Biochar Derived from Sawdust Embedded with Molybdenum Disulfide for Highly Selective Removal of Pb²⁺

Surface interactions between the adsorbents and heavy metal ions play an important role in the adsorption process, and appropriately decorating the material’s surface can significantly improve the removal capacity of the adsorbents. So, the objective of this study is to modify biochar by coating with molybdenum disulfide (MoS2) for enhancing the adsorption of Pb2+. The biochar pyrolyzed at 600 °C was chosen as the base to combine the flowerlike MoS2 (MoS2@biochar) by solvothermal reaction, in which the abundant S-containing functional groups may promote the elimination of Pb2+. The prepared MoS2@biochar exhibits excellent adsorption capacity (189 mg/g) to Pb2+ in water solution. The adsorption of Pb2+ maintains a high level under the circumstance of coexisting ions (Mg2+, Ca2+, Co2+, and Cd2+), suggesting the high selectivity for Pb2+. The adsorption mechanism of Pb2+ on MoS2@biochar is mainly ascribed to the inner-sphere surface complexation, in particular, metal–sulfur chemical complexation. The easily recycled MoS2@biochar still has high adsorption capacity for Pb2+. This work demonstrates that the MoS2@biochar is an excellent candidate of adsorbent for Pb2+ removal.