Comparative kinetic analysis of eggplant biomass and biochar as green adsorbents for lead removal from aqueous solutions

This study presents a comparative kinetic analysis of biomass and biochar as green adsorbents for removing Pb²⁺ from aqueous solutions. The adsorption efficiency of biochar (99% removal in 20 minutes) was markedly higher than that of biomass (72% removal in 30 minutes), attributed to an increase in surface area from 6.994 m²/g (biomass) to 8.664 m²/g (biochar) and the transition from an amorphous to a crystalline structure, as confirmed by X-ray diffraction (XRD) analysis. Elemental composition and surface morphology were characterized using EDX mapping and SEM analysis. Adsorption kinetics were investigated using pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models. The kinetic data for biomass conformed better to the pseudo-first-order model, suggesting physical adsorption. In contrast, biochar better fits the pseudo-second-order model, indicating superior chemisorption. Additionally, the Elovich and intraparticle diffusion models demonstrated higher correlation coefficients for biochar, underscoring its enhanced adsorption capabilities. These findings emphasize the potential of biochar as an effective adsorbent for heavy metal removal from aqueous solutions.