N-Doping of Biochar and Support Strategies to Enhance the Catalytic Activity of CuFe2O4 for Persulfate-Promoted Methylene Blue Degradation

The copper ferrite/nitrogen-doped biochar (CuFe2O4/Nx-BC) was synthesized by a one-step sol–gel pyrolysis method, and its efficiency in activating PS to degrade MB was evaluated. The influences of preparation conditions, degradation conditions, and common anions on the degradation efficiency of MB were investigated, and the mechanism of CuFe2O4/N0.5-BC activating PS was inferred. The results showed the saturation magnetization of CuFe2O4/N0.5-BC was 25.53 emu/g. Under the optimal degradation conditions, compared to PS alone, the degradation efficiency of MB in the CuFe2O4/N0.5-BC + PS system increased from 26.2% to 94.1%, the reaction rate constant in the CuFe2O4/N0.5-BC + PS system (0.02954 min−1) was 9.12 times higher than that in the PS alone system (0.00324 min−1); Compared to the CuFe2O4/BC system, the degradation efficiency of MB in the CuFe2O4/N0.5-BC + PS system increased from 34% to 94.1%, while the reaction rate constant is 1.1 times that in the CuFe2O4/BC + PS system. After CuFe2O4/N0.5-BC underwent five cycles of application, the degradation efficiency of MB in the CuFe2O4/N0.5-BC + PS still reached 87.5%. SO4•− plays a major role, •OH played a certain role and O2•− was also responsible for the degradation of MB in the CuFe2O4/N0.5-BC + PS system. CuFe2O4/N0.5-BC is a green and effective catalyst for the PS-AOP method to treat MB-contaminated water.