Electrochemical approach for sustainable metallurgical process and recycling

Through electrolysis, the electrochemical operation, efficient extraction metallurgical and refining process can be operated. This lecture introduces resent development with electrochemical approach for upcycling aluminium scrap and new titanium extraction process.

Aluminium is considered as a well-recycled metal. Approximately 1/3 of aluminum is supplied from aluminum scrap. However, the current aluminum recycling by remelting process is downgrading one because the alloying elements contained in the aluminum scrap cannot be efficiently separated and will be enriched in the recycled aluminum and the final sink of this down-graded recycled aluminium is aluminium casting alloys. To meet the demand for high-grade aluminium in the future, a new aluminium recycling method capable of upgrading scrap to a level similar to that of primary aluminium is required. Here we propose a solid-state electrolysis (SSE) process using molten salts for upcycling aluminium scrap. The SSE produces aluminium with a purity comparable to that of primary aluminium from aluminium casting alloys.

Commercial application of titanium is, to a great degree, restricted by the costly extraction method, e.g. the Kroll process, although titanium is the fourth richest element among all structural metals in the earth’s crust and has many desirable engineering and functional properties. We propose a novel method to produce titanium from titanium ore through a combination of carbothermic reduction and electrolysis. This method used an anode of oxy-carbide (TiCxOy) which was prepared from titanium oxide (rutile, titania slag, ilmenite) via carbothermic reduction. During the electrolysis in molten salts, the titanium oxy-carbide anode dissolves into the electrolyte as an ion of titanium, and carbon monoxide was detected as the main gas product. At the same time, metallic titanium was obtained on the cathode. In the entail metallurgical process from the ore to the metal, there are only two chemical steps. Through this new process, the production cost is expected to be reduced remarkably from the current Kroll process.