Degradation of bisphenol A using a MOF@COF-modified polyacrylonitrile ultrafiltration membrane

Certain endocrine disrupting chemicals, such as Bisphenol A were found to persist in water after conventional water treatment processes due to their hydrophobicity and stability. This necessitates efficient removal methods due to a variety of limitations in conventional water treatment processes, such as harmful byproducts, saturation, and membrane fouling. This study explored the application of a novel MIL-101-NH₂@TpMA (MOF@COF)- doped polyacrylonitrile (PAN) ultrafiltration membrane in its efficacy to degrade BPA and reduce membrane fouling through photocatalysis. This study also aimed to determine the mechanism involved in the photocatalytic degradation of BPA. The composite was successfully synthesised using solvothermal synthesis and structurally analysed via XRD and FTIR, confirming crystal structure and covalent bonding between MIL-101-NH₂ and TpMA via the adsorption bands detected at 765 and 1247-1257 cm⁻¹ (N-H wagging band and C-N stretching bands). UV–vis diffuse reflectance analysis revealed a narrowed band gap upon hybridisation (0.92 eV) signifying enhanced photocatalytic activity, while photoluminescence spectra indicated reduced electron–hole recombination. Electrochemical impedance spectroscopy further identified MIL-101-NH_₂[30]@TpMA as the optimal composite for efficient charge transfer. Surface and cross-sectional SEM analysis showed favourable morphology with well-defined pores and macro voids in the PAN/(MIL-101-NH₂[30]@TpMA)_[0.7] membrane. Hydrophilicity and flux also improved in this membrane, reducing water contact angle from 48.2° in pristine PAN to 43.7°, and superior flux (1278.24 L/m²/h), flux recovery ratio (96.4 %), and minimal irreversible fouling (4.2 %) for the PAN/(MIL-101-NH_₂[30]@TpMA)_[0.7] membrane. Lastly, A BPA degradation rate of 97 % was achieved within 3 h of filtration at neutral pH and 10 mg/L BPA concentration. Mechanistic studies suggested that BPA degradation proceeds predominantly via hydroxyl radicals and hole-induced oxidation.