TiO_2光触媒懸濁下における亜リン酸の酸化反応

概要

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Photochemical oxidations reactions of phosphite ions in the presence and absence of H2O2 as well as TiO2 catalyst were studied in order to develop a simple and efficient process for the treatment of spent liquor containing phosphite ions of electroless plating. The principal results obtained are as follows: (1) Aqueous phosphite ions were oxidized to phosphate ions by dissolved oxygen under UV irradiation, showing an initial induction period. Their oxidation rate became quickly high in alkaline solution, slowing down in the order of acidic and neutral. The concentration of dissolved oxygen affected the oxidation rate in an alkaline solution, but no distinct effect was detectable in the acidic range; (2) the oxidation of phosphite ions proceeded by the addition of H2O2 under UV irradiation; (3) the oxidation reaction of phosphite ions was greatly enhanced by UV irradiation in the presence of TiO2 catalyst, and the induction period disappeared. The dependency of pH for both the oxidation rate and amount of phosphite ions absorbed onto TiO2 catalyst showed a similar tendency, indicating that the adsorption of phosphite ions onto the TiO2 catalyst played an important role in the photocatalytic oxidation of phosphite ions; (4) other factors, such as the TiO2 amount and UV irradiation intensity, were also examined.
2008-07-25