Preparation of Some Mesoporous Polysiloxane Immobilized Ligand Systems and Their Applications for Extraction of Heavy Metals

Abstract

Polysiloxane-immobilized biligand systems have been prepared by sol-gel process. This process proceeded by hydrolytic polycondensation of tetraethylorthosilicate (TEOS) with appropriate silane agents bearing organofunctional groups. The prepared immobilized-polysiloxane biligand systems are: - Polysiloxane-(monoamine-thiol) triethylacetate, P-(N-S)-TrEA. - Polysiloxane-(monoamine-thiol) triacetic acid, P-(N-S)-TrAA. - Polysiloxane-(monoamine-thiol)-tris(N-2-aminoethylacetamide), P-(N-S)-TrEANN. - Polysiloxane-(monoamine-thiol)-tris(N-3,6-diazahexaylacetamide), P-(N-S)- TrEA-NNN. - Polysiloxane-(diamine-thiol) tetraethylacetate, P-(NN-S)-TEA. - Polysiloxane-(diamine-thiol) tetraacetic acid, P-(NN-S)-TAA. - Polysiloxane-(diamine-thiol)-tetrakis(N-2-aminoethylacetamide), P-(NN-S)-TEANN. - Polysiloxane-(diamine-thiol)-tetrakis(N-2,3-diazahexaylacetamide), P-(NN-S)- TEA-NNN. - Polysiloxane-(triamine-thiol) pentaethylacetate, P-(NNN-S)-PEA. - Polysiloxane-(triamine-thiol) pentaacetic acid, P-(NNN-S)-PAA. - Polysiloxane-(triamine-thiol)-pentakis(N-2-aminoethylacetamide), P-(NNN-S)- PEA-NN. - Polysiloxane-(triamine-thiol)-pentakis(N-3,6-diazahexaylacetamide), P-(NNN-S)-PEANNN. The prepared immobilized biligand systems have been characterized by many analytical methods such as elemental analysis, FTIR spectroscopy, solid state NMR (13C CP MAS NMR), X-ray photoelectron spectroscopy (XPS) and thermal analysis (TGA). FTIR spectroscopy gives valuable strong qualitative evidences about functional groups (especially ester, acid and amide) of the immobilized biligand systems. High resolution 13C CP MAS NMR provided an essential information on the structural nature of the apendent biligand groups, such as the presence of unhydrolyzed /uncondenced alkoxy groups. xv i XPS technique provided valuable information about the surface chemical composition of these materials. The results showed an increase in C and N percentages of the immobilized biligand surfaces after introduction of ethylenediamine and diethylenetriamine chelating ligands. The XPS also indicated that the amine groups almost exist in three forms, the free, hydrogen bonding and the protonated forms. Thermal analysis of these immobilized biligand systems showed high thermal stability up to 250 ºC. Polarized Optical Microscope technique, the surface morphology of the prepared immobilized-polysiloxane biligand systems was characterized using polarized optical microscope. The metal uptake capacities of these prepared biligand systems toward metal ions were found at pH 6 to be in order: Cu2+ > Pb2+ > Ni2+ > Co2+