FUNCTIONALIZED SURFACES: SILICA STRUCTURE AND METAL ION ADSORPTION BEHAVIOR

摘要

Two silica gels with different sized mesopores and one nanoparticulate fumed silica, were modified with amino- and mercapto-functional silanes. One aminofunctional silane used was monofunctional preventing polymerization, the other trifunctional which permits surface polymerization. Structural and textural characteristics of these silicas before and after surface modification were probed using N_2 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 ΔG_(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 under the conditions studied.