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

Abstract

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 degrees C were obtained, and CO2 uptake was also measured at 30 degrees 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 degrees 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 degrees C.