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Sample records for alkaline aqueous solution

  1. Transient species produced in irradiated alkaline aqueous solutions containing oxygen

    International Nuclear Information System (INIS)

    The spectra and decay kinetics of the optical absorption in the UV region and at 430nm (maximum of the ozonide ion absorption), were investigated in oxygenated neutral, slightly and strongly alkaline aqueous solutions. It is assumed that the initial absorption after the pulse in oxygenated alkaline solutions is due to the ozonide ion O3-, superoxide radical ion O2- and ozone O3. The long-living absorption in these solutions cannot be excluded as to be probably caused by the ozone O3 or some product formed from O2- or an alkaline stabilized form of this radical-ion. The advantage of applying additional non-optical measurements of the system is shown on the example of H2O2 role played in the mechanism. (author)

  2. The autoreduction of pertechnetate in aqueous, alkaline solutions

    International Nuclear Information System (INIS)

    The autoreduction of pertechnetate (99TcO4-) to Tc(IV/V) alkoxide complexes in aqueous, alkaline, solutions is described. Solutions of sodium pertechnetate (0.01M) reacted with nitrogen and oxygen donor ligands (1.0M) in 2M sodium hydroxide. Solutions containing nitrogen donor ligands (e.g., EDTA) showed the initial formation of lightly colored complexes followed by rapid decomposition in air. In contrast, stable, reduced complexes were formed within minutes of mixing pertechnetate with mono- and disaccharides in strong base, as indicated by a persistent color change. Chemical yields of these reactions were determined by thin layer chromatography or paper chromatography and radiochemically assayed with a Bioscan imaging scanner. Analysis by UV-vis spectroscopy suggested that Tc(IV) or Tc(V) complexes were produced, with the oxidation state dependent on the reducing ligand. These experiments may help explain the reduction of pertechnetate to the soluble complexes that have been found in the Hanford nuclear waste tanks. (author)

  3. Decomposition Studies of Triphenylboron, Diphenylborinic Acid and Phenylboric Acid in Aqueous Alkaline Solutions Containing Copper

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, C.L. [Westinghouse Savannah River Company, AIKEN, SC (United States); Peterson, R. A.

    1997-02-11

    This report documents the copper-catalyzed chemical kinetics of triphenylboron, diphenylborinic acid and phenylboric acid (3PB, 2PB and PBA) in aqueous alkaline solution contained in carbon-steel vessels between 40 and 70 degrees C.

  4. Dual fluorescence of naphthylamines in alkaline aqueous solution

    Science.gov (United States)

    Ma, Li-Hua; Wen, Zhen-Chang; Lin, Li-Rong; Jiang, Yun-Bao

    2001-10-01

    Dual fluorescence was observed with N-(1-naphthyl)aminoacetate (1-NAA) in aqueous solution of pH 13.0 in the presence of cationic surfactants, cetyltrimethylammonium bromide (CTAB) and chloride (CTAC), below and after the critical micelle concentration (CMC). Similar dual fluorescence was also found with 1- and 2-naphthylamine (1-NA, 2-NA), N-(2-naphthyl)aminoacetate (2-NAA) and (1-naphthyl)ethylenediamine (1-NEDA), in the presence and absence of the cationic surfactants, but not with N, N-disubstituted 1- and 2-NAs. We concluded that the dual fluorescence was due to the excited-state deprotonation of the amino group in these NAs. The p Ka*s of the dual fluorescent NAs were estimated to be around 14 from the dual fluorescence pH titrations. No clear correlation was found for p Ka* with the amino substitution and the presence of cationic micelle.

  5. Enhanced oxygen evolution at hydrous oxy-hydroxide modified iron electrodes in aqueous alkaline solution

    OpenAIRE

    Lyons, Michael; Doyle, Richard

    2011-01-01

    Outstanding issues regarding the film formation and the oxygen evolution reaction (OER) electrocatalytic behaviour of multicycled iron oxyhydroxide films in aqueous alkaline solution have been revisited. The oxide is grown using a repetitive poltential multicycling technique, and the mechanism of the latter hydrous oxide formation process has been discussed. A duplex layer model of the oxide/solution interphase region is proposed. The acid/base behaviour of the hydrous oxide and the microdisp...

  6. Ternary diffusion of carbon dioxide in alkaline solutions of aqueous sodium hydroxide and aqueous sodium carbonate

    Energy Technology Data Exchange (ETDEWEB)

    Leaist, D.G.

    1985-07-01

    Carbon dioxide dissolved in alkaline solutions diffuses as bicarbonate and carbonate ions produced by the reactions CO/sub 2/+OH/sup -/=HCO/sub 3//sup -/ and CO/sub 2/+2OH/sup -/=CO/sub 3//sup 2 -/+H/sub 2/O. Ternary diffusion coefficients of the systems NaHCO/sub 3/+Na/sub 2/CO/sub 3/+H/sub 2/O and Na/sub 2/CO/sub 3/+NaOH+H/sub 2/O have been measured by a conductimetric technique at 298.15 K. The mixed electrolyte data are transformed by use of the solution equilibria to ternary diffusion coefficients of the systems CO/sub 2/+Na/sub 2/CO/sub 3/+H/sub 2/O and CO/sub 2/+NaOH+H/sub 2/O. Unlike the binary diffusivity of CO/sub 2/ in water (1.9 . 10/sup -9/ m/sup 2/ s/sup -1/), the ternary diffusivity of CO/sub 2/ in alkaline solutions is sensitive to concentration and varies from 0.9 . 10/sup -9/ to 3.5 . 10/sup -9/ m/sup 2/ s/sup -1/ at 298.15 K. Expressions are derived to estimate the transport coefficients of the components from the concentrations and diffusion coefficients of the constituent ions. At high pH values hydroxide-coupled transport leads to rapid diffusion of CO/sub 2/ as CO/sub 3//sup 2 -/. The results are consistent with the Onsager reciprocal relation for isothermal ternary diffusion.

  7. Alkaline deoxygenated graphene oxide as adsorbent for cadmium ions removal from aqueous solutions.

    Science.gov (United States)

    Liu, Jun; Du, Hongyan; Yuan, Shaowei; He, Wanxia; Yan, Pengju; Liu, Zhanhong

    2015-01-01

    Alkaline deoxygenated graphene oxide (aGO) was prepared through alkaline hydrothermal treatment and used as adsorbent to remove Cd(II) ions from aqueous solutions for the first time. The characterization results of transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and Fourier transform infrared (FT-IR) spectra indicate that aGO was successfully synthesized. The batch adsorption experiments showed that the adsorption kinetics could be described by the pseudo-second-order kinetic model, and the isotherms equilibrium data were well fitted with the Langmuir model. The maximum adsorption capacity of Cd(II) on aGO was 156 mg/g at pH 5 and T=293 K. The adsorption thermodynamic parameters indicated that the adsorption process was a spontaneous and endothermic reaction. The mainly adsorption mechanism speculated from FT-IR results may be attributed to the electrostatic attraction between Cd2+ and negatively charged groups (-CO-) of aGO and cation-π interaction between Cd2+ and the graphene planes. The findings of this study demonstrate the potential utility of the nanomaterial aGO as an effective adsorbent for Cd(II) removal from aqueous solutions. PMID:26038925

  8. Electrodeposition of actinide traces from aqueous alkaline solutions and tributyl phosphate

    International Nuclear Information System (INIS)

    The electrodeposition of uranium and trace quantities of 239Pu, 234Th, 144Ce on a stainless steel disk was investigated from 0.5-2.0M NaOH and the two-phase system, extract of actinides in TBP-aqueous solution of NaOH. The electrodeposition yield of the above elements reaches 98-100% in 40 min of electrolysis with current density 0.4-0.5 A/cm2. The presence of 0.5M Na2CO3, 2.0M NaNO3, 2.0M NaNO2, 0.2M NaF in alkaline solutions does not decrease the electrodeposition yield. The electrodeposited films meet all the requirements of α-spectrometry. The uranium oxidation states (V) and (IV) were determined in the electrodeposited films. (author) 9 refs.; 3 figs.; 1 tab

  9. The cathodic reduction of dioxygen on uranium oxide in dilute alkaline aqueous solution

    International Nuclear Information System (INIS)

    The cathodic reduction of dioxygen on uranium oxide in dilute alkaline aqueous solutions has been investigated within the context of a program to develop a comprehensive model to predict the behaviour of used CANDU (Canada Deuterium Uranium) nuclear fuel under disposal-vault conditions. Two different kinds of ceramic UO2 were studied: reactor-grade CANDU fuel with normal p-type electrical conductivity and low-resistance material that exhibits n-type photoelectrochemical behaviour. The transport of electroactive species in solution was controlled by varying the rotation rate of rotating disc electrodes (RDE) and rotating ring-disc electrodes (RRDE). Steady-state polarization measurements were made using the current-interrupt method to compensate for the potential drop caused by ohmic resistance. Any release of peroxide to solution from the UO2 (disc) surface could be monitored by oxidizing it at the Au ring of an RRDE. The existing theory for the cathodic 02-reduction process as applied to RDE and RRDE experiments has been reviewed as a starting point for the interpretation of the results obtained in our work. (37 figs., 2 tabs., 170 refs.)

  10. Distribution of alkaline earth elements between aqueous solutions and polymer sorbents impregnated by 8-hydroxyquinoline

    International Nuclear Information System (INIS)

    Interphase distribution of alkaline-earth element (AEE) microimpurities between solutions of alkali metal chlorides and macroporous copolymer of styrene with divinylbenzene impregnated by 8-hydroxyquinoline is investigated. The effect of phase composition on AEE and 8-hydroxyquinoline distribution coefficient is considered. Advantages of the mixture sorption with impregnated sorbent as compared with liquid extraction for thorough purification of salt solution are shown

  11. The oxygen evolution reaction on passive oxide covered transition metal electrodes in aqueous alkaline solution. Part 1 - Nickel

    OpenAIRE

    LYONS, MICHAEL EDWARD

    2008-01-01

    Various aspects of the oxygen evolution reaction (OER) at passive oxide covered polycrystalline Ni electrodes in aqueous alkaline solution were investigated using electrochemical techniques. Steady state polarisation and electrochemical impedance spectroscopy (EIS) were used to measure kinetically significant parameters including the Tafel slope and the reaction order with respect to OH- activity. While reproducible values of the Tafel slope were readily observed, the recorded cur...

  12. The reactivity of the electron formed in the radiolysis of aerated alkaline aqueous solutions containing tetracycline hydrochloride, at 77 Ksup(+)

    International Nuclear Information System (INIS)

    The radiolysis of tetracycline hydrochloride dissolved in aerated alkaline aqueous solutions containing 0.1, 0.5 and 1M NaOH at 77 K, followed by ESR is reported. The rate constants for the reactions between the electron and physical or chemical traps which are present in these solutions are calculated. The reactivity of electrons that are formed in the radiolysis of water decreases in the following proportions: physical traps: chemical traps: molecules of water (4.8x10sup(14) : 6.5x10sup(8) : 1.0). The electrons react preferentially with the solute instead of the solvent. (author)

  13. Distribution of alkaline earth elements between aqueous solutions and polymeric sorbent impregnated with 8-hydroxyquinoline

    International Nuclear Information System (INIS)

    The interphase distribution of microimpurities of alkaline earth elements (AEE) between solutions of alkali metal chlorides and a macroporous styrene-divinyl-benzene copolymer impregnated with 8-hydroxyquinoline was studied. The influence of the phase composition on the distribution coefficients of AEE and 8-hydroxyquinoline was examined. The advantages of sorption of the impurities by an impregnated sorbent over liquid extraction for thorough purification of salt solutions were shown

  14. On the decay of the ozonide radical in aqueous alkaline solutions

    Science.gov (United States)

    Bhattacharyya, P. K.; Saini, R. D.

    1982-11-01

    In flash photolysis of an oxygenated aqueous potassium persulphate solution at pH 12.5 the decay of the ozonide radical has been found to follow 3/2 order kinetics which has been explained by reactions O -3 + O - ⇌ 2 O -2 and O -3 + HO 2 → 2 O 2 + OH -

  15. Galvanic Corrosion between Alloy 690 and Magnetite in Alkaline Aqueous Solutions

    OpenAIRE

    Soon-Hyeok Jeon; Geun-Dong Song; Do Haeng Hur

    2015-01-01

    The galvanic corrosion behavior of Alloy 690 coupled with magnetite has been investigated in an alkaline solution at 30 °C and 60 °C using a potentiodynamic polarization method and a zero resistance ammeter. The positive current values were recorded in the galvanic couple and the corrosion potential of Alloy 690 was relatively lower. These results indicate that Alloy 690 behaves as the anode of the pair. The galvanic coupling between Alloy 690 and magnetite increased the corrosion rate of All...

  16. Investigation into formation of nanoparticles of tetravalent neptunium in slightly alkaline aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Husar, Richard

    2015-08-20

    Considering the worldwide growing discharge of minor actinides and the current need for geological disposal facilities for radioactive waste, this work provides a contribution to the safety case concerning Np transport if it would be released from deep repository sites and moving from alkaline cement conditions (near-field) to more neutral environmental conditions (far-field). The reducing conditions in a nuclear waste repository render neptunium tetravalent, which is assumed to be immobile in aqueous environment due to the low solubility solution of Np(IV). For tetravalent actinide nuclides, the most significant transport should occur via colloidal particles. This work demonstrates the formation of intrinsic neptunium dioxide nanocrystals and amorphous Np(IV) silica colloids under environmentally relevant conditions. The dissociation of the initial soluble Np(IV) complex (i.e. [Np(IV)(CO{sub 3}){sub 5}]{sup 6-}) induces the intrinsic formation of nanocrystalline NpO{sub 2} in the solution phase. The resulting irregularly shaped nanocrystals with an average size of 4 nm exhibit a face-centered cubic (fcc), fluorite-type structure (space group Fm anti 3m). The NCs tend to agglomerate under ambient conditions due to the weakly charged hydrodynamic surface at neutral pH (zetapotential ζ ∝0 mV). The formation of micron-sized agglomerates, composed of nanocrystals of 2-5 nm in size, and the subsequent precipitation cause immobilization of the major amount of Np(IV) in the Np carbonate system. Agglomeration of NpO{sub 2} nanocrystals in dependence on time was indicated by PCS and UV-vis absorption spectroscopy with the changes of baseline characteristics and absorption maximum at 742 nm. Hitherto, unknown polynuclear species as intermediate species of NpO{sub 2} nanocrystal formation were isolated from solution and observed by HR-TEM. These polynuclear Np species appear as dimers, trimers and hexanuclear compounds in analogy with those reported for other actinides

  17. Investigation into formation of nanoparticles of tetravalent neptunium in slightly alkaline aqueous solution

    International Nuclear Information System (INIS)

    Considering the worldwide growing discharge of minor actinides and the current need for geological disposal facilities for radioactive waste, this work provides a contribution to the safety case concerning Np transport if it would be released from deep repository sites and moving from alkaline cement conditions (near-field) to more neutral environmental conditions (far-field). The reducing conditions in a nuclear waste repository render neptunium tetravalent, which is assumed to be immobile in aqueous environment due to the low solubility solution of Np(IV). For tetravalent actinide nuclides, the most significant transport should occur via colloidal particles. This work demonstrates the formation of intrinsic neptunium dioxide nanocrystals and amorphous Np(IV) silica colloids under environmentally relevant conditions. The dissociation of the initial soluble Np(IV) complex (i.e. [Np(IV)(CO3)5]6-) induces the intrinsic formation of nanocrystalline NpO2 in the solution phase. The resulting irregularly shaped nanocrystals with an average size of 4 nm exhibit a face-centered cubic (fcc), fluorite-type structure (space group Fm anti 3m). The NCs tend to agglomerate under ambient conditions due to the weakly charged hydrodynamic surface at neutral pH (zetapotential ζ ∝0 mV). The formation of micron-sized agglomerates, composed of nanocrystals of 2-5 nm in size, and the subsequent precipitation cause immobilization of the major amount of Np(IV) in the Np carbonate system. Agglomeration of NpO2 nanocrystals in dependence on time was indicated by PCS and UV-vis absorption spectroscopy with the changes of baseline characteristics and absorption maximum at 742 nm. Hitherto, unknown polynuclear species as intermediate species of NpO2 nanocrystal formation were isolated from solution and observed by HR-TEM. These polynuclear Np species appear as dimers, trimers and hexanuclear compounds in analogy with those reported for other actinides. Intrinsic formation of NpO2 (fcc

  18. Galvanic Corrosion between Alloy 690 and Magnetite in Alkaline Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Soon-Hyeok Jeon

    2015-12-01

    Full Text Available The galvanic corrosion behavior of Alloy 690 coupled with magnetite has been investigated in an alkaline solution at 30 °C and 60 °C using a potentiodynamic polarization method and a zero resistance ammeter. The positive current values were recorded in the galvanic couple and the corrosion potential of Alloy 690 was relatively lower. These results indicate that Alloy 690 behaves as the anode of the pair. The galvanic coupling between Alloy 690 and magnetite increased the corrosion rate of Alloy 690. The temperature increase led to an increase in the extent of galvanic effect and a decrease in the stability of passive film. Galvanic effect between Alloy 690 and magnetite is proposed as an additional factor accelerating the corrosion rate of Alloy 690 steam generator tubing in secondary water.

  19. Electrochemistry in aqueous solution at high temperature and under pressure: study of nickel in a highly alkaline environment

    International Nuclear Information System (INIS)

    This research thesis reports the study of the corrosion resistance and anodic behaviour of various metals and alloys used in conventional thermal or nuclear power stations, more particularly the case of nickel in a highly alkaline environment (KOH 5 N) which is widely used for hydrogen production by water electrolysis. The author studied the influence of temperature and pressure on the electrochemical behaviour of nickel, and more particularly the first-oxidation kinetics. The report discusses the physicochemical and thermodynamic properties of aqueous systems at high temperature and under pressure, presents the general techniques of high-temperature electrochemistry, describes the experimental installation, and reports the development of a reference electrode which can operate in those experimental conditions. The author reports the study of the electrochemical behaviour of nickel in alkaline environment and at high temperature, reports a surface analysis performed by Auger spectroscopy, electron spectroscopy for chemical analysis or ESCA, and scanning electronic microscopy, reports the study of the electrochemical behaviour of nickel in a potassium hydroxide solution under normal temperature and pressure, but also in acid environment. Results are interpreted with respect to temperature

  20. Investigation into the Formation of Nanoparticles of Tetravalent Neptunium in Slightly Alkaline Aqueous Solution

    OpenAIRE

    Husar, Richard

    2015-01-01

    Considering the worldwide growing discharge of minor actinides and the current need for geological disposal facilities for radioactive waste, this work provides a contribution to the safety case concerning Np transport if it would be released from deep repository sites and moving from alkaline cement conditions (near-field) to more neutral environmental conditions (far-field). The reducing conditions in a nuclear waste repository render neptunium tetravalent, which is assumed to be immobile i...

  1. Redox switching and oxygen evolution at hydrous oxyhydroxide modified nickel electrodes in aqueous alkaline solution: effect of hydrous oxide thickness and base concentration

    OpenAIRE

    Lyons, Michael

    2012-01-01

    Outstanding issues regarding the film formation, the redox switching reaction and the oxygen evolution reaction (OER) electrocatalytic behaviour of multi-cycled nickel oxy-hydroxide films in aqueous alkaline solution have been discussed. The oxide is grown using a repetitive potential multi-cycling technique, and the mechanism of the latter hydrous oxide formation process has been discussed. A duplex layer model of the oxide/solution interphase region is proposed. The acid/base behaviour of t...

  2. The solubility of amorphous and crystalline schoepite in neutral to alkaline aqueous solutions

    International Nuclear Information System (INIS)

    The solubility of schoepite UO2(OH)2H2O has been investigated by potentiometric titration at 250C in 0.5 mol dm.-3NaCIO4 solution. The data indicates the predominance of the species (UO2)3(OH)5+ and either UO2(OH)3- or (UO2)3)(OH)7- in the pH range studied. The formation constants of these species as well as the solubility product of the amorphous and microcrystalline schoepite have been determined. The consequences of these data on the hypothesis of schoepite as the solubility limiting phase in spent fuel dissolution studies is discussed

  3. Preparation, stability, and structural characterization of plutonium(VII) in alkaline aqueous solution.

    Science.gov (United States)

    Antonio, Mark R; Williams, C W; Sullivan, James A; Skanthakumar, S; Hu, Yung-Jin; Soderholm, L

    2012-05-01

    A freshly prepared solution of Pu(VI) in 2 M NaOH was oxidized to Pu(VII), via ozonolysis, while simultaneously collecting X-ray absorption spectra. Analyses of the XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) data, acquired throughout the in situ experiments, show a dioxo coordination environment for Pu(VI), PuO(2)(2+), typical for it and the hexavalent actinyl species of U and Np, and its evolution into a tetraoxo-coordination environment for Pu(VII), PuO(4)(-), like that known for Np(VII). The EXAFS data provide average Pu-O distances of 1.79(1) and 1.88(1) Å, respectively. The second coordination shells, also fit as O atoms, provide Pu-O distances of 2.29-2.32 Å that are independent of the Pu oxidation state. The coordination numbers for the distant O atoms in sums with those for the nearest O atoms are consistent with 6-O environments for both Pu(VI) and Pu(VII) ions in accordance with their previously proposed speciation as [Pu(VI)O(2)(OH)(4)](2-) and [Pu(VII)O(4)(OH)(2)](3-), respectively. This solution speciation accounts precisely for the Pu(VI) and Pu(VII) coordination environments reported in various solid state structures. The Pu(VII) tetraoxo-dihydroxo anion was found to have a half-life of 3.7 h. Its instability is attributed to spontaneous reduction to Pu(VI) and not to a measurable extent of disproportionation. We found no direct evidence for Pu(VIII) in the X-ray data and, furthermore, the stoichiometry of the oxidation of Cr(III) by Pu is consistent with that expected for a valence-pure Pu(VII) preparation by ozonation and, in turn, stoichiometrically equivalent to the established Np(VII)/Cr(III) redox reaction. PMID:22524489

  4. Formation of ozone in the reaction between the ozonide radical ion, O3-, and the carbonate radical ion, CO3-, in aqueous alkaline solutions

    International Nuclear Information System (INIS)

    Ozone forms in aqueous alkaline solutions by a reaction between the O3- and CO3- radical ions. This reaction has been demonstrated under conditions favorable for the generation of suitable concentrations of these ions by a high-pressure pulse radiolysis technique. The reaction is O3- + CO3- → O3 + CO32-. Its rate constant k/sub (O3-+CO3-)/ of (6 +- 2) x 107 dm3 mol-1 s-1 has been determined by computer simulation of the reactions involved

  5. Room temperature phosphorescence lifetime and quantum yield of erythrosine B and rose bengal in aerobic alkaline aqueous solution

    International Nuclear Information System (INIS)

    The room-temperature phosphorescence behavior of erythrosine B (ER) and rose bengal (RB) in aerobic aqueous solution at pH 10 (10−4 M NaOH) is investigated. The samples were excited with sliced second harmonic pulses of a Q-switched Nd:glass laser. A gated photomultiplier tube was used for instantaneous fluorescence signal discrimination and a digital oscilloscope was used for signal recording. For phosphorescence lifetime measurement the oscilloscope response time was adjusted to appropriate time resolution and sensitivity by the ohmic input resistance. In the case of phosphorescence quantum yield determination the gated photomultiplier – oscilloscope arrangement was operated in integration mode using 10 MΩ input resistance. Phosphorescence quantum yield calibration was achieved with erythrosine B and rose bengal doped starch films of known quantum yields. The determined phosphorescence lifetimes (quantum yields) of ER and RB in 0.1 mM NaOH are τP=1.92±0.1 μs (φP=(1.5±0.3)×10−5) and 2.40±0.1 μs ((5.7±0.9)×10−5), respectively. The results are discussed in terms of triplet state deactivation by dissolved molecular oxygen. - Highlights: ► Phosphorescence lifetime of fluorone dyes in aerobe aqueous solution is measured. ► Phosphorescence quantum yield of fluorone dyes in aerobe solution is determined. ► Experimental setup with Q-switched laser and gated PMT detection is described. ► Phosphorescence quenching by dissolved molecular oxygen is analyzed. ► Absorption and fluorescence behavior of fluorones in aqueous solution is studied.

  6. An optimization study on removal of Zn from aqueous solution by ultrasound assisted preparation of activated carbon from alkaline impregnated hazelnut shell

    International Nuclear Information System (INIS)

    Nowadays, ultrasound has gained importance in a wide variety of industrial fields especially in wastewater and sewage treatment. Ultrasound exhibits several beneficial effects in solid liquid systems by means of the cavitations phenomenon by causing the formation of many microcracks on the solid surface; thus, it increases the surface area between the reactants and cleans solid reactant or catalyst particle surfaces. In this study, activated carbon adsorbent for removing heavy metal cations such as Zn2+ from aqueous solutions has been prepared. For this purpose, KOH solution was impregnated into hazelnut shells under ultrasonic irradiation. After filtration, hazelnut shells have been carbonized under inert N2 atmosphere. The experiments were planned by statistical design methods. Finally, activated carbons were characterized by the evolution of their zinc adsorption capacity. Optimum preparation conditions were obtained by using constrained optimization program by means of the Matlab computer software. Activated carbon with the maximum adsorption capacity was further characterized by using scanning electron microscopy. The alkaline impregnation into hazelnut shells under ultrasonic irradiation was found to be beneficial for preparation of activated carbon for use as adsorbents to remove Zn2+ from aqueous solutions. (author)

  7. Alkaline earth cation extraction from acid solution

    Science.gov (United States)

    Dietz, Mark; Horwitz, E. Philip

    2003-01-01

    An extractant medium for extracting alkaline earth cations from an aqueous acidic sample solution is described as are a method and apparatus for using the same. The separation medium is free of diluent, free-flowing and particulate, and comprises a Crown ether that is a 4,4'(5')[C.sub.4 -C.sub.8 -alkylcyclohexano]18-Crown-6 dispersed on an inert substrate material.

  8. Enhanced removal of trace Cr(VI) from neutral and alkaline aqueous solution by FeCo bimetallic nanoparticles.

    Science.gov (United States)

    Qin, Nannan; Zhang, Ya; Zhou, Hongjian; Geng, Zhigang; Liu, Gang; Zhang, Yunxia; Zhao, Huijun; Wang, Guozhong

    2016-06-15

    The reactivity of zero valent iron (Fe(0)) for removing Cr(VI) is self-inhibiting under neutral and alkaline conditions, due to the precipitation of ferrous hydroxide on the surface of Fe(0). To overcome this difficulty, we incorporated a second metal (Co) into Fe(0) to form FeCo bimetallic nanoparticles (FeCo BNPs), which can achieve higher activity and significant improvement in the reaction kinetics for the removal of Cr(VI) compared with Fe(0). The FeCo BNPs were synthesized by a hydrothermal reduction method without using any templates. The characterization analysis indicated that the products were highly uniform in large scale with 120-140nm size in diameter. The obtained FeCo BNPs exhibited a remarkable removal ability for Cr(VI) in the pH range of 5.3-10.0. Especially, FeCo BNPs were able to reduce trace Cr(VI) (1.0mgL(-1), pH=7.5) down to about 0.025mgL(-1) within 1h. XPS analysis confirmed that Cr(VI) was reduced to Cr(III) by FeCo BNPs, while Fe and Co was oxidized, implying a chemical reduction process. The enhanced removal of trace Cr(VI) could be originated from the introduction of Co, which not only served as a protecting agent against surface corrosion by galvanic cell effect, but also enhanced the efficient flow of electron transfer between iron and Cr(VI). All the results primarily imply that FeCo BNPs can be employed as high efficient material for wastewater treatment. PMID:26998785

  9. Lyoluminescence of luminol in aqueous alkaline metal hydroxides

    International Nuclear Information System (INIS)

    The lyoluminescence emission spectra of luminol, induced by γ-irradiated NaCl in aqueous alkaline earth metal hydroxides, are recorded. Continuous emission bands are observed in the visible region from 390 to 535 nm. These emission bands on resolution showed two peaks at 430 and 460 nm, respectively in all hydroxides. An additional band of 490 appears in the case of calcium hydroxide. The colour centres released during disintegration of irradiated NaCl crystals in aqueous solution react with luminol to produce various excited molecular species, which are responsible for observed lyoluminescence of luminol. (author) 26 refs.; 7 figs.; 1 tab

  10. Orientation- and concentration-dependent surfactant adsorption on silicon in aqueous alkaline solutions: explaining the changes in the etch rate, roughness and undercutting for MEMS applications

    International Nuclear Information System (INIS)

    We combine spectroscopic ellipsometry (SE), Fourier transform infrared spectroscopy (FT-IR), kinetic Monte Carlo simulations (KMC) and convex corner undercutting analysis in order to characterize and explain the effect of the addition of small amounts of surfactant in alkaline aqueous solutions, such as Triton X-100 in tetra methyl ammonium hydroxide (TMAH). We propose that the surfactant is adsorbed at the silicon–etchant interface as a thin layer, acting as a filter that moderates the surface reactivity by reducing the amount of reactant molecules that reach the surface. According to the SE and FT-IR measurements, the thickness of the adsorbed layer is an orientation- and concentration-dependent quantity, mostly due to the orientation dependence of the surface density of H-terminations and the concentration dependence of the relative rates of the underlying oxidation and etching reactions, which have a direct impact on the number of OH terminations. For partial OH coverage of the surface, the hydration of the OH group effectively acts as an anchoring location for the hydration shell of a surfactant molecule, thus enabling the formation of hydration bridges that amplify the adsorption density of the surfactant. At high concentration, the model explains the large reduction in the etch rate of the exact and vicinal Si{1 1 0} surfaces, and the small changes in the etch rates for the exact and vicinal Si{1 0 0} surfaces. At low concentration, it explains how the etch rate for both families is significantly reduced. The orientation and concentration dependence of the surfactant adsorption explains the dramatic differences in the micron-scale wet-etched patterns obtained using TMAH and TMAH+Triton for microelectromechanical systems applications

  11. Investigation of the reaction of the ozonide ion with neptunium (VI) ions in aqueous alkaline solutions by the method of pulse radiolysis

    International Nuclear Information System (INIS)

    The method of pulse radiolysis with spectrophotometric recording of short-lived particles is used to investigate the kinetics of the reactions of O3- ion-radicals with Np(V) and Np(VI) in alkaline solutions. The rate constant of the first reaction is equal to (2.0 ± 0.3)·106, and of the second, (2.1 ± 0.2)·105 liter/(mole·sec) in 0.2-2.0 M LiOH. The peculiarities of γ-radiolysis of Np(VI) in alkaline solutions containing N2O and in aerated solutions containing K2S2O8 are elucidated. The yield of Np(VII) is determined by the behavior of O3-, which depends on the concentration of Np(VI) and OH-

  12. Aqueous polyethylene oxide solutions

    International Nuclear Information System (INIS)

    A number of aspects concerning the reorientation of polymer, water and ion hydration complexes have been studied in aqueous solution of polyethylene oxide (PEO). The polymer dynamics are investigated by 1H-PEO and 13C-PEO nuclear relaxation experiments. 162 refs.; 30 figs.; 19 tabs

  13. Technetium recovery from high alkaline solution

    Science.gov (United States)

    Nash, Charles A.

    2016-07-12

    Disclosed are methods for recovering technetium from a highly alkaline solution. The highly alkaline solution can be a liquid waste solution from a nuclear waste processing system. Methods can include combining the solution with a reductant capable of reducing technetium at the high pH of the solution and adding to or forming in the solution an adsorbent capable of adsorbing the precipitated technetium at the high pH of the solution.

  14. Influence of acid and alkaline sources on optical, structural and photovoltaic properties of CdSe nanoparticles precipitated from aqueous solution

    Science.gov (United States)

    Coria-Monroy, C. Selene; Sotelo-Lerma, Mérida; Hu, Hailin

    2016-06-01

    CdSe is a widely researched material for photovoltaic applications. One of the most important parameters of the synthesis is the pH value, since it determines the kinetics and the mechanism of the reaction and in consequence, the optical and morphological properties of the products. We present the synthesis of CdSe in solution with strict control of pH and the comparison of ammonia and KOH as alkaline sources and diluted HCl as acid medium. CdSe formation was monitored with photoluminescence emission spectra (main peak in 490 nm, bandgap of CdSe nanoparticles). XRD patterns indicated that CdSe nanoparticles are mainly of cubic structure for ammonia and HCl, but the hexagonal planes appear with KOH. Product yield decreases with pH and also decreases with KOH at constant pH value since ammonia has a double function, as complexing agent and alkaline source. Changes in morphology were observed in SEM images as well with the different alkaline source. The effect of alkaline sources on photovoltaic performance of hybrid organic solar cells with CdSe and poly(3-hexylthiophene) as active layers was clearly observed, indicating the importance of synthesis conditions on optoelectronic properties of promising semiconductor nanomaterials for solar cell applications.

  15. Process for separating cesium ions from aqueous solutions

    International Nuclear Information System (INIS)

    A precipitation agent is added to the aqueous solution and the resulting precipitate containing Cs+ ions is separated from the solution. By this process, caesium is to be separated selectively compared with other alkaline metal ions with great efficiency from aqueous solutions, particularly aqueous MAW (medium activity waste). This is achieved by using a sodium tetraphenyl borate attracting electrons to the phenyl rings and having substitutes. (orig./PW)

  16. Formation of ozone in the reaction between the ozonide radical ion, O/sub 3//sup -/, and the carbonate radical ion, CO/sub 3//sup -/, in aqueous alkaline solutions. [Electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Holcman, J.; Sehested, K.; Bjergbakke, E.; Hart, E.J.

    1982-05-27

    Ozone forms in aqueous alkaline solutions by a reaction between the O/sub 3//sup -/ and CO/sub 3//sup -/ radical ions. This reaction has been demonstrated under conditions favorable for the generation of suitable concentrations of these ions by a high-pressure pulse radiolysis technique. The reaction is O/sub 3//sup -/ + CO/sub 3//sup -/ ..-->.. O/sub 3/ + CO/sub 3//sup 2 -/. Its rate constant k/sub (O/sub 3//sup -/+CO/sub 3//sup -/)/ of (6 +- 2) x 10/sup 7/ dm/sup 3/ mol/sup -1/ s/sup -1/ has been determined by computer simulation of the reactions involved.

  17. A Revisit to the Corrosion Inhibition of Aluminum in Aqueous Alkaline Solutions by Water-Soluble Alginates and Pectates as Anionic Polyelectrolyte Inhibitors

    Directory of Open Access Journals (Sweden)

    Refat Hassan

    2013-01-01

    Full Text Available The corrosion behavior of aluminum (Al in alkaline media in presence of some natural polymer inhibitors has been reinvestigated. The inhibition action of the tested inhibitors was found to obey both Langmuir and Freundlich isotherms models. The inhibition efficiency was found to increase with increasing the inhibitors concentration and decrease with increasing the temperature, suggesting physical adsorption mechanism. Factors such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and temperature affecting the corrosion rates were examined. The kinetic parameters were evaluated, and a suitable corrosion mechanism consistent with the kinetic results obtained is suggested and discussed.

  18. Spectroscopic studies of solutes in aqueous solution.

    Science.gov (United States)

    Chai, Bing-hua; Zheng, Jian-ming; Zhao, Qing; Pollack, Gerald H

    2008-03-20

    Absorption and fluorescence characteristics of aqueous solutions of salts, sugars, and amino acids were studied using UV-vis spectroscopy and spectrofluorometry. Motivation stemmed from unanticipated absorption spectral and fluorescence features of the "exclusion zone" seen adjacent to various hydrophilic surfaces. Those features implied a structure distinct from that of bulk water (Adv. Colloid Interface Sci. 2006, 127, 19). Absorption peaks at approximately 270 nm similar to those observed in the exclusion zone were seen in solutions of the following substances: salts, Nafion 117 solution/film, l-lysine, d-alanine, d-glucose and sucrose. To determine the fate of the absorbed energy, we studied the fluorescence properties of these solutions. The salts showed fluorescence emission around 480-490 nm under different excitation wavelengths. The fluorescence intensity of LiCl was higher than NaCl, which was in turn higher than KCl-the same ordering as the absorption intensities. Fluorescence of Nafion 117 solution/film, l-lysine, d-alanine, d-glucose and sucrose were observed as well, with multiple excitation wavelengths. Hence, at least some of the absorbed energy is released as fluorescence. The results show features closely similar to those observed in the exclusion zone, implying that the aqueous region around the solutes resembles the aqueous zone adjacent to hydrophilic surfaces. Both may be more extensively ordered than previously thought. PMID:18298105

  19. 2010 Water & Aqueous Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Dor Ben-Amotz

    2010-08-13

    Water covers more than two thirds of the surface of the Earth and about the same fraction of water forms the total mass of a human body. Since the early days of our civilization water has also been in the focus of technological developments, starting from converting it to wine to more modern achievements. The meeting will focus on recent advances in experimental, theoretical, and computational understanding of the behavior of the most important and fascinating liquid in a variety of situations and applications. The emphasis will be less on water properties per se than on water as a medium in which fundamental dynamic and reactive processes take place. In the following sessions, speakers will discuss the latest breakthroughs in unraveling these processes at the molecular level: Water in Solutions; Water in Motion I and II; Water in Biology I and II; Water in the Environment I and II; Water in Confined Geometries and Water in Discussion (keynote lecture and poster winners presentations).

  20. Stability of selenourea in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Mel' chekova, Z.E.

    1983-06-10

    Studies of the synthesis of metal selenides from aqueous solutions are being conducted within the framework of investigations on the creation of new semiconductor materials. Selenourea in solution is a complex multicomponent system. The products of hydrolytic decomposition are H/sub 2/CN/sub 2/, Se/sup 2 -/, and HSe/sup -/. As a result of the oxidation of selenium-containing decomposition products by atmospheric oxygen, elementary selenium is formed. The decomposition of selenourea in alkaline sulfite solutions is accompanied by the dissolution of Se/sup 2 -/ and HSe/sup 0/ ions (Se/sup 0/), with the formation of selenosulfate. A study of the kinetics of decomposition was conducted under the conditions of formation of metal selenides, which do not exclude the oxidation process. The end product of the decomposition of selenourea in alkaline sulfite solutions is selenosulfate. The formation of selenosulfate was demonstrated by the isolation of elementary selenium under the action of formaldehyde. The rate constants of the decomposition of selenourea were calculated by the method of changes in concentration, slope of the straight lines, and a logarithmic method. The use of methods of monitoring of selenourea and its decomposition products permitted a theoretical substantiation of the selection of the optimum conditions of formation of metal selenides.

  1. Progress of research on the influence of alkaline cation and alkaline solution on bentonite properties

    International Nuclear Information System (INIS)

    Based on the previous laboratory studies and numerical simulation on bentonite in alkaline environments, the effects of alkaline cation and alkaline solution on mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite are emphasized in this paper, temperature, pH values and concentration are discussed as main affecting factors. When bentonite is exposed to alkaline cation or alkaline solution, microstructure of bentonite will be changed due to the dissolution of montmorillonite and the formation of secondary minerals, which results in the decrease of swelling pressure. The amount of the reduction of swelling pressure depends on the concentration of alkaline solution. Temperature, polyvalent cation, salinity and concentration are the main factors affecting hydraulic properties of bentonite under alkaline conditions. Therefore, future research should focus on the mechanism of coupling effects of weak alkaline solutions on the mineral composition, microstructure, swelling capacity and hydraulic properties of bentonite under different temperatures and different pH values. (authors)

  2. EXTRACTION OF BETULIN BY ALIPHATIC ALCOHOLS C3-C4 FROM AN EXTERNAL LAYER OF A BIRCH BARK HYDROLYZED IN AQUEOUS ALKALINE SOLUTION

    Directory of Open Access Journals (Sweden)

    Владимир Александрович Левданский

    2014-09-01

    Full Text Available It was established, that after hydrolysis of birch bark in water solution of alkali in the presence of isopropanol, butanol and isobutanol two layers were formed. The top layer contained betulin dissolved in alcohol, and the bottom layer contained a water-soluble alkali and its hydrolysis products of bark. Betulin was isolated by the separation and concentration of the alcohol layer. The structure of betulin was confirmed by methods of IR and NMR spectroscopy.

  3. Solubility of pllutonium in alkaline salt solutions

    International Nuclear Information System (INIS)

    Plutonium solubility data from several studies have been evaluated. For each data set, a predictive model has been developed where appropriate. In addition, a statistical model and corresponding prediction intervals for plutonium solubility as a quadratic function of the hydroxide concentration have been developed. Because of the wide range of solution compositions, the solubility of plutonium can vary by as much as three orders of magnitude for any given hydroxide concentration and still remain within the prediction interval. Any nuclear safety assessments that depend on the maximum amount of plutonium dissolved in alkaline salt solutions should use concentrations at least as great as the upper prediction limits developed in this study. To increase the confidence in the prediction model, it is recommended that additional solubility tests be conducted at low hydroxide concentrations and with all of the other solution components involved. To validate the model for application to actual waste solutions, it is recommended that the plutonium solubilities in actual waste solutions be determined and compared to the values predicted by the quadratic model

  4. Radiolysis of Aqueous Toluene Solutions

    International Nuclear Information System (INIS)

    Aqueous toluene solutions have been irradiated with Co γ-rays. In unbuffered solutions the various cresol isomers are formed in a total yield of 0.45, 0.87 and 0.94 molecules/100 eV absorbed energy in argon-, N2O- and air - saturated solutions, respectively. The yields are reduced in acid (pH 3) solutions (G 0.14, 0.14 and 0.52, respectively) but the reduction is compensated by the formation of 1,2-di-phenylethane in yields of 0.49 and 1.60 in argon- and N2O-saturated solutions, respectively. Benzyl radicals are formed through an acid catalysed water elimination reaction from the initially formed hydroxymethylcyclohexadienyl radical. Phenyltolylmethanes, dimethylbiphenyls and partly reduced dimers are also formed during the radiolysis. Hydrogen is formed in the same yield as the molecular yield, g(H2). Xylene isomers and benzene are formed in trace quantities. The most remarkable effects of the addition of Fe(III) ions to deaerated acid toluene solutions are the formation of benzyl alcohol and benzaldehyde and an increase in the yield of 1,2-diphenylethane

  5. Analysis of the electrodeposition process of rhenium and rhenium oxides in alkaline aqueous electrolyte

    International Nuclear Information System (INIS)

    Highlights: • The electrodeposition of rhenium and rhenium oxides from alkaline aqueous electrolyte was investigated. • The authors propose that the electrocrystallization process follows a multi-step reduction mechanism. • The electrodeposited material corresponds to a mixture of metallic rhenium, rhenium (IV) oxide and rhenium (VI) oxide. -- Abstract: The electrodeposition of rhenium and rhenium oxides from an alkaline aqueous solution containing 0.125 mol dm−3 NH4ReO4 + 0.01 mol dm−3 NaOH (pH 13.3 ± 0.1) has been studied. Cyclic voltammetry studies were carried out using two electrodes, polycrystalline platinum and polycrystalline gold, and the galvanostatic electrodeposition was conducted on a pure copper electrode (99.9%). Information regarding rhenium electrodeposits has been obtained by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results in an alkaline aqueous electrolyte suggest that the electrocrystallization process follows a multi-step mechanism influenced by hydrogen adsorption. The main conclusion was that rhenium, rhenium (IV) oxide and rhenium (VI) oxide coexist in the electrodeposited material

  6. DEHYDRATION CONDENSATION IN AQUEOUS SOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Steinman, Gary; Kenyon, Dean H.; Calvin, Melvin

    1965-04-01

    EARLIER investigations have demonstrated that di-cyandiamide (DCDA), the dimer of cyanamide, can successfully promote the dehydration condensation of: (1) glucose and orthophosphate to give glucose-6-phosphate; (2) adenosine and orthophosphate to give adenosine-5'-monophosphate; (3) orthophosphate to give pyrophosphate; (4) alanine to give alanylalanine and alanylalanylalanine. These reactions were carried out in dilute aqueous solutions in the dark. (It was also demonstrated that the combination of ultra-violet light and dicyandiamide could promote the synthesis of dipeptides. This observation has since been confirmed by other investigators.) These experiments were designed to demonstrate one possible means by which such compounds could have been formed on the prebiotic Earth, thus providing materials needed for the origin of living systems. Dicyandiamide itself could have been, present on the primitive Earth as was demonstrated with the ultra-violet irradiation of cyanide solution.

  7. Revisiting zinc passivation in alkaline solutions

    International Nuclear Information System (INIS)

    Highlights: • Zinc passive films were characterised by electrochemical tests coupled with cross sectional FIB-SEM. • Passive layers at pH > 12 comprised of an outer precipitated layer and inner compact oxide. • The electrolyte pH influences the nature/stability of the outer precipitated layer and this impacts the passive state on zinc. • The precipitated layers on zinc at pH 12 support cathode reactions and catalyse oxide growth. -- Abstract: Passive films nominally consist of an inner compact oxide and the outer precipitated layer. In the case of zinc (Zn), the outer layer is mainly precipitated ZnO/Zn(OH)2. Electrolyte pH controls the stability of the outer precipitated layer. In a pH 13 solution, formation of soluble Zn(OH)3− and Zn(OH)42− phases render the precipitated layer unstable increasing zinc corrosion, whereas at pH 12, the precipitated layer (ZnO/Zn(OH)2) is more stable making it an effective anodic barrier upon zinc. These precipitated oxides formed at pH 12 support cathodic reactions on their surface which in turn catalyse further oxide growth by a cathodically driven process. Focused ion beam-scanning electron microscopy (FIB-SEM) was used to support some of the electrochemical assertions, revealing the form and morphology of the passive layers that grow upon zinc exposed to alkaline solutions

  8. Radiolysis of Aqueous Benzene Solutions

    International Nuclear Information System (INIS)

    Aerated and deaerated aqueous solutions of benzene have been irradiated with 60Co γ-rays. The products of radiolysis in deaerated, unbuffered or acid, solutions were phenol, biphenyl, hydrogen and in acid solutions also hydrogen peroxide with the following yields: G(phenol) = 0. 37 (0. 37), G(biphenyl) = 1.3 (1.7), G(H2) = 0.44 (0. 43) and G(H2O2) = 0 (0.60), the figures in brackets giving the results for acid solutions. The results are shown to agree with the conclusion that k(e-aq + H2O2) >> k(H + H2O2). Furthermore, the results indicate that a competition takes place between the reactions: 2 C6H6OH · -> dimer -> biphenyl. C6H7 · + C6H6OH · -> dimer -> biphenyl. The yields in aerated, unbuffered or acid, solutions were: G(phenol) = 2.1 (2.3), G(biphenyl) = 0 (0), and G(H2O2) = 2.2 (3.1), the figures in brackets being valid for acid solutions. The ratio k(H + C6H6)/k(H + O2) was 1.4x10-2. The results indicate that peroxides, or more probably hydroperoxides, take part in the reactions. After the addition of Fe2+ or Fe3+ to aerated acid solutions G(phenol) was increased to 6.6 and 3.4 respectively. Oxygen was consumed more rapidly in the presence of Fe. Reaction mechanisms are discussed

  9. Extraction of lithium ion from alkaline aqueous media by a liquid surfactant membrane

    International Nuclear Information System (INIS)

    Extraction of lithium ion from aqueous alkaline media by a liquid surfactant membrane was performed using a mixture of LIX54 and TOPO as the extractant. Stripping of lithium from the kerosene solution to the acid solution was suppressed with increasing content of polyamine (ECA) surfactant. The extraction rate of lithium by the liquid membrane could be interpreted taking account of an interfacial resistance due to ECA. It was confirmed that swelling of the (W/O) emulsion drops by water permeation through the liquid membrane is evaluated in terms of a change in osmotic pressure gradient between the external and internal aqueous phases during the lithium extraction. In the present operation, the extraction ratio of Li+ from the external feed and the uptake into the internal phase reached as high as 95%. (author)

  10. Modeling reactive geochemical transport of concentrated aqueous solutions

    Science.gov (United States)

    Zhang, Guoxiang; Zheng, Zuoping; Wan, Jiamin

    2005-02-01

    Aqueous solutions with ionic strength larger than 1 M are usually considered concentrated aqueous solutions. These solutions can be found in some natural systems and are also industrially produced and released into accessible natural environments, and as such, they pose a big environmental problem. Concentrated aqueous solutions have unique thermodynamic and physical properties. They are usually strongly acidic or strongly alkaline, with the ionic strength possibly reaching 30 M or higher. Chemical components in such solutions are incompletely dissociated. The thermodynamic activities of both ionic and molecular species in these solutions are determined by the ionic interactions. In geological media the problem is further complicated by the interactions between the solutions and sediments and rocks. The chemical composition of concentrated aqueous solutions when migrating through the geological media may be drastically altered by these strong fluid-rock interactions. To effectively model reactive transport of concentrated aqueous solutions, we must take into account the ionic interactions. For this purpose we substantially extended an existing reactive transport code, BIO-CORE2D©, by incorporating a Pitzer ion interaction model to calculate the ionic activity. In the present paper, the model and two test cases of the model are briefly introduced. We also simulate a laboratory column experiment in which the leakage of highly alkaline waste fluid stored at Hanford (a U.S. Department of Energy site, located in Washington State) was studied. Our simulation captures the measured pH evolution and indicates that all the reactions controlling the pH evolution, including cation exchanges and mineral dissolution/precipitation, are coupled.

  11. Nanoporous activated carbon cloth for capacitive deionization of aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Han-Jun [Department of Materials Science, Hanseo University, Seosan, 352-820 (Korea, Republic of); Lee, Jong-Ho [Department of Chemistry, Hanseo University, Seosan, 352-820 (Korea, Republic of); Ahn, Hong-Joo [Korea Atomic Energy Research Institute, Daejeon, 305-600 (Korea, Republic of); Jeong, Yongsoo [Korea Institute of Machinery and Materials, Changwon, 641-010 (Korea, Republic of); Kim, Young-Jig [Department of Metallurgical Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Chi, Choong-Soo [School of Advanced Materials Engineering, Kookmin University, Seoul, 136-702 (Korea, Republic of)]. E-mail: cschi@kookmin.ac.kr

    2006-09-25

    Activated nanostructured-carbon cloths with a high ratio of surface area to volume are used as electrode for capacitive deionization. The electrochemical properties on capacitive deionization for NaCl solution have been investigated to improve efficiency of capacitive deionization properties from aqueous solution, employing chemical surface-modification by etching in alkaline and acidic solution. The removal efficiency of inorganic salts of activated carbon cloths by chemical modification significantly increased. Specially the carbon cloth surface modified in HNO{sub 3} showed an effect of improvement in the CDI efficiency due to not only ion adsorption by an electric double layer, but also electron transfer by Faradaic reaction.

  12. The aluminum chemistry and corrosion in alkaline solutions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Jinsuo [International Nuclear System Engineering, MS-K 575, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)], E-mail: jszhang@lanl.gov; Klasky, Marc; Letellier, Bruce C. [International Nuclear System Engineering, MS-K 575, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2009-02-15

    Aluminum-alkaline solution systems are very common in engineering applications including nuclear engineering. Consequently, a thorough knowledge of the chemistry of aluminum and susceptibility to corrosion in alkaline solutions is reviewed. The aluminum corrosion mechanism and corrosion rate are examined based on current experimental data. A review of the phase transitions with aging time and change of environment is also performed. Particular attention is given to effect of organic and inorganic ions. As an example, the effect of boron is examined in detail because of the application in nuclear reactor power systems. Methods on how to reduce the corrosion rate of aluminum in alkaline solutions are also highlighted.

  13. γ-radiation induced tetracycline removal in an aqueous solution

    International Nuclear Information System (INIS)

    Degradation effect of tetracycline (TC) by γ-radiation was investigated in an aqueous solution. The effects of initial concentrations of TC, pH values, combining with H2O2 or CH3OH on degradation of TC were studied. Results showed that TC can be effectively degradated by γ-irradiation in an aqueous solution. Degradation of TC could be remarkably improved both in acid solution and alkaline solution, especially when pH value was 9.0. In addition, H2O2 could gently promote degradation of TC induced by γ-radiation. While, CH3OH markedly restrained degradation of TC induced by γ-radiation. The degradation mechanism of TC was supposed by results of quantum chemical calculations and LC-MS. Results proved that degradation of TC induced by γ-radiation was mainly ascribed to · OH oxidation. (authors)

  14. Interfacial Thermodynamics of Coexisting Aqueous Polymer Solutions

    NARCIS (Netherlands)

    Vis, M.

    2015-01-01

    Phase separation is commonly observed when two different polymers are present in aqueous solution, forming aqueous two-phase systems which typically consist for 90% of water. It is demonstrated that the presence of charge on one of the polymers results in an electric potential difference between the

  15. Electron beam irradiation induced degradation of polyvinyl alcohol in aqueous solution

    International Nuclear Information System (INIS)

    Background: Polyvinyl alcohol (PVA) has been widely used in the industry of textile, however, its aqueous solution was difficult to be biodegraded under natural conditions. Purpose: In this study, the PVA in aqueous solution was degraded by electron beam irradiation. Methods: Radioactive ray from electron accelerator was used for degradation of PVA aqueous solution. The effects of different radiation dose and pH on the CODCr and BOD5 values of PVA aqueous solution were investigated. The precipitation generated from acidic irradiated PVA aqueous solution was used for infrared spectroscopy analysis. Results: CODCr values of neutral and alkaline PVA aqueous solution were not significantly changed in the radiation dose range of 0-30 kGy. Acidic PVA aqueous solution after 20-30 kGy dose irradiation produced precipitation obviously. The CODCr values were significantly reduced by 97%-98%. Infrared spectrum analysis showed that precipitation was cross-linked PVA. With radiation dose increasing, BOD5 values of different pH of PVA aqueous solution was gradually reduced, the acidic BOD5 values were minimal under the same radiation dose. The B/C values of neutral and alkaline PVA aqueous solution irradiated by the dose range of 0-30 kGy was no significantly changed. However, the B/C values of acidic PVA aqueous solution increased obviously after 20-30 kGy irradiation, and it increased 14-16 times. Conclusions: This study indicated that under the acidic circumstance, the CODCr values of PVA aqueous solution decreased significantly, PVA in aqueous solution was removed efficiently by electron beam irradiation, and the potential of biodegradation was also improved. (authors)

  16. Tannin (Polyphenol) Stability in Aqueous Solutions

    Science.gov (United States)

    Understanding the chemical stability of tannins (polyphenolics) in soils is critical to understanding their biological activities and fate. We examined the stability of chemically defined tannins in aqueous solutions under conditions simulating natural and laboratory conditions. We evaluated tanni...

  17. E-beam radiolysis of aqueous dimethyl phthalate solution

    International Nuclear Information System (INIS)

    To investigate the influence of radiolysis on kinetics and factors of dimethyl phthalate (DMP), the aqueous DMP solution is degraded by 1.8 MeV E-beam, following pseudo-first-order kinetics. The rate constant of DMP degradation decreased exponentially with increasing initial DMP concentration. The DMP is favorably degraded by radical scavengers under its low concentration and alkaline condition. At high doses, the DMP is attacked by eaq- and ·OH, producing monomethyl phthalate, phthalate acid, and a series of aliphatic carboxylic acids, which are completely mineralized into H2O and CO2. (authors)

  18. Study of the physicochemical properties of the interface between titanium dioxide and various aqueous solutions

    International Nuclear Information System (INIS)

    The aim of this work is the study of ion exchange capacity of titanium dioxide in view of high temperature water purification and radioactive effluent processing because of its resistance to heat and radiations. Titanium dioxide is obtained by alkaline hydrolysis of an aqueous solution of Ti (IV) and is characterized by analytical physical chemistry methods. Interface between Ti02 and simple aqueous solutions (electrolytes) is more particularly studied by potentiometry

  19. Radiolysis of HA in aqueous solutions using gamma rays

    International Nuclear Information System (INIS)

    The present work investigated the radiolysis of HA (Humic acids) in aqueous solutions and under gamma radiation. Absorbances at the range of 200-800 nm and chemical oxygen demand (COD) were used to characterize the degree of degradation of HA, The results indicated that absorbances and the concentrations of COD were decreased with increasing of irradiation dose while with increasing of irradiation dose the pH of the solutions was decreased at first and then increase. In addition, the effects of initial pH and primary solution concentrations on HA degradation were also investigated. It is shown that the higher primary solution concentrations, the lower degradation efficiency under the same irradiation dose. And the degradation efficiency of HA under neutral conditions is better than in acidic or alkaline conditions. (authors)

  20. Alkaline solution absorption of carbon dioxide method and apparatus

    Science.gov (United States)

    Hobbs, D.T.

    1991-01-01

    Disclosed is a method for measuring the concentration of hydroxides (or pH) in alkaline solutions, using the tendency of hydroxides to adsorb CO{sub 2}. The method comprises passing CO{sub 2} over the surface of an alkaline solution in a remote tank before and after measurements of the CO{sub 2} concentration. Comparison of the measurements yields the adsorption fraction from which the hydroxide concentration can be calculated using a correlation of hydroxide or pH to adsorption fraction. A schematic is given of a process system according to a preferred embodiment of the invention. 2 figs.

  1. Interfacial Thermodynamics of Coexisting Aqueous Polymer Solutions

    OpenAIRE

    Vis, M

    2015-01-01

    Phase separation is commonly observed when two different polymers are present in aqueous solution, forming aqueous two-phase systems which typically consist for 90% of water. It is demonstrated that the presence of charge on one of the polymers results in an electric potential difference between the two phases. Upon phase separation, the polyelectrolyte is confined in majority to one of the phases. Although small ions can equilibrate freely between the phases, the restriction of macroscopic c...

  2. Precipitation of neptunium dioxide from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, K E

    1999-12-01

    Tens of thousands of metric tons of highly radioactive, nuclear waste have been generated in the US. Currently, there is no treatment or disposal facility for these wastes. Of the radioactive elements in high-level nuclear waste, neptunium (Np) is of particular concern because it has a long half-life and may potentially be very mobile in groundwaters associated with a proposed underground disposal site at Yucca Mountain, Nevada. Aqueous Np concentrations observed in previous, short-term solubility experiments led to calculated potential doses exceeding proposed long-term regulatory limits. However, thermodynamic data for Np at 25 C showed that these observed aqueous Np concentrations were supersaturated with respect to crystalline NpO{sub 2}. It was hypothesized that NpO{sub 2} is the thermodynamically stable solid phase in aqueous solution, but it is slow to form in an aqueous solution of NpO{sub 2}{sup +} on the time scale of previous experiments. The precipitation of NpO{sub 2} would provide significantly lower aqueous Np concentrations leading to calculated doses below proposed regulatory limits. To test this hypothesis, solubility experiments were performed at elevated temperature to accelerate any slow precipitation kinetics. Ionic NpO{sub 2}{sup +} (aq) was introduced into very dilute aqueous solutions of NaCl with initial pH values ranging from 6 to 10. The reaction vessels were placed in an oven and allowed to react at 200 C until steady-state aqueous Np concentrations were observed. In all cases, aqueous Np concentrations decreased significantly from the initial value of 10{sup {minus}4} M. The solids that formed were analyzed by x-ray powder diffraction, x-ray absorption spectroscopy, and scanning electron microscopy. The solids were determined to be high-purity crystals of NpO{sub 2}. This is the first time that crystalline NpO{sub 2} has been observed to precipitate from NpO{sub 2}{sup +}(aq) in near-neutral aqueous solutions. The results obtained

  3. An experimental study of magnesite precipitation rates at neutral to alkaline conditions and 100-200 °C as a function of pH, aqueous solution composition and chemical affinity

    Science.gov (United States)

    Saldi, Giuseppe D.; Schott, Jacques; Pokrovsky, Oleg S.; Gautier, Quentin; Oelkers, Eric H.

    2012-04-01

    Magnesite precipitation rates were measured at temperatures from 100 to 200 °C as a function of saturation state and reactive fluid composition in mixed flow reactors. Measured rates were found to increase systematically with increasing saturation state but to decrease with increasing reactive fluid aqueous CO32- activity and pH. Measured rates are interpreted through a combination of surface complexation models and transition state theory. In accord with this formalism, constant saturation state BET surface area normalized magnesite precipitation rates (rMg) are a function of the concentration of protonated Mg sites at the surface (>MgOH2+) and can be described using: rMg=kMg-Kn 1-ΩMgn where kMg- represents a rate constant, KOH and KCO3 stand for equilibrium constants, ai designates the activity of the subscripted aqueous species, n refers to a reaction order equal to 2, and ΩMg denotes the saturation state of the reactive solution with respect to magnesite. Retrieved values of n are consistent with magnesite precipitation control by a spiral growth mechanism. The temperature variation of the rate constant can be described using kMg-=Aaexp(-Ea/RT), where Aa represents a pre-exponential factor equal to 5.9 × 10-5 mol/cm2/s, Ea designates an activation energy equal to 80.2 kJ/mol, R denotes the gas constant, and T corresponds to the absolute temperature. Comparison of measured magnesite precipitation rates with corresponding forsterite dissolution rates suggest that the relatively slow rates of magnesite precipitation may be the rate limiting step in mineral carbonation efforts in ultramafic rocks.

  4. Diffusion coefficients of paracetamol in aqueous solutions

    International Nuclear Information System (INIS)

    Highlights: ► Mutual diffusion coefficients of paracetamol in aqueous dilute solutions. ► Influence of the thermodynamic factors on the variation of their mutual diffusion coefficients. ► Estimation of the mutual limiting diffusion coefficients of the molecular, Dm0, and ionized forms, D±0, of this drug. - Abstract: Binary mutual diffusion coefficients measured by the Taylor dispersion method, for aqueous solutions of paracetamol (PA) at concentrations from (0.001 to 0.050) mol·dm−3 at T = 298.15 K, are reported. From the Nernst–Hartley equation and our experimental results, the limiting diffusion coefficient of this drug and its thermodynamic factors are estimated, thereby contributing in this way to a better understanding of the structure of such systems and of their thermodynamic behaviour in aqueous solution at different concentrations.

  5. Qualitative aspects of the degradation of mitomycins in alkaline solution.

    Science.gov (United States)

    Beijnen, J H; den Hartigh, J; Underberg, W J

    1985-01-01

    The major degradation product in alkaline solution of mitomycin A, mitomycin C and porfiromycin is the corresponding 7-hydroxymitosane. The isolation and the physico-chemical and analytical properties of these compounds and their derivatized analogues are discussed. Data are presented on the degradation of mitomycin C at extremely high pH values. PMID:16867711

  6. Potentiodynamic characteristics of cadmium and silver in alkaline solutions

    International Nuclear Information System (INIS)

    The potentiodynamic and ellipsometric characteristics of cadmium and silver in alkaline solutions are studied. The phenomenology of both electrodes shows some common features which are interpreted in termo of a complex hydrated oxide anodic film structure resulting from simultaneous electrochemical and chemical reactions. The kinetics of film growth fits the predictions of nucleation and growth models. (C.L.B.)

  7. Hydrophobic Solvation: Aqueous Methane Solutions

    Science.gov (United States)

    Konrod, Oliver; Lankau, Timm

    2007-01-01

    A basic introduction to concept of a solvation shell around an apolar solute as well as its detection is presented. The hydrophobic solvation of toluene is found to be a good teaching example which connects macroscopic, phenomenological thermodynamic results with an atomistic point of view.

  8. Investigation of adsorption interaction of cadmium oxide with antimony (3) in alkaline solutions

    International Nuclear Information System (INIS)

    Adsorption processes on cadmium oxide in pure antimonite alkaline (KOH) solutions and in the presence of organic additions (sodium salt of carboxymethylcellulose, straw oil) have been studied. It is shown, that in the systems being studied, the chemosorptional interaction, leading to a sharp change in the adsorbent surface state is observed. It is established that the formation of a surface high-disperse cadmium oxide-antimony com ound on the cadmium oxide results in practically complete suppression of the cadmium oxide hydration process in aqueous solutions

  9. Experiences in the capture of combustion gases of rice husk with alkaline solutions

    OpenAIRE

    Abelardo Prada Matiz; Caroll Edith Cortés Castillo

    2011-01-01

    The present work is aimed at studying the processes of capture of combustion gases of rice husk with alkaline solutions of sodium hydroxide (NaOH) and potassium hydroxide (KOH) and its subsequent transformation into calcium carbonate (CaCO3), a substance useful in agriculture, by adding calcium chloride(CaCl2) in aqueous solution. Was determined the basic characteristics of the process of capture of combustion gases such as reaction time, pH, mass and performance of calcium carbonate (CaCO3) ...

  10. Issues in Freeze Drying of Aqueous Solutions

    Institute of Scientific and Technical Information of China (English)

    王维; 陈墨; 陈国华

    2012-01-01

    Freeze drying or lyophilization of aqueous solutions is widely used in pharmaceutical industry. The in-creased importance Of the process is gaining a worldwide interest of research. A growing body of literature has demonstrated that the scientific approach can result in improved product quality with minimum trial and error em-piricism. Formulation and process development need a systematical understanding of the physical chemistry of freezing and freeze drying, material science and mechanisms of heat and mass transfer. This paper presents an overview on freeze ding of aqueous solutions based on publications in the past few decades. The important issuesof the process are analyzed.

  11. IUPAC-NIST Solubility Data Series. 95. Alkaline Earth Carbonates in Aqueous Systems. Part 1. Introduction, Be and Mg

    Science.gov (United States)

    De Visscher, Alex; Vanderdeelen, Jan; Königsberger, Erich; Churagulov, Bulat R.; Ichikuni, Masami; Tsurumi, Makoto

    2012-03-01

    The alkaline earth carbonates are an important class of minerals. This volume compiles and critically evaluates solubility data of the alkaline earth carbonates in water and in simple aqueous electrolyte solutions. Part 1, the present paper, outlines the procedure adopted in this volume in detail, and presents the beryllium and magnesium carbonates. For the minerals magnesite (MgCO3), nesquehonite (MgCO3.3H2O), and lansfordite (MgCO3.5H2O), a critical evaluation is presented based on curve fits to empirical and/or thermodynamic models. Useful side products of the compilation and evaluation of the data outlined in the introduction are new relationships for the Henry constant of CO2 with Sechenov parameters, and for various equilibria in the aqueous phase including the dissociation constants of CO2(aq) and the stability constant of the ion pair MCO30(aq) (M = alkaline earth metal). Thermodynamic data of the alkaline earth carbonates consistent with two thermodynamic model variants are proposed. The model variant that describes the Mg2+-HCO3- ion interaction with Pitzer parameters was more consistent with the solubility data and with other thermodynamic data than the model variant that described the interaction with a stability constant.

  12. Mechanism of gold dissolving in alkaline thiourea solution

    Institute of Scientific and Technical Information of China (English)

    CHAI Li-yuan; WANG Yun-yan

    2007-01-01

    Reaction mechanism of gold dissolving in alkaline thiourea solution was studied by electrochemical methods, such as cyclic voltammetry, chronopotentiometry, AC impedance, linear sweep voltammetry. Apparent activation energy of anodic process of gold electrode dissolving in alkaline thiourea solution is 14.91 kJ/mol. Rate determining step is the process of gold thiourea complex diffusing away from electrode surface to solution. The results of AC impedance and chronopotentiometry indicate that thiourea adsorbs on gold electrode surface before dissolving in solution. There does not exist proceeding chemical reactions. Formamidine disulfide, the decomposed product of thiourea, does not participate the process of gold dissolution and thiourea complex. Species with electro-activity produced in the process of electrode reaction adsorbs on the electrode surface. In alkaline thiourea solution, gold dissolving mechanism undergoes the following courses: adsorption of thiourea on electrode surface; charge transfer from gold atom to thiourea molecule; Au[SC(NH2)2]ads+ receiving a thiourea molecule and forming stable Au[SC(NH2)2]2+; and then Au[SC(NH2)2]2+diffusing away from the electrode surface to solution, the last step is the rate-determining one.

  13. Quasi-Immiscible Spreading of Aqueous Surfactant Solutions on Entangled Aqueous Polymer Solution Subphases

    OpenAIRE

    Sharma, Ramankur; Corcoran, Timothy E.; Garoff, Stephen; Przybycien, Todd M.; Swanson, Ellen R.; Tilton, Robert D.

    2013-01-01

    Motivated by the possibility of enhancing aerosol drug delivery to mucus-obstructed lungs, the spreading of a drop of aqueous surfactant solution on a physically entangled aqueous poly(acrylamide) solution subphase that mimics lung airway surface liquid was investigated. Sodium dodecyl sulfate was used as the surfactant. To visualize spreading of the drop and mimic the inclusion of a drug substance, fluorescein, a hydrophilic and non-surface active dye, was added to the surfactant solution. T...

  14. Radium removal from aqueous sulphate solutions

    International Nuclear Information System (INIS)

    A process for removing radium from an aqueous sulphate solution also containing magnesium is claimed. The pH of the solution is less than 10. A soluble barium salt is added to the solution to precipitate radium as barium radium sulphate. The pH of the solution is then raised to at least 11 to precipitate an insoluble magnesium compound which collects the barium radium sulphate precipitate. The precipitates are separated from the solution. If the sulphate solution contains dissolved magnesium and other impurities at a pH not greater than 7, then the first step in the process involves raising the pH of the solution to a value not greater than 10 to precipitate some of the magnesium and a substantial proportion of the other impurities and separating the precipitate from the solution. The radium removal is a step in the treatment of liquids resulting from the sulphuric acid leaching of uranium ores

  15. Aqueous solutions of ionic liquids: microscopic assembly

    NARCIS (Netherlands)

    J.M. Vicent-Luna; D. Dubbeldam; P. Gómez-Álvarez; S. Calero

    2016-01-01

    Aqueous solutions of ionic liquids are of special interest, due to the distinctive properties of ionic liquids, in particular, their amphiphilic character. A better understanding of the structure-property relationships of such systems is hence desirable. One of the crucial molecular-level interactio

  16. SEPARATION OF SCANDIUM FROM AQUEOUS SOLUTIONS

    Science.gov (United States)

    Peppard, D.F.; Nachtman, E.S.

    1958-02-25

    This patent relates to a process for the separation of scandium from yttrium, thorium, and trivalent rare earths and with their separation from each other. It has been found that scandium and yttrium can be separated from trivalent rare earths in acidic solution, for example, a solution 6 M in HCl, by contacting with tributyl phosphate, whereupon the scandum is preferentially extracted into the organic phase, leaving the yttrium and trivalent rare earths in the aqueous phase.

  17. Study of aqueous solutions of sodium linoleate

    Energy Technology Data Exchange (ETDEWEB)

    Van der Linde, G.J. (Phosphate Development Corporation, Phalaborwa); Van Berge, P.C. (Rand Afrikaans Univ., Johannesburg (South Africa))

    1983-12-01

    During the development of a technique for measuring fatty acid absorption on finely divided minerals using a radiochemical method, absorption isotherms were obtained which displayed maxima. It was found that these results were due to the presence of stable micelles in the solutions. This has been established by measuring the surface tension, surface film pressure, and specific conductance of dilute aqueous solutions of sodium linoleate.

  18. [Photochemical degradation of chlorothalonil in aqueous solution].

    Science.gov (United States)

    Li, Xuede; Hua, Rimao; Yue, Yongde; Li, Ying; Tang, Feng; Tang, Jun

    2006-06-01

    The study on the effects of light source, solution pH and temperature, and surfactant on the photochemical degradation of chlorothalonil showed that the half-life of chlorothalonil photodegradation under high pressure mercury lamp (HPML), UV lamp and sunlight was 22.4, 82.5 and 123.8 min, respectively. Under HPML and sunlight, chlorothalonil had a higher photolysis rate in alkaline solution than in neutral and acid solution. The photolysis rate increased with increasing solution temperature in the range of 10 degrees C - 40 degrees C, which was doubled when the temperature increased every 10 degrees C. Sodium laurylsulfonate (SDS), sodium dodecylbenzene sulfonate (SDBS), Tween 60 and Span 20 showed significant photosensitizing effects, while cetyltrimethylammonium bromide (CTAB) had significant photoquench effect on the photolysis of chlorothalonil. PMID:16964947

  19. A new electrochemical oscillatory system of bromate in alkaline solution

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new electrochemical oscillatory system of bromate in alkaline solution is reported. In PtBromate-Alkaline solution system, two different types of electrochemical oscillations (Type Ⅰ and Type Ⅱ) can be observed. Type Ⅰ appears before hydrogen evolution and Type Ⅱ involves periodic hydrogen evolution. Type Ⅰ relates to the adsorption/desorption of the hydrogen on platinum electrode, and Type Ⅱ with periodic oscillation stems from the coupling of electrochemical reactions (the reduction of bromate and evolution hydrogen reaction) with mass transfer (diffusion and convection). More over, under the right conditions, the two types appear in different oscillatory modes, for example,simple periodical mode and mixed one, etc,, Crossed cycle in the cyclic voltammograms, which is the basiccharacteristics for electrochemical oscillatory systems, has also been observed as expected.

  20. Mechanism of zinc electroplating in alkaline zincate solution

    Institute of Scientific and Technical Information of China (English)

    PENG Wen-jie; WANG Yun-yan

    2007-01-01

    The cathodic deposition properties and mechanism of Zn in alkaline zincate solution were studied by electrochemical techniques. The results show that Zn2+ exists in the alkaline solution in the form of Zn(OH)42-. The apparent activation energy of the electrode reaction is 38.93 kJ/mol, which indicates that the discharge of Zn(OH)42- on cathode is controlled by electrochemical polarization, and accompanied by a preceding chemical reaction. The diflusion coefficient of Zn(OH)42- is 2.452×10~cm2/s. Zn(OH)2 is the species directly discharged on the cathode surface. Based on the above results the mechanism of zinc electroplating in alkaline zincate solution was put forward.The discharged species is Zn(OH)2 formed from the preceding chemical reaction, which becomes Zn(OH)ad when gaining one electron, and then gaining the second electron to become Zn.The first electron gaining step is rate determining one.

  1. Flocculation performance of a cationic biopolymer derived from a cellulosic source in mild aqueous solution.

    Science.gov (United States)

    Liimatainen, Henrikki; Sirviö, Juho; Sundman, Ola; Visanko, Miikka; Hormi, Osmo; Niinimäki, Jouko

    2011-10-01

    The flocculation behavior of cationic, quaternary ammonium groups containing cellulosic biopolymers, CDACs, synthesized by cationizing dialdehyde cellulose in mild aqueous solution was studied in a kaolin suspension. In particular, the role of CDAC dosage and solution pH, NaCl concentration, and temperature were clarified. In addition, the initial apparent charge densities (CDs), particle sizes, ζ-potential, and stability of CDs were determined. CDACs possessed a high flocculation activity in neutral and acidic solutions, but a significant decrease was observed in alkaline solutions (pH >9). This was also seen as a decline in the apparent CD and particle size of the CDACs in alkaline conditions. The measurements also indicated that the apparent CD decreased to a constant level of 3 mmol/g in aqueous solutions. However, no notable decrease in flocculation performance was obtained after several days of storage. Moreover, the variation of NaCl concentration and temperature did not affect the flocculation activity. PMID:21862324

  2. Characterization of aqueous silver nitrate solutions for leakage tests

    Directory of Open Access Journals (Sweden)

    José Ferreira Costa

    2011-06-01

    Full Text Available OBJECTIVE: To determine the pH over a period of 168 h and the ionic silver content in various concentrations and post-preparation times of aqueous silver nitrate solutions. Also, the possible effects of these factors on microleakage test in adhesive/resin restorations in primary and permanent teeth were evaluated. MATERIAL AND METHODS: A digital pHmeter was used for measuring the pH of the solutions prepared with three types of water (purified, deionized or distilled and three brands of silver nitrate salt (Merck, Synth or Cennabras at 0, 1, 2, 24, 48, 72, 96 and 168 h after preparation, and storage in transparent or dark bottles. Ionic silver was assayed according to the post-preparation times (2, 24, 48, 72, 96, 168 h and concentrations (1, 5, 25, 50% of solutions by atomic emission spectrometry. For each sample of each condition, three readings were obtained for calculating the mean value. Class V cavities were prepared with enamel margins on primary and permanent teeth and restored with the adhesive systems OptiBond FL or OptiBond SOLO Plus SE and the composite resin Filtek Z-250. After nail polish coverage, the permanent teeth were immersed in 25% or 50% AgNO3 solution and the primary teeth in 5% or 50% AgNO3 solutions for microleakage evaluation. ANOVA and the Tukey's test were used for data analyses (α=5%. RESULTS: The mean pH of the solutions ranged from neutral to alkaline (7.9±2.2 to 11.8±0.9. Mean ionic silver content differed depending on the concentration of the solution (4.75±0.5 to 293±15.3 ppm. In the microleakage test, significant difference was only observed for the adhesive system factor (p=0.000. CONCLUSIONS: Under the tested experimental conditions and based on the obtained results, it may be concluded that the aqueous AgNO3 solutions: have neutral/alkaline pH and service life of up to 168 h; the level of ionic silver is proportional to the concentration of the solution; even at 5% concentration, the solutions were

  3. Characterization of aqueous silver nitrate solutions for leakage tests

    Science.gov (United States)

    COSTA, José Ferreira; SIQUEIRA, Walter Luiz; LOGUERCIO, Alessandro Dourado; REIS, Alessandra; de OLIVEIRA, Elizabeth; ALVES, Cláudia Maria Coelho; BAUER, José Roberto de Oliveira; GRANDE, Rosa Helena Miranda

    2011-01-01

    Objectives To determine the pH over a period of 168 h and the ionic silver content in various concentrations and post-preparation times of aqueous silver nitrate solutions. Also, the possible effects of these factors on microleakage test in adhesive/resin restorations in primary and permanent teeth were evaluated. Material and Methods A digital pHmeter was used for measuring the pH of the solutions prepared with three types of water (purified, deionized or distilled) and three brands of silver nitrate salt (Merck, Synth or Cennabras) at 0, 1, 2, 24, 48, 72, 96 and 168 h after preparation, and storage in transparent or dark bottles. Ionic silver was assayed according to the post-preparation times (2, 24, 48, 72, 96, 168 h) and concentrations (1, 5, 25, 50%) of solutions by atomic emission spectrometry. For each sample of each condition, three readings were obtained for calculating the mean value. Class V cavities were prepared with enamel margins on primary and permanent teeth and restored with the adhesive systems OptiBond FL or OptiBond SOLO Plus SE and the composite resin Filtek Z-250. After nail polish coverage, the permanent teeth were immersed in 25% or 50% AgNO3 solution and the primary teeth in 5% or 50% AgNO3 solutions for microleakage evaluation. ANOVA and the Tukey's test were used for data analyses (α=5%). Results The mean pH of the solutions ranged from neutral to alkaline (7.9±2.2 to 11.8±0.9). Mean ionic silver content differed depending on the concentration of the solution (4.75±0.5 to 293±15.3 ppm). In the microleakage test, significant difference was only observed for the adhesive system factor (p=0.000). Conclusions Under the tested experimental conditions and based on the obtained results, it may be concluded that the aqueous AgNO3 solutions: have neutral/alkaline pH and service life of up to 168 h; the level of ionic silver is proportional to the concentration of the solution; even at 5% concentration, the solutions were capable of

  4. Removal of radium from aqueous sulphate solutions

    International Nuclear Information System (INIS)

    Radium is often present in ores and an aqueous solution associated with the ore may consequently contain dissolved radium. It is frequently necessary to remove radium from such solutions to reduce the total radium content to a prescribed low level before the solution can be returned to the environment. The present invention is based on the discovery that the total radium content can be reduced to a satisfactory level within a reasonable time by adding a soluble barium salt to a radium-containing sulphate solution which also contains dissolved magnesium at a pH not greater than about 0 to precipitate radium as barium radium sulphate, raising the pH to at least 11 to precipitate an insoluble magnesium compound which collects the barium radium sulphate precipitate, and separating substantially all of the precipitates from the solution

  5. Uranyl fluoride luminescence in acidic aqueous solutions

    International Nuclear Information System (INIS)

    Luminescence emission spectra and decay rates are reported for uranyl species in acidic aqueous solutions containing HF or added NaF. The longest luminescence lifetime, 0.269 ± 0.006 ms, was observed from uranyl in 1 M HF + 1 M HClO4 at 296 K and decreased with increasing temperature. Based on a luminescence dynamics model that assumes equilibrium among electronically excited uranyl fluoride species and free fluoride ion, this long lived uranyl luminescence in aqueous solution is attributed primarily to UO2F2. Studies on the effect of added LiNO3 or Na2WO4·2H2O showed relatively weak quenching of uranyl fluoride luminescence which suggests that high sensitivity determination of the UF6 content of WF6 gas should be feasible via uranyl luminescence analysis of hydrolyzed gas samples of impure WF6

  6. Zeolites as alcohol adsorbents from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Cekova Blagica

    2006-01-01

    Full Text Available The potential usage of zeolites as adsorbents for the removal of organic molecules from water was investigated in a series of experiments with aqueous solutions of lower alcohols. This could represent a simple solution to the problem of cleaning up industrial wastewater as well as recovering valuable chemicals at relatively low costs. Adsorption isotherms of the Langmuir type were applied, and calculations showed that the amount of propanol adsorbed on silicalite corresponded to approximately 70% of the pore volume. The adsorption process is simple, and recovery of the more concentrated products is easily done by heat treatment and/or at lowered pressures. Adsorption experiments with aqueous acetone showed that silicalite had approximately the same adsorption capacity for acetone as for n-propanol. Heats of adsorption were determined calorimetrically.

  7. Interactions of N,N'-dimethylaminoethanol with steel surfaces in alkaline and chlorine containing solutions

    Science.gov (United States)

    Welle, A.; Liao, J. D.; Kaiser, K.; Grunze, M.; Mäder, U.; Blank, N.

    1997-10-01

    Formulations based on dilute aqueous solutions of N,N'-dimethylethanolamine (DMEA) are used to protect reinforcement steel bars ('rebar') in concrete from corrosion. In a previous paper we discussed the usefulness of X-ray photoelectron spectroscopy (XPS) to detect DMEA adsorbed from solution and the application of secondary neutral mass spectrometry (SNMS) to study migration of DMEA through a cement matrix. In this report we present XPS data of DMEA adsorbed on steel surfaces from alkaline and chlorine containing solutions of variable concentration range and discuss models for the interaction of DMEA with the oxidized steel surface and the mechanism of corrosion inhibition of DMEA. DMEA is strongly bonded to the steel surface and displaces ionic species from the substrate/solution interface hence protecting the ironoxide surface from ionic attack.

  8. Does Dimeric Melittin Occur in Aqueous Solutions?

    OpenAIRE

    Schubert, D; Pappert, G.; Boss, K.

    1985-01-01

    Melittin, a peptide from bee venom, is known to undergo a monomer / tetramer conversion in aqueous solutions. We have studied the possible participation of dimers in the association equilibrium of melittin by sedimentation equilibrium experiments in the analytical ultracentrifuge and subsequent mathematical analysis of the concentration distributions obtained. It was found that the dimeric state is not significantly populated, the contribution of dimer to the total peptide weight probably bei...

  9. Aqueous solution dispersement of carbon nanotubes

    Science.gov (United States)

    Kim, Jae-Woo (Inventor); Park, Cheol (Inventor); Choi, Sang H. (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

    2011-01-01

    Carbon nanotubes (CNTs) are dispersed in an aqueous buffer solution consisting of at least 50 weight percent water and a remainder weight percent that includes a buffer material. The buffer material has a molecular structure defined by a first end, a second end, and a middle disposed between the first and second ends. The first end is a cyclic ring with nitrogen and oxygen heteroatomes, the middle is a hydrophobic alkyl chain, and the second end is a charged group.

  10. Photolysis of imidacloprid in aqueous solution

    International Nuclear Information System (INIS)

    The photolysis of the insecticide imidacloprid in aqueous solution has been examined. Irradiation at 290 nm resulted in 90 % substrate transformation in 4 h. The degradation approximately followed first order kinetics; the rate constant is 1.6 × 10−4s−1 and half-life 1.2 h. 6-Chloronicotinaldehyde, N-methylnicotinacidamide, 1-(6-chloronicotinyl)imidazolidone and 6-chloro-3-pyridyl-methylethylendiamine were the main photoproducts identified by CG-MS analysis. (author)

  11. Simple Molecular Models of Aqueous Solutions

    Czech Academy of Sciences Publication Activity Database

    Jirsák, Jan; Škvor, J.; Nezbeda, Ivo

    - : -, 2013. ISBN N. [EMLG - JMLG Annual Meeting 2013 Global Perspectives in the Structure and Dynamics in Liquids and Mixtures: Experiment and Simulation. Lille (FR), 09.09.2013-13.09.2013] Grant ostatní: GA ČR(CZ) GPP208/12/P710 Institutional support: RVO:67985858 Keywords : aqueous solutions * thermodynamic modeling * simulation data Subject RIV: CF - Physical ; Theoretical Chemistry http://emlg2013.univ-lille1.fr/

  12. Preferential adsorption of uranium ions in aqueous solutions by polymers

    International Nuclear Information System (INIS)

    Amidoxime fiber and triazine fiber were prepared by chemical modification of commercially available polyacrylonitril fiber. It was found that the Amidoxime fiber is efficient to adsorb uranium ions in the artificial sea water. The efficiency of the preferential adsorption decreases by treatment the material with an acid-or an alkaline-solution. The triazine fiber adsorbs uranium ions only in aqueous solutions of such uranyl acetate, in the absence of other ions. In the artificial sea water, it adsorbs other ions instead of uranium. The preferential adsorption of uranium ions was further investigated with a series of polystyrenesulfonamides. Among the polystyrene derivatives, those having carboxyl groups, derived from imino diacetic acid (PSt-Imi), β-alanine (PSt-Ala), glycine (PSt-Gly), and sarcosine (PSt-Sar) were qualified for further discussion. However, it was found that the amount of adsorption of uranium ions by PSt-Imi decreases with increasing the volume of the artificial sea water and/or the duration of the treatment. Taking into account the facts, the preferential adsorption of uranium ions by PSt-Imi in aqueous solution was discussed in detail. (author)

  13. Autoxidation of tryptophan in aqueous solutions

    OpenAIRE

    LJUBICA R. JOSIMOVIC; IVANA A. JANKOVIC

    2001-01-01

    Autoxidation of tryptophan was investigated in aqueous solutions by the gamma radiolytic technique. The oxygen uptake and formation of peroxide materials was followed as a function of pH, dose rate and concentration of tryptophan. The results obtained indicate that TrpH(OH)OO. radicals react with tryptophan by adduct formation thus propagating autoxidation. The chain propagation length (CPL) for a 2·102 mol dm3 tryptophan solution at pH 9.5 and a dose rate 0.01 Gy s1 was estimated to be ~ 5.8...

  14. Electrochemical processing of alkaline nitrate and nitrite solutions

    International Nuclear Information System (INIS)

    Processing of high-level waste at the Savannah River Plant (SRP) will produce, as a by product, a low- level, alkaline salt solution containing approximately 17% sodium nitrate and sodium nitrite. This solution will be incorporated into a cement formulation, saltstone, and placed in an engineered landfill. Electrochemical methods have been investigated to decrease the nitrate and nitrite in this solution in order to lower the leaching of nitrate and nitrite from saltstone and to reduce the volume of saltstone. Laboratory experiments have demonstrated the technical feasibility of electrolytically reducing the nitrate and nitrite in a synthetic salt solution similar in composition to that expected to be produced at SRP. Greater than 99% of the sodium nitrate and sodium nitrite can be reduced, producing ammonia, nitrogen, oxygen, and sodium hydroxide. In addition, significant reductions in the volume of saltstone may be realized if the sodium hydroxide produced by electrolysis can be recycled

  15. OPTICAL PROPERTIES OF CARBAMIDE AQUEOUS SOLUTIONS

    Directory of Open Access Journals (Sweden)

    E. V. Avramenko

    2016-03-01

    Full Text Available Subject of Research. The paper presents the results of measurements of refractometric properties (refractive index n, its temperature factor dn/dt and the ultraviolet spectral absorption in carbonic acid diamide aqueous solutions (carbamide depending on solid residue mass fraction md = 0-50 % and on temperaturet = 10-70 °C.Method of Research. Laboratory methods ofliquid-phase medium refractometry and ultraviolet spectrophotometry were applied for the research. We carried out computational modeling of electronic states spectrum for the carbonic acid diamide molecule and theoretical calculation of the fundamental electronic absorption of the molecule in the ultraviolet wavelenght region.Main Results. We have established that the solution concentration md has a nonlinear character and may be represented by the quadratic polynomial with the error Δn= ± 0,0005. We have shown the refractive indexdependence on temperature n(t changes in linear fashion att = 10-70 °C.At that, the inclination of lines n(t increases at the increase of md; so, the temperature factor dn/dt may be approximated by the quadratic polynomial. Transmission spectra of solutions in the spectral region λ= 225-760 nm have no special features except for the sharp edge in the short-wavelength region; the fundamental electronic absorptionis responsible for it. We have established that dispersion dependences of the refraction index n(λ;md in aqueous solutions of carbamide at λ= 360-760 nm and at md = 0-50 % may be calculated with the satisfactory error without additional adjustable parameters from the ultraviolet absorption data in terms of the one-dimentional oscillator Lorentz model.PracticalRelevance. Representedmeasurements of carbonic acid diamide aqueous solutions optical properties may be applied for the adjustment and calibration of commercial refractometers at processing lines of the AdBlue reagent manufacture for the selective catalytic reduction (SCR of motor transport

  16. Density of aqueous solutions of CO2

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Julio E.

    2001-10-10

    In this report, we present a numerical representation for the partial molar volume of CO2 in water and the calculation of the corresponding aqueous solution density. The motivation behind this work is related to the importance of having accurate representations for aqueous phase properties in the numerical simulation of carbon dioxide disposal into aquifers as well as in geothermal applications. According to reported experimental data the density of aqueous solutions of CO2 can be as much as 2-3% higher than pure water density. This density variation might produce an influence on the groundwater flow regime. For instance, in geologic sequestration of CO2, convective transport mixing might occur when, several years after injection of carbon dioxide has stopped, the CO2-rich gas phase is concentrated at the top of the formation, just below an overlaying caprock. In this particular case the heavier CO2 saturated water will flow downward and will be replaced by water with a lesser CO2 content.

  17. Sorption of 137Cs from Aqueous Waste Solutions using Pottery

    International Nuclear Information System (INIS)

    A simple and inexpensive method for sorption of 137Cs from aqueous solutions using a highly available vase shape pottery material has been investigated. Porosity of the used pottery allowed for the penetration of the radioactive solution through its permeable body. Two routes had been investigated for cesium removal from the radioactive solutions. In the first one, pottery bodies were immersed into the radioactive solutions. In the second method; the radioactive solutions were filled the inner volumes of the pottery bodies. Vase shape pottery showed higher sorption capability for 137Cs much more than its powder forms, especially in the alkaline medium. Pottery bodies showed high potential for 137Cs removal. Adsorption isotherms revealed good lit to the Freundlich and Langumir isotherms. During sorption processes outside and inside the pottery body, 137Cs was well captured inside the amorphous microstructure of the pottery body. In this respect, micro filtration of cesium radionuclides through the used pottery could be postulated. Desorption experiments indicated higher immobilization affinity for radiocesium into pottery bodies, which indicates a high containment for 137Cs with an irreversible fixation mechanism

  18. Electrolytic denitrification of alkaline nitrate and nitrite solution

    International Nuclear Information System (INIS)

    Processing of high-level waste at the Savannah River Plant (SRP) will produce a low-level alkaline salt solution, containing approximately 17% sodium nitrate and sodium nitrite. This solution will be incorporated into a cement wasteform, saltstone, and placed in an engineered landfill. Laboratory experiments have demonstrated the technical feasibility of electrochemically reducing the nitrate and nitrite in a synthetic, nonradioactive salt solution similar in composition to that expected to be produced at SRP. Greater than ninety-five percent of the sodium nitrate and sodium nitrite can be reduced electrolytically, producing ammonia, nitrogen, oxygen, and sodium hydroxide. Reduction of the nitrate and nitrite will reduce the leaching of nitrate and nitrite from the saltstone monolith. In addition, significant reductions in the volume of saltstone may be realized if the sodium hydroxide produced by electrolysis can be recycled

  19. Optical manipulation of proteins in aqueous solution

    International Nuclear Information System (INIS)

    Optical trapping of lysozyme, cytochrome c, or myoglobin based on photon pressure generated by focusing 1064 nm laser beam in an aqueous solution was explored. For all the proteins, microparticle formation was observed at the focal point under an optical microscope. Furthermore, the microparticles were identified to the molecular assemblies of the corresponding protein by means of confocal Raman microspectroscopy. For lysozyme, molecular clusters in solution were optically trapped to form the microparticle and it took more than 1 h to produce the microparticle. By contrast, molecular assembling proceeded within 1 min for cytochrome c and myoglobin. Since heme in cytochrome c or myoglobin would have a high polarizability, that would contribute to rapid assembling of the protein. Thus we demonstrated that a focused laser beam was a powerful tool to manipulate protein molecules in solution.

  20. NIR Spectroscopic Properties of Aqueous Acids Solutions

    Directory of Open Access Journals (Sweden)

    Mohd Zubir MatJafri

    2012-06-01

    Full Text Available Acid content is one of the important quality attributes in determining the maturity index of agricultural product, particularly fruits. Despite the fact that much research on the measurement of acidity in fruits through non-destructive spectroscopy analysis at NIR wavelengths between 700 to 1,000 nm has been conducted, the same response towards individual acids is not well known. This paper presents NIR spectroscopy analysis on aqueous citric, tartaric, malic and oxalic solutions through quantitative analysis by selecting a set of wavelengths that can best be used to measure the pH of the solutions. The aquaphotomics study of the acid solutions has generated R2 above 0.9 for the measurement of all acids. The most important wavelengths for pH are located at 918–925 nm and 990–996 nm, while at 975 nm for water.

  1. Aqueous Solution Vessel Thermal Model Development II

    Energy Technology Data Exchange (ETDEWEB)

    Buechler, Cynthia Eileen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-10-28

    The work presented in this report is a continuation of the work described in the May 2015 report, “Aqueous Solution Vessel Thermal Model Development”. This computational fluid dynamics (CFD) model aims to predict the temperature and bubble volume fraction in an aqueous solution of uranium. These values affect the reactivity of the fissile solution, so it is important to be able to calculate them and determine their effects on the reaction. Part A of this report describes some of the parameter comparisons performed on the CFD model using Fluent. Part B describes the coupling of the Fluent model with a Monte-Carlo N-Particle (MCNP) neutron transport model. The fuel tank geometry is the same as it was in the May 2015 report, annular with a thickness-to-height ratio of 0.16. An accelerator-driven neutron source provides the excitation for the reaction, and internal and external water cooling channels remove the heat. The model used in this work incorporates the Eulerian multiphase model with lift, wall lubrication, turbulent dispersion and turbulence interaction. The buoyancy-driven flow is modeled using the Boussinesq approximation, and the flow turbulence is determined using the k-ω Shear-Stress-Transport (SST) model. The dispersed turbulence multiphase model is employed to capture the multiphase turbulence effects.

  2. Study of the electrochemical oxidation mechanism of formaldehyde on gold electrode in alkaline solution

    Institute of Scientific and Technical Information of China (English)

    Rui-Wen Yan; Bao-Kang Jin

    2013-01-01

    The oxidation of formaldehyde in alkaline solution was studied by in situ rapid-scan time-resolved IR spectroelectrochemistry (RS-TR-FTIRS) method.In the potential range between-0.7 V and 0.2 V,the gem-diol anions were oxidized (according to the 2765 cm-1 ofvH-o and 1034 cm-1 ofvco downward IR bands) and the formate ions appeared (according to the 1588,1357 cm-1 of the asymmetric and symmetricvoco and 1380 cm-1 ofδc-H upward IR bands) in aqueous solution.It was also confirmed that gem-diol anion was oxidized (according to the 2026,1034 cm-1 downward IR bands) to formate ions (according to the 1595,1357,1380 cm-1 upward IR bands) and water (according to the 3427 cm-1 ofvH-o upward IR band) in heavy water solution.The results illustrated that formaldehyde formed gem-diol anion in alkaline solution and was absorbed on the electrode surface; then gem-diol anion was oxidized to formate ions and water.

  3. The oxygen evolution reaction on passive oxide covered transition metal electrodes in alkaline solution. Part 2-Cobalt.

    OpenAIRE

    LYONS, MICHAEL EDWARD

    2008-01-01

    Details are outlined of an electrochemical investigation of the oxygen evolution reaction (OER) at passive oxide covered polycrystalline Co electrodes in aqueous alkaline solution. Kinetic studies on electrodes subjected to different pre-treatment routines, yielded different values of the Tafel slope and the reaction order with respect to OH- activity. Only one mechanistic pathway could account for all observed values of these kinetic parameters. This pathway is similar, although ...

  4. The oxygen evolution reaction on passive oxide covered transition metal electrodes in alkaline solution. Part III - Iron.

    OpenAIRE

    LYONS, MICHAEL EDWARD

    2008-01-01

    The kinetics of the oxygen evolution reaction (OER) at passive oxide covered polycrystalline Fe electrodes in aqueous alkaline solution were examined using both dc steady state polarisation and ac impedance techniques. It proved difficult to obtain reproducible polarisation data for bright anodes, and so an electrochemical pre-treatment routine was devised. Upon ageing of a given electrode specimen, and with application of the pre-treatment regime before each experiment, it was po...

  5. Apparent Dissolution Kinetics of Diatomite in Alkaline Solution

    Institute of Scientific and Technical Information of China (English)

    DU Gaoxiang; L(U) Guocheng; HE Xuwen

    2013-01-01

    The dissolution kinetics of diatomite in alkaline solution is the theoretical basis for the process optimization of alkali-diatomite reaction and its applications.In this study,the dissolution kinetics of diatomite in NaOH solution is investigated.The results indicate that the dissolution reaction fits well the unreacted shrinking core model for solid-liquid heterogeneous reactions.The apparent reaction order for NaOH is 2 and the apparent activation energy for the reaction (Ea) is 28.06 kJ.mol-1.The intra-particle diffusion through the sodium silicate layer is the rate-controlling step.When the dissolution reaction occurs at the interface of unreacted diatomite solid core,the diffusion in the trans-layer (the liquid film around the wetted particle) reduces the rate of whole dissolution process.

  6. Corrosion of silicon nitride in high temperature alkaline solutions

    Science.gov (United States)

    Qiu, Liyan; Guzonas, Dave A.; Qian, Jing

    2016-08-01

    The corrosion of silicon nitride (Si3N4) in alkaline solutions was studied at temperatures from 60 to 300 °C. Si3N4 experienced significant corrosion above 100 °C. The release rates of silicon and nitrogen follow zero order reaction kinetics and increase with increasing temperature. The molar ratio of dissolved silicon and nitrogen species in the high temperature solutions is the same as that in the solid phase (congruent dissolution). The activation energy for silicon and nitrogen release rates is 75 kJ/mol which agrees well with that of silica dissolution. At 300 °C, the release of aluminum is observed and follows first order reaction kinetics while other minor constituents including Ti and Y are highly enriched on the corrosion films due to the low solubility of their oxides.

  7. Pulse Radiolysis of Aqueous Thiocyanate Solution

    International Nuclear Information System (INIS)

    The pulse radiolysis of N2O saturated aqueous solutions of KSCN was studied under neutral pH conditions. The observed optical absorption spectrum of the SCN#lgbullet# radical in solution is more complex than previously reported, but it is in good agreement with that measured in the gas phase. Kinetic traces at 330 nm and 472 nm corresponding to SCN#lgbullet# and (SCN)2#lgbullet#-, respectively, were fit using a Monte Carlo simulation kinetic model. The rate coefficient for the oxidation of SCN- ions by OH radicals, an important reaction used in competition kinetics measurements, was found to be 1.4 ± 0.1 x 1010 M-1 s-1, about 30% higher than the normally accepted value. A detailed discussion of the reaction mechanism is presented

  8. On the complex structural diffusion of proton holes in nanoconfined alkaline solutions within slit pores.

    Science.gov (United States)

    Muñoz-Santiburcio, Daniel; Marx, Dominik

    2016-01-01

    The hydroxide anion OH(-)(aq) in homogeneous bulk water, that is, the solvated proton hole, is known to feature peculiar properties compared with excess protons solvated therein. In this work, it is disclosed that nanoconfinement of such alkaline aqueous solutions strongly affects the key structural and dynamical properties of OH(-)(aq) compared with the bulk limit. The combined effect of the preferred hypercoordinated solvation pattern of OH(-)(aq), its preferred perpendicular orientation relative to the confining surfaces, the pronounced layering of nanoconfined water and the topology of the hydrogen bond network required for proton hole transfer lead to major changes of the charge transport mechanism, in such a way that the proton hole migration mechanism depends exquisitely on the width of the confined space that hosts the water film. Moreover, the anionic Zundel complex, which is of transient nature in homogeneous bulk solutions, can be dynamically trapped as a shallow intermediate species by suitable nanoconfinement conditions. PMID:27550616

  9. Catalyzed reduction of nitrate in aqueous solutions

    International Nuclear Information System (INIS)

    Sodium nitrate and other nitrate salts in wastes is a major source of difficulty for permanent disposal. Reduction of nitrate using aluminum metal has been demonstrated, but NH3, hydrazine, or organic compounds containing oxygen would be advantageous for reduction of nitrate in sodium nitrate solutions. Objective of this seed money study was to determine minimum conditions for reduction. Proposed procedure was batchwise heating of aqueous solutions in closed vessels with monitoring of temperatures and pressures. A simple, convenient apparatus and procedure were demonstrated for observing formation of gaseous products and collecting samples for analyses. The test conditions were 250 degree C and 1000 psi max. Any useful reduction of sodium nitrate to sodium hydroxide as the primary product was not found. The nitrate present at pHs 3 or NH4NO3 is easily decomposed, and the effect of nitromethane at these low pHs was confirmed. When acetic acid or formic acid was added, 21 to 56% of the nitrate in sodium nitrate solutions was reduced by methanol or formaldehyde. With hydrazine and acetic acid, 73 % of the nitrate was decomposed to convert NaNO3 to sodium acetate. With hydrazine and formic acid, 36% of the nitrate was decomposed. If these products are more acceptable for final disposal than sodium nitrate, the reagents are cheap and the conversion conditions would be practical for easy use. Ammonium acetate or formate salts did not significantly reduce nitrate in sodium nitrate solutions

  10. Heterogeneous nucleation of aspartame from aqueous solutions

    Science.gov (United States)

    Kubota, Noriaki; Kinno, Hiroaki; Shimizu, Kenji

    1990-03-01

    Waiting times, the time from the instant of quenching needed for a first nucleus to appear, were measured at constant supercoolings for primary nucleation of aspartame (α-L-aspartyl-L-phenylalanine methylester) from aqueous solutions, which were sealed into glass ampoules (solution volume = 3.16 cm 3). Since the waiting time became shorter by filtering the solution prior to quenching, the nucleation was concluded to be heterogeneously induced. The measured waiting time consisted of two parts: time needed for the nucleus to grow to a detactable size (growth time) and stochastic time needed for nucleation (true waiting time). The distribution of the true waiting time, is well explained by a stochastic model, in which nucleation is regarded to occur heterogeneously and in a stochastic manner by two kinds of active sites. The active sites are estimated to be located on foreign particles in which such elements as Si, Al and Mg were contained. The amount of each element is very small in the order of magnitude of ppb (mass basis) of the whole solution. The growth time was correlated with the degree of supercooling.

  11. Electron beam induced degradation of clopyralid in aqueous solutions

    International Nuclear Information System (INIS)

    The degradation characteristics of clopyralid irradiated by electron beam (EB) was studied in aqueous solutions. The effects of factors, such as initial clopyralid concentrations, addition of radicals scavenger, initial solution pH and addition of H2O2, were investigated on clopyralid degradation efficiency and mechanism. It was found that the EB-radiolysis was an effective way to degrade clopyralid and its degradation rate decreased with the increasing of substrate concentration. In the investigated initial concentrations range of 100-400 mg L-1, the radiolytic degradation of clopyralid followed a pseudo-first kinetic order. The results from addition of radicals scavenger indicated that both ·OH and eaq- played significant roles in the degradation of clopyralid. Furthermore, the alkaline condition and addition of H2O2 (<10 mM) in the solution also slightly enhanced the efficiency of clopyralid degradation. The ion chromatography analysis showed that some organic acids (formic acid, acetic acid and oxalic acid) were formed, while the completely dechlorination of the substrate was achieved and organic nitrogen was recovered in the form of ammonium and nitrate ions during the irradiation process. (author)

  12. Absorption and Chemisorption of Small Levitated Single Bubbles in Aqueous Solutions

    OpenAIRE

    Alexander Tollkötter; Norbert Kockmann

    2014-01-01

    The absorption and chemisorption of small bubbles with N2 or CO2 were investigated experimentally in aqueous and alkaline solutions. Different bubble sizes were studied ranging from 0.1 to 2.5 mm in alkaline concentrations of 0.1 mM to 1 M NaOH. The experiments were conducted in a device consisting of a converging microchannel with a down flowing liquid. Levitation positions of single bubbles were optically characterized. A correlation was developed for the drag force coefficient, CD, includi...

  13. Zinc electrodeposition from alkaline zincate solution by pulsating overpotentials

    Directory of Open Access Journals (Sweden)

    MILOS V. SIMICIC

    2000-09-01

    Full Text Available It is well known that smooth zinc deposits cannot be obtained from alkaline zincate using constant overpotential and current rate. During prolonged metal deposition, spongy and dendritic deposits are formed. It has been shown that the deposits are less agglomerated in the case of square-wave pulsating overpotentials regime than the ones obtained in case of constant overpotential regime. This is explained in a semiquantitative way by two phenomena: selective anodic dissolution during overpotentials “off” period and decreasing diffusion control. These effects is more pronounced at higher pause-to-pulse ratio. Increasing the pause-to-pulse ratio causes a reduction of the ratio between diffusion and activation overpotential, resulting in a more compact deposit. Confirmation of the proposed semiquantitative mathematical model was obtained by zinc electrodeposition onto a copper wire from a 0.1 M zincate solution in 1.0 M KOH at room temperature.

  14. Functionalized polymers for binding to solutes in aqueous solutions

    Science.gov (United States)

    Smith, Barbara F.; Robison, Thomas W.

    2006-11-21

    A functionalized polymer for binding a dissolved molecule in an aqueous solution is presented. The polymer has a backbone polymer to which one or more functional groups are covalently linked. The backbone polymer can be such polymers as polyethylenimine, polyvinylamine, polyallylamine, and polypropylamine. These polymers are generally water-soluble, but can be insoluble when cross-linked. The functional group can be for example diol derivatives, polyol derivatives, thiol and dithiol derivatives, guest-host groups, affinity groups, beta-diphosphonic acids, and beta-diamides

  15. Photodegradation of Lincomycin in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available Aqueous solutions of lincomycin were irradiated with UV light in homogeneous and heterogeneous systems. Lincomycin disappeared in both systems but the presence of TiO 2 noticeably accelerated the degradation of the antibiotic in comparison with direct photolysis. The rate of decomposition was dependent on the concentration of lincomycin and followed a pseudo-first-order kinetics. Photolysis involved only the oxidation of lincomycin without mineralization. Differently, the treatment with TiO 2 and UV light resulted in a complete mineralization of the antibiotic. The degradation pathways involved S- and N-demethylation and propyldealkylation. The mineralization of the molecule led to the formation of sulfate, ammonium, and nitrate ions.

  16. Radiolysis of paracetamol in dilute aqueous solution

    International Nuclear Information System (INIS)

    Using radiolytic experiments hydroxyl radical (main reactant in advanced oxidation processes) was shown to effectively destroy paracetamol molecules. The basic reaction is attachment to the ring. The hydroxy-cyclohexadienyl radical produced in the further reactions may transform to hydroxylated paracetamol derivatives or to quinone type molecules and acetamide. The initial efficiency of aromatic ring destruction in the absence of dissolved O2 is c.a. 10%. The efficiency is 2–3 times higher in the presence of O2 due to its reaction with intermediate hydroxy-cyclohexadienyl radical and the subsequent ring destruction reactions through peroxi radical. Upon irradiation the toxicity of solutions at low doses increases with the dose and then at higher doses it decreases. This is due to formation of compounds with higher toxicity than paracetamol (e.g. acetamide, hidroquinone). These products, however, are highly sensitive to irradiation and degrade easily. - Highlights: ► Paracetamol is easily degraded in aqueous solution by low dose irradiation. ► Main degradation products are hydroxylated molecules, acetamide and hydroquinone. ► Toxicity of solutions goes through a maximum as a function of dose.

  17. Removal of radium from aqueous solutions using adsorbent produced from coconut coir pith

    International Nuclear Information System (INIS)

    A study was conducted to evaluate the potential use of the coconut coir pith as an adsorbent for the removal of radium from aqueous solutions. Experiments to establish adsorptions as a function of pH and contact time were carried out. The results showed that radium adsorption are dependent upon pH and contact time of coconut coir pith with aqueous solutions. 70-80% of radium were adsorbed in the neutral to alkaline pH range. The amount of radium adsorbed also increased with contact time, reaching an optimum after 250 min. Thus, it can be concluded that the coconut coir pith has the potential to be used as an adsorbent in radium removal from aqueous solutions. (Author)

  18. Pulse radiolysis of tetraalkylammonium hydroxides in alkaline solution containing oxygen

    International Nuclear Information System (INIS)

    In the pulse radiolysis of aqueous oxygenated solutions of tetraalkylammonium hydroxides there is a build-up of ozonide ion lasting up to 100 μs after the pulse. The build-up does not occur in solutions containing a twenty fold (reactivity) excess of N2O to O2. The influence of various concentrations of tetraalkylammonium cations, oxygen and different reactivity ratios of N2O to O2 on the build-up of ozonide ion after the pulse was investigated. The reaction rates of O2-and O- with peroxy radicals and organic cations, respectively, control the nature of the observed build-up and decay of ozonide ion. (author)

  19. The effect of acrylic comonomers on the hydrolytic stability of polyacrylamides at high temperature in alkaline solution

    Energy Technology Data Exchange (ETDEWEB)

    Dexter, R.W.; Ryles, R.G.

    1988-05-01

    A major cause of instability in acrylamide-based polymers used in tertiary oil recovery is hydrolysis of the amide groups, especially at alkaline pH and high temperatures. Changes in polymer composition resulting from hydrolysis can cause precipitation from sea-water solutions. This work has studied the effects of the sodium salts of acrylic acid and acrylamidomethyl propane sulfonic acid (AMPS) on the rate of hydrolysis of acrylamide copolymers in alkaline solutions at high temperatures. Copolymers were prepared containing 0 - 50% of the anionic comonomers and hydrolyzed in aqueous solution at pH 8.5 at 90/sup 0/, 107/sup 0/, and 120/sup 0/C. The extent of hydrolysis was measured by a conductimetric method, analyzing for the total carboxylate content. It was found that the rate of hydrolysis decreased as the mole ratio of either of the anionic comonomers increased and that AMPS was more effective in preventing hydrolysis at all of the temperatures studied.

  20. Humic acid removal from aqueous solutions by peroxielectrocoagulation process

    Directory of Open Access Journals (Sweden)

    Ahmad Reza Yazdanbakhsh

    2015-06-01

    Full Text Available Background: Natural organic matter is the cause of many problems associated with water treatment such as the presence of disinfection by-products (DBPs and membrane fouling during water filtration. In this study, the performance of the peroxi-electrocoagulation process (PEP was investigated for the removal of humic acids (HAs from aqueous solutions. Methods: PEP was carried out for the removal of HA using a plexiglas reactor with a volume of 2 L and fitted with iron electrodes and a direct current supply (DC. Samples were taken at various amounts of pH (2-4, current density (1 and 2A/cm2, hydrogen peroxide (50-150 mg/L and reaction time (5-20 minutes and then filtered to remove sludge formed during reaction. Finally, the HA concentration was measured by UV absorbance at 254 nm (UV254. Results: Results indicated that increasing the concentration of H2O2 from 50 to 150 mg/L increased HA removal efficiency from 83% to 94.5%. The highest removal efficiency was observed at pH 3.0; by increasing the pH to the alkaline range, the efficiency of the process was reduced. It was found that HA removal efficiency was high in current density 1A/cm2. Increasing current density up to 1 A cm-2 caused a decrease in removal efficiency. Results of this study showed that under the optimum operating range for the process ([current density] = 1A/cm2, [hydrogen peroxide concentration] = 150 mg/L, [reaction time]= 20 minutes and [pH]= 3.0, HA removal efficiency reached 98%. Conclusion: It can be concluded that PEP has the potential to be utilized for cost-effective removal of HA from aqueous solutions.

  1. The radiation chemistry of aqueous dihydropyrimidine solutions

    International Nuclear Information System (INIS)

    The radiation chemistry of N2O-saturated aqueous solutions of dihydropyrimidines in the presence pf various oxidants has been studied. From dihydrouracil (DHU) solutions in the presence of Fe(CN)63- the major products are uracil and 5-hydro-6-hydroxyuracil which have been isolated by chromatographic techniques using DHU-14C. From 6-methyldihydrouracil (6-MeDHU), under similar conditions, the parent pyrimidine and the 6-hydroxy compound are also formed. The pH-dependence of the yields of these products in the above DHU and 6-MeDHU systems have been determined and the results interpreted in terms of an electron transfer reaction from the organic radicals to the oxidant. Pulse radiolysis has shown that the isomerisation of the isopyrimidine is base catalysed. The influence of the oxidants IO4-, S2O82-, H2O2 and p-nitroacetophenone has been investigated using various dihydropyrimidines. Specific effects have been noted, particularly a chain reaction in the case of IO4- and S2O82-, and also the formation of barbituric acid derivatives in addition to pyrimidines and the 6-hydroxy compounds, more particularly in the case of IO4- and H2O2. The pH-dependencies of the yields have been studied and possible specific mechanisms discussed. These particular studies are of interest with regard to radiation sensitisation in vivo. (author)

  2. Direct Solar Charging of an Organic-Inorganic, Stable, and Aqueous Alkaline Redox Flow Battery with a Hematite Photoanode.

    Science.gov (United States)

    Wedege, Kristina; Azevedo, João; Khataee, Amirreza; Bentien, Anders; Mendes, Adélio

    2016-06-13

    The intermittent nature of the sunlight and its increasing contribution to electricity generation is fostering the energy storage research. Direct solar charging of an auspicious type of redox flow battery could make solar energy directly and efficiently dispatchable. The first solar aqueous alkaline redox flow battery using low cost and environmentally safe materials is demonstrated. The electrolytes consist of the redox couples ferrocyanide and anthraquinone-2,7-disulphonate in sodium hydroxide solution, yielding a standard cell potential of 0.74 V. Photovoltage enhancement strategies are demonstrated for the ferrocyanide-hematite junction by employing an annealing treatment and growing a layer of a conductive polyaniline polymer on the electrode surface, which decreases electron-hole recombination. PMID:27151516

  3. Quick analytical method for the determination of iodide and iodate ions in aqueous solutions

    International Nuclear Information System (INIS)

    An analytical quick-test method was developed to determine iodide and iodate ions in aqueous solutions using solid phase extraction cartridges for sample preparation. Work was focussed on finding simple, but efficient conditions for quantitative separation of iodate and iodide. Iodine amounts were then determined by standard methods. Ion-exchange absorbers in cartridge form were used. Selectivity and yield of the species separation were studied at pH value of 5-10 and various solution compositions using 131I radioactive tracer. The electrolytes used were diluted alkaline, nitrate and boric acid-borate solutions. Application to nuclear reactor cooling water analysis or environmental investigations and monitoring is proposed. (author)

  4. New sand consolidation technique using hot alkaline solutions: laboratory evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, F.E.; Rico, A.; Mendez, Z. [PDVSA-Intevep, Caracas (Venezuela); Materan, S. [Simon Bolivar Univ., Caracas (Venezuela)

    2002-06-01

    Some well known problems in the petroleum industry are related to sanding problems caused by pressure falls, friction and dissolution of minerals during steam injection. The prospect of using hot alkaline solutions to achieve sand consolidation was investigated in this paper. Experimental work was performed using Venezuelan sand samples (S-1, S-2, and S-3) from various unconsolidated heavy oil reservoirs and commercial Silboca (S-4) sands to validate this new reservoir sand consolidation technique. A pressure of 500 pounds per square inch was applied to samples that had been packed into Teflon tubes and placed in a horizontal stainless steel cell. Following this, for a period varying from 2 to 5 hours, a hot sodium carbonate solution between 120 and 250 Celsius was injected. Every twenty minutes, the effluent solution was sampled. Before and after each run, permeability measurements were obtained to monitor the variations. Sand packs were dried at 100 Celsius after each test. An electron microscope was used to observe the morphology of secondary phases. For S-1 and S-2, sodium aluminium silicates were identified in the secondary phases for tests with temperature above 240 Celsius. In the case of S-3 and S-4, no consolidation was observed. The authors believe that large grain sizes and a 98 per cent quartz content respectively explain this phenomenon. It is suspected that sand consolidation requires the presence of aluminium contained in clays and/or feldspar. The critical parameters for sand consolidation were identified as temperature, pore volume, composition, and grain size. The process did not seem greatly affected by soaking time and injection rate. The advantages of this technique would be principally the minimization of sanding problems and reductions in the costs associated with production operations. 7 refs., 12 figs.

  5. Acetic acid extraction from aqueous solutions using fatty acids

    NARCIS (Netherlands)

    IJmker, H.M.; Gramblicka, M.; Kersten, S.R.A.; Ham, van der A.G.J.; Schuur, B.

    2014-01-01

    A major challenge for production of acetic acid via bio-based routes is cost-effective concentration and purification of the acetic acid from the aqueous solutions, for which liquid–liquid extraction is a possible method. A main challenge in extraction of acetic acid from dilute aqueous solutions is

  6. ESR study on carboxymethyl chitosan radicals in an aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Saiki, Seiichi, E-mail: saiki.seiichi@jaea.go.j [Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Nagasawa, Naotsugu; Hiroki, Akihiro; Morishita, Norio; Tamada, Masao [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Muroya, Yusa; Kudo, Hisaaki [Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Katsumura, Yosuke [Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1195 (Japan)

    2010-03-15

    Carboxymethyl chitosan (CMCTS) at a highly concentrated aqueous solution forms hydrogel by ionizing irradiation. To study on radiation-induced reaction mechanism of CMCTS in an aqueous solution, CMCTS radicals formed by reactions with OH radical were observed by ESR method. As a result of ESR spectral analysis, CMCTS radicals were identified as radicals on carboxymethyl groups.

  7. Raman spectroscopy application to analyses of components in aqueous solutions

    Science.gov (United States)

    Li, Gang; Zhang, Guoping

    2006-09-01

    The characterization of species in aqueous solutions has presented a challenge to analytical and physical chemist, because the JR absorption of the aqueous solvent is so intense that it becomes difficult to observe the solute in the water by JR absorption. In contrast, Raman spectrum of the solute is unaffected by the water, so the weak scattering of water makes the technique well suited to aqueous samples, and the Raman spectrum exhibits well-defined bands corresponding to fundamental modes of vibration. In addition, Raman spectroscopy has some inherent advantages in aqueous solution analysis, because the spectral features of signals from different species are much more distinct, and it provides characteristic signatures for samples, such as blood, protein and cholesterol. All the advantages make Raman spectroscopy be a potential alternative for the study of aqueous solutions. Now, Raman spectroscopy has been applied to studying samples in aqueous solutions, blood serum, intracellular protein levels. Now, industrial wasted water contains many organic contaminants, and it is necessary to determine and monitor these contaminants. The paper first introduces Raman spectroscopy, and then describes its applications to determining the components in aqueous solutions, analyzes and assignes the Raman spectra of o-dichlorobenzene, o-xylene, m-xyiene and p-xylene in detail. The experimental results demonstrate that Raman spectroscopy is a particularly powerful technique for aqueous solutions analyses.

  8. Reactions of alkoxy radicals in aqueous solutions

    International Nuclear Information System (INIS)

    The kinetic and mechanistic properties of alkoxy radicals in organic solvents are briefly reviewed. Owing to the scarcity of such data in aqueous solutions and since reactions at the membrane/water interface may be also biologically important, we have studied the reactivity of these radicals in water and the results of our investigations are reported. Alkoxy radicals were generated by photolytic or radiolytic cleavage of peroxide precursors (tert-butyl hydroperoxide and di-tert-butyl peroxide as well as hydroperoxides of polyunsaturated fatty acids). A quantitative correlation between the structure of various substances, in particular, phenolic antioxidants, and their activity in inhibiting the alkoxy radical-induced bleaching of the water-soluble carotenoid crocin will be discussed. Rate constants for intermolecular reactions of t-BuO. radicals were determined by pulse radiolysis. The diffusion-controlled reaction with the catechol antioxidant nordihydroguaiaretic acid demonstrates an effective competition with the very rapid intra molecular β-fragmentation in water. The results aupport the view that a considerable amount of alkoxy radicals interact with substrates before they can rearrange intramolecularly

  9. Reactions of alkoxy radicals in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Bors, W.; Tait, D.; Michel, C.; Saran, M.; Erben-Russ, M. (Gesellschaft fuer Strahlen- und Umweltforschung m.b.H. Muenchen, Neuherberg (Germany, F.R.). Abt. fuer Strahlenbiologie)

    1984-01-01

    The kinetic and mechanistic properties of alkoxy radicals in organic solvents are briefly reviewed. Owing to the scarcity of such data in aqueous solutions and since reactions at the membrane/water interface may be also biologically important, we have studied the reactivity of these radicals in water and the results of our investigations are reported. Alkoxy radicals were generated by photolytic or radiolytic cleavage of peroxide precursors (tert-butyl hydroperoxide and di-tert-butyl peroxide as well as hydroperoxides of polyunsaturated fatty acids). A quantitative correlation between the structure of various substances, in particular, phenolic antioxidants, and their activity in inhibiting the alkoxy radical-induced bleaching of the water-soluble carotenoid crocin will be discussed. Rate constants for intermolecular reactions of t-BuO. radicals were determined by pulse radiolysis. The diffusion-controlled reaction with the catechol antioxidant nordihydroguaiaretic acid demonstrates an effective competition with the very rapid intra molecular ..beta..-fragmentation in water. The results aupport the view that a considerable amount of alkoxy radicals interact with substrates before they can rearrange intramolecularly.

  10. Removal of radium from aqueous solutions

    International Nuclear Information System (INIS)

    Adsorption of radium from aqueous solution with montmorillonite clay was investigated. Adsorption isotherm data of the radium and montmorillonite clay system were developed and fitted to both the Langmuir and Freundlich isotherm equations. The Langmuir isotherm equation was determined to be q = 6.700 C/1 + 8.447 x 10-5C and the Freundlich isotherm equation is q = 45.431 C/sup 1/1.401/. A rotary precoat filtration technique was used for dewatering the slurries of the montmorillonite clay and diatomaceous earth mixture. The rate of filtration was found to be a function of the weight percent of the clay, applied vacuum, drum speed and precoat thickness. The functional relationship is of the form Q = (0.682 + 0.035 X1 - 0.014 X2 + 0.140 X3 + 0.007 X1X2)/1 + (3.744 - 0.767 X3 + 0.079 X1X2)C125. 15 figures, 11 tables

  11. The redox speciation of neptunium in acidic and alkaline solutions

    International Nuclear Information System (INIS)

    Newly developed in situ capabilities at the Advanced Photon Source have been used to obtain X-ray absorption spectroscopy (XAS) data from Np in aqueous solutions. L-edge XAS data have been obtained from acidic solutions in which Np was electrochemically stabilised in the (III) to (VI) states. A purpose-built electrochemical cell housed in appropriate safety containment allows the acquisition of XAS data while the solution is maintained under controlled applied potentials. This electrochemical cell has been used in a proof-of-concept experiment designed to demonstrate the use of X-ray absorption near-edge structural (XANES) data for the determination of thermodynamic formal potentials. XANES data were obtained at a series of applied potentials from a 1 M perchloric acid solution containing 5 mm Np. The relative concentrations of Np redox species as a function of applied potential were extracted from the data using principal component (factor) analyses. The formal potentials determined for the Np(VI)/Np(V) and Np(IV)/Np(III) couples agree with those previously published. Extended X-ray absorption fine structure (EXAFS) data were obtained from the same solution, held at potentials chosen to optimise the concentration of a single Np redox species. These data have been used to verify the co-ordination environment of Np ions as a function of oxidation state. Density functional theory (DFT), simple geometric modelling and results from the EXAFS data analysis are in agreement for the co-ordination environment of Np(III). In a related set of experiments, L-edge XAS data of Np(V), Np(VI) and Np(VII) were obtained from a basic solution. The Np oxidation state was varied by sparging the solution with ozone. Data were collected as the sample was sparged and also after the sparging gas was turned off. Np optical data were obtained in the same XAS cell and confirm the oxidation of Np(VI) to hepta-valent Np. The concentration of Np(VII) was determined using trivalent Cr as a

  12. SCC Behavior of Alloy 690 in Leaded Aqueous Solution

    International Nuclear Information System (INIS)

    Alloy 690 (Ni 60wt%, Cr 30wt%, Fe 10wt%) is used and planned to use as a heat exchanger tube of the steam generator (SG) and an alternative of Alloy 600 (Ni 75wt%, Cr 15wt%, Fe 10wt%) due to a relatively high stress corrosion cracking (SCC) susceptibility of Alloy 600 under operating condition of nuclear power plant (NPP). Secondary water pH which affects SCC behavior substantially is widely spanned from acid to alkaline in crevice depending on water chemistry control, water chemistry in crevice, plant specific condition, etc. Especially, specific chemical species are accumulated in the crevice of the sludge leading to a specific condition of crevice chemistry. Among these chemical species, lead is known to be one of the most deleterious species in the reactor coolants that cause SCC of the alloy. Even Alloy 690 is not strong in alkaline solution with lead. Lead has been effectively detected in all tubesheet samples, crevice deposits and surface scales removed from SGs. Typical concentrations are 100 to 500 ppm but in some plants, concentrations as high as 2,000 to 10,000ppm has been detected. The best method to prevent lead induced SCC (PbSCC) is to eliminate the harmful lead from the NPP chemistry, which is not possible and most NPPs are already contaminated by lead. Moreover only a very low level of sub ppm affects PbSCC. Therefore the mechanistic understanding of PbSCC is very crucial to control and mitigate PbSCC. It is expected that an addition of lead into a solution modifies the oxide property considering that a passivity of oxide is directly related to SCC behavior. A finding of the way to avoid this modification can give us a key to control PbSCC such as an inhibitor. In the present work, an SCC susceptibility was investigated in the presence of lead and NiB as an inhibitor as well as in the absence of both impurities by using a slow strain rate tensile (SSRT) test. Moreover the oxides formed on Alloy 690 in aqueous solutions with and without lead were

  13. Ozone photolysis of paracetamol in aqueous solution.

    Science.gov (United States)

    Neamţu, Mariana; Bobu, Maria; Kettrup, Antonius; Siminiceanu, Ilie

    2013-01-01

    The degradation of a paracetamol (N-acetil-para-aminofenol) aqueous solution (C (0) P = 5 mmol L(-1)) is studied in a bench-scale setup by means of simple ozonation (O3) and ozonation catalyzed with UV light (O3/UV) in order to quantify the influence of UV light on the degradation process. The results have shown that under the adopted experimental conditions (25°C, applied ozone dose = 9.8 mg L(-1) and gas flow rate of 20 L h(-1)) both oxidative systems are capable of removing the substrate with mineralization degrees up to 51% for ozonation and 53% for O3/UV. HPICE chromatography allowed the detection of nitrate ions and maleic and oxalic acids as ultimate carboxylic acids. The experimental data have been interpreted through 5 indicators: the conversion of paracetamol (XP ), the conversion degree of TOC (XTOC ), the apparent rate constant (kap ), the Hatta number (Ha) and the enhancement factor (E). The main advantage of photo-ozonation compared to simple ozonation was a more advanced conversion (79% vs. 92% after 90 min). The paracetamol decay follows a pseudo-first-order reaction with a superior rate constant (higher by 54%) for the UV catalyzed system in comparison with direct ozonation. Mineralization is slightly accelerated (+4%) in the O3/UV system, due to the additional production of hydroxyl radicals induced by the UV light and a higher Hatta number (+24%). Nevertheless, the process was still in the slow reaction kinetic regime (Ha < 0.3), and the enhancement factor was not significantly increased. The results are useful for the design and scale-up of the gas-liquid processes. PMID:23647117

  14. The absorption of Mn-54 onto some kinds of clay in aqueous solution

    International Nuclear Information System (INIS)

    The absorption of radioactive Mn-54 from aqueous solutions by natural treated clay of Dilinh region has been investigated. The effect of many factors such as time, pH, carrier concentration... were studied. It was found that the uptake is maximum in neutral or slightly alkaline solutions. The experimental results show that natural clay is suited for the moval of radioactive Mn-54. These types of clay may be considered superior to synthetic exchangers for the removal of Mn-54 if the availability and price of the former are taken into account. (author)

  15. Thermophysical Properties of Aqueous Solutions Used as Secondary Working Fluids

    OpenAIRE

    Melinder, Åke

    2007-01-01

    Secondary working fluids (secondary refrigerants, heat transfer fluids, antifreezes, brines) have long been used in various indirect re-frigeration and heat pump systems. Aqueous solutions (water solu-tions) have long been used as single phase (liquid only) secondary working fluids for cooling in supermarkets, ice rinks, heat recovery systems, heat pumps and other applications. However, aqueous solutions are increasingly used also for freezers in supermarkets and other applications in low tem...

  16. Structure of hydrated complexes formed by metal ions of groups I-III of the Periodic table in aqueous electrolyte solutions under ambient conditions

    International Nuclear Information System (INIS)

    Published and authors' experimental data on the structure of aqueous electrolyte solutions under standard conditions were generalized to ascertain the dependences of the solution structural parameters on chemical nature of dissolved compounds of alkali, alkaline-earth metals, cadmium, scandium, yttrium, lanthanum and indium. Hydrate complexes of metal ions formed in aqueous solutions were systematized, depending on cation size, charge and structure of their external electronic shell

  17. Reactive transport modeling of column experiments on the evolution of saline-alkaline waste solutions.

    Science.gov (United States)

    Zheng, Zuoping; Zhang, Guoxiang; Wan, Jiamin

    2008-04-01

    Leakage of saline-alkaline tank waste solutions often creates a serious environmental contamination problem. To better understand the mechanisms controlling the fate of such waste solutions in the Hanford vadose zone, we simulated reactive transport in columns designed to represent local site conditions. The Pitzer ion interaction module was used, with principal geochemical processes considered in the simulation including quartz dissolution, precipitation of brucite, calcite, and portlandite, multi-component cation exchange, and aqueous complexation reactions. Good matches were observed between the simulated and measured column data at ambient temperature ( approximately 21 degrees C). Relatively good agreement was also obtained at high temperature ( approximately 70 degrees C). The decrease of pH at the plume front is examined through formation of secondary mineral phases and/or quartz dissolution. Substantial formation of secondary mineral phases resulting from multi-component cation exchange suggests that these phases are responsible for a decrease in pH within the plume front. In addition, a sensitivity analysis was conducted with respect to cation exchange capacity, selectivity coefficient, mineral assemblage, temperature, and ionic strength. This study could serve as a useful guide to subsequent experimental work, to thermodynamic models developed for the concentrated solutions at high ionic strength and to other types of waste plume studies. PMID:18313795

  18. Reactive transport modeling of column experiments on the evolution of saline alkaline waste solutions

    Science.gov (United States)

    Zheng, Zuoping; Zhang, Guoxiang; Wan, Jiamin

    2008-04-01

    Leakage of saline-alkaline tank waste solutions often creates a serious environmental contamination problem. To better understand the mechanisms controlling the fate of such waste solutions in the Hanford vadose zone, we simulated reactive transport in columns designed to represent local site conditions. The Pitzer ion interaction module was used, with principal geochemical processes considered in the simulation including quartz dissolution, precipitation of brucite, calcite, and portlandite, multi-component cation exchange, and aqueous complexation reactions. Good matches were observed between the simulated and measured column data at ambient temperature (˜ 21 °C). Relatively good agreement was also obtained at high temperature (˜ 70 °C). The decrease of pH at the plume front is examined through formation of secondary mineral phases and/or quartz dissolution. Substantial formation of secondary mineral phases resulting from multi-component cation exchange suggests that these phases are responsible for a decrease in pH within the plume front. In addition, a sensitivity analysis was conducted with respect to cation exchange capacity, selectivity coefficient, mineral assemblage, temperature, and ionic strength. This study could serve as a useful guide to subsequent experimental work, to thermodynamic models developed for the concentrated solutions at high ionic strength and to other types of waste plume studies.

  19. Radiolysis of aqueous-ethanolic solution of tryptophan

    International Nuclear Information System (INIS)

    The effect of ethanol on radiation stability of tryptophan during γ-irradiation of its aqueous solutions was investigated. In comparison with radiation losses of tryptophan irradiated in pure water, the losses in aqueous-ethanolic solutions are considerably higher and they increase with increasing ethanol concentration. Basic radiation products of tryptophan formed on irradiation of its aqueous-ethanolic solutions in consequence of the reaction of tryptophan with acetaldehyde as the main product of radiolysis of ethanol were followed by paper electrophoresis. (author)

  20. Fabrication of ZnO:Mn nanoparticles with organic shell in a highly alkaline aqueous environment

    Science.gov (United States)

    Chawla, Santa; Sharda; Jayanthi, K.

    2011-01-01

    Synthesis of undoped and Mn doped ZnO nanoparticles by an inclusive co precipitation method and in situ capping with heteromultifunctional organic stabilizer mercaptosuccinic acid (MSA) in a core shell structure, in highly alkaline aqueous matrix have been accomplished. Near room temperature synthesis resulted in high quality monophasic wurtzite hexagonal structure of rod shaped nanoparticles of bare ZnO:Mn with no signature of dopant as separate phase. MSA capping resulted in nanoball like formation. Thermo gravimetric analysis (TGA) and FTIR confirmed MSA capping. ZnO: Mn particles emit in orange and red when excited by UV and blue light. Surface modification makes the nanoparticles hydrophilic with active organic surface easy for bioconjugation with any ligand and can have applications in drug delivery or as nanoscale fluorescent probe in a biological system.

  1. Spectroscopic and mechanistic investigations into oxidation of aspartame by diperiodatocuprate(III in aqueous alkaline medium

    Directory of Open Access Journals (Sweden)

    Jayant I. Gowda

    2015-12-01

    Full Text Available The oxidation of aspartame (ASP by diperiodatocuprate(III (DPC in aqueous alkaline medium at 298 K and a constant ionic strength of 0.30 mol dm−3 was studied spectrophotometrically. The reaction between aspartame and diperiodatocuprate(III in alkaline medium exhibits 1:6 stoichiometry in the reaction. The order of the reaction with respect to [diperiodatocuprate(III] was unity, while the apparent order with respect to [aspartame] was less than unity over the concentration range studied. The rate of the reaction increased with increase in [OH−] whereas the rate decreased with increase in [$ {\\text{IO}}^-_4 $]. Increasing the ionic strength of the medium increased the rate. The main products were identified by FT-IR, NMR, and LC-MS spectral studies. The probable mechanism was proposed. The activation parameters with respect to slow step of the mechanism were computed and discussed. Thermodynamic quantities were also calculated. Kinetic studies suggest that [Cu(H2IO6(H2O2] is the reactive species of Cu(III.

  2. Nanoscale lubricating film formation by linear polymer in aqueous solution

    Science.gov (United States)

    Liu, Shuhai; Guo, Dan; Xie, Guoxin

    2012-11-01

    Film-forming properties of polymer in aqueous solution flowing through a nanogap have been investigated by using a thin film interferometry. The film properties of linear polymer in aqueous solution flowing through a confined nanogap depend on the ratio of water film thickness to averaged radius of polymer chains H0/RPolymer. It was found that the lubrication film thickness of linear polymer in aqueous solution decreases as the polymer molecular weight increasing when H0/RPolymer < 2 ˜ 3. A new lubrication map was proposed, which includes the lubrication regime of weak confinement influence, the lubrication regime of strong confinement influence (LRSCI), and the transition regime of confinement influence. It is very difficult to increase the lubrication film thickness using the higher molecule weight in the LRSCI regime. The lubrication mechanism inferred from our experimental results may help to better understand the dynamic film properties of linear polymer in aqueous solution flowing through a nanogap.

  3. Surface tension and related thermodynamic quantities of aqueous electrolyte solutions

    CERN Document Server

    Matubayasi, Norihiro

    2013-01-01

    Surface tension provides a thermodynamic avenue for analyzing systems in equilibrium and formulating phenomenological explanations for the behavior of constituent molecules in the surface region. While there are extensive experimental observations and established ideas regarding desorption of ions from the surfaces of aqueous salt solutions, a more successful discussion of the theory has recently emerged, which allows the quantitative calculation of the distribution of ions in the surface region. Surface Tension and Related Thermodynamic Quantities of Aqueous Electrolyte Solutions provides a d

  4. γ-Irradiation-induced radiolysis of inulin in aqueous solutions

    International Nuclear Information System (INIS)

    Radiochemical transformations of inulin in aqueous solutions, in air, in the presence of inert gases, helium, nitrogen and in nitrous oxide exposed to various doses of 60Co γ-irradiation were investigated. It was shown that interactions in inulin with OH radicals are principally responsible for radiolytic decomposition of inulin. The data on radiolysis of more simple model systems were used to make available decomposition spectra of γ-irradiated aerated aqueous solution of inulin. 9 refs., 6 figs

  5. Removal of toxic metals from aqueous solutions by fungal biomass of Agaricus macrosporus

    Energy Technology Data Exchange (ETDEWEB)

    Melgar, M.J. E-mail: mjmelgar@lugo.usc.es; Alonso, J.; Garcia, M.A

    2007-10-15

    Fungi such as Agaricus macrosporus show potential for the removal of heavy metals from aqueous solutions contaminated by zinc, copper, mercury, cadmium or lead. This study investigated biosorption of these metals by living or non-living biomass of A. macrosporus from an acid solution, an acid solution supplemented with potassium and phosphorus, and an alkaline solution. Uptake showed a pH-dependent profile. Maximum percentage uptake of all metals was found to occur at alkaline pH (Cu 96%, Pb 89%). With living biomass, metal biosorption was greater and faster in K/P-supplemented acid medium than in non-supplemented acid medium, with equilibrium reached within 15 min for all metals, and the highest percentage uptake being of cadmium (96%). In general, the greatest differences in biosorption capacity were seen for living biomass, between supplemented and non-supplemented acid medium; the smallest differences were between living and dead biomass in alkaline medium. These results support the potential utility of A. macrosporus for heavy metal removal.

  6. PHYSICAL, MECHANICAL, AND DURABILITY PERFORMANCE OF GFRP SQUARE REINFORCING BARS EXPOSED TO ALKALINE SOLUTION

    OpenAIRE

    Ahmed H. Ali; Awad El hashimy; Hesham Haggag

    2015-01-01

    This paper presents an experimental study that investigated the mechanical, physical , and durability characterization of square glass fibre - reinforced polymer (GFRP) bars exposed to alkaline solution. The GFRP square bars were exposed to alkaline solution at 22, 40, and 60°C to accelerate the effect of the concrete environment. The measured tensile strengths of the GFRP square bars before and after exposure were considered as a measure of ...

  7. Electrochemical study of benzene on Pt of various surface structures in alkaline and acidic solutions

    OpenAIRE

    Montilla Jiménez, Francisco; Morallón Núñez, Emilia; Vázquez Picó, José Luis

    2002-01-01

    The electrochemical behaviour of benzene on platinum electrodes (polycrystalline and single-crystal electrodes) has been studied in acidic and alkaline solutions. In acid solutions the reduction of benzene to cyclohexane takes place in all the platinum surface structure employed, however it does not occur in alkaline media (0.1 M NaOH). In this case, the hydrogen adsorption/desorption processes displace the adsorbed benzene from the electrode surface. The oxidation of benzene is also af...

  8. Study on Gold(Ⅰ) Solvent Extraction from Alkaline Cyanide Solution by TBP with Addition of Surfactant

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The new solvent extraction system for gold(Ⅰ) from alkaline cyanide solution by TBP with addition of surfactant in aqueous phase was studied. The effect of various factors, such as equilibrium pH, constitution of organic phase, molar ratio of CPB∶Au(CN)2-, extraction time, aqueous/organic phase ratio, different initial gold concentration, equilibrium temperature, different diluent, different types of extractants and surfactants etc., was inspected. The results show that gold(Ⅰ) can be extracted quantitatively by controlling the quantity of surfactant (CPB); both the equilibrium pH and diluent hardly influence percent extraction. Gold(Ⅰ) percent extraction reaches more than 98% under the optimal experimental conditions. 30% vol TBP diluted by sulphonating kerosene can load gold(Ⅰ) to rather high levels. Loading capacity is in excess of 38 g/L. The extraction mechanism is discussed and the overall extraction reaction is deduced.

  9. Interactions between crystal violet and AOT in aqueous solutions and in AOT/isooctane/water microemulsions

    Institute of Scientific and Technical Information of China (English)

    HAO Xiaojuan; AN Xueqin; CHEN Zhiyun; SHEN Weiguo

    2004-01-01

    The absorbance of crystal violet (CV) in a series of aqueous solutions and a series of sodium bis(2-ethyl- hexyl) sulfosuccinate (AOT)/isooctane/water microemulsions has been determined. Association models have been used to analyse the experimental data to obtain the association constants of CV and AOT in the above two media. It was found that about up to 57% CV was associated by AOT in AOT/ isooctane/water microemulsions, which reduced the reaction rate of alkaline fading of crystal violet in the microemulsions.

  10. Methanol oxidation on Pd/Pt(poly) in alkaline solution

    Science.gov (United States)

    Maksic, A.; Rakocevic, Z.; Smiljanic, M.; Nenadovic, M.; Strbac, S.

    2015-01-01

    Bimetallic electrodes prepared by Pd nanoislands spontaneously deposited on polycrystalline platinum, Pt(poly), at submonolayer coverage were explored for methanol oxidation in alkaline media. Characterization of obtained Pd/Pt(poly) nanostructures was performed ex situ by AFM imaging, spectroscopic ellipsometry and by X-ray photoelectron spectroscopy. In situ characterization of the obtained electrodes and subsequent methanol oxidation measurements were performed by cyclic voltammetry in 0.1 M KOH. Platinum surface with 35% Pd coverage exhibited the highest catalytic activity for methanol oxidation in alkaline media, exceeding those of bare Pt and Pd. Both synergistic and electronic effects are responsible for such enhanced catalysis. The origin of the synergistic effect and possible reaction pathways for methanol oxidation were discussed taking into account the activity of obtained bimetallic electrodes for the oxidation of CO and formaldehyde, as the most probable reaction intermediates.

  11. Kinetics of absorption of trace iodine vapor in aqueous solution of sodium hydroxide, 1

    International Nuclear Information System (INIS)

    The absorption rate of iodine vapor in the air to water or aqueous solution of sodium hydroxide is varied considerably by the concentration of iodine vapor and sodium hydroxide in the solution. Here, experiments have been carried out on the short contact time absorption of trace iodine vapor contained in decarboxylated air into water or sodium hydroxide solution, using a laminar flow liquid column, and the absorption mechanism and the rate of iodine removal by a alkaline washing have been theoretically considered. In the case that water is used as absorbing liquid, it is necessary to evaluate the rate of hypoiodite formation in order to estimate the overall absorption rate, since hypoiodite reaction progresses at finite rate. While if aqueous solution of sodium hydroxide is used, the hypoiodite formation is fast enough to treat the absorption as the instantaneous reversible reaction at the interface. The main factors determining the reaction rate in a liquid film are the concentration of molecular iodine and hydroxyl ions, and the latter is mainly varied by electric charge balance condition in aqueous solution. (Wakatsuki, Y.)

  12. Absorption and Chemisorption of Small Levitated Single Bubbles in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Alexander Tollkötter

    2014-02-01

    Full Text Available The absorption and chemisorption of small bubbles with N2 or CO2 were investigated experimentally in aqueous and alkaline solutions. Different bubble sizes were studied ranging from 0.1 to 2.5 mm in alkaline concentrations of 0.1 mM to 1 M NaOH. The experiments were conducted in a device consisting of a converging microchannel with a down flowing liquid. Levitation positions of single bubbles were optically characterized. A correlation was developed for the drag force coefficient, CD, including wall effects based on the force equilibrium. A linear decrease of bubble diameters was identified with and without chemical reaction, which is referred to as a rigid bubble surface area. Measured Sherwood numbers agree well with the literature values for the investigated Reynolds number range.

  13. Study on specific enthalpy of ice including solute in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Kumano, Hiroyuki; Hirata, Tetsuo; Izumi, Yasuyuki [Department of Mechanical Systems Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan)

    2010-05-15

    Effects of solute included in a sample on the specific enthalpy of ice are investigated experimentally. In the experiments, ice including the solute was made from an aqueous solution, and the specific enthalpy was measured by melting the ice in the aqueous solution. Moreover, a physical model of the ice including the solute is proposed. As a result, when the concentration of the aqueous solution is set at a value equivalent to the concentration of the sample, the specific enthalpy of the sample increases with the concentration of the sample. The measurement results and the calculated values agree well, and it was found that the method for calculating the specific enthalpy of the sample is valid. Moreover, when the concentration of the aqueous solution is higher than that of the ice including the solute, it was found the calculation method for the specific enthalpy of the sample is appropriate. (author)

  14. Acidities of Water and Methanol in Aqueous Solution and DMSO

    Science.gov (United States)

    Gao, Daqing

    2009-01-01

    The relative acidities of water and methanol have been a nagging issue. In gas phase, methanol is more acidic than water by 36.0 kJ/mol; however, in aqueous solution, the acidities of methanol and water are almost identical. The acidity of an acid in solution is determined by both the intrinsic gas-phase ionization Gibbs energy and the solvent…

  15. SEPARATION OF TECHNETIUM FROM AQUEOUS SOLUTIONS BY COPRECIPITATION WITH MAGNETITE

    Science.gov (United States)

    Rimshaw, S.J.

    1961-10-24

    A method of separating technetium in the 4+ oxidation state from an aqueous basic solution containing products of uranium fission is described. The method consists of contacting the solution with finely divided magnetite and recovering a technetium-bearing precipitate. (AEC)

  16. Radiolysis of aqueous solutions of sodium sulfides. Chapter 8

    International Nuclear Information System (INIS)

    To study the radiolysis of the aqueous solutions of sodium sulphide, use was made of infrared spectroscopy, mass-spectrometry and iodometric titration. During the γ-irradiation of the aqueous solutions of sodium sulphide one can observe the appearance of various stable sulphur-containing products. Data are discussed on the radiolysis in a nitrous environment, on oxygen bubbling, at varying radiation doses, pH and temperature values. Consideration is also given to the low-temperature radiolysis of the aqueous solutions of sodium sulphide by the EPR method. In the radiolysis of both crystalline and glassy solutions of Na2S there appear an ion-radical S- and a radical SO2-

  17. Antiscalant properties of Spergularia rubra and Parietaria officinalis aqueous solutions

    Science.gov (United States)

    Cheap-Charpentier, Hélène; Gelus, Dominique; Pécoul, Nathalie; Perrot, Hubert; Lédion, Jean; Horner, Olivier; Sadoun, Jonathan; Cachet, Xavier; Litaudon, Marc; Roussi, Fanny

    2016-06-01

    The formation of calcium carbonate in water has important implications in industry. Chemical antiscalant is usually used to control scale depositions. Plant extracts have been recently used as new green antiscalant agents, as they can be easily prepared and are environmentally friendly. In this study, stock aqueous solutions of Spergularia rubra and Parietaria officinalis, two plants used in traditional medicine to treat or prevent urolithiasis, were obtained by infusion. The antiscaling properties of these extracts towards CaCO3 formation were tested by using chronoamperometry and Fast Controlled Precipitation methods. The aqueous solution of S. rubra was further fractionated to isolate compounds of lower polarity. Their efficiency towards CaCO3 precipitation was characterized by Fast Controlled Precipitation method. The inhibiting efficiency of this fractionated solution was greater than that of the stock aqueous solution.

  18. Tritium exchange reactions in imidazole in aqueous and organic solutions

    International Nuclear Information System (INIS)

    Tritium exchange reactions were studied in aqueous and organic solutions of imidazole and methylimidazole. For the exchange in an aqueous solution the mechanism through ylide intermediate formation postulated by VAUGHAN et al. was modified in this study. The rate constant obtained by MASLOVA et al. was found to be too small compared to ours. For the exchange reaction of methylimidazole in an aqueous solution the rate decreased due to the effect of a methyl group attached to the aromatic ring. The C-2 tritiation of imidazole was studied in chloroform, acetone and dioxane for the first time. It was dependent on polymer properties. An intramolecular exchange mechanism was applicable to the trimer while an intermolecular exchange mechanism was applicable to the dimer. The rate constants of the exchange reactions in organic solutions were obtained for both mechanisms. (orig.)

  19. Synthesis and Aqueous Solution Viscosity of Hydrophobically Modified Xanthan Gum

    Institute of Scientific and Technical Information of China (English)

    QIAN Xiao-lin; WU Wen-hui; YU Pei-zhi; WANG Jian-quan

    2007-01-01

    Two xanthan gum derivatives hydrophobically modified by 4 or 8 tetradecyl chains per 100 xanthan gum structure units were synthesized. The derivatives were studied by scanning electron microscope and pyrene fluorescence spectrometry. And the aqueous solution apparent viscosity of the derivatives was investigated. The results indicate that the network of the derivatives with more hydrophobic groups is closer and tighter. With increasing of alkyl chain substitution degree, the hydrophobically associating interactions enhance in aqueous solution. Aqueous solution apparent viscosity of the derivatives increases with increasing of polymer concentration and alkyl substitution degree, and decreases with the increase of temperature. In the brine solution, the strong viscosity enhancement phenomenon appears. The interaction between the derivatives and surfactant sodium dodecylbenzene sulfonate is strong.

  20. Partitioning high-level waste from alkaline solution: A literature survey

    International Nuclear Information System (INIS)

    Most chemical partitioning procedures are designed for acidic feed solutions. However, the high-level waste solutions in the underground storage tanks at US Department of Energy defense production sites are alkaline. Effective partitioning procedures for alkaline solutions could decrease the need to acidify these solutions and to dissolve the solids in acid, which would simplify subsequent processing and decrease the generation of secondary waste. The author compiles candidate technologies from his review of the chemical literature, experience, and personal contacts. Several of these are recommended for evaluation

  1. Flotation separation of hafnium(IV) from aqueous solutions

    International Nuclear Information System (INIS)

    A simple, rapid method for the separation of hafnium from aqueous solutions was investigated using sup(175+181)Hf tracer. Cationic hafnium complex ions were floated from dilute acid solutions with sodium lauryl sulfate (SLS) and anionic hafnium complexes were floated from basic and oxalic acid solutions with hexadecyltrimethyl ammonium bromide (HTMAB). The conditions necessary for quantitative recovery of the metal and mechanisms of flotation are described. (author)

  2. Method and device for removing ruthenium in aqueous solution

    International Nuclear Information System (INIS)

    Highly soluble and reactive high order ruthenium oxides assumed to be ruthenium tetraoxide, it they are not reduced on a cathode immediately, would evaporate as they are or react with nitrogen oxides formed by oxidation-decomposition of nitrosyl complex to return again to their nitrosyl complex. Accordingly, it is necessary for the aqueous solution to brought into contact with the anode and the cathode repeatedly. The present invention complies with the demand, in which one or plural pairs of plate-like electrodes are stacked as layers and an aqueous solution incorporating ruthenium is passed between the layers so that it is brought into contact with the anode and the cathode repeatedly to repeat oxidations and reductions. In view of the above, since the water soluble high order ruthenium oxides generated on the anode in the aqueous solution are immediately brought into contact with the cathode and reduced into insoluble lower order oxides, ruthenium can be removed. (T.M.)

  3. Study of free acidity determinations in aqueous solution

    International Nuclear Information System (INIS)

    The object of this work is the study of the principal methods which can be applied to the measurement of 'free' acidity. In the first part, we define the various types of acidity which can exist in aqueous solution; then, after having studied some hydrolysis reactions, we compare the value of the neutralisation pH of the hydrated cation and that of the precipitation of the hydroxide. In the second part we have started to study the determination of the acidity of an aqueous solution. After having rapidly considered the 'total' acidity determination, we deal with the problem of the 'free' acidity titration. We have considered in particular certain methods: extrapolation of the equivalent point, colorimetric titrations with or without a complexing agent, and finally the use of ion-exchange resins with mixed aqueous and solvent solutions. (author)

  4. Molecular Weight and Aggregation of Erwinia Gum in Aqueous Solutions

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Erwinia(E) gum is composed of glucose, fucose, galactose and glucuronic acid. The weight-average molecular weights Mw, number-average molecular weights Mn and intrinsic viscosities[η] of the four fractions and the unfractionated E gum in aqueous solutions at desired temperatures were studied by light scattering, membrane osmometry, size exclusion chromatography(SEC) and viscometry. The experimental results prove that E gum formed aggregates in the aqueous solution at 25 ℃ and the aggregates were broken gradually with increasing temperature. The dissociation of the aggregates of E gum in the aqueous solution started at 36 ℃, and was completed at around 90 ℃. The [η] values of E gum and its fractions are much higher than those of the conventional polymers with the similar molecular weights, and decrease with increasing NaCl concentration.

  5. Self-aggregation of liquids from biomass in aqueous solution

    International Nuclear Information System (INIS)

    Highlights: • Aggregation behaviour of liquids from biomass in aqueous solution has been studied. • Standard Gibbs free energies of aggregation have been calculated. • Solubility in water of these compounds has been determined. • Critical aggregation concentration decreases as the solubility in water does. -- Abstract: Aggregation of several chemicals from biomass: furfural derived compounds (furfural, 5-methylfurfural, furfuryl alcohol and tetrahydrofurfuryl alcohol), lactate derived compounds (methyl lactate, ethyl lactate and butyl lactate), acrylate derived compound (methyl acrylate) and levulinate compounds (methyl levulinate, ethyl levulinate and butyl levulinate) in aqueous solution has been characterised at T = 298.15 K through density, ρ, speed of sound, u, and isentropic compressibilities, κS, measurements. In addition the standard Gibbs free energies of aggregation have been also calculated. Furthermore, in order to deepen insight the behaviour of these chemicals in aqueous solution, the solubility of these compounds has been measured at T = 298.15 K

  6. Mutual diffusion coefficients of L-lysine in aqueous solutions

    International Nuclear Information System (INIS)

    Highlights: • Mutual diffusion coefficients of L-lysine in aqueous solutions. • Influence of the thermodynamic factors on the variation of their mutual diffusion coefficients. • Estimation of the hydrodynamic radius of L-lysine. - Abstract: Mutual diffusion coefficients, D, were determined for aqueous solutions of L-lysine at T = 298.15 K at concentrations from (0.001 to 0.100) mol · dm−3. From these experimental results, the hydrodynamic radius Rh, diffusion coefficients at infinite dilution D0, the thermodynamic factors and activity coefficients γ, by using the Hartley equation, have been estimated, permitting us to have a better understanding of the thermodynamic of these systems of L-lysine in aqueous solutions

  7. Anodic dissolution of gold in alkaline solutions containing thiourea, thiosulfate and sulfite ions

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Gold dissolves electrochemically in alkaline solutions containing ligands to form complex ions with gold ion. Therefore, selective leaching of noble metals is expected without dissolution of base metals such as steels, aluminum alloys in scrap treatment. Gold electrodes were investigated using linear sweep voltammetry, EQCM method and potentiostatic electrolysis in alkaline solutions containing thiourea, Na2SO3 and Na2S2O3. The solution composition, electrode potential affect gold dissolution rate and current efficiency. The gold dissolved from anode electrode forms complex ions, suspension particles as compound precipitates and deposits on cathode electrode as a metal. Anodic efficiency for gold dissolution is between 10% and 22%. This is caused by the oxidation decomposition of sulfite ions and thiourea. The stability of the alkaline solution containing these elements was also estimated by capillary electrophoresis technique.

  8. Effect of electron beam irradiation on the degradation of monochlorophenols in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    ADELEKE Olukunle Francis; ZHOU Rui-min; Zu Jian-hua; Ekoko Bakambo Gracien

    2005-01-01

    Electron beam was successfully used for the degradation of 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) in aqueous solutions in this research. The effect of radiation dose on substrate degradation and dechlorination of solutions with concentration of 50 mg/L was investigated. The effect of initial concentration, pH and presence of oxygen was also investigated. The concentration of 2-CP and 4-CP remaining in solution after irradiation were measured by HPLC. The results showed that increased radiation dose led to increased degradation of the chlorophenols and increased Cl- yield. Deaeration was also found to significantly increase the rate of degradation of chlorophenols in water while degradation and dechlorination under alkaline condition was lower than at low to neutral pH.

  9. Reaction mechanism of 3-chlorophenol with OH, H in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The reaction mechanism of 3-chlorophenol with OH, H inaqueous solution was studied by transient technology. The3-chlorophenol aqueous solutions have been saturated with air or N2previously. Under alkaline condition, the reaction of OH radicalwith 3-chlorophenol produces 3-chlorinated phenoxyl radical, withthe absorption peaks at 400 nm and 417 nm. Under neutral condition,the reaction of OH radical with 3-chlorophenol produces OH-adductwith the maximal absorption at about 340 nm. And in acid solution,the reaction of H with 3-chlorophenol produces H-adduct with themaximal absorption at about 320 nm. 3-chlorophenol is compared with4- and 2-chlorophenols from the free radical pathways. The resultsshow that the positions of chlorine on the aromatic ring stronglyinfluence the dehalogenation and degradation process.

  10. Removal of Phosphate from Aqueous Solution with Modified Bentonite

    Institute of Scientific and Technical Information of China (English)

    唐艳葵; 童张法; 魏光涛; 李仲民; 梁达文

    2006-01-01

    Bentonite combined with sawdust and other metallic compounds was used to remove phosphate from aqueous solutions in this study. The adsorption characteristics of phosphate on the modified bentonite were investigated, including the effects of temperature, adsorbent dosage, initial concentration of phosphate and pH on removal of phosphate by conducting a series of batch adsorption experiments. The results showed that 98% of phosphate removal rate was obtained since sawdust and bentonite used in this investigation were abundantly and locally available. It is concluded that modified bentonite is a relatively efficient, low cost and easily available adsorbent for the removal of phosphate from aqueous solutions.

  11. Degradation kinetics of benzyl nicotinate in aqueous solution

    Directory of Open Access Journals (Sweden)

    Mbah C

    2010-01-01

    Full Text Available The degradation of benzyl nicotinate in aqueous solution over a pH range of 2.0-10.0 at 50±0.2 o was studied. The degradation was determined by high performance liquid chromatography. The degradation was observed to follow apparent first-order rate kinetics and the rate constant for the decomposition at 25 o was estimated by extrapolation. The reaction was shown to be hydroxide ion catalyzed and the Arrhenius plots showed the temperature dependence of benzyl nicotinate degradation. A significant increase in the stability of benzyl nicotinate was observed when glycerol or polyethylene glycol 400 was incorporated into the aqueous solution.

  12. Ionisation constants of inorganic acids and bases in aqueous solution

    CERN Document Server

    Perrin, D D

    2013-01-01

    Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution, Second Edition provides a compilation of tables that summarize relevant data recorded in the literature up to the end of 1980 for the ionization constants of inorganic acids and bases in aqueous solution. This book includes references to acidity functions for strong acids and bases, as well as details about the formation of polynuclear species. This text then explains the details of each column of the tables, wherein column 1 gives the name of the substance and the negative logarithm of the ionization constant and column 2

  13. Valence Electronic Structure of Aqueous Solutions: Insights from Photoelectron Spectroscopy

    Science.gov (United States)

    Seidel, Robert; Winter, Bernd; Bradforth, Stephen E.

    2016-05-01

    The valence orbital electron binding energies of water and of embedded solutes are crucial quantities for understanding chemical reactions taking place in aqueous solution, including oxidation/reduction, transition-metal coordination, and radiation chemistry. Their experimental determination based on liquid-photoelectron spectroscopy using soft X-rays is described, and we provide an overview of valence photoelectron spectroscopy studies reported to date. We discuss principal experimental aspects and several theoretical approaches to compute the measured binding energies of the least tightly bound molecular orbitals. Solutes studied are presented chronologically, from simple electrolytes, via transition-metal ion solutions and several organic and inorganic molecules, to biologically relevant molecules, including aqueous nucleotides and their components. In addition to the lowest vertical ionization energies, the measured valence photoelectron spectra also provide information on adiabatic ionization energies and reorganization energies for the oxidation (ionization) half-reaction. For solutes with low solubility, resonantly enhanced ionization provides a promising alternative pathway.

  14. Contact nuclei formation in aqueous dextrose solutions

    Science.gov (United States)

    Cerreta, Michael K.; Berglund, Kris A.

    1990-06-01

    A laser Raman microprobe was used in situ to observe the growth of alpha dextrose monohydrate on alpha anhydrous dextrose crystals. The Raman spectra indicate growth of the monohydrate below 28.1°C, but the presence of only the anhydrous form above 40.5°C. Contact nucleation experiments with parent anhydrous crystals yielded only monohydrate nuclei below 28.1°C, while contacts in solutions between 34.5 and 41.0°C produced both crystalline forms, and contacts in solutions above 43.5°C produced only anhydrous nuclei. The inability of the monohydrate to grow on anhydrous crystals in the same solution that forms the two crystalline phases with a single contact precludes a simple attrition mechanism of nuclei formation. For the same reason, the hypothetical mechanism involving parent crystal stabilization of pre-crystalline clusters, allowing the clusters to grow into nuclei, is also contradicted. A third, mechanism, which may be a combination of the two, is believed to apply.

  15. Nb-TiO{sub 2} supported platinum nanocatalyst for oxygen reduction reaction in alkaline solutions

    Energy Technology Data Exchange (ETDEWEB)

    Elezovic, N.R., E-mail: nelezovic@tmf.bg.ac.rs [Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, Belgrade (Serbia); Babic, B.M. [Vinca Institute of Nuclear Sciences, Belgrade (Serbia); Radmilovic, V.R. [National Center for Electron Microscopy, LBNL University of California, Berkely (United States); Vracar, Lj.M.; Krstajic, N.V. [Faculty of Technology and Metallurgy, University of Belgrade, Belgrade (Serbia)

    2011-10-30

    Highlights: > Nb doped TiO{sub 2} catalyst support was successfully synthesized. > Synthesized support surface area was much higher comparing with sub-stoichiometric titanium oxides as supporting material. > The Nb-TiO{sub 2} supported Pt catalyst was successfully prepared and characterized by TEM technique. > Nb doped TiO{sub 2} support seems to be more suitable than carbon based support. > The change in the rate-determining step was proposed for reaction mechanism explanation. - Abstract: Platinum based nanocatalyst at home made Nb-TiO{sub 2} support was synthesized and characterized as the catalyst for oxygen reduction reaction in 0.1 mol dm{sup -3} NaOH, at 25 deg. C. Nb doped TiO{sub 2} catalyst support, containing 5% of Nb, has been synthesized by modified acid-catalyzed sol-gel procedure in non-aqueous medium. BET and X-ray diffraction (XRD) techniques were applied for characterization of synthesized supporting material. XRD analysis revealed only presence of anatase TiO{sub 2} phase in synthesized support powder. Existence of any peaks belonging to Nb compounds has not been observed, indicating Nb incorporated into the lattice. Nb-TiO{sub 2} supported Pt nanocatalyst synthesized, using borohydride reduction method, was characterized by TEM and HRTEM techniques. Platinum nanoparticles distribution, over Nb doped TiO{sub 2} support, was quite homogenous. Mean particle size of about 4 nm was found with no pronounced particle agglomeration. Electrochemical techniques: cyclic voltammetry and linear sweep voltammetry at rotating disc electrode were applied in order to study kinetics and estimate catalytic activity of this new catalyst for the oxygen reduction reaction in alkaline solution. Two different Tafel slopes were found: one close to -90 mV dec{sup -1} in low current density region and other approximately -200 mV dec{sup -1} in high current density region, which is in good accordance with literature results for oxygen reduction at Pt single crystals, as

  16. Preliminary study on lithium-salt aqueous solution blanket

    International Nuclear Information System (INIS)

    Aqueous solution blanket using lithium salts such as LiNO3 and LiOH have been studied in the US-TIBER program and ITER conceptual design activity. In the JAERI/LANL collaboration program for the joint operation of TSTA (Tritium Systems Test Assembly), preliminary design work of blanket tritium system for lithium ceramic blanket, aqueous solution blanket and liquid metal blanket, have been performed to investigate technical feasibility of tritium demonstration tests using the TSTA. Detail study of the aqueous solution blanket concept have not been performed in the Japanese fusion program, so that this study was carried out to investigate features of its concept and to evaluated its technical problems. The following are the major items studied in the present work: (i) Neutronics of tritium breeding ratio and shielding performance Lithium concentration, Li-60 enrichment, beryllium or lead, composition of structural material/beryllium/solution, heavy water, different lithium-salts (ii) Physicochemical properties of salts Solubility, corrosion characteristics and compatibility with structural materials, radiolysis (iii) Estimation of radiolysis in ITER aqueous solution blanket. (author)

  17. Phytoremediation of Heavy Metals in Aqueous Solutions

    OpenAIRE

    Felix Aibuedefe AISIEN; Oluwole FALEYE; Eki Tina AISIEN

    2010-01-01

    One of the major environmental problems is the pollution of water and soil by toxic heavy metals. This study investigated the phytoremediation potential of water hyacinth, for the removal of cadmium (Cd), lead (Pb) and zinc (Zn). Water hyacinths were cultured in bore-hole water, supplemented with 5mg/l of Zn and Pb and 1mg/l of Cd at pH 4.5, 6.8 and 8.5. The plants were separately harvested each week for six weeks. The results showed that removal of these metals from solution was fast especia...

  18. Chemical denitration of aqueous nitrate solutions

    International Nuclear Information System (INIS)

    The Plant for Active Waste Liquids (PAWL) at CRNL will immobilize in glass the fission products in waste from Mo-99 production. The nitrate ions in the waste can be destroyed by heating, but also by chemical reaction with formic acid (HCOOH). Since chemical denitration has several advantages over thermal denitration it was studied in the course of vitrification process development. Two free radical mechanisms are examined here to explain kinetic data on chemical denitration of nitric acid solutions with formic acid. One mechanism is applicable at > 1 mol/L HNO3 and involves the formate radical (HCOO.). The second mechanism holds at 3 and involves the hyponitrous radical (HNO.). Mass balances for various species were written based on the law of mass action applied to the equations describing the reaction mechanism. Analytical and numerical solutions were obtained and compared. Literature data on batch denitration were used to determine some of the rate constants while others were set arbitrarily. Observed stoichiometry and trends in reactant concentrations are predicted accurately for batch data. There are no literature data to compare with the prediction of negligible induction time

  19. Photocatalytic degradation of molinate in aqueous solutions.

    Science.gov (United States)

    Bizani, E; Lambropoulou, D; Fytianos, K; Poulios, I

    2014-11-01

    In this study, the degradation of molinate through heterogeneous photocatalysis, using two different types of the semiconductor TiO2 as photocatalyst, as well as through homogeneous treatment, applying the photo-Fenton reaction, has been investigated. As far as heterogeneous photocatalysis is concerned, the degradation of the pesticide follows apparent first-order kinetics, while the type of the catalyst and the pH value of the solution affect the degradation rate. The effect of the addition of electron scavengers (H2O2 and K2S2O8) was also studied. In the case of photo-Fenton-assisted system, the degradation also follows pseudo-first-order kinetics. Parameters such as iron's and electron scavenger's concentration and inorganic ions strongly affect the degradation rate. The extent of pesticide mineralization was investigated using dissolved organic carbon (DOC) measurements. The toxicity of the treated solution was evaluated using the Microtox test based on the luminescent bacteria Vibrio fischeri. The detoxification and mineralization efficiency was found to be dependent on the system studied, and although it did not follow the rate of pesticide disappearance, it took place in considerable extent. The study of the photodegradation treatment was completed by the determination of the intermediate by-products formed during the process, which was carried out using LC-MS/MS technique and led to similar compounds with both processes. PMID:24928378

  20. Drag enhancement of aqueous electrolyte solutions in turbulent pipe flow.

    Science.gov (United States)

    Doherty, Andrew P; Spedding, Peter L; Chen, John J J

    2010-04-22

    Detailed experimental results are presented for both laminar and turbulent flow of aqueous solutions in pipes of different diameters. Nonelectrolytes, such as sugar solutions followed the normal Moody pressure loss curves. Drag enhancement was demonstrated for turbulent flow of aqueous electrolyte solutions but not for laminar flow. The increased pressure drop for turbulent electrolyte flow was attributed to an electroviscous effect and a theory was developed to explain the drag enhancement. The increased pressure drop for the turbulent region of flow was shown to depend on the Debye length in the laminar sublayer on the pipe wall. Reasonable predictions of the increasing drag were obtained for both 1:1 and 2:1 electrolyte solutions. PMID:20337452

  1. Dissociation of methane hydrate in aqueous NaCl solutions.

    Science.gov (United States)

    Yagasaki, Takuma; Matsumoto, Masakazu; Andoh, Yoshimichi; Okazaki, Susumu; Tanaka, Hideki

    2014-10-01

    Molecular dynamics simulations of the dissociation of methane hydrate in aqueous NaCl solutions are performed. It is shown that the dissociation of the hydrate is accelerated by the formation of methane bubbles both in NaCl solutions and in pure water. We find two significant effects on the kinetics of the hydrate dissociation by NaCl. One is slowing down in an early stage before bubble formation, and another is swift bubble formation that enhances the dissociation. These effects arise from the low solubility of methane in NaCl solution, which gives rise to a nonuniform spatial distribution of solvated methane in the aqueous phase. We also demonstrate that bubbles form near the hydrate interface in dense NaCl solutions and that the hydrate dissociation proceeds inhomogeneously due to the bubbles. PMID:25237735

  2. Mercury removal from aqueous and organo-aqueous solutions by natural Mexican erionite

    International Nuclear Information System (INIS)

    The sorption of Hg(II) from aqueous and organo aqueous solutions was investigated by Mexican natural erionite. The mercury chemical species (anionic, cationic or neutral) were determined by high voltage electrophoresis, and the mercury chemical species present in the aqueous media were simulated by a program MEDUSA. The mercury sorption process was monitored during 48 hours. The mercury content was determined by neutron activation analysis. Mixtures of benzene/water[Hg(II)], toluene/water[Hg(II)] and ethanol/water[Hg(II)] were chosen as organo-aqueous media. It was found that both the mercury chemical species and the dielectric constant of solvents play an important role in the mercury sorption by erionite. (author)

  3. Radiolysis of paracetamol in dilute aqueous solution

    Science.gov (United States)

    Szabó, László; Tóth, Tünde; Homlok, Renáta; Takács, Erzsébet; Wojnárovits, László

    2012-09-01

    Using radiolytic experiments hydroxyl radical (main reactant in advanced oxidation processes) was shown to effectively destroy paracetamol molecules. The basic reaction is attachment to the ring. The hydroxy-cyclohexadienyl radical produced in the further reactions may transform to hydroxylated paracetamol derivatives or to quinone type molecules and acetamide. The initial efficiency of aromatic ring destruction in the absence of dissolved O2 is c.a. 10%. The efficiency is 2-3 times higher in the presence of O2 due to its reaction with intermediate hydroxy-cyclohexadienyl radical and the subsequent ring destruction reactions through peroxi radical. Upon irradiation the toxicity of solutions at low doses increases with the dose and then at higher doses it decreases. This is due to formation of compounds with higher toxicity than paracetamol (e.g. acetamide, hidroquinone). These products, however, are highly sensitive to irradiation and degrade easily.

  4. Influence if acidity and concentration of aqueous uranyl nitrate solutions on the efficiency of uranium absorption by hydrolytic wood lignin

    International Nuclear Information System (INIS)

    Efficiency of uranium(VI) absorption by hydrolytic wood lignin from uranyl nitrate aqueous solutions under static conditions at room temperature, depending on solution acidity and uranium concentration, was studied using the methods of elementary analysis and IR spectroscopy. It was ascertained that hydrolytic lignin manifests a high ability to strong uranium(VI) absorption from low-acid and alkaline solutions. Interaction of uranium(VI) and hydrolytic lignin occurs both according to ion exchange mechanism and at the expense of donor-acceptor bonds formation

  5. Photocatalytical oxidation of de-icing agents in aqueous solutions and aqueous extract of jet fuel.

    Science.gov (United States)

    Krichevskaya, M; Malygina, T; Preis, S; Kallas, J

    2001-01-01

    Improper handling of jet fuel at abandoned military bases has resulted in heavy pollution of the soil and groundwater. Experimental research of photocatalytical oxidation (PCO) of jet fuel aqueous extract and aqueous solutions of de-icing agents was undertaken. The influence of different parameters - pH, concentration of substances to be oxidised, presence of inorganic admixtures, effect of OH. radical generators--on the PCO of solutions of de-icing agents and jet fuel aqueous extract was determined. The role of OH. radicals was found to be less important in determining the PCO rate. The PCO of organic pollutants was also investigated using a catalyst immobilised onto the surface of buoyant hollow glass microspheres. Attached titanium dioxide (TiO2) showed lower photocatalytical activity than when suspended in slurry, although it allows waters to be treated in simple shallow ponds without intensive stirring. The biodegradability of aqueous solutions of de-icing agents and jet fuel aqueous extract increased as PCO proceeded. PMID:11695445

  6. The coacervation of aqueous solutions of tetraalkylammonium halides

    International Nuclear Information System (INIS)

    The coacervation of aqueous solutions of tatraalkylammonium halides in the presence of not of inorganic halides and acids has been studied, considering thermodynamic and spectroscopic aspects. The importance of dispersion forces as well as forces resulting from hydrophobic hydration has been assessed. The analogy between these systems and anionic ion exchange resins has been shown especially for Uranium VI extraction

  7. Ion equilibrium in aqueous solutions of pectin materials

    International Nuclear Information System (INIS)

    By means of electro conductivity method the comparative study of ion equilibrium of pectin materials of apple, orange and sunflower in aqueous solution at various ph was conducted. According to experimental data on specific conductivity the value of equivalent conductivity, level, functions and dissociation constant were evaluated. (author)

  8. Why Urea Eliminates Ammonia Rather Than Hydrolyzes in Aqueous Solution

    OpenAIRE

    Alexandrova, Anastassia N.; Jorgensen, William L.

    2007-01-01

    A joint QM/MM and ab initio study on the decomposition of urea in the gas phase and in aqueous solution is reported. Numerous possible mechanisms of intramolecular decomposition and hydrolysis have been explored; intramolecular NH3-elimination assisted by a water molecule is found to have the lowest activation energy. The solvent effects were elucidated using the TIP4P explicit w...

  9. Reactive Extraction of Alcohols from Apolar Hydrocarbons with Aqueous Solutions

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The aqueous solutions are evaluated as sustainable reactive extraction solvents for the recovery of monohydroxyl alcohols (benzyl alcohol, 1-hexanol, cyclohexanol) present in few-percent concentrations in apolar hydrocarbons (toluene, n-hexane, and cyclohexane) by considering two approaches. An aqueous solution containing a reactive extractant, like borate salts, borate complexes, a monosalt of dicarboxylic acid,hydroxypropyl-cyclodextrins, and silver nitrate, shows limited potential to be used. Another approach, in which the alcohol is chemically modified prior to the extraction into an easy-extractable form, in this case a monoesterlcarboxylic acid, shows much more potential. An environmentally benign aqueous solution of sodium hydrogen carbonate can provide a distribution ratio of benzyl alcohol up to 200, leaving the solubility of the organic solvent in the aqueous solution unchanged relative to pure water and therefore increasing the selectivity with two orders of magnitude. The modification of aromatic, cyclo-aliphatic, and linear aliphatic alcohols can be performed efficiently in the apolar organic solvent without need for a catalyst. The recovery of the modified alcohol can be performed by back-extraction in combination with a spontaneous hydrolysis.

  10. Photolysis of Periodate and Periodic Acid in Aqueous Solution

    DEFF Research Database (Denmark)

    Sehested, Knud; Kläning, U. K.

    1978-01-01

    The photochemistry of periodate and periodic acid in aqueous solution was studied (i) by quantum yield measurements at low light intensity (ii) by flash photolysis, and (iii) by photolysis of glassy samples at 77 K. The photochemical studies were supplemented with pulse radiolysis studies of...

  11. NMR study of thermosensitive homopolymers and copolymers in aqueous solutions

    Czech Academy of Sciences Publication Activity Database

    Spěváček, Jiří; Šťastná, J.; Starovoytova, Larisa; Hanyková, L.

    Ireland : University College Dublin, 2012. s. 198. [EUROMAR 2012. Magnetic Resonance Conference. 01.07.2012-05.07.2012, Dublin] R&D Projects: GA ČR GA202/09/1281 Institutional research plan: CEZ:AV0Z40500505 Institutional support: RVO:61389013 Keywords : thermosensitive polymer * aqueous solution * phase transition Subject RIV: CD - Macromolecular Chemistry

  12. Accurate Description of Calcium Solvation in Concentrated Aqueous Solutions

    Czech Academy of Sciences Publication Activity Database

    Kohagen, Miriam; Mason, Philip E.; Jungwirth, Pavel

    2014-01-01

    Roč. 118, č. 28 (2014), s. 7902-7909. ISSN 1520-6106 R&D Projects: GA ČR GBP208/12/G016; GA MŠk LH12001 Institutional support: RVO:61388963 Keywords : calcium chloride * aqueous solution * molecular dynamics * neutron scattering Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.302, year: 2014

  13. Neodymium(3) complexing with bischloromethylphosphinic acid in aqueous solution

    International Nuclear Information System (INIS)

    High resolution spectrography is used to study Nd3+ complexing with (ClCH2)2POOH(HL) in aqueous solution. NdL2+ complex (lg Kstab = 0.44±0.04) with the corresponding absorption band with a maximum at λ=4283 A is formed in a system

  14. Densities concentrations of aqueous of uranyl nitrate solutions

    International Nuclear Information System (INIS)

    The ratio density-concentration of aqueous uranyl nitrate solutions expressed as U3O8 grams/liter, U grams/liter and hexahydrate uranyl nitrate weight percent at different temperatures, are established. Experimental values are graphically correlated and compared whit some published data. (Author) 2 refs

  15. [Pulsed radiolysis of aqueous solutions of serum albumin containing naphthoquinones].

    Science.gov (United States)

    Pribush, A G; Savich, A V

    1987-01-01

    As was shown by the pulse radiolysis method the simultaneous presence of naphthoquinone and human serum albumin molecules in an aqueous solution leads to the adsorption of the former on the surface of the latter. It is suggested that in these conditions the protein tertiary structure changes. New conformation reduces the reactivity of albumin toward the hydrated electron. PMID:3628723

  16. Gamma radiolysis of aqueous solutions of glycerin α-monochlorohydrin

    International Nuclear Information System (INIS)

    Data on γ-radiolysis of 0.1 mol/l aqueous solutions of glycerin α-monochlorohydrin (GMC) are presented. The radiolysis mechanism is considered. The rate constant of GMC reaction with esub(aq) k=(6.8+-0.8)x108 l/molxs is determined on the basis of experimental data

  17. Solubility of carbon dioxide in aqueous piperazine solutions

    NARCIS (Netherlands)

    Derks, P. W. J.; Dijkstra, H. B. S.; Hogendoorn, J. A.; Versteeg, G. F.

    2005-01-01

    In the present work, new experimental data are presented on the solubility of carbon dioxide in aqueous piperazine solutions, for concentrations of 0.2 and 0.6 molar piperazine and temperatures of 25, 40, and 70°C respectively. The present data, and other data available in the literature, were corr

  18. Demonstration of reverse symmetry waveguide sensing in aqueous solutions

    DEFF Research Database (Denmark)

    Horvath, R.; Pedersen, H.C.; Larsen, N.B.

    2002-01-01

    A reverse symmetry waveguide is presented for evanescent wave sensing in aqueous solutions. The waveguide consists of a thin polystyrene film, supported by a thicker substrate layer of nanoporous silica on glass. The nanoporous substrate layer has a refractive index of n(S)=1.193, hence, with an ...

  19. EXAFS studies of actinide ions in aqueous solution

    International Nuclear Information System (INIS)

    The applicability of the EXAFS technique in the study of actinide systems is discussed. Uranium L/sub III/-edge spectra obtained on an in-lab rotating anode EXAFS facility are presented and analyzed for crystalline UO2F2 and aqueous solutions containing hexavalent uranium ions. Methods for the extension of the technique to more dilute systems are discussed

  20. Adsorption of lead ions from aqueous solutions using clinoptilolite

    OpenAIRE

    Golomeova, Mirjana; Zendelska, Afrodita; Krstev, Boris; Golomeov, Blagoj; Blažev, Krsto; Krstev, Aleksandar

    2014-01-01

    The adsorption of lead ions from synthetic aqueous solutions was performed by using natural zeolite (clinoptilolite). In order to determine the effectivity of clinoptilolite a series of experiments were performed under batch conditions from single ion solutions. Experiments were carried out at different initial concentration of lead ions, different initial pH values and different adsorbent mass. The adsorption kinetics is reasonably fast. It means that in the first 20 min approximately 90...

  1. Adsorption of copper ions from aqueous solutions on natural zeolite

    OpenAIRE

    Zendelska, Afrodita; Golomeova, Mirjana; Blažev, Krsto; Krstev, Boris; Golomeov, Blagoj; Krstev, Aleksandar

    2015-01-01

    The adsorption of copper ions from synthetic aqueous solutions on natural zeolite (clinoptilolite) was examined. In order to determine the rate of adsorption and the copper uptake at equilibrium, a series of experiments were performed under batch conditions from single ion solutions. Equilibrium data were evaluated based on adsorption (Langmuir and Freundlich) isotherms. The adsorption kinetics is reasonably fast. In the first 20 min of the experiment, approximately 80% of Cu2+ io...

  2. A study of aqueous solutions of sodium linoleate

    International Nuclear Information System (INIS)

    During the development of a technique for measuring fatty acid absorption on finely divided minerals using a radiochemical method, absorption isotherms were obtained which displayed maxima. It was found that these results were due to the presence of stable micelles in the solutions. This has been established by measuring the surface tension, surface film pressure, and specific conductance of dilute aqueous solutions of sodium linoleate

  3. Removal of azo dye from aqueous solutions using chitosan

    OpenAIRE

    Zuhair Jabbar; G. Hadi Ferdoos Sami; A , Angham

    2014-01-01

    Adsorption of Congo Red (CR) from aqueous solution onto chitosan was investigated in a batch system. The effects of solution pH, initial dye concentration, and temperature were studied. Results indicated that chitosan could be used as a biosorbent to remove the azo dyes from contaminated water. Synthesize of chitosan involved three main stages as preconditioning, demineralization, deproteinization and deacetylation. Chitosan was characterized using Fourier Transform Infrared Spectroscopy (FTI...

  4. Block copolymer membranes for aqueous solution applications

    KAUST Repository

    Nunes, Suzana Pereira

    2016-03-22

    Block copolymers are known for their intricate morphology. We review the state of the art of block copolymer membranes and discuss perspectives in this field. The main focus is on pore morphology tuning with a short introduction on non-porous membranes. The two main strategies for pore formation in block copolymer membranes are (i) film casting and selective block sacrifice and (ii) self-assembly and non-solvent induced phase separation (SNIPS). Different fundamental aspects involved in the manufacture of block copolymer membranes are considered, including factors affecting the equilibrium morphology in solid films, self-assembly of copolymer in solutions and macrophase separation by solvent-non-solvent exchange. Different mechanisms are proposed for different depths of the SNIPS membrane. Block copolymer membranes can be prepared with much narrower pore size distribution than homopolymer membranes. Open questions and indications of what we consider the next development steps are finally discussed. They include the synthesis and application of new copolymers and specific functionalization, adding characteristics to respond to stimuli and chemical environment, polymerization-induced phase separation, and the manufacture of organic-inorganic hybrids.

  5. Phytoremediation of Heavy Metals in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Felix Aibuedefe AISIEN

    2010-12-01

    Full Text Available One of the major environmental problems is the pollution of water and soil by toxic heavy metals. This study investigated the phytoremediation potential of water hyacinth, for the removal of cadmium (Cd, lead (Pb and zinc (Zn. Water hyacinths were cultured in bore-hole water, supplemented with 5mg/l of Zn and Pb and 1mg/l of Cd at pH 4.5, 6.8 and 8.5. The plants were separately harvested each week for six weeks. The results showed that removal of these metals from solution was fast especially in the first two weeks, after which it became gradual till saturation point was reached. The accumulation of Cd and Zn in leaves and roots increased with increase in pH. The highest accumulation was in the roots with metal concentration of 4870mg/kg, 4150mg/kg and 710mg/kg for Zn, Pb and Cd respectively at pH 8.5. The maximum values of bioconcentration factor (BCF for Zn, Pb and Cd were 1674, 1531 and 1479 respectively, suggesting that water hyacinth was good accumulator of Zn, Pb and Cd, and could be used to treat industrial wastewater contaminated with heavy metals such as Zn, Pb and Cd.

  6. Assembly of DNA Architectures in a Non-Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Thomas J. Proctor

    2012-08-01

    Full Text Available In the present work, the procedures for the creation of self-assembled DNA nanostructures in aqueous and non-aqueous media are described. DNA-Surfactant complex formation renders the DNA soluble in organic solvents offering an exciting way to bridge the transition of DNA origami materials electronics applications. The DNA retains its structural features, and these unique geometries provide an interesting candidate for future electronics and nanofabrication applications with potential for new properties. The DNA architectures were first assembled under aqueous conditions, and then characterized in solution (using circular dichroism (CD spectroscopy and on the surface (using atomic force microscopy (AFM. Following aqueous assembly, the DNA nanostructures were transitioned to a non-aqueous environment, where butanol was chosen for optical compatibility and thermal properties. The retention of DNA hierarchical structure and thermal stability in non-aqueous conditions were confirmed via CD spectroscopy. The formation and characterization of these higher order DNA-surfactant complexes is described in this paper.

  7. Methylene blue adsorption of GMZ bentonite and the effect of hyper-alkaline solution erosion

    International Nuclear Information System (INIS)

    The method of combining the halo method with the spectrometer method, was used to study on the Methylene blue (MB) adsorption of Gaomiaozi (GMZ) bentonite, which had been eroded by hyper-alkaline solution, to investigate the mechanism of the effect of hyper-alkaline pore water on the buffer/backfill properties of GMZ bentonite. Results present, method employed in this article is brief and feasible, and high accuracy; The total specific surface area calculated by the test of MB adsorption is more accurate than the method of ethylene glycol monomethyl ether (EGIVIE). The MB adsorption of samples, which had been eroded by hyper-alkaline solution, decreases with the increase of the concentration of hyper-alkaline solution, and the change law agrees with the variation of the mass percentage of montmorillonite in bentonite tested by X- Ray diffraction (XRD). Therefore, the erosion of hyper-alkaline pore water might dissolve montmorillonite, which is the effective composition of bentonite, and destroy the tetrahedron- octahedron-tetrahedron (T-O-T) structure of montmorillonite, then lead to the decrease of cation exchange capability and the specific surface area of montmorillonite, and the the macroscopic expressions are the decrease of MB adsorption, the swelling potential and the increase of permeability. (authors)

  8. Electrodeposition of metals from non-aqueous solutions

    International Nuclear Information System (INIS)

    Electrodeposition of metals from non-aqueous solutions is reviewed. Attention is paid mainly to surface morphology of deposits and their adhesion. The major reasons for carrying out electrodeposition in non-aqueous electrolytes (such as conventional organic solvents, ionic liquids and molten salts) are the water and air stability and the wide electrochemical window of these media. The following metals have been electrodeposited and investigated for the last 15 years: aluminum, zinc, silver, palladium, tantalum, zirconium, gadolinium, plutonium, nickel, cobalt, and other alloys.

  9. Carbonate complexation of Np(IV) in alkaline solutions

    International Nuclear Information System (INIS)

    Reliable thermodynamic data for actinide (IV) have been required. The solubility of Np(IV) in carbonate media was studied for determination of thermodynamic data. The concentration of dissolved Np(IV) was measured with ionic strengths from 0.5 to 2.9 M (M ≡ mol·dm-3), hydrogen-ion concentration exponent (pHc = -log[H+]) from 8 to 13 and with the total carbonate concentration (CT) from 5x10-3 M to 7x10-1 M by an oversaturation method. It was found that the solubility of Np(IV) decreased with increasing pHc and increased with increasing CT. On the basis of analysis of the solubility data, the dominant aqueous species of Np(IV) were expected to be Np(CO3)44-, Np(CO3)2(OH)22- and Np(CO3)2(OH)44- in the present study. The apparent equilibrium constants of the carbonate and carbonatohydroxo complexes were obtained in the respective ionic strength and the equilibrium constants at the zero ionic strength were extrapolated. The obtained equilibrium constants supported the literature values strongly, and contributed to improve the reliability of the thermodynamic data. (author)

  10. Adsorption of EDTA on activated carbon from aqueous solutions

    International Nuclear Information System (INIS)

    In this study, the adsorption of EDTA on activated carbon from aqueous solutions has been investigated in a batch stirred cell. Experiments have been carried out to investigate the effects of temperature, EDTA concentration, pH, activated carbon mass and particle size on EDTA adsorption. The experimental results manifest that the EDTA adsorption rate increases with its concentration in the aqueous solutions. EDTA adsorption also increases with temperature. The EDTA removal from the solution increases as activated carbon mass increases. The Langmuir and Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data, with R2 = 0.9920 and 0.9982, respectively. The kinetic study shows that EDTA adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The thermodynamic parameters (Ea, ΔG0, ΔH0, ΔS0) obtained indicate the endothermic nature of EDTA adsorption on activated carbon.

  11. Photolysis kinetics and influencing factors of bisphenol S in aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    Guiping Cao; Jilai Lu; Gongying Wang

    2012-01-01

    The photodegradation of bisphenol S (BPS) in aqueous solutions was studied under different conditions.Photolysis and kinetics were investigated,as were the photolysis mechanism and the influences of initial pH value,light source,and environmental substances in water.The results showed that the photolysis of BPS occurred under UV light,and the rate increased with light source intensity.The photolysis of 5.0-50.0 mg/L BPS in water followed first-order kinetics:the rate was Υ =0.0161Caps under a 40-W UV-lamp,and the degradation half-life was 43.1 min.Due to its absorption of light,direct photolysis of BPS was a predominant pathway for BPS but was not obviously affected by reactive oxygen species.The results confirmed that the photolysis rates of BPS in alkaline water solution were faster than those in acidic and neutral water solution because of the ionization of BPS.The photodegradation rate of BPS increased in the presence of chloride and ferric ions,while the rate was inhibited by nitrate and phosphate in aqueous solution.

  12. Radiolysis of capric acid in an alkaline nitrate solution

    International Nuclear Information System (INIS)

    Effect of absorbed dose of γ-radiation on radiation chemical yields of n-capric acid (CA) loss in nitrate-caustic solutions (0.52 mol/l of NaNO3, 0.24 mol/l NaOH, 0.02 mol/l Na2CO3) modelling composition of liquid radioactive wastes has been studied. Initial yield of decomposition of CA consists of 27 molecule/100 eV. Circuit of radiation-chemical degradation of CA by chain mechanism is justified. Reduction of decomposition of CA under irradiation of the solution in the presence of sandy-clay geological formation from injection well of underground waste disposal has been revealed

  13. ESR spectra of VOBr2 in alcohols and aqueous solutions

    International Nuclear Information System (INIS)

    ESR spectra of VOBr2 solutions in absolutized alcohols ROH (R - Me, Et, i-Pr) and aqueous solutions in the presence of LiBr and HBr are investigated and parameters of spin-hamiltonian of vanadium oxocomplexes are determined. Stabilization of [VOBr(ROH)4]+ complex, in which bromide-ion occupies position in xy plane, is detected. Isotropic additional HFS from 79,81Br atoms at the temperature close to the solution boiling point is found, and at 77 K -anisotropic additional HFS in the range of transitions corresponding to perpendicular orientation of particles as to magnetic field

  14. Solid / solution interaction: The effect of carbonate alkalinity on adsorbed thorium

    Science.gov (United States)

    LaFlamme, Brian D.; Murray, James W.

    1987-02-01

    Elevated activities of dissolved Th have been found in Soap Lake, an alkaline lake in Eastern Washington. Dissolved 232Th ranges from less than 0.001 to 4.9 dpm/L compared to about 1.3 × 10 -5 dpm/ L in sea water. The enhanced activity in the lake coincides with an increase in carbonate alkalinity. Experiments were conducted to evaluate the effect of pH, ionic strength and carbonate alkalinity on Th adsorption on goethite. Thorium (10 -13 M total) in the presence of 5.22 mg/L α-FeOOH and 0.1 M NaNO 3 has an adsorption edge from pH 2-5. At pH 9.0 ± 0.6 the percent Th absorbed on the solid began to decrease from 100% at 100 meq/L carbonate alkalinity and exhibited no adsorption above 300 meq/L. The experimental data were modeled to obtain the intrinsic adsorption equilibrium constants for Th hydrolysis species. These adsorption constants were incorporated in the model to interpret the observed effect of carbonate alkalinity on Th adsorption. There are two main effects of the alkalinity. To a significant degree the decrease in Th adsorption is due to competition of HCO -3 and CO 2-3 ions for surface sites. Dissolved Th carbonate complexes also contribute to the increase of Th in solution.

  15. Dephosphorization of Steelmaking Slag by Leaching with Acidic Aqueous Solution

    Science.gov (United States)

    Qiao, Yong; Diao, Jiang; Liu, Xuan; Li, Xiaosa; Zhang, Tao; Xie, Bing

    2015-12-01

    In the present paper, dephosphorization of steelmaking slag by leaching with acidic aqueous solution composed of citric acid, sodium hydroxide, hydrochloric acid and ion-exchanged water was investigated. The buffer solution of C6H8O7-NaOH-HCl system prevented changes in the pH values. Kinetic parameters including leaching temperature, slag particle size and pH values of the solution were optimized. The results showed that temperature has no obvious effect on the dissolution ratio of phosphorus. However, it has a significant effect on the dissolution ratio of iron. The dephosphorization rate increases with the decrease of slag particle size and the pH value of the solution. Over 90% of the phosphorus can be dissolved in the solution while the corresponding leaching ratio of iron was only 30% below the optimal condition. Leaching kinetics of dephosphorization follow the unreacted shrinking core model with a rate controlled step by the solid diffusion layer, the corresponding apparent activation energy being 1.233 kJ mol-1. A semiempirical kinetic equation was established. After leaching, most of the nC2S-C3P solid solution in the steelmaking slag was selectively dissolved in the aqueous solution and the iron content in the solid residue was correspondingly enriched.

  16. Formation of magnetite (Fe3O4)in aqueous media and properties of the interface magnetite/solution

    International Nuclear Information System (INIS)

    The formation of Fe3O4 particles in aqueous media and the properties of the Fe3O4/aqueous solution interface are studied. This system is of particular interest in nuclear reactor chemistry, since Fe3O4 was identified as the main component of the corrosion products of nuclear power plants cooled with pressurized water, of the Atucha I and II, and Embalse type. Four methods for the synthesis of Fe3O4 are described: a) controlled oxidation of Fe(OH)2 in the presence of NaNO3 at 25 deg C; b) controlled oxidation of Fe(OH)2 in the presence of NaNO3 and N2H4 and at 100 deg C; c) alkalinization of a F2+ and Fe3+ solutions at 80 deg C; d) simultaneous oxidation and alkalinization of a Fe2+. The interfacial properties of Fe3O4 particles suspended in aqueous solutions of indifferent electrolytes are described. These properties are essential for the activity transport associated with the corrosion products. Finally, the adsorption of H3BO3, Hsub(n)PO4sup(n-3) and n Co(II) in the Fe3O4/solution interface at 30 deg C. It is concluded that the adsorbed species are chemically bonded to surface metal ions. (M.E.L.)

  17. Application of dolochar in the removal of cadmium and hexavalent chromium ions from aqueous solutions

    International Nuclear Information System (INIS)

    Graphical abstract: Dolochar - a waste material from sponge iron industry, is put to test as an adsorbent for removal of cadmium and hexavalent chromium ions from aqueous solutions. The sample consists of lots of voids and pores. Batch adsorption experiments have indicated that, higher pH and temperature enhances sorption for cadmium ions. The adsorption for chromium is found better at acidic pH in comparison to alkaline pH. The adsorption is well fitted to Langmuir isotherm model compared to the Freundlich model indicating monolayer adsorption. The kinetics of adsorption better fit to pseudo second order model.. Display Omitted Highlights: → Dolochar, a waste material is generated during the production of sponge iron. → Dolochar consists of metallic iron, carbon, and lime bearing phases along with lots of voids and pores. → It was found to be an good adsorbent for the removal of cadmium and hexavalent chromium ions from aqueous solutions. → The adsorption follows Langmuir isotherm and kinetics of adsorption better fit of pseudo second order model. - Abstract: Dolochar, a waste material generated in sponge iron industry, is processed and put to test as an adsorbent for removal of Cd(II) and Cr(VI) ions from aqueous solutions. The dolochar samples were characterised to determine the different phases and their distribution by reflection microscopy. The analysis indicated that the sample consists of metallic iron, fused carbon, and Ca-Mg bearing phases (Ca-Mg-silicate-oxide) along with lots of voids and pores. The fixed carbon (FC) content of the material is 13.8% with a Langmuir surface area of 81.6 m2/g and micropore area of 34.1 m2/g. Batch adsorption experiments have been conducted to study the sorption behaviour of Cd(II) and Cr(VI) ions on dolochar as a function of particle size, contact time, adsorbent dosages, pH and temperature. It is observed that higher pH and temperature enhances sorption of Cd(II) ions. In contrast, the adsorption for Cr(VI) is

  18. Purification and concentration of DNA from aqueous solutions.

    Science.gov (United States)

    Moore, David; Dowhan, Dennis

    2007-09-01

    This unit presents basic procedures for manipulating solutions of single- or double-stranded DNA through purification and concentration steps. These techniques are useful when proteins or solute molecules need to be removed from aqueous solutions, or when DNA solutions need to be concentrated. The Basic Protocol, using phenol extraction and ethanol (or isopropanol) precipitation, is appropriate for purification of DNA from small volumes (DNA using butanol, and extract residual organic solvents with ether, respectively. An alternative to these methods is nucleic acid purification using glass beads, and this technique is also presented. These protocols may also be used for purifying RNA. The final two alternate protocols are used for concentrating RNA and extracting and precipitating DNA from larger volumes and from dilute solutions, and for removing low-molecular-weight oligonucleotides and triphosphates. PMID:21948158

  19. Radiation induced intra-track reactions in aqueous solutions

    International Nuclear Information System (INIS)

    Radiation chemistry of aqueous solutions is inevitably important not only in physics and chemistry but also in biology and medicine. More than five decades much effort has been paid to clarify the elementary processes induced by irradiation. Then, pulse radiolysis study in the time scale of picosecond is now available. In addition, radiation chemistry studies with high LET radiation have been actively investigated. Furthermore, radiolysis study of aqueous solution at high temperatures and even in supercritical water is under progress. In the present lecture, experimental results on the radiolysis of water in ps time scale and LET effect obtained at Nuclear Engineering Research Laboratory (NERL), the University of Tokyo, will be presented relevant to the theoretical calculation. (author)

  20. Vapor Pressure of Aqueous Solutions of Ethylene Glycol

    Science.gov (United States)

    Fujita, Toshihiko; Kikuchi, Sakae

    Vapor pressures of aqueous solutions of ethylene glycol are measured in the range of temperature from -10 to 60°C and concentration from 20 to 50wt%. In a low concentration range, the measured values of vapor pressure decrease according to the Raoult's law independent of temperature, while in a high concentration range, they show a trend to decrease towards the estimated values of freezing point with decreasing temperature. The following correlation equation is obtained for practical calculations on heating towers and the like. log(p/P0) = 5.351 - 6.4×10-4y + (1817 + 0.008y(y + 10))/(t + 240) where p, vapor perssure of aqueous solutions of ethylene glycol [kPa] ; P0, atmospheric pressure [=101.325kPa] ; y, concentration [wt%] ; t, temperature [°C].

  1. A lithium ion battery using an aqueous electrolyte solution

    Science.gov (United States)

    Chang, Zheng; Li, Chunyang; Wang, Yanfang; Chen, Bingwei; Fu, Lijun; Zhu, Yusong; Zhang, Lixin; Wu, Yuping; Huang, Wei

    2016-01-01

    Energy and environmental pollution have become the two major problems in today’s society. The development of green energy storage devices with good safety, high reliability, high energy density and low cost are urgently demanded. Here we report on a lithium ion battery using an aqueous electrolyte solution. It is built up by using graphite coated with gel polymer membrane and LISICON as the negative electrode, and LiFePO4 in aqueous solution as the positive electrode. Its average discharge voltage is up to 3.1 V and energy density based on the two electrode materials is 258 Wh kg−1. It will be a promising energy storage system with good safety and efficient cooling effects. PMID:27328707

  2. A lithium ion battery using an aqueous electrolyte solution

    Science.gov (United States)

    Chang, Zheng; Li, Chunyang; Wang, Yanfang; Chen, Bingwei; Fu, Lijun; Zhu, Yusong; Zhang, Lixin; Wu, Yuping; Huang, Wei

    2016-06-01

    Energy and environmental pollution have become the two major problems in today’s society. The development of green energy storage devices with good safety, high reliability, high energy density and low cost are urgently demanded. Here we report on a lithium ion battery using an aqueous electrolyte solution. It is built up by using graphite coated with gel polymer membrane and LISICON as the negative electrode, and LiFePO4 in aqueous solution as the positive electrode. Its average discharge voltage is up to 3.1 V and energy density based on the two electrode materials is 258 Wh kg‑1. It will be a promising energy storage system with good safety and efficient cooling effects.

  3. A lithium ion battery using an aqueous electrolyte solution.

    Science.gov (United States)

    Chang, Zheng; Li, Chunyang; Wang, Yanfang; Chen, Bingwei; Fu, Lijun; Zhu, Yusong; Zhang, Lixin; Wu, Yuping; Huang, Wei

    2016-01-01

    Energy and environmental pollution have become the two major problems in today's society. The development of green energy storage devices with good safety, high reliability, high energy density and low cost are urgently demanded. Here we report on a lithium ion battery using an aqueous electrolyte solution. It is built up by using graphite coated with gel polymer membrane and LISICON as the negative electrode, and LiFePO4 in aqueous solution as the positive electrode. Its average discharge voltage is up to 3.1 V and energy density based on the two electrode materials is 258 Wh kg(-1). It will be a promising energy storage system with good safety and efficient cooling effects. PMID:27328707

  4. Polyamide nanofiltration membranes to remove aniline in aqueous solutions.

    Science.gov (United States)

    Hidalgo, A M; León, G; Gómez, M; Murcia, M D; Bernal, M D; Ortega, S

    2014-01-01

    Aniline is commonly used in a number of industrial processes. It is known to be a harmful and persistent pollutant and its presence in wastewater requires treatment before disposal. In this paper, the effectiveness of nanofiltration (NF) to remove aniline from aqueous solutions is studied in a flat membrane test module using two thin-layer composite membranes of polyamide (NF97 and NF99HF). The influence of different operational variables (applied pressure, feed concentration and pH) on the removal of aniline from synthetic aqueous solutions was analysed. The experimental NF results are compared with results previously obtained by reverse osmosis. Based on this comparative study, the effective order for aniline rejection is: HR98PP > NF97 > DESAL3B > SEPA-MS05 > NF99HF. PMID:24701913

  5. Photodegradation of Norfloxacin in aqueous solution containing algae

    Institute of Scientific and Technical Information of China (English)

    Junwei Zhang; Dafang Fu; Jilong Wu

    2012-01-01

    Photodegradation of Norfloxacin in aqueous solution containing algae under a medium pressure mercury lamp (15 W,λmax =365 nm) was investigated.Results indicated that the photodegradation of Norfloxacin could be induced by the algae in the heterogeneous algaewater systems.The photodegradation rate of Norfloxacin increased with increasing algae concentration,and was greatly influenced by the temperature and pH of solution.Meanwhile,the cooperation action of algae and Fe(Ⅲ),and the ultrasound were beneficial to photodegradation of Norfloxaciu.The degradation kinetics of Norfloxacin was found to follow the pseudo zero-order reaction in the suspension of algae.In addition,we discussed the photodegradation mechanism of Norfloxacin in the suspension of algae.This work will be helpful for understanding the photochemical degradation of antibiotics in aqueous environment in the presence of algae,for providing a new method to deal with antibiotics pollution.

  6. Degradation of Sodium-Polyacrylate in Dilute Aqueous Solution, II

    Science.gov (United States)

    Saita, Takao; Matumura, On

    1983-08-01

    It has been found that Na-PAA molecules in dilute aqueous solution are degraded by shearing stress, oxidation and photolysis during usual viscosity measurements with a capillary viscometer. The results of previous viscosity measurements, mainly about the mechanochemical degradation in air and in air-free conditions, showed that the degradation rate increases with increasing shear stress, and with decreasing polymer concentration. In this work, the effects of the molecular weight and temperature on the degradation rate are measured using a capillary viscometer in air, and the photodegradation of Na-PAA and PAA in aqueous solution irradiated with UV light are studied by viscosity measurements in air, and by UV absorption and ESR methods. The results show that the degradation of molecules is enhanced by an increase in the molecular weight and strongly accelerated by a rise in temperature and by UV irradiation, and is accompanied by free-radical chain reactions.

  7. Ternary mutual diffusion in aqueous (ethambutol dihydrochloride + hydrochloric acid) solutions

    International Nuclear Information System (INIS)

    Highlights: • Ternary diffusion coefficients for aqueous system ethambutol dihydrochloride and hydrochloric acid. • Diffusion of ethambutol dihydrochloride driven by hydrochloric acid gradients. • Coupled diffusion as indicated by cross-diffusion coefficients. - Abstract: Ternary mutual diffusion coefficients measured by the Taylor dispersion method are reported for aqueous solutions of {ethambutol dihydrochloride (1) + HCl (2)} at 25 °C and various carrier solution compositions. Mutual diffusion coefficients estimated from limiting ionic conductivities using Nernst equations are used to discuss the composition dependence of the measured diffusion coefficients. 1H NMR studies, combined with DFT calculations, confirm a fully extended conformation for the diprotonated form of the drug present under these conditions, and are consistent with an electrostatic mechanism for the strongly coupled diffusion of diprotonated ethambutol and HCl

  8. Laser purification of ultradispersed diamond in aqueous solution

    International Nuclear Information System (INIS)

    The effect of pulsed radiation from a 2.92-μm, 130-ns Cr3+:Yb3+:Ho3+:YSGG holmium laser and a 510-nm, 20-ns copper vapour laser on an aqueous suspension of ultradispersed diamond is studied. X-ray photoelectron spectroscopy and electron energy loss spectroscopy revealed that exposure of the suspension to holmium laser radiation reduces the concentration of nondiamond carbon impurity in it. This is due to the dissolution of carbon impurity in supercritical aqueous solution, caused by radiation absorption. Dissolution of the nondiamond fraction may serve as an indicator of the solution being in the supercritical state as a result of laser irradiation of liquids. This process can be used for efficient purification of ultradispersed diamonds. (laser applications and other topics in quantum electronics)

  9. Zinc chloride aqueous solution as a solvent for starch.

    Science.gov (United States)

    Lin, Meiying; Shang, Xiaoqin; Liu, Peng; Xie, Fengwei; Chen, Xiaodong; Sun, Yongyi; Wan, Junyan

    2016-01-20

    It is important to obtain starch-based homogeneous systems for starch modification. Regarding this, an important key point is to find cheap, low-cost and low-toxicity solvents to allow complete dissolution of starch and its easy regeneration. This study reveals that a ZnCl2 aqueous solution is a good non-derivatizing solvent for starch at 50 °C, and can completely dissolve starch granules. The possible formation of a "zinc-starch complex" might account for the dissolution; and the degradation of starch, which was caused by the H(+) inZnCl2 aqueous solution, could not contribute to full dissolution. From polarized light microscopic observation combined with the solution turbidity results, it was found that the lowest ZnCl2 concentration for full dissolution was 29.6 wt.% at 50 °C, with the dissolving time being 4h. Using Fourier-transform infrared (FTIR), solid state (13)C nuclear magnetic resonance (NMR), and X-ray diffraction (XRD), it was revealed that ZnCl2 solution had no chemical reaction with starch glucosides, but only weakened starch hydrogen bonding and converted the crystalline regions to amorphous regions. In addition, as shown by intrinsic viscosity and thermogravimetric analysis (TGA), ZnCl2 solution caused degradation of starch macromolecules, which was more serious with a higher concentration of ZnCl2 solution. PMID:26572355

  10. Radiolytic degradation of malathion and lindane in aqueous solutions

    International Nuclear Information System (INIS)

    Degradation of malathion and lindane pesticides present in an aqueous solution was investigated on a laboratory scale upon gamma-irradiation from a 60Co source. The effects of pesticide group, presence of various additives and absorbed dose on efficiency of pesticide degradation were investigated. Gamma-irradiation was carried out in distilled water solutions (malathion and lindane) and in combination with humic solution (HS), nitrous oxide (N2O) and HS/N2O (lindane) over the range 0.1-2 kGy (malathion) and 5-30 kGy (lindane). Malathion was easily degraded at low absorbed doses compared to lindane in distilled water solutions. Absorbed doses required to remove 50% and 90% of initial malathion and lindane concentrations in distilled water solutions were 0.53 and 1.77 kGy (malathion) and 17.97 and 28.79 kGy (lindane), respectively. The presence of HS, N2O and HS/N2O additives in aqueous solutions, significantly improved the effectiveness of radiolytic degradation of lindane. Chemical analysis of the pesticides and the by-products resulted from the radiolytic degradation were made using a gas chromatography associated with mass spectrometry (GC-MS). Additionally, the final degradation products of irradiation as detected by ion chromatography (IC) were acetic acid and traces of some anions (phosphate and chloride).

  11. Determination of concentration of saturated ferrocene in aqueous solution

    OpenAIRE

    Aoki, Koichi

    2013-01-01

    Chun Ouyang, Koichi Jeremiah Aoki, Jingyuan Chen, Toyohiko Nishiumi, Bo Wang Department of Applied Physics, University of Fukui, Bunkyo, Fukui, Japan Abstract: The solubility of ferrocene in aqueous solution is known to be approximately 0.04 mmol/dm3. The solubility values determined by voltammetry have been overestimated because of adsorption on electrodes. This work deals with discerning diffusion from adsorption by altering not only the voltammetric time scale but also the solvents used. ...

  12. Liquid crystalline phases in concentrated aqueous solutions of Na+ DNA.

    OpenAIRE

    Rill, R L

    1986-01-01

    Concentrated aqueous saline solutions of short (146-base-pair) DNA fragments suddenly become turbid and iridescent when the DNA concentration is slightly increased or the temperature is decreased. Microscopic examination through crossed polarizing filters shows that turbidity and iridescence is due to formation of a liquid crystalline DNA phase similar to cholesteric liquid crystals formed by other semirigid, but nonelectrolyte, chiral polymers. Several distinct textures of the liquid crystal...

  13. Ozone chemistry in aqueous solution : ozone decomposition and stabilisation

    OpenAIRE

    Eriksson, Margareta

    2005-01-01

    Ozone is used in many applications in the industry as an oxidising agent for example for bleaching and sterilisation. The decomposition of ozone in aqueous solutions is complex, and is affected by many properties such as, pH, temperature and substances present in the water. Additives can either accelerate the decomposition rate of ozone or have a stabilising effect of the ozone decay. By controlling the decomposition of ozone it is possible to increase the oxidative capacity of ozone. In this...

  14. Pulse radiolysis of aqueous lignin solutions with acryl monomers

    International Nuclear Information System (INIS)

    Radiation-induced polymerization in aqueous solutions of methylmethacrylate and methylacrylate with and without lignin added was studied by pulse radiolysis method. Optical spectra of intermediates taking part in the chain evolution were obtained. The rate constant of the chain polymerization termination diminished when lignin added from 1.2 x 109 up to 2 x 108 mol-1 s-1. A reaction scheme of radiation-induced polymerization was proposed which included the lignin entering in chain propagation reactions. (author)

  15. NMR studies of thermoresponsive polymers in aqueous solutions and hydrogels

    Czech Academy of Sciences Publication Activity Database

    Spěváček, Jiří

    Poznań : Department of Macromolecular Physics, Faculty of Physics and NanoBioMedical Centre, Adam Mickiewicz University in Poznań, The Centre for European Integration, 2014 - (Jurga, S.). s. 27 [Ampere NMR School. 22.06.2014-28.06.2014, Zakopane] R&D Projects: GA ČR(CZ) GA13-23392S Institutional support: RVO:61389013 Keywords : NMR * thermoresponsive polymer * aqueous solution Subject RIV: CD - Macromolecular Chemistry

  16. NMR investigations of thermoresponsive polymers in aqueous solutions

    Czech Academy of Sciences Publication Activity Database

    Spěváček, Jiří

    Poznaň : Department of Macromolecular Physics, Faculty of Physics, Adam Mickiewicz University, 2012. s. 26. [Ampere NMR School. 24.06.2012-30.06.2012, Poznaň] R&D Projects: GA ČR GA202/09/1281 Institutional research plan: CEZ:AV0Z40500505 Institutional support: RVO:61389013 Keywords : thermoresponsive polymer * aqueous solution * NMR Subject RIV: CD - Macromolecular Chemistry

  17. Fluorescence of lanthanide(III) complexes in aqueous solutions

    International Nuclear Information System (INIS)

    The fluorescence of lanthanide ions and of their complexes with EDTA, NTA and AA in aqueous solutions was investigated. It has been shown that the fluorescence band intensities of Sm(III), Eu(III), Gd(III), Tb(III) and Dy(III) complexes depend on the pH and the complexing agent concentration. Fluorescence measurements were used to characterise the lanthanide complexes formed and an attempt was made to interpret the results theoretically. (Author)

  18. Degradation of α-naphthol by plasma in aqueous solution

    International Nuclear Information System (INIS)

    Degradation of α-naphthol induced by plasma in aqueous solution was investigated in different initial concentration with contact glow discharge electrolysis (CGDE). The results showed that the degradation of α-naphthol obeyed the first-rate law. Some of predominant products were analyzed by a high performance liquid chromatography (HPLC). A path of α-naphthol disappearance caused by plasma was proposed according to the detected intermediate products

  19. Photocatalytic oxidation of fuel oxygenated additives in aqueous solutions

    OpenAIRE

    Krichevskaya, M.; Kachina, A.; T. Malygina; Preis, S.; J. Kallas

    2003-01-01

    Experimental research of photocatalytical oxidation (PCO) of aqueous solutions of de-icing agents (ethylene glycol and ethylene glycol monoethyl ether) and methyl tert-butyl ether (MTBE) was undertaken. These chemicals are water-soluble components of jet and motor fuels accidentally disposed to the environment. Titanium dioxide (Degussa P25) under near-UV irradiation was selected as a photocatalyst. A slightly acidic medium was preferable for the process efficiency for MTBE, whereas a neutral...

  20. Pulse Radiolysis of Methyl Viologen in Aqueous Solutions

    DEFF Research Database (Denmark)

    Solar, S.; Solar, W.; Getoff, N.; Holcman, Jerzy; Sehested, Knud

    Pulse radiolysis of air-free aqueous methyl viologen (MV2+) solutions was carried out at various pH. The attack of e–aq on MV2+, with k(e–aq+ MV2+)= 7.5 × 1010 dm3 mol–1 s–1, leads to the formation of the long-lived radical cation (MV˙+), which possesses two absorption maxima at 392.5 nm (ε392...

  1. Adsorption of Cr (III) from aqueous solution by groundnut shell

    OpenAIRE

    Tasrina Rabia Choudhury; Mustafa, A. I.

    2012-01-01

    Adsorption and de-sorption of chromium (III) ions on groundnut shell from aqueous solutions have been studied using batch adsorption techniques with respect to the influence of contact time, pH, adsorbent dose, initial chromium concentration and particle size. Appropriate adsorption isotherm and kinetic parameters of chromium (III) adsorption on groundnut shell have also been determined. The results of this study showed that adsorption of chromium (III) by groundnut shell reached to equilibr...

  2. Pulse Radiolysis of Adrenaline in Acid Aqueous Solutions

    DEFF Research Database (Denmark)

    Gohn, M.; Getoff, N.; Bjergbakke, Erling

    1976-01-01

    Pulse radiolysis of adrenaline in acid aqueous solutions (pH 1–3) was carried out. The rate constants for the reactions of adrenaline with H and OH were determined: k(H + adr.) = (0·9±0·1) × 109 dm3 mol−1s−1; k(OH + adr.) = (1·65±0·15) × 1010 dm3 mol−1s−1. The H-adduct of adrenaline has two λmax...

  3. Solubility of chlorine in aqueous hydrochloric acid solutions.

    Science.gov (United States)

    Alkan, Mahir; Oktay, Münir; Kocakerim, M Muhtar; Copur, Mehmet

    2005-03-17

    The solubility of chlorine in aqueous hydrochloric acid solutions was studied. The effects of HCl concentration and temperature on the solubility were evaluated, and the thermodynamic parameters of the dissolution were calculated. It was found that the solubility isotherms had a minimum at about 0.5M HCl concentration at all the temperatures studied and that solubility decreased with the increase of temperature at all the HCl concentration range investigated. PMID:15752843

  4. Dermal absorption of a dilute aqueous solution of malathion

    Directory of Open Access Journals (Sweden)

    Scharf John

    2008-01-01

    Full Text Available Malathion is an organophosphate pesticide commonly used on field crops, fruit trees, livestock, agriculture, and for mosquito and medfly control. Aerial applications can result in solubilized malathion in swimming pools and other recreational waters that may come into contact with human skin. To evaluate the human skin absorption of malathion for the assessment of risk associated with human exposures to aqueous solutions, human volunteers were selected and exposed to aqueous solutions of malathion. Participants submerged their arms and hands in twenty liters of dilute malathion solution in either a stagnant or stirred state. The "disappearance method" was applied by measuring malathion concentrations in the water before and after human exposure for various periods of time. No measurable skin absorption was detected in 42% of the participants; the remaining 58% of participants measured minimal absorbed doses of malathion. Analyzing these results through the Hazard Index model for recreational swimmer and bather exposure levels typically measured in contaminated swimming pools and surface waters after bait application indicated that these exposures are an order of magnitude less than a minimal dose known to result in a measurable change in acetylcholinesterase activity. It is concluded that exposure to aqueous malathion in recreational waters following aerial bait applications is not appreciably absorbed, does not result in an effective dose, and therefore is not a public health hazard.

  5. Dissolution of gaseous methyl iodide into aqueous sodium hydroxide solutions

    International Nuclear Information System (INIS)

    Absorption process of gaseous methyl iodide by water or sodium hydroxide solutions was investigated using a semi-flow type experimental apparatus by measuring the concentration of all measurable chemical species in both the gas and the liquid phase. The experimental temperature ranged from 288 to 311 K and the gaseous methyl iodide and aqueous sodium hydroxide concentrations were approximately 0.6 x 10-3 to 7 x 10-3 and 0 to 0.2 mol/dm3, respectively. It is estimated that the dissolution of methyl iodide into the sodium hydroxide solution proceeds according to the following steps. Step (1) Methyl iodide in air dissolves physically into the aqueous phase. Physical dissolution process obeys Henry's law. Step (2) Methyl iodide dissolved into the aqueous phase is decomposed by a base catalytic hydrolysis and produces methyl alcohol and iodide ion. The equilibrium constants of physical dissolution were obtained from the steady concentration in both the gas and the liquid phases in the semi-flow type experiment because the hydrolysis reaction rate of methyl iodide is very slow in comparison with the physical dissolution in this experimental conditions. The obtained value of the standard heat of solution of methyl iodide into water was 7.2 kcal/mol. Salting-out effect was observed when the concentration of sodium hydroxide in the absorbent was over 0.01 mol/dm3. (auth.)

  6. Catalytic oxidation of calcium sulfite in solution/aqueous slurry

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-qin; WU Zhong-biao; WANG Da-hui

    2004-01-01

    Forced oxidation of calcium sulfite aqueous slurry is a key step for the calcium-based flue gas desulfurization(FGD) residue. Experiments were conducted in a semi-batch system and a continuous flow system on lab scales. The main reactor in semi-batch system is a 1000 ml volume flask. It has five necks for continuous feeding of gas and a batch of calcium sulfite solution/aqueous slurry. In continuous flow system, the main part is a jacketed Pyrex glass reactor in which gas and solution/aqueous slurry are fed continuously. Calcium sulfite oxidation is a series of complex free-radical reactions. According to experimental results and literature data, the reactions are influenced significantly by manganese as catalyst. At low concentration of manganese and calcium sulfite, the reaction rate is dependent on 1.5 order of sulfite concentration, 0.5 order of manganese concentration, and zero order of oxygen concentration in which the oxidation is controlled by chemical kinetics. With concentrations of calcium sulfite and manganese increasing, the reactions are independent gradually on the constituents in solution but are impacted by oxygen concentration. Manganese can accelerate the free-radical reactions, and then enhances the mass transfer of oxygen from gas to liquid. The critical concentration of calcium sulfite is 0.007 mol/L, manganese is 10-4 mol/L, and oxygen is of 0.2-0.4 atm.

  7. Some Corrosion Characteristics of Aged Aluminum Alloy 6061 in Neutral and Alkaline Solutions

    International Nuclear Information System (INIS)

    The composition and microstructure of the alloy as well as the corrosive nature of the environment play an important role in modifying the corrosion resistance of aluminum alloys. This work was intended to study the influence of the solution ph on the corrosion characteristics of 6061 aluminum alloy, (Al-Mg-Si alloy containing 0.22 wt % Cu) after aging at 225, 185 and 140 degree degree C for different periods of time. The investigation was performed by applying potentiodynamic polarization technique in neutral deaerated 0.5 % M NaCl solution as well as in alkaline NaOH solution (ph 10). Analysis of the potentiodynamic polarization curves showed similar dependence of Icorr and cathodic current densities on the aging treatment in both solutions. It was found that Ecorr values in the NaCl solution were shifted in the more noble direction while in the NaOH solution they were shifted in the more active direction compared to the solution treated condition. The magnitude of the noble or active shift in Ecorr increased with aging time for the under aged specimens and decreased towards Ecorr of the solution treated condition for the overaged specimens in both solutions. The Icorr values were higher in the alkaline solution for the same aging treatment

  8. Radiolysis of berberine or palmatine in aqueous solution

    Science.gov (United States)

    Marszalek, Milena; Wolszczak, Marian

    2011-01-01

    The reactions of hydrated electron (eaq-), hydrogen atom (H rad ) (reducing species) and Cl2•-, Br2•-, N,O•H radicals (oxidizing species) with berberine or palmatine in aqueous solution have been studied by steady-state and pulse radiolysis. The spectra of transient intermediates, leading to the final products, are presented. The rate constants of the reaction of eaq- and rad OH radical with both alkaloids in the homogenous solution and in the presence of DNA are reported. It is demonstrated that the primary products of the reaction of berberine and palmatine with eaq- and radicals generated during radiolysis are unstable and undergo further reactions.

  9. Recovery of Ionic Liquids from aqueous solution by Nanofiltration

    OpenAIRE

    Fernández Dámaso, José Francisco

    2011-01-01

    The T-SAR methodology was combined with membrane characterization methods. An application of the combined approach was demonstrated with two commercial nanofiltration membranes and it was possible to successfully predict their performance for the recovery of ionic liquids from aqueous solution. Using model solutions of Pyr16 (CF3SO2)2N, it could be evidenced the formation of a new phase of ionic liquid during the concentration process. In this case, 66% of the ionic liquid was separated and t...

  10. Observations on the Solubility of Skeletal Carbonates in Aqueous Solutions.

    Science.gov (United States)

    Chave, K E; Deffeyes, K S; Weyl, P K; Garrels, R M; Thompson, M E

    1962-07-01

    Carbonate skeletal materials of marine organisms exhibit a wide range of solubilities in aqueous solutions. In most cases, the dissolution of the carbonate mineral is irreversible and therefore the material can have no true equilibrium solubility. Relative solubilities have been measured in distilled water and in sea water. The least soluble mineral appears to be calcite with low magnesium content; the most soluble is calcite containing 20 to 30 percent MgCO(3) in solid solution. Aragonite has an intermediate solubility. PMID:17774123

  11. Characterization of aqueous silver nitrate solutions for leakage tests

    OpenAIRE

    José Ferreira Costa; Walter Luiz Siqueira; Alessandro Dourado Loguercio; Alessandra Reis; Elizabeth de Oliveira; Cláudia Maria Coelho Alves; José Roberto de Oliveira Bauer; Rosa Helena Miranda Grande

    2011-01-01

    OBJECTIVE: To determine the pH over a period of 168 h and the ionic silver content in various concentrations and post-preparation times of aqueous silver nitrate solutions. Also, the possible effects of these factors on microleakage test in adhesive/resin restorations in primary and permanent teeth were evaluated. MATERIAL AND METHODS: A digital pHmeter was used for measuring the pH of the solutions prepared with three types of water (purified, deionized or distilled) and three brands of silv...

  12. Kinetic studies of cadmium sulfide precipitation from aqueous thiourea solutions

    International Nuclear Information System (INIS)

    Kinetics of cadmium sulfide precipitation by thiourea from aqueous solutions containing ammonia complexes of cadmium(II) under conditions of spontaneous initiation of solid phase within solution volume at temperatures of 298-318 K was studied. It was ascertained that the process activation energy is 77843 J/mol, while the reaction order by initial cadmium complex equals unity. Kinetic equation, which permits control over cadmium sulfide precipitation and preparation of CdS films of desired morphology was derived on the basis of the experimental data

  13. Some reactions of oxidizing radicals with enzymes in aqueous solution

    International Nuclear Information System (INIS)

    A range of oxidizing radicals including some inorganic radical anions and the superoxide radical, can be generated by radiolysis of aqueous solutions. These radicals are more selective in their reactions with amino acids than the hydroxyl radical. Factors controlling the apparent reactivity of radical anions with proteins, such as free radical equilibria and ion-binding, are described. The superoxide radical inactivates papain by reaction with the cysteine residue. This reaction has been studied in solutions subjected to radiations of varying linear energy transfer. (Auth.)

  14. Approach to the extreme safety in a nuclear fuel reprocessing system in mild aqueous solutions

    International Nuclear Information System (INIS)

    The purpose of the experiment is to establish a new nuclear fuel reprocessing system, which is aimed to achieve the extreme safety. In order to avoid any potential danger of explosion, all processes are made by the precipitation method at room temperature. The system consists of the following processes: 1. crystallization of uranyl nitrate from a dissolved fuel solution by cooling the solution; 2. complex formation of UO22+ and Pu4+ with carbonate ion by the addition of Na2CO3-NaHCO3 solution adjusting pH to 9, followed by the separation of a precipitate containing the major fission products by the centrifugation method; 3. separation of Cs as a precipitate of cesium tetraphenylborate; 4. recovery of U and Pu as precipitates of hydroxo compounds from the alkaline solution by the addition of NaOH solution ; 5. separation of Sr from the precipitate in process 2; 6. recovery of NaHCO3 from the NaOH solution by bubbling CO2 gas. As a result, 99.95% of the U was recovered with the least amount of fission products. Pu are expected to be recovered in the same way as U. In conclusion, the present reprocessing system enables us to recover U and Pu in high ratios from spent nuclear fuel by means of a simple precipitation method, to separate hazardous Cs and Sr from high-level waste, and to exclude any potential danger owing to chemical processes under mild aqueous conditions. (author)

  15. Genotoxicity study of photolytically treated 2-chloropyridine aqueous solutions

    International Nuclear Information System (INIS)

    2-Chloropyridine (2-CPY) has been identified as a trace organic chemical in process streams, wastewater and even drinking water. Furthermore, it appears to be formed as a secondary pollutant during the decomposition of specific insecticides. As reported in our previous work, 2-CPY was readily removed and slowly mineralised when subjected to ultraviolet (UV) irradiation at 254 nm. Moreover, 2-CPY was found to be genotoxic at 100 μg ml-1 but it was not genotoxic at or below 50 μg ml-1. In this work 2-CPY aqueous solutions were treated by means of UV irradiation at 254 nm. 2-CPY mineralisation history under different conditions is shown. 2-CPY was found to mineralise completely upon prolonged irradiation. Identified products of 2-CPY photolytic decomposition are presented. Solution genotoxicity was tested as a function of treatment time. Aqueous solution samples, taken at different photo-treatment times were tested in cultured human lymphocytes applying the cytokinesis block micronucleus (CBMN) assay. It was found that the solution was genotoxic even when 2-CPY had been practically removed. This shows that photo-treatment of 2-CPY produces genotoxic products. Upon prolonged irradiation solution genotoxicity values approached the control value.

  16. Corrosion behavior of bulk metallic glasses in different aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The corrosion behavior of as-cast fully amorphous, structural relaxed amorphous and crystallized Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk metallic glasses (BMGs) in NaCl, HCl and NaOH solutions was investigated by electrochemical polarization and immersion methods. X-ray photoelectron spectroscopy measurements was used to analyze the changes of the elements on the alloy surface before and after immersion in various solutions. The corrosion resistance of the Fe65.5Cr4Mo4Ga4P12C5B5.5 BMG was better than its structural relaxation/crystallization counterparts and common alloys (such as stainless steel, carbonized steel, and steel) in the selected aqueous solutions. The high corrosion resistance of this alloy in corrosive solutions leads to the formation of Fe-, Cr- and Mo-enriched protective thin surface films.

  17. Depolarization of negative muons in water and aqueous solutions

    International Nuclear Information System (INIS)

    The dependence of negative muon depolarization on temperature and hydrogen peroxide concentration is measured in various aqueous solutions located in longitudinal or transverse magnetic fields. It is shown that the experimental data are mot inconsistent with the familiar concepts regarding the behaviour of free radicals in aqueous solutions. The residual polarization in pure water solution of hydrogen peroxide is found to 1.8 times higher than that in pure water. This is interpreted as being the result of chemical interaction between meso nitrogen and hydrogen peroxide molecules leading to the formation of diamagnetic compounds. It is shown that the degree of depolarization does not depend on the magnetic field strength. According to the depolarization model in which meso nitrogen chemical reactions are taken into account this signifies that the meso atom enters the chemical reactions during a time t≅10-11 sec. at T=300 K; the paramagnetic products of these primary reactions which contain meso nitrogen then participate in secondary reactions during a time t1≤10-7 sec. The rate constants of the reactions leading to the formation of diamagnetic products can be obtained by treating the concentration and temperature dependences of depolarization in an aqueous solution of hydrogen peroxide in accordance with the model assuming chemical reactions between the meso atom and H2O molecules. The order of magnitude of the constant k≅10-11 sec-1⋅sm3is the same as that of the constant for reactions between free H and OH radicals in water. The temperature dependences of depolarization in water and a water solution of hydrogen peroxide are same consistent with the concept that the meso nitrogen reactions are chemical reactions by diffusion. (author)

  18. Characterization of aqueous solution of congored for food irradiation dosimetry

    International Nuclear Information System (INIS)

    Aqueous solution of congored has been investigated spectrophotometrically for possible applications in food irradiation dosimetry. Absorption spectra of the solution showed two absorption bands with peaks at 346 and 498 nm. Radiation induced bleaching of the dye was measured at the wavelengths of maximum absorbance (346 and 498 nm) as well as at several other wavelengths (491, 540 and 570 nm). At 498 mn, the decrease in absorbance of the dosimeter was linear with respect to the absorbed dose from 50 to 600 Gy. At the other peak wavelength (346 mn), the response was linear up to 400 Gy, however, the upper limit was increased to 600 Gy when the response was measured at longer wavelengths (491, 540 or 570 mn). If the negative logarithm of the absorbance (-log A) at these wavelengths is plotted versus absorbed dose, a linear response was observed from 50 to 1200 Gy. Postirradiation stability of dosimetric solution was studied at room temperature and showed almost stable response up to 50 days when stored in dark. The response was found almost stable for 50 days when the solution after irradiation was exposed to white fluorescent light or to diffused sunlight inside the laboratory. The aqueous congored solution is unstable when exposed to direct sunlight, showing rapid decrease in absorbance for the first few hours followed by a slower decrease. The results suggest that the aqueous congored dosimeter with linear response up to 1200 Gy is suitable for a number of food irradiation applications, such as, sprout inhibition of potatoes, onion and garlic and for ripening delay and ripening stimulation of fruits and vegetables. (author)

  19. Reaction mechanism studies on isoquinoline with hydroxyl radical in aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    ZHU Dazhang; WANG Shilong; SUN Xiaoyu; NI Yarning; YAO Side

    2007-01-01

    The reaction mechanism between isoquinoline and .OH radical in aqueous dilute solutions under different conditions was studied by pulse radiolysis. The main chara-cteristic peaks in these transient absorption spectra were attributed and the growth-decay trends of several transient species were investigated. Under neutral or alkaline condi-tions, the reaction of-OH radical and isoquinoline produces OH-adducts with respective rate constants of 3.4 × 109 and 6.6× 109 mol-1.dm3·s-1 while under acidic conditions, the isoquinoline was firstly protonated and then -OH added to the benzene ring and produced protonated isoquinoline OH-adducts with a rate constant of 3.9× 109 mol-1.dm3·s-1.With a better understanding on radiolysis ofisoquinoline, this study is of help for its degradation and for environmental protection.

  20. The Gibbs-free-energy landscape for the solute association in nanoconfined aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    赵亮; 王春雷; 方海平; 涂育松

    2015-01-01

    The theoretical model and the numerical analyses on the Gibbs-free-energy of the association states of am-phiphilic molecules in nanoconfined aqueous solutions are presented in detail. We exhibit the continuous change of the Gibbs-free-energy trend, which plays a critical role in the association states of the system transforming from the dispersion state, through the “reversible state”, and finally to the aggregation state in amphiphilic molecule solutions. Furthermore, for the“reversible state”, we present the difference in the free-energy bar-rier heights of the dispersion state and aggregation state, resulting from the competition between the entropy, which makes the solute molecules evenly disperse in the solution and the energy contribution driving the am-phiphilic molecules to aggregate into a larger cluster. These findings provide a comprehensive understanding of confinement effects on the solute association processes in aqueous solutions and may further improve the techniques of material fabrication.

  1. Characterization of actinides in simulated alkaline tank waste sludges and leach solutions

    International Nuclear Information System (INIS)

    Current plans call for an alkaline scrub of actinide-bearing sludges in the Hanford Waste tanks prior to their incorporation in glass waste forms. Though it is assumed that actinides will remain in the sludge phase during this procedure, this assumption is based on insufficient supporting thermodynamic and kinetic data. In this project the authors will investigate the fundamental chemistry of actinides in strongly alkaline solution and solid phases to strengthen the foundation and identify potential limitations of this approach. They will focus on the characterization of the leaching of actinides from simulated BiPO4, REDOX, and PUREX sludges, the identification of actinide mineral phases in the sludge simulants, and the possible solubilization of actinides by complexation and radiolysis effects. This program will provide new fundamental information on the chemical behavior and speciation of uranium, neptunium, plutonium, and americium in simulated alkaline tank waste sludges and alkaline scrub liquors. Sludge simulants will be prepared from the appropriate matrix components using published data for guidance. Actinide ions will be introduced in the oxidation states pertinent to process conditions. The authors will characterize the speciation of the actinides in the sludges using a variety of techniques. In parallel studies, they will address the chemistry of actinide ions in alkaline solutions, principally those containing chelating agents. The third critical element of this research will be to assess the impact of radiolysis on actinide behavior. By correlating actinide speciation in the solid and solution phases with sludge composition, it will be possible to predict conditions favoring mobilization (or immobilization) of actinide ions during sludge washing. The new information will increase predictability of actinide behavior during tank sludge washing, and so contribute to minimization of the volume of high level waste created

  2. Bioprecipitation of uranium from alkaline waste solutions using recombinant Deinococcus radiodurans

    International Nuclear Information System (INIS)

    Highlights: • Deinococcus radiodurans was genetically engineered to overexpress alkaline phosphatase (PhoK). • Deino-PhoK bioprecipitated U efficiently over a wide range of input U concentration. • A maximal loading of 10.7 g U/g of biomass at 10 mM input U was observed. • Radioresistance and U precipitation by Deino-PhoK remained unaffected by γ radiation. • Immobilization of Deino-PhoK facilitated easy separation of precipitated U. -- Abstract: Bioremediation of uranium (U) from alkaline waste solutions remains inadequately explored. We engineered the phoK gene (encoding a novel alkaline phosphatase, PhoK) from Sphingomonas sp. for overexpression in the radioresistant bacterium Deinococcus radiodurans. The recombinant strain thus obtained (Deino-PhoK) exhibited remarkably high alkaline phosphatase activity as evidenced by zymographic and enzyme activity assays. Deino-PhoK cells could efficiently precipitate uranium over a wide range of input U concentrations. At low uranyl concentrations (1 mM), the strain precipitated >90% of uranium within 2 h while a high loading capacity of around 10.7 g U/g of dry weight of cells was achieved at 10 mM U concentration. Uranium bioprecipitation by Deino-PhoK cells was not affected in the presence of Cs and Sr, commonly present in intermediate and low level liquid radioactive waste, or after exposure to very high doses of ionizing radiation. Transmission electron micrographs revealed the extracellular nature of bioprecipitated U, while X-ray diffraction and fluorescence analysis identified the precipitated uranyl phosphate species as chernikovite. When immobilized into calcium alginate beads, Deino-PhoK cells efficiently removed uranium, which remained trapped in beads, thus accomplishing physical separation of precipitated uranyl phosphate from solutions. The data demonstrate superior ability of Deino-PhoK, over earlier reported strains, in removal of uranium from alkaline solutions and its potential use in

  3. Bioprecipitation of uranium from alkaline waste solutions using recombinant Deinococcus radiodurans

    Energy Technology Data Exchange (ETDEWEB)

    Kulkarni, Sayali; Ballal, Anand; Apte, Shree Kumar, E-mail: aptesk@barc.gov.in

    2013-11-15

    Highlights: • Deinococcus radiodurans was genetically engineered to overexpress alkaline phosphatase (PhoK). • Deino-PhoK bioprecipitated U efficiently over a wide range of input U concentration. • A maximal loading of 10.7 g U/g of biomass at 10 mM input U was observed. • Radioresistance and U precipitation by Deino-PhoK remained unaffected by γ radiation. • Immobilization of Deino-PhoK facilitated easy separation of precipitated U. -- Abstract: Bioremediation of uranium (U) from alkaline waste solutions remains inadequately explored. We engineered the phoK gene (encoding a novel alkaline phosphatase, PhoK) from Sphingomonas sp. for overexpression in the radioresistant bacterium Deinococcus radiodurans. The recombinant strain thus obtained (Deino-PhoK) exhibited remarkably high alkaline phosphatase activity as evidenced by zymographic and enzyme activity assays. Deino-PhoK cells could efficiently precipitate uranium over a wide range of input U concentrations. At low uranyl concentrations (1 mM), the strain precipitated >90% of uranium within 2 h while a high loading capacity of around 10.7 g U/g of dry weight of cells was achieved at 10 mM U concentration. Uranium bioprecipitation by Deino-PhoK cells was not affected in the presence of Cs and Sr, commonly present in intermediate and low level liquid radioactive waste, or after exposure to very high doses of ionizing radiation. Transmission electron micrographs revealed the extracellular nature of bioprecipitated U, while X-ray diffraction and fluorescence analysis identified the precipitated uranyl phosphate species as chernikovite. When immobilized into calcium alginate beads, Deino-PhoK cells efficiently removed uranium, which remained trapped in beads, thus accomplishing physical separation of precipitated uranyl phosphate from solutions. The data demonstrate superior ability of Deino-PhoK, over earlier reported strains, in removal of uranium from alkaline solutions and its potential use in

  4. Aqueous Solutions on Silica Surfaces: Structure and Dynamics from Simulations

    Science.gov (United States)

    Striolo, Alberto; Argyris, Dimitrios; Tummala, Naga Rajesh

    2009-03-01

    Our group is interested in understanding the properties of aqueous electrolyte solutions at interfaces. The fundamental questions we seek to answer include: (A) how does a solid structure perturb interfacial water? (B) How far from the solid does this perturbation persist? (C) What is the rate of water reorientation and exchange in the perturbed layer? (D) What happens in the presence of simple electrolytes? To address such topics we implemented atomistic molecular dynamics simulations. Recent results for water and simple electrolytes near silicon dioxide surfaces of various degrees of hydroxylation will be presented. The data suggest the formation of a layered aqueous structure near the interface. The density profile of interfacial water seems to dictate the density profiles of aqueous solutions containing NaCl, CaCl2, CsCl, and SrCl2 near the solid surfaces. These results suggest that ion-ion and ion-water correlations are extremely important factors that should be considered when it is desired to predict the distribution of electrolytes near a charged surface. Our results will benefit a number of practical applications including water desalination, exploitation of the oil shale in the Green River Basin, nuclear waste sites remediation, and design of nanofluidic devices.

  5. Uranium, thorium and rare earth extraction and separation process by processing their chloride aqueous solutions

    International Nuclear Information System (INIS)

    The different steps of the process are the following: uranium and iron extraction by a neutral organic phosphorus compound and thorium and rare earth recovery in an aqueous solution, iron recovery in acid aqueous phase, concentration of the thorium and rare earth aqueous solution followed by thorium extraction with a organic phosphorus compound and rare earth recovery in the aqueous phase, thorium recovery in acid aqueous phase

  6. RHEOLOGICAL BEHAVIOR OF ERWINIA GUM IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Li-na Zhang; Mei Zhang; Jing-hua Chen; Hideki Iijima; Hiromichi Tsuchiya

    1999-01-01

    Erwinia (E) gum, an extracellular polysaccharide, is composed of fucose, galatose, glucose and glucuronic acid. Its viscosity behavior was investigated by a low-shear-rate multiball viscometer and a rotational viscometer. Its weight-average molecular weight Mw and intrinsic viscosity [η] in 0.2 mol/L NaCl aqueous solution were measured by light scattering method at 35℃ and viscometry at 25℃ and found to be 1.06 × 106 g/mol and 1050 mL/g, respectively, and its aggregates in aqueous solution were proved by gel permeation chromatography (GPC). These results indicated that E gum in water has exceedingly high viscosity and exhibits Binham fluid behavior, owing to its aggregation. The viscosity of E gum decreased with increasing temperature, and the turning point appeared at 38℃ for dilute solution and 80℃ for concentrated solution suggesting that the aggregates of E gum in water started to disaggregate under these temperatures. In addition, the aggregates can be disrupted by adding either acid or base. The experimental results indicated that the E gum is a good thickening agent, and its fluid behavior is similar to xanthan.

  7. An electrochemical treatment for aqueous radioactive solutions using pottery

    International Nuclear Information System (INIS)

    A bench scale electrolytic cell made from plexiglas was used for electrochemical separation of 137Cs and 60Co from simullated aqueous radioactive solutions. In this cell, a stainless steel plate represented the anode. The electrochemical treatment technique used depends on forcing the radioactive cations of the solution (137Cs+ and 60Co++) towards the opposite electrode under the influence of applied electric current, where they highly sorbed in the pottery body. The highest removal for137Cs+ and 60Co was in the alkalina medium, especially at pH>9. The investigated factors affected the electrochemicla processes are, applied voltage, treatment duration, hydrogen ion concentration of the radioactive solution, and the consumed electrical energy . It was found that at pH 11, applied voltage 30V and current 100 mA, the highest removal of 137Cs is 99.8% after 2.5 hours, and 99.3% and 99.3% for 60Co after 1.25 hour.The total consumed energy for 137Cs and 60Co were 33.75 and 16.88 W.h.dm-3, respectively. Comparing with other treatment methods, the electrochemical method revealed three advantages: shorter treatment time, low-cost materials, and low consumed energy. The results obtained showed that the dual application of electric current and sorption on the surface of pottery are feasible for the treatment of aqueous radioactive solutions

  8. Aqueous solution of basic fuchsin as food irradiation dosimeter

    International Nuclear Information System (INIS)

    Dosimetric characterization of aqueous solution of basic fuchsin has been studied spectrophotometrically for the possible application in the low-dose food irradiation dosimetry. Absorption spectra of unirradiated and irradiated solutions were determined and decrease in the absorption with the radiation dose was noted down. Radiation-induced bleaching of the dye was measured at wavelengths of maximum absorption λmax (540nm) as well as 510, 460 and 400 nm wavelengths. At all these wavelengths, the decrease in the absorbance of the dosimeter was linear with respect to the absorbed dose from 0.05 to 0.6 kGy. The stability of dosimetric solution during the post-irradiation storage in the dark at room temperature showed that after initial bleaching during first eight days, the response was almost stable for about 34 days. The effect of different light and temperature conditions also showed that the response gradually decreased during the storage period of 34 days, which shows that the basic fuchsin dye is photosensitive as well as thermally sensitive. The possibility of using aqueous solution of basic fuchsin as food irradiation dosimeter will be discussed. (authors)

  9. Particularities of anodic dissolution of rhenium in neutral and alkaline solutions at high current densities

    International Nuclear Information System (INIS)

    A study has been made of anodic dissolution of rhenium using potentiodynamic dissolution curves for a rotating disk electrode made of vacuum-melted rhenium. Dissolution of rhenium at 23 deg starts at potentials of approximately + 0.2 V for alkaline solutions (NaOH) and at potentials of approximately +0.1 V for neutral solutions (2N NaCl and NaNO3). No limitation of the process rate is observed during dissolution in neutral solutions unlike dissolution in alkalies for which a limiting current strength is characteristic

  10. Wash Solution Bath Life Extension for the Space Shuttle Rocket Motor Aqueous Cleaning System

    Science.gov (United States)

    Saunders, Chad; Evans, Kurt; Sagers, Neil

    1999-01-01

    A spray-in-air aqueous cleaning system, which replaced 1,1,1 trichloroethane (TCA) vapor degreasing, is used for critical cleaning of Space Shuttle Redesigned Solid Rocket Motor (RSRM) metal parts. Small-scale testing demonstrated that the alkaline-based wash solution possesses adequate soil loading and cleaning properties. However, full-scale testing exhibited unexpected depletion of some primary components of the wash solution. Specifically, there was a significant decrease in the concentration of sodium metasilicate which forced change-out of the wash solution after eight days. Extension of wash solution bath life was necessary to ease the burden of frequent change-out on manufacturing. A laboratory study supports a depletion mechanism that is initiated by the hydrolysis of sodium tripolyphosphate (STPP) lowering the pH of the solution. The decrease in pH causes polymerization and subsequent precipitation of sodium metasilicate (SM). Further investigation showed that maintaining the pH was the key to preventing the precipitation of the sodium metasilicate. Implementation to the full scale operation demonstrated that periodic additions of potassium hydroxide (KOH) extended the useful bath life to more than four months.

  11. Mutual diffusion of sodium hyaluranate in aqueous solutions

    International Nuclear Information System (INIS)

    Highlights: • Binary diffusion coefficients for the systems containing sodium hyaluronate. • Influence of the aggregation on diffusion of the sodium hyaluronate in the aqueous media. • Estimation of the thermodynamic and mobility factors from mutual diffusion. -- Abstract: The Taylor dispersion technique has been used for measuring mutual diffusion coefficients of sodium hyaluronate in aqueous solutions at T = 298.15 K, and concentrations ranging from (0.00 to 0.50) g · dm−3. The results are interpreted on the basis of Nernst, and Onsager and Fuoss theoretical equations. From the diffusion coefficient at infinitesimal concentration, the limiting ionic conductivity and the tracer diffusion coefficient of hyaluronate ion were estimated. These studies have been complemented by molecular mechanics calculations

  12. Physical chemistry of the interface between oxide and aqueous solution

    International Nuclear Information System (INIS)

    The behavior and properties of small oxide particles in aqueous suspension are dominated by the physico-chemistry of their surface. It is electrostatically charged and strongly solvated. The origin of the surface charge is discussed through the MUSIC model [Hiemstra 1996], allowing to estimate the acid-base behavior of surface oxygen atoms. The stability of aqueous dispersions of particles is analysed following the DLVO model, with a special attention on the hydration layers allowing the peptization of flocs. Different adsorption mechanisms of metal cations are presented in terms of coordination chemistry (outer- and inner-sphere complexes) emphasizing the coordinating ability of the surface towards metal complexes in solution. The anion adsorption is also studied in relation with some interesting consequences on spinel iron oxide nano-particles. (author)

  13. Nano particles@Calix arenas via aqueous solution

    Directory of Open Access Journals (Sweden)

    Sahar Dehghani

    2016-05-01

    Full Text Available The electronic structure and magnetic properties of Al2O3, GaN and Fe3O4@ Calix (8 COOH have been studied using ONIOM and DFT methods. The studies focus on how to improve the adsorption of some nano particles solution aqueous for achieving good magnetic and functionalized potential performances. The results revealed that the Fe3O4@ Calix (8 COOH and some of its derivations exhibited better thermodynamic stability. Furthermore, the particle size and magnetic property of the GaN@ Calix (8 COOH nano particles can be controlled by the aqueous. The electrical properties such as NMR Shielding, electron densities, energy densities, potential energy densities, ELF, LOL, ellipticity of electron density, eta index and ECP for nano particles@ Calix (8COOH have been calculated.

  14. Magnetic composite nanofibers fabricated by electrospinning of Fe3O4/gelatin aqueous solutions

    International Nuclear Information System (INIS)

    Graphical abstract: Superparamagnetic Fe3O4/GE composite nanofibers with saturation magnetization of 12.87 emμ g−1 were prepared from gelatin aqueous solution at an elevated temperature by electrospinning. - Highlights: • Electrospinning GE aqueous solution at higher temperature. • Presenting a simple and effective technique, combining wet blending with high temperature electrospinning to prepare magnetic composite nanofibers. • Developing composite nanofibers with higher superparamagnetic properties is expected to be useful in application for the biomedical field. - Abstract: We have fabricated magnetic composite nanofibers containing superparamagnetic Fe3O4 nanoparticles by the electrospinning method. Highly dispersed Fe3O4 magnetic nanoparticles were synthesized by one-step co-precipitation of Fe2+/Fe3+ under an alkaline condition with 4 wt% poly(vinyl alcohol) (PVA) aqueous solution as the stabilizer. Gelatin (GE) was used as a polymeric matrix for fabricating the nanocomposites. The prepared Fe3O4/GE composite nanofibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. These composite nanofibers show uniform and continuous morphology with the Fe3O4 nanoparticles embedded in the nanofibers. By studying the magnetic properties of the Fe3O4/GE composite nanofibers, we confirm that the composite nanofibers possess superparamagnetic properties with a high saturated magnetization (Ms = 12.87 emμ g−1) at room temperature. The features of this approach for getting one-dimensional magnetic nanostructure are its simplicity, effectiveness and safety. The Fe3O4/GE nanofibers with superparamagnetic properties would be potentially applied in biomedical field

  15. Temperature dependence of the absorbance of alkaline solutions of 4-nitrophenyl phosphate--a potential source of error in the measurement of alkaline phosphatase activity.

    Science.gov (United States)

    Burtis, C A; Seibert, L E; Baird, M A; Sampson, E J

    1977-09-01

    The absorbance of an alkaline solution of 4-nitrophenyl phosphate is a function of temperature. Quantitative evaluation of this phenomenon indicates that it (a) depends on the concentration of the compound and is independent of source, buffer concentration, and pH above 9.0; (b) is reversible; (c) is not a result of alkaline hydrolysis or 4-nitrophenol contamination; and (d) correlates with a temperature-induced shift of its absorbance spectrum. The phenomenon may represent a potential analytical problem in methods for alkaline phosphatase in which this compound is the substrate. If thermal equilibrium is not reached and maintained during an alkaline phosphatase assay, the thermochromic response will be included in the measured rate. The magnitude of this error depends on the thermal response and control characteristics of each particular instrument and the reaction conditions under which such an analysis is performed. PMID:19164

  16. Bifunctional, Carbon-Free Nickel/Cobalt-Oxide Cathodes for Lithium-Air Batteries with an Aqueous Alkaline Electrolyte

    International Nuclear Information System (INIS)

    Highlights: • High activity bi-functional catalyst combination for ORR and OER . • An optimum ratio of high active bi-functional catalysts was found. • Novel electrodes without carbon to avoid carbon corrosion during OER mode. • EIS model for OER describes influence of a growing oxide layers. • Long-term test exhibited an excellent long-term stability over 1200 cycles. - Abstract: Lithium-air batteries with an aqueous alkaline electrolyte promise a very high practical energy density and capacity. These batteries are mainly limited by high overpotentials on the bifunctional cathode during charge and discharge. To reduce overpotentials the bifunctional cathode of such batteries must be improved significantly. Nickel is relatively inexpensive and has a good catalytic activity in alkaline media. Co3O4 was found to be a promising metal oxide catalyst for oxygen evolution in alkaline media but it has a low electronic conductivity. On the other hand since nickel has a good electronic conductivity Co3O4 can be added to pure nickel electrodes to enhance performance due to a synergetic effect. Due to the poor stability of carbon materials at high anodic potentials, gas diffusion electrodes were prepared without carbon to improve especially long-term stability. Gas diffusion electrodes were electrochemically investigated in a half cell. In addition, cyclic voltammogrametry (CV) and electrochemical impedance spectroscopy (EIS) were carried out. SEM was used for the physical and morphological investigations. Investigations showed that electrodes containing 20 wt.% Co3O4 exhibited the highest performance

  17. Thermodynamic, kinetic and mechanistic investigations of Piperazine oxidation by Diperiodatocuprate(III) complex in aqueous alkaline medium

    Indian Academy of Sciences (India)

    Vijay P Pattar; Prashant A Magdum; Deepa G Patil; Sharanappa T Nandibewoor

    2016-03-01

    The kinetics of oxidation of piperazine by the copper complex, diperiodatocuprate(III) in alkaline medium was studied at 298 K, at an ionic strength of 2.0*10-2 mol dm-3. The reaction between piperazine and diperiodatocuprate(III) in aqueous alkaline medium exhibited 1:2 stoichiometry. The oxidation products were identified by UV-Visible, GC-MS and IR spectral studies. In the present study we have obtained different kinetic observations. The reaction exhibited unit order in case of diperiodatocuprate(III), while less than unit order with respect to piperazine. The addition of alkali and periodate retarded the rate of reaction. The effects of added products, ionic strength and dielectric constant on the rate of the reaction were also studied. The active species of diperiodatocuprate(III) in alkaline media is [Cu(OH)2(H3IO6)]-. The activation parameters with respect to the rate determining step and the thermodynamic quantities with respect to the equilibrium steps were evaluated and discussed. The plausible mechanism consistent with the experimental results was proposed and discussed in detail.

  18. Gamma-ray inactivation of biotin in dilute aqueous solution

    International Nuclear Information System (INIS)

    The relative roles of the radicals produced by water radiolysis in the inactivation of biotin in aqueous solution were investigated. The effects of nitrous oxide and isopropanol used as selective free radical scavengers allowed the inactivation efficiencies per unit G-value of OH, H, and esub(aq)- to be estimated; these efficiencies were 0.73, 0.10, and 0.02 in neutral solution, respectively. Hydrogen gas and hydrogen peroxide unaffected the activity of biotin. G0-Value for biotin inactivation in oxygen-free neutral solution was 2.08. Under these conditions the hydroxyl radical attack was found to be responsible for the large part of inactivation. On the other hand, in oxygenated neutral solution, G0-value was 4.16. This large increase of inactivation in oxygenated solution suggested that, although hydrated electrons were considerably ineffective as an inactivating species in oxygen-free solution, superoxide ions would be much more effective in causing inactivation of biotin in oxygenated solution. A rate constant for the reaction of biotin with hydroxyl radical was 1.34 x 1010M-1 sec-1 as determined by the PNDA method. (auth.)

  19. Enthalpy of solution of CO2 in aqueous solutions of 2-amino-2-methyl-1-propanol

    International Nuclear Information System (INIS)

    The enthalpies of solution of CO2 in aqueous solution of 2-amino-2-methyl-1-propanol (AMP) 15 wt% and 30 wt% were measured at 322.5 K and pressures range from (0.2 to 5) MPa using a flow calorimetric technique. The gas solubilities were simultaneously determined from the calorimetric data. The solubilities were compared to available literature values obtained by direct measurements. The experimental enthalpies of solution were compared to the values derived from the literature vapor liquid equilibrium data. This work provides calorimetric data that will be used later for the development of a thermodynamic model to predict both solubilities and enthalpies of solution of acid gases in aqueous amine solutions

  20. Characterization of Laboratory Prepared Concrete Pastes Exposed to High Alkaline and High Sodium Salt Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C. A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-06-30

    The objective of this study was to identify potential chemical degradation mechanisms for the Saltstone Disposal Unit (SDU) concretes, which over the performance life of the structures may be exposed to highly alkaline sodium salt solutions containing sulfate, hydroxide, and other potentially corrosive chemicals in salt solution and saltstone flush water, drain water, leachate and / or pore solution. The samples analyzed in this study were cement pastes prepared in the SIMCO Technologies, Inc. concrete laboratory. They were based on the paste fractions of the concretes used to construct the Saltstone Disposal Units (SDUs). SDU 1 and 4 concrete pastes were represented by the PV1 test specimens. The paste in the SDU 2, 3, 5, and 6 concrete was represented by the PV2 test specimens. SIMCO Technologies, Inc. selected the chemicals and proportions in the aggressive solutions to approximate proportions in the saltstone pore solution [2, 3, 5, and 6]. These test specimens were cured for 56 days in curing chamber before being immersed in aggressive solutions. After exposure, the samples were frozen to prevent additional chemical transport and reaction. Selected archived (retrieved from the freezer) samples were sent to the Savannah River National Laboratory (SRNL) for additional characterization using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray (EDX) spectroscopy. Characterization results are summarized in this report. In addition, a correlation between the oxide composition of the pastes and their chemical durability in the alkaline salt solutions is provided.

  1. Solvation of electrolytes and nonelectrolytes in aqueous solutions.

    Science.gov (United States)

    Afanas'ev, V N

    2011-05-26

    A new theory of electrolyte and nonelectrolyte solutions has been developed which, unlike the Debye-Hückel method applicable for small concentrations only, makes it possible to estimate thermodynamic properties of a solution in a wide range of state parameters. One of the main novelties of the proposed theory is that it takes into account the dependence of solvation numbers upon the concentration of solution, and all changes occurring in the solution are connected with solvation of the stoichiometric mixture of electrolyte ions or molecules. The present paper proposes a rigorous thermodynamic analysis of hydration parameters of solutions. Ultrasound and densimetric measurements in combination with data on isobaric heat capacity have been used to study aqueous solutions of electrolytes NaNO3, KI, NaCl, KCl, MgCl2, and MgSO4 and of nonelectrolytes urea, urotropine, and acetonitrile. Structural characteristics of hydration complexes have been analyzed: hydration numbers h, the proper volume of the stoichiometric mixture of ions without hydration shells V(2h), compressibility β(1h), and the molar volume of water in hydration shells V(1h), their dependencies on concentration and temperature. It has been shown that for aqueous solutions the electric field of ions and molecules of nonelectrolytes has a greater influence on the temperature dependence of the molar volume of solution in hydration shells than a simple change of pressure. The cause of this effect may be due to the change in the dielectric permeability of water in the immediate vicinity of hydrated ions or molecules. The most studied compounds (NaCl, KCl, KI, MgCl2) have been studied in a wider range of solute concentrations of up to 4-5 mol/kg. Up to the complete solvation limit (CSL), the functions V(1h) = f(T) and β(1h) = f(T) are linear with a high correlation factor, and the dependence Y(K,S) = f(β1V1*) at all investigated concentrations of electrolytes and nonelectrolytes up to the CSL enables h and

  2. Electromigration behavior of SSDNA fragments in highly alkaline solutions of linear polyacrylamide

    Czech Academy of Sciences Publication Activity Database

    Malá, Zdeňka; Klepárník, Karel; Boček, Petr

    Boston: CaSSS, 2001, s. 156. [HPCE 2001. International Symposium on Microscale Separations and Analysis Includes mini-symposia on Genomics and Proteomics /14./. Boston (US), 13.01.2001-18.01.2001] R&D Projects: GA ČR GA203/00/0772; GA ČR GA303/00/0928 Institutional research plan: CEZ:AV0Z4031919 Keywords : DNA sequencing * bare capillary * alkaline solution Subject RIV: CB - Analytical Chemistry, Separation

  3. Electrochemical Reduction of Oxygen on Multi-walled Carbon Nanotubes Electrode in Alkaline Solution

    Institute of Scientific and Technical Information of China (English)

    You Qun CHU; Chun An MA; Feng Ming ZHAO; Hui HUANG

    2004-01-01

    The multi-walled carbon nanotubes (MWNTs) electrode was constructed using poly- tetrafluoroethylene as binder, and the electrochemical reductive behavior of oxygen in alkaline solution was first examined on this electrode. Compared with other carbon materials, MWNTs show higher electrocatalytic activity, and the reversibility of O2 reduction reaction is greatly improved. The experiments reveal that the electrochemical reduction of O2 to HO2- is controlled by adsorption. The preliminary results illustrate the potential application of MWNTs in fuel cells.

  4. Electrochemical Characterization of New Silver Gas Diffusion Electrodes during Oxygen Reduction in Alkaline Solution

    OpenAIRE

    Wagner, Norbert

    2013-01-01

    In order to analyze in detail the kinetics of the oxygen reduction reaction (ORR) and the influence of the porous electrode structure on the electrode performance in alkaline solution (10 M NaOH) at 80°C electrochemical impedance measurements (EIS) and cyclic voltammograms (CV) have been performed. The investigated electrodes were technical silver gas diffusion electrodes (GDE) and porous silver membranes with different pore radii ranging from 0.2 µm to 5 µm. Silver gas diffusion electrodes w...

  5. Process for the separation of uranium in an alkaline solution, particularly extracted from an uraniferous ore

    International Nuclear Information System (INIS)

    Process for the treatment of an alkaline uraniferous liquor containing solubilised uranium, particularly sodium uranyl-tricarbonate, characterised in that this liquor is placed into contact with a cationic ion exchange resin, previously put into ammonium form and, in that after the ion exchange has taken place a solution is collected in which the previous sodium salts and complexes have been mainly transformed in ammonium salts and complexes

  6. Removal of radioruthenium from alkaline intermediate level radioactive waste solution : a laboratory investigation

    International Nuclear Information System (INIS)

    Various methods were investigated in the laboratory for the removal of radioruthenium from alkaline intermediate level radioactive waste solutions of reprocessing plant origin. The methods included batch equilibration with different ion exchangers and sorbents, column testing and chemical precipitation. A column method using zinc-activated carbon mixture and a chemical precipitation method using ferrous salt along with sodium sulphite were found to be promising for plant scale application. (author). 10 refs., 3 figs., 7 tabs

  7. Removal of Cholera Toxin from Aqueous Solution by Probiotic Bacteria

    Directory of Open Access Journals (Sweden)

    Jussi A. O. Meriluoto

    2012-06-01

    Full Text Available Cholera remains a serious health problem, especially in developing countries where basic hygiene standards are not met. The symptoms of cholera are caused by cholera toxin, an enterotoxin, which is produced by the bacterium Vibrio cholerae. We have recently shown that human probiotic bacteria are capable of removing cyanobacterial toxins from aqueous solutions. In the present study we investigate the ability of the human probiotic bacteria, Lactobacillus rhamnosus strain GG (ATCC 53103 and Bifidobacterium longum 46 (DSM 14583, to remove cholera toxin from solution in vitro. Lactobacillus rhamnosus strain GG and Bifidobacterium longum 46 were able to remove 68% and 59% of cholera toxin from aqueous solutions during 18 h of incubation at 37 °C, respectively. The effect was dependent on bacterial concentration and L. rhamnosus GG was more effective at lower bacterial concentrations. No significant effect on cholera toxin concentration was observed when nonviable bacteria or bacterial supernatant was used.

  8. Boron removal from aqueous solution by direct contact membrane distillation

    International Nuclear Information System (INIS)

    The removal of boron from aqueous solution by direct contact membrane distillation (DCMD) was studied with self-prepared polyvinylidene fluoride (PVDF) hollow fiber membranes in the present work. The effect of pH, boron concentration, temperature and salt concentration of the feed solution on the boron rejection was investigated. The experimental results indicated that boron rejection was less dependent on the feed pH and salt concentration. DCMD process had high boron removal efficiency (>99.8%) and the permeate boron was below the maximum permissible level even at feed concentration as high as 750 mg/L. Although the permeate flux was enhanced exponentially with the feed temperature increasing, the influence of feed temperature on the boron rejection could be neglected. Finally, the natural groundwater sample containing 12.7 mg/L of boron was treated by DCMD process. The permeate boron kept below 20 μg/L whether the feed was acidified or not, but pre-acidification was helpful to maintain the permeate flux stability. All the experimental results indicated that DCMD could be efficiently used for boron removal from aqueous solution.

  9. Removing Phosphorus from Aqueous Solutions Using Lanthanum Modified Pine Needles.

    Directory of Open Access Journals (Sweden)

    Xianze Wang

    Full Text Available The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO4(2-, NO3(- and Cl(-; however, CO3(2- exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions.

  10. Removing Phosphorus from Aqueous Solutions Using Lanthanum Modified Pine Needles

    Science.gov (United States)

    Wang, Xianze; Liu, Zhongmou; Liu, Jiancong; Huo, Mingxin; Huo, Hongliang; Yang, Wu

    2015-01-01

    The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI) failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH) showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO42-, NO3- and Cl-); however, CO32- exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC) assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions. PMID:26630014

  11. Preparation of fluorescent polyaniline nanoparticles in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Alves, Kleber G. B. [Universidade Federal de Pernambuco, Departamento de Engenharia Mecanica (Brazil); Melo, Etelino F. de [Universidade Federal de Pernambuco, Departamento de Quimica Fundamental (Brazil); Andrade, Cesar A. S. [Universidade Federal de Pernambuco, Departamento de Bioquimica (Brazil); Melo, Celso P. de, E-mail: celso@df.ufpe.br [Universidade Federal de Pernambuco, Departamento de Fisica (Brazil)

    2013-01-15

    We report the synthesis of stable polyaniline nanoparticles (PANI{sub N}Ps) based on the chemical oxidative polymerization of aniline in aqueous solutions of surfactants. Surfactants of three different types-cationic (dodecyltrimethylammonium bromide-DTAB), anionic (sodium dodecyl sulfate-SDS), and non-ionic (Triton X-405-TX-405)-were used. The resulting PANI{sub N}Ps{sub s}urfactant samples were characterized through UV-Vis, fluorescence and Fourier transform infrared spectroscopies, and scanning electronic microscopy (SEM). We have verified that the color of the PANI{sub N}Ps{sub s}urfactant dispersions is affected by a change in the pH of the solution. The PANI-NPs{sub s}urfactant colloidal suspensions in aqueous solution present a surprising high fluorescence quantum yield value (ranging from 1.9 Multiplication-Sign 10{sup -3} to 6.9 Multiplication-Sign 10{sup -3}) that can be controlled as a function of the pH, a fact that we associate to the corresponding protonation degree of the PANI polymeric chains. We suggest that these fluorescent nanocomposites can find important technological applications in different areas such as organic light emitting devices, biosensors, and pigments for coatings.

  12. Radiolysis of some aqueous solutions of neutron absorbers

    International Nuclear Information System (INIS)

    The initial yield of molecular hydrogen formed by radiolytic decomposition of water in reactor and 60Co gamma radiation is decreased by the presence of salts of polyvalent elements possessing only one stable valence, i.e cadmium, zinc, magnesium, gadolinium. This effect is favourable for the use of cadmium and gadolinium as soluble neutron absorber in heavy water reactors. Cations of these salts are not inert toward the primary products of water radiolysis. They have a high degree of reactivity toward the hydrated electron, which is the precursor of molecular hydrogen in neutral or alkaline aqueous media. The value of the rate constant for the reaction between cadmium ion and hydrated electron was shown to be (6.1 ± 1.8) 1010 M-1 s-1. Boric acid at low concentration has no effect on the radiation chemistry of water. An isotope effect has been found in the radiolysis of heavy water, corresponding to a lowering of initial yield [G0(D2) 0(H2)]. additionally it was necessary to determine the influence of organic impurities, remaining after the purification of water, on the mechanism of its radiolytic decomposition. (author)

  13. Electrochemical reduction of /Ru edta L/ compounds in aqueous solution

    International Nuclear Information System (INIS)

    Electrochemical reduction of the complexes [Ru edta L], [L= 2,2' bipyridine (2,2' bipy) pyrazinamide (pz CONH2); 4-cyanopyridine 4-cyanopyridine (4-CNpy); nicotinamide (NIC); hydroxil; 3-aminophenol (3-NH2 φ OH) and 2-aminopyridine (2-NH2 py)] in aqueous solution (acetate buffer, pH 4.65 or phosphate buffer, pH=8.2), μ=0,2 M p-cH3φSO3Li is investigated. The measurements have been made by cyclic voltammetry technique, using platinum, gold and mercury pool as working electrodes. (M.J.C.)

  14. Standard Electrode Potentials Involving Radicals in Aqueous Solution: Inorganic Radicals

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, David A.; Huie, Robert E.; Koppenol, Willem H.; Lymar, Sergei V.; Merenyi, Gabor; Neta, Pedatsur; Ruscic, Branko; Stanbury, David M.; Steenken, Steen; Wardman, Peter

    2015-12-01

    Recommendations are made for standard potentials involving select inorganic radicals in aqueous solution at 25 °C. These recommendations are based on a critical and thorough literature review and also by performing derivations from various literature reports. The recommended data are summarized in tables of standard potentials, Gibbs energies of formation, radical pKa’s, and hemicolligation equilibrium constants. In all cases, current best estimates of the uncertainties are provided. An extensive set of Data Sheets is appended that provide original literature references, summarize the experimental results, and describe the decisions and procedures leading to each of the recommendations

  15. Effect of Surface Quality in Viscometry of Aqueous Polymer Solutions

    Czech Academy of Sciences Publication Activity Database

    Večeř, M.; Wein, Ondřej

    Praha: Process Engineering Publisher, 2010, s. 1093. ISBN 978-80-02-02248-0. [International Congress of Chemical and Process Engineering CHISA 2010 and 7th European Congress of Chemical Engineering ECCE-7 /19./. Prague (CZ), 28.08.2010-01.09.2010] R&D Projects: GA ČR GA104/09/0972; GA ČR GA104/08/0428 Institutional research plan: CEZ:AV0Z40720504 Keywords : apparent wall slip * surface quality * aqueous polymer solutions Subject RIV: CI - Industrial Chemistry, Chemical Engineering www.chisa.cz/2010, www.ecce7.com

  16. Strong adhesion and cohesion of chitosan in aqueous solutions

    OpenAIRE

    Lee, DW; Lim, C. (Cheryl); Israelachvili, JN; Hwang, DS

    2013-01-01

    Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is a promising biopolymer for the replacement of synthetic plastic compounds. Here, surface interactions mediated by chitosan in aqueous solutions, including the effects of pH and contact time, were investigated using a surface forces apparatus (SFA). Chitosan films showed an adhesion to mica for all tested pH ranges (3.0-8.5), achieving a maximum value at pH 3.0 after a contact time of 1 h (Wad ∼ ...

  17. Strong adhesion and cohesion of chitosan in aqueous solutions

    OpenAIRE

    Lee, Dong Woog; Lim, Chanoong; Israelachvili, Jacob N.; Hwang, Dong Soo

    2013-01-01

    Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is a promising biopolymer for the replacement of synthetic plastic compounds. Here, surface interactions mediated by chitosan in aqueous solutions, including the effects of pH and contact time, were investigated using a surface forces apparatus (SFA). Chitosan films showed an adhesion to mica for all tested pH ranges (3.0–8.5), achieving a maximum value at pH 3.0 after a contact time of 1 hr (Wad ~...

  18. Nano particles@Calix arenas via aqueous solution

    OpenAIRE

    Sahar Dehghani

    2016-01-01

    The electronic structure and magnetic properties of Al2O3, GaN and Fe3O4@ Calix (8) COOH have been studied using ONIOM and DFT methods. The studies focus on how to improve the adsorption of some nano particles solution aqueous for achieving good magnetic and functionalized potential performances. The results revealed that the Fe3O4@ Calix (8) COOH and some of its derivations exhibited better thermodynamic stability. Furthermore, the particle size and magnetic property of the GaN@ Calix (8) C...

  19. Recovery of niobium anions from aqueous solutions by ion flotation

    International Nuclear Information System (INIS)

    In principle the feasibility of recovering niobates (K2NbOF5 and K2NbF7) from aqueous media by ion flotation was established. When using quaternary ammonium bases or amines as the collectors, the optimal conditions lie in the interval pH = 5.0-9.0. The interaction of niobates with cationic surfactants may proceed through an anion-exchange mechanism. The presence of acid in the solution suppresses this interaction, owing to the competition from the anions that are present and owing to binding of the surface-active collectors into a complex. 3 figures

  20. Removal of heavy metals from aqueous solutions using opalized tuff

    OpenAIRE

    Golomeova, Mirjana; Zendelska, Afrodita; Golomeov, Blagoj; Krstev, Boris; Jakupi, Shaban

    2015-01-01

    This paper presents the results of the examination of the possibility of applying opalized tuff as a natural raw material for disposal of heavy metals (copper, zinc, manganese and lead) from aqueous solutions. Of actual experiments obtained results show that working conditions attaching to the removal of Cu and Pb ions is more than 91% of zinc ions is above 81%, while manganese ions are removed about 77% .On this can be concluded that the removal of examined heavy metals using opalized tuff i...

  1. VUV irradiation studies of plasmid DNA in aqueous solution

    Science.gov (United States)

    Śmialek, M. A.; Hoffmann, S. V.; Folkard, M.; Prise, K. M.; Shuker, D. E. G.; Braithwaite, N. S.; Mason, N. J.

    2008-02-01

    Interactions of VUV light and DNA samples in aqueous solutions are reported. The damage induced by such radiation is quantified by monitoring both loss of supercoiled DNA and formation of single and double strand breaks using agarose gel electrophoresis. Irradiations were performed using synchrotron VUV photons of 130, 150, 170 and 190 nm. VUV irradiation experiments revealed enhanced damage upon irradiation with 170 nm photons as compared with irradiations with photons of 150 nm and 130 nm. Irradiations carried at 190 nm caused the least damage.

  2. Polymerization of beta-amino acids in aqueous solution

    Science.gov (United States)

    Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    We have compared carbonyl diimidazole (CDI) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as activating agents for the oligomerization of negatively-charged alpha- and beta-amino acids in homogeneous aqueous solution. alpha-Amino acids can be oligomerized efficiently using CDI, but not by EDAC. beta-Amino acids can be oligomerized efficiently using EDAC, but not by CDI. Aspartic acid, an alpha- and beta-dicarboxylic acid is oligomerized efficiently by both reagents. These results are explained in terms of the mechanisms of the reactions, and their relevance to prebiotic chemistry is discussed.

  3. Fluorescence of aqueous solutions of commercial humic products

    Science.gov (United States)

    Gosteva, O. Yu.; Izosimov, A. A.; Patsaeva, S. V.; Yuzhakov, V. I.; Yakimenko, O. S.

    2012-01-01

    We have studied the spectral luminescence characteristics of aqueous solutions of humic products obtained from different raw material sources, and their behavior as the excitation wavelength increases from 270 nm to 355 nm. We have identified differences in the spectral properties of industrial humic products from coalified materials, lignin-containing organic waste, and humic products from plant raw material (peat, sapropel, vermicompost). We have shown that humic products from plant raw material have spectral properties closer to those for humic substances in natural water or soil than humic products from coalified materials.

  4. The characterization methods for colloids in aqueous solutions

    International Nuclear Information System (INIS)

    This literature review deals with characterization methods for colloids in aqueous solutions and in groundwater. The basis for the review has been the needs of nuclear waste disposal studies and methods applicable in such studies. The methods considered include non-destructive laserspectroscopic methods (e.g. TRLFS, LPAS, PALS), several separation methods (e.g. ultrafiltration, dialysis, electrophoresis, field-flow-fractionation) and also some surface analytical methods, as well as some other methods giving additional information on formation and migration properties of colloids. (au.) (71 refs., 13 figs., 3 tabs.)

  5. Radiolysis of phenol in aqueous solution at elevated temperatures

    International Nuclear Information System (INIS)

    γ-Radiolysis and pulse radiolysis of phenol in aqueous solution up to supercritical condition have been carried out. G-values of phenol consumption and product formation have been determined. While dihydroxybenzenes were major products at room temperature, multi-ring compounds and benzene were formed above 300 deg. C. This indicates reaction mechanism was changed above 300 deg. C, where phenoxyl radical plays a predominant role. This is supported by the observation of phenoxyl radical in pulse radiolysis. In supercritical water, the G-values increased with decrease of density

  6. Degradation of Sodium-Polyacrylate in Dilute Aqueous Solution

    Science.gov (United States)

    Saita, Takao

    1980-12-01

    It is shown using a capillary viscometer that the viscosity of a dilute aqueous solution of sodium-polyacrylate at 20°C decreases gradually for each flow time measurement and also decreases with the time of rest. Assuming that the polymer degradation is caused by shearing stress and oxidation, their effects are discussed with the data obtained using a closed-type capillary viscometer derived for this investigation. It is proved from the results that rupture of the Na-PAA molecule is caused by mechanochemical degradation, and also photo-degradation under the usual illumination and sunlight in a laboratory.

  7. VUV irradiation studies of plasmid DNA in aqueous solution

    International Nuclear Information System (INIS)

    Interactions of VUV light and DNA samples in aqueous solutions are reported. The damage induced by such radiation is quantified by monitoring both loss of supercoiled DNA and formation of single and double strand breaks using agarose gel electrophoresis. Irradiations were performed using synchrotron VUV photons of 130, 150, 170 and 190 nm. VUV irradiation experiments revealed enhanced damage upon irradiation with 170 nm photons as compared with irradiations with photons of 150 nm and 130 nm. Irradiations carried at 190 nm caused the least damage

  8. Analysis and modeling of alkali halide aqueous solutions

    DEFF Research Database (Denmark)

    Kim, Sun Hyung; Anantpinijwatna, Amata; Kang, Jeong Won;

    2016-01-01

    calculations for various electrolyte properties of alkali halide aqueous solutions such as mean ionic activity coefficients, osmotic coefficients, and salt solubilities. The model covers highly nonideal electrolyte systems such as lithium chloride, lithium bromide and lithium iodide, that is, systems that are...... very soluble in water, for example, up to more than 30 mol kg-1. Phase behaviors for the systems are analyzed at concentrations of salt up to the solubility in water at temperatures between 273 and 373 K by comparing calculated results with available experimental data and available models....

  9. Decomposition of aqueous solutions of phenol using high energy electron beam irradiation - a large scale study

    International Nuclear Information System (INIS)

    High-energy electron-beam irradiation was used to remove phenol from aqueous solution. The variables that affected phenol decomposition were solute concentration, absorbed dose and total alkalinity. Experiments were conducted at large scale (480 L min-1, at solute concentrations of 10.6, 106 and 531 μmol L-1 (1, 10 and 50 mg L-1) over the pH range 5-9, and in the presence and absence of solids (3% w/w kaolin clay). Absorbed doses ranged from 0-7 kGy (0-700 krad). At low absorbed doses, catechol, hydroquinone and resorcinol were identified as the major reaction byproducts. These compounds are consistent with hydroxyl radical (OH·) addition to phenol. Subsequent ring cleavage of hydroxylated phenolic radicals and continued oxidative processes resulted in the formation of formaldehyde, acetaldehyde, glyoxal and formic acid. At high doses only trace amounts of the carbonyl derivatives were observed. Two recirculation experiments were conducted at higher phenol concentrations (∼950 μmol L-1 and it was shown that phenol was removed while the total organic carbon of the solution decreased only slightly. These results that phenol was not mineralized but, rather, that irradiation resulted in the possible formation of higher molecular weight polymers. (Author)

  10. Excess Thermodynamic Properties of Concentrated Aqueous Solutions at High Temperatures

    International Nuclear Information System (INIS)

    Measurements of the vapor pressure of the solvent in wide ranges of concentration and temperature provide information on solute solvation and ion pairing--the two phenomena most often invoked for description of dilute solutions. Even in moderately concentrated solutions, as interionic distances become comparable to ionic diameters, these simple concepts gradually lose their meaning and solutions behave like molten salts. The usefulness of experimental vapor pressure results increases rapidly with their accuracy, since derived properties, such as solution enthalpies and heat capacities, can be calculated. Very accurate results can be obtained by the isopiestic method, but primary vapor pressure data for standard solutions are needed. In order to obtain vapor pressures at conditions where accurate isopiestic standards are not available and to establish more accurate standards, the ORNL isopiestic apparatus was modified for simultaneous direct vapor pressure measurements and isopiestic comparisons. There are no comprehensive solution theories derived from molecular level models and able to predict thermodynamic properties of various electrolytes as the composition changes from dilute solutions to molten salts in a wide range of temperatures. Empirical and semi-empirical models are useful for representation of experimental results, interpretation of measurements of other properties such as conductance., solubility or liquid-vapor partitioning of solutes, and for verification of theoretical predictions. Vapor pressures for aqueous CaCl(sub 2), CaBr(sub 2), LiCl, LiBr, LiI, NaI were measured at temperatures between 380 and 523 K in the concentration range extended to water activities below 0.2 (over 30 mol/kg for LiCl). General equations based on the modified Pitzer ion-interaction model were used to obtain enthalpy and heat capacity surfaces, which are compared with direct calorimetric measurements

  11. Novel Ag/Kaolin Nanocomposite as Adsorbent for Removal of Acid Cyanine 5R from Aqueous Solution

    OpenAIRE

    Saeedeh Hashemian; Mohammad Reza Shahedi

    2013-01-01

    Ag/kaolin nanocomposite was prepared by reduction of Ag+ ion with ethanol at alkaline condition on kaolin surface. Nanocomposite was characterized by FTIR, XRD, TEM, and BET methods. Results showed the Ag/kaolin composite has particle size 50 nm. The surface area was increased from kaolin to Ag/kaolin from 1.0215 to 7.409 m2 g−1, respectively. Ag/kaolin nanocomposite was used for adsorption of acid cyanine 5R (AC5R) from aqueous solution. The effect of parameters such as contact time, pH, an...

  12. Radiolysis of berberine or palmatine in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Marszalek, Milena [Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz (Poland); Wolszczak, Marian, E-mail: marianwo@mitr.p.lodz.p [Institute of Applied Radiation Chemistry, Technical University of Lodz, Wroblewskiego 15, 93-590 Lodz (Poland)

    2011-01-15

    The reactions of hydrated electron (e{sub aq}{sup -}), hydrogen atom (H{sup {center_dot}}) (reducing species) and Cl{sub 2}{sup {center_dot}}{sup -},Br{sub 2}{sup {center_dot}}{sup -},{sup {center_dot}}N{sub 3},{sup {center_dot}}OH radicals (oxidizing species) with berberine or palmatine in aqueous solution have been studied by steady-state and pulse radiolysis. The spectra of transient intermediates, leading to the final products, are presented. The rate constants of the reaction of e{sub aq}{sup -} and {sup {center_dot}}OH radical with both alkaloids in the homogenous solution and in the presence of DNA are reported. It is demonstrated that the primary products of the reaction of berberine and palmatine with e{sub aq}{sup -} and radicals generated during radiolysis are unstable and undergo further reactions.

  13. Rheological properties of aqueous solutions of biopolymeric hyaluronan

    Science.gov (United States)

    Szwajczak, Elzbieta

    2004-09-01

    Aqueous solutions of hyaluronic acid (hyaluronan, HA) were studied. The HA compound is a natural polysaccharide, bipolymer. It plays an important role in numerous biological processes as a component of the extracellular matrix, connective tissues and, especially, human and animal synovial joints. Natural and artificial solutions of the HA have demonstrated the viscoelastic nature. These properties are shown to be related to the microstructure parameters (bulk concentration, molecular weight) and external parameters (temperature, stress, shear rate). We emphasize the role of the flow properties of polymeric systems. It is found a liquid crystalline "order" can be "induced" during the material flow. The dynamic properties, such as the elastic shear modulus and viscous shear modulus, are given. These results are discussed in relation to the postulated function of hyaluronic acid in synovial joint and with respect to possibilities o their application in medicine and pharmacology.

  14. Dielectric properties of aqueous solutions of holmium formates

    International Nuclear Information System (INIS)

    SHF-dielectric properties in the range of free-quenches 7-23.5 GHz and electric conductivity of aqueous solutions of holmium formates in the temperature range from 10 to 40 deg C were studied. Parameters of the process of dipole relaxation of water molecules: static dielectric constant, relaxation time and parameters of relaxation time distribution have been ascertained. Activation characteristics of the dipole relaxation and specific electric conductivity have been calculated. The change in the structural-kinetic state of water H-bond net in solution under the action of Ho3+ and HCOO- ions is considered on the basis of the data obtained. 10 refs., 2 figs.; 3 tabs

  15. Influence of coal properties on mercury uptake from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Lakatos, J.; Brown, S.D.; Snape, C.E. [Miskolc University, Miskolc-Egyetemvaros (Hungary). Research Inst. of Applied Chemistry

    1999-10-01

    The uptake of mercury (II) from aqueous solution by a range of coals has been studied and the results have been compared to those for a number of other sorbents, including commercial active carbons and cation-exchange resins. At pH 5 in a buffer medium, the capacities for mercury removal of the low-rank coals and the oxidized bituminous coals investigated are comparable to those of the other sorbents tested. For the lignites investigated, a high content of organic sulfur does not markedly affect the capacity for mercury uptake in relatively neutral and low chloride media, owing to redox reactions being the most likely mechanism involved. However, in highly acidic solutions, the capacities for mercury uptake are considerably greater for the high-sulfur coals investigated than for their low-sulfur counterparts due to chelation being the major sorption process involved. 36 refs., 4 figs., 7 tabs.

  16. Molybdenum trioxide reaction kinetics with magnesium molybdate aqueous solution

    International Nuclear Information System (INIS)

    The influence of temperature (40, 60, 75, 100 deg C) and concentration of aqueous solution of magnesium molybdate on kientics of MoO3 interaction with MgMoO4 solution was studied. It is shown that interaction between MoO3 and MgMoO4 proceeds by the following mechnism: molybdenum trioxide interacts with water with formation of molybdate-ion, and MgMoO4 dissociates with formation of MoO42- and Mg2+ ions. Appearance of excess molybdate-ions breaks the equilibrium between MoO42-and Mg2+, which is restored at the expense of polymerization of molybdate-ions and their transfer to dimolybdate-ions

  17. Radiation chemistry of amino acids and peptides in aqueous solutions

    International Nuclear Information System (INIS)

    Radiation chemistry relevant to radiation preservation of high protein foods is reviewed. Some conclusions concerning the chemistry of irradiated amino acids, peptides, and proteins have been derived from product analysis of γ-irradiated solutions while the main mechanistic considerations result from the chemistry and kinetics of free radical intermediates observed by pulse radiolysis. The precursors of chemistry in not too concentrated solutions (-, OH, and H. Their reactivity with molecules and their preference for characteristic groups within the molecule are discussed. The reviewed reactions of the model systems are accountable for a variety of radiolytic products found in irradiated foods. From detailed understanding of radiation chemistry in aqueous and frozen systems formation of many classes of compounds can be predicted or entirely eliminated in order to corroborate and extend the conclusions reached from the animal feeding experiments concerning the formation of toxic, mutagenic, and carcinogenic compounds and/or reduction of the nutritional value of foods

  18. The radiation chemistry of aqueous sodium terephthalate solutions

    International Nuclear Information System (INIS)

    The radiation chemistry of cobalt-60 gamma-irradiated aqueous sodium terephthalate solutions has been studied. In aerated 4 x 10-4M sodium hydroxide solutions, the main products are hydroxyterephthalate (HTA) (G = 0.99 +- 0.01), carbonate (G = 1.31 +- 0.08), and peroxides (G = 2.84 +- 0.04). The HTA and carbonate species are both formed as a result of hydroxyl radical attack and account for approximately 90 per cent of hydroxyl radical reactions. Oxygen needs to be present for efficient conversion of the terephthalate-OH radical adduct to HTA and oxygenation increases G(HTA) above the aerated solution value. G(HTA) is unaffected by changes in terephthalate concentration between 1 x 10-4M and 1 x 10-2M in sodium hydroxide solutions at pH 10. Decreasing the solution pH does however affect G(HTA). In phosphate buffered solutions pH 6.85, G(HTA) is 0.93 +- 0.01 and lower values are obtained with further decrease in solution pH. The lowering of the G(HTA) value is attributed to recombination reactions between the terephthalate-OH radical products and reducing radical products. Experimental evidence supporting the recombination postulate was obtained from the measurement of a parallel decrease in the peroxide yield and the observation of a dose rate effect on G(HTA). Competition kinetic studies with the added solutes carbonate and bicarbonate gave the rate ratios k (OH + TA2-) : k(OH + CO32-) : k(OH + HCO3-) = 1 : 0.105 : 0.0036

  19. Solution properties of the acrylamide-modified cellulose polyelectrolytes in aqueous solutions.

    Science.gov (United States)

    Song, Yongbo; Zhou, Jinping; Li, Qian; Lue, Ang; Zhang, Lina

    2009-07-27

    A novel cellulose-based polyelectrolyte (AM-C) containing acylamino (DS=0.625) and carboxyl (DS=0.148) groups was homogeneously synthesized from cellulose with acrylamide in NaOH/urea aqueous solutions. Solution properties of AM-C in aqueous solutions were investigated by laser light scattering, rheometry, and viscometry. The results indicated that AM-C could form large aggregates spontaneously in water with or without the addition of salts by the strong hydrogen bonds and electrostatic interaction between acylamino and carboxyl groups. Steady-shear flow study showed a Newtonian behavior of the solutions in the dilute regime while a shear-thinning behavior as the concentration increases. The critical concentration (c(e)) for transition from dilute to concentrated solution was determined to be 0.7wt%. Aqueous solutions of AM-C displayed good thermo-stability, reversible liquid-like characters attributing to the chemical modification. The derivation from Cox-Merz rule at relatively low concentration was related to the co-existence of single chain and large aggregates of AM-C in dilute regime. As the polymer concentration increased, the AM-C system was transformed into a homogeneous entanglement structure, resulting in the disappearance of deviations from the Cox-Merz rule. PMID:19464674

  20. Structural rearrangement of mesostructured silica nanoparticles incorporated with ZnO catalyst and its photoactivity: Effect of alkaline aqueous electrolyte concentration

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Hierarchical-like structure of MSN was formed in alkaline aqueous electrolyte. • Desilication generated abundant silanol groups and oxygen vacancies. • Zn2+ inserted to external –OH groups of the MSN to form Si–O–Zn bonds. • Oxygen vacancies trapped electrons to enhance electron–hole pair separation. • Hydroxyl radical generated from three main sources greatly influenced photoactivity. - Abstract: ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the introduction of Zn ions into the framework of MSN via a simple electrochemical system in the presence of various concentrations of NH4OH aqueous solution. The physicochemical properties of the catalysts were studied by XRD, 29Si MAS NMR, nitrogen adsorption–desorption, FE-SEM, TEM, FTIR, and photoluminescence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simply generated abundant silanol groups on the surface of the catalysts as a consequence of desilication to form the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by the creation of oxygen vacancies and formation of Si–O–Zn during the electrolysis, as well as formation of new Si–O–Si bonds during calcination seemed to be the main factors that enhanced the catalytic performance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH4OH (ZM-1.0) was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rate of 3.87 × 10−1 h−1 than unsupported ZnO (1.13 × 10−1 h−1) that prepared under the same conditions in the absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generated from the three main sources; reduced O2 at the conduction band, decomposed water at the valence band and irradiated H2O2 in the solution, are key factors that influenced the reaction. It is also noted

  1. Structural rearrangement of mesostructured silica nanoparticles incorporated with ZnO catalyst and its photoactivity: Effect of alkaline aqueous electrolyte concentration

    Energy Technology Data Exchange (ETDEWEB)

    Jusoh, N.W.C. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Jalil, A.A., E-mail: aishah@cheme.utm.my [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Institute of Hydrogen Economy, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Triwahyono, S.; Karim, A.H. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Salleh, N.F. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Annuar, N.H.R.; Jaafar, N.F.; Firmansyah, M.L. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Mukti, R.R. [Division of Inorganic and Physical Chemistry, Faculty of Mathematics and Natural Science, Institut Teknologi Bandung, Jl Ganesha No 10, Bandung 40132 (Indonesia); Ali, M.W. [Department of Chemical Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia); Institute of Hydrogen Economy, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor (Malaysia)

    2015-03-01

    Graphical abstract: - Highlights: • Hierarchical-like structure of MSN was formed in alkaline aqueous electrolyte. • Desilication generated abundant silanol groups and oxygen vacancies. • Zn{sup 2+} inserted to external –OH groups of the MSN to form Si–O–Zn bonds. • Oxygen vacancies trapped electrons to enhance electron–hole pair separation. • Hydroxyl radical generated from three main sources greatly influenced photoactivity. - Abstract: ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the introduction of Zn ions into the framework of MSN via a simple electrochemical system in the presence of various concentrations of NH{sub 4}OH aqueous solution. The physicochemical properties of the catalysts were studied by XRD, {sup 29}Si MAS NMR, nitrogen adsorption–desorption, FE-SEM, TEM, FTIR, and photoluminescence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simply generated abundant silanol groups on the surface of the catalysts as a consequence of desilication to form the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by the creation of oxygen vacancies and formation of Si–O–Zn during the electrolysis, as well as formation of new Si–O–Si bonds during calcination seemed to be the main factors that enhanced the catalytic performance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH{sub 4}OH (ZM-1.0) was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rate of 3.87 × 10{sup −1} h{sup −1} than unsupported ZnO (1.13 × 10{sup −1} h{sup −1}) that prepared under the same conditions in the absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generated from the three main sources; reduced O{sub 2} at the conduction band, decomposed water at the valence band and irradiated H{sub 2}O{sub 2} in the solution

  2. Preparation of metallic nanoparticles by irradiation in starch aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Nemţanu, Monica R., E-mail: monica.nemtanu@inflpr.ro; Braşoveanu, Mirela, E-mail: monica.nemtanu@inflpr.ro; Iacob, Nicuşor, E-mail: monica.nemtanu@inflpr.ro [National Institute for Lasers, Plasma and Radiation Physics, Electron Accelerators Laboratory, 409 Atomiştilor St., PO Box MG-36, 077125, Bucharest-Măgurele (Romania)

    2014-11-24

    Colloidal silver nanoparticles (AgNPs) were synthesized in a single step by electron beam irradiation reduction of silver ions in aqueous solution containing starch. The nanoparticles were characterized by spectrophotocolorimetry and compared with those obtained by chemical (thermal) reduction method. The results showed that the smaller sizes of AgNPs were prepared with higher yields as the irradiation dose increased. The broadening of particle size distribution occurred by increasing of irradiation dose and dose rate. Chromatic parameters such as b* (yellow-blue coordinate), C* (chroma) and ΔE{sub ab} (total color difference) could characterize the nanoparticles with respect of their concentration. Hue angle h{sup o} was correlated to the particle size distribution. Experimental data of the irradiated samples were also subjected to factor analysis using principal component extraction and varimax rotation in order to reveal the relation between dependent variables and independent variables and to reduce their number. The radiation-based method provided silver nanoparticles with higher concentration and narrower size distribution than those produced by chemical reduction method. Therefore, the electron beam irradiation is effective for preparation of silver nanoparticles using starch aqueous solution as dispersion medium.

  3. Gamma radiolytic degradation of naphthalene in aqueous solution

    Science.gov (United States)

    Chu, Libing; Yu, Shaoqing; Wang, Jianlong

    2016-06-01

    The decomposition of naphthalene in aqueous solution was studied using gamma irradiation combined with both H2O2 and TiO2 nanoparticles. Gamma irradiation led to a complete degradation of naphthalene and a partial mineralization. With initial concentration of 5-32 mg/L, more than 98% of naphthalene was removed and TOC reduction reached 28-31% at an absorbed dose of 3.0 kGy. The degradation of naphthalene was faster at neutral pH and the initial degradation rate increased with increasing the initial concentration of naphthalene. Addition of H2O2 and TiO2 nanoparticles all enhanced the degradation and mineralization of naphthalene. TOC removal efficiency increased from 28% (irradiation alone) to 35% with addition of H2O2 (40 mg/L), and to 48% with addition of TiO2 (0.8 g/L). The degradation of naphthalene in aqueous solution by gamma irradiation was mainly through the oxidation by ·OH radicals. The intermediate naphthol and carboxylic acids such as formic acid and oxalic acid were identified by LC-MS and IC.

  4. New terahertz dielectric spectroscopy for the study aqueous solutions

    CERN Document Server

    George, Deepu K; Vinh, N Q

    2015-01-01

    We present a development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-to-terahertz frequency. As a first application we report on the measurement of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17 to 37.36 cm-1 or 0.268 to 60 mm). The system provides a coherent radiation source with a power up to 20 mW in the gigahertz-to-terahertz region. The power signal-to-noise ratio of our instrument reaches 1015 and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with an error bars of 0.02 oC from above 0 oC to 90 oC. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

  5. Removal of Some Chelators from Aqueous Solutions Using Polymeric Ingredients

    International Nuclear Information System (INIS)

    This work tries to throw a light on the removal of thenoyl trifluoroacetone (TTA) and ethylene diamine tetraacetic acid (EDTA), extractants extensively used in many nuclear facilities, from aqueous solutions under different experimental conditions using Amberlite XAD resins. The applied resins exhibit high retention ability for the studied chelators with a maximum sorption capacity has the values of 23.9 and 38.0 mgg-1 for sorption of TTA and EDTA on Amberlite XAD4 and 18.6 and 21.2 mgg-1 for their sorption of on Amberlite XAD7. Factors affecting the resin retention ability such as ph value of aqueous solution and presence of co solvent have been studied. The kinetics of sorption behavior, in the applied system, indicate the process to be controlled by more than one diffusion mechanism. Therefore, two diffusion models were utilized to understand and verify the mechanism of sorption processes; they are the film mass transfer model and the interparticle diffusion model. The first model, based on film resistance, gave a successful depiction for sorption of TTA onto Amberlite XAD4 and XAD7 and the second one displayed an acceptable prediction for sorption of EDTA onto Amberlite XAD4

  6. Pulse radiolysis of aqueous solutions of sodium tetraphenylborate

    International Nuclear Information System (INIS)

    In previous work on the 60Co γ-radiolysis of aqueous tetraphenylborate (TPB-) solutions carried out in this laboratory, it was found that several organic products, including benzene, phenol and biphenyl, are produced with substantial yield. However, the reaction mechanism was not established. In the present study, reactions initiated by OH· radicals, N3· radicals and e-aq in aqueous TPB- solutions were studied by pulse radiolysis using a 600 keV Febetron electron accelerator. The lack of reactivity between TPB- and e-aq was demonstrated by directly monitoring the transient optical absorbance of e-aq. Concerning the reaction with OH·, two schemes were considered: (1) electron transfer from B(C6H5)4- to OH·; or (2) OH· addition to B(C6H5)4-. Comparison of observed transient absorption spectra with expectations based on the two different schemes suggests that OH· addition is the dominant reaction pathway under conditions of N2O saturation, with an experimentally determined second-order rate constant of 6.2 x 109 M-1 s-1. A mechanism based on an initial first-order self-decomposition of the OH· adduct, (C6H5)3BC6H5OH·-, with measured rate constant of 4 x 104s-1 is proposed. Kinetic modeling on the proposed mechanistic scheme gives good agreement with our experimental results. (author)

  7. New terahertz dielectric spectroscopy for the study of aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    George, Deepu K.; Charkhesht, Ali; Vinh, N. Q., E-mail: Vinh@vt.edu [Department of Physics, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2015-12-15

    We present the development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-to-terahertz frequency. As an important benchmark system, we report on the measurements of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17–37.36 cm{sup −1} or 0.268–60 mm). The system provides a coherent radiation source with power up to 20 mW in the gigahertz-to-terahertz region. The dynamic range of our instrument reaches 10{sup 12} and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with error bars of ±0.02 °C from 0 °C to 90 °C. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

  8. Examination of rheological properties of aqueous solutions of sodium caseinate

    Directory of Open Access Journals (Sweden)

    Jolanta Gawałek

    2012-12-01

    Full Text Available Application of sodium caseinate as a functional additive in manufacturing processes requires production of its concentrated aqueous solutions which, in industrial conditions, presents a number of difficulties. In order to develop an effective and optimal industrial process of mixing – manufacturing a concentrated solution of sodium caseinate, it is essential to know rheological properties in a definite range of concentrations changing in the course of the dissolving process. The material for investigations was typical commercial sodium caseinate in the form of dry powder manufactured in Poland from acid casein using the method of extrusion. The objective of the undertaken empirical studies was the assessment of the impact of the concentration on rheological properties of sodium caseinate concentrates. Investigations were carried out for five concentrates manufactured in a mixer equipped in a mechanical agitator at concentrations ranging X (% Î (2.5¸12.5 and changing mass proportions of sodium caseinate in the aqueous solution as follows: GS/G (kgS·kg-1 = 0.025. On the basis of the obtained research results, classical flow curves were plotted for individual concentrates. The determined values of viscosity and density of the examined solutions were correlated in the form of h = f(GS/G and r = f(GS/G dependencies which were used during the determination of classical characteristics of mixing forces essential for the assessment of energetic expenditures required to manufacture concentrates in a mixer equipped in a mechanical agitator. The density of the examined concentrates increased in a way directly proportional, while the dynamic viscosity coefficient increased exponentially together with the increase of sodium caseinate concentration. Sodium caseinate concentrates exhibited Newtonian character in the examined range of concentrations.

  9. Method of precipitating uranium from an aqueous solution and/or sediment

    Science.gov (United States)

    Tokunaga, Tetsu K; Kim, Yongman; Wan, Jiamin

    2013-08-20

    A method for precipitating uranium from an aqueous solution and/or sediment comprising uranium and/or vanadium is presented. The method includes precipitating uranium as a uranyl vanadate through mixing an aqueous solution and/or sediment comprising uranium and/or vanadium and a solution comprising a monovalent or divalent cation to form the corresponding cation uranyl vanadate precipitate. The method also provides a pathway for extraction of uranium and vanadium from an aqueous solution and/or sediment.

  10. Investigation of heterogeneous equilibria in saturated aqueous solutions of uranosilicates of uranophane-kasolite group

    International Nuclear Information System (INIS)

    State of mineral-like uranosilicates of uranophane-kasolite group in saturated aqueous solutions at 25 Deg Cis investigated. Using experimental data on solubility quantitative physicochemical model of state of heterogeneous crystalline uranosilicate - aqueous solution system is built. Using this model equilibrium constants of solution reactions and formation standard Gibbs functions of the investigated compounds are calculated. The model permits forecasting the processes of solution of uranosilicates in a wide range of aqueous phase acidity at standard conditions

  11. Comparative study of polypyrrole films electrosynthesized in alkaline and acid solutions

    International Nuclear Information System (INIS)

    The influence of the pH of electropolymerization solutions on the properties of polypyrrole films has been studied using potentiodynamic techniques and faradaic impedance spectroscopy. Scanning electron microscopy (SEM), IR and Raman spectroscopies, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were also used for products characterization. Results indicate that, contrary to what happen with the polymer electrogenerated in acid solutions, the films prepared in alkaline media are stable and present good electrochemical activity in basic solutions. Possible explanations for the observed differences are discussed and it is proposed that the pH of electropolymerization medium directly affects chains organization. Electrosynthesis in solutions of increased basicity results in a more compact and closed polymer structure.

  12. Melittin Aggregation in Aqueous Solutions: Insight from Molecular Dynamics Simulations.

    Science.gov (United States)

    Liao, Chenyi; Esai Selvan, Myvizhi; Zhao, Jun; Slimovitch, Jonathan L; Schneebeli, Severin T; Shelley, Mee; Shelley, John C; Li, Jianing

    2015-08-20

    Melittin is a natural peptide that aggregates in aqueous solutions with paradigmatic monomer-to-tetramer and coil-to-helix transitions. Since little is known about the molecular mechanisms of melittin aggregation in solution, we simulated its self-aggregation process under various conditions. After confirming the stability of a melittin tetramer in solution, we observed—for the first time in atomistic detail—that four separated melittin monomers aggregate into a tetramer. Our simulated dependence of melittin aggregation on peptide concentration, temperature, and ionic strength is in good agreement with prior experiments. We propose that melittin mainly self-aggregates via a mechanism involving the sequential addition of monomers, which is supported by both qualitative and quantitative evidence obtained from unbiased and metadynamics simulations. Moreover, by combining computer simulations and a theory of the electrical double layer, we provide evidence to suggest why melittin aggregation in solution likely stops at the tetramer, rather than forming higher-order oligomers. Overall, our study not only explains prior experimental results at the molecular level but also provides quantitative mechanistic information that may guide the engineering of melittin for higher efficacy and safety. PMID:26208115

  13. Stoichiometric C6-oxidation of hyaluronic acid by oxoammonium salt TEMPO⁺Cl⁻ in an aqueous alkaline medium.

    Science.gov (United States)

    Ponedel'kina, Irina Yu; Khaibrakhmanova, Elvira A; Tyumkina, Tatyana V; Romadova, Irina V; Odinokov, Victor N

    2015-10-01

    This paper reports the selective oxidation of hyaluronic acid (HA) by stoichiometric quantity of 2,2,6,6-tetramethylpiperidine-1-oxoammonium chloride (TEMPO(+)) in aqueous alkaline medium. High efficiency of the HA oxidation and quantitative yield of carboxy-HA per starting TEMPO(+), as well as unusual behavior of the oxidation system generating an oxygen upon alkali-induced oxoammonium chloride decomposition are demonstrated. The scheme for HA oxidation involving both TEMPO(+) and oxygen produced upon the TEMPO(+)Cl(-) decomposition and/or air oxygen is proposed. For comparison, the data on stoichiometric oxidation of such substrates as dermatan sulfate, water-soluble potato starch, methyl 2-acetamido-2-deoxy-β-d-glucopyranoside and ethanol are presented. PMID:26076602

  14. Carbon footprint of geopolymeric mortar: Study of the contribution of the alkaline activating solution and assessment of an alternative route

    OpenAIRE

    Mellado Romero, Ana María; CATALAN, C; Bouzón, N.; Borrachero Rosado, María Victoria; Monzó Balbuena, José Mª; Paya Bernabeu, Jorge Juan

    2014-01-01

    CO2 emissions associated with geopolymeric mortar prepared using spent fluid catalytic cracking catalyst (FCC) were compared to those calculated for plain ordinary Portland cement (OPC) mortar. Commercial waterglass used for preparing the alkaline activating solution for geopolymeric mortar was the main contributing component related to CO2 emission. An alternative route for formulating alkaline activating solution in the preparation of the geopolymeric binder was proposed: refluxing of rice ...

  15. Pulse Radiolysis of Aqueous Solutions of Aniline and Substituted Anilines

    International Nuclear Information System (INIS)

    The primary reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals with aniline and the aniline cation in aqueous solutions have been studied by the technique of pulse radiolysis and by determination of end products after y-radiolysis. Hydrogen atoms and hydrated electrons react with aniline under formation of the cyclohexadienyl type radical with absorption maximum at 355 nm and an extinction coefficient of 4100/M/cm. A similar radical formed by reaction of hydrogen atoms with the aniline cation has its absorption maximum at 31 0 nm and an extinction coefficient of 3200/M/cm. Hydrogen atoms react with the acid and neutral forms of aniline with rate constants of (1.3 ± 0.2 ) x 109/M/s and (2.9 ± 0.7) x 109/M/s, respectively. OH radicals react with aniline with a rate constant of (1.4 ± 0.3) x 1010/M/s under formation of the cyclohexadienyl radical with absorption maximum at 355 nm and the anilino radical with absorption maxima at 300 and 400 nm. The cyclohexadienyl radical decayed in a first order process with a rate constant of 1.4 x 105/s by elimination of NH3, whereas the anilino radical disappeared in a second order reaction under formation of hydrazobenzene. O- radicals react with aniline at pH 13.3 with a rate constant of (3.1 ± 0.6) x 109 under formation of anilino radicals. The reaction of OH radicals with the aniline cation produced the anilino radical cation with a rate constant of (4.8 ± 0.8) x 109 . The absorption maximum was placed at 415 nm, The cyclohexadienyl type radical with absorption maximum at 350 nm was also found in aqueous solutions of 2-amino-1,3-dimethylbenzene but was not formed in solutions of N,N' -dimethylaniline

  16. Characterization of alkaline-earth oxide additions to the MnO2 cathode in an aqueous secondary battery

    International Nuclear Information System (INIS)

    Highlights: → Adding MgO in MnO2 cathode enhances the battery discharge capacity. → Mechanism appears to be different with those of our previously published results. → Capacity fade with subsequent cycling is reduced only for MgO but not for BaO. → Transferred the primary battery into a secondary while using LiOH as electrolyte. - Abstract: The effect of alkaline-earth oxide additions on aqueous rechargeable battery is investigated using microscopic and spectroscopic techniques. The alkaline-earth oxide additions such as magnesium oxide (MgO) and barium oxide (BaO) were physically mixed to the manganese dioxide (MnO2) cathode of a cell comprising zinc as an anode and aqueous lithium hydroxide as the electrolyte. The results showed that such additions greatly improved the discharge capacity of the battery (from 145 to 195 for MgO and 265 mAh/g for BaO). Capacity fade with subsequent cycling is reduced only for MgO but not for BaO. With an aim to understand the role of these additives and its improvement in cell performance, we have used microscopy, spectroscopy, ion beam analysis and diffraction based techniques to study the process. Transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy analysis (EDS) results showed evidence of crystalline MnO2 particles for MgO as additive, whereas, MnO2 particles with diffused structure leading to mixture of phases is observed for BaO additives which is in agreement with X-ray diffraction (XRD) data. This work relates to improvement in the electrochemical behaviour of the Zn-MnO2 battery while the MgO additive helps to reduce the formation of manganese and zinc such as hetaerolite that hinders the lithium intercalation.

  17. Preparation1 and utilization of wheat straw anionic sorbent for the removal of nitrate from aqueous solution

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In order to reduce the impact of eutrophication caused by agricultural residues (i.e. excess nitrate) in aqueous solution, economic and effective anionic sorbents are required. In this article, we prepared anionic sorbent using wheat straw. Its structural characteristics and adsorption properties for nitrate removal from aqueous solution were investigated. The results indicate that the yield of the prepared anionic sorbent, the total exchange capacity, and the maximum adsorption capacity were 350%, 2.57 mEq/g, and 2.08 mmol/g, respectively. The Freundlich isotherm mode is more suitable than the Langmuir mode and the adsorption process accords with the first order reaction kinetic rate equation. When multiple anions (SO42-, H2PO4-, NO3-, and NO2-) were present, the isotherm mode of prepared anionic sorbent for nitrate was consistent with Freundlich mode; however, the capacity of nitrate adsorption was reduced by 50%. In alkaline solutions, about 90% of adsorbed nitrate ions could be desorbed from prepared anionic sorbent. The results of this study confirmed that the wheat straw anionic sorbent can be used as an excellent nitrate sorbent that removes nitrate from aqueous solutions.

  18. DNA dynamics in aqueous solution: opening the double helix

    Science.gov (United States)

    Pohorille, A.; Ross, W. S.; Tinoco, I. Jr; MacElroy, R. D. (Principal Investigator)

    1990-01-01

    The opening of a DNA base pair is a simple reaction that is a prerequisite for replication, transcription, and other vital biological functions. Understanding the molecular mechanisms of biological reactions is crucial for predicting and, ultimately, controlling them. Realistic computer simulations of the reactions can provide the needed understanding. To model even the simplest reaction in aqueous solution requires hundreds of hours of supercomputing time. We have used molecular dynamics techniques to simulate fraying of the ends of a six base pair double strand of DNA, [TCGCGA]2, where the four bases of DNA are denoted by T (thymine), C (cytosine), G (guanine), and A (adenine), and to estimate the free energy barrier to this process. The calculations, in which the DNA was surrounded by 2,594 water molecules, required 50 hours of CRAY-2 CPU time for every simulated 100 picoseconds. A free energy barrier to fraying, which is mainly characterized by the movement of adenine away from thymine into aqueous environment, was estimated to be 4 kcal/mol. Another fraying pathway, which leads to stacking between terminal adenine and thymine, was also observed. These detailed pictures of the motions and energetics of DNA base pair opening in water are a first step toward understanding how DNA will interact with any molecule.

  19. Forecasting of thermodynamic properties of solution for non-polar molecules in aqueous salt solutions and in aqueous organic solutions

    International Nuclear Information System (INIS)

    The scaled particle theory has been used rather successfully to predict the values of thermodynamic properties of solution for non-polar molecules. Two very important parameters has been used in the equations of the scaled particle theory: the hard sphere diameter of the solute and the closeness of the solvent (closeness in which the diameters of the hard sphere particles forming the solvent are taken into account). With non-polar solutes, a correlation exists between calculated and experimental values of: free enthalpy of solution - enthalpy of solution - molar heat capacity change for the solution process. The fit between calculated and experimental values is only more qualitative than quantitative. However the variation of thermodynamic properties with the temperature and the modality is consistent with the variation calculated according to the scaled particle theory. (author)

  20. Comparison of Photochemical Reactions of m-Cresol in Aqueous Solution and in Ice

    Institute of Scientific and Technical Information of China (English)

    PENG Fei; XUE Hong-hai; TANG Xiao-jian; KANG Chun-li; LI Lin-lin; LI Zhe

    2012-01-01

    We compared the photochemical reaction of m-cresol containing OH precursors such as H2O2,NO2- and NO3- in aqueous solution with those in ice.The results show that the conversion rate of m-cresol in aqueous solution was higher than that in ice,H2O2,NO2- and NO3- all accelerated the photoconversion of m-cresol in both aqueous solution and ice.The photochemical reactions of m-cresol obeys the first order kinetics equation.According to the photoproducts identified by GC-MS,we proposed that hydroxylation and nitration reactions occurred in both aqueous solution and ice.Coupling reaction was common in ice,however,in aqueous solution it was found only in UV system.Our results suggest that the photochemical reactions of m-cresol were different in aqueous solution and in ice.

  1. Adsorption of Anthraquinone Dyes from Aqueous Solutions by Penicillium Terrestre

    Institute of Scientific and Technical Information of China (English)

    XIN Bao-ping; LIU Xiao-mei

    2006-01-01

    Penicillium terrestre was used for removing four anthraquinone dyes from aqueous solution. The experiments were performed in Erlenmeyer flasks and spore suspension was used for inoculation. The results show that the mechanism of dye removal by penicillium terrestre is biosorption and the growing pellets exhibit higher adsorptive capacity than the resting or dead ones. The maximum removals of disperse blue 2BLN, reactive brilliant blue KN-R, acid anthraquinone blue and bromamine acid at the concentration of 120 mg/L by biosorption of growing pellets are 100 %, 100 %, 96 % and 91%, respectively. The 100.0 % and 91.4 % KN-R removals are achieved respectively at the much higher concentration of 250 and 400 mg/L. 2.5 g/L glucose is sufficient for 100% KN-R removal by growing pellets. Salinity (NaC1) increase from 0 to 2% (W/V) moderately accelerates both mycelium growth and KN-R removal.

  2. Sweet aqueous solution for electrochemical synthesis of polypyrrole

    Energy Technology Data Exchange (ETDEWEB)

    Bazzaoui, M. [Faculdade de Engenharia, Departamento de Engenharia Quimica, Universidade do Porto, Rua Roberto Frias, 4200-465 Porto (Portugal) and Faculdade de Engenharia, Departamento de Electrotecnica, Universidade do Porto, Rua Roberto Frias, 4200-465 Porto (Portugal)]. E-mail: bazzaoui@fe.up.pt; Martins, J.I. [Faculdade de Engenharia, Departamento de Engenharia Quimica, Universidade do Porto, Rua Roberto Frias, 4200-465 Porto (Portugal) and Faculdade de Engenharia, Departamento de Electrotecnica, Universidade do Porto, Rua Roberto Frias, 4200-465 Porto (Portugal)]. E-mail: jipm@fe.up.pt; Costa, S.C. [Faculdade de Engenharia, Departamento de Engenharia Quimica, Universidade do Porto, Rua Roberto Frias, 4200-465 Porto (Portugal); Bazzaoui, E.A. [Faculte des Sciences, Departement de Chimie, Universite Mohammed Ier, 60 000 Oujda (Morocco); Reis, T.C. [Faculdade de Engenharia, Departamento de Engenharia Quimica, Universidade do Porto, Rua Roberto Frias, 4200-465 Porto (Portugal); Martins, L. [Faculdade de Engenharia, Departamento de Electrotecnica, Universidade do Porto, Rua Roberto Frias, 4200-465 Porto (Portugal)

    2006-02-25

    The electrosynthesis of polypyrrole (PPy) has been achieved on aluminum electrode in aqueous medium of 0.1 M saccharin sodium salt and 0.5 M pyrrole. Scanning electron microscopy shows that the PPy coating obtained in galvanostatic and potentiostatic modes starts with small islands at weak applied potentials or current densities. Moreover, energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) reveal a good homogeneity of the film achieved in cyclic voltammetry during 10 cycles. The electrochemical impedance spectroscopy (EIS) results show that the coating decreases the polarization resistance of the aluminum electrode. The open circuit potential (OCP) and dc polarization measurements achieved in HCl and NaCl solutions displayed a large positive displacement of corrosion potential and a reduction of corrosion current in the case of PPy coating electrode in comparison with electrode bare.

  3. Degradation of chlorophenols in aqueous solution by {gamma}-radiation

    Energy Technology Data Exchange (ETDEWEB)

    Hu Jun [INET, Tsinghua University, Beijing 100084 (China)]. E-mail: hujun@mail.tsinghua.edu.cn; Wang Jianlong [INET, Tsinghua University, Beijing 100084 (China)

    2007-08-15

    Degradation of chlorophenols (CPs) in aqueous solutions by {gamma}-radiation was studied. The effect of absorbed dose on degradation, dechlorination and mineralization of CPs were investigated. The results indicated that the degradation of CPs, Cl{sup -} release and mineralization increased with increase in absorbed dose. When the initial concentration was 100 mg L{sup -1} and the dosage was 6 kGy, the removal efficiencies of CPs were 44.54% for 2-CP, 91.46% for 3-CP, 82.72% for 4-CP and 93.25% for 2,4-DCP, respectively. The combination of irradiation and H{sub 2}O{sub 2} leads to a synergistic effect, which remarkably increased the degradation efficiency of CPs and TOC removal. The kinetics of CPs during irradiation are also mentioned.

  4. Degradation of chlorophenols in aqueous solution by γ-radiation

    Science.gov (United States)

    Hu, Jun; Wang, Jianlong

    2007-08-01

    Degradation of chlorophenols (CPs) in aqueous solutions by γ-radiation was studied. The effect of absorbed dose on degradation, dechlorination and mineralization of CPs were investigated. The results indicated that the degradation of CPs, Cl - release and mineralization increased with increase in absorbed dose. When the initial concentration was 100 mg L -1 and the dosage was 6 kGy, the removal efficiencies of CPs were 44.54% for 2-CP, 91.46% for 3-CP, 82.72% for 4-CP and 93.25% for 2,4-DCP, respectively. The combination of irradiation and H 2O 2 leads to a synergistic effect, which remarkably increased the degradation efficiency of CPs and TOC removal. The kinetics of CPs during irradiation are also mentioned.

  5. Radiation-induced degradation of 4-chloroaniline in aqueous solution

    International Nuclear Information System (INIS)

    The radiation-induced decomposition of 4-chloroaniline (4-ClA) was studied under steady-state conditions using aqueous solutions saturated with air, pure oxygen, N2O, argon and argon in the presence of t-Butanol. Using HPLC-method, the initial G-values of the substrate degradation as well as of a number of radiolytic products were determined. The formation of aminophenols, chlorophenols, aniline and phenol in addition to chloride, ammonia, formaldehyde and mixture of aldehydes as well as carboxylic acids was studied as a function of absorbed dose. Based on the experimental data, probable reaction mechanisms for the degradation of 4-ClA by γ-rays and the formation of the identified products are presented

  6. Photo-degradation behaviour of roseoflavin in some aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, A. [Institut II - Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitaetsstrasse 31, D-93053 Regensburg (Germany); Penzkofer, A., E-mail: alfons.penzkofer@physik.uni-regensburg.de [Institut II - Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitaetsstrasse 31, D-93053 Regensburg (Germany); Mathes, T.; Hegemann, P. [Institut fuer Biologie/Experimentelle Biophysik, Humboldt Universitaet zu Berlin, Invalidenstrasse 42, D-10115 Berlin (Germany)

    2010-03-24

    An absorption and emission spectroscopic characterization of roseoflavin (8-dimethylamino-8-demethyl-riboflavin, RoF) in aqueous solutions was carried out. The studies were concentrated on roseoflavin in pH 8 phosphate buffer. Absorption cross-section spectra, fluorescence excitation spectra, fluorescence quantum distributions, fluorescence quantum yields and fluorescence lifetimes were determined. The fluorescence of RoF is quenched by photo-induced intra-molecular charge-transfer at room temperature. The photo-degradation of RoF in un-buffered water, in Tris-HCl buffer, and in phosphate buffer was studied. Phosphate buffer and to a smaller extent Tris buffer catalyse the RoF photo-degradation. Photo-excitation of the primary photoproduct, 8-methylamino-riboflavin (8-MNH-RF), enhanced the RoF degradation by triplet 8-MNH-RF - singlet RoF excitation transfer with subsequent triplet-state RoF degradation.

  7. Gamma-irradiation of malic acid in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Negron-Mendoza, A.; Graff, R.L.; Ponnamperuma, C.

    1980-12-01

    The gamma-irradiation of malic acid in aqueous solutions was studied under initially oxygenated and oxygen-free conditions in an attempt to determine the possible interconversion of malic acid into other carboxylic acids, specifically those associated with Krebs cycle. The effect of dose on product formation of the system was investigated. Gas-liquid chromatography combined with mass spectrometry was used as the principal means of identification of the nonvolatile products. Thin layer chromatography and direct probe mass spectroscopy were also employed. The findings show that a variety of carboxylic acids are formed, with malonic and succinic acids in greatest abundance. These products have all been identified as being formed in the gamma-irradiation of acetic acid, suggesting a common intermediary. Since these molecules fit into a metabolic cycle, it is strongly suggestive that prebiotic pathways provided the basis for biological systems.

  8. Hydrate-based heavy metal separation from aqueous solution

    Science.gov (United States)

    Song, Yongchen; Dong, Hongsheng; Yang, Lei; Yang, Mingjun; Li, Yanghui; Ling, Zheng; Zhao, Jiafei

    2016-01-01

    A novel hydrate-based method is proposed for separating heavy metal ions from aqueous solution. We report the first batch of experiments and removal characteristics in this paper, the effectiveness and feasibility of which are verified by Raman spectroscopy analysis and cross-experiment. 88.01–90.82% of removal efficiencies for Cr3+, Cu2+, Ni2+, and Zn2+ were obtained. Further study showed that higher R141b–effluent volume ratio contributed to higher enrichment factor and yield of dissociated water, while lower R141b–effluent volume ratio resulted in higher removal efficiency. This study provides insights into low-energy, intensive treatment of wastewater. PMID:26887357

  9. Theoretical analysis of XANES for aqueous aluminum salt solutions

    Science.gov (United States)

    Matsuo, Shuji; Shirozu, Kaori; Tateishi, Yuichi; Wakita, Hisanobu; Yokoyama, Takushi

    In order to understand the coordination behavior of Al(III) ions in hydrosphere, discrete variational X[alpha] molecular orbital calculations were performed to analyze Al K-edge XANES spectra for the aqueous solutions of Al(NO3)3·9H2O and Al-EDTA (EDTA = ethylenediaminetetraacetate) complex. As to Al(NO3)3·9H2O, the hydrate structure was presumed to be rather an asymmetric hexahydrated structure than an high-symmetric structure. As to Al-EDTA, the 5-fold coordinated Al-EDTA was concluded to be the coexistence of the pyramidal and trigonal bipyramidal structures in proportion of 4 to 6.

  10. Radiolysis of Aqueous Benzene Solutions at higher temperatures

    International Nuclear Information System (INIS)

    Aqueous solutions of benzene have been irradiated with Co γ-rays with doses of up to 2.3 Mrad in the temperature region 100 - 200 C. At 100 C a linear relationship between the phenol concentration and the absorbed dose was obtained, but at 150 C and at higher temperatures the rate of the phenol formation increased significantly after an initial constant period. With higher doses the rate decreased again, falling almost to zero at 200 C after a dose of 2.2 Mrad. The G value of phenol in the initial linear period increased from 2.8 at 100 C to 8.0 at 200 C. The reaction mechanism is discussed and reactions constituting a chain reaction are suggested. The result of the addition of iron ions and of a few inorganic oxides to the system is presented and briefly discussed

  11. Angular correlation of annihilation photons in frozen aqueous solutions

    DEFF Research Database (Denmark)

    Milosevic-Kvajic, M.; Mogensen, O. E.; Kvajic, G.; Eldrup, Morten Mostgaard

    1972-01-01

    Linear‐slit angular correlation curves were obtained at about −140°C for frozen aqueous solutions of HF, HCl, HBr, HI, NH3, FeCl2, FeCl3, NaI, H2SO4, NHO3, MnSO4, KMnO4, K2Cr2O7, NaOH, and LiOH. We found no appreciable influence of a 4% concentration of the last seven impurities. Only halide......‐containing impurities strongly changed the form of the curves; ppm concentrations of HCl and HF could be seen. The main change was a broadening of the part of the curve where the narrow and broad components meet. This fact is interpreted as being caused by trapping of para‐positronium in holes in the structure created...

  12. Protein thermal stabilization in aqueous solutions of osmolytes.

    Science.gov (United States)

    Bruździak, Piotr; Panuszko, Aneta; Jourdan, Muriel; Stangret, Janusz

    2016-01-01

    Proteins' thermal stabilization is a significant problem in various biomedical, biotechnological, and technological applications. We investigated thermal stability of hen egg white lysozyme in aqueous solutions of the following stabilizing osmolytes: Glycine (GLY), N-methylglycine (NMG), N,N-dimethylglycine (DMG), N,N,N-trimethylglycine (TMG), and trimethyl-N-oxide (TMAO). Results of CD-UV spectroscopic investigation were compared with FTIR hydration studies' results. Selected osmolytes increased lysozyme's thermal stability in the following order: Gly>NMG>TMAO≈DMG>TMG. Theoretical calculations (DFT) showed clearly that osmolytes' amino group protons and water molecules interacting with them played a distinctive role in protein thermal stabilization. The results brought us a step closer to the exact mechanism of protein stabilization by osmolytes. PMID:26495438

  13. Degradation of aqueous solutions of camphor by heterogeneous photocatalysis.

    Science.gov (United States)

    Sirtori, Carla; Altvater, Priscila K; de Freitas, Adriane M; Peralta-Zamora, Patricio G

    2006-02-28

    In this study the photocatalytic degradation of aqueous solutions of camphor was investigated by using TiO2 and ZnO photocatalysts. In the presence of artificial UV-light the highly photosensitive camphor was almost totally degraded after reaction times of 60 min. However, under these conditions the mineralization degree was lower than 25%. In the presence of semiconductors the degradation was complete after a treatment time of about 30 min. Moreover, the mineralization was considerably greater, mainly with the use of TiO2 (> 80% at reaction time of 60 min). Heterogeneous photocatalytic processes applied in the presence of solar radiation show a promising degradation capability. TiO2-based processes afforded mineralization degrees of about 90% after a reaction time of 120 min, when the system was assisted by aeration. PMID:16221528

  14. Experimental study on thermophoresis of colloids in aqueous surfactant solutions

    Science.gov (United States)

    Dong, Ruo-Yu; Zhou, Yi; Yang, Chun; Cao, Bing-Yang

    2015-12-01

    Thermophoresis refers to the motion of particles under a temperature gradient and it is one of the particle manipulation techniques. Regarding the thermophoresis of particles in liquid media, however, many open questions still remain, especially the role of the interfacial effect. This work reports on a systematic experimental investigation of surfactant effects, especially the induced interfacial effect, on the thermophoresis of colloids in aqueous solutions via a microfluidic approach. Two kinds of commonly used surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), are selected and the results show that from relatively large concentrations, the two surfactants can greatly enhance the thermophilic mobilities. Specifically, it is found that the colloid-water interfaces modified with more polar end groups can potentially lead to a stronger thermophilic tendency. Due to the complex effects of surfactants, further theoretical model development is needed to quantitatively describe the dependence of thermophoresis on the interface characteristics.

  15. Micellar effects on positronium lifetime in aqueous SDS solutions

    International Nuclear Information System (INIS)

    Positron lifetime measurements have been performed in aqueous SDS (Sodium Dodecyl Sulphate) solutions. The lifetime distributions measured by fast-slow coincidence technique have been found to be influenced by surfactant concentration, which varied in the range of 1.25x10-3 - 3.2x10-1 mol/dm3 (i.e. 2.27x10-5 - 5.82x10-3 mole fractions). The lifetime of the long living component connected to positronium formation and decay increases with increasing surfactant concentration. Lifetime data suggest that a direct positronium-micelle electron-exchange reaction leading to pick-off annihilation is contraindicated. (author)

  16. Adsorption of basic dye from aqueous solution onto fly ash

    Energy Technology Data Exchange (ETDEWEB)

    J.X. Lin; S.L. Zhan; M.H. Fang; X.Q. Qian; H. Yang [Zhejiang University, Hangzhou (China). College of Civil Engineering and Architecture

    2008-04-15

    The fly ash treated by H{sub 2}SO{sub 4} was used as a low-cost adsorbent for the removal of a typical dye, methylene blue, from aqueous solution. An increase in the specific surface area and dye-adsorption capacity was observed after the acid treatment. The adsorption isotherm and kinetics of the treated fly ash were studied. The experimental results were fitted using Langmuir and Freundlich isotherms. It shows that the Freundlich isotherm is better in describing the adsorption process. Two kinetic models, pseudo-first order and pseudo-second order, were employed to analyze the kinetic data. It was found that the pseudo-second-order model is the better choice to describe the adsorption behavior. The thermodynamic study reveals that the enthalpy ({Delta}H{sup 0}) value is positive (5.63 kJ/mol), suggesting an endothermic nature of the adsorption.

  17. Aqueous dispersions of silver nanoparticles in polyelectrolyte solutions

    Indian Academy of Sciences (India)

    Dan Donescu; Raluca Somoghi; Marius Ghiurea; Raluca Ianchis; Cristian Petcu; Stefania Gavriliu; Magdalena Lungu; Claudia Groza; Carmen R Ionescu; Carmen Panzaru

    2013-03-01

    In this report, we present the versatile and effective technique, using environmental friendly reductant glucose, to prepare stable silver nanodispersions by reduction of Ag+ ions. Alternant copolymers of maleic anhydride with vinyl acetate and styrene sulphonate sodium acid salt polyelectrolytes were synthesized in aqueous solution and used as stabilizers. The formation of nano silver particles was confirmed by UV-Vis spectrophotometry and TEM measurements. Dynamic Light Scattering (DLS) measurements were needed to study how the reagents and their concentrations influence particle size. SEM images show the nanostructure of the hybrid films and indicate a strong interaction between the polyelectrolyte and the silver NPs. Moreover, the silver NPs could be stored for one year without observation of aggregates or sedimentation. The final solid products obtained after evaporating to dryness can be used to produce stable dispersions upon mixing with water. Few of the final products were found to exhibit a high antibacterial and antifungal activity.

  18. The radiolysis of aqueous solutions containing dithiothreitol and oxidized dithiothreitol

    Science.gov (United States)

    John Elliot, A.; Sopchyshyn, Frederick C.

    The radiation chemistry of aqueous solutions (pH 1-9) of dithiothreitol (DTT) has been investigated by pulsed and steady-state techniques. From G( H2S) in N 2- and N 2O-saturated solutions it was concluded for pH 5-9 that the majority of the solvated electrons and 25-40% of the hydroxyl radicals reacted with DTT to form H 2S. Oxidized dithiothreitol (DTT- ox) was the other major product observed for pH 5-9. However, DTT- ox was not formed when DTT solutions were irradiated at pH 1 and 2. When nitrate ions were added as an electron scavenger over the pH range 5-9, G( DTT- ox) was not affected; at pH 9.0 G( H2S) decreased slightly but at pH 5-6, G( H2S) was reduced to that arising from the reaction of the hydroxyl radical. The reaction of CO 2- with DTT- ox was studied at pH 4.6 and pH 9.0. At pH 9.0 the G( DTT)=3.3-0.2 indicated a simple two electron reduction of DTT- ox while at pH 4.6 the G( DTT) >25 implied a chain reaction had occurred.

  19. The radiolysis of aqueous solutions containing dithiothreitol and oxidized dithiothreitol

    International Nuclear Information System (INIS)

    The radiation chemistry of aqueous solutions (pH 1 to 9) of dithiothreitol (DTT) has been investigated by pulsed and steady-state techniques. From G(H2S) in N2- and N2O-saturated solutions it was concluded for pH 5 to 9 that the majority of the solvated electrons and 25 to 40% of the hydroxyl radicals reacted with DTT to form H2S. Oxidized dithiothreitol (DDT-ox) was the other major product observed for pH 5 to 9. However, DTT-ox was not formed when DTT solutions were irradiated at pH 1 and 2. When nitrate ions were added as an electron scavenger over the pH range 5 to 9, G(DTT-ox) was not affected; at pH 9.0 G(H2S) decreased slightly but at pH 5 to 6, G(H2S) was reduced to that arising from the reaction of the hydroxyl radical. The reaction of CO2- with DTT-ox was studied at pH 4.6 and pH 9.0. At pH 9.0 the G(DTT) = 3.3 +- 0.2 indicated a simple two electron reduction of DTT-ox while at pH 4.6 the G(DTT) > 25 implied a chain reaction had occurred. (author)

  20. Extraction of certain radionuclides from aqueous schungite solutions

    International Nuclear Information System (INIS)

    The sorption of 90Sr, 106Ru, 137Cs, and 238Pu from aqueous solutions over a wide pH range was studied. Swelled schungite chips (Nigozero, Kondopozhsk region) (1) and schungite (Onezhsk lake) (2) were tested as sorbents. The minerals were used both untreated and after oxidation (HNO3, 1:1, contact time 1 day). The oxidation, judging from the literature, facilitates the formation of carboxylic and phenolic functional groups on the surface of the carbon-containing sorbents. The presence of such groups is responsible for the high selectivity of the sorbents for multicharged cations. Futhermore, the hydrophobicity of the schungites enormously decreases after the oxidation. The studied sorbents had an average particle size of 0.08-0.1 mm. The schungite was contacted with the solution under static conditions with periodic stirring in order to establish equilibrium. The concentration of the radionuclides was 2-4 MBq/liter. The solution volumes were 10 ml. The sorbent content was 0.01 g. The required pH was set by adding HCl or NaOH

  1. Radiation-induced reduction of ditetrazolium salt in aqueous solutions

    International Nuclear Information System (INIS)

    Color formation in aqueous solutions of the ditetrazolium salt blue tetrazolium (BT2+) in the absence or presence of oxygen is a complex radiation chemical reaction. The final stable product is the poorly soluble diformazan violet to blue pigment having a broad spectral absorption band (λmax=552 nm). The reaction of BT2+ with the hydrated electron proceeds by rapid reduction of BT2+ followed by protonation at the nitrogen closest to the unsubstituted phenyl group, via the two intermediate tetrazolinyl radicals shared by the ditetrazole ring nitrogens. The effect of solution pH, N2O saturation, and the presence of the reducing agent dextrose are examined. The system serves as a radiochromic sensor and a dosimeter of ionizing radiations. Solutions of 5 mmol l-1 BT2+ at pH 7.3 serve as dosimeters over an absorbed-dose range of approximately 0.2-6 kGy (dearated, with a range of 1-8 mmol l-1 dextrose) and of about 1-15 kGy (aerated, with 0.1 mol l-1 sodium formate and 5 mmol l-1 dextrose)

  2. Aqueous solution of basic fuchsin as food irradiation dosimeter

    Institute of Scientific and Technical Information of China (English)

    Hasan M. KHAN; Shagufta NAZ

    2007-01-01

    Dosimetric characterization of aqueous solution of basic fuchsin was studied spectrophotometrically for possible application in the low-dose food irradiation dosimetry. Absorption spectra of unirradiated and irradiated solutions were determined and the decrease in absorbance with the dose was noted down. Radiation-induced bleaching of the dye was measured at wavelengths of maximum absorption λmax (540nm) as well as 510nm and 460 nm. At all these wavelengths, the decrease in absorbance of the dosimeter was linear with respect to the absorbed dose from 50 Gy to 600 Gy. The stability of dosimetric solution during post-irradiation storage in the dark at room temperature showed that after initial bleaching during first ten to twenty days, the response was almost stable for about 34 days. The study on the effect of different light and temperature conditions also showed that the response gradually decreased during the storage period of 34 days, which shows that basic fuchsin dye is photosensitive as well as thermally sensitive.

  3. Experimental tests for 36cl removal from aqueous solution

    International Nuclear Information System (INIS)

    This paper presents the experimental tests of a chlorine separation and purification method from aqueous samples with knowing content of Co, Cs, Eu, Ni and Sr stable elements. The method is based on the property of chloride ions to form a silver chloride white precipitate, followed by the use of the extraction chromatography on the strong anionic resin (Bio-Rad AG® 1-X4) to purify chlorine. The concentrations of Co, Cs, Eu, Ni and Sr (separated from Cl by using precipitation method) were measured by ICP-OES. The silver chloride precipitate was dissolved in 25 % NH3 solution and loaded onto the anionic resin. The chloride ions were strongly retained on the resin and eluted with a proper solution. The final solution, containing chloride ions, was converted to a form compatible with the spectrophotometric and Mohr titration techniques, which were used to determine chloride concentration. The separation yields of Co, Cs, Eu, Ni and Sr from Cl are very good. More than 98 % from the initial concentration of chlorine was recovered. (authors)

  4. Cr(VI) reduction in aqueous solutions by siderite.

    Science.gov (United States)

    Erdem, Mehmet; Gür, Faruk; Tümen, Fikret

    2004-09-10

    Hexavalent chromium is a common and toxic pollutant in soils and wastewaters. Reduction of the mobile Cr(VI) to less mobile and less toxic Cr(III) is a solution for decontamination of industrial effluents. In this study, the reduction of hexavalent chromium in aqueous solutions by siderite was investigated. The influences of amount of acid, contact time, siderite dosage, initial Cr(VI) concentration, temperature and particle size of siderite have been tested in batch runs. The process was found to be acid, temperature and concentration dependent. The amount of acid is the most effective parameter affecting the Cr(VI) reduction since carbonaceous gangue minerals consume acid by side reactions. The highest Cr(VI) reduction efficiency (100%) occurred in the 50 mg/l Cr(VI) solution containing two times acid with respect to stoichiometric amount of Cr(VI) and at the conditions of siderite dosage 20 g/l, contact time 120 min and temperature 25 degrees C. Reduction efficiency increased with increase in temperature and decrease in particle size. The reduction capacity of siderite was found to be 17 mg-Cr(VI)/g. PMID:15363534

  5. Ultrasonic Measurements of Temperature in Aqueous Solutions: Why and How

    Directory of Open Access Journals (Sweden)

    A. Afaneh

    2011-01-01

    Full Text Available The paper describes two different approaches to ultrasonic measurements of temperature in aqueous solutions. The first approach uses two narrowband ultrasonic transducers and support electronics that form an oscillating sensor which output frequency is related to the measured temperature. This low-cost sensor demonstrated sensitivity of about 40 Hz/K at the distance of 190 mm and the operating frequency of about 25 kHz. The second approach utilised pulse-echo mode at the centre frequency of 20 MHz. The reflector featured a cavity that was filled with deionised water. The ultrasound propagation delay in the cavity was related to the temperature in the solution. The experiments were conducted for deionised water, and solutions of sodium persulfate, sodium chloride, and acetic acid with concentrations up to 0.5 M. In the experiments (conducted within the temperature range from 15 to 30°C, we observed increases in the ultrasound velocity for increased temperatures and concentrations as was expected. Measurement results were compared with literature data for pure and seawater. It was concluded that ultrasonic measurements of temperature were conducted with the resolution well below 0.1 K for both methods. Advantages of ultrasonic temperature measurements over conventional thermometers were discussed.

  6. Effect of gamma irradiation on viscosity of aqueous solutions of some natural polymers

    International Nuclear Information System (INIS)

    Effect of gamma irradiation on viscosity of aqueous solution of alginate and carbon xylmethyl cellulose (CMC) irradiated in solid state has been carried out. the viscosity of aqueous solution of alginate and CMC decreased remarkably with increasing dose and the viscosity of 2% solution of above polymers irradiated at 50 kGy was about 100 times lower than the original one. (author)

  7. Catalytic destruction of hazardous organics in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Baker, E.G.; Sealock, L.J. Jr.

    1988-04-01

    Pacific Northwest Laboratory (PNL) is developing a process for destroying hazardous organics and chlorinated organics in aqueous solutions. The process is targeted at liquid waste streams that are difficult and costly to treat with conventional or developing technologies. Examples of these waste streams include contaminated groundwater and surface water and industrial wastewater. Aqueous solutions are treated with a transition metal catalyst at 300/degree/C to 460/degree/C and 2000 to 5000 psig pressure to convert the wastes to innocuous gases. During proof-of-principle tests conducted in a 1-L batch reactor, destruction of over 99/percent/ (in most cases approaching 99.9/percent/) of the organic material was achieved. Hexone (methyl is isobutyl ketone, MIBK), p-cresol, hexane, benzene, and naphthalene were used as model waste materials. The only major product with all of the organic compounds was a gas containing 50/percent/ to 75/percent/ methane, 25/percent/ to 45/percent/ carbon dioxide, and 0/percent) to 5/percent/ hydrogen. Reduced nickel was the only effective catalyst and that the optimal operating conditions for destroying nonchlorinated organics were 350/degree/C to 400/degree/C, 2000 to 4000 psig, and 30/endash/ to 60/endash/min residence time. These tests also indicated that catalyst deactivation or fouling would not be a problem at these conditions. Chlorobenzene and trichloroethylene (TEC), were also tested. Destruction of both compounds was 99/percent/ or greater, but the products were different from those obtained from hydrocarbons. With TCE, the major product was carbon dioxide; with chlorobenzene the major product identified was benzene. In the tests with the chlorinated hydrocarbons, the chlorine was converted to HC1 and the reduced nickel was converted to nickel hydroxide, which may be detrimental to long-term catalyst activity. (15 refs., 8 figs., 6 tabs).

  8. Adsorption of U(VI) from aqueous solutions onto dolomite

    International Nuclear Information System (INIS)

    Full text of publication follows: The release of radioactive substances into aqueous media is a very important subject in the context of high-level nuclear waste geologic repositories. Adsorption onto mineral surfaces is a very important process leading to the reduction of radionuclide concentrations in solution. Uranium is one of the well known radioactive substance whose adsorption behaviour may strongly vary depending on the environmental conditions such as adsorbent type and pH. Dolomite is a major and cheap source of magnesium and calcium. It is generally used in food and pharmaceutical industries, glass and building materials. In some conditions, dolomite can be used as an appropriate adsorbent for removal of some metal ions. Metal removal occurs because of the dual effect of electrostatic and chemical forces between mineral surfaces and ions. Adsorption of U(VI) onto dolomite is investigated by varying parameters such as solid to liquid ratio, contact time, pH and concentration of U(VI). 238U as uranyl nitrate is used for the experiments. The optimum solid to liquid ratio and contact time are found as 0.04 and 1 h, respectively. Formation of insoluble aqueous complexes of the U(VI) at higher pH values (pH>5), may change the mechanism of the adsorption phenomena on dolomite. Precipitation may occur at high pH values at studied uranium concentration (1.10-3 moL-1). The maximum adsorption is observed near pH 3. At this pH value UO22+ is dominant species in the solution. The data obtained from adsorption experiments are fitted to Frumkin, Langmuir and Dubinin-Radushkevich isotherms. The results calculated from adsorption isotherms evaluate the type of the adsorption. The adsorption dependence of uranium on temperature is investigated and thermodynamic parameters ΔHo, ΔSo and ΔGo are calculated. (authors)

  9. Biosorption of arsenic from aqueous solution using dye waste.

    Science.gov (United States)

    Nigam, Shubha; Vankar, Padma S; Gopal, Krishna

    2013-02-01

    The purpose of this study is to examine on removal of arsenic from water by biosorption through potential application of herbal dye wastes. Four different flower dye residues (after extraction of natural dye) viz. Hibiscus rosasinensis, Rosa rosa, Tagetes erecta, and Canna indica were utilized successfully for the removal of arsenic from aqueous solution. Batch studies were carried out for various parameters viz. pH, sorbent dose, contact time, initial metal ion concentration, and temperature. Data were utilized for isothermal, kinetic, and thermodynamic studies. Scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDAX), and Fourier transform infrared (FTIR) analyses of biomass were performed. The results showed that 1 g/100 ml for 5.0-5.5 h contact time at pH 6.0-7.5 with agitation rate 150 rpm provided 98, 96, 92, and 85 % maximum absorption of arsenic by R. rosa, H. rosasinensis, T. erecta, and C. indica, respectively, at initial concentration of 500 ppb. Data followed Langmuir isotherm showing sorption to be monolayer on heterogeneous surface of biosorbent. Negative values of ΔG° indicated spontaneous nature, whereas ΔH° indicates exothermic nature of system followed by pseudo-first-order adsorption kinetics. FTIR results showed apparent changes in functional group regions after metal chelation. SEM and EDAX analyses showed the changes in surface morphology of all test biosorbents. Herbal dye wastes, used as biosorbent, exhibited significant (85-98 %) removal of arsenic from aqueous solution. Hence, these biosorbents are cost-effective, easily available, eco-friendly, and comparatively more effective than other biosorbents already in use. These may be used to remove arsenic and other toxic metals from water. PMID:22661261

  10. Thermodynamics of dilute aqueous solutions of imidazolium based ionic liquids

    International Nuclear Information System (INIS)

    Research highlights: → The thermodynamic behaviour of aqueous imidazolium ILs has been investigated. → Volumetric and ultrasonic results indicated the hydrophobic hydration of ILs. → Viscometric studies revealed studied ionic liquids as water-structure makers. → Hydration number increased with increase in alkyl chain length of the cation. - Abstract: Experimental measurements of density ρ, speed of sound u, and viscosity η of aqueous solutions of various 1-alkyl-3-methylimidazolium based ionic liquid (IL) solutions have been performed in dilute concentration regime at 298.15 K to get insight into hydration behaviour of ILs. The investigated ILs are based on 1-alkyl-3-methylimidazolium cation, [Cnmim] having [BF4]-, [Cl]-, [C1OSO3]-, and [C8OSO3]- as anions where n = 4 or 8. Several thermodynamic parameters like apparent molar volume φV, isentropic compressibility βs, and viscosity B-coefficients have been derived from experimental data. Limiting value of apparent molar volume has been discussed in terms of intrinsic molar volume (Vint) molar electrostriction volume (Velec), molar disordered (Vdis), and cage volume (Vcage). Viscosity B-coefficients have been used to quantify the kosmotropic or chaotropic nature of ILs. Hydration number of ILs obtained using elctrostriction volume, isentropic compressibility, viscosity, and differential scanning calorimetry have been found to be comparative within the experimental error. The hydrophobic hydration has found to play an important role in hydration of ILs as compared to hydration due to hydrogen bonding and electrostriction. Limiting molar properties, hydration numbers, and B-coefficients have been discussed in terms of alkyl chain length of cation or nature of anion.

  11. Comparison of Inactivation and Unfolding of Calf Intestinal Alkaline Phosphatase in Guanidinium Chloride Solution

    Institute of Scientific and Technical Information of China (English)

    张英侠; 闫淑莲; 刘永利; 席宏伟; 周海梦

    2002-01-01

    The changes in activity and unfolding of calf intestinal alkaline phosphatase (CIP) during denaturation in guanidinium chloride solutions of different concentrations were investigated using ultraviolet difference absorption spectra and fluorescence emission spectra. Unfolding and inactivation rate constants were measured and compared. The inactivation course is much faster than that of unfolding, which suggests that the active site of CIP containing two zinc ions and one magnesium ion is situated in a limited and flexible region of the enzyme molecule, which is more fragile to the denaturant than the protein as a whole.

  12. Pitting corrosion of friction stir welded aluminum alloy thick plate in alkaline chloride solution

    Energy Technology Data Exchange (ETDEWEB)

    Xu Weifeng, E-mail: xwf1982@mail.nwpu.edu.c [School of Materials and Engineering, Northwestern Polytechnical University, Xi' an 710072 (China); Liu Jinhe; Zhu Hongqiang [School of Materials and Engineering, Northwestern Polytechnical University, Xi' an 710072 (China)

    2010-03-01

    The pitting corrosion of different positions (Top, Middle and Bottom) of weld nugget zone (WNZ) along thickness plate in friction stir welded 2219-O aluminum alloy in alkaline chloride solution was investigated by using open circuit potential, cyclic polarization, scanning electron microscopy and atomic force microscope. The results indicate that the material presents significant passivation, the top has highest corrosion potential, pitting potential and re-passivation potential compared with the bottom and base material. With the increase of traverse speed from 60 to 100 mm/min or rotary speed from 500 to 600 rpm, the corrosion resistance decreases.

  13. Kinetics of leaching of the aluminum hydroxide in bauxites by alkaline solutions at atmospheric pressure

    Science.gov (United States)

    Burtsev, A. V.; Lainer, Yu. A.; Gorichev, I. G.; Kipriyanov, N. A.; Izotov, A. D.

    2011-11-01

    The kinetics of leaching of the aluminum hydroxide from the gibbsite bauxites of Guinea (Kindia deposit) is studied under atmospheric conditions. The activation energy of the process is found to be 34.75 kJ/mol, which indicates that the process proceeds in a kinetic mode. The leaching of the aluminum hydroxide from bauxite in an alkaline solution is simulated using acid-base equilibria (ion exchange) and the electrochemical theory of the structure of a double electrical layer (Gram-Parsons theory).

  14. EIS ANALYSIS ON THE ANODIC PROCESS OF ZINC IN AN ALKALINE SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Y. Zheng; J.M. Wang; H. Chen; J.Q. Zhang; C.N. Cao

    2004-01-01

    The EIS on the anodic process of pure Zn in an alkaline solution were performed and fitted using the expression of Faradic admittance, based on which the mechanism of the process was proposed. The results showed that besides electrode potential E the electrochemical reaction rate was affected by the adsorption of Zn(OH)ads on the electrode surface and the diffusion of in the electrolyte in active region, and only by the covering of passivation layer on the electrode surface in both transitive and passivation regions. The equivalent circuits applied in these various circumstances were proposed and the variation of some parameters and state variables was also discussed.

  15. Pitting corrosion of friction stir welded aluminum alloy thick plate in alkaline chloride solution

    International Nuclear Information System (INIS)

    The pitting corrosion of different positions (Top, Middle and Bottom) of weld nugget zone (WNZ) along thickness plate in friction stir welded 2219-O aluminum alloy in alkaline chloride solution was investigated by using open circuit potential, cyclic polarization, scanning electron microscopy and atomic force microscope. The results indicate that the material presents significant passivation, the top has highest corrosion potential, pitting potential and re-passivation potential compared with the bottom and base material. With the increase of traverse speed from 60 to 100 mm/min or rotary speed from 500 to 600 rpm, the corrosion resistance decreases.

  16. Influence aqueous solutions on the mechanical behavior of argillaceous rocks

    International Nuclear Information System (INIS)

    The hydration of the shale with an aqueous solution induces a swelling deformation which plays an important role in the behaviour of the structures excavated in this type of grounds. This deformation is marked by a three-dimensional and anisotropic character and involves several mechanisms like adsorption, osmosis or capillarity. Several researches were dedicated to swelling and were often much debated due to the complexity of the implied phenomena. The goal of this thesis is therefore to contribute to a better understanding of shale swelling when the rock is confined and hydrated with an aqueous solution. The main part of the work accomplished was related to the Lorraine shale and to the Tournemire shale. To characterize swelling and to identify the main governing parameters, it was necessary to start the issue with an experimental approach. Many apparatus were then developed to carry out tests under various conditions of swelling. In order to facilitate the interpretation of the tests and thereafter the modelling of the behaviour, the experimental procedure adopted consisted of studying first the mechanical aspect and then the chemical aspect of swelling. In the mechanical part, swelling was studied by imposing on the sample a mechanical loading while maintaining during the tests the same aqueous solution. The principal parameters which were studied are the effect of the lateral conditions on axial swelling (impeded strain or constant stress) as well as the influence of the axial stress on radial swelling. The anisotropy of swelling was studied by carrying out, for different orientations of the sample, tests of free swelling, impeded swelling and uniaxial swelling. These various mechanical tests allowed to study the three-dimensional anisotropic swelling in all the conditions and to select the most appropriate test to be used in the second phase of the research. The precise analysis performed to explain the mechanisms behind the swelling of an argillaceous rock

  17. The Removal of Dye from Aqueous Solution by Adsorption on Low Cost Adsorbents

    OpenAIRE

    J. J. Chamargore; Bharad, J. V.; Madje, B. R.; Ubale, M. B.

    2010-01-01

    Removal of color from aqueous solution by using low cost easily available adsorbent was conducted by batch experiment. The potential of the low cost adsorbent (Marble powder-treated and untreated) to remove methylene red from aqueous solution were assessed at room temperature. Laboratory investigation of the potential of marble powder and sulphuric acid treated marble powder to remove dye color from aqueous solution has been studied. Parameters studied included pH, adsorbent dose, initial dye...

  18. Preparation, characterization and application of alkaline leached CuNiZn ternary coatings for long-term electrolysis in alkaline solution

    Energy Technology Data Exchange (ETDEWEB)

    Solmaz, Ramazan [Bingoel University, Science and Letters Faculty, Chemistry Department, 12000 Bingoel (Turkey); Doener, Ali; Kardas, Guelfeza [Cukurova University, Science and Letters Faculty, Chemistry Department, 01330 Balcali Adana (Turkey)

    2010-10-15

    The NiCuZn ternary coating was electrochemically deposited on a copper electrode. Then, it was etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the hydrogen evolution reaction (HER). The surface composition of coating before and after alkaline leaching was determined by energy dispersive X-ray (EDX) analysis. The surface morphologies were investigated by scanning electron microscopy (SEM). The long-term stability of electrode prepared for alkaline water electrolysis was investigated in 1 M KOH solution with the help of cathodic current-potential curves and electrochemical impedance spectroscopy (EIS) techniques. It was found that, the NiCuZn coating has a compact and porous structure with good physical stability. Alkaline leaching process further improved the activity of NiCuZn coating in comparison with binary NiCu deposit for the HER. The long-term operation at -100 mA cm{sup -2} showed good electrochemical stability over 120 h. (author)

  19. Measurement and correlation of physical properties of aqueous solutions of tetrabutylammonium hydroxide, piperazine and their aqueous blends

    Institute of Scientific and Technical Information of China (English)

    Rizwan Safdar; Abdul Aziz Omar; Lukman B Ismail; Arhama Bari; Bhajan Lal

    2015-01-01

    The density, viscosity and refractive index of aqueous solutions of tetrabutylammonium hydroxide (TBAOH), pi-perazine (PZ) and their aqueous blends are determined at several temperatures (303.15 to 333.15 K). All these measured physicochemical properties decreases with an increase in temperature. The density data is used to cal-culate the coefficient of thermal expansion and excess molar volume of al aqueous binary and ternary solutions. The coefficient of thermal expansion increases with increase in temperatures and concentrations. The negativity of excess molar volume for al the aqueous solution decreased with increase in temperature. Each physical prop-erty is correlated with temperature by least square method and the corresponding coefficients for each property are presented. The prediction values from correlations for the physical properties are in good agreement with the experimental values.

  20. Radiolysis of Aqueous Benzene Solutions in the Presence of Inorganic Oxides

    International Nuclear Information System (INIS)

    Aqueous 0.1 N alkaline solutions of benzene have been irradiated with Co γ-rays in the presence of various inorganic oxides. The addition to the solution of silica gel, copper(ll) oxide and chromium(lll) oxide did not increase the yield of phenol. When chromium(lll) oxide gel, zinc oxide or titanium dioxide were added, we obtained a 9 - 13 per cent increase, and the addition of uranium dioxide and thorium dioxide caused a 31 and 39 per cent increase respectively. The increase of the phenol yield was related to the energy absorbed by the solid, and Gox values defined in this way were calculated as follows: GZnO = 4.0, GTiO2 = 3.7, a GUO2 = 6.4, GThO2 = 8.0. The specific surface areas of the oxides were determined and the possibility that the increase of the phenol yield may be dependent on this quantity is discussed

  1. Fluorescent silver nanoclusters for ultrasensitive determination of chromium(VI) in aqueous solution.

    Science.gov (United States)

    Zhang, Jian Rong; Zeng, Ai Lian; Luo, Hong Qun; Li, Nian Bing

    2016-03-01

    In this work, a simple and sensitive Cr(VI) sensor is proposed based on fluorescent polyethyleneimine-stabilized Ag nanoclusters, which allows the determination over a wide concentration range of 0.1 nM-3.0 μM and with a detection limit as low as 0.04 nΜ and a good selectivity. The quenching mechanism was discussed in terms of the absorption and fluorescence spectra, suggesting that Cr(VI) is connected to Ag nanoclusters by hydrogen bond between the oxygen atom at the vertex of tetrahedron structure of Cr(VI) and the amino nitrogen of polyethyleneimine that surrounded Ag nanoclusters and electron transfer from Ag nanoclusters to highly electron-deficient Cr(VI) results in fluorescence quenching. Despite the failure to quench the fluorescence efficiently, Cr(III) can also be measured using the proposed Ag nanoclusters by being oxidized to Cr(VI) in alkaline solution (pH ∼ 9) containing H2O2. Therefore, our approach could be used to detect Cr(VI), Cr(III) and the total chromium level in aqueous solution. In addition, Cr(VI) analysis in real water samples were satisfactory, indicating this method could be practically promising for chromium measurements. PMID:26546705

  2. Adsorption of cesium on cement mortar from aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Volchek, Konstantin, E-mail: konstantin.volchek@ec.gc.ca [Emergencies Science and Technology Section, Environment Canada, 335 River Road, Ottawa, Ontario, Canada K1A 0H3 (Canada); Miah, Muhammed Yusuf [Emergencies Science and Technology Section, Environment Canada, 335 River Road, Ottawa, Ontario, Canada K1A 0H3 (Canada); Department of Applied Chemistry and Chemical Technology, Noakhali Science and Technology University (Bangladesh); Kuang, Wenxing; DeMaleki, Zack [Emergencies Science and Technology Section, Environment Canada, 335 River Road, Ottawa, Ontario, Canada K1A 0H3 (Canada); Tezel, F. Handan [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada)

    2011-10-30

    Highlights: {yields} The adsorption of cesium on cement mortar was investigated in a range of temperatures and cesium concentrations. {yields} The pseudo-second order kinetic model produced a good fit with the experimental kinetic data. {yields} Equilibrium test results correlated well with the Freundlich isotherm adsorption model. {yields} The interaction between cesium ions and cement mortar was dominated by chemical adsorption. - Abstract: The adsorption of cesium on cement mortar from aqueous solutions was studied in series of bench-scale tests. The effects of cesium concentration, temperature and contact time on process kinetics and equilibrium were evaluated. Experiments were carried out in a range of initial cesium concentrations from 0.0103 to 10.88 mg L{sup -1} and temperatures from 278 to 313 K using coupons of cement mortar immersed in the solutions. Non-radioactive cesium chloride was used as a surrogate of the radioactive {sup 137}Cs. Solution samples were taken after set periods of time and analyzed by inductively coupled plasma mass spectroscopy. Depending on the initial cesium concentration, its equilibrium concentration in solution ranged from 0.0069 to 8.837 mg L{sup -1} while the respective surface concentration on coupons varied from 0.0395 to 22.34 {mu}g cm{sup -2}. Equilibrium test results correlated well with the Freundlich isotherm model for the entire test duration. Test results revealed that an increase in temperature resulted in an increase in adsorption rate and a decrease in equilibrium cesium surface concentration. Among several kinetic models considered, the pseudo-second order reaction model was found to be the best to describe the kinetic test results in the studied range of concentrations. The adsorption activation energy determined from Arrhenius equation was found to be approximately 55.9 kJ mol{sup -1} suggesting that chemisorption was the prevalent mechanism of interaction between cesium ions and cement mortar.

  3. Poorly crystalline hydroxyapatite: A novel adsorbent for enhanced fulvic acid removal from aqueous solution

    Science.gov (United States)

    Wei, Wei; Yang, Lei; Zhong, Wenhui; Cui, Jing; Wei, Zhenggui

    2015-03-01

    In this study, poorly crystalline hydroxyapatite (HAP) was developed as an efficient adsorbent for the removal of fulvic acid (FA) from aqueous solution. Surface functionality, crystallinity, and morphology of the synthetic adsorbent were studied by Fourier-transformation infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of various parameters such as crystallinity of adsorbent, contact time, adsorbent dosage, pH, initial adsorbate concentration, temperature, ionic strength and the presence of alkaline earth metal ions on FA adsorption were investigated. Results indicated that the nanosized HAP calcined at lower temperature was poorly crystalline (Xc = 0.23) and had better adsorption capacity for FA than those (Xc = 0.52, 0.86) calcined at higher temperature. FA removal was increased with increases of adsorbent dosage, temperature, ionic strength and the presence of alkali earth metal ions, but decreased as the pH increased. Kinetic studies showed that pseudo-second-order kinetic model better described the adsorption process. Equilibrium data were best described by Sips models, and the estimated maximum adsorption capacity of poorly crystalline HAP was 90.20 mg/g at 318 K, displaying higher efficiency for FA removal than previously reported adsorbents. FT-IR results revealed that FA adsorption over the adsorbent could be attributed to the surface complexation between the oxygen atom of functional groups of FA and calcium ions of HAP. Regeneration studies indicated that HAP could be recyclable for a long term. Findings of the present work highlight the potential for using poorly crystalline HAP nanoparticles as an effective and recyclable adsorbent for FA removal from aqueous solution.

  4. Resonant X-ray scattering studies of concentrated aqueous solutions

    International Nuclear Information System (INIS)

    The microscopic structure of concentrated aqueous electrolyte solutions has been studied by resonant X-ray diffraction (RXD). This technique provides a method for the measurement of the structure around a specific atom or ion in solution. In that sense, RXD is the X-ray equivalent of neutron diffraction with isotopic substitution (NDIS). The use of RXD as an alternative to NDIS has been considered of interest for some time; it is potentially one of the best methods for overcoming the most important limitation of the neutron diffraction technique, i.e. the lack of suitable isotopes for every atomic species. Third generation synchrotron sources offer an unprecedented opportunity for the further development of RXD to study the microscopic structure of liquids and amorphous materials. One of the main aims of this thesis was to check whether it could be possible to obtain results of comparable accuracy to those of NDIS. In this work, the hydration structures of Br-, Rb+, Sr2+ and Y3+ in concentrated aqueous solutions have been studied by RXD. A detailed account of how the experiments were carried out and the data analysis procedure is given. The results are compared with those obtained for the same ion by other techniques and to those obtained for similar systems by NDIS. The reliability of these results and the observed trends in the measured structure when compared to other ions in the same series are discussed. A comparative study of the structure of the three cations is also presented in this thesis. This work illustrates one of the main advantages of RXD: the possibility of carrying out systematic structural studies on all elements with atomic number greater than 28 (Ni). Finally, a critical discussion on the actual stage of development of RXD is presented. The results shown offer evidence of the future prospects of the technique and justify further efforts to develop it to the level of reliability and ease of use that NDIS has reached after more than three decades

  5. Micellization properties of cationic gemini surfactants in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Łudzik, K., E-mail: kasialudzik@tlen.pl [Department of Physical Chemistry, University of Łódź, Pomorska 165, 90-236 Łódź (Poland); Piekarski, H.; Kubalczyk, K.; Wasiak, M. [Department of Physical Chemistry, University of Łódź, Pomorska 165, 90-236 Łódź (Poland)

    2013-04-20

    Highlights: ► We measured the d and c{sub p} of for the aqueous solutions of 8-6-8 and 8-12-8 surfactants. ► We analyzed the α{sub T} = f (m), V{sub ϕ} = f (m), c{sub p} = f (m) and C{sub p,ϕ} = f (m). ► The inflection point in the curves of the C{sub p,ϕ} = f (m) corresponds to the c.m.c. ► We analyzed thermodynamics parameters of the micellization for the surfactants. - Abstract: The main goal of this work was to investigate the self-assembly process for water solutions of two gemini surfactants, which differ in spacer chain length, at wide range of temperatures. For this reason the aqueous solutions of hexylene-1,6-bis(dimethyl-octylammonium bromide) and dodecylene-1,12-bis(dimethyloctylammonium bromide) have been examined by the calorimetric (DSC) and densimetric methods within the 293–323 K and 288–323 K temperature range, respectively. The analysis of c{sub p} values obtained for the examined systems allowed to propose an alternative way to estimate the region where micellization process can occur. The observed temperature dependence of the c.m.c. for surfactants investigated shows a typical shape for ionic gemini surfactants. This behavior was explained as a resultant of two competing effect: decrease in the hydrophilic properties of the surfactant molecule and decrease in the hydrophobic hydration of the alkyl chain along with the temperature increase. The enthalpy of micellization ΔH{sub mic} and other thermodynamics parameters associated with the micellization process: ΔG{sub mic}, ΔS{sub mic} and ΔC{sub p} {sub mic} were calculated on the base of the pseudo-phase separation model. As expected, more exothermic enthalpies of micellization are observed with increasing temperature for both the surfactants investigated in this work.

  6. Sorption characteristics of technetium on crosslinked chitosan from aqueous solutions

    International Nuclear Information System (INIS)

    Removal of radioactive ions from the wastewaters is a huge problem because these ions are extremely dangerous for environment and human health by their high toxicity at very low concentrations and long half lives. These pollutants arise into the wastewaters as a result of different industrial activities like: mining, production of nuclear fuels, laboratory investigations, etc. The methods developed for removal of radioisotopes from wastewaters include: chemical precipitation, ion exchange, membrane-related processes, biological processes and electrochemical techniques. The application of polymer such as chitosan is one of the emerging adsorption methods for removal of dyes and heavy metal ions, even at low concentrations. Chitosan is a type of natural polyaminosaccharide, synthesized from deacetylation of chitin. It is composed of β (1→4) linked 2-amino-2-deoxy-D-glucopyranose units. Chitosan is very sensitive to pH as it can either form gel or dissolve depending on the pH values. To improve chitosan's performance as an adsorbent, cross-linking reagents such as glyoxal, formaldehyde, glutaraldehyde, epichlorohydrin have been used. Cross-linking agents do not only stabilize chitosan in acid solutions so that is becomes insoluble but also enhance its mechanical properties and adsorption capacity. Crosslinked chitosan is suitable for the sorption of radionuclides from aqueous solutions, such as cesium, cobalt, europium, uranium, thorium, technetium, plutonium, and americium due to the presence of amino and hydroxyl groups, which are the active sites. Technetium has no stable isotope in nature, it has essentially all been created by human activities. Among radioactive isotopes, 99Tc has a half-life 2.1·105 years sufficiently long enough to warrant concern and it is produced in the fission of 235U and 239Pu with a relatively high yield of about 6 %. The radionuclide, 99Tc, has been released into the environment during nuclear weapons testing. Since discharges

  7. Lead removal from aqueous solutions by a Tunisian smectitic clay

    Energy Technology Data Exchange (ETDEWEB)

    Chaari, Islem [Laboratoire de Georessources CERTE BP 95, 2050 Hamam-Lif (Tunisia)], E-mail: chaariislem@yahoo.fr; Fakhfakh, Emna; Chakroun, Salima [Laboratoire de Georessources CERTE BP 95, 2050 Hamam-Lif (Tunisia); Bouzid, Jalel; Boujelben, Nesrine [Laboratoire Eau Energie et Environnement, departement de genie geologique, Ecole Nationale d' Ingenieurs de Sfax, BP W 3038 Sfax (Tunisia); Feki, Mongi [Unite de chimie industrielle I, Ecole Nationale d' Ingenieurs de Sfax, BP W 3038 Sfax (Tunisia); Rocha, Fernando [MIA, Universite d' Aveiro, Campus de Santiago, 3810 Aveiro (Portugal)], E-mail: frocha@geo.ua.pt; Jamoussi, Fakher [Laboratoire de Georessources CERTE BP 95, 2050 Hamam-Lif (Tunisia)

    2008-08-15

    The adsorption of Pb{sup 2+} ions onto Tunisian smectite-rich clay in aqueous solution was studied in a batch system. Four samples of clay (AYD, AYDh, AYDs, AYDc) were used. The raw AYD clay was sampled in the Coniacian-Early Campanian of Jebel Aidoudi in El Hamma area (South of Tunisia). AYDh and AYDs corresponds to AYD activated by 2.5 mol/l hydrochloric acid and 2.5 mol/l sulphuric acid, respectively. AYDc corresponds to AYD calcined at different temperatures (100, 200, 300, 400, 500 and 600 deg. C). The raw AYD clay was characterized by X-ray diffraction, chemical analysis, infrared spectroscopy and coupled DTA-TGA. Specific surface area of all the clay samples was determined from nitrogen adsorption isotherms. Preliminary adsorption tests showed that sulphuric acid and hydrochloric acid activation of raw AYD clay enhanced its adsorption capacity for Pb{sup 2+} ions. However, the uptake of Pb{sup 2+} by AYDs was very high compared to that by AYDh. This fact was attributed to the greater solubility of clay minerals in sulphuric acid compared to hydrochloric acid. Thermic activation of AYD clay reduced the Pb{sup 2+} uptake as soon as calcination temperature reaches 200 deg. C. All these preliminary results were well correlated to the variation of the specific surface area of the clay samples. The ability of AYDs sample to remove Pb{sup 2+} from aqueous solutions has been studied at different operating conditions: contact time, adsorbent amount, metal ion concentration and pH. Kinetic experiments showed that the sorption of lead ions on AYDs was very fast and the equilibrium was practically reached after only 20 min. The results revealed also that the adsorption of lead increases with an increase in the solution pH from 1 to 4.5 and then decreases, slightly between pH 4.5 and 6, and rapidly at pH 6.5 due to the precipitation of some Pb{sup 2+} ions. The equilibrium data were analysed using Langmuir isotherm model. The maximum adsorption capacity (Q{sub 0

  8. Structure and phase behavior of aqueous methylcellulose solutions

    Science.gov (United States)

    McAllister, John; Schmidt, Peter; Lodge, Timothy; Bates, Frank

    2015-03-01

    Cellulose ethers (CE) constitute a multi-billion dollar industry, and have found end uses in a broad array of applications from construction materials, food products, personal care products, and pharmaceuticals for more than 80 years. Methylcellulose (MC, with the trade name METHOCEL™) is a CE in which there is a partial substitution of -OH groups with -OCH3 groups. This results in a polymer that is water-soluble at low temperatures, and aqueous solutions of MC display gelation and phase separation at higher temperatures. The nature of MC gelation has been debated for many years, and this project has made significant advances in the understanding of the solution properties of CEs. We have characterized a fibrillar structure of MC gels by cryogenic transmission electron microscopy (cryo-TEM) and small angle neutron scattering (SANS). Using light scattering, turbidity measurements, and dynamic mechanical spectroscopy (DMS) we report that MC microphase separates by nucleation and growth of fibril aggregates, and is a different process from LCST phase separation.

  9. Photocatalytic decomposition of cortisone acetate in aqueous solution.

    Science.gov (United States)

    Romão, Joana Sobral; Hamdy, Mohamed S; Mul, Guido; Baltrusaitis, Jonas

    2015-01-23

    The photocatalytic decomposition of cortisone 21-acetate (CA), a model compound for the commonly used steroid, cortisone, was studied. CA was photocatalytically decomposed in a slurry reactor with the initial rates between 0.11 and 0.46 mg L(-1)min(-1) at 10 mg L(-1) concentration, using the following heterogeneous photocatalysts in decreasing order of their catalytic activity: ZnO>Evonik TiO2 P25>Hombikat TiO2>WO3. Due to the lack of ZnO stability in aqueous solutions, TiO2 P25 was chosen for further experiments. The decomposition reaction was found to be pseudo-first order and the rate constant decreased as a function of increasing initial CA concentration. Changing the initial pH of the CA solution did not affect the reaction rate significantly. The decomposition reaction in the presence of the oxidizing sacrificial agent sodium persulfate showed an observed decomposition rate constant of 0.004 min(-1), lower than that obtained for TiO2 P25 (0.040 min(-1)). The highest photocatalytic degradation rate constant was obtained combining both TiO2 P25 and S2O8(2-) (0.071 min(-1)) showing a synergistic effect. No reactive intermediates were detected using LC-MS showing fast photocatalytic decomposition kinetics of CA. PMID:24953705

  10. Cast iron deterioration with time in various aqueous salt solutions

    Indian Academy of Sciences (India)

    Rita Mehra; Aditi Soni

    2002-02-01

    The changes with time in the corrosion rate and corrosion current density on a cast iron electrode in various aqueous salt solutions have been carried out using total immersion test and potentiostatic polarization curves. The concentration of salts taken is expected to be present in potable water. The relative behaviour of these salts towards corrosion has also been studied, which is found to be different from previous studies. The total immersion test parameters viz. weight loss, corrosion rate as well as potentiostatic parameters, open circuit potential, corr, Tafel slopes, corrosion rate, have been calculated by standard methods. Besides these the relative increase in corrosion rate with time as well as the percentage to which corrosion rate should be decreased so as to provide protection towards corrosion have also been calculated. It was found that KCl and NaCl are major contributors than MnSO4, Pb(NO3)2, KI and KBr. The relative increase in corrosion is high in KBr, KI, NaNO3, CaCl2, and less in Pb(NO3)2, NaHCO3 and CaCO3 test solutions. For the reliability of results the data has been statistically analysed.

  11. Single Molecule Electrochemical Detection in Aqueous Solutions and Ionic Liquids.

    Science.gov (United States)

    Byers, Joshua C; Paulose Nadappuram, Binoy; Perry, David; McKelvey, Kim; Colburn, Alex W; Unwin, Patrick R

    2015-10-20

    Single molecule electrochemical detection (SMED) is an extremely challenging aspect of electroanalytical chemistry, requiring unconventional electrochemical cells and measurements. Here, SMED is reported using a "quad-probe" (four-channel probe) pipet cell, fabricated by depositing carbon pyrolytically into two diagonally opposite barrels of a laser-pulled quartz quadruple-barreled pipet and filling the open channels with electrolyte solution, and quasi-reference counter electrodes. A meniscus forms at the end of the probe covering the two working electrodes and is brought into contact with a substrate working electrode surface. In this way, a nanogap cell is produced whereby the two carbon electrodes in the pipet can be used to promote redox cycling of an individual molecule with the substrate. Anticorrelated currents generated at the substrate and tip electrodes, at particular distances (typically tens of nanometers), are consistent with the detection of single molecules. The low background noise realized in this droplet format opens up new opportunities in single molecule electrochemistry, including the use of ionic liquids, as well as aqueous solution, and the quantitative assessment and analysis of factors influencing redox cycling currents, due to a precisely known gap size. PMID:26398675

  12. Columnar molecular aggregation in the aqueous solutions of disodium cromoglycate

    Science.gov (United States)

    Agra-Kooijman, Dena M.; Singh, Gautam; Lorenz, Alexander; Collings, Peter J.; Kitzerow, Heinz-S.; Kumar, Satyendra

    2014-06-01

    Stack, chimneylike, and threadlike assemblies have previously been proposed for the structure of disodium cromoglycate (DSCG) aggregates in aqueous solutions. The results of the synchrotron x-ray scattering investigations reported here reveal the formation of simple columnar assemblies with π-π stacking at a separation of 3.4 Å between the DSCG molecules. Lateral separation between the assemblies is concentration and temperature dependent, varying from ˜35 to 42 Å in the orientationally ordered nematic (N) phase and from 27 to 32 Å in the columnar or middle (M) phase having long range lateral positional order. The assemblies' length depends on concentration and consists of ˜23 molecules in the N phase, becoming three to ten times larger in the M phase. The scission energy is concentration dependent in the N phase with values ˜7.19 ± 0.14 kBT (15 wt %), 2.73 ± 0.4 kBT (20 wt %), and 3.05 ± 0.2 kBT (25 wt %). Solutions of all concentrations undergo a spinodal decomposition at temperatures above ˜40 °C, resulting in DSCG-rich regions with the M phase and water-rich regions in the N and isotropic phases.

  13. Hydroxyl radical induced degradation of salicylates in aerated aqueous solution

    International Nuclear Information System (INIS)

    Ionizing radiation induced degradation of acetylsalicylic acid, its hydrolysis product salicylic acid and a salicylic acid derivative 5-sulpho-salicylic acid, was investigated in dilute aqueous solutions by UV–vis spectrophotometry, HPLC separation and diode-array or MS/MS detection, chemical oxygen demand, total organic carbon content and by Vibrio fischeri toxicity measurements. Hydroxyl radicals were shown to degrade these molecules readily, and first degradation products were hydroxylated derivatives in all cases. Due to the by-products, among them hydrogen peroxide, the toxicity first increased and then decreased with the absorbed dose. With prolonged irradiation complete mineralization was achieved. - Highlights: • In OH induced reactions of salicylates first products are hydroxylated derivatives. • With prolonged irradiation dihydroxy derivatives also form. • In aerated solutions the one-electron oxidant OH induces 3–4 oxidations. • Toxicity first increases and then decreases with dose mainly due to H2O2 formation. • The toxicity in tap water is smaller than in pure water

  14. Electrosorption of inorganic salts from aqueous solution using carbon aerogels.

    Science.gov (United States)

    Gabelich, Christopher J; Tran, Tri D; Suffet, I H Mel

    2002-07-01

    Capacitive deionization (CDI) with carbon aerogels has been shown to remove various inorganic species from aqueous solutions, though no studies have shown the electrosorption behavior of multisolute systems in which ions compete for limited surface area. Several experiments were conducted to determine the ion removal capacity and selectivity of carbon aerogel electrodes, using both laboratory and natural waters. Although carbon aerogel electrodes have been treated as electrical double-layer capacitors, this study showed that ion sorption followed a Langmuir isotherm, indicating monolayer adsorption. The sorption capacity of carbon aerogel electrodes was approximately 1.0-2.0 x 10(-4) equiv/g aerogel, with ion selectivity being based on ionic hydrated radius. Monovalent ions (e.g., sodium) with smaller hydrated radii were preferentially removed from solution over multivalent ions (e.g., calcium) on a percent or molar basis. Because of the relatively small average pore size (4-9 nm) of the carbon aerogel material, only 14-42 m2/g aerogel surface area was available for ion sorption. Natural organic matter may foul the aerogel surface and limit CDI effectiveness in treating natural waters. PMID:12144279

  15. Adsorption of itaconic acid from aqueous solutions onto alumina

    Directory of Open Access Journals (Sweden)

    JELENA J. GULICOVSKI

    2008-08-01

    Full Text Available Itaconic acid, IA (C5H6O4, was investigated as a potential flocculant for the aqueous processing of alumina powders. The adsorption of IA, as a function of its concentration and pH value of the solution, onto the alumina surface was studied by the solution depletion method. The stability of the suspensions in the presence of itaconic acid was evaluated in light of the surface charge of the alumina powder used, the degree of dissociation of IA, as well as the sedimentation behavior and rheology of the suspensions. It was found that the adsorption process is extremely pH dependent; the maximum adsorption of IA onto alumina surface occurring at a pH close to the value of the first IA dissociation constant, pKa1. Also, IA does not influence the value of the point of zero charge of alumina. It was shown that IA represents an efficient flocculant for concentrated acidic alumina suspensions.

  16. Speciation of aluminum in aqueous solutions using ion chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Bertsch, P.M.; Anderson, M.A.

    1989-03-15

    An ion chromatographic method in which aluminum (AI) is quantitatively determined via postcolumn derivatization with Tiron (4,5-dihydroxy-m-benzenedisulfonic acid) was evaluated for its utility as a method for speciating AI in aqueous solutions. Fluro-, oxalato-, and citratoaluminum complexes were identified by distinct peaks within chromatograms of AI solutions when the appropriate ligand was added. Excellent quantitative agreement between predicted species concentrations (via the thermodynamic speciation model GEOCHEM) and those determined by ion chromatography was obtained for samples prepared in the eluent matrix. The predominantly outer sphere sulfatoaluminum complexes were not observed to elute as singly charged species, but rather exhibited a retention time indistinguishable from the AI(H/sub 2/O)6(3+) species. It is concluded that inner sphere AI complexes (generally possessing relatively high association constants) possess adequate kinetic stability to withstand degradation during the ion exchange process, whereas outer sphere complexes apparently readily dissociate in the presence of the sulfonate exchange sites. Deviations in sample ionic strength (mu) and pH from that of the eluent resulted in some redistribution among species, the degree of which was ligand specific.

  17. Thermodynamics of micellization of alkylimidazolium surfactants in aqueous solution

    International Nuclear Information System (INIS)

    Alkylimidazolium salts are a very important class of compounds. So far, calorimetry has hardly been used to characterize their solution behaviour. The enthalpies obtained from indirect methods have an intrinsic large uncertainty, and nowadays it is clear that calorimetry is the most sensitive technique for directly measuring the thermodynamic properties of aggregation. In this work, isothermal titration calorimetry (ITC) was used along with conductivity to determine the thermodynamics of aggregation of 1-alkyl-3-methylimidazolium chlorides ([Cnmim]Cl, n = 8, 10, 12, and 14) in aqueous solution. The critical micelle concentrations, cmc, were obtained from conductivity and calorimetry, and the enthalpies of micelle formation, ΔHmic, were derived from the calorimetric titrations. From conductivity, we could also derive the values for the degree of ionisation of the micelles (α), the molar conductivity (ΛM) of the [Cnmim]Cl micellar species and the molar conductivity at infinite dilution (Λ∞) for the [Cnmim]+ cations. Values are therefore reported for the enthalpy (ΔHmic), the Gibbs free energy (ΔGmic) and entropy (ΔSmic) changes for micelle formation. Further, the aggregate sizes and aggregation numbers were obtained by light scattering (LS) measurements. The observed variation of the thermodynamic properties with the alkyl chain length is discussed in detail and compared with the traditional cationic surfactants 1-alkyl-trimethylammonium chlorides, [CnTA]Cl. The difference in the values of the thermodynamic parameters for both types of surfactants is here related to the structure of their head groups

  18. Processes for working-up an aqueous fluosilicic acid solution

    Directory of Open Access Journals (Sweden)

    Alpha O. Toure

    2012-11-01

    Full Text Available Aqueous fluosilicic acid solutions were once considered to be only adverse by-products of phosphoric acid production, which required treatment to prevent ecosystem destruction when discharged into the sea. However, a range of chemicals can be generated by the transformation of this industrial waste product. Through experiments undertaken in the laboratory, we have shown the possibility of caustic soda production. Volumetric analysis showed caustic soda to be present as a 6%– 7%solution with yields of about 70% – 80%by weight. Two processes were investigated for the caustification of sodium fluoride, using different precipitates: sodium chloride and ethanol and are described by modelling caustification curves. The activation energies of precipitation determined by semi-empirical correlations showed that precipitation by ethanol (EA = 933.536 J/mol was more successful than precipitation by sodium chloride (EA = 7452.405 J/mol. Analyses performed on the precipitates highlighted compositions that are essential and useful constituents in the cement industry.

  19. Removal of Nitrate From Aqueous Solution Using Rice Chaff

    Directory of Open Access Journals (Sweden)

    Dehghani

    2015-09-01

    Full Text Available Background Nitrate is largely dissolved in the surface and ground water, due to its high solubility. Continual uptake of nitrite through drinking water can lead to problems and diseases (such as blue baby for humans, especially children. Objectives The aim of this study was to develop a new and inexpensive method for the removal of nitrate from water. In this regard, the possibility of using chaff for removal of nitrate from aqueous solutions was studied and the optimum operating conditions of nitrate removal was determined. Materials and Methods This is a cross-sectional study conducted in laboratory scale. The UV spectrophotometer at a wavelength of maximum absorbance (220 nm was used to determine the nitrate concentration. The effect of pH, amount of chaff, temperature, and contact time were investigated. Results The result of this study revealed that chaff as an absorbent could remove nitrate from solutions, and the efficiency of adsorption increased as contact time increased from 5 to 30 minutes, amount of chaff increased from 1 to 3 g, temperature increased in a range of 300 - 400°C and the amount of pH decreased from 10 to 3. The maximum adsorption rate was around pH 3 (53.14%. Conclusions It was shown that the removal efficiency of nitrate was directly proportional to the amount of chaff, temperature, and contact time but inversely to the pH. This study showed that nitrate removal by chaff is a promising technique.

  20. From solution to oxide. Cations condensation in aqueous solution. Surface chemistry of oxides

    International Nuclear Information System (INIS)

    How is formed a solid from a solution? What are the properties of a dispersion of particles? The aim of this book is to answer to these questions. From an overview of the condensation processes of the cations in aqueous solution and the revealing of the structural relationships between species in solution and the formed solids, this book gives a logic in the phenomenon of oxides precipitation. The relationship that is established between the solutions chemistry and the solid chemistry allows to rationalize the behaviour of cations and to discuss the various factors whose structure, morphology and particles size are depending. It is from basic concepts relative to the oxide - aqueous solution interface that is presented the surface chemistry of oxides nano-particles. This one establishes the properties and the behaviour of the dispersions. Different phenomena bound to adsorption (arranged aggregation, control of particles size, interfacial electronic transfer, magnetic interactions between particles...) are studied. This book develops some aspects of the chemistry of metallic cations which is very important in a fundamental and technological point of view (synthesis of nano-materials, ceramics powders, catalysts, geochemical processes, biological phenomena, sol-gel techniques...). It is intended for university or engineers students and industrial searchers. (O.M.)

  1. Reaction of montmorillonite in alkaline solution at 60 C, 90 C, 120 C and 180 C

    International Nuclear Information System (INIS)

    The reaction of montmorillonite was investigated. Three kinds of bentonites with different montmorillonite composition were mixed with 0.3M NaOH solution and 0.3M Ca(OH)2 slurry. They were immersed at 60 C, 90 C, 120 C, and 180 C for one month, three months and six months. The concentrations of the soluble ions were measured and the bentonites were analyzed quantitatively after the immersion. 50% of the montmorillonite was reacted within two weeks at greater than 90 C. Montmorillonite reacts less when mixed with Si-minerals. It extensively reacted in 0.3M Ca(OH)2 slurry. These results suggest that the reaction mechanism of the montmorillonite in alkaline solution was dominantly Si dissolution, and would decrease by controlling the concentration of Si ion. The cement/bentonite system under Si saturated conditions is discussed

  2. Poorly crystalline hydroxyapatite: A novel adsorbent for enhanced fulvic acid removal from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Wei [Department of Environmental Science and Engineering, Nanjing Normal University, Nanjing 210023 (China); Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing Normal University, Nanjing 210023 (China); Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023 (China); Yang, Lei; Zhong, Wenhui; Cui, Jing [Department of Environmental Science and Engineering, Nanjing Normal University, Nanjing 210023 (China); Wei, Zhenggui, E-mail: weizhenggui@gmail.com [Department of Environmental Science and Engineering, Nanjing Normal University, Nanjing 210023 (China); Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing Normal University, Nanjing 210023 (China); Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023 (China)

    2015-03-30

    Graphical abstract: - Highlights: • Poorly crystalline HAP was firstly used for FA removal from aqueous solution. • The maximum adsorption capacity was determined to be 90.20 mg/g at 318 K. • Adsorption kinetics, isotherms and thermodynamic have been studied in detail. • Adsorption mechanism involved surface complexation, electrostatic interaction and hydrogen bonding. - Abstract: In this study, poorly crystalline hydroxyapatite (HAP) was developed as an efficient adsorbent for the removal of fulvic acid (FA) from aqueous solution. Surface functionality, crystallinity, and morphology of the synthetic adsorbent were studied by Fourier-transformation infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of various parameters such as crystallinity of adsorbent, contact time, adsorbent dosage, pH, initial adsorbate concentration, temperature, ionic strength and the presence of alkaline earth metal ions on FA adsorption were investigated. Results indicated that the nanosized HAP calcined at lower temperature was poorly crystalline (X{sub c} = 0.23) and had better adsorption capacity for FA than those (X{sub c} = 0.52, 0.86) calcined at higher temperature. FA removal was increased with increases of adsorbent dosage, temperature, ionic strength and the presence of alkali earth metal ions, but decreased as the pH increased. Kinetic studies showed that pseudo-second-order kinetic model better described the adsorption process. Equilibrium data were best described by Sips models, and the estimated maximum adsorption capacity of poorly crystalline HAP was 90.20 mg/g at 318 K, displaying higher efficiency for FA removal than previously reported adsorbents. FT-IR results revealed that FA adsorption over the adsorbent could be attributed to the surface complexation between the oxygen atom of functional groups of FA and calcium ions of HAP. Regeneration studies indicated that HAP could be recyclable for a long

  3. The reducibility of sulphuric acid and sulphate in aqueous solution

    International Nuclear Information System (INIS)

    In connection with the Swedish project for final storage of spent fuel elements it was necessary to assess whether dissolved sulphate can corrode the copper canister. A simple reaction between copper and sulphate is thermodynamically impossible, but copper can react to give copper sulphide if an additional electron donor such as iron(II) is available. The problem was extended to the more general question of the reducibility of sulphur(VI) in dilute aqueous solution. Chemical reduction of sulphate does not take place in dilute solution at temperatures below 100oC. In experiments on the reduction of sulphates under hydrothermal conditions a reaction only takes place at temperatures above 275-300oC. The oxidising action of sulphuric acid on metals becomes perceptible only at acid concentrations over 45-50%. In experiments on the cathodic reduction of 74% sulphuric acid the formation of hydrogen sulphide and elementary sulphur starts, depending on the current density, at 50-130oC, and polarographic measurements suggest that the reducible species is not the hydrogen sulphate ion but molecular sulphuric acid. The resistance of copper to oxygen-free sulphuric acid up to a concentration of 60% is well-known. Numerous processes in industrial electrochemistry take place in sulphuric acid or sulphate electrolytes. The reversible metal/metal-sulphate electrodes of lead and cadmium are unstable relative to the corresponding metal sulphides. Nevertheless the reversible lead sulphate electrode does not fail from sulphide formation. All these facts confirm that sulphur(VI) in dilute solution is completely inert towards chemical reducing agents and also to cathodic reduction. Thus corrosion of copper by sulphate under final-storage conditions and in the absence of sulphate reducing bacteria can be almost certainly be ruled out. (author) 5 figs., 85 refs

  4. Alkaline leaching of metal melting industry wastes dseparation of zinc and lead in the leach solution

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this work, a thorough examinations on the extractability of zinc and lead present in the steelmaking dusts using alkaline leaching process and the effectiveness of the zinc and lead separation in the resultant leaching solutions using sulfide precipitation method were made. It was found that only about 53% of zinc and over 70% of the lead could be leached out of the dusts, while the other 47% of zinc and 306 of lead were left in the leaching residues. The zinc and lead in the resultant leaching solution can be effectively and selectively separated. When the weight ratio of sodium sulfide (M. W. = 222-240) to Pb was kept at 1.8, the lead in the solution could be precipitated out quantitatively while all the zinc was remained in the solution. The zinc left in the solution can be further recovered by the addition of extra sodium sulfide with a weight ratio of sodium sulfide to the zinc over 2.6. The resultant filtrate can be recycled to the leaching of dust in the next leaching process.

  5. Sorption properties of hydrous manganese oxide for the removal of radioactive manganese from aqueous solution

    International Nuclear Information System (INIS)

    Radioactive manganese (54Mn) is formed in the structural and clad components of fast nuclear reactors due to the high energy neutron flux encountered in the core. It is a corrosion activation product having a half-life of 312.5 days and gamma energy of 835 keV. Hence, its removal from the waste which generates after washing the above mentioned components is very important. The removal properties of radioactive manganese, 54Mn, from an aqueous solution were studied here in a batch process using hydrous manganese oxide (HMO) coated with polyurethane foam as an inorganic sorbent. The HMO was synthesized by alkaline precipitation in air using manganese sulphate monohydrate and potassium permanganate. The synthesized material was found to be in powder form which took lot of time for settlement in solution; hence, it was coated with polyurethane foam, so that it can be easily used in a batch process. The removal of the radioisotope by the sorbent was studied by varying different experimental conditions such as solution pH, contact time, and effect of presence of other divalent ions. The studies carried out in our laboratory found that the sorption of manganese by hydrous manganese oxide followed pseudo-second order kinetics. On the other hand, with increasing pH of the solution (pH range studied: 1-8), the removal of manganese by the sorbent also increases until pH reaches 4.5, after that the sorption was almost same. The present studies confirmed that in the presence of other divalent ions, e.g. cobalt (ii) ions, the sorption was effected which may be due to the sorption of both the ions on hydrous manganese oxide. The sorption was very fast and more than 95% of manganese was removed within one hour of contact with hydrous manganese oxide. (author)

  6. Formation of quasi-free and bubble positronium states in water and aqueous solutions

    CERN Document Server

    Stepanov, Serge V; Byakov, Vsevolod M; Zvezhinskiy, D S; Subrahmanyam, V S

    2013-01-01

    It is shown that in aqueous solutions a positronium atom is first formed in the quasi-free state, and, after 50-100 ps, becomes localized in a nanobubble. Analysis of the annihilation spectra of NaNO3 aqueous solutions shows that the hydrated electron is not involved in the positronium (Ps) formation.

  7. Effect of Conductivity of the Aqueous Solution on the Size of Printable Nanoparticle

    OpenAIRE

    Mi-Hyun Oh; Nam-Soo Kim; Sun-Mee Kang

    2012-01-01

    Direct writing technology using nano/microsize particles in aqueous solution is currently one of the leading candidates to bring a substantial advancement to the technical arena. However, little is known about an effect of conductivity of the solution including metal ions on nanoparticle size for the direct writing technology. It is believed that conductivity of solution can influence the size of particles in reducing environmental of aqueous solutions. In this study parameters which affect e...

  8. Optical properties of chitosan in aqueous solution of L- and D-ascorbic acids

    Science.gov (United States)

    Malinkina, Olga N.; Shipovskaya, Anna B.; Kazmicheva, Olga F.

    2016-04-01

    The optical properties of aqueous chitosan solutions in L- and D-ascorbic acids were studied by optical rotatory dispersion and spectrophotometry. The specific optical rotation [α] of all chitosan solutions tested was positive, in contrast to aqueous solutions of the ascorbic acid enantiomers, which exhibit an inverse relationship of [α] values. Significant differences in the absolute values of [α] of the chitosan solutions at polymer-acid ratios exceeding the equimolar one were found.

  9. Pseudohydroxide Extraction from Aqueous Sodium Hydroxide Solutions with 3,5-di-tert-Butylphenol in Isopar L Modified with 1-Octanol

    International Nuclear Information System (INIS)

    Pseudohydroxide extraction (PHE) was investigated for recovery of sodium hydroxide (NaOH) from alkaline process solutions. PHE relies on the deprotonation of a lipophilic weak acid by hydroxide ion with concomitant transfer of sodium ion into an organic phase. Contact of the sodium-loaded organic phase with water results in the reconstitution of the extractant in the organic phase and NaOH in the aqueous phase, thus leading to a process in which NaOH equivalents are transferred from an alkaline feed solution to an aqueous stripping solution. In this work, we researched PHE using a process-friendly diluent Isopar L. The lipophilic cation exchanger 3,5-di-tert-butylphenol (35-DTBP) was used as the extractant. The Isopar L diluent was modified with 1-octanol to improve its solvation properties and the solubility of 35-DTBP so that practical Na+ concentrations could be achieved in the process solvent. The PHE mechanism at process-relevant conditions was explored by Raman and FTIR spectroscopic measurements. Electrospray mass spectroscopic results indicated extensive aggregation of the sodium phenolate at high Na+ loading. An equilibrium computer modeling suggested that the Na+ extraction behavior can be largely explained by the formation of 1:1 and 1:2 Na/35-DTBP species in the organic phase. Extraction isotherms obtained using caustic leaching simulant solutions indicate the potential utility of this approach for recycling NaOH from complex alkaline mixtures

  10. A fuel-cell reactor for the direct synthesis of hydrogen peroxide alkaline solutions from H(2) and O(2).

    Science.gov (United States)

    Yamanaka, Ichiro; Onisawa, Takeshi; Hashimoto, Toshikazu; Murayama, Toru

    2011-04-18

    The effects of the type of fuel-cell reactors (undivided or divided by cation- and anion-exchange membranes), alkaline electrolytes (LiOH, NaOH, KOH), vapor-grown carbon fiber (VGCF) cathode components (additives: none, activated carbon, Valcan XC72, Black Pearls 2000, Seast-6, and Ketjen Black), and the flow rates of anolyte (0, 1.5, 12 mL h(-1)) and catholyte (0, 12 mL h(-1)) on the formation of hydrogen peroxide were studied. A divided fuel-cell system, O(2) (g)|VGCF-XC72 cathode|2 M NaOH catholyte|cation-exchange membrane (Nafion-117)|Pt/XC72-VGCF anode|2 M NaOH anolyte at 12 mL h(-1) flow|H(2) (g), was effective for the selective formation of hydrogen peroxide, with 130 mA cm(-2) , a 2 M aqueous solution of H(2)O(2)/NaOH, and a current efficiency of 95 % at atmospheric pressure and 298 K. The current and formation rate gradually decreased over a long period of time. The cause of the slow decrease in electrocatalytic performance was revealed and the decrease was stopped by a flow of catholyte. Cyclic voltammetry studies at the VGCF-XC72 electrode indicated that fast diffusion of O(2) from the gas phase to the electrode, and quick desorption of hydrogen peroxide from the electrode to the electrolyte were essential for the efficient formation of solutions of H(2)O(2)/NaOH. PMID:21400665

  11. Uranium biosorption from aqueous solution onto Eichhornia crassipes.

    Science.gov (United States)

    Yi, Zheng-ji; Yao, Jun; Chen, Hui-lun; Wang, Fei; Yuan, Zhi-min; Liu, Xing

    2016-04-01

    Batch experiments were conducted to investigate the biosorption of U(VI) from aqueous solutions onto the nonliving biomass of an aquatic macrophyte Eichhornia crassipes. The results showed that the adsorption of U(VI) onto E. crassipes was highly pH-dependent and the best pH for U(VI) removal was 5.5. U(VI) adsorption proceeded rapidly with an equilibrium time of 30 min and conformed to pseudo-second-order kinetics. The Langmuir isotherm model was determined to best describe U(VI) biosorption with a maximum monolayer adsorption capacity of 142.85 mg/g. Thermodynamic calculation results indicated that the U(VI) biosorption process was spontaneous and endothermic. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis implied that the functional groups (amino, hydroxyl, and carboxyl) may be responsible for the U(VI) adsorption process, in which the coordination and ion exchange mechanisms could be involved. We conclude that E. crassipes biomass is a promising biosorbent for the removal of uranium pollutants. PMID:26854553

  12. Biosorption of carbaryl from aqueous solution onto Pistia stratiotes biomass

    Science.gov (United States)

    Chattoraj, Soumya; Mondal, Naba Kumar; Das, Biswajit; Roy, Palas; Sadhukhan, Bikash

    2014-03-01

    In this work, adsorption of carbaryl from aqueous solution on Pistia stratiotes biomass was investigated. The effects of operating parameters such as initial concentration, pH, adsorbent dose and contact time on the adsorption of carbaryl were analyzed using response surface methodology. The proposed quadratic model for central composite design fitted very well to the experimental data that it could be used to navigate the design space according to analysis of variance results. Response surface plots were used to determine the interaction effects of main factors and optimum conditions of the process. The optimum adsorption conditions were found to be initial carbaryl concentration = 15.57 mg L-1, pH 2.01, adsorbent dose = 0.72 g and contact time = 30 min. The Langmuir, Freundlich and Temkin isotherm models were applied to the equilibrium data. The maximum biosorption capacity of P. stratiotes biomass for carbaryl was found to be 3.1 mg g-1. The pseudo-second-order kinetic model described the carbaryl biosorption process with a good fitting.

  13. Absolute rate constants of alkoxyl radical reactions in aqueous solution

    International Nuclear Information System (INIS)

    The pulse radiolysis technique was used to generate the alkoxyl radical derived from tert-butyl hydroperoxide (/sup t/BuOOH) in aqueous solution. The reactions of this radical with 2,2'-azinobis(3-ethyl-6-benzothiazolinesulfonate) (ABTS) and promethazine were monitored by kinetic spectroscopy. The unimolecular decay rate constant of the tert-butoxyl radical (/sup t/BuO) was determined to be 1.4 x 106 s-1. On the basis of this value, the rate constants for /sup t/BuO attack on quercetin, crocin, crocetin, ascorbate, isoascorbate, trolox c, glutathione, thymidine, adenosine, guanosine, and unsaturated fatty acids were determined. In addition, the reaction of /sup t/BuO with the polyunsaturated fatty acids (PUFA) was observed by directly monitoring the formation of the fatty acid pentadienyl radicals. Interestingly, the attack of /sup t/BuO on PUFA was found to be faster by about one order of magnitude as compared to the same reaction in a nonpolar solvent

  14. Photo-induced reduction of flavin mononucleotide in aqueous solutions

    Science.gov (United States)

    Song, S.-H.; Dick, B.; Penzkofer, A.

    2007-01-01

    The photo-induced reduction of flavin mononucleotide (FMN) in aqueous solutions is studied by absorption spectra measurement under aerobic and anaerobic conditions. Samples without exogenous reducing agent and with the exogenous reducing agents ethylene-diamine-tetraacetic acid (EDTA) and dithiothreitol (DTT) are investigated. Under anaerobic conditions the photo-induced reduction with and without reducing agents is irreversible. Under aerobic conditions the photo-reduction without added reducing agent is small compared to the photo-degradation, and the photo-reduction of FMN by the reducing agents is reversible (re-oxidation in the dark). During photo-excitation of FMN the dissolved oxygen is consumed by singlet oxygen formation and subsequent chemical reaction. After light switch-off slow re-oxidation (slow absorption recovery) occurs due to air in-diffusion from surface. EDTA degradation by FMN excitation leads to oxygen scavenging. The quantum efficiencies of photo-reduction under aerobic and anaerobic conditions are determined. The re-oxidation of reduced FMN under aerobic conditions and due to air injection is investigated.

  15. Photo-induced reduction of flavin mononucleotide in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Song, S.-H.; Dick, B. [Institut fuer Physikalische und Theoretische Chemie, Universitaet Regensburg, 93053 Regensburg (Germany); Penzkofer, A. [Institut II - Experimentelle und Angewandte Physik, Universitaet Regensburg, Universitaetstrasse 31, D-93053 Regensburg (Germany)], E-mail: alfons.penzkofer@physik.uni-regensburg.de

    2007-01-25

    The photo-induced reduction of flavin mononucleotide (FMN) in aqueous solutions is studied by absorption spectra measurement under aerobic and anaerobic conditions. Samples without exogenous reducing agent and with the exogenous reducing agents ethylene-diamine-tetraacetic acid (EDTA) and dithiothreitol (DTT) are investigated. Under anaerobic conditions the photo-induced reduction with and without reducing agents is irreversible. Under aerobic conditions the photo-reduction without added reducing agent is small compared to the photo-degradation, and the photo-reduction of FMN by the reducing agents is reversible (re-oxidation in the dark). During photo-excitation of FMN the dissolved oxygen is consumed by singlet oxygen formation and subsequent chemical reaction. After light switch-off slow re-oxidation (slow absorption recovery) occurs due to air in-diffusion from surface. EDTA degradation by FMN excitation leads to oxygen scavenging. The quantum efficiencies of photo-reduction under aerobic and anaerobic conditions are determined. The re-oxidation of reduced FMN under aerobic conditions and due to air injection is investigated.

  16. Direct Photolysis of Chlorophenols In Aqueous Solution By Ultraviolet Excilamps

    Science.gov (United States)

    Matafonova, Galina; Philippova, Natalya; Batoev, Valeriy

    2011-08-01

    The direct photolysis of 2-chlorophenol (2-CP), 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) in model aqueous solution was studied using UV XeBr (282 nm) and KrCl (222 nm) excilamps. The highest pseudo-first order rate constants and quantum yields were found for molecular form of 4-CP (at pH 2 and 5.7) and anionic forms of 2-CP and 2,4-DCP (at pH 11) when irradiated by XeBr excilamp. The maximum removal efficiency of molecular form of 2-CP and 2,4-DCP with the lowest UV dose of absorbed energy was observed using KrCl excilamp. On the contrary, the XeBr excilamp required the lowest dose (˜2 Jṡcm-2) for complete degradation of molecular 4-CP and anionic 2-CP. The highest removal efficiency of anionic form of 4-CP (65%) was achieved when using KrCl excilamp.

  17. Pulse radiolysis study of 5-amino tetrazole in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Dey, G.R.; Naik, D.B.; Kishore, K.; Moorthy, P.N. [Bhabha Atomic Research Centre, Bombay (India). Chemistry Div.

    1996-04-01

    Reactions of e{sub aq}{sup -}, H-atoms and {sup .}OH radicals have been studied with 5-amino tetrazole (ATZ) in aqueous solution. e{sub aq}{sup -}reaction in the pH range 4.5-9 did not give any light absorbing transient species but NH{sub 3} was obtained as a product indicating that the site for e{sub aq}{sup -} reactions is the -NH{sub 2} group. In the case of {sup .}OH radical reaction, a transient spectrum with {lambda}{sub max} at 340 nm was obtained at pH 7.5. An identical spectrum was produced by the reaction of SO{sub 4}{sup -.} radicals with ATZ at neutral pH indicating that both {sup .}OH radical and SO{sub 4}{sup -.} radical react by one electron oxidation. The rate constants for the reactions of e{sub aq}{sup -} and {sup .}OH with ATZ at pH 7.5 were found to be 6 x 10{sup 7} and 5.2 x 10{sup 9} dm{sup 3} mol{sup -1} s{sup -1} respectively, whereas the rate constant for H-atom reaction may be < 10{sup 7} dm{sup 3} mol{sup -1} s{sup -1}. (author).

  18. Pulse radiolysis study of 5-amino tetrazole in aqueous solutions

    International Nuclear Information System (INIS)

    Reactions of eaq-, H-atoms and .OH radicals have been studied with 5-amino tetrazole (ATZ) in aqueous solution. eaq-reaction in the pH range 4.5-9 did not give any light absorbing transient species but NH3 was obtained as a product indicating that the site for eaq- reactions is the -NH2 group. In the case of .OH radical reaction, a transient spectrum with λmax at 340 nm was obtained at pH 7.5. An identical spectrum was produced by the reaction of SO4-. radicals with ATZ at neutral pH indicating that both .OH radical and SO4-. radical react by one electron oxidation. The rate constants for the reactions of eaq- and .OH with ATZ at pH 7.5 were found to be 6 x 107 and 5.2 x 109 dm3 mol-1 s-1 respectively, whereas the rate constant for H-atom reaction may be 7 dm3 mol-1 s-1. (author)

  19. Removal of uranyl ions from aqueous solutions using barium titanate

    International Nuclear Information System (INIS)

    Remediation of water sources contaminated with radioactive waste products is a major environmental issue that demands new and more efficient technologies. For this purpose, we report a highly efficient ion-exchange material for the removal of radioactive nuclides from aqueous solutions. The kinetic characteristics of adsorption of uranyl ions on the surface of barium titanate were investigated using a spectrophotometric method under a wide range of conditions. By controlling the pH it was possible to exert fine control over the speciation of uranium, and by optimizing the temperature and grain size of the exchanger, almost total removal was achieved in a matter of just hours. The highest efficiency (>90 % removal) was realized at high temperature (80 deg C). Moreover, the effect of competitive ion adsorption from a range of different cations and anions was quantified. Adsorption was found to follow first-order kinetics and both Freundlich and Langmuir isotherms could be applied to this system. The results of a mathematical treatment of the kinetic data combined with the observation that adsorption was independent of stirring speed and dependent on the ion-exchanger grain size, indicate that the dominant mechanism influencing adsorption is particle spreading. The adsorption behavior was not influenced by exposure to high-intensity gamma radiation, indicating potential for use of this ion-exchanger in systems containing radioactive material. These results will be of use in the development of uranium extraction systems for contaminated water sources. (author)

  20. Intrinsic viscosity and related parameters of PEOX aqueous solutions

    Science.gov (United States)

    Tothova, J.; Paulovicova, K.; Kopcansky, P.; Timko, M.; Lisy, V.

    2015-12-01

    Poly(2-ethyl-2-oxazoline) (PEOX) is a polymer used in many applications. In this work we present the steady-state shear viscosity experiment on low-concentrated high-molecular PEOX aqueous solutions near the presumed theta temperature. In the interpretation of these experiments we consider the polymer being partially permeable to water, with a finite draining parameter h, contrary to the usual approach when the polymer coil is assumed to be impermeable and h approaches the infinite value. By this way we have determined important polymer parameters, such as the gyration and hydrodynamic radii. The calculated Huggins coefficient kH was compared to its value extracted from the measured intrinsic viscosity. We have found that at the temperature 20°C the theoretically predicted kH(h) agrees with the experiment. Since the theory is built for the theta condition, we propose that the theta temperature for PEOX is notably lower than 25°C known from the previous studies. This finding is supported by our measurements of the dependence of the intrinsic viscosity on the PEOX molecular weight.

  1. Ethylbenzene Removal by Carbon Nanotubes from Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Bijan Bina

    2012-01-01

    Full Text Available The removal of ethylbenzene (E from aqueous solution by multiwalled, single-walled, and hybrid carbon nanotubes (MWCNTs, SWCNTs, and HCNTs was evaluated for a nanomaterial dose of 1 g/L, concentration of 10–100 mg/L, and pH 7. The equilibrium amount removed by SWCNTs (E: 9.98 mg/g was higher than by MWCNTs and HCNTs. Ethylbenzene has a higher adsorption tendency on CNTs, so that more than 98% of it adsorbed in first 14 min, which is related to the low water solubility and the high molecular weight. The SWCNTs performed better for ethylbenzene sorption than the HCNTs and MWCNTs. Isotherms study indicates that the BET isotherm expression provides the best fit for ethylbenzene sorption by SWCNTs. Carbon nanotubes, specially SWCNTs, are efficient and rapid adsorbents for ethylbenzene which possess good potential applications to maintain high-quality water. Therefore, it could be used for cleaning up environmental pollution to prevent ethylbenzene borne diseases.

  2. Lifetimes of -halo and -azidobenzyl carbocations in aqueous solution

    Indian Academy of Sciences (India)

    R Sanjeev; V Jagannadham

    2002-02-01

    The title cations were produced in aqueous solution by chemical initiation (solvolysis) of benzyl-gem-dihalides and benzyl-gem-diazides. The solvolysis reactions of benzyl-gem-dihalides and benzyl-gem-diazides in water proceed by a stepwise mechanism through -halobenzyl carbocation and -azidobenzyl carbocation intermediates, which are captured by water to give the corresponding carbonyl compounds as the sole detectable products. Rate constant ratio / (M-1) for partitioning of the carbocation between reaction with halide/azide ion and reaction with water is determined by analysis of halide/azide common ion inhibition of the solvolysis reaction. The rate constants (s-1) for the reaction of the cation with solvent water were determined from the experimental values of / and solv, for the solvolysis of the benzyl-gem-dihalides and benzyl-gem-diazides respectively, using = 5 × 109 M-1 s-1 for diffusion-limited reaction of halide/azide ion with -substituted benzyl carbocations. The values of 1/ are thus the lifetimes of the -halobenzyl carbocations and -azidobenzyl carbocations respectively.

  3. Sonochemical degradation of organophosphorus pesticide in dilute aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    Robina Farooq; FENG Kai-lin; S. F. Shaukat; HUANG Jian-jun

    2003-01-01

    Ultrasonic irradiation was found to accelerate the rate of hydrolysis of omethoate in aqueous solution over the pH range of 2-12. Process parameters studied include pH, steady-state temperature, concentration, and the type of gases. Greater than 96% hydrolysis was observed in 30 minutes through this process and the rate of destruction increased with the help of more soluble and low thermal inert gas. So with Krypton, omethoate was found to undergo rapid destruction as compared with Argon. In the presence of ultrasound, the observed first-order rate of hydrolysis of omethoate is found to be independent of pH. The formation of transient supercritical water(SCW) appears to be an important factor in the acceleration of chemical reactions in the presence of ultrasound. A detailed chemical reaction mechanism for omethoate destruction in water was formulated. Experimental results and theoretical kinetic mechanism demonstrated that the most of the omethoate undergo destruction inside the cavitating holes. A very less effect of temperature on the degradation of omethoate within a temperature range of 20-70℃ proves that a small quantity of omethoate undergoes secondary destruction in the bulk liquid.

  4. ADSORPTION FROM AQUEOUS SOLUTION ONTO NATURAL AND ACID ACTIVATED BENTONITE

    Directory of Open Access Journals (Sweden)

    Laila Al-Khatib

    2012-01-01

    Full Text Available Dyes have long been used in dyeing, paper and pulp, textiles, plastics, leather, paint, cosmetics and food industries. Nowadays, more than 100,000 commercial dyes are available with a total production of 700,000 tones manufactured all over the world annually. About 10-15% of dyes are being disposed off as a waste into the environment after dyeing process. This poses certain hazards and environmental problems. The objective of this study is to investigate the adsorption behavior of Methylene Blue (MB from aqueous solution onto natural and acid activated Jordanian bentonite. Both bentonites are firstly characterized using XRD, FTIR and SEM techniques. Then batch adsorption experiments were conducted to investigate the effect of initial MB concentration, contact time, pH and temperature. It was found that the percentage of dye removal was improved from 75.8% for natural bentonite to reach 99.6% for acid treated bentonite. The rate of MB removal followed the pseudo second order model with a high correlation factor. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The Langmuir isotherm model was found more representative. The results indicate that bentonite could be employed as a low cost adsorbent in wastewater treatment for the removal of colour and dyes.

  5. Electric dichroism transients of aqueous solutions of DNA

    Energy Technology Data Exchange (ETDEWEB)

    Bertolotto, J A; Corral, G M; Farias de La Torre, E M; Roston, G B [Department of Physics, Faculty of Natural Sciences, National University of La Pampa, Santa Rosa, La Pampa (Argentina)

    2010-12-15

    In this work we develop a theory of reduced electric linear dichroism transients of DNA fragments in aqueous solution. The DNA fragments are modelled as rigid 'bent-rod molecules' (BRM) with the following physical parameters: electric charge, electric polarizability tensors and hydrodynamical ones, and the average transition probability tensor per molecule. In order to study the growth and decay of electric dichroism transients, the orientational distribution function of the molecules is needed. This function is obtained by solving the time-dependent Fokker-Planck equation in the presence of a low electric field E, using a perturbation method and the Fourier method with time-dependent coefficients. In our calculations the origin of the coordinate system is the mass centre of the BRM. With respect to this centre, the electric dipole moment of the molecule is zero. The developed theory adequately explains the experimental results. We show that the theoretical approach used in this work is equivalent to the one applied in the Brownian dynamics simulation work performed by Porschke and co-workers. We also analyse the effect of a possible electric dipole moment on the transients of the reduced electric linear dichroism in DNA bent fragments.

  6. Adsorption of naphthalene onto sonicated talc from aqueous solutions.

    Science.gov (United States)

    Sener, Savaş; Ozyilmaz, Azat

    2010-06-01

    The adsorption behavior of naphthalene onto naturally hydrophobic talc from aqueous solution was investigated in this study. The natural talc was first pretreated by sonication to improve the surface characteristics and enhance the uptake capacity by increasing the specific surface area (SSA) of talc. The naphthalene uptake of talc was found as 276 mg g(-1) and increased to 359 mg g(-1) after the sonication. Adsorption studies also showed that the adsorption of naphthalene onto the sonicated talc was not affected by changes in pH suggesting that the main driving forces for naphthalene adsorption onto talc was hydrophobic bonding rather than electrostatic force. The pseudo-first and pseudo-second orders and intraparticle diffusion equation were used to evaluate the kinetic data and the constants were determined. Adsorption process of naphthalene onto talc followed the pseudo-second-order rate expression for different initial naphthalene concentrations. The Langmuir and Freundlich isotherm models were used to model the isotherm data for their applicability. The Freundlich isotherm best fitted for the adsorption of naphthalene onto talc. PMID:20163977

  7. Methylene blue adsorption from aqueous solution by dehydrated peanut hull

    International Nuclear Information System (INIS)

    Dyes are colour organic compounds which can colorize the other substances. These substances usually presents in the effluent water of many industries, such as textiles, leather, paper, printing and cosmetics. To observe the potential feasibility of removing colour, peanut hull as an agricultural by-product was dehydrated with sulphuric acid (DPH) and used for adsorption of methylene blue (MB) from aqueous solution. The effects of various parameters such as initial methylene blue concentrations, temperatures and particle sizes were examined and optimal experimental conditions were determined. Adsorption data were well described by the Langmuir model, although they could be modelled by the Freundlich model as well. The adsorption process followed the pseudo-second order kinetic model. The mass transfer model as intraparticle diffusion was applied to the experimental data to examine the mechanisms of rate controlling step. It was found that at the higher initial MB concentration, intraparticle diffusion is becoming significant controlling step. The thermodynamic constants of the adsorption process were also evaluated by using the Langmuir constants related to the equilibrium of adsorption at different temperatures. The results in this study indicated that dehydrated peanut hull was a good adsorbent for removing methylene blue

  8. Formation and reactivity of phenylperoxyl radicals in aqueous solutions

    International Nuclear Information System (INIS)

    The reaction of phenyl radicals with oxygen, to produce phenylperoxyl radicals, and the reactions of several phenylperoxyl radicals with a number of organic compounds in aqueous solutions have been studied by pulse radiolysis. Phenyl radicals were produced by reduction of aryl halides with hydrated electrons. The rate constant for the reaction of 4-carboxyphenyl with O2 was determined from the rate of buildup of the peroxyl radical absorption at 520 nm as a function of [O2] and found to be 1.6 x 109 L mol-1 s-1. Phenyl radicals react with 2-PrOH by H abstraction; a rate constants of 4 x 106 L mol-1 s-1 was determined for 4-carboxyphenyl by competition with the reaction of this radical with O2. Phenylperoxyl radicals react with 4-methoxyphenolate ions, trolox C(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), ascorbate ions, chlorpromazine, and ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate ion)] by one-electron oxidation. The rate constants for such reactions, determined from the rate of formation of the one-electron oxidation product as a function of substrate concentration, were found to be near 108-109 L mol-1 s-1. 24 refs., 4 figs., 1 tab

  9. Growth kinetics of sulfur nanoparticles in aqueous surfactant solutions.

    Science.gov (United States)

    Chaudhuri, Rajib Ghosh; Paria, Santanu

    2011-02-15

    Sulfur is an important element has many practical applications when present as nanoparticles. Despite the practicable applications, limited studies are available in the literature related to synthesis of sulfur nanoparticles. Growth kinetics of colloidal sulfur particles synthesized from aqueous solutions using different surfactants have been studied here. The effects of different parameters such as reactant concentration, temperature, sonication, types of acids, types of surfactants, and even surfactant concentration are studied on the growth kinetics. Since the reaction rate is fast, particle growth depends on the parameters which affect diffusion of sulfur molecules. There is a linear relationship found among the reactant concentration and the particle coarsening rate constant. The growth kinetics was studied in the presence of different surfactants such as nonionic (poly(oxyethylene) p-tert-octylphenyl ether, TX-100), anionic (sodium dodecylbenzene sulfonate, SDBS), cationic (cetyltrimethyammonium bromide, CTAB) and results show the coarsening constant changes according to the following order: water>TX-100>SDBS>CTAB. The particle growth rate also depends on the surfactant concentration, coarsening rate constant decreases with the increase in surfactant concentration and become constant close to the critical micellar concentration (CMC). The coarsening rate constant also highly depends on the types of acid used as catalyst. PMID:21147482

  10. Fenton Oxidation of Methyl Violet in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Saeedeh Hashemian

    2013-01-01

    Full Text Available In this study, oxidative discoloration of methyl violet (MV dye in aqueous solution has been studied using Fenton (Fe2+/H2O2 process. The parameters such as concentration of Fe2+, H2O2, MV, temperature, and Cl− and ions that affected of discoloration in Fenton process were investigated. The rate of degradation is dependent on initial concentration of Fe2+ ion, initial concentration of H2O2, and pH of media. Discoloration of MV was increased by increasing the temperature of reaction. Optimized condition was determined and it was found that the obtained efficiency was about 95.5% after 15 minutes of reaction at pH 3. TOC of dye sample, before and after the oxidation process, was determined. TOC removal indicates partial and significant mineralization of MV dye. The results of experiments showed that degradation of MV dye in Fenton oxidation can be described with a pseudo-irst-order kinetic model. The thermodynamic constants of the Fenton oxidation process were evaluated. The results implied that the oxidation process was feasible, spontaneous, and endothermic.

  11. Cadmium Removal from Aqueous Solutions by Ground Pine Cone

    Directory of Open Access Journals (Sweden)

    H Izanloo, S Nasseri

    2005-01-01

    Full Text Available A study on the removal of cadmium ions from aqueous solutions by pine cone was conducted in batch conditions. Kinetic data and equilibrium removal isotherms were obtained. The influence of different experimental parameters such as contact time, initial concentration of cadmium, pine cone mass and particle size, and temperature on the kinetics of cadmium removal was studied. Results showed that the main parameters that played an important role in removal phenomenon were initial cadmium concentration, particle size and pine cone mass. The necessary time to reach equilibrium was between 4 and 7 hours based on the initial concentration of cadmium. The capacity of cadmium adsorption at equilibrium increased with the decrease of pine cone particle size. The capacity of cadmium adsorption at equilibrium by pine cone increased with the quantity of pine cone introduced (1–4 g/L. Temperature in the range of 20-30°C showed a restricted effect on the removal kinetics (13.56 mg/g at 20°C and a low capacity of adsorption about 11.48 mg/g at 30°C. The process followed pseudo second-order kinetics. The cadmium uptake of pine cone was quantitatively evaluated using adsorption isotherms. Results indicated that the Langmuir model gave a better fit to the experimental data in comparison with the Freundlich equation.

  12. Flash photolysis of chlorine dioxide in aqueous solution

    International Nuclear Information System (INIS)

    The primary process when aqueous solutions of chlorine dioxide are flash photo-lysed by light with a wave length greater than 270 nm is: OClO →hν ClO (2Π) + O (3P). The photochemical decomposition is characterized by the formation of small quantities of O (3P) atoms and of equal amounts of chlorine atoms and molecular oxygen, the latter originating in the reaction: ClOO → Cl + O2. The isomer ClOO is formed by the germinate recombination of ClO and O, a process which is twice as important as diffusion of the fragments into the mass of the solution and one which represents 30 per cent of the decomposition of the chlorine dioxide. Under our experimental conditions, the lifetime of the ClOO is less than one microsecond. Chlorine atoms are precursors of Cl2O2, whose UV absorption spectrum has been determined, and which is formed by the reactions: Cl + OClO → Cl2O2; Cl + Cl- → Cl2-; Cl2- + OClO → Cl2O2 + Cl- k = (1,0 ±0,1) 109 M-1s-1. Cl2O2 disappears by a first-order process which leads to the formation of the ions Cl- and ClO3-. Competition between the reactions: O (3P) + O2 → O3; O (3P) + OClO → ClO3. (kOClO + O)/(kO2 + O) = 1.85±0.25 has been studied and the molar extinction coefficient of ClO3 determined at its absorption maximum (255 nm): ε255nm = (920 ± 90) M-1 cm-1. (author)

  13. Ethylbenzene Removal from Aqueous Solutions by Nano Magnetic Particles

    Directory of Open Access Journals (Sweden)

    Mostafa Hadei

    2016-02-01

    Full Text Available Background and Objectives : Ethylbenzene (EB is a dangerously organic compound which the presence of this pollutant in water solutions can be considered as an environmental and public health hazard. In this study, nano magnetic particles (Fe 3 O 4 were used as an adsorbent to remove ethylbenzene from aqueous solutions. Methods : The specification of the adsorbent was investigated by transmission electronic microscope (TEM and X-ray diffraction (XRD pattern. A 4×4 factorial design including initial concentration of ethylbenzene, nano magnetic particles dose, contact time and pH were studied. Results : The results showed that the maximum ethylbenzene removal by nano magnetic particles was achieved in the following conditions; 100 mg.L -1 , 2000 mg.L -1 , 20 minutes and 8, in initial concentration, nano magnetic concentration, contact time and pH respectively. The most amounts of ethylbenzene adsorption and distribution ratio in optimum condition was 49.9 mg.g -1 and 261.9 l.g -1 respectively. The results demonstrated that the removal rate of ethylbenzene was higher in batch (99.8 % rather than continuous (97.4% condition. Conclusion: the removal rate of ethylbenzene was higher in batch rather than continuous condition.The study of isotherm showed that adsorption data follow up linear isotherm. Comparing adsorption rate of NM particles and other adsorbents proved that Fe 3 o 4 , as a material with high capacity of adsorption can apply for removing ethylbenzene as an efficient and also cheap adsorbent.  

  14. XANES Demonstrates the Release of Calcium Phosphates from Alkaline Vertisols to Moderately Acidified Solution.

    Science.gov (United States)

    Andersson, Karl O; Tighe, Matthew K; Guppy, Christopher N; Milham, Paul J; McLaren, Timothy I; Schefe, Cassandra R; Lombi, Enzo

    2016-04-19

    Calcium phosphate (CaP) minerals may comprise the main phosphorus (P) reserve in alkaline soils, with solubility dependent on pH and the concentration of Ca and/or P in solution. Combining several techniques in a novel way, we studied these phenomena by progressively depleting P from suspensions of two soils (low P) using an anion-exchange membrane (AEM) and from a third soil (high P) with AEM together with a cation-exchange membrane. Depletions commenced on untreated soil, then continued as pH was manipulated and maintained at three constant pH levels: the initial pH (pHi) and pH 6.5 and 5.5. Bulk P K-edge X-ray absorption near-edge structure (XANES) spectroscopy revealed that the main forms of inorganic P in each soil were apatite, a second more soluble CaP mineral, and smectite-sorbed P. With moderate depletion of P at pHi or pH 6.5, CaP minerals became more prominent in the spectra compared to sorbed species. The more soluble CaP minerals were depleted at pH 6.5, and all CaP minerals were exhausted at pH 5.5, showing that the CaP species present in these alkaline soils are soluble with decreases of pH in the range achievable by rhizosphere acidification. PMID:26974327

  15. Study on 99Mo production by solution irradiation method (1). Characterization of aqueous molybdate solutions under unirradiation

    International Nuclear Information System (INIS)

    The solution irradiation method is proposed as a new production technique for 99Mo, which is the parent nuclide of 99mTc used as a radiopharmaceutical. In this new method, an aqueous molybdenum solution is irradiated with neutrons in a nuclear reactor, and more efficient and lower-cost 99Mo production than conventional 99Mo production can be realized by using the 98Mo (n, γ) 99Mo reaction and the molybdenum adsorbent of PZC. Aiming at the practical application of this method, unirradiation tests, gamma-ray irradiation tests, and neutron irradiation tests should be needed in order to characterize the aqueous molybdenum solution as the irradiation target. In the present study, the schematic structure of the 99Mo production system with the new method was investigated, and two kinds of aqueous molybdate solutions (an aqueous ammonium molybdate solution and an aqueous potassium molybdate solution) were selected as candidates for the irradiation target of the new method, and then the molybdenum adsorption performance of PZC with the solutions, the properties of the molybdates to be materials of the solutions, the compatibility between the solutions and structural materials, and the chemical stability of the solutions were investigated under unirradiation. As a result, it was found that the aqueous potassium molybdate solution is promising as the target in terms of the molybdenum content, the compatibility with the structural materials, and the chemical stability and that the aqueous ammonium molybdate solution with suitable pH adjustment has an aptitude for the target. In addition, it became clear that stainless steel having good compatibility with the solutions has a potential as the structural material of capsules, pipes and so on. (author)

  16. Formation of an 8-hydroxyguanine moiety in deoxyribonucleic acid on gamma-irradiation in aqueous solution

    International Nuclear Information System (INIS)

    Isolation and characterization of a novel radiation-induced product, i.e., the 8-hydroxyguanine residue, produced in deoxyribonucleic acid (DNA), 2'-deoxyguanosine, and 2'-deoxyguanosine 5'-monophosphate by gamma-irradiation in aqueous solution, are described. For this purpose, gamma-irradiated DNA was first hydrolyzed with a mixture of four enzymes, i.e., DNase I, spleen and snake venom exonucleases, and alkaline phosphatase. Analysis of the resulting mixture by capillary gas chromatography-mass spectrometry after trimethylsilylation revealed the presence of a product, which was identified as 8-hydroxy-2'-deoxyguanosine on the basis of the typical fragment ions of its trimethylsilyl (Me3Si) derivative. This product was then isolated by using reversed-phase high-performance liquid chromatography. The UV and proton nuclear magnetic resonance spectra taken from the isolated product confirmed the structure suggested by the mass spectrum of its Me3Si derivative. The yield of 8-hydroxyguanine was also measured. Its mechanism of formation is believed to involve OH radical addition to the C-8 position of guanine followed by oxidation of the radical adduct

  17. CRIEPI's research results (2006-2011) and clarified future issues on alteration behavior of bentonite barrier by alkaline solutions

    International Nuclear Information System (INIS)

    In radioactive waste disposal facilities, bentonite barrier would be altered by alkaline solutions which arise by leaching of cementitious materials. Consequently suitable properties of the bentonite barrier would be degraded for a long time period. In CRIEPI, the investigation on the alteration of the bentonite under alkaline conditions was started in 2006, and several CRIEPI reports have been published. Specifically, we have investigated the kinetics of montmorillonite dissolution, the mineralogical alteration of compacted bentonite (with high- and low-dry density) and the change of permeability of the compacted bentonite (with high- and low-dry density) during alteration under the alkaline conditions. Furthermore, stability of saponite, which has similar physical properties to the bentonite, under the alkaline conditions was also examined. In this report, we show the outline of those research results, and lay out the clarified future issues extracted from our results. Ten clarified future issues were divided three categories as follows: 1) the estimation of the alteration behavior of the bentonite by alkaline solutions, 2) the elucidation of the mechanism of physical properties (e.g., permeability, swelling properties and mechanistic properties) change of the compacted bentonites during alteration, and 3) the development of the model building and simulation technology concerning the change in physical properties during alteration under alkaline conditions. (author)

  18. γ-radiolysis of 1,3-dimethyluracil in N2O-saturated aqueous solutions

    International Nuclear Information System (INIS)

    The γ-radiolysis of N2O-saturated aqueous solutions generates OH radicals and a small amount of H atoms. In 1,3-dimethyluracil solutions (10-3 M) these radicals add mainly to the 5-position of the C(5)-C(6) double bond of the solute. The resulting products have been identified by GC-MS after trimethylsilylation. The major products (G values in brackets) are dimers of the C(5)-OH-adduct radicals (3.4), 5,6-dihydro-5,6-dihudroxy-1,3-dimethyluracil (0.85), 5,6-dihydro-5-hydroxy-1,3-dimethyluracil (0.75), dimer of the C(5)-OH-adduct with the C(5)-H-adduct radical (0.2) and 5,6-dihydro-6-hydroxy-1,3-dimethyluracil (0.2). G(1,3-dimethyluracil consumption) has been found to be 5.7. The major reaction in this system is the dimerisation of the primary radicals. To a small extent the primary radicals also disproportionate by electron transfer to give the glycol 5,6-dihydro-5,6-dihydrocy-1,3-dimethyluracil as one of the products. Radiolytically formed H2O2 which could oxidise the C(5)-OH-adduct radical does not contribute to the formation of the glycol because the H2O2 yield is not reduced with respect to its expected ''molecular yield'' (G = 0.075). In contrast to the uracil system where it has been reported that drastic changes in radiolytic yields occur on going from neutral to alkaline irradiation conditions no such changes have been observed with 1,3-dimethyluracil. However, an acid-catalysed rearrangement from the C(5)-OH-adduct to the C(6)-OH-adduct radical is observed in the present system. (orig.)

  19. Gold leaching with elemental sulfur in alkaline solutions under oxygen pressure

    Institute of Scientific and Technical Information of China (English)

    方兆珩; 石伟

    2003-01-01

    A gold leaching process by using oxidation products of elemental sulfur in alkaline solutions was pro-posed and investigated. A gold concentrate and a residue from an arsenic refractory gold concentrate by acidic oxida-tion leaching were tested. The residue contains 16.3% elemental sulfur and no more elemental sulfur was added intests. For the concentrate elemental sulfur was added before leaching tests. The leaching ratio of gold depends main-ly on the initial equivalent ratio of elemental sulfur to hydroxyl ions, the consumption of oxygen and the reactiontemperature in the process. Analysis of the experimental results shows that thiosulfate is the majority complexingreagent for gold in the process. Over 90% gold was leached from the residue and 82%-87% from the concentrate byusing this process.

  20. Reomoval of Heavy Metals from Aqueous Solutions using Bascteria

    Institute of Scientific and Technical Information of China (English)

    HUANGMin-sheng; PANjing; 等

    2001-01-01

    The accumulation of heavy metals by microbial biomass with high surface area-to-volume ratio holds great potential for heavy metal removal in both soluble and particular forms,especially when the heavy metal concentrations are low(<50mg/L),E.coli and B.Subtilis are effective agents for metal removal.We further investigated the effect of pH,temperature,equilibration time,and pre-treatment reagents on the removal of pH(Ⅱ),Cd(Ⅱ) and Cr(VI) from aqueous solutions by E.Coli and B.subtilis.E.coli and B.subtilis were cultivated for 60 hours,the experimentally determined optimal cultivation time before they were used in metal removal experiments,Under the optimal conditions of pH 6.0,equilibration temperature 30℃ and equilibration time 1 hour,63.39% and 69.90%Cd(Ⅱ) can be removed by E.coli and B.subtilis.Under the optimal conditions of pH5.5,equilibration temperature 30℃ and equliobration time 1 hour,68.51% and 67.36% pB(Ⅱ) can be removed by E.coli and B.subtilis.And under the optimal conditons of pH5.5,equilibration temperature 30℃,and equilibration time 1 hour,60.26% and 54.56% Cr(VI) can be removed by E.coli and B.subtilis.Chemical treatment of cultivated bacteria(0.1mol/L NaOH,0.1mol/L HCl,30% ethanol,and distilled water)affects the efficiency of metal removal by E.coli and B.subtilis,pretreatment of biomass by NaOH enhanced Cd(Ⅱ),Pb(Ⅱ)and Cr(VI) removal,while preteatment by HCl,ethanol and distilled water reduced Ca(Ⅱ) ,Pb(Ⅱ) and Cr(VI) removal,For metal removal from industrial waste discharges,pretreated biomass of E.coli can remove 68.5% of Cd and 58.1% of Cr from solutions,while pretreated biomass of B.subtilis can remove 62.6% of Cd and 57% of Cr from Solutions.

  1. Inhibition of cobalt active dissolution by benzotriazole in slightly alkaline bicarbonate aqueous media

    International Nuclear Information System (INIS)

    The efficiency of benzotriazole as inhibiting agent for the corrosion of cobalt was probed at pH ranging from 8.3 to 10.2 in a sodium bicarbonate solution, chosen to simulate mild natural environments. From electrochemical, Raman spectroscopy, atomic force microscopy and ellipsometry experiments, we have demonstrated that benzotriazole markedly affects the electrodissolution reactions, which become modeled by the formation of a [Co(II)(BTA)2.H2O] n film according to two different mechanisms. Surface-enhanced Raman spectroscopy has shown that the polarization of a cobalt electrode at cathodic potentials with respect to its potential of zero charge allows a mechanism of specific adsorption of the neutral form of benzotriazole to take place through a suspected metal-to-molecule electron transfer and which follows Frumkin's adsorption isotherms. At the onset of the anodic dissolution, some experimental evidence suggests that these adsorbed neutral benzotriazole molecules deprotonate to yield a very thin [Co(II)(BTA)2.H2O] n polymer-like and water-insoluble protective film, responsible for the inhibition of active dissolution processes occurring at slightly more anodic potentials. In the anodic dissolution region, deprotonated benzotriazole species present in the bulk solution favors the formation of a multilayered [Co(II)(BTA)2.H2O] n film, which also contributes to the inhibition of any further cobalt dissolution usually observed at higher electrode potentials

  2. Ultrasound assisted enzymatic depolymerization of aqueous guar gum solution.

    Science.gov (United States)

    Prajapat, Amrutlal L; Subhedar, Preeti B; Gogate, Parag R

    2016-03-01

    The present work investigates the effectiveness of application of low intensity ultrasonic irradiation for the intensification of enzymatic depolymerization of aqueous guar gum solution. The extent of depolymerization of guar gum has been analyzed in terms of intrinsic viscosity reduction. The effect of ultrasonic irradiation on the kinetic and thermodynamic parameters related to the enzyme activity as well as the intrinsic viscosity reduction of guar gum using enzymatic approach has been evaluated. The kinetic rate constant has been found to increase with an increase in the temperature and cellulase loading. It has been observed that application of ultrasound not only enhances the extent of depolymerization but also reduces the time of depolymerization as compared to conventional enzymatic degradation technique. In the presence of cellulase enzyme, the maximum extent of depolymerization of guar gum has been observed at 60 W of ultrasonic rated power and ultrasonic treatment time of 30 min. The effect of ultrasound on the kinetic and thermodynamic parameters as well as the molecular structure of cellulase enzyme was evaluated with the help of the chemical reaction kinetics model and fluorescence spectroscopy. Application of ultrasound resulted in a reduction in the thermodynamic parameters of activation energy (Ea), enthalpy (ΔH), entropy (ΔS) and free energy (ΔG) by 47%, 50%, 65% and 1.97%, respectively. The changes in the chemical structure of guar gum treated using ultrasound assisted enzymatic approach in comparison to the native guar gum were also characterized by FTIR. The results revealed that enzymatic depolymerization of guar gum resulted in a polysaccharide with low degree of polymerization, viscosity and consistency index without any change in the core chemical structure which could make it useful for incorporation in food products. PMID:26584988

  3. Arsenate removal from aqueous solution using synthetic siderite

    International Nuclear Information System (INIS)

    The study was carried out to evaluate the feasibility of synthetic siderite for As(V) removal from aqueous solution. Batch experiments were performed to investigate effects of various experimental parameters such as contact time (10 min-8 h), initial As(V) concentration (0.5-60.0 mg/L), temperature (15, 25, 35 and 45 deg. C), pH (2.0-10.0) and the presence of competing anions on As(V) adsorption on the synthetic siderite. Kinetic data reveal that the uptake rate of As(V) was rapid at the beginning and 90% adsorption was completed within 10 min at 45 deg. C and equilibrium was achieved within 3 h. The adsorption process was well described by pseudo-second-order kinetics model. The adsorption data better fitted Langmuir isotherm at low temperatures (i.e., 15 and 25 deg. C), while Freundlich isotherm at relatively high temperatures (35-45 deg. C). The maximum adsorption capacity calculated from Langmuir isotherm model was up to 31 mg/g. Thermodynamic study indicates an exothermic nature of adsorption and a spontaneous and favorable process. The optimum pH for As(V) removal was broad, ranging from 3.0 to 10.0. The As(V) adsorption was impeded by the presence of SiO32-, followed by PO43- and NO3-. The adsorption process appeared to be controlled by the chemical process. The high As uptake may attribute to both coprecipitation of As with goethite and lepidocrocite forming during the reaction and subsequent adsorption of As on these minerals.

  4. Ion aggregation in high salt solutions. III. Computational vibrational spectroscopy of HDO in aqueous salt solutions.

    Science.gov (United States)

    Choi, Jun-Ho; Kim, Heejae; Kim, Seongheun; Lim, Sohee; Chon, Bonghwan; Cho, Minhaeng

    2015-05-28

    The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O-D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O-D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O-D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O-D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O-D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quantum chemistry calculations on not only water clusters but also ion-water clusters, we first developed a distributed vibrational solvatochromic charge model for the O-D stretch mode in aqueous salt solutions. Furthermore, the non-Condon effect on the vibrational transition dipole moment of the O-D stretch mode was fully taken into consideration with the charge response kernel that is non-local polarizability density. From the fluctuating O-D stretch mode frequencies and transition dipole vectors obtained from the molecular dynamics simulations, the O-D stretch Raman scattering and IR absorption spectra of HDO in salt solutions could be calculated. The polarization effect on the transition dipole vector of the O-D stretch mode is shown to be important and the asymmetric line shapes of the O-D stretch Raman scattering and IR absorption spectra of HDO especially in highly concentrated NaCl and KSCN solutions are in quantitative agreement with experimental results. We anticipate that this

  5. Photocatalytic decomposition of cortisone acetate in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Romão, Joana Sobral; Hamdy, Mohamed S.; Mul, Guido, E-mail: g.mul@utwente.nl; Baltrusaitis, Jonas, E-mail: j.baltrusaitis@utwente.nl

    2015-01-23

    Graphical abstract: - Highlights: • Most efficient photocatalysts for cortisone 21-acetate (CA) degradation were ZnO and TiO{sub 2} (P25). • The decomposition rate increased at low CA concentrations. • No pH dependence was observed allowing CA photocatalytic degradation at native pH. • Synergistic CA degradation effects between TiO{sub 2} and S{sub 2}O{sub 8}{sup 2−} were found. • LC–MS confirmed a decrease in CA concentration, but no intermediate products were detected. - Abstract: The photocatalytic decomposition of cortisone 21-acetate (CA), a model compound for the commonly used steroid, cortisone, was studied. CA was photocatalytically decomposed in a slurry reactor with the initial rates between 0.11 and 0.46 mg L{sup −1} min{sup −1} at 10 mg L{sup −1} concentration, using the following heterogeneous photocatalysts in decreasing order of their catalytic activity: ZnO > Evonik TiO{sub 2} P25 > Hombikat TiO{sub 2} > WO{sub 3}. Due to the lack of ZnO stability in aqueous solutions, TiO{sub 2} P25 was chosen for further experiments. The decomposition reaction was found to be pseudo-first order and the rate constant decreased as a function of increasing initial CA concentration. Changing the initial pH of the CA solution did not affect the reaction rate significantly. The decomposition reaction in the presence of the oxidizing sacrificial agent sodium persulfate showed an observed decomposition rate constant of 0.004 min{sup −1}, lower than that obtained for TiO{sub 2} P25 (0.040 min{sup −1}). The highest photocatalytic degradation rate constant was obtained combining both TiO{sub 2} P25 and S{sub 2}O{sub 8}{sup 2−} (0.071 min{sup −1}) showing a synergistic effect. No reactive intermediates were detected using LC–MS showing fast photocatalytic decomposition kinetics of CA.

  6. Addition and elimination kinetics in OH radical induced oxidation of phenol and cresols in acidic and alkaline solutions

    International Nuclear Information System (INIS)

    The rates of the two consecutive reactions, OH radical addition and H2O/OH- elimination, were studied by pulse radiolysis in highly acidic (pH=1.3-1.9) and alkaline (pH∼11) solutions, respectively, for phenol and for the three cresol isomers. The rate coefficient of the addition as measured by the build-up of phenoxyl radical absorbance and by a competitive method is the same (1.4±0.1)x1010 mol-1 dm3 s-1 both in acidic and alkaline solution. The rate coefficient of the H2O elimination in acidic solution is (1.6±0.2)x106 s-1, whereas the coefficient of the OH- elimination in alkaline solutions is 6-8 times higher. The kinetics of the phenoxyl radical formation was described by the two-exponential equation of the consecutive reactions: the first exponential is related to the pseudo-first-order addition, while the second to the elimination reaction. No considerable structure dependence was found in the rate coefficients, indicating that the methyl substitutent in these highly acidic or alkaline solutions influences neither the addition nor the elimination rate

  7. Viscosity changes and unperturbed dimensions of gamma degradable HEC in aqueous solution

    International Nuclear Information System (INIS)

    Radiative degradation curve of high molecular hydroxyethylcellulose (HEC) in aqueous solution have been reported. Values of density for aqueous HEC before and after γ-irradiation have been measured. Ostwald-viscometric technique was used to measure viscosity values of the polymer before and after γ-irradiation. Gamma-irradiation of HEC decreases the values of density, relative, specific, reduced and intrinsic viscosities, molar mass, hydrodynamic volume, hydrodynamic expansion factor, real and ideal chain dimensions of the polymer in solution. In contrary, it increases the value of Schulz-Blaschke constant, critical concentration, solute-solvent interaction and decreases the solute-solute contact in the solution of degradable HEC. (author)

  8. Behavior of the sorption of 60 Co in aqueous solution on inorganic materials as function of p H

    International Nuclear Information System (INIS)

    The sorption of the 60 Co is evaluated in aqueous solution on Mg O, MnO2, TiO2, Sn O, activated carbon and hydrotalcite calcined as a function of the p H, using the method for lots and quantifying at the 60 Co for gamma spectrometry. Likewise it was explained the one behavior of the sorption of the 60 Co in the materials with base in the chemical species of this radioactive isotope in aqueous solution. The chemical species of the 60 Co in solution were identified by electrophoresis of high voltage for the different p H values. It was found that under the experimental conditions, the 60 Co showed a significant sorption on MnO2, TiO2 and activated carbon. On the other hand, in Mg O, Sn O and calcined hydrotalcite also was observed a sorption, although in smaller quantities. The studied hydrated metallic oxides retained the 60 Co for ion exchange via. It was found that the 60 Co was present as a cationic specie to p H 1, 3, 5 and 7 and like a neutral specie to alkaline p H. (Author)

  9. Adsorption of Heavy Metal Ions from Aqueous Solutions by Zeolite Based on Oil Shale Ash: Kinetic and Equilibrium Studies

    Institute of Scientific and Technical Information of China (English)

    BAO Wei-wei; ZOU Hai-feng; GAN Shu-cai; XU Xue-chun; JI Gui-juan; ZHENG Ke-yan

    2013-01-01

    Na-A zeolite was successfully synthesized via the alkaline fusion method with oil shale ash as the raw material.The adsorption capacity of it was tested by removing CU2+,Ni2+,Pb2+ and Cd2+ from aqueous solutions.The results reveal the maximum adsorption capacity of adsorbent for Pb2+,Cu2+,Cd2+ and Ni2+ were 224.72,156.74,118.34 and 53.02 mg/g,respectively.The effects of contact time and pH value of solutions on the adsorption efficiency of the zeolite were evaluated.Besides,The equilibrium adsorption data and the batch kinetic data were correlated with Langmuir and Freundlich models and the pseudo-first-order and pseudo-second-order models separately.The results show that the Langmuir isotherm and the pseudo-second-order equation were more suitable for the adsorption of Na-A zeolite for the metal ions.In addition,Thermodynamic parameters of the adsorption(the Gibbs free energy,entropy,and enthalpy) were also evaluated and discussed.The results demonstrate that the adsorption process was spontaneous and endothermic under natural conditions and the synthesized zeolite was an effective adsorbent for the removal of metal ions from aqueous solution.

  10. Kinetics of the decomposition and the estimation of the stability of 10% aqueous and non-aqueous hydrogen peroxide solutions

    Directory of Open Access Journals (Sweden)

    Zun Maria

    2014-12-01

    Full Text Available In this study, the stability of 10% hydrogen peroxide aqueous and non-aqueous solutions with the addition of 6% (w/w of urea was evaluated. The solutions were stored at 20°C, 30°C and 40°C, and the decomposition of hydrogen peroxide proceeded according to first-order kinetics. With the addition of the urea in the solutions, the decomposition rate constant increased and the activation energy decreased. The temperature of storage also affected the decomposition of substance, however, 10% hydrogen peroxide solutions prepared in PEG-300, and stabilized with the addition of 6% (w/w of urea had the best constancy.

  11. Ion Association, Solubilities, and Reduction Potentials in Aqueous Solution.

    Science.gov (United States)

    Russo, Steven O.; Hanania, George I. H.

    1989-01-01

    Incorporates the combined effects of ionic strength and ion association to show how calculations involving ionic equilibria are carried out. Examines the variability of reduction potential data for two aqueous redox systems. Provides several examples. (MVL)

  12. Reactivity of the cement-bentonite interface with alkaline solutions using transport cells

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, Raul [Dpto. Quimica Agricola, Geologia y Geoquimica, Facultad de Ciencias, Universidad Autonoma de Madrid, Campus Cantoblanco, 28049 Madrid (Spain); Cuevas, Jaime [Dpto. Quimica Agricola, Geologia y Geoquimica, Facultad de Ciencias, Universidad Autonoma de Madrid, Campus Cantoblanco, 28049 Madrid (Spain)]. E-mail: jaime.cuevas@uam.es; Sanchez, Laura [Dpto. Quimica Agricola, Geologia y Geoquimica, Facultad de Ciencias, Universidad Autonoma de Madrid, Campus Cantoblanco, 28049 Madrid (Spain); Villa, Raquel Vigil de la [Dpto. Quimica Agricola, Geologia y Geoquimica, Facultad de Ciencias, Universidad Autonoma de Madrid, Campus Cantoblanco, 28049 Madrid (Spain); Leguey, Santiago [Dpto. Quimica Agricola, Geologia y Geoquimica, Facultad de Ciencias, Universidad Autonoma de Madrid, Campus Cantoblanco, 28049 Madrid (Spain)

    2006-06-15

    Clayey formations are considered as suitable host rocks to develop a Deep Geological Repository (DGR) for nuclear wastes. A concrete ring, located between the clayey formation and the bentonite barrier, is needed as structural support for the galleries. This material will act as a source of alkaline fluids when the formation's pore water saturates the system. This investigation evaluates the performance of the concrete-bentonite system by means of both geochemical codes and experimental results. A column made of compacted bentonite from La Serrata (Almeria, Spain) (1.4 g/cm{sup 3}, dry density) was held in contact with an ordinary Portland cement (OPC) mortar. Two alkaline solutions (Ca(OH){sub 2} saturated and NaOH 0.25 M) were injected from the mortar's side at 25, 60 and 120 deg. C. The permeability of the system and the effluent fluid composition were determined periodically. Finally, the solid phase was sampled and analyzed after 1 year of treatment. Ca(OH){sub 2} saturated fluids does not alter the mineralogy over the experiment time scale. NaOH fluids produced minor changes at 60-25 deg. C but at 120 deg. C a thin tobermorite layer of 1.5 mm precipitates in the clay aggregate surfaces at the interface. After this layer, analcime nucleates in heterogeneous patches affecting the whole compacted bentonite probe (2 cm thickness). The use of the PHREEQC code thermodynamic approach predicts the mineralogical transformations. However, it is necessary to introduce kinetic laws and to consider the existence of stagnant zones in the model in order to simulate the heterogeneous spatial alteration observed.

  13. Hydrate phase equilibria of CO2+N2+aqueous solution of THF, TBAB or TBAF system

    DEFF Research Database (Denmark)

    Sfaxi, Imen Ben Attouche; Durand, Isabelle; Lugo, Rafael;

    2014-01-01

    We report hydrate dissociation conditions of CO2 (15 and 30mol%)+N2 (85 and 70mol%) in the presence of aqueous solutions of THF, TBAB or TBAF. The concentrations of TBAB and TBAF in the aqueous solutions are 5wt% and 9wt% while THF concentration in aqueous solution is 3mol%. Two different...... experimental techniques including isochoric pressure search method and a DSC method are used to measure the hydrate dissociation conditions. A comparison is finally made with the literature data. It is expected that this study provides better understanding of hydrate phase equilibria associated with CO2...... capture. © 2014 Elsevier Ltd....

  14. Preparation of CdTe nanocrystal-polymer composite microspheres in aqueous solution by dispersing method

    Institute of Scientific and Technical Information of China (English)

    LI Minjie; WANG Chunlei; HAN Kun; YANG Bai

    2005-01-01

    Highly fluorescent CdTe nanocrystals were synthesized in aqueous solution, and then processible CdTe nanocrystal-polymer composites were fabricated by coating the aqueous nanocrystals with copolymers of styrene and octadecyl-p-vinyl-benzyldimethylammonium chloride (SOV- DAC) directly. A dichloromethane solution of CdTe nano- crystal-polymer composites was dispersed in the aqueous solution of poly (vinyl alcohol) (PVA) generating highly fluorescent microspheres. Experimental parameters such as the concentration of nanocrystal-polymer composites, the concentration of PVA, and stirring speed which had important effect on the preparation of the microspheres were investigated in detail with fluorescent microscope characterization.

  15. Sensitizing effect of cerium (4) sulfate on photooxidation of organic compounds in aqueous solutions

    International Nuclear Information System (INIS)

    Influence of Ce(SO4)2 addition on the photooxidation rate of organic substances in aqueous solutions has been discussed. It is shown that to a certain value, the rate constant of oxalic acid oxidation increases linearly with increasing oxidant amount. Using a combination of chemical and photochemical oxidation of oxalic acid in aqueous solution with Ce(SO4)2 as a sensitizer, one can increase the oxidation rate by a factor of 45 and to reduce the time required for carbon determination in aqueous solutions from 4-5 hours down to 8-9 min

  16. Modeling experimental results of diffusion of alkaline solutions through a compacted bentonite barrier

    International Nuclear Information System (INIS)

    The interaction between concrete/cement and swelling clay (bentonite) has been modeled in the context of engineered barrier systems for deep geological disposal of high-level radioactive waste. The geochemical transformations observed in laboratory diffusion experiments at 60 and 90 oC between bentonite and different high-pH solutions (K-Na-OH and Ca(OH)2-saturated) were reconciled with the reactive transport code CrunchFlow. For K-Na-OH solutions (pH = 13.5 at 25 oC) partial dissolution of montmorillonite and precipitation of Mg-silicates (talc-like), hydrotalcite and brucite at the interface are predicted at 60 oC, while at 90 oC the alteration is wider. Alkaline cations diffused beyond the mineralogical alteration zone by means of exchange with Mg2+ in the interlayer region of montmorillonite. Very slow reactivity and minor alteration of the clay are predicted in the Ca(OH)2-bentonite system. The model is a reasonable description of the experiments but also demonstrates the difficulties in modeling processes operating at a small scale under a diffusive regime.

  17. Oxygen reduction at platinum nanoparticles supported on carbon cryogel in alkaline solution

    Directory of Open Access Journals (Sweden)

    N. R. ELEZOVIC

    2007-07-01

    Full Text Available The oxygen reduction reaction was investigated in 0.1 M NaOH solution, on a porous coated electrode formed of Pt particles supported on carbon cryogel. The Pt/C catalyst was characterized by the X-ray diffraction (XRD, transmission electron microscopy (TEM and cyclic voltammetry techniques. The results demonstrated a successful reduction of Pt to metallic form and homogenous Pt particle size distribution with a mean particle size of about 2.7 nm. The ORR kinetics was investigated by linear sweep polarization at a rotating disc electrode. The results showed the existence of two E – log j regions, usually referred to polycrystalline Pt in acid and alkaline solution. At low current densities (lcd, the Tafel slope was found to be close to –2.3RT/F, while at high current densities (hcd it was found to be close to –2×2.3RT/F. It is proposed that the main path in the ORR mechanism on Pt particles was the direct four-electron process, with the transfer of the first electron as the rate determining step. If the activities are expressed through the specific current densities, a small enhancement of the catalytic activity for Pt/C was observed compared to that of polycrystalline Pt. The effect of the Pt particle size on the electrocatalysis of oxygen reduction was ascribed to the predominant (111 facets of the platinum crystallites.

  18. Establishing the potential dependent equilibrium oxide coverage on platinum in alkaline solution and its influence on the oxygen reduction

    DEFF Research Database (Denmark)

    Wiberg, Gustav; Arenz, Matthias

    2012-01-01

    Publication year: 2012 Source:Journal of Power Sources, Volume 217 Gustav K.H. Wiberg, Matthias Arenz The oxidation process of polycrystalline platinum subjected to alkaline solution is re-examined using a combination of cyclic voltammetry and potential hold techniques in Ar, H2 and O2 purged 0.1 M...

  19. Separation of radiostrontium from alkaline reprocessing waste solution using a fixed-bed column of chelating iminodiacetic acid resin

    International Nuclear Information System (INIS)

    A fixed-bed ion exchange column filled with a chelating resin containing iminodiacetic acid functional groups has been tested for removal of strontium from simulated alkaline reprocessing waste solution. The breakthrough curve has been established. Column loading performance is correlated with batch equilibration results. The loaded strontium is eluted in a small volume of 0.5 M HNO3. (author)

  20. Proton Transfer in Aqueous Solution: Exploring the Boundaries of Adaptive QM/MM

    NARCIS (Netherlands)

    Jiang, Tao; Boereboom, J.M.; Michel, C.; Fleurat-Lessard, P.; Bulo, R.E.

    2015-01-01

    In this chapter, we review the current state-of-the-art in quantum mechanical/molecular mechanical (QM/MM) simulations of reactions in aqueous solutions, and we discuss how proton transfer poses new challenges for its successful application. In the QM/MM description of an aqueous reaction, solvent m

  1. Study on 99Mo production by solution irradiation method (2). Characterization of aqueous molybdate solutions under gamma-ray irradiation

    International Nuclear Information System (INIS)

    The solution irradiation method is proposed as a new production technique for 99Mo, which is the parent nuclide of 99mTc used as a radiopharmaceutical. In this new method, an aqueous molybdenum solution is irradiated with neutrons in a nuclear reactor, and more efficient and lower-cost 99Mo production than conventional 99Mo production can be realized by using the 98Mo (n,γ) 99Mo reaction and the molybdenum adsorbent of PZC. Aiming at the practical application of this method, unirradiation tests, gamma-ray irradiation tests, and neutron irradiation tests should be needed in order to characterize the aqueous molybdenum solution as the irradiation target. In the present study, using two kinds of aqueous molybdate solutions (an aqueous ammonium molybdate solution and an aqueous potassium molybdate solution) selected as candidates for the irradiation target of the new method, the compatibility between the solutions and structural materials, the chemical stability, the circulation characteristics, the radiolysis, and the gamma heating of the solutions were investigated under gamma-ray irradiation. In addition, the integrity of PZC was investigated under gamma-ray irradiation. As a result, the following were found: 1) the compatibility between the solutions and stainless steel is very well, 2) the solutions are chemically stable and have a smooth circulation, 3) the ratios of hydrogen in the gases generated by the radiolysis of the solutions are higher than that of pure water, 4) the effect of gamma heating on the solutions is the same level as that on pure water, and 5) the integrity of PZC is maintained. (author)

  2. Formation of anhydrotetracycline in gamma irradiated aqueous tetracycline solutions (Preprint No. RC-12)

    International Nuclear Information System (INIS)

    Gamma radiolysis of antibiotic tetracycline in aqueous solutions has been studied under various conditions. Anhydrotetracycline, a potential toxic substance, was identified as a major radiation degradation product formed under deoxygenated conditions mainly because of H atom attack on tetracycline. (author)

  3. Determination of alcohol- and sugar concentration in aqueous solutions using reflection terahertz time-domain spectroscopy

    OpenAIRE

    Møller, Uffe; Merbold, H.; Folkenberg, J. R.; Jepsen, Peter Uhd

    2007-01-01

    We use self-referencing reflection THz spectroscopy to measure the alcohol- and sugar concentration with high precision in small volumes of aqueous solutions, independent of carbonation and the contents of yeast or other small organic particles.

  4. The solubility of Ag sub 2 S in near-neutral aqueous sulfide solutions at 25 to 300 degree C

    Energy Technology Data Exchange (ETDEWEB)

    Gammons, C.H.; Barnes, H.L. (Pennsylvania State Univ., University Park (USA))

    1989-02-01

    The solubility of Ag{sub 2}S (acanthite/argentite) was measured in vapor-saturated aqueous sulfide solutions at 25-300{degree}C, total sulfide = 0.2-1.4 m, and pH{sub 25{degree}} = 5.8-7.3. Although Seward (1976) has shown that considerable silver can be dissolved as chloride complexes, the authors data indicate that Ag(HS){sup {minus}}{sub 2} is the dominant silver species in hydrothermal fluids with near-neutral to alkaline pH, relatively low oxidation state, high total sulfide, and T < 300{degree}C (e.g., Broadlands, N.Z.; Brown, 1986). Silver transported as Ag(HS){sup {minus}}{sub 2} is precipitated in response to a decrease in aqueous sulfide concentration, a change in pH away from the pK{sub 1} for H{sub 2}S or, in the native silver field, a decrease in oxidation state. Cooling is a less important depositional mechanism, particularly for solutions whose pH is buffered by feldspar alteration reactions.

  5. Equilibrium, kinetic and thermodynamic studies for sorption of Ni (II from aqueous solution using formaldehyde treated waste tea leaves

    Directory of Open Access Journals (Sweden)

    Jasmin Shah

    2015-05-01

    Full Text Available The sorption characteristic of Ni (II from aqueous solution using formaldehyde treated waste tea leaves as a low cost sorbent has been studied. The effect of pH, contact time, sorbent dose, initial metal ion concentration and temperature were investigated in batch experiments. The equilibrium data were fitted into four most common isotherm models; Freundlich, Langmuir, Tempkin and Dubinin–Radushkevich (D–R. The Langmuir model described the sorption isotherm best with maximum monolayer sorption capacity of 120.50 mg g−1. Four kinetic models, pseudo-first-order, pseudo-second-order, intraparticle diffusion and Elovich were employed to explain the sorption mechanism. The kinetics of sorption data showed that the pseudo-second-order model is the best with correlation coefficient of 0.9946. The spontaneous and exothermic nature of the sorption process was revealed from thermodynamic investigations. The effect of some common alkali and alkaline earth metal ions were also studied which showed that the presence of these ions have no effect on the sorption of Ni (II. The results showed that waste tea leaves have the potential to be used as a low cost sorbent for the removal of Ni (II from aqueous solutions.

  6. Determination of deuterium in brines and in hypersaline aqueous solutions by mass spectrometry using zinc as reducing agent

    International Nuclear Information System (INIS)

    A procedure was developed for the determination of deuterium concentration in brines and in hypersaline aqueous solutions, without the removal of alkaline earth metal cations. Aqueous salt solutions of nine salts, LiCl, NaCl, NaI, Na2CO3, KCl, K2SO4, CsCl, CaCl2 and Mg(ClO4)2, with molalities ranging from 0.5 to 11.8 mol kg-1 were prepared by dissolving the dry anhydrous salts in de-ionized water of known isotopic composition. Only 8 μl of sample were required to be reduced with zinc metal at 460oC in a special glass container equipped with a Teflon stopper, to prepare hydrogen for isotopic analysis. The salts NaCl, NaI, Na2CO3, KCl, K2SO4 and CsCl required 0.25 g, LiCl and CaCl2 0.75 g and Mg(ClO4)2 1.00 g of zinc for complete reduction. Deuterium concentrations in brines containing large amounts of Ca2+, Mg2+, Cl- and SO42- ions were measured with an accuracy of ±1%o (1σ). In addition, the deuterium content in Dead Sea water was determined with the same method and gave δD = + 5.4 ±0.3%o using 1.50 g of zinc. (author)

  7. Physical nature of the peculiar points of aqueous-alcohol solutions

    International Nuclear Information System (INIS)

    This manuscript is devoted to the discussion of anomalous properties of aqueous solutions of alcohol at low concentrations, where it should described by the properties of ideal binary solution. The main attention is focused on the peculiar point of such solutions. It is paid the main attention on dependence of properties of water-alcohol solutions on the characteristic time, which separates the measurement processes from the preparation time of solution. (authors)

  8. Magnetic composite nanofibers fabricated by electrospinning of Fe{sub 3}O{sub 4}/gelatin aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shuhong, E-mail: openair@163.com [Key Laboratory of Functional Inorganic Material Chemistry (School of Chemical Engineering and Material, Heilongjiang University), Ministry of Education, Harbin 150080 (China); Sun, Zhiyao [Key Laboratory of Functional Inorganic Material Chemistry (School of Chemical Engineering and Material, Heilongjiang University), Ministry of Education, Harbin 150080 (China); Yan, Eryun [College of Materials Science and Engineering, Qiqihar University, Qiqihar 161006 (China); Yuan, Jihong; Gao, Yang; Bai, Yuhao; Chen, Yu [Key Laboratory of Functional Inorganic Material Chemistry (School of Chemical Engineering and Material, Heilongjiang University), Ministry of Education, Harbin 150080 (China); Wang, Cheng, E-mail: wangc_93@163.com [Key Laboratory of Functional Inorganic Material Chemistry (School of Chemical Engineering and Material, Heilongjiang University), Ministry of Education, Harbin 150080 (China); Zheng, Yongjie; Jing, Tao [College of Materials Science and Engineering, Qiqihar University, Qiqihar 161006 (China)

    2014-12-15

    Graphical abstract: Superparamagnetic Fe{sub 3}O{sub 4}/GE composite nanofibers with saturation magnetization of 12.87 emμ g{sup −1} were prepared from gelatin aqueous solution at an elevated temperature by electrospinning. - Highlights: • Electrospinning GE aqueous solution at higher temperature. • Presenting a simple and effective technique, combining wet blending with high temperature electrospinning to prepare magnetic composite nanofibers. • Developing composite nanofibers with higher superparamagnetic properties is expected to be useful in application for the biomedical field. - Abstract: We have fabricated magnetic composite nanofibers containing superparamagnetic Fe{sub 3}O{sub 4} nanoparticles by the electrospinning method. Highly dispersed Fe{sub 3}O{sub 4} magnetic nanoparticles were synthesized by one-step co-precipitation of Fe{sup 2+}/Fe{sup 3+} under an alkaline condition with 4 wt% poly(vinyl alcohol) (PVA) aqueous solution as the stabilizer. Gelatin (GE) was used as a polymeric matrix for fabricating the nanocomposites. The prepared Fe{sub 3}O{sub 4}/GE composite nanofibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. These composite nanofibers show uniform and continuous morphology with the Fe{sub 3}O{sub 4} nanoparticles embedded in the nanofibers. By studying the magnetic properties of the Fe{sub 3}O{sub 4}/GE composite nanofibers, we confirm that the composite nanofibers possess superparamagnetic properties with a high saturated magnetization (M{sub s} = 12.87 emμ g{sup −1}) at room temperature. The features of this approach for getting one-dimensional magnetic nanostructure are its simplicity, effectiveness and safety. The Fe{sub 3}O{sub 4}/GE nanofibers with superparamagnetic properties would be potentially applied in biomedical field.

  9. Supercooling of aqueous dimethylsulfoxide solution at normal and high pressures: Evidence for the coexistence of phase-separated aqueous dimethylsulfoxide solutions of different water structures

    Science.gov (United States)

    Kanno, H.; Kajiwara, K.; Miyata, K.

    2010-05-01

    Supercooling behavior of aqueous dimethylsulfoxide (DMSO) solution was investigated as a function of DMSO concentration and at high pressures. A linear relationship was observed for TH (homogeneous ice nucleation temperature) and Tm (melting temperature) for the supercooling of aqueous DMSO solution at normal pressure. Analysis of the DTA (differential thermal analysis) traces for homogeneous ice crystallization in the bottom region of the TH curve for a DMSO solution of R =20 (R: moles of water/moles of DMSO) at high pressures supported the contention that the second critical point (SCP) of liquid water should exist at Pc2=˜200 MPa and at Tc2<-100 °C (Pc2: pressure of SCP, Tc2: temperature of SCP). The presence of two TH peaks for DMSO solutions (R =15, 12, and 10) suggests that phase separation occurs in aqueous DMSO solution (R ≤15) at high pressures and low temperatures (<-90 °C). The pressure dependence of the two TH curves for DMSO solutions of R =10 and 12 indicates that the two phase-separated components in the DMSO solution of R =10 have different liquid water structures [LDL-like and HDL-like structures (LDL: low-density liquid water, HDL: high-density liquid water)] in the pressure range of 120-230 MPa.

  10. Biosorption of Lead Ions from Aqueous Solution Using Ficus benghalensis L.

    OpenAIRE

    Venkateswara Rao Surisetty; Janusz Kozinski; L. Rao Nageswara

    2013-01-01

    Ficus benghalensis L., a plant-based material leaf powder, is used as an adsorbent for the removal of lead ions from aqueous solution using the biosorption technique. The effects of process parameters such as contact time, adsorbent size and dosage, initial lead ion concentration, and pH of the aqueous solution on bio-sorption of lead by Ficus benghalensis L. were studied using batch process. The Langmuir isotherm was more suitable for biosorption followed by Freundlich and Temkin isotherms w...

  11. Reaction Pathway and Free Energy Barrier for Urea Elimination in Aqueous Solution

    OpenAIRE

    Yao, Min; Chen, Xi; Zhan, Chang-Guo

    2015-01-01

    To accurately predict the free energy barrier for urea elimination in aqueous solution, we examined the reaction coordinates for the direct and water-assisted elimination pathways, and evaluated the corresponding free energy barriers by using the surface and volume polarization for electrostatics (SVPE) model-based first-principles electronic-structure calculations. Based on the computational results, the water-assisted elimination pathway is dominant for urea elimination in aqueous solution,...

  12. Determination of alcohol- and sugar concentration in aqueous solutions using reflection terahertz time-domain spectroscopy

    DEFF Research Database (Denmark)

    Møller, Uffe; Merbold, H; Folkenberg, J R; Jepsen, Peter Uhd

    2007-01-01

    We use self-referencing reflection THz spectroscopy to measure the alcohol- and sugar concentration with high precision in small volumes of aqueous solutions, independent of carbonation and the contents of yeast or other small organic particles.......We use self-referencing reflection THz spectroscopy to measure the alcohol- and sugar concentration with high precision in small volumes of aqueous solutions, independent of carbonation and the contents of yeast or other small organic particles....

  13. Synthesis and aggregation properties of amphiphilic mono and bisadducts of fullerene in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    Pu Zhang; Zhi Xin Guo; Shuang Lv

    2008-01-01

    New amphiphilic[60]fullerene monoadduet TPF and bisadducts BTPF were synthesized and well-characterized. Their aggregation properties in aqueous solution was investigated by UV-vis and TEM methods. In aqueous solution, monoadduct TPF forms irregularly shaped and some rod-like aggregates, whereas bisadducts BTPF gives spherical aggregates with diameters of 50-150 nm. It indicated that the aggregation properties of amphiphilic fullerene derivatives depend on the number of hydrophilic appendage on the C60 cage.

  14. Separation of Co2+ present in aqueous solution on calcium carbonate

    International Nuclear Information System (INIS)

    The CaCO3 was synthesized by precipitation method and characterized using SEM, EDS, TGA and IR. It was studied the adsorption behavior of Co2+ present in aqueous solution on the synthesized material by experiments batch type at room temperature. Was found that removal of cobalt ions was greater than 40% indicating that this material can be used to remove Co2+ present in aqueous solution. (Author)

  15. Radiation-induced destruction peculiarities of hydroxyl containing amino acids in diluted aqueous solution

    International Nuclear Information System (INIS)

    Amino acids aqueous solution of alpha-alanine and beta-alanine, serine, threonine (concentration 5*10-4 M) were irradiated with dose rate 0.35 Gy/s in range 100-1100 Gy and analysed. Effectiveness of radiation-induced decomposition process depends on row of factors: concentration of amino acid aqueous solution, pH, oxygen presence and other acceptors

  16. Comparison of physicomechanical properties of films prepared from organic solutions and aqueous dispersion of Eudragit RL

    OpenAIRE

    H Afrasiabi Garekani; M. Shahabi; F Sadeghi

    2011-01-01

    Background and the purpose of the study: Mechanical properties of films prepared from aqueous dispersion and organic solutions of Eudragit RL were assessed and the effects of plasticizer type, concentration and curing were examined. Methods: Films were prepared from aqueous dispersion and solutions of Eudragit RL (isopropyl alcohol-water 9:1) containing 0, 10 or 20% (based on polymer weight) of PEG 400 or Triethyl Citrate (TEC) as plasticizer using casting method. Samples of films were stored...

  17. Electronic structure tautomerism, and mechanism of H-D exchange in imidazole aqueous solutions

    International Nuclear Information System (INIS)

    The imidazole electronic structure in a gaseous phase is studied taking into account the influence of solvation effects in aqueous solutions. Possible mechanisms of tautomeric transformations and H-D exchange reactions with water molecules are discussed. Using the quantum chemistry methods, it is shown that the intramolecular mechanism of imidazole isomerization in the gaseous phase and the aqueous solution is unprofitable, and the intermolecular mechanism can proceed through the stage of protonated and carbene form formation

  18. Evaluating the possibility of desalinization of a saline aqueous solution of diethylene glycol

    Energy Technology Data Exchange (ETDEWEB)

    Gurbanyazov, O.A.; Khudayberenov, S.; Mamedov, M.

    1982-01-01

    A device is proposed for desalinating a saline aqueous solution of diethylene glycol based on a change in solubility of NaCl. The possibility is evaluated of desalinating the saline aqueous solution of diethylene glycol with the help of this device. Introduction into production of the device will yield a perceptible economic effect. If solar energy is used as the energy source in combination with secondary energy resource of gas production, then the effect will rise.

  19. Reactant-solute encounters in aqueous solutions studied by kinetic methods : hydration cosphere overlap and camouflage effects

    NARCIS (Netherlands)

    Engberts, Jan B.F.N.; Blandamer, Michael J.

    1998-01-01

    Rates of chemical reactions in aqueous solutions are often sensitive to low concentrations of added solutes such as ureas, alcohols, α-amino acids and carbohydrates. In this work, several simple chemical reactions were used to probe this sensitivity, which arises from interactions between added solu

  20. Photo-Fenton oxidation of phenol and organochlorides (2,4-DCP and 2,4-D) in aqueous alkaline medium with high chloride concentration.

    Science.gov (United States)

    Luna, Airton J; Chiavone-Filho, Osvaldo; Machulek, Amilcar; de Moraes, José Ermírio F; Nascimento, Cláudio A O

    2012-11-30

    A highly concentrated aqueous saline-containing solution of phenol, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) was treated by the photo-Fenton process in a system composed of an annular reactor with a quartz immersion well and a medium-pressure mercury lamp (450 W). The study was conducted under special conditions to minimize the costs of acidification and neutralization, which are usual steps in this type of process. Photochemical reactions were carried out to investigate the influence of some process variables such as the initial concentration of Fe(2+) ([Fe(2+)](0)) from 1.0 up to 2.5 mM, the rate in mmol of H(2)O(2) fed into the system (FH(2)O(2);in) from 3.67 up to 7.33 mmol of H(2)O(2)/min during 120 min of reaction time, and the initial pH (pH(0)) from 3.0 up to 9.0 in the presence and absence of NaCl (60.0 g/L). Although the optimum pH for the photo-Fenton process is about 3.0, this particular system performed well in experimental conditions starting at alkaline and neutral pH. The results obtained here are promising for industrial applications, particularly in view of the high concentration of chloride, a known hydroxyl radical scavenger and the main oxidant present in photo-Fenton processes. PMID:22809483

  1. Electrodeposition of cerium from aqueous cerous chloride solutions

    International Nuclear Information System (INIS)

    Cerium was plated as a grey, metallic, adherent deposit from aqueous cerous chloride baths containing certain organic addition agents. The cathodic current efficiency was determined for each case. Chemical analysis indicates that the purity of the metal is better than 99.0 per cent. (author). 7 refs

  2. Characterization of trehalose aqueous solutions by neutron spin echo

    CERN Document Server

    Branca, C; Magazù, S; Maisano, G; Mangione, A; Pappas, C; Triolo, A

    2002-01-01

    The present work reports neutron spin-echo (NSE) results on aqueous mixtures of trehalose, a naturally occurring disaccharide of glucose, which shows an extraordinary bioprotective effectiveness against dehydration and freezing. The aim of the work is to furnish new results on the dynamics of the trehalose/water system on the nano- and picosecond scales. (orig.)

  3. Critical anomalies of alkaline fading of phenolphthalein in the critical solution of 2-butoxyethanol + water.

    Science.gov (United States)

    Du, Zhongyu; Yin, Handi; Hao, Zhiguo; Zheng, Peizhu; Shen, Weiguo

    2013-12-14

    We have used three-wavelength UV-spectrophotometry to study the reaction of the alkaline fading of phenolphthalein in the critical solution of 2-butoxyethanol + water. It was found that when the temperature was far away from the critical point, the values of the natural logarithm of the rate constant k and the natural logarithm of the chemical equilibrium K determined in our experiments had good linear relationships with the reciprocal of temperature, which served as the backgrounds and were used for correcting k and K in the critical region. The critical slowing down of the reaction and the critical anomaly of the chemical equilibrium were detected near the critical point. The value of the critical exponent characterizing the slowing down effect of the reaction rate was obtained to be 0.156, which was close to the value 0.11 associated with the heat capacity divergence and agreed with the theoretical prediction. The experimental result also confirmed the theoretical prediction of 0.11 for the critical exponent characterizing the weak divergence of the singularity of the chemical equilibrium. PMID:24329072

  4. Ultraviolet spectrum and decay of the ozonide ion radical, O3-, in strong alkaline solution

    International Nuclear Information System (INIS)

    Pulse radiolytic experiments in strong alkaline solution (pH 13-14) on the formation and the decay of the ozonide ion radical, O3-, are reported. The high-pressure cell technique was used applying 4 MPa of nitrous oxide and 0.1 MPa of oxygen. The spectrum of O3- in the uv was measured and the decay product was identified as the peroxy radical ion, O2-. A complete mechanism for the decay of O3- is based on the following reactions: O3- + O- → 2O2- and O2- + O- + H2O → O2 + 2OH-. A computer simulation of the high-pressure system as well as the atmospheric-pressure oxygenated system supports this mechanism and yields a rate constant, k/sub (O3- + O-)/ of (7.0 +- 1.0) x 108 dm3 mol-1s-1. As a consequence of our mechanism, a k/sub (O2- + O-)/ of (6.0 +- 1.0) x 108 dm3 mol-1 s-1 is also derived from the computations

  5. Production of ultrafine zinc powder from wastes containing zinc by electrowinning in alkaline solution

    Directory of Open Access Journals (Sweden)

    Zhao Youcai

    2013-12-01

    Full Text Available Production of ultrafine zinc powder from industrial wastes by electrowinning in alkaline solution was studied. Stainless steel and magnesium electrodes were used as anode and cathode, respectively. Morphology, size distribution and composition of the Zn particles were characterized by Scanning Electron Microscopy, Laser Particle Size Analyzer, and Inductive Coupled Plasma Emission Spectrometer. The required composition of the electrolyte for ultrafine particles was found to be 25-35 g/L Zn, 200-220 g/L NaOH and 20-40 mg/L Pb. The optimal conditions were a current density of 1000-1200 A/m² and an electrolyte temperature of 30-40 °C. The results indicated that the lead additive exerted a beneficial effect on the refining of the particles, by increasing the cathodic polarization. Through this study, ultrafine zinc powder with a size distribution of around 10 μm could be produced, and considerably high current efficiencies (97-99 % were obtained.

  6. Reusable nanocomposite of CoFe2O4/chitosan-graft-poly(acrylic acid) for removal of Ni(II) from aqueous solution

    International Nuclear Information System (INIS)

    In this paper, CoFe2O4/chitosan-graft-poly(acrylic acid) (CoFe2O4/CS-graft-PAA) nanocomposites were prepared successfully by coprecipitation of the compounds in alkaline solution and were used for removal of nickel (II) ions from aqueous solution. The sorption rate was affected significantly by the initial concentration of the solution, sorbent amount, and pH value of the solution. Batch experiments were conducted to investigate the adsorption capacity under different initial concentration (ranging from 25 to 150 mg L−1), solution pH (4.1, 5.3, 6.4 and 7.6), and contact time. These nanocomposites can be recycled conveniently from water with the assistance of an external magnet because of their exceptional properties. The prepared nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), x-ray powder diffraction (XRD), and thermogravimetric analysis (TGA). (papers)

  7. Effect of alkaline solutions on the tensile properties of glass-polyester pipes

    Directory of Open Access Journals (Sweden)

    Putić Slaviša S.

    2011-01-01

    Full Text Available Construction materials, traditionally used in process equipment, are today successfully replaced by composite materials. Hence, many pipes are made of these materials. The subject of this study was the influence of liquids on the state of stresses and tensile strengths in the longitudinal and circumferential direction of glass-polyester pipes of a definite structure and known fabrication process. These analyses are of great importance for the use of glass-polyester pipes in the chemical industry. The tensile properties (the ultimate tensile strength and the modulus of elasticity were tested and determined for specimens cut out of the pipes; flat specimens for the tensile properties in the longitudinal direction and ring specimens for the tensile properties in the circumferential direction. First, the tension test was performed on virgin samples (without the influence of any liquid, to obtain knowledge about the original tensile properties of the material composite studied. Subsequently, the specimens were soaked in alkaline solutions: sodium hydroxide (strong alkali and ammonium hydroxide (weak alkali. These solutions were selected because of their considerable difference in pH values. The specimens and rings were left for 3, 10, 30 and 60 days in each liquid at room temperature. Then, the samples were tested on tension by the standard testing procedure. A comparison of the obtained results was made based on the pH values of the aggressive media in which the examined material had been soaked, as well as based on the original tensile properties and the number of days of treatment. Micromechanical analyses of sample breakage helped in the elucidation of the influence of the liquids on the structure of the composite pipe and enabled models and mechanisms that produced the change of strength to be proposed.

  8. Removal of U(VI) from aqueous solutions by the nano-iron oxyhydroxides

    International Nuclear Information System (INIS)

    The nano-iron oxyhydroxides (α- and γ-FeOOH) were synthesized by oxidation of the various raw materials (FeSO4 and FeCl2) as iron precursors under alkaline conditions. Morphologies of nano-iron oxyhydroxides were characterized by high resolution transmission electron microscope (HRTEM), X-ray powder diffraction (XRD) and specific surface area (SSA), respectively. The removal of U(VI) from aqueous solution by nano-iron oxyhydroxides was also investigated as a function of contact time, U(VI) concentration, pH, ionic strength and temperature under ambient conditions. The occurrence of needle-like shape of nano-goethite and rod-like shape of nano- lepidocrocite were attributed to oxidization of Fe2+ under different conditions in terms of XRD analysis and HRTEM images. The sorption results indicated that the removal of U(VI) strongly depended on pH and were independent of ionic strength. Langmuir model was employed to model the sorption isotherms of U(VI) at three various temperatures of 293, 313 and 333 K. The thermodynamic parameters (ΔH , ΔS and ΔG ) computed from the temperature showed that sorption process of U(VI) on nano-iron oxyhydroxides was endothermic and spontaneous. The mechanism of U(VI) sorption on nano-iron oxyhydroxides was assumed to outer-sphere surface complexation at low pH (pH 4), whereas the uptake of U(VI) was dominated by surface precipitation at high pH conditions. Thereby nano-iron oxyhydroxides can be used as an efficient backfill materials for the in situ disposal of U(VI)-bearing contaminated groundwater. (orig.)

  9. Modeling reactive geochemical transport of concentrated aqueous solutions in variably saturated media

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guoxiang; Zheng, Zuoping; Wan, Jiamin

    2004-01-28

    Concentrated aqueous solutions (CAS) have unique thermodynamic and physical properties. Chemical components in CAS are incompletely dissociated, especially those containing divalent or polyvalent ions. The problem is further complicated by the interaction between CAS flow processes and the naturally heterogeneous sediments. As the CAS migrates through the porous media, the composition may be altered subject to fluid-rock interactions. To effectively model reactive transport of CAS, we must take into account ion-interaction. A combination of the Pitzer ion-interaction and the ion-association model would be an appropriate way to deal with multiple-component systems if the Pitzer' parameters and thermodynamic data of dissolved components and the related minerals are available. To quantify the complicated coupling of CAS flow and transport, as well as the involved chemical reactions in natural and engineered systems, we have substantially extended an existing reactive biogeochemical transport code, BIO-CORE{sup 2D}{copyright}, by incorporating a comprehensive Pitzer ion-interaction model. In the present paper, the model, and two test cases against measured data were briefly introduced. Finally we present an application to simulate a laboratory column experiment studying the leakage of the high alkaline waste fluid stored in Hanford (a site of the U.S. Department of Energy, located in Washington State, USA). With the Pitzer ion-interaction ionic activity model, our simulation captures measured pH evolution. The simulation indicates that all the reactions controlling the pH evolution, including cation exchanges, mineral precipitation and dissolution, are coupled.

  10. Development of analytical technique of alteration minerals formed in bentonite by the reaction with alkaline solution

    International Nuclear Information System (INIS)

    Bentonite will be used as a buffer material, according to the TRU waste disposal concept in Japan, to retard radionuclides migration, to restrict seepage of ground water and to filtrate colloids. One of the concern about the buffer material is the long term alteration of bentonite with cementitious material. Long term alteration of bentonite-based materials with alkaline solution has been studied by means of analytical approaches, coupling mass transport and chemical reactions, which suggest changes in various properties of buffer materials. Long term performance assessment of engineered barriers under disposal conditions is important to achieve a reasonable design, eliminating excessive conservatism in the safety assessment. Therefore it is essential for improving the reliance of the performance assessment to verify the analytical results through alteration tests and/or natural analogue. The geochemical analyses indicate that major alteration reactions involve dissolution of portlandite, chalcedony and montmorillonite and formation of C-S-H gel and analcime at the interface between cement and bentonite. However, in the alteration tests assuming interaction between bentonite and cement, secondary minerals due to alteration under the expected condition for geological disposal (equilibrated water with cement at low liquid/solid ratio) had not been observed, though the alteration was observed under accelerated hyper alkaline and high temperatures conditions. The reason is considered that it is difficult to analyze C-S-H gel formed at the interface because of its small quantity. One of examples is the Kunigel V1, a potential buffer material in Japan, which consists of montmorillonite, chalcedony, plagioclase, and calcite. In the XRD analysis of the Kunigel V 1, the locations of the primary peak of the calcite and that of the C-S-H gel overlap, which makes identification of small quantity of C-S-H gel formed as a secondary mineral difficult. Thus development of

  11. The alkaline solution to the emergence of life: energy, entropy and early evolution.

    Science.gov (United States)

    Russell, Michael J

    2007-01-01

    The Earth agglomerates and heats. Convection cells within the planetary interior expedite the cooling process. Volcanoes evolve steam, carbon dioxide, sulfur dioxide and pyrophosphate. An acidulous Hadean ocean condenses from the carbon dioxide atmosphere. Dusts and stratospheric sulfurous smogs absorb a proportion of the Sun's rays. The cooled ocean leaks into the stressed crust and also convects. High temperature acid springs, coupled to magmatic plumes and spreading centers, emit iron, manganese, zinc, cobalt and nickel ions to the ocean. Away from the spreading centers cooler alkaline spring waters emanate from the ocean floor. These bear hydrogen, formate, ammonia, hydrosulfide and minor methane thiol. The thermal potential begins to be dissipated but the chemical potential is dammed. The exhaling alkaline solutions are frustrated in their further attempt to mix thoroughly with their oceanic source by the spontaneous precipitation of biomorphic barriers of colloidal iron compounds and other minerals. It is here we surmise that organic molecules are synthesized, filtered, concentrated and adsorbed, while acetate and methane--separate products of the precursor to the reductive acetyl-coenzyme-A pathway-are exhaled as waste. Reactions in mineral compartments produce acetate, amino acids, and the components of nucleosides. Short peptides, condensed from the simple amino acids, sequester 'ready-made' iron sulfide clusters to form protoferredoxins, and also bind phosphates. Nucleotides are assembled from amino acids, simple phosphates carbon dioxide and ribose phosphate upon nanocrystalline mineral surfaces. The side chains of particular amino acids register to fitting nucleotide triplet clefts. Keyed in, the amino acids are polymerized, through acid-base catalysis, to alpha chains. Peptides, the tenuous outer-most filaments of the nanocrysts, continually peel away from bound RNA. The polymers are concentrated at cooler regions of the mineral compartments through

  12. Catalytic condensation of formaldehyde in aqueous solution initiated by UV irradiation as putative "prebiological" route of the monosaccharides formation

    Science.gov (United States)

    Pestunova, O. P.; Simonov, A. N.; Matvienko, L. G.; Snytnikov, V. N.; Parmon, V. N.; Snytnikova, O. A.; Tsentalovich, Yu. P.

    The condensation of formaldehyde into higher monosaccharides in aqueous alkaline solutions catalyzed by several metal ions in particular Ca 2 and Mg 2 named as formose reaction is considered as a probable source of carbohydrates in prebiotic conditions Formaldehyde is detected in significant amounts in molecular clouds in space Undoubtedly it was an important gas component of circumsolar protoplanet disk Naturally formaldehyde could be dissolved in water of the Protoearth Calcium and magnesium that are capable of creating an alkaline medium are the abundant elements Thus the basic conditions for the formose reaction and for formation of monosaccharides in nature could be met However the formose reaction is autocatalytic since it can be initiated only in the presence of carbohydrates In spite of the fact that Russian chemist Butlerov discovered the formose reaction almost 150 years ago the reason of autocatalytic character of the process and the mechanism of initiation till now remained not quite clear In our work regular investigation of the mechanism of the formose reaction was carried out Influence of various initiators on reaction kinetics and composition of products was studied The composition of the formose reaction products in presence of different initiators is practically invariable under steady-state conditions and is caused by an aldol condensation of the lowest N 2 - and C 3 -carbohydrates The ability of the C 4 -C 6 sugars to initiate the formose reaction is revealed to correlate with the

  13. Aqueous solutions of acidic ionic liquids for enhanced stability of polyoxometalate-carbon supercapacitor electrodes

    Science.gov (United States)

    Hu, Chenchen; Zhao, Enbo; Nitta, Naoki; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

    2016-09-01

    Nanocomposites based on polyoxometalates (POMs) nanoconfined in microporous carbons have been synthesized and used as electrodes for supercapacitors. The addition of the pseudocapacitance from highly reversible redox reaction of POMs to the electric double-layer capacitance of carbon lead to an increase in specific capacitance of ∼90% at 1 mV s-1. However, high solubility of POM in traditional aqueous electrolytes leads to rapid capacity fading. Here we demonstrate that the use of aqueous solutions of protic ionic liquids (P-IL) as electrolyte instead of aqueous sulfuric acid solutions offers an opportunity to significantly improve POM cycling stability. Virtually no degradation in capacitance was observed in POM-based positive electrode after 10,000 cycles in an asymmetric capacitor with P-IL aqueous electrolyte. As such, POM-based carbon composites may now present a viable solution for enhancing energy density of electrical double layer capacitors (EDLC) based on pure carbon electrodes.

  14. Extraction of dye from aqueous solution in rotating packed bed.

    Science.gov (United States)

    Modak, Jayant B; Bhowal, Avijit; Datta, Siddhartha

    2016-03-01

    The influence of centrifugal acceleration on mass transfer rates in liquid-liquid extraction was investigated experimentally in rotating packed bed (RPB) contactor. The extraction of methyl red using xylene was studied in the equipment. The effect of rotational speed (300-900rpm), flow rate of the aqueous (4.17-20.8×10(-6)m(3)/s), and organic phase (0.83-2.5×10(-6)m(3)/s) on the mass transfer performance was examined. The maximum stage efficiency attained was ∼0.98 at aqueous to organic flow rate ratio of 10. The results suggest that contactor volume required to carry out a given separation can be reduced by an order of magnitude with RPB in comparison to conventional extractors. PMID:26571002

  15. Compositions for preparation of aqueous solutions of salts of lower valence /sup 99/Tc

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt-Dunker, M.; Greb, W.

    1979-01-09

    Aqueous solutions of /sup 99/Tc salts in which the /sup 99/Tc is in reduced valencey state, when administered to mammals, permit identification of the skeleton and of calcareous tumors by scintigraphy (radiographic scanning). The solutions are conveniently prepared by mixing one or more phosphonic acids (or their salts) with one or more reducing salts, and adding the mixture to an aqueous solution of a pharmaceutically acceptable /sup 99/pertechnetate salt. Reduction of the valence of the technetium occurs rapidly, and the resulting solution is adequately stable for use in scintigraphy. The phosphonic acid and reducing salt components can be premixed. Aqueous solutions of the premix are stable for long periods of time in the absence of free oxygen and the premix is stable to air so long as it is dry.

  16. The kinetics of dye formation by pulse radiolysis of pararosaniline cyanide in aqueous or organic solution

    International Nuclear Information System (INIS)

    The radiation-induced conversion of the leucocyanide of pararosaniline dye to the highly colored salt-isomer of the dye in acidic aqueous solution (wavelength of maximum absorption lambda sub(max)=540 nm) or polar organic solution (lambda sub(max)=550 nm), takes place in two separate processes. The first is very fast (within 3 s-1 to 106 s-1, as the acidity or concentration of an oxidizing agent increases. In oxygen-free acidic aqueous or organic solutions (argon saturated) there is an unstable transient species (lambdasub(max)=380 nm). When using O2 or N2O-saturated aqueous or organic solution, there is no intermediate absorption band at 380 nm, but the slow process of dye formation at 540 or 550 nm is still sequential to the initial fast process having somewhat faster kinetics than in Ar-saturated solution. (author)

  17. Influence of starch origin on rheological properties of concentrated aqueous solutions

    OpenAIRE

    Stojanović Željko P.; Jeremić Katarina B.; Jovanović Slobodan M.

    2011-01-01

    The rheological properties of corn and potato starch concentrated aqueous solutions were investigated at 25ºC. The starches were previously dispersed in water and the solutions were obtained by heating of dispersions at 115-120ºC for 20 minutes. The solutions of potato starch were transparent, while the corn starch solutions were opalescent. The results of dynamic mechanical measurements showed that the values of viscosity, h, storage modulus, G′, and loss modulus, G″, of the corn starc...

  18. Oscillometric and conductometric analysis of aqueous and organic dosimeter solutions

    DEFF Research Database (Denmark)

    Kovacs, A.; Slezsak, I.; McLaughlin, W.L.; Miller, A.

    Conductometric and oscillometric evaluation methods have earlier been developed to determine absorbed dose in the ethanol-monochlorobenzene dosimeter solution. Recent investigations on the same solution as well as on alanine solutions included the study of the possible use of different type ''con...... the applicable concentration of the alanine solute and the dose (1 to 50 kGy) and dose-rate range using both electron (2.6 mu s at 13 mu A to 4 mu s at 1.0 A pulse length and beam current) and gamma radiation (0.13 to 30 kGy h(-1))....

  19. Oscillometric and conductometric analysis of aqueous and organic dosimeter solutions

    DEFF Research Database (Denmark)

    Kovacs, A.; Slezsak, I.; McLaughlin, W.L.; Miller, A.

    Conductometric and oscillometric evaluation methods have earlier been developed to determine absorbed dose in the ethanol-monochlorobenzene dosimeter solution. Recent investigations on the same solution as well as on alanine solutions included the study of the possible use of different type...... the applicable concentration of the alanine solute and the dose (1 to 50 kGy) and dose-rate range using both electron (2.6 mu s at 13 mu A to 4 mu s at 1.0 A pulse length and beam current) and gamma radiation (0.13 to 30 kGy h(-1))....

  20. Gamma-radiolysis of aqueous solutions of tryptophan

    International Nuclear Information System (INIS)

    The nature of stable radiolytic products of tryptophan was investigated under different experimental conditions. Solutions of various tryptophan concentrations (10-2-10-4 mol dm-3) at pH 2 and 6.6 were analysed by paper and thin layer chromatography. In deaerated neutral solutions six products, which appeared to be invariant of initial tryptophan concentration, were observed. Chromatograms developed from deaerated solution at pH 2 revealed only one spot. In N2O-saturated solutions four products whose relative concentrations depended on the initial tryptophan concentration were observed. (author)