Removal of heavy metal ions with the use of chelating polymers obtained by grafting pyridine–pyrazole ligands onto polymethylhydrosiloxane

Abstract

Abstract New chelating polymers soluble in organic non-polar solvents were synthesized by hydrosilylation reaction of polymethylhydrosiloxane with pyridine–pyrazole ligands. Two types of linkers were used to graft pyridine–pyrazole ligands onto polymethylhydrosiloxane. The composition and properties of the polymers obtained were studied by NMR spectroscopy, Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis and derivative scanning calorimetry. The effects of various parameters such as initial metal ion concentration, contact time, temperature and pH were examined in the processes of extraction of Cu 2+ , Cd 2+ , Cr 3+ , Ni 2+ and Co 2+ . The equilibrium data were best represented by Langmuir isotherm and the uptake capacities of polymers obtained varied between 0.24 mmol (for Co 2+ ) and 1.48 mmol (for Cu 2+ ) per 1 g of polymer. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. The polymers adsorption capacity was more than 90% level after five cycles of adsorption–desorption. Treatment of real wastewater samples showed good ability of the polymers to absorb metal ions.