Photocatalytic reactions of Cr(VI) reduction

M.I. LITTER

Conferencia; Conferencia; 2012

Studies on removal of hexavalent chromium (Cr(VI)) using reductive TiO2 heterogeneous photocatalysis (RHP) under UV and visible will be reported, especially in the presence of donor agents such as EDTA, oxalic acid, and citric acid. It has been proposed for the first time that Cr(VI) RHP takes place by successive one electron transfer reducing steps ending in Cr(III), the stable final product. These assumptions were validated by EPR experiments in which Cr(V) species were detected. Our research group also showed no particular effect of O2 in the photocatalytic system, confirmed by studies with platinized TiO2 and by spectroscopic evidences of the formation of a charge-transfer complex between Cr(VI) and TiO2. The behavior of Cr(VI) contrasts strongly with that of other metal ions such as Hg(II), whose reduction is greatly inhibited by O2. In this sense, Cr(VI) RHP is a unique system and the fact that its photocatalytic reduction can be made in air represents an important technological advantage. In addition, an overview on the ECOS-MINCYT project between Prof. Colbeau-Justin and Prof. Litter will be presented.