Sustainable recovery of pure aluminum from scrap aluminum alloy via soluble anode electrolysis: Cathodic deposition behavior of Al and Mg ions in MgCl2–KCl–NaCl molten salt system

Scrap aluminum (Al) alloy recycling is critical for energy conservation and decreasing carbon emissions. Conventional remelting process does not remove alloying elements, severely limiting the value and applications of recycled Al. To overcome this limitation, this study develops an efficient process for recovering pure Al from scrap Al alloys via soluble anode electrolysis in a designed MgCl 2 -KCl-NaCl (MKN) molten salt system. Real-time monitoring of the electrolysis process, time-dependent characterization of cathodic deposits, and electrochemical analyses reveal a three-stage cathodic deposition mechanism in the MKN molten salt system: initial underpotential deposition of Mg 2+ transitions to co-deposition of Mg 2+ and Al 3+ , and ultimately to exclusive reduction of Al 3+ , which is driven by progressive Al 3+ accumulation. The introduction of AlCl 3 proves pivotal, simultaneously enhancing Al 3+ deposition efficiency while effectively suppressing Mg 2+ co-reduction. Systematic optimization identifies 12.5 wt% AlCl 3 addition, 500 °C, and 0.15 A/cm 2 as the ideal operational parameters, achieving recycled Al with 99.84 wt% purity. The soluble anode electrolysis process in the MKN molten salt system represents an efficient and scalable alternative to conventional remelting. The developed process is capable of producing recycled Al with purity comparable to that of primary Al while addressing critical sustainability challenges in the Al industry.