Adsorption of metal and metalloid ions onto nanoporous microparticles functionalized by atomic layer deposition

A novel material was prepared by depositing ultrathin TiO2 films on nanoporous micron-sized silica gel particles by atomic layer deposition (ALD). Silica gel particles were coated with 20 and 40 cycles of TiO2 films by ALD. Half samples were heated at 500 degrees C to change the crystal structure of TiO2. Their adsorption ability for a mixture of 19 trace elements of heavy metals and other toxic elements, including As(V), Se (IV), Be(II), Al(III), V(V), Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Ba(II), Tl(I), Sb(III), Cd(II), Ag(I), Sr(II), Mo (VI), and Pb(II), from aqueous solutions was investigated. The removal efficiencies of As(V), Se(IV), V(V), Mo(VI), and Pb(II) were higher than 75% simultaneously in the mixed solution at pH 3 for 20 and 40 cycles of TiO2 coated silica gel particles without heat treatment. In contrast, the uncoated silica gel particles did not adsorb any ions under this pH condition. At pH 5, the 20 cycles of TiO2 coated samples without heat treatment removed 95% As(V), 95% Se(IV), 86% V(V), 94% Mo(VI), 60% Pb(II), 40% Sb(III), 73% Ag(I), 72% Cu (II), and 49% Ba(II) simultaneously. Before heat treatment, the TiO2 coated samples showed better adsorption performance than the samples with heat treatment due to the fact that the TiO2 surface area decreased and thereby the amount of adsorption sites reduced after heat treatment. The micron-sized adsorbent particles were separated easily from water due to their large particle size, making it practically suitable for trace contaminant remediation in water. (C) 2016 Elsevier Ltd. All rights reserved.