Study on enhancing permeation and retention performance of precoating dynamic membrane

Key words: 
• dynamic membrane /
• precoating /
• permeation /
• retention /
• emulsified oily wastewater

Abstract: The precoating dynamic membrane was prepared using the titanium dioxide powders and the ceramic tube as precoating material and substrate membrane, respectively. Through inducing the flux enhancement coefficient Zi and retention enhancement coefficient Fi, the influences of the preparing conditions of the dynamic membrane on its permeation and retention performance were investigated. The surface topography of the dynamic membrane and substrate membrane were characterized by the SEM. The results showed that the surface of the dynamic membrane was very uniform and smooth. The pore diameter of the dynamic membrane was lower than the average pore diameter of the substrate membrane. The permeation and retention performance increased with the rise of the pH of the coating solution. When the parameters such as the transmembrane pressure, the crossflow velocity, coating time and concentration of the coating solution were less than 0.2 MPa, 1.5 m/s, 30 min and 0.4 g/L, respectively, the rise of these parameters was favorable for improving the permeation and retention performance. But little effect of the crossflow velocity was observed. Beyond these ranges, the permeation and retention performance changed very little with the increasing of the parameter values. The optimal preparing conditions of the precoating dynamic membrane includes: the transmembrane pressure 0.2 MPa, the crossflow velocity 1.5 m/s, the coating time 30 min, the concentration of the coating solution 0.4 g/L and the pH value of the coating solution 10.2.