Comparison of TiO2 powder suspensions and TiO2 ceramic membranes supported on glass as photocatalytic systems in the reduction of chromium(VI)

A comparative study of semiconductor particle suspensions and semiconductor membranes as photocatalytic systems is presented. Both suspensions of TiO2 powder and TiO2 ceramic membranes supported on glass act as photocatalysts for the reduction of chromium(VI) to chromium(III). In both cases, the overall kinetic characteristics were the same. The reaction rate increases as pH decreases, and the order of reaction with respect to Cr(VI) is 0.5 at low pH (< 2). For this pH no deactivation of the catalyst is noted. The efficiency of the suspended particles was ca. four times higher than that of the membrane system.