Extraction of Thorium from Tin Slag Using Acidic Roasting and Leaching Method.

Slag as the secondary product (waste) of tin smelter still contains not only valuable elements e.g. rare earth elements but also radioactive such as Th. Both radioactive elements are accumulated in the slag phase since the raw materials used in smelting i.e. cassiterite minerals, is closely associated with Th and U containing monazite. Due to valuable element content, the slag becomes major of interest in mineral processing industries, hence the slag needs to be decontaminated before it could be processed further. The common approach to reducing Th content from the slag using the leaching process is considered ineffective due to association of Th with refractory phase e.g. SiO₂ and TiO₂ in the slag. To break down the refractory phases, the roasting approach by using the fusing agent is required to release Th so that they could be leached out using mild lixiviant. In this research, potassium hydrogen sulfate (KHSO₄) and sulfuric acid were used as a fusing agent and lixiviant, respectively. The parameters studied include the molar ratio between fusing agent and refractory elements in slag, roasting temperature, roasting time, sulfuric acid concentration in lixiviant and pulp density during the leaching stage. The studies so far demonstrated that optimum condition in Th removal occurred at roasting temperature 400 ℃, roasting time 2 hours, the molar ratio of potassium hydrogen sulfate to tin slag is 5:1, sulfuric acid concentration 2 M and pulp density 15 mL/gr. [ABSTRACT FROM AUTHOR]