Researchers in India Build Self-Cleaning Glass That Uses Only Sunlight to Purify Water

In a significant development, researchers at IIT Mandi in Himachal Pradesh, have developed self- cleaning transparent calcium (silicated) borate glasses and titanium dioxide glass nano-composites that use sunlight and clean wastewater by killing bacteria and microbes present in dyes, drugs and detergents.

The three people behind this innovation are Dr Rahul Vaish, an associate professor at IIT-Mandi, and research scholars, Gurpreet Singh and Sandeep Kumar.

“Existing technologies can clean up solid pollutants besides dissolved inorganic compounds, but microbes and organic pollutants like dyes and detergents that dissolve in water cannot be removed. This self-cleaning glass can only clean up microbes and organic pollutants, and not solid particles,” says Dr Vaish, in a conversation with The Better India.

Take the example of the textile industry, which releases wastewater into various lakes and rivers carrying effluents that have dissolved into the water.

While sewage treatment plants can filter out the solid particles and toxic inorganic compounds, removing dissolved organic dye compounds that are considered carcinogenic remains a challenge.

How does the self-cleaning glass purify water?
“Photocatalysis is similar to photosynthesis. The glass has a delicate outer coating of titanium dioxide. When ultraviolet light hits the titanium dioxide coating of a self-cleaning glass, electrons are generated. These electrons break the molecules,” says Dr Vaish.

For example, if you have CH4 (methane) in the wastewater, what the electrons mainly do is destabilise the organic compound and break it down into CO2 and H2O. When we are talking about organic compounds, we are referring to the presence of carbon molecules. When we imbalance the structure, we change the compound’s properties, he explains.

“There is no extra cost or capital involved. You only need sunlight,” adds Dr Vaish.

These glasses are developed using a technique called melt quenching, which is the traditional technique of glass making in bulk form which includes mixing of ingredients, heating up to a temperature usually higher than 1300°C and quenching of the glass melt to obtain a glass frit.

“What we have before us is a massive range of glass chemistry. Glass windows, mobile phone screens and dinner sets have different compositions of ingredients, and we have found out which type of self-cleaning glass we would like to make. We are in touch with a few firms seeking our expertise on the subject. Let’s see how we can transfer our technology to these companies,” says Dr Vaish.

According to the press release issued by IIT-Mandi, these easy to fabricate glasses can be made in the form of large panels which can have a wide range of applications from water bottles to large water cleaning tanks. Many researchers have successfully demonstrated the removal of such toxic chemicals from water. However, cost and efficiency associated with existing technologies are significant obstacles in their commercial usage.

The question now is cost and scaling up the production of these glasses.

“Cost-wise, we still have to figure things out. In terms of economic utility, we must also ensure the material does not cause harmful effects, possesses eco-friendly properties, and if the whole production ecosystem works properly, we will look at efficiency and other potential uses,” says Dr Vaish.