Enhanced 4-FP removal with MnFe2O4 catalysts under dielectric barrier discharge plasma: Economical synthesis, catalytic performance and degradation mechanism

The dielectric barrier discharge plasma (DBDP) process has received extensive attention for the removal of organic contaminants from water. A novel microwave-assisted hydrothermal method was used to easily and rapidly synthesize MnFe2O4 catalysts. Based on the DBDP process, MnFe2O4 can enhance 4-fluorophenol (4-FP) abatement from 44.15% to 58.78% through the catalysis within 18 min. Then, the adjunction of O3 generated by discharge can further boost 4-FP degradation to 94.94%. After the whole optimization process is complete, the associated pseudo-first-order reaction kinetic constant and energy efficiency were enhanced from 0.0327 to 0.1536 min−1 and 2067.13 mg kW h−1 to 4444.75 mg kW h−1, respectively. With the help of the condition, blank and radical capture experiments, the catalytic performance caused by MnFe2O4 and O3 was attributed to the joint action of Fenton-like reactions, photocatalysis (ultraviolet, UV), photoassisted Fenton reactions and O3 catalysis. The overall downward trend of the possible intermediate toxicities indicated that the DBDP/MnFe2O4/O3 process can effectively remove and mineralize 4-FP without the generation of more toxic intermediates. In addition, during the 5 cycles, MnFe2O4 can maintain excellent recovery, efficiency and durability. In summary, the coupling of discharge plasma and MnFe2O4 sheds new light on catalysis for wastewater treatment.