Mechanisms of Se(iv) incorporation in jarosite and its migration behavior during thermal aging†

Secondary minerals such as jarosite have pivotal implications for the migration of trace elements. The long-term fate of selenium is directly related to its behavior during thermal aging after adsorption on minerals, and understanding the behavior of selenium during mineral phase transitions is important for the safe disposal of radioactive anions in solid phases. By combining macroscopic sorption experiments with basic characterization, we investigated the mechanisms of Se(IV) sorption on jarosite and the thermal conversion process (180 °C) of jarosite under alkaline conditions. The results showed that the adsorption process of jarosite is induced by ion exchange between SO₄²⁻ and SeO₃²⁻, jarosite can be converted into hematite during the aging process after Se(IV) adsorption, and Se(IV) remains solidified in the mineral in the form of ferric selenite despite the phase change. This study improves our understanding of how the thermal transformation of jarosite can influence Se(IV) mobility and Se(IV) partitioning.