Preparation And Characterization Of PES/SPES Blend Nanofiltration Membrane

polyethersulfone(PES)/Sulfonated poluethersulfone(SPES) flat nano filtration membrane and hollow fiber nano filtration membrane was prepared by the nonsolvent induced phase separation(NIPS) method, and the properties such as permeation properties, rejection, contact angle, pore size distribution, SEM were also tested. In this study, the effects of solvents, concentration of polymers, the ratio of SPES to PES, the ratio of solvent to nonsolvent, the composition of coagulation bath and the evaporation time under60℃were considered on the plate nano filtration membrane. And the effect of bore fluid composition and the air gap were considered on the hollow fiber membrane.Firstly, the mixed parameters of SPES, solvents Dimethylacetamide(DMAc), N,N-Dimethylformamide(DMF), N-methyl-2-pyrrolidone(NMP) and nonsolvents Glycerol, Ethylene Glycol(EG),1,2-Propylene Glycol(l,2-PG), Dipropylene Glycol(DPG), Diethylene Glycol(DEG) were achieved through turbidity titration. And the solvent parameters were also calculated through group contribution method. The results showed that, DMAc was a good solvent of SPES, DEG was a weak solvent of SPES.Sencondly, the effects of solvents, concentration of polymers, the ratio of SPES to PES, the ratio of solvent to nonsolvent, the composition of coagulation bath and the evaporation time under60℃were considered on the structure and properties of plate nano filtration membrane. The results showed that, solvent had a huge effect on the properties of membrane, which made by DMAc had a better properties on permeation and rejection. The flux decreased and the rejection of PEG-10000increased first and then tended to be flat when the concentration of polymers became denser. And the rejection reached the highest when the concentration of polymers was as high as34%. The hydrophilicity of nano filtration membrane decreased as the ratio of SPES decreased, thus the flux decreased while the rejection of PEG-10000increased first then decreased, it reached the peak when PES:SPES was1:1. When the nonsolvent increased, the flux decreased while the rejection of PEG-10000increased first then almost kept the same. The molecular-weight cut-off (MWCO) was under4000Da, and the membrane was negatively charged NF membrane by measuring the rejections of different solutions.At last, the hollow fiber nano filtration membranes were prepared via dry-wet spinning process. The compositon of dope solution was SPES/PES/DMAc/DEG(17%wt.%/17%wt.%/4%wt.%/62%wt.%), the effect of bore fluid compositon and air gap on the permeation and rejection properties, pore size distribution and SEM were studied. The results showed that, the mean pore size and flux increased when the ratio of DMAc increased in bore fluid, but the rejection of PEG-10000almost kept the same. And the same conclusion could be gotten when the air gap became longer. The mean pore size of hollow fiber nano filtration membrane was2.41nm, and the membrane was negatively charged NF membrane by measuring the rejections of different solutions.