New sponge-like material turns harmful dyes colourless

Researchers at the University of Washington (US) have created an environmentally friendly sponge-like material that can turn harmful dyes spilled into the environment colourless.

Dyes are widely used in industries such as textiles, cosmetics, plastics and food processing. Each year, 700,000 tonnes of dye are produced globally, to colour our clothing, toys and candy. During the manufacturing process, about a tenth of all dye products disappear in the waste stream. Often, they escape conventional wastewater treatment plants, leaching into the environment. Even a little colour can block sunlight from reaching aquatic plants, preventing photosynthesis and disrupting the ecosystem.

In order to remove the colour from these dyes, a team led by the University of Washington created an environmentally friendly way to remove the colour from dyes in a matter of seconds. They developed a sponge-like material made from wood pulp and small bits of metal. The backbone of the material is cellulose, the main structure in plant cell walls and the most abundant natural material on earth. The added metal palladium serves as a catalyst to remove colour quickly.

The material is created through a relatively simple process. The cellulose molecules are combined with palladium, heated and mixed in a blender. After that, the mixture is purified and freeze-dried, turning into a porous, reusable substance. The resulting sponge is more than 99 per cent air. The large pores allow water to flow in and oute, while the metal catalyst particles remove any colour present.

While the material does not remove the dye, it does make sure sunlight can reach into the water, allowing plants to grow normally again. The sponge material alters the dye structure to change its colour to clear.

Photos: Mark Stone/University of Washington