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 degrees 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 degrees 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 degrees 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).