Olive Mill Waste-Derived Activated Carbon for CO 2 Capture Using Realistic Conditions

Olive mill waste (OMW) is a solid residue largelygenerated in the production of olive oil, whose haphazard dumpingcauses soil and water contamination due to its high content of organiccompounds and characteristic acidic nature. This agroindustrial wastesource can be used as a potential sustainable precursor for theproduction of activated carbon that can be used as an outstandingsorbent for CO2 capture. In this work, OMW was utilized as theactivated carbon precursor, and KOH was used as the activatingagent. Activation temperature, time, and KOH/carbon ratio wereinvestigated in order to produce suitable activated carbons for CO2capture. Textural and chemical characterizations were made byscanning electron microscopy (SEM), adsorption−desorption N2isotherms at 77K and CO2 isotherms at 273 K, and Fourier transforminfrared spectroscopy (FTIR). CO2 adsorption isotherms between 0 and 6 bar at 25 °C were obtained, and CO2 uptake was alsomeasured 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 andactivated 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) in15% vol CO2, as measured in a TGA at 30 °C.