Olive Mill Waste-Derived Activated Carbon for CO₂ Capture Using Realistic Conditions

Olive mill waste (OMW) is a solid residue largely generated in the production of olive oil, whose haphazard dumping causes soil and water contamination due to its high content of organic compounds and characteristic acidic nature. This agroindustrial waste source can be used as a potential sustainable precursor for the production of activated carbon that can be used as an outstanding sorbent for CO₂ capture. In this work, OMW was utilized as the activated carbon precursor, and KOH was used as the activating agent. Activation temperature, time, and KOH/carbon ratio were investigated in order to produce suitable activated carbons for CO₂ capture. Textural and chemical characterizations were made by scanning electron microscopy (SEM), adsorption-desorption N₂ isotherms at 77K and CO₂ isotherms at 273 K, and Fourier transform infrared spectroscopy (FTIR). CO₂ adsorption isotherms between 0 and 6 bar at 25 °C were obtained, and CO₂ uptake was also measured at 30 °C in 100 mL/min of 15% vol CO₂ for 180 min. The adsorption kinetic curves were fitted with pseudo-first-order (PFO) and pseudo-second-order (PSO) models. Also, the cyclic performance of the best adsorbent was explored for 10 adsorption/desorption cycles. The highest CO₂ uptake was observed for the activated carbon synthesized with a KOH/precursor ratio of 2:1 and activated at 650 °C for 45 min, which had a CO₂ uptake of 105.7 mg/g (2.4 mmol/g) in pure CO₂ and 37.2 mg/g (0.84 mmol/g) in 15% vol CO₂, as measured in a TGA at 30 °C.