Sustainable removal of cadmium and copper ions using peanut shell-based adsorbent: fixed-bed column performance and phenomenologic insights

The discharge of industrial effluents containing cadmium (Cd²⁺) and copper (Cu²⁺) ions poses significant risks to human health and the environment, necessitating the removal of these contaminants before disposal into water bodies. This study aimed to evaluate the adsorption of Cd²⁺ and Cu²⁺ ions onto carbonized peanut shells (BPS) in mono and bicomponent systems using a fixed-bed column. Key parameters, including volumetric flow rate ($Q_f$), initial concentration ($C_0$), bed height (L), and regeneration cycles, were analyzed. The results showed that adsorption capacity (q, mmol·g⁻¹) increased with higher $Q_f$ (Cd²⁺: 0.085–0.182; Cu²⁺: 0.130–0.258) and $C_0$ (Cd²⁺: 0.075–0.289; Cu²⁺: 0.125–0.306), while it decreased with increasing L (Cd²⁺: 0.325–0.129; Cu²⁺: 0.357–0.170). The experimental data aligned well with the Thomas and Yoon-Nelson models, as well as a phenomenological model. BPS demonstrated consistent efficiency across four adsorption/desorption cycles (Cd²⁺: 0.132–0.095; Cu²⁺: 0.177–0.146). In conclusion, this study enhanced the understanding of the adsorption process and demonstrated the technical viability of BPS for removing Cd²⁺ and Cu²⁺ ions in fixed-bed systems. These findings provide a foundation for further applications and research in this area, such as scale-up for wastewater treatment plants, development of hybrid adsorption systems using agricultural systems, application in permeable reactive barriers, metal recovery, promoting environmental sustainability.