Comparative adsorption of Pb(II), Cu(II) and Cd(II) on chitosan saturated montmorillonite: Kinetic, thermodynamic and equilibrium studies

The montmorillonite-chitosan composite could provide hydrophobicity and functional groups to enhance the performances of montmorillonite in wastewater treatment. The composites showed good abilities to remove the pollutants, such as heavy metals and dyes. However, the comparative adsorption of multiple metals on the fixed C-content nanocomposite needs to be studied further. This paper presents the adsorption of Pb2+, Cu2+, and Cd2+ by the nanocomposite of chitosan saturated montmorillonte. The composite was synthetized and characterized by X-ray diffraction and Fourier transform infrared spectrometer. The kinetics (single and binary systems), thermodynamics and isotherm adsorption studies of the three cations on the nanocomposite were conducted, and the data were fitted with models. Results showed, the affinity sequence of the adsorption toward the 3 cations is Pb2+ > Cu2+ > Cd2+. Under most experimental conditions, one of the cations could enhance the adsorption of the other present in the binary system. The adsorption of the 3 cations could be best fitted with pseudo-second order equation. The metal adsorption is a heterogeneous and exothermic reaction on the surface of the composite, and Pb2+, Cu2+ adsorption are spontaneous reaction at 25-50 degrees C.