Malachite green degradation by persulfate activation with CuFe2O4@biochar composite: Efficiency, stability and mechanism

If dye wastewater discharges directly into the environment, it will make detrimental effects on the environment. Thus, it is urgently needed to develop an effective catalyst to activate persulfate for degrading dye wastewater. The CuFe2O4@biochar composite (CuFe2O4@BC) was synthesized by one-step sol-gel pyrolysis method and was evaluated for efficiency, stability and mechanism activating PS to degrade malachite green (MG). It was found that the degradation efficiency of MG in the CuFe2O4@BC/PS system was 98.9%, suggesting that CuFe2O4@BC exhibited the best catalytic activity among all the catalysts at optimum conditions. Furthermore, the MG degradation efficiency and TOC removal efficiency in the various systems followed an order: CuFe2O4@BC/PS > CuFe2O4@BC/PMS > CuFe2O4@BC/H2O2. Cl- at low (< 10 mM) and high (> 10 mM) concentrations exhibited dual effects. CuFe2O4@BC exhibited a favorable, stable catalytic performance in multiple runs. Free radical quenching experiments showed that O-2(center dot-) was also contributed to MG degradation in the CuFe2O4@BC/PS system except the surface-adsorbed radicals, providing new insight into the mechanism of activation of PS by CuFe2O4@BC. The PS activation mechanism and the two possible degradation pathways of MG were analyzed. The CuFe2O4@BC composite with high catalytic efficiency and stability and reusability possesses promising prospects to activate PS for treating MG-contaminated wastewater.