Adsorption Dynamics of Cd2+ (aq) on Microwave-synthetized Pristine Biochar from Cocoa pod husk: Green, Experimental, and DFT Approaches.

Biochar (BC) obtained via microwave-assisted pyrolysis (MAP) at 720 watts and 15 minutes from cocoa pod husk (CPH) is an efficient adsorbent of Cd2+(aq). BCCPH possesses favorable physico-chemical 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.