Adsorption of Pb in Solution By Modified Bean Cake Biochar

In this study, bean cake derived biochar (SYB) was modified by potassium hydroxide (KOH) (SYBK) to improve sorptive removal of Pb²⁺ from aqueous solutions. Batch sorption experiments were carried out with different sorption time, initial sorbate concentrations and pH values. The pristine and Pb²⁺ spent sorbents were characterized with the field emission scanning electron microscopy (SEM), specific surface area and pore size analyzer (BET), X-ray spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Results show that the SYBK has more abundant surface functional groups and higher specific surface area. Pb²⁺ adsorption data by SYB and SYBK were well fitted with the Langmuir adsorption model and the predicted maximum adsorption capacities were 711.0 and 293.0 mg·g^-1 for SYBK and SYB, respectively. The XRD spectra of both spent sorbents revealed that Pb₃(CO₃)₂(OH)₂ precipitate was formed after sorption reaction. Besides, large quantities of alkaline cations (e. g., Ca²⁺ and Mg²⁺) was released into solution after sorption. The results above can provide reference for preparation of biochar-based sorbents for Pb²⁺ removal from aqueous solutions.