Improved dye and heavy metal ions removal in saline solutions by electric field-assisted gravity driven filtration using nanofiber membranes with asymmetric micro/nano channels

•Formation of asymmetric micro/nano channels in nanofiber membrane by phase inversion.•Rejection of 98% dye and 4% salt, for a solution of 100 ppm methyl blue and 3% NaNO3 at 10 V.•Flux of 75 L m−2 h−1 at 0.1 bar for 98% rejection of methyl blue at 10 V.•Over 99% removal of Cu2+ and Ni2+ from 5000 ppm NaCl solution at 10 V.