Reversible CO2 capture by ZnO slurry leading to formation of fine ZnO particles

Abstract

ZnO powders were synthesized by heating precursors, prepared by the addition of ethylene diamine tetraacetate to an aqueous solution of zinc acetate, at 500 °C in air. A ZnO slurry was prepared by adding distilled water to the synthesized ZnO powder. X-ray diffraction studies confirmed that the ZnO slurry adsorbed CO2 at 25 °C under a CO2 gas flow to produce Zn5(CO3)2(OH)6. The CO2 adsorption ratio of the ZnO slurry was influenced by the amount of added water. When the weight ratio of water/ZnO was 1, the ZnO slurry had the largest CO2 adsorption ratio. Scanning electron microscopy and thermal gravimetry showed that the plate-like Zn5(CO3)2(OH)6 particles thermally decomposed at 300 °C in air leading to a single-phase ZnO powder consisting of nanoparticles with approximately 20 nm in diameter. The specific surface area of the reformed ZnO powder increased to approximately 82 m2/g through the thermal decomposition of Zn5(CO3)2(OH)6. The ZnO slurry was capable of adsorbing CO2 under a CO2 flow at 25 °C and desorbing CO2 under an air flow at 300 °C. The CO2 adsorption ratio of the ZnO slurry reached 80%–90% at 25 °C even after the fifth CO2 adsorption and desorption cycle.