Keynote Presentation International Solvent Extraction Conference 2025

Critical minerals are increasingly coming into focus due to the important role that they play in our modern world where they are essential ingredients in the manufacture of high-tech and high-value products, including electric vehicles, wind turbines, rechargeable batteries, electronics, mobile devices and defence technologies. Critical minerals are defined by the complexity and concentration of their supply chains and the consequent elevated risk of interruptions to supply. 

Governments around the world have published critical minerals strategies and provided incentives to encourage diversification of critical minerals supply chains. In the Australian context, with its rich mineral endowment, this means more on-shore processing of its natural resources into higher value products rather than exporting mineral concentrates. The application of solvent extraction to the recovery of rare earths and other critical metals is the subject of this paper.

Solvent Extraction for Rare Earth Separation

Australia has many significant rare earth deposits, the Lynas mine and processing facility already in operation and many advanced rare earth projects in the pipeline including those being developed by Iluka, Arafura, Australian Strategic Materials, Northern Minerals, VHM and Hastings Technology Metals.

The rare earth supply chain is long and complicated involving mining, beneficiation, extractive metallurgy and rare earth separation and refining into high purity oxides, which then need to be reduced into metals and alloys. Australia is a great mining jurisdiction well known for upstream mining and beneficiation operations, but not so much for midstream and downstream processing. ANSTO, through its Minerals business unit, supports commercial companies in the development of their rare earth projects, including designing and testing of rare earth solvent extraction circuits.

Rare earth solvent extraction refineries are notoriously complex chemical facilities, with as many as 100 stages per rare earth separation circuit, and about 1000 mixer settlers required for a full separation of all 15 elements. The fundamental chemistry of the processes used has been well understood for a number of decades, but the design of individual solvent extraction separation processes is complex and access to the know-how not widely available. Requirements that underpin effective and economic rare earth solvent extraction flowsheet designs are discussed including the challenges that need to be overcome to experimentally verify these flowsheets.

Solvent Extraction for the Separation of Zirconium, Niobium and Hafnium

The processing of the Toongi polymetallic deposit in Dubbo, New South Wales, poses specific challenges associated with the relatively low grade and the requirement for simultaneous recovery of zirconium, niobium, hafnium and the rare earths. A sulfuric acid bake process operated at > 200°C is used to attack the minerals assemblage and this is followed by a water leach to produce a pregnant leach liquor containing all the valuable metal elements as well as other impurities. There are multiple solvent extraction processes targeting individual high purity products. Zirconium is present in the deposit at higher concentrations and is recovered in the primary solvent extraction process, which also provides the nexus for the separation of various major product streams. This presentation provides highlights on how conventional flowsheets have been adapted in innovative ways to accommodate multiple drivers.

 Solvent Extraction Pilot Facility at the Australian Nuclear Science and Technology Organisation