The use of carbon and gold electrodes in anodic stripping voltammetric heavy metal sensors.

The use of anodic stripping voltammetry (ASV)has been proven in the past to be a precise and sensitive analytical method with an excellent limit of detection. Electrochemical sensors could help to avoid expensive and time consuming procedures as sample taking and storage and provide a both sensitive and reliable method for the direct monitoring of heavy metals in the aquatic environment. Solid electrodes which have been used in this work, were produced using previously developed methods. Commercially available and newly designed, screen printed carbon and gold plated working electrodes (WE) were compared. Good results were achieved with the screen printed and plated electrodes under conditions optimized for each electrode material. The electrode stability, reproducibility of single measurements and the limit of detection obtained for Pb were satisfactory (3*10-6mol/l on screen printed carbon WEs after 60 s of deposition and 6*10-6 mol/l on gold plated WEs after 5 min of deposition). Complete 3-electrode-sets (counter, reference and working electrode) were screen printed on different substrates (glass, polycarbonate and alumina). Also here, both carbon and gold were used as WE. Using 3-electrode-sets with a gold plated WE on glass was a limit of detection of 7*10-7 mol/l was achieved after only 60 s of deposition

Energy efficient operation of photocatalytic reactors based on UV LEDs for pollution remediation in water.

Photocatalytic technology using TiO2 is one of the emerging approaches for water treatment, especially as a final step to remove complex organics such as pesticides, hormones or humic acids. Titanium dioxide (TiO2) is a semiconductor material with strong UV absorption band and exhibits strong photocatalytic activity. The photocatalytic activity of TiO2 powders have been extensively studied, using UV light sources. However, the incident photons that initiate the process of photocatalytic oxidation using titanium dioxide are not efficiently used, this is responsible for the low photonic efficiency that characterise oxidation of aqueous pollutants hence its limitation in industrial applications. Periodic illumination has been investigated as a means of increasing the photonic efficiency in a photoreactor with acid orange as a model pollutant. Results indicate more than four-fold increase in photonic efficiency through periodic illumination compared to continuous illumination. This approach can improve the energy efficiency of the photocatalytic water treatment systems