Removal and recovery of heavy metal ions in fixed and semi-fluidized beds

Uptakes of heavy metal ions such as Pb²⁺ and Ni²⁺ were studied experimentally in fixed and semifluidized beds packed with a strong cation exchange resin, Amberlite 200. Single and binary aqueous solutions of lead and nickel ions were passed through ion exchange columns, and the exit concentrations were measured to get the breakthrough behavior of the ions. From the exit concentration profiles, the breakthrough time and the ion exchange capacity were evaluated. After removal of heavy metal ions from binary solution of lead and nickel ions until the breakthrough time, two metal ions were recovered by precipitation and resolubilization of lead. In this paper, the recovery yield and separation efficiency are rigorously discussed.     

Ion Exchange Kinetics of Heavy Metal Ions on Organic–Inorganic Composite Cation Exchanger Poly-o-toluidine Zr(IV) Tungstate

To study the ion exchange kinetics of heavy metal ions on the organic–inorganic composite cation exchanger poly-o-toluidine Zr(IV) tungstate, Nernst–Planck was computer simulated. Simulated numerical results for counter ions (Cu, Zn, Cd and Pb) of equal valence and four different ionic mobilities are presented to understand the ionic diffusion process. These results are based on the fractional attainment of equilibrium U(τ), of the counter ions under study. The forward (M²⁺–H⁺) and reverse (H⁺–M²⁺) ion exchange processes are justified as the particle diffusion phenomenon. The self-diffusion coefficient (D _o ), energy of activation (E _a ), and entropy of activation (?S*) have also been estimated to understand the ion exchange process occurring over the surface of this cation exchanger and indicated that the ion exchange process is feasible and spontaneous. It is concluded that the difference in activation energies and entropy of activation may facilitate the separation of metal ions. The regeneration capability of this cation exchanger was also explained.     

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.     

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 a Novel Hybrid Chelating Ion Exchanger and its Application as an Amphoteric Exchanger

A new and novel, hybrid chelating ion exchanger zirconium tri ethylene tetra amine (ZrT) has been synthesized by a simple sol-gel route using inexpensive and easily available chemicals. ZrT has been characterized for elemental analysis, TGA, FTIR, X-ray diffraction, SEM, and EDX. Physical and ion exchange characteristics as well as chemical stability of the material in various acids, bases, and organic solvent media have also been studied. Anion exchange capacity (AEC) for Cl^?, Br^?, Cr₂O₇^2?, F^?, and AsO₄^3? has been determined and distribution coefficient K_d for Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ (transition metal ions) and Hg²⁺,Cd²⁺, Pb²⁺ (heavy metal ions) has been evaluated by batch equilibration techniques in aqueous and various electrolyte media/concentrations. Based on α, the separation factor, a few binary separations have been performed on a chromatographic column packed with ZrT. The amphoteric behavior of ZrT has been demonstrated using CuCl₂ and HgCl₂ and amount of cation and anion simultaneously exchanged determined. The practical applicability of ZrT as an amphoteric exchanger has been further highlighted by performing a case study. A study on the regeneration and reuse of ZrT indicates that it is effective up to six cycles without much decline in performance.     

LITHIUM-ION SIEVE PROPERTY OF λ;-TYPE MANGANESE OXIDE

The adsorptive properties of A-Mn0₂for mono and divalent metal ions were investigated by pH titration and by measurements of the distribution coefficients(Kd's) of the metal ions. The pH titration curve showed an apparently monobasic acid type for a H⁺-Li⁺exchange. Those for H⁺-K⁺and H⁺-Cs⁺exchanges were nearly the same as that for blank titration. The lithium ion uptake increased with increasing solution pH and reached 5 meq/g at pH 11. X-ray diffraction analyses showed that the adsorption of lithium ions caused an increase in the lattice constant of a cubic unit cell. The potassium and cesium ion uptakes were nearly zero over a pH range between 4 and 11. A-Mn0₂showed a remarkably high Kd value for lithium ions, compared to a cation exchange resin. The selectivity sequences were Na⁺< K⁺< Rb⁺< Cs⁺<< Li⁺for alkali metal ions, Mg²⁺< Ca²⁺< Sr²⁺< Ba²⁺for alkaline earth metal ions, and Ni²⁺< Zn²⁺< Co²⁺< Cu²⁺for transition metal ions.     

Separation of Gallium and Indium Isotopes by Cation and Anion Exchange Chromatography

Ion exchange chromatography was applied to study chemical isotope effects of gallium and indium in ligand exchange reactions. A strongly acidic cation and a strongly basic anion exchange resin were used as a solid phase, and aqueous HCl as a liquid phase. On the cation exchanger, the light isotope ⁶⁹Ga was enriched at the front part of the elution band and the heavy isotope ⁷¹Ga at the end part. Instead, the light ¹¹³In isotope was enriched at the end part, and the heavy isotope ¹¹⁵In at the front part. The isotope separation factor ? is equal to 3.3?×?10^–5 for gallium and 2.0?×?10^–4 for indium. On the anion exchanger, the heavy gallium isotope was enriched at the front part, whereas the heavy indium isotope at the end part of the band, with ? equal to ～10^–3 and 1.7?×?10^–4, respectively. This pattern of enrichment is caused by stronger Ga³⁺–OH₂ than Ga³⁺–Cl^? bond, and by inverse order of bond strength for indium. In the displacement method, gallium and indium on anion exchanger also show opposite enrichment of their isotopes, but the ? values (1.5?×?10^–2 for gallium and 5?×?10^–3 for indium) are greater than those found in the elution method, probably due to much higher concentrations of the metals.     

Removal of toxic metal ions by using composite cation-exchange material

Polyanilinezirconium(IV) arsenate composite cation exchange material was synthesized under different experimental conditions by the incorporation of polyaniline into the matrices of inorganic precipitate (zirconium(IV)arsenate). The experimental parameters such as concentration, mixing volume ratio, and pH were established for the synthesis of the material. Ion-exchange material that was synthesized at pH 1.0 showed an ion exchange capacity of 1.33 meq g⁻¹ for Na⁺ ions. The composite material exhibits improved ion-exchange capacity along with chemical and thermal stability. The exchanger was characterized based on FTIR, TGA, XRD, and SEM analysis. The X-ray diffraction study shows semi-crystalline nature of the material. The distribution coefficient studies (K_d) of metal ions on the material were performed in diverse solvent systems. Based on K_d values the material was found to be selective for Pb(II) and Hg(II) ions. Some analytically important binary separations of metal ions in synthetic mixtures viz. Ba²⁺-Pb²⁺, Pb²⁺-Ni²⁺, Cd²⁺-Hg²⁺, Ni²⁺-Hg²⁺, Zn²⁺-Pb²⁺, Ca²⁺-Bi³⁺, Al³⁺-Hg²⁺, and Ca²⁺-Pb²⁺ were achieved on the columns of polyanilinezirconium(IV) arsenate cation exchanger. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

THERMODYNAMICS OF ALKALI AND ALKALINE EARTH METAL ION - EXCHANGE ON CERIUM(IV) HYDROGEN PHOSPHATE

ABSTRACT

Thermodynamics of alkali and alkaline earth metal ions/hydrogen ions exchange on a fibrous cerium(IV) hydrogen phosphate have been investigated. Selectivities for alkali and alkaline earth metal ions increase in the order; Na⁺<<K⁺<Rb⁺<Cs⁺ and Mg²⁺<Ca²⁺<Sr²⁺<Ba²⁺, respectively. The enthalpy changes for alkali metal and Ba2+ ions/H⁺ exchange are negative, those for the other alkaline earth metal ions/H⁺ exchange are positive, indicating that the enthalpy changes for monovalent ions are more favorable than those for divalent ions. In comparison with ions of the same valency, the enthalpy change decreases with the atomic number of the metal ion corresponding to a decrease in the entropy change of dehydration in response to enthalpy-entropy compensation.     

SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS XXX III. SELECTIVITIES OF ALKALI METAL IONS ON TIN(IV) ANTIMONATE CATION-EXCHANGER PREPARED AT DIFFERENT CONDITIONS

ABSTRACT

A tin(IV) antimonate(SnSbA) cation exchanger has been synthesized under different conditions; changes in the concentration, the molar ratio of Sb/Sn in the starting solution, and hydrolysis temperature. The products obtained were characterized by powdered X-ray diffraction and thermal analysis, and infrared spectra. The pH titration curves on SnSbA showed apparently mono-basic acid, but can be expected to the presence of the number of the functional groups with overlapping different pKa values. The increased acidities were observed with increasing the molar ratio (Sb/Sn) in the exchanger. The equilibrium distribution coefficients were determined at micro-amount of alkali metal ions in the hydrochloric acid solution. The SnSbA showed an unusual selectivity for alkali metal ions compared to cation exchange resins and other inorganic ion-exchangers.

The selectivity sequence shows; Na⁺ < K⁺ < Rb⁺ < Cs⁺ < Li⁺

An extremely high selectivity of lithium ions was found on the SnSbA hydrolyzed at relatively high temperature and with high Sb/Sn molar ratio     

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.     

EDTA-stannic(IV)iodate: preparation, characterization and its analytical applications for metal content determination in real and synthetic samples

A new organic–inorganic cation exchanger EDTA-stannic(IV)iodate was synthesized. The materials possess good chemical and thermal stability. The exchanger was characterized on the basis of X-ray, TGA, FTIR, UV–Visible spectrophotometery and SEM studies. ion exchange capacity, pH titration, elution and distribution studies were also carried out to determine the primary ion exchange properties of the material. The SEM study confirms the fibrous nature of the material. The exchanger behaves as a monofunctional cation exchanger with ion exchange capacity of 1.30 meq/g for Na⁺ ions. The material can perform well upto the temperature of 500 °C and retains the 76.4% of ion exchange capacity. The material is fairly stable in dilute solutions of some common mineral acids, bases and organic solvents. The differential selectivity of metal ions on EDTA-stannic(IV)iodate has been utilized to perform analytically and industrially important binary separations.     

THERMODYNAMIC STUDY OF M3+/H+ EXCHANGE SYSTEMS ON TITANIUM ANTIMONATE CATION EXCHANGER

ABSTRACT

Selectivity coefficients K_H ^M for trivalent metal ions / hydrogen ions (M³⁺/H⁺) exchanges on titanium antimonate cation exchanger (TiSbA) have been determined for group 13 metals (Al³⁺, Ga³⁺, and In³⁺) and rare earth metals (La³⁺, Nd³⁺, Eu³⁺, Yb³⁺, and Y³⁺) ions by batch equilibration at 30, 45, and 60 ^°c in nitric acid media. Kielland plots (logK_H ^M vs. the fractional exchange X¯_M) for these exchange systems have been analyzed and found to show a break point at X¯_M=0.005-0.01. This behavior can be interpreted assuming a two-site model. A site available at infinitesimal X¯_M value has a large steric effect. The selectivity in this site increased in the order: Al³⁺ < Ga³⁺ < In³⁺ for group 13 metal ions and Y³⁺ < Yb³⁺ < Eu³⁺ < Nd³⁺ < La³⁺ for rare earth metal ions in the X¯M<0.02 region at 30^°C. The amounts of Ga³⁺ exchanged by TiSbA increased with a rise in temperature. The selectivity of group 13 metal ions changed to: AI³⁺ < In³⁺ < Ga³⁺ at 60^°C. On the other hand, the selectivity order for rare earth metal ions was independent of temperature. The hypothetical thermodynamic data (ΔG^o _ideal, ΔH^o _ideal and ΔS^o _ideal) at 25^°C were evaluated.     

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     

Synthesis,Ion Exchange Properties,and Applications of Amorphous Cerium(III) Tungstosilicate

Abstract

A novel hetropolyacid-based cation exchanger cerium(III) tungstosilicate was synthesized in amorphous form by mixing tungstosilisic acid (TSA) solutions to cerium(III) nitrate solutions at different Ce:TSA ratios. The materials were precipitated from the liquid phase by raising the pH of the solutions using sodium hydroxide. The produced ion exchange powders were characterized using powder X-ray diffractometry, thermogravimetry, infrared spectrometry, inductively coupled plasma and atomic absorption elemental analysis. The materials which were dried at 50°C were found to be stable in water, dilute acids, alkaline solutions, and high temperature up to 1000°C. The Ion exchange properties of the synthesized samples were studied by measuring the distribution coefficients (K_d) for 29 metal ions in demineralized water and nitric acid media. On the basis of K_d values, some quantitative separations such as Co²⁺-Pb²⁺, Cr³⁺-Zr⁴⁺, and Mo⁶⁺- W⁶⁺ are achieved on their columns.     

Selective Recovery of Copper,Cobalt, and Nickel from Aqueous Chloride Media using Solvent Impregnated Resins

Selective recovery of copper, cobalt, and nickel from acidic chloride media was investigated with solvent impregnated resins (SIRs) containing acidic organophosphorus extractants. The adsorption of each metal with the SIR proceeds via a cation exchange mechanism. An SIR containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC-88A) has high selectivity for Cu²⁺, and the order of selectivity is Cu²⁺ > Co²⁺ > Ni²⁺. Effective adsorption-elution can be achieved by chromatographic operation for the selective recovery of Cu²⁺ from a ternary metal solution. High selectivity for Co²⁺ was observed using a SIR comprising bis-2,4,4-trimethylpentylphosphinic acid (Cyanex 272) and can be effectively separated from a Co and Ni binary metal solution by column adsorption. A simple and effective process flow sheet is proposed for selective recovery of Cu²⁺, Co²⁺, and Ni²⁺ from aqueous chloride media using the two SIRs.     

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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Phase Transfer Catalyzed Bromide—Chloride Exchange: Dependence of Equilibrium Position and Selectivity Constant on Nature and Composition of Aqueous Phase

The position of the equilibrium in the PTC exchange reaction of alkyl chloride with metal bromide salts RCl + MBr ⇌ RBr + MCI under various condtions is utilized for calculation of the selectivity constant K^sel_Cl/Br. This constant is found to be dependent on the nature of the metal cation and the inorganic phase composition. K^sel_Cl/Br can be defined for any point on the phase diagram MCl—MBr—H₂O at a given temperature, solvent and quaternary cation.     

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.     

SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS. XXXXI. ION EXCHANGE EQUILIBRIA OF ALKALI METAL IONS/HYDROGEN IONS ON TIN(IV) ANTIMONATE

Ion exchange equilibria of alkali metal ions (Li⁺, Na⁺, K⁺,, Rb⁺, and Cs⁺)H⁺, systems have been studied in MNO-j-HNOj media with ionic strength of 0.1 at 30, 45 and 60 °C on tin(IV) antimonate as a cation exchanger. The ion exchange isotherms have been measured for both forward and backward reactions by the batch technique. The isotherms showed S-shaped curves for all exchange systems studied. The selectivity coefficients (logarithmic scale) vary with the equivalent fraction X_M of alkali metal ions in the exchanger and give two linear functions of X_M with a break point (X_M= 0.14, except 0.04 for Li⁺, /H⁺) indicating two different exchanging sites. The selectivity sequence, Na⁺, ? K⁺, ? Rb⁺, ? Cs⁺, ? ? Li, holds in the range of Xu= (0 - 0.04) and the sequence, Cs < Rb ⁺, ? K ⁺, ? Na ⁺, < Li ⁺, applies when X_M is higher than 0.14.

Hypothetical thermodynamic data on “zero loading” of the ion exchange reaction was evaluated.