The behaviour of thallium(III) during jarosite precipitation

• Published in: Hydrometallurgy 2005-10, Vol.79 (3), p.138-153
• Main Authors: Dutrizac, J.E., Chen, T.T., Beauchemin, S.
• Format: Article
• Language: English
• Subjects: Applied sciences; CHEMICAL REACTIONS; ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; Exact sciences and technology; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IRON SULFATES; Jarosite precipitation; Metals. Metallurgy; MINERAL INDUSTRY; national synchrotron light source; PHASE STUDIES; POTASSIUM SULFATES; PRECIPITATION; Production of metals; THALLIUM; Thallium (III); ZINC
• ISSN: 0304-386X; 1879-1158
• DOI: 10.1016/j.hydromet.2005.06.003

The behaviour of thallium(III) under the general conditions employed for jarosite precipitation in the zinc industry was investigated in a series of laboratory experiments. Thallium(III) does not appear to form end-member jarosite-type compounds, MTl 3(SO 4) 2(OH) 6, where M is Na, K, NH 4, etc. In acid solutions at pH > 0.7, the thallium(III) hydrolyzes to Tl 2O 3; in more strongly acid media, two K–Tl(III) sulphate phases crystallize at temperatures < 90 °C. The K–Tl(III) sulphate phases were investigated by chemical and X-ray diffraction analyses and by thermogravimetry. Although end-member Tl(III) analogues of jarosite-type compounds could not be synthesized, it is possible to incorporate significant amounts of Tl(III) in potassium jarosite (KFe 3(SO 4) 2(OH) 6), and over 20 at.% substitution of Tl(III) for Fe(III) was achieved. The presence of Tl(III) in the potassium jarosite structure was confirmed by microscopic methods, electron microprobe analyses and X-ray absorption near-edge structure (XANES) spectroscopy. The Tl(III)-bearing species forms rapidly, and excess Fe(III) precipitates as nearly Tl-free potassium jarosite which envelops the initially formed Tl(III)-bearing potassium jarosite phase.