High-flux, high-selectivity loose nanofiltration membrane mixed with zwitterionic functionalized silica for dye/salt separation

A kind of charged nano-material SiO 2 -SBMA was prepared by reverse atom transfer radical polymerization (RATRP) with nano SiO 2 and 2-methacryloyloxy ethyl dimethyl (3-sulfopropyl)-ammonium hydroxide sulfobetaine methacrylate (SBMA). This material was dispersed with polyvinylpyrrolidone (PVP) and polyethersulfone (PES) in N, N-dimethylacetamide (DMAc) to obtain a casting solution, with which the loose nanofiltration (NF) membrane SiO 2 -PSBMA/PES was constructed using phase inversion on a sheet of glass with the automatic film applicator. The membrane structure and separation performance were investigated. The results indicated that the surface roughness, hydrophilicity, pure water flux and permeability selectivity of the loose NF membrane all improved. When the addition amount of SiO 2 -PSBMA was 0.5%, the order for retention of inorganic salts was R (Na 2 SO 4 ) > R (NaCl) > R (MgCl 2 ), which exhibited typical characteristics of the negatively charged membrane. At 0.4 MPa, the rejection of the membrane for Na 2 SO 4 was 11.4%. The rejection of reactive black 5 (RB5) and reactive green 19 (RG19) were 97.9% and 99.0%, and the corresponding permeation flux were 32.3 L m −2 h −1 bar −1 and 28.1 L m −2 h −1 bar −1 , respectively. The prepared membrane had higher flux and selectivity in dye wastewater treatment and was expected to be used in the treatment of salt-containing dye wastewater.