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.