Browsing by Autor "Cabrera, Elvia V"

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    Adsorption dynamics of Cd2+(aq) on microwave-synthetized pristine biochar from cocoa pod husk: Green, experimental, and DFT approaches.
    (2024) Correa-Abril, Jhonny; Stahl, Ullrich; Cabrera, Elvia V; Parra, Yonathan J; Vega, Michael A; Taamalli, Sonia; Louis, Florent; Rodríguez-Díaz, Joan Manuel
    Biochar obtained via microwave-assisted pyrolysis (MAP) at 720 W and 15 min from cocoa pod husk (CPH) is an efficient adsorbent of Cd2+(aq). Biochar of residual biomass of CPH (BCCPH) possesses favorable physicochemical and morphological properties, featuring a modest surface area yet a suitable porous structure. Adsorption, predominantly governed by physisorption, is influenced by the oxygen-containing active sites (-COOR, -C(R)O, and -CH2OR; R = H, alkyl). CdCO3 formation occurs during adsorption. Experimental data were well-fitted into various kinetic models for a broad understanding of the sorption process. Langmuir model indicates a maximum adsorption capacity of 14.694 mg/g. The thermodynamic study confirms the spontaneous and endothermic sorption. Studies at the molecular level have revealed that the Cd2+ ion tends to bind to surface aromatic carbon atoms. This sustainable approach produces BCCPH via MAP as a solution for waste transformation into water-cleaning materials.
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    Kinetic, equilibrium, and thermodynamic study of Methylene Blue adsorption on orange peel biochar prepared by microwave-assisted pyrolysis.
    (2026) Correa-Abril, Jhonny; Cabrera, Elvia V; Robles, Nilo; López Terán, J L; Stahl, Ullrich
    UNLABELLED: This study presents a sustainable approach for Methylene Blue (MB) dye removal using pristine, non-activated biochar derived from orange peel waste via Microwave-Assisted Pyrolysis (MAP). The key novelty lies in the systematic comparison of the biochar's adsorption performance under both pH-controlled (constant pH 4) and unregulated pH conditions, demonstrating that pH regulation is essential for optimizing adsorption efficiency. The resulting biochar exhibited a high fixed carbon content (60.89%), an alkaline surface (Point of zero charge (pHpzc) = 11.20, ZPotential = 0.1 mV @ pH 9), and oxygenated functional groups. Best MB removal of 83% was achieved at pH 4, despite the expected electrostatic repulsion. Kinetic studies showed the best fit with the Elovich model, indicating a heterogeneous surface. The Langmuir isotherm accurately described the equilibrium data, revealing a maximum adsorption capacity (qmax) of 20.57 mg g⁻1 under pH-controlled conditions, representing an 83% increase over the 11.24 mg g⁻1 obtained in the unregulated scenario. Thermodynamic analysis confirmed the process is spontaneous (ΔG° < 0), endothermic (ΔH° = + 4.88 kJ mol⁻1 at constant pH), and governed by physisorption mechanisms, including hydrogen bonding and π-π interactions. This work demonstrates that pristine orange peel biochar generated via MAP is a highly effective adsorbent and highlights the critical impact of pH control on improving adsorption capacity and elucidating the dominant physisorption mechanisms. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1038/s41598-026-36741-6.