Photooxidation of As(III) by electrophoretically deposited TiO2 monitored by advanced electroanalytical techniques

The presence of heavy metals in wastewaters causes great environmental damages and human health problems. Among hazardous metal ions, arsenic (III) is one of the highly harmful pollutant especially in drinking water, due to its acute toxicity and easy migration. Arsenic is a carcinogen and its ingestion may deleteriously affect the gastrointestinal tract, cardiac, vascular system and central nervous system. [1] Various treatment technologies have been developed for arsenic removal from drinking water. The commonly used technologies include coagulation and precipitation with iron and aluminum salts [2], adsorption onto activated alumina, activated carbon, ion exchange and reverse osmosis. Moreover, coagulation, precipitation and other adsorption techniques such as, activated alumina, and activated carbon, have been found to be not as efficient for As(III) removal as for As(V) removal. Recently, many efforts have been devoted to the development of removal processes based on photocatalysis assisted by TiO2 nanoparticles [3]. Several studies on photoinduced pollutant redox reactions are commonly based on the use of highly dispersed titania nanopowders [4]. However, the application of photocatalysis in slurry for industrial purposes is limited due to the highly expensive filtration steps (especially for nanosized powders) and to the difficulty in recycling these particles. To overcome these problems, several methods have been employed to immobilize particles on metal substrates, including sputtering, physical and chemical vapour deposition, screen-printing, dip- and spin-coating techniques [5]. In our previous work [6], electrophoretic deposition (EPD) has been proposed as a versatile and low cost alternative procedure to deposit titania in dense layers onto electrodes to be used in photocatalytic degradation of pollutants, avoiding slurry filtration steps. The present work aims to investigate the photocatalytic performances of different titania films, obtained by electrophoretic deposition (EPD), towards the As(III) oxidation followed by two electroanalytical determinations. Electroanalysis was chosen among different analytical techniques since electrochemical methodologies show several advantages: high speed of analysis, good sensitivity and selectivity, low detection limits (ng/L or µg/L), relative simplicity and low cost equipments. Moreover, voltammetric pulsed techniques (Differential Pulse Voltammetry, DPV, Square Wave Voltammetry, SWV), preceded by cathodic or anodic stripping pre-treatments, have given excellent results adopting various types of bulk electrodes.