Rainbow Rare Earths (Rainbow), in collaboration with K-Technologies (K-Tech), has announced the successful extraction of rare earth elements (REEs) using a newly developed process flowsheet utilising phosphogypsum stacks at the company’s Phalaborwa project in South Africa.

Phosphogypsum (PG) is a waste by-product derived from the processing of phosphate rock in plants producing phosphoric acid and phosphate fertilizers. While PG contains many valuable materials, including REEs, it is considered a complex feedstock with a wide range of contaminants and radioactive materials. As a result, this by-product is usually dumped in stockpiled controlled areas with only about 15% recycled, typically as building products. Historically, processing and utilizing PG was considered highly challenging with little to no effective and environmentally friendly solutions available for commercialisation.

As outlined by Rainbow, the new process includes the initial leaching of phosphogypsum with sulphuric acid, followed by a rapid concentration of REEs in the pregnant leach solution. The concentrated REE solution is then upgraded in K-Tech’s proprietary continuous ion exchange and ion chromatography process to deliver high-purity oxides of the target REEs. Test work reports recoveries of between 65% to 70% of contained REEs. Rainbow and K-Tech are in the process of jointly patenting the intellectual property.

High volumes of PG have been accumulated worldwide, with estimates reported of more than a billion tons produced and stockpiled in countries such as the USA, China, Russia, India, and Ukraine. Therefore, any process flowsheet that can successfully commercialise REE recovery from waste PG would attract wide-reaching interest across the globe. For Rainbow, the interest goes together with its Phalaborwa REE project, which the company acquired under a joint venture with Bosveld Phosphates in December 2020.