Sorption of sodium dodecyl sulfate by highly basic anion-exchange resins

The interaction in the system of sodium dodecyl sulfate (SDS) solution and AB-17 highly basic anion-exchange resins in OH⁻ and Cl⁻ forms were considered, and the distribution coefficients (K _d) of the substance in the resin-solution ion exchange system were calculated. It was found that K _d decreases with increasing concentration of the initial solution, reaching a maximum value at the critical micelle concentration (CMC) of SDS. The effective diffusion coefficients of the surfactant in the anion-exchange resin phase were calculated; based on the IR spectroscopy data, the mechanism of SDS absorption was proposed.     

Separation of pyridine compounds on ion-exchange resins

The reaction of pyridine compounds (pyridine, 4-methylpyridine, 4-hydroxypyridine, 4-carboxypyridine, pyridine-4-aldehyde, and pyridine-4-aldoxime) with KU-2 cation-exchange resins in the H⁺, K⁺, and NH₄ ⁺ forms and with AV-17 anion-exchange resins in the OH^– and Cl^– forms was investigated. A dependence of the maximum partition coefficients of the pyridine compounds on the composition and concentration of the eluent was found. The chromatogram of the separation of a mixture of pyridine compounds on AV-17 (Cl^– form) is presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 220–224, February, 1971.     

Equilibria in the system of aquachlorohydroxogold(III) complexes in aqueous solution

AuCl₄⁻ + jOH⁻ + kH₂O = AuCl_{4 − j − k} OH _j (H₂O) _k ^{k − 1} + (j + k)Cl⁻ equilibria at 20°C were studied spectrophotometrically, and the constants β _jk in acid aqueous solutions were determined for I = 2.0 mol/L (HClO₄).     

Iodide interaction with natural pyrite

¹²⁹I is one of the major dose-determining nuclides in the safety analysis of deep storage of radioactive waste. Iodine forms anionic species that hardly sorb on the surfaces of common host-rock minerals. Recently, interest has arisen on the role of pyrite, an accessory mineral capable of binding anionic selenium. Whereas the interaction of selenium with pyrite is well documented, corresponding results on iodine sorption are still scarce and controversial. Pyrite is present in argicilleous rocks which are being considered in many countries as potential host rocks for a radioactive waste repository. The uptake of iodide (I⁻) on natural pyrite was investigated under nearly anoxic conditions (O₂ < 5 ppm) over a wide concentration range (10⁻¹¹–10⁻³ M total I⁻) using ¹²⁵I as the radioactive tracer. Weak but measurable sorption was observed; distribution coefficients (R _d) were less than 0.002 m³ kg⁻¹ and decreased with increasing total iodide concentration. Iodide sorption was connected to the presence of oxidized clusters on the pyrite surface, which were presumably formed by reaction with limited amounts of dissolved oxygen. The results obtained indicated that pyrite cannot be considered as an effective scavenger of ¹²⁹I under the geochemical conditions prevailing in underground radioactive waste geologic storage.     

Kinetics and mechanism of the reactions of hexaaqua rhodium (III) with sulphur (IV) in aqueous medium

An O-bonded sulphito complex, Rh(OH₂)₅(OSO₂H)²⁺, is reversibly formed in the stoppedflow time scale when Rh(OH₂) ₆ ³⁺ and SO₂/HSO ₃ ⁻ buffer (1 <pH< 3) are allowed to react. For Rh(OH₂)₅OH₂₊+ SO₂ □ Rh(OH₂)₅(OSO₂H)²⁺ (k₁/k_-1), k₁ = (2.2 ±0.2) × 10³ dm³ mol⁻¹ s⁻¹, k₋1 = 0.58 ±0.16 s⁻¹ (25°C,I = 0.5 mol dm⁻³). The protonated O-sulphito complex is a moderate acid (K _d = 3 × 10⁻⁴ mol dm⁻³, 25°C, I= 0.5 mol dm⁻³). This complex undergoes (O, O) chelation by the bound bisulphite withk= 1.4 × 10⁻³ s⁻¹ (31°C) to Rh(OH₂)₄(O₂SO)⁺ and the chelated sulphito complex takes up another HSO ₃ ⁻ in a fast equilibrium step to yield Rh(OH₂)₃(O₂SO)(OSO₂H) which further undergoes intramolecular ligand isomerisation to the S-bonded sulphito complex: Rh(OH₂)₃(O₂SO)(OSO₂)^- → Rh(OH₂)₃(O₂SO)(SO₃)⁻ (k _iso = 3 × 10⁻⁴ s⁻¹, 31°C). A dinuclear (μ-O, O) sulphite-bridged complex, Na₄[Rh₂(μ-OH)₂(OH)₂(μ-OS(O)O)(O₂SO)(SO₃) (OH₂)]5H₂O with (O, O) chelated and S-bonded sulphites has been isolated and characterized. This complex is sparingly soluble in water and most organic solvents and very stable to acid-catalysed decomposition     

Complex formation of thiocyanate ions with iron(III) on the solid phase of fibrous ion exchangers

Characteristics of complex formation of SCN^–-ions with iron(III) on fibrous materials filled with an AV-17 anion exchanger (PANV–AV-17) and a KU-2 cation exchanger (PANV–KU-2) are studied by diffuse reflection spectroscopy. Sorption conditions of thiocyanate ions on PANV–AV-17 in the dynamic mode and the influence of concentrations of Cl^–, SO ₄ ^2- and NO ₃ ^- on the sorption and analytical signals of thiocyanate complexes are studied. Sorption conditions of iron(III) on PANV–KU-2 and the conditions of formation of thiocyanate complexes are studied. Systems for the sorption–spectroscopic determination of 0.1–0.7 μg/mL of SCN^–-ions in aqueous solutions of pH 5 ± 1 on PANV–AV-17 and test-determination of 5–30 μg of SCN^–-ions on PANV–KU-2 are proposed.     

The sorption of molybdenum(VI) by ionites from solutions in hydrochloric acid

The sorption of molybdenum(VI) by KU-2 × 8 and AV-17 × 8 ionites from solutions in hydrochloric acid (1 × 10⁻⁵−6 N) was studied. Changes in the sorption of molybdenum(VI) by cationite and anionite were observed. The isoelectric point of molybdenum in solutions in hydrochloric acid was determined from sorption and electrical migration measurements.     

How synthesis parameters influence the structure and properties of calcium fluoroapatite

A moderate-temperature method for the synthesis of calcium fluoroapatite in chloride and carbonate melts is developed. It is shown that fluoroapatite can contain CO₃²⁻ and OH⁻ groups in different ratios depending on the parameters of its synthesis. The influence of CO₃²⁻ and OH⁻ groups on the sorption properties of apatite, in particular, on the sorption of Cu²⁺ ions is considered. The greater the number of the CO₃²⁻- and OH⁻ groups in the structure of apatite, the higher is the value of sorption.     

Comparison of the sorption properties of crystalline and amorphous samarium(III) oxohydroxides

The influence of the pH of precipitation (pH₁) and the ionic medium on the sorption properties of as-precipitated samarium(III) oxohydroxides,i.e., the pH of zero charge point and the rate of heterogeneous hydrolysis of the IrCl₆ ²⁻, RhCl₆ ³⁻, and PtCl₄ ²⁻ complexes, was studied. The composition of precipitates was studied by the drop titration of solutions of samarium nitrate and thermography. It was found that as-predipitated samarium oxohydroxides are amorphous and the substitution of NO₃ ⁻ ions by OH⁻ is not complete even at pH₁ 11. Heterogeneous hydrolysis occurs on the surface of samarium oxohydroxide, and its rate increases with increasing pH₁. The as-precipitated samarium oxohydroxides have much higher sorption activities than crystalline Sm₂O₃, and their activities are similar to those of ferrogels. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 583–588, April, 1998.     

Effect of bromide salts on cationic micellar catalysis

 The effect of bromide salts, MBr [M=Na, (CH₃)₄N, (C₂H₅)₄N, (C₄H₉)₄N, C₈H₁₇N(CH₃)₃], on the first-order rate constant, k ₁, of basic hydrolysis of 2,4-dinitrochlorobenzene in micelle solutions of cetyltrimethylammonium bromide has been studied. The main results are as follows. The molar ratio concentrations of OH⁻, m ^S _OH, on the micelle surface in the presence of different concentrations of Br⁻ ions, were calculated on the basis of the pseudophase ion-exchange model, and there is a linear relation between k ₁ and m ^S _OH. The relation between k ₁ and the concentrations of various bromides could be presented with a single curve, and the cations of the bromides have little effect on k ₁. Under the experimental conditions, there is a linear relation between 1/k ₁ and the concentrations of Br⁻; thereby a new method calculating the competition binding constant between OH⁻ and Br⁻ from dynamic data is proposed. The hydrodynamic radii of the micelles increase with the addition of bromide salts. Received: 1 August 2000 Accepted: 31 January 2001     

Base hydrolysis ofcis-(methyl/ethylamine)bis(ethylenediamine) (salicylato)cobalt(III) complexes

The kinetics of the base hydrolysis ofcis-[Co(en)₂(RNH₂)-(SalH)]²⁺ (R=Me or Et; SalH=HOC₆H₄CO ₂ ⁻ ) were investigated in aqueous ClO ₄ ⁻ in the 0.004–0.450 mol dm⁻³ [OH⁻] range, I=0.50 mol dm⁻³ at 30–40°C. The phenoxide species is hydrolysed via [OH⁻]-independent and [OH⁻]-dependent paths, the latter being first order in [OH⁻]. The high rate of alkali-independent hydrolysis of the phenoxide species is associated with high ΔH^≠ and ΔS^≠ values, in keeping with the SNICB mechanism involving an amido conjugate base generated by the phenoxide-assisted NH-deprotonation of the coordinated amine. The [OH⁻]-dependent path also involves the conventional SN₁ CB mechanism. The rate constant, k₁, for the SNICB path exhibits a steric acceleration with the increasing size of the non-labile alkylamine, whereas the rate constant, k₂, for the SN₁CB path shows a reverse trend. TMC 2578     

Kinetics and mechanism of complexation of iron(III) bycis-(salicylato)(methyl/ethylamine)bis(ethylenediamine)cobalt(III) ions

The formation and dissociation of the binuclear complexes of Fe^III withcis-[Co(en)₂(RNH₂)SalH]²⁺ [R=Me, Et and SalH=C₆H₄(OH)CO ₂ ⁻ ] were studied by a stopped-flow technique at 20–35°C, and I=1.0 mol dm⁻³ (ClO ₄ ⁻ ). The formation of the binuclear species, N₅CoSalFe⁴⁺, involves reactions of the phenol form of the Co^III substrates with Fe(OH₂) ₆ ³⁺ and Fe(OH₂)₅OH²⁺. The mechanism of reaction of Fe(OH₂)₅OH²⁺ is essentially Id, while that of Fe(OH₂) ₆ ³⁺ appears to be Ia. The formation rate constant, k₁, for Fe(OH₂) ₆ ³⁺ /N₅CoSalH²⁺ reaction decreases as the amine chain length increases, whereas the same (k₂) for the Fe(OH₂)₅OH²⁺/N₅CoSalH²⁺ reaction does not show any such trend. The binuclear species, N₅CoSalFe⁴⁺, dissociates to yield a Co^III substrate and Fe^III speciesvia a predominantly spontaneous dissociation path and a minor acid catalysed path which are relatively insensitive to the variation in size of the non-labile amine chain length.     

Bioadsorption and ion exchange of Cr3+ and Pb2+ solutions with algae

Heavy metals can be removed from effluents and recovered using physico-chemical mechanisms as biosorption processes. In this work “Arribada” seaweed biomass was employed to assess its biosorptive capacity for the chromium (Cr³⁺) and lead (Pb²⁺) cations that usually are present in waste waters of plating industries. Equilibrium and kinetic experiments were conducted in a mixed reactor on a batch basis. Biosorption equilibrium and fluid-solid mass transfer constants data were analyzed through the concept of ion exchange sorption isotherm. The respective equilibrium exchange constants (K _eqCr=173.42, K _eqPb=58.86) and volumetric mass transfer coefficients ((k _mCr a)′=1.13×10⁻³ s⁻¹, (k _mPb a)′=0.89×10⁻³ s⁻¹) were employed for the dynamic analysis of Cr and Pb sorption in a fixed-bed flow-through sorption column. The breakthrough curves obtained for both metals were compared with the predicted values by the heterogeneous model (K _eqCr=171.29, K _eqPb=60.14; k _mCr a=7.81×10⁻² s⁻¹, k _mPb a=2.43×10⁻² s⁻¹), taking into account the mass transfer process. The results suggest that these algae may be employed in a metal removal/recovery process at low cost. An erratum to this article can be found at     

Comparative study on uni-univalent and uni-bivalent ion-exchange reaction on Doulite A-116

Determination of ion-exchange equilibrium constant (K) for Cl⁻/I⁻ and Cl⁻/C₂O₄²⁻ system was studied at different temperatures from 25 to 45°C and by varying concentration of iodide and oxalate ion solution. For both uni-univalent and uni-bivalent exchange systems, using 0.5 g of ion-exchange resin DUOLITE A-116 (in chloride form), the value of K increases with rise in temperature i.e., from 13.0 at 25°C to 19.05 at 45°C for Cl⁻/I⁻ system and 33.0 at 25°C to 63.0 at 45°C for Cl⁻/C₂O₄²⁻ system indicating the endothermic ion-exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution.     

Study of temperature effect on uni-univalent and uni-bivalent ion exchange reaction

Ion exchange equilibrium constant (K) for Cl⁻/Br⁻ and Cl⁻/C₂O₄²⁻ system was studied at different temperatures from 30 to 45°C. For both uni-univalent and uni-bivalent exchange systems, the value of K increases with rise in temperature i.e., from 1.16 at 30°C to 2.95 at 45°C for Cl⁻/Br⁻ system and 19.5 at 30°C to 30.0 at 45°C for Cl⁻/C₂O₄²⁻ system indicating the endothermic ion exchange reaction. The difference in K values at the same temperature for the two was related to the ionic charge of exchangeable ions in the solution. The article is published in the original.     

Anion adsorption in the course of dichromate reduction on a smooth gold electrode in aqueous acid solutions

The specific adsorption of anions (HSO₄ ⁻, Cl⁻) present in low concentration (c < 10⁻³ mol dm⁻³) was studied by radiotracer techniques in the course of the reduction of dichromate (chromate) species in 1 mol dm⁻³ HClO₄ supporting electrolyte. In accordance with the results of preliminary studies reported earlier, enhancement of the anion adsorption was found, induced by some adsorbed intermediates of the reduction process. Potential dependence of the induced adsorption and its correlation with the reduction rate was investigated. The role of adsorption competition between various anions is discussed. It is concluded that study of the induced anion adsorption could be a tool for the investigation of the sorption of intermediates formed in the course of the reduction. Received: 3 May 1999 / Accepted: 10 June 1999     

Cation mobility in modified Li1 ? xTi2 ? xNbx(PO4)3 lithium titanium NASICON phosphates

Li_{1 − x} Ti_{2 − x} Nb _x (PO₄)₃ NASICON materials are prepared and studied by X-ray diffraction, ⁷Li and ³¹P NMR spectroscopy, and impedance spectroscopy. Vacancy mobility in Li_{1 − x} Ti_{2 − x} Nb _x (PO₄)₃ is lower than interstitial lithium mobility. Nb⁵⁺ cations with low doping levels increase cation mobility in LiTi₂(PO₄)₃. Original Russian Text ? I.Yu. Pinus, I.A. Stenina, A.I. Rebrov, N.A. Zhuravlev, A.B. Yaroslavtsev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 8, pp. 1240–1244.     

Modelling spur chemistry for alkaline and acidic water at high temperatures

The effect of pH and associated ionic strength on the primary yields in the radiolysis of pressurised water has been assessed by diffusion-kinetic calculations for temperatures in the range 100–300°C. Account has been taken for ionic strength I up to 0.1 mol kg⁻¹, assuming that the counter ions of H⁺ in acid solutions and of OH⁻ in base solutions have unit charge. In acid solutions, the H⁺ ions react with e⁻ _aq. The decrease in G(e⁻ _aq) and the increase in G(H) with decreasing pH becomes substantial for [H⁺] ≥ 1 × 10⁻⁴ m, but the primary yields of oxidising species are almost constant. In alkaline solutions, the OH⁻ anions affect the spur chemistry of radiation-generated protons and hydroxyl radicals for [OH⁻] ≥ 1 × 10⁻⁴ m. The scavenging of H atoms and hydrogen peroxide becomes significant for [OH⁻] ≥ 1 × 10⁻² m. The total yields G(OH) + G(O⁻) and G(H₂O₂) + G(HO₂ ⁻) are independent of base concentration below 0.01 m. In more alkaline solutions, G(OH) + G(O⁻) increases, whereas G(H₂O₂) + G(HO₂ ⁻) decreases with increasing [OH⁻]. Calculations showed the substantial yield of the reaction O⁻ + e⁻ _aq in 0.1 m base solution. Spur chemistry in alkaline hydrogenated water is not affected by the presence of H₂ if less than 0.001 m of hydrogen is added.     

Osmotic and Activity Coefficients of the {<Emphasis Type="Italic">x</Emphasis>ZnCl<Subscript>2</Subscript>+(1−<Emphasis Type="Italic">x</Emphasis>)ZnSO<Subscript>4</Subscript>}(aq) System at 298.15 K

Isopiestic vapor pressure measurements were made for {xZnCl₂+(1−x)ZnSO₄}(aq) solutions with ZnCl₂ molality fractions of x=(0,0.3062,0.5730,0.7969, and 1) at the temperature 298.15 K, using KCl(aq) as the reference standard. These measurements cover the water activity range 0.901–0.919≤a _w≤0.978. The experimental osmotic coefficients were used to evaluate the parameters of an extended ion-interaction (Pitzer) model for these mixed electrolyte solutions. A similar analysis was made of the available activity data for ZnCl₂(aq) at 298.15 K, while assuming the presence of equilibrium amounts of ZnCl⁺(aq) ion-pairs, to derive the ion-interaction parameters for the hypothetical pure binary electrolytes (Zn²⁺,2Cl⁻) and (ZnCl⁺,Cl⁻). These parameters are required for the analysis of the mixture results. Although significant concentrations of higher-order zinc chloride complexes may also be present in these solutions, it was possible to represent the osmotic coefficients accurately by explicitly including only the predominant complex ZnCl⁺(aq) and the completely dissociated ions. The ionic activity coefficients and osmotic coefficients were calculated over the investigated molality range using the evaluated extended Pitzer model parameters.     

A study of ion exchange equilibrium for some uni-univalent and uni-divalent reaction systems using strongly basic anion exchange resin Indion-830 (Type 1)

A study of the thermodynamics of ion exchange equilibrium for uni-univalent Cl⁻/I⁻, Cl⁻/Br⁻ and uni-divalent Cl⁻/SO ₄ ²⁻ , Cl⁻/C₂O ₄ ²⁻ reaction systems was carried out using ion exchange resin Indion-830 (Type 1). The equilibrium constant K was calculated by taking into account the activity coefficients of ions both in solution and in the resin phase. For uni-univalent ion exchange reaction systems, the equilibrium constants K′ were also calculated from the mole fraction of ions in the resin phase. The K values calculated for uni-univalent and uni-divalent anion exchange reaction systems increased as the temperature grew, indicating the endothermic character of the exchange reactions with enthalpies of 38.2, 32.3, 7.6, and 11.4 kJ/mol, respectively. The article is published in the original.