Ultra-fine electrospun nanofibrous membranes for multicomponent wastewater treatment: Filtration and adsorption

Electrospun sulfonated polyethersulfone (SPES) nanofibrous membranes with ultra-fine mean fiber diameter, e.g., 62 ± 16 nm, were fabricated by a two-nozzle electrospinning approach and employed as a multi-functional membrane for removal of nanoparticles, dyes, and heavy metal ions from multicomponent wastewater through filtration and adsorption, simultaneously. The pore size and pore size distribution of the membrane could be varied and adjusted by controlling the fiber diameter, which affects the filtration retention of nanoparticles while the sulfonic groups located on the surface of the nanofibers work as active sites for the adsorption of dyes and heavy metal ions by electrostatic interaction. Increase in the degree of sulfonation and decrease in the concentration of solution led to the reduction of fiber diameter of the electrospun nanofibrous membranes, as evidenced by SEM and TEM measurements, in addition to the increase in the molecular weight of SPES. The adsorption kinetics and thermodynamics of the nanofibrous membrane for cationic dye and heavy metal ions were investigated, separately, in addition to the filtration performance of nanoparticle suspensions. The ultra-fine nanofibrous SPES membrane was finally tested, with simulated multicomponent wastewater containing 0.2 μm-particles, methylene blue (MB), and Pb (II) ions. The membrane exhibited high permeation flux of 320 L/m²h, high retention of >99.0% against nanoparticles, MB and Pb (II), as well as high treated capacity in the filtration performance. The nanofibrous SPES membranes after adsorption of MB and Pb (II) were able to be recovered which indicated the sustainable nature of the membrane for real wastewater treatment.