Titanium

This activity is aimed at students who have some knowledge of electrolysis and the extraction of metals. The reminder sheet Extracting metals – words could be used as an introductory activity for those who might need it.

Background information

The story of the discovery of the FFC (Fray-Farthing-Chen) Cambridge electrolysis method for extracting titanium is fascinating. Titanium is currently extracted by the Kroll process, which was invented by William Kroll in the 1930s. This method involves carbo-chlorinating the titanium minerals rutile and ilmenite to remove oxygen, iron and other impurities and form titanium tetrachloride (TiCl4) vapour. The TiCl4 is reduced by treatment with magnesium metal and the magnesium chloride is removed by vacuum distillation. If sodium metal is used the process is called the Hunter Process. This step has to be carried out under a protective atmosphere of argon or another Noble gas as titanium is extremely reactive.

Titanium

Titanium is a metal with incredible properties: it is lighter than steel; strong and tough enough to survive in space or at the bottom of the ocean; oxidation and corrosion resistant. And it looks good. What is more, it is very common – the ninth most common element in the Earth’s crust (found in the form of titanium oxide).

You might wonder why we do not use it more, but titanium has one real drawback: its cost. It is currently more than five times the price of stainless steel.

Reactivity series of metals

Note: Carbon and hydrogen are not metals.

Questions

1. How is iron extracted from its ore?
2. Why is this method not suitable for extracting titanium?
3. What method is used to extract aluminium from its ore?
4. Why is aluminium more expensive than iron?

Scientists have been trying to extract titanium by electrolysis since the 1950s without success. Instead, it is extracted using a more reactive metal to displace it from its ore.

5. Suggest a metal that could be used to displace titanium from its ore

Answers

1. Iron is extracted from its ore by heating the ore with carbon.
2. Titanium cannot be extracted in this way because it is more reactive than carbon so would not be displaced by it. In addition, titanium carbide (TiC) might form.
3. Aluminium is extracted by electrolysis.
4. Aluminium is more expensive than iron because electrolysis of its ore uses a lot of electricity, which is more expensive than the carbon used in the blast furnace to extract iron.
5. Titanium could be extracted using magnesium/calcium/sodium/potassium/any more reactive metal.