The Study Of Preparation Of Anti-contamination And High Flux Polyethersulfone Ultrafiltration Membranes

In this dissertation, anti-contamination high flux ultrafiltration membranes were prepared with polyethersulfone (PES) as the membrane-forming material through phase inversion technique, when NMP was chosen as the solvent. One type of polyvinylpyrrolidone (PVPK30) was firstly chosen as the additive. Three classes of research works were performed in the experiments. First, the effects of the composition of casting solutions (e.g.'the concentrations of polymer and additive) and the preparing conditions (e.g. the evaporation time, coagulation temperature, and ambient temperature) on the membrane performances were researched. It was found that with the increase of polymer concentration in the casting solutions, the water flux of the prepared UF membranes decreased, but the rejection to BSA increased. With the increase of PVP concentration, the water flux firstly increased, then decreased, but the rejection constantly increased. With the increase of the coagulation temperature, the water flux increased but the rejection decreased. With the elongation of evaporation time, the water flux firstly increased then decreased, but the rejection slightly increased. With the increased of ambient temperature, the water flux firstly increased then decreased, but the rejection didn't change. The best preparing condition was:PES concentration was 17wt.%, PVP concentration was 12wt.%, coagulation temperature was 35℃, evaporation time was 40s, and the humidity was 52%. The water flux of the prepared membrane under this condition was 441 L·m-2·h-1 and the rejection to BSA was 92%. Compared with other reported performances of the UF membranes, the water flux of the prepared membrane was larger than others.Based on the above work, one UF membrane prepared at a condition (PES concentration was 17%, PVP concentration was 4%) was chosen to concentrate a gelatin solution. The surface tension components theory was used to explain the concentration performances of the membrane. It was found that the membrane had a good separation performance when concentrating the gelatin solution. The average rejection to gelatin protein reached 70%, and the largest flux was 17 L·m-2·h-1. With the increase of the feed flow, the flux increased, but the rejection didn't change. With the increase of operation pressure, the flux firstly linear increased, then the increasing speed of the flux became slow, but the rejection didn't change. With the increase of temperature of the feed solution, the flux increased, but the rejection decreased. With the increase of concentration of feed solution, the flux decreased, but the rejection slightly increased. The results of the measured surface tensions showed that when the interfacial tension between the membrane and the gelatin protein was larger, the membrane was more easily contaminated by the gelatin.In order to enhance the anti-contamination property of the membrane to protein, an external high voltage method was applied in this dissertation to prepare an electret UF membrane. The surface potential of the membrane was measured and the protein adsorption performances of the membrane were also measured. It was found that when the external was 0-5KV, the surface of the prepared membrane had negative charges. The external voltage had almost no influence on the membrane structure. The flux of the membrane was 135-150 L·m-2·h-1. In the basic solution with pH=8.0, the rejection of the membrane to BSA was larger than 90%. In the acidic solution with pH=2.2, the rejection was lower than 70%. Consequently, the electret UF membrane had a perfect anti-contamination property at certain pH condition when it was used to separate protein. The researched results will be benefit to further researching high performances polyethersulfone UF membranes.