From Trace to Pure: Pilot-Scale Scandium Recovery from TiO₂ Acid Waste

Abstract

Scandium (Sc), declared a critical raw material in the European Union (EU), could face further supply issues as the EU depends almost entirely on imports from China, Russia, and Ukraine. In this study, a tandem nanofiltration-solvent extraction procedure for Sc recovery from titania (TiO2) acid waste was piloted and then augmented by antisolvent crystallization. The new process, comprising advanced filtration (hydroxide precipitation, micro-, ultra-, and nanofiltration), solvent extraction, and antisolvent crystallization, was assessed in relation to material and energy inputs and benchmarked on ScF3 production. From ∼1 m3 of European acid waste containing traces of Sc (81 mg L–1), ∼13 g of Sc (43% yield, nine stages) was recovered as (NH4)3ScF6 with a purity of approximately 95%, demonstrating the technical feasibility of the approach. The production costs per kilogram of ScF3 were lower than reported market prices, which underscores a competitive process at scale. Although a few technical bottlenecks (e.g., S/L separation and electricity consumption) need to be overcome, combining advanced filtration with solvent extraction and antisolvent crystallization promises a future supply of this critical raw material from European secondary sources.

Industrial ecotoxicology in focus: The unexplored environmental impacts of pilot-scale advanced filtration in Sc recovery

“…The received AW contained more than 30 different elements, with concentrations ranging from mg/L to multiple g/L [ 32 ]. In total the concentrations of measured elements in the AW summed up to ∼57 g/L.…”

“…3.2 L/h. For more detailed description and discussion of the applied technology, please refer to Hedwig et al [ 32 ].…”