A Comparative Study of Gel-Type and Macroreticular Cation Exchange Resins for the Separation of Rare Earth Elements

Abstract

Owing to the macro- and micro- pores in the matrix, macroreticular resins have larger micro-void volume ratio in the ion exchange column chromatography. It is advantageous in the ion exchange kinetics resulting from the quicker mass transfer. By means of EDTA displacement column chromatography for the Pr-Nd separation study, we have found that macroreticular cation exchange resins have higher separation efficiency in HETP, single stage time, and the pure Pr production rate, e. g. for AG 50W-X8, 200～400 mesh resin (gel-type) and AG MP-50, 200～400 mesh resin (macroreticular), the HETP values are 0.40 cm and 0.24 cm; the single stage times are 3.11 min and 1.30 min; the pure Pr production rates are 0.19 and 0.68 m mole/hr, respectively. Because both types of resins contain the same functional group, the single stage separation factors for Pr-Nd separation have the same value of 2.0±0.1 at 92°C. The cation exchange resins which were prepared in our laboratory with higher micro-void volume ratio could improve the separation efficiency as well as reduce the pressure drop in the ion exchange column. It is suggested that new macroreticular cation exchange resins with high micro-void volume ratio and high degree of crosslinking can improve the rare earth separation efficiency which is an important design factor in the large-scale separation process for rare earth elements.     

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 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     

Synthesis and Characterization of Site-Selective Ion-Exchange Resins Templated for Lead(II) Ion

Abstract

Ion-exchange resins that exhibit enhanced selectivity for the Pb(II) ion have been synthesized by the copolymerization of styrene with lead(II) vinylbenzoate. Removal of the Pb(II) ion by acid washing left cavities templated for the Pb(II) ion. Sorption characteristics of the template resins have been studied over a large range of template loadings by varying the degrees of crosslinking, and with or without the use of ultrasonification during copolymerization. The capacity of the lead templated resins increases logarithmically with the increase of template complex content for levels of lead template content below 5 mol%. The complexation equilibrium constants of the resins reach a maximum at 3 mol% template complex content. The resins show marked preference for binding the Pb(II) ion. The selectivity,α _pb,cd, has been found to be 174 for the 1 mol% templated polymer. In comparison to untemplated resins, the template process enhances the selectivity by roughly a factor of 3 over Cu²⁺ and 2 over Cd²⁺. The selectivity enhancement is mainly ascribed to “coordination-geometry selectivity.”     

Preparation of phosphoric acid resins with large cation exchange capacities from macroreticular poly(glycidyl methacrylate-co-divinylbenzene) beads and their behavior in uptake of metal ions

In order to prepare phosphoric acid resins (RGPs) with large cation exchange capacities, effects of porosity and cross-linking of the precursory poly(glycidyl methacrylate-co-divinylbenzene) beads on their functionalization with phosphoric acid were studied. Two series of precursory copolymers were prepared: one was prepared by changing the amount of divinylbenzene (1–25 mol %) but by fixing that of isobutyl acetate (porogen) at 140 vol % per monomer mixture; the other by changing the amount of the porogen (40–160 vol %) but by fixing that of the cross-linker at 10 mol %. It was clarified that porosity of the precursors plays an important role in the functionalization. Highly porous precursors were functionalized with high efficiency; for example, even the precursors containing 10 mol % of divinylbenzene resulted in RGPs having cation exchange capacities as large as 6–7 meq/g, so long as BET specific surface areas of the precursors were greater than ca. 30 m²/g. The selectivity study has revealed that RGP exhibits the characteristic metal ion selectivity. Lithium ion was adsorbed in preference to sodium and potassium ions; and so-called hard Lewis acid cations, such as uranyl, ferric, and aluminum ions, are adsorbed even from strongly acidic media (1 < pH < 2). Among common divalent metal ions, in addition, the resin exhibits the highest selectivity toward lead ion. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1327–1334, 1997     

Distribution Coefficients of 60 Elements on Cation and Anion-Exchange Resin in Ammonium Chloride Solutions

ABSTRACT

Ammonium chloride is a widely available non-corrosive and non-toxic chemical. When in contact with protein NH₄Cl is non-destructive and allows softer conditions for labeling of organic substances. These properties make NH₄Cl appropriate for use in multiple areas such as pharmaceutical production, low-background research, etc. For such purposes, a multitude of pure elements could be applied. In order to obtain pure elements their separation (purification) is necessary. One of the most successful methods of elements separation is ion exchange. In this work, we study the distribution coefficient of 60 elements on anion exchange (Dowex 1-x8) and cation exchange (Dowex 50w-x8) resins with NH₄Cl solutions with varying concentrations via ICP-MS.     

Chemical Modification of Poly(Vinyl Chloride) with Ethylene Glycol and its Application in Ion-Chromatography

ABSTRACT

Poly(vinyl chloride) (PVC) has been chemically modified through crosslinking with different molar ratios of sodium ethylene glycoxide in ethylene glycol. The crosslinked PVC was used for coating of silica gel 60 particles and the obtained products were impregnated with tetramethylammonium hydroxide (TMAH). The crosslinking reaction as well as the insertion of TMAH were followed up and quantitatively determined with the aid of FT-IR spectroscopic and elemental analyses. The obtained materials were roughly tested for ion chromatographic separation of different ions. Retention time ( t _R) was determined for lithium, magnesium, strontium, and calcium cations whereas chloride, nitrate, and sulfate were selected as representatives for anions.     

Synthesis,characterization, and application of new low‐cost ion exchangers

This paper represents a simple method for preparing and characterizing of low‐cost ion exchangers of sulfonated carbon prepared from Terminalia Chebula‐Retz., (family–combretaceae) as a source of cheap plant material blended with phenol‐formaldehyde as a crosslinking agent. The prepared ion exchange resins (IERs) are characterized by infrared (IR) spectral and thermal studies. All the important physicochemical properties of the ion exchangers have been determined. The synthesized resins have cation exchange capacity upto 1.84 mmol g^?1. The rational thermodynamic equilibrium constant (ln K) are calculated for H⁺ and Zn²⁺ exchanges on the resin having various amount of sulfonated Terminalia Chebula Retz. carbon (STCC). The thermodynamic parameters were calculated, and suitable explanations are given. It is concluded from the present study that PFR sample could be blended with 20% (w/w) of STCC, without affecting its physicochemical, spectral, and thermal properties. Hence blending with STCC will definitely lower the cost of the ion exchange resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4104–4113, 2006     

Salt Splitting Using Ceramic Membranes

Abstract

Inorganic ceramic membranes for salt splitting of radioactively contaminated sodium salt solutions are being developed for treating U.S. Department of Energy tank wastes. The process consists of electrochemical separation of sodium ions from the salt solution using sodium (Na) Super Ion Conductors (NASICON) membranes. In contrast to conventional organic-based bipolar or ion exchange membranes used in salt splitting, NaSICON membranes are resistant to gamma/beta radiation and are highly selective for sodium ions. Potential applications include 1) caustic recycle for sludge leaching, regeneration of ion exchange resins, inhibition of corrosion in carbon steel tanks, or retrieval of tank wastes; 2) pH adjustmet and reduction of competing cations to enhance cesium ion exchange processes; 3) sodium reduction in high-level waste sludges; and 4) sodium removal from acidic wastes to facilitate calcining. Initial experiments with dysprosium-based NaSICON membranes have demonstrated the feasibility of the process.     

RADIUM SEPARATION THROUGH COMPLEXATION BY AQUEOUS CROWN ETHERS AND ION EXCHANGE OR SOLVENT EXTRACTION

ABSTRACT

The effect of three water-soluble, unsubstituted crown ethers (15-crown-5 (15C5), 18-crown-6 (18C6) and 21-erown-7 (21C7) on the uptake of Ca, Sr, Ba and Ra cations by a sulfonic acid cation exchange resin, and on the extraction of the same cations by xylene solutions of dinonylnaphthalenesulfonic acid (HDNNS) from aqueous hydrochloric acid solutions has been investigated. The crown ethers enhance the sorption of the larger cations by the ion exchange resin, thereby improving the resin selectivity over calcium, a result of a synergistic interaction between the crown ether and the ionic functional groups of the resin. Similarly, the extraction of the larger alkaline earth cations into. xylene by HDNNS is strongly synergized by the presence of the crown ethers in the aqueous phase. Promising results for intra-Group IIa cation separations have been obtained using each of the three crown ethers as the aqueous ligands and the sulfonic acid cation exchange resin. Even greater separation factors for the radium - calcium couple have been measured with the crown-ethers and HDNNS solutions in the solvent extraction mode. The application of the uptake and extraction results to the development of radium separation schemes it discussed and a possible flowchart for the determination of ²²⁶Ra/²²⁸Ra in natural waters is presented.

     

Detection of lead ion binding on bifunctional chelating/ion‐exchange resins by cross‐polarization/magic‐angle spinning solid‐state nuclear magnetic resonance

Solid‐state nuclear magnetic resonance (S‐NMR) can reveal much useful information, including conformations, stereoregularity, defect structures, and comonomer sequence. S‐NMR is especially useful for revealing microstructural differences that can alter local polymer chains. A series of bifunctional chelating/ion‐exchange resins, containing differing ratios of iminodiacetic acid to acetic acid, were synthesized. Cross‐polarization magic‐angle spinning (CP/MAS) ¹³C‐NMR was employed to measure conformation changes both before and after the bonding of ligands and lead ion adsorbed on bifunctional chelated/ion‐exchange resins in this investigation. From the ¹³C‐NMR spectra, as the lead ion was adsorbed by the iminodiacetic acid chelating group, the motion of molecular chain would be inhibited and the resonance peaks of the carboxylate anion at 170 ppm would shift downfield. Compared to the FTIR results, the downfield shift of the resonance peaks indicated that the bonding of carboxylate anion and lead ion adsorbed displayed an ionic trend. Furthermore, the bonding of the carboxylic group and lead ion adsorbed changed from ionic to covalent as the chelating group in bifunctional/ion‐exchange resins decreased. The linear relationship between the areas of those resonance peaks and the amount of lead ion adsorbed was obtained from the spectra fitting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 919–928, 2002     

Template-Assisted Synthesis and Characterization of Passivated Nickel Nanoparticles

Potential applications of nickel nanoparticles demand the synthesis of self-protected nickel nanoparticles by different synthesis techniques. A novel and simple technique for the synthesis of self-protected nickel nanoparticles is realized by the inter-matrix synthesis of nickel nanoparticles by cation exchange reduction in two types of resins. Two different polymer templates namely strongly acidic cation exchange resins and weakly acidic cation exchange resins provided with cation exchange sites which can anchor metal cations by the ion exchange process are used. The nickel ions which are held at the cation exchange sites by ion fixation can be subsequently reduced to metal nanoparticles by using sodium borohydride as the reducing agent. The composites are cycled repeating the loading reduction cycle involved in the synthesis procedure. X-Ray Diffraction, Scanning Electron Microscopy, Transmission Electron microscopy, Energy Dispersive Spectrum, and Inductively Coupled Plasma Analysis are effectively utilized to investigate the different structural characteristics of the nanocomposites. The hysteresis loop parameters namely saturation magnetization and coercivity are measured using Vibrating Sample Magnetometer. The thermomagnetization study is also conducted to evaluate the Curie temperature values of the composites. The effect of cycling on the structural and magnetic characteristics of the two composites are dealt in detail. A comparison between the different characteristics of the two nanocomposites is also provided.     

Studies on α-pinene–furfural-based cation exchange resins. I. Preparation of polymeric compositions and resins

A crosslinked polymer based on α-pinene and furfural suitable for processing into ion exchangers was prepared. The polymer has been processed chemically into different types of cation exchange resins. The role of various parameters such as catalyst concentration, proportion of crosslinking agent, etc., for preparing the polymer is systematically studied and presented. Similarly, the conditions for preparing the various cation exchange resins (sulfonic, phosphonic, and hydroxy phosphonic acid type from the polymer) are also described. A probable/possible composition for the repeating unit in the basic polymer is proposed and supported by experimental evidences.     

Ion exchange properties and selectivity of PSS in an electrochemically switchable PPy matrix

A composite of polypyrrole (PPy) and polystyrenesulfonate (PSS) exchanges cations and is a promising material for the technical application of water softening. The ion exchange properties of electrochemically prepared PPy(PSS) are studied by investigating the polymer using a electrochemical quartz crystal microbalance (EQCM) and by analysing the solution surrounding the polymer by atomic adsorption spectroscopy (AAS). The exchange of cations by PPy(PSS) is found to be caused by three driving forces: electrochemical oxidation/reduction of PPy; chemical oxidation of PPy by dissolved oxygen; gradients of cation concentration between polymer and solution. The ion selectivity of PPy(PSS) is investigated and ion exchange isotherms for the binary systems Ca²⁺/Na⁺ and Ca²⁺/Mg²⁺ are determined.     

The effect of temperature on the stability of ion-exchange resins in aqueous medium

The effect on ion-exchange resins of the polystyrene type of a thermal treatment has been studied by heating strong cation and strong anion resins in water at 95°C and 250°C and obtaining the IR spectra of the remaining resins as well as those of the decomposition products extracted by the water. The degradation of the resins is highly dependent on their ionic form. The ? (OH^?) and the ? (H⁺) forms are more labile, losing completely their exchange capacity at 250°C, while the ? (Li⁺) form retains considerable ion-exchange capacity. On the other hand, the hydrothermal process affects differently the backbone of the anion and the cation resins. There are similarities in the type of decomposition products found after hydrothermal treatment with those observed after radiolytic exposure of the resins. Heating the resins in water reduces the crosslinking of the polystyrene matrix.     

Transport Properties of Ion‐Exchange Membranes During Pervaporation of Water‐Alcohol Mixtures

Abstract

Pervaporation properties of PESS ion‐exchange membranes in contact with water‐aliphatic alcohol mixtures were obtained. PESS ion‐exchange membranes were prepared by chemical modification of the interpenetrating polymer network system polyethylene‐poly(styrene‐co‐divinylbenzene). PESS membranes were loaded with different alkali metal ions as counterions. The obtained data showed that properties of PESS membranes depended strongly on the kind of counterions, degree of crosslinking, and difference in the polarities between water and organic component of the binary mixture. Results obtained for PESS membranes were compared with data obtained for Nafion 117 ion‐exchange membrane.     

Synthesis,characterization, and metal adsorption properties of tannin–phenol–formaldehyde resins produced using tannin from dried fruit of Terminalia chebula (Aralu)

In this study, tannin extracted from Terminalia chebula (Aralu) was used to produce tannin–phenol–formaldehyde resins. They were produced to obtain resins with different tannin to phenol ratio in an attempt to optimize the ion exchange capacities of resins produced. The resins made were sulfonated to improve their properties further. Bivalent cations, such as Zn²⁺, Pb²⁺, Ca²⁺, Mg²⁺, and Cu²⁺, were used to estimate the adsorption properties of both unsulfonated and sulfonated resins. The glass transitions of representative resins were estimated using differential scanning calorimeter thermograms. Fourier transform infrared spectroscopic analysis was used to gauge changes on resins by sulfonation and adsorption of cations. The glass transition values of unsulfonated, sulfonated, and metal‐adsorbed sulfonated resins showed a similar increasing trend with the increase of phenol content in the resin. The glass transition temperature values reach a plateau beyond the tannin/phenol ratio of 1 : 0.5, indicating the formation of large molar masses facilitating entanglements beyond that ratio. The phenol ratio of 1 : 0.5 has shown the highest adsorption capacity for all the metal ions used. The highest adsorption capacity was shown for sulfonated tannin–phenol–formaldehyde resin with the tannin/phenol ratio of 1 : 0.5 for Pb²⁺, which is 0.610 meq/g. The adsorption equilibrium data obtained using the column technique were found fitting Freundlich isotherm. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Cation exchange kinetics on carboxylic acid resins in a multicomponent system H-Me+Me2+

The exchange kinetics in systems where a carboxylic cation exchange resin in the free acid form comes into contact with solutions, containing Na⁺, Mg²⁺, Ca²⁺, HCO^?₃ and SO^2?₄ have been followed by a shallow bed technique.The relations between the sorption rates of univalent and bivalent cations as well as kinetics of competitive exchange in a ternary system $\text{H}\text{-}$Na⁺Mg²⁺ were studied at low solution concentrations. The effect of polymer matrix crosslinking is studied. The behavior of sulfonic acid resin under the same conditions is given for comparison. The results are discussed in terms of different degrees of selectivities and degrees of dissociation of the carboxylic and sulfonic functional groups.     

Ion Exchange of Th(IV), U(VI), and Pu(IV) on Macroreticular Resins in TBP-Shell Sol-T Solutions

Abstract

Absorption of thorium, uranium, and plutonium by macroreticular cation and anion exchange resins from solutions of TBP in Shell Sol-T as a function of TBP and HNO₃ concentrations in the organic phase has been investigated. The absoiption behavior is compared with that on conventional gel-type resins from TBP medium on the one hand and on macroreticular resins from aqueous nitric acid on the other.     

Adsorption of Cations from a Cement Suspension onto Lignocellulosic Substrates and its Influence on Cement Setting

Abstract

The calcium (Ca), sodium (Na), and potassium (K) contents of blue gum, maritime pine, and cork increased after these lignocellulosics were stirred with the filtrate of a cement suspension or a solution of calcium hydroxide. The adsorbed cations could be released easily by treatment with an acidic solution. It is suggested that those raw materials, and lignocellulosics in general, act as cation exchange substrates when they are mixed with cement and water to make wood–cement composites. The implications that such phenomena may have on cement hardening reactions, and how they could hinder them are discussed. The possibility that the phenomenon is related to well‐known compatibility problems that many woods present when manufacturing wood–cement composites is discussed.