Fabrication of L-cysteine stabilized α-FeOOH nanocomposite on porous hydrophilic biochar as an effective adsorbent for Pb2+ removal.

Lead (Pb) pollution has caused worldwide attention as it can cause hazards to humans and the environment. Chemical properties and structures of the adsorbent greatly influence the Pb2+ removal efficiency. L-cysteine (L-cy) stabilized porous hydrophilic biochar-supported α-FeOOH nanocomposites (L-cy/FeOOH@PHB) are prepared as an efficient adsorbent via a cheap and simple one-step hydrothermal method for removing Pb2+ from aqueous solution. Characterizations of the synthesized L-cy/FeOOH@PHB revealed that the iron particles distributed uniformly on the surface of porous hydrophilic biochar. The equilibrium adsorption capacity of the L-cy/FeOOH@PHB reaches up to 103.04 mg g-1for Pb2+ removal, higher than other typical materials reported preiously. The adsorption kinetics and isotherms were fitted well with the pseudo-second-order model and the Freundlich model, respectively, suggesting chemical adsorption on the heterogeneous surface and pores of L-cy/FeOOH@PHB. The introduction of L-cysteine provides abundant surface N- and S-containing functional groups as active sites for Pb2+ adsorption and also plays an important role in altering the porous structure, distribution of α-FeOOH nanoparticles, affinity of iron species to biochar, and surface functional groups, which determined the performance of the resultant composites. Notably, regeneration experiments show that Pb2+ adsorption capacity still maintains at 77.3 mg g-1 on L-cy/FeOOH@PHB after five successive utilizations, indicating the potential applicability for removing Pb2+ from aqueous solution.