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

Sebastian Hedwig; Bengi Yagmurlu; Edward Michael Peters; Victor Misev; Dirk Hengevoss; Carsten Dittrich; Kerstin Forsberg; Edwin C Constable; Markus Lenz

doi:10.1021/acssuschemeng.2c06979

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

ACS Sustain Chem Eng. 2023 Apr 6;11(15):5883-5894. doi: 10.1021/acssuschemeng.2c06979. eCollection 2023 Apr 17.

Authors

Affiliations

¹ FHNW, Institute for Ecopreneurship, Hofackerstrasse 30, 4132 Muttenz, Switzerland.
² Department of Chemistry, University of Basel, Mattenstrasse 24a, 4058 Basel, Switzerland.
³ TU Clausthal, Institute of Mineral and Waste Processing, Recycling and Circular Economy Systems, Walter-Nernst-Str. 9, 38678 Clausthal-Zellerfeld, Germany.
⁴ MEAB Chemie Technik GmbH, 52068 Aachen, Germany.
⁵ Department of Chemical Engineering, KTH Royal Institute of Technology, 100-44 Stockholm, Sweden.
⁶ Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, 6700 AA Wageningen, The Netherlands.

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.