The influence mechanism of cross-linking agent relative molecular mass on in-situ cross-linking in PES membrane matrix

Abstract

In this paper, three cross-linking agents with varying relative molecular mass (RMM) were used to initiate in-situ cross-linking reaction in polyether sulfone (PES) membrane matrix, novel PES membranes were prepared through non-solvent induced phase separation (NIPS). Thereafter, the mechanism underlying cross-linking agent RMM’s influence on membrane structure and properties was analyzed. The results indicated that for the same proportion of dope solution system, cross-linking agents with smaller RMM will have more molar mass epoxy groups participating in the ring-opening reaction, which can form more hydroxyl groups in the subsequent cross-linking reaction, leading to a significant improvement in the hydrophilicity of PES membrane. Meanwhile, system with lower RMM of cross-linking agent had faster double diffusion rate in phase separation, and the larger most probable pore size formed in our modified membrane will further improve the permeation flux. The cross-linking network generated by the membrane formation system with low RMM of the cross-linking agent was more complete, and this modified membrane had a tensile strength maintained at 3.5Mpa. Relative to the original PES membrane, our optimal modified membrane has fourfold increased permeation flux, reaching 667.8 L·m⁻²·h⁻¹. Meanwhile, BSA rejection of the membrane can be maintained at 96.7 %. Our modified membrane has improved antifouling efficiency, exhibiting persistent hydrophilicity during the 21-day washing experiment.