Functionalized surfaces: silica structure and metal ion adsorption behavior

Two silica gels with different sized mesopores and one natioparticulate fumed silica, were modified with amino- and mercapto-functional silanes. One aminofunctional silane used was monofunctional preventing polymerization, the other trifunctional which pen-nits surface polymerization. Structural and textural characteristics of these silicas before and after surface modification were probed using N, adsorption. The trifunctional aminosilane resulted in a material with less porosity than the monofunctional silane, which affected adsorption capacity of tested Cu(II) and Pb(II) from aqueous solution. Surface functionalization with the mercaptofunctional silane resulted in the smallest loss in porosity. A narrow pore size results in a more favorable Delta G(ads), but a larger pore size insures greater access of surface groups to adsorbed ions resulting in enhanced adsorption capacity. A comparison of the adsorption behavior of amino and mercapto groups for Cu(II) and Pb(II) shows that Cu(II) adsorbs to a greater extent on amino-functionalized than mercapto-functionalized surfaces. Pb(II) adsorption is not as greatly affected by the type of surface functionalization tinder the conditions studied.