Pollution caused by toxic heavy metals emanating from various anthropogenic activities poses a significant risk to the environment owing to their non-biodegradability and tendency to bioaccumulate in living organisms. Biochar derived from agricultural waste has emerged as a promising, eco-friendly adsorbent for removing heavy metals from wastewater. This review critically evaluates the adsorption performance of biochars derived from corncob (CCB) and sugarcane bagasse (SBB) for the removal of different heavy metals, including Pb, Cu, Cr, Ni, As, Hg, Cd, and Zn from wastewater. Reported studies indicate that biochars produced via pyrolysis at 300-700 °C exhibit well-developed porous structures, with surface areas reaching up to 520 m 2 /g for CCB and 697 m 2 /g for SBB. Under optimized conditions (pH of 2-11, contact time of 5min-24 h, adsorbent dosage of 0.05-4.0 g, and temperature of 25-50 °C), adsorption efficiencies typically range from 47.3 to 99.4% for CCB and up to 92% for SBB, with substantially higher capacities achieved following surface modification. This is consistently supported by the kinetic, isotherm, and thermodynamic analyses. Regeneration studies further demonstrate that both biochars retain significant adsorption capacity over multiple cycles. Generally, this review highlights the comparative advantages of CCB and SBB, identifies key knowledge gaps, and outlines future research directions to optimize their application as low-cost, sustainable adsorbents in wastewater treatment, thereby contributing to the achievement of Sustainable Development Goals 6, 11, and 12. • Corncob and sugarcane bagasse biochars are effective biomass-derived adsorbents for heavy metals. • Pyrolysis conditions significantly influence biochar structure and adsorption performance. • Chemical and nano-modifications enhance surface functionality and metal uptake. • Adsorption mechanisms involve pore filling, ion exchange, and surface complexation. • Biochar valorization supports sustainable biomass utilization and circular bioeconomy.
Muritala et al. (Fri,) studied this question.