Sustainable Scandium Recovery Method from Metallic 3D Printing Powders

Abstract

With the upcoming limitations on gasoline-based vehicles, especially in Europe under the Paris Accord, research on electrical/hydrogen powered vehicles and lightweight alloys for lower CO2 emission has peaked. Scandium (Sc) became one of the key elements for advanced Al-based lightweight alloys due to major improvements in physical properties. Due to extreme prices and rare primary sources, recovery of Sc from available end-of-life (EoL) products has clearly became the focus of research. Al-Sc-containing 3D printing powders are one of the promising products to be utilized in the industry. To recover the critical metals from these EoL products or from the production wastes, hydrometallurgical processes are great alternatives due to possibility of elemental separation with low energy consumption. However, conventional leaching of electronegative metallic particles and alloys with a strong mineral acid can result in generation of H2 gas and an aggressive exothermic reaction. While such a leaching process can be made safe at laboratory scale there are significant challenges at commercial scale from a control and zero harm perspective. Hence, there is a need for greener and sustainable process with easier control, lower chemical use, energy, and CO2 emission without any H2 gas evolution. Thus, an innovative leaching approach was applied with a metal salt solution with higher reduction potential to dissolve the metallic powders with cementation of the metal from the leaching solution. Then, the target was separated and purified from the impurities via refining operations. The flexibility of end product is another advantage since metal carbonates, metal sulfates, metal oxides, metal fluorides and metal oxides could be produced via this processing route. The process is also scaled up and tested in a continuous mini-pilot scale.KeywordsRecyclingScandiumEnd-of-lifeSolvent extractionLeaching3D printing