Biosorption of Cd(II) and Co(II) Ions‏ ‏from ‎Contaminated Water‏ ‏onto Cyanophyta: Single ‎And Binary Ion Exchange Isotherm

This study used both single and binary biosorption of Cd(II) and Co(II) ions from a synthetic contaminated water onto a dead blue-green (Cyanophyta) algae \ as biosorbent of heavy metals. Experimental parameters included pH, initial metal concentrations, agitation speeds, contact time and temperatures were investigated. The uptake capacities were 38.4 and 23.5 mg/g for Cd (II) and Co(II), respectively. The best pH values were 5 for Co (II) and Cd (II), respectively, and the contact time was1. 5 hr. A sequence of batch experiments was performed in a batch device in order to get equilibrium isotherm data of single and binary metals solutions for biosorption. The ion exchange mechanism was the base absorption of these metals, along with the light metal release like sodium, magnesium, calcium and potassium therefore a model ion exchange had been found appropriate to describe the process of biosorption. However, the calculated affinity constant (K) sequence for both single and binary system was 2.33, 5.43 respectively, for Cd (II) and 1.87, 2.46 for Co (II) with less than 5% percentage error; these values remain in both systems that the Cd(II) was the strongest one. The affinity constant in the single and binary system was KCd > KCo

Determination of the Competitive Ion Exchange Isotherms of Taurine and Glycine on D290 Resin by Inverse Method

With the elution curves of glycine and taurine, the ion exchange isotherm parameters of glycine and taurine on D290 anion exchange resin are determined by the inverse method. In this work, with the multi-component competitive ion exchange isotherm and the equilibrium dispersion chromatographic model, the elution curves of glycine and taurine on D290 anionic fixed bed are fitted. The parameters of competitive isotherm are determined, Ktau is 2.55, Kgly is 1.65. The result s showed good agreement between the elute curves fitted by the model and the separation data which confirmed the validity of the model selected.Keywords-taurine; glycine;competitive isotherm;inverse method;

Thermodynamics of Ion-Exchange Between Na+/Sr2+ Solutions and the Zeolite Mineral Cinoptilolite

ABSTRACTIon-exchange experiments were conducted at 25 °C between the zeolite mineral clinoptilolite and aqueous solutions of varying equivalent ratios of Na+ and Sr2+ and total concentrations of 0.005, 0.05, and 0.5 N. The experiments were designed to investigate the effects of changes in total solution concentration and in the relative concentrations of exchangeable cations on the following ion-exchange equilibrium:Sr2+ + 2NaZ ⇄ SrZ2 + 2Na+Using the isotherm data at 0.05 N solution concentration, a thermodynamic model for the ion-exchange reaction was derived using a Margules formulation for the activity coefficients of zeolite components and the Pitzer ion-interaction approach for activity coefficients of aqueous ions. The results of the forward experiments showed that the ion-exchange isotherm strongly depends on the total solution concentration. Additional experiments demonstrated that the above ion-exchange reaction is reversible. The derived equilibrium constant, K, and Gibbs energy of ion-exchange, ΔG°, are equal to 0.321±0.021 and 2,820±170 J/mol, respectively.Using thermodynamic parameters derived from the 0.05 N isotherm experiment, the model was used to predict isotherm values at 0.005 and 0.5 N, which showed excellent agreement with measured data. Because the thermodynamic model used in this study can be easily extended to ternary and more complicated mixtures, it may be useful for modeling ion-exchange equilibria in multicomponent geochemical systems.