Beyond pigment and catalysis, TiO₂ is also serving water treatment applications

It is estimated that only 71% of the world population has access to safe drinking water. This means 29% of the world does not. 1

The use of coagulants to purify drinking water is a very old story, dating back to 1500 B.C. by the Egyptians. In 1911, phosphorous removal with iron coagulants was successfully tested in England and became standard practice by the 70s. Now, coagulants are widely used to purify drinking water, as well as to clean municipal wastewater and have an important role in the treatment of industrial water.

Inorganic coagulants support the separation of dissolved and particulate impurities from the water. They are positively charged metal salts (e.g. Fe2+) and react with negatively charged colloids in the water to form bigger flocs (loose clumps of particles).

To remove phosphorous from industrial wastewater, FeSO4.7H2O, also known as copperas, is a major coagulant used in the industry. It is a well-known co-product from the TiO2 sulphate manufacturing process. As such, Tronox contributes to the circular economy by reusing this material originating from its synthesis process for applications like sewage and industrial effluent treatment.

Another way of treating water is to use adsorbents. This is nearly as old a story as coagulants. In 400 B.C., the ancient Hindus and Phoenicians discovered the antiseptic properties of activated charcoal and began to purify their water with it.

Adsorption is a wastewater purification technique for removing a wide range of compounds from industrial wastewater. Adsorption takes place when molecules in a liquid bind themselves to the surface of a solid substance.  Adsorption is often used for water purification, because of good processability, low cost and less secondary pollution to the environment.

The main adsorbent is active carbon, although some advanced TiO2 products, like Tronox’s CristalACTiV™ ultrafine TiO2, can also be used for specific applications.

For example2, arsenic is naturally present at high levels in the groundwater of a number of countries. It can be removed by passing untreated water through adsorptive granular media contained in a pressure vessel. As the water passes through the media, the negatively charged arsenic V ions are adsorbed onto the surfaces of the positively charged media particles.

Interestingly, TiO2 contributes to water treatment applications, both as an oxide for adsorption but also through its co-products as coagulants.

As a leading TiO2 manufacturer, Tronox proposes both solutions.

For more information on co-products used as coagulants and the CristalACTiV™ ultrafine TiO2 product range for adsorption in water treatment, please visit us at https://www.cristalactiv.com/ and https://www.tronox.com/products/.

 

1 https://ourworldindata.org/water-access

2 https://www.who.int/news-room/fact-sheets/detail/arsenic

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