WASHINGTON: Scientists have created a sponge-like material using wood pulp and small bits of metal that can remove harmful dyes in water in a matter of seconds.
Globally, about 700,000 metric tonnes of dye is produced each year to colour our clothing, eye shadow, toys and vending machine candy.
During manufacturing, about a tenth of all dye products are discharged into the waste stream.
Most of these dyes escape conventional wastewater-treatment processes and remain in the environment, often reaching lakes, rivers and holding ponds, and contaminating the water for the aquatic plants and animals that live there.
Even just a little added colour can block sunlight and prevent plant photosynthesis, which disrupts the entire aquatic ecosystem.
“A small amount of dye can pollute a large volume of water, so we needed to find a way to very quickly and efficiently remove the colour,” said Anthony Dichiara, an assistant professor at University of Washington in the US.
“We were pretty impressed with what we were able to achieve,” said Dichiara.
The researchers developed a method that removes colour from water using a sponge-like material they created from wood pulp and small bits of metal.
Cellulose, the main structure in plant cell walls and the most abundant natural material on Earth, provides the backbone of the material, which is decorated with tiny pieces of palladium. This metal serves as a catalyst to help remove colour quickly.
Instead of removing dye from water, researchers sought to change the colour of the dyes to something that falls outside of what we can see in the visible spectrum.
In a study published in the journal Applied Catalysis B: Environmental, researchers described the simple and sustainable process they developed to make the colour-removing material.
The researchers combined cellulose molecules with palladium metal, heated the solution and mixed it in a blender. Then they purified and freeze-dried the material so it became a porous, reusable substance.
The resulting sponge is over 99 per cent air – its large pores allow water to flow in and out, while the metal catalyst particles within the material work to remove any colour present.
The researchers tested their sponge in the lab using blue and red dyes commonly found in the textile industry. They poured the coloured water – already mixed with the existing molecule that helps reduce colour – over the sponge.
As the liquid passed through the material, the resulting water was clear. In another test, they swirled the sponge material inside a jar containing blue-dyed water, and after about 10 seconds the colour disappeared.
Outside of lab tests, the researchers say that many small sponge-like materials could be released into a lake polluted with dye, along with the molecule to help reduce the colour.
“Just a little amount of dye can change the colour of a lake dramatically. This method could work well when you have low concentrations of dye in water that you need to take care of really quickly,” Dichiara said. (AGENCIES)
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