Tailor-made highly negatively charged nanofiltration membrane prepared by polyphenol derivatives for anionic dye/salt separation

Nanofiltration (NF) techniques are becoming increasingly advantageous for treating salt-containing dye wastewater. A novel NF membrane was successfully fabricated using grape seed oligomeric proanthocyanidins (OPC) as aqueous phase monomer by interfacial polymerization with isophorone diisocyanate (IPDI). The membrane surface exhibited an extremely high negative zeta potential. The experimental results showed that the negatively charged OPC/IPDI nanofiltration membranes could effectively remove anionic dyes and exhibited high NaCl/dye selectivity. Specifically, the optimal OPC/IPDI membrane exhibited a rejection of 99.4 % against Reactive Red 195 with a high permeance of 67.9 L m−2 h−1 bar−1 and a desirable NaCl/RR 195 selectivity factor of 85.3. In addition, the smooth and hydrophilic surface endowed the membranes with a desirable antifouling property. The optimized membrane achieved high flux recovery ratio values of 89.1 %, 85.5 %, and 24.75 % for the foulants of Reactive Red 195, humic acid, and bovine serum albumin, respectively. A 50-hour investigation of continuous cross-flow filtration processes showed the outstanding separation stability of the membranes. Furthermore, the membranes exhibited excellent anti-bacterial activity. Integrating all the findings, the strategy proposed in this paper for the use of polyphenol derivatives to prepare highly negatively charged membranes for the removal of anionic pollutants from saline wastewater is feasible.