Thin Film Filtration Composite Membrane Based On Nanofibrous Scaffolds And Cellulose Triacetate (CTA) Coatings

Electrospinning is a technology which can prepare continuous and very thin nanofibers whose diameter is low to several nanometers. Its principle is:the polymer solution or fused mass is influenced by electric field. It overcome the surface tension of itself; pour out from spinneret and form a narrow stream. The solvent evaporated or the fused mass froze while the narrow stream form very thin fibers on the receive equipment. Elcetrospinning is an alternative technology that can be used to prepare a porous support which exhibits a high porosity and an improved pore-size distribution. Here, cellulose triacetate thin film composite nanofiltration (NF) and ultrafiltration (UF) membrane based on electrospun nanofibrous substrate were prepared by remelt method and sol-gel phase inversion method. Furthermore, the relationship between the structure and their performance of the composite membranes under relevant experimental conditions were studied in detail.Electrospun PAN nanofibers were used as the substrate in this experiment. For guarantee the performance of the CTA composite membrane prepared later, we studied the parameters of the Electrospun PAN. We chose the 10wt% PAN solution to electrospin. Furthermore, the PAN nanofibrous substrate was heat-press-treated. The treated PAN nanofibrous membranes possessing lower surface pores and smooth surface.At the process of preparing CTA composite nanofiltration membrane by remenlt method, the CTA nanofibers were electrospun on the surface of electrospun PAN nanofibrous substrate. Subsequently, the CTA surface layer was treated by solvent bath. Relation between CTA concentrations and remelt condition was investigated to get optimized film formation techniques.Scanning electron microscopy (SEM) was used to characterize the structure of CTA composite membrane. The membranes were optimized for preparation a thin barrier layer of cellulose triacetate on PAN nanofibrous substrate, and the optimized solvent bath time was 12min. Filtration perfonnances of cellulose triacetate NF composite membranes were investigated for water desalination. When the operating pressure is fixed at 0.7MPa, solute rejection of CTA composite membranes for separation of artificial dye solution(1000 mg/L) reached 98.4% and the corresponding permeate flux is 44.1L/m2·h, separation of MgSO4 solution(1000 mg/L) reached 86.8% and the corresponding permeate flux is 58.6L/m2·h; Separation of NaCl solution (1000 mg/L) reached 44.7% and the corresponding permeate flux is 71.3 L/m2·h.The CTA coating was prepared using sol-gel phase inversion method based on PAN nanofibrous substrate. In this way, we prepared the CTA composite NF membrane. The effect of coagulation bath temperature, CTA concentration in cast solution and the filtration pressure was demonstrated in this paper.As for the CTA/PAN composite ultrafiltration membranes, increasing coagulation bath temperature or CTA concentration in cast solution both lead water flux decreased while rejection rate for oil/water emulsion separations increased. CTA/PAN composite NF membranes with 10wt% CTA coating exhibited good organic rejection rate(99.1%) and high corresponding permeate flux is 276.3 L/m2·h.