Reusable polymer can remove dyes from wastewater

Researchers from North Carolina State University have demonstrated that a synthetic polymer can remove certain dyes from water and that the polymer can be recovered and reused. The results offer a potential new method for cleaning up wastewater after it has been used by textiles, cosmetics or other industries.

“Dyestuffs are used everywhere, including in the textile industry, as well as in pharmaceuticals, cosmetics, paper, leather and even in medicines,” said Januka Budhathoki-Uprety, lead author of a paper. on labor and assistant professor of textile engineering. , chemistry and science at NC State. “If these contaminants are not properly removed from wastewater after dyeing and finishing, they can be a significant source of environmental pollution and pose risks to human health.”

In the study published in ACS Applied Polymer Materials, the researchers made a synthetic polymer called polycarbodiimide. The researchers then tested the material’s ability to clean sewage by first dissolving it in a solvent and then mixing it with dye-contaminated water. They tested the polymer solution against a series of 20 anionic dyes, also called acid dyes, which are used in the textile industry. For the first evaluations, the researchers performed a visual test with the naked eye to see if the polymer worked. The researchers then quantified how well the polymer removed the dye using UV-Vis spectroscopy.

“We mixed the polymer solution and the dye-contaminated water so that the polymer in the solution could cling to the dye. It is a two-phase solution, just like oil and water. The polymer part of the solution clings to the dyes,” Budhathoki-Uprety said. “Then we were able to easily separate the clean water from the contaminated solution mixture by emptying it, similar to separating water from an oil and water mixture.”

The polymer solution removed all but four of the 20 acid dyes they tested. Additionally, they found it easy to recover the polymer within minutes. They found characteristics of the dyes – related to their molecular structures – that helped determine whether the polymer worked or not.

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

In future studies, the researchers plan to develop a library of polymers that have the potential to work with more types of dyes. Additionally, they want to develop a more convenient mechanism for using polycarbodiimide to clean wastewater.

“We are working to develop materials that can do the same job without having to use the polymer in the solution phase,” Budhathoki-Uprety said. “If you have a dye spill, you don’t want to have to use a flammable solution – you want a solid material that’s easier to handle.”

Reference: Lord MD, Neve G, Keating M, Budhathoki-Uprety J. Polycarbodiimide for the removal of textile dyes from contaminated water. ACS Appl Polym Mater. 2022;4(8):6192-6201. doi: 10.1021/acsapm.2c00959

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