Characterizing the removal of Pb2+ and Zn2+ from an acidic smelting wastewater using electrocatalytic internal Fe0/C micro-electrolysis

•ECIME fluidized-bed was optimized to co-removal of Pb2+, Zn2+ for zero discharge.•Reaction characteristics difference of Pb2+ and Zn2+ by ECIME were investigated.•Polarization Fe0/C particles act as microelectrodes promoted Pb2+ and Zn2+ reduction.•Two main mechanisms with four reaction processes contribute to metal ions removal.•Pb remove main depended on electrodeposition (64%) and Zn was iron flocculation (63%).