In this study, a novel method to treat the persulfate-ZVI dewatered WAS by producing a magnetic biochar as an environmentally friendly biosorbent (nZVI-WSBC) to remove heavy metals (HMs) from wastewaters was proposed. The nZVI-WSBC exhibited good adsorption property of Pb2+ and the adsorption isotherm data were fitted well to Langmuir isotherm. Corresponding reaction kinetics fitted well with the pseudo second-order adsorption model. Notably, nZVI-WSBC was successfully used for efficient removal of HMs from real. This study comprehensively demonstrates the mechanisms between Pb2+ and nZVI-WSBC surfaces, providing a breakthrough in making a sustainable biosorbent from the dewatered iron-containing WAS.