The supply and demand for clean water in our society is becoming more difficult due to the industrial and domestic activities that introduce a range of pollutants into the water systems.
The anodised titanium electrodes are tested in a parallel plate electrochemical cell that has the possibility of scale-up. Performance parameters such as current efficiency, percentage of degradation of the pollutant, energy consumed per volume of effluent treated and space time yield can be determined. Electrochemical technologies have been applied in effluent treatment for more than three decades and an efficient mass transport rates is necessary to achieve the maximum performance. This is particularly important when the concentration of the reactant (the pollutant) is low. Mass transport can be increased by: a) high flow rates, b) design of flow distributors and c) turbulence promoters. The mass transport can be investigated by calculating the limiting current IL given by:
IL = nFAkmc
where n is the number of electrons involved in the reaction, F is the Faraday constant, A is the electrochemical surface area, km is the mass transport coefficient and c the concentration of the reactive species. The cell design should also consider the current and potential distribution on the electrodes in order to increase the current efficiency and the selectivity of the reaction.
Due to their low area/electrolyte volume ratio, parallel plate electrochemical cells are often used in the electrochemical process. Their design is simple and can easily be scaled-up. Other cell designs include: a parallel plate cell containing three-dimensional electrodes offering a large surface area and, therefore, great capacity to treat large volumes of contaminated water and the rotating cylinder electrode which offers an even current and potential distributions, and high mass transport rates.
In this context, it is interesting to investigate new types of oxide semiconductor surfaces at the nanometer scale and a pilot photocatalytic cell design for possible applications in the waste water treatment of effluents. These materials need to be of an excellent quality and have a high photoelectrochemical response, to be economically viable and to present characteristics which are the same or superior to the ones already existing in the market (DSA and TiO2 particles, PbO2 and BDD electrodes).