Chemical Ion Exchange Research Articles

Adsorption Thermodynamics and Kinetics of Malachite Green onto Ca(OH)2-Treated Fly Ash

Fly ash, an industrial by-product abundant in India, was treated with alkali and tested as a low-cost adsorbent for the removal of malachite green from an aqueous solution in a batch adsorption procedure. Effects of stirring rate, temperature, pH, initial dye concentration, contact time, and adsorbent dose were investigated. The adsorption was found to be strongly dependent on pH of the medium and the adsorption capacity decreased with an increase in temperature. The Langmuir isotherm model showed a good fit to the equilibrium adsorption data at all temperatures. The mean free energy (E) estimated from the Dubinin-Radushkevich model indicated that the adsorption mechanism was chemical ion exchange. The kinetic data were found to follow the pseudo second-order kinetic model. The rate constant decreased with the increase in temperature indicating the exothermic nature of adsorption. Intraparticle diffusion was not the sole rate-controlling factor. The Arrhenius and Eyring equations were used to evaluate the...

Solvent extraction of molybdenum blue from alkaline leaching solution of the Ni–Mo ore

Molybdenum in the Ni–Mo ore was leached by air oxidation in an alkaline solution. Due to the high concentrations of SO 4 2−, S 2O 3 2−, SO 3 2− and AsO 4 3− in the solution, it was difficult to efficiently extract Mo by chemical precipitation or ion exchange process. So the extraction of Mo from the solution with the mixture of tertiary amine (N-235) and secondary caprylic alcohol dissolved in kerosene was investigated. The effects of several process parameters such as extractant concentration, feed solution pH, O/A ratio, temperature of extraction, and contact time were studied. Results proved that the extraction efficiency of Mo was 99.4% at pH 3, time 2 min and O/A ratio 1:4 with 15 v% N-235. Stripping of Mo with a 15 m% ammonia solution was essentially completed (99.9%) in a single stage at an O/A ratio of 3. Comparison of the chemical oxygen demand (COD) concentration of the feed solution (12,400 mg/L) and raffinate (8600 mg/L) indicated that the separation of Mo and reductive substances, such as S 2O 3 2− and SO 3 2−, was achieved after solvent extraction. The Mo concentration in the strip liquor obtained in a single stage can be increased by contacting a new loaded organic phase. After repeated stripping, the concentration of Mo, As, P, W and V in the strip liquor were 125.82 g/L, 15.63 g/L, 0.73 g/L, 0.09 g/L, and 0.074 g/L respectively.

Concentration of Cesium and Strontium Elements Involved in a LiCl Waste Salt by a Melt Crystallization Process

As an alternative to conventional Group I and II separation methods (such as adding a chemical agent and ion exchange), melt crystallization processes, zone freezing, and layer melt crystallization were tested for the separation (or concentration) of cesium and strontium fission products in a LiCl waste salt generated from an electrolytic reduction process of a spent oxide fuel. In these melt crystallization processes, impurities (CsCl and SrCl2) are concentrated in a small fraction of the LiCl salt by the solubility difference between the melt phase and the crystal phase. As experimental variables, initial molten salt temperature, crucible rising velocity in the zone freezing case, and cooling air flow rate in the layer crystallization case were used. In the zone freezing process, although the operating time is long (1.7 mm/h of crucible rising velocity) when assuming a LiCl salt reuse rate of 90 wt%, >90% separation efficiency for both CsCl and SrCl2 was shown. In the layer crystallization process, the crystal growth rate strongly affects the crystal structure and therefore the separation efficiency. At a 25 to 30 [script l]/min cooling air flow rate, 700 to 710°C initial molten salt temperature, and <5 g/min crystal growth rate, the separation efficiency of both CsCl and SrCl2 exceeded 90% by the layer crystallization process, assuming a LiCl salt reuse rate of 90 wt%.

Adsorption thermodynamics, kinetics and isosteric heat of adsorption of malachite green onto chemically modified rice husk

Rice husk treated with NaOH was tested as a low cost adsorbent for the removal of malachite green from aqueous solution in batch adsorption procedure. The adsorption experiments were carried out as a function of solution pH, initial dye concentration, contact time and temperature. The adsorption was found to be strongly dependent on pH of the medium. The Freundlich isotherm model showed good fit to the equilibrium adsorption data. The mean free energy ( E) estimated from the Dubinin–Radushkevich model indicated that the main mechanism governing the sorption process was chemical ion-exchange. The kinetics of adsorption followed the pseudo-second-order model and the rate constant increased with increase in temperature indicating endothermic nature of adsorption. The Arrhenius and Eyring equations were used to obtain the activation parameters such as activation energy ( E a), and enthalpy ( ΔH #), entropy ( ΔS #) and free energy ( ΔG #) of activation for the adsorption system. Thermodynamic studies suggested the spontaneous and endothermic nature of adsorption of malachite green by treated rice husk. The isosteric heat of adsorption ( ΔH X ) was also determined from the equilibrium information using the Clausius–Clapeyron equation. ΔH X increased with increase in surface loading indicating some lateral interactions between the adsorbed dye molecules.

Biosorption of antimony from aqueous solution by lichen ( Physcia tribacia) biomass

The biosorption characteristics of antimony(III) from aqueous solution using lichen ( Physcia tribacia) biomass was investigated in terms of equilibrium, thermodynamics and kinetics. Optimum biosorption conditions were determined with respect to pH, biomass concentration, contact time, and temperature. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models were applied to the equilibrium data. The maximum Sb(III) sorption capacity of P. tribacia was found to be 81.1 mg/g at pH 3, biomass concentration 4 g/L, contact time 30 min, and temperature 20 °C. The calculated mean biosorption energy (10.2 kJ/mol) using D–R model indicated that the biosorption of Sb(III) on the biomass was occurred by chemical ion exchange. The highest desorption efficiency (95%) was achieved using 0.5 M HCI. The biosorption capacity of P. tribacia slightly decreased about 10% after ten times of sorption–desorption process. The calculated thermodynamic parameters showed that the biosorption of Sb(III) onto P. tribacia biomass was feasible, spontaneous and exothermic, respectively. The experimental data was also examined using the Lagergren's first-order and pseudo-second-order kinetic models. The results revealed that the pseudo-second-order kinetic model provided the best description of the equilibrium data.

Ion exchange as a simple and effective tool for screening possible cation conductors

Although kinetics of the low-temperature cation exchange in mixed oxide materials (aluminates, gallates, titanates, niobates, tantalates, antimonates, phosphates etc.) cannot provide quantitative information on self-diffusion and ionic conductivity in the starting material due to the mixed cation effect, it is the most direct and simple qualitative indication of the cation mobility in the solid state. It does not need using ceramics and single crystals and thus represents a useful tool for rapid selection of prospective cation conductors for subsequent detailed studies of dense samples with electrical methods. Examples of solid electrolytes discovered owing to their ion-exchange properties are reviewed, and rational principles of the ion-exchange testing are discussed. Laws of ion-exchange equilibria are based on ionic size compliance and the principle of hard and soft acids and bases. The former is most important for alkali/alkali exchange and the latter for exchanging cations of similar size but having different electronic structures: those of the rare-gas type and those having 18- or 18 + 2-electron shells, like Na+ and Ag+ or K+ and Tl+. Ion-exchange testing is especially useful for structures with non-intersecting conduction paths. It is shown that the resistivity of crystals with non-parallel and non-intersecting conduction paths cannot be described by the classical tensor formalism. Significant differences between isotope exchange, chemical ion exchange and ion conduction, quasi-one-dimensional and true one-dimensional conductors and single- and multiple-barrelled non-intersecting channels are disclosed and discussed.

Isocratic anion exchange separations of Group V elements

Isocratic anion exchange separations of Group V elements from solutions containing HF have been considered for the development of Db aqueous phase chemistry experiments. Separation of Nb/Ta from an HF/NH4F system has been demonstrated but has limited utility due to interferences with alpha and spontaneous fission (SF) source preparation. The physical parameters associated with ion exchange chromatography have been optimized for the separation and sequential isolation of Pa, Nb and Ta from mixed HF/HNO3 solutions. A suitable procedure incorporating a series of successive chemical separation techniques, i.e. precipitation and ion exchange chromatography, has been suggested for off-line Db characterization studies.

Equilibrium, kinetic and thermodynamic studies on aluminum biosorption by a mycelial biomass ( Streptomyces rimosus)

This work focused on kinetic, equilibrium and thermodynamic studies on aluminum biosorption by Streptomyces rimosus biomass. Infrared spectroscopy analysis shows that S. rimosus present some groups: hydroxyl, methyl, carboxyl, amine, thiol and phosphate. The maximum biosorption capacity of S. rimosus biomass was found to be 11.76 mg g −1 for the following optimum conditions: particle size,]250–560] μm, pH 4–4.25, biomass content of 25 g L −1, agitation of 250 rpm and temperature of 25 °C. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were applied to describe the biosorption isotherms at free pH (pH i 4) and fixed pH (pH f 4). Langmuir model is the most adequate. With fixed pH, the maximum biosorption capacity is enhanced from 6.62 mg g −1 to 11.76 mg g −1. The thermodynamic parameters (Δ G°, Δ H° and Δ S°) showed the feasibility, endothermic and spontaneous nature of the biosorption at 10–80 °C. The activation energy (Ea) was determined as 52.18 kJ mol −1 using the Arrhenius equation and the rate constant of pseudo-second-order model (the most adequate kinetic model). The mean free energy was calculated as 12.91 kJ mol −1 using the D–R isotherm model. The mechanism of Al(III) biosorption on S. rimosus could be a chemical ion exchange and carboxyl groups are mainly involved in this mechanism.

Removal of Pb(II) ions from aqueous solutions using Bombax ceiba saw dust activated carbon

The isotherms, kinetics and thermodynamics of Pb(II) ions from aqueous solution by activated carbon prepared from Bombax ceiba sawdust (SDC) were carried out in a batch adsorption system. The effects of pH, adsorbent dosage, contact time, initial concentration of Pb(II) and temperature on the adsorption were studied. Maximum adsorption of Pb(II) occurred at pH 5. Pseudo first order, pseudo second order and intraparticle diffusion models were applied to kinetic data. The sorptive mechanism followed the pseudo second-order kinetics and intra particle diffusion model. The equilibration data fitted well with both Langmuir and Freundlich isotherm model with maximum sorption capacity of 209 mg g−1. The mean free energy of adsorption calculated from Dubinin-Radushkevich (D-R) isotherm model indicated that the adsorption of metal ions was found to be by chemical ion exchange. Thermodynamic parameters and Tempkin constant showed that the sorption process of Pb(II) onto SDC was feasible, spontaneous and endothermic...

Zero-Liquid Discharge: Desalination of Waters with High Organic Content

A Water Research Foundation Tailored Collaboration project is being conducted to evaluate zero-liquid discharge (ZLD) desalination of waters with high concentrations of natural organic matter (NOM). The technical approach involves treating reverse osmosis (RO) or nanofiltration (NF) membrane concentrate to reduce fouling potential so the concentrate can be desalinated in a second membrane application. Concentrate generated from waters with high organic content must be treated to remove total organic carbon to prevent organic fouling and calcium, sulfate, and silica to prevent inorganic fouling. The research consists of three phases: preliminary analysis to identify concentrate treatment goals, evaluation of concentrate treatment options, and evaluation of the selected treatment approach. The processes evaluated for concentrate treatment were chemical softening, fluidized-bed crystallization, activated alumina, coagulation, ion exchange, and electrodialysis metathesis. Testing was conducted on five water sources. Results for one water source are reported here. The final Water Research Foundation report will be published in November 2010.

Biosorption of As(III) and As(V) from Aqueous Solution by Lichen (Xanthoria parietina) Biomass

The biosorption of As(III) and As(V) from aqueous solution on lichen (Xanthoria parietina) biomass were investigated using different experimental parameters such as solution pH, biomass concentration, contact time, and temperature. The equilibrium data were evaluated by Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherm models. The biosorption capacity of X. parietina for As(III) and As(V) was found to be 63.8 mg/g and 60.3 mg/g. The mean sorption energy values calculated from D–R model indicated that the biosorption of As(III) and As(V) onto X. parietina biomass took place by chemical ion-exchange. The thermodynamic parameters showed that the biosorption of As(III) and As(V) ions onto X. parietina biomass was feasible, spontaneous, and exothermic in nature. Kinetic examination of the sorption data revealed that the biosorption processes of both As(III) and As(V) followed well the pseudo-second-order kinetics. The arsenic ions were desorbed from X. parietina using both 1 M HCl and 1 M HNO3. The recovery yield of arsenic ions was found to be 80-90% and the biosorbent had good reusability after consecutive seven sorption-desorption cycles.

Biosorption of selenium from aqueous solution by green algae (Cladophora hutchinsiae) biomass: Equilibrium, thermodynamic and kinetic studies

The equilibrium, thermodynamics and kinetics of selenium(IV) biosorption from aqueous solution by dead green algae ( Cladophora hutchinsiae ) biomass was investigated. Optimum biosorption conditions were determined with respect to pH, biomass concentration, contact time, and temperature. The equilibrium data were analyzed using the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. The maximum biosorption capacity of C. hutchinsiae biomass for Se(IV) was found to be 74.9 mg/g at pH 5, biomass concentration 8 g/L, contact time 60 min, and temperature 20 °C. The biosorption percentage decreased from 96% to 60% as temperature was increased from 20 to 50 °C during the equilibrium time. From D–R model, the calculated mean biosorption energy (10.9 kJ/mol) indicated that the biosorption of Se(IV) onto C. hutchinsiae biomass was taken place by chemical ion-exchange. The highest recovery (95%) was achieved using 0.5 M HCI. The high stability of C. hutchinsiae permitted a slightly decrease about 20% in recovery of Se(IV) ions after ten times of adsorption-elution process. The calculated thermodynamic parameters, Δ G ° (between −18.39 and −16.08 kJ/mol at 20–50 °C) and Δ H ° (−45.96 kJ/mol) showed that the biosorption of Se(IV) onto C. hutchinsiae biomass was feasible, spontaneous and exothermic, respectively. The experimental data was also fitted to the Lagergren's first-order and pseudo second-order kinetic models. The results revealed that the pseudo second-order reaction model provided the best description these data with coefficients of determination in range of 0.992–0.999. The biosorption rate constant was calculated as 24.9 × 10 −2 g/(mg min).

A Comparative Study on the Sorption Characteristics of Pb(II) and Hg(II) onto Activated Carbon

Biosorption equilibrium and kinetics of Pb(II) and Hg(II) on coconut shell carbon (CSC) were investigated by batch equilibration method. The effects of pH, adsorbent dosage, contact time, temperature and initial concentration of Pb(II) and Hg(II) on the activated carbon of coconut shell wastes were studied. Maximum adsorption of Pb(II) occurred at pH 4.5 and Hg(II) at pH 6. The sorptive mechanism followed the pseudo second order kinetics. The equilibrium data were analysed by Langmuir, Freundlich and Dubinin‐Radushkevich isotherm models. The equilibration data fitted well with both Langmuir and Freundlich isotherm model. The Langmuir adsorption capacity for Pb(II) was greater than Hg(II). The mean free energy of adsorption calculated from Dubinin‐Radushkevich (D‐R) isotherm model indicated that the adsorption of metal ions was found to be by chemical ion exchange. Thermodynamic parameter showed that the sorption process of Pb(II) onto SDC was feasible, spontaneous and endothermic under studied conditions. A comparison was evaluated for the two metals.

Adsorption of Cu(II) onto silica gel-immobilized Schiff base derivative

4-chloroisonitroacetophenone 4-aminobenzylhydrazone (CAAH) chemically anchored on a silica gel surface, has been used for Cu(II) sorption from aqueous solution. The surface modification processes was performed after silanization of silica, then analyzed by elemental analysis, infrared spectroscopy, and thermogravimetry. The sorption behavior of copper(II) was evaluated by the use of batch and column methods. The influences of the concentration, temperature and pH for sorption on the immobilized silica gel with Schiff base were investigated. The obtained dynamic data were fitted to Freundlich, Langmuir and Dubinin–Raduskevich (D–R) isotherms. The mean sorption energy ( E) of copper sorption onto silica gel was calculated from D–R isotherm indicating a chemical ion-exchange. The thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated from the adsorption isotherms which were used to explain the mechanism of the adsorption.

Equilibrium, thermodynamic and kinetic studies on aluminum biosorption from aqueous solution by brown algae ( Padina pavonica) biomass

This paper presents the equilibrium, thermodynamic and kinetic studies on aluminum biosorption from aqueous solution by brown algae ( Padina pavonica) biomass. Optimum biosorption conditions were determined as a function of pH, biomass dosage, contact time, and temperature. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were applied to describe the biosorption isotherm of Al(III) by P. pavonica biomass. The biosorption capacity of P. pavonica biomass was found as 77.3 mg/g. The metal ions were desorbed from P. pavonica using 1 M HCl. The high stability of P. pavonica permitted a slight decrease about 20% in the recovery of Al(III) ions after 10 times of adsorption–elution process. The mean free energy value evaluated from the D–R model indicated that the biosorption of Al(III) onto P. pavonica biomass was taken place by chemical ion exchange. The calculated thermodynamic parameters, Δ G°, Δ H° and Δ S° showed that the biosorption of Al(III) onto P. pavonica biomass was feasible, spontaneous and endothermic under examined conditions. Experimental data was also tested in terms of biosorption kinetics using pseudo-first-order and pseudo-second-order kinetic models. The results showed that the biosorption processes of Al(III) onto P. pavonica biomass followed well pseudo-second-order kinetics.

Removal of mercury(II) from aqueous solution using moss ( Drepanocladus revolvens) biomass: Equilibrium, thermodynamic and kinetic studies

The equilibrium, thermodynamics and kinetics of the biosorption of Hg(II) onto moss ( Drepanocladus revolvens) biomass from aqueous solution were investigated. Optimum experimental parameters were determined to be pH 5.5, contact time 60 min, biomass concentration 4 g L −1 of solution, and temperature 20 °C. From the Langmuir model the maximum biosorption capacity of the moss biomass was found to be 94.4 mg g −1. The mean free energy value (10.2 kJ mol −1) evaluated by using the Dubinin–Radushkevich (D–R) model indicated that the biosorption of mercury ions onto D. revolvens was taken place by chemical ion-exchange. The kinetic studies indicated that the biosorption process of mercury ions followed well pseudo-second-order model. The calculated thermodynamic parameters (Δ G°, Δ S°, Δ H°) showed the biosorption to be exothermic and spontaneous with decreased randomness at the solid–solution interface. The recovery of the Hg(II) from D. revolvens biomass was found to be 99% using 1 M HCl. It was concluded that the D. revolvens biomass can be used as biosorbent for the treatment of wastewaters containing Hg(II) ions.

Growth of nanocrystalline CuIn 3Se 5 (OVC) thin films by ion exchange reactions at room temperature and their characterization as photo-absorbing layers

Nanocrystalline CuIn 3Se 5 thin films have been grown on ITO glass substrates using chemical ion exchange reactions with CdS, in alkaline medium at pH 11. The as-deposited films were annealed in air at 200 °C for 30 min and characterized using X-ray diffraction (XRD), transmission electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy to study the structural, compositional and morphological properties. The XRD patterns reveal the nanoparticles size to be of 18–20 nm diameter, while from the SEM images the nanoparticles size is estimated to be 20–30 nm. It is observed that the annealed films contain nanocrystallites connected with each other through grain boundaries, with grain size of about 100–125 nm and have an overall n-type electrical conductivity and higher photoconductivity. The current–voltage ( I– V) characteristics (in dark and light) of these films indicated the formation of a Schottky like junction between the n-CuIn 3Se 5 (OVC) and CdS/ITO layers.

Biosorptive removal of mercury(II) from aqueous solution using lichen ( Xanthoparmelia conspersa) biomass: Kinetic and equilibrium studies

The potential use of the lichen biomass ( Xanthoparmelia conspersa) to remove mercury(II) ions from aqueous solution by biosorption was evaluated using the batch method. Effects of pH, contact time, biomass concentration and temperature on the removal of Hg(II) ions were studied. The Langmuir isotherm models defined the equilibrium data precisely compared to Freundlich model and the maximum biosorption capacity obtained was 82.8 mg g −1. From the D–R isotherm model, the mean free energy was calculated as 9.5 kJ mol −1. It shows that the biosorption of Hg(II) ions onto X. conspersa biomass was taken place by chemical ion-exchange. Experimental data were also performed to the pseudo-first-order and pseudo-second-order kinetic models. The results indicated that the biosorption of Hg(II) on the lichen biomass followed well the second-order kinetics. Thermodynamic parameters, Δ G o, Δ H o and Δ S o indicated the Hg(II) sorption to be exothermic and spontaneous with decreased randomness at the solid–solution interface. Furthermore, the lichen biomass could be regenerated using 1 M HCl, with up to 85% recovery, which allowed the reuse of the biomass in ten biosorption–desorption cycles without any considerable loss of biosorptive removal capacity.

Removal of zinc and nickel ions by complexation–membrane filtration process from industrial wastewater

Many industrial wastewater streams contain toxic metal cations, for example, Ni 2+, Zn 2+, etc. or their oxyanions in up to few hundred mg/dm 3, which must be removed before water recycling or discharging directly into surface waters. The conventional processes to treat this kind of wastewater are, e.g. chemical precipitation, ion exchange, membrane separations (such as electrodialysis, nanofiltration, reverse osmosis and ultrafiltration), adsorption or biosorption. In this work a membrane technique, ultrafiltration, completed with complexation was investigated. During the experiments, impact of conditions of membrane, pH and polymer/metal ratio have been investigated. The study series were carried out both of zinc and nickel. According to our studies, the most effective composition both tested metals is the following: PES-10 membrane, PAA complexation agent and pH>8. The volume ratio of the polymer bounding agent and metal ion because of environmental and economical aspects should be about unit.

Equilibrium, thermodynamic and kinetic studies on biosorption of Pb(II) and Cd(II) from aqueous solution by macrofungus ( Lactarius scrobiculatus) biomass

The equilibrium, thermodynamics and kinetics of the biosorption of Pb(II) and Cd(II) onto ( Lactarius scrobiculatus) macrofungus from aqueous solution were investigated at different experimental conditions. Optimum experimental parameters were determined to be pH 5.5, contact time 60 min, biomass concentration 4 g/L of solution, and temperature 20 °C. The maximum biosorption capacity of L. scrobiculatus was found to be 56.2 mg/g for Pb(II) and to be 53.1 mg/g for Cd(II). The mean free energy values evaluated by using the Dubinin–Radushkevich (D–R) model indicated that the biosorption of the metal ions onto L. scrobiculatus biomass was taken place by chemical ion-exchange. The kinetic studies indicated that the biosorption process of the metal ions followed well pseudo-second order model. The calculated thermodynamic parameters (Δ G°, Δ H° and Δ S°) showed that the biosorption of Pb(II) and Cd(II) ions onto L. scrobiculatus biomass was feasible, spontaneous and exothermic in nature. The recovery of the metal ions from L. scrobiculatus biomass was found as higher than 95% using 1 M HCl and 1 M HNO 3. Furthermore, the reusability of the biosorbent was determined after six consecutive sorption-desorption cycles.