Sorption of Pb~(2+) on Montmorillonite and Kaolinite

Sorption activities of Pb2+ on montmorillonite and kaolinite were studied and a sorption mechanism was proposed.The sorption kinetics and the sorption isotherms of Pb2+ on montmorillonite and kaolinite can be described by the pseudo-second-order kinetics and Langmuir isotherm respectively.The sorption mechanism of Pb2+ on the montmorillonite and kaolinite is the surface complex mechanism,simultaneously forming inner-sphere surface complexes and outer-sphere surface complexes.The relative content of inner(or outer)-sphere surface complexes is pH dependent and is dominant beyond(or within) the pH range of 4~8,respectively.The sorption amount in mg/g of Pb2+ on montmorillonite is obviously higher than that on kaolinite.The affinity of montmorillonite for Pb2+ is higher than that of kaolinite for Pb2+.