Fabrication of ZIF-67@PVDF ultrafiltration membrane with improved antifouling and separation performance for dye wastewater treatment via sulfate radical enhancement

Efficient separation and excellent antifouling performance of ultrafiltration (UF) membrane are highly desirable for sustainable wastewater treatment. This work reports a novel ZIF-67-imbedded PVDF (ZIF-67@PVDF) mixed-matrix UF membrane fabricated by nonsolvent-induced phase separation (NIPS) technique to reinforce efficient removal of dye wastewater via sulfate radical enhancement. The imbedded ZIF-67 well-dispersed within the membrane improved the membrane pore structure and benefited peroxymonosulfate (PMS) activation to generate sulfate radical that were confirmed by Electron spin resonance (ESR) spectroscopy. As a synergistic effect of pore structure and sulfate radical generation, the separation, antifouling and catalytic performance of the ZIF-67@PVDF membranes were greatly enhanced over a wide pH range. Even at a high pH of 11, the PMS on-line cleaning assisted ZIF-67@PVDF-1.0 membrane achieved high dye removal efficiency for orange Ⅱ (AO7, 97.3%), Methylene blue (98.2%), Rhodamine B (90.5%). The ZIF-67@PVDF membrane also showed good reusability and stability. This work demonstrates great potential of using self-cleaning UF membranes to treat dye wastewater.