Biochars from Lignin-rich Residue of Furfural Manufacturing Process for Heavy Metal Ions Remediation

The pentose/furfural industrial manufacturing process uses corn cob residue as a raw material, where such a process yields significant amount of lignin-rich residue (LCR) at the end, which is commonly disposed by burning. In this study, the conversion of LCR to biochars (BCs), and their subsequent applications for heavy metal ion removal, were investigated. The BCs were prepared through hydrothermal carbonization and post-activation, using either ZnCl₂ or H₃PO₄ treatment. The as-prepared activated BCs were characterized using N₂ adsorption-desorption isotherms, XRD, FT-IR, SEM and TEM, and their performance in removing heavy metal ions (Pb²⁺, Cu²⁺, Cd²⁺) from aqueous solutions was assessed. The ZnCl₂-activated BCs (BC-ZnCl₂) exhibit a higher adsorption capacity than the H₃PO₄-activated BCs (BC-H₃PO₄), mainly due to the differences in their chemical/physical characteristics. The related adsorption kinetics and isotherms were analyzed.