POLYETHERSULFONE/CELLULOSE CRYSTAL BLEND MEMBRANES AND THEIR ULTRAFILTRATION PERFORMANCE

The casting solution was obtained by blending polyethersulfone (PES) and cellulose crystal in dimethylacetamide (DMAC). PES/cellulose crystal blend membranes were prepared by the immersion precipitation phase inversion process. The effects of cellulose crystal content on the properties of blend membranes were discussed. The pure water flux, rejection ratio, porosity, mean pore size and anti-fouling property were tested in the ultrafiltration equipments. Also, the mechanical properties, thermal stability and morphology were characterized by tensile testing, thermogravimetric analysis (TGA) and atomic force microscopy (AFM). The results showed that at first, the pure water flux of blend membranes was greatly improved with the increasing of cellulose crystal content, but then it decreased to some extent. All the rejection ratios remained at 91% similar to 95%. The tendencies of tensile strength and elongation curses were the same as the one of pure water flux curve. The anti-fouling property of blend membrane had been improved. When the mass fraction of cellulose crystal was 1%, the pure water flux got to a maximum,813.3 L.m(-2).h(-1); porosity was 88.8% and mean pore size was 70.9 nm. At the same condition, tensile strength was 7.25 MPa and elongation was 11.6%. In addition, fouling degree (FR value) and attenuation coefficient of fouling (m value) were 22. 0% and 35.8%, respectively. There were two weight loss stages in the blend membrane, due to thermal degradation of PES and cellulose crystal, respectively. The typical asymmetric membrane structure was displayed in the blend membrane. The surface layer of the blend membrane was dense, and the support layer had larger size pores. Both of them composed the typical asymmetric membrane structure.