Removal of Lead from Aqueous Solutions Using Iranian Natural Sepiolite: Effects of Contact Time, Temperature, pH, Dose and Heat-Pretreatments

Sepiolite is a low-cost mineral widely distributed in arid regions of the world. Due to the structural properties, sepiolite has high sorption capacity for heavy metals. The objectives of this study were to investigate the effects of solution temperature, initial pH of suspension, contact time and dose of Iranian natural sepiolite on the removal efficiency of lead from aqueous solutions. Before use, sepiolite powder (25-53 µm) was saturated with calcium and the specific surface area and cation exchange capacity was determined. The experimental data were fitted with pseudo first order and pseudo second order kinetic models. Results obtained from kinetic studies indicated that pseudo-second order model better fitted to the experimental data. The results also implied that with the increasing contact time more amounts of lead ions were adsorbed by sepiolite. Similarly, with the increasing the solution temperature from 20 to 40 ˚C the adsorption rate of lead by sepiolite decreased. Furthermore, the results indicated that increasing the pH of solution from 3 to 9 and dose of sepiolite from 2 to 16 g l-1 increases the adsorption efficiency of lead ions from the aqueous solutions.