Extraction and Preconcentration Capacity of Bifunctionalized Diamine-Thiol Polysiloxane Immobilized Ligand System Towards Some Divalent Cations

N.M. El-Ashgar

Department of Chemistry, the Islamic University of Gaza, P.O. Box 108, Palestine

Porous solid bi-organofunctionalized diamine-thiol polysiloxane immobilized ligand system of the general formula P-(CH₂)₃-X, (where P represents [Si-O]_n siloxane network and X represents a mixture of diamine; -NH(CH)₂NH₂ and thiol; -SH functional groups) has been prepared by hydrolytic polycondensation of TEOS with a mixture of 3-mercaptopropyltrimethoxysilane and 3-(2-aminoethylimino)propyltrimethoxysilane agents. The ligand system was evaluated for extraction and preconcentartion of a series of divalent metal ions from aqueous solutions including: Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺. Both batch and dynamic methods were used to examine maximum sorption capacity. The maximum binding capacity followed the sequence; Cu²⁺> Pb²⁺> Cd²⁺> Ni²⁺> Zn²⁺> Co²⁺ at pH 5.5. Measurement of variation of sorption of metal ions with temperature yielded negative values of ΔG° and positive values of DS° and ΔH° indicating a spontaneous and endothermic process of binding metal ions to the ligand system.

Keywords: Immobilized-polysiloxanes, Metal ions extraction, Thermodynamic parameters, Diamine-thiol