Electric charge for solar disinfection
Scientists at the University of Aberdeen in Scotland are developing new solar disinfection technology that simultaneously creates electricity. Three industrial partners, OpTIC Technium, Yorkshire Water and Scotoil Services, along with the UK Department of Trade and Industry (DTI), have committed over €1.7million to commercially develop novel technology for breaking up pollutants found in all types of water supplies.
Professor Ken Killham, Donald Macphee and Richard Wells have been developing a biosensor technology which utilises visible light to sustain an oxidative degradation of organic pollutants on a nano-sized catalyst surface. The process differs from conventional photocatalytic oxidation processes because the catalyst is sustained by visible rather than UV radiation, so sunlight-driven decontamination may be envisaged.
However, more fundamentally, the catalyst is supported on an electronically conducting substrate and mounted as an anode in a cell, together with an electrolyte membrane and cathode, in the configuration of a fuel cell.
“Coupling the catalyst in an electrochemical cell has enhanced the rate of degradation of model pollutants compared with conventional photocatalytic processes,” explained Dr Macphee. “The lab-scale prototype has already provided impressive performances for a range of robust environmental pollutants including 2,4-dichlorophenol, naphthalene, humic substances responsible for the discolouration of water, oestrogens, atrazine and pathogenic materials such as E.coli O157.”
The cell also produces usable current, which may be available to power ancillary equipment such as pumps and valves. This is particularly important because the technology is self-monitoring and could be self-regulating.
Professor Killham, who is developing robust luminescent bacteria as integral microbial sensors, indicates that systems which oxidise pollutants often generate by-products which are much more harmful than the primary pollutant. “The biosensors are able to monitor the increased toxicity associated with toxic degradation products. This was evident in the treatment of naphthalene-contaminated solutions, which produced highly toxic catechols.
“Continued exposure of these in the photoelectrocatalytic fuel cell (PECFC) led to their rapid degradation, the corresponding drop in toxicity being confirmed independently by the biosensors and conventional chemical analysis,” he explained.
Potential applications for this technology platform are numerous and include oil and gas, domestic, land remediation, industrial effluents and landfill leachates. The technology has the potential to be more cost-effective and environmentally-friendly than current methods. Perhaps the most attractive application is sustainable water purification in remote regions of sun-rich developing countries.
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