Kinetics of removal of chromium from water and electronic process wastewater by ion exchange resins: 1200H, 1500H and IRN97H

The removal of chromium from aqueous solution by an ion exchange resin is described. Ion exchange resins 1200H, 1500H and IRN97H show a remarkable increase in sorption capacity for chromium, compared to other adsorbents. The adsorption process, which is pH dependent show maximum removal of chromium in the pH range 2-6 for an initial chromium concentration of 10mg/l. The metal ion adsorption obeyed linear, Langmuir and Freundlich isotherms. The adsorption of chromium on these cation exchange resins follows first-order reversible kinetics and pseudo-first-order kinetics. The intraparticle diffusion of chromium on ion exchange resins represents the rate-limiting step. The uptake of chromium by the ion exchange resins was reversible and thus have good potential for the removal/recovery of chromium from aqueous solutions. We conclude that such ion exchange resins can be used for the efficient removal of chromium from water and wastewater.     

Removal of chromium from water and wastewater by ion exchange resins

Removal of chromium from water and wastewater is obligatory in order to avoid water pollution. Batch shaking adsorption experiments were carried out to evaluate the performance of IRN77 and SKN1 cation exchange resins in the removal of chromium from aqueous solutions. The percentage removal of chromium was examined by varying experimental conditions viz., dosage of adsorbent, pH of the solution and contact time. It was found that more than 95% removal was achieved under optimal conditions. The adsorption capacity (k) for chromium calculated from the Freundlich adsorption isotherm was found to be 35.38 and 46.34 mg/g for IRN77 and SKN1 resins, respectively. The adsorption of chromium on these cation exchange resins follows the first-order reversible kinetics. The ion exchange resins investigated in this study showed reversible uptake of chromium and, thus, have good application potential for the removal/recovery of chromium from aqueous solutions.     

Sorption of Cr(VI) ions on two Lewatit-anion exchange resins and their quantitative determination using UV-visible spectrophotometer

The sorption of Cr(VI) from aqueous solutions with macroporous resins which contain quarternary amine groups (Lewatit MP 64 and Lewatit MP 500) was studied at varying Cr(VI) concentration, adsorbent dose, pH, contact time and temperature. Batch shaking sorption experiments were carried out to evaluate the performance of Lewatit MP 64 and Lewatit MP 500 anion exchange resins in the removal of Cr(VI) from aqueous solutions. The concentration of Cr(VI) in aqueous solution was determined by UV-visible spectrophotometer. The ion exchange process, which is dependent on pH, showed maximum removal of Cr(VI) in the pH range 3-7 for an initial Cr(VI) concentration of 1x10(-3) M. The optimum pH for Cr(VI) adsorption was found as 5.0 for Lewatit MP 64 and 6.0 for Lewatit MP 500. The maximum Cr(VI) adsorption at pH 5.0 is 0.40 and 0.41 mmol/g resin for Lewatit MP 64 and Lewatit MP 500 anion exchangers, respectively. The maximum chromium sorption occurred at approximately 60 min for Lewatit MP 64 and 75 min for Lewatit MP 500. The suitability of the Freundlich and Langmuir adsorption models was also investigated for each chromium-sorbent system. The uptake of Cr(VI) by the anion exchange resins was reversible and so it has good potential for the removal of Cr(VI) from aqueous solutions. Both ion exchangers had high bonding constants but Lewatit MP 500 showed stronger binding. The rise in the temperature caused a slight decrease in the value of the equilibrium constant (K(c)) for the sorption of Cr(VI) ion.     

Optimization using central composite design (CCD) for the biosorption of Cr(VI) ions by cross linked chitosan carbonized rice husk (CCACR)

The presence of heavy metals in aqueous streams arising from the discharge of industrial effluents into water bodies is one of the most important environmental issues because of their toxic nature and its removal is highly essential. This paper deals with the adsorption studies for the removal of hexavalent chromium ions from aqueous solutions using Schiff based chitosan activated carbonized rice husk composites as adsorbent. The activation and surface properties of the adsorbent were characterized by Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brauner Emmet and Teller (BET) analyzer. Central Composite Design (CCD) was used to optimize the process variables such as initial metal ion concentration, adsorbent dosage and pH of the solution on the performance of percentage removal and adsorption capacity. The experimental data were validated with different isotherms and kinetic models to evaluate the solute interaction behavior and nature of adsorption.     

Heavy metal adsorption onto agro-based waste materials: a review

Adsorption has been proved to be an excellent way to treat industrial waste effluents, offering significant advantages like the low-cost, availability, profitability, easy of operation and efficiency. Biosorption of heavy metals from aqueous solutions is a relatively new process that has proven very promising in the removal of contaminants from aqueous effluents. Biosorption is becoming a potential alternative to the existing technologies for the removal and/or recovery of toxic metals from wastewater. The major advantages of biosorption technology are its effectiveness in reducing the concentration of heavy metal ions to very low levels and the use of inexpensive biosorbent materials. Metal adsorption and biosorption onto agricultural wastes is a rather complex process affected by several factors. Mechanisms involved in the biosorption process include chemisorption, complexation, adsorption-complexation on surface and pores, ion exchange, microprecipitation, heavy metal hydroxide condensation onto the biosurface, and surface adsorption.     

Removal of hexavalent chromium from aqueous solutions by D301, D314 and D354 anion-exchange resins

Removal of hexavalent chromium from electroplating industry wastewater is obligatory in order to avoid pollution. Batch shaking experiments were carried out to evaluate the adsorption capacity of resins (D301, D314 and D354) in the removal of chromium from aqueous solutions. Varying experimental conditions were studied, including Cr(6+) concentrations, resin amounts, initial pH, contact time and temperatures. The ion-exchange process, which is pH-dependent, indicated the maximum removal of Cr(6+) in the pH range of 1-5 for an initial concentration 100 ppm of Cr(6+). It was found that more than 99.4% of the removal was achieved under optimal conditions. High adsorption rates of chromium for the three resins were observed at the onset, and then plateau values were gradually reached within 30 min. The experimental results obtained at various concentrations (27+/-1 degrees C) showed that the adsorption pattern on the resins have followed Langmuir isotherms and the calculated maximum sorption capacities of D301, D314 and D354 were 152.52, 120.48 and 156.25mg/g, respectively. The thermodynamic parameters (free energy change DeltaG, enthalpy change DeltaS and entropy change DeltaH) for the sorption have been evaluated. It was also found that the adsorption of chromium on these anion-exchange resins follows first-order reversible kinetics.     

Clay minerals as sorbents for nuclear reactor activation products

A comparison is presented of cobalt and chromium uptake on different clays. It is shown that clay minerals are good adsorbents for cobalt and chromium in waste effluents. The sorption of cobalt and chromium on the clays studied was by ion exchange and surface complex formation, respectively. In addition, the percentage of either cobalt or chromium removed in a mixed solution environment is higher than the individual adsorption in single-component experiments. This proves a synergistic mechanism. The optimum uptake of each metal ion from mixed species was achieved by montmorillonite clay in the calcium form.     

Removal of Cd and Zn from inorganic industrial waste leachate by ion exchange

This paper presents a study of the removal of Cd and Zn present in the leachate from an inorganic industrial waste landfill using cationic exchange resins (Amberlite 200, 252-C, IR-120, Duolite C-464), a chelating resin, Amberlite IRC 718, and an adsorbent resin, XAD-2. The chelating resin Amberlite IRC 718 presented the higher removal in batch experiments for both metals (93% for Zn and 50% for Cd). Five hundred ten bed volumes of leachate were treated in column experiments using this material, reducing the concentrations of Cd and Zn from 18 mg/dm3 to 0.1 and 1.0mg/dm3, respectively. Regeneration of the saturated bed was achieved with 11 BV of 2M HCl.     

Comparison of Amberlite IR 120 and dolomite's performances for removal of heavy metals

The presence of heavy metals in the environment is major concern due to their toxicity. Contamination of heavy metals in water supplies has steadily increased over the last years as a result of over population and expansion of industrial activities. A strong cation-exchange resin, Amberlite IR 120 and a natural zeolite, dolomite were used for the removal of lead(II) and cadmium(II). The optimum conditions were determined in a batch system as concentration range was between 5 and 100 mg/L, pH range between 1 and 8, contact time between 5 and 90 min, and the amount of adsorbent was from 0.1 to 1g. A constant stirring speed, 2000 rpm, was chosen during all of the experiments. The optimum conditions were found to be a concentration of 20 mg/L, pH of 5, contact time of 60 min and 0.5 g of adsorbent. Also, for investigation of exchange equilibria different amounts of ion exchange resin and dolomite were contacted with a fixed volume and concentration of a heavy metal bearing solutions. Sorption data have been interpreted in terms of Langmuir and Freundlich equations. The effect of adsorption temperature on the heavy metals adsorption onto dolomite was investigated at three different temperatures (20, 40 and 60 degrees C). Thermodynamic parameters were calculated. The results obtained show that the Amberlite IR 120 strong cation-exchange resin and dolomite performed well for the removal of these heavy metals. As a low cost adsorbent, dolomite can preferable for removal of heavy metals from wastewaters.     

Removal of chromium(III) from aqueous solutions using Lewatit S 100: the effect of pH, time, metal concentration and temperature

The removal of the Cr(III) ion from aqueous solutions with the Lewatit S 100 ion-exchange resin is described; and the performance of this resin was compared with Chelex-100 resin. The effect of adsorbent dose, initial metal concentration, contact time, pH and temperature on the removal of Cr(III) was investigated. Lewatit S 100 shows a remarkable increase in sorption capacity for Cr(III). The Batch ion-exchange process was relatively fast; and it reached equilibrium after about 150 min of contact. The ion-exchange process, which is pH dependent show maximum removal of Cr(III) in the pH range 2.8-4.0 for an initial Cr(III) concentration of 1.0 x 10(-3)M. The equilibrium constants were 36.67 at pH value 3.5 for Lewatit S 100 and 6.64 at pH value 4.5 for Chelex-100 resin. Both of the resins had high-bonding constants. The equilibrium related to their ion-exchange capacity and the amount of the ion exchange was obtained by using the plots of the Langmuir adsorption isotherm. It was observed that the maximum ion-exchange capacity of 0.39 mmol of Cr(III)/g for Lewatit S 100 and 0.29 mmol of Cr(III)/g for Chelex-100 was achieved at optimum pH values of 3.5 and 4.5, respectively. The thermodynamic equilibrium constant and the Gibbs free energy flow were calculated for each system. The ion exchange of Cr(III) on these cation-exchange resins followed first-order reversible kinetics. The intra-particle diffusion of Cr(III) on ion-exchange resin represented the rate-limiting step. The rise in temperature caused a slight increase in the value of the equilibrium constant (K(c)) for the sorption of Cr(III) ion for both resins.     

Ion-exchange of Pb2+, Cu2+, Zn2+, Cd2+, and Ni2+ ions from aqueous solution by Lewatit CNP 80

Removal of trace amounts of heavy metals can be achieved by means of selective ion-exchange processes. The newly developed resins offered a high resin capacity and faster sorption kinetics for the metal ions such as Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) ions. In the present study, the removal of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) ions from aqueous solutions was investigated. Experimental investigations were undertaken using the ion-exchange resin Lewatit CNP 80 (weakly acidic) and were compared with Lewatit TP 207 (weakly acidic and chelating). The optimum pH range for the ion-exchange of the above mentioned metal ions on Lewatit CNP 80 and Lewatit TP 207 were 7.0-9.0 and 4.5-5.5, respectively. The influence of pH, contact time, metal concentration and amount of ion-exchanger on the removal process was investigated. For investigations of the exchange equilibrium, different amounts of resin were contacted with a fixed volume of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) ion containing solution. The obtained sorption affinity sequence in the presented work was Ni(2+)>Cu(2+)>Cd(2+)>Zn(2+)>Pb(2+). The metal ion concentrations were measured by AAS methods. The distribution coefficient values for metal ions of 10(-3)M initial concentration at 0.1mol/L ionic strength show that the Lewatit CNP 80 was more selective for Ni(2+), Cu(2+) than it was for Cd(2+), Zn(2+) and Pb(2+). Langmuir isotherm was applicable to the ion-exchange process and its contents were calculated. The uptake of metal ions by the ion-exchange resins was reversible and thus has good potential for the removal of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) from aqueous solutions. The amount of sorbed metal ion per gram dry were calculated as 4.1, 4.6, 4.7, 4.8, and 4.7mequiv./g dry resin for Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+), respectively. Selectivity increased in the series: Cd(2+)>Pb(2+)>Cu(2+)>Ni(2+)>Zn(2+). The results obtained showed that Lewatit CNP 80 weakly acidic resin had shown better performance than Lewatit TP 207 resin for the removal of metals. The change of the ionic strength of the solution exerts a slight influence on the removal of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+). The presence of low ionic strength or low concentration of NaNO(3) does not have a significant effect on the ion-exchange of these metals by the resins. We conclude that Lewatit CNP 80 can be used for the efficient removal of Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+) from aqueous solutions.     

Design of novel polymeric adsorbents for metal ion removal from water using computer-aided molecular design

Heavy metals in drinking water act as contaminants that can cause serious health problems. These metal ions in drinking water are generally removed using cation exchange resins that are used as adsorbents. Generally, chelating resins with limited adsorption capacity are commercially available. Manufacturing novel resin polymers with enhanced adsorption capacity of metal ion requires ample experimental efforts that are expensive as well as time consuming. To overcome these difficulties, application of computer-aided molecular design (CAMD) will be an efficient way to develop novel chelating resin polymers. In this paper, CAMD based on group contribution method (GCM) has been used to design novel resins with enhanced adsorption capability of removing heavy metal ions from water. A polymer consists of multiple monomer units that repeat in a polymer chain. Each repeat unit of the polymer can be subdivided into different structural and functional groups. The adsorption mechanism of heavy metals on resin depends on the difference between activities in adsorbents and the bulk fluid phase. The contribution of the functional groups in the adsorption process is found by estimating the activity coefficient of heavy metal in the solid phase and bulk phase using a modified version of the UNIFAC GCM. The interaction parameters of the functional groups are first determined and then they are used in a combinatorial optimization method for CAMD of novel resin polymers. In this work, designs of novel resin polymers for the removal of Cu ions from drinking water are used as a case study. The proposed new polymer resin has an order of magnitude higher adsorption capacity compared to conventional resin used for the same purpose.     

Use of Raman spectroscopy to evaluate the selectivity of bifunctional anion exchange resins for perchlorate

Raman spectroscopy is used to evaluate the selectivity of two bifunctional anion exchange resins, Purolite A-530 and Amberlite PWA-2. It was found that the adsorption of anions on the resins is described by a Frumkin isotherm, which is determined by the ion pair constant, K, and the Frumkin parameter, g. The ion pair constant, K, is a measure of the strength of interaction between the resin and the anion and the Frumkin parameter, g, takes into account interactions between adsorbed anions. Although both resins have a polystyrene backbone and trihexylammonium and triethylammonium functional groups, the Purolite A-530 resin exhibits greater selectivity for perchlorate. The only discernable differences between the two resins is that the Amberlite PWA-2 has a higher trihexylamine content and the Purolite A-530 resin exhibits greater cross-linking. How the trihexylamine/triethylamine content and the degree of cross-linking affects the performance of these resins is discussed.     

Kinetic models for uranium recovery from sulfuric acid leach streams by strong-base anion resins

Ion exchange resins are used commercially to concentrate and purify uranium from sulfuric acid leach streams. Three important resin parameters are capacity, loading, and elution kinetics. When a plant engineer evaluates resin kinetic performance, he generally relies on batch loading and elution expert ments with changing bulk concentration. These experiments are easy to set up and maintain and are useful for relative comparison of resins. However, the loading driving force is not constant. Mathematical models for this condition are not readily available. Thus, the resin's diffusion coefficients remain undetermined. A shell progressive batch loading model with changing bulk concentration and a shell progressive elution model with zero bulk concentration were analytically derived. Loading data which could not be fit by constant concentration literature models were readily fit by the shell progressive changing bulk concentration model. The loading diffusion coefficients agree with those calculated from data by Streat and Takel. The elution diffusion coefficients were much smaller than the loading diffusion coefficients. The small elution diffusion coefficients can be accounted for by dynamic equilibrium within the ion exchange resin, i.e., a low concentration of free urany1 sulfate ion in the resin.     

Application of radioactive tracer technique for characterization of strongly basic anion-exchange resins duolite A 101D and duolite A 102D<Superscript>1</Superscript>

The radioactive ⁸²Br was used as a tracer to study the bromide self-diffusion reactions. The effect of temperature, concentration of ionic solution, and amount of ion-exchange resin on the kinetics of exchange reactions was examined. Under identical experimental conditions, the specific reaction rate, amount of bromide ions exchanged, and initial rate of bromide ion exchange calculated for Duolite A 101D resin were higher than those calculated for Duolite A 102D resin. The difference in the values calculated for the two resins was attributed to their water-holding capacities. The probable mechanism of bromide isotope exchange reaction was also predicted by comparing the specific reaction rate of rapid and slow exchange process. It is expected that the same technique can be employed to assess the efficiency of various ion exchangers under different operating conditions.     

The study of various parameters affecting the ion exchange of Cu2+, Zn2+, Ni2+, Cd2+, and Pb2+ from aqueous solution on Dowex 50W synthetic resin

A gel resin containing sulfonate groups (Dowex 50W) was investigated for its sorption properties towards copper, zinc, nickel, cadmium and lead metal ions. The use of selective ion exchange to recover metals from aqueous solution has been studied. The ion exchange behavior of five metals on Dowex 50W, depending on pH, temperature, and contact time and adsorbate amount was studied. Experimental measurements have been made on the batch sorption of toxic metals from aqueous solutions using cation exchanger Dowex 50W. The maximum recoveries (about 97%) Cu(2+), Zn(2+), Ni(2+), Cd(2+) and (about 80%) Pb(2+) were found at pH ranges 8-9. The amount of sorbed metal ion was calculated as 4.1, 4.6, 4.7, 4.8, and 4.7mequiv./gram dry resin for Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+), respectively. The precision of the method was examined at under optimum conditions. Selectivity increased in the series: Pb>Cd>Cu>Zn>Ni. It has been observed that, selectivity of the -SO(3)H group of the resin increases with atomic number, valance, degree of ionization of the exchanged metals. The equilibrium ion exchange capacity of resin for metal ions was measured and explored by using Freundlich and Langmuir isotherms. Langmuir type sorption isotherm was suitable for equilibrium studies.     

Dual mechanism bifunctional polymers: Phosphinic acid ion-exchange/redox resins and the kinetics of metal-ion complexation

The detailed study of bifunctional phosphinic acid resins has recently been introduced. It has been shown that they operate through the dual mechanism of ion exchange and metal-ion reduction. A key component in the synthesis is the Friedel-Crafts catalyst used for the reaction between PCl₃ and polystyrene. We now find that the order of catalyst activity is AlCl₃ > FeCl₃ > ZnCl₂ > SnCl₄. Ferric chloride catalysis also operates by an additional redox mechanism which yields a phosphonic acid resin. The extent of loading onto phosphinic and sulfonic acid resins by zinc ions at equilibrium was studied as a function of the anion present both with and without the presence of an excess of sodium ions. Both sets of resins exchange at a comparable rate upon the introduction of macroporosity into the polystyrene support. The influence of the redox process as an additional variable in the phosphinic resin kinetics was studied with silver and mercury(II) nitrate solutions. All of the primary acid sites are oxidized after a 9-hour contact time with Ag(I) ions and a 2-hour contact time with Hg(II) ions. The mercury loading curves and the different behavior of silver, which shows more ion exchange than redox at short times while leaving a residual ion concentration on the resin irrespective of whether all of the primary acid sites have been oxidized or not, can be explained by the termolecular nature of the Ag(I) redox reaction in contrast to the bimolecular nature of the Hg(II) reaction. Studies with other ions show that the minimum metal-ion reduction potential below which no redox occurs with the phosphinic resins is probably between 0.0 and 0.3 V.     

Partial demineralization of water by ion exchange using carbon dioxide as regenerant part iii field tests for drinking water treatment

The combined application of a weak-acid ion exchange resin in the free-acid form and of an anion exchange resin in the bicarbonate form allows a partial demineralization of water. The particular advantage of this process is that CO₂ can be used for the simultaneous regeneration of both resins. As a consequence, the effluent contains only the amount of salt which has been eliminated in the service cycle. The present paper discusses results of field tests of the process with a mobile pilot plant in the case of drinking water demineralization.     

Kinetics study on separation of cadmium from tellurium in acidic solution media using ion-exchange resins

The feasibility of using ion-exchange resins to separate cadmium from tellurium in acidic solutions of the two metals was investigated. We studied the competitive adsorption of cadmium and tellurium in such resins under varying acid strengths and contact time. We found that low sulfuric acid strength (i.e., 0.5 M) was most effective in removing cadmium from solutions. Different ion-exchange resins were tested for their affinity for cadmium and tellurium ions. In the selected systems, the ion-exchange rate of cadmium was rapid in the first 20 min, and reached equilibrium within 2 h. The Lagergren first-order model described the kinetic data with high coefficient of determination and correlation values. At room temperatures the ion-exchange for cadmium onto the resin followed the Freundlich isotherm model. The maximum removal of cadmium obtained from batch studies using resin A was 91%. Column studies with the same resin showed a removal of cadmium of 99.99% or higher.     

Removal of lead (II) ions from synthetic and real effluents using immobilized Pinus sylvestris sawdust: adsorption on a fixed-bed column

The purpose of this work was to evaluate the potential of Pinus sylvestris sawdust, in a continuous flow removal of lead (II) ions from synthetic and industrial aqueous effluents. The kinetic parameters obtained in a batch process were used to scale-up the process on a mini-column and to choose the breakthrough model. The column experimental data concerning the volumes treated were correlated using the bed depth service time model. These experimental data closely fitted the bed depth service time model at 10% of the breakthrough curve. The results from the bed depth service time model on the mini-column were then used to design a pilot plant adsorption unit. The performance of the pilot plant column accurately agreed with that obtained from the mini-column. The experiments carried out in a dynamic reactor allowed to bring out the influence of various parameters on the efficiency of the P. sylvestris sawdust. In addition, the process was checked for the treatment of industrial aqueous effluents on a pilot plant scale and the results were in accordance with those obtained from synthetic effluents.