Green extraction of pure aluminum from coarse AlSiCu alloys via centrifugal separation under isothermal semi-solid conditions: A novel upcycling strategy

Abstract

The aluminum industry is facing a “dead metal” crisis, primarily due to the unsustainable aluminum cycle. With the rapid rise of electric vehicles, the demand for cast aluminum has gradually failed to support the continued accumulation of “down-cycling” of aluminum scraps, at which point the upcycling of low-grade aluminum has become a new challenge to solve the crisis. To this end, this paper introduces a new technique which combines semi-solid isothermal treatment with centrifugal separation to directly extract industrial-grade pure aluminum from coarse AlSiCu alloys. This method is a new upgrading strategy that does not involve secondary pollution. Firstly, excess precipitated impurities were removed from the melt by centrifugal filtration, where the impurity phases accumulated at grain boundaries. Subsequently, under centrifugal force, the removal of dissolved elements was promoted by controlling the liquefaction and separation of intergranular phases during isothermal treatment, and ultimately high-purity aluminum with Al content up to 99.4 wt% was successfully obtained after secondary purification. In addition, more high-value refined silicon was easily extracted from the filtrates. Based on this, an efficient recycling process was designed, achieving an extraction efficiency of over 92% for metallic Al. Given its promising application prospects in recycled aluminum industry, this process is expected to be a more economical and green option for solving “dead metal” crisis in the future.