A visible light driven photoelectrocatalytic fuel cell for clean-up of contaminated water supplies

A visible light driven photoelectrocatalytic fuel cell (PECFC) recently developed at Aberdeen has been shown to have the capacity to oxidatively degrade a wide range of contaminants commonly found in water supplies and associated with risk to human health. It has also shown great potential to kill human pathogens such as toxigenic strains of Escherichia coli. Remediation of chemical contaminants has been confirmed by analytical chemistry, and we have integrated a biosensor based assay into the process to confirm concomitant removal of all chemical toxicity. We have also used a biosensor approach to confirm considerable reduction in infection potential associated with human pathogens. The PECFC used to generate the data comprised a basic, batch system with sub-optimal catalyst and static conditions. We are now evaluating the performance of a dynamic, flow reactor (with catalyst optimisation) which continually delivers water borne contaminants (molecules or cells) to the catalyst surface.

In this paper, the combined use of chemical analysis and biological toxicity assessment proved a highly useful approach to assess the capacity of a novel, visible light driven PEC batch reactor to degrade the common water pollutants PCP and 2,4-DCP, and identify the possible appearance of toxic intermediates. Use of a lux marked E. coli O157 highlighted the further potential of the PECFC to target human pathogens. Despite the slow degradation rates associated with the small active catalyst surface area and sub-optimal flow characteristics of this trial reactor, promising remediation of the PCP and DCP was observed, with some evidence of reductions in E. coli O157 population density. This identifies the considerable potential of this advanced oxidative process for the remediation of water contaminated with both organo-xenobiotics and pathogens, despite the relatively low efficiency observed using the current electrode configuration. The authors have recently developed a flow reactor PECFC with a WO3 catalyst integrated into a 400 cm2 Nafion membrane held in a baffled flow cell and illuminated by a visible light LED array. Initial testing of this flow reactor (using 4l working volume and a flow (re-circulating) rate of 1 L minÀ1 demonstrated approximately an order of magnitude greater contaminant (DCP) degradation performance on a mass per unit volume basis over a similar time period (data not shown), compared to the batch reactor proof of concept results reported in this paper. This further highlights the potential of this technology for water sanitation, and particularly in solar rich developing countries.