Study on the photocatalytic reduction of dichromate and photocatalytic oxidation of dichlorvos

In this paper, dichromate and dichlorvos are selected as the deputies of inorganic and organic pollutants, respectively, and TiO 2/beads is used as a photocatalyst. The effects of various parameters, such as the amount of the photocatalyst, H 2O 2 concentration, metal ions, anions, pH value, and organic compounds on the photocatalytic reduction of dichromate and photocatalytic oxidation of dichlorvos are studied. From the studies, the differences of the parameters effect on the photocatalytic degradation of organic and inorganic pollutants are obtained. The results show that the optimum amount of the photocatalyst used is 6.0 g cm −3 for the photocatalytic reactions. With the addition of a small amount of H 2O 2, the photocatalytic reduction of dichromate is inhibited while the photocatalytic oxidation of dichlorvos is accelerated. With the addition of trace amounts of Fe 3+ or Cu 2+, both the reactions are accelerated, and with the addition of Zn 2+ and Na +, no obvious effects on the reactions are observed. Acidic solution is favorable for the photocatalytic reduction of dichromate; and acidic and alkaline solutions are favorable for the photocatalytic oxidation of dichlorvos. Adding SO 4 2 - , the photocatalytic oxidation is accelerated and adding Cl − the reaction is inhibited; and with the addition of trace amounts of SO 4 2 - , Cl − and NO 3 - , no obvious effects on the photocatalytic reduction of dichromate are observed. With the addition of methanol and toluene, the photocatalytic reduction of dichromate is accelerated, and the photocatalytic oxidation of dichlorvos is inhibited. The possible roles of the additives on the reactions are also discussed.