The Studies Of Preparation And Performance Of Polyethersulfone Ultrafiltration Membrane Modified By Nano-Silver Particles

During the permeation of polymer membrane, the existence of a large sewage in waste water, such as colloids, proteins and microbes can cause membranes fouling, which lead to reductions of water flux and separation property, thereby increasing the cost of the membrane application. Customary water purification methods usually use ozone and sodium hypochlorite to sterilization. The residual disinfectants in water can cause secondary pollution. Silver as traditional anti-bacterial material, has strong abilities of sterilization and inhibition bacterial growing.In this dissertation, an in situ reduction method was used to prepare nano-silver modified polyethersulfone (PES-Ag) ultrafiltration (UF) membrane casting solution. Under the portaction of polyvinylpyrrolidone (PVP), ethylene glycol was used as reducing agent to reduce AgNO3into nano-silver particles in the PES solution. PES-Ag flat and hollow fiber UF membranes were prepared by immersion-precipitation phase inversion.UF performance experimental data showed that the water flux and bovine serum albumin (BSA) protein rerejection rate of PES-Ag UF membranes were greater than the unmodified PES membranes. Flux recovery rate experiments showed that the against BSA contamination capacity of PES-Ag membranes were stronger than original PES membranes. As the meantime, PES-Ag membrane could inhibit E. coli from growing and improve the ability of anti-biological contamination.In this work, the effect of coagulation bath temperature (CBT) on the nano-silver particles modified PES flat UF membranes structures and separation performances, and the stability of the nano-silver particles were researched. With the increase of CBT, the thickness of sponge-like sublayer of PES-Ag flat membranes decreased and the size of finger-like pores enlarged. The water flux and rejection rate largely depended on the morphology of the membranes. Thus, as the CBT increasing, the water flux of PES-Ag flat membranes increased while the rejection rate decreased. The tensile strength of PES and PES-Ag flat membranes reduced with the increase of CBT. The results of silver stability revealed that PES-Ag flat membrane prepared in40℃coagulation bath showed a low nano-silver loss rate that was only18.5%; the water flux and rejection rate were393L·m-2·h-1and95.2%, respectively.Effect of PVP content on PES-Ag hollow fiber structures and performances, and the stability of nano-silver particles were also researched in this work. With the increase of PVP content, the structures of PES and PES-Ag hollow fiber changed from asymmetric structure with finger-like sublayer and sponge-like support layer into double row finger-like symmetrical structure. With the raise of PVP content, the water flux increased, while the rejection rate decreasd. When the PVP content was7.5%, antifouling ability of PES-Ag hollow fiber achieved the strongest, at this time the overall performances of the PES-Ag hollow fiber were best. The silver content of the PES-Ag hollow fiber was98.7%of added amount; the water flux, rejection rate and breaking strength were183L·m-2·h-1,94.5%and2.87MPa, respectively.