Statistical optimization of iodine adsorption for <i>Pentaclethra macrophylla</i> pods activated carbon production

Abstract

Efficient production of activated carbon (AC) depends on variables such as feedstock properties, preparation conditions, and activating agents. This study aimed to identify optimal conditions for AC production from African Oil Bean (Pentaclethra macrophylla) Pods (PMps) using potassium hydroxide (KOH) and phosphoric acid (H₃PO₄) as activating agents. Through a systematic iodine adsorption characterization approach and leveraging Response Surface Methodology as a chemometric tool, the study fine-tuned chemical activation and carbonization parameters (temperature, time, and impregnation ratio) for producing PMACs. The adjustments directly impacted the iodine number (I_n) and yields (C_y) of the PMACs (PMAC-KOH_op and PMAC-H₃PO_4op). The predicted I_n and C_y values closely aligned with the observed values – (PMAC-KOH_op: 918.58 mg/g predicted vs. 916.56 mg/g observed; PMAC-H₃PO_4op: 593.44 mg/g predicted vs. 592.88 mg/g observed) and (PMAC-KOH_op: 39.60% predicted vs. 39.15% observed; PMAC-H₃PO_4op: 51.30% predicted vs. 51.10% observed), demonstrating precision of the production process. Key structural properties, including BET specific surface areas (SSA), total pore volumes (V_t), and average pore diameters, exhibited notable differences between the PMAC-KOH_op and PMAC-H₃PO_4op, with the former demonstrating superiority. Particularly, FTIR spectra highlighted higher aromaticity in PMAC-KOH_op, revealing the preference for KOH over H₃PO₄ in the chemical activation of PM_ps. The high I_n achieved with the PMAC-KOH_op indicated its efficacy as a pollutant adsorbent, aligning with the established attributes of commercial granular activated carbons for pollutants removal from wastewater. This study establishes PMps as a dependable AC precursor, emphasizing the advantages of KOH over H₃PO₄ in chemical activation. Future research should be directed at investigating PMAC-KOH_op adsorption capabilities for diverse pollutants and exploring PMps' potential contributions to metallic or nanocomposite formations with other adsorbents.