iScience (Jun 2024)

Adsorption dynamics of Cd2+(aq) on microwave-synthetized pristine biochar from cocoa pod husk: Green, experimental, and DFT approaches

  • Jhonny Correa-Abril,
  • Ullrich Stahl,
  • Elvia V. Cabrera,
  • Yonathan J. Parra,
  • Michael A. Vega,
  • Sonia Taamalli,
  • Florent Louis,
  • Joan Manuel Rodríguez-Díaz

Journal volume & issue
Vol. 27, no. 6
p. 109958

Abstract

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Summary: 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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