(89b) Synthesis of Surface Functionalized Adsorbents for Adsorption of Metal Ions and Organic Pollutants By Atomic Layer Deposition (Invited)

Different thicknesses of TiO₂ and Al₂O₃ films were applied on micron-sized silica gel particles and biochars by atomic layer deposition (ALD), respectively. TiO₂ coated silica gel particles were used as adsorbents for adsorption of metal and metalloid ions; 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. Al₂O₃ deposited biochars were used for removal of organic pollutants and the adsorption capacities were evaluated by adsorption of methylene blue (MB). The data fit well with the Langmuir isotherm and the maximum adsorption capacities were found to be 26.8 and 35.0 mg/g at 25 ºC for the uncoated biochar and 5 cycles Al₂O₃ (5Al) coated biochar, respectively. The adsorbed MB amount per square meter achieved 1.3 mg/m² onto the 5Al biochar, and it was twice the amount on the uncoated biochar. The improvement of adsorption capacity after Al₂O₃ ALD coating was due to its improved hydrophilia.