محمود تاجبخش

A cyclodextrin-triazole-titanium based nanocomposite (CD.COM) was prepared and its structure was characterized. The CD.COM exhibited a good adsorption performance for removal of Zn+2, Cd2+ and Pb2+ ions from aqueous solutions. The adsorption parameters were evaluated to find the optimal condition of pH = 7, contact time = 1 h, adsorbent dosage = 0.01 g and initial metal ion concentration = 20 mg L−1 at 25 °C. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models were investigated using adsorption equilibrium data. The Langmuir model showed best fitted with the experimental data, resulting in the maximum adsorption capacities of 147.1, 158.7 and 200.0 mg g−1 for Zn+2, Cd+2 and Pb+2 ions, respectively. Among the pseudo-first order, pseudo-second order, intraparticle diffusion and Elovich models, the kinetic data was well matched with the pseudo-second order model. Thermodynamic parameters indicated a spontaneous and endothermic adsorption process. By these results a plausible mechanism involving a monolayer chemical adsorption as the rate-determining step was suggested. The bioadsorbent showed high selectivity for Pb+2 ions in the presence of other coexisting metal ions. The CD.COM can be easily regenerated in HCl, HNO3 or EDTA solutions and reused for at least five cycles without significant loss of the adsorption capability.