Preparation of IrO2-Ta2O5|Ti electrodes by immersion, painting and electrophoretic deposition for the electrochemical removal of hydrocarbons from water

Abstract

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.

IrO2-Ta2O5|Ti electrodes prepared by electrodeposition from different Ir:Ta ratios for the degradation of polycyclic aromatic hydrocarbons

“…The precursor solutions were prepared using H 2 IrCl 6 [31][32][33][34] and TaCl 5 [47], both purchased from Strem Chemicals (≥ 99.9% purity). They were then dissolved in HCl [44] and isopropanol [34,44], respectively, under vigorous stirring. Four different test precursor solutions were further prepared to be used in the coating process by mixing the appropriate amount of prepared metal solutions to obtain Ir:Ta molar ratios of 100:0, 70:30, 30:70, and 0:100.…”

“…Four different test precursor solutions were further prepared to be used in the coating process by mixing the appropriate amount of prepared metal solutions to obtain Ir:Ta molar ratios of 100:0, 70:30, 30:70, and 0:100. Before electrodeposition, the Ti-plates (each 5.0 mm × 15.0 mm × 1.0 mm) that were to be used as substrates were pretreated by sandblasting [34,44], etching in a 40% oxalic acid solution for 20 min [31,44], and finally rinsed with deionized water and dried. Electrochemical deposition was performed at a constant current density of 14 mA cm -2 for 20 min under constant stirring at 825 rpm [44].…”

“…Before electrodeposition, the Ti-plates (each 5.0 mm × 15.0 mm × 1.0 mm) that were to be used as substrates were pretreated by sandblasting [34,44], etching in a 40% oxalic acid solution for 20 min [31,44], and finally rinsed with deionized water and dried. Electrochemical deposition was performed at a constant current density of 14 mA cm -2 for 20 min under constant stirring at 825 rpm [44]. Once the coated Tielectrodes were prepared, the coatings were transformed into metal oxides using a 2-step thermal decomposition procedure: heating at 523 K for 10 min, followed by heating to 723 K and holding for 1 h [34,44].…”

“…Several authors have reported the electrochemical treatment of various PAHs with different types of mixed metal oxides [41][42][43]. Our teams have recently shown the feasibility of PAHs removal by EO with IrO 2 -based anodes synthesized using different techniques [44]. Classical synthesis routes have included thermal decomposition and the sol-gel 'Pechini' method [28].…”

Facile crosslinking of poly(vinylpyrrolidone) by electro-oxidation with IrO2-based anode under potentiostatic conditions

“…This means that it mainly exists as a superoxide (MO) and pre-eminently favors a milder reactivity with organic molecules [29,30]. These kinds of anodes are made of metal and mixed-metal oxides [30,31], being IrO 2 -based anodes preferred for O 2 evolution with M( • OH ) as intermediate [32][33][34][35][36][37][38]. As a result, the attack of this species on PVP may be more controlled.…”