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Nanocluster Catalysts Remove Toxic Organic Chemicals from Wastewater

Water contamination from dyes used in food, cosmetics, textiles, and other production processes has become a major ecological problem. Numerous chemical companies, such as those that produce textiles, cosmetics, and dyes, discharge hazardous and non-biodegradable dyes into the environment. Azole dyes, including methyl orange, make up over half of the dyes used in the textile and dye industry.

Traditional wastewater treatment frequently fails to eliminate harmful chemicals from wastewater because some chemicals, especially those with aromatic rings, are resistant to chemical, photochemical and biological degradation.

Using a chemical photocatalysis process powered by UV light, Flinders University Prof. Gunther Andersson and Griffith University Research Fellow Dr Anahita Motamedisade have found a unique approach to degrade and potentially eliminate harmful organic compounds, including azo dyes, from wastewater.

The novel process involves creating metallic clusters of just nine gold (Au) atoms chemically ‘anchored’ to titanium dioxide. These clusters drive the degradation of azo dyes into water and carbon dioxide molecules by converting the energy of absorbed UV light to fuel the reaction.

Credit: Flinders University

According to Prof Andersson, this new technology provides a significant advantage over the variety of physical, chemical and biological processes that are currently used to remove carcinogens and other organic compounds from wastewater.These gold nanocluster co-catalysts improve the titanium dioxide’s photocatalytic activity and cut down on the reaction’s completion time by a factor of six.

Flinders University nanotech researchers continue to explore how these gold cluster co-catalysts could be used to create innovative photocatalysis systems for methyl orange degradation.

Investigating surface atoms and clusters that are below the nanometre scale is no easy task. To achieve this, Prof Andersson’s team combined a range of nanoscale imaging and analysis techniques, supported by the Australian National Fabrication Facility (ANFF) and Microscopy Australia.

One of these instruments was custom-built to combine six analysis techniques that allows for detailed analysis of the sample’s surface. Constructed in collaboration with German-based SPECS group and supported by ANFF, the unique instrument incorporates Metastable Induced Electron Spectroscopy (MIES) and allows investigation of the electronic structure of only the outermost layer of atoms – which is where all the interesting chemistry occurs. This new instrument allows rapid fine tuning and monitoring of the cluster properties.

To further investigate this surface, Prof Andersson’s team accessed a range of instrumentation across Microscopy Australia’s Flinders University and University of Adelaide facilities. This included scanning transmission electron microscopy enabling chemical and structural investigation of the co-catalysts at near atomic resolution. This was used to reveal not only the elemental composition of the photocatalysts but also to provide evidence that the gold atoms had indeed ‘anchored’ to the titanium dioxide. Scanning electron microscopy was also used to reveal how rough the surface of the catalyst was. Increased roughness increases the surface area of the catalyst, increasing the rate of chemical reaction. This is why the researchers need to be able to measure and control this morphology.

Both ANFF and Microscopy Australia are funded through the Australian Government Department of Education’s National Collaborative Research Infrastructure Strategy (NCRIS). The 26 projects funded by NCRIS give researchers and industry access to equipment, data, services and expertise to enable world-leading research and development for the benefit of all Australians.

With continuing NCRIS support, Prof Andersson and Dr Motamedisade can continue their development of robust and efficient nano-photocatalytic solutions that ensure full degradation of dyes and other water pollutants, providing a new wastewater treatment solution to tackle water pollution.