Preparation of CoFe2O4/MWNTs/sponge electrode to enhance dielectric barrier plasma discharge for degradation of phenylic pollutants and Cr(VI) reduction

• A new type of CoFe 2 O 4 /MWNTs/sponge electrode was used in DBD reactor. • CoFe 2 O 4 NWs produced tip discharge to improve energy utilization of DBD system. • The system synergistically promotes elimination of phenylic pollutants and Cr(VI). • Possible reaction pathways of phenylic pollutants and Cr(VI) are proposed. • The system provided a new design concept for further removal of mixed pollutants. CoFe 2 O 4 /MWNTs/sponge electrodes were prepared by co-adsorption of CoFe 2 O 4 nanowires and multiwalled carbon nanotubes (MWNTs) onto a pure sponge, which were combined in a dielectric barrier discharge (DBD) plasma reactor to enhance discharge performance. The optimum concentration of CoFe 2 O 4 nanowires contained in the CoFe 2 O 4 /MWNTs/sponge electrode was 0.5 g/L with a degradation rate of phenol of 98.52 % in 40 min. The CoFe 2 O 4 /MWNTs/sponge–DBD system significantly had the highest energy utilization efficiency with the tip discharge formed by CoFe 2 O 4 nanowires and uniform discharge zone enlarged by modified sponge electrode. Further, phenol, hydroquinone, nitrobenzene, and p -nitrophenol as phenylic pollutants combined with hexavalent chromium (Cr(VI)) were treated simultaneously in CoFe 2 O 4 /MWNTs/sponge–DBD system. CoFe 2 O 4 nanowires in DBD process formed photocatalytic and Fenton-like reaction could enhance phenylic pollutants degradation and Cr(VI) reduction. The synergistic removal effect between phenylic pollutants and Cr(VI) was discussed and the reaction mechanism in the CoFe 2 O 4 /MWNTs/sponge–DBD system was also explored.