Optimization of COD Removal from an Aqueous Lignin Solution Using Photo-Fenton Reaction over Fe-Ce-Zn Catalysts

Abstract

This work is an investigation of the effectiveness of chemical oxygen demand (COD) removal from synthesized lignin wastewater using photo-Fenton reaction over Fe-Ce-Zn catalysts. The synthesized lignin wastewater had the same COD concentration as the pulp processing wastewater. The treatment was done using photo-Fenton reaction with the metal catalysts (Fe-Ce-Zn). They were prepared by co-precipitation. The catalysts efficacies in reducing COD were tested. It was found that the addition of zinc influenced its reaction due to the increasing of semiconductor property to the light. Moreover, the high surface area of Fe-Ce-Zn catalyst enhanced the COD removal due to the synergy of the high adsorption capacity. Therefore, the Fe-Ce-Zn catalyst was studied to obtain the optimal condition for COD reduction. The conditions and parameters investigated were: pH, the concentration of hydrogen peroxide (H2O2), and the concentration of catalyst. The optimal condition was obtained using the Box-Behnken statistical experiment design (BBD) and the response surface methodology (RSM). It has been found that the pH and the concentration of catalyst had the significant effects on the reduction of COD. The concentration of H2O2 has no effect on the COD removal. The maximum COD removal (60%) was achieved at the pH of 5.2, 4 g/L of catalyst loading, and 366 mg/L of H2O2.