Rainbow’s Smaller Phalaborwa Circuit Moves the Risk From Chemistry to Finance

Rainbow Rare Earths has pushed its Phalaborwa project closer to a bankable design by shrinking the most technically demanding part of the flowsheet. The next test is whether the company can turn that process simplification into a financed plant on schedule.

The July definitive-feasibility-study update said roughly 75% of the flowsheet had moved into engineering, after pilot work simplified the front end and reduced the volume feeding the separation circuit from about 340 cubic metres an hour to only 4–5 cubic metres an hour. ANSTO’s modelling indicates the project may need roughly 75 mixer-settlers across two solvent-extraction circuits, compared with around 1,500 or more at some traditional rare-earth separation plants.

That is not a cosmetic change. Separation is where many non-Chinese rare-earth projects become expensive, chemically complex and slow to commission. Fewer stages, a cleaner feed and a smaller liquid volume should reduce equipment count, reagent use, energy demand and working capital. It also narrows the number of points where impurity control or phase separation can destabilise the circuit.

Phalaborwa is unusual because Rainbow is not planning to mine and crack fresh hard rock. It intends to reclaim about 35 million tonnes of phosphogypsum left by historic phosphoric-acid production in Limpopo. The material has already been mined, crushed and chemically processed once. Rainbow’s task is to leach the waste, remove impurities and separate saleable rare-earth products from a feed grading about 0.44% total rare-earth oxides.

The planned products are separated neodymium-praseodymium oxide and a SEG+ mixed rare-earth carbonate containing dysprosium, terbium, samarium, europium, gadolinium and yttrium. That product mix matters because the heavy magnet elements command strategic value well beyond their tonnage. Dysprosium and terbium improve magnet performance at high temperatures and remain difficult to source outside China.

The project’s advantage is therefore less about headline grade than about what previous processing has already done to the mineralogy. Phosphogypsum is effectively a chemically cracked stockpile. Rainbow avoids conventional mining, crushing and much of the beneficiation burden, while also turning an environmental liability into feedstock. The trade-off is that low-concentration secondary materials can become uneconomic if acid consumption, neutralisation or impurity removal is poorly controlled.

Rainbow’s pilot campaign is aimed directly at that risk. The Johannesburg plant has been generating the mass-balance, equipment-sizing and cost data needed for the DFS, while Mintek has supported the testwork and ANSTO is modelling the final solvent-extraction configuration. The company has also shifted away from an earlier ion-chromatography route in favour of conventional solvent extraction, using standard equipment in a novel but more financeable configuration.

That choice strengthens the engineering case but raises the burden of proof on economics. Investors now need a final capital estimate, operating-cost range, recovery assumptions and commissioning schedule that reflect the simplified design rather than the older preliminary studies. The project is still targeting construction from 2027 and first production in 2028, leaving little room for another long optimisation cycle.

Funding is the second unresolved issue. The U.S. International Development Finance Corporation has committed $50 million to TechMet to support Phalaborwa, underscoring Washington’s interest in non-Chinese magnet materials. But the funding is tied to project development rather than a blank cheque for construction. Rainbow still has to assemble the rest of the equity, debt and offtake package after the DFS.

The geopolitical backdrop helps. The United States and South Africa have continued discussing critical-mineral cooperation despite wider diplomatic friction, and Phalaborwa is one of the few projects that can offer both light and heavy magnet rare earths without opening a new mine. Yet strategic importance does not eliminate execution risk. Western governments have backed several rare-earth projects that later struggled with cost overruns, qualification delays or weak pricing.

Phalaborwa’s next catalyst is therefore not another laboratory purity milestone. It is a DFS showing that the smaller circuit produces a repeatable, financeable plant with realistic contingency, recovery and ramp-up assumptions. If Rainbow can prove that, the project could become a template for recovering rare earths from industrial waste. If it cannot, the simplified chemistry will still leave the company with the same problem facing much of the Western sector: a strategically valuable flowsheet without enough capital to build it.