Research on Leaching Cesium from Medium and Low Pollucite Concentrates by the Sulfuric Acid Process

Abstract With the sharp decrease in high-grade pollucite resources, medium and low grade pollucite concentrate will become the main raw material for extracting cesium in the future. The main process conditions for leaching cesium from medium- and low grade pollucite concentrate by the sulfuric acid process were studied, and the effects of the ratio of leaching liquid to solid, leaching time, leaching temperature and of leaching liquid on the leaching rate of cesium were investigated. The results show that CsAl(SO 4 ) 2 ·3H 2 O is formed from 2Cs 2 O·2Al 2 O 3 ·9SiO 2 ·H 2 O after the medium and low grade pollucite concentrates are leached by sulfuric acid. The optimum conditions for the leaching process were as follows: the concentration of sulfuric acid was approximately 3.5 mol/L, L/S≈2, the leaching temperature was 120 °C, the heat preservation time was 2.0 h, and the leaching rate of cesium exceeded 93%. The leaching residue was washed and discarded, and the leaching solution was recycled three times and then concentrated to precipitate alum. The [Cs] in the mother liquor resulting from CsAl(SO 4 ) 2 ·3H 2 O crystallization ranged from 1 g/L to 1.28 g/L, and the [Al] ranged from 0.29 g/L to 0.33 g/L, which could be recycled for leaching.