Adsorption of Pb from aqueous solutions using Fe-Mn binary oxides-loaded biochar: kinetics, isotherm and thermodynamic studies.

This study evaluated the removal of Pb in aqueous solution using Fe-Mn binary oxides-loaded biochar (BFMs). The characteristics of BFM were obtained using a scanning electron microscopy, an energy dispersive spectrometer (EDS), Brunauer-Emmett-Teller, a X-ray diffraction (XRD), and a X-ray photoelectron spectroscopy (XPS). The effects of pH, adsorbent dose, contact time, initial Pb concentration, and temperature in the batch sorption experiments were investigated. Adsorption was evaluated by adsorption kinetics, isotherm models, and thermodynamics. With the initial Pb concentration of 200 mg/L, pH 4, and 298.15 K, the optimum adsorption of BFM was obtained at a reaction time of 300 min, adsorbent dose of 2 g/L, and maximum adsorption capacity of 113.715 mg/g. Furthermore, the kinetics was best fitted to the pseudo-second-order model, whereas the adsorption equilibrium was best described by the Langmuir isotherm model. This result indicated that Pb was adsorbed onto BFM by chemical interactions through the monolayer. The adsorption was spontaneous (ΔG < 0) and endothermic (ΔH > 0).