The Study Of Preparation Of Polysulfone Ultrafiltration Membranes Modified By Silver Particles

Nowadays, ultrafiltration membrane has become an important chemical operation unit for its wide applications. People take more attention on the antibacterial property and the biofouling of the membrane. We know that silver has natural antibacterial property. Therefore, if adding the silver particles into the membrane, we would get a new kind of polysulfone ultrafiltration membrane which possesses the separation and antibacterial properties.In this work, polysulfone (PSF) was used as raw material, N,N-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) were used as mixed solvent. Different molecular weight of polyvinyl pyrrolidone (PVP) were chosen as porogen. The effects of the experimental conditions for the preparation of the sheet membranes by phase inversion technique, such as molecular weight of porogen; the concentration of casting solution and the forming process parameters on the membranes’performance were investigated. As a result, with the increasing of the molecular weight for PVP, the water flux and rejection ratio to bovine serum albumin (BSA,68kDa) solution were increased at first, and then decreased. It was found that if adding PVP K30, the water flux of the pure membrane reached178L·m-2·h-1, and the rejection ratio was91%. On the basis, silver particles were obtained from silver nitrate through reduction by DMF. New kinds of composite PSF ultrafiltration membrane with silver particles were gotten. Compared with the pure membrane, its water flux had slightly decreased, but the rejection ratio had increased. It was also found that the breaking strength of all of the composite membranes was significantly improved by38%-48%compared with the PSF membranes. What’s more, the membrane using PVP K30as porogen was excellent, its water flux was159L·m-2·h-1and the rejection ratio was94%. Qualitative antibacterial experiment showed that Ag/PSF ultrafiltration membranes have a significant antibacterial property against E.coli, and the PSF ultrafiltration membrane does not have antimicrobial properties.Based on the above results, the Ag/PSF hollow fiber ultrafiltration membrane were successfully prepared. The effects of porogen content, gas distance, the concentration of inner core fluid and the temperature of outer coagulation bath on membrane properties were investigated. The experiment found that the change of process parameters had a significantly effect on membrane separation property. With the increase of gas distance, the water flux was decreased at first, and then increased, the rejection ratio was gradually decreased, the water flux and rejection ratio were all increased at first and then decreased with the increasing of the temperature of outer coagulation bath. According to the experimental results, the excellent spinning process parameters were determined as below:the spinning solution contained PSF/DMF/AgNO3/PVP K30/NMP at a ratio of20:20:0.5:8:51.5, the gas distance was1cm, the surrounding temperature and coagulation bath temperature were20℃and40℃, respectively. The breaking strength of Ag/PSF hollow fiber membrane was6.6MPa, under0.1MPa, its pure water flux and the rejection ratio reached92.1L·m-2·h-1and91.8%, respectively. The research in this work will has efficient value for preparing a new kind of membrane which possess antibacterial and anti-fouling properties via phase inversion technique.