Study on structure and properties of polysulfone membranes using ionic liquid [n-C16mim][BF4] as a new structure-controlled additive

Introducing ionic liquid [n-C(16)mim][BF4] as a new structure-controlled additive, Polysulfone (PSf) membranes were prepared by the wet-phase-inversion using [n-C(16)mim][BF4] into the casting solution (PSf/NMP). The scanning electron microscope and the atomic force microscopy were utilized to visualize the cross-sections of the membranes to gain more better understanding the structure-controlled ability of [n-C(16)mim][BF4] and surface morphologies of the membrane. The results indicate that the structures of the membranes were typical bilayer asymmetric finger-pores structure. [n-C(16)mim][BF4] has stronger ability of the pore-forming. Especially, at the 4:76 ratio of [n-C(16)mim][BF4]/NMP in the polymer solution,the membrane has the asymmetric structure and good separation properties of the solution flux. The PSf membrane has the 0.45 similar to 0.65 mu m dimpling close to surface layer, and the retention rate and solution flux of the prepared membrane are 95.2% and 137.5 L.h(-1).m(-2). Meanwhile, [n-C(16)mim][BF4] partially retained in the prepared Polysulfone membrane reduced the contact angles of Polysulfone membranes, improving the hydrophilic properties of the membranes.