Research On The Formation And Desalination Performance Of Desalting Layer Of Cellulose Acetate Hollow Fiber Membranes

In this paper,cellulose acetate(CA)flat membranes and CA hollow fiber membranes were prepared via complex thermally induced phase separation(c-TIPS)method.Poly(ehtyleneglyeol)(PEG400)was used as pore forming additive,N-Methyl-2-pyrrolidone and Lipid substances(LA)were used as casting solvent.To study the effect of bath temperature and diluent mixture ratio of CA flat membrane structure and performance,explored the spinning process such as spinning temperature,winding speed,air gap length on membrane structure and performance of CA hollow fiber.The desalination layer of CA film was constructed by heat treatment and surface crosslinking treatment.The effects of heat treatment temperature,crosslinking temperature,crosslinking time,and the mass fraction of aldehyde solution on the structure and properties of CA membrane were investigated.The properties of CA membranes were characterized by the water flux,desalination rate,tensile strength,SEM and so on.The best casting liquid formula,spinning process and surface crosslinking process have been obtained within the scope of this study.The results showed that the higher the temperature of the coagulation bath,the more obvious the finger hole structure in the CA flat film,and the lower the coagulation bath temperature to 10 degrees Celsius,it can effectively reduce the finger hole structure.The quality regulation of diluent mixture ratio,pore structure can control CA flat membrane,when the mass ratio of NMP/LA was 8:2,brane gradient distribution;the quality of further optimization of diluent mixture ratio,the mass ratio of NMP/LA was 8.2:1.8,structure and morphology of CA flat membrane more perfect,water flux and desalination rate of CA flat membrane were 28.27 L/(m2·h),15.43%,the tensile strength was 4.05 MPa,the best comprehensive performance.In the spinning process,in order to improve the CA hollow fiber membrane desalination,spinning temperature preparation rate increased slowly,and the water flux decreased sharply,when spinneret temperature was 130 ?,CA hollow fiber membrane cross section morphology variation,the stability of spinning system;Increasing the air gap length of the hollow fiber membrane,finger-like hole became less CA,and the morphology was more and more perfect,the water flux of membrane wire decreases and the desalination rate increased;and improved the winding speed,desalination of CA hollow fiber membranes was less affected,contributed to water flux and tensile strength;the spinneret temperature was 100 ?,the air gap length was 10 cm,wire speed 100 m/min conditions,the water flux of CA hollow fiber membrane was 15.06 L/(m2·h),desalination rate was 62.34%.In order to further improve the CA membrane and desalination,desalination layer construction of CA film was more compact,the acetalization of surface crosslinking reaction in the curing process of crosslinking temperature of 95 ?,aldehyde solution 12% mass fraction and crosslinking time 40 min,CA flat membrane desalination rate was 95.68%,the water flux was 9.85 L/(m2·h),and the desalination of CA hollow fiber membrane was 83.26%,the water flux was 6.09 L/(m2·h),desalination performance of CA hollow fiber membrane was greatly improved.