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.     

Separation and extraction of some heavy and toxic metal ions from their wastes by grafted membranes

Preparation and characterization of a series of ion‐exchange membranes for the purpose of separation and extraction of some heavy and toxic metal ions from their wastes were studied. Such ion‐exchange membranes were prepared by γ‐radiation grafting of acrylonitrile (AN) and vinyl acetate (VAc) in a binary monomer mixture onto low‐density polyethylene (LDPE) using the direct technique of grafting. The reaction conditions at which the grafting process proceeds successfully were determined. Many modification treatments were attempted for the prepared membranes to improve their ion‐exchange properties. The possibility of their practical use in waste‐water treatment to remove some heavy and toxic metal ions such as Pb²⁺, Cd ²⁺, Cu²⁺, Fe³⁺, Sr²⁺, and Li⁺ were investigated. These grafted membranes showed great promise for possible use in the field of extraction and removal of some heavy and toxic metals from their wastes. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 849–860, 2001     

Nonionic adsorption of aromatic amino acids on a cation-exchange resin

Nonionic adsorption of aromatic amino acids on a cation-exchange resin (Dowex 50W-X8) was studied. At low concentrations, phenylalanine and tyrosine were adsorbed on the resin by monovalent ion-exchange process. Deviation from stoichiometric ion exchange became large as phenylalanine and tyrosine concentrations increased. On the other hand, aliphatic amino acids, glycine and alanine, were adsorbed on the resin by monovalent ion-exchange process. In column breakthrough experiments, the bed capacities for phenylalanine and tyrosine were higher than those for metal ions (Na⁺, Pb²⁺, and Ni²⁺) and the aliphatic amino acids. The increased capacities may be due to nonionic interaction between the aromatic amino acids and the polystyrene resin matrix. The nonionic interaction could be suppressed in 25% ethanol solution.     

Unconventional ion exchange resins and their retention properties for Hg2+ ions

Synthesis of two unconventional ion exchange resins and their behaviour on the mercury sorption experiments were investigated.The ion exchange resins were obtained by the quaternization reaction of 4-vinylpyridine:divinylbenzene copolymer, gel-type, by two ways namely, the nucleophilic substitution of the pyridine matrix with 2-chloroacetamide and the nucleophilic addition of protonated copolymer to acrylamide.Comparative sorptions of Hg²⁺ ions on the synthesized pyridine resins by batch experiments in mono- and binary system were analyzed. Mercury retention experiments aimed to study the influence of the solution concentration, contact time and solution pH. The removal of Hg²⁺ ions from aqueous solutions depends on the pH values, the amount of the retained mercury increased with the pH value.The studied strong base pyridine anion exchange resins presented a good selectivity for the Hg²⁺ ions during the competitive sorption of Hg²⁺/Cu²⁺, Hg²⁺/Zn²⁺ and Hg²⁺/Fe³⁺ at metal cations ratio of 1:1.     

Binding of several heavy metal ions by polyaspartyl polymers and their application to some Chinese herbal medicines

Water‐insoluble polyaspartyl polymers were synthesized by using water as medium instead of organic medium. Taking Ca²⁺ as a reference, the binding of several heavy‐metal ions, including Pb²⁺, Cd²⁺, Hg²⁺, Cr³⁺, Cu²⁺, and Mn²⁺, by polyaspartyl polymers was studied. The experimental results revealed that polyaspartate is an excellent binding agent for the investigated heavy‐metal ions. These cation ions were bound to polyaspartate polymer by the same mechanism as Pb²⁺, which can be explained by ion exchange model. Since polyaspartate has a protein‐resembling structure that is sensitive to trace heavy metal, it was used to remove some trace heavy‐metal elements in Chinese herbal medicines. It was found that polyaspartate material was an effective agent for the removal of Pb²⁺, Cd²⁺, and Hg²⁺ ions from glycyrrhizin, angelica, and gynostemma pentaphyllum. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Removal of Cu2+ and Pb2+ ions from aqueous solutions by starch-graft-acrylic acid/montmorillonite superabsorbent nanocomposite hydrogels

In this study, the removal of copper(II) and lead(II) ions from aqueous solutions by Starch-graft-acrylic acid/montmorillonite (S-g-AA/MMT) nanocomposite hydrogels was investigated. For this purpose, various factors affecting the removal of heavy metal ions, such as treatment time with the solution, initial pH of the solution, initial metal ion concentration, and MMT content were investigated. The metal ion removal capacities of copolymers increased with increasing pH, and pH 4 was found to be the optimal pH value for maximum metal removal capacity. Adsorption data of the nanocomposite hydrogels were modeled by the pseudo-second-order kinetic equation in order to investigate heavy metal ions adsorption mechanism. The observed affinity order in competitive removal of heavy metals was found Cu²⁺ > Pb²⁺. The Freundlich equations were used to fit the equilibrium isotherms. The Freundlich adsorption law was applicable to be adsorption of metal ions onto nanocomposite hydrogel.     

Lead removal from aqueous solutions by 732 cation‐exchange resin

Kinetics and thermodynamics of the removal of Pb²⁺ from an aqueous solution by 732 cation‐exchange resin in hydrogen type (732‐CR) were studied in the temperature range of 298–328 K and Pb²⁺ concentration range of 5–50 mol/m³. The effects of ion exchange temperature and initial lead ion concentration on the time evolution of the experimental concentration for the metal ion were investigated. Ion exchange kinetics of Pb²⁺ onto 732‐CR follow the Nernst‐Planck equation and unreacted‐core model (UCM). The diffusion coefficients of counter ions and the efficient diffusion coefficient of lead ions within the resin were calculated. The results show that the ion exchange process is favoured under the particle diffusion control mechanism. The ion exchange isotherm data agreed closely with the Langmuir isotherm. The maximum monolayer exchange capacity for Pb²⁺ was found to be 484.0 mg/g at 308 K. Thermodynamic studies show that Pb²⁺ onto 732‐CR is spontaneous and exothermic in nature. The ion exchange processes were verified by Energy Disperse Spectroscopy (EDS).     

Adsorption of selected toxic metals by modified peanut shells

The objective of this study was to modify peanut shells to enhance their adsorptive properties toward the metal ions cadmium (Cd²⁺), copper (Cu²⁺), nickel (Ni²⁺), lead (Pb²⁺) and zinc (Zn²⁺). Milled peanut shells were initially washed with water or 0.1 N NaOH or left unwashed. Following these treatments or lack of treatment, the shells were either left unmodified or modified by a heat treatment in the presence of either 1.0 M phosphoric acid or 0.6 M citric acid. Modified peanut shells were evaluated either for adsorption efficiency or for adsorption capacity using the five metal ions listed above. Adsorption efficiencies and capacities were compared with efficiencies and/or capacities for the commercial chelating or cation exchange resins Amberlite 200, Amberlite IRC‐718, Duolite GT‐73, and carboxymethylcellulose. For the adsorption efficiencies of individual metal ions, modified peanut shells met or exceeded the adsorption values for cadmium, copper, nickel or zinc ions compared with the commercial resins Duolite GT‐73 and carboxymethylcellulose. In a solution containing all five metal ions, modified peanut shells met or exceeded the adsorption efficiencies for cadmium, copper and lead ions compared with Duolite GT‐73, Amberlite IRC‐718 and carboxymethylcellulose. Adsorption capacities of modified peanut shells met or exceeded the adsorption capacity of Duolite GT‐73 for lead ions only. Citric or phosphoric acid‐modified peanut shells showed a preference for Cu²⁺ and Pb²⁺ and appear promising as potentially inexpensive adsorbents for selected metal ions. © 2001 Society of Chemical Industry     

Synthesis,Characterization, and Applications of a New Ion Exchanger Tamarind 4-aminobenzoic Acid (TABA) Resin in Industrial Wastewater Treatment

Chromatographic column separations of toxic metal ions from industrial wastewater were achieved in acid media at optimized (K_d) values with a synthesized cation exchange TABA resin. The prepared TABA resin was characterized by FTIR, elemental, and thermogravimetric analysis. Studies of total ion exchange capacity, resin durability, and swelling were carried out. The distribution coefficient values of metal ions, viz Cu²⁺, Fe²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ at different pH, were also studied using a batch equilibration method. The different factors affecting metal ions adsorption on this substrate, such as treatment time, agitation speed, and temperature, were studied in detail.     

Binary component sorption of Cu(II) and Pb(II) with activated carbon from Eucalyptus camaldulensis Dehn bark

The objective of this work is to illustrate the potential in the use of activated carbon in the binary component sorption of copper and lead ions. Eucalyptus bark was used as a precursor for the activated carbon which was prepared through the phosphoric acid activation process. This activated carbon was then used for the sorption of copper and lead ions. The quantity of the metal ions in the solution was measured with the Flame & Graphite Furnace Atomic Adsorption Spectrophotometer. The results indicated that the optimal pH for sorption was 5. The maximum sorption capacities for Cu(II) and Pb(II) were 0.45 and 0.53 mmol g⁻¹. Carboxylic, amine and amide groups were found to involve in the sorptions of Cu(II) and Pb(II). A major mechanism for the uptake of both heavy metals was proven not to be ion exchange but adsorption. In binary component sorptions, activated carbon still could sorb Pb(II) in a greater amount than Cu(II). However, the presence of the secondary metal ions suppressed the sorption of the primary metal ions. There seemed to have a linear inverse dependency between the sorption capacity and the concentration of the secondary metal ion.     

Preparation and characterization of a phosphonylated polypropylene ion exchanger

Because typical ion exchange resins used for treating wastewater contain sulfur binding sites and suffer from application limitations, a new ion exchange system was developed by phosphonylating nonwoven polypropylene fabric (PP). These fabrics were phosphonylated for 0.5, 1, 2, and 4 h; amount of phosphorus on phosphonylated PP increased with an increase in phosphonylation time. After hydrolysis, the appropriate phosphonylated sample was placed in a glass column where a europium (Eu³⁺), lead (Pb²⁺), or mercury (Hg²⁺) salt solution was passed through the fabrics after an equilibration period of 5 min. Filtrate samples were then analyzed by atomic absorption spectroscopy for metal concentration. Results showed that metal binding efficiency for Eu³⁺ increased with an increase in phosphonylation time; Pb²⁺ binding efficiency increased up to 2 h phosphonylation time and then decreased; Hg²⁺ binding efficiency was practically independent of phosphonylation time. PP fabrics were also sulfonated and tested for binding efficiency to determine if phosphorus was a better binding site than sulfur. By comparing the results from phosphonylated PP and sulfonated PP, data showed that phosphonylated PP bound metal ions at a higher efficiency than sulfonated PP. Also, phosphonylated PP had higher binding efficiencies with Eu³⁺ and Pb²⁺ than a commercial exchange resin. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 93–100, 2000     

Treatment of aqueous solutions containing nickel using crandallite‐type compounds

The removal of nickel from aqueous solutions streams has been investigated using an artificial amorphous crandallite‐type compound, CaAl₃(OH)₆(HPO₄)(PO₄) (Ca‐crandallite), synthesized in our laboratory. Equilibrium ion‐exchange isotherms in an aqueous medium of Ca²⁺/Ni²⁺ at different pH values at 293 K have been determined. The experimental equilibrium data were satisfactorily correlated using a Langmuir‐type empirical equation. At low pH values, the hydrogen ion competes with the heavy metal cation and the percentage removal of metal declines. It was found that the operating capacity of Ca‐crandallite with respect to the metal ion increased with the pH of the solution, in accordance with a second‐degree polynomial equation. However, the pH should not be allowed to rise to levels at which chemical precipitation as nickel hydroxide would occur, with 7.00 the highest value tested. Taking into account the variation of operating capacity with pH, the system exhibited a unique separation factor, namely all the experimental points can be described by a unique isotherm in a dimensionless form. The Ca‐crandallite showed a high capacity, 2.176 meq g^?1, for the exchange of Ni(II) from nickel nitrate solutions and the rate of exchange of metal increases with increasing solution temperature due to the enhancement of effective intraparticle diffusivity. Copyright © 2005 Society of Chemical Industry     

Molecular Dynamics Simulation of Heavy Metal Ions in Aqueous Solution Using Lennard-Jones 12-6 Potential

The dynamic and structural properties of some heavy metal ions, such as Cd²⁺, Ni²⁺, and Zn²⁺ solved in water, were studied using molecular dynamics (MD) simulation. In this paper, the radial distribution function (RDF) and self-diffusion coefficient were determined and compared with the experimental data. The results showed that the surrounding water molecules around the metal ions form a shell-like arrangement. The number of water molecules contributing in this arrangement (N_c) for Ni²⁺, Cd²⁺, and Zn²⁺ were, respectively, 8.8, 7.4, and 6. Noticeable differences between the simulation results and experimental data were observed for the nickel ion structural properties when the MM2 Lennard-Jones parameters were used to predict the interaction of nickel and water molecules. To resolve this problem, the new Ni²⁺-water Lennard-Jones interaction parameters were used in the MD simulation program to predict the structural properties of Ni²⁺ solution, which gave acceptable results.     

An investigation into transition metal ion binding properties of silk fibers and particles using radioisotopes

Silk is a structural protein fiber that is stable over a wide pH range making it attractive for use in medical and environmental applications. Variation in amino acid composition has the potential for selective binding for ions under varying conditions. Here we report on the metal ion separation potential of Mulberry and Eri silk fibers and powders over a range of pH. Highly sensitive radiotracer probes, ⁶⁴Cu²⁺, ¹⁰⁹Cd²⁺, and ⁵⁷Co²⁺ were used to study the absorption of their respective stable metal ions Cu²⁺, Cd²⁺, and Co²⁺ into and from the silk sorbents. The total amount of each metal ion absorbed and time taken to reach equilibrium occurred in the following order: Cu²⁺ > Cd²⁺ > Co²⁺. In all cases the silk powders absorbed metal ions faster than their respective silk fibers. Intensive degumming of the fibers and powders significantly reduced the time to absorb respective metal ions and the time to reach equilibrium was reduced from hours to 5–15 min at pH 8. Once bound, 45–100% of the metal ions were released from the sorbents after exposure to pH 3 buffer for 30 min. The transition metal ion loading capacity for the silk sorbents was considerably higher than that found for commercial ion exchange resins (AG MP‐50 and AG 50W‐X2) under similar conditions. Interestingly, total Cu²⁺ bound was found to be higher than theoretically predicted values based on known specific Cu²⁺ binding sites (AHGGYSGY), suggesting that additional (new) sites for transition metal ion binding sites are present in silk fibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

New Organic-Inorganic Type Acrylamide Aluminumtungstate: Preparation,Characterization and Analytical Applications as a Cation Exchange Material

Abstract

A crystalline sample of organic-inorganic cation exchanger acrylamide aluminumtungstate has been synthesized. The material behaves as a mono-functional cation-exchanger with an ion–exchange capacity 1.25 meq/g for Na⁺ ions. The material has been characterized on the basis of thermal stability, chemical stability, FTIR, TGA-DTA, X-ray, and SEM studies. The effect of time and temperature on the distribution coefficient of metal ion was studied. It was concluded that 30°C appeared to be the most favorable temperature. Sorption behavior of the metal ions was studied in different solvent systems. On the basis of distribution studies, the material was found to be selective for Pb²⁺ ions. Its selectivity was examined by achieving some important binary separations like Mg²⁺-Pb²⁺, Hg²⁺-Pb²⁺, Ca²⁺-Pb²⁺ Zn²⁺-Pb²⁺, Ni²⁺-Pb²⁺, and Al³⁺-Pb²⁺. The practical applicability of the cation-exchanger was demonstrated in the separation of Pb²⁺ ions from a synthetic mixture.     

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.     

Uptake of cadmium,copper, and lead by microporous synthetic Na-birnessite

Removal of cadmium, copper and lead with microporous synthetic Na-birnessite (sodium-birnessite) was investigated by carrying out batch-type sorption experiments with 2 days of equilibration at room temperature. The sorption isotherms indicated that synthetic Na-birnessite showed high affinity for all three heavy metal cations. The Na-birnessite was able to take up Cd, Cu and Pb up to approximately 140, 106 and 60%, respectively of its theoretical cation exchange capacity. The above higher uptakes of Cd and Cu than the theoretical cation exchange capacity of birnessite were probably caused by exchange of not only Cd²⁺ but also CdCl⁺ species with Na⁺ and by exchange of not only Cu²⁺ but also CuCl⁺ species with Na⁺. Some exchange of CdCl⁺ and CuCl⁺ species as well as some pH-dependent specific adsorption of the Cd and Cu cations resulted in higher than theoretical uptakes. The XRD patterns after sorption of Cd with Na-birnessite showed an increase in the d(001)-spacing from 7.144 to 7.244 Å with high Cd²⁺ concentration, which indicated that interlayer Na⁺ ions were replaced by Cd²⁺ ions. After the sorption reactions with high Cu concentrations, the XRD patterns showed that the main d(001)-spacing of the birnessite slightly increased from 7.144 to ~7.179 Å. In the case of Pb sorption, the d(001)-spacing slightly decreased to 7.133 Å from 7.144 Å of the as synthesized Na-birnessite. These results suggest that removal of heavy metal cations by Na-birnessite is likely due to both ion exchange and chemisorption, the latter due to surface complexation at the edges and outer planar surfaces of Na-birnessite. Based on these results, Na-birnessite is proposed as a potential candidate material to remove heavy metal cations from groundwater as well as industrial wastewater.     

Conversion of coal fly ash into zeolite and heavy metal removal characteristics of the products

Fly ash obtained from a power generation plant was used for synthesizing zeolite. Zeolites could be readily synthesized from the glassy combustion residues and showed potential for the removal of heavy metal ions. By the use of different temperatures and NaOH concentration, five different zeolites were obtained: Na-P1, faujasite, hydroxy sodalite, analcime, and cancrinite. The synthesized zeolites had greater adsorption capabilities for heavy metals than the original fly ash and natural zeolites. Na-P1 exhibited the highest adsorption capacity with a maximum value of about 1.29 mmole Pb g^-1 and had a strong affinity for Pb²⁺ ion. The metal ion selectivity of Na-P1 was determined as: Pb²⁺> Cu²⁺> Cd²⁺> Zn²⁺, consistent with the decreasing order of the radius of hydrated metal ion. The adsorption isotherm for lead by Na-P1 fitted the Freundlich rather than the Langmuir isotherm.     

Synthesis,Characterization, and Analytical Applications of a New Composite Cation Exchange Material Acetonitrile Stannic(IV) Selenite: Adsorption Behavior of Toxic Metal Ions in Nonionic Surfactant Medium

A composite cation exchange material acetonitrile stannic(IV) selenite was prepared under different experimental conditions. The ion exchange capacity of the material was improved from 0.75 to 1.83 meq g^?1 in comparison to its inorganic counterpart, stannic selenite. The material was characterized on the basis of X-ray, TGA, FTIR, and SEM studies. Ion-exchange capacity, pH titration, elution behavior, and distribution studies were also carried out to determine the preliminary ion-exchange properties of the material. Furthermore, it was investigated that this ion exchange material has a good reusability after 8 times regeneration. The sorption behavior of metal ions was studied in nonionic surfactants namely triton x-100 and tween. On the basis of distribution coefficient studies, several binary separations of metal ions viz- Pb²⁺-Th⁴⁺, Ni²⁺-Th⁴⁺, Ni²⁺-Zn²⁺, Cu²⁺-Ce⁴⁺, Al³⁺-Bi³⁺, and Al³⁺Zn²⁺ was achieved on the packed column of this ion exchange material. The practical applicability of this cation-exchanger was demonstrated in the separation of Th⁴⁺ from a synthetic mixture of Th⁴⁺, Ca²⁺, Sr²⁺, Ni²⁺, and Mg²⁺ as well as Cu²⁺ and Zn²⁺ from a brass alloy sample. Thus, all the studies suggest that acetonitrile stannic(IV) selenite has excellent potential for the removal of metal ionic pollutant species from aqueous media effectively.