Sorption of Metals by an Amidoxime Chelating Resin. Part I: Equilibrium

ABSTRACT

The complexation equilibrium of metals (copper, lead, and zinc) by using a chelating ion-exchange resin (Duolite ES-346) is analyzed. Two potentiometric titrations of the resin which allow evaluation of the exchange capacity and the pKvalues are carried out. Two equilibrium models (mass action type model and surface complex formation model) are proposed, and their parameters are estimated by fitting model equations to data from batch experiments. The degradation of the amidoxime groups in acidic media and a possible way to minimize that problem is discussed.     

Recovery of Zinc,Cadmium, and Lanthanum by Biopolymer Gel Particles of Alginic Acid

Abstract

Biopolymer gel particles of alginic acid were found to be a useful material for recovering zinc, cadmium, and lanthanum from aqueous solutions. The metals sorbed by the gel particles could be completely eluted by using dilute HCl solution of 0.1 kmol/m³. The distribution ratios of the individual metals between the gel and liquid phases were measured by using a batch method. The equilibrium data were consistent with predictions made assuming that sorption takes place with the ion-exchange reaction between metal ions and alginic acid. The maximum sorption capacity of the gel particles and the distribution equilibrium constants for the metals were determined by comparing the experimental data with the theoretical predictions. The observed effect of temperature on the distribution equilibrium was insignificant in the range from 15 to 35°C.     

Lysine Adsorption on Cation Exchange Resin. IV. Temperature Effects on Equilibrium and Kinetics in Batch and Column Systems

Abstract

Ion exchange equilibria and kinetics are determined for lysine adsorption on the strong acid cation exchanger DIAION SK‐1B at temperatures of 25, 40, and 60°C. The ion exchange equilibrium is found to be independent of temperature. Conversely, the kinetics of ion exchange increases dramatically as the temperature is increased. Average ion exchange selectivity coefficients of 6.0 g/cm³ and 0.52 are obtained for the ion exchange of divalent and monovalent cationic lysine with hydrogen ion, respectively. Resin phase diffusivities are determined by fitting batch binary ion‐exchange data with a mass transfer model based on the Nernst‐Planck equations. As the temperature is increased from 25 to 60°C, the resin phase diffusivity increases from 0.04×10^?6 to 0.14×10^?6 cm²/s for divalent lysine and from 0.16×10^?6 to 0.55×10^?6 cm²/s for monovalent lysine. The combination of temperature‐independent ion exchange equilibria and faster mass transfer at higher temperatures results in higher dynamic binding capacity and more efficient desorption of lysine when ion exchange is operated at an elevated temperature. This behavior is confirmed by means of column adsorption/desorption experiments whose results are found to be in agreement with a model incorporating the equilibrium and mass transfer data obtained in this work.     

Removal of Chlorophenols from Aqueous Solution by Anion-Exchange Resins

Abstract

The effects of pH value and chloride ion concentration on the removal of chlorophenols from aqueous solutions by Purolite A-510 resin [macroreticular polystyrene-divinylbenzene resin with R(CH₃)₂(C₂H₄OH)N⁺ group] are discussed by the species distributions of chlorophenols. Those chlorophenols include phenol, 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. The investigations showed that the chlorophenols could be removed effectively at alkaline conditions where the ion-exchange reaction was dominant. Also, the removal of chlorophenols increased with the number of chlorine atoms on the chlorophenols. The removal of chlorophenols via the ion-exchange reaction was hindered by the presence of chloride ions. The effect of chloride ions, however, was diminished in acidic solutions where the adsorption reaction was dominant. The proposed equilibrium model, which considers both adsorption and ion-exchange reactions, adequately describes the sorption behavior of chlorophenols. The partition constants of the protonated chlorophenols can be estimated from the octanol/water partition coefficients of the phenolic compounds.     

Evaluation of New Anion Exchange Resins for Plutonium Processing

Abstract

This paper presents the results of studies comparing the performance of two new anion exchange resins for plutonium processing with the well proven and widely used benchmark, Dowex 1X4 resin. In this connection, the experiments on distribution ratio measurement of plutonium as a function of nitric acid concentration, Pu(IV) sorption kinetics, chemical, thermal, and radiation degradation of the two commercially available anion exchange resins namely, Tulsion A‐PSL 4 and Tulsion A‐PSL 6 have been studied, vis‐à‐vis the benchmark. Tulsion A‐PSL 6 was found to have higher plutonium sorption capacity and polymer matrix stability as well as better kinetics of sorption than the other two resins, while Tulsion A‐PSL 4 and Dowex 1X4 were found to have comparable sorption capacity, kinetics, and resistance to chemical and radiation degradation. The small‐scale evaluation of these new anion exchange resins shows that they can be used for the purification and concentration of plutonium.     

γ-Radiation activation of carbon adsorbents prepared from shale oil

Carbon adsorbents from shale oil were modified in 0.01–0.1 N solutions of NaOH in propanol at 20-25°C by a nondestructive low-power-consuming method using γ-radiation at a dose of 4.5 × 10⁵ Gy. The adsorbents acquired ion-exchange properties (exchange capacity to 3.28 mg-equiv/g) upon irradiation. The activated adsorbents had an increased sorption activity toward ethyl chloride.     

An attempt to differentiate the affinity of individual lanthanides to the resin using temperature driven swelling of the thermosensitive copolymer of N-isopropylacrylamide and 2-(methacryloyloxy)ethyl phosphate – Thermodynamic studies

A thermosensitive polymeric gel: N-isopropylacrylamide (NIPAM) copolymerized with 2-(methacryloyloxy)ethyl phosphate (MR) and crosslinked with ethylene glycol dimethacrylate (EGDMA) was used in preliminary experiments aimed at determination of thermodynamic functions associated with the exchange and separation of metal ions using temperature swing adsorption/desorption. This polymer shows a phase transition, which involves the structural change of the gel from swollen to shrunken form at ca. 37 °C. The batch experiments of ion-exchange of lanthanide ions (Ce, Eu, Tb, Tm), Sc as well as Co, Ba, Cs and Pa were carried out at 20, 30, 40, 50 and 60 °C, that is both below and above volume phase transition temperature (VPTT) of the gel. The temperature was changed upwards and downwards and a distinct hysteresis of thermodynamic functions is observed i.e. the equilibrium depends on the thermal history of the thermosensitive ion-exchange gel. It was observed that the free energy change of ion-exchange (especially for lanthanides) shows extremum in the range 40–50 °C, what confirms that structural changes and exclusion of water from resin phase has an effect on the equilibrium position of individual ion-exchange reaction. It was found that in the case of lanthanides the enthalpy change well exceeds 3 kcal/equiv., what suggests that not pure ion-exchange is responsible for the uptake of metal ions by the resin.     

Ammonium Removal from Aqueous Solutions Using Sulfonated Polystyrene Grafted Silica Gel Sorbent

Abstract

A novel non‐swelling sulfonated polystyrene grafted silica gel sorbent was synthesized for use in ammonium removal from aqueous solutions. The ammonium sorption equilibrium isotherm was determined at 298 K by batch experiments, and the effects of flow rate and initial solution pH on the sorption were measured by breakthrough experiments in a laboratory scale fixed bed column. The equilibrium data were fitted to the Langmuir, Freundlich, Langmuir‐Freundlich, and Toth isotherm models. The breakthrough data were fitted to a dynamic isothermal mathematical model with an axial dispersion term to obtain the effective diffusion coefficient. The sorption rate of the sulfonated polystyrene grafted silica gel is higher than that of ion‐exchange resins, which enables shorter cycle times in column processes for the grafted silica gel.     

Synthesis,Characterization, and Evaluation of Gel‐Type Poly(4‐Vinylpyridine) Resins for Plutonium Sorption

Abstract

Three different cross‐linked (4, 8, and 12%) gel‐type strong‐base poly(4‐vinylpyridine) resins (PVP) have been synthesized and characterized by elemental analysis, IR, exchange capacity, and moisture content. The uptake of plutonium and uranium was measured as a function of nitric acid concentration using all the three PVP resins. Plutonium sorption and elution kinetics experiments were also performed on all three PVP resins and compared with the benchmark, a gel‐type quarternary ammonium type anion‐exchange resin. The plutonium sorption rate decreases with the increase in cross‐linkage of the resin. All the three PVP resins exhibit better elution kinetics compared to the benchmark. The results on kinetic experiments performed on all three‐gel‐type resins indicated 8% gel‐type PVP resin with 50–100 mesh as a better candidate for plutonium processing or purification. Radiation degradation studies were carried out on the 8% PVP resin by gamma irradiation up to 200 MRad. The irradiated resins were characterized by IR, TGA, and SEM.

The exchange capacity, moisture content, and plutonium uptake were also evaluated for the irradiated PVP resins in comparison with the benchmark. The results indicated a better radiation stability for PVP resin over the benchmark.     

REACTION KINETICS OF POLYSTYRENE-BASED PHOSPHINIC ACID ION EXCHANGE/REDOX RESINS WITH METAL IONS

ABSTRACT

The ion exchange/redox kinetics displayed by the phosphinic acid polymer with aqueous solutions of silver and mercury is presented as a function of reaction temperature (6° to 45° C) and solution pH (0 to 5). The network variables studied include the crosslink level and macroporosity. At each pH, increasing the temperature leads to a more rapid approach to equilibrium. The amount complexed at equilibrium is lowest at pH Q relative to the higher pH solutions due to increased H⁺ competition for ligating sites. Metal ion reduction, rather than ion exchange, is the dominant component at equilibrium. Matrix rigidity and macroporosity do not affect Ag(I) kinetics. The rate of Hg(II) sorption is much faster than for Ag(I). Macroporosity is an important variable with mercury: macroporous resins complex more than twice the amount found with gels at 15 minutes contact. It is proposed that Ag kinetics are limited by a slow redox reaction while the Hg kinetics are diffusion-limited due to a fast redox reaction. Differences in reactivity arise from the reaction stoichiometry     

Metal-Metal Chelating Ion-Exchange Processes on 8-Hydroxyquinoline and 8-Hydroxyquinaldine Resins

Abstract

The metal capacity vs pH contours and the separation ratios for copper, zinc, and aluminum have been studied for an oxine-containing, chelating ion-exchange resin. Metal-metal exchange studies on this resin involving the three metals have demonstrated that this is not a simple substitution process, sorption and desorption of the ions being controlled by solution concentration. The sterically hindered ligand, 8-hydroxyquinaldine, incorporated in a resin, demonstrated much greater selectivity for other metals over aluminum and confirmed published solvent extraction data for this ligand.     

Ion Exchange on LIX 65N and Kelex 100 Impregnated Foams

Abstract

The metal capacity vs pH contours and the separation ratios for copper, zinc, and aluminum have been studied for an oxine containing, chelating ion-exchange resin. Metal-metal exchange studies on this resin involving the three metals have demonstrated that this is not a simple substitution process, sorption and desorption of the ions being controlled by solution concentration. The sterically hindered ligand, 8-hydroxyquinaldine, incorporated in a resin, demonstrated much greater selectivity for other metals over aluminum and confirmed published solvent extraction data for this ligand.     

EFFECT OF COPPER AND CADMIUM BINDING ON FLOCCULATION OF FERRIC OXIDE PARTICLES

ABSTRACT

The sorption of copper and cadmium ions from aqueous solutions by ferric oxide particles was studied using batch equilibrium and kinetic experiments. The sorption process was found to be pH dependent, with the uptake increasing at high pH values. An increase in equilibrium pH was observed when the initial pH was in the acidic range, and a decrease from initial values was observed in the basic range, in the case of both copper and cadmium sorption. The former phenomenon is due to competition between metal and proton binding, and the latter is due to precipitation mechanisms at high initial pH values. A large increase in the zeta potential of the particles from baseline values was observed during equilibrium sorption. This increase occurs as a result of surface charge neutralization due to metal ion uptake. Particle destabilization appears to occur as a result of metal ion sorption. Kinetic experiments indicate that the uptake of copper by ferric oxide particles is a slow process. The pH histories were similar to those obtained in the sorption equilibrium experiments. Changes in the size distribution of the ferric oxide particles due to aggregate formation during uptake of ions were observed in the kinetic studies. These findings indicate a potential role of metal ion uptake in particle flocculation kinetics through alteration of the surface electrostatic potential.     

Behavior of Silver-Thiourea Complexes in Nafion Resin

Abstract

The behavior of silver-thiourea complexes in Nafion 117 resin was investigated with thiourea sorption and sodium-silver ion-exchange experiments. It was observed that the sorption of thiourea by the Ag-form of the ion exchanger was much higher than that obtained with the H- and Na-forms. The thiourea to silver molar ratio within the resin was found to be about 1.8. In the presence of thiourea, the fraction of silver species in the ion exchanger was about 20% greater than that in the absence of this ligand. The strong interaction between the silver-thiourea species and Nafion material may be attributed to the formation of an insoluble Ag₂T₃(SO₃R)₂ compound inside the ion exchanger.     

Dual-Temperature Ion-Exchange Separation of Copper and Zinc by Different Techniques

Abstract

Separation of copper from zinc-containing acidic solutions has been advanced by different techniques of dual-temperature ionexchange fractionation on iminodiacetic resin Amberlite IRC 718. Cycling-zone adsorption and parametric pumping (using single-column as well as double-column set-ups) experiments have been carried out in fixed-bed ion-exchange column. Measurement of equilibrium characteristics of the resin-solution system has shown that separation results from the variation of the ions sorbability with temperature. It has been found that temperature variation leads to reverse of selectivity between copper and hydrogen ions. Cycling-zone adsorption technique has allowed the copper content to be decreased up to 4 times in the resin phase and increased up to 1.7 times in the effluent when carrying out the process at 80 and 20 °C, respectively. The copper concentration has been decreased 4.4 fold after 9 treatment cycles of solution aliquot (15 BV) by single-column mode of the parametric pumping method. Two steps of the fractionation process (loading and elution) have been performed by continuous mode of operation in two counter-current columns. Continuous separation is preferred over fixed-bed column techniques. The steady-state sorption fronts have been formed on both stages of the process due to the reverse of selectivity mentioned above.     

Biosorption of Zinc from Aqueous Solutions by Rice Bran: Kinetics and Equilibrium Studies

Abstract

Rice bran, an agricultural by‐product, was used for the removal of zinc ions from aqueous solution. The work considered the determination of zinc‐biomass equilibrium data in batch system. These studies were carried out in order to determine some operational parameters of zinc sorption such as the time required for the Zinc‐biosorbent equilibrium, the effects of biomass particle size, pH, and temperature. The results showed that pH has an importance effect on zinc biosorption capacity. The biosorbent size also affects the zinc biosorption capacity. The sorption process follows pseudo‐second‐order kinetics. The intraparticle diffusion may be the rate‐controlling step involved in the adsorption zinc ions onto the rice bran up to 30 min. The equilibrium data could be best fitted by the Langmuir sorption isotherm equation over the entire concentration range (40–160 mg/dm³). Thermodynamic parameters, such as ΔG°, ΔH°, ΔS°, have been calculated. The thermodynamics of zinc ion/rice bran system indicate spontaneous and endothermic nature of the process.     

SWELLING OF A CHELATING MACROPOROUS RESIN DURING METAL ION EXCHANGE

ABSTRACT

The kinetics of heavy metal ion exchange onto a commercial chelating resin was investigated from the standpoint of the swelling-shrinking experienced by the resin bead during the overall ion exchange process. Temporal measurements of the volume variations were carried out for every step of an operational cycle, metal load, elution and regeneration of the ion exchanger, using a microreactor mainly composed by a reaction cell, an optical microscope and an image treatment system. Experimental results were properly fitted to an empirical equation, whose parameters were used to characterize and compare different systems. A pseudosteady state kinetic model, which takes into account the volume variations of the resin bead during the ion exchange reaction, fits fairly well to experimental results, and was used to obtain the effective diffusion coefficients of the metals through the macroporous matrix. Finally, the study of the batch ion exchange kinetics of transition metal cations was completed with a potentiometric titration and other equilibrium determinations. These results were compared with those derived from swelling measurements.     

ION EXCHANGE OF SEVERAL RADIONUCLIDES ON THE HYDROUS CRYSTALLINE SILICOTITANATE,UOP IONSIV IE-911

ABSTRACT

The crystalline silicotitanate, UOP IONSIV IE-911, is a proven material for removing radionuclides from a wide variety of waste streams. It is superior for removing several radionuclides from the highly alkaline solutions typical of DOE wastes. Our laboratory previously developed an equilibrium model applicable to complex solutions for IE-910 (the powder form of the granular IE-911), and more recently, we have developed several single component ion-exchange kinetic models for predicting column breakthrough curves and batch reactor concentration histories. In this paper, we model ion-exchange column performance using effective diffusivities determined from batch kinetic experiments. This technique is preferable because the batch experiments are easier, faster, and cheaper to perform than column experiments. We also extend these ideas to multicomponent systems. Finally, we evaluate the ability of our equilibrium model to predict data for IE-911.     

SORPTION BEHAVIOUR OF URANIUM AND THORIUM ON CRYPTOMELANE-TYPE HYDROUS MANGANESE DIOXIDE FROM AQUEOUS SOLUTION

Abstract

The kinetics of sorption of uranium and thorium from aqueous nitrate solutions on cryptomelane-type hydrous manganese dioxide (CRYMO) was studied. The exchange of uranium is particle diffusion controlled while that of thorium is chemical reaction at the exchange sites. Sorption of uranium and thorium by CRYMO has been also studied as a function of metal concentrations and temperature. The sorption of both cations is found to be an endothermic process and increases markedly with temperature between 30 and 60°C. The sorption results have been analysed by the langmuir adsorption isotherm over the entire range of uranium and thorium concentrations investigated.     

Studies on Sorption of Radiocesium on Copper-Hexacyanoferrate-Loaded Resins

Abstract

Copper hexacyanoferrate(II) was incorporated in the matrix of the strongly basic anion-exchange resin Indion-810 for the sorption of radiocesium from aqueous solutions. Its efficiency for the removal of cesium was tested under both static and dynamic conditions. The resin was found to be highly selective for radiocesium from a variety of salt and acid solutions. With the help of x-ray diffraction patterns, infrared spectrometry, thermal gravimetry, and differential thermal analysis, the interaction of copper hexacyanoferrate(II) with the quaternary amine of Indion-810 resin was investigated. Pilot-scale studies using this resin indicated that radiocesium can be effectively removed from thousands of bed volumes of spent fuel storage bay water.