Multiple Characterization for Mechanistic Insights of Pb(II) Sorption onto Biochars Derived from Herbaceous Plant, Biosolid, and Livestock Waste

Biochars are considered as promising sorbents for the removal of aqueous metal ions. The aim of this study was to explore the adsorption mechanisms through the integrated characterization of the pristine and Pb(II)-loaded biochars derived from herbaceous plant, biosolid, and livestock waste with different physicochemical properties. The biochar derived from livestock waste exhibited higher Pb sorption capacity than the others. Experimental data of sorption kinetics and isotherms were well fitted by kinetic models and Langmuir isotherm model, respectively. Comparisons of Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) between the pre- and post-adsorption biochars revealed the formation of Pb-carbonate, suggesting that the surface precipitation was the dominant adsorption mechanism. The combination of multiple characterizations and batch adsorption can make further exploration on the adsorption mechanism of Pb(II) adsorption onto the resultant biochars.