Synergistic photocatalysis mediated by TiO2:: mutual rate enhancement in the photoreduction of Cr(VI) and Cu(II) in aqueous media

Copper ill) ions were found to accelerate the heterogeneous photocatalytic reduction of Cr(VI) in N-2-purged UV-irradiated TiO2 suspensions. Conversely, Cr(VI) enhanced the rate of reduction of Cu(II) to metallic form on the TiO2 particle surfaces. Thus 800 muM Cr(VI) was not completely converted to Cr(III) even after similar to4 h irradiation, in the absence of Cu(II), while the presence of 800 muM Cu(II) resulted in complete Cr(VI) conversion within similar to 20 min. Similarly, the half-life for the photocatalytic reduction of 600 muM Cu(II) decreased from similar to1 h with no Cr(VI) to similar to5 min in the presence of 1.6 mM Cr(VI). (C) 2001 Published by Elsevier Science B.V.