Dual role of polyethyleneimine as membrane matrix and additive for PEEKWC-PEI crosslinked ultrafiltration membrane

In this study, the dual role of polyethyleneimine (PEI) in the PEEKWC-PEI crosslinked ultrafiltration (UF) membrane was achieved through a two-stage addition method. PEI acted as membrane matrix and additive for the formation and enhancement of PEEKWC-PEI crosslinked UF membrane. The morphological structure, filtration, and permeability properties of UF membranes were studied by selecting suitable PEI concentration and molecular weight. Compared with previously reported studies, the filtration flux was significantly improved while maintaining excellent dye flux, and exhibited extremely low salt ion retention rates, resulting in significantly superior dye/salt separation factors. Increasing the PEI concentration in the casting solution from 0.5 to 4 wt% enhanced the surface pore density and rejection of layer, and the total porosity rose from 71.9 % to 84.5 %. The optimized PEI-1800–2.0 membrane exhibited a pure water flux of 1210.9 LMH and a 99.8 % rejection of Congo red (CR) solution at 3 bar. The molecular weight of additive PEI also showed a significant effect on membrane performances. Among them, the PEI-10000 additive further improved hydrophilicity, elevating the water and dye fluxes to 1309.06 LMH and 786.70 LMH, respectively. The PEI-1800–2.0 membrane can achieve a flux recovery rate (FRR) of 85.8 %, showing excellent contamination resistance. In the test of dye/salt mixed solution with high salt concentration (60 g/L Na 2 SO 4 ), it also showed good retention stability, and the dye removal rate was maintained at 85.5 %. The present work provides a reliable and effective method for the preparation of UF membranes with high filtration performance and high retention capacity even at high salinity. From the comparison of dye/salt separation performance results between membrane in this work and membranes reported in literatures for dye/salt separation, it could be noted that the dye solution flux of PEEKWC-PEI crosslinked UF membrane based on PEI additive significantly improve and the salt retention rate is significantly reduced.