Extraction of Thorium

 

THORIUM(Th)

• Atomic number: 90
• Colour: silvery or tarnishes black

Properties:

• Thorium metal exists the face centered cubic form in the high melting point and it also exists the body centered cubic form in above the high melting point.
• Low tensile strength
• Thorium attacked with water is very low and its only dissolved in hydrochloric acid.
• Thorium is more stable in air.
• Thorium is very soft and ductile and it can be rolled, forged and swaged.

Ores:

• Monazite (Ce,La,Nd,Th)PO₄
• Thorite (ThSiO₄)
• Thorianite (ThO₂)

Extraction of thorium from its ore

              Thorium is extracted from the ore containing many processes such as mining, digestion, leaching, solvent extraction and refining process and so on.

Mining and concentration:

              Thorium is extracted from monazite ore by using the mining process. In this process, the monazite sand is mined with conventional place mining equipment and procedures. These sands are mixed with the other minerals like silica, magnetite, zircon and then the lighter minerals are washed out by using the shaking tables in the process of electromagnetic separators.

Digestion:

              The monazite ore is treated with concentrated sulphuric acid to give the thorium sulphate and phosphoric acid.

Th(PO₄)₄ + 6 H₂SO₄→ 3Th(SO₄)₂ + 4H₃PO₄

                        The resulted product is treated with nitric acid and tributyl phosphate. it gives the thorium nitrate containing feed solution suitable for final solvent reaction.

3Th(SO₄)₂ + NH₄OH →Th(OH₄) + 2(NH₄)2SO₄

Th(NO₃)₄ + TBP→ Th(NO₃)₄.TBP

This tributyl phosphate solution is treated with nitric acid solution to remove the other metallic impurities, strips and thorium from the organic solutions into the aqueous solution. This nitration process is also calcined to thorium oxide (ThO₂).

Th(NO₃)₄.TBP + H₂O →Th(NO₃)₄ + TBP.H₂O

Th(NO₃)₄ + 2 C₂H₂O₄ →Th (C₂O₄)₂.4H₂O + 4HNO₃

Th(C₂O₄).4H₂0 →ThO₂ + 2CO₂ + 2CO +4H₂O

Reduction:

              The ThO₂ is treated with hydrogen fluoride to give the thorium tetrafluoride. This process is called the spedding process. This ThF4 is treated with calcium and zinc halide. It reduces the thorium and zinc to metal and produces the slag of calcium chloride and calcium fluoride. After solidification the zinc- thorium alloy product is heated the above melting point of the zinc but below the melting temperature of the thorium. This evaporate the zinc and pure thorium sponge which is melted.

ThF₄ + 3Ca + ZnCl₂→ Th +Zn+2CaF₂+CaCl₂ 

Uses:

• It is used as a nuclear fuel because thorium is radioactive element.
• It is used in the manufacturing of lenses for cameras and scientific instruments.
• It is used in radiometric dating.
• Thorium is used for cancer theraphy.
• Thorium is used to strengthen magnesium, this is used for coating tungsten wire in electrical equipment.