High flux photocatalytic self-cleaning nanosheet C₃N₄ membrane supported by cellulose nanofibers for dye wastewater purification

Hazardous dye substances discharged from the textile and dyestuff industries not only threaten local the surrounding ecosystems but are also hard to degraded. We report the preparation of process for a photocatalytic membrane device that can degrade dye pollution under visible light. This filtration membrane, with a well-organized multilayer structure, simultaneously achieves continuous and flow-through separation of degradation products. Cellulose nanofibers (CNFs) were used as a template for nanosheet C₃N₄ (NS C₃N₄) preparation; the performance for the photocatalytic degradation of dyes improved as the morphology changed from bulking to nanosheet. NS C₃N₄ was then attached to the surface of a prepared CNF membrane via vacuum filtration. This device exhibited high efficiency (the degradation rates of both Rhodamine B and Methylene blue both reached 96%), high flux (above 160 L·h^-1·m^-2·bar^-1) and excellent stability (maintaining steady flux and high separation were maintained after 4 h). This easy-preparation, easy-scale-up, and low-cost process provides a new method of fabricating photocatalytic membrane devices for dye wastewater treatment.