Alumina Solubility in NaF-KF-LiF-AlF3-Based Low-Temperature Melts

NaF-KF-LiF-AlF 3 -based low-temperature electrolytes have attracted great interest because of their potential to optimize and improve current industrial aluminum production methods. In the present study, the saturated alumina solubility in quaternary NaF-KF-LiF-AlF 3 -based melts (total cryolite molar ratio \( {\text{CR}} = \left( {n_{\text{NaF}} + n_{\text{KF}} + n_{\text{LiF}} } \right)/n_{{{\text{AlF}}_{3} }} \) of 1.3) with both KF and LiF content of 0 mol.% to 20 mol.% were evaluated by measuring the weight loss of a rotating corundum disk over the temperature range of 800–920°C. The effects of the KF content, LiF content, and temperature on alumina solubility are discussed in detail. The results fit well with the following empirical equation within the temperature of 830–890°C: ω (Al 2 O 3 ) sat  =  A  × ( t /1000) B , where A  = 0.3101[KF] − 0.1254[LiF] − 0.0057[KF] 2  + 0.0028[LiF] 2  + 4.486, B  = 0.3839[KF] + 0.0368[LiF] − 0.0140[KF] 2  + 0.0057[LiF] 2  + 4.913, and t is the temperature in Celsius. Alumina solubility diagrams at various temperatures are illustrated based on the empirical regression equation obtained. Finally, some problems and challenges preventing the application of these low-temperature melts in industry are discussed.