In countries such as India, large amounts of toxic dye waste from the textile industry are discharged directly into waterways, which can harm people and the environment. It can be removed – and it comes from wood.
Developed by scientists from Chalmers University of Technology in Sweden and Malabya National University of Technology Jaipur in India, the material takes the form of a powder composed of cellulose nanocrystals.
The cellulose used for these tiny crystals is extracted from the wood that forms the cell walls. The wood can be obtained as a waste product from pulp/paper manufacturing or the wood industry. That means you don’t have to cut down trees just to make powder.
A negative charge is applied to the surface of the nanocrystals using a ‘simple acid treatment’. This allows selective absorption of dye molecules while allowing water molecules to pass through. And importantly, when the powder is exposed to sunlight, the trapped dye rapidly decomposes into a less toxic form.
No pressure or heat is required at any stage of the filtration process.
As the technology develops further, it is expected that filters made of cellulose nanocrystalline powder will be placed in the wastewater stream of textile mills. Lab tests performed so far have removed up to 80% of dye contaminants from contaminated water samples.
Scientists hope to increase this number by tweaking variables such as treatment time and water pH. Furthermore, the addition of similar cellulose-based materials developed previously may also capture heavy metal contaminants such as chromium.
“Imagine a simple purification system like a portable box connected to a sewage pipe,” says lead scientist Chalmers’ Assoc. Professor Gunnar Westman. “When contaminated water passes through a cellulose powder filter, it absorbs contaminants and sunlight entering the treatment system breaks them down quickly and efficiently. It is a system that could be of great benefit in countries where water treatment is currently inadequate or non-existent.”
A paper on this study was recently published in the journal Industrial Chemistry/Engineering Chemistry Research.
Source: Chalmers Institute of Technology
