Enhanced Lead Sorption by Biochar Derived from Anaerobically Digested Sugarcane Bagasse

This study examined the ability of two sugarcane bagasse biochars to remove lead from water. The sorption of lead by biochars made from raw (BC) and anaerobically digested sugarcane bagasse (DBC) was compared with a commercial activated carbon (AC) using batch sorption experiments. DBC was a more effective sorbent of lead from water than AC, and far more effective than BC. The maximum lead sorption capacity of DBC (653.9 mmol kg−1) was about double that of AC (395.3 mmol kg−1) and about twenty times higher than that of BC (31.3 mmol kg−1). Post-sorption characterizations using X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated that the enhanced sorption of lead by DBC was at least partly related to a precipitation mechanism, while surface adsorption was the principal mechanism of sorption of lead onto BC. These results suggest that biochars made from bagasse and other agricultural residues may be effective alternative, low-cost environmental sorbents of lead or other metals. In addition, the enhanced lead sorption ability of the digested bagasse biochar introduces the possibility of developing a novel carbon production method to use anaerobic digestion as a means of biological activation to create high-efficiency sorbents.