PHOTOCATALYTIC REDUCTION OF HEAVY-METAL IONS ON DERIVATIZED TITANIUM-DIOXIDE NANO-PARTICLE SURFACE STUDIED BY XAFS

Photoreduction of heavy metal ions, Cu2+ and Hg2+, on TiO2 nano-partic le surfaces, has been investigated by XAFS measurements. The effects o f TiO2 surface modification reagents on the reaction efficiency have b een studied. We observed a significant reaction efficiency enhancement when amino acid alanine was added to a mixture of 0.01M Cu2+ and TiO2 nano-particles. Fifty percent of the adsorbed Cu2+ has been reduced t o Cu-0 after 1-h illumination with a UV-enhanced xenon lamp. Photoredu ction of Hg2+ on TiO2 colloid surfaces was also investigated without a nd with thiolactic acid (TLA). In this case, the photoreduction effici ency for Hg2+ was lowered. Structures of metal ion surroundings in var ious complexes as well as their role in photoreduction of metal ions a re discussed. (C) 1997 Published by Elsevier Science B.V.