Environmentally valorization of olive tree pruning residue: Activated carbons for CO2 capture and energy storage in supercapacitors

Abstract

Fossil fuels are still the main energy source, and their consumption has caused significant CO₂ emissions. In this work, the synthesis of chemically activated carbons from olive tree pruning residues for environmental and energy applications is proposed. The residues were carbonized at 500 °C and then activated with KOH at different activation temperatures and impregnation ratios. Textural and chemical characterization were evaluated by scanning electron microscopy, infrared spectroscopy, and N₂ adsorption/desorption isotherms. The influence of activation temperature and impregnation ratio on textural properties and CO₂ capture and energy storage performance was investigated. Activated carbons showed a high surface area range of 786–1985 m² g⁻¹ and significant microporosity development from 0.43 to 1.03 cm³ g⁻¹. For CO₂ capture applications, an equilibrium, thermodynamic, and kinetic analysis was performed. The AC600-3/1 presented a maximum adsorption capacity of 265.7 mg of CO₂ g⁻¹ at 0 °C and 1 bar. The carbon presented an excellent performance in 10 successive cycles of CO₂ adsorption-desorption; the adsorption capacity was just reduced by 2.7 % at 30 °C. For applications in the energy storage field, all the activated carbons shown an adequate electrochemical performance for their use as active materials in supercapacitors. AC600-6/1 showed the maximum specific capacitance and energy, with values up to 707.5 F g⁻¹ and 196.53 Wh kg⁻¹, respectively at 0.33 A g⁻¹. The valorization of olive tree pruning residue through activated carbons provides a solution to a disposal problem and it generates two environmentally friendly applications (CO₂ capture and energy storage).