Prparation And Chemical Modification Of Ultrafiltration Membrane

Ultrafiltration(UF) has become an increasingly important separation process because its processing efficiency is high, its energy consumption is relatively low, it is easy to operate and it is simple to scale up. Poly(vinylidene ?uoride) (PVDF) membranes are widely used in ultrafiltration (UF) due to their excellent chemical resistance, well-controlled porosity, and good thermal property. However, as traditional hydrophobic polymer membranes, exposure of the PVDF membranes to protein and other biomacromolecular-containing solutions during filtration can readily result in the fouling of the membranes,as a result,limited its application. Thus, an ideal hydrophilic membrane with better fouling resistances and excellent properties of a hydrophobic material is required to deal with this problem.In this study, PVDF ultrafiltration membrane was prepared by the phase transformation technique. Effect of content of PVDF, the organic solvents, additives, coagulation composition and temperature on the properties of PVDF ultrafiltration membrane have been investigated. When DMF as solvent, the content of PVDF is 10%, the content of PEG-600 is 3%, and coagulation system is cold water about 22℃, the PVDF ultrafiltration membrane with a high properties can be obtained.In order to improve the hydrophilicity and anti-fouling of membrane, plasma-induced grafting of polymer including polyacrylic acid (PAA)、poly(ethylene glycol) (PEG) and polyglycerol(PG) have been studied. The results show that PEG/PG could be covalently grafted onto the PVDF ultrafiltration membrane surfaces by low-temperature plasma-induced grafting of polymer and by changing the discharge power and discharge time, surface concentration of the grafted polymer can be controlled; the water ?ux decreased with the increase in surface polymer graft concentration, as the treatment time is 3 minutes and the RF power of the Argon plasma is 30 W, the membrane exhibited good anti-fouling performance while the membrane pore structure is almost unchanged. Furthermore, CO2/O2 plasma modification of PVDF ultrafiltration membrane was also carried out. The results reveal that it is a reasonable approach for introducing–OH and–C=O to the surface of membrane, consequently, the hydrophilicity and anti-fouling of membrane were improved. As the discharge time is 3 min, the RF power of the plasma is 30 W, and the pressure of CO2 is 40 Pa, the PVDF ultrafiltration membrane with high properties can be obtained.