Research On Composite Nanofiltration Membranes Based On Sulfated Chitosan, Carboxymethyl Chitosan, And Carboxymethyl Cellulose Sodium

Nanofiltration, a new type of separation membrane technology developed since 1980's, is a pressure driven process that forms the transition between ultrafiltration and reverse osmosis. Most of NF membranes developed recently are composite membranes, i.e., with an active layer on top of the base membrane.Cellulose is the most abundant natural polymer on the earth, chitin is the second abundant and renewable natural polymer just second to cellulose, and chitosan is a cationic polysaccharide made from alkaline N-deacetylation of chitin. The active layer materials for composite NF membranes explored in this study were sulfated chitosan (SCS), N, O-carboxymethyl chitosan (NOCC), and carboxymethyl cellulose sodium (CMC-Na). Glutaraldehyde (GA), epichlorohydrin (ECH), and hexamethylene diisocyanate (HDI) were used to be the cross-linking agents. Under the certain membrane preparation techniques, three novel series of composite NF membranes were developed through the method of coating and cross-linking. Attenuated total reflection infrared spectroscopy (ATR-IR), environmental scanning electron microscopy (ESEM), and atomic force microscopy (AFM) were employed to characterize the resulting membranes. The characteristics and the rejection performances of the resulting membranes were investigated and discussed.It was found that the amphoteric composite NF membranes prepared from SCS and NOCC show the similar rejection performance to the negatively charged composite NF membranes. For the composite NF membranes prepared from the same active layer material, the permeation flux increased with the increase of the average roughness of the membrane surface (Ra). The rejection properties of the developed composite membranes could be adjusted by changing the composition of the casting...