Preparation of a high performance PES/PES-OH Loose nanofiltration membrane based on reactive porogen

Loose nanofiltration membranes (LNF) have wide applications in the field of precise separation of small organic molecules. However, high separation precision of organic molecules with salts and a high water flux are still the challenges in the commercial applications of LNF membranes. In the current work, polyethersulfone (PES)/ hydroxylated polyethersulfone (PES-OH) LNF membranes were synthesized by nonsolvent-induced phase separation (NIPS) based on reactive porogen (butyl dicarbonate, BDC) for the first time. The reactive porogen was decomposed to produce nanobubbles during heat-treated casting solution and phase inversion in HCl coagulation. It was found that the heat-treatment temperature of the casting solution was higher, the viscosity of the solution at 20 degrees C was higher due to the existence of more nanobubbles from BDC decomposition in the casting solution. Moreover, heat-treatment temperature had decisive impacts on the structure and separation property of the formed LNF membranes as nanobubbles actually acted as pore-forming agents. The HCl coagulation/immersion baths also promoted the BDC decomposition to produce the nanobubbles and improved the transmembrane water flux without sacrificing rejection and separation precision performance. The synthesized LNF membrane had a pore diameter approximately 3.81 nm, with a flux up to 200.2 L & sdot;m(-2)& sdot;h(-1). Direct Black 38 shows a rejection of > 99 %, whereas NaCl shows a rejection of < 5 %, exhibiting a good separation accuracy and found superior to the separation performance in the literature. This research result has offered a novel approach for the preparation of superior performance LNF membranes, which can be utilized for precise separation.