thorium extraction process

Thorium (Th) is a radioactive chemical element discovered in 1828. It is a silvery-white metal that turns gray or black when exposed to air and is more abundant than uranium in Earth's crust. Thorium is commercially extracted from minerals like monazite.12

Extraction and Refining

The extraction process typically begins with concentrating the ore, often monazite sands, using physical separation methods like magnetic and electrostatic separation. The concentrated ore then undergoes either an acid or alkaline digestion process.2

• Acid Digestion: Monazite is treated with concentrated sulfuric acid, converting its components into water-soluble forms. This is followed by treatment with ammonia to precipitate hydrated thorium phosphate, which is then converted to thorium hydroxide and dissolved in nitric acid for purification.2
• Alkaline Digestion: Monazite is treated with a concentrated sodium hydroxide solution. The resulting solid hydroxide product is then dissolved in a mineral acid. Thorium is partially separated from rare earths by adding sodium hydroxide, precipitating crude thorium hydroxide, which is then dissolved in nitric acid for purification.2

Following digestion, solvent extraction is used to purify thorium from residual rare earths and other contaminants. This typically involves using tributyl phosphate diluted in a hydrocarbon solvent. The purified thorium nitrate solution can then be processed further.2

Chemical Properties and Uses

Thorium exhibits a +4 oxidation state in its compounds. Thorium dioxide (ThO₂) is a refractory substance with industrial applications, and thorium nitrate is used in the production of gas mantles. Thorium-232, the most common isotope, is slightly radioactive and can be converted into fissile uranium-233 in nuclear reactors, presenting a potential source of nuclear energy.12