Search results for "aqueous solution"
showing 10 items of 1610 documents
Electrochemically triggered iodide-vacancy BiOI film for selective extraction of iodide ion from aqueous solutions
2021
Abstract The effective extraction and regeneration of radioactive iodide remains an urgent concern for safe nuclear energy utilization. Herein, we developed a novel electrochemically triggered iodide-vacancy BiOI film, which exhibited excellent I− ion extraction capacity of 328.3 mg·g−1. Especially, due to the ion vacancy trap effect, the film showed high selectivity towards I− ions in the existence of a large number of competitive anions. Additionally, the electrochemically switched ion extraction (ESIE) process with this iodide-vacancy BiOI film possessed fast extraction kinetics and high stability. More importantly, the trapped I− ions were easily desorbed from the film without the secon…
Photocatalytic degradation of organic compounds in aqueous systems by transition metal doped polycrystalline TiO2
2002
Abstract Some probe catalytic photooxidation reactions with aliphatic and aromatic organic compounds having different acid strengths, i.e. methanoic acid, ethanoic acid, benzoic acid and 4-nitrophenol, were carried out in aqueous systems by using polycrystalline TiO2 powders doped with various transition metal ions (Co, Cr, Cu, Fe, Mo, V and W). The Co-doped powder showed to be more photoactive than the bare TiO2 for methanoic acid degradation while the behaviour of TiO2/Cu and TiO2/Fe was similar to that of the support. TiO2/W was the most efficient sample for the photodegradation of benzoic acid and 4-nitrophenol, TiO2 the most active powder for ethanoic acid. A tentative explanation is p…
Hydrolysis of (CH3)Hg+ in Different Ionic Media: Salt Effects and Complex Formation
1998
The hydrolysis of monomethylmercury(II) was studied potentiometrically, in NaNO3, Na2SO4, and NaCl aqueous solution, in a wide range of ionic strengths (NaNO3, 0 ≤ I ≤ 3.25; Na2SO4, 0 ≤ I ≤ 1; NaCl, 0 ≤ I ≤ 3 mol dm-3) and at t = 25 °C. For the reaction (CH3)Hg+ = (CH3)Hg(OH)° + H+, we found log K1 = −4.528 (I = 0 mol dm-3). The species [(CH3)Hg]2(OH)+ was also found, with log β2 = −2.15. Monomethylmercury(II) forms quite strong complexes with Cl- (log K = 5.45, I = 0 mol dm-3) and SO42- (log K = 2.64, I = 0 mol dm-3). The dependence on ionic strength of formation constants was considered by using a Debye−Huckel type equation. Hydrolysis and complex formation constants (at different ionic s…
Immobilization of vegetable tannins on tannery chrome shavings and their use for the removal of hexavalent chromium from contaminated water
2011
Abstract Chestnut (C) and mimosa (M) tannins immobilized on chrome shavings (CS) as an adsorbent have been proposed to be an efficient and economical alternative in hexavalent chromium removal from aqueous solutions. The adsorption of hexavalent chromium onto chrome shavings-tannin (CS-T) adsorbents was performed using batch equilibrium technique at 25 ± 2 °C. The effect of pH is highly important especially in the case of high concentrations of hexavalent chromium. The maximum chromium uptake was obtained at pH 4. Two hours of contact time are enough to reach equilibrium. Sorption of chromium on CS-T was found to follow a pseudo-second order kinetic model (with correlation coefficients grea…
Reversible swelling of polyanion/polycation multilayer films in solutions of different ionic strength
1996
Immersion of consecutively adsorbed polyanion/polycation multilayer films in solutions of different ionic strength causes reversible thickness changes. Swelling of the films up to 18% was observed after soaking the films in aqueous solutions of NaCl at concentrations up to 1.0 mol/l. X-ray reflectivity clearly shows that the thickness changes are reversible within experimental error and that the films seem to get smoother after several cycles of immersion in salt solutions and in pure water. The extent of swelling depends on the internal film structure, namely on the number of polyanion/polycation interfaces in a film of a given thickness. Interestingly, the swelling levels off at salt conc…
Transfer of Some Alkyl Substituted Ferrocenes from Water to Cationic Surfactant Micelles Studied by Kinetic Method
1994
Abstract Binding of ferrocene and its 1,1′-dimethyl and n -butyl derivatives to dodecyl and tetradecyltrimethylammonium nitrate micellar aggregates has been studied at 20.0°C and ionic strength 0.02 tool dm -3 by examining the micellar retarding effects on the rates of iron(III) oxidation of these substrates. Solubilization of the ferrocenes in the cationic micellar phase increases as the substrate hydrophobic character increases and, to a lesser extent, as the surfactant hydrocarbon chain length becomes longer. The critical micelle concentrations of the surfactants used and the incremental free energy of transfer of methylene groups of both the substrate and the surfactant from the aqueous…
Ionic polymers based on dextran: hydrodynamic properties in aqueous solution and solvent mixtures.
2009
Hydrodynamic properties of a series of ionic polysaccharides with different charge density but the same molecular weight have been evaluated in salt-free aqueous solution and aqueous/organic solvent mixtures by means of capillary viscometry. The polyelectrolytes investigated contain quaternary ammonium salt groups, N-ethyl-N,N-dimethyl-2-hydroxypropylammonium chloride, attached to a dextran backbone. The experimental viscometric data have been plotted in terms of the Wolf method. The results show that the experimental data fit well with this model and allow the calculation of intrinsic viscosities and other hydrodynamic parameters, which provide new information about the dependence of the p…
Compounds of molybdenum(VI) with aspartic acid: A spectrophotometric and potentiometric study of the formation and interconversion equilibria in aque…
1990
Addition of Na2MoO4 to an excess of aspartic acid (AspH2) can produce any of four different complexes depending on the pH, namely [MoO3(Asp)]2−, [Mo2O5(Asp)2]2−, [Mo2O4(OH)(Asp)2]− and [Mo2O4(Asp)2]. The ranges of formation of these species with pH, the number of equivalents of acid necessary for their formation, and their stoichiometries, condensation degrees and stability constants, have been calculated by potentiometric and spectrophotometric techniques. The aspartic acid acts as a tridentate ligand in all cases.
Speciation of polyelectrolytes in natural fluids Protonation and interaction of polymethacrylates with major components of seawater.
2002
Acid–base properties of two sodium polymethacrylates (W= 4000 and 5400 Da) were studied potentiometrically in aqueous solution at 25 °C. Measurements were made in different salt solutions: LiCl 0.1–1.5, NaCl 0.1–2, KCl 0.1–2, Et4NI 0.1–0.75 mol l − 1 , and in artificial seawater in the salinity range 10 S 45. Protonation data were analysed by two different models and the dependence of the relative parameters on ionic strength were calculated. Measurements performed in interacting media (alkali metal chlorides and artificial seawater) were interpreted in terms of complex formation, and the relative formation parameters are reported. Previous data on the interaction of a higher molecular weig…