University UK
The nanotechnology theme which they are active in is related to the integration of nanodimensional (approx. 20 nm) photoelectrocatalyst particulates in a photoelectrocatalytic fuel cell (PECFC). The PECFC is currently being developed under DTI-industry funding and has already demonstrated effective degradation of organic and microbiological pollutants at the laboratory scale. The current funded programme is aimed at producing a scaled up demonstration prototype.
The catalyst provides a high area surface on which the organic pollutants (including biological cell membranes) are adsorbed and oxidised. This chemical process extracts electrons from the pollutant molecule which are withdrawn into an external circuit to regenerate the catalysts and in doing so, provides a useable current. The catalyst also behaves as a photocatalyst, generating electrons and holes under illumination by visible light so that the oxidising potential and current delivering characteristics of the catalyst are increased. Therefore, unlike conventional photocatalysts which require UV radiation, the degradation processes in the PECFC are sustained by visible light illumination, providing an opportunity for sunlight sustained water purification.
The effectiveness of the cell is monitored using integrated biosensor technology currently being developed. This addresses concern over formation of toxic degradation products which can arise during alternative treatments. They have demonstrated that during the oxidation of naphthalene, a common groundwater pollutant in areas of former industrial activity, the formation of more toxic catechols show a rise in system toxicity. However, the cell continues to degrade the catechols and the biosensors confirm the consequent reduction in system toxicity. Coupled with the cell’s electrical output, this feature provides means of regulating discharge from the cell. This coupled approach currently utilises a batch configuration and confirms the effectiveness of the PECFC against a range of ubiquitous environmental pollutants, including chlorinated phenolics, polyaromatic hydrocarbons, oestrogens and pathogens (E-coli O157).
As the world’s population continues to rise the provision of clean drinking water becomes increasingly challenging. The world water supply industries have invested £57 billion in the last 10 years on technologies to meet regulatory requirements and this rate of investment is expected to increase with increasing health risk issues and continually changing regulation. Discharge from sewage, agricultural run-off and storm water drainage all contribute to water contamination and in developing countries in particular, these problems are especially acute.
Of special difficulty in water treatment technologies is the removal of persistent organic and microbiological pollutants. Existing technologies only have limited effectiveness against these but as they pose a continuing threat to the health of the population, the pressure to introduce innovative technologies is continually rising. The PECFC is principally a water clean-up technology and having demonstrated, at the laboratory scale, oxidatative degradation of robust environmental pollutants, including some of the key targets; it represents a platform for development and exploitation in domestic and international applications and markets. Already focussed toward the water supply and treatment industry (regional and domestic), other significant business opportunities are envisaged in contaminated land, offshore waste management, trade effluent clean-up and domestic consumer markets.
