PHOTOCATALYTIC REDUCTION AND IMMOBILIZATION OF HEXAVALENT CHROMIUM AT TITANIUM-DIOXIDE IN AQUEOUS BASIC-MEDIA

The thermodynamic aspects of the photocatalytic reduction of Cr(VI) at TiO2 are first discussed and contrasted for pH 0 and pH 10 aqueous media. The photocorrosion of TiO2 is shown to be thermodynamically less favorable in basic media. A scheme for the one-step removal of Cr(VI) at TiO2 Via its reduction and subsequent immobilization [as Cr(OH)3] is demonstrated for pH 10 chromate solutions. Dissolved oxygen is shown to inhibit the reduction of Cr(VI). A preliminary kinetics analysis reveals adherence of the initial rate of Cr(VI) reduction to the simple Langmuir model.