Water & Wastewater Treatment

30 | november 2014 | WWT | www.wwtonline.co.uk In the know Getting to grips with catalysis How could catalysis be used domestically? Another project that the CCI is working on could find an application closer to home. In the UK, we have clean drinking water pumped directly into our homes. But that same water is used to wash clothes and flush toilets, mak- ing for an expensive and inefficient domestic water cycle. We see that there are ways to improve this, by making more use of greywater - the wastewater generated from sinks, showers, washing machines and dishwashers. The CCI's approach uses palladium- gold nanobeads as the catalysts in a process to directly synthesise dilute hydrogen peroxide (H2O2) from greywater. How does this process work? The process has three steps. First, a filter is used to remove solids from the greywater; an electrolyser then splits a small amount of water into hydrogen and oxygen; finally, hydrogen and oxygen are recombined in a catalytic reactor containing Au-Pd nanobeads. This produces a dilute solution of hydrogen peroxide that acts as a decontaminant. H2O2 is also an effective disinfect- ant and bleaching agent, which is more environmentally-friendly than chlorine. When produced in this very dilute form, it can be used to purify recirculated water for baths, sinks and washing machines in the average home. The project is currently at the proof-of-concept stage, but eventually, it is hoped that this technology could provide a new 'white good' in the average kitchen. What are the next steps for catalysis research? As in all applied research, the key to developing commercially viable catalytic water treatment systems is through open, timely, cross- disciplinary collaborations. We still have a number of engineering challenges to solve in order to grow our research beyond the academic lab environment. We're engaging with stakeholders across a wide-range of sectors, and we're moving toward testing both systems in realistic test-bed environments. For us, this catalytic approach to wastewater treatment can solve a range of challenges on both a domestic and industrial scale. For more info go to wwtonline.co.uk A schematic of the Catalytic Wet Air oxidation (CWAo) process, which works in a similar way to a car's catalytic converter An electron microscope map of a single bi-metallic Au-Pd nano- particle, with a diameter of 5 nm, used in the synthesis of H202. Colour has been added to show the metal distribution.

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