Novel catalytic self-cleaning membrane with peroxymonosulfate activation for dual-function wastewater purification: Performance and mechanism

The integration of in-situ chemical oxidation (ISCO) and membrane separation technology (MST) was appealing for one-step efficient removal of complex dye-contaminated oily wastewater. However, the construction of catalytic membranes remains an arduous challenge due to the critical restriction of unsatisfactory degradation and poor stability. In current work, manganese dioxide (MnO2)/carboxyl functionalized carbon nanotube (C-CNT) composites were prepared through a facile hydrothermal process. It was found that, the degradation rate of rhodamine B (Rh B, 100 ppm) in MnO2/C-CNT (0.2 g/L)/peroxymonosulfate (PMS, 0.5 g/L) system reached 2.071 min(-1), which was 4.6 and 10.9 times higher than that of MnO2 and C-CNT (0.4541 and 0.1942 min(-1)), respectively. The vacuum-assisted filtration was utilized to construct MnO2/C-CNT@ polyvinylidene fluoride (PVDF) membrane, which exhibited excellent filtration catalytic activity and stability for dyes and natural small molecular organics. Scavenger experiments and electron paramagnetic resonance (EPR) analysis verified the synergistic effect of radicals and nonradicals while O-1(2) was the dominator for Rh B degradation. The MnO2/C-CNT@PVDF membrane also possessed high permeation flux (170.2 L/(m(2).h)), separation efficiency (99.5%) and anti-oil properties for filtrating n-hexane/water emulsion. Moreover, the modified membrane could achieve the dual purification for one-step catalytic degradation of dyes and oil/water separation. Meanwhile, the flux recovery rate of the prepared membrane reached 91% after filtering the PMS solution for 10 min, indicating its brilliant self-cleaning performance. This study provided a novel insight into development of dual-function catalytic self-cleaning membranes for water treatment.