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NOVIDADES
Removing pathogens from drinking water is especially difficult when the germs are too tiny to be caught by conventional filters. Researchers at Empa and Eawag are developing new materials and processes to free water from pathogenic microorganisms such as viruses. Water is life, biology teaches us. Reality teaches us something different: Water contaminated with pathogens causes hundreds of thousands of deaths each year in places where water treatment is lacking or poorly functioning. To put an end to this, the availability of clean water for all mankind has been included in the United Nations (UN) Global Sustainability Agenda since 2015. In accordance with this goal, Empa researchers, in collaboration with their colleagues at Eawag, are developing new materials and technologies to remove pathogens from drinking water, which until now could hardly be eliminated with conventional measures, or only with expensive and complex processes. "Conventional water filters are ineffective against rotaviruses," explains Empa researcher Thomas Graule from Empa's High Performance Ceramics lab in Dübendorf. However, it is precisely these tiny germs that are among the most common pathogens causing gastrointestinal infections. According to the World Health Organization (WHO), in 2016 around 130,000 children worldwide died from rotavirus infections. The researchers have now developed strategies for filtration technologies based on new materials that cleverly circumvent the problem of minuteness. This is because one property of the virus particles can be used for a new type of filter: the negative electrical charge of the virus particles. Empa researchers are developing novel filter systems made of composite materials such as ceramic granules with a copper nanocoating as depicted here (electron microscopy, colored). Image: Sena Yüzbasi / Empa
For their investigations, the researchers therefore chose a model virus that is even smaller than the rotavirus: the bacteriophage MS2, which is only 27 nanometers in size a virus that attacks bacteria but is harmless to humans. Using this model virus, the scientists were able to show that viruses in water adsorb to the filter surface to varying degrees depending on the water's pH. "This must be taken into account when developing new water treatment and filter technologies," says Graule. "In water, the surface of the virus particles is negatively charged. We were able to show how the virus particles attach themselves to positively charged surfaces," he explains. For example, the researcher is working in an international team on ceramic granules made of aluminum oxide, whose fine granules are coated with nanometer-thin layers of copper oxide. "Together with the ceramic, the highly porous copper layer forms a composite material with a positively charged and immensely large specific surface," says Graule. The researchers were also able to coat tiny multi-layer carbon nanotubes with copper oxide, thus enabling virus elimination.
Multilayer carbon nanotubes (shown here in the model) can be coated with copper oxide and eliminate viruses from contaminated water. Image: istock
At the end of the project, a filter technology is expected to be available that is also suitable for water treatment in developing countries with their particularly high numbers of rotavirus and other water-borne diseases. Empa. Posted: April 29, 2021.
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