Lead and cadmium clean removal from wastewater by sustainable biochar derived from poplar saw dust

Biochar is produced at 400–800 °C by pyrolysis of poplar saw dust, which is used as the sustainable adsorbent to investigate the adsorption performance of Pb2+/Cd2+ from wastewater. The adsorption kinetics and isotherms of Pb2+/Cd2+ on biochar were determined. The maximum adsorption amount of Pb2+ is 62.68 mg/g, while that of Cd2+ is 49.32 mg/g at pH of 5 based on Langmuir equation. The Cd2+ adsorption was seriously inhibited, while the uptake of Pb(II) was not significantly affected in the multimetal system. The adsorption performance of Pb2+/Cd2+ was also investigated in different water systems. Mineral precipitation with Pb2+ is predominant mechanism for Pb2+ removal with the contribution proportion of 51.76%. Coordination with π electrons is the primary mechanism for Cd2+ adsorption, at 59.36% of the total adsorption capacity. Our findings provide a successful example of poplar saw dust converting into the sustainable adsorbent for Pb2+/Cd2+ removal from wastewater to implement the concept of “clean production”, which is worthy of further study.