Researchers have developed a new method that can easily purify contaminated water using a cellulose-based material.
- So far, laboratory tests with industrial water have shown that more than 80% of the dye pollutants are removed with the new method.
- This discovery could have implications for countries with poor water treatment technologies and combat the widespread problem of toxic dye discharge from the textiles industry.
- The method has been developed by a research group at the Chalmers University of Technology led by Gunnar Westman, Associate Professor of Organic Chemistry.
- The research group focuses on new uses for cellulose and wood-based products, and is part of the Wallenberg Wood Science Center.
- The findings have been recently published in the scientific journal Industrial & Engineering Chemistry Research.
- The research was conducted in collaboration with the Malaviya National Institute of Technology, Jaipur in India, where dye pollutants in textile industry wastewater are a widespread problem.
The Research: The researchers have shown how toxic dyes can be filtered out of wastewater using the method and material developed by the group.
- They first built up a solid knowledge base about cellulose nanocrystals, and this is where the key to water purification lies. These tiny nanoparticles have an outstanding adsorption capacity, which the researchers have now found a way to utilise. [Nanocrystals are nanoparticles in crystal form that are extremely small: a nanoparticle is between 1 and 100 nanometres in at least one dimension, i.e. along one axis. (one nanometre = one billionth of a metre).]
- The treatment requires neither pressure nor heat, and uses sunlight to catalyse the process. It is akin to pouring raspberry juice into a glass with grains of rice, which soak up the juice to make the water transparent again.
Method to be Tested in India: India is one of the developing countries in Asia with extensive textile production, where large amounts of dyes are released into lakes, rivers and streams every year. The consequences for humans and the environment are serious.
- Water contaminant contains dyes and heavy metals and can cause skin damage with direct contact and increase the risk of cancer and organ damage when they enter into the food chain. Additionally, nature is affected in several ways, including the impairment of photosynthesis and plant growth.
- Conducting field studies in India is an important next step, and the Chalmers researchers are now supporting their Indian colleagues in their efforts to get some of the country's small-scale industries to test the method in reality.
Other Uses: There are opportunities to use cellulose nanocrystals for the treatment of other water pollutants than dyes.
In a previous study, the research group showed that pollutants of toxic hexavalent chromium, which is common in wastewater from mining, leather and metal industries, could be successfully removed with a similar type of cellulose-based material.
- The group is also exploring how the research area can contribute to the purification of antibiotic residues.
The Backdrop: The Wallenberg Wood Science Center, WWSC, is a research centre that aims to develop new sustainable biobased materials using raw materials from the forest.
- Over two billion people in the world live with limited or no access to clean water. It is estimated that over 3.5 million people die each year from lack of access to clean water and proper sanitation.
- The global textile industry, which is concentrated in Asia, contributes to widespread water pollution. Production often takes place in low-wage countries, where much of the technology is antiquated and environmental legislation and oversight may be lacking.
- Emissions contribute to eutrophication and toxic effects in water and soil. There are examples in China and India where groundwater has been contaminated by dye and processing chemicals.
- Producing one kilogram of new textiles requires between 7,000 and 29,000 litres of water, and between 1.5 and 6.9 kg of chemicals.
- In 2021, around 327 thousand tonnes of dyes and pigments were produced in India. A large proportion of the country's dye pollutants is discharged untreated.
What They Said:
Imagine a simple purification system, like a portable box connected to the sewage pipe. As the contaminated water passes through the cellulose powder filter, the pollutants are absorbed and the sunlight entering the treatment system causes them to break down quickly and efficiently. It is a cost-effective and simple system to set up and use, and we see that it could be of great benefit in countries that currently have poor or non-existent water treatment.
— Gunnar Westman
Associate Professor of Organic Chemistry
Chalmers University of Technology
