Photocatalytic Decomposition of 2，4-Dichlorophenoxyacetic Acid over Amorphous Titania Modified Pt（IV）under Visible Light

Amorphous microporous metal oxides of titanium（AMM-Ti）which can induce photocatalytic reactions under visible light irradiation was prepared by using Na2PtCl6 according to the sol-gel procedure affording high specific surface areas of 160-200 m2/g. The most active photocatalysts contained 3.0% P（t Ⅳ）. According to extended X-ray absorption fine structure（EXAFS）results，isolated PtCl4 molecules were homogeneously distributed in an almost exclusively amorphous matrix of titania. During the photocatalytic degradation of 2，4-dichlorophenoxyacetic acid（2，4-D）in aqueous solution containing a suspension of AMM-Ti，it was found that 2，4-dichlorophenol was the major intermediate. The initial rate of photo-degradation was studied as a function of the initial concentration of reactants by the linearised form of the Langmuir-Hinshelwood equation，by which rate constants k and equilibrium adsorption constants K were evaluated. The postulated charge separation mechanism at Pt （Ⅳ）/ AMM-Ti and photocatalytic degradation mechanism of 2，4-D were also proposed.