| Abstract |
| Thorium-containing radioactive wastewater has been produced from anthropogenic activities such as mining for rare-earth minerals. The removal of thorium from wastewater is important as it may harm humans and environment. Precipitation is one of the methods used for the removal of thorium. In this study, Pourbaix diagrams were used to examine changes in thorium precipitation aqueous solution with changing temperature. Through comparing these Pourbaix diagrams, the following conclusions are drawn: (i) at the same temperature condition, the boundary potential of Th4+-Th reaction decreases and boundary pH of Th4+-Th(OH)4 reaction increases with decrease in ion activity of Th4+; (ii) the slope of the boundary of Th-Th(OH)4 reaction decreases as temperature increases, which means pH has a greater influence on Th-Th(OH)4 reaction at high temperature; and (iii) the stable area of Th4+ and Th(OH)4 decreases and increases, respectively with increasing temperature. Furthermore, the stable areas of Th(OH)4 at 288 K, 298 K, and 318 K were estimated to be 90.7%, 93.1%, and 97.9%, respectively, of the area at 328 K. In conclusion, temperature increases decline the efficiency of thorium precipitate treatment. |
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| Key Words |
| Thorium, Th(OH)4, Thermodynamic. Radioactive wastewater. Pourbaix diagram, 열역학, 방사성 폐수, 전위-pH도 |
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