Recent Developments in Low-Temperature Electrolysis of Aluminum

Abstract

Recent developments in the field of low-temperature electrolytes and electrolysis are considered. Although the investigations have not found fundamental problems in low-temperature aluminum electrolysis development as an industrial process, challenges remain in cell design, construction, and operation of cells with these emerging technologies.

Review of measures for improved energy efficiency in production-related processes in the aluminium industry – From electrolysis to recycling

“…If successful, the K3AlF6-based electrolytes can lower the electrolysis temperature to 700-750 °C and thus provide energy savings [90]. A combination of sodium and potassium electrolytes can also be used [88,91]. However, the electrolysis temperature used for this combination may be around 800-850 °C [91].…”

“…A combination of sodium and potassium electrolytes can also be used [88,91]. However, the electrolysis temperature used for this combination may be around 800-850 °C [91]. Additionally, the alumina solubility is lower for the potassium and sodium cryolite combination than for only potassium cryolite, which results in lower electrolysis efficiency [88].…”

Existence of Al2F7− in molten MF–AlF3 (M = K, Cs) systems as determined by Raman spectroscopy and structural simulation

“…The ionic structures of the molten systems of alkali metal fluorides and aluminum fluoride have attracted significant interest from the research community. At present, the existence of AlF 6 3 − , AlF 5 2 − , and AlF 4 − complex ions have been proven by Raman spectroscopy [9][10][11][12][13][14] . It is acknowledged that the equilibria among the Al-F complex ions in molten systems exist as AlF 6 3 − = AlF 5 2 − + F − and AlF 5 2 − = AlF 4 − + F − .…”

“…At present, the existence of AlF 6 3 − , AlF 5 2 − , and AlF 4 − complex ions have been proven by Raman spectroscopy [9][10][11][12][13][14] . It is acknowledged that the equilibria among the Al-F complex ions in molten systems exist as AlF 6 3 − = AlF 5 2 − + F − and AlF 5 2 − = AlF 4 − + F − . However, besides the above three Al-F complex ions, several researchers have suggested the very possible existence of a fourth Al-F complex ion in the mixtures of alkali metal fluorides and aluminum fluoride, namely Al 2 F 7…”

“…NaF-AlF 3 -based systems are used as electrolytes in industrial aluminum electrolysis [1,2] , while KF-AlF 3 and CsF-AlF 3 molten systems are used as brazing fluxes [3,4] . Furthermore, KF-AlF 3 -based systems are considered as potential aluminum electrolytes [5,6] , particularly when they used in connection with the inert anode [7] and wettable cathode [8] .…”