The sorption of thiocyanate ions on complex-forming ionites

The ligand sorption of thiocyanate ions on several complex-forming ionites was studied. The ionites were preliminarily transformed into metal forms by saturation with copper(II) ions. ANKB-2 amphoteric ionite in the Cu form had the strongest affinity for thiocyanate ions. The optimum conditions for their extraction were pH ∼ 2 and solution ionic strength 1. IR spectroscopy was used to study the ligand sorption of SCN⁻ ions by ANKB-2 ionite in the Cu form. The stability constants of thiocyanate ionite copper complexes were calculated from formation function [`(n)] \bar n .     

Selective extraction and concentration of dispersed copper from dilute solutions of copper and zinc ions with weakly basic aminoanionites

The possibility of selective extraction and multiple concentration of copper in the form of ultrafine precipitate from dilute Cu²⁺-Zn²⁺ solutions by using a suitable sorbent and an effective mode of its regeneration was demonstrated. The extraction was performed in the dynamic mode in column-type reactors filled with an aminoanionite as a selective complexing sorbent, the regeneration of which was conducted by chemical reduction of Cu²⁺ in the ionite after its saturation. It was established that saturation-reduction cycles repeated many times result in the accumulation of metallic copper at the surface and in the bulk of the sorbent. The mechanism of the process includes the formation of complexes of copper and zinc with amino groups of the ionite and the subsequent displacement of Zn²⁺ ions from the anionite due to its higher affinity to Cu²⁺ ions followed by the conversion of Cu²⁺ ions to an unsorbable form (dispersed metallic copper). It was demonstrated that the presence of dispersed copper stimulates the additional sorption of Cu²⁺ ions via redox conproportionation. This method makes it possible to obtain a degree of concentration of copper ions in three cycles >300% higher than that attainable in the purely ion-exchange mode (without chemical reduction).     

Thermodynamics of the sorption of cerium complex compounds on anionite

Sorption of cerium in the form of complexes with Trilon B (EDTA) from acid media at pH 3 using weakly basic anionite D-403 in nitrate, chloride, or sulfate forms is studied. The equation of the mass action law is linearized for ion exchange reactions, allowing us to calculate the limiting sorption of ethylenediaminetetraacetate cerate (EDTA cerate) ions on anionite and the constants of the exchange of complex cerium ions by chloride, nitrate, and sulfate ions. The limiting sorption of EDTA cerate ions in the anionite phase transitioning to the sulfate form is lower than that of ions on nitrate or chloride anionite, due to the high ionic potential of the sulfate ions. A sorption series of EDTA cerate ions on anionite D-403 in different ion exchange forms is presented according to the Gibbs energy of the ion exchange equilibrium.     

Determination of the Working Exchange Capacity of Weakly Basic Polyacrylic Anionites

The nonequilibrium dynamics of sorption of hydrochloric acid by weakly basic polyacrylic anionites was studied. An equation for calculating the working capacity of ion-exchange filters as a function of variable parameters (filtration rate, concentration of the starting solution, and height of the ionite bed in a filter) was derived using the theory of nonequilibrium dynamics of sorption.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 6, 2005, pp. 905–911.Original Russian Text Copyright © 2005 by Mamchenko, Savchenko.     

A microcalorimetric study of the sorption of copper(II) on KB-4 carboxyl cationite

The thermokinetics of sorption of copper(II) ions on KB-4 carboxyl cationite in the salt and hydrogen forms was studied microcalorimetrically. The total heat effect of sorption and its dependence on the degree of ionite filling were determined.     

Thermodynamic characteristics of sorption extraction and chromatographic separation of anionic complexes of erbium and cerium with Trilon B on weakly basic anionite

The adsorption of anionic complexes of erbium with Trilon B on D-403 anionite is studied at ionic strengths of 1 and 2 mol/kg (NaNO₃) and temperatures of 298 and 343 K. The values of the stability constants of complex ions of REE with Trilon B and the Gibbs energies of complexation are calculated. The values of the Gibbs energy and the enthalpy and entropy of ion exchange are determined. Using the obtained thermo-dynamic and sorption characteristics, the possible separation of anionic complexes of erbium and cerium with Trilon B is demonstrated via frontal ion-exchange chromatography. A series of sorption capacities of anionic complexes of cerium, yttrium, and erbium is presented using the values of the Gibbs energy of ion exchange.     

Complexation of Cu(II) with Hetarylformazanes in Solutions,Polycrystals, and Modified Anionite

The Cu(II) complexes with hetarylformazanes (HF) formed in solutions, polycrystals, and AN-18 polymeric ionite modified with HF were studied by EPR method and were found to have almost identical structures. The configuration of the Cu²⁺ coordination surrounding (square-planar or pseudotetrahedral) is specified by the substituents at N¹ in formazane fragments. Complexes with coordination unit Cu(4N) were formed mainly, when the ligands were taken in excess, while in the case of the ligand deficiency and with the coordinating OH group in benzene ring, the complexes with the Cu(3NO) coordination unit were formed. The covalence of in-plane metal-ligand σ-bond was found to be affected by the substituents. The formation of binuclear copper complexes in solutions and polycrystals was established in the case of deficiency of the ligand with SO₃H substituent in benzene ring.     

Synthesis and structure of Co(II), Ni(II), and Cu(II) complexes with Schiff bases,condensation products of 2-amino-4,8-naphthalenedisulfonic acid and aromatic carbinols

Ten new cobalt(II), nickel(II), and copper(II) complexes with Schiff bases obtained by condensation of 2-amino-4,8-naphthalenedisulfonic acid with carbinols (salicylaldehyde, benzoin, and 2-hydroxy-1-naphthaldehyde) have been synthesized. The compounds were studied by the X-ray powder diffraction method, thermal analysis, magnetic susceptibility and electric conductance measurements, and IR, EPR, diffuse reflectance, and EXAFS spectroscopy. The compositions of coordination cores in the complexes have been established. It was noted that the diversity of the resulting polyhedra is determined by the synthesis conditions, specific features of the stereochemistry of the ligands, and the electronic structure of the complex-forming metal.     

The influence of structural factors on the solvation and coordination unsaturation of metal complexes of several structurally related alkyl substituted dipyrrolylmethenes-2,2′ and porphin

The literature data and new results of calorimetric studies of the solution of copper(II), cobalt(II), zinc(II), nickel(II), and mercury(II) complexes with 3,3′,4,4′,5,5′-hexamethyldipyrrolylmethene-2,2′; 3,3′,5,5′-tetramethyl-4,4′-diethyldipyrrolylmethene-2,2′; 3,3′,5,5′-tetramethyl-4,4′-dibutyldipyrrolylmethene-2,2′ (A), and 2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphin in various organic solvents were used to calculate the enthalpies of transfer Δ_tr H ^o from benzene and estimate the contribution of specific solvation caused by the additional coordination (Δ_c H ^o) of electron donor solvent molecules (pyridine and dimethylformamide). The greatest degree of coordination unsaturation and ability to extracoordination was characteristic of copper(II) and mercury(II) complexes with ligand A. The influence of the nature of the complex-forming metal, differences in the alkylation of the ligands, solvent properties, and the macrocyclization effect on the solvation and coordination unsaturation of metal complexes was discussed.     

Complexation of transition metals with 8-hydroxyquinoline chemically immobilized on the surface of a silica gel-polyaniline composite

The complex-forming properties of a silica gel-polyaniline composite with 8-hydroxyquinoline covalently immobilized by the Mannich reaction with respect to Pb(II), Cd(II), Cu(II), Ni(II), Co(II), Al(III), Fe(III), and Mo(VI) ions were studied. The resulting adsorbent had a high sorption capacity and satisfactory kinetic characteristics, which allowed us to use it for the separation or preconcentration of transition metal ions. Data on the composition and structure of the test metal complexes with 8-hydroxyquinoline immobilized on the composite surface were obtained from an analysis of electronic diffuse reflectance spectra and corresponding adsorption isotherms.     

Peculiarities of electroosmosis of the second kind at the surfaces of one and two ionite granules

Electroosmosis of the second kind at the surfaces of one and two granules of a cationite and an anionite are studied by experimental methods. Dependences of the velocity of electroosmotic flow on the electric field strength, electrolyte concentration, and distance between the granules are measured. It is shown that the angular distribution and the velocity depend on the composition of an electrolyte and the type of an ionite. The absolute values and the angular distributions of the velocities are compared with the values observed for classical electroosmosis.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 2, 2005, pp. 192–200.Original Russian Text Copyright © 2005 by Mishchuk, Barinova.     

Comparative estimate of the efficiency of the sorption extraction of iodine from chloride solutions

The possibility of applying activated carbon and polymeric sorbents poly(4-vinylpyridine), polytrimethylsilylpropyne (PTMSP), bromo-substituted PNMSP (Br-PNMSP), poly(N-methyl-4-vinylpyridinium iodide) for the sorption recovery of iodine from a 0.5 M solution of sodium chloride is studied. The dependence of iodine sorption on the pH of solution, the amount of adsorbent, and the duration of contact between the solution and adsorbent is studied. The highest sorption capacity (G = 616.78 mg/g) is attained by using poly(N-methyl-4-vinylpyridinium iodide) anionite with the addition of iodine to form complex triiodide ions. The dynamics of iodine adsorption on poly(4-vinylpyridine) is described by a kinetic model of pseudosecond order. The composition and structure of the iodine compounds sorbed by polymers and activated carbon are studied by Raman spectroscopy (RS).     

The sorption of molybdenum from solutions of nitric acid

The sorption of molybdenum(VI) on KU-2 × 8 and AV-17 × 8 ionites from 6 n solutions of nitric acid was studied. The sorption of molybdenum(VI) on the cationite and anionite changed depending on solution composition and nitric acid concentration. The sorption and electromigration data were used to determine the isoelectric point of molybdenum in solutions of nitric acid.     

Use of radiotracer in adsorption studies of copper on peat

In this work copper adsorption by peat was studied using ⁶⁴Cu as tracer considering kinetic and thermodynamic aspects of the process. The study was carried out in agitated batch experiments with copper ion solutions with different initial concentrations at pH 4.5. Adsorption isotherms determined from equilibrium experiments by fitting experimental data to the Langmuir equation showed good correlations. Data obtained from kinetics experiments were fitted to a pseudo-second order model and also in this case a good correlation was obtained. Some parameters calculated from these studies such as rate constant or peat sorption capacity can be used in the development of a waste treatment process based on peat adsorption in batch or in column. The use of the ⁶⁴Cu radiotracer is presented as a simple, rapid and efficient technique to assess the copper adsorption by the peat. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaluation of copper(II)-binding ability of humic acids in peat using sulphopropyl-Sephadex C-25 cation exchanger

A method for the determination of copper(II) complexes with humic acids was developed by batch operation with the cation exchanger sulphopropyl-Sephadex C-25 (C-25). The copper-binding ability (conditional stability constants and copper-complexing capacities) of humic acids which were extracted from peat in Hokkaido was evaluated. A solution containing copper(II) ions and humic acids was shaken with the C-25 exchanger. The copper-humic acid complexes remained in the supernatant and the uncomplexed free copper ion was retained on the C-25. The copper-humic acid complexes were determined by flame atomic absorption spectrometry. The copper-binding ability of nitrilotriacetic acid (NTA) as a model ligand was similarly determined with a Scatchard plot. The conditional stability constant obtained at pH 4.5 was in good agreement with the reported value. The copper-binding abilities of the humic acids from peat were estimated using a Scatchard plot adopting a two-site model. The functional groups in the humic acids which contribute to the complexation with copper were investigated by conductimetric and pH titration, and the relationship between the copper-binding sites and functional groups in the humic acids was investigated.     

Investigation into sorption processes in the anodic stripping voltammetric speciation of Cu in natural waters

In the anodic stripping voltammetric speciation of copper significant errors may be introduced as a result of sorption of Cu²⁺ onto active surfaces of the voltammetric cell assembly. A correction method was developed based on monitoring of the total copper concentration in solution using a -radiotracer; additionally this allowed us to study sorption phenomena in the voltammetric cell assembly.For copper speciation in a fresh water sorption-corrected complexing capacity data (total natural ligand concentration and conditional stability constant of formed complex) showed considerable discrepancies with uncorrected data. From the same sorption data it could be deducted that this was accountable to the presence of two active surface sites in the voltammetric cell assembly.     

Influence of d-Electron Divalent Metal Ions in Complex Formation with L-Tartaric and L-Malic Acids

Binary complexes of α-hydroxy acids (L-Tartaric acid and L-Malic acid) with d-electron metal ions (copper, cobalt, nickel) were investigated. Potentiometric measurements have been performed in aqueous solution with computer analysis of the data for determination of the stability constants of complexes formed in the studied systems. The coordination mode of the complexes was defined using spectroscopic methods: electron paramagnetic resonance (EPR), ultraviolet-visible (UV-Vis), circular dichroism (CD), and infrared (IR). Results of the equilibrium studies have provided evidence for the formation of dimers with copper(II) ions and monomers with cobalt(II) and nickel(II) ions.     

Sorption Studies of Acid Dye by Mixed Sorbents

The sorption of Acid Blue 9 onto the mixture of activated clay and activated carbon has been studied in terms of pseudo-first order and pseudo-second order chemical sorption processes. The batch sorption model, based on the assumption of a pseudo-second order mechanism, has been developed to predict the rate constant of sorption and the equilibrium capacity with the effect of initial dye concentration, mass of mixed sorbent, temperature and initial solution pH. The rates of sorption were found to conform to pseudo-second order kinetics with good correlation. Batch isotherm studies showed that the sorption of Acid Blue 9 by the mixed sorbent from aqueous solution was described by the Langmuir isotherm equation. A comparison of the evaluated equilibrium capacity of sorption has been made by the pseudo-second order rate equation as well as by the Langmuir isotherm and operating line method. In addition, an activation energy of sorption has also been determined based on the pseudo-second order rate constants.     

Fungal biomass with grafted poly(acrylic acid) for enhancement of Cu(II) and Cd(II) biosorption

The biomass of Penicillium chrysogenum was modified by graft polymerization of acrylic acid (AAc) on the surface of ozone-pretreated biomass. The sorption capacity for copper and cadmium increased significantly as a large number of carboxyl groups were present on the biomass surface, especially when the carboxylic acid group was converted to carboxylate ions using NaOH. When modeled using the Langmuir isotherm, the sorption capacities were 1.70 and 1.87 mmol g(-1) for copper and cadmium, respectively. The loaded biosorbent was regenerated using HCl solution and used repeatedly over five cycles with little loss of uptake capacity beyond the second cycle. The sorption of the two metals was time-dependent, and the kinetics fitted the pseudo-second-order equation well. The Freundlich, Langmuir, Temkin, and Dubinin-Redushkevich isotherms were used to model the metal sorption isotherms, and the thermodynamic parameters calculated show that the sorption was spontaneous and endothermic under the condition applied and that the biomass has similar sorption affinities for the two metals. Fourier transform infrared and X-ray photoelectron spectroscopy reveal that carboxyl, amide, and hydroxyl groups on the biomass surface were involved in the sorption of copper and cadmium and ion exchange and complexation dominated the sorption process.