After intense years of great development, the electrochemical technologies have become very suitable alternatives in niche markets like industrial wastewater reclamation and soil remediation. A key role to achieve a high efficiency in such treatments is played by the characteristics of the coating of the electrodes employed. This paper compares three techniques, namely immersion, painting and electrophoresis, for the preparation of IrO2-Ta2O5ǀTi, so-called dimensionally stable anodes (DSA(®)). The quality of the coatings has been investigated by means of surface and electrochemical analysis. Their ability to generate hydroxyl radicals and degrade aqueous solutions of hydrocarbons like phenanthrene, naphthalene and fluoranthene has been thoroughly assessed. Among the synthesis techniques, electrophoretic deposition yielded the best results, with DSA(®) electrodes exhibiting a homogeneous surface coverage that led to a good distribution of active sites, thus producing hydroxyl radicals that were able to accelerate the degradation of hydrocarbons.

Most commonly employed anodes for photoelectrochemical degradation of organic contaminants in water are too thick, resulting in a lower degradation efficiency due to an excessive electron-hole recombination. Multilayer-type TiO2/Au/TiO2 nanocomposites have been prepared as photoanode thin films by pulsed laser deposition (PLD). The films were composed of six TiO2 and five Au alternate layers, with total thickness of about 212 nm, aimed to optimize the absorption of photons and minimize the recombination. The influence of gold on the optical, structural, and chemical properties of the semiconductor nanocomposites was investigated. The band gap determined from Tauc model was 3.22 eV, close to that obtained by spectroscopic ellipsometry and lower than that of the TiO2 film, revealing an enhancement of visible light absorption. The catalytic performance of PLD films was evaluated by using them as anodes in electro-oxidation (EO) and photoanodes in photoelectrocatalysis (PEC) to degrade 39-157 mg L -1 paracetamol in sulfate medium. The drug removal was very slow in EO, due to the low ability to form • OH on the anode surface, which was significantly enhanced upon UVA irradiation in PEC. The presence of Cl − allowed a faster degradation by produced active chlorine. Finally, a hybrid process involving PEC + photoelectro-Fenton (PEF) with an air-diffusion cathode yielded total paracetamol decay in 4-5 min at an anodic potential of +4.0 V because of the efficient • OH generation from Fenton's and photo-Fenton reactions. Hydroquinone, p-benzoquinone and hydroxylated products were detected during EO and PEC. The generation of active chlorine was confirmed by identifying a chlorinated derivative, N-(4-chloro-2-hydroxyphenyl)acetamide, in PEC + PEF treatment.

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Electrochemical incineration using boron-doped diamond electrodes was applied to samples obtained from a refinery and compared to the photo-electro-Fenton process in order to selectively eliminate the phenol and phenolic compounds from a complex matrix. Due to the complex chemical composition of the sample, a pretreatment to the sample in order to isolate the phenolic compounds was applied. The effects of the pretreatment and of pH on the degradation of the phenolic compounds were evaluated. The results indicate that the use of a boron-doped diamond electrode in an electrochemical incineration process mineralizes 99.5% of the phenolic sample content. Working in acidic medium (pH = 1), and applying 2 A at 298 K under constant stirring for 2 hours, also results in the incineration of the reaction intermediates reflected by 97% removal of TOC. In contrast, the photo-electro-Fenton process results in 99.9% oxidation of phenolic compounds with only a 25.69% removal of TOC.