The findings from a team at North Carolina State University are claimed to offer a new potential method for cleaning wastewater after use by textiles, cosmetics or other industries. Their research is published in ACS Applied Polymer Materials.
“Dyes 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 the work and an assistant professor of textile engineering, chemistry and science at NC State. “If these contaminants aren’t properly removed from wastewater after dyeing and finishing, they can be a significant source of environmental pollution and pose risks for human health.”
For their study, the researchers made polycarbodiimide and tested the material’s ability to clean wastewater by dissolving it in a solvent and then mixing it with water contaminated with dyes. They tested the polymer solution against a series of 20 anionic dyes (acid dyes), which are used in the textile industry. For initial assessments, the researchers did a visual test with the naked eye to see if the polymer worked. The researchers later quantified how well the polymer removed the colourant using UV-Vis spectroscopy.
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“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,” Budhathoki-Uprety said in a statement. “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 solution removed all but four of the 20 acid dyes they tested. In addition, they found it was easy to recover the polymer within minutes. They found characteristics of the dyes – related to their molecular structures – that contributed to 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 dye from contaminated water again,” Budhathoki-Uprety said.
In future studies, researchers are planning to develop a library of polymers that would have the potential to work with more types of dyes. They also want to develop a more practical mechanism for using polycarbodiimide to clean wastewater.
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