references, 7 figures

Adsorption of tetracycline on Fe (hydr)oxides: effects of pH and metal cation (Cu2+, Zn2+ and Al3+) addition in various molar ratios

Science.gov (United States)

Hsu, Liang-Ching; Liu, Yu-Ting; Syu, Chien-Hui; Huang, Mei-Hsia; Teah, Heng Yi

2018-01-01

Iron (Fe) (hydr)oxides control the mobility and bioavailability of tetracycline (TC) in waters and soils. Adsorption of TC on Fe (hydr)oxides is greatly affected by polyvalent metals; however, impacts of molar metal/TC ratios on TC adsorptive behaviours on Fe (hydr)oxides remain unclear. Results showed that maximum TC adsorption on ferrihydrite and goethite occurred at pH 5–6. Such TC adsorption was generally promoted by the addition of Cu2+, Zn2+ and Al3+. The greatest increase in TC adsorption was found in the system with molar Cu/TC ratio of 3 due to the formation of Fe hydr(oxide)–Cu–TC ternary complexes. Functional groups on TC that were responsible for the complexation with Cu2+shifted from phenolic diketone groups at Cu/TC molar ratio adsorption at a molar Al/TC ratio of 1. However, TC adsorption decreased for Al/TC molar ratio > 1 as excess Al3+ led to the competitive adsorption with Al/TC complexes. For the Zn2+ addition, no significant correlation was found between TC adsorption capacity and molar Zn/TC ratios. PMID:29657795

Competitive adsorption of heavy metals by extracellular polymeric substances extracted from Klebsiella sp. J1.

Science.gov (United States)

Yang, Jixian; Wei, Wei; Pi, Shanshan; Ma, Fang; Li, Ang; Wu, Dan; Xing, Jie

2015-11-01

The adsorption of Cu(2+) and Zn(2+) by extracellular polymeric substances (EPS) extracted from Klebsiella sp. J1 and competitive adsorption mechanism were investigated. Equilibrium adsorption capacities of Cu(2+) (1.77mMg(-1)) on Klebsiella sp. J1 EPS were higher than those of Zn(2+) (1.36mMg(-1)) in single systems. The competitive Langmuir and Langmuir-Freundlich isotherm models were proven to be effective in describing the experimental data of binary component system. The three dimensional sorption surfaces of binary component system demonstrated that the presence of Cu(2+) more significantly decreased the sorption of Zn(2+), but the sorption of Cu(2+) was not disturbed by the presence of Zn(2+). FTIR and EEM results revealed the adsorption sites of Cu(2+) entirely overlapped with those of Zn(2+). Cu(2+) and Zn(2+) showed competitive adsorption in binary systems, and Cu(2+) was preferentially adsorbed because of the stronger complexation ability of the protein-like substances in Klebsiella sp. J1 EPS. Copyright © 2015 Elsevier Ltd. All rights reserved.

Adsorption, hydrogenation and dehydrogenation of C2H on a CoCu bimetallic layer

Science.gov (United States)

Wu, Donghai; Yuan, Jinyun; Yang, Baocheng; Chen, Houyang

2018-05-01

In this paper, adsorption, hydrogenation and dehydrogenation of C2H on a single atomic layer of bimetallic CoCu were investigated using first-principles calculations. The CoCu bimetallic layer is formed by Cu replacement of partial Co atoms on the top layer of a Co(111) surface. Our adsorption and reaction results showed those sites, which have stronger adsorption energy of C2H, possess higher reactivity. The bimetallic layer possesses higher reactivity than either of the pure monometallic layer. A mechanism of higher reactivity of the bimetallic layer is proposed and identified, i.e. in the bimetallic catalyst, the catalytic performance of one component is promoted by the second component, and in our work, the catalytic performance of Co atoms in the bimetallic layer are improved by introducing Cu atoms, lowing the activation barrier of the reaction of C2H. The bimetallic layer could tune adsorption and reaction of C2H by modulating the ratio of Co and Cu. Results of adsorption energies and adsorption configurations reveal that C2H prefers to be adsorbed in parallel on both the pure Co metallic and CoCu bimetallic layers, and Co atoms in subsurface which support the metallic or bimetallic layer have little effect on C2H adsorption. For hydrogenation reactions, the products greatly depend on the concentration and initial positions of hydrogen atoms, and the C2H hydrogenation forming acetylene is more favorable than forming vinylidene in both thermodynamics and kinetics. This study would provide fundamental guidance for hydrocarbon reactions on Co-based and/or Cu-based bimetallic surface chemistry and for development of new bimetallic catalysts.

Competitive adsorption of heavy metals onto sesame straw biochar in aqueous solutions.

Science.gov (United States)

Park, Jong-Hwan; Ok, Yong Sik; Kim, Seong-Heon; Cho, Ju-Sik; Heo, Jong-Soo; Delaune, Ronald D; Seo, Dong-Cheol

2016-01-01

Objective of this research was to evaluate adsorption of heavy metals in mono and multimetal forms onto sesame straw biochar (SSB). Competitive sorption of metals by SSB has never been reported previously. The maximum adsorption capacities (mgg(-1)) of metals by SSB were in the order of Pb (102)≫Cd (86)≫Cr (65)>Cu (55)≫Zn (34) in the monometal adsorption isotherm and Pb (88)≫Cu (40)≫Cr (21)>Zn (7)⩾Cd (5) in the multimetal adsorption isotherm. Based on data obtained from the distribution coefficients, Freundlich and Langmuir adsorption models, and three-dimensional simulation, multimetal adsorption behaviors differed from monometal adsorption due to competition. Especially, during multimetal adsorption, Cd was easily exchanged and substituted by other metals. Further competitive adsorption studies are necessary in order to accurately estimate the heavy metal adsorption capacity of biochar in natural environments. Copyright © 2015 Elsevier Ltd. All rights reserved.

Adsorption of H2O and CO2 on supported amine sorbents

NARCIS (Netherlands)

Veneman, Rens; Frigka, Natalia; Zhao, Wenying; Li, Zhenshan; Kersten, Sascha R.A.; Brilman, Derk Willem Frederik

2015-01-01

In this work the adsorption of H2O and CO2 on Lewatit VP OC 1065 was studied in view of the potential application of this sorbent in post combustion CO2 capture. Both CO2 and H2O were found to adsorb on the amine active sites present on the pore surface of the sorbent material. However, where the

Amine–mixed oxide hybrid materials for carbon dioxide adsorption from CO2/H2 mixture

Science.gov (United States)

Ravi, Navin; Aishah Anuar, Siti; Yusuf, Nur Yusra Mt; Isahak, Wan Nor Roslam Wan; Shahbudin Masdar, Mohd

2018-05-01

Bio-hydrogen mainly contains hydrogen and high level of carbon dioxide (CO2). High concentration of CO2 lead to a limitation especially in fuel cell application. In this study, the amine-mixed oxide hybrid materials for CO2 separation from bio-hydrogen model (50% CO2:50% H2) have been studied. Fourier-transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) characterizations showed that the amine–mixed oxide hybrid materials successfully adsorbed CO2 physically with no chemical adsorption evidence. The dry gas of CO2/H2 mixture adsorbed physically on amine–CuO–MgO hybrid material. No carbonates were detected after several times of adsorption, which indicated the good recyclability of adsorbents. The adsorbent system of diethanolamine (DEA)/15% CuO–75% MgO showed the highest CO2 adsorption capacity of 21.2 wt% due to the presence of polar substance on MgO surface, which can adsorb CO2 at ambient condition. The alcohol group of DEA can enhance the CO2 solubility on the adsorbent surface. In the 20% CuO–50% MgO adsorbent system, DEA as amine type showed a high CO2 adsorption of 19.4 wt%. The 10% amine loading system showed that the DEA adsorption system provided high CO2 adsorption. The BET analysis confirmed that a high amine loading contributed to the decrease in CO2 adsorption due to the low surface area of the adsorbent system.

Biochars as Potential Adsorbers of CH4, CO2 and H2S

Directory of Open Access Journals (Sweden)

Sumathi Sethupathi

2017-01-01

Full Text Available Methane gas, as one of the major biogases, is a potential source of renewable energy for power production. Biochar can be readily used to purify biogas contaminants such as H2S and CO2. This study assessed the adsorption of CH4, H2S, and CO2 onto four different types of biochars. The adsorption dynamics of biochars were investigated in a fixed-bed column, by determining the breakthrough curves and adsorption capacities of biochars. The physicochemical properties of biochars were considered to justify the adsorption performance. The results showed that CH4 was not adsorbed well by the subjected biochars whereas CO2 and H2S were successfully captured. The H2S and CO2 breakthrough capacity were related to both the surface adsorption and chemical reaction. The adsorption capacity was in the following order: perilla > soybean stover > Korean oak > Japanese oak biochars. The simultaneous adsorption also leads to a competition of sorption sites. Biochars are a promising material for the biogas purification industry.

CO2/H2O adsorption equilibrium and rates on metal-organic frameworks: HKUST-1 and Ni/DOBDC.

Science.gov (United States)

Liu, Jian; Wang, Yu; Benin, Annabelle I; Jakubczak, Paulina; Willis, Richard R; LeVan, M Douglas

2010-09-07

Metal-organic frameworks (MOFs) have recently attracted intense research interest because of their permanent porous structures, huge surface areas, and potential applications as novel adsorbents and catalysts. In order to provide a basis for consideration of MOFs for removal of carbon dioxide from gases containing water vapor, such as flue gas, we have studied adsorption equilibrium of CO(2), H(2)O vapor, and their mixtures and also rates of CO(2) adsorption in two MOFs: HKUST-1 (CuBTC) and Ni/DOBDC (CPO-27-Ni or Ni/MOF-74). The MOFs were synthesized via solvothermal methods, and the as-synthesized products were solvent exchanged and regenerated before experiments. Pure component adsorption equilibria and CO(2)/H(2)O binary adsorption equilibria were studied using a volumetric system. The effects of H(2)O adsorption on CO(2) adsorption for both MOF samples were determined, and the results for 5A and NaX zeolites were included for comparison. The hydrothermal stabilities for the two MOFs over the course of repetitive measurements of H(2)O and CO(2)/H(2)O mixture equilibria were also studied. CO(2) adsorption rates from helium for the MOF samples were investigated by using a unique concentration-swing frequency response (CSFR) system. Mass transfer into the MOFs is rapid with the controlling resistance found to be macropore diffusion, and rate parameters were established for the mechanism.

Competitive adsorption of a two-component gas on a deformable adsorbent

International Nuclear Information System (INIS)

Usenko, A S

2014-01-01

We investigate the competitive adsorption of a two-component gas on the surface of an adsorbent whose adsorption properties vary due to the adsorbent deformation. The essential difference of adsorption isotherms for a deformable adsorbent both from the classical Langmuir adsorption isotherms of a two-component gas and from the adsorption isotherms of a one-component gas is obtained, taking into account variations in the adsorption properties of the adsorbent in adsorption. We establish bistability and tristability of the system caused by variations in adsorption properties of the adsorbent in competitive adsorption of gas particles on it. We derive conditions under which adsorption isotherms of a binary gas mixture have two stable asymptotes. It is shown that the specific features of the behavior of the system under study can be described in terms of a potential of the known explicit form. (paper)

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.

Enhancement of the secondary ion emission from Si by O/sub 2 and H/sub 2/O adsorption

International Nuclear Information System (INIS)

Huan, C.H.; Wee, A.T.S.; Tan, K.L.

1992-01-01

The positive and negative secondary ion emission of Si are examined as a function of O/sub 2 and H/sub 2/O surface coverage under conditions of simultaneous adsorption and Ar/sup+ ion bombardment. It is found that the ion-molecule mechanism accounts for the adsorbate-induced signals and that yield enhancement by H/sub 2/O adsorption is less effective than O/sub 2 adsorption. (authors)

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.

Experimental Microkinetic Approach of De-NO x by NH 3 on V 2 O 5 /WO 3 /TiO 2 Catalysts. 4. Individual Heats of Adsorption of Adsorbed H 2 O Species on Sulfate-Free and Sulfated TiO 2 Supports

KAUST Repository

Giraud, Franç ois; Couble, Julien; Geantet, Christophe; Guilhaume, Nolven; Puzenat, Eric; Gros, Sé bastien; Porcheron, Lynda; Kanniche, Mohamed; Bianchi, Daniel

2015-01-01

© 2015 American Chemical Society. The present study is a part of an experimental microkinetic approach of the removal of NOx from coal-fired power plants by reduction with NH3 on V2O5/WO3/TiO2 catalysts (NH3-selective catalytic reduction, NH3-SCR). It is dedicated to the characterization of the heats of adsorption of molecularly adsorbed H2Oads species formed on sulfate-free and sulfated TiO2 supports. Water, which is always present during the NH3-SCR, may be in competition and/or react (formation of NH4⁺) with the adsorbed NH3 species controlling the coverage of the adsorbed intermediate species of the reaction. Mainly, an original experimental procedure named adsorption equilibrium infrared spectroscopy (AEIR) previously used for the adsorption of NH3 species on the same solids is adapted for the adsorption of H2O. At Ta = 300 K and for PH2 O ≤ 1 kPa, three main H2Oads species are formed (associated with a minor amount of dissociated H2O species) on the two TiO2 solids. The species are identified by the positions of their IR bands in the 3750-3000 cm^-1 range. Considering the decreasing order of stability, they are (a) coordinated to strong (L2) and weak (L1) Lewis sites and denoted H2O ads-L2 and H2Oads-L1, respectively, and (b) hydrogen bonded to the H2Oads-L species and on O^2-/OH sites of the solids (denoted H2Owads). The three species have a common well-defined δH2O IR band at a position in the range 1640-1610 cm^-1 according to the total coverage of the surface. According to the AEIR method, the evolution of the intensity of this IR band during the increase in the adsorption temperature Ta in isobaric condition provides the evolution of the average coverage of the three species and then to their individual heats of adsorption as a function of their coverage. It is shown that there are no significant differences on the two TiO2 solids. In particular, the heat of adsorption of the H2Oads-L2 species varies from �

Experimental Microkinetic Approach of De-NO x by NH 3 on V 2 O 5 /WO 3 /TiO 2 Catalysts. 4. Individual Heats of Adsorption of Adsorbed H 2 O Species on Sulfate-Free and Sulfated TiO 2 Supports

KAUST Repository

Giraud, François

2015-07-16

© 2015 American Chemical Society. The present study is a part of an experimental microkinetic approach of the removal of NOx from coal-fired power plants by reduction with NH3 on V2O5/WO3/TiO2 catalysts (NH3-selective catalytic reduction, NH3-SCR). It is dedicated to the characterization of the heats of adsorption of molecularly adsorbed H2Oads species formed on sulfate-free and sulfated TiO2 supports. Water, which is always present during the NH3-SCR, may be in competition and/or react (formation of NH4⁺) with the adsorbed NH3 species controlling the coverage of the adsorbed intermediate species of the reaction. Mainly, an original experimental procedure named adsorption equilibrium infrared spectroscopy (AEIR) previously used for the adsorption of NH3 species on the same solids is adapted for the adsorption of H2O. At Ta = 300 K and for PH2 O ≤ 1 kPa, three main H2Oads species are formed (associated with a minor amount of dissociated H2O species) on the two TiO2 solids. The species are identified by the positions of their IR bands in the 3750-3000 cm^-1 range. Considering the decreasing order of stability, they are (a) coordinated to strong (L2) and weak (L1) Lewis sites and denoted H2O ads-L2 and H2Oads-L1, respectively, and (b) hydrogen bonded to the H2Oads-L species and on O^2-/OH sites of the solids (denoted H2Owads). The three species have a common well-defined δH2O IR band at a position in the range 1640-1610 cm^-1 according to the total coverage of the surface. According to the AEIR method, the evolution of the intensity of this IR band during the increase in the adsorption temperature Ta in isobaric condition provides the evolution of the average coverage of the three species and then to their individual heats of adsorption as a function of their coverage. It is shown that there are no significant differences on the two TiO2 solids. In particular, the heat of adsorption of the H2Oads-L2 species varies from �

Synthesis of Zeolite-X from Bottom Ash for H2 Adsorption

Science.gov (United States)

Kurniawan, R. Y.; Romadiansyah, T. Q.; Tsamarah, A. D.; Widiastuti, N.

2018-01-01

Zeolite-X was synthesized from bottom ash power plant waste using fusion method on air atmosphere. The fused product dissolved in demineralized water and aluminate solution was added to adjust the SiO2/Al2O3 molar ratio gel prior hydrothermal process. The synthesis results were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Fourier Transform Infrared (FTIR). The results showed that the zeolite-X has a high crystallinity with octahedral particle. The pure-form zeolite-X then was characterized and tested for H2 gas adsorption by gravimetric method to determine the H2 gas adsorption capacity of zeolite-X from bottom ash and it was compared to synthetic zeolite-X.

Competitive adsorption of copper(II), cadmium(II), lead(II) and zinc(II) onto basic oxygen furnace slag

International Nuclear Information System (INIS)

Xue Yongjie; Hou Haobo; Zhu Shujing

2009-01-01

Polluted and contaminated water can often contain more than one heavy metal species. It is possible that the behavior of a particular metal species in a solution system will be affected by the presence of other metals. In this study, we have investigated the adsorption of Cd(II), Cu(II), Pb(II), and Zn(II) onto basic oxygen furnace slag (BOF slag) in single- and multi-element solution systems as a function of pH and concentration, in a background solution of 0.01 M NaNO 3 . In adsorption edge experiments, the pH was varied from 2.0 to 13.0 with total metal concentration 0.84 mM in the single element system and 0.21 mM each of Cd(II), Cu(II), Pb(II), and Zn(II) in the multi-element system. The value of pH 50 (the pH at which 50% adsorption occurs) was found to follow the sequence Zn > Cu > Pb > Cd in single-element systems, but Pb > Cu > Zn > Cd in the multi-element system. Adsorption isotherms at pH 6.0 in the multi-element systems showed that there is competition among various metals for adsorption sites on BOF slag. The adsorption and potentiometric titrations data for various slag-metal systems were modeled using an extended constant-capacitance surface complexation model that assumed an ion-exchange process below pH 6.5 and the formation of inner-sphere surface complexes at higher pH. Inner-sphere complexation was more dominant for the Cu(II), Pb(II) and Zn(II) systems

Competitive adsorption of copper(II), cadmium(II), lead(II) and zinc(II) onto basic oxygen furnace slag

Energy Technology Data Exchange (ETDEWEB)

Xue Yongjie [School of Resource and Environment Science, Wuhan University, Hubei, Wuhan (China); Wuhan Kaidi Electric Power Environmental Protection Co. Ltd., Hubei, Wuhan (China)], E-mail: xueyj@mail.whut.edu.cn; Hou Haobo; Zhu Shujing [School of Resource and Environment Science, Wuhan University, Hubei, Wuhan (China)

2009-02-15

Polluted and contaminated water can often contain more than one heavy metal species. It is possible that the behavior of a particular metal species in a solution system will be affected by the presence of other metals. In this study, we have investigated the adsorption of Cd(II), Cu(II), Pb(II), and Zn(II) onto basic oxygen furnace slag (BOF slag) in single- and multi-element solution systems as a function of pH and concentration, in a background solution of 0.01 M NaNO{sub 3}. In adsorption edge experiments, the pH was varied from 2.0 to 13.0 with total metal concentration 0.84 mM in the single element system and 0.21 mM each of Cd(II), Cu(II), Pb(II), and Zn(II) in the multi-element system. The value of pH{sub 50} (the pH at which 50% adsorption occurs) was found to follow the sequence Zn > Cu > Pb > Cd in single-element systems, but Pb > Cu > Zn > Cd in the multi-element system. Adsorption isotherms at pH 6.0 in the multi-element systems showed that there is competition among various metals for adsorption sites on BOF slag. The adsorption and potentiometric titrations data for various slag-metal systems were modeled using an extended constant-capacitance surface complexation model that assumed an ion-exchange process below pH 6.5 and the formation of inner-sphere surface complexes at higher pH. Inner-sphere complexation was more dominant for the Cu(II), Pb(II) and Zn(II) systems.

Competitive adsorption of copper(II), cadmium(II), lead(II) and zinc(II) onto basic oxygen furnace slag.

Science.gov (United States)

Xue, Yongjie; Hou, Haobo; Zhu, Shujing

2009-02-15

Polluted and contaminated water can often contain more than one heavy metal species. It is possible that the behavior of a particular metal species in a solution system will be affected by the presence of other metals. In this study, we have investigated the adsorption of Cd(II), Cu(II), Pb(II), and Zn(II) onto basic oxygen furnace slag (BOF slag) in single- and multi-element solution systems as a function of pH and concentration, in a background solution of 0.01M NaNO(3). In adsorption edge experiments, the pH was varied from 2.0 to 13.0 with total metal concentration 0.84mM in the single element system and 0.21mM each of Cd(II), Cu(II), Pb(II), and Zn(II) in the multi-element system. The value of pH(50) (the pH at which 50% adsorption occurs) was found to follow the sequence Zn>Cu>Pb>Cd in single-element systems, but Pb>Cu>Zn>Cd in the multi-element system. Adsorption isotherms at pH 6.0 in the multi-element systems showed that there is competition among various metals for adsorption sites on BOF slag. The adsorption and potentiometric titrations data for various slag-metal systems were modeled using an extended constant-capacitance surface complexation model that assumed an ion-exchange process below pH 6.5 and the formation of inner-sphere surface complexes at higher pH. Inner-sphere complexation was more dominant for the Cu(II), Pb(II) and Zn(II) systems.

Competitive Adsorption of Metals onto Magnetic Graphene Oxide: Comparison with Other Carbonaceous Adsorbents

Directory of Open Access Journals (Sweden)

Jin Hur

2015-01-01

Full Text Available Competitive adsorption isotherms of Cu(II, Pb(II, and Cd(II were examined on a magnetic graphene oxide (GO, multiwalled carbon nanotubes (MWCNTs, and powered activated carbon (PAC. A series of analyses confirmed the successful synthesis of the magnetic GO based on a simple ultrasonification method. Irrespective of the adsorbents, the adsorption was highly dependent on pH, and the adsorption was well described by the Langmuir isotherm model. The maximum adsorption capacities of the adsorbents were generally higher in the order of Pb(II > Cu(II > Cd(II, which is the same as the degree of the electronegativity and the hydrated radius of the metals, suggesting that the metal adsorption may be governed by an ion exchange between positively charged metals and negatively charged surfaces, as well as diffusion of metals into the surface layer. The adsorption of each metal was mostly lower for multi- versus single-metal systems. The antagonistic effects were influenced by solution pH as well as the type of metals, and they were higher in the order of the magnetic GO > MWCNT > PAC. Dissolved HS played a greater role than HS adsorbed onto the adsorbents, competing with the adsorption sites for metal complexation.

Application of AlMCM-41 for competitive adsorption of methylene blue and rhodamine B: Thermodynamic and kinetic studies

International Nuclear Information System (INIS)

Eftekhari, S.; Habibi-Yangjeh, A.; Sohrabnezhad, Sh.

2010-01-01

AlMCM-41 was applied for adsorption of methylene blue (MB) and rhodamine B (RB) in single and binary component systems. In the single component systems, AlMCM-41 represents higher adsorption capacity for MB than RB with the maximal adsorption capacity of 2.08 x 10 -4 and 8.74 x 10 -5 mol/g at 25 deg. C for MB and RB, respectively. In the binary component system, MB and RB exhibit competitive adsorption onto the adsorbent. The adsorption is approximately reduced to 94 and 79% of single component adsorption systems for MB and RB (initial concentration of 8 x 10 -6 M) at 25 deg. C. In single and binary component systems, kinetic and adsorption isotherm studies demonstrate that the data are following pseudo-second-order kinetic model and Langmuir isotherm. Effect of solution pH on the adsorption in single and binary component systems was studied and the results were described by electrostatic interactions.

Competitive Adsorption of a Two-Component Gas on a Deformable Adsorbent

OpenAIRE

Usenko, A. S.

2013-01-01

We investigate the competitive adsorption of a two-component gas on the surface of an adsorbent whose adsorption properties vary in adsorption due to the adsorbent deformation. The essential difference of adsorption isotherms for a deformable adsorbent both from the classical Langmuir adsorption isotherms of a two-component gas and from the adsorption isotherms of a one-component gas taking into account variations in adsorption properties of the adsorbent in adsorption is obtained. We establi...

Competitive protein adsorption to polymer surface from human serum

DEFF Research Database (Denmark)

Holmberg, Maria; Jensen, Karin Bagger Stibius; Larsen, Niels Bent

2008-01-01

Surface modification by "soft" plasma polymerisation to obtain a hydrophilic and non-fouling polymer surface has been validated using radioactive labelling. Adsorption to unmodified and modified polymer surfaces, from both single protein and human serum solutions, has been investigated. By using...... different radioisotopes, albumin and Immunoglobulin G (IgG) adsorption has been monitored simultaneously during competitive adsorption processes, which to our knowledge has not been reported in the literature before. Results show that albumin and IgG adsorption is dependent on adsorption time...... and on the presence and concentration of other proteins in bulk solutions during adsorption. Generally, lower albumin and IgG adsorption was observed on the modified and more hydrophilic polymer surfaces, but otherwise the modified and unmodified polymer surfaces showed the same adsorption characteristics....

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.

Adsorption and dissociation of H{sub 2}S on Mo{sub 2}C(001) surface-A first-principle study

Energy Technology Data Exchange (ETDEWEB)

Fu, Dianling; Guo, Wenyue, E-mail: wyguo@upc.edu.cn; Liu, Yunjie; Chi, Yuhua

2015-10-01

Highlights: • Adsorption of reactants, intermediates involved was investigated. • The Mulliken charge and partial density of states were analyzed. • The dissociation mechanism was investigated. • The optimal pathway for the dissociation of H{sub 2}S on the Mo{sub 2}C(001) surface was given. - Abstract: The adsorption and decomposition reaction mechanisms of H{sub 2}S on Mo{sub 2}C(001) has been systematically studied using self-consistent periodic density functional theory. Results show that the molecular of H{sub 2}S is adsorbed either on the Mo top site or bridge site. Mulliken population analysis and density of states for H{sub 2}S/Mo-terminated Mo{sub 2}C(001) adsorption system are examined to confirm the adsorption mechanism of H{sub 2}S with the Mo{sub 2}C(001) surface, which can involve the donation of charge from the “s lone pair electrons” that are LUMO orbitals into the surface and the back donation of electrons from the surface into the HOMO orbital. The optimal pathway for the dissociation of H{sub 2}S on the Mo{sub 2}C(001) surface can be H{sub 2}S{sub top} → SH{sub fcc} + H{sub fcc} → S{sub fcc} + H{sub fcc} + H{sub fcc}. The first step is the rate-determining step because it has the smallest rate constant among the possible reactions pathways.

First-principles study of H2 adsorption and dissociation on Zr(0 0 0 1)

International Nuclear Information System (INIS)

Zhang Peng; Wang Shuangxi; Zhao Jian; He Chaohui; Zhang Ping

2011-01-01

Highlights: → The stability of the equilibrium adsorption states is determined after the geometry optimization. → The origin of the stable chemisorbed state is analyzed by the electronic structure and charge redistribution calculation. → The dissociation energetics of H2 are investigated in details by the PES and CINEB calculation. - Abstract: The adsorption and dissociation of H 2 molecules on the Zr(0 0 0 1) surface are systematically investigated by using density functional theory within the generalized gradient approximation and a supercell approach. After geometry optimization, the most stable equilibrium adsorption state is found to be along the top-y entrance. By calculating the adiabatic potential energy surface, the chemisorbed molecular adsorption states are also identified to be along the parallel channel at the top site. The electronic properties of the stable chemisorbed molecular state are analyzed, which show that the interaction between the molecule and substrate is of covalent characteristic with a sizeable charge redistribution. On the other hand, the hcp site is turned out to be the most stable equilibrium adsorption site for hydrogen atom on Zr(0 0 0 1) surface after the dissociation of H 2 . The dissociation energetics of H 2 are studied by calculating the potential energy surface and the minimum energy path of the transition state is determined by using the climb image nudged elastic band method, wherein the fcc-y channel is found to be most stable and favorable for dissociative adsorption of H 2 among the five possible dissociative paths. Remarkably, we find that the adiabatic dissociation process of H 2 is an activated type but with a small energy barrier, which is well consistent with the macroscopic phenomenon that the zirconium metal is easily hydrogenated.

Initial heats of H{sub 2}S adsorption on activated carbons: Effect of surface features

Energy Technology Data Exchange (ETDEWEB)

Bagreev, A.; Adib, F.; Bandosz, T.J.

1999-11-15

The sorption of hydrogen sulfide was studied on activated carbons of various origins by means of inverse gas chromatography at infinite dilution. The conditions of the experiment were dry and anaerobic. Prior to the experiments the surface of some carbon samples was oxidized using either nitric acid or ammonium persulfate. Then the structural parameters of carbons were evaluated from the sorption of nitrogen. From the IGC experiments at various temperatures, heats of adsorption were calculated. The results showed that the heat of H{sub 2}S adsorption under dry anaerobic conditions does not depend on surface chemistry. The dependence of the heat of adsorption on the characteristic energy of nitrogen adsorption calculated from the Dubinin-Raduskevich equation was found. This correlation can be used to predict the heat of H{sub 2}S adsorption based on the results obtained from nitrogen adsorption.

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.

The investigation of adsorption and dissociation of H2O on Li2O (111) by ab initio theory

International Nuclear Information System (INIS)

Kong, Xianggang; Yu, You; Ma, Shenggui; Gao, Tao; Lu, Tiecheng; Xiao, Chengjian; Chen, Xiaojun; Zhang, Chuanyu

2017-01-01

Highlights: • The adsorption structures of H 2 O on Li 2 O (111) are obtained by calculations. • By Bader charge analysis, the charge translation from slab to adsorbate is found. • The vibrational frequencies of adsorbate are in line with the experimental values. - Abstract: The adsorption and dissociation mechanism of H 2 O molecule on the Li 2 O (111) surface have been systematically studied by using the density functional theory calculations. The parallel and vertical configurations of H 2 O at six different symmetry adsorption sites on the Li 2 O (111) surface are considered. In our calculations, it is suggested that H 2 O can dissociate on the perfect Li 2 O surface, of which the corresponding adsorption energy is 1.118 eV. And the adsorption energy decrease to be 0.241 eV when oxygen atom of H 2 O bonds to lithium atom of the slab. The final configurations are sensitive to the initial molecular orientation. By Bader charge analysis, the charge transfer from slab to adsorbed H 2 O/OH can be found due to the downward shift of lowest-unoccupied molecular orbital. We also analyze the vibrational frequencies at the Brillouin Zone centre for H 2 O molecule adsorbed on the stoichiometric surface. Due to the slightly different structure parameters, the calculated values of the vibrational frequencies of hydroxyl group range from 3824 to 3767 cm −1 . Our results agree well with experimental results performed in FT-IR spectrum, which showed that an absorption peak of OH group appeared at 3677 cm −1 at room temperature.

Adsorption of H atoms on cubic Er2O3 (0 0 1) surface: A DFT study

International Nuclear Information System (INIS)

Mao, Wei; Chikada, Takumi; Shimura, Kenichiro; Suzuki, Akihiro; Yamaguchi, Kenji; Terai, Takayuki

2013-01-01

First-principles plane wave calculations based on spin-polarized density functional theory (DFT) and generalized gradient approximation (GGA) have been used to study the adsorption of H atoms on cubic Er 2 O 3 (0 0 1) surface. We identify stable adsorption positions and find that H preferentially adsorbs on top of fourfold-hollow sites and transfers electrons to the surface, resulting in the formations of covalent bonds to the nearest neighboring four oxygen atoms. In the most energetically favorable adsorption sites, It was found that H bonds with O atoms at the cubic Er 2 O 3 (0 0 1) surface with an adsorption energy of −295.68 kJ mol −1 at coverage 1/8 ML, and the adsorption energy is inclined to decrease with the increase of H coverage (>1/4 ML). In addition, our calculations indicate that the dissociative H atom configurations have adsorption energies that are at least 152.64 kJ mol −1 greater than the H 2 molecule configurations on the surface. These results discussed in the context of erbium oxide slabs are employed to rationalize some processes regarding to the hydrogen isotope permeation behavior of tritium permeation barrier

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.

Molecular simulation of methane adsorption characteristics on coal macromolecule

Science.gov (United States)

Yang, Zhiyuan; He, Xiaoxiao; Meng, Zhuoyue; Xue, Wenying

2018-02-01

In this paper, the molecular model of anthracite named Wender2 was selected to study the adsorption behaviour of single component CH4 and the competitive adsorption of CH4/CO2, CH4/H2O and CH4/N2. The molecular model of anthracite was established by molecular simulation software (Materials Studio 8.0), and Grand Canonical Monte Carlo (GCMC) simulations were carried out to investigate the single and binary component adsorption. The effects of pressure and temperature on the adsorption position, adsorption energy and adsorption capacity were mainly discussed. The results show that for the single component adsorption, the adsorption capacity of CH4 increases rapidly with the pressure ascending, and then tends to be stable after the first step. The low temperature is favourable for the adsorption of CH4, and the high temperature promotes desorption quantity of CH4 from the coal. Adsorbent molecules are preferentially adsorbed on the edge of coal macromolecules. The order of adsorption capacity of CH4/CO2, CH4/H2O and CH4/N2 in the binary component is H2O>CO2>CH4>N2. The change of pressure has little effect on the adsorption capacity of the adsorbent in the competitive adsorption, but it has a great influence on the adsorption capacity of the adsorbent, and there is a positive correlation between them.

Corrosion Inhibition and Adsorption Characteristics of Tarivid on Mild Steel in H2SO4

Directory of Open Access Journals (Sweden)

N. O. Eddy

2010-01-01

Full Text Available The corrosion inhibition and adsorption characteristics of (+/--9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl-7-oxo-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylic acid (Tarivid on the corrosion of mild steel has been studied using thermometric and gasometric methods. The study reveals that tarivid inhibits the corrosion of mild steel in H2SO4. The values of inhibition efficiency of tarivid were found to increase as its concentration increased but decreased with increase in temperature. Activation energies of the inhibited corrosion of mild steel ranged from 39.05 to 50.61 kJ/mol. Values of enthalpy change and free energy of adsorption were negative which indicated exothermic and spontaneous adsorption process. Physical adsorption mechanism is proposed from the obtained kinetic and thermodynamic parameters. Langmuir adsorption isotherm model is obeyed from the fit of the experimental data.

The investigation of adsorption and dissociation of H2O on Li2O (111) by ab initio theory

Science.gov (United States)

Kong, Xianggang; Yu, You; Ma, Shenggui; Gao, Tao; Lu, Tiecheng; Xiao, Chengjian; Chen, Xiaojun; Zhang, Chuanyu

2017-06-01

The adsorption and dissociation mechanism of H2O molecule on the Li2O (111) surface have been systematically studied by using the density functional theory calculations. The parallel and vertical configurations of H2O at six different symmetry adsorption sites on the Li2O (111) surface are considered. In our calculations, it is suggested that H2O can dissociate on the perfect Li2O surface, of which the corresponding adsorption energy is 1.118 eV. And the adsorption energy decrease to be 0.241 eV when oxygen atom of H2O bonds to lithium atom of the slab. The final configurations are sensitive to the initial molecular orientation. By Bader charge analysis, the charge transfer from slab to adsorbed H2O/OH can be found due to the downward shift of lowest-unoccupied molecular orbital. We also analyze the vibrational frequencies at the Brillouin Zone centre for H2O molecule adsorbed on the stoichiometric surface. Due to the slightly different structure parameters, the calculated values of the vibrational frequencies of hydroxyl group range from 3824 to 3767 cm-1. Our results agree well with experimental results performed in FT-IR spectrum, which showed that an absorption peak of OH group appeared at 3677 cm-1 at room temperature.

Nuclear quantum effects on adsorption of H2 and isotopologues on metal ions

Science.gov (United States)

Savchenko, Ievgeniia; Gu, Bing; Heine, Thomas; Jakowski, Jacek; Garashchuk, Sophya

2017-02-01

The nuclear quantum effects on the zero-point energy (ZPE), influencing adsorption of H2 and isotopologues on metal ions, are examined using normal mode analysis of ab initio electronic structure results for complexes with 17 metal cations. The lightest metallic nuclei, Li and Be, are found to be the most 'quantum'. The largest selectivity in adsorption is predicted for Cu, Ni and Co ions. Analysis of the nuclear wavepacket dynamics on the ground state electronic potential energy surfaces (PES) performed for complexes of Li+ and Cu+2 with H2/D2/HD shows that the PES anharmonicity changes the ZPE by up to 9%.

Chemical and physicochemical characterization of vermicompost from bovine manure and evaluation of competitive adsorption of cadmium and lead

International Nuclear Information System (INIS)

Lamim, Soraida Sozzi Miguel; Jordao, Claudio Pereira; Brune, Walter; Pereira, Jose Luis

1996-01-01

The chemical and physicochemical characterization of vermicompost from bovine manure has been studied. It was examined the pH and cation exchangeable capacity (CTC), moistness, ash, organic carbon, total nitrogen, lignin, cellulose and metal concentrations, among other characteristics. The vermicompost was then applied to the retention and competition of metal pollutants (Cd and Pb) from metal nitrate solutions. The retention was affected by both the pH and time of adsorption, while the competitive character of these metals for the substrate was not relevant to each pH examined. (author)

Preparation of H2TiO3-lithium adsorbent by the sol–gel process and its adsorption performance

International Nuclear Information System (INIS)

Zhang, Liyuan; Zhou, Dali; Yao, Qianqian; Zhou, Jiabei

2016-01-01

Graphical abstract: - Highlights: • Nano-Li 2 TiO 3 was synthesized with CH 3 COOLi and Ti(OC 4 H 9 ) 4 by the sol–gel process. • H 2 TiO 3 -lithium adsorbent was obtained by treating Li 2 TiO 3 with HCl. • Langmuir and Freundlich models were used to analyze the adsorption process. • The adsorption performance of the obtained adsorbent was studied. - Abstract: CH 3 COOLi and Ti(OC 4 H 9 ) 4 were employed as lithium and titanium sources, respectively to synthesize Li 2 TiO 3 by the sol–gel process, followed by treating with hydrochloric acid to yield H 2 TiO 3 -lithium adsorbent. Various concentrations of LiOH and lithium sources were used as adsorption liquid to carry out adsorption experiment, the data from which were analyzed by Langmuir and Freundlich models. The results indicate that the optimal calcination temperature is 650 °C, and Li 2 TiO 3 with particle size 60–80 nm is observed. The Li + drawn out ratio from Li 2 TiO 3 reaches 78.9%, and the dissolution of titanium ions can be as low as 0.07%. The protonated sample obtained has a lower basal spacing, while the crystal morphology is retained. The main factors affecting the adsorptive capacity are the Li + concentration and pH in the liquid. The adsorption process of H 2 TiO 3 -lithium adsorbent can be seen as a process including surface adsorption and ion exchange. Compared with Langmuir model, Freundlich model is more suitable for describing the actual adsorption process.

pH dependent polymeric micelle adsorption

Energy Technology Data Exchange (ETDEWEB)

McLean, S C; Gee, M L [The University of Melbourne, VIC (Australia). School of Chemistry

2003-07-01

Full text: Poly(2-vinylpyridine)-poly(ethylene oxide) (P2VP-PEO) shows potential as a possible drug delivery system for anti-tumour drugs since it forms pH dependent polymeric micelles. Hence to better understand the adsorption behaviour of this polymer we have studied the interaction forces between layers of P2VP-PEO adsorbed onto silica as a function of solution pH using an Atomic Force Microscope (AFM). When P2VP-PEO is initially adsorbed above the pKa of the P2VP block, P2VP-PEO adsorbs from solution as micelles that exist as either partially collapsed- or a hemi-micelles at the silica surface. Below the pKa of P2VP, the P2VP-PEO adsorbs as unimers, forming a compact layer with little looping and tailing into solution. When initial adsorption of P2VP-PEO is in the form of unimers, any driving force to self-assembly of the now charge neutral polymer is kinetically hindered. Hence, after initial adsorption at pH 3.6, a subsequent increase in pH to 6.6 results in a slow surface restructuring towards self-assembly and equilibrium. When the pH is increased from pH 6.6 to 9.7 there is a continuation of the evolution of the system to its equilibrium position during which the adsorbed P2VP-PEO unimers continue to 'unravel' from the surface, extending away from it, towards eventual complete surface self-assembly.

Removal of diethyl phthalate from water solution by adsorption, photo-oxidation, ozonation and advanced oxidation process (UV/H2O2, O3/H2O2 and O3/activated carbon)

International Nuclear Information System (INIS)

Medellin-Castillo, Nahum A.; Ocampo-Pérez, Raúl; Leyva-Ramos, Roberto; Sanchez-Polo, Manuel; Rivera-Utrilla, José; Méndez-Díaz, José D.

2013-01-01

The objective of this work was to compare the effectiveness of conventional technologies (adsorption on activated carbon, AC, and ozonation) and technologies based on advanced oxidation processes, AOPs, (UV/H 2 O 2 , O 3 /AC, O 3 /H 2 O 2 ) to remove phthalates from aqueous solution (ultrapure water, surface water and wastewater). Diethyl phthalate (DEP) was chosen as a model pollutant because of its high water solubility (1080 mg/L at 293 K) and toxicity. The activated carbons showed a high adsorption capacity to adsorb DEP in aqueous solution (up to 858 mg/g), besides the adsorption mechanism of DEP on activated carbon is governed by dispersive interactions between π electrons of its aromatic ring with π electrons of the carbon graphene planes. The photodegration process showed that the pH solution does not significantly affect the degradation kinetics of DEP and the first-order kinetic model satisfactorily fitted the experimental data. It was observed that the rate of decomposition of DEP with the O 3 /H 2 O 2 and O 3 /AC systems is faster than that with only O 3 . The technologies based on AOPs (UV/H 2 O 2 , O 3 /H 2 O 2 , O 3 /AC) significantly improve the degradation of DEP compared to conventional technologies (O 3 , UV). AC adsorption, UV/H 2 O 2 , O 3 /H 2 O 2 , and O 3 /AC showed a high yield to remove DEP; however, the disadvantage of AC adsorption is its much longer time to reach maximum removal. The best system to treat water (ultrapure and natural) polluted with DEP is the O 3 /AC one since it achieved the highest DEP degradation and TOC removal, as well as the lower water toxicity. -- Highlights: ► Activated carbons showed a high adsorption capacity (up to 858 mg/g) to remove DEP. ► The pH solution did not significantly affect the photodegradation kinetics of DEP. ► The O 3 /H 2 O 2 and O 3 /AC systems were more efficient than O 3 to degrade DEP. ► The generation of HO • from O 3 was enhanced by ACs, mainly by those of basic nature. ► O

Pt-decorated graphene as superior media for H2S adsorption: A first-principles study

International Nuclear Information System (INIS)

Ganji, Masoud Darvish; Sharifi, Narges; Ardjmand, Mahdi; Ahangari, Morteza Ghorbanzadeh

2012-01-01

Highlights: ► We report the first DFT study in the H 2 S/Pt–graphene system. ► The adsorption properties of H 2 S at different possible site on the surface of pristine graphene are slightly stable presenting energies from 0.02 to 0.06 eV. ► When Pt decorates the graphene sheet on the single and double sides the H 2 S adsorption energy increase to −3.2 eV. ► A single Pt atom can locate up to seven H 2 S molecules stably binded with energies from −6.73 to −0.95 eV. ► The DOS plot indicates strong hybridization between H 2 S molecules and Pt–graphene sheet. - Abstract: The adsorption mechanism of hydrogen sulfide (H 2 S) molecules on pristine and Pt-decorated graphene sheets was studied using density functional theory calculations based on local density approximation and generalized gradient approximation methods. Our calculations show that a Pt-decorated graphene system has much higher binding energy, higher net charge transfer values and shorter connecting distances than pristine graphene due to chemisorption of the H 2 S molecule. Furthermore, the calculated density of states show that orbital hybridization is visible between the H 2 S and Pt-decorated graphene sheets, while there is no evidence for hybridization between the H 2 S molecule and the pristine graphene sheet. Interestingly, we find that up to seven H 2 S molecules can stably bind to a Pt atom on each side of the graphene sheet with desirable binding energy.

In vitro study of vitamins B1, B2 and B6 adsorption on zeolite

Directory of Open Access Journals (Sweden)

Basić Zorica

2011-01-01

Full Text Available Background/Aim. Zeolites are the hydratised alumosilicates of alcali and earthalcali cations, which have a long three-dimensional crystal structure. Preparations on the basis of zeolites are used for adsorption of organic and nonorganic toxic substances and they, also, find more and more use in veterinary and human medicine and pharmacy. The aim of this study was to evaluate the possibilities of zeolite to adsorb vitamins B1, B2 and B6 in acid and neutral solutions, as well as the characteristics of the process (saturability, reversibility and competitivness. Methods. The specific and sensitive HPLC method with fluorescent detector was used for determination of vitamins B1, B2 and B6. Analyte separation and detection were carried out by applying the reverse-phase method on column C18. An in vitro experiment was done by testing the influence of pH value (2 and 7, concentration of vitamin solution (1, 2 and 5 mg/L, the lenght of contact with zeolite (10-180 min and cation competitiveness on the exchange capacity, which is achieved by media and zeolite contact, as well as a possible vitamins desorption through changing pH value of the solution at 37°C. Jon competitiveness was examined by adding commercial feed mixture (grower with a defined content of the examined vitamines in zeolite solutions the pH = 2 and pH = 7. Results. Vitamins B1, B2 and B6 were stable in both pH=2 and pH = 7 solutions at 37°C, in the defined time intervals. In acid solution concentrations of vitamins significantly declined in the first 10 min, with no significant decline in further 30 min for all the three concentrations testch. In neutral solution, after the addition of 1% zeolite, decrease in vitamins concentrations was slightly lower than in acid solution, but also significant in the first 10 min of the contact with zeolite. It was found that zeolite, which adsorbed vitamins in acid solution, transferred in the neutral one released a significant quantity of adsorbed

Nuclear quantum effects on adsorption of H_2 and isotopologues on metal ions

International Nuclear Information System (INIS)

Savchenko, Ievgeniia; Gu, Bing; Heine, Thomas; Jakowski, Jacek; Garashchuk, Sophya

2017-01-01

The nuclear quantum effects on the zero-point energy (ZPE), influencing adsorption of H_2 and isotopologues on metal ions, are examined in this study using normal mode analysis of ab initio electronic structure results for complexes with 17 metal cations. To estimate for the anharmonicity, a nuclear wavepacket dynamics on the ground state electronic potential energy surfaces (PES) have been employed for complexes of Li"+ and Cu"+"2 with H_2, D_2, HD. The dynamics analysis shows that incorporation of the PES anharmonicity changes the ZPE by up to 9%. Finally, the lightest metallic nuclei, Li and Be, are found to be the most 'quantum'. The largest selectivity in adsorption is predicted for Cu, Ni and Co ions.

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)

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.

Edge functionalised & Li-intercalated 555-777 defective bilayer graphene for the adsorption of CO2 and H2O

Science.gov (United States)

Lalitha, Murugan; Lakshmipathi, Senthilkumar; Bhatia, Suresh K.

2017-04-01

The adsorption of CO2 and H2O on divacanacy (DV) defected graphene cluster, and its bilayer counterpart is investigated using first-principles calculations. Both single and bilayer DV graphene cluster, are functionalised with H and F atoms. On these sheets the gas molecules are physisorbed, and the divacancy defect effectively improves the adsorption of CO2, while fluorination enhances the hydrophobicity of the graphene cluster. Among the convex and concave curvature regions induced due to the DV defect, the adsorption of the gas molecules on the concave meniscus is more favourable. Fluorine termination induces 73% reduction in Henry law constants for H2O, while for the CO2 molecule it increases by 8%, which indicates the DV defective sheet is a better candidate for CO2 capture compared to the STW defective sheet. Besides, both AA and AB divacant defect bilayer sheets are equally stable, wherein AA stacking results in a cavity between the sheets, while in AB stacking, the layers slide one over the other. Nevertheless, both these bilayer sheets are comparatively stabler than the monolayer. However, intercalation of lithium decreases the interlayer separation, particularly in AA stacking, which enhances the CO2 adsorption, but in the Bernal stacking enhances it hydrophobicity.

The investigation of adsorption and dissociation of H{sub 2}O on Li{sub 2}O (111) by ab initio theory

Energy Technology Data Exchange (ETDEWEB)

Kong, Xianggang [Institute of Atom and Molecular physics, Sichuan University, Chengdu, 610065 (China); Yu, You [College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu, 610225 (China); Ma, Shenggui [Institute of Atom and Molecular physics, Sichuan University, Chengdu, 610065 (China); Gao, Tao, E-mail: gaotao@scu.edu.cn [Institute of Atom and Molecular physics, Sichuan University, Chengdu, 610065 (China); Lu, Tiecheng [Department of Physics and Key Laboratory for Radiation Physics & Technology of Ministry of Education, Sichuan University, Chengdu, 610065 (China); Xiao, Chengjian; Chen, Xiaojun [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang, 621900 (China); Zhang, Chuanyu [College of Geophysics, Chengdu University of Technology, Chengdu, 610059 (China)

2017-06-15

Highlights: • The adsorption structures of H{sub 2}O on Li{sub 2}O (111) are obtained by calculations. • By Bader charge analysis, the charge translation from slab to adsorbate is found. • The vibrational frequencies of adsorbate are in line with the experimental values. - Abstract: The adsorption and dissociation mechanism of H{sub 2}O molecule on the Li{sub 2}O (111) surface have been systematically studied by using the density functional theory calculations. The parallel and vertical configurations of H{sub 2}O at six different symmetry adsorption sites on the Li{sub 2}O (111) surface are considered. In our calculations, it is suggested that H{sub 2}O can dissociate on the perfect Li{sub 2}O surface, of which the corresponding adsorption energy is 1.118 eV. And the adsorption energy decrease to be 0.241 eV when oxygen atom of H{sub 2}O bonds to lithium atom of the slab. The final configurations are sensitive to the initial molecular orientation. By Bader charge analysis, the charge transfer from slab to adsorbed H{sub 2}O/OH can be found due to the downward shift of lowest-unoccupied molecular orbital. We also analyze the vibrational frequencies at the Brillouin Zone centre for H{sub 2}O molecule adsorbed on the stoichiometric surface. Due to the slightly different structure parameters, the calculated values of the vibrational frequencies of hydroxyl group range from 3824 to 3767 cm{sup −1}. Our results agree well with experimental results performed in FT-IR spectrum, which showed that an absorption peak of OH group appeared at 3677 cm{sup −1} at room temperature.

H2S adsorption and decomposition on the gradually reduced α-Fe2O3(001) surface: A DFT study

Science.gov (United States)

Lin, Changfeng; Qin, Wu; Dong, Changqing

2016-11-01

Reduction of iron based desulfurizer occurs during hot gas desulfurization process, which will affect the interaction between H2S and the desulfurizer surface. In this work, a detailed adsorption behavior and dissociation mechanism of H2S on the perfect and reduced α-Fe2O3(001) surfaces, as well as the correlation between the interaction characteristic and reduction degree of iron oxide, have been studied by using periodic density functional theory (DFT) calculations. Results demonstrate that H2S firstly chemisorbs on surface at relatively higher oxidation state (reduction degree χ 33%. Reduction of iron oxide benefits the H2S adsorption. Further, dissociation processes of H2S via molecular and dissociative adsorption were investigated. Results show that after reduction of Fe2O3 into the oxidation state around FeO and Fe, the reduced surface exhibits very strong catalytic capacity for H2S decomposition into S species. Meanwhile, the overall dissociation process on all surfaces is exothermic. These results provide a fundamental understanding of reduction effect of iron oxide on the interaction mechanism between H2S and desulfurizer surface, and indicate that rational control of reduction degree of desulfurizer is essential for optimizing the hot gas desulfurization process.

Evaluation of the impact of H2O, O2, and SO2 on postcombustion CO2 capture in metal-organic frameworks.

Science.gov (United States)

Yu, Jiamei; Ma, Yuguang; Balbuena, Perla B

2012-05-29

Molecular modeling methods are used to estimate the influence of impurity species: water, O(2), and SO(2) in flue gas mixtures present in postcombustion CO(2) capture using a metal organic framework, HKUST-1, as a model sorbent material. Coordinated and uncoordinated water effects on CO(2) capture are analyzed. Increase of CO(2) adsorption is observed for both cases, which can be attributed to the enhanced binding energy between CO(2) and HKUST-1 due to the introduction of a small amount of water. Density functional theory calculations indicate that the binding energy between CO(2) and HKUST-1 with coordinated water is ~1 kcal/mol higher than that without coordinated water. It is found that the improvement of CO(2)/N(2) selectivity induced by coordinated water may mainly be attributed to the increased CO(2) adsorption on the hydrated HKUST-1. On the other hand, the enhanced selectivity induced by uncoordinated water in the flue gas mixture can be explained on the basis of the competition of adsorption sites between water and CO(2) (N(2)). At low pressures, a significant CO(2)/N(2) selectivity increase is due to the increase of CO(2) adsorption and decrease of N(2) adsorption as a consequence of competition of adsorption sites between water and N(2). However, with more water molecules adsorbed at higher pressures, the competition between water and CO(2) leads to the decrease of CO(2) adsorption capacity. Therefore, high pressure operation should be avoided in HKUST-1 sorbents for CO(2) capture. In addition, the effects of O(2) and SO(2) on CO(2) capture in HKUST-1 are investigated: The CO(2)/N(2) selectivity does not change much even with relatively high concentrations of O(2) in the flue gas (up to 8%). A slightly lower CO(2)/N(2) selectivity of a CO(2)/N(2)/H(2)O/SO(2) mixture is observed compared with that in a CO(2)/N(2)/H(2)O mixture, especially at high pressures, due to the strong SO(2) binding with HKUST-1.

Tuning patterning conditions by co-adsorption of gases: Br2 and H2 on Si(001).

Science.gov (United States)

Biswas, Sananda; Deshpande, Sadanand V; Dunn, Derren N; Narasimhan, Shobhana

2013-11-14

We have studied the co-adsorption of Br2 and H2 on Si(001), and obtained co-adsorption energies and the surface phase diagram as a function of the chemical potential and pressure of the two gases. To do this, we have used density functional theory calculations in combination with ab initio atomistic thermodynamics. Over large ranges of bromine and hydrogen chemical potentials, the favored configuration is found to be either one with only Br atoms adsorbed on the surface, at full coverage, in a (3 × 2) pattern, or a fully H-covered surface in a (2 × 1) structure. However, we also find regions of the phase diagram where there are configurations with either only Br atoms, or Br and H atoms, arranged in a two-atom-wide checkerboard pattern with a (4 × 2) surface unit cell. Most interestingly, we find that by co-adsorbing with H2, we bring this pattern into a region of the phase diagram corresponding to pressures that are significantly higher than those where it is observed with Br2 alone. We also find small regions of the phase diagram with several other interesting patterns.

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.

Competitive Protein Adsorption on Polysaccharide and Hyaluronate Modified Surfaces

Science.gov (United States)

Ombelli, Michela; Costello, Lauren; Postle, Corinne; Anantharaman, Vinod; Meng, Qing Cheng; Composto, Russell J.; Eckmann, David M.

2011-01-01

We measured adsorption of bovine serum albumin (BSA) and fibrinogen (Fg) onto six distinct bare and dextran- and hyaluronate-modified silicon surfaces created using two dextran grafting densities and three hyaluronic acid (HA) sodium salts derived from human umbilical cord, rooster comb and streptococcus zooepidemicus. Film thickness and surface morphology depended on HA molecular weight and concentration. BSA coverage was enhanced on surfaces upon competitive adsorption of BSA:Fg mixtures. Dextranization differentially reduced protein adsorption onto surfaces based on oxidation state. Hyaluronization was demonstrated to provide the greatest resistance to protein coverage, equivalent to that of the most resistant dextranized surface. Resistance to protein adsorption was independent of the type of hyaluronic acid utilized. With changing bulk protein concentration from 20 to 40 µg ml−1 for each species, Fg coverage on silicon increased by 4×, whereas both BSA and Fg adsorption on dextran and HA were far less dependent of protein bulk concentration. PMID:21623481

The adsorption of Cs+, Sr2+ and Ni2+ on bitumen: a mechanistic model

International Nuclear Information System (INIS)

Loon, L.R. Van; Kopajtic, Z.

1991-01-01

The adsorption of radionuclides on the waste matrix is a positive effect and contributes to the retardation of released radionuclides migrating to the geo-and biosphere. For the safety assessment studies, it is important to know whether or not radionuclides do adsorb on the waste matrix. In the present work the adsorption of 134 Cs + , 85 Sr 2+ and 63 Ni 2+ on bitumen was studied as a function of the pH and ionic strength of the equilibrium solution. Bitumen emulsions with well defined surfaces were used. The surface of bitumen is negatively charged due to the deprotonation of weak acid carboxyl groups at the interface. The functional group density amounts to 1.37.10 18 groups/m 2 and their deprotonation behaviour can be well described by the 'Ionizable Surface Group' model. Cs + , Sr 2+ and Ni 2+ adsorb on the surface by three different processes, i.e. ion exchange, outer sphere complexation and inner sphere surface complexation respectively. The adsorption depends on the pH and the ionic strength of the contact solution. Under near field conditions, Cs + and Sr 2+ do not adsorb on the bitumen due to the competition with Na + , K + and Ca 2+ present in the cement pore water in contact with the bitumen. Ni 2+ adsorption can also be neglected because the formation of neutral and anionic hydroxo complexes in solution competes strongly with the adsorption reaction. Other hydrolysable radionuclides of interest are expected to behave similarly to Ni 2+ . The main conclusion of the study is that the adsorption of radionuclides under near field conditions is expected to be very low. Consequently, this process need not to be considered in safety assessment studies. (author) figs., tabs., 30 refs

Competitive Adsorption of Plasma Proteins on Polysaccharide-Modified Silicon Surfaces

National Research Council Canada - National Science Library

Ombelli, Michela; Costello, Lauren B; Meng, Qing C; Composto, Russell J; Eckmann, David M

2005-01-01

.... Competitive protein adsorption plays a key role in the hemocompatibility of the surface. The synthesis of nonfouling surfaces is therefore one of the major prerequisites for devices for biomedical applications...

Simulations and experimental investigations of the competitive adsorption of CH4 and CO2 on low-rank coal vitrinite.

Science.gov (United States)

Yu, Song; Bo, Jiang; Jiahong, Li

2017-09-16

The mechanism for the competitive adsorption of CH 4 and CO 2 on coal vitrinite (DV-8, maximum vitrinite reflectance R o,max  = 0.58%) was revealed through simulation and experimental methods. A saturated state was reached after absorbing 17 CH 4 or 22 CO 2 molecules per DV-8 molecule. The functional groups (FGs) on the surface of the vitrinite can be ranked in order of decreasing CH 4 and CO 2 adsorption ability as follows: [-CH 3 ] > [-C=O] > [-C-O-C-] > [-COOH] and [-C-O-C-] > [-C=O] > [-CH 3 ] > [-COOH]. CH 4 and CO 2 distributed as aggregations and they were both adsorbed at the same sites on vitrinite, indicating that CO 2 can replace CH 4 by occupying the main adsorption sites for CH 4 -vitrinite. High temperatures are not conducive to the adsorption of CH 4 and CO 2 on vitrinite. According to the results of density functional theory (DFT) and grand canonical Monte Carlo (GCMC) calculations, vitrinite has a higher adsorption capacity for CO 2 than for CH 4 , regardless of whether a single-component or binary adsorbate is considered. The equivalent adsorption heat (EAH) of CO 2 -vitrinite (23.02-23.17) is higher than that of CH 4 -vitrinite (9.04-9.40 kJ/mol). The EAH of CO 2 -vitrinite decreases more rapidly with increasing temperature than the EAH of CH 4 -vitrinite does, indicating in turn that the CO 2 -vitrinite bond weakens more quickly with increasing temperature than the CH 4 -vitrinite bond does. Simulation data were found to be in good accord with the corresponding experimental results.

Adsorption of Dissolved Gases (CH4, CO2, H2, Noble Gases) by Water-Saturated Smectite Clay Minerals

Science.gov (United States)

Bourg, I. C.; Gadikota, G.; Dazas, B.

2016-12-01

Adsorption of dissolved gases by water-saturated clay minerals plays important roles in a range of fields. For example, gas adsorption in on clay minerals may significantly impact the formation of CH4 hydrates in fine-grained sediments, the behavior of CH4 in shale, CO2 leakage across caprocks of geologic CO2 sequestration sites, H2 leakage across engineered clay barriers of high-level radioactive waste repositories, and noble gas geochemistry reconstructions of hydrocarbon migration in the subsurface. Despite its importance, the adsorption of gases on clay minerals remains poorly understood. For example, some studies have suggested that clay surfaces promote the formation of CH4 hydrates, whereas others indicate that clay surfaces inhibit the formation of CH4 hydrates. Here, we present molecular dynamics (MD) simulations of the adsorption of a range of gases (CH4, CO2, H2, noble gases) on clay mineral surfaces. Our results indicate that the affinity of dissolved gases for clay mineral surfaces has a non-monotone dependence on the hydrated radius of the gas molecules. This non-monotone dependence arises from a combination of two effects: the polar nature of certain gas molecules (in particular, CO2) and the templating of interfacial water structure by the clay basal surface, which results in the presence of interfacial water "cages" of optimal size for intermediate-size gas molecules (such as Ne or Ar).

Examination of the Effects of Activated Carbon Produced from Coal Using Single-Step H3PO4/N2+H2O Vapor Activation on the Adsorption of Bovine Serum Albumin at Different Temperatures and pH Values

Directory of Open Access Journals (Sweden)

Atakan Toprak

2017-12-01

Full Text Available This study examined protein adsorption equilibrium and kinetics on activated carbon (AC that we obtained from coal by single-step H3PO4 activation under N2+H2O vapor at 800 °C. Surface properties, pore size distribution, and volumes of AC were determined using the volumetric method with N2 adsorption at 77 K. Also, the textural properties were characterized by SEM-EDAX and XRD. The zeta potential values were measured to elucidate the electrostatic interactions between the protein and AC. The obtained AC discrete system was also used as an adsorbent for adsorbing bovine serum albumin (BSA from aqueous solution. The effects of pH (4.0, 5.0, and 7.4 and temperatures (20, 30 and 40 °C on the adsorption of BSA on AC were examined. The surface area, micropore, mesopore and total pore volumes of AC were found to be 1175 m2/g, 0.477 cm3/g, 0.061 cm3/g and 0.538 cm3/g, respectively. The optimum temperature for AC in BSA adsorption was found to be 40 °C and the pH was found to be 4.0. The highest BSA adsorption was found to be 159 mg/g and pH to be 4.0. The experimental equilibrium data were compared with the Langmuir and Freundlich models and found to be compatible with both models. The adsorption process is best described by the pseudo-first-order kinetic model. As a result, it was found out that AC obtained by single step H3PO4/N2+H2O vapor activation is an effective adsorbent for the adsorption of BSA from aqueous solution.

Breakthrough curve of H/sub 2/-Ti-sponge adsorption system

Energy Technology Data Exchange (ETDEWEB)

Yasufuku, K [Kawasaki Heavy Industries Ltd., Kobe (Japan)

1977-11-01

Experimental work concerning H/sub 2/-Ti-sponge adsorption system has been undertaken at Kawasaki Heavy Industry Co. to obtain necessary data for the design of hydrogen removal tower (Ti-sponge trap) to be used as an purification component of a VHTR plant. In this study, the effects of equilibrium curve, H/sub 2/ inlet concentration, and the ratio of the solid-side capacity factor to the gas-side capacity factor on the breakthrough curve were investigated. The Freundlich's equation with the diffusion model of Carter et al. was numerically solved by the Crank-Nicholson method, and the results of calculations are presented. The flow diagram and the photographs of the facilities for He gas purification experiments are also presented.

Rediscovering the Schulze-Hardy rule in competitive adsorption to an air-water interface.

Science.gov (United States)

Stenger, Patrick C; Isbell, Stephen G; St Hillaire, Debra; Zasadzinski, Joseph A

2009-09-01

The ratio of divalent to monovalent ion concentration necessary to displace the surface-active protein, albumin, by lung surfactant monolayers and multilayers at an air-water interface scales as 2(-6), the same concentration dependence as the critical flocculation concentration (CFC) for colloids with a high surface potential. Confirming this analogy between competitive adsorption and colloid stability, polymer-induced depletion attraction and electrostatic potentials are additive in their effects; the range of the depletion attraction, twice the polymer radius of gyration, must be greater than the Debye length to have an effect on adsorption.

Sequential and simultaneous adsorption of Sb(III) and Sb(V) on ferrihydrite: Implications for oxidation and competition.

Science.gov (United States)

Qi, Pengfei; Pichler, Thomas

2016-02-01

Antimony (Sb) is a naturally occurring element of growing environmental concern whose toxicity, adsorption behavior and other chemical properties are similar to that of arsenic (As). However, less is known about Sb compared to As. Individual and simultaneous adsorption experiments with Sb(III) and Sb(V) were conducted in batch mode with focus on the Sb speciation of the remaining liquid phase during individual Sb(III) adsorption experiments. The simultaneous adsorption and oxidation of Sb(III) was confirmed by the appearance of Sb(V) in the solution at varying Fe/Sb ratios (500, 100 and 8) and varying pH values (3.8, 7 and 9). This newly formed Sb(V) was subsequently removed from solution at a Fe/Sb ratio of 500 or at a pH of 3.8. However, more or less only Sb(V) was observed in the liquid phase at the end of the experiments at lower Fe/Sb ratios and higher pH, indicating that competition took place between the newly formed Sb(V) and Sb(III), and that Sb(III) outcompeted Sb(V). This was independently confirmed by simultaneous adsorption experiments of Sb(III) and Sb(V) in binary systems. Under such conditions, the presence of Sb(V) had no influence on the adsorption of Sb(III) while Sb(V) adsorption was significantly inhibited by Sb(III) over a wide pH range (4-10). Thus, in the presence of ferrihydrite and under redox conditions, which allow the presence of both Sb species, Sb(V) should be the dominant species in aquatic environments, since Sb(III) is adsorbed preferentially and at the same time oxidized to Sb(V). Copyright © 2015 Elsevier Ltd. All rights reserved.

Phosphorus recovery from biogas slurry by ultrasound/H2O2 digestion coupled with HFO/biochar adsorption process.

Science.gov (United States)

He, Xuemeng; Zhang, Tao; Ren, Hongqiang; Li, Guoxue; Ding, Lili; Pawlowski, Lucjan

2017-02-01

Phosphorus (P) recovery from biogas slurry has recently attracted considerable interest. In this work, ultrasound/H 2 O 2 digestion coupled with ferric oxide hydrate/biochar (HFO/biochar) adsorption process was performed to promote P dissolution, release, and recovery from biogas slurry. The results showed that the optimal total phosphorus release efficiency was achieved at an inorganic phosphorus/total phosphorus ratio of 95.0% at pH 4, 1mL of added H 2 O 2 , and ultrasonication for 30min. The P adsorption by the HFO/biochar followed pseudo second-order kinetics and was mainly controlled by chemical processes. The Langmuir-Freundlich model matched the experimental data best for P adsorption by HFO/biochar at 298 and 308K, whereas the Freundlich model matched best at 318K. The maximum amount of P adsorbed was 220mg/g. The process was endothermic, spontaneous, and showed an increase in disorder at the solid-liquid interface. The saturated adsorbed HFO/biochar continually releases P and is most suitable for use in an alkaline environment. The amount of P released reached 29.1mg/g after five extractions. P mass balance calculation revealed that 11.3% of the total P can be made available. Copyright © 2016. Published by Elsevier Ltd.

CO 2 adsorption in mono-, di- and trivalent cation-exchanged metal-organic frameworks: A molecular simulation study

KAUST Repository

Chen, Yifei

2012-02-28

A molecular simulation study is reported for CO 2 adsorption in rho zeolite-like metal-organic framework (rho-ZMOF) exchanged with a series of cations (Na +, K +, Rb +, Cs +, Mg 2+, Ca 2+, and Al 3+). The isosteric heat and Henry\\'s constant at infinite dilution increase monotonically with increasing charge-to-diameter ratio of cation (Cs + < Rb + < K + < Na + < Ca 2+ < Mg 2+ < Al 3+). At low pressures, cations act as preferential adsorption sites for CO 2 and the capacity follows the charge-to-diameter ratio. However, the free volume of framework becomes predominant with increasing pressure and Mg-rho-ZMOF appears to possess the highest saturation capacity. The equilibrium locations of cations are observed to shift slightly upon CO 2 adsorption. Furthermore, the adsorption selectivity of CO 2/H 2 mixture increases as Cs + < Rb + < K + < Na + < Ca 2+ < Mg 2+ ≈ Al 3+. At ambient conditions, the selectivity is in the range of 800-3000 and significantly higher than in other nanoporous materials. In the presence of 0.1% H 2O, the selectivity decreases drastically because of the competitive adsorption between H 2O and CO 2, and shows a similar value in all of the cation-exchanged rho-ZMOFs. This simulation study provides microscopic insight into the important role of cations in governing gas adsorption and separation, and suggests that the performance of ionic rho-ZMOF can be tailored by cations. © 2012 American Chemical Society.

Competitive adsorption of heavy metal by extracellular polymeric substances (EPS) extracted from sulfate reducing bacteria.

Science.gov (United States)

Wang, Jin; Li, Qing; Li, Ming-Ming; Chen, Tian-Hu; Zhou, Yue-Fei; Yue, Zheng-Bo

2014-07-01

Competitive adsorption of heavy metals by extracellular polymeric substances (EPS) extracted from Desulfovibrio desulfuricans was investigated. Chemical analysis showed that different EPS compositions had different capacities for the adsorption of heavy metals which was investigated using Cu(2+) and Zn(2+). Batch adsorption tests indicated that EPS had a higher combined ability with Zn(2+) than Cu(2+). This was confirmed and explained by Fourier transform infrared (FTIR) and excitation-emission matrix (EEM) spectroscopy analysis. FTIR analysis showed that both polysaccharides and protein combined with Zn(2+) while only protein combined with Cu(2+). EEM spectra further revealed that tryptophan-like substances were the main compositions reacted with the heavy metals. Moreover, Zn(2+) had a higher fluorescence quenching ability than Cu(2+). Copyright © 2014 Elsevier Ltd. All rights reserved.

Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5.

Science.gov (United States)

Ding, Wenjin; Baracchini, Giulia; Klumpp, Michael; Schwieger, Wilhelm; Dittmeyer, Roland

2016-08-25

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 °C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 °C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 °C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 °C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example.

Competitive adsorption and selectivity sequence of heavy metals by chicken bone-derived biochar: Batch and column experiment.

Science.gov (United States)

Park, Jong-Hwan; Cho, Ju-Sik; Ok, Yong Sik; Kim, Seong-Heon; Kang, Se-Won; Choi, Ik-Won; Heo, Jong-Soo; DeLaune, Ronald D; Seo, Dong-Cheol

2015-01-01

The objective of this research was to evaluate adsorption of heavy metals in single- and ternary-metal forms onto chicken bone biochar (CBB). Competitive sorption of heavy metals by CBB has never been reported previously. The maximum adsorption capacities of metals by CBB were in the order of Cu (130 mg g(-1)) > Cd (109 mg g(-1)) > Zn (93 mg g(-1)) in the single-metal adsorption isotherm and Cu (108 mg g(-1)) > Cd (54 mg g(-1)) ≥ Zn (44 mg g(-1)) in the ternary-metal adsorption isotherm. Cu was the most retained cation, whereas Zn could be easily exchanged and substituted by Cu. Batch experimental data best fit the Langmuir model rather than the Freundlich isotherms. In the column experiments, the total adsorbed amounts of the metals were in the following order of Cu (210 mg g(-1)) > Cd (192 mg g(-1)) > Zn (178) in single-metal conditions, and Cu (156) > Cd (123) > Zn (92) in ternary-metal conditions. Results from both the batch and column experiments indicate that competitive adsorption among metals increases the mobility of these metals. Especially, Zn in single-metal conditions lost it adsorption capacity most significantly. Based on the 3D simulation graphs of heavy metals, adsorption patterns under single adsorption condition were different than under competitive adsorption condition. Results from both the batch and column experiments show that competitive adsorption among metals increases the mobility of these metals. The maximum metal adsorption capacity of the metals in the column experiments was higher than that in the batch experiment indicating other metal retention mechanisms rather than adsorption may be involved. Therefore, both column and batch experiments are needed for estimating retention capacities and removal efficiencies of metals in CBB.

Lithium recovery from salt lake brine by H2TiO3.

Science.gov (United States)

Chitrakar, Ramesh; Makita, Yoji; Ooi, Kenta; Sonoda, Akinari

2014-06-21

The details of the ion exchange properties of layered H2TiO3, derived from the layered Li2TiO3 precursor upon treatment with HCl solution, with lithium ions in the salt lake brine (collected from Salar de Uyuni, Bolivia) are reported. The lithium adsorption rate is slow, requiring 1 d to attain equilibrium at room temperature. The adsorption of lithium ions by H2TiO3 follows the Langmuir model with an adsorptive capacity of 32.6 mg g(-1) (4.7 mmol g(-1)) at pH 6.5 from the brine containing NaHCO3 (NaHCO3 added to control the pH). The total amount of sodium, potassium, magnesium and calcium adsorbed from the brine was lithium ions from the brine containing competitive cations such as sodium, potassium, magnesium and calcium in extremely large excess. The results indicate that the selectivity order Li(+) ≫ Na(+), K(+), Mg(2+), Ca(2+) originates from a size effect. The H2TiO3 can be regenerated and reused for lithium exchange in the brine with an exchange capacity very similar to the original H2TiO3.

Competitive adsorption of heavy metals in soil underlying an infiltration facility installed in an urban area.

Science.gov (United States)

Hossain, M A; Furumai, H; Nakajima, F

2009-01-01

Accumulation of heavy metals at elevated concentration and potential of considerable amount of the accumulated heavy metals to reach the soil system was observed from earlier studies in soakaways sediments within an infiltration facility in Tokyo, Japan. In order to understand the competitive adsorption behaviour of heavy metals Zn, Ni and Cu in soil, competitive batch adsorption experiments were carried out using single metal and binary metal combinations on soil samples representative of underlying soil and surface soil at the site. Speciation analysis of the adsorbed metals was carried out through BCR sequential extraction method. Among the metals, Cu was not affected by competition while Zn and Ni were affected by competition of coexisting metals. The parameters of fitted 'Freundlich' and 'Langmuir' isotherms indicated more intense competition in underlying soil compared to surface soil for adsorption of Zn and Ni. The speciation of adsorbed metals revealed less selectivity of Zn and Ni to soil organic matter, while dominance of organic bound fraction was observed for Cu, especially in organic rich surface soil. Compared to underlying soil, the surface soil is expected to provide greater adsorption to heavy metals as well as provide greater stability to adsorbed metals, especially for Cu.

A computational study on the adsorption configurations and reactions of SiH{sub x}(x = 1-4) on clean and H-covered Si(100) surfaces

Energy Technology Data Exchange (ETDEWEB)

Le, Thong N-M [Molecular Science and Nano-Materials Laboratory, Institute for Computational Science and Technology, Quang Trung Software Park, Dist. 12, Ho Chi Minh City (Viet Nam); Raghunath, P. [Center for Interdisciplinary Molecular Science, Department of Applied Chemistry, National Chiao Tung University, Hsinchu 300, Taiwan (China); Huynh, Lam K., E-mail: lamhuynh.us@gmail.com [Department of Applied Chemistry, School of Biotechnology,International University, VNU-HCMC, Quarter 6, Linh Trung, Thu Duc District, Ho Chi Minh City (Viet Nam); Lin, M.C., E-mail: chemmcl@emory.edu [Center for Interdisciplinary Molecular Science, Department of Applied Chemistry, National Chiao Tung University, Hsinchu 300, Taiwan (China)

2016-11-30

Highlights: • Possible adsorption configurations of all adsorbates on Si(100) surface are systematically explored. • The mechanisms leading to the formation of silicon adatoms on the surface are proposed. • The barriers for hydrogen abstractions from the surface are negligible comparing to the barriers for the hydrogen migrations. • The barriers for hydrogen abstractions from the adsorbed speices are negligible comparing to the barriers for the decompositions. - Abstract: Possible adsorption configurations of H and SiH{sub x} (x = 1 − 4) on clean and H-covered Si(100) surfaces are determined by using spin-polarized DFT calculations. The results show that, on the clean surface, the gas-phase hydrogen atom and SiH{sub 3} radicals effectively adsorb on the top sites, while SiH and SiH{sub 2} prefer the bridge sites of the first layer. Another possibility for SiH is to reside on the hollow sites with a triple-bond configuration. For a partially H-coverd Si(100) surface, the mechanism is similar but with higher adsorption energies in most cases. This suggests that the surface species become more stable in the presence of surface hydrogens. The minimum energy paths for the adsorption/migration and reactions of H/SiH{sub x} species on the surfaces are explored using the climbing image-nudged elastic band method. The competitive surface processes for Si thin-film formation from SiH{sub x} precursors are also predicted. The study reveals that the migration of hydrogen adatom is unimportant with respect to leaving open surface sites because of its high barriers (>29.0 kcal/mol). Alternatively, the abstraction of hydrogen adatoms by H/SiH{sub x} radicals is more favorable. Moreover, the removal of hydrogen atoms from adsorbed SiH{sub x}, an essential step for forming Si layers, is dominated by abstraction rather than the decomposition processes.

H_{2} adsorption on multiwalled carbon nanotubes at low temperatures and low pressures

Directory of Open Access Journals (Sweden)

F. Xu

2008-11-01

Full Text Available We present an experimental study on H_{2} adsorption on multiwalled carbon nanotubes (MWCNTs at low temperatures (12–30 K and low pressures (2×10^{-5}  Torr using the temperature programmed desorption technique. Our results show that the molecular hydrogen uptake increases nearly exponentially from 6×10^{-9}  wt. % at 24.5 K to 2×10^{-7}  wt. % at 12.5 K and that the desorption kinetics is of the first order. Comparative measurements indicate that MWCNTs have an adsorption capacity about two orders higher than that of activated carbon (charcoal making them a possible candidate as hydrogen cryosorber for eventual applications in accelerators and synchrotrons.

Comparisons of multilayer H2O adsorption onto the (110) surfaces of alpha-TiO2 and SnO2 as calculated with density functional theory.

Science.gov (United States)

Bandura, Andrei V; Kubicki, James D; Sofo, Jorge O

2008-09-18

Mono- and bilayer adsorption of H2O molecules on TiO2 and SnO 2 (110) surfaces has been investigated using static planewave density functional theory (PW DFT) simulations. Potential energies and structures were calculated for the associative, mixed, and dissociative adsorption states. The DOS of the bare and hydrated surfaces has been used for the analysis of the difference between the H2O interaction with TiO2 and SnO 2 surfaces. The important role of the bridging oxygen in the H2O dissociation process is discussed. The influence of the second layer of H2O molecules on relaxation of the surface atoms was estimated.

DFT study on stability and H2 adsorption activity of bimetallic Au79−nPdn (n = 1–55) clusters

International Nuclear Information System (INIS)

Liu, Xuejing; Tian, Dongxu; Meng, Changgong

2013-01-01

Highlights: ► Stability of Pd substitution type is face > mid-edge > corner > edge. ► H 2 adsorption activity is in contrast with the stability of Pd substitution type. ► Non-activated dissociation of H 2 occurs in Au 36 Pd 43−3 with high thermal stability. ► ε d agrees with that Pd at edge and corner are more active than face and mid-edge. - Abstract: The stability and H 2 adsorption activity of bimetallic Au 79−n Pd n (n = 1–55) clusters were studied by density functional theory with GGA-PW91 functional. The stability order for four Pd substitution types is face > mid-edge > corner > edge, and the stability is improved with increasing Pd content. In contrast with the stability order, H 2 adsorption activity is corner ≈ edge > mid-edge > face. The Au 36 Pd 43 (3) with Au:Pd ≈ 1:1 ratio and twenty-four Pd substitutions at (1 1 1) facets and nineteen Pd substitutions at subshell sites shows high stability and H 2 non-activated dissociation activity. The partial density of d-states and d band center revealed that the electronic properties are closely associated with the geometric characteristic and adsorption activity. Correlating the d band center ε d and the adsorption energies, the ε d order agrees with the adsorption activity that the Pd substitution at edge and corner sites are more active than at face and mid-edge sites

Study on the adsorption of H2O and CO2 from the carrier gas of high-temperature gas-cooled reactor

International Nuclear Information System (INIS)

Liao Cuiping; Zheng Zhenhong; Shi Fuen; Zhou Dasen

1998-01-01

The author is focused on the experimental studies of the adsorption of moisture and carbon dioxide from the carrier gas of high-temperature gas-cooled reactor (HTGR). A suitable adsorbent--5A type molecular sieve spherical particles with an average diameter of 3 mm is chosen to purify the carrier gas with impurities of moisture and carbon dioxide. Experimental data at different concentration, flow rate, adsorptive temperature, pressure and bed depth are obtained from isothermal adsorption tests in order to examine the effects of these parameters on adsorption dynamic and for the optimal parameters selection of adsorption process. Experimental breakthrough curves, dynamic single component and multicomponent adsorption curves are obtained. The outlet concentration of H 2 O and CO 2 can reach below 1.0 x 10 -5 , so this purification system can meet the demands of HTGR

An in-situ IR study on the adsorption of CO2 and H2O on hydrotalcites

NARCIS (Netherlands)

Coenen, K.T.; Gallucci, F.; Mezari, B.; Hensen, E.J.M.; van Sint Annaland, M.

2018-01-01

In-situ IR technique was used to study the reversible adsorption of CO2 and H2O at elevated temperatures on a potassium-promoted hydrotalcite for its use in sorption-enhanced water-gas shift (SEWGS). It was found that mainly bidentate carbonate species are responsible for the reversible (cyclic)

Adsorption properties of CO, H{sub 2} and CH{sub 4} over Pd/γ-Al{sub 2}O{sub 3} catalyst: A density functional study

Energy Technology Data Exchange (ETDEWEB)

Song, Zijian; Wang, Ben, E-mail: benwang@hust.edu.cn; Yu, Jie; Ma, Chuan; Qu, Qinggong; Zeng, Zhao; Xiang, Jun; Hu, Song; Sun, Lushi, E-mail: sunlushi@hust.edu.cn

2016-11-30

Highlights: • Model of dimer Pd supported on γ-Al{sub 2}O{sub 3} (1 1 0) surface was established. • CO, H{sub 2} and CH{sub 4} adsorption on clean γ-Al{sub 2}O{sub 3} and on Pd/γ-Al{sub 2}O{sub 3} surface was studied by DFT calculations. • CO, H{sub 2} and CH{sub 4} adsorptions are energetically more favorable in the presence of dimer Pd. • Mechanism of CO, H{sub 2} and CH{sub 4} adsorption on Pd/γ-Al{sub 2}O{sub 3} (1 1 0) surface was explained. - Abstract: Density functional theory (DFT) calculations were employed to investigate the adsorption characteristics of carbon monoxide (CO), hydrogen (H{sub 2}), and methane (CH{sub 4}) on the surface of clean γ-Al{sub 2}O{sub 3} and Pd supported γ-Al{sub 2}O{sub 3}, which is of significant for catalytic combustion. The adsorption intensities of the three gas molecules in pure γ-Al{sub 2}O{sub 3} (1 1 0) and Pd/γ-Al{sub 2}O{sub 3} (1 1 0) were in the order of CO > H{sub 2} > CH{sub 4}. The corresponding adsorption energies on the Pd/γ-Al{sub 2}O{sub 3} (1 1 0) surface were at least three times higher than those on γ-Al{sub 2}O{sub 3} (1 1 0). Anlysis of Mulliken population and partial density of states (PDOS) showed that the adsorption mechanisms were as follow: (a) CO stably adsorbed on the bridge site of dimer Pd with two C−Pd bonds because of charges transfer from the surface to CO, and the triple bond (C≡O) was broken to a double bond (C=O); (b) H{sub 2} was dissociated into hydrogen atoms on the dimer Pd and produced a stable planar configuration; and (c) the tetrahedral structure of CH{sub 4} was destroyed on the surface and formed a −CH{sub 3} species bonded to the Pd atom, which contributes to the orbital hybridization between C and Pd atoms.

Removal of diethyl phthalate from water solution by adsorption, photo-oxidation, ozonation and advanced oxidation process (UV/H{sub 2}O{sub 2}, O{sub 3}/H{sub 2}O{sub 2} and O{sub 3}/activated carbon)

Energy Technology Data Exchange (ETDEWEB)

Medellin-Castillo, Nahum A. [Centro de Investigacion y Estudios de Posgrado, Facultad de Ingenieria, Universidad Autonoma de San Luis Potosi, Av. Dr. M. Nava No.6, San Luis de Potosi, 78290 (Mexico); Ocampo-Perez, Raul [Centro de Investigacion y Estudios de Posgrado, Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, San Luis Potosi, 78290 (Mexico); Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Granada, 18071, Granada (Spain); Leyva-Ramos, Roberto [Centro de Investigacion y Estudios de Posgrado, Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, San Luis Potosi, 78290 (Mexico); Sanchez-Polo, Manuel [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Granada, 18071, Granada (Spain); Rivera-Utrilla, Jose, E-mail: jrivera@ugr.es [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Granada, 18071, Granada (Spain); Mendez-Diaz, Jose D. [Departamento de Quimica Inorganica, Facultad de Ciencias, Universidad de Granada, 18071, Granada (Spain)

2013-01-01

The objective of this work was to compare the effectiveness of conventional technologies (adsorption on activated carbon, AC, and ozonation) and technologies based on advanced oxidation processes, AOPs, (UV/H{sub 2}O{sub 2}, O{sub 3}/AC, O{sub 3}/H{sub 2}O{sub 2}) to remove phthalates from aqueous solution (ultrapure water, surface water and wastewater). Diethyl phthalate (DEP) was chosen as a model pollutant because of its high water solubility (1080 mg/L at 293 K) and toxicity. The activated carbons showed a high adsorption capacity to adsorb DEP in aqueous solution (up to 858 mg/g), besides the adsorption mechanism of DEP on activated carbon is governed by dispersive interactions between {pi} electrons of its aromatic ring with {pi} electrons of the carbon graphene planes. The photodegration process showed that the pH solution does not significantly affect the degradation kinetics of DEP and the first-order kinetic model satisfactorily fitted the experimental data. It was observed that the rate of decomposition of DEP with the O{sub 3}/H{sub 2}O{sub 2} and O{sub 3}/AC systems is faster than that with only O{sub 3}. The technologies based on AOPs (UV/H{sub 2}O{sub 2}, O{sub 3}/H{sub 2}O{sub 2}, O{sub 3}/AC) significantly improve the degradation of DEP compared to conventional technologies (O{sub 3}, UV). AC adsorption, UV/H{sub 2}O{sub 2}, O{sub 3}/H{sub 2}O{sub 2}, and O{sub 3}/AC showed a high yield to remove DEP; however, the disadvantage of AC adsorption is its much longer time to reach maximum removal. The best system to treat water (ultrapure and natural) polluted with DEP is the O{sub 3}/AC one since it achieved the highest DEP degradation and TOC removal, as well as the lower water toxicity. -- Highlights: Black-Right-Pointing-Pointer Activated carbons showed a high adsorption capacity (up to 858 mg/g) to remove DEP. Black-Right-Pointing-Pointer The pH solution did not significantly affect the photodegradation kinetics of DEP. Black

Edge functionalised & Li-intercalated 555-777 defective bilayer graphene for the adsorption of CO{sub 2} and H{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Lalitha, Murugan [School of Chemical Engineering, The University of Queensland, Brisbane 4072, QLD (Australia); Department of Physics, Bharathiar University, Coimbatore 641046, Tamil Nadu (India); Lakshmipathi, Senthilkumar, E-mail: lsenthilkumar@buc.edu.in [School of Chemical Engineering, The University of Queensland, Brisbane 4072, QLD (Australia); Department of Physics, Bharathiar University, Coimbatore 641046, Tamil Nadu (India); Bhatia, Suresh K., E-mail: s.bhatia@uq.edu.au [School of Chemical Engineering, The University of Queensland, Brisbane 4072, QLD (Australia)

2017-04-01

Highlights: • DV defect in fluorinated graphene sheet enhances hydrophobicity. • Intercalation of Li atom decreases the separation in bilayer graphene sheets. • Bernal stacking increases hydrophobicity of the bilayer graphene sheets. - Abstract: The adsorption of CO{sub 2} and H{sub 2}O on divacanacy (DV) defected graphene cluster, and its bilayer counterpart is investigated using first-principles calculations. Both single and bilayer DV graphene cluster, are functionalised with H and F atoms. On these sheets the gas molecules are physisorbed, and the divacancy defect effectively improves the adsorption of CO{sub 2}, while fluorination enhances the hydrophobicity of the graphene cluster. Among the convex and concave curvature regions induced due to the DV defect, the adsorption of the gas molecules on the concave meniscus is more favourable. Fluorine termination induces 73% reduction in Henry law constants for H{sub 2}O, while for the CO{sub 2} molecule it increases by 8%, which indicates the DV defective sheet is a better candidate for CO{sub 2} capture compared to the STW defective sheet. Besides, both AA and AB divacant defect bilayer sheets are equally stable, wherein AA stacking results in a cavity between the sheets, while in AB stacking, the layers slide one over the other. Nevertheless, both these bilayer sheets are comparatively stabler than the monolayer. However, intercalation of lithium decreases the interlayer separation, particularly in AA stacking, which enhances the CO{sub 2} adsorption, but in the Bernal stacking enhances it hydrophobicity.

Adsorption of carbamazepine by carbon nanotubes: Effects of DOM introduction and competition with phenanthrene and bisphenol A

International Nuclear Information System (INIS)

Lerman, Ilya; Chen, Yona; Xing, Baoshan; Chefetz, Benny

2013-01-01

Carbon nanotubes, organic contaminants and dissolved organic matter (DOM) are co-introduced into the environment. Thus, the interactions between these components have to be evaluated to better understand their environmental behavior. In this study, single-walled carbon nanotubes (SWCNTs) were used as sorbent, carbamazepine was the primary adsorbate, and bisphenol A and phenanthrene were used as competitors. Strong competition with bisphenol A and no effect of phenanthrene on adsorption of carbamazepine was obtained. The hydrophobic neutral fraction of the DOM exhibited the strongest reductive effect on carbamazepine adsorption, most probably due to interactions in solution. In contrast, the hydrophobic acid fraction decreased carbamazepine adsorption mainly via direct competition. When DOM and bisphenol A were co-introduced, the adsorption of carbamazepine was significantly reduced. This study suggests that the chemical nature of DOM can significantly affect the sorptive behavior of polar organic pollutants with carbon nanotubes when all are introduced to the aquatic system. Highlights: •Bisphenol A is an efficient competitor for carbamazepine. •Phenanthrene does not compete with carbamazepine. •DOM exhibited strong reductive effect on carbamazepine adsorption by SWCNTs. •HoN fraction decreased carbamazepine adsorption due to interactions in solution. •HoA fraction decreased carbamazepine adsorption via direct competition. -- In multi-component system including the main adsorbate and competitor, DOM exhibited significant effect on adsorption of contaminants by carbon nanotubes

Langmuir Isotherm application to the competitive adsorption of Cadmium, Nickel and Zinc on a Bentonite

International Nuclear Information System (INIS)

Silva Giraldo, German Dario; Pinzon Bello, Jorge Alejo

1999-01-01

In the present work, it was studied the simultaneous adsorption of binary and ternary mixtures of cadmium, nickel and zinc ions in aqueous solution at 25oC over a bentonite from the Cauca Valley, in its native state as well as in its sodium homo ionic form. The Langmuir isotherm, initially introduced by Murali and Aylmore for the competitive adsorption of various adsorbents, adequately describes the simultaneous adsorption of the three ions over the studied bentonite. The lineal correlation coefficient is greater than 0.900 in the major part of the systems. The competitive effect was interpreted by means of the thermodynamic distribution coefficient, Kdm. The degree of adsorption in the binary mixtures is nickel > zinc, cadmium over the natural bentonite, and nickel > cadmium > zinc over the sodium homo ionic form, whereas in the ternary mixture the order Nickel > Cadmium > Zinc is found over both adsorbents

A DFT-Based Model on the Adsorption Behavior of H2O, H+, Cl−, and OH− on Clean and Cr-Doped Fe(110 Planes

Directory of Open Access Journals (Sweden)

Jun Hu

2018-01-01

Full Text Available The impact of four typical adsorbates, namely H2O, H+, Cl−, and OH−, on three different planes, namely, Fe(110, Cr(110 and Cr-doped Fe(110, was investigated by using a density functional theory (DFT-based model. It is verified by the adsorption mechanism of the abovementioned four adsorbates that the Cr-doped Fe(110 plane is the most stable facet out of the three. As confirmed by the adsorption energy and electronic structure, Cr doping will greatly enhance the electron donor ability of neighboring Fe atoms, which in turn prompts the adsorption of the positively charged H+. Meanwhile, the affinity of Cr to negatively charged adsorbates (e.g., Cl− and O of H2O, OH− is improved due to the weakening of its electron donor ability. On the other hand, the strong bond between surface atoms and the adsorbates can also weaken the bond between metal atoms, which results in a structure deformation and charge redistribution among the native crystal structure. In this way, the crystal becomes more vulnerable to corrosion.

Molecular Simulations and Theoretical Predictions for Adsorption and Diffusion of CH{sub 4}/H{sub 2} and CO{sub 2}/CH{sub 4} Mixtures in ZIFs

Energy Technology Data Exchange (ETDEWEB)

Liu, Jinchen; Keskin, Seda; Sholl, David S; Johnson, J. Karl

2011-05-01

Adsorption and diffusion of CO{sub 2}/CH{sub 4} and CH{sub 4}/H{sub 2} mixtures were computed in zeolite imidazolate frameworks (ZIFs), ZIF-68 and ZIF-70, using atomically detailed simulations. Adsorption selectivity, diffusion selectivity, and membrane selectivity of ZIFs were calculated based on the results of atomistic simulations. Mixture adsorption isotherms predicted by the ideal adsorbed solution theory agree well with the results of molecular simulations for both ZIFs. Mixture diffusivity calculations indicate that diffusion of CH{sub 4} is increased with increasing concentration of H{sub 2} in the CH{sub 4}/H{sub 2} mixture, while the diffusivity of H{sub 2} decreases with increasing CH{sub 4} concentration. In contrast, the diffusivity of CH{sub 4} is essentially independent of the concentration of CO{sub 2} in the CO{sub 2}/CH{sub 4} mixture, while CO{sub 2} diffusivity decreases with increased CH{sub 4} loading, even though the diffusivity of CH{sub 4} is substantially larger than that of CO{sub 2}. This unusual behavior can be explained in terms of differences in adsorption site preferences due to charge–quadrupole interactions.

Investigation of mono/competitive adsorption of environmentally relevant ionized weak acids on graphite: impact of molecular properties and thermodynamics.

Science.gov (United States)

Moustafa, Ahmed M A; McPhedran, Kerry N; Moreira, Jesús; Gamal El-Din, Mohamed

2014-12-16

The thermodynamics of adsorption and competitive interactions of five weak acids on a graphite surface was assessed in alkaline solutions. Adsorption of the acids in mono- and multicompound solutions followed their Freundlich isotherms which suggest a diversity of graphite adsorption sites as confirmed by the presence of carboxylic and phenolic groups observed on graphite surfaces. Thermodynamic calculations assigned the formation of the negatively charged assisted hydrogen bond (-CAHB) between ionized solutes and adsorbent surface groups as the possible adsorption mechanism. However, the similar pKa values of current acids resulted in comparable free energies for -CAHB formation (ΔG(-CAHB)) being less than solvation free energies (ΔGSolv). Thus, additional ΔG is supplemented by increased hydrophobicity due to proton exchange of ionized acids with water (ΔΔG Hydrophobicity). Adsorption capacities and competition coefficients indicated that ΔΔG Hydrophobicity values depend on the neutral and ionized acid Kow. Competitive adsorption implies that multilayer adsorption may occur via hydrophobic bonding with the CH3 ends of the self-assembled layer which affects the acid adsorption capacities in mixtures as compared to monocompound solutions. The determination of adsorption mechanisms will assist in understanding of the fate and bioavailability of emerging and classical weak acids released into natural waters.

Molecular dynamics simulations of H2 adsorption in tetramethyl ammonium lithium phthalocyanine crystalline structures.

Science.gov (United States)

Lamonte, Kevin; Gómez Gualdrón, Diego A; Cabrales-Navarro, Fredy A; Scanlon, Lawrence G; Sandi, Giselle; Feld, William; Balbuena, Perla B

2008-12-11

Tetramethyl ammonium lithium phthalocyanine is explored as a potential material for storage of molecular hydrogen. Density functional theory calculations are used to investigate the molecular structure and the dimer conformation. Additional scans performed to determine the interactions of a H2 molecule located at various distances from the molecular sites are used to generate a simple force field including dipole-induced-dipole interactions. This force field is employed in molecular dynamics simulations to calculate adsorption isotherms at various pressures. The regions of strongest adsorption are quantified as functions of temperature, pressure, and separation between molecules in the adsorbent phase, and compared to the regions of strongest binding energy as given by the proposed force field. It is found that the total adsorption could not be predicted only from the spatial distribution of the strongest binding energies; the available volume is the other contributing factor even if the volume includes regions of much lower binding energy. The results suggest that the complex anion is primarily involved in the adsorption process with molecular hydrogen, whereas the cation serves to provide access for hydrogen adsorption in both sides of the anion molecular plane, and spacing between the planes.

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 +}.

Combined microcalorimetric and IR spectroscopic study on carbon dioxide adsorption in H-MCM-22

Energy Technology Data Exchange (ETDEWEB)

Arean, C.O., E-mail: co.arean@uib.es [Department of Chemistry, University of the Balearic Islands, 07122 Palma de Mallorca (Spain); Delgado, M.R. [Department of Chemistry, University of the Balearic Islands, 07122 Palma de Mallorca (Spain); Bulánek, R.; Frolich, K. [Department of Physical Chemistry, Faculty of Chemical Technology, University of Pardubice, 532 10 Pardubice (Czech Republic)

2014-10-15

Highlights: • Adsorption calorimetry and variable temperature IR spectroscopy is used to study adsorption of CO{sub 2} in the protonic zeolite H-MCM-22. • By simultaneously recording IR absorbance over a temperature range, temperature and equilibrium pressure, standard adsorption enthalpy and entropy of CO{sub 2} was determined. • The results are discussed in the broader context of carbon dioxide capture from the flue gas of fossil fuel fired power stations. - Abstract: The thermodynamics of carbon dioxide adsorption in the protonic zeolite H-MCM-22 (Si:Al = 16:1) was investigated by means of adsorption calorimetry and variable-temperature IR spectroscopy, a technique that affords determination of standard adsorption enthalpy (ΔH{sup 0}) and entropy (ΔS{sup 0}) from analysis of a series of IR spectra recorded over a temperature range while simultaneously measuring equilibrium pressure inside a closed IR cell. ΔH{sup 0} resulted to be −24.5 (±2) kJ mol{sup −1}, while for the entropy change the value of ΔS{sup 0} = −115 (±10) J mol{sup −1} K{sup −1} was obtained. The obtained ΔH{sup 0} value is compared with those reported in the literature for the adsorption of CO{sub 2} on other zeolites, and discussed in the context of carbon dioxide capture and sequestration.

Selective adsorption behavior of Cd(II) ion imprinted polymers synthesized by microwave-assisted inverse emulsion polymerization: Adsorption performance and mechanism

Energy Technology Data Exchange (ETDEWEB)

Zhu, Fang, E-mail: zhufang@tyut.edu.cn [College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, 030024 (China); Li, Luwei [College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, 030024 (China); Xing, Junde [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi, 030024 (China)

2017-01-05

Highlights: • Microwave assisted inverse emulsion polymerization was applied to prepare Cd(II) imprinted polymers. • The adsorption capacity was evaluated by static adsorption experiments. • Pseudo-second-order model and Langmuir adsorption isotherm model had the best agreement with the experimental data. • The adsorption was a spontaneous and endothermic process. • Cd(II) imprinted polymers have specific identification for Cd(II). - Abstract: Microwave-assisted inverse emulsion polymerization method was used to prepare Cd(II) imprinted polymer (IIP) by using β-cyclodextrin (β-CD) and acrylamide (AM) as functional monomer, epichlorohydrin (ECH) as crossing-linking agent, ammonium persulfate as initiator. The Cd(II) imprinted polymer was characterized by SEM, FTIR and TGA. The influences of initial concentration of Cd(II), pH values, temperature, time and competitive ions on adsorption capacity and recognition properties are investigated. Under the optimal conditions, the adsorption capacity could reach 107 mg/g. Furthermore, pseudo first order kinetic model, pseudo second order kinetic model and intra-particular diffusion model were used to describe the adsorption kinetic behavior. Results showed that the pseudo-second-order model (R{sup 2} 0.9928–0.9961) had the best agreement with the experimental data. Langmuir adsorption isotherm model described the experimental data well, which indicated that adsorption was mainly monolayer absorption. Moreover, the study of adsorption thermodynamics (ΔG{sup 0} < 0, ΔH{sup 0} > 0, ΔS{sup 0} > 0) suggested that the adsorption process was a spontaneous and endothermic process. Competitive selectivity experiment revealed that imprinted polymer could selectively recognize Cd(II). It provides a new idea for removing Cd(II) from aqueous solution.

pH-dependence of pesticide adsorption by wheat-residue-derived black carbon.

Science.gov (United States)

Yang, Yaning; Chun, Yuan; Sheng, Guangyao; Huang, Minsheng

2004-08-03

The potential of black carbon as an adsorbent for pesticides in soils may be strongly influenced by the properties of the adsorbent and pesticides and by the environmental conditions. This study evaluated the effect of pH on the adsorption of diuron, bromoxynil, and ametryne by a wheat (Triticum aestivum L.) residue derived black carbon (WC) as compared to a commercial activated carbon (AC). The pH drift method indicated that WC had a point of zero charge of 4.2, much lower than that of 7.8 for AC. The density of oxygen-containing surface functional groups, measured by the Boehm titration, on WC was 5.4 times higher than that on AC, resulting in a pesticide adsorption by WC being 30-50% of that by AC, due to the blockage of WC surface by the waters associated with the functional groups. A small decrease (5.5%/unit pH) in diuron adsorption by WC with increase in pH resulted from increased deprotonation of surface functional groups at higher pH values. A much larger decrease (14-21%/unit pH) in bromoxynil adsorption by WC with increase in pH resulted from the deprotonation of both the adsorbate and surface functional groups of the adsorbent. The deprotonation reduced the adsorptive interaction between bromoxynil and the neutral carbon surface and increased the electrical repulsion between the negatively charged WC surface and bromoxynil anions. Deprotonation of ametryne with increase in pH over the low pH range increased its fraction of molecular form and thus adsorption on WC by 15%/unit pH. Further increase in pH resulted in a 20%/unit pH decrease in ametryne adsorption by WC due primarily to the development of a negative charge on the surface of WC. The pH-dependent adsorption of pesticides by black carbon may significantly influence their environmental fate in soils.

The Tunable Bandgap of AB-Stacked Bilayer Graphene on SiO2 with H2O Molecule Adsorption

International Nuclear Information System (INIS)

Wang Tao; Guo Qing; Liu Yan; Wang Wen-Bo; Sheng Kuang; Ao Zhi-Min; Yu Bin

2011-01-01

The atomic and electronic structures of AB-stacking bilayer graphene (BLG) in the presence of H 2 O molecules are investigated by density functional theory calculations. For free-standing BLG, the bandgap is opened to 0.101 eV with a single H 2 O molecule adsorbed on its surface. The perfectly suspended BLG is sensitive to H 2 O adsorbates, which break the BLG lattice symmetry and open an energy gap. While a single H 2 O molecule is adsorbed on the BLG surface with a SiO 2 substrate, the bandgap widens to 0.363 eV. Both the H 2 O molecule adsorption and the oxide substrate contribute to the BLG bandgap opening. The phenomenon is interpreted with the charge transfer process in 2D carbon nanostructures. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Single and Competitive Adsorption of 17α-Ethinylestradiol and Bisphenol A with Estrone, β-Estradiol, and Estriol onto Sediment

Directory of Open Access Journals (Sweden)

Yu Li

2014-03-01

Full Text Available The competitive adsorption of bisphenol A (BPA and17α-ethinylestradiol (EE2 with different endocrine disrupting compounds (EDCs, such as estrone (E1, β-estradiol (E2, and estriol (E3 was investigated in the water-sediment system. The primary and interaction effects of coexisted EDCs on the adsorption of BPA and EE2 were studied in binary and multiple systems. The adsorption selectivity of sediment at different initial concentrations of EDCs was also considered, based on the distribution coefficient (β. In binary systems, coexisted EDCs exhibited a positive effect on the adsorption of BPA, while E3 showed a negative effect on the adsorption of EE2. In ternary systems, the interaction of E1*E3 and E2*BPA showed a synergistic effect on the sorption of BPA and EE2, respectively. In quaternary systems, the interaction of E1*E2*E3 showed a synergistic effect on the adsorption of both BPA and EE2. In the quinary system, coexisted EDCs all showed an antagonistic effect on the adsorption of BPA and EE2, which indicated that the coexisted EDCs competed for adsorption with BPA and EE2. EDCs in the E2-EE2-BPA system presented a superior selectivity of sediment with β values of 43.48–87.86. The order of sediment selectivity (E1 > EE2 > E2 > E3 > BPA in binary systems was in agreement with EDCs’ adsorption capacity, which suggested that the adsorption was dominated by partition adsorption.

Competitive Adsorption of Chloroform and Bromoform Using ...

African Journals Online (AJOL)

The results obtained were checked with Freundlich adsorption isotherm model. This model expresses well adsorption of one THM species in the presence of another with R2 > 0.95. Based on the model, adsorption capacity of Calgon F200 and Norit GCN1240 were found higher for bromoform than chloroform. Calgon F200 ...

Effect of pH on boron adsorption in some soils of Paraná, Brazil

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Fábio Steiner

2013-06-01

Full Text Available Temporary B deficiency can be triggered by liming of acid soils because of increased B adsorption at higher soil pH. Plants respond directly to the activity of B in soil solution and only indirectly to B adsorbed on soil constituents. Because the range between deficient and toxic B concentration is relatively narrow, this poses difficulty in maintaining appropriate B levels in soil solution. Thus, knowledge of the chemical behavior of B in the soil is particularly important. The present study investigated the effect of soil pH on B adsorption in four soils of Paraná State, and to correlate these values with the physical and chemical properties of the soils. Surface samples were taken from a Rhodic Hapludox, Arenic Hapludalf, Arenic Hapludult, and one Typic Usthorthent. To evaluate the effect of pH on B adsorption, subsamples soil received the application of increasing rates of calcium carbonate. Boron adsorption was accomplished by shaking 2.0 g soil, for 24 h, with 20 mL of 0.01 mol L¹ NaCl solution containing different concentrations (0.0, 0.1, 0.2, 0.4, 0.8, 1.2, 1.6, 2.0, and 4.0 mg B L-1. Sorption was fitted to non-linear form of the Langmuir adsorption isotherm. Boron adsorption increased as concentration increased. Boron adsorption was dependent on soil pH, increasing as a function of pH in the range between 4.6 and 7.4, although the bonding energy has decreased. Maximum adsorption capacity (MAC of B was observed in the Arenic Hapludalf (49.8 mg B kg-1 soil followed by Arenic Hapludult (22.5 mg kg-1, Rhodic Hapludox (17.4 mg kg-1, and Typic Usthorthent (7.0 mg kg-1. The organic matter content, clay content, and aluminum oxide content (Al2O3 were the soils properties that affecting the B adsorption on Paraná soils.

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

Adsorption of water on O(2x2)/Ru(0001): thermal stability and inhibition of dissociation by H2O-O bonding

Energy Technology Data Exchange (ETDEWEB)

Mugarza, Aitor; Shimizu, Tomoko; Cabrera-Sanfelix, Pepa; Sanchez-Portal, Daniel; Arnau, Andres; Salmeron, Miquel

2008-08-01

The effect of preadsorbed oxygen on the subsequent adsorption and reactions of water on Ru(0001) has been studied using low temperature scanning tunneling microscopy and DFT calculations. Experiments were carried out for O coverages close to 0.25 ML. It was found that no dissociation of water takes place up to the desorption temperature of {approx}180-230 K. DFT calculations show that intact water on O(2x2)/Ru(0001) is {approx} 0.49 eV more stable than the dissociation products, H and OH, at their preferred fcc and top adsorption sites.

High-throughput screening of small-molecule adsorption in MOF-74

Science.gov (United States)

Thonhauser, T.; Canepa, P.

2014-03-01

Using high-throughput screening coupled with state-of-the-art van der Waals density functional theory, we investigate the adsorption properties of four important molecules, H2, CO2, CH4, and H2O in MOF-74-  with  = Be, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Zr, Nb, Ru, Rh, Pd, La, W, Os, Ir, and Pt. We show that high-throughput techniques can aid in speeding up the development and refinement of effective materials for hydrogen storage, carbon capture, and gas separation. The exploration of the configurational adsorption space allows us to extract crucial information concerning, for example, the competition of water with CO2 for the adsorption binding sites. We find that only a few noble metals--Rh, Pd, Os, Ir, and Pt--favor the adsorption of CO2 and hence are potential candidates for effective carbon-capture materials. Our findings further reveal significant differences in the binding characteristics of H2, CO2, CH4, and H2O within the MOF structure, indicating that molecular blends can be successfully separated by these nano-porous materials. Supported by DOE DE-FG02-08ER46491.

Competitive biosorption of thorium and uranium by Micrococcus luteus

International Nuclear Information System (INIS)

Nakajima, A.; Tsuruta, T.

2004-01-01

Eighteen species of bacteria were screened for abilities to adsorb thorium and uranium. High adsorption capacity was observed for thorium by Arthrobacter nicotianae and Micrococcus luteus, and for uranium by Arthrobacter nicotianae. The adsorption of both thorium and uranium by Micrococcus luteus cells was rapid, was affected by the solution pH, and obeyed the Langmuir adsorption isotherm for binary systems in a competitive manner taking the ionic charge of the metal ion into account. The thorium selectivity in the competitive adsorption is assumed to be caused by the faster adsorption and the slower desorption rates of thorium than those of uranium. (author)

Studies of surface adsorption on LiAlO2

International Nuclear Information System (INIS)

Fischer, A.K.; Johnson, C.E.; McDaniel, J.A.

1986-01-01

Computational and experimental approaches are being taken to understanding surface adsorption/desorption effects on tritium inventory and release. The computational survey integrates a thermodynamic treatment of surface adsorption and bulk phase effects such as solubility and gas phase composition. The system T 2 O:T 2 :LiAlO 2 was examined. The calculations indicate that surface adsorption can be expected to contribute most to tritium inventory under the conditions of lower temperatures and higher oxygen activities. Higher temperature and lower oxygen activity favor lower surface inventory. In the experimental work, a high temperature gas chromatograph was constructed in order to measure the H 2 O:H 2 surface adsorption isotherms and the solubility of hydroxide in LiAlO 2 . Preliminary data indicate that at 478 K approximately 15% of the surface is coverred for a partial pressure of H 2 O of approximately 52 Pa. Calculated values can be obtained that are in reasonable agreement with this. (orig.)

Studies of surface adsorption on LiAlO2

International Nuclear Information System (INIS)

Fischer, A.K.; McDaniel, J.A.; Johnson, C.E.

1986-01-01

Computational and experimental approaches are being taken to understanding surface adsorption/desorption effects on tritium inventory and release. The computational survey integrates a thermodynamic treatment of surface adsorption and bulk phase effects such as solubility and gas phase composition. The system T 2 O:T 2 :LiAlO 2 was examined. The calculations indicate that surface adsorption can be expected to contribute most to tritium inventory under the conditions of lower temperatures and higher oxygen activities. Higher temperature and lower oxygen activity favor lower surface inventory. In the experimental work, a high temperature gas chromatograph was constructed in order to measure the H 2 O:H 2 surface adsorption isotherms and the solubility of hydroxide in LiAlO 2 . Preliminary data indicate that at 478K approximately 15% of the surface is covered for a partial pressure of H 2 O of approximately 52 Pa. Calculated values can be obtained that are in reasonable agreement with this

Adsorption and dissociation of H2O on Al(1 1 1) surface by density functional theory calculation

International Nuclear Information System (INIS)

Guo, F.Y.; Long, C.G.; Zhang, J.; Zhang, Z.; Liu, C.H.; Yu, K.

2015-01-01

Highlights: • O 2 on Al(1 1 1) surface can spontaneously dissociate, but H 2 O can not. • H 2 O, OH and H on top sites are favorable on Al(1 1 1) surface. • O on the hollow (fcc) site is preferred. • O which plays a key role in the dissociate reaction of H 2 O. - Abstract: Using the first-principles calculations method based on the density functional theory, we systematically study the adsorption behavior of a single molecular H 2 O on a clean and a pre-adsorbed O atom Al(1 1 1) surface, and also its corresponding dissociation reactions. The equilibrium configuration on top, bridge, and hollow (fcc and hcp) site were determined by relaxation of the system relaxation. The adsorptions of H 2 O, OH and H on top sites are favorable on the Al(1 1 1) surface, while that of O on the hollow (fcc) site is preferred. The results show that the hydrogen atom dissociating from H 2 O needs a 248.32 kJ/mol of energy on clean Al(1 1 1) surface, while the dissociating energy decreases to 128.53 kJ/mol with the aid of the O absorption. On the other hand, these phenomena indicate that the dehydrogenated reaction energy barrier of the pre-adsorbed O on metal surface is lower than that of on a clean one, because O can promote the dehydrogenation of H 2 O

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.

A computational study on the adsorption configurations and reactions of SiHx(x = 1-4) on clean and H-covered Si(100) surfaces

Science.gov (United States)

Le, Thong N.-M.; Raghunath, P.; Huynh, Lam K.; Lin, M. C.

2016-11-01

Possible adsorption configurations of H and SiHx (x = 1 - 4) on clean and H-covered Si(100) surfaces are determined by using spin-polarized DFT calculations. The results show that, on the clean surface, the gas-phase hydrogen atom and SiH3 radicals effectively adsorb on the top sites, while SiH and SiH2 prefer the bridge sites of the first layer. Another possibility for SiH is to reside on the hollow sites with a triple-bond configuration. For a partially H-coverd Si(100) surface, the mechanism is similar but with higher adsorption energies in most cases. This suggests that the surface species become more stable in the presence of surface hydrogens. The minimum energy paths for the adsorption/migration and reactions of H/SiHx species on the surfaces are explored using the climbing image-nudged elastic band method. The competitive surface processes for Si thin-film formation from SiHx precursors are also predicted. The study reveals that the migration of hydrogen adatom is unimportant with respect to leaving open surface sites because of its high barriers (>29.0 kcal/mol). Alternatively, the abstraction of hydrogen adatoms by H/SiHx radicals is more favorable. Moreover, the removal of hydrogen atoms from adsorbed SiHx, an essential step for forming Si layers, is dominated by abstraction rather than the decomposition processes.

Concurrent separation of CO2 and H2O from air by a temperature-vacuum swing adsorption/desorption cycle.

Science.gov (United States)

Wurzbacher, Jan Andre; Gebald, Christoph; Piatkowski, Nicolas; Steinfeld, Aldo

2012-08-21

A temperature-vacuum swing (TVS) cyclic process is applied to an amine-functionalized nanofibrilated cellulose sorbent to concurrently extract CO(2) and water vapor from ambient air. The promoting effect of the relative humidity on the CO(2) capture capacity and on the amount of coadsorbed water is quantified. The measured specific CO(2) capacities range from 0.32 to 0.65 mmol/g, and the corresponding specific H(2)O capacities range from 0.87 to 4.76 mmol/g for adsorption temperatures varying between 10 and 30 °C and relative humidities varying between 20 and 80%. Desorption of CO(2) is achieved at 95 °C and 50 mbar(abs) without dilution by a purge gas, yielding a purity exceeding 94.4%. Sorbent stability and a closed mass balance for both H(2)O and CO(2) are demonstrated for ten consecutive adsorption-desorption cycles. The specific energy requirements of the TVS process based on the measured H(2)O and CO(2) capacities are estimated to be 12.5 kJ/mol(CO2) of mechanical (pumping) work and between 493 and 640 kJ/mol(CO2) of heat at below 100 °C, depending on the air relative humidity. For a targeted CO(2) capacity of 2 mmol/g, the heat requirement would be reduced to between 272 and 530 kJ/mol(CO2), depending strongly on the amount of coadsorbed water.

Adsorption and decomposition of H{sub 2}O on cobalt surfaces: A DFT study

Energy Technology Data Exchange (ETDEWEB)

Ma, F.F.; Ma, S.H., E-mail: msh8586@163.com; Jiao, Z.Y.; Dai, X.Q.

2016-10-30

Highlights: • Molecular water weakly binds to Co surfaces and it is feasible to desorption from the clean surfaces. • The presence of atomic oxygen has a prominent promotion effect on the dissociation of water into hydroxyl, especially on O-covered Co(110) no extra energy is needed to dissociate H{sub 2}O. • Distinctively, the presence of hydroxyl hinders the dissociation of water molecule. • The analysis of microscopic decomposition behaviors demonstrates that molecular water adsorbs dissociatively with the aid of pre-adsorbed oxygen atom, forming OH radicals chemisorbed on the considered surfaces. - Abstract: Water adsorption and dissociation on clean and O-covered Co(100), Co(110) and Co(111) surfaces are studied using the density functional theory calculations. The results indicate that molecular water weakly binds to the surfaces and is feasible to desorption from the clean surfaces. Moreover, the pre-adsorption of O atom increases the binding of water to the surfaces, and prominently decreases the activation barriers of water dissociation into OH, especially on Co(110) surface. In contrast, the activation barrier for OH dissociation is slightly affected in the presence of O atom. Overall, this study reveals that O-assisted H{sub 2}O favorably adsorbs dissociatively, forming OH chemisorbed on the surfaces, which further hinders H{sub 2}O dissociation, and also illustrates the fact that molecular water dissociation is structure-sensitive on metal surfaces.

Support effects in single atom iron catalysts on adsorption characteristics of toxic gases (NO2, NH3, SO3 and H2S)

Science.gov (United States)

Gao, Zhengyang; Yang, Weijie; Ding, Xunlei; Lv, Gang; Yan, Weiping

2018-04-01

The effects of support on gas adsorption is crucial for single atom catalysts design and optimization. To gain insight into support effects on gas adsorption characteristics, a comprehensive theoretical study was performed to investigate the adsorption characteristics of toxic gases (NO2, NH3, SO3 and H2S) by utilizing single atom iron catalysts with three graphene-based supports. The adsorption geometry, adsorption energy, electronic and magnetic properties of the adsorption system have been explored. Additionally, the support effects have been analyzed through d-band center and Fermi softness, and thermodynamic analysis has been performed to consider the effect of temperature on gas adsorption. The support effects have a remarkable influence on the adsorption characteristics of four types of toxic gases which is determined by the electronic structure of graphene-based support, and the electronic structure can be characterized by Fermi softness of catalysts. Fermi softness and uplift height of Fe atom could be good descriptors for the adsorption activity of single atom iron catalysts with graphene-based supports. The findings can lay a foundation for the further study of graphene-based support effects in single atom catalysts and provide a guideline for development and design of new graphene-based support materials utilizing the idea of Fermi softness.

Effect of the pH on the radiocesium adsorption in tropical soils

International Nuclear Information System (INIS)

Roque, Mario Lucio; Boaretto, Antonio E.; Moniz, Antonio C; Smolders, Erik E. T.

2002-01-01

The objective was to demonstrate that the pH dependent charges are specific change sites for radiocesium. Clay minerals occurrence in superficial samples of eight tropical soils was analyzed by X-Ray diffractometry. The variation of superficial charge of these soils were quantify by potentiometric titration in a range from 3 to 8 pH values. The results of radiocesium interception potential showed the presence of specific sites of adsorption of this radionuclide for all the soils. The variation of radiocesium adsorption for all soils was quantified in a pH defined range. The increase on the pH values caused increase on the radiocesium adsorption by the soils and a consequent decrease in the radiocesium activity in the equilibrium solution. The soil with predominance of the 2:1 clay minerals showed higher radiocesium adsorption than the soils with 1:1 clay minerals or iron and aluminum oxides. The increase on the negative charge in consequence of pH increase caused increase on radiocesium adsorption. The correction of soil acidity with lime by increasing the specific sites charge for radiocesium and decreasing the radionuclide activity in soil solution may cause decrease on the transference of radiocesium from soil to plant. (author)

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)

Effects of wood vinegar on properties and mechanism of heavy metal competitive adsorption on secondary fermentation based composts.

Science.gov (United States)

Liu, Ling; Guo, Xiaoping; Wang, Shuqi; Li, Lei; Zeng, Yang; Liu, Guanhong

2018-04-15

In this study, secondary municipal solid waste composts (SC) and wood vinegar treated secondary compost (WV-SC) was prepared to investigate the capability for single-heavy metals and multi-metal systems adsorption. The adsorption sequence of WV-SC for the maximum single metals sorption capacities was Cd (42.7mgg -1 ) > Cu (38.6mgg -1 ) > Zn (34.9mgg -1 ) > Ni (28.7mgg -1 ) and showed higher than that of SC adsorption isotherm. In binary/quaternary-metal systems, Ni adsorption showed a stronger inhibitory effect compared with Zn, Cd and Cu on both SC and WV-SC. According to Freundlich and Langmuir adsorption isotherm models, as well as desorption behaviors and speciation analysis of heavy metals, competitive adsorption behaviors were differed from single-metal adsorption. Especially, the three-dimensional simulation of competitive adsorption indicated that the Ni was easily exchanged and desorbed. The amount of exchangeable heavy metal fraction were in the lowest level for the metal-loaded adsorbents, composting treated by wood vinegar improved the adsorbed metals converted to the residue fraction. This was an essential start in estimating the multiple heavy metal adsorption behaviors of secondary composts, the results proved that wood vinegar was an effective additive to improve the composts quality and decrease the metal toxicity. Copyright © 2017 Elsevier Inc. All rights reserved.

Adsorption competition study between oxygenated compounds and hydrocarbons on molecular sieves; Etude de la competition d`adsorption entre les composes oxygenes et les hydrocarbures sur les tamis moleculaires

Energy Technology Data Exchange (ETDEWEB)

Kong Ming, L.

1996-11-29

The aim of this study is to determine the competitive behavior of methanol and l -hexene in an n-hexane solvent system using a 13-x and a molecular sieves as the adsorbent. Adsorption was carried out in liquid phase. Parameters such as concentration, flowrate, temperature and column, length were varied in order to assess their effects on the breakthrough curves. In methanol-n-hexane system, it was found that the concentration profiles of the breakthrough curves were not very much influenced by the parameters except for the amount of volume of feed processes. However, changes in the flowrate does not have a significant effect on the concentration profile. A higher flowrate, the profile assumes a more dispersive pattern which of course is expected due to lower contact time if internal diffusion is rate determining. In the case of l -hexane carries out at different temperatures and column lengths there were some differences in concentration profiles. This may be due to experimental difficulties in controlling the flowrate at the start of the experiment rather than inherent adsorption behavior. In the 3-component system, 1 -hexene breakthrough was very much earlier as compared to methanol. Desorption carried out at 383 k and with flowrate of 28{+-}l g/min and for 100 minutes for all cases showed little variation. Re-adsorption under various conditions showed marked reduction in the amount of feed processed. The breakthrough curves were simulated using an Institut Francais du Petrole (IFP) proprietary computer program which is based on selectivity and theoretical plates and which predicts very well for xylene separation. In the 1 -hexene-n-hexane system, the simulator predicted reasonably well in terms of bed volume processed, however, for the methanol-n-hexane system the simulator failed. For the program to be effective, some mathematical treatments needs to be done with respect to the handling of the numerical analysis. To describe the adsorption equilibrium, two

DFT study of adsorption and dissociation behavior of H2S on Fe-doped graphene

International Nuclear Information System (INIS)

Zhang, Hong-ping; Luo, Xue-gang; Song, Hong-tao; Lin, Xiao-yan; Lu, Xiong; Tang, Youhong

2014-01-01

Highlights: • Fe-doped and Pt-doped graphene can significantly improve the interactions between H 2 S and graphene. • The location of S had an important role in the interactions between H 2 S and Fe-doped graphene. • The influence of Fe-S distance can be very weak in a certain range and H 2 S can be dissociated into S and H 2 . - Abstracts: Understanding the interaction mechanisms of hydrogen sulfide (H 2 S) with graphene is important in developing graphene-based sensors for gas detection and removal. In this study, the effects of doped Fe atom on interaction of H 2 S with graphene were investigated by density functional theory calculations. Analyses of adsorption energy, electron density difference, and density of states indicated that the doped Fe atom can significantly improve the interaction of H 2 S gas molecules with graphene, as well as Pt-doped graphene. The location of the sulfur atom is important in the interactions between H 2 S and Fe-doped graphene. The influence of the Fe-S distance can be very weak within a certain distance, as simulated in this study

Adsorption of H{sub 2}S or SO{sub 2} on an activated carbon cloth modified by ammonia treatment

Energy Technology Data Exchange (ETDEWEB)

Boudou, J.P.; Chehimi, M.; Broniek, E.; Siemieniewska, T.; Bimer, J. [University of Paris, Paris (France)

2003-07-01

The aim of this research is to investigate how ammonia treatment of the surface can influence the activity of a viscose-based activated carbon cloth (ACC) for the oxidative retention of H{sub 2}S and SO{sub 2} in humid air at 25{sup o}C. Surface basic nitrogen groups were introduced either by treatment with ammonia/air at 300{sup o}C or with ammonia/steam at 800{sup o}C. The pore structure of the samples so prepared was examined by adsorption measurements. Changes in the surface chemistry were assessed by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and temperature programmed desorption (TPD). The change of ACC activity could not be merely attributed to surface nitrogen groups but to other changes in the support. Ammonia/steam treatment improved ACC performance the most, not only by introducing nitrogen surface groups, but also by extending the microporosity and by modifying the distribution of surface oxygen groups. Successive adsorption-regeneration cycles showed important differences between oxidative retention of H{sub 2}S and SO{sub 2} and the subsequent catalyst/support regeneration process.

Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2)

Energy Technology Data Exchange (ETDEWEB)

Chang, Po-Hsiang [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Jiang, Wei-Teh, E-mail: atwtj@mail.ncku.edu.tw [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Li, Zhaohui, E-mail: li@uwp.edu [Department of Geosciences, University of Wisconsin – Parkside, 900 Wood Road, Kenosha, WI 53144 (United States); Kuo, Chung-Yih [Department of Public Health, College of Health Care and Management, Chung Shan Medical University, No. 110, Sec. 1, Chien-kuo N Road, Taichung 40242, Taiwan (China); Jean, Jiin-Shuh [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Chen, Wan-Ru [Department of Environmental Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Lv, Guocheng [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China)

2014-07-30

Graphical abstract: XRD patterns to show AMI intercalation into SAz-2 vs. direct mixing of the same amount of AMI with SAz-2. - Highlights: • Ca-montmorillonite is proven to be an efficient adsorbent or sink for amitriptyline. • The high adsorption capacity is accompanied with intercalation into interlayers. • The adsorption is mainly governed by a cation exchange mechanism. • Horizontal mono- and bi-layer conformations occur at low and high adsorption levels. • The process is an endothermic physisorption at high adsorption levels. - Abstract: The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330 mg/g (1.05 mmol/g) at pH 6–7. The adsorption kinetics was fast, almost reaching equilibrium in 2 h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d{sub 0} {sub 0} {sub 1} spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater.

Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2)

International Nuclear Information System (INIS)

Chang, Po-Hsiang; Jiang, Wei-Teh; Li, Zhaohui; Kuo, Chung-Yih; Jean, Jiin-Shuh; Chen, Wan-Ru; Lv, Guocheng

2014-01-01

Graphical abstract: XRD patterns to show AMI intercalation into SAz-2 vs. direct mixing of the same amount of AMI with SAz-2. - Highlights: • Ca-montmorillonite is proven to be an efficient adsorbent or sink for amitriptyline. • The high adsorption capacity is accompanied with intercalation into interlayers. • The adsorption is mainly governed by a cation exchange mechanism. • Horizontal mono- and bi-layer conformations occur at low and high adsorption levels. • The process is an endothermic physisorption at high adsorption levels. - Abstract: The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330 mg/g (1.05 mmol/g) at pH 6–7. The adsorption kinetics was fast, almost reaching equilibrium in 2 h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d 0 0 1 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater

Investigating the adsorption of H2O on ZnO nanoclusters by first principle calculations

KAUST Repository

Al-Sunaidi, Abdullah A.

2011-04-01

The interaction of a single H2O molecule on selected ZnO nanoclusters is investigated by carrying out calculations based on the density-functional theory at the hybrid-GGA (B97-2) level. These clusters have ring, drum, tube and bubble shapes and their physical properties like the binding energy and the band gap energy depend strongly on the shape and size of the cluster. Depending on the stability of the cluster, H2O show both chemisorption and dissociation on the surfaces of the clusters. We analyzed the effect of H2O adsorption on the properties of clusters of size n = 12 via the density of state, HOMO-LUMO orbitals and the changes in the IR frequencies. © 2011 Elsevier B.V. All rights reserved.

Adsorption of cationic dye on a biohybrid SiO2-alginate

International Nuclear Information System (INIS)

Barrón Zambrano, J A; Ávila Ortega, A; Muñoz Rodríguez, D; Carrera Figueiras, C; López-Pérez, A J

2013-01-01

In this work, a biohybrid material based on SiO 2 -alginate was obtained and its properties of adsorption evaluated using methylene blue as a model dye. The experimental results showed that the biohybrid SiO 2 -alginate has a higher adsorption ability compared to their base compounds (SiO 2 and alginate). Methylene blue adsorption is pH dependent, resulting in a maximum adsorption at pH = 8. The sorption kinetics rate is similar to SiO 2 . Kinetic data were fitted to a model of pseudosecond order. The experimental isotherms fit well the Langmuir model.

Modeling the adsorption of metal ions (Cu 2+, Ni 2+, Pb 2+) onto ACCs using surface complexation models

Science.gov (United States)

Faur-Brasquet, Catherine; Reddad, Zacaria; Kadirvelu, Krishna; Le Cloirec, Pierre

2002-08-01

Activated carbon cloths (ACCs), whose efficiency has been demonstrated for microorganics adsorption from water, were here studied in the removal of metal ions from aqueous solution. Two ACCs are investigated, they are characterized in terms of porosity parameters (BET specific surface area, percentage of microporosity) and chemical characteristics (acidic surface groups, acidity constants, point of zero charge). A first part consists in the experimental study of three metal ions removal (Cu 2+, Ni 2+ and Pb 2+) in a batch reactor. Isotherms modeling by Freundlich and Brunauer-Emmett-Teller (BET) equations enables the following adsorption order: Cu 2+>Ni 2+>Pb 2+ to be determined for adsorption capacities on a molar basis. It may be related to adsorbates characteristics in terms of electronegativity and ionic radius. The influence of adsorbent's microporosity is also shown. Adsorption experiments carried out for pH values ranging from 2 to 10 demonstrate: (i) an adsorption occurring below the precipitation pH; (ii) the strong influence of pH, with a decrease of electrostatic repulsion due to the formation of less charged hydrolyzed species coupled with a decrease of activated carbon surface charge as pH increases. The second part focuses on the modeling of adsorption versus the pH experimental data by the diffuse layer model (DLM) using Fiteql software. The model is efficient to describe the system behavior in the pH range considered. Regarding complexation constants, they show the following affinity for ACC: Pb 2+>Cu 2+>Ni 2+. They are related to initial concentrations used for the three metal ions.

DFT study on stability and H{sub 2} adsorption activity of bimetallic Au{sub 79−n}Pd{sub n} (n = 1–55) clusters

Energy Technology Data Exchange (ETDEWEB)

Liu, Xuejing [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Tian, Dongxu, E-mail: tiandx@dlut.edu.cn [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Meng, Changgong [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China)

2013-03-29

Highlights: ► Stability of Pd substitution type is face > mid-edge > corner > edge. ► H{sub 2} adsorption activity is in contrast with the stability of Pd substitution type. ► Non-activated dissociation of H{sub 2} occurs in Au{sub 36}Pd{sub 43−3} with high thermal stability. ► ε{sub d} agrees with that Pd at edge and corner are more active than face and mid-edge. - Abstract: The stability and H{sub 2} adsorption activity of bimetallic Au{sub 79−n}Pd{sub n} (n = 1–55) clusters were studied by density functional theory with GGA-PW91 functional. The stability order for four Pd substitution types is face > mid-edge > corner > edge, and the stability is improved with increasing Pd content. In contrast with the stability order, H{sub 2} adsorption activity is corner ≈ edge > mid-edge > face. The Au{sub 36}Pd{sub 43} (3) with Au:Pd ≈ 1:1 ratio and twenty-four Pd substitutions at (1 1 1) facets and nineteen Pd substitutions at subshell sites shows high stability and H{sub 2} non-activated dissociation activity. The partial density of d-states and d band center revealed that the electronic properties are closely associated with the geometric characteristic and adsorption activity. Correlating the d band center ε{sub d} and the adsorption energies, the ε{sub d} order agrees with the adsorption activity that the Pd substitution at edge and corner sites are more active than at face and mid-edge sites.

Selective adsorption behavior of Cd(II) ion imprinted polymers synthesized by microwave-assisted inverse emulsion polymerization: Adsorption performance and mechanism

International Nuclear Information System (INIS)

Zhu, Fang; Li, Luwei; Xing, Junde

2017-01-01

Highlights: • Microwave assisted inverse emulsion polymerization was applied to prepare Cd(II) imprinted polymers. • The adsorption capacity was evaluated by static adsorption experiments. • Pseudo-second-order model and Langmuir adsorption isotherm model had the best agreement with the experimental data. • The adsorption was a spontaneous and endothermic process. • Cd(II) imprinted polymers have specific identification for Cd(II). - Abstract: Microwave-assisted inverse emulsion polymerization method was used to prepare Cd(II) imprinted polymer (IIP) by using β-cyclodextrin (β-CD) and acrylamide (AM) as functional monomer, epichlorohydrin (ECH) as crossing-linking agent, ammonium persulfate as initiator. The Cd(II) imprinted polymer was characterized by SEM, FTIR and TGA. The influences of initial concentration of Cd(II), pH values, temperature, time and competitive ions on adsorption capacity and recognition properties are investigated. Under the optimal conditions, the adsorption capacity could reach 107 mg/g. Furthermore, pseudo first order kinetic model, pseudo second order kinetic model and intra-particular diffusion model were used to describe the adsorption kinetic behavior. Results showed that the pseudo-second-order model (R"2 0.9928–0.9961) had the best agreement with the experimental data. Langmuir adsorption isotherm model described the experimental data well, which indicated that adsorption was mainly monolayer absorption. Moreover, the study of adsorption thermodynamics (ΔG"0 0, ΔS"0 > 0) suggested that the adsorption process was a spontaneous and endothermic process. Competitive selectivity experiment revealed that imprinted polymer could selectively recognize Cd(II). It provides a new idea for removing Cd(II) from aqueous solution.

Competitive adsorption of albumin and monoclonal immuno upsilon globulin molecules on polystyrene surfaces

NARCIS (Netherlands)

Elgersma, F.

1990-01-01

The subject of this thesis is proteins at interfaces. The main purpose of the work was to acquire more insight into the mechanism of adsorption of Bovine Serum Albumin (BSA) and monoclonal Immuno gamma Globulins (IgG's). both individually and in competition. Another aim was to achieve

Adsorption of Hydrophobin-Protein Mixtures at the Air-Water Interface: The Impact of pH and Electrolyte.

Science.gov (United States)

Tucker, Ian M; Petkov, Jordan T; Penfold, Jeffrey; Thomas, Robert K; Cox, Andrew R; Hedges, Nick

2015-09-15

The adsorption of the proteins β-casein, β-lactoglobulin, and hydrophobin, and the protein mixtures of β-casein/hydrophobin and β-lactoglobulin/hydrophobin have been studied at the air-water interface by neutron reflectivity, NR. Changing the solution pH from 7 to 2.6 has relatively little impact on the adsorption of hydrophobin or β-lactoglobulin, but results in a substantial change in the structure of the adsorbed layer of β-casein. In β-lactoglobulin/hydrophobin mixtures, the adsorption is dominated by the hydrophobin adsorption, and is independent of the hydrophobin or β-lactoglobulin concentration and solution pH. At pH 2.6, the adsorption of the β-casein/hydrophobin mixtures is dominated by the hydrophobin adsorption over the range of β-casein concentrations studied. At pH 4 and 7, the adsorption of β-casein/hydrophobin mixtures is dominated by the hydrophobin adsorption at low β-casein concentrations. At higher β-casein concentrations, β-casein is adsorbed onto the surface monolayer of hydrophobin, and some interpenetration between the two proteins occurs. These results illustrate the importance of pH on the intermolecular interactions between the two proteins at the interface. This is further confirmed by the impact of PBS, phosphate buffered saline, buffer and CaCl2 on the coadsorption and surface structure. The results provide an important insight into the adsorption properties of protein mixtures and their application in foam and emulsion stabilization.

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

MgO-based adsorbents for CO2 adsorption: Influence of structural and textural properties on the CO2 adsorption performance.

Science.gov (United States)

Elvira, Gutiérrez-Bonilla; Francisco, Granados-Correa; Víctor, Sánchez-Mendieta; Alberto, Morales-Luckie Raúl

2017-07-01

A series of MgO-based adsorbents were prepared through solution-combustion synthesis and ball-milling process. The prepared MgO-based powders were characterized using X-ray diffraction, scanning electron microscopy, N 2 physisorption measurements, and employed as potential adsorbents for CO 2 adsorption. The influence of structural and textural properties of these adsorbents over the CO 2 adsorption behaviour was also investigated. The results showed that MgO-based products prepared by solution-combustion and ball-milling processes, were highly porous, fluffy, nanocrystalline structures in nature, which are unique physico-chemical properties that significantly contribute to enhance their CO 2 adsorption. It was found that the MgO synthesized by solution combustion process, using a molar ratio of urea to magnesium nitrate (2:1), and treated by ball-milling during 2.5hr (MgO-BM2.5h), exhibited the maximum CO 2 adsorption capacity of 1.611mmol/g at 25°C and 1atm, mainly via chemisorption. The CO 2 adsorption behaviour on the MgO-based adsorbents was correlated to their improved specific surface area, total pore volume, pore size distribution and crystallinity. The reusability of synthesized MgO-BM2.5h was confirmed by five consecutive CO 2 adsorption-desorption times, without any significant loss of performance, that supports the potential of MgO-based adsorbent. The results confirmed that the special features of MgO prepared by solution-combustion and treated by ball-milling during 2.5hr are favorable to be used as effective MgO-based adsorbent in post-combustion CO 2 capture technologies. Copyright © 2016. Published by Elsevier B.V.

Effect of pH on the adsorption of carbendazim in Polish mineral soils

International Nuclear Information System (INIS)

Paszko, Tadeusz

2012-01-01

The study aimed to determine the influence of pH on the adsorption of carbendazim in soil profiles of three mineral agricultural soils: Hyperdystric Arenosol, Haplic Luvisol and Hypereutric Cambisol. In the examined pH range between 3 and 7 the adsorption of carbendazim was inversely correlated to the pH of the soil. The adsorption coefficients were in the range between 0.3 and 151.8 mL g −1 . Decreasing the pH in the soil suspensions from 7 to 3 increased the value of this coefficient by 3 to 70 times. A decrease in the amounts of organic matter down the soil profiles was not associated with weaker carbendazim adsorption. In the samples from all soil horizons, at pH values between 3 and 6, the predominant sorption process was carbendazim adsorption on clay minerals. The adsorption of carbendazim on organic matter prevailed over that on clays only at pH > 6 and only in the Ap horizon of the examined soils. The developed mathematical models yielded very good results when the adsorption of the protonated form of carbendazim was assumed to be the predominant adsorption process on clays together with the adsorption of neutral molecules on organic matter and clays. The results from both the model fitting and the experiments revealed the negative effect of Al oxides and hydroxides and Al cations on the adsorption of the protonated form of carbendazim on clay minerals. The developed models successfully described the pH-dependent adsorption processes of carbendazim for both data from particular soil horizons and those from all three examined soil profiles. -- Highlights: ► Adsorption of carbendazim in soils was inversely correlated to soil pH. ► At low pH carbendazim was adsorbed predominantly by clay minerals. ► Al 3+ influenced adsorption of the protonated form of carbendazim on clays. ► Created models predict pH-dependent sorption processes in the whole soil profiles.

Prediction of equilibrium parameters of adsorption of lead (II) ions onto diatomite

Science.gov (United States)

Salman, Taylan; Ardalı, Yüksel; Gamze Turan, N.

2013-04-01

Heavy metals from industrial wastewaters are one of the most important environmental issues to be solved today. Due to their toxicity and nonbiodegradable nature, heavy metals cause environmental and public health problems. Various techniques have been developed to remove heavy metals from aqueous solutions. These include chemical precipitation, reverse osmosis, ion Exchange and adsorption. Among them, adsorption is considered to be a particularly competitive and effective process for the removal of heavy metals from aqueous solutions. There is growing interest in using low cost, commercially available materials for the adsorption of heavy metals. Diatomite is a siliceous sedimentary rock having an amorphous form of silica (SiO2. nH2O) containing a small amount of microcrystalline material. It has unique combination of physical and chemical properties such as high porosity, high permeability, small particle size, large surface area, and low thermal conductivity. In addition, it is available in Turkey and in various locations around the world. Therefore, diatomite has been successfully used as adsorbent for the removal of heavy metals. The aim of the study is to investigate the adsorption properties of diatomite. The equilibrium adsorption data were applied to the Langmuir, Freundlich and Dubinin-Radushkevic (D-R) isotherm models. Adsorption experiments were performed under batch process, using Pb (II) initial concentration, pH of solution and contact time as variables. The results demonstrated that the adsorption of Pb (II) was strongly dependent on pH of solution. The effect of pH on adsorption of Pb(II) on diatomite was conducted by varying pH from 2 to 12 at 20 oC. In the pH range of 2.0-4.0, the adsorption percentage increases slightly as the pH increasing. At pH>4, the adsorption percentage decreases with increasing pH because hydrolysis product and the precipitation begin to play an important role in the sorption of Pb (II). At pH4, the maximum adsorption

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)

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)

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.

Reactivity of transition metal atoms supported or not on TiO2(110) toward CO and H adsorption

KAUST Repository

Helali, Zeineb

2015-04-01

Following our strategy to analyze the metal–support interaction, we present periodic DFT calculations for adsorption of metal atoms on a perfect rutile TiO2(110) surface (at low coverage, θ = 1/3) to investigate the interaction of an individual metal atom, M, with TiO2 and its consequence on the coadsorption of H and CO over M/TiO2. M under investigation varies in a systematic way from K to Zn. It is found that the presence of the support decreases or increases the strength of M–H or M–CO interaction according to the nature of M. The site of the adsorption for H and the formation of HCO/M also depend on M. From the left- to the right-hand side of the period, C and O both interact while O progressively detaches from M. On the contrary, for M = Fe–Cu, CO dissociation is more likely to happen. For CO and H coadsorption, two extreme cases emerge: For Ni, the hydrogen adsorbed should easily move on the support and CO dissociation is more likely. For Ti or Sc, H is easily coadsorbed with CO on the metal and CO hydrogenation could be the initial step. © 2015, Springer-Verlag Berlin Heidelberg.

Predicting heavy metals' adsorption edges and adsorption isotherms on MnO2 with the parameters determined from Langmuir kinetics.

Science.gov (United States)

Hu, Qinghai; Xiao, Zhongjin; Xiong, Xinmei; Zhou, Gongming; Guan, Xiaohong

2015-01-01

Although surface complexation models have been widely used to describe the adsorption of heavy metals, few studies have verified the feasibility of modeling the adsorption kinetics, edge, and isotherm data with one pH-independent parameter. A close inspection of the derivation process of Langmuir isotherm revealed that the equilibrium constant derived from the Langmuir kinetic model, KS-kinetic, is theoretically equivalent to the adsorption constant in Langmuir isotherm, KS-Langmuir. The modified Langmuir kinetic model (MLK model) and modified Langmuir isotherm model (MLI model) incorporating pH factor were developed. The MLK model was employed to simulate the adsorption kinetics of Cu(II), Co(II), Cd(II), Zn(II) and Ni(II) on MnO2 at pH3.2 or 3.3 to get the values of KS-kinetic. The adsorption edges of heavy metals could be modeled with the modified metal partitioning model (MMP model), and the values of KS-Langmuir were obtained. The values of KS-kinetic and KS-Langmuir are very close to each other, validating that the constants obtained by these two methods are basically the same. The MMP model with KS-kinetic constants could predict the adsorption edges of heavy metals on MnO2 very well at different adsorbent/adsorbate concentrations. Moreover, the adsorption isotherms of heavy metals on MnO2 at various pH levels could be predicted reasonably well by the MLI model with the KS-kinetic constants. Copyright © 2014. Published by Elsevier B.V.

Adsorption of Ca2+ on single layer graphene oxide.

Science.gov (United States)

Terracciano, Amalia; Zhang, Jianfeng; Christodoulatos, Christos; Wu, Fengchang; Meng, Xiaoguang

2017-07-01

Graphene oxide (GO) holds great promise for a broad array of applications in many fields, but also poses serious potential risks to human health and the environment. In this study, the adsorptive properties of GO toward Ca 2+ and Na + were investigated using batch adsorption experiments, zeta potential measurements, and spectroscopic analysis. When pH increased from 4 to 9, Ca 2+ adsorption by GO and the zeta potential of GO increased significantly. Raman spectra suggest that Ca 2+ was strongly adsorbed on the GO via -COOCa + formation. On the other hand, Na + was adsorbed into the electrical diffuse layer as an inert counterion to increase the diffuse layer zeta potential. While the GO suspension became unstable with increasing pH from 4 to 10 in the presence of Ca 2+ , it was more stable at higher pH in the NaCl solution. The findings of this research provide insights in the adsorption of Ca 2+ on GO and fundamental basis for prediction of its effect on the colloidal stability of GO in the environment. Copyright © 2017. Published by Elsevier B.V.

Effects of copper and aluminum on the adsorption of sulfathiazole and tylosin on peat and soil

International Nuclear Information System (INIS)

Pei, Zhiguo; Yang, Shuang; Li, Lingyun; Li, Chunmei; Zhang, Shuzhen; Shan, Xiao-quan; Wen, Bei; Guo, Baoyuan

2014-01-01

Effects of copper (Cu) and aluminum (Al) on the adsorption of sulfathiazole (STZ) and tylosin (T) to peat and soil were investigated using a batch equilibration method. Results show that Cu suppressed STZ adsorption onto peat and soil at pH 5.0 due to the formation of STZ–Cu complexes and/or Cu bridge. In contrast, Al only decreased STZ adsorption at pH 6.0. As for T, both Cu and Al suppressed its adsorption over the entire pH range owing to three reasons: 1) electrostatic competition between Cu/Al and T + ; 2) Cu/Al adsorption made the soil and peat surface less negatively charged, which was unfavorable for T + adsorption; 3) the shrunken pore size of peat and soil retarded the diffusion of large-sized T into these pores. -- Highlights: • Cu decreases STZ adsorption at pH 5.0. • Al decreases STZ adsorption at pH 6.0. • Cu and Al suppress T adsorption. • Cu and Al change partial properties of peat and soil. -- Cu and Al changed the adsorption behavior of STZ and T in soil and peat via complexation and/or change in partial properties of peat and soil

Molecular Insights into the pH-Dependent Adsorption and Removal of Ionizable Antibiotic Oxytetracycline by Adsorbent Cyclodextrin Polymers

Science.gov (United States)

Zhang, Yu; Cai, Xiyun; Xiong, Weina; Jiang, Hao; Zhao, Haitong; Yang, Xianhai; Li, Chao; Fu, Zhiqiang; Chen, Jingwen

2014-01-01

Effects of pH on adsorption and removal efficiency of ionizable organic compounds (IOCs) by environmental adsorbents are an area of debate, because of its dual mediation towards adsorbents and adsorbate. Here, we probe the pH-dependent adsorption of ionizable antibiotic oxytetracycline (comprising OTCH2 +, OTCH±, OTC−, and OTC2−) onto cyclodextrin polymers (CDPs) with the nature of molecular recognition and pH inertness. OTCH± commonly has high adsorption affinity, OTC− exhibits moderate affinity, and the other two species have negligible affinity. These species are evidenced to selectively interact with structural units (e.g., CD cavity, pore channel, and network) of the polymers and thus immobilized onto the adsorbents to different extents. The differences in adsorption affinity and mechanisms of the species account for the pH-dependent adsorption of OTC. The mathematical equations are derived from the multiple linear regression (MLR) analysis of quantitatively relating adsorption affinity of OTC at varying pH to adsorbent properties. A combination of the MLR analysis for OTC and molecular recognition of adsorption of the species illustrates the nature of the pH-dependent adsorption of OTC. Based on this finding, γ-HP-CDP is chosen to adsorb and remove OTC at pH 5.0 and 7.0, showing high removal efficiency and strong resistance to the interference of coexisting components. PMID:24465975

Adsorption behavior of hydrophobin and hydrophobin/surfactant mixtures at the air-water interface.

Science.gov (United States)

Zhang, Xiaoli L; Penfold, Jeffrey; Thomas, Robert K; Tucker, Ian M; Petkov, Jordan T; Bent, Julian; Cox, Andrew; Campbell, Richard A

2011-09-20

The adsorption of the surface-active protein hydrophobin, HFBII, and the competitive adsorption of HFBII with the cationic, anionic, and nonionic surfactants hexadecyltrimethylammonium bromide, CTAB, sodium dodecyl sulfate, SDS, and hexaethylene monododecyl ether, C(12)E(6), has been studied using neutron reflectivity, NR. HFBII adsorbs strongly at the air-water interface to form a dense monolayer ∼30 Å thick, with a mean area per molecule of ∼400 Å(2) and a volume fraction of ∼0.7, for concentrations greater than 0.01 g/L, and the adsorption is independent of the solution pH. In competition with the conventional surfactants CTAB, SDS, and C(12)E(6) at pH 7, the HFBII adsorption totally dominates the surface for surfactant concentrations less than the critical micellar concentration, cmc. Above the cmc of the conventional surfactants, HFBII is displaced by the surfactant (CTAB, SDS, or C(12)E(6)). For C(12)E(6) this displacement is only partial, and some HFBII remains at the surface for concentrations greater than the C(12)E(6) cmc. At low pH (pH 3) the patterns of adsorption for HFBII/SDS and HFBII/C(12)E(6) are different. At concentrations just below the surfactant cmc there is now mixed HFBII/surfactant adsorption for both SDS and C(12)E(6). For the HFBII/SDS mixture the structure of the adsorbed layer is more complex in the region immediately below the SDS cmc, resulting from the HFBII/SDS complex formation at the interface. © 2011 American Chemical Society

Adsorption-Desorption of Hexaconazole in Soils with Respect to Soil Properties, Temperature, and pH

Directory of Open Access Journals (Sweden)

Maznah Zainol

2016-06-01

Full Text Available The effect of temperature and pH on adsorption-desorption of fungicide hexaconazole was studied in two Malaysian soil types; namely clay loam and sandy loam. The adsorption-desorption experiment was conducted using the batch equilibration technique and the residues of hexaconazole were analysed using the GC-ECD. The results showed that the adsorption-desorption isotherms of hexaconazole can be described with Freundlich equation. The Freundlich sorption coefficient (Kd values were positively correlated to the clay and organic matter content in the soils. Hexaconazole attained the equilibrium phase within 24 h in both soil types studied. The adsorption coefficient (Kd values obtained for clay loam soil and sandy loam soil were 2.54 mL/g and 2.27 mL/g, respectively, indicating that hexaconazole was weakly sorbed onto the soils due to the low organic content of the soils. Regarding thermodynamic parameters, the Gibb’s free energy change (ΔG analysis showed that hexaconazole adsorption onto soil was spontaneous and exothermic, plus it exhibited positive hysteresis. A strong correlation was observed between the adsorption of hexaconazole and pH of the soil solution. However, temperature was found to have no effect on the adsorption of hexaconazole onto the soils; for the range tested.

First-principles study on the structure and electronic property of gas molecules adsorption on Ge2Li2 monolayer

Science.gov (United States)

Hu, Yiwei; Long, Linbo; Mao, Yuliang; Zhong, Jianxin

2018-06-01

Using first-principles methods, we have studied the adsorption of gas molecules (CO2, CH4, H2S, H2 and NH3) on two dimensional Ge2Li2 monolayer. The adsorption geometries, adsorption energies, charge transfer, and band structures of above mentioned gas molecules adsorption on Ge2Li2 monolayer are analyzed. It is found that the adsorption of CO2 on Ge2Li2 monolayer is a kind of strong chemisorption, while other gas molecules such as CH4, H2S, H2 and NH3 are physisorption. The strong covalent binding is formed between the CO2 molecule and the nearest Ge atom in Ge2Li2 monolayer. This adsorption of CO2 molecule on Ge2Li2 monolayer leads to a direct energy gap of 0.304 eV. Other gas molecules exhibit mainly ionic binding to the nearest Li atoms in Ge2Li2 monolayer, which leads to indirect energy gap after adsorptions. Furthermore, it is found that the work function of Ge2Li2 monolayer is sensitive with the variation of adsorbents. Our results reveal that the Ge2Li2 monolayer can be used as a kind of nano device for gas molecules sensor.

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

In situ SERS and X-ray photoelectron spectroscopy studies on the pH-dependant adsorption of anthraquinone-2-carboxylic acid on silver electrode

Energy Technology Data Exchange (ETDEWEB)

Li, Dan, E-mail: dany@sit.edu.cn [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China); Jia, Shaojie [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China); Fodjo, Essy Kouadio [Laboratory of Physical Chemistry, University Felix Houphouet Boigny, 22 BP 582, Abidjan 22, Cote d’Ivoire (Cote d' Ivoire); Xu, Hu [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China); Wang, Yuhong, E-mail: yuhong_wang502@sit.edu.cn [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China); Deng, Wei [School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Road, Shanghai 201418 (China)

2016-03-30

Graphical abstract: The orientation of anthraquinone-2-carboxylic acid (AQ-2-COOH) has been investigated by in situ surface-enhanced Raman scattering (in situ SERS) spectroelectrochemistry and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) on silver surface. - Highlights: • The adsorption behavior of anthraquinone-2-carboxylic acid (AQ-2-COOH) on Ag electrode is influenced by the pH. • The pH-dependant adsorption of AQ-2-COOH has been confirmed by in situ surface-enhanced Raman scattering (in situ SERS) spectroelectrochemistry and angle-resolved X-ray photoelectron spectroscopy (AR-XPS). • The results can provide insights into electron transfer reactions of AQ-2-COOH in biological systems. - Abstract: In this study, in situ surface-enhanced Raman scattering (SERS) spectroelectrochemistry and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) are used to investigate the redox reaction and adsorption behavior of anthraquinone-2-carboxylic acid (AQ-2-COOH) on an Ag electrode at different pH values. The obtained results indicate that AQ-2-COOH is adsorbed tilted on the Ag electrode through O-atom of ring carbonyl in a potential range from −0.3 to −0.5 V vs. SCE, but the orientation turns to more tilted orientation with both O-atom of the ring carbonyl and carboxylate group in positive potential region for pH 6.0 and 7.4. However, at pH 10.0, the orientation adopts tilted conformation constantly on the Ag electrode with both O-atom of the anthraquinone ring and carboxylate group in the potential range from −0.3 to −0.5 V vs. SCE or at positive potentials. Moreover, the adsorption behavior of AQ-2-COOH has been further confirmed by AR-XPS on the Ag surface. Proposed reasons for the observed changes in orientation are presented.

A DFT study of SO2 and H2S gas adsorption on Au-doped single-walled carbon nanotubes

International Nuclear Information System (INIS)

Zhang, Xiaoxing; Dai, Ziqiang; Chen, Qinchuan; Tang, Ju

2014-01-01

Intrinsic carbon nanotubes (CNTs) show limited toxic gas detection, thus, we need to develop a method to fabricate a novel CNT sensor that has good sensitivity. In this study, density functional theory (DFT) was applied to determine the adsorption behavior of Au-doped single-walled carbon nanotubes (Au-SWCNTs) to SO 2 and H 2 S. The calculated results show that Au-SWCNTs have a high sensitivity to SO 2 and H 2 S. When SO 2 adsorbs on the surface of the nanotube, a large number of electrons transfer from the Au-SWCNT to SO 2 , which results in a decrease in the frontier orbital energy gap and an increase in electrical conductivity. On the other hand, when H 2 S adsorbs on the surface of the nanotube, the electrons transfer from H 2 S to the Au-SWCNT, the frontier orbital energy gap increases, and the electrical conductivity decreases. Thus, SO 2 and H 2 S could be detected by Au-SWCNTs. This conclusion is useful for the development of CNT-based gas sensors and provides a theoretical basis to fabricate Au-SWCNT-based gas sensors. (papers)

Molecular dynamics simulation of the effect of pH on the adsorption of rhodamine laser dyes on TiO2 hydroxylated surfaces

OpenAIRE

2009-01-01

Abstract We have carried out a study of the adsorption, on the (101) surface of anatase TiO2, of two industrially relevant rhodamines molecules (rhodamine 6G and rhodamine 800) employing Molecular Dynamics. These theoretical studies have shown that Rhodamine 6G must adsorb on surfaces under basic conditions. Moreover, the adsorption of this molecule shows a strong dependence upon the pH of the system, i.e. under neutral conditions the adsorption energy is quite smaller, and under ...

The influence of pH on the adsorption of lead by Na-clinoptilolite ...

African Journals Online (AJOL)

The influence of pH on the adsorption of lead by Na-clinoptilolite: Kinetic and equilibrium studies. ... At high pH of the contact solution, the adsorption process occurs by ion exchange and at low pH; i.e., it is physical. The variation of the Gibbs free energy demonstrates that adsorption occurs spontaneously. The process was ...

A theoretical study of hydrogen atoms adsorption and diffusion on PuO_2 (110) surface

International Nuclear Information System (INIS)

Yu, H.L.; Tang, T.; Zheng, S.T.; Shi, Y.; Qiu, R.Z.; Luo, W.H.; Meng, D.Q.

2016-01-01

The mechanisms of adsorption and diffusion of hydrogen atoms on the PuO_2 (110) surface are investigated by density functional theory corrected for onsite Coulombic interactions (GGA + U). In order to find out the energetically more favorable adsorption site and optimum diffusion path, adsorption energy of atomic H on various sites and the diffusion energy barrier are derived and compared. Our results show that both chemisorption and physisorption exist for H atoms adsorption configurations on PuO_2 (110) surface. Two processes for H diffusion are investigated using the climbing nudged-elastic-band (cNEB) approach. We have identified two diffusion mechanisms, leading to migration of atomic H on the surface and diffusion from surface to subsurface. The energy barriers indicate that it is energetically more favorable for H atom to be on the surface. Hydrogen permeation through purity PuO_2 surface is mainly inhibited from hydrogen atom diffusion from surface to subsurface. - Highlights: • H atoms adsorption on PuO_2 (110) surface are investigated by GGA + U. • Both chemisorption and physisorption exist for H atoms adsorption configurations. • H atoms migration into PuO_2 (100) surface are inhibited with the barrier of 2.15 eV. • H atoms diffusion on PuO_2 (110) surface are difficult at room temperature.

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.

Increased adsorption of histidine-tagged proteins onto tissue culture polystyrene

DEFF Research Database (Denmark)

Holmberg, Maria; Hansen, Thomas Steen; Lind, Johan Ulrik

2012-01-01

and ethylenediaminetetraacetic acid (EDTA), as well as adsorption performed at different pH and ionic strength indicates that the high adsorption is caused by electrostatic interaction between negatively charged carboxylate groups on the TCPS surface and positively charged histidine residues in the proteins. Pre......In this study we compare histidine-tagged and native proteins with regards to adsorption properties. We observe significantly increased adsorption of proteins with an incorporated polyhistidine amino acid motif (HIS-tag) onto tissue culture polystyrene (TCPS) compared to similar proteins without...... a HIS-tag. The effect is not observed on polystyrene (PS). Adsorption experiments have been performed at physiological pH (7.4) and the effect was only observed for the investigated proteins that have pI values below or around 7.4. Competitive adsorption experiments with imidazole...

Carbonate adsorption onto goethite as a function of pH and ionic strength

International Nuclear Information System (INIS)

Rundberg, R.S.; Albinsson, Y.

1991-01-01

The adsorption of carbonate onto geothite was studied as a function of both pH and ionic strength (NaClO 4 electrolyte) using 14 C tracer. The pH ranged from 2.5 to 11.6. The ionic strength was controlled by varying the NaClO 4 concentration and ranged from 0.01 to 0.1 molar. The results indicate that carbonate is adsorbed on goethite as primarily an inner-sphere complex at pH values above the point of zero charge. This is inferred from the lack of dependence on ionic strength in the adsorption of carbonate. Below the point of zero charge carbonate is adsorbed by an additional outer-sphere mechanism. An adsorption isotherm was measured at pH 7.0 with an electrolyte concentration of 0.01M. Deconvolution of the isotherm proved that at least two sorption mechanisms exist. These mechanisms lead to large distribution coefficients at low pH. Thereby making the complete removal and exclusion of carbonate from an aqueous goethite system difficult, for the purpose of characterizing a ''clean'' goethite surface

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.)

Comparative adsorption of Pb2+ and Cd2+ by cow manure and its vermicompost.

Science.gov (United States)

Zhu, Weiqin; Du, Wenhui; Shen, Xuyang; Zhang, Hangjun; Ding, Ying

2017-08-01

Organic waste has great potential for use as an amendment to immobilize heavy metals in the environment. Therefore, this study investigates various properties of cow manure (CM) and its derived vermicompost (CV), including the pH, cationic exchangeable capacity (CEC), elemental composition and surface structure, to determine the potential of these waste products to remove Pb 2+ and Cd 2+ from solution. The results demonstrate that CV has a much higher pH, CEC and more irregular pores than CM and is enriched with minerals and ash content but has a lower C, H, O and N content. Adsorption isotherms studies shows that the adsorption of Pb 2+ and Cd 2+ onto either CM or CV follows a Langmuir model and presents maximum Pb 2+ and Cd 2+ adsorption capacities of 102.77 mg g -1 and 38.11 mg g -1 onto CM and 170.65 and 43.01 mg g -1 onto CV, respectively. Kinetic studies show that the adsorption of Pb 2+ onto CM and CV fits an Elovich model, whereas the adsorption of Cd 2+ onto CM and CV fits a pseudo-second-order model. Desorption studies indicate that CV is more effective than CM in removing Pb 2+ and Cd 2+ . FTIR analysis demonstrates that the adsorption of Pb 2+ and Cd 2+ onto CM mainly depends on existed aliphatic alcohol, aromatic acid as well as new produced carbonates, whereas that onto CV may be contributed by the existed aliphatic alcohol, aromatic acids as well as some carbonates and phosphates. Thus, vermicomposting disposal of cow manure with destination mineral addition may broaden the way of its recycle and environmental usage. Copyright © 2017 Elsevier Ltd. All rights reserved.

Experimental Study of Effects of pH, Temperature and H2O2 on Gasoline Removal from Contaminated Water Using Granular Activated Carbon

Directory of Open Access Journals (Sweden)

Hasti Hasheminejad

2010-01-01

Full Text Available Contamination of water with petroleum compounds is a serious environmental problem in Iran. Old fuel storage tanks, gasoline stations, and oil refineries are the main sources of gasoline leakage into water resources. In this study, the batch adsorption technique was used to investigate adsorption of petroleum compounds (gasoline on granular activated carbon. Experiments showed that the adsorption capacity of activated carbon is a function of pH, temperature, and H2O2 concentration in solution. Maximum adsorption of petroleum compounds was obtained at pH of 8. Adsorption of petroleum compounds was increased by decreasing temperature (due to decreasing van der Waals forces between the adsorbent and the adsorbate and H2O2 concentration in solution (due to the decrease in the initial concentration of the adsorbate by oxidation . In this experiment, the maximum equilibrium capacity of granular activated carbon was 129.05 mg COD/g GAC at pH 8 and at an ambient temperature of 10˚C. The experimental adsorption data were fitted to the Freundlich and Langmuir adsorption model. The correlation coefficients calculated indicate that the Freundlich model was best fitted. Also, the regression analysis was used with a correlation coefficient of 0.981 to develop a model for describing the relationship between absorption variation in equilibrium state, pH, temperature, and H2O2. On the whole, the correlation coefficient calculated by the proposed model was found to be higher than Freundlich’s.

Adsorption characteristics of hexavalent chromium on HCB/TiO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Zhang, Li; Zhang, Yonggang, E-mail: 13502182420@163.com

2014-10-15

Graphical abstract: - Highlights: • Sol–gel method was adopted to prepare HCB/TiO{sub 2}. • Its adsorption performance of Cr(VI) was investigated. • The maximum adsorption capacity for Cr(VI) was at 27.33 mg g{sup −1} in an acidic medium. • The value is worth comparable with other low-cost adsorbents. - Abstract: Sol–gel method was adopted to prepare HCB/TiO{sub 2} and its adsorption ability of hexavalent chromium, Cr(VI), and removal from aqueous solution were investigated. The samples were characterized by Power X-ray diffraction (XRD) and a transmission electron microscope (TEM) which showed that the TiO{sub 2} was deposited on the surface of HCB. FTIR was used to identify the changes of the surface functional groups before and after adsorption. Potentiometric titration method was used to characterize the zero charge (pH{sub pzc}) characteristics of the surface of HCB/TiO{sub 2} which showed more acidic functional groups containing. Batch experiments showed that initial pH, absorbent dosage, contact time and initial concentration of Cr(VI) were important parameters for the Cr(VI) adsorption studies. The Freundlich isotherm model better reflected the experimental data better. Cr(VI) adsorption process followed the pseudo-second order kinetic model, which illustrated chemical adsorption. The thermodynamic parameters, such as Gibbs free energy (ΔG), changes in enthalpy change (ΔH) and changes in entropy change (ΔS) were also evaluated. Negative value of free energy occurred at temperature range of 25–45 °C, so Cr(VI) adsorption by HCB/TiO{sub 2} is spontaneous. Desorption results showed that the adsorption capacity could maintain 80% after five cycles. The maximum adsorption capacity for Cr(VI) was at 27.33 mg g{sup −1} in an acidic medium, of which the value is worth comparable with other low-cost adsorbents.

Adsorption of a reactive dye on chemically modified activated carbons--influence of pH.

Science.gov (United States)

Orfão, J J M; Silva, A I M; Pereira, J C V; Barata, S A; Fonseca, I M; Faria, P C C; Pereira, M F R

2006-04-15

The surface chemistry of a commercial activated carbon with a slightly basic nature was modified by appropriate treatments in order to obtain two additional samples, respectively with acidic and basic properties, without changing its textural parameters significantly. Different techniques (N2 adsorption at 77 K, temperature programmed desorption, and determination of acidity, basicity, and pH at the point of zero charge) were used to characterize the adsorbents. Kinetic and equilibrium adsorption data of a selected textile reactive dye (Rifafix Red 3BN, C.I. reactive red 241) on the mentioned materials were obtained at the pH values of 2, 7, and 12. The kinetic curves are fitted using the second-order model. The respective rate constants seem to diminish progressively with the initial concentration for the more diluted solutions tested, reaching a constant value at higher concentrations, which depends on the experimental system under consideration (adsorbent and pH). In general, the Langmuir model provides the best fit for the equilibrium data. The different uptakes obtained are discussed in relation to the surface chemical properties of the adsorbents. It is shown that the adsorption of the reactive (anionic) dye on the basic sample (prepared by thermal treatment under H2 flow at 700 degrees C) is favored. This conclusion is explained on the basis of the dispersive and electrostatic interactions involved. Moreover, it is also shown that the optimal adsorption condition for all the activated carbons tested corresponds to solution pH values not higher than the pH(pzc) of the adsorbents, which may be interpreted by taking into account the electrostatic forces present.

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.

Catalytic activity of Cu4-cluster to adsorb H2S gas: h-BN nanosheet

Science.gov (United States)

Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh

2018-05-01

We have investigated the electronic properties, adsorptions strength and charge transfer using first principles calculations using density functional theory (DFT). The hexagonal boron nitride (h-BN) substrate shows metallic behavior, which helps to enhance the absorption process. The adsorption of three different orientations (S, D and T) of the H2S gas molecules to analyze the maximum adsorption strength from them onto a copper cluster (Cu4) based on h-BN nanosheet. The maximum adsorption energy of the H2S gas molecule is -1.50 eV for the S orientation and for D and U, it is -0.71 eV and -0.78 eV, respectively. The results show that Cu4 cluster helps to capture H2S gas from the environment and results are useful for the cleaning environment from the toxic gases.

The cianimetalatos as model materials for studying the adsorption of H2 and interactions that determine

International Nuclear Information System (INIS)

Reguera, E.; Reguera, L.; Rodríguez, C.

2015-01-01

An overview of the work done in recent years in the IMRE and the Faculties of Chemistry and Physics at the University of Havana, in collaboration with the Applied Research Center for Advanced Science and Technology at the National Polytechnic Institute of Mexico is presented; on the synthesis, physico-chemical characterization, assessment and modeling of potentially usable as nanoporous materials cianometalatos model to study the adsorption of H2 at high densities, and interactions that determine it. The mechanisms of interaction of the hydrogen molecule with the crystal lattice and its consequences for the adsorption and diffusion of hydrogen in these materials are discussed. The results have been reported in dozens of articles, published in international journals, they were presented at numerous scientific events and contributed to the preparation of several thesis, master's and Ph.D. (full text)

Single, binary and multi-component adsorption of some anions and heavy metals on environmentally friendly Carpobrotus edulis plant.

Science.gov (United States)

Chiban, Mohamed; Soudani, Amina; Sinan, Fouad; Persin, Michel

2011-02-01

A low-cost adsorbent and environmentally friendly adsorbent from Carpobrotus edulis plant was used for the removal of NO(3)(-), H(2)PO(4)(-), Pb(2+) and Cd(2+) ions from single, binary and multi-component systems. The efficiency of the adsorbent was studied using batch adsorption technique under different experimental conditions by varying parameters such as pH, initial concentration and contact time. In single component systems, the dried C. edulis has the highest affinity for Pb(2+), followed by NO(3)(-), Cd(2+) and H(2)PO(4)(-), with adsorption capacities of 175mg/g, 125mg/g, 28mg/g and 26mg/g, respectively. These results showed that the adsorption of NO(3)(-) and H(2)PO(4)(-) ions from single and binary component systems can be successfully described by Langmuir and Freundlich isotherms. Freundlich adsorption model, showed the best fit to the single and binary experimental adsorption data. These results also indicated that the adsorption yield of Pb(2+) ion was reduced by the presence of Cd(2+) ion in binary metal mixture. The competitive adsorption of NO(3)(-), H(2)PO(4)(-), Pb(2+) and Cd(2+) ions on dried C. edulis plant shows that NO(3)(-) and H(2)PO(4)(-) anions are able to adsorb on different free binding sites and Pb(2+) and Cd(2+) cations are able to adsorb on the same active sites of C. edulis particles. The dried C. edulis was found to be efficient in removing nitrate, phosphate, cadmium and lead from aqueous solution as compared to other adsorbents already used for the removal of these ions. Copyright © 2010 Elsevier B.V. All rights reserved.

Correlation between the Microstructure of Porous Materials and the Adsorption Properties of H2 and D2

International Nuclear Information System (INIS)

Krkljus, Ivana Biljana

2011-01-01

ligands, employed as linkers. The material properties can be optimized by changing these two main components. Owing to their high porosity, high storage capacity at low temperature, and excellent reversibility kinetics, MOFs have attracted a considerable attention as potential solid-state hydrogen storage materials. This novel class of porous adsorbents has been extensively investigated within this thesis. The greatest challenge for porous adsorbents is to increase the strength of the H2 binding interaction, and bring adsorption closer to RT conditions. Several strategies, aimed at improving hydrogen adsorption potential in MOFs are closely investigated. These strategies comprise the inclusion of open metal sites and the optimization of the pore size and, thus, the adsorption energy by ligand modification. The influence of the coordinatively unsaturated metal centers, liberated by the removal of metal-bound volatile species, has been particularly investigated. As for carbon materials, the H 2 -MOF interaction potential is especially enhanced in materials with the pore size comparable to the kinetic diameter of the hydrogen molecule. Such effects may result from the overlap of the potential field due to the proximity of the pore wall, which strengthen the interaction potential with the adsorbate molecule. However, smaller pores prevent hydrogen penetration and induce diffusion limitations. Furthermore, the molecular transport in confined pores at low temperatures may be significantly affected by quantum effects.

Adsorption of Hg2+ from aqueous solution onto polyacrylamide/attapulgite

International Nuclear Information System (INIS)

Zhao Yijiang; Chen Yan; Li Meisheng; Zhou Shouyong; Xue Ailian; Xing Weihong

2009-01-01

Polyacrylamide/attapulgite (PAM/ATP) was prepared by the solution polymerization of acrylamide (AM) onto γ-methacryloxypropyl trimethoxy silane (KH-570)-modified attapulgite (ATP). PAM/ATP was characterized using Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The effects of contact time, adsorbent dosage, and pH of the initial solution on the adsorption capacities for Hg 2+ were investigated. The adsorption process was rapid; 88% of adsorption occurred within 5 min and equilibrium was achieved at around 40 min. The equilibrium data fitted the Langmuir sorption isotherms well, and the maximum adsorption capacity of Hg 2+ onto PAM/ATP was found to be 192.5 mg g -1 . The adsorption kinetics of PAM/ATP fitted a pseudo-second-order kinetic model. Our results suggest that chemisorption processes could be the rate-limiting steps in the process of Hg 2+ adsorption. Hg 2+ adsorbed onto PAM/ATP could be effectively desorbed in hot acetic acid solution, and the adsorption capacity of the regenerated adsorbents could still be maintained at 95% by the sixth cycle.

Influence of metal doping of a MOF-74 framework on hydrogen adsorption

Energy Technology Data Exchange (ETDEWEB)

Botas, J.A.; Calleja, G.; Orcajo, M.G. [Rey Juan Carlos Univ., Madrid (Spain). Dept. of Chemical and Energy Technology; Sanchez-Sanchez, M. [CSIC, Madrid (Spain). Inst. de Catalisis y Petroleoquimica

2010-07-01

Microporous Metal-Organic Framework (MOF) adsorbents are considered an interesting option for hydrogen storage. Due to their porous nature and unusually high surface areas, these materials show an exceptional H{sub 2} uptake. Unfortunately, their interaction with H{sub 2} molecules is weak, so cryogenic temperatures are required to reach competitive H{sub 2} storage capacities. In this sense, the presence of coordinatively unsaturated and exposed metal centers in some MOF frameworks could increase the affinity for H{sub 2} through stronger metal-H{sub 2} interactions. In this preliminary work, the effect of doping a Zn{sup 2+}-MOF-74 framework with Co{sup 2+}, Cu{sup 2+} and Mg{sup 2+} on its adsorption properties for H{sub 2} has been studied. Characterization studies suggest that the samples prepared have actually the MOF-74 structure, in which the different tested heteroatom ions have been successfully incorporated. The differences in H{sub 2} adsorption at 77 K and 87 K between the MOF-74 samples doped with the mentioned divalent metal ions were discussed as a function of their free pore volume and amount of metal incorporation. (orig.)

Adsorption of antimony onto iron oxyhydroxides: Adsorption behavior and surface structure

Energy Technology Data Exchange (ETDEWEB)

Guo, Xuejun; Wu, Zhijun [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, No. 19 Xinjiekouwai Street, Beijing 100875 (China); He, Mengchang, E-mail: hemc@bnu.edu.cn [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, No. 19 Xinjiekouwai Street, Beijing 100875 (China); Meng, Xiaoguang [Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Jin, Xin [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, No. 19 Xinjiekouwai Street, Beijing 100875 (China); Qiu, Nan; Zhang, Jing [Beijing Synchrotron Radiation Facility (BSRF), Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

2014-07-15

Graphical abstract: - Highlights: • Antimony adsorption depended on the Sb species, pH, and the type of iron oxides. • Sb(V) adsorption favored at acidic pH, Sb(III) adsorption optimized in wider pH. • Antimony was adsorbed onto the iron oxides by the inner-sphere surface complex. • Bidentate mononuclear ({sup 2}E) was the dominant form of Sb incorporated into HFO. • XAFS and XPS indicated Sb(III) adsorbed was slowly oxidized to Sb(V). - Abstract: Antimony is detected in soil and water with elevated concentration due to a variety of industrial applications and mining activities. Though antimony is classified as a pollutant of priority interest by the United States Environmental Protection Agency (USEPA) and Europe Union (EU), very little is known about its environmental behavior and adsorption mechanism. In this study, the adsorption behaviors and surface structure of antimony (III/V) on iron oxides were investigated using batch adsorption techniques, surface complexation modeling (SCM), X-ray photon spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS). The adsorption isotherms and edges indicated that the affinity of Sb(V) and Sb(III) toward the iron oxides depended on the Sb species, solution pH, and the characteristics of iron oxides. Sb(V) adsorption was favored at acidic pH and decreased dramatically with increasing pH, while Sb(III) adsorption was constant over a broad pH range. When pH is higher than 7, Sb(III) adsorption by goethite and hydrous ferric oxide (HFO) was greater than Sb(V). EXAFS analysis indicated that the majority of Sb(III), either adsorbed onto HFO or co-precipitated by FeCl{sub 3}, was oxidized into Sb(V) probably due to the involvement of O{sub 2} in the long duration of sample preservation. Only one Sb–Fe subshell was filtered in the EXAFS spectra of antimony adsorption onto HFO, with the coordination number of 1.0–1.9 attributed to bidentate mononuclear edge-sharing ({sup 2}E) between Sb and

Effect of solution chemistry on the adsorption of perfluorooctane sulfonate onto mineral surfaces.

Science.gov (United States)

Tang, Chuyang Y; Shiang Fu, Q; Gao, Dawen; Criddle, Craig S; Leckie, James O

2010-04-01

Perfluorooctane sulfonate (PFOS) is an emergent contaminant of substantial environmental concerns, yet very limited information has been available on PFOS adsorption onto mineral surfaces. PFOS adsorption onto goethite and silica was investigated by batch adsorption experiments under various solution compositions. Adsorption onto silica was only marginally affected by pH, ionic strength, and calcium concentration, likely due to the dominance of non-electrostatic interactions. In contrast, PFOS uptake by goethite increased significantly at high [H+] and [Ca2+], which was likely due to enhanced electrostatic attraction between the negatively charged PFOS molecules and positively charged goethite surface. The effect of pH was less significant at high ionic strength, likely due to electrical double layer compression. PFOS uptake was reduced at higher ionic strength for a strongly positively charged goethite surface (pH 3), while it increased for a weakly charged surface (pH 7 and 9), which could be attributed to the competition between PFOS-surface electrostatic attraction and PFOS-PFOS electrostatic repulsion. A conceptual model that captures PFOS-surface and PFOS-PFOS electrostatic interactions as well as non-electrostatic interaction was also formulated to understand the effect of solution chemistry on PFOS adsorption onto goethite and silica surfaces. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Adsorptive Removal of Artificial Sweeteners from Water Using Metal-Organic Frameworks Functionalized with Urea or Melamine.

Science.gov (United States)

Seo, Pill Won; Khan, Nazmul Abedin; Hasan, Zubair; Jhung, Sung Hwa

2016-11-02

A highly porous metal-organic framework (MOF), MIL-101, was modified to introduce urea or melamine via grafting on open metal sites of the MOF. Adsorptive removal of three artificial sweeteners (ASWs) was studied using the MOFs, with or without modifications (including nitration), and activated carbon (AC). The adsorbed quantities (based on the weight of the adsorbent) of saccharin (SAC) under various conditions decreased in the order urea-MIL-101 > melamine-MIL-101 > MIL-101 > AC > O 2 N-MIL-101; however, the quantities based on unit surface area are in the order melamine-MIL-101 > urea-MIL-101 > MIL-101 > O 2 N-MIL-101. Similar ASWs [acesulfame (ACE) and cyclamate (CYC)] showed the same tendency. The mechanism for very favorable adsorption of SAC, ACE, and CYC over urea- and melamine-MIL-101 could be explained by H-bonding on the basis of the contents of -NH 2 groups on the MOFs and the adsorption results under a wide range of pH values. Moreover, the direction of H-bonding could be clearly defined (H acceptor: ASWs; H donor: MOFs). Urea-MIL-101 and melamine-MIL-101 could be suggested as competitive adsorbents for organic contaminants (such as ASWs) with electronegative atoms, considering their high adsorption capacity (for example, urea-MIL-101 had 2.3 times the SAC adsorption of AC) and ready regeneration.

Kinetics of protein adsorption/desorption mediated by pH-responsive polymer layer

International Nuclear Information System (INIS)

Su Xiao-Hang; Lei Qun-Li; Ren Chun-Lai

2015-01-01

We propose a new way of regulating protein adsorption by using a pH-responsive polymer. According to the theoretical results obtained from the molecular theory and kinetic approaches, both thermodynamics and kinetics of protein adsorption are verified to be well controlled by the solution pH. The kinetics and the amount of adsorbed proteins at equilibrium are greatly increased when the solution environment changes from acid to neutral. The reason is that the increased pH promotes the dissociation of the weak polyelectrolyte, resulting in more charged monomers and more stretched chains. Thus the steric repulsion within the polymer layer is weakened, which effectively lowers the barrier felt by the protein during the process of adsorption. Interestingly, we also find that the kinetics of protein desorption is almost unchanged with the variation of pH. It is because although the barrier formed by the polymer layer changes along with the change of pH, the potential at contact with the surface varies equally. Our results may provide useful insights into controllable protein adsorption/desorption in practical applications. (paper)

Tetrahedral silsesquioxane-C2H2Ti complex for hydrogen storage

Science.gov (United States)

Konda, Ravinder; Tavhare, Priyanka; Ingale, Nilesh; Chaudhari, Ajay

2018-04-01

The interaction of molecular hydrogen with tetrahedral silsesquioxane (T4)-C2H2Ti complex has been studied using Density Functional Theory with M06-2X functional and MP2 method with 6-311++G** basis set. T4-C2H2Ti complex can absorb maximum five hydrogen molecules with the gravimetric hydrogen storage capacity of 3.4 wt %. Adsorption energy calculations show that H2 adsorption on T4-C2H2Ti complex is favorable at room temperature by both the methods. We have studied the effect of temperature and pressure on Gibbs free energy corrected adsorption energies. Molecular dynamics simulations for H2 adsorbed T4-C2H2Ti complex have also been performed at 300K and show that loosely bonded H2 molecule flies away within 1fs. Various interaction energies within the complex are studied. Stability of a complex is predicted by means of a gap between Highest Occupied Molecular Orbital (HUMO) and Lowest Unoccupied Molecular Orbital (LUMO). The H2 desorption temperature for T4-C2H2Ti complex is calculated with Van't Hoff equation and it is found to be 229K.

Comparison of H2S adsorption by two hydrogel composite (HBC) derived by Empty Fruit Bunch (EFB) biochar and Coal Fly Ash (CFA)

Science.gov (United States)

Meri, N. H.; Alias, A. B.; Talib, N.; Rashid, Z. A.; Ghani, W. A. W. A. K.

2018-03-01

This study are covered the adsorption performance of two adsorbent Empty Fruit Bunch Hydrogel Biochar Composite (EFB-HBC) and Coal Fly Ash Hydrogel Composite (CFA-HC) on hydrogen sulphide. The EFB biochar were produce by pyrolysed and heated from room temperature to 550˚C at 10˚C/min under the Nitrogen flow. Meanwhile, coal fly ash collected from a power plant located in Selangor, Malaysia. Both of the materials is a waste from different industries and became the precursor to our adsorbents. EFB biochar and coal fly ash has been synthesized to become hydrogel by polymerization process with acrylamide (AAm) as monomer, N,N’-methylene bisacry lamide (MBA) as cross linker and ammonium persulfate (APS) as initiator. In addition, because of the speciality of hydrogel itself, which is has high ability in storing water, the effect of H2O wetness on EFB-HBC and CFA-HC were investigate in adsorption of H2S. EFB-HBC gave a longest breakthrough time and highest adsorption capacity compared with CFA-HC in both condition (dry/wet). The result also indicated that, the increased the bed height, increased the adsorption capacity.

Phosphate adsorption from wastewater using zirconium (IV) hydroxide: Kinetics, thermodynamics and membrane filtration adsorption hybrid system studies.

Science.gov (United States)

Johir, M A H; Pradhan, M; Loganathan, P; Kandasamy, J; Vigneswaran, S

2016-02-01

Excessive phosphate in wastewater should be removed to control eutrophication of water bodies. The potential of employing amorphous zirconium (Zr) hydroxide to remove phosphate from synthetic wastewater was studied in batch adsorption experiments and in a submerged membrane filtration adsorption hybrid (MFAH) reactor. The adsorption data satisfactorily fitted to Langmuir, pseudo-first order and pseudo-second order models. Langmuir adsorption maxima at 22 °C and pHs of 4.0, 7.1, and 10.0 were 30.40, 18.50, and 19.60 mg P/g, respectively. At pH 7.1 and temperatures of 40 °C and 60 °C, they were 43.80 and 54.60 mg P/g, respectively. The thermodynamic parameters, ΔG° and ΔS° were negative and ΔH° was positive. FTIR, zeta potential and competitive phosphate, sulphate and nitrate adsorption data showed that the mechanism of phosphate adsorption was inner-sphere complexation. In the submerged MFAH reactor experiment, when Zr hydroxide was added at doses of 1-5 g/L once only at the start of the experiment, the removal of phosphate from 3 L of wastewater containing 10 mg P/L declined after 5 h of operation. However, when Zr hydroxide was repeatedly added at 5 g/L dose every 24 h, satisfactory removal of phosphate was maintained for 3 days. Copyright © 2015 Elsevier Ltd. All rights reserved.

Influence of pH on the adsorption of uranium ions by oxidized activated carbon and chitosan

International Nuclear Information System (INIS)

Park, G.I.; Park, H.S.; Woo, S.I.

1999-01-01

The adsorption characteristics of uranyl ions on surface-oxidized carbon were compared with those of powdered chitosan over a wide pH range. In particular, an extensive analysis was made on solution pH variation during the adsorption process or after adsorption equilibrium. Uranium adsorption on the two adsorbents was revealed to be strongly dependent on the initial pH of the solution. A quantitative comparison of the adsorption capacities of the two adsorbents was made, based on the isotherm data obtained at initial pH 3, 4, and 5. In order to analyze the adsorption kinetics incorporated with pH effects, batch experiments at various initial pH values were carried out, and solution pH profiles with the adsorption time were also evaluated. The breakthrough behavior in a column packed with oxidized carbon was also characterized with respect to the variation of effluent pH. Based on these experimental results, the practical applicability of oxidized carbon for uranium removal from acidic radioactive liquid waste was suggested

Competitive adsorption of Reactive Orange 16 and Reactive Brilliant Blue R on polyaniline/bacterial extracellular polysaccharides composite-A novel eco-friendly polymer

Energy Technology Data Exchange (ETDEWEB)

Janaki, V. [Department of Chemistry, Periyar University, Salem 636011, Tamil Nadu (India); Vijayaraghavan, K. [Singapore-Delft Water Alliance, National University of Singapore, 117577 (Singapore); Ramasamy, A.K. [Department of Chemistry, Periyar University, Salem 636011, Tamil Nadu (India); Lee, Kui-Jae [Division of Biotechnology, Advanced Institute of Environment and Bioscience, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570752 (Korea, Republic of); Oh, Byung-Taek, E-mail: btoh@jbnu.ac.kr [Division of Biotechnology, Advanced Institute of Environment and Bioscience, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570752 (Korea, Republic of); Kamala-Kannan, Seralathan, E-mail: kannan@jbnu.ac.kr [Division of Biotechnology, Advanced Institute of Environment and Bioscience, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570752 (Korea, Republic of)

2012-11-30

Highlights: Black-Right-Pointing-Pointer Competitive adsorption of reactive dyes onto polyaniline/bacterial extracellular polysaccharides composite. Black-Right-Pointing-Pointer The composite have functional groups of both polyaniline and bacterial extracellular polysaccharides. Black-Right-Pointing-Pointer The presence of Reactive Brilliant Blue R diminished the uptake of Reactive Orange 16. Black-Right-Pointing-Pointer Electrostatic interaction was identified as a major mechanism in adsorption process. Black-Right-Pointing-Pointer Reactive Brilliant Blue R and Reactive Orange 16 adsorption was endothermic process. - Abstract: The performance of polyaniline/extracellular polymeric substances (Pn/EPS) composite as an adsorbent to remove the anionic reactive dyes, Reactive Brilliant Blue R (RBBR) and Reactive Orange 16 (RO), was investigated in single and binary systems. The pH{sub pzc} of Pn/EPS composite was calculated as 3.7 through potentiometric mass titration method. Electrostatic interaction between the dye anion and the nitrogen present in the polymer was identified as a major mechanism in adsorption process. Single component isotherms followed the Langmuir model with the maximum adsorption capacity of 0.5775 mmol g{sup -1} for RBBR and 0.4748 mmol g{sup -1} for RO. In binary system, both the reactive dye anions compete with each other and resulted in lower uptake. Binary adsorption data were interpreted well by the Sheindorf-Rehbun-Sheintuch equation as compared to extended Langmuir model with constant interaction factor. Kinetic analysis of single solute followed pseudo-first order model. Thermodynamic studies computed that RBBR and RO adsorption was endothermic, spontaneous, and feasible process.

Adsorption of 2,4,6-trinitrotoluene on carboxylated porous polystyrene microspheres

International Nuclear Information System (INIS)

Ye Zhengfang; Meng Qingqiang; Lu Shengtao

2012-01-01

Large-pore-size (150 nm) polystyrene (PSt) microspheres were carboxylated with phthalic anhydride (PA) through Friedel-Crafts acetylation to study the adsorption of 2,4,6-trinitrotoluene (TNT) on this material from aqueous solution. The scanning electron microscope (SEM) images and mercury porosimetry measurements (MPM) of the microspheres showed that the pore structure was unchanged during the reaction. High adsorption capacity (11.2 mg g -1 of suction-dried adsorbent) and adsorption rate (33.9 mg g -1 h -1 ) for TNT were observed during the study. As shown by the adsorption isotherm, the adsorption of TNT on PA-PSt can be described by the Freundlich adsorption equation, indicating heterogeneous adsorption process. On-column adsorption of TNT on PA-PSt and elution indicated that TNT can be completely removed from aqueous solution and condensed into acetone.

Relationship between carbon microstructure, adsorption energy and hydrogen adsorption capacity at different temperatures

International Nuclear Information System (INIS)

Jacek Jagiello; Matthias Thommes

2005-01-01

Various microporous materials such as activated carbons, nano-tubes, synthetic microporous carbons as well as metal organic framework materials are being considered for hydrogen storage applications by means of physical adsorption. To develop materials of practical significance for hydrogen storage it is important to understand the relationships between pore sizes, adsorption energies and adsorption capacities. The pore size distribution (PSD) characterization is traditionally obtained from the analysis of nitrogen adsorption isotherms measured at 77 K. However, a portion of the pores accessible to H 2 may not be accessible to N 2 at this temperature. Therefore, it was recently proposed to use the DFT analysis of H 2 adsorption isotherms to characterize pore structure of materials considered for hydrogen storage applications. In present work, adsorption isotherms of H 2 and N 2 at cryogenic temperatures are used for the characterization of carbon materials. Adsorption measurements were performed with Autosorb 1 MP (Quantachrome Instruments, Boynton Beach, Florida, USA). As an example, Fig 1 compares PSDs calculated for the activated carbon sample (F400, Calgon Carbon) using combined H 2 and N 2 data, and using N 2 isotherm only. The nitrogen derived PSD does not include certain amount of micropores which are accessible to H 2 but not to N 2 molecules. Obviously, the difference in the calculated PSDs by the two methods will depend on the actual content of small micropores in a given sample. Carbon adsorption properties can also be characterized by the isosteric heat of adsorption, Qst, related to the adsorption energy and dependent on the carbon pore/surface structure. Fig 2 shows Qst data calculated using the Clausius-Clapeyron equation from H 2 isotherms measured at 77 K and 87 K for the carbon molecular sieve CMS 5A (Takeda), oxidized single wall nano-tubes (SWNT), and graphitized carbon black (Supelco). The Qst values decrease with increasing pore sizes. The

Adsorption heats of olefins on supported MoO3/Al2O3 catalists

International Nuclear Information System (INIS)

Grinev, V.E.; Madden, M.; Khalit, V.A.; Aptekar', E.L.; Aldag, A.; Krylov, O.V.

1983-01-01

Adsorption heats of C 2 H 4 , C 3 H 6 and C 4 H 8 on supported MoO 3 /Al 2 O 3 catalysts containing 6, 10 and 15 wt. % of MoO 3 at 25, 77 and 195 deg are determimed. Adsorption heat of an olefin increases with a growing length of its carbonic chain. The number of adsorbed olefin molecules grows with an increase in the MoO 3 concentration, while initial adsorption heats decrease. The number of adsorbed olefins is proportional to mean rate of molybdenum reduction in catalysts. Adsorption heats of oxygen on the surface of the catalysts with preliminarily adsorbed olefins are determined. It is shown that adsorption of oxygen and olefins proceeeds both on the same and on different centres of the surface. Mechanisms of surface interactions are discussed

Protein adsorption resistance of PVP-modified polyurethane film prepared by surface-initiated atom transfer radical polymerization

International Nuclear Information System (INIS)

Yuan, Huihui; Qian, Bin; Zhang, Wei; Lan, Minbo

2016-01-01

Highlights: • Antifouling PVP brushes were successfully grafted on PU films by SI-ATRP. • The effect of polymerization time on surface property and topography was studied. • Hydrophilicity and protein fouling resistance of PVP–PU films were greatly promoted. • Competitive adsorption of three proteins on PVP–PU films was evaluated. - Abstract: An anti-fouling surface of polyurethane (PU) film grafted with Poly(N-vinylpyrrolidone) (PVP) was prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). And the polymerization time was investigated to obtain PU films with PVP brushes of different lengths. The surface properties and protein adsorption of modified PU films were evaluated. The results showed that the hydrophilicity of PU–PVP films were improved with the increase of polymerization time, which was not positive correlation with the surface roughness due to the brush structure. Additionally, the protein resistance performance was promoted when prolonging the polymerization time. The best antifouling PU–PVP (6.0 h) film reduced the adsoption level of bovine serum albumin (BSA), lysozyme (LYS), and brovin serum fibrinogen (BFG) by 93.4%, 68.3%, 85.6%, respectively, compared to the unmodified PU film. The competitive adsorption of three proteins indicated that LYS preferentially adsorbed on the modified PU film, while BFG had the lowest adsorption selectivity. And the amount of BFG on PU–PVP (6.0 h) film reduced greatly to 0.08 μg/cm"2, which was almost one-tenth of its adsorption from the single-protein system. Presented results suggested that both hydrophilicity and surface roughness might be the important factors in all cases of protein adsorption, and the competitive or selective adsorption might be related to the size of the proteins, especially on the non-charged films.

Protein adsorption resistance of PVP-modified polyurethane film prepared by surface-initiated atom transfer radical polymerization

Energy Technology Data Exchange (ETDEWEB)

Yuan, Huihui; Qian, Bin; Zhang, Wei [Shanghai Key Laboratory of Functional Materials Chemistry and Research Center of Analysis and Test, East China University of Science and Technology, Shanghai 200237 (China); Lan, Minbo, E-mail: minbolan@ecust.edu.cn [Shanghai Key Laboratory of Functional Materials Chemistry and Research Center of Analysis and Test, East China University of Science and Technology, Shanghai 200237 (China); State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237 (China)

2016-02-15

Highlights: • Antifouling PVP brushes were successfully grafted on PU films by SI-ATRP. • The effect of polymerization time on surface property and topography was studied. • Hydrophilicity and protein fouling resistance of PVP–PU films were greatly promoted. • Competitive adsorption of three proteins on PVP–PU films was evaluated. - Abstract: An anti-fouling surface of polyurethane (PU) film grafted with Poly(N-vinylpyrrolidone) (PVP) was prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). And the polymerization time was investigated to obtain PU films with PVP brushes of different lengths. The surface properties and protein adsorption of modified PU films were evaluated. The results showed that the hydrophilicity of PU–PVP films were improved with the increase of polymerization time, which was not positive correlation with the surface roughness due to the brush structure. Additionally, the protein resistance performance was promoted when prolonging the polymerization time. The best antifouling PU–PVP (6.0 h) film reduced the adsoption level of bovine serum albumin (BSA), lysozyme (LYS), and brovin serum fibrinogen (BFG) by 93.4%, 68.3%, 85.6%, respectively, compared to the unmodified PU film. The competitive adsorption of three proteins indicated that LYS preferentially adsorbed on the modified PU film, while BFG had the lowest adsorption selectivity. And the amount of BFG on PU–PVP (6.0 h) film reduced greatly to 0.08 μg/cm{sup 2}, which was almost one-tenth of its adsorption from the single-protein system. Presented results suggested that both hydrophilicity and surface roughness might be the important factors in all cases of protein adsorption, and the competitive or selective adsorption might be related to the size of the proteins, especially on the non-charged films.

Superior lithium adsorption and required magnetic separation behavior of iron-doped lithium ion-sieves

Energy Technology Data Exchange (ETDEWEB)

Wang, Shulei; Zheng, Shili; Wang, Zheming; Cui, Wenwen; Zhang, Hailin; Yang, Liangrong; Zhang, Yi; Li, Ping

2018-01-01

The recent research on adsorption-based lithium recovery from lithium-containing solutions has been centred on adsorption capacity and separation of lithium ion-sieves powder from solutions. Herein, an effective iron-doped lithium titanium oxide (Fe-doped Li2TiO3) was synthesized by Fe-doping via solid state reactions followed by acid treatment to form iron-doped lithium ion-sieves (Fe/Ti-x(H)). The resulting solid powder displays both superior adsorption capacity of lithium and high separation efficiency of the adsorbent from the solutions. SEM imaging and BET surface area measurement results showed that at Fe doping levels x0.15, Fe-doping led to grain shrinkage as compared to Li2TiO3 and at the same time the BET surface area increased. The Fe/Ti-0.15(H) exhibited saturated magnetization values of 13.76 emu g-1, allowing effective separation of the material from solid suspensions through the use of a magnet. Consecutive magnetic separation results suggested that the Fe/Ti-0.15(H) powders could be applied at large-scale and continuously removed from LiOH solutions with separation efficiency of 96% or better. Lithium adsorption studies indicated that the equilibrium adsorption capacity of Fe/Ti-0.15(H) in LiOH 2 solutions (1.8 g L-1 Li, pH 12) reached 53.3 mg g-1 within 24 h, which was higher than that of pristine Li2TiO3 (50.5 mg g-1) without Fe doping. Competitive adsorption and regeneration results indicated that the Fe/Ti-0.15(H) possessed a high selectivity for Li with facile regeneration. Therefore, it could be expected that the iron-doped lithium ion-sieves have practical applicability potential for large scale lithium extraction and recovery from lithium-bearing solutions.

Insights into the Hydrothermal Stability of Triamine-Functionalized SBA-15 Silica for CO2 Adsorption.

Science.gov (United States)

Jahandar Lashaki, Masoud; Ziaei-Azad, Hessam; Sayari, Abdelhamid

2017-10-23

The hydrothermal stability of triamine-grafted, large-pore SBA-15 CO 2 adsorbents was studied by using steam stripping. Following two 3 h cycles of steam regeneration, lower CO 2 uptakes, lower CO 2 /N ratios, and slower adsorption kinetics were observed relative to fresh samples, particularly at the lowest adsorption temperature (25 °C). CO 2 adsorption measurements for a selected sample exposed to 48 h of steam stripping depicted that after the initial loss during the first exposure to steam (3-6 h), the adsorptive properties stabilized. For higher adsorption temperatures (i.e., 50 and 75 °C), however, all adsorptive properties remained almost unchanged after steaming, indicating the significance of diffusional limitations. Thermogravimetric analysis and FTIR spectroscopy on grafted samples before and after steam stripping showed no amine leaching and no change in the chemical nature of the amine groups, respectively. Also, a six-cycle CO 2 adsorption/desorption experiment under dry conditions showed no thermal degradation. However, N 2 adsorption measurement at 77 K showed significant reductions in the BET surface area of the grafted samples following steaming. Based on the pore size distribution of calcined, grafted samples before and after steaming, it is proposed that exposure to steam restructured the grafted materials, causing mass transfer resistance. It is inferred that triamine-grafted, large-pore SBA-15 adsorbents are potential candidates for CO 2 capture at relatively high temperatures (50-75 °C; for example, flue gas) combined with steam regeneration. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of pH and Calcium on the Adsorptive Removal of Cadmium and Copper by Iron Oxide–Coated Sand and Granular Ferric Hydroxide

KAUST Repository

Uwamariya, V.

2015-08-17

Iron oxide-coated sand (IOCS) and granular ferric hydroxide (GFH) were used to study the effect of Ca2+ and pH on the adsorptive removal of Cu2+ and Cd2+ from groundwater using batch adsorption experiments and kinetic modeling. It was observed that Cu2+ and Cd2+ were not stable in synthetic waters. The extent of precipitation increased with increasing pH. Removal of Cu2+ and Cd2+ was achieved through both precipitation and adsorption, with IOCS showing higher adsorption efficiency. Increase of pH (from 6 to 8) resulted in a higher overall removal efficiency of both Cu2+ and Cd2+, with precipitation as predominant removal mechanisms at higher pH values, especially for Cu2+. An increase in Ca2+ concentration increased the precipitation of Cu2+ [as Cu2(OH)2CO3 and Cu3(OH)2(CO3)2] and Cd2+ [as Cd(OH)2 and CdCO3]. In addition, Ca2+ competes with Cu2+ and Cd2+ for surface adsorption sites on IOCS and GFH, and reduces their adsorption capacity. The kinetic modeling revealed that the adsorption of Cd2+ onto IOCS is a complex process, with limited contribution of chemisorption that increases in the presence of Ca2+. © 2015 American Society of Civil Engineers.

Kinetics of protein adsorption/desorption mediated by pH-responsive polymer layer

Science.gov (United States)

Su, Xiao-Hang; Lei, Qun-Li; Ren, Chun-Lai

2015-11-01

We propose a new way of regulating protein adsorption by using a pH-responsive polymer. According to the theoretical results obtained from the molecular theory and kinetic approaches, both thermodynamics and kinetics of protein adsorption are verified to be well controlled by the solution pH. The kinetics and the amount of adsorbed proteins at equilibrium are greatly increased when the solution environment changes from acid to neutral. The reason is that the increased pH promotes the dissociation of the weak polyelectrolyte, resulting in more charged monomers and more stretched chains. Thus the steric repulsion within the polymer layer is weakened, which effectively lowers the barrier felt by the protein during the process of adsorption. Interestingly, we also find that the kinetics of protein desorption is almost unchanged with the variation of pH. It is because although the barrier formed by the polymer layer changes along with the change of pH, the potential at contact with the surface varies equally. Our results may provide useful insights into controllable protein adsorption/desorption in practical applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 21274062, 11474155, and 91027040).

Chemical and physicochemical characterization of vermicompost from bovine manure and evaluation of competitive adsorption of cadmium and lead; Caracterizacao quimica e fisico-quimica de vermicomposto de esterco bovino e avaliacao da adsorcao competitiva por cadmio e chumbo

Energy Technology Data Exchange (ETDEWEB)

Lamim, Soraida Sozzi Miguel [Juiz de Fora Univ., MG (Brazil). Dept. de Quimica; Jordao, Claudio Pereira; Brune, Walter; Pereira, Jose Luis [Vicosa Univ., MG (Brazil). Dept. de Quimica

1996-09-01

The chemical and physicochemical characterization of vermicompost from bovine manure has been studied. It was examined the pH and cation exchangeable capacity (CTC), moistness, ash, organic carbon, total nitrogen, lignin, cellulose and metal concentrations, among other characteristics. The vermicompost was then applied to the retention and competition of metal pollutants (Cd and Pb) from metal nitrate solutions. The retention was affected by both the pH and time of adsorption, while the competitive character of these metals for the substrate was not relevant to each pH examined. (author) 46 refs., 4 figs., 7 tabs.

Influence of preadsorbed oxygen on the sign and magnitude of the chemisorption-induced resistance change for H2 adsorption onto Fe films

Science.gov (United States)

Shanabarger, M. R.

1986-01-01

Measurements have been made of the chemisorption-induced resistance change for H2 adsorbed onto Fe film substrates predosed with fixed coverages of chemisorbed oxygen. The measurements were made at temperatures from 295 to 340 K and for estimated oxygen coverages of less than 0.1 monolayers. Two distinct resistance change components were observed in both the adsorption kinetics and the equilibrium isotherms: a positive component which is associated with the adsorption of H2 onto a clean Fe surface, and a negative component which was correlated with the presence of the chemisorbed oxygen. The resistance change isotherms can be fit with a model which assumes that each of the resistance change components result from dissociative chemisorbed hydrogen. Possible mechanisms for the chemisorbed-oxygen-induced negative resistance change are discussed.

Adsorption of Sr(II) and Eu(III) on Na-rectorite. Effect of pH, ionic strength, concentration and modelling

Energy Technology Data Exchange (ETDEWEB)

Hu, J.; Wang, X.K. [School of Nuclear Science and Engineering, North China Electric Power Univ., BJ (China); Key Lab. of Novel Thin Film Solar Cells, Inst. of Plasma Physics, Chinese Academy of Sciences, Hefei (China); Chen, C.L.; Sheng, G.D.; Li, J.X. [Key Lab. of Novel Thin Film Solar Cells, Inst. of Plasma Physics, Chinese Academy of Sciences, Hefei (China); Chen, Y.X. [School of Nuclear Science and Engineering, North China Electric Power Univ., BJ (China)

2010-07-01

The surface charge characteristics of Na-rectorite (NaAl{sub 4}[Si,Al]{sub 8}O{sub 20}(OH){sub 4}.nH{sub 2}O;) were studied by potentiometric acid-base titrations. Sr(II) and Eu(III) adsorptions on Na-rectorite as a function of pH, ionic strength, and Sr(II)/Eu(III) concentrations were carried out to investigate the surface interactions between Sr(II)/Eu(III) with Na-rectorite. The results indicated that the adsorptions of Sr(II) and Eu(III) on Na-rectorite increased with increasing pH and decreased with increasing ionic strength and initial Sr(II)/Eu(III) concentrations, and that the affinity of Na-rectorite for Eu(III) was much higher than for Sr(II). The experimental data of Sr(II)/Eu(III) adsorption were simulated by the diffuse-layer model (DLM) well with the aid of FITEQL 3.2. Simultaneous adsorptions of Sr(II) and Eu(III) on Na-rectorite were also modeled using the DLM. The adsorption mechanisms of Sr(II) and Eu(III) on Na-rectorite may be dominated by ion exchange interaction at low pH or moderate pH, and by surface complexation interaction at high pH. (orig.)

Competitive adsorption of (phosphorylated) ethoxylated styrene oxide polymer and polyacrylic acid on silica coated iron oxide pigment

NARCIS (Netherlands)

Wijting, W.K.; Reenen, van A.; Laven, J.; Benthem, van R.A.T.M.; With, de G.

2014-01-01

The colloidal stabilization in waterbased paint is poorly understood due to its complexity in composition, usually containing mixtures of particles and of surface active agents ("dispersants"). In this study we make a step forward by analyzing the competitive adsorption of a few widely used

A novel highly efficient adsorbent {[Co4(L)2(μ3-OH)2(H2O)3(4,4‧-bipy)2]·(H2O)2}n: Synthesis, crystal structure, magnetic and arsenic (V) absorption capacity

Science.gov (United States)

Zhang, Chong; Xiao, Yu; Qin, Yan; Sun, Quanchun; Zhang, Shuhua

2018-05-01

A novel highly efficient adsorbent-microporous tetranuclear Co(II)-based polymer, {[Co4(L)2(μ3-OH)2(H2O)3(4,4‧-bipy)2]·(H2O)2}n (1, H3L = 4-(N,N‧-bis(4-carboxybenzyl)amino) benzenesulfonic acid, 4,4‧-bipy = 4,4‧-bipyridine), was hydrothermally synthesized. The complex 1 is a metal-organic framework (MOF) material which was characterized by single-crystal X-ray diffraction, BET and platon software. Co-MOF (complex 1) reveals excellent adsorption property. The capacity of Co-MOF to remove arsenic As(V) from sodium arsenate aqueous solutions was investigated (The form of As(V) is AsO43-). The experimental results showed that Co-MOF had a higher stable and relatively high As(V) removal rate (> 98%) at pH 4-10. The adsorption kinetics followed a pseudo-second-order kinetic model, and the adsorption isotherm followed the Langmuir equation. Co-MOF exhibits a very high adsorption capacity of As(V) in aqueous solution (Qmax of 96.08 mg/g). Finally, the optimal adsorption conditions for the model were obtained through a Box-Behnken response surface experiment which was designed with adsorption time, dose, temperature and rotational speed of the shaker as the influencing factors to determine two-factor interaction effects. Co-MOF was further characterized using FTIR, PXRD, X-ray photoelectron spectroscopy before and after adsorption As (V). The magnetism of Co-MOF was also discussed.

Competitive adsorption of dyes and heavy metals on zeolitic structures.

Science.gov (United States)

Hernández-Montoya, V; Pérez-Cruz, M A; Mendoza-Castillo, D I; Moreno-Virgen, M R; Bonilla-Petriciolet, A

2013-02-15

The adsorption of Acid blue 25, basic blue 9, basic violet 3, Pb(2+), Ni(2+), Zn(2+) and Cd(2+) ions has been studied in single and dye-metal binary solutions using two mineral materials: Clinoptilolite (CL) and ER (Erionite). These zeolites were characterized by FT-IR spectroscopy; potentiometric titration and nitrogen adsorption isotherms at 77 K to obtain their textural parameters. Results indicated that ER has an acidic character and a high specific surface (401 m(2) g(-1)) in contrast with the zeolite CL (21 m(2) g(-1)). Surprisingly, the removal of dyes was very similar for the two zeolites and they showed a considerable selectivity by the basic dyes in comparison with the acid dyes. In the case of heavy metals, ER was more effective in the adsorption process showing a selectivity of: Pb(2+) > Ni(2+) > Zn(2+) > Cd(2+). In the multicomponent adsorption experiments an antagonistic effect was observed in the removal of basic dyes and heavy metals. Particularly, the adsorbed amount of basic violet 3 decreased more significantly when the heavy metals are presents in contrast with the basic blue 9. Copyright © 2012 Elsevier Ltd. All rights reserved.

Adsorption of selected endocrine disrupting compounds and pharmaceuticals on activated biochars

Energy Technology Data Exchange (ETDEWEB)

Jung, Chanil [Department of Civil and Environmental Engineering, University of South Carolina, Columbia, SC 29208 (United States); Park, Junyeong [Department of Forest Biomaterials, North Carolina State University, Raleigh, NC 27695 (United States); Lim, Kwang Hun [Department of Chemistry, East Carolina University, Greenville, NC 27858 (United States); Park, Sunkyu [Department of Forest Biomaterials, North Carolina State University, Raleigh, NC 27695 (United States); Heo, Jiyong [Department of Civil and Environmental Engineering, Korea Army Academy at Young-Cheon, PO Box 135-1, Changhari, Gogyeongmeon, Young-cheon 770-849, Gyeongbuk (Korea, Republic of); Her, Namguk [Department of Chemistry and Environmental Sciences, Korea Army Academy at Young-Cheon, PO Box 135-1, Changhari, Gogyeongmeon, Young-cheon 770-849, Gyeongbuk (Korea, Republic of); Oh, Jeill; Yun, Soyoung [Department of Civil and Environmental Engineering, Chung-Ang University, Dongjak-Ku, Seoul 156-756 (Korea, Republic of); Yoon, Yeomin, E-mail: yoony@cec.sc.edu [Department of Civil and Environmental Engineering, University of South Carolina, Columbia, SC 29208 (United States)

2013-12-15

Highlights: • Biochars were prepared at different gas environments. • The competitive adsorption among EDCs/PhACs were investigated. • Aromaticity of adsorbent plays a significant role for EDCs/PhACs adsorption. -- Abstract: Chemically activated biochar produced under oxygenated (O-biochar) and oxygen-free (N-biochar) conditions were characterized and the adsorption of endocrine disrupting compounds (EDCs): bisphenol A (BPA), atrazine (ATR), 17 α-ethinylestradiol (EE2), and pharmaceutical active compounds (PhACs); sulfamethoxazole (SMX), carbamazepine (CBM), diclofenac (DCF), ibuprofen (IBP) on both biochars and commercialized powdered activated carbon (PAC) were investigated. Characteristic analysis of adsorbents by solid-state nuclear magnetic resonance (NMR) was conducted to determine better understanding about the EDCs/PhACs adsorption. N-biochar consisted of higher polarity moieties with more alkyl (0–45 ppm), methoxyl (45–63 ppm), O-alkyl (63–108 ppm), and carboxyl carbon (165–187 ppm) content than other adsorbents, while aromaticity of O-biochar was higher than that of N-biochar. O-biochar was composed mostly of aromatic moieties, with low H/C and O/C ratios compared to the highly polarized N-biochar that contained diverse polar functional groups. The higher surface area and pore volume of N-biochar resulted in higher adsorption capacity toward EDCs/PhACs along with atomic-level molecular structural property than O-biochar and PAC. N-biochar had a highest adsorption capacity of all chemicals, suggesting that N-biochar derived from loblolly pine chip is a promising sorbent for agricultural and environmental applications. The adsorption of pH-sensitive dissociable SMX, DCF, IBP, and BPA varied and the order of adsorption capacity was correlated with the hydrophobicity (K{sub ow}) of adsorbates throughout the all adsorbents, whereas adsorption of non-ionizable CBM, ATR, and EE2 in varied pH allowed adsorbents to interact with hydrophobic property

Adsorption of selected endocrine disrupting compounds and pharmaceuticals on activated biochars

International Nuclear Information System (INIS)

Jung, Chanil; Park, Junyeong; Lim, Kwang Hun; Park, Sunkyu; Heo, Jiyong; Her, Namguk; Oh, Jeill; Yun, Soyoung; Yoon, Yeomin

2013-01-01

Highlights: • Biochars were prepared at different gas environments. • The competitive adsorption among EDCs/PhACs were investigated. • Aromaticity of adsorbent plays a significant role for EDCs/PhACs adsorption. -- Abstract: Chemically activated biochar produced under oxygenated (O-biochar) and oxygen-free (N-biochar) conditions were characterized and the adsorption of endocrine disrupting compounds (EDCs): bisphenol A (BPA), atrazine (ATR), 17 α-ethinylestradiol (EE2), and pharmaceutical active compounds (PhACs); sulfamethoxazole (SMX), carbamazepine (CBM), diclofenac (DCF), ibuprofen (IBP) on both biochars and commercialized powdered activated carbon (PAC) were investigated. Characteristic analysis of adsorbents by solid-state nuclear magnetic resonance (NMR) was conducted to determine better understanding about the EDCs/PhACs adsorption. N-biochar consisted of higher polarity moieties with more alkyl (0–45 ppm), methoxyl (45–63 ppm), O-alkyl (63–108 ppm), and carboxyl carbon (165–187 ppm) content than other adsorbents, while aromaticity of O-biochar was higher than that of N-biochar. O-biochar was composed mostly of aromatic moieties, with low H/C and O/C ratios compared to the highly polarized N-biochar that contained diverse polar functional groups. The higher surface area and pore volume of N-biochar resulted in higher adsorption capacity toward EDCs/PhACs along with atomic-level molecular structural property than O-biochar and PAC. N-biochar had a highest adsorption capacity of all chemicals, suggesting that N-biochar derived from loblolly pine chip is a promising sorbent for agricultural and environmental applications. The adsorption of pH-sensitive dissociable SMX, DCF, IBP, and BPA varied and the order of adsorption capacity was correlated with the hydrophobicity (K ow ) of adsorbates throughout the all adsorbents, whereas adsorption of non-ionizable CBM, ATR, and EE2 in varied pH allowed adsorbents to interact with hydrophobic property of

Adsorption of Ni2+ from aqueous solution by magnetic Fe@graphite nano-composite

Directory of Open Access Journals (Sweden)

Konicki Wojciech

2016-12-01

Full Text Available The removal of Ni2+ from aqueous solution by iron nanoparticles encapsulated by graphitic layers (Fe@G was investigated. Nanoparticles Fe@G were prepared by chemical vapor deposition CVD process using methane as a carbon source and nanocrystalline iron. The properties of Fe@G were characterized by X-ray Diffraction method (XRD, High-Resolution Transmission Electron Microscopy (HRTEM, Fourier Transform-Infrared Spectroscopy (FTIR, BET surface area and zeta potential measurements. The effects of initial Ni2+ concentration (1–20 mg L−1, pH (4–11 and temperature (20–60°C on adsorption capacity were studied. The adsorption capacity at equilibrium increased from 2.96 to 8.78 mg g−1, with the increase in the initial concentration of Ni2+ from 1 to 20 mg L−1 at pH 7.0 and 20oC. The experimental results indicated that the maximum Ni2+ removal could be attained at a solution pH of 8.2 and the adsorption capacity obtained was 9.33 mg g−1. The experimental data fitted well with the Langmuir model with a monolayer adsorption capacity of 9.20 mg g−1. The adsorption kinetics was found to follow pseudo-second-order kinetic model. Thermodynamics parameters, ΔHO, ΔGO and ΔSO, were calculated, indicating that the adsorption of Ni2+ onto Fe@G was spontaneous and endothermic in nature.

Selective adsorption of bovine hemoglobin on functional TiO2 nano-adsorbents: surface physic-chemical properties determined adsorption activity

Science.gov (United States)

Guo, Shiguang; Zhang, Jianghua; Shao, Mingxue; Zhang, Xia; Liu, Yufeng; Xu, Junli; Meng, Hao; Han, Yide

2015-04-01

Surface functionalized nanoparticles are efficient adsorbents which have shown good potential for protein separation. In this work, we chose two different types of organic molecules, oleic acid (OA) and 3-glycidoxypropyltrimethoxy silane (GPTMS), to functionalize the surface of TiO2 nanoparticles, and we studied the effects of this modification on their surface physicochemical properties in correlation with their selective adsorption of proteins. The results showed that the surface zeta potential and the surface water wettability of the modified TiO2 were significantly changed in comparison with the original TiO2 nanoparticles. The adsorption activities of bovine hemoglobin (BHb) and bovine serum albumin (BSA) on these functionalized TiO2 samples were investigated under different conditions, including pH values, contact time, ion strength, and initial protein concentration. In comparison with the non-specific adsorption of original TiO2, however, both the OA-TiO2 and GPTMS-TiO2 exhibited increased BHb adsorption and decreased BSA adsorption at the same time. Using a binary protein mixture as the adsorption object, a higher separation factor (SF) was obtained for OA-TiO2 under optimum conditions. The different adsorption activities of BHb and BSA on the modified TiO2 were correlated with different interactions at the protein/solid interface, and the chemical force as well as the electrostatic force played an important role in the selective adsorption process.

A first principle simulation of competitive adsorption of SF6 decomposition components on nitrogen-doped anatase TiO2 (101) surface

Science.gov (United States)

Dong, Xingchen; Zhang, Xiaoxing; Cui, Hao; Zhang, Jun

2017-11-01

Gas insulated switchgear has been widely used in modern electric systems due to its significantly excellent performances such as compact structure and low land occupation as well as the security stability. However, inside defects caused during manufacture process can lead to partial discharge which might develop into serious insulation failure. Online monitoring method on basis of gas sensors is considered a promising way of detecting partial discharge for alarm ahead of time. Research has found that TiO2 nanotubes sensors show good response to SO2, SOF2, SO2F2, the decomposition components as a result of partial discharge. In order to investigate the gas-sensing mechanism of nitrogen-doped TiO2 prepared via plasma treatment methods to SO2, SOF2, and SO2F2, the adsorption structures of both three gas molecules and anatase TiO2 (101) surface were built, and DFT calculations were then carried out for calculation and analysis of adsorption parameters. Adsorption property comparison of anatase TiO2 (101) surface after nitrogen doping with Au doping and without doping shows that nitrogen doping can obviously enhance the adsorption energy for SO2 and SOF2 adsorption and no charge transfer for SO2F2 adsorption, further explaining the adsorption mechanism and doping influence of different doping elements.

Adsorption and Desorption Characteristics of Cd2+ and Pb2+ by Micro and Nano-sized Biogenic CaCO3

Science.gov (United States)

Liu, Renlu; Guan, Yong; Chen, Liang; Lian, Bin

2018-01-01

The purpose of this study was to elucidate the characteristics and mechanisms of adsorption and desorption for heavy metals by micro and nano-sized biogenic CaCO3 induced by Bacillus subtilis, and the pH effect on adsorption was investigated. The results showed that the adsorption characteristics of Cd2+ and Pb2+ are well described by the Langmuir adsorption isothermal equation, and the maximum adsorption amounts for Cd2+ and Pb2+ were 94.340 and 416.667 mg/g, respectively. The maximum removal efficiencies were 97% for Cd2+, 100% for Pb2+, and the desorption rate was smaller than 3%. Further experiments revealed that the biogenic CaCO3 could maintain its high adsorption capability for heavy metals within wide pH ranges (3–8). The FTIR and XRD results showed that, after the biogenic CaCO3 adsorbed Cd2+ or Pb2+, it did not produce a new phase, which indicated that biogenic CaCO3 and heavy metal ions were governed by a physical adsorption process, and the high adsorptive capacity of biogenic CaCO3 for Cd2+ and Pb2+ were mainly attributed to its large total specific surface area. The findings could improve the state of knowledge about biogenic CaCO3 formation in the environment and its potential roles in the biogeochemical cycles of heavy metals. PMID:29434577

Relationship between carbon microstructure, adsorption energy and hydrogen adsorption capacity at different temperatures

International Nuclear Information System (INIS)

Jagiello, J.; Thommes, M.

2005-01-01

Various microporous materials such as activated carbons, nano-tubes, synthetic micro-porous carbons as well as metal organic framework materials are being considered for hydrogen storage applications by means of physical adsorption. To develop materials of practical significance for hydrogen storage it is important to understand the relationships between pore sizes, adsorption energies and adsorption capacities. The pore size distribution (PSD) characterization is traditionally obtained from the analysis of nitrogen adsorption isotherms measured at 77 K. However, a portion of the pores accessible to H 2 may not be accessible to N 2 at this temperature. Therefore, it was recently proposed to use the DFT analysis of H 2 adsorption isotherms to characterize pore structure of materials considered for hydrogen storage applications [1]. In present work, adsorption isotherms of H 2 and N 2 at cryogenic temperatures are used for the characterization of carbon materials. Adsorption measurements were performed with Autosorb 1 MP [Quantachrome Instruments, Boynton Beach, Florida, USA]. As an example, Fig 1 compares PSDs calculated for the activated carbon sample (F400, Calgon Carbon) using combined H 2 and N 2 data, and using N 2 isotherm only. The nitrogen derived PSD does not include certain amount of micro-pores which are accessible to H 2 but not to N 2 molecules. Obviously, the difference in the calculated PSDs by the two methods will depend on the actual content of small micro-pores in a given sample. Carbon adsorption properties can also be characterized by the isosteric heat of adsorption, Qst, related to the adsorption energy and dependent on the carbon pore/surface structure. Fig 2 shows Qst data calculated using the Clausius-Clapeyron equation from H 2 isotherms measured at 77 K and 87 K for the carbon molecular sieve CMS 5A (Takeda), oxidized single wall nano-tubes (SWNT) [2], and graphitized carbon black (Supelco). The Qst values decrease with increasing pore

Physical adsorption and charge transfer of molecular Br2 on graphene.

Science.gov (United States)

Chen, Zheyuan; Darancet, Pierre; Wang, Lei; Crowther, Andrew C; Gao, Yuanda; Dean, Cory R; Taniguchi, Takashi; Watanabe, Kenji; Hone, James; Marianetti, Chris A; Brus, Louis E

2014-03-25

We present a detailed study of gaseous Br2 adsorption and charge transfer on graphene, combining in situ Raman spectroscopy and density functional theory (DFT). When graphene is encapsulated by hexagonal boron nitride (h-BN) layers on both sides, in a h-BN/graphene/h-BN sandwich structure, it is protected from doping by strongly oxidizing Br2. Graphene supported on only one side by h-BN shows strong hole doping by adsorbed Br2. Using Raman spectroscopy, we determine the graphene charge density as a function of pressure. DFT calculations reveal the variation in charge transfer per adsorbed molecule as a function of coverage. The molecular adsorption isotherm (coverage versus pressure) is obtained by combining Raman spectra with DFT calculations. The Fowler-Guggenheim isotherm fits better than the Langmuir isotherm. The fitting yields the adsorption equilibrium constant (∼0.31 Torr(-1)) and repulsive lateral interaction (∼20 meV) between adsorbed Br2 molecules. The Br2 molecule binding energy is ∼0.35 eV. We estimate that at monolayer coverage each Br2 molecule accepts 0.09 e- from single-layer graphene. If graphene is supported on SiO2 instead of h-BN, a threshold pressure is observed for diffusion of Br2 along the (somewhat rough) SiO2/graphene interface. At high pressure, graphene supported on SiO2 is doped by adsorbed Br2 on both sides.

Adsorption mechanism of 2,4-dichlorophenoxyacetic acid onto nitric-acid-modified activated carbon fiber.

Science.gov (United States)

Li, Qun; Sun, Jie; Ren, Tianhao; Guo, Lin; Yang, Zhilin; Yang, Qi; Chen, Hai

2018-04-01

Adsorption by carbon materials is one of the relatively fast methods in present research, which is widely used in emergency events. Activated carbon fiber (ACF) modified by nitric acid (N-ACF) was studied in this research to determine the adsorption performance for 2,4-dichlorophenoxyacetic acid (2,4-D). Subsequently, influence factors, adsorption isotherm models, kinetics and thermodynamic were investigated in a batch system to realize this adsorption. Experimental results showed that ACF modified by 0.1M nitric acid had a better removal ability than 2,4-D. Removal rate of 2,4-D by N-ACF was greatly influenced by pH with the optimum pH at 2. The superiority of the Langmuir isotherm model in describing the adsorption equilibrium was revealed by correlation coefficients R2 (R 2  ≥ 0.997). Furthermore, adsorption kinetics was well described by pseudo-second-order model. The results of thermodynamic showed that adsorption was a spontaneous, endothermic process with randomness increasing. Additionally, surface structure properties of adsorbent were characterized by Scanning electron microscopy, Fourier transform infrared spectroscopy, Specific surface area analysis of Brunauer, Emmett and Teller and Boehm's titration. It turned out that the micropore structure and functional groups on N-ACF all can contribute to the removal of 2,4-D.

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)

Microporous metal organic framework [M2(hfipbb)2(ted)] (M=Zn, Co; H2hfipbb=4,4-(hexafluoroisopropylidene)-bis(benzoic acid); ted=triethylenediamine): Synthesis, structure analysis, pore characterization, small gas adsorption and CO2/N2 separation properties

Science.gov (United States)

Xu, William W.; Pramanik, Sanhita; Zhang, Zhijuan; Emge, Thomas J.; Li, Jing

2013-04-01

Carbon dioxide is a greenhouse gas that is a major contributor to global warming. Developing methods that can effectively capture CO2 is the key to reduce its emission to the atmosphere. Recent research shows that microporous metal organic frameworks (MOFs) are emerging as a promising family of adsorbents that may be promising for use in adsorption based capture and separation of CO2 from power plant waste gases. In this work we report the synthesis, crystal structure analysis and pore characterization of two microporous MOF structures, [M2(hfipbb)2(ted)] (M=Zn (1), Co (2); H2hfipbb=4,4-(hexafluoroisopropylidene)-bis(benzoic acid); ted=triethylenediamine). The CO2 and N2 adsorption experiments and IAST calculations are carried out on [Zn2(hfipbb)2(ted)] under conditions that mimic post-combustion flue gas mixtures emitted from power plants. The results show that the framework interacts with CO2 strongly, giving rise to relatively high isosteric heats of adsorption (up to 28 kJ/mol), and high adsorption selectivity for CO2 over N2, making it promising for capturing and separating CO2 from CO2/N2 mixtures.

Effects of hydration and oxygen vacancy on CO2 adsorption and activation on beta-Ga2O3(100).

Science.gov (United States)

Pan, Yun-xiang; Liu, Chang-jun; Mei, Donghai; Ge, Qingfeng

2010-04-20

The effects of hydration and oxygen vacancy on CO(2) adsorption on the beta-Ga(2)O(3)(100) surface have been studied using density functional theory slab calculations. Adsorbed CO(2) is activated on the dry perfect beta-Ga(2)O(3)(100) surface, resulting in a carbonate species. This adsorption is slightly endothermic, with an adsorption energy of 0.07 eV. Water is preferably adsorbed molecularly on the dry perfect beta-Ga(2)O(3)(100) surface with an adsorption energy of -0.56 eV, producing a hydrated perfect beta-Ga(2)O(3)(100) surface. Adsorption of CO(2) on the hydrated surface as a carbonate species is also endothermic, with an adsorption energy of 0.14 eV, indicating a slightly repulsive interaction when H(2)O and CO(2) are coadsorbed. The carbonate species on the hydrated perfect surface can be protonated by the coadsorbed H(2)O to a bicarbonate species, making the CO(2) adsorption exothermic, with an adsorption energy of -0.13 eV. The effect of defects on CO(2) adsorption and activation has been examined by creating an oxygen vacancy on the dry beta-Ga(2)O(3)(100) surface. The formation of an oxygen vacancy is endothermic, by 0.34 eV, with respect to a free O(2) molecule in the gas phase. Presence of the oxygen vacancy promoted the adsorption and activation of CO(2). In the most stable CO(2) adsorption configuration on the dry defective beta-Ga(2)O(3)(100) surface with an oxygen vacancy, one of the oxygen atoms of the adsorbed CO(2) occupies the oxygen vacancy site, and the CO(2) adsorption energy is -0.31 eV. Water favors dissociative adsorption at the oxygen vacancy site on the defective surface. This process is spontaneous, with a reaction energy of -0.62 eV. These results indicate that, when water and CO(2) are present in the adsorption system simultaneously, water will compete with CO(2) for the oxygen vacancy sites and impact CO(2) adsorption and conversion negatively.

CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles exhibit fast and selective adsorption of arsenic with high adsorption capacity

Science.gov (United States)

Yang, Ji-Chun; Yin, Xue-Bo

2017-01-01

In this study, we report the synthesis and application of mesoporous CoFe2O4@MIL-100(Fe) hybrid magnetic nanoparticles (MNPs) for the simultaneous removal of inorganic arsenic (iAs). The hybrid adsorbent had a core-shell and mesoporous structure with an average diameter of 260 nm. The nanoscale size and mesoporous character impart a fast adsorption rate and high adsorption capacity for iAs. In total, 0.1 mg L−1 As(V) and As(III) could be adsorbed within 2 min, and the maximum adsorption capacities were 114.8 mg g−1 for As(V) and 143.6 mg g−1 for As(III), higher than most previously reported adsorbents. The anti-interference capacity for iAs adsorption was improved by the electrostatic repulsion and size exclusion effects of the MIL-100(Fe) shell, which also decreased the zero-charge point of the hybrid absorbent for a broad pH adsorption range. The adsorption mechanisms of iAs on the MNPs are proposed. An Fe-O-As structure was formed on CoFe2O4@MIL-100(Fe) through hydroxyl substitution with the deprotonated iAs species. Monolayer adsorption of As(V) was observed, while hydrogen bonding led to the multi-layer adsorption of neutral As(III) for its high adsorption capacity. The high efficiency and the excellent pH- and interference-tolerance capacities of CoFe2O4@MIL-100(Fe) allowed effective iAs removal from natural water samples, as validated with batch magnetic separation mode and a portable filtration strategy. PMID:28102334

Effect of pH on-Sr adsorption on bentonite Lieskovec

International Nuclear Information System (INIS)

Galambos, M.

2009-01-01

Effect of changes in pH environment on the adsorption of Sr 2+ has been studied by radioisotope indications, using of radioisotope 85 Sr with energy γ-rays 0.514 MeV, in a static arrangement of the experiment, under aerobic conditions. The concentration range was 1 · 10 -5 - 5 · 10 -2 mol dm -3 . The samples of bentonite from Lieskovec deposit were tested which could be assigned into the Fe-montmorillonite group. (Author)

Experimental and theoretical study using DFT method for the competitive adsorption of two cationic dyes from wastewaters

Energy Technology Data Exchange (ETDEWEB)

Regti, Abdelmajid [Equipe de Chimie Analytique & Environnement, Faculté Poly-disciplinaire, Université Cadi Ayyad, BP 4162, 46000 Safi (Morocco); Instituto de Ciencia Molecular/ICMol, Universidad de Valencia, C/. Catedrático José Beltrán, 2, 46980 Paterna, Valencia (Spain); Ayouchia, Hicham Ben El [Equipe de Chimie Moléculaire, Matériaux et Modélisation, Faculté Poly-disciplinaire, Université Cadi Ayyad, BP 4162, 46000 Safi (Morocco); Instituto de Ciencia Molecular/ICMol, Universidad de Valencia, C/. Catedrático José Beltrán, 2, 46980 Paterna, Valencia (Spain); Laamari, My Rachid [Equipe de Chimie Analytique & Environnement, Faculté Poly-disciplinaire, Université Cadi Ayyad, BP 4162, 46000 Safi (Morocco); Instituto de Ciencia Molecular/ICMol, Universidad de Valencia, C/. Catedrático José Beltrán, 2, 46980 Paterna, Valencia (Spain); Stiriba, Salah Eddine; Anane, Hafid [Equipe de Chimie Moléculaire, Matériaux et Modélisation, Faculté Poly-disciplinaire, Université Cadi Ayyad, BP 4162, 46000 Safi (Morocco); Instituto de Ciencia Molecular/ICMol, Universidad de Valencia, C/. Catedrático José Beltrán, 2, 46980 Paterna, Valencia (Spain); and others

2016-12-30

Highlights: • The adsorption efficiency increases with increasing pH, thus more negatively charged surface was available. • Monolayer adsorption and homogeneous adsorbent surface. • The experimental and theoretical data are in good agreement showing that MB has ability to accept electrons allowing more adsorption than BY28 dye. - Abstract: The adsorption of cationic dyes, Basic Yellow (BY28) and Methylene Blue (MB) on a new activated carbon from medlar species were studied in both single and binary system. Some experimental parameters, namely, pH, amount of adsorbent and contact time are studied. Quantum chemical results indicate that the adsorption efficiency was directly related to the dye electrophilicity power. Some theorical parameters were calculated and proved that MB is more electrophilic than BY28, than greatest interaction with surface sites. Kinetic study showed that the adsorption follows the pseudo-second-order model and Freundlich was the best model to describe the phenomenon in the single and binary system. According to the local reactivity results using Parr functions, the sulphur and nitrogen atoms will be the main adsorption sites.

Hydrogen production from food wastes and gas post-treatment by CO2 adsorption

International Nuclear Information System (INIS)

Redondas, V.; Gómez, X.; García, S.; Pevida, C.; Rubiera, F.; Morán, A.; Pis, J.J.

2012-01-01

Highlights: ► The dark fermentation process of food wastes was studied over an extended period. ► Decreasing the HRT of the process negatively affected the specific gas production. ► Adsorption of CO 2 was successfully attained using a biomass type activated carbon. ► H 2 concentration in the range of 85–95% was obtained for the treated gas-stream. - Abstract: The production of H 2 by biological means, although still far from being a commercially viable proposition, offers great promise for the future. Purification of the biogas obtained may lead to the production of highly concentrated H 2 streams appropriate for industrial application. This research work evaluates the dark fermentation of food wastes and assesses the possibility of adsorbing CO 2 from the gas stream by means of a low cost biomass-based adsorbent. The reactor used was a completely stirred tank reactor run at different hydraulic retention times (HRTs) while the concentration of solids of the feeding stream was kept constant. The results obtained demonstrate that the H 2 yields from the fermentation of food wastes were affected by modifications in the hydraulic retention time (HRT) due to incomplete hydrolysis. The decrease in the duration of fermentation had a negative effect on the conversion of the substrate into soluble products. This resulted in a lower amount of soluble substrate being available for metabolisation by H 2 producing microflora leading to a reduction in specific H 2 production. Adsorption of CO 2 from a gas stream generated from the dark fermentation process was successfully carried out. The data obtained demonstrate that the column filled with biomass-derived activated carbon resulted in a high degree of hydrogen purification. Co-adsorption of H 2 S onto the activated carbon also took place, there being no evidence of H 2 S present in the bio-H 2 exiting the column. Nevertheless, the concentration of H 2 S was very low, and this co-adsorption did not affect the CO 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.

Background electrolytes and pH effects on selenate adsorption using iron-impregnated granular activated carbon and surface binding mechanisms.

Science.gov (United States)

Zhang, Ning; Gang, Daniel Dianchen; McDonald, Louis; Lin, Lian-Shin

2018-03-01

Iron-impregnated granular activated carbon (Fe-GAC) has been shown effective for selenite adsorptive removal from aqueous solutions, but similar effectiveness was not observed with selenate. This study examined the effects of background electrolytes and pH on selenate adsorption on to Fe-GAC, and surface bindings to elucidate the selenate adsorption mechanisms. The decrease magnitude of selenate adsorption capacity under three background electrolytes followed the order: LiCl > NaCl > KCl, as ionic strength increased from 0.01 to 0.1 M. Larger adsorption capacity differences among the three electrolytes were observed under the higher ionic strengths (0.05 and 0.1 M) than those under 0.01 M. Multiplet peak fittings of high resolution X-ray photoelectron spectra for O1s and Fe2p 3/2 indicated the presence of iron (III) on adsorbent surface. pH variations during the adsorbent preparation within 3-8 in NaCl solutions did not cause appreciable changes in the iron redox state and composition. Raman spectra showed the formation of both monodentate and bidentate inner sphere complexes under pHs adsorption under alkaline conditions. Mechanisms for monodentate and bidentate formations and a stable six-member ring structure were proposed. Two strategies were recommended for modifying Fe-GAC preparation procedure to enhance the selenate adsorption: (1) mixed-metal oxide coatings to increase the point of zero charge (pH zpc ); and (2) ferrous iron coating to initially reduce selenate followed by selenite adsorption. Copyright © 2017 Elsevier Ltd. All rights reserved.

Facile hydrothermal preparation of recyclable S-doped graphene sponge for Cu2+ adsorption

International Nuclear Information System (INIS)

Zhao, Lianqin; Yu, Baowei; Xue, Fumin; Xie, Jingru; Zhang, Xiaoliang; Wu, Ruihan; Wang, Ruijue; Hu, Zhiyan; Yang, Sheng-Tao; Luo, Jianbin

2015-01-01

Graphical abstract: S-doped graphene sponge was prepared via hydrothermal treatment, where S-doped graphene sponge had an adsorption capacity of 228 mg/g for Cu 2+ . - Highlights: • S-doped graphene sponge was prepared by hydrothermal treatment for heavy metal adsorption. • S-doped graphene sponge had a huge adsorption capacity for Cu 2+ , which was 40 times higher than that of active carbon. • S-doped graphene sponge could be easily regenerated by washing with acidic thiourea. - Abstract: Graphene sponge (GS) has been widely employed for water purification, but adsorption capacity loss frequently occurs during the formation of spongy structure. In this study, we reported the hydrothermal preparation of S-doped GS for the removal of Cu 2+ with a huge adsorption capacity of 228 mg/g, 40 times higher than that of active carbon. The adsorption isotherm could be well fitted into the Freundlich model with a K F value of 36.309 (L/mg) 1/n . The equilibrium adsorption could be fully achieved in the first 5 min. In the thermodynamics study, the negative ΔG indicated that the adsorption was spontaneous and physisorption in nature. The positive ΔH implied that the adsorption was endothermic. The changes of both pH and ionic strength had no apparent influence on the adsorption. S-doped GS could be easily regenerated by washing with acidic thiourea. Moreover, S-doped GS could be used for the adsorption of other heavy metal ions, too. The implication to the applications of S-doped GS in water treatment is discussed

Effects of nano-SiO2 on the adsorption of chiral metalaxyl to agricultural soils.

Science.gov (United States)

Huang, Junxing; Liang, Chuanzhou; Zhang, Xu

2017-06-01

The application of nanotechnology in agriculture, pesticide delivery and other related fields increases the occurrence of engineered nanoparticles (ENPs) in soil. Since ENPs have larger surface areas and normally a high adsorption capacity for organic pollutants, they are thought to influence the transport of pesticides in soils and thereafter influence the uptake and transformation of pesticides. The adsorption pattern of racemic-metalaxyl on agricultural soils including kinetics and isotherms changed in the presence of nano-SiO 2 . The adsorption of racemic-metalaxyl on agricultural soil was not enantioselective, in either the presence or the absence of SiO 2 . The adsorption of racemic-metalaxyl on SiO 2 decreased to some extent in soil-SiO 2 mixture, and the absolute decrease was dependent on soil properties. The decreased adsorption of metalaxyl on SiO 2 in soil-SiO 2 mixture arose from the competitive adsorption of soil-dissolved organic matter and the different dispersion and aggregation behaviors of SiO 2 in the presence of soil. Interactions between SiO 2 and soil particles also contributed to the decreased adsorption of metalaxyl on SiO 2 , and the interactions were analyzed by extended Derjaguin-Landau-Verwey-Overbeek theory. The results showed that the presence of nano-particles in soils could decrease the mobility of pesticides in soils and that this effect varied with different soil compositions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Kinetic studies of adsorption of thiocyanate onto ZnCl2 activated carbon from coir pith, an agricultural solid waste.

Science.gov (United States)

Namasivayam, C; Sangeetha, D

2005-09-01

The adsorption of thiocyanate onto ZnCl2 activated carbon developed from coir pith was investigated to assess the possible use of this adsorbent. The influence of various parameters such as agitation time, thiocyanate concentration, adsorbent dose, pH and temperature has been studied. Adsorption followed second-order rate kinetics. Two theoretical adsorption isotherms, namely, Langmuir and Freundlich were used to describe the experimental results. The Langmuir adsorption capacity (Q0) was found to be 16.2 mg g(-1) of the adsorbent. The per cent adsorption was maximum in the pH range 3.0-7.0. pH effect and desorption studies showed that ion exchange and chemisorption mechanism are involved in the adsorption process. Thermodynamic parameters such as DeltaG0, DeltaH0 and DeltaS0 for the adsorption were evaluated. The negative values of DeltaH0 confirm the exothermic nature of adsorption. Effects of foreign ions on the adsorption of thiocyanate have been investigated. Removal of thiocyanate from ground water was also tested.

Increased adsorption of histidine-tagged proteins onto tissue culture polystyrene.

Science.gov (United States)

Holmberg, Maria; Hansen, Thomas Steen; Lind, Johan Ulrik; Hjortø, Gertrud Malene

2012-04-01

In this study we compare histidine-tagged and native proteins with regards to adsorption properties. We observe significantly increased adsorption of proteins with an incorporated polyhistidine amino acid motif (HIS-tag) onto tissue culture polystyrene (TCPS) compared to similar proteins without a HIS-tag. The effect is not observed on polystyrene (PS). Adsorption experiments have been performed at physiological pH (7.4) and the effect was only observed for the investigated proteins that have pI values below or around 7.4. Competitive adsorption experiments with imidazole and ethylenediaminetetraacetic acid (EDTA), as well as adsorption performed at different pH and ionic strength indicates that the high adsorption is caused by electrostatic interaction between negatively charged carboxylate groups on the TCPS surface and positively charged histidine residues in the proteins. Pre-adsorption of bovine serum albumin (BSA) does not decrease the adsorption of HIS-tagged proteins onto TCPS. Our findings identify a potential problem in using HIS-tagged signalling molecule in assays with cells cultured on TCPS, since the concentration of the molecule in solution might be affected and this could critically influence the assay outcome. Copyright © 2011 Elsevier B.V. All rights reserved.

A computational study on the energetics and mechanisms for the dissociative adsorption of SiH{sub x}(x = 1–4) on W(1 1 1) surface

Energy Technology Data Exchange (ETDEWEB)

Lin, Y.H.; Raghunath, P.; Lin, M.C., E-mail: chemmcl@emory.edu

2016-01-30

Graphical abstract: - Highlights: • Behavior of the SiH{sub x} species on the W surface under cat-CVD conditions. • The adsorption and dissociation mechanisms of SiH{sub x}(x = 1–4) species on W(1 1 1) surface. • H-migration to its neighboring W atoms is more favorable compared to H{sub 2} elimination. - Abstract: The adsorption and dissociation mechanisms of SiH{sub x}(x = 1–4) species on W(1 1 1) surface have been investigated by using the periodic density functional theory with the projector-augmented wave approach. The adsorption of all the species on four surface sites: top (T), bridge (B), shallow (S), and deep (D) sites have been analyzed. For SiH{sub 4} on a top site, T-SiH{sub 4(a)}, it is more stable with an adsorption energy of 2.6 kcal/mol. For SiH{sub 3}, the 3-fold shallow site is most favorable with adsorption energy of 46.0 kcal/mol. For SiH{sub 2}, its adsorption on a bridge site is most stable with 73.0 kcal/mol binding energy, whereas for SiH and Si the most stable adsorption configurations are on 3-fold deep sites with very high adsorption energies, 111.8 and 134.7 kcal/mol, respectively. The potential energy surfaces for the dissociative adsorption of all SiH{sub x} species on the W(1 1 1) surface have been constructed using the CINEB method. The barriers for H-atom migration from SiH{sub x(a)} to its neighboring W atoms, preferentially on B-sites, were predicted to be 0.4, 1.0, 4.5 and, 8.0 kcal/mol, respectively, for x = 4, 3, 2, and 1, respectively. The adsorption energy of the H atom on a bridge site on the clean W(1 1 1) surface was predicted to be 65.9 kcal/mol, which was found to be slightly affected by the co-adsorption of SiH{sub x−1} within ± 1 kcal/mol.

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.)

Predicting mixed-gas adsorption equilibria on activated carbon for precombustion CO2 capture.

Science.gov (United States)

García, S; Pis, J J; Rubiera, F; Pevida, C

2013-05-21

We present experimentally measured adsorption isotherms of CO2, H2, and N2 on a phenol-formaldehyde resin-based activated carbon, which had been previously synthesized for the separation of CO2 in a precombustion capture process. The single component adsorption isotherms were measured in a magnetic suspension balance at three different temperatures (298, 318, and 338 K) and over a large range of pressures (from 0 to 3000-4000 kPa). These values cover the temperature and pressure conditions likely to be found in a precombustion capture scenario, where CO2 needs to be separated from a CO2/H2/N2 gas stream at high pressure (~1000-1500 kPa) and with a high CO2 concentration (~20-40 vol %). Data on the pure component isotherms were correlated using the Langmuir, Sips, and dual-site Langmuir (DSL) models, i.e., a two-, three-, and four-parameter model, respectively. By using the pure component isotherm fitting parameters, adsorption equilibrium was then predicted for multicomponent gas mixtures by the extended models. The DSL model was formulated considering the energetic site-matching concept, recently addressed in the literature. Experimental gas-mixture adsorption equilibrium data were calculated from breakthrough experiments conducted in a lab-scale fixed-bed reactor and compared with the predictions from the models. Breakthrough experiments were carried out at a temperature of 318 K and five different pressures (300, 500, 1000, 1500, and 2000 kPa) where two different CO2/H2/N2 gas mixtures were used as the feed gas in the adsorption step. The DSL model was found to be the one that most accurately predicted the CO2 adsorption equilibrium in the multicomponent mixture. The results presented in this work highlight the importance of performing experimental measurements of mixture adsorption equilibria, as they are of utmost importance to discriminate between models and to correctly select the one that most closely reflects the actual process.

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...

Adsorption and removal of arsenic (V) using crystalline manganese (II,III) oxide: Kinetics, equilibrium, effect of pH and ionic strength.

Science.gov (United States)

Babaeivelni, Kamel; Khodadoust, Amid P; Bogdan, Dorin

2014-01-01

Manganese (II,III) oxide (Mn3O4) crystalline powder was evaluated as a potential sorbent for removal of arsenic (V) from water. Adsorption isotherm experiments were carried out to determine the adsorption capacity using de-ionized (DI) water, a synthetic solution containing bicarbonate alkalinity, and two natual groundwater samples. Adsorption isotherm data followed the Langmuir and Freundlich equations, indicating favorable adsorption of arsenic (V) onto Mn3O4, while results from the Dubinin-Radushkevich equation were suggestive of chemisorption of arsenic (V). When normalized to the sorbent surface area, the maximum adsorption capacity of Mn3O4 for arsenic (V) was 101 μg m(-2), comparable to that of activated alumina. Arsenic (V) adsorption onto Mn3O4 followed pseudo-second-order kinetics. Adsorption of arsenic (V) was greatest at pH 2, while adsorption at pH 7-9 was within 91% of maximum adsorption, whereas adsorption decreased to 32% of maximum adsorption at pH 10. Surface charge analysis confirmed the adsorption of arsenic (V) onto the acidic surface of the Mn3O4 sorbent with a pHPZC of 7.32. The presence of coexisting ions bicarbonate and phosphate resulted in a decrease in arsenic (V) uptake. Comparable adsorption capacities were obtained for the synthetic solution and both groundwater samples. Overall, crystalline Mn3O4 was an effective and viable sorbent for removal of arsenic (V) from natural water, removing greater than 95% of arsenic (V) from a 1 mg L(-1) solution within 60 min of contact time.

Nanomaterials application for heavy metals recovery from polluted water: The combination of nano zero-valent iron and carbon nanotubes. Competitive adsorption non-linear modeling.

Science.gov (United States)

Vilardi, Giorgio; Mpouras, Thanasis; Dermatas, Dimitris; Verdone, Nicola; Polydera, Angeliki; Di Palma, Luca

2018-06-01

Carbon Nanotubes (CNTs) and nano Zero-Valent Iron (nZVI) particles, as well as two nanocomposites based on these novel nanomaterials, were employed as nano-adsorbents for the removal of hexavalent chromium, selenium and cobalt, from aqueous solutions. Nanomaterials characterization included the determination of their point of zero charge and particle size distribution. CNTs were further analyzed using scanning electron microscopy, thermogravimetric analysis and Raman spectroscopy to determine their morphology and structural properties. Batch experiments were carried out to investigate the removal efficiency and the possible competitive interactions among metal ions. Adsorption was found to be the main removal mechanism, except for Cr(VI) treatment by nZVI, where reduction was the predominant mechanism. The removal efficiency was estimated in decreasing order as CNTs-nZVI > nZVI > CNTs > CNTs-nZVI* independently upon the tested heavy metal. In the case of competitive adsorption, Cr(VI) exhibited the highest affinity for every adsorbent. The preferable Cr(VI) removal was also observed using binary systems of the tested metals by means of the CNTs-nZVI nanocomposite. Single species adsorption was better described by the non-linear Sips model, whilst competitive adsorption followed the modified Langmuir model. The CNTs-nZVI nanocomposite was tested for its reusability, and showed high adsorption efficiency (the q max values decreased less than 50% with respect to the first use) even after three cycles of use. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dubinin-Astakhov model for acetylene adsorption on metal-organic frameworks

International Nuclear Information System (INIS)

Cheng, Peifu; Hu, Yun Hang

2016-01-01

Graphical abstract: It was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model for C2H2 adsorption on metal-organic frameworks (MOFs), including MOF-5, ZIF-8, HKUST-1, and MIL-53. - Highlights: • Dubinin-Astakhov equation is demonstrated to be a general model for C_2H_2 adsorption on metal-organic frameworks (MOFs). • Surface areas obtained with Dubinin-Astakhov equation from C_2H_2 adsorption on MOFs are consistent with BET surface areas from N_2 adsorption. • C_2H_2 on MOF-5, ZIF-8, and MIL-53 is a physical adsorption, whereas its adsorption on HKUST-1 is due to a chemical bonding. - Abstract: Acetylene (C_2H_2) is explosive at a pressure above 29 psi, causing a safety issue for its storage and applications. C_2H_2 adsorption on metal-organic frameworks (MOFs) has been explored to solve the issue. However, a suitable isotherm equation for C_2H_2 adsorption on various MOFs has not been found. In this paper, it was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model to depict C_2H_2 adsorption on MOF-5, ZIF-8, HKUST-1, and MIL-53. In contrast, commonly used Langmuir and BET models exhibited their inapplicability for C_2H_2 adsorption on those MOFs.

Powdered activated carbon adsorption of two fishy odorants in water: Trans,trans-2,4-heptadienal and trans,trans-2,4-decadienal.

Science.gov (United States)

Li, Xin; Wang, Jun; Zhang, Xiaojian; Chen, Chao

2015-06-01

Powdered activated carbon (PAC) adsorption of two fishy odorants, trans,trans-2,4-heptadienal (HDE) and trans,trans-2,4-decadienal (DDE), was investigated. Both the pseudo first-order and the pseudo second-order kinetic models well described the kinetics curves, and DDE was more readily removed by PAC. In isotherm tests, both Freundlich and Modified Freundlich isotherms fitted the experimental data well. PAC exhibited a higher adsorption capacity for DDE than for HDE, which could be ascribed to the difference in their hydrophobicity. The calculated thermodynamic parameters (ΔG0, ΔH0, and ΔS0) indicated an exothermic and spontaneous adsorption process. PAC dosage, pH, and natural organic matter (NOM) presence were found to influence the adsorption process. With increasing PAC dosage, the pseudo first-order and pseudo second-order rate constants both increased. The value of pH had little influence on HDE or DDE molecules but altered the surface charge of PAC, and the maximum adsorption capacity occurred at pH9. The presence of NOM, especially the fraction with molecular weight less than 1k Dalton, hindered the adsorption. The study showed that preloaded NOM impaired the adsorption capacity of HDE or DDE more severely than simultaneously fed NOM did. Copyright © 2015. Published by Elsevier B.V.

Effect of active zinc oxide dispersion on reduced graphite oxide for hydrogen sulfide adsorption at mid-temperature

Science.gov (United States)

Song, Hoon Sub; Park, Moon Gyu; Croiset, Eric; Chen, Zhongwei; Nam, Sung Chan; Ryu, Ho-Jung; Yi, Kwang Bok

2013-09-01

Composites of Zinc oxide (ZnO) with reduced graphite oxide (rGO) were synthesized and used as adsorbents for hydrogen sulfide (H2S) at 300 °C. Various characterization methods (TGA, XRD, FT-IR, TEM and XPS) were performed in order to link their H2S adsorption performance to the properties of the adsorbent's surface. Microwave-assisted reduction process of graphite oxide (GO) provided mild reduction environment, allowing oxygen-containing functional groups to remain on the rGO surface. It was confirmed that for the ZnO/rGO synthesize using the microwave-assisted reduction method, the ZnO particle size and the degree of ZnO dispersion remained stable over time at 300 °C, which was not the case for only the ZnO particles themselves. This stable highly dispersed feature allows for sustained high surface area over time. This was confirmed through breakthrough experiments for H2S adsorption where it was found that the ZnO/rGO composite showed almost four times higher ZnO utilization efficiency than ZnO itself. The effect of the H2 and CO2 on H2S adsorption was also investigated. The presence of hydrogen in the H2S stream had a positive effect on the removal of H2S since it allows a reducing environment for Znsbnd O and Znsbnd S bonds, leading to more active sites (Zn2+) to sulfur molecules. On the other hand, the presence of carbon dioxide (CO2) showed the opposite trend, likely due to the oxidation environment and also due to possible competitive adsorption between H2S and CO2.

Effect of active zinc oxide dispersion on reduced graphite oxide for hydrogen sulfide adsorption at mid-temperature

International Nuclear Information System (INIS)

Song, Hoon Sub; Park, Moon Gyu; Croiset, Eric; Chen, Zhongwei; Nam, Sung Chan; Ryu, Ho-Jung; Yi, Kwang Bok

2013-01-01

Composites of Zinc oxide (ZnO) with reduced graphite oxide (rGO) were synthesized and used as adsorbents for hydrogen sulfide (H 2 S) at 300 °C. Various characterization methods (TGA, XRD, FT-IR, TEM and XPS) were performed in order to link their H 2 S adsorption performance to the properties of the adsorbent's surface. Microwave-assisted reduction process of graphite oxide (GO) provided mild reduction environment, allowing oxygen-containing functional groups to remain on the rGO surface. It was confirmed that for the ZnO/rGO synthesize using the microwave-assisted reduction method, the ZnO particle size and the degree of ZnO dispersion remained stable over time at 300 °C, which was not the case for only the ZnO particles themselves. This stable highly dispersed feature allows for sustained high surface area over time. This was confirmed through breakthrough experiments for H 2 S adsorption where it was found that the ZnO/rGO composite showed almost four times higher ZnO utilization efficiency than ZnO itself. The effect of the H 2 and CO 2 on H 2 S adsorption was also investigated. The presence of hydrogen in the H 2 S stream had a positive effect on the removal of H 2 S since it allows a reducing environment for Zn-O and Zn-S bonds, leading to more active sites (Zn 2+ ) to sulfur molecules. On the other hand, the presence of carbon dioxide (CO 2 ) showed the opposite trend, likely due to the oxidation environment and also due to possible competitive adsorption between H 2 S and CO 2 .

Batch and flow-through continuous stirred reactor experiments of Sr2+-adsorption onto smectite: influence of pH, concentration and ionic strength

International Nuclear Information System (INIS)

Guimaraes, V.; Azenha, M.; Silva, A.F.; Bobos, I.

2012-01-01

Document available in extended abstract form only. Strontium-90 (t 1/2 = 29.1 years) resulting from the nuclear fission process is one of the main constituents connected with nuclear waste fuel. Concerning the physical properties and sorption behaviour one of the suitable buffer materials used as a backfill in the geological disposal systems for high-level radioactive wastes is smectite. The 2 μm clay fractions of di-octahedral smectite were used for adsorption experiments in batch and flow-through experiments. Flow-through experiments were carried out at different pH (4 and 8) and concentrations (8.00x10 -2 mmolSr 2+ /L, 2.0x10 -1 mmolSr 2+ /L, 3.3x10 -1 mmolSr 2+ /L and 4.1 x10 -1 mmol Sr 2+ /L). Batch experiments were carried out at different ionic strength ([KNO 3 ]=10 -2 M and [KNO 3 ]=10 -3 M), pH (4 and 8), whereas the concentration ranged between 0.19 mmolSr 2+ /L and 9.60 mmolSr 2+ /L. The adsorption strontium rate in flow-through experiments was found higher at pH 4 than at pH 8, where less of 20% amount of strontium was adsorbed on clay surface after 34 hours. This is explained by the surface charge of smectite layers with a permanent negative charge on the basal planes due essentially to isomorphic substitution. Also additional polar sites are conditionally charged by direct protonation of outer edge surfaces. Therefore, more negative sites become available for the strontium ions sorption, as the pH increasing. After adsorption, the clays were submitted to a desorption process. The rate of desorption at pH 4 is initially too fast due to the elevated amount of strontium released by smectite. After 255 min, the strontium amount desorbed is very low and the rate of desorption approached to zero. By contrast at pH 8 the rate of desorption is practically constant, and after 255 min there is a significant amount of strontium released by clay. Due to these different behaviors in different pH conditions, after 10 hours of desorption, the amount of strontium

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.

Speciation of Co(II) and Ni(II) in anaerobic bioreactors measured by competitive ligand exchange - adsorptive stripping voltammetry

NARCIS (Netherlands)

Jansen, S.; Steffen, F.; Threels, W.F.; Leeuwen, van H.P.

2005-01-01

Competitive ligand exchange-adsorptive stripping voltammetry is applied to speciation analysis of dissolved Ni(II) and Co(II) in an anaerobic bioreactor and similar batch media. Co and Ni speciation in these media can be measured down to concentration levels of ca. 1 nM. Sulfide interference is

Adsorption of Pb{sup 2+} and Cd{sup 2+} onto a novel activated carbon-chitosan complex

Energy Technology Data Exchange (ETDEWEB)

Ge, H.; Fan, X. [College of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640 (China)

2011-10-15

A novel activated carbon-chitosan complex adsorbent (ACCA) was prepared via the crosslinking of glutaraldehyde and activated carbon-(NH{sub 2}-protected) chitosan complex under microwave irradiation. The surface morphology of this adsorbent was characterized. The adsorption of ACCA for Pb{sup 2+} and Cd{sup 2+} was investigated. The results demonstrate that ACCA has higher adsorption capacity than chitosan. The adsorption follows pseudo first-order kinetics. The isotherm adsorption equilibria are better described by Freundlich and Dubinin-Radushkevich isotherms than by the Langmuir isotherm. The adsorbent can be recycled. These results have important implications for the design of low-cost and effective adsorbents in the removal of heavy metal ions from wastewaters. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

In situ SERS and X-ray photoelectron spectroscopy studies on the pH-dependant adsorption of anthraquinone-2-carboxylic acid on silver electrode

Science.gov (United States)

Li, Dan; Jia, Shaojie; Fodjo, Essy Kouadio; Xu, Hu; Wang, Yuhong; Deng, Wei

2016-03-01

In this study, in situ surface-enhanced Raman scattering (SERS) spectroelectrochemistry and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) are used to investigate the redox reaction and adsorption behavior of anthraquinone-2-carboxylic acid (AQ-2-COOH) on an Ag electrode at different pH values. The obtained results indicate that AQ-2-COOH is adsorbed tilted on the Ag electrode through O-atom of ring carbonyl in a potential range from -0.3 to -0.5 V vs. SCE, but the orientation turns to more tilted orientation with both O-atom of the ring carbonyl and carboxylate group in positive potential region for pH 6.0 and 7.4. However, at pH 10.0, the orientation adopts tilted conformation constantly on the Ag electrode with both O-atom of the anthraquinone ring and carboxylate group in the potential range from -0.3 to -0.5 V vs. SCE or at positive potentials. Moreover, the adsorption behavior of AQ-2-COOH has been further confirmed by AR-XPS on the Ag surface. Proposed reasons for the observed changes in orientation are presented.

Dubinin-Astakhov model for acetylene adsorption on metal-organic frameworks

Energy Technology Data Exchange (ETDEWEB)

Cheng, Peifu; Hu, Yun Hang, E-mail: yunhangh@mtu.edu

2016-07-30

Graphical abstract: It was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model for C2H2 adsorption on metal-organic frameworks (MOFs), including MOF-5, ZIF-8, HKUST-1, and MIL-53. - Highlights: • Dubinin-Astakhov equation is demonstrated to be a general model for C{sub 2}H{sub 2} adsorption on metal-organic frameworks (MOFs). • Surface areas obtained with Dubinin-Astakhov equation from C{sub 2}H{sub 2} adsorption on MOFs are consistent with BET surface areas from N{sub 2} adsorption. • C{sub 2}H{sub 2} on MOF-5, ZIF-8, and MIL-53 is a physical adsorption, whereas its adsorption on HKUST-1 is due to a chemical bonding. - Abstract: Acetylene (C{sub 2}H{sub 2}) is explosive at a pressure above 29 psi, causing a safety issue for its storage and applications. C{sub 2}H{sub 2} adsorption on metal-organic frameworks (MOFs) has been explored to solve the issue. However, a suitable isotherm equation for C{sub 2}H{sub 2} adsorption on various MOFs has not been found. In this paper, it was demonstrated that Dubinin-Astakhov equation can be exploited as a general isotherm model to depict C{sub 2}H{sub 2} adsorption on MOF-5, ZIF-8, HKUST-1, and MIL-53. In contrast, commonly used Langmuir and BET models exhibited their inapplicability for C{sub 2}H{sub 2} adsorption on those MOFs.

Comparative adsorption of Pb2+ and Cd2+ by cow manure and its vermicompost

International Nuclear Information System (INIS)

Zhu, Weiqin; Du, Wenhui; Shen, Xuyang; Zhang, Hangjun; Ding, Ying

2017-01-01

Organic waste has great potential for use as an amendment to immobilize heavy metals in the environment. Therefore, this study investigates various properties of cow manure (CM) and its derived vermicompost (CV), including the pH, cationic exchangeable capacity (CEC), elemental composition and surface structure, to determine the potential of these waste products to remove Pb 2+ and Cd 2+ from solution. The results demonstrate that CV has a much higher pH, CEC and more irregular pores than CM and is enriched with minerals and ash content but has a lower C, H, O and N content. Adsorption isotherms studies shows that the adsorption of Pb 2+ and Cd 2+ onto either CM or CV follows a Langmuir model and presents maximum Pb 2+ and Cd 2+ adsorption capacities of 102.77 mg g −1 and 38.11 mg g −1 onto CM and 170.65 and 43.01 mg g −1 onto CV, respectively. Kinetic studies show that the adsorption of Pb 2+ onto CM and CV fits an Elovich model, whereas the adsorption of Cd 2+ onto CM and CV fits a pseudo-second-order model. Desorption studies indicate that CV is more effective than CM in removing Pb 2+ and Cd 2+ . FTIR analysis demonstrates that the adsorption of Pb 2+ and Cd 2+ onto CM mainly depends on existed aliphatic alcohol, aromatic acid as well as new produced carbonates, whereas that onto CV may be contributed by the existed aliphatic alcohol, aromatic acids as well as some carbonates and phosphates. Thus, vermicomposting disposal of cow manure with destination mineral addition may broaden the way of its recycle and environmental usage. - Graphical abstract: The existed aliphatic alcohol, aromatic acids and its only carbonates and phosphates may underlie much higher efficiency of vermicompost (CV) on Pb 2+ and Cd 2+ removal than cow manure (CM). - Highlights: • Less irregular pores in cow manure (CM) than its vermicompost (CV). • More Pb 2+ or Cd 2+ could be removed from solution by vermicompost (CV) than by cow manure (CM). • The existed aliphatic

Inhibition performance of a gemini surfactant and its co-adsorption effect with halides on mild steel in 0.25 M H{sub 2}SO{sub 4} solution

Energy Technology Data Exchange (ETDEWEB)

Wang Xiumei [State Key Laboratory for Corrosion and Protection, Institute of Metal Research Chinese Academy of Sciences, Shenyang 110016 (China); School of Materials Science and Engineering, Shenyang Jianzhu University, Shenyang 110168 (China); Yang Huaiyu, E-mail: hyyang@imr.ac.cn [State Key Laboratory for Corrosion and Protection, Institute of Metal Research Chinese Academy of Sciences, Shenyang 110016 (China); Wang Fuhui [State Key Laboratory for Corrosion and Protection, Institute of Metal Research Chinese Academy of Sciences, Shenyang 110016 (China)

2012-02-15

Highlights: Black-Right-Pointing-Pointer 1,4-Bis (1-chlorobenzyl-benzimidazolyl)-butane has good inhibition effect for mild steel in H{sub 2}SO{sub 4}. Black-Right-Pointing-Pointer The compound acts as a mixed-type inhibitor and obeys Langmuir adsorption isotherm. Black-Right-Pointing-Pointer Halide ions can improve the inhibition property of compound via the co-adsorption effect. Black-Right-Pointing-Pointer The adsorbed halides play an important intermediate bridge role in co-adsorption process. Black-Right-Pointing-Pointer The obtained results can supply the bases for the future using of cationic inhibitor. - Abstract: The inhibition performance of a cationic gemini-surfactant (CBB) and its co-adsorption behavior with halides on mild steel in 0.25 M H{sub 2}SO{sub 4} solution was studied by weight loss and electrochemical techniques. Results showed that the compound could effectively inhibit the mild steel corrosion and acted as a mixed-type inhibitor by suppressing simultaneously anodic and cathodic reactions. Addition of the halides improve the inhibition efficiency of CBB and the synergistic effect increase in the order of I{sup -} > Br{sup -} > Cl{sup -}, revealing that halides radii and their electronegativity may play significant roles in co-adsorption with the cationic inhibitor.

Atomic Layer Deposition of Al2O3 on H-Passivated GeSi: Initial Surface Reaction Pathways with H/GeSi(100)-2 × 1

International Nuclear Information System (INIS)

Yu, Shi; Qing-Qing, Sun; Lin, Dong; Han, Liu; Shi-Jin, Ding; Wei, Zhang

2009-01-01

The reaction mechanisms of Al(CH 3 ) 3 (TMA) adsorption on H-passivated GeSi(100)-2 × 1 surface are investigated with density functional theory. The Si–Ge and Ge–Ge one-dimer cluster models are employed to represent the GeSi(100)-2 × 1 surface with different Ge compositions. For a Si-Ge dimer of a H-passivated SiGe surface, TMA adsorption on both Si–H * and Ge–H * sites is considered. The activation barrier of TMA with the Si–H * site (1.2eV) is higher than that of TMA with the Ge-H * site (0.91 eV), which indicates that the reaction proceeds more slowly on the Si-H * site than on the Ge-H * site. In addition, adsorption of TMA is more energetically favorable on the Ge–Ge dimer than on the Si–Ge dimer of H-passivated SiGe. (atomic and molecular physics)

Adsorption of Pb(II) ions from aqueous solutions by date bead carbon activated with ZnCl{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Danish, Mohammed; Hashim, Rokiah; Rafatullah, Mohd; Sulaiman, Othman [Division of Bioresource, Paper and Coatings Technology, School of Industrial Technology, Universiti Sains Malaysia, Penang (Malaysia); Ahmad, Anees [Division of Environmental Technology, School of Industrial Technology, Universiti Sains Malaysia, Penang (Malaysia); Govind [Surface Physics and Nanostructures Group, National Physical Laboratory, New Delhi (India)

2011-04-15

This study reports on the adsorption characteristics of Pb(II) ions from aqueous solutions using ZnCl{sub 2}-activated date (Phoenix dactylifera) bead (ADB) carbon with respect to change in adsorbent dosage, initial pH, contact time, initial concentration, and temperature of the solution. Kinetic studies of the data showed that the adsorption follows the pseudo-second-order kinetic model. Thermodynamic parameters, enthalpy change ({Delta}H = 55.11 kJ/mol), entropy change ({Delta}S = - 0.193 kJ/mol/K), and Gibbs free energy change ({Delta}G ) were also calculated for the uptake of Pb(II) ions. These parameters show that adsorption on the surface of ADB was feasible, spontaneous in nature, and endothermic between temperatures of 298.2 and 318.2 K. The equilibrium data better fitted the Langmuir and Freundlich isotherm models than the D-R adsorption isotherm model for studying the adsorption behavior of Pb(II) onto the ADB carbon. It could be observed that the maximum adsorption capacity of ADB was 76.92 mg/g at 318.2 K and pH 6.5. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Competitive adsorption behaviors of carbon dioxide and n-dodecane mixtures in 13X molecular sieve

Science.gov (United States)

Zhu, Chaofan; Dong, Mingzhe; Gong, Houjian

2018-01-01

The CO2 cyclic injection has been proven to be effective to enhance tight oil recovery under constant reservoir temperature and down hole pressure conditions. However, the enhance tight oil recovery mechanism was unclear, especially the adsorption of the CO2 and alkane in the surface. Therefore, it is great important to study the adsorption mechanism of CO2 and alkane mixtures in tight oil. In this study, a new experimental method and apparatus have been designed to test the change of the mole fraction of CO2 and n-C12 before and after the adsorption equilibrium. Then, the adsorption amount of CO2 and n-C12 was obtained by a mathematical method. Moreover, the adsorption character of CO2 and n-C12 mixtures in 13X molecular sieve and the effect of pressure on the adsorption and amount were studied. The results show that the adsorption of CO2 and the desorption of n-C12 follow the Langmuir adsorption. This study provides a straightforward method to experimentally determine the adsorption properties of the tight oil, which can be used to evaluate enhanced tight oil recovery by CO2 injection.

Adsorption study of CO and H2O on carbon materials, Ni and stainless steel

International Nuclear Information System (INIS)

Kato, S.

1991-01-01

Adsorption of CO and water vapor on single crystalline graphite, diamond and an amorphous carbon film at room temperature was investigated by low energy ion scattering (ISS) and compared with stainless steel and nickel surfaces. Even for a CO exposure up to 10 4 L, the C intensity stayed constant and no O peak appeared in the ISS spectra from graphite while Ni and O intensities from Ni surface changed strikingly. Intensities of FE and O signals from stainless steel seriously decrease and increase with increasing exposure of H 2 O, respectively, but did not reach saturation even at an exposure of 10 3 L. On the other hand, C and O intensities from carbon surfaces changed moderately to reach saturation at an exposure of some 100 L. These results indicate that CO and H 2 O do not adsorb significantly on carbon surfaces in contrast to nickel and stainless steel surfaces. As a by-product survival probabilities of scattered He + ions from graphite for the primary energy of 0.6-2 keV were measured to be in a range of 10 -4 to 10 -2 and the survival parameter was deduced to be 5.0 x 10 7 cm s -1 . (author)

Temperature and pH influence adsorption of cellobiohydrolase onto lignin by changing the protein properties.

Science.gov (United States)

Lu, Xianqin; Wang, Can; Li, Xuezhi; Zhao, Jian

2017-12-01

Non-productive adsorption of cellulase onto lignin restricted the movement of cellulase and also hindered the cellulase recycling in bioconversion of lignocellulose. In this study, effect of temperature and pH on adsorption and desorption of cellobiohydrolase (CBH) on lignin and its possible mechanism were discussed. It found that pH value and temperature influenced the adsorption and desorption behaviors of CBH on lignin. Different thermodynamic models suggested that the action between lignin and CBH was physical action. More CBH was adsorbed onto lignin, but lower initial adsorption velocity was detected at 50°C comparing with 4°C. Elevating pH value could improve desorption of cellulase from lignin. The changes of hydrophobicity and electric potential on protein surface may partially explain the impact of environmental conditions on the adsorption and desorption behaviors of CBH on lignin, and comparing to electrical interaction, the hydrophobicity may be the dominating factor influencing the behaviors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Remediation of Groundwater Polluted by Aromatic Compounds by Means of Adsorption

Directory of Open Access Journals (Sweden)

Silvana Canzano

2014-07-01

Full Text Available In this work, an experimental and modeling analysis of the adsorption of four aromatic compounds (i.e., toluene, naphthalene, o-xylene and ethylbenzene onto a commercial activated carbon is carried out. The aim is to assess the suitability of the adsorption process for the treatment of polluted groundwater, also when a multiple contamination is detected. Batch adsorption tests from simulated polluted groundwater are performed in single-compound systems and in two binary systems (i.e., toluene + naphthalene and o-xylene + ethylbenzene, at constant temperature (20 °C and pH (7. Experimental results in single-compound systems reveal that all of the analytes are significantly adsorbed on the tested activated carbon. In particular, toluene and naphthalene adsorption capacities are the highest and of similar value, while for o-xylene and ethylbenzene, the performances are lower. The adsorption of these compounds seems to be influenced by a combined effect of several parameters, such as hydrophobicity, molecule size, structure of the molecule, etc. Experimental results in binary systems show a different behavior of the two systems, which confirms their complexity and explains the interest in these complex adsorption systems. In particular, toluene and naphthalene are mutually competitive, while in the case of o-xylene + ethylbenzene, only the former undergoes competitive effects. The analysis of the entire experimental data set is integrated with a dedicated modeling analysis using the extended Langmuir model. For both single-compound and binary systems, this model provides acceptable results, in particular for low equilibrium concentrations, like those more commonly found in groundwater, and for the compounds involved in adsorptive competitive effects.

Bimetallic AgCu/Cu2O hybrid for the synergetic adsorption of iodide from solution.

Science.gov (United States)

Mao, Ping; Liu, Ying; Liu, Xiaodong; Wang, Yuechan; Liang, Jie; Zhou, Qihang; Dai, Yuexuan; Jiao, Yan; Chen, Shouwen; Yang, Yi

2017-08-01

To further improve the capacity of Cu 2 O to absorb I - anions from solution, and to understand the difference between the adsorption mechanisms of Ag/Cu 2 O and Cu/Cu 2 O adsorbents, bimetallic AgCu was doped into Cu 2 O through a facile solvothermal route. Samples were characterized and employed to adsorb I - anions under different experimental conditions. The results show that the Cu content can be tuned by adding different volumes of Ag sols. After doping bimetallic AgCu, the adsorption capacity of the samples can be increased from 0.02 mmol g -1 to 0.52 mmol g -1 . Moreover, the optimal adsorption is reached within only 240 min. Meanwhile, the difference between the adsorption mechanisms of Ag/Cu 2 O and Cu/Cu 2 O adsorbents was verified, and the cooperative adsorption mechanism of the AgCu/Cu 2 O hybrid was proposed and verified. In addition, the AgCu/Cu 2 O hybrid showed excellent selectivity, e.g., its adsorption efficiencies are 85.1%, 81.9%, 85.9% and 85.7% in the presence of the Cl - , CO 3 2- , SO 4 2- and NO 3 - competitive anions, respectively. Furthermore, the AgCu/Cu 2 O hybrid can worked well in other harsh environments (e.g., acidic, alkaline and seawater environments). Therefore, this study is expected to promote the development of Cu 2 O into a highly efficient adsorbent for the removal of iodide from solution. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of active zinc oxide dispersion on reduced graphite oxide for hydrogen sulfide adsorption at mid-temperature

Energy Technology Data Exchange (ETDEWEB)

Song, Hoon Sub [Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L3G1 (Canada); Greenhouse Gas Department, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon, 305-343 (Korea, Republic of); Park, Moon Gyu [Department of Chemical Engineering Education, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 305-764 (Korea, Republic of); Croiset, Eric, E-mail: ecroiset@uwaterloo.ca [Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L3G1 (Canada); Chen, Zhongwei [Department of Chemical Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L3G1 (Canada); Nam, Sung Chan; Ryu, Ho-Jung [Greenhouse Gas Department, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon, 305-343 (Korea, Republic of); Yi, Kwang Bok, E-mail: cosy32@cnu.ac.kr [Department of Chemical Engineering Education, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon, 305-764 (Korea, Republic of)

2013-09-01

Composites of Zinc oxide (ZnO) with reduced graphite oxide (rGO) were synthesized and used as adsorbents for hydrogen sulfide (H{sub 2}S) at 300 °C. Various characterization methods (TGA, XRD, FT-IR, TEM and XPS) were performed in order to link their H{sub 2}S adsorption performance to the properties of the adsorbent's surface. Microwave-assisted reduction process of graphite oxide (GO) provided mild reduction environment, allowing oxygen-containing functional groups to remain on the rGO surface. It was confirmed that for the ZnO/rGO synthesize using the microwave-assisted reduction method, the ZnO particle size and the degree of ZnO dispersion remained stable over time at 300 °C, which was not the case for only the ZnO particles themselves. This stable highly dispersed feature allows for sustained high surface area over time. This was confirmed through breakthrough experiments for H{sub 2}S adsorption where it was found that the ZnO/rGO composite showed almost four times higher ZnO utilization efficiency than ZnO itself. The effect of the H{sub 2} and CO{sub 2} on H{sub 2}S adsorption was also investigated. The presence of hydrogen in the H{sub 2}S stream had a positive effect on the removal of H{sub 2}S since it allows a reducing environment for Zn-O and Zn-S bonds, leading to more active sites (Zn{sup 2+}) to sulfur molecules. On the other hand, the presence of carbon dioxide (CO{sub 2}) showed the opposite trend, likely due to the oxidation environment and also due to possible competitive adsorption between H{sub 2}S and CO{sub 2}.

Calcium phosphate–gold nanoparticles nanocomposite for protein adsorption and mediator-free H2O2 biosensor construction

International Nuclear Information System (INIS)

Xu Qin; Lu Guiju; Bian XiaoJun; Jin Gendi; Wang Wei; Hu Xiaoya; Wang Yang; Yang Zhanjun

2012-01-01

This work reports a new method for the preparation and application of a kind of biocompatible calcium phosphate–gold nanoparticles (Ca 3 (PO 4 ) 2 –AuNPs) nanocomposite. UV–vis spectroscopy and transmittance electron microscopy (TEM) have been used to monitor the formation process of the nanocomposite and to examine the interaction between calcium phosphate and gold nanoparticles (AuNPs). The nanocomposite has multiple sites and improved conductivity which make it suitable for the binding of proteins to construct electrochemical sensors. Myoglobin (Mb) adsorbed on the nanocomposite retained its native structure which was proved by Fourier transform infrared spectroscopy (FTIR). Direct electron transfer between the adsorbed Mb and the electrode was observed. Further results demonstrated that the adsorbed Mb has good electrocatalytic activity towards the reduction of H 2 O 2 in the absence of any mediator. Highlights: ► Using gelatin modified gold nanoparticles to prepare needle-like calcium phosphate. ► Calcium phosphate provides multiple sites for protein adsorption. ► Gold nanoparticles act as electron tunneling. ► Myoglobin adsorbed on the material showed direct electrochemistry and good catalysis.

Effect of the pH in the adsorption and in the immersion enthalpy of monohydroxylated phenols from aqueous solutions on activated carbons.

Science.gov (United States)

Blanco-Martínez, D A; Giraldo, L; Moreno-Piraján, J C

2009-09-30

An activated carbon Carbochem--PS230 was modified by chemical and thermal treatment in flow of H(2) in order to evaluate the influence of the activated carbon chemical surface in the adsorption of the monohydroxylated phenols. The solid-solution interaction was determined by analyzing the adsorption isotherms at 298 K at pH 7, 9 and 11 during 48 h. The adsorption capacity of activated carbons increases when the pH solution decreases. The amount adsorbed increases in the reduced carbon at the maximum adsorption pH and decreases in the oxidized carbon. In the sample of granulated activated carbon, CAG, the monohydroxylated phenols adsorption capacity diminishes in the following order catechol >hydroquinone >resorcinol, at the three pH values. The experimental data are evaluated with Freundlich's and Langmuir's models. The immersion enthalpies are determined and increase with the retained amount, ranging between 21.5 and 45.7 J g(-1). In addition, the immersion enthalpies show more interaction with the reduced activated carbon that has lower total acidity contents.

Adsorption of Pb2+ on Thiol-functionalized Mesoporous Silica, SH-MCM-48

Science.gov (United States)

Taba, P.; Mustafa, R. D. P.; Ramang, L. M.; Kasim, A. H.

2018-03-01

Modification of mesoporous silica, MCM-48, by using 3- mercaptopropyltrimethoxysilane has been successfully conducted. MCM-48 and SH-MCM-48 were characterized using XRD and FTIR. SH-MCM-48 was used as an adsorbent of Pb2+ ions from solution. A number of Pb2+ ions adsorbed were studied as the function of time, pH, and concentration. The concentration of the ions after adsorption was determined by an Atomic Absorption Spectrophotometer. The removal of the adsorbed ions from the SH-MCM-48 was also studied using several desorbing agents. The result showed that the optimum time was 20 minutes and optimum pH was 4. The adsorption of Pb(II) ion followed the pseudo-second-order with the rate constant of 0,2632 g•mg-1•min-1. Adsorption of Pb(II) ion fitted the Langmuir isotherm with the adsorption capacity of 0,1088 mmol/g. The best desorbing agent to remove the adsorbed ion from SH-MCM-48 was 0.3 M HCl solution with the desorption percentage of 58.6%.

Removal of elemental mercury by bamboo charcoal impregnated with H{sub 2}O{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Zengqiang Tan; Jianrong Qiu; Hancai Zeng; Hao Liu; Jun Xiang [Huazhong University of Science and Technology, Wuhan (China). Key Laboratory of Coal Combustion

2011-04-15

Mercury emission from coal combustion is an increasing environmental concern due to its high volatility and toxicity, and activated carbon (AC) adsorption has been proven an effective mercury-control method, with high-cost limit. The renewable bioresource of bamboo constitutes an important precursor for activated carbon, and the bamboo charcoal (BC) may act as low-cost sorbent used in the mercury-control. The adsorptive potential of BC and modified BC using H{sub 2}O{sub 2} for elemental mercury was investigated for the first time through a parametric study conducted with a bench-scale bed. The effects of pore structure and surface chemistry were investigated based on BET, XPS. Which suggest that BC materials have excellent adsorption potential for elemental mercury, especially after modified by H{sub 2}O{sub 2}. The modification using H{sub 2}O{sub 2} altered the physical and chemical properties of BC materials, making the sorbents more effective in mercury adsorption even at a relative higher temperature, and the enhancing-effect was more obvious with increasing H{sub 2}O{sub 2}. 32 refs., 6 figs., 5 tabs.

Investigation of protein adsorption performance of Ni2+-attached diatomite particles embedded in composite monolithic cryogels.

Science.gov (United States)

Ünlü, Nuri; Ceylan, Şeyda; Erzengin, Mahmut; Odabaşı, Mehmet

2011-08-01

As a low-cost natural adsorbent, diatomite (DA) (2 μm) has several advantages including high surface area, chemical reactivity, hydrophilicity and lack of toxicity. In this study, the protein adsorption performance of supermacroporous composite cryogels embedded with Ni(2+)-attached DA particles (Ni(2+)-ADAPs) was investigated. Supermacroporous poly(2-hydroxyethyl methacrylate) (PHEMA)-based monolithic composite cryogel column embedded with Ni(2+)-ADAPs was prepared by radical cryo-copolymerization of 2-hydroxyethyl methacrylate (HEMA) with N,N'-methylene-bis-acrylamide (MBAAm) as cross-linker directly in a plastic syringe for affinity purification of human serum albumin (HSA) both from aqueous solutions and human serum. The chemical composition and surface area of DA was determined by XRF and BET method, respectively. The characterization of composite cryogel was investigated by SEM. The effect of pH, and embedded Ni(2+)-ADAPs amount, initial HSA concentration, temperature and flow rate on adsorption were studied. The maximum amount of HSA adsorption from aqueous solution at pH 8.0 phosphate buffer was very high (485.15 mg/g DA). It was observed that HSA could be repeatedly adsorbed and desorbed to the embedded Ni(2+)-ADAPs in poly(2-hydroxyethyl methacrylate) composite cryogel without significant loss of adsorption capacity. The efficiency of albumin adsorption from human serum before and after albumin adsorption was also investigated with SDS-PAGE analyses. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of granular activated carbons from yellow mombin fruit stones for CO2 adsorption.

Science.gov (United States)

Fiuza, Raildo Alves; Medeiros de Jesus Neto, Raimundo; Correia, Laise Bacelar; Carvalho Andrade, Heloysa Martins

2015-09-15

Stones of yellow mombin, a native fruit of the tropical America and West Indies, were used as starting materials to produce activated carbons, subsequently used as adsorbent for CO2 capture. The carbonaceous materials were either chemically activated with HNO3, H3PO4 and KOH or physically activated with CO2. The carbon samples were characterized by SEM, EDX, TG/DTA, Raman spectroscopy, physical adsorption for textural analysis and by acid-base titrations. The CO2 adsorption capacity and adsorption cycles were investigated by TG. The results indicate that the capacity of CO2 adsorption may be maximized on highly basic surfaces of micropores smaller than 1 nm. The KOH activated carbon showed high and stable capacity of CO2 adsorption after 10 cycles. Copyright © 2015 Elsevier Ltd. All rights reserved.

The influence of a fulvic acid on the adsorption of europium and strontium by alumina and quartz: effects of pH and ionic strength

International Nuclear Information System (INIS)

Norden, M.; Ephraim, J.H.; Allard, B.

1994-01-01

A batch method has been employed to study the adsorption of trace quantities of Eu and Sr on α-Al 2 O 3 and SiO 2 as a function of pH (3-9), ionic strength (0.10 and 0.01 M NaClO 4 ) and the presence of a well-characterized aquatic fulvic acid (FA). A comparison of Eu and Sr adsorption by alumina showed that FA could both reduce and enhance metal ion adsorption. In the absence of FA the adsorption of the metal ions onto alumina was a function of both pH and ionic strength. In the presence of FA the ionic strength effect on the Eu adsorption vanished, while the Sr adsorption showed a clear dependence on ionic strength. The adsorption of Eu and Sr on quartz was lower than the adsorption of the metals on alumina. Additionally, the adsorption of Eu and Sr on quartz was apparently lower than the adsorption on alumina in the presence of Fa. For both metal ions the adsorption on quartz was higher at 0.10 M than at 0.01 M NaClO 4 - an observation that was reversed in the case of alumina. Increasing concentrations of FA lowered the pH at which Eu adsorption on alumina would be reduced. (orig.)

Evaluation of dyes adsorption properties of TiO2-alginate biohybrid material

International Nuclear Information System (INIS)

Barrón Zambrano, J A; Ávila Ortega, A; Muñoz Rodríguez, D; Carrera Figueiras, C; Sánchez Morales, G

2013-01-01

In this study a TiO 2 -alginate biohybrid material was obtained by the sol gel method and its adsorption properties were compared to those of its precursors using eosin B (anionic) as model dye. The results showed that the TiO 2 and biohybrid have a greater affinity for eosine B than alginate. The maximum adsorption capacity for the eosin B was obtained at pH = 10. Kinetic studies showed that the biohybrid has greater rate and adsorption capacity than its precursors. Kinetic data were fitted to a pseudo-second order kinetic model. The experimental isotherms were fitted to the Langmuir model.

Comparison of 4-chloro-2-nitrophenol adsorption on single-walled and multi-walled carbon nanotubes

Directory of Open Access Journals (Sweden)

Mehrizad Ali

2012-09-01

Full Text Available Abstract The adsorption characteristics of 4-chloro-2-nitrophenol (4C2NP onto single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs from aqueous solution were investigated with respect to the changes in the contact time, pH of solution, carbon nanotubes dosage and initial 4C2NP concentration. Experimental results showed that the adsorption efficiency of 4C2NP by carbon nanotubes (both of SWCNTs and MWCNTs increased with increasing the initial 4C2NP concentration. The maximum adsorption took place in the pH range of 2–6. The linear correlation coefficients of different isotherm models were obtained. Results revealed that the Langmuir isotherm fitted the experimental data better than the others and based on the Langmuir model equation, maximum adsorption capacity of 4C2NP onto SWCNTs and MWCNTs were 1.44 and 4.42 mg/g, respectively. The observed changes in the standard Gibbs free energy, standard enthalpy and standard entropy showed that the adsorption of 4C2NP onto SWCNTs and MWCNTs is spontaneous and exothermic in the temperature range of 298–328 K.

Adsorption of various antimicrobial agents to endotoxin removal polymyxin-B immobilized fiber (Toraymyxin®). Part 2: Adsorption of two drugs to Toraymyxin PMX-20R cartridges.

Science.gov (United States)

Shimokawa, Ken-ichi; Takakuwa, Ryotaro; Wada, Yuko; Yamazaki, Noriko; Ishii, Fumiyoshi

2013-01-01

In our previous study, the degree of adsorption of 9 representative antimicrobial agents to Toraymyxin(®) PMX-F sheets was quantitatively evaluated. As a result, the adsorption rate was 22.1% for Linezolid in the presence of serum. Therefore, we investigated whether two types of antimicrobial agents (Ciprofroxacin and Linezolid) can be better adsorbed on PMX-F sheets. When the number of PMX-F sheets was increased in a step wise manner, specifically 2, 4, 6, 8 and 12, the adsorption rate increased linearly. In addition, the adsorption to polymyxin-B immobilized fiber (Toraymyxin(®) PMX-20R) cartridges, widely used to remove endotoxins from circulating blood in the treatment of sepsis, was quantitatively evaluated. As a result, in the presence of serum, Linezolid showed adsorption to PMX-20R, and the adsorption rate after 2h was 54.5%, and that after 4h was 65.8%. The results of this study suggest the necessity of monitoring blood antimicrobial concentration during treatment for sepsis with Linezolid, which showed adsorption to PMX-20R in an environment close to a clinical environment. Copyright © 2012 Elsevier B.V. All rights reserved.

Study on adsorption properties and mechanism of Pb2+ with different carbon based adsorbents.

Science.gov (United States)

Song, Min; Wei, Yuexing; Cai, Shipan; Yu, Lei; Zhong, Zhaoping; Jin, Baosheng

2018-03-15

Different activated carbon materials are prepared from a series of solid wastes (sawdust, acrylic fabric, tire powder and rice husk) by combination of the KOH activation method and steam activation method. The influences of several parameters such as pH, contact time, adsorbent dosage and temperature on adsorption performance of Pb 2+ with those different carbon adsorbents are investigated. The results demonstrate that C rice husk performance well in the adsorption process. In the following, the C rice husk is used to explain the adsorption mechanism of Pb 2+ by SEM-EDS, FT-IR and XPS. The results illustrate that the surface oxygen-containing functional groups such as carboxyl, lactone group, phenolic hydroxyl and other alkaline metal ions like Na + and K + have significant effect on the adsorption process. A reasonable mechanism of Pb 2+ adsorption is proposed that the ion exchange play key roles in the adsorption process. In addition, the effects of Cu 2+ , Zn 2+ on the Pb 2+ adsorption capacity with the four carbon adsorbents are also studied and the results demonstrate that other heavy metals play positive effects on the adsorption of Pb 2+ . Copyright © 2017 Elsevier B.V. All rights reserved.

Zinc(II Adsorption by Low-Carbon Shungite: The Effect of pH

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Axel R. Fischer

2018-04-01

Full Text Available Shungite is a carbonaceous rock which is abundant in Karelia (Russian Federation. Large deposits of shungite with low levels of carbon (approx. 10% C are also found in Kazakhstan, where it is mined under the trade name Taurit (Koksu Mining Company. Although Taurit has been reported to be used as an adsorbent for hazardous compounds in water treatment, there is very little precise data about its adsorption capacity or the compounds adsorbed. In this study, the ability of Taurit to adsorb Zn(II was investigated and Freundlich isotherms were determined for both distilled water and tap water. Taurit was found to have a high buffer capacity leading to pH values > 7.0 in aqueous solution. Because dissolved zinc precipitates as Zn(OH2 under alkaline conditions, the pH must be carefully controlled and kept ≤7.0. Despite the small inner surface area (BET of Taurit (13.4 m2 g−1, Freundlich coefficients for distilled water (Kf = 2.4, n = 4.0 and tap water (Kf = 1.5, n = 2.5 were similar to other adsorbents. Our results indicate that Taurit could provide a cheap alternative to activated carbon since both substances have a similar adsorption capacity (at least for Zn(II.

Adsorption of cobalt (II) octaethylporphyrin and 2H-octaethylporphyrin on Ag(111): new insight into the surface coordinative bond

International Nuclear Information System (INIS)

Bai Yun; Buchner, Florian; Kellner, Ina; Schmid, Martin; Vollnhals, Florian; Steinrueck, Hans-Peter; Marbach, Hubertus; Michael Gottfried, J

2009-01-01

The adsorption of cobalt (II) octaethylporphyrin (CoOEP) and 2H-octaethylporphyrin (2HOEP) on Ag(111) was investigated with scanning tunneling microscopy (STM) and photoelectron spectroscopy (XPS/UPS), in order to achieve a detailed mechanistic understanding of the surface chemical bond of coordinated metal ions. Previous studies of related systems, especially cobalt (II) tetraphenylporphyrin (CoTPP) on Ag(111), have revealed adsorption-induced changes of the oxidation state of the Co ion and the appearance of a new valence state. These effects were attributed to a covalent interaction of the Co ion with the silver substrate. However, recent studies show that the porphyrin ligand of adsorbed CoTPP undergoes a pronounced saddle-shape distortion, which could alter the electronic structure and thus provide an alternative explanation for the new valence state previously attributed to the formation of a surface coordinative bond. With the octaethylporphyrins investigated here, which were found to adsorb in a flat, undistorted conformation on Ag(111), the effects of geometric distortion can be separated from those of the electronic interaction with the substrate. The CoOEP monolayer gives rise to an adsorption-induced shift of the Co 2p signal (-1.9 eV relative to the multilayer), a new valence state at 0.6 eV below the Fermi energy, and a work-function shift of -0.84 eV (2HOEP: -0.44 eV) relative to the clean surface. Comparison with data for the distorted CoTPP confirms the existence of a covalent ion-surface interaction that is insensitive to the conformation of the ligand.

Adsorption of Sr(II) on clay minerals: effects of salt concentration, loading and pH

International Nuclear Information System (INIS)

Rafferty, P.; Shiao, S.Y.; Binz, C.M.; Meyer, R.E.

1981-01-01

The adsorption of Sr(II) on a number of clay minerals has been investigated by means of a batch technique in solutions of sodium salts. Generally the results can be approximated by ideal ion exchange equations. Distribution coefficients at trace loading follow the linear relation log D = s log [Na(I)sub(aq)] + b where b is a constant and s had values of from about - 1.5 to - 2.0, which are fairly close to the ideal valve of - 2. Adsorption isotherms at constant pH and salt concentration are linear in the low loading region. Distribution coefficients for montmorillonite are almost independent of pH in the intermediate pH region 5 to 7 but for illite and kaolinite, increases in the distribution coefficient with pH are observed. Comparison of these results with literature values, insofar as it is possible, shows that distribution coefficients are usually within a factor of two or three for the same mineral with similar capacities under the same conditions even if techniques of preparation and measurement are different, but values may vary considerably more if the capacities of the different mineral samples are greatly different. Values of the distribution coefficient at very high salt concentration are very low, considerably less than unity at 4 M NaCl. Thus migration rates of Sr(II), relative to water flow, through geologic formations whose adsorption behavior is dominated by these clay minerals are likely to be high at high salt concentrations. (author)

Elucidating adsorption mechanisms of phthalate esters upon carbon nanotubes/graphene and natural organic acid competitive effects in water by DFT and MD calculations

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhuang; Wang, Se; Chen, Min Dong; Xu, Defu [Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Jiangsu KeyLaboratory of Atmospheric Environment Monitoring and Pollution Control (AEMPC), School ofEnvironmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing (China); Tang, Lili [Jiangsu Environmental Monitoring Centre, Nanjing (China); Wang, Degao [Dept. of Environmental Science and Engineering, Dalian Maritime University, Dalian (China)

2015-06-15

Simulations at multiple levels were performed to investigate the aqueous adsorption of phthalate esters (PAEs) on carbon nanoparticles and to find the competitive effect of a low molecular weight natural organic acid (benzoic acid) on the adsorption process. Six PAEs of varying alkyl side chain lengths and three carbon-based nanomaterials including a single-walled carbon nanotube (SWNT), double-walled carbon nanotube (DWNT), and graphene (G) were studied. Results showed that the adsorption energies calculated using density functional theory increase with increasing length of the PAE alkyl chain. G exhibits higher adsorption capacity for the PAEs than SWNT and DWNT. The absolute adsorption energies of these systems also display a positive linear correlation with the hydrophobicity of the PAE molecules. Molecular dynamics simulations indicate that the presence of neutral/anionic benzoic acid in water alleviates the PAE adsorption. Furthermore, anionic benzoic acid exerts more impact on the PAE adsorption than the neutral form.

TG-FTIR measurement of CO2-H2O co-adsorption for CO2 air capture sorbent screening

NARCIS (Netherlands)

Smal, I.M.; Yu, Qian; Veneman, Rens; Fränzel-Luiten, B.; Brilman, Derk Willem Frederik

2014-01-01

Capturing atmospheric CO2 using solid sorbents is gaining interest. As ambient air normally contains much more (up to 100 times) water than CO2, a selective sorbent is desirable as co-adsorption will most likely occur. In this study, a convenient method based on an TG-FTIR analysis system is

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.)

Adsorption of Reactive Red M-2BE dye from water solutions by multi-walled carbon nanotubes and activated carbon.

Science.gov (United States)

Machado, Fernando M; Bergmann, Carlos P; Fernandes, Thais H M; Lima, Eder C; Royer, Betina; Calvete, Tatiana; Fagan, Solange B

2011-09-15

Multi-walled carbon nanotubes and powdered activated carbon were used as adsorbents for the successful removal of Reactive Red M-2BE textile dye from aqueous solutions. The adsorbents were characterised by infrared spectroscopy, N(2) adsorption/desorption isotherms and scanning electron microscopy. The effects of pH, shaking time and temperature on adsorption capacity were studied. In the acidic pH region (pH 2.0), the adsorption of the dye was favourable using both adsorbents. The contact time to obtain equilibrium at 298K was fixed at 1h for both adsorbents. The activation energy of the adsorption process was evaluated from 298 to 323K for both adsorbents. The Avrami fractional-order kinetic model provided the best fit to the experimental data compared with pseudo-first-order or pseudo-second-order kinetic adsorption models. For Reactive Red M-2BE dye, the equilibrium data were best fitted to the Liu isotherm model. Simulated dyehouse effluents were used to check the applicability of the proposed adsorbents for effluent treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

Synthesis, characterization, and application of Zn(NH 3)(CO3) for selective adsorptive separation of CO2

Science.gov (United States)

Khazeni, Naasser

This study explores the potential of Zn(NH3)(CO3) for selective CO2 separation. It develops a novel, highly controllable, single-pot synthesis approach based on urea hydrolysis and solvothermal aging to increase the feasibility of synthesizing Zn(NH3)(CO3), determines the structure of Zn(NH3)(CO3) in detail through single crystal X-ray diffraction and powder X-ray diffraction analyses, and performs adsorption analyses for the compound using CO2, N 2, H2, O2, and CH4 as adsorptives. Through adsorptive characterization, a systematic adsorbent selection screening is performed to assess the potential application of Zn(NH3)(CO 3) for adsorptive separation of CO2 from an upstream gas mixture of power generation, hydrogen production, and natural gas industries. Structural analysis shows Zn(NH3)(CO3) to have an inorganic helical framework that consists of a small helix of (ZnOCO) 2 and a large helix of (ZnOCO)4 with two ammines (NH 3) pendant from every other zinc. In terms of adsorption capacity and CO2 selectivity, Zn(NH3)(CO3) adsorbed 0.550 mmole/g CO2 at 293 K and 4500 mmHg, but only 0.047 mmole/g N 2, 0.084 mmole/g H2, 0.207 mmole/g 02, and 0.060 mmole/g CH4 at the same temperature and pressure. This behavior demonstrates considerable equilibrium selectivities - 36, 31, 63, and 11 - for separating CO2 from CH4, CO2 from H 2, CO2 from N2, and CO2 from 02, respectively. During adsorption, the pendant ammines act as the gates of check-valves: applied pressure opens the gates for adsorption; and during desorption, the gates are closed, trapping the adsorbates, until a reduction of pressure to near-atmospheric levels. Therefore, Zn(NH3)(CO3) exhibits low-pressure H3 or H4 hysteresis, indicating that the Zn(NH3)(CO3) framework can achieve gas storage at near-atmospheric pressures. Additionally, the compound proves structurally stable, with an adsorption decrease of 0.8% after 20 adsorption/desorption cycles - a factor that, considered with the other characteristics of Zn

Density functional study on the heterogeneous oxidation of NO over α-Fe_2O_3 catalyst by H_2O_2: Effect of oxygen vacancy

International Nuclear Information System (INIS)

Song, Zijian; Wang, Ben; Yu, Jie; Ma, Chuan; Zhou, Changsong; Chen, Tao; Yan, Qianqian; Wang, Ke; Sun, Lushi

2017-01-01

Highlights: • NO and H_2O_2 adsorption on perfect and oxygen defect α-Fe_2O_3 (0 0 1) surface were studied by DFT calculations. • H_2O_2 shows high chemical reactivity for its adsorption on oxygen defect α-Fe_2O_3 (0 0 1) surface. • Oxygen vacancy plays an important role of the catalytic oxidation of NO by H_2O_2 over the α-Fe_2O_3 catalyst surfaces. • Mechanism of NO oxidation over α-Fe_2O_3 (0 0 1) surface by H_2O_2 was explained. - Abstract: Catalytic oxidation with H_2O_2 is a promising method for NOx emission control in coal-fired power plants. Hematite-based catalysts are attracting increased attention because of their surface redox reactivity. To elucidate the NO oxidation mechanism on α-Fe_2O_3 surfaces, density functional theory (DFT) calculations were conducted by investigating the adsorption characteristics of nitric oxide (NO) and hydrogen peroxide (H_2O_2) on perfect and oxygen defect α-Fe_2O_3 (0 0 1) surfaces. Results show that NO was molecularly adsorbed on two kinds of surfaces. H_2O_2 adsorption on perfect surface was also in a molecular form; however, H_2O_2 dissociation occurred on oxygen defect α-Fe_2O_3 (0 0 1) surface. The adsorption intensities of the two gas molecules in perfect α-Fe_2O_3 (0 0 1) surface followed the order NO > H_2O_2, and the opposite was true for the oxygen defect α-Fe_2O_3 (0 0 1). Oxygen vacancy remarkably enhanced the adsorption intensities of NO and H_2O_2 and promoted H_2O_2 decomposition on catalyst surface. As an oxidative product of NO, HNO_2 was synthesized when NO and H_2O_2 co-adsorbed on the oxygen defect α-Fe_2O_3 (0 0 1) surface. Analyses of Mulliken population, electron density difference, and partial density of states showed that H_2O_2 decomposition followed the Haber–Weiss mechanism. The trends of equilibrium constants suggested that NO adsorption on α-Fe_2O_3 (0 0 1) surface was more favorable at low than at high temperatures, whereas H_2O_2 adsorption was favorable between 375 and

Carbon and TiO_2 synergistic effect on methylene blue adsorption

International Nuclear Information System (INIS)

Simonetti, Evelyn Alves Nunes; Simone Cividanes, Luciana de; Campos, Tiago Moreira Bastos; Rossi Canuto de Menezes, Beatriz; Brito, Felipe Sales; Thim, Gilmar Patrocínio

2016-01-01

Due to its high efficiency, low cost and a simple operation, the adsorption process is an important and widely used technique for industrial wastewater treatment. Recent studies on the removal of artificial dyes by adsorption include a large number of adsorbents, such as: activated carbon, silicates, carbon nanotube, graphene, fibers, titanates and doped titanates. The carbon insertion in the TiO_2 structure promotes a synergistic effect on the adsorbent composite, improving the adsorption and the charge-transfer efficiency rates. However, there are few studies regarding the adsorption capacity of TiO_2/Carbon composites with the carbon concentration. This study evaluates the effect of carbon (resorcinol/formaldehyde) insertion on TiO_2 structure through the adsorption process. Adsorbents were prepared by varying the carbon weight percentages using the sol-gel method. The physicochemical properties of the catalysts prepared, such as crystallinity, particle size, surface morphology, specific surface area and pore volume were investigated. The kinetic study, adsorption isotherm, pH effect and thermodynamic study were examined in batch experiments using methylene blue as organic molecule. In addition, the effect of carbon phase on the adsorption capacity of TiO_2-carbon composite was deeply investigated. SEM micrographs showed that TiO_2 phase grows along the carbon phase and FT-IR results showed the presence of Ti−O−C chemical bonding. The experiments indicate that the carbon phase acted as a nucleation agent for the growth of TiO_2 during the sol-gel step, with a TiO_2 structure suitable for blue methylene adsorption, resulting in a material with large surface area and slit-like or wedge-shaped pores. Further experiments will show the best carbon concentration for methylene blue adsorption using a TiO_2 based material. - Highlights: • This article deals with the adsorption of methylene blue onto TiO_2-Carbon composite. • The sol-gel synthesis was efficient

Adsorption mechanism of alkyl polyglucoside (APG) on calcite nanoparticles in aqueous medium at varying pH

Science.gov (United States)

Suh, Seokjin; Choi, Kyeong-Ok; Yang, Seung-Chul; Kim, Yeong Eun; Ko, Sanghoon

2017-07-01

In this study, adsorption mechanism of alkyl polyglucoside (APG) on calcium carbonate (CaCO3) nanoparticles (CCNPs) in aqueous medium at varying pH was identified. An initial adsorption of APG on CCNP surface seemed to be occurred due to the van der Waals force. An initial surface charge influenced determination of a major driving force, which resulted in hydrogen bonds (pH 7) and the hydrophobic interaction (pH 10) as a main sources of adsorption of APG on the CCNP surface. Even if the initial surface charge of CCNPs had little effect on a quantitative adsorption of APG on CCNPs, eventually, it influence on the definitive adsorption structure between APG and CCNPs and improvement of dispersion stability of CCNPs in water. In conclusion, it was revealed that 0.39% APG aqueous solution was most appropriate to improve the dispersion stability of CCNPs, which is postulated to be used effectively in food and pharmaceutical fields.

Removal of arsenic from water by Friedel's salt (FS: 3CaO·Al2O3·CaCl2·10H2O).

Science.gov (United States)

Zhang, Danni; Jia, Yongfeng; Ma, Jiayu; Li, Zhibao

2011-11-15

Low levels of arsenic can be effectively removed from water by adsorption onto various materials and searching for low-cost, high-efficiency new adsorbents has been a hot topic in recent years. In the present study, the performance of Friedel's salt (FS: 3CaO·Al(2)O(3)·CaCl(2)·10H(2)O), a layered double hydroxide (LDHs), as an adsorbent for arsenic removal from aqueous solution was investigated. Friedel's salt was synthesized at lower temperature (50°C) compared to traditional autoclave methods by reaction of calcium chloride with sodium aluminate. Kinetic study revealed that adsorption of arsenate by Friedel's salt was fast in the first 12h and equilibrium was achieved within 48 h. The adsorption kinetics are well described by second-order Lageren equation. The adsorption capacity of the synthesized sorbent for arsenate at pH 4 and 7 calculated from Langmuir adsorption isotherms was 11.85 and 7.80 mg/g, respectively. Phosphate and silicate markedly decreased the removal of arsenate, especially at higher pH, but sulfate was found to suppress arsenate adsorption at lower pH and the adverse effect was disappeared at pH ≥ 6. Common metal cations (Ca(2+), Mg(2+)) enhanced arsenate adsorption. The results suggest that Friedel's salt is a potential cost-effective adsorbent for arsenate removal in water treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

Influences of H on the Adsorption of a Single Ag Atom on Si(111-7 × 7 Surface

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Lin Xiu-Zhu

2009-01-01

Full Text Available Abstract The adsorption of a single Ag atom on both clear Si(111-7 × 7 and 19 hydrogen terminated Si(111-7 × 7 (hereafter referred as 19H-Si(111-7 × 7 surfaces has been investigated using first-principles calculations. The results indicated that the pre-adsorbed H on Si surface altered the surface electronic properties of Si and influenced the adsorption properties of Ag atom on the H terminated Si surface (e.g., adsorption site and bonding properties. Difference charge density data indicated that covalent bond is formed between adsorbed Ag and H atoms on 19H-Si(111-7 × 7 surface, which increases the adsorption energy of Ag atom on Si surface.

Study of cesium and strontium adsorption on slovak bentonite

International Nuclear Information System (INIS)

Galambos, M.

2010-01-01

Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for high-level radioactive waste and spent nuclear fuel. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by adsorption. Slovak Republic avails of many significant deposits of bentonite. Adsorption of Cs and Sr on five Slovak bentonite of deposits (Jelsovy potok, Kopernica, Lieskovec, Lastovce and Dolna Ves) and montmorillonite K10 (Sigma-Aldrich) has been studied with the using batch of radiometric techniques. Natural, irradiated and natrified samples, in three different kinds of grain size: 15, 45 and 250 μm have been used in the experiments. The adsorptions of Cs and Sr on bentonite under various experimental conditions, such as contact time, adsorbent and adsorbate concentrations, pH after adsorption and effect of pH change, chemical modification, competitive ions and organic agents on the adsorption have been studied. The K d have been determined for adsorbent-Cs/Sr solution system as a function of contact time and adsorbate and adsorbent concentration. The data have been interpreted in terms of Langmuir isotherm. The adsorption of Cs and Sr has increased with increasing metal concentrations. Adsorption of Cs and Sr has been suppressed by presence of organic agents; and of bivalent cations more than univalent cations. By adsorption on natrified samples colloidal particles and pH value increase have been formed. Adsorption experiments carried out show that the most suitable materials intended for use as barriers surrounding a canister of spent nuclear fuel are bentonite of the Jelsovy potok and Kopernica deposits. (author)