Enhancing rapid removal of iron from recycled aluminium based on reducing interfacial mass transfer resistance by an immersion rotational segregation process

Recycling of aluminum scrap is a crucial pathway for carbon reduction in the aluminum industry, as its carbon emissions represent only 3%-5% of those from primary aluminum production. However, a great challenge is to further remove trace iron content to a certain range in order to meet the requirements of multi grade high-end aluminum alloys. Herein, a novel immersion rotational segregation process (IRSP) is proposed to remove trace iron content in short time, which effectively reduces interfacial mass transfer resistance due to boundary layer thinning. Kilogram-scale experiments show that a single-stage process achieves a 60% iron removal efficiency within 3 min. By employing a two-stage treatment, the Fe content is successfully reduced from 0.8 wt% to below 0.15 wt%, meeting the stringent purity standards for high-quality aluminum alloy raw materials. This rapid purification is driven by intense shear forces that induce complex fluid interactions within high-speed shear zone and vortex zones, compressing the concentration boundary layer to 0.31 mm and significantly reducing interfacial mass transfer resistance. Furthermore, 100-kg scale-up experiments were performed to validate the industrial viability of the process, achieving an iron removal efficiency exceeding 70% within 20 min. This method provides a efficient pathway for the high-value upcycling of aluminium scrap, significantly reducing reliance on primary aluminum consumption and contributing to substantial carbon emission reductions in the global aluminum industry.