Synergistic effect of underwater arc discharge plasma and Fe2O3-CoFe2O4 enhanced PMS activation to efficiently degrade refractory organic pollutants

• A novel underwater arc discharge plasma reactor was designed. • A low-temperature plasma-catalyst-oxidant method for the efficient degradation of phenolic and nitrochlorobenzene organic pollutants was constructed. • The synergistic catalytic mechanism between plasma and Fe 2 O 3 -CoFe 2 O 4 for PMS activation was revealed. This study employed a self-designed underwater arc discharge (UAD) plasma reactor, which combined advanced oxidation process (Fe 2 O 3 -CoFe 2 O 4 /PMS) and low-temperature plasma technology to efficiently degrade refractory organic pollutants (i.e. phenol, p-chlorophenol, p-nitrochlorobenzene). The results illustrated that the plasma/PMS/Fe 2 O 3 -CoFe 2 O 4 system possessed high degradation efficiency and TOC removal rate towards three target pollutants (phenol: 99.8%, 96.12%; 4-CP: 98.4%, 86.48%; p-NCB: 99.9%, 88.31%). With the help of in-situ variable temperature EPR and Indigo colorimetry method, ·OH, SO 4 ·- , O 2 ·- , 1 O 2 and O 3 were identified as the main reactive oxygen species (ROS) for the degradation of target pollutants, revealing the synergistic catalytic mechanism between plasma and Fe 2 O 3 -CoFe 2 O 4 for PMS activation and inferring the degradation pathways of target pollutants. The results confirmed that the plasma/PMS/Fe 2 O 3 -CoFe 2 O 4 system was feasible for the degradation of refractory organic pollutants, has the advantages of high efficiency and low energy consumption, and could provide an effective strategy for the treatment of refractory organic pollutants in groundwater/soil.