Cleaning water with nanoscience

The research lab of Associate Professor of Fiber Science Juan Hinestroza is using metal oxide nanoparticles –particles less than 100 nanometers in dimension – to create filtration systems designed to selectively capture or decompose contaminants such as dyes from textile manufacturing, arsenic from fracking, mercury and cyanide from coal mining, and insecticides and fertilizers from agricultural production.

Indigo used to dye textiles such as blue jeans – a process that involves repeated washes and produces massive amounts of contaminated water – goes back into the water stream and creates negative environmental and health consequences, largely in parts of the world with limited environmental regulations.

“Indigo creates problems for organisms living in the water,” Hinestroza explained, “darkening it and decreasing the amount of sunlight that can penetrate the water, which decreases the ability of the organisms living there to capture oxygen, asphyxiating them. It contaminates the drinking water of people living downstream, and they swim and shower in that water, causing skin problems.”

Hinestroza’s research takes advantage of the porosity of natural fibers such as cotton or fique by incapsulating nanoparticles of different metal oxides into cavities in the fibers. This creates nanoreactors where the water polluted with indigo comes into contact with manganese oxide nanoparticles and is broken down into smaller molecules that eventually become carbon dioxide and water, the process of oxidation.

“Materials on a nanoscale behave differently than they do at a larger scale. The property that enables the chemical reaction is amplified if the dimensions of the material are smaller. At a smaller size there are more atoms on the surface of the material, with a higher number of atoms you have an increased surface area and increased chances for the chemical reaction.”

In lab testing, Hinestroza’s fiber filtration removes around 98% of indigo in five minutes.

Although the filters could be used as water enters a treatment facility, Hinestroza explained that the filters are more effective where the contamination is the most concentrated – at the source.

“We envision putting this into the factory water system. Basically, we fill a pipe with these fibers and as the water goes through the pipe system the indigo is decomposed, before going back into the water stream.”

This same technology could be utilized in laundromats and residential applications to remove micropollutants found in water streams, such as microplastics or pharmaceuticals like diabetes and birth control medications that are eliminated from the body and end up in rivers and lakes.

“The next step in our research is exploring the use of the same materials to capture or decompose other contaminants, whether from agriculture, from mining, manufacturing, or from your home,” he said.