Nucleation Kinetics of Rare Earth Scandium Salt: An Experimental Investigation of the Metastable Zone Width

Scandium is a rare earth element that has been declared critical raw material by the EU. Its availability low but demand for it increasing. Bauxite residue presents possible European source. A novel process to extract scandium from incorporates anti-solvent crystallization, which delivers salt (NH4)3ScF6 can be calcined ScF3 direct use in an aluminum alloy. However, this crystallization produces small crystals single-digit micrometer scale, hindering solid–liquid separation. In order facilitate separation, needs better understood and controlled. Therefore, nucleation kinetics are investigated measuring metastable zone width (MSZW) with optical endoscope probe inside 300 mL stirred fed-batch crystallizer varying operating parameters. To study influence of mixing on MSZW, stirring rate, antisolvent addition dilution before injection varied. The latter proven widen MSZW multiple. It could confirmed times different scales greatly growth process. With these results, boundaries parameters studied control thus crystal growth.