A substance that scrubs textile dyes from wastewater

The fashion, art, design and paint industries can’t do without them, but over-use of dyes harms the planet and its people.

But the fashion industry at least has now found a way to clean them up. A team of US researchers has recently developed a polymer which can clean water which has been mixed with a class of dyes.

“Dyes are used everywhere, including in the textile industry, as well as in pharmaceuticals, cosmetics, paper, leather and even in medicines,” says Januka Budhathoki-Uprety, an assistant professor of textile engineering, chemistry and science at North Carolina State University in the US, and lead author on a paper published in ACS Applied Polymer Nanomaterials.

“If these contaminants aren’t properly removed from wastewater they can be a significant source of environmental pollution and pose risks for human health.”

The researchers made a substance, called polycarbodiimide, and mixed it into a solvent before combining it with dye-contaminated wastewater.

“We mixed the polymer solution and dye-contaminated water so the polymer in the solution can grab on to the dye. This is a two-phase solution, just like oil and water. The polymer part of the solution grabs onto the dyes,” says Budhathoki-Uprety.

“Then we were able to easily separate the clean water from the contaminated solution mixture by draining it out, similar to separation of water from a mixture of oil and water.”

The polymer could extract 16 out of the 20 dyes they tested. All of the dyes they tested were anionic dyes, or acid dyes – commonly used in the textile industry.

 “We found that the polymer solution can remove dyes from contaminated water, and we can recover the polymer and use it again,” says Budhathoki-Uprety.

The dye-cleaning polymer isn’t ready to roll out industrially just yet – the solvent it needs to be dissolved in to work is flammable, making it less than ideal for big wastewater clean-ups.

“We are working to develop materials that can do the same work without having to use the polymer in the solution phase,” says Budhathoki-Uprety.

“If you have dye spill, you don’t want to have to use a flammable solution – you want a solid material that is easier to handle.”

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