Abstract:
Rare earth elements (REE) are present at concentrations of approximately 0.36 % in phosphogypsum
stacks located in Phalaborwa, South Africa. The REE are present in the phosphogypsum in solid
solution in the gypsum and as fluorine and aluminium rich precipitates. Recovery of the REE offers
opportunities for valorization and reducing the environmental impact of the phosphogypsum
waste. This paper presents the results of investigations into the leaching behaviour of rare earth
elements and other impurities from phosphogypsum using aqueous sulfuric acid. The effects of
acid concentration, temperature, residence time, and the influence of impurities were evaluated
for their impact on the solubility of rare earth elements in a sulfate medium. It was found that a
significant fraction of the REE can be leached from the phosphogypsum in a range of conditions
much less severe than traditional hard rock rare earth processing conditions. The REE were leached
at a sulfuric acid concentration of 110 g/l, temperature of 30°C – 40°C and a residence time of
approximately 8 hours.
