Valorization of coffee grounds into activated carbon using physic-chemical activation by KOH/CO2

Coffee grounds were employed for the synthesis of activated carbons (ACs) by combined activation with CO2 and KOH. The influence of CO2 on the morphological properties and the sorption capacities of adsorbents prepared for phenol (phOH) and methylene blue (MB) was studied. The powders were investigated by infrared spectroscopy, N2 isotherms and scanning electron microscopy. The activation by KOH under CO2 flow slightly improves the porous structure (pore volume and specific surface area). The Langmuir isotherm provides a good correlation for both phenol and methylene blue and the adsorption kinetics obey a pseudo-second-order kinetic.