Facile synthesis of oxidized activated carbons for high-selectivity and low-enthalpy CO2 capture from flue gas

Abstract

The prospect of a worsening climatic situation prompts us to develop energy-saving and cost-effective CO₂ capture technologies. In this work, three oxidized activated carbons (ACO-n, n is 1–3) were prepared through a facile synthesis approach via oxidation in the presence of KMnO₄ and concentrated H₂SO₄ for 0.5, 1.0 or 2.0 hours. Interestingly, these carbon materials ACO-n can exhibit high CO₂ capacity with low adsorption enthalpy and the selectivity toward flue gas can be adjusted by altering the period of oxidation. Among the pristine activated carbon and ACO-n materials, ACO-2 can exhibit the highest CO₂ capacity of 3.01 mmol g⁻¹ under ambient conditions with an adsorption enthalpy of only 23.1 kJ mol⁻¹, slightly larger than the CO₂ vaporization enthalpy. Its selectivity of 48.5 is double the value of the pristine activated carbon. A column breakthrough experiment was conducted to evaluate the CO₂ separation capability on ACO-2 toward a CO₂/N₂ (15 : 85 v/v) mixture under kinetic flow conditions, which suggests that the oxidized activated carbon made from sustainable sources is promising for CO₂ capture.