Water flux response analysis of PVDF ultrafiltration membrane by plasma modified

Abstract

Four low temperature plasma modification methods (only plasma modification, hybrid plasma-chemical deposition, plasma liquid graft and plasma-chemical deposition) had been used to modify PVDF hollow-fiber membrane. In this paper, it studied the responsiveness of flux of four different modification membrane for the pH value, temperature and different electrolyte solution (potassium chloride, sodium chloride, sodium chloride, and sodium sulphate). The results showed that low temperature plasma modification method can graft or aggregate effectively on membrane surface, so it influences the membrane flux responsiveness. The membranes which are modified by acrylic plasma chemical deposition method and nitrogen acrylic mixed with plasma chemical deposition have a stronger acid, and the latter has a higher ionization degree. Only plasma modification and Plasma Liquid graft membranes had larger flux response in acid condition than in alkali condition. As the temperature increases, the grafted polymer on the surface of modification membrane contracts, which reduces the boundary layer thickness and viscosity. Therefore, the flux increasing rate of modification membrane is higher than that of the original film. The flux response of PVDF plasma modification membrane in the four electrolyte solutions with different concentration is more complicated. The main reason is the absorption- permeability of grafted polymer in film hole, the electrical shielding and neutralizing action of electrolyteion to grafted polymerization polymer chain, and electro-viscous effect caused by countra-ion reverse migration due to flow potential. Thus membrane aperture changes and flux response changes as well.