Preparation And Application In Oil-Water Separation Of Cellulose Asymmetric Hollow Fiber Ultrafiltration Membrane

Ultrafiltration (UF) is one of the most effective methods for oil-water separation in comparison with the traditional separation methods. However, membrane fouling is a main drawback in the practical application of UF in oil-water separation.We have developed a hydrophilic hollow fiber UF membrane for oil-water separation. The membrane was fabricated from a new dope containing cellulose /monohydrate N-methylmorpholine-N-oxide (NMMO·H2O) using the immersion precipitation technique.Spinning parameters include salt additive, air-gap, kinds of bore fluids, outside coagulation, showed great influence on the morphology and permeation performance of cellulose hollow fiber UF membrane. Different types of bore fluids were tested and DMSO was selected as the optimal bore fluid to eliminate the inner skin. Various concentrations of DMSO in the outside coagulation bath (0-60%) and different coagulation temperature (20-80℃) were investigated. The structure of the hollow fiber was examined using scanning electron microscopy (SEM). Thickness of the outer skin decreased with increasing the coagulation temperature. Addition of salt in the casting dope can enhance the pure flux to 16 L·m-2·h-1.The influences of concentration of feed flux, transmembrane pressure, oil-in-water, feed flux, temperature and pH on separation are investigated. Thebetter cleaning method was given by comparing the effect of various cleaning agents on the recovery of permeation flux. The influences of concentration of different cleaning agents and times on the cleaning of fouled cellulose membranes were discussed. The oil eliminating efficiency over 98% and flux decay ratio less than 10% in filtration water were achieved,Different fouling resistances were analyzed with the osmotic pressure-adsorption model. The flux reduction of the cellulose membrane in treatment of the oily wastewater was dominated by the concentration- polarization. It was concluded that the cellulose hollow fiber UF membrane developed in the study was resistant to fouling and treatment of the oily wastewater using the developed cellulose membrane was feasible and desirable. The distribution of cellulose membrane resistance, osmotic pressure and oil adsorption resistance is analyzed based on the experiment. Model for cellulose membrane separation was set up. Oil-field water, machine oil water and cabin oil water were separated. A good agreement between experiment and model was found for oil-water separartion.