The background
Trona is a mineral comprising sodium sesquicarbonate and is found in a number of prominent soda ash deposit sites around the world, including Wyoming (United States), Magadi (Kenya) and Lake Natron (Tanzania) as well as in countries such as Turkey, Venezuela and Egypt.

 

Company: Tata Chemicals Innovation: The removal of fluoride from trona

Trona is a naturally occurring mineral, a mixture of sodium carbonate (soda ash), sodium bicarbonate, sodium fluoride, sodium chloride and other impurities. It is generally used for the manufacture of soda ash by well-established techniques, most prolifically through the milling of the mineral. This process takes place after the trona has been mined or dredged (depending on the location of deposits), and the calcination — the conversion of metals into their oxides by heating to a high temperature — of the crushed material produces soda ash.

 

The soda ash produced from trona tends to retain a few impurities from the original mineral deposit and is less pure than the soda ash produced by the synthetic ammonia soda process. Various purification processes tried over the years to produce a less-tainted form of trona-derived soda ash have shown fluoride to be the culprit. The amount of fluoride in trona varies to a significant extent, often causing problems in high value-added applications. For safe and best use the amount of fluoride in trona should be less than 300ppm.

 

The innovation
A team from the Tata Chemicals Innovation Centre has developed a simple process through which sodium bicarbonate is prepared by bubbling carbon dioxide gas through a saturated solution of trona. Through this process trona is dissolved in water at room temperature. The insoluble impurities present in the mineral are separated by a standard filtration process and at a low cost.

 

The sodium bicarbonate formed in the process has fluoride impurities of less than 300ppm, and the yield in the process can be easily improved by using nano-additives. This sodium bicarbonate is heated to produce soda ash. A big advantage of this singular process is that it uses recycled water.

 

The process that has been created by the Tata Chemicals team — which comprised Murali Sastry, the chief innovation officer at the company's innovation centre, and Soumen Sensarma and Sumant Phadtare, both lead scientists — is easily scalable. It took almost a year to be developed and has now been covered by patents filed in India and other countries.

 

The payoff
The trona breakthrough is estimated, by those who were part of the project, to increase Tata Chemicals' profits by Rs1 billion a year. The company can, by employing this method, deliver more value-added products and secure new business opportunities.

 

There are environmental benefits, too, with the removal of fluoride content in sodium bicarbonate leading to products that are green-friendly. That translates into a cleaner business and the long-term sustainability of Tata Chemicals' soda ash operations.

 

The task now is to complete the pilot studies currently underway in Magadi. Cross-functional teams from different Tata Chemicals locations are working together on this and they are betting their pure baby will be up and running in quick time.