A designed experimental approach for photocatalytic degradation of paraquat using α-Fe2O3@MIL-101(Cr)@TiO2 based on metal-organic framework

A new magnetic alpha-Fe2O3@MIL-101(Cr)@TiO2 photocatalyst was successfully prepared. The structural and morphological properties of synthesized photocatalyst were studied by FTIR, XRD, SEM, EDX and BET analysis. Optimizing of the removal of paraquat herbicide from aqueous solution was investigated by response surface methodology based on Box-Behnken design. The interactive effects of four parameters including the dosage of catalyst, pH, the initial concentration of paraquat and contact time, all have been studied on the photocatalytic degradation and COD reduction. A quadratic polynomial model was adjusted to the data with an R-2 of 0.89 for photocatalytic degradation and R-2 of 0.92 for COD reduction, respectively. The photocatalytic degradation and COD reduction were obtained 87.46% and 90.09% at the optimal conditions, after 45 min using 0.2 g L-1 of alpha-Fe2O3@MIL-101(Cr)@TiO2, pH 7 and the concentration of paraquat 20 mg L-1. The kinetics of paraquat adsorption on the surface of alpha-Fe2O3@MIL-101(Cr)@TiO2 photocatalyst were obtained by the pseudo-second-order and parabolic diffusion models.