A novel composite nanofiltration (NF) membrane prepared from sodium alginate/polysulfone by epichlorohydrin cross-linking

A novel composite nanofiltration (NF) membrane was prepared by over-coating the polysulfone ultrafiltration (UF) membrane with an alginate thin layer. The effects of the membrane preparation techniques and operating conditions on the rejection performance of the composite membranes were studied. The structure of the composite NF membrane was characterized by scanning electron microscopy (SEM) and atom force microscopy (AFM). The results suggested that the composite membrane with optimal performances was prepared while the concentration of sodium alginate was 1.0%, the concentration of epichlorohydrin was 1.5%, and the cross-linking time was 18 h at 60 C. The salt rejections to Na2SO4, K2SO4, MgSO4, NaCl, KO and MgCl2 (1,000 mg L-1) were 88.7%, 87.2%, 65.8%, 35.2%, 29.9%, 11.1%, respectively, while the permeation fluxes were 21.4, 28.5, 45.9, 58.1, 68.3, 48.9 L h(-1) m(-2), respectively. In addition, the curve of the streaming potential illustrated the negatively charged characteristics of this membrane, with a pressure osmobic coefficient of -232.8 mV MPa-1.