Letter: Rare earth solution

From Richard Durrant

There is a possible remedy to the shortage of rare earths reported by Katharine Comisso (30 October, p 14). Why not extract these elements from the red mud waste from bauxite mining?

According to a study by M. Ochsenkühn-Petropulu and colleagues, a tonne of red mud will contain a few kilograms of rare earth elements (Analytica Chimica Acta, vol 296, p 305). These metals could be extracted with ammonium salts.

Yttrium hydroxide is soluble in ammonium chloride and so could be extracted in solution. The residual rare earth phosphate mineral monazite, left over from the original bauxite, could be treated with alkali to yield other rare earth hydroxides.

Worldwide, 70 million tonnes of red mud are generated each year, according to the Red Mud Project, which promotes the utilisation of this waste. Consider the potential benefits of processing it in this way.

St Albans, Hertforshire, UK