Changing conventional blending photocatalytic membranes (BPMs): Focus on improving photocatalytic performance of Fe3O4/g-C3N4/PVDF membranes through magnetically induced freezing casting method

Blending photocatalytic membranes (BPMs) are favored materials for wastewater treatment due to their photocatalytic activity, high permeability and fouling resistance. However, using conventional blending modification to prepare BPMs always suffers significant reduction of photocatalytic efficiency due to the maldistribution of photocatalysts, especially a number of photocatalysts embedded inside the membrane, losing photocatalytic activity and blocking the membrane channels. To overcome this problem, we proposed an alternative magnetically induced freezing casting method to prepare highly effective macroporous Fe3O4/g-C3N4/PVDF membranes (FCMs). The magnetic Fe3O4/g-C3N4 could be directionally and highly exposed to the membrane surface and ordered latticed macroporous structure was formed. The FCMs exhibited significantly enhanced visible-light absorption probably due to more exposed photocatalytic active sites available on membrane surface and the macroporous structure facilitating the light penetration. The photodegradation rate constant of optimal FCM was 2.7 times higher than that of conventional BPMs. Moreover, the FCM had extremely high porosity and water flux, up to 88.5% and 15835.2 Lm(-2) h(-1), respectively. The FCMs also had good stability (retained over 90% of photocatalytic activity after 5 recycles) and fouling resistant (2.38% BSA adsorption). Therefore, this work provides an alternative and easily scale-up strategy to construct highly effective BPMs for wastewater treatment.