London-listed Rainbow Rare Earths has announced that the front end of its pilot plant for the Phalaborwa project, in South Africa, has started operations and is on track to produce the first high-value mixed rare earth sulphate in the third quarter.

The company said this would confirm Phalaborwa’s status as a near-term producer of magnet rare earths, capable of being commercialised on a standalone basis, thereby materially de-risking the project.

“Work has continued apace on the Phalaborwa pilot plant and the production of the first mixed rare earth sulphate is expected shortly,” Rainbow CEO George Bennett said on June 6, adding that the pilot plant back end, to produce separated magnet rare earth oxides, was also well-advanced in terms of its construction, with commissioning scheduled to start in the third quarter.

The pilot plant is split into two phases. Phase 1 comprises a front end, where material from the historic gypsum stacks at the Phalaborwa site will be consolidated into a rare earth sulphate, containing economic quantities of the four most important rare earth elements used to make permanent magnets, being neodymium and praseodymium (NdPr), dysprosium and terbium.

The front-end process is situated at mineral processing and extractive metallurgy technology developer the Council for Mineral Technology (Mintek), in Johannesburg, where commissioning of the first stage is complete, in line with Rainbow’s project development timetable and budget.

The front-end process incorporates the front-end gypsum washing, acid leach, fluoride removal via continuous ion-exchange (CIX), rare earth precipitation and a sulphuric acid agitated bake to produce a high-value mixed rare earth sulphate.

This will subsequently be shipped to Rainbow’s rare earth separation plant situated at K-Technologies (K-Tech), in the US, for separation into rare earth oxides.

The front end will produce its first mixed rare earth sulphate solids in the third quarter. Most rare earth mining projects produce a mixed rare earth mineral concentrate, a mixed rare earth sulphate, a mixed rare earth oxide or a mixed rare earth carbonate as their end product.

Rainbow believes this milestone will establish Phalaborwa as an economically viable producer of mixed rare earth sulphates on a standalone basis. The company has previously established that there is a high demand in favourable jurisdictions for a mixed rare earth sulphate product ahead of the final beneficiation step that will be undertaken using the K-Tech process.

The mixed rare earth sulphate solids produced by the pilot plant front end at Mintek will be shipped to the US to undergo further downstream processing in the pilot plant back end, in order to deliver separated magnet rare earth oxides.

As part of Phase 2 – the back end of the pilot plant – K-Tech, in Florida, in the US, will water leach the mixed rare earth sulphate into a pregnant leach solution, perform a cerium rejection step to minimise flows downstream – thereby further reducing operating costs and capital expenditure – into the CIX circuit for loading onto the cation resin before stripping and going into the final continuous ion chromatography (CIC) step, which will produce the separated rare earth oxides using K-Tech’s patented CIX/CIC technology.

The ability to produce separated rare earth oxides highlights Rainbow’s unique position within the magnet rare earth supply chain, as it expects to be able to produce a separated rare earth oxide product at 99.95% purity that can be sold directly to permanent magnet manufacturers currently being developed in the US and other countries.

Rainbow is also exploring the option of permanently establishing its back-end rare earth oxide separation process in the US and has identified a potential site for a commercial scale plant.

“We are exploring the possibility of establishing this commercial final separation process permanently in the US, as we see it adding huge value to Rainbow.

“This would position the company as one of the first producers of separated rare earth oxides within the US, which is urgently trying to establish a domestic rare earths supply chain, given the importance of rare earths to decarbonisation, defence and other strategic products vital to the twenty-first century global economy,” Bennett said.