High performance loose nanofiltration membranes with enhanced fouling-resistance by rapid covalent co-deposition of dopamine and diamine-zwitterion

Nanofiltration (NF) membranes have been extensively employed for the treatment of textile wastewater to produce clean water, due to their capability of retaining small organic molecules. In this study, zwitterionic loose nanofiltration (Z-NF) membranes have been successfully fabricated by the rapid co-deposition of dopamine and diamine-zwitterion (Z-DNMA) via covalent bonds. The fabricated Z-NF membranes show improved hydrophilicity and enhanced fouling-resistant ability due to the incorporation of the zwitterionic functionality. Following the systematic investigation on the ratio between dopamine and Z-DNMA as well as the co-deposition time, the identified optimum membrane (Z-NF3) exhibits a high pure water permeability (PWP) of 32.0 LMH bar−1 and high organic dye rejections of 99.7 % and 98.6 % for Congo red (CR) and methyl blue (MB), respectively. In addition, the fouling experiments of Z-NF3 show that the flux recovery ratios (FRRs) for the filtration of bovine serum albumin (BSA), sodium alginate (NaAlg), and CR are 99.1 %, 92.0 %, and 82.2 %, respectively, along with lower irreversible fouling ratios (Rir) and higher reversible fouling ratios (Rr) values compared to those of the control membrane. The high PWP and high rejections to organic dyes, coupled with its superior fouling-resistant performance, indicate its great potential for practical applications in the treatment of textile wastewater.