Adsorptive filtration of lead by electrospun PVA/PAA nanofiber membranes in a fixed-bed column

Poly(vinyl) alcohol/poly(acrylic) acid (PVA/PAA) nanofiber membranes were fabricated using electrospinning and showed good water stability and mechanical strength. Their application in lead (Pb(II)) removal from water was evaluated in a continuous fixed-bed column under varying conditions. The filtration was more efficient with a low feed concentration and low flow rate in terms of the elevated adsorption capacity and better bed utilization efficiency. The dynamic adsorption process was independent of bed height, so the fibers can be used as multilayer membranes in a fixed-bed column. The saturated column material could be regenerated and reused. The breakthrough curves were well fitted with the dose-response model, and the maximum adsorption capacity was 288 mg/g with the initial Pb(II) concentration of 1 mg/L. When tap water was used, the amount of water that can be treated before the effluent reached 15 μg/L increased by three times compared to the treatment of NaCl solutions, and a very high improvement was observed at pH 7 (4.5 L) than pH 5 (2.0 L) in tap water. These differences were further confirmed by the extended X-ray absorption fine structure (EXAFS) spectroscopy, where a decreased coordination number and decreased interatomic distance between Pb and C were observed for tap water. This study provides valuable insights in the application of PVA/PAA nanofiber membranes in a dynamic system for Pb(II) removal, and sheds light on the interatomic behavior between Pb(II) and the nanofiber membranes in a flow-through system.