Photocatalytic Bi2WO6/pg-C3N4-embedded in polyamide microfiltration membrane with enhanced performance in synergistic adsorption-photocatalysis of 17β-estradiol from water

17β-estradiol (E2) is one of the endocrine disrupting chemicals (EDCs) ubiquitously with significant impacts on ecosystem and organisms even at extremely low concentrations. Photocatalytic membranes, with the combination of photocatalysis and membrane filtration, have great potential to enhance E2 removal. In this work, a photocatalytic membrane was fabricated from the polyamide (PA) microfiltration membrane and visible light responsive Bi2WO6/protonated g-C3N4 (BPG) photocatalyst. The BPG photocatalyst was embedded into calcium alginate hydrogel followed by immobilizing onto PA membrane through vacuum filtration and crosslinking. The transparent calcium alginate hydrogel guaranteed 100% light transmittance which contributed to visible light induced photodegradation. Under static and dynamic conditions, the removal efficiency of E2 reached 99.5% and remained 95.1%, which was mainly owing to the synergistic effects of the adsorption of PA and photodegradation of the BPG nanocomposites. The synergistic interaction was fitted by modified Elovich model, and a strong positive correlation (r = 0.834, rs = 0.965) was confirmed by Pearson’s and Spearman’s correlation coefficient, indicating that adsorption could enhance photocatalysis by concentrating contaminants around the photocatalyst and photocatalysis could promote the adsorption by regenerating adsorption sites. The photocatalytic membrane can be reused, and the removal efficiency of E2 was 96.6% after 5 cycles. This work provided not only a facile fabrication of photocatalytic membrane, but also a deep understanding of the synergistic adsorption-photocatalysis for effective removal of E2.