Preparation Of Cellulose Acetate Ultrafiltration Membrane And Its Properties

Membrane separation technology has some advantages compared with the traditional separation process, such as its simple equipment, easy operation, low energy consumption and pollution-free. As a green and energy-efficient separation technology, ultrafiltration has been widely applied in ultra-pure water's production, industrial wastewater's treating, concentration and purification of biologicals. However, the adsorption and precipitation of biomacromolecule on the ultrafiltration membrane surface causes membrane fouling, which decreases the life of membrane modules and increase cost, so improvement in the prevention of membrane fouling has become a problem that is exigent to be solved in the entire membrane process. Modification of existing membrane materials by blend method was frequently used. The cellulose acetate becomes main material in preparating of microfiltration and ultrafiltration membrane due to the advantages such as its source, low prices, simple film-processing and good film-forming properties. Here we use the basic material of cellulose acetate (CA) to produce the UF membrane by the phase transformation technology. The main experiments and results were summarized as follows:The cellulose acetate ultrafiltration membranes were prepared by the immersion precipitation phase transformation from a solution containing DMF/AC as blended solvent. The influences of polymer mass fraction, the coagulant's temperature and composition were investigated. It was found that the effect of polymer concentration on penneant property of CA ultrafiltration membrane is remarkable, an increase in polymer concentration causes a decrease in the flux of pure water and increases in the BSA rejection rate of membrane, and the optimal concentration is 17.5%. The pure water flux of CA membrane decreased with the increasing of the coagulation temperature, while the rejection rate of BSA did not change significantly. Various concentrations of solvent in the coagulation bath also were investigated. An increase in solvent concentration in the coagulation bath causes a decrease in the flux of pure water and increases in the BSA rejection rate of membrane.Polymeric blend ultrafiltration membranes based on CA and PU have been prepared by the immersion precipitation phase transformation. The influence of polymer blending ratio, the effect of the polymer concentration and composition of solvent were investigated. The results showed that with the increase of the PU content in blended polymer, the pure water flux of blend membrane decreased. However, the rejection rate of BSA was nearly unchanged. With the increase of the proportion of acetone in AC/DMF mixed-solvent, pure water flux of the membrane reduced and the rejection rate nearly unchanged.