Co-processing Method for the Stabilization of Aluminum Dross and the Production of Valuable Substrates via Hydrothermal Treatment

The main objective of this study was to develop a coprocessing method for the detoxification of dross and the production of valuable materials via CO2/hydrothermal treatment. The possibility of producing valuable substances (such as organic acids) via the CO2 reduction of H2 generated during the hydrothermal reaction was investigated. H2 and organic acids can be produced by the reaction of metallic Al in aluminum dross with water and CO2. The amounts of organic acids produced increased as the Al content of the dross increased. The optimum conditions for organic acid production using 1 mmol of Al were 1 mmol of NaHCO3, 300 °C, and 30 min of holding. H2 production during the hydrothermal treatment of dross increased with an increasing dross addition (Al content). The AlN in the dross was converted to NH4+ ions by hydrothermal treatment, and more than 90% of the dross N could be removed from the solid phase. The metallic Al and AlN in the dross were converted to Al2O3·H2O by hydrothermal treatment. These results indicate that this method (CO2/hydrothermal treatment) can be used as a coprocessing method for the detoxification of aluminum dross (conversion of AlN to Al2O3·H2O) and the production of valuable resources (H2 and organic acids).