In wastewater produced by the textile industry and others, dye is one of the primary pollutants. A newly developed synthetic polymer is capable of removing that dye from the water, plus it can be cleaned up and reused to treat more wastewater.
The nitrogen-rich, water-insoluble polymer is known as polycarbodiimide, and it was created by a team at North Carolina State University.
In lab tests, the polymer was first dissolved in a solvent, then mixed into water samples contaminated with 20 different types of acid dye commonly used in the textile industry. Depending on factors such as acidity and the surface area of the dye molecules, the polymer was successfully able to remove all of the dye from 16 of the samples – this was assessed both by eye, and using ultraviolet-visible spectroscopy.
The polymer works by bonding with the dye molecules then rising to the top of the polymer/water solution, where it forms a separate layer (like oil lying on water). It can then be decanted from the container, leaving the now dye-free water behind. Lead scientist Prof. Januka Budhathoki-Uprety told us that because both the polymer and the solvent aren't water-soluble, traces of neither remain in the water.
By modulating the pH of the poured-off dye-laden polymer, it's possible to get the polymer to release the dye molecules within a matter of minutes. The polymer can then be reused in subsequent wastewater treatments.
Budhathoki-Uprety and colleagues now plan on creating other versions of the polymer, which will work on a wider variety of dyes. They also hope to incorporate the polymer into a solid filtration medium.
"We are working to develop materials that can do the same work without having to use the polymer in the solution phase," she said. "If you have a dye spill, you don’t want to have to use a flammable solution – you want a solid material that is easier to handle."
A paper on the research was recently published in the journal ACS Applied Polymer Materials.
Source: North Carolina State University