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On the solubility of aluminum in cryolitic melts |
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| Authors: | R Ødegård Å Sterten J Thonstad |
| Affiliation: | 1. Brookhaven National Laboratory, 11973, Upton, NY 2. Division of Metallurgy, Electrolysis Group, SINTEF (The Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology), N-7034, Trondheim, Norway 3. Laboratories of Industrial Electrochemistry, The Norwegian Institute of Technology, N-7034, Trondheim, Norway |
| Abstract: | The solubility of aluminum in NaF-AlF3-Al2O3 melts with various additives was found to increase with increasing NaF/AlF3 molar ratio (CR) and increasing temperature and to decrease with additions of A12O3, CaF2, MgF2, and LiF to the melts. With the use of literature data for the activities of NaF and A1F3 in cryolitic melts, three dissolution reaction models were found to give a good fit to the experimental solubility data. According to the most probable of these models the total concentration of dissolved aluminum (aluminum and sodium species) is given by cAl = cNa(diss) + cAlF2- + cAl2F3- + cAl3F4- + cAl4F5- In NaF rich melts, aluminum will dominantly dissolve as sodium, while at cryolite ratios commonly used in aluminum electrowinning (CR = 2.25 to 2.7) the AlF -2 - -ion is the predominant dissolved metal species. Other species (A12F3 -, A13F4-, A14F5-) were found to be of some significance only in melts with high excess A1F3 (CR < 2). |
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