Enhancing membrane separation performance in the conditions of different water electrical conductivity and fouling types via surface grafting modification of a nanofiltration membrane, NF90

• Published in: Environmental research Vol. 239; p. 117346
• Main Authors: Lin, Yi-Li, Zheng, Nai-Yun, Hsu, Yu-Jhen
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 15.12.2023
• Subjects: Electrical conductivity (EC); Fouling; Pharmaceuticals and personal care products (PPCPs); Polyamide nanofiltration (NF) membrane; Surface grafting modification; Polyamide nanofiltration (NF) membrane; Fouling; Electrical conductivity (EC); Surface grafting modification; Pharmaceuticals and personal care products (PPCPs)
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2023.117346

A commercialized and widely applied nanofiltration membrane, NF90, was in-situ modified through a surface grafting modification method by using 3-sulfopropyl methacrylate potassium salt and initiators. The effects of water electrical conductivity (EC) and fouling types on membrane separation efficiency were examined before and after membrane modification. Results reveal that both the pristine membrane (PTM) and surface grafting modification membrane (SGMM) had a declining permeate flux and salt (NaCl) removal efficiency but an increasing trend of pharmaceuticals and personal care products (PPCPs) removal with increasing water EC from 250 to 10,000 μs cm−1. However, SGMM exhibited a slightly declining permeate flux but 13%–17% and 1%–42% higher rejection of salt and PPCPs, respectively, compared with PTM, due to electrostatic repulsion and size exclusion provided by the grafted polymer. After sodium alginate (SA) and humic acid (HA) fouling, SGMM had 17%–26% and 16%–32% higher salt rejection and 1%–12% and 1%–51% greater PPCP removal, respectively, compared with PTM due to the additional steric barrier layer contributed by the foulants. The successful grafting and increasing hydrophilicity of the SGMM were confirmed by contact angle analysis, which was beneficial for mitigating membrane fouling. Overall, the proposed in-situ surface grafting modification of NF90 can considerably mitigate organic and biological fouling while raising the rejection of salt and PPCPs at different background water EC, which is beneficial for practical applications in producing clean and high quality water for consumers. [Display omitted] •SGMM can maintain a stable water permeability at different water EC.•Size exclusion and electrostatic repulsion dominate salt and PPCP rejection for SGMM.•An additional barrier enhanced salt and PPCP rejection by PTM and SGMM after fouling.•A trace amount of the hydrophobic PPCPs adsorbed on the membrane and fouling layer.