Progress and challenges in batch and optimization studies on the adsorptive removal of heavy metals using modified biomass-based adsorbents

Surface modification increases the porosity and surface area of biomass materials, thereby enhancing their adsorption capacity. This study explores recent advancements in different surface modification technologies of biomass-based materials for the adsorption of heavy metals, including As, Cd, Cr, Cu, Co, Fe, Hg, Mn, Ni, Pb, Zn, and their ions in waters/wastewaters. Chemical structure and surface characteristics of the biomass were discussed in relation to different surface modification techniques and their impact on adsorption. Furthermore, we evaluated the adsorption performance using different operating parameters, isotherms, kinetics, and computational and Artificial intelligent techniques. This study shows that acid-activated Posidonia oceanica displayed the maximum adsorption capacity of 631.13 mg/g for removing Pb²⁺, whereas the least (0.1576 mg/g) was displayed by H₃PO₄/furnace-modified oil palm biomass for Cd²⁺ removal. To further the advancement in the field, important insight into knowledge gaps for modifying these materials for highly effective adsorption performance was highlighted.