On titanium dioxide, 'the whitest of white' pigments

In the latest controversy surrounding land acquisition for corporate projects, the titanium dioxide plant proposed to be set up the Tata Group in Tirunelveli district of Tamil Nadu has run into rough weather, with the local population expressing opposition and several political parties threatening agitations. The project is being opposed on environmental grounds and fear of loss of livelihood.

But what exactly is ilmenite and what are the industrial uses of titanium, which is extracted from it, and its dioxide?

Speaking to Business Line on the extraction and applications of titanium metal and titanium dioxide, Dr C.H. Krishnamurthi Rao, Chairman of Titanium Equipment and Anode Mfg Co Ltd (TEAM), a Chennai-based company, said that titanium dioxide, as the "whitest of white" pigments, finds extensive use in quality paints, paper and plastics.

"It is also used as an opacifying agent in cosmetics and printing inks, radioactive decontamination of the skin, glassware, ceramics and floor coverings. Besides, it finds application in delustering of synthetic fibres and lustrous finishing of cottons."

According to him, titanium dioxide is also used in high-temperature transducers in electronics and in the coating of welding rods.

On titanium metal, he said that as a non-corrosive metal having the "great advantage" of strength-to-weight ratio and high temperature heat resistance, it is the preferred structural material in aircraft, jet engines, missiles and satellites.

"It finds special applications in desalination, chlorine production and textile equipment."

Dr Rao's company, TEAM, has undertaken manufacture of titanium electrodes for use in caustic soda and other electrolytic industries.

"The availability of titanium electrodes was also responsible for the development and propagation of membrane cell technology in India, thus completely eliminating mercury pollution from the caustic soda industries."

TEAM had also involved itself in life science operations by manufacturing titanium hip and shoulder orthopaedic replacements and inserts.

According to Dr Rao, titanium metal is preferred because of its compatibility with biological fluids.

Desalination plants are another area offering immense potential, he added.

Stating that ilmenite, the titanic iron ore, is available in beach sand in areas like Kanyakumari in Tamil Nadu, Dr Rao said that after mining and beneficiation, it takes three streams of commercial products – upgraded ilmenite or synthetic rutile, chemical titanium dioxide and titanium metal.

"DCW Ltd manufactures upgraded ilmenite or synthetic rutile, which has 95 per cent of titanium dioxide content. It is only a raw material used in the manufacture of the dioxide. DCW produces around 42,000 tonnes of upgraded synthetic rutile."

Informing that titanium dioxide is manufactured by the chlorination of the ilmenite, he said that Kerala Minerals and Metals manufactures the dioxide through the rutile process, "wherein ilmenite ore is upgraded to make synthetic rutile, which is further upgraded to titanium tetrachloride. This is used in making titanium dioxide of rutile grade. Kerala Minerals and Metals produces around 36,000 tonnes of titanium dioxide." There are, however, environmental issues, especially relating to effluents.

For extraction of titanium metal, ilmenite is subjected to the process of reduction, using sodium or magnesium.

"The titanium sponge thus obtained is consolidated by melting, which requires highly sophisticated technology."

Dr Rao added that the Tatas have only said that they would be making titanium dioxide "but not specified what process they will be using – rutile or sulphate. For the rutile process, hydrochloric acid is used to leach ilmenite ore, while in sulphuric acid is used in the other. The rutile grade dioxide is superior in quality and price."

He also said that ilmenite ore containing minor quantities of monazite was earlier classified under the category of radioactive materials.

"The exploration, processing, export and import of these ores were under the vigilant control of the Mines and Minerals Act and the Atomic Energy Commission."

So far, the manufacture of titanium dioxide was the monopoly of public sector undertakings.

"Kerala Minerals and Metals remains the only indigenous source for titanium dioxide, and MIDHANI, Hyderabad, for titanium-rolled products out of imported titanium metal sponge (similar to ingots)."

Dr Rao attributed the flurry of investment in products based on ilmenite ore to the constant demand and bright prospects for both the chemical and metallic versions of titanium. – The Hindu




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