Pb(II) sorption on molecular sieve analogues of MCM-41 synthesized from kaolinite and montmorillonite

Abstract

Mesoporous molecular sieves were prepared with montmorillonite and kaolinite as silica sources, respectively, (denoted as P-M and P-K) by a hydrothermal method. The two prepared materials were characterized by XRD, FTIR and N2 adsorption–desorption. The results indicated that both P-M and P-K are typical mesoporous molecular sieves with high specific surface areas. Sorption of Pb(II) from aqueous solution to P-M and P-K was studied by using a batch technique. The effect of contact time, pH and temperature on the sorption of Pb(II) to P-M and P-K was investigated. A simplified surface complexation model was used to simulate the complexation of Pb(II) ions onto molecular sieves. The results suggested that sorption of Pb(II) was strongly dependent on pH values. Kinetics of sorption showed that the pseudo-second-order kinetic model held for the sorption process. Equilibrium modeling showed that the sorption of Pb(II) was fitted well by the Langmuir isotherm model. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated from the sorption of Pb(II) at three different temperatures of 283K, 303K and 333K. The sorption reaction was endothermic and the process was favored at high temperature. The results indicated that both P-M and P-K are suitable materials for removal of Pb(II) from large volumes of aqueous solutions.