ZnO powders were synthesized by heating precursors, prepared by the addition of ethylene diamine tetraacetate to an aqueous solution of zinc acetate, at 500 degrees 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 degrees C under a CO2 gas flow to produce Zn-5(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 Zn-5(CO3)(2)(OH)(6) particles thermally decomposed at 300 degrees 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 m(2)/g through the thermal decomposition of Zn-5(CO3)(2)(OH)(6). The ZnO slurry was capable of adsorbing CO2 under a CO2 flow at 25 degrees C and desorbing CO2 under an air flow at 300 degrees C. The CO2 adsorption ratio of the ZnO slurry reached 80%-90% at 25 degrees C even after the fifth CO2 adsorption and desorption cycle. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.