Effect of cross-linking agent concentration on adsorption performance of PVDF ultrafiltration membrane

Small molecule organic pollutants in water endanger both environmental safety and human health. However, because of their small molecular size, they are challenging to remove using conventional polyvinylidene difluoride (PVDF) ultrafiltration membranes for permeate separation. In this study, a regenerable PVDF ultrafiltration membrane with excellent small molecule organic pollutant adsorption capacity was prepared by controlling the epichlorohydrin (EPI) concentration during the cross-linking of hydroxypropyl-cyclodextrin (HP-beta-CD). It was found that raising the EPI concentration had no apparent effect on the membrane's composition but produced a dense membrane structure. When the EPI volume percentage was 2%, the cross-linked PVDF ultrafiltration membrane showed superior permeate separation and phenolphthalein adsorption compared to the base membrane (uncross-linked with HP-beta-CD). The separation/adsorption experiments under long running time revealed that the ultrafiltration membrane had good stability, and when BSA was present in the feed solution, the adsorption rates of bisphenol A and 2-naphthol with ultrafiltration membranes were 55% (240 min) and 64% (180 min), respectively, and the rejection of BSA was 90%. After 10 adsorption-desorption cycles, the cycle index of the cross-linked PVDF ultrafiltration membrane was 44% for bisphenol A adsorption and 60% for 2-naphthol adsorption.