Catalytic approach to greywater

Most of you reading this will be lucky enough to have clean water pumped directly into your homes. In the UK, the quality of the domestic water supply is exceptionally high – in most cases, we can drink it directly from the mains supply. But this drinking-quality water is also used for everything else – to flush our toilets, wash our laundry (and ourselves) and water our plants. Surely there is a better way to use and reuse our water in the home?

I recently met Prof Stan Golunski, Co-Director of the Cardiff Catalysis Institute (CCI) and he told me about a project that may go some way to achieving this aim. CCI’s approach is to make more of greywater - the wastewater generated from sinks, showers, washing machines and dishwashers. CCI are developing a system that uses palladium-gold (Pd-Au) nanobeads as the catalysts in a process to directly synthesize dilute hydrogen peroxide (H₂O₂) from greywater. Their unique alloyed nanobeads behave as selective catalysts for the process. Palladium can catalyze this reaction, but the addition of gold doubles the rate of hydrogen peroxide formation by ‘switching off’ further hydrogenation of H₂O₂ to water.

So how do the team at the CCI see their catalytic system working? “We are currently at the proof-of-concept stage of the project,” said Golunski, “but eventually, we hope that this technology could provide a new ‘white good’ in the average kitchen.”

In such a system, the process would have three steps: (i) a filter removes solids from the greywater (ii) an electrolyzer then splits a small amount of water into hydrogen and oxygen, and (iii) in a catalytic reactor containing Au-Pd nanobeads, hydrogen and oxygen are recombined, creating a dilute solution of hydrogen peroxide that acts as a decontaminant. H₂O₂ is also an effective disinfectant 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.

Earlier this year, the CCI joined forces with the Knowledge Centre for Materials Chemistry (KCMC), an organization that enables collaborations across the UK chemistry landscape, from industry to academia. For institutions like the CCI, this partnership is helping them to grow their research in new applications. According to John Conti-Ramsden, Director of the KCMC, the use of catalysts in wastewater treatment is gaining real traction in the UK. Conti-Ramsden says that “…because catalysts are not consumed in chemical reactions, they could offer an environmentally sustainable solution to the growing question of water purity and security.”

This story is provided courtesy of the Knowledge Centre for Materials Chemistry (KCMC) material and Proof Communication. The views expressed in this article do not necessarily represent those of Elsevier.