Abstract:For the clean and economical production of chromium compounds, it is crucial to remove aluminates from chromate alkali solutions and utilize aluminum-containing compounds. In this work, carbonization was used to remove aluminates from a synthetic chromate leaching solution containing a high K₂O/Al₂O₃ mole ratio. The influence of reaction temperature, carbonization time, flow rate of carbon dioxide, and seed ratio on the precipitation of Al was investigated. The optimal output was obtained under the following experimental conditions: a reaction temperature of 50 °C, a carbonization time of 100 min, a carbon dioxide flow rate of 0.1 L/min, and a seed ratio of 1.0. Gibbsite was obtained following carbonization. The structure and morphology of the gibbsite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser particle size analyzer. The particle size distribution and morphology of the gibbsite were significantly influenced by the experimental conditions. The gibbsite had a mean particle size (d₅₀) of 16.72 μm. The thermal decomposition of the gibbsite was analyzed by XRD and the decomposition path was determined. The obtained coarse α-Al₂O₃ precipitate, which contains 0.08% Cr₂O₃ and 0.10% K₂O, was suitable for subsequent utilization.

Key words: gibbsite; secondary nucleation; carbonization; chromate leaching solution