Thermochemical kinetics of the formation of supramolecular compounds of amino acids with carboxylic cation exchangers

The kinetics of sorption of glycine and methionine from aqueous solutions with various acidities on the carboxylic cation exchangers KB-2 and KB-4 in protonated, deprotonated, and copper forms at 298 K was studied by microcalorimetry. In the sorption of the amino acids on the copper forms of the cation exchangers, the heat flux changes its sign. The character of the aliphatic amino acid-carboxylic cation exchanger interparticle interaction depends on the ionic form of the cation exchanger. As determined by the sorption method and IR spectroscopy, the nature of the glycine and methionine sorption sites in the ion exchanger phase changes on passing from the protonated to the copper form of the sorbent.     

Test Determination of Cu(II), Ni(II), and Cr(VI) in a Single Sample

It was shown that Cr(VI), Ni(II), and Cu(II) can be simultaneously adsorbed on a solid phase consisting of two filled fibrous disks and then determined visually using organic reagents. One sorbent disk, a fibrous material filled with an AB-17 anion exchanger, was used to determine chromium by its reaction with 1,5-diphenylcarbazide. Another disk filled with an KU-2 cation exchanger was used for the simultaneous sorption of copper and nickel followed by the consecutive determination of nickel with dimethylglyoxime and copper with sodium diethyldithiocarbamate. The conditions were optimized for the determination of nickel in the presence of copper and of copper in the presence of nickel after decomposing its dimethylglyoxime complex with 1 M HCl. The detection limits were 0.02, 0.1, and 0.05 mg/L for Cr, Ni, and Cu, respectively. The time of analysis was no longer that 20 min.     

Composition,structure, and functional properties of organomineral composite sorbents KU-2×8-ZnS and KU-2×8-PbS

Organomineral composite sorbents KU-2×8-ZnS and KU-2×8-PbS were synthesized on the basis of the matrix of a strongly acidic KU-2×8 cation exchanger. Scanning electron microscopy and elemental analysis were used to study their microstructure and chemical composition. With the use of potentiometric titration, their bifunctional nature was revealed and the dissociation constants and the total exchange capacities of the ionogenic groups were determined. The sorption of copper(II), zinc, and cadmium by KU-2×8-ZnS and KU-2×8-PbS sorbents from 0.005 M solutions of their salts was examined. The total dynamic sorption capacity of the composite sorbents for the above metals, found in the study, exceeds similar values for the individual KU-2×8 cation exchanger by a factor of 1.6–2.0 and that in 0.001–0.050 M solutions of potassium and calcium chlorides, by a factor of 1.3–4.5. An explanation is suggested for the sorption process of heavy nonferrous metals on composite sorbents with an active sulfide component by the mechanism of coordination copolymerization.     

Sorption of chromium(III) and chromium(VI) on lead sulfide

The sorption of chromium(III) and chromium(VI) on lead sulfide has been investigated in dependence on pH, time of sorption and the concentrations of sorbate and sorbent. The mechanisms of the sorption of Cr³⁺ and CrO ₄ ^2– traces on lead sulfide are discussed; a difference between CrO ₄ ^2– sorption on PbS and -Fe₂O₃ has been found. Sulfates and molybdates affect the removal of chromates from aqueous solutions. Lead sulfide carrier prepared in this work was also used for the preconcentration of chromium(III) and chromium(VI) from tap water.     

Simultaneous sorption of nonionic surfactant (alkylmonoethers) and copper(II) in a weak acid polyacrylic cation exchanger

The mutual influence of copper(II) cations and nonionic surfactant alkylmonoethers on their simultaneous sorption by the hydrogen form of Purolite C 106 polyacrylic acid functionalized cation exchanger was investigated considering the suitability for the prevention of environmental contamination. Sorption isotherms were measured and sorption equilibrium coefficients calculated. The modelling of copper(II) sorption and copper(II) carboxyl complex formation was carried out. The sorption of copper(II) proceeds predominantly by complex (ionic and coordinate) bonding followed by the change in pH, also by single coordinate bonding. The mutual action of copper(II) and alkylmonoethers leads to a decrease in the equilibrium sorption for both copper(II) and the surfactant. The sorption of copper(II) and alkylmonoethers could be applicable for the purification of sewage including copper plating rinsewater from both contaminants simultaneously for the control of copper(II) and the surfactant in sewage effluents. Received: 15 May 2000 Accepted: 9 May 2001     

Application of a new nanoporous sorbent for extraction and pre-concentration of lead and copper ions

The authors describe a method for the trace determination of copper (II) and lead (II) in water and fish samples using solid-phase extraction via siliceous mesocellular foam functionalised by dithizone. Siliceous mesocellular was functionalised with dithizone, and the resulting sorbent was characterised by scanning electron microscopy, surface area analysis, thermogravimetric/differential thermal analysis and FTIR. Following solid-phase extraction of target ions by the sorbent, copper and lead ions were quantified by flame atomic absorption spectrometry. Factors affecting the sorption and desorption of target ions by the sorbent were evaluated and optimised. The calibration plot is linear in the 1 – 500 μg L^?1 copper (II) and 3–700 μg L^?1 lead (II) concentration range. The relative recovery efficiency in real sample analysis is in the range from 96 to 102%, and precision varies between 1.7 and 2.8%. It is should be noted that the limits of detection for the copper and lead analysis were 0.8 and 1.6 μg L^?1, respectively. Also, the adsorption capacities for copper and lead ions were 120 and 160 mg g^?1, respectively. The obtained pre-concentration factor for the lead and copper ions by the proposed solid-phase extraction was 75. The method was successfully applied to the determination of low levels of copper (II) and lead (II) in tap, Caspian sea, Persian gulf and lake water and also their detection in fish samples.     

Simultaneous purification of sewage from Cd(II) and nonionic surfactant with cation exchanger

The sorption of nonionic surfactant (alkylmonoethers ALM-10), taking place simultaneously with the sorption of Cd(II) in H-form of polyacrylic cation exchangers KB-2 and KB-2-12P was investigated. Increasing the sorption of surfactant the decrease in both the stability of Cd(II) complex with cation exchanger and the equilibrium sorption of Cd(II) was observed. The isotherms of the sorption were measured; the coefficients of intraparticle diffusion (D) were calculated. The integration of the filter filled with polyacrylic cation exchanger into the system of sewage purification is suggested.     

Sorption Purification of Scandium(III) To Remove Zirconium(IV) Impurity in Hydrochloric Acid Solutions

A study was made on separation of the Zr(IV) impurity from scandium(III) in hydrochloric acid solutions by sorption with KRF-20t-60 cation exchanger, including sorption kinetics and sorption under dynamic conditions. The sorbent regeneration with 5% ammonium fluoride or 10% potassium carbonate at 22°C was considered.     

Flocculation of starch-coated solidified emulsion droplets and calcium carbonate particles

Zirconium phosphate (ZrP) has recently been demonstrated as an excellent sorbent for heavy metals due to its high selectivity, high thermal stability, and absolute insolubility in water. However, it cannot be readily adopted in fixed beds or any other flowthrough system due to the excessive pressure drop and poor mechanical strength resulting from its fine submicrometer particle sizes. In the present study a hybrid sorbent, i.e., polymer-supported ZrP, was prepared by dispersing ZrP within a strongly acidic cation exchanger D-001 and used for enhanced lead removal from contaminated waters. D-001 was selected as a host material for sorbent preparation mainly because of the Donnan membrane effect resulting from the nondiffusible negatively charged sulfonic acid group on the exchanger surface, which would enhance permeation of the targeted metal ions. The hybrid sorbent (hereafter denoted ZrP-001) was characterized using a nitrogen adsorption technique, scanning electron microscope (SEM), and X-ray diffraction (XRD). Lead sorption onto ZrP-001 was found to be pH dependent due to the ion-exchange mechanism, and its sorption kinetics onto ZrP-001 followed the pseudo-first-order model. Compared to D-001, ZrP-001 exhibited more favorable lead sorption particularly in terms of high selectivity, as indicated by its substantially larger distribution coefficients when other competing cations Na(+), Ca(2+), and Mg(2+) coexisted at a high level in solution. Fixed-bed column runs showed that lead sorption on ZrP-001 resulted in a conspicuous decrease of this toxic metal from 40 mg/L to below 0.05 mg/L. By comparison with D-001 and ZrP-CP (ZrP dispersion within a neutrally charged polymer CP), enhanced removal efficiency of ZrP-001 resulted from the Donnan membrane effect of the host material D-001. Moreover, its feasible regeneration by diluted acid solution and negligible ZrP loss during operation also helps ZrP-001 to be a potential candidate for lead removal from water. Thus, all the results suggested that ZrP-001 offers excellent potential for lead removal from contaminated water.     

Sulfide Ion-Selective Electrode as Potentiometric Sensor for Lead(II) Ion in Aqueous and Nonaqueous Medium

Abstract

The possibilities of a sulfide ion-selective electrode (SISE) for the determination of lead(II) at different pH values is presented. Potential - time curves recorded after addition of lead(II) in sulfide solution constitute the primary data in this study. The influence of the pH and ethanol in ethanol-aqueous mixtures on the behaviour of a SISE and on formation of PbS was investigated. A relationship between the initial rate of decrease of the sulfide concentration in test solution and various amounts of lead(II) is discussed. The results of measurements showed the possibility of determining up to micromole quantities of lead(II).     

Zeolite-modified paraffin-impregnated graphite electrode

This paper describes a new kind of zeolite-modified electrodes (ZMEs) based on the physical immobilization of zeolite particles onto the surface of paraffin-impregnated graphite electrodes (PIGEs). Their electrochemical behavior was first evaluated by ion-exchange voltammetry using methylviologen as a model redox probe, indicating better performance in comparison to the corresponding zeolite-modified carbon paste electrodes. The zeolite-modified-PIGEs were then applied to the study of lead(II)-loaded zeolites to monitor their reaction with sulfide ions at various sulfidation levels. Both Pb(II) ions and PbS nanoparticles gave rise to well-defined voltammetric signals, but peak currents due to the more mobile Pb(II) ions were much higher than those recorded for PbS nanoparticles. This is due to the fact that Pb(II) ions underwent ion exchange for the electrolyte cation prior to the electron transfer whereas the PbS nanoparticles are immobilized in the microporous structure of the zeolite particles and thus less available for the redox reactions. Nevertheless, these signals were useful to discriminate between the various sulfidation levels, as ascertained by additional X-ray photoelectron spectroscopy measurements.     

Sorption selectivity of cobalt(II), nickel(II), and copper(II) ions by KB-2E macroreticular carboxylic cation exchanger from aqueous-salt solutions of alkali metals

Sorption selectivity of copper(II), nickel(II), and cobalt(II) ions by KB-2E macroreticular carboxylic cation exchanger in the Na-form from dilute solutions was studied in the target concentration range (0.52.6) 103 M. The equilibrium distribution coefficients of Co²⁺, Ni²⁺, and Cu²⁺ were calculated. The role played by hydration of ions in their sorption by KB-2E cation exchangers is analyzed with consideration for IR spectroscopic, thermal analysis, and scanning electron microscopic data.     

Sorption of uranium(VI) compounds on fibrous anion exchanger surface from aqueous solutions

The effect of sorbent consumption and the kinetics and mechanism of sorption of uranium(VI) compounds on the surface of FIBAN A-6 fibrous anion exchanger from aqueous uranyl acetate solutions have been studied in the presence of sulfuric acid or sodium hydrocarbonate. The degree of sorption of uranium(VI) compounds by FIBAN A-6 anion exchanger has been found to be as high 97.0–99.5% at an interfacial contact time of 3–7 min and a sorbent consumption of 2–5 g/dm³. Diffusion and chemical kinetics models have been employed to show that the sorption kinetics of uranyl sulfate and carbonate complexes corresponds to the mixed diffusion mechanism and is described by a pseudo-second-order equation. The sorption isotherms of uranium(VI) compounds have the pattern of L-type isotherms according to the Giles classification and are satisfactorily described by the Langmuir, Freundlich, and Dubinin–Radushkevich equations. It has been found that, within 40 min, the sorbent may be regenerated by 65–82% with a 1 M NaHCO₃ solution.     

Epoxy resin modified with amine as an effective complexing agent of metal cations

A simple synthesis of a material capable of metal cation removal is proposed. The material was a derivative of epoxy resin containing amine groups. It is insoluble in water and in this study it was characterized by elemental analysis and infrared spectroscopy. The sorbent obtained was tested for its ability to remove coper(II), cadmium(II) and lead(II) from water solutions. The tests were performed for different concentrations of metal ions (10–200 mg L^?1) and at different pH (2.0–9.0). The effects of temperature and stirring time, as well as reusability of the sorbent were also studied in batch experiments. In the optimum conditions, the decrease in the cation concentration in aqueous solutions was observed in the order Cu>Pb>Cd but for each ion the decrease was at least 50% of the initial concentration. The sorbent has demonstrated high effectiveness in cation sorption and after regeneration it can be applied repeatedly in the process described.      

Aspects of the super-equivalent sorption of glycine by cation exchanger KU-2-8

The structure formed in a sorbent during the super-equivalent sorption of glycine by cation exchanger KU-2-8 is optimized via quantum chemical simulation. The differential thermodynamic characteristics of ion exchange and super-equivalent sorption in the studied system are calculated using a thermodynamic approach that allows us to describe the simultaneous exchange and super-equivalent sorption of compounds by ion-exchangers.     

Effect of Complex-Former Ion Concentration on the Selectivity of Metal Ion Sorption on Cross-Linked <Emphasis Type="Italic">N</Emphasis>-2-Sulfoethylchitosan

Copper(II), silver(I), cobalt(II), nickel(II), zinc(II), manganese(II), and magnesium(II) sorption isotherms on cross-linked sulfoethylated chitosan with the degree of sulfoethylation DS = 0.7 (SEC 0.7) have been plotted for the individual or collective presence of these ions in solution have been constructed. The capacities of the studied sorbents for the studied metal ions have been calculated by processing the sorption isotherms. SEC 0.7 is found to have the greatest affinity to copper(II) and silver(I); their presence almost completely suppresses the sorption of associated metal ions. The Redlich–Peterson model gives the best fit to the sorption isotherms for collectively present metal ions, indicating the chemical inhomogeneity of the sorbent surface.     

Purification of Ammonium Molybdate and Tungstate Aqueous Solutions To Remove Phosphate,Arsenate, and Silicate Anions with a Composite Sorbent Based on KU-23 and KM-2p Cation Exchangers

Selectivity sorption of phosphate, arsenate, and silicate anionic impurities from concentrated aqueous solutions of ammonium molybdate and tungstate by a composite sorbent consisting of macroporous KU-23 (or KM-2p) cation exchanger and hydrated zirconium oxide was studied.     

Activity coefficients of components of the sorbent phase in the nonexchange sorption of chloride-containing electrolytes on AN-31 low-basicity anion exchanger in the Cl form

Activity coefficients of components of the sorbent phase in the nonexchange sorption of chloride-containing electrolytes (hydrochloric acid and potassium, sodium, and magnesium chlorides) on AN-31 low-basicity anion exchanger in the Cl form are calculated and analyzed. Peculiarities of the sorption of the investigated electrolytes on the anion exchanger are discussed.     

Sorption of Copper(II) Ions with Nanosized Magnesium Phosphate

A new approach to the preparation of a nanosized sorbent based on magnesium phosphate has been developed. The patterns of copper(II) ions sorption with nanosized magnesium phosphate from aqueous solutions have been investigated. The sorption parameters have been determined, and the kinetics and mechanism of the processes have been elucidated. The high sorption ability of the nanoscale sorbent has been shown in comparison with existing sorbents based on magnesium phosphate.     

Solvent-Mediated Room Temperature Synthesis of Highly Crystalline Cu(9)S(5) (Cu(1.8)S), CuSe, PbS, and PbSe from Their Elements

Highly crystalline Cu(9)S(5) (Cu(1.8)S), CuSe, PbS, and PbSe are obtained by reacting the elements in 2-mercaptoethanol as the solvent for 24 h at room temperature. The elemental reactions of copper and lead with sulfur in ethylene glycol were successful, yielding CuS and PbS, respectively. Metal sulfide formation was not observed using dimercaptoethane.