Comparative study of lead sorption onto natural perlite, dolomite and diatomite

In this work, natural clays of Iran including perlite, dolomite and diatomite have been used as an adsorbent for removing lead from aqueous solution in a batch system. The BET analysis of clays showed that the pore size, surface area and pore volume of diatomite are greater than those of perlite and dolomite. The effect of several variables like pH, contact time, initial concentration and temperature on lead sorption by perlite, dolomite and diatomite was investigated. Kinetic data were analyzed using pseudo-first-order, pseudo-second-order and double-exponential models. The equilibrium experimental data were tested with Freundlich, Langmuir and Dubbin–Radushkevich (D–R) isotherm models. It was observed that the maximum lead adsorption capacity of lead of natural clays followed the order of diatomite (25.01 mg g−1) > dolomite (19.69 mg g−1) > perlite (8.906 mg g−1). Thermodynamic parameters showed that the lead sorption onto the dolomite and diatomite is endothermic and lead sorption by perlite is exothermic. The results indicated that the lead sorption by studied adsorbents is spontaneous and thermodynamically feasible. Because of low-cost and local availability of natural clays, these adsorbents have suitable potential for removal of lead ions in practical process.