Production of anhydrite–gypsum and recovery of rare earths as a by-product

A mixture of anhydrite and gypsum was obtained by reacting a yttrium-bearing fluorite (CaF2) with sulfuric acid liberating hydrogen fluoride. Thorium and uranium were extracted from the leach liquor using DEHPA/TBP. The raffinate was then adjusted to pH 1.0 and the rare earths precipitated with oxalic acid leaving commercially viable concentrations of niobium, tantalum and titanium in solution. The overall recovery of rare earths was 89.9% at a product purity of 96% RE2O3. Pure calcium fluoride was recovered from the released hydrogen fluoride by reaction with limestone.