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 (In) and yields (Cy) of the PMACs (PMAC-KOHop and PMAC-H3PO4op). The predicted In and Cy values closely aligned with the observed values – (PMAC-KOHop: 918.58 mg/g predicted vs. 916.56 mg/g observed; PMAC-H3PO4op: 593.44 mg/g predicted vs. 592.88 mg/g observed) and (PMAC-KOHop: 39.60% predicted vs. 39.15% observed; PMAC-H3PO4op: 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 (Vt), and average pore diameters, exhibited notable differences between the PMAC-KOHop and PMAC-H3PO4op, with the former demonstrating superiority. Particularly, FTIR spectra highlighted higher aromaticity in PMAC-KOHop, revealing the preference for KOH over H3PO4 in the chemical activation of PMps. The high In achieved with the PMAC-KOHop 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-KOHop adsorption capabilities for diverse pollutants and exploring PMps' potential contributions to metallic or nanocomposite formations with other adsorbents.