Ion Exchange in Selected Low Rank Coals. Part I: Equilibrium

ABSTRACT

The ion exchange behavior of 4 low rank coals has been investigated. Their total carboxyl group contents ranged from 1.52 meq/g for a subbituminous coal to 2.78 meq/g for a lignite. The coverage of the carboxyl groups by metal cations varied from 30% to 60% (on an equivalent basis) for the raw coals. For all raw coals, Ca²⁺was the predominant metal cation. The equilibrium ion exchange behavior of metal cations for H⁺was found to be a linear function of pH regardless of the cation concentration in solution. Thus, the extent of exchange is a function of available hydrogen ions. From equilibrium ion exchange measurements, the following cation exchange selectivity pattern for a subbituminous coal was determined:

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while that for a lignite was:

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THE MECHANISM OF DIFFUSION AND IONIC TRANSPORT OF Li+, Na+ AND K+ ON SEMICRYSTALLINE NIOBIUM PHOSPHATE

A computer simulation technique has been applied to solve the Nernst-Planck equations for the kinetics of exchange of alkali metal ions (Li⁺, Na⁺ and K⁺). Activation energy and the self diffusion coefficient were found to be linear functions of hydration energies and the ionic radii of these ions, respectively. It has been proposed, on the basis of kinetic parameters, that the exchange of alkali metal ions occurs in the unhydrated form. They shed most of their water of hydration at the surface of the beads and then again get hydrated after being exchanged. The exchanger appears to have a zeolite type structure.     

Uptake of Traces of Selenite by Manganese Dioxide from Aqueous Solutions

Abstract

Sorption of selenite onto manganese dioxide has been investigated with respect to shaking time, concentration of sorbent and sorbate, nature of electrolyte, and influence of cations and anions. The sorption of other metal ions has been studied using optimal conditions selected for maximum sorption of selenite. The surface area, average pore diameter, porosity, and solid phase density of the sorbent have been measured. The sorption data followed only the Dubinin–Radushkevich (D–R) sorption isotherm among all the isotherms tested. The sorption capacity of 51.2 nmol·g^?1 and a constant β related to sorption energy have been estimated to be ?0.007521 mol²·kJ^?2. The sorption energy is found to be 8.15 kJ·mol^?1. The kinetics of the sorption follows the Lagergren equation in the initial stages. The first-order rate constant, k′, was evaluated to be 0.498 min^?1 and of intraparticle diffusion rate 3.06 × 10^?5 mol·g^?1·min^?2. Among all the anions and cations tested, only carbonate, Fe(III), and citrate reduced the sorption significantly. The sorption data for other metal ions showed that Te(IV) can be separated from ions showing higher degree of sorption; especially Se(IV), As(III), Sb(V), and Eu(III). It can be concluded that manganese dioxide may be used for the separation of certain metal ions, their preconcentration from very dilute solutions, and for decontamination and treatment of industrial effluents.     

Kinetic and thermodynamic effects during the adsorption of heavy metals on ETS-4 and ETS-10 microporous materials

ETS-10 and ETS-4 microporous materials were synthesized in presence of tetralkylammonium (TAA) ions from gels of molar composition w Na₂O–0.10 TAABr–1 SiO₂–z TiO₂–0.6 KF–1.28 w HCl–39.5 H₂O with TAA = tetramethyl-, tetraethyl-, tetrapropyl- and tetrabutyl-ammonium in hydrothermal conditions at 190 °C. The TAA ions enter the microporous channel of ETS-10, while they cannot penetrate the void spaces of ETS-4. The ETS-10 microcrystals are all cubic, while the ETS-4 crystals are laminar and irregular. The microporous volume of ETS-10 is equal to 0.11–0.13 cm³ g^?1, the microporous volume of ETS-4 is very small, 0.002–0.008 cm³ g^?1. The ion exchange of Cs⁺, Cd⁺⁺, Pb⁺⁺ and Hg⁺⁺ ions using their corresponding nitrates show kinetic effects, i.e. the efficiency of ion exchange is higher at 1 than 2 h, the thermodynamic equilibrium. For ETS-10, partially dehydrated cations intervene in the ion exchange, while for ETS-4 well dehydrated ions can only penetrate the available pores.     

Synthesis and characterization of novel organo-montmorillonites

Sodium Montmorillonite (NaMMT) has been modified via cation exchange reaction using three different organic cations. Basal spacings, interlamellar structure and thermal stability of these organo-montmorillonites (OMMT) clays have been characterized using wide angle X-ray diffraction (WAXD) and thermogravimetric analysis (TGA) techniques. Increase in the basal spacing due to organic modification is in good agreement with simple theoretical calculations based on van der Waals volume of the cationic ammonium ions. TGA characterization and analysis show that the amount of organic modifier in the OMMT's is in good agreement with theoretically calculated stoichiometric content expected for almost complete exchange of Na⁺ ions by organic cations. The OMMT's shows stepwise decomposition corresponding to initial weight loss from residual water desorption, followed by decomposition of the organic surfactant and the dehydroxylation of structural water of the montmorillonite layers.     

SYNTHESIS AND CHARACTERIZATION OF THE ION EXCHANGE PROPERTIES OF A SPHERICALLY GRANULATED SODIUM ALUMINOPHOSPHATESILICATE

ABSTRACT

Spherically granulated sodium aluminosilicophosphate (APS) of the empirical formula Na₄Al₄PS₁₈O_46.5 18H₂O was synthesized by a gel method. The APS was characterized by elemental analysis, X-ray diffraction, TGA and ²⁷AI, ²⁸Si and ³¹P MAS NMR spectroscopy methods. Ion exchange of alkali, alkaline earth and some other divalent metal cations by APS was studied in batch conditions. It was found that the APS has a cation exchange capacity of 2.5 meq/g and exhibits rapid kinetics of ion exchange. The ion exchange isotherms of alkali, alkaline earth and some other divalent cations were determined and the corrected selectivity coefficients as a function of metal loading were analyzed. It was found that APS exhibits a high affinity for cesium ion, a moderate affinity for some heavy metal cations (Pb²⁺, Zn⁺) and a low affinity for alkali and alkaline earth metal ions. A testing of the APS in complex solutions suggests that it could be a promising exchanger for treatment of some specific nuclear waste and contaminated environmental and biological liquors from radioactive cesium and toxic heavy metal ions.     

The conditions of cationic exchange with the use of recycling polystyrene derivative,the product of sulfonation by silica sulfuric acid

Growing amount of waste plastics has become an environmental problem on a global scale. This study presents an investigation of the conditions of cleaning water from heavy metal ions using chemically recycled polystyrene. To get effective ion exchangers, the sulfonation of virgin polystyrene and expanded polystyrene wastes were obtained using silica sulfuric acid. As it turned out, the use of this solid sulfonating agent simplifies the separation of the polymeric product from the acid and the solvent in comparison to conventional sulfonation methods. The ion exchange behavior of copper and zinc cations in the yielded sulfonated derivatives of polystyrene was studied. Batch shaking adsorption experiments depending on contact time, pH, temperature, and dosage of adsorbate were carried out. The stability of resin to cyclical adsorption and regeneration (column experiment) was also investigated. We report that resins have a high adsorption efficiency with total ion exchange capacity (IEC) about 2.6 meq g^?1, which drops with decreasing pH owing to competition between protons H⁺ and metal cations, whereas with the increasing resin doses the removal of cations rises for a constant initial metal concentration. The speed of cation exchange for yielded adsorbents was even better than for commercial resins. After 360 cyclical adsorption and regeneration in column, resin had working IEC of about 2.3 meq g^?1. The study shows that cation exchange resin from polystyrene wastes can be used as an efficient adsorbent for the removal of heavy metal ions from water. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

ION EXCHANGE PROPERTIES OF THE SULFUR-MODIFIED BIOTITE

ABSTRACT

The ion exchange behavior of a sulfur-modified biotite towards Pb²⁺, Hg²⁺, Co²⁺, Cu²⁺, Cd²⁺ and Zn²⁺ ions has been studied. The ion exchange isotherms of divalent cations were determined and concentration equilibrium constants as a function of metal loading were analyzed. Sulfur modified biotite exhibits high affinity for Hg²⁺, Pb²⁺, Cu²⁺ and Cd²⁺ ions in individual solutions and in the presence of electrolytes. About 200 mg Hg/g uptake in 1·10^?3 M Hg²⁺ solution and ～ 35 mg Hg/g in groundwater simulant or an alkaline simulant 2 M in NaN0₃ + 1 M in NaOH was found. The possibility of a complex ion exchange and precipitation mechanism of the sulfur modified biotite towards the soft cations is proposed.     

Application of a Novel Hybrid Cation Exchange Material in Metal Ion Separations

A novel hybrid cation exchange material of the class of tetravalent metal acid (TMA) salt, titanium diethylene triamine pentamethylene phosphonate (TiDETPMP) has been synthesized by the sol gel method. The material has been analyzed by spectroscopy and thermal methods. Physico-chemical and ion exchange characteristics have also been studied. The distribution coefficient (K _d ) has been determined in aqueous as well as various electrolyte media/concentrations for Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ (transition metal ions) and Cd²⁺, Hg²⁺, Pb²⁺, Bi³⁺ (heavy metal ions) using TiDETPMP. Based on the differential affinity/selectivity, the breakthrough capacity (BTC) and elution behavior of various metal ions towards TiDETPMP, a few binary and ternary metal ions separations have been carried out.     

The Effect of Lowering the Surface Free Energy of Water on the Thermodynamic Work of Adhesion

The dispersive and polar force components of surface free energy have been measured for water left in contact with films dried from various emulsion adhesives. The polar component was lowered but the dispersive components were about 28 mJ m^?2 in each case. From these measurements of thermodynamic work of adhesion in the presence of contaminated water have been calculated for adhesive-polystyrene interfaces. An equation has been derived giving the dependence of thermodynamic work of adhesion upon the total surface free energy of water. It shows that the thermodynamic work of adhesion decreases as the surface free energy of water is lowered, but it eventually reaches a minimum and then may increase slightly.     

ION-EXCHANGE EQUILIBRIUM OF THE Cu2+/H+, Zn2+/H+ AND Pb2+/H+ IONS ON HYDRATED FERRIC OXIDE

ABSTRACT

The ion exchange of trace amounts of Cu²⁺, Zn²⁺ and Pb²⁺ with the hydrogen-form of hydrated ferric oxide as a function of nitric acid concentration has been studied at 25, 30,35 and 60^°C. Ion exchange of these cations increases with increasing temperature in the investigated temperature range. From these results, equilibrium constants for the Cu²⁺/H⁺, Zn²⁺/H⁺ and Pb²⁺/H⁺ ion exchange on hydrated ferric oxide and thermodynamic quantities for these reactions were calculated, and some predictions made for the exchange process taking place in this material. The selectivity series is Zn²⁺ > Cu²⁺ > Pb²⁺.     

Studies with inorganic precipitate membranes—XII: Consideration of membrane field strength and energetics of permeation

Electrolytic transfort processes occuring across parchment supported membranes have been described by Nernst Planck flux equation taking into account the membrane resistance R_m, membrane potential E_metc.E_m values for various electrolytes display very interesting phenomena. In the case of 1:1 electrolyte the E_m values are all positive, while in the case of (2:1) and (3:1) electrolytes surface charge reversal takes place. The diffusion rate sequence and selectivity of the membrane for different uni- bi- and trivalent cations was found to be primarily dependent on the difference in the hydration energies of counter ions in the external solution. On the basis of Eisenman-Sherry theory the diffusion rate sequence of alkali metal cations point towards the weak field strength of the fixed charge groups. Various thermodynamic parameters, ΔH^≠, ΔF^≠ and ΔS^≠ were evaluated by applying the theory of absolute reactions rates to the diffusion process through parchment supported membranes. The values of ΔS^≠ were found to be negative, indicating that diffusion takes place with partial immobilization in the membrane phase. The relative partial immobility was found to increase with increase in the valence of the ions constituting the electrolyte. A formal relation between ΔH_hydration, ΔF_hydration and ΔS_hydration of cations with the corresponding values of ΔH^≠, ΔF^≠ and ΔS^≠ for diffusion, was also found to exist for these membranes.     

Sequestering and exchange of metal ions in edible oils containing phospholipids

Metal ions (Zn²⁺ and Fe³⁺) are transferred from water into vegetable and marine oils when these oils contain phospholipids. Ions present in the oil may be exchanged with the same or with other kinds of cations in a water phase in contact with the oils. Radioactive isotopes of zinc and iron were used for measuring the exchange rate. The sequestering action by the oil strongly depends on the contents of phospholipids and reaches a maximum (ions v/s phospholipids) in the concentration range between 3 and 60 ppm of phospholipids (0.1–2 ppm of phosphorus) in the oil. The same sequestering effect is demonstrated when purified phospholipids (phosphoethanolamine and acetone-refined soybean lecithin) are added to edible oils from which the natural content of phospholipids has been removed. Free fatty acids do not appear to sequester multivalent ions nor to influence the sequestering action by the phospholipids when added to the oil.     

Comparative ion-exchange characterization of zeolitic and clayey materials for pedotechnical applications—Part 2: interaction with nutrient cations

With the purpose to evaluate the possible use of a phillipsite-rich tuff, in place of the naturally occurring clay minerals, as inorganic ion-exchanger component of organo-mineral aggregates of pedotechnical interest, the ion-exchange behavior of Neapolitan yellow tuff and a reference montmorillonite-rich material towards some nutrient cations was investigated. Accordingly, exchange kinetics and isotherms of Na⁺, K⁺, and NH₄ ⁺ for Ca²⁺, at 25 °C and 0.1 total normality, were determined, and the related kinetic and thermodynamic quantities computed. The obtained results point out that the zeolitic material, apart from a higher cation exchange capability, exhibits selectivity performances towards nutrient cations comparable or even better than those of the montmorillonitic material, confirming, on the basis of the previous data concerning noxious cations, that phillipsite-rich tuffs can be considered potential substitutes of clay materials to recover and/or rebuild polluted and degraded soils.     

Investigation of some new solid cation exchange membrane electrodes for activity determination of mono-valent cations

Solid cation exchange membrane electrodes prepared by incorporating weak cation exchangers stilbite, bentonite clay and ammonium phosphomolybdate in cellulose nitrate inert matrix, have been characterized by determination of their thermodynamic effective charge densities. Null potentiometry method has been used for the determination of activities of Na⁺, K⁺ and NH⁺₄ cations in their chloride solutions separately and in the mixture of two cations using these electrodes. The selectivity of these electrodes for cations has been interpreted on the basis of Thermodynamic effective charge density of the membrane electrode and the results have been confirmed by determining the selectivity coefficients of these electrodes for the investigated cations by an IUPAC method. The error in the determination of activities of cations and response time (t/min) of electrode have been correlated with the thermodynamic effective charge density of the electrode. It has been found that the electrodes with low thermodynamic effective charge density are more suitable for this purpose and that selectivity of an electrode for a particular cation in mixture depends upon the characteristics of both cation and electrode.     

Synthesis of V-MCM-41 by template-ion exchange method and its catalytic properties in propane oxidative dehydrogenation

Vanadium has been introduced to MCM-41 without collapse of the mesoporous structure by exchanging VO²+ ions in the aqueous solution with the template cations in the uncalcined MCM-41. This template-ion exchange (TIE) method provides tetrahedrally coordinated vanadyl species dispersed in the channel of MCM-41. Such synthesized V-MCM-41 shows higher catalytic activity in the oxidative dehydrogenation of propane than that prepared by direct hydrothermal method.     

Synthesis and studies of egyptian bagasse pith phenol formaldehyde cationic exchangers

The article is concerned with a simple method for preparing cationic resins from polycondensation of Egyptian bagasse pith (as a source of cheap and renewable material) with phenol and paraformaldehyde as a cross-linking agent. Optimum principal reaction conditions of the preparation and properties are determined and compared with resin without bagasse pith content. The Synthesized resins are stable in water, organic solvents, thermal treatment, and mineral acids (1M). The sample having a cation exchange capacity up to 3.92 meq g^?1 of dry resins are being introduced as new cationic exchangers. The synthesized resins are used in the study of the possible separation of univalent cations. The rational thermodynamic equilibrium constants (In K) are calculated for Li⁺ ?Na⁺ exchanges on the resins having a various amount of bagasse pith. The thermodynamic parameters are computed and suitable explanations are described. © 1994 John Wiley & Sons, Inc.     

Ion-crosslinked carboxymethyl cellulose/polyaniline bio-conducting interpenetrated polymer network: preparation,characterization and application for an efficient removal of Cr(VI) from aqueous solution

A simple, cheap, and environmentally friendly bio-conducting interpenetrated polymer blend network was prepared and introduced as a highly efficient system with suitable physical and mechanical properties for industrial removal of toxic Cr(VI) ions from aqueous solution. Carboxymethyl cellulose/polyaniline (CMC/PANI) interpenetrated network (IPN) blend was prepared by simple simultaneous ion-cross-linking of CMC and PANI chains using Al³⁺ cations. The CMC/PANI bio-conducting nanocomposite was characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy equipped with an "energy dispersive X-ray spectroscopy" (SEM–EDX) technique. The CMC/PANI blend, ion-cross-linked by Al³⁺ cations, showed good stability and high surface area, proper for the removal of toxic Cr(VI) ions of the aqueous solution. Batch removal experiments were accomplished and the impression of effective variables including solution pH, initial concentration of Cr(VI) ions, contact time, and adsorbent dosage were checked and optimized. The outcome of our findings revealed that the removal of Cr(VI) ions by CMC/PANI nanocomposite IPN strongly depends on solution pH. The removal information was matched with the Langmuir adsorption isotherm model and the utmost monolayer adsorption capacity at pH 2 was 136.98 mg/g at 25 °C. The pseudo-second-order kinetics were operated and the thermodynamic parameters suggested spontaneous and exothermic nature of the adsorption process. Consequences indicated that CMC/PANI nanocomposite IPN could be an affective eco/environmentally friendly adsorbent for the removal of Cr(VI) ions from aqueous solutions.

     

Modification of layer charge in smectites by microwaves

The layer charge reduction of two Li-saturated montmorillonites is referred to application of microwave radiation at 2.45 GHz for dispersions and 30.0 GHz for the solid powders. Efficiency of these treatments was compared to the same conditions applying conventional heating. The samples were heated in the temperature and time windows corresponding to 190–270 °C and 30–120 min, respectively. Changes in the mean layer charge were monitored by the determination of cation exchange capacity values using exchange of triethylene tetraamino copper ions. The charge reduction of the montmorillonites in aqueous dispersions was rather low (< 30%) despite the fact, that high Li⁺ concentration dissolved in solution was selected (1 mol L^− 1). This behaviour was attributed to the very high water content in used dispersions and high hydration enthalpy of Li⁺ cations. Nevertheless, the microwave heated dispersions (2.45 GHz) showed detectable layer charge reduction as compared to conventionally heated dispersions, where no significant changes were found.Solid powders with different content of exchangeable lithium ions were prepared with solutions having different molar fraction of Li⁺ and Na⁺ cations (0%, 20%, 40%, 60%, 80%, 100% of Li⁺). Final composition of interlayer cations was analysed with ICP-OES. In contrary to dispersions, the microwave treatment of the prepared powders revealed high layer charge reduction, which was much higher than for conventionally heated powders. The efficiency was enhanced with increasing interlayer lithium content but reached a limiting value depending on the montmorillonite used. Migration of the lithium into the structure of the montmorillonite supported with microwaves was extremely fast, finished probably within the few minutes of the treatments. The exchangeable Li⁺ cations are accelerated through alternating electric field of microwaves and highly efficient layer charge neutralisation occurs. Infrared spectroscopy showed that the products obtained with microwave treatments correspond to the materials heated conventionally for much longer periods of time. Hence, applying microwaves the time and energy requirement can be significantly reduced. The X-ray diffraction showed that montmorillonite layers were able to swell in ethyleneglycol upon charge reduction, if the cation exchange capacity was not reduced more than 20–40%.     

New Sorbents for Metal Salts based on Cation Exchange Extractants and Anion Exchange Resins: Their Preparation and Properties

Preparation and properties of binary sorbents containing a salt of cation exchange organic extractant in the matrix of a strongly basic anion exchanger were studied. Analysis of isotherms of exchange of chloride ions for dialkyldithiophosphate ions in the systems of various anion exchangers led to the conclusion that the stability of the binary sorbents depends on the amount of free water in the sorbent matrix. To improve the stability, it was proposed to use low cross-linked anion exchange resins or to use cation exchange extractants of moderate molecular volume. On the example of anion exchanger ММ-22x6.5 in the dibutyldithiophosphate form, it was shown that the binary sorbents efficiently recover chlorides of non-ferrous metals. The recovery increases in the series Ca²⁺<<Ni²⁺<Zn²⁺<<Cu²⁺. Because, in the systems studied, the anions are recovered together with cations, this leads to an increase in metal recovery in the presence of salting-out agents, and allows the desorbtion of the salts with water or with solutions of complexing agents. The binary sorbents offer good prospects for the recovery and separation of metal salts.