The metal and chemical industry, although essential to the global economy, faces a major challenge: the contamination of wastewater with heavy metals. To mitigate this problem, highly advanced filter systems have been developed. However, the production of these filters has, until now, been anything but environmentally friendly. Aware of this contradiction, a team of researchers in Vienna is working on developing biofilter systems that not only promise to be more environmentally friendly, but also more cost-effective.
A persistent problem in the industry
In recent decades, strict EU regulations have succeeded in drastically reducing emissions of heavy metals into European waters from the chemical industry, metallurgy and metal processing. Despite these advances, the current technology used to filter out metals such as lead, zinc, copper and chromium, although effective, involves the use of petroleum-derived materials and complex processes that in turn generate hazardous waste.
Lignin: a natural solution with potential
A research group at the University of Vienna, led by Alexander Bismarck, Hande Barkan and Philip Verdross, is developing a promising alternative based on lignin, a by-product of the paper industry. This project, funded by the Austrian Science Fund (FWF), aims to create bio-based macroporous materials that act as heavy metal absorbers. Lignin, which gives stability to plant cell walls, is the main component of these new filters.
“Lignin is obtained as a by-product in the production of cellulose in the paper industry, specifically from black liquor, which in addition to lignin contains chemical residues used in extraction,” explains Hande Barkan, a chemist and member of the research team. “It is a cheap and abundant starting material, which makes it an excellent option for developing more sustainable and economical solutions for wastewater filtration.”
Technology and sustainability: a winning combination
The key to the success of these new filtration systems lies in the permeable polymer structure that is obtained by integrating biological raw materials such as lignin. The pore structure, which can be specifically tuned for the adsorption of heavy metals, is essential to maximise filtration efficiency. “In the project we focused on the adsorption of chromium VI, a highly toxic metal used, for example, in leather tanning and which often ends up unfiltered in rivers, especially in South-East Asia,” says Barkan. “New sustainable and cost-effective technologies are urgently needed to improve this situation.”
The filters developed in this project not only effectively adsorb chromium VI, but also transform this toxic compound into harmless chromium III. “The highly toxic and carcinogenic chromium VI is converted into chromium III, a step that in conventional processes would require additional treatment,” says Philip Verdross, PhD student and member of the research team. This transformation is a significant advance, as it allows the filtration process to be not only safer, but also simpler and cheaper.
Implications for industry
The technology developed by the Viennese team has great potential for large-scale implementation in industry. Filtration systems based on lignin and other renewable raw materials are not only more environmentally friendly, but also prove to be cheaper to produce. Furthermore, the use of these biofilters could significantly reduce heavy metal pollution in rivers around the world, providing a sustainable solution to a persistent problem.
While lignin is the main component, other agricultural by-products such as vegetable fats and glycerin are also used in the production of these filters. “Amines, although derived from petroleum, play a crucial role in cross-linking natural molecules and binding heavy metals to polymers,” adds Barkan, stressing that despite the inclusion of these compounds, the overall environmental impact of the development is significantly lower compared to conventional technologies.
A promising future
Research into these biofilter systems marks an important step towards a greener and more sustainable industry. If these filters can be implemented on a large scale, they would not only reduce heavy metal pollution in water bodies, but would also open the door to new applications in the separation of other metals such as copper, lead, arsenic and mercury.
The project “Bio-based macroporous materials as heavy metal sorbents” is funded by the Austrian Science Fund with 330,000 euros and will run until 2025. Alexander Bismarck, director of the Institute of Materials Chemistry at the University of Vienna, and his team hope that their work will not only have an impact on science, but will also offer practical and sustainable solutions for industry worldwide.
Publications
Verdross P., Woodward RT, Bismarck A.: Lignin-based flexing: lignin-based elastomers synthesized from untreated kraft black liquorin: Polymer Chemistry 2024
Barkan-Öztürk H., Verdross P., Bismarck A.: Macroporous lignin adsorbents: a bio-based toolkit to deactivate the Cr(VI) threat in wastewaterin: Journal of Environmental Chemical Engineering 2024
Byambatsogt K., Jiang Q., Jaiswal AK et al.: Pilot-scale cast-coated foam nanocellulose filters for water treatmentin: Chemical Monthly 2024
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