London-listed Rainbow Rare Earths has confirmed the development of a process flowsheet to extract rare earth elements efficiently from the phosphogypsum stacks at the company’s Phalaborwa Project in South Africa. This innovative process has been developed by Rainbow in collaboration with K-Technologies, following extensive test work carried out at ANSTO Minerals, Australia, and at K-Tech’s facilities in Florida, U.S.A.

Rainbow confirms successful development of Rare Earths extraction flowsheet

Historically, the extraction of rare earths from phosphogypsum has proven technically, environmentally and economically challenging. However, Rainbow and K-Tech have developed a process flowsheet at Phalaborwa, underpinned by comprehensive test work, which successfully delivers an overall recovery of between 65% to 70% of the contained rare earths. This compares very favourably to the overall recovery of separated rare earth oxides via standard processes. Importantly, the process employs standard, proven equipment and readily available reagents in a novel combination. Rainbow and K-Tech will jointly patent the process with a view to applying this to further rare earths projects.

Following leaching of the phosphogypsum with sulphuric acid and subsequent rapid concentration of the rare earths in the pregnant leach solution, the concentrated rare earths solution is upgraded in K-Tech’s proprietary continuous ion exchange (CIX) and continuous ion chromatography (CIC) process to deliver high-purity oxides of the target magnet rare earths, namely neodymium, praseodymium, dysprosium and terbium.

CIX and CIC have both been applied commercially in multiple applications since their development in the 1980s. These processes are now found globally in the food, biotech, chemical, water treatment, pharmaceutical and mining industries. Several of these industrial installations are found in South Africa.

The CIX/CIC process has several economic and environmental advantages over the conventional solvent extraction route, which include:

  • Nine process stages are required for the CIC separation, versus hundreds of stages in the solvent extraction ("SX”) method depending on the desired product mix;
  • No hazardous or toxic solvents are required, whereas they are integral to the SX process;
  • Capital and operating costs are significantly lower for CIX/CIC compared to SX; and
  • Working capital requirements for CIX/CIC are minimised when compared to SX, due to the shorter time required for the production and delivery of saleable product.

Now that this important milestone has been successfully delivered, Rainbow looks forward to completing the technical feasibility study, which is expected to demonstrate this to be one of the lowest cost global producers of separated rare earth oxides.

Rainbow Rare Earths CEO, George Bennett, commented: “We are now in the process of jointly patenting this intellectual property with K-Tech and believe it will allow us to secure additional rare earths opportunities, such as the previously announced collaboration with a major chemicals group in South Africa.

Importantly, whilst the configuration of this new flowsheet is innovative, each individual stage is well tested on a commercial basis, with the required equipment and reagents being readily available.

Since introducing Phalaborwa to our portfolio in December 2020, we have always indicated that we believe it to be an exciting and near-term development opportunity to produce critical rare earths required for the green energy transition. The confirmation of an efficient and economic rare earths extraction flowsheet for the Project represents within 18 months a remarkable achievement for our business and underlines the significant amount of work carried out at the Project to date.”

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Nellie Moodley 
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