From Trace to Pure: Pilot-Scale Scandium Recovery from TiO 2 Acid Waste.

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 (TiO 2 ) 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 ScF 3 production. From ∼1 m 3 of European acid waste containing traces of Sc (81 mg L -1 ), ∼13 g of Sc (43% yield, nine stages) was recovered as (NH 4 ) 3 ScF 6 with a purity of approximately 95%, demonstrating the technical feasibility of the approach. The production costs per kilogram of ScF 3 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.