Preparation of activated carbon from Moroccan argan press cake using KOH activation and its application for CO2 adsorption

Abstract

Activated carbon (AC) materials were synthesized from argan press cake (APC), leveraging its unique structure and composition, which makes it an ideal precursor for activated carbon production. The synthesis involved initial carbonization of raw APC, followed by activation with potassium hydroxide (KOH) using a 1:1 KOH weight ratio. This study systematically examined the influence of activation temperature on the properties of the resulting activated carbons crucial for their carbon dioxide (CO₂) adsorption performance at 0 and 25 °C. Comprehensive characterization of the ACs was performed using gas adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). XRD analysis revealed the amorphous nature of the activated carbons, while FTIR provided insights into the surface functional groups, confirming the presence of oxygen-containing functionalities essential for CO₂ adsorption. The results underscored the significant impact of microporous structure on CO₂ adsorption performance, with activation temperatures ranging from 700 to 850 °C yielding ACs with BET surface areas between 1200 and 1750 m²/g for the 1:1 KOH weight ratio. CO₂ adsorption modeling was performed to predict adsorption behavior under various conditions. The optimal CO₂ adsorption capacity was achieved at 800 °C, with 4.58 mmol/g at 0 °C and 2.63 mmol/g at 25 °C up to 1 bar pressure. Specifically, APC-300-800 KOH exhibited a promising surface area of 1756 m²/g, a total micropore volume of 0.76 cm³/g, and a narrow micropore volume of 0.30 cm³/g. The experimental isotherm data of activated carbon were analysed using Langmuir, Freundlich, Sips, Toth and Redlich–Peterson isotherm equations. The fitting details showed that the multitemperature Sips equation is a powerful tool to mathematically represent CO₂ isotherms on activated carbon produced from argan press cake. These findings highlight the importance of optimizing activation conditions to tailor the material’s textural properties for enhanced carbon adsorption applications.