Adsorption properties of silica sols modified with thiol groups

The surfaces of silica particles, prepared by the sol-gel method, were chem ically modified with thiol groups to change the adsorption properties of th e metal ions. The flocculation kinetics of silica sols, with and without th e thiol groups, were measured in presence of various metal ions in alcoholi c solution by monitoring their growth with time using dynamic light scatter ing. The flocculation experiments were carried out by adding small amounts of metal ions until a critical flocculation concentration was reached. The amounts of metal ions adsorbed on the surface of silica and thiol-modified silica particles were determined by using atomic absorption. The flocculati on process was improved when the silica surface was modified with thiol gro ups. The silica particles were observed with transmission electron microsco py, Fourier transform infra-red and Raman spectroscopy. (C) 1999 Elsevier S cience B.V. All rights reserved.