Design of nitrogen-phosphorus-doped biochar and its lead adsorption performance.

The surface properties of the adsorbents and the acidic environment have an influence effect on Pb adsorption. In order to further improve the adsorption performance of biochar, we herein reported an effective method to synthesize high-adsorbed biochar by co-doping with nitrogen and phosphorus. After atom doping, the N/P co-doped biochar (NP-BC) showed the enhanced adsorption capacity for lead ion (Pb). The adsorption kinetics, isotherm, pH value, and influencing factors were studied. The results show that the synthesized NP-BC has high Pb adsorption capacity in aqueous solution, and can be maintained with various environmental interference factors including pH, natural organic matter, and other metal ions. High adsorption performance shows that the material may be well used to remove Pb in various water bodies. Various characterization experiments prove that surface properties contribute to Pb adsorption, and the high performance of NP-BC is mainly due to the surface complexation between functional groups and Pb. This work demonstrates that the surface functional groups of biochar are critical to the development of high-performance heavy metal adsorbents.