Competitive adsorption of two phenolic pollutants compounds using a novel biosorbent: Analytics (HPLC), Statistical (experimental design), and theoretical studies (DFT)

In this study, we focused on a novel agricultural waste material, specifically a plant known as Nicotiana glauca Graham (NgG), which is highly abundant in Morocco. The investigation involved testing four activating agents H₃PO₄, H₂SO₄, NaOH, and ZnCl₂ on Nicotiana glauca Graham (NgG) to assess their effects. By employing an experimental design, we successfully determined the optimal conditions for this activation process. The resulting activated carbon was then evaluated for its effectiveness in removing two phenolic pollutants, Bisphenol A (BPA) and β-naphthol (BNL). Analysis using FTIR revealed various functional groups on the activated carbon surface, including P = O, P-O-C aromatics, and O-H groups, which played a crucial role in the adsorption of BPA and BNL. XRD analysis indicated that the optimal adsorbent was amorphous, while Zeta potential measurements showed a significant decrease in pollutant removal rates after reaching a pH level of nearly 10. The activated carbon produced from H₃PO₄ exhibited a surface area of 1078 m²/g. Experimental adsorption results at the highest removal rate showed q_BPAs = 125.82 mg/g for BPA and q_BNLs = 62.82 mg/g for BNL in individual mode, while in the mixed mode, q_BPAm = 16.22 mg/g for BPA and q_BNLm = 16.04 mg/g for BNL were observed. To enhance our study, we utilized Density Functional Theory (DFT) calculations to identify the most electrophilic and nucleophilic regions on BPA and BNL. The analysis highlighted the hydroxyl groups (–OH) of BNL and BPA as the most significant negative zones, crucial for understanding the underlying mechanisms and explaining the experimental observations. In the isotherm analysis, we identified the Temkin model in a singular mode and the Langmuir model in a mixture mode, showcasing a notable distinction between the two modes.