Heterostructural amorphous catalyst decorated membranes with excellent anti-fouling performances in wastewater purification

Abstract

Hydrophilic and underwater superoleophobic membranes can handle membrane pollution from low-viscous oils in oily wastewater, but application in high-viscous oils and other foulants is limited. In this study, a filtration membrane with outstanding anti-fouling performances in complicated wastewater purification is designed and developed, which not only prevents oils from the membrane bulk because of the underwater superoleophobicity but also activates peroxymonosulfate advanced oxidation processes (PMS-AOPs) generating reactive species for the degradation of various pollutants on the membrane. Briefly, amorphous Fe-based metal–organic frameworks (aMOF) were covered on the polyvinylidene difluoride/polyacrylic acid (PVDF/PAA) blend membrane and further modified by amorphous Co(OH)₂ nanosheets, therefore an amorphous Fe/Co synergistic catalyst-modified membrane (M-aMOF-Co) was engineered for the first time. Compared with the membrane modified by crystalline MOF (M-cMOF) and the membrane decorated by amorphous Co(OH)₂ nanosheets (M-Co), M-aMOF-Co exhibits more stability and greater PMS-AOP performances against dyes and antibiotics (such as methylene blue, rhodamine B, tetracycline, levofloxacin, and enrofloxacin), due to the fast redox reaction between Co²⁺ and Fe³⁺ on the amorphous catalysts. For the separation of a soybean oil-in-water emulsion containing rhodamine B and tetracycline, M-aMOF-Co has a high flux recovery rate (FRR_P) of 98.1% and low pollution resistance (R_fp) of 0.1 × 10¹¹ m⁻¹, which are superior to M-cMOF (86.8% and 0.6 × 10¹¹ m⁻¹) and pure PVDF/PAA membrane without modification (called M, 21.0% and 7.1 × 10¹¹ m⁻¹). This study not only pioneers a novel application of amorphous Fe/Co catalysts in PMS-AOPs but also offers an innovative solution for membrane fouling in wastewater reclamation.