Removal of Cd(II) and Ni(II) from aqueous solution by PVA/TEOS/TMPTMS hybrid membrane

Functionalized poly(vinyl alcohol)/tetraethyl orthosilicate (PVA/TEOS) hybrid membranes with 3-mercaptopropyltrimethoxysilane (TMPTMS) groups have been prepared by sol–gel method and studied for the removal of cadmium and nickel ions from the aqueous solutions. The prepared membranes were characterized by FTIR, SEM and BET analyses. The influence of several variables such as TEOS content, TMPTMS content, pH, contact time, initial concentration and temperature was studied in a batch mode. The kinetic data were found to follow the pseudo-second-order model for both metal ions. The equilibrium data were well described by the Freundlich isotherm model for cadmium and nickel ions, respectively. The selectivity of cadmium and nickel sorption onto the membrane was in order of Cd(II) > Ni(II). The maximum monolayer capacity of the hybrid membrane was found to be 61.43 and 10.29 mg g−1 for cadmium and nickel ions, respectively, at 45 °C. Thermodynamic parameters were evaluated to understand the nature of adsorption process for both metal ions. The reusability of the membrane was also determined after five sorption–desorption cycles.

► The synthesized hybrid membranes were characterized by FTIR and SEM analyses.
► The selectivity adsorption of membrane was in order of Cd(II) > Ni(II).
► We observed different mechanisms for Cd(II) and Ni(II) adsorption.
► The Cd and Ni adsorption was endothermic/spontaneous and non-spontaneous, respectively.
► The metals adsorption capacity did not change after five sorption–desorption cycles.