Thermodynamic study of K₂CrO₄-KAlO₂-KOH-H₂O and Na₂CrO₄-NaAlO₂-NaOH-H₂O systems

Xidong Wang , Jinlan Cui, Xinlei Ge, Shili Zheng, Mei Zhang, and Yi Zhang Metallurgical and Ecological Engineering School, University of Science and Technology Beijing, Beijing 100083, China Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100080, China

摘 要：<正>Phase diagrams of complex multi-component aqueous chromium salt system are the important theoretical bases for increasing the recovery ratio of chromium and reducing the poisonous waste in the chromate production process. Phase equilibrium of multi-component system has been calculated from the limited known data with thermodynamic models. The phase equilibriums of KOH-K2CrO4-H2O, KOH-KAlO2-H2O, NaOH-Na2CrO4-H2O and NaOH-NaAlO2-H2O systems were calculated with thermodynamic models. The solubilities of Cr and Al was measured in the systems at different temperatures. The results were compared with experimental data and they are consistent with each other. It shows that the lower concentration of KOH （or NaOH） is favorable for the crystallization of KAlO2 （or NaAlO2） and higher concentration of KOH （or NaOH） is favorable for the crystallization of K2CrO4 （Na2CrO4）. Therefore, K2CrO4 （or Na2CrO4） can be separated from KAlO2 （or NaAlO2） with controlling the KOH concentration in solutions of KOH-K2CrO4-KAlO2-H2

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