Photocatalytic oxidation of phenolic compounds using zinc oxide and sulphate radicals under artificial solar light

Photocatalytic degradation of phenolic compounds in aqueous solution was investigated in TiO2/persulphate/UV–vis and ZnO/persulphate/UV–vis light. It is found that ZnO exhibits higher activity than TiO2 in photocatalytic degradation of phenol under simulated solar light. The oxidation of phenol in either ZnO/UV–vis or persulphate/UV–vis system occurs at a similar rate while the degradation will be significantly enhanced with ZnO/persulphate/UV–vis system. The kinetics of phenol oxidation in ZnO/persulphate/UV–vis system follows the first order model. Several parameters influencing the reaction rate were also investigated including power intensity, phenol, ZnO and persulphate concentrations. It is shown that stronger light intensity will increase phenol oxidation. An optimal concentration of ZnO and persulphate will be required for maximum degradation of phenol. For phenol, dichlorophenol and trichlorophenol, photocatalytic activity in ZnO/persulphate/UV–vis shows an order of phenol > dichlorophenol > trichlorophenol.