Preparation Of PVDF Hollow Fiber Membranes And Application Of Dye Desalination

In this study,a PVDF hollow fiber nanofiltration membrane was successfully prepared using a single orifices spinneret.The spinning process does not need bore liquid with using NIPS cooperated with gas generation.Eventually the hollow structure formed by hydrogen gas gathering into interconnected large cavity,which generated by reacting NaBH4 with hydrochloric acid in the coagulation bath.By adding hydrophilic TiO₂ to the cast solution,the performance of the hollow fiber membrane with different amount TiO₂ was optimized by comparing the Congo red flux and rejection of the hollow fiber membrane,and it was determined that the TiO₂ was 0.5%is the best.SEM test showed that adding 0.5%TiO₂ could make the structure of hollow fiber membrane more regular,and the test of zeta potential on the membrane surface showed that the TiO₂ could enhance the positive and negative potential value of the film.The molecular weight of the hollow fiber membrane rejection PEG is 1273 Da,the rejection rate of Congo red and methylene blue is above 99.9%,and the rejection rate of NaCl and Na2SO4 is 4.8%and 14%respectively,which can be applied to dye desalting.After 10 hours of continuous operation,the hollow fiber membrane to the Congo red dye retention rate remained stableAfter adding anhydrous LiCl to the cast solution,by comparing the flux and rejection of Congo red by the hollow fiber membrane prepared under different dosage,the best performance of the hollow fiber membrane was determined when the addition of LiCl was 3%.The rejection rate of the hollow fiber membrane to Congo red is 100%,the pure water flux is 13.51 L·m-2·h-1·bar-1 and has good mechanical properties.SEM shows that the outer layer of the hollow fiber membrane is a dense separation layer,and the inner surface is a spherical crystal structure with no skin layer,and the structure of the finger-like pore and the cavernous pore is clear.The zeta potential test of the surface shows that in the electric point is pH=3.8,and the membrane is negatively charged in the neutral solute.The molecular weight of PEG rejection was 6798 Da,the average effective pore size was 1.32 nm and the pore size distribution was narrow.The retention rates of the hollow fiber membrane were more than 99.9%for Congo red,chrome black T,methyl blue,reactive black 5,and alphazurine A.The retention rate of the disperse black 9 dye with the molecular weight of 300 Da is 99.69%.The retention rates of Na2SO4 and NaCl were 16.01%and 4.47%respectively.In the range of pH=2-10,the hollow fiber membrane was stable for the retention of Congo red dye.In the process of desalination from dye solution,changed dye concentration and salt concentration the retention rate of dye was stable.After 48 hours continuous dye desalting test,the retention rate of dye and NaCl remained stable,which showed that the hollow fiber membrane has a wide application prospect in the field of dye desalination.