Bipolar jet electrospinning bi-functional nanofibrous membrane for simultaneous and sequential filtration of Cd2+ and BPA from water: Competition and synergistic effect

Novel bi-functional nanofibrous membrane (APAN/CS/PVA-NM) was prepared by modified bipolar jets electrospinning for chemical filtration of BPA and Cd2+ from water. Due to opposite charge, chelating fiber (APAN) and mesopore fiber (CS/PVA) intertwined each other in a rotating collector, and formed fibrous membrane APAN/CS/PVA-NM. With high mechanical strength and permeation performance, APAN/CS/PVA-NM was preferably applied in filtration model. Cd2+ removal by APAN/CS/PVA-NM was primary due to chelating interaction, while BPA removal was mainly by intermolecular force and hydrogen bonds. Although the operation model of chemical filtration was much different from that of fix-bed adsorption, APAN/CS/PVA-NM could be considered as a thin layer fix-bed so that filtration breakthrough curves of BPA and Cd2+ from single solution were well predicted by Thomas model. As simultaneous filtration of binary solution, Cd2+ show adverse effect on BPA removal because of the competition for APAN/CS/PVA-NM amino groups. However, with the increase of filtration time, more BPA adsorbed on APAN/CS/PVA-NM by intermolecular force could subsequently act as bridge molecular to increase the Cd2+ removal. Furthermore, although preload of Cd2+ or BPA were replaced by each other and released into solution during the sequential filtration experiment, APAN/CS/PVA-NM could still remove BPA or Cd2+ sequentially. Multiple filtration-elution experiments indicated that more than 96% of Cd2+ and BPA could be sequentially desorbed by HCl solution (2.0 mol/L) and ethanol, respectively. Even after 10 times cycles, APAN/CS/PVA-NM could still remain high removal rate for Cd2+ and BPA. Thus, the present work not only provided a promising membrane for simultaneous/sequential filtration of Cd2+ and BPA from water/wastewater but also expanded the application of electrospinning fibrous membrane in environmental protection.