Preparation and characterization of N, O-carboxymethyl chitosan (NOCC)/polysulfone (PS) composite nanofiltration membranes

Abstract

N, O-carboxymethyl chitosan (NOCC) composite nanofiltration membranes having a polysulfone (PS) UF membrane as the substrate were prepared using a method of coating and cross-linking, in which a glutaraldehyde (GA) aqueous solution was used as the cross-linking agent. Attenuated total reflection infrared spectroscopy (ATR-IR) was employed to characterize the resulting membrane. The effects of the composition of the casting solution of the active layer, the concentration of the cross-linking agent, and the membrane preparation techniques on the performance of the composite membrane were investigated. At 13–15 °C and 0.40 MPa the rejections of the resulting membrane to Na 2SO 4 and NaCl solutions (1000 mg L −1) were 92.7 and 30.2%, respectively, and the permeate fluxes were 3.0 and 5.1 kg m −2 h −1, respectively. The rejection of this kind of membrane to the electrolyte solutions decreased in the order of Na 2SO 4, NaCl, MgSO 4, and MgCl 2. This suggests that the membrane active layer acquires a negative surface charge distribution by the adsorption of anions from the electrolyte solution and this charge distribution mainly determines the membrane performance.