Preparation And Characterization Of PES-SPPESK Nanofiltration Membrane

A new low pressure nanofiltration (NF) membrane was firstly prepared via phase inversion method from casting solution composed of polyethersulfones (PES), sulfonated poly(phthalazinone ether sulfone ketone)(SPPESK), diethylene glycol (DEG) and N-methyl pyrrolidone (NMP). And the properties such as mechanical properties, water permeability, pore size distribution, dynamic contact angle and scanning electron microscope (SEM) analysis of PES-SPPESK NF membranes were characterized. In this study, effects of the total polymer content, SPPESK content, DEG content, composition of coagulation bath and temperature of casting solution on PES-SPPESK flat-sheet NF membrane performances have been investigated. Meanwhile, the effects of bore fluid composition, distance of air gap and temperature of external coagulation bath were considered on the hollow fiber membrane.Firstly, the mixed parameters of SPPESK, solvents (NMP) and nonsolvents [glycerol, ethylene glycol (EG),1,2-propylene glycol (1,2-PG), dipropylene glycol (DPG), diethylene glycol (DEG)] were tested and calculated through turbidity titration. The results showed that, DEG was the best nonsolvent for SPPESK/NMP solution.Secondly, the effect of the total polymer content, ratio of PES and SPPESK, PEG content, composition of coagulation bath had been investigated on flat-sheet NF membranes. The results showed that, when the mass ratio of PES/SPPESK was fixed, the rejection was increased obviously with the increase of the total polymer content, and there was an optimum value of SPPESK content by increasing the SPPESK content in total polymer. When the PES/SPPESK/NMP was16/16/68, the permeation of membrane was14.6L·m-2·h-1under1bar, and the rejection of Na2SO4and PEG4000arrived at41.4%and75.9%, respectively. When DEG was added into the casting solution, the cross-sectional morphology of the prepared membrane changed to regular finger-like pores. Through changing the composition of coagulation bath, the gel rate had been controlled, and the cross-sectional morphology of the prepared membranes changed from exhibiting finger-like pores to exhibiting sponge-like pores.Then, the prepared membranes under optimization conditions were used to deal with X-BR dye wastewater. The flux and rejection arrived at10L-m-1·h-1and86%, respectively. With the increase of dye concentration and operation time, the membrane exhibited excellent stability and anti-fouling on dye waste water treatment.Finally, on the basis of the experimental results of PES-SPPESK flat-sheet NF membrane under optimization conditions, the hollow fiber NF membranes were prepared via dry-wet spinning process. The compositon of dope solution was PES/SPPESK/NMP/DEG (16wt%/16wt%/62wt%/6wt%), the effects of bore fluid composition, distance of air gap and temperature of external coagulation bath on the performance and structure of hollow fiber membranes were studied. The results showed that, with the increase of external coagulation bath temperature and air gap distance, the difference in temperature between external coagulation bath and dope solution decreased. It was not conducive to the formation of dense layer surface. Thus, the flux increased and rejection decreased. The gel rate of membrane inside surface slowed down by changing the composition of internal coagulation bath (adding NMP or DEG to the internal coagulation bath). It was conducive to form pores on the membrane inside surface. Therefore, the flux increased.