Electrochemical degradation of Reactive Red 120 using DSA and BDD anodes

Abstract

Electrochemical oxidation of an azo dye (Reactive Red 120) was studied in acidic media (1 M HClO 4 ) using DSA type (Ti/IrO 2 -RuO 2 ) and boron doped diamond (BDD) anodes. Ti/IrO 2 -RuO 2 exhibited low oxidation power with high selectivity to organic intermediates and low TOC removal (10% at 25°C and 40% at 80°C). On the other hand BDD was found to be suitable for total mineralization of the organic loading to CO 2 . In both cases, the decoloration of the solution was almost 100% achieved very quickly with BDD (2 Ah L -1 ) but only after long treatment with Ti/IrO 2 -RuO 2 (25 Ah L -1 ). The instantaneous current efficiency (ICE) was up to 0.13 in the case of Ti/IrO 2 -RuO 2 and up to 0.45 in the case of BDD.

A first pre‐pilot system for the combined treatment of dye pollutants by electrocoagulation/EAOPs

“…It has been proven that Ru‐based anodes are more effective, although strong mineralization is only feasible in Cl − media due to the action of active chlorine formed via reaction . Some authors preferred the use of mixed metal oxides (Ti/IrO 2 –RuO 2 ) because of their good electrochemical properties and high corrosion resistance, giving an increased durability and efficiency …”

Electrochemical and Morphology Study of the BDD/Ti Electrodes with Different Doping Levels

“…The BDD/Ti with dimensions of 25x25x0.5 mm was grown from a standard gas mixture consisting of 99 % of H 2 and 1 % of CH 4 . The temperature and pressure inside the chamber reactor were kept at 650 ºC and 50 Torr, respectively for 7 h. The doping control was obtained from an additional H 2 gas flux passing through a bubbler containing a solution of B 2 O 3 dissolved in CH 3 OH with the B/C ratio of 2,000 ppm (E 1 ) and 15,000 ppm (E 2 ). This additional hydrogen flow into the reactor was controlled by a rotameter which was maintained at 40 sccm for both experiments.…”

Electrochemical oxidation of methyl orange azo dye at pilot flow plant using BDD technology

“…The high standard reduction potential of OH (E o ( OH/ H 2 O) = 2.80 V/SHE) makes possible its non-selective reaction with most organics yielding dehydrogenated or hydroxylated derivatives, which can be in turn completely mineralized, i.e., converted into CO 2 , water and inorganic ions. Recently, the degradation of a large variety of azo dyes has been reported by different electrochemical AOPs (EAOPs) such as electrochemical oxidation [1][2][3][4]6,12,[15][16][17][18][19][20][21][22][23][24][25][26], electro-Fenton [27][28][29][30][31][32][33][34] and photoelectro-Fenton [31,32]. The most popular EAOP is electrochemical oxidation or electro-oxidation, where the pollutants are oxidized by direct electron transfer to the anode and/or mediated oxidation with OH formed from water discharge at the anode surface at high current [12,35].…”

“…The most popular EAOP is electrochemical oxidation or electro-oxidation, where the pollutants are oxidized by direct electron transfer to the anode and/or mediated oxidation with OH formed from water discharge at the anode surface at high current [12,35]. The best anodes for this procedure are non-active borondoped diamond (BDD) thin-film electrodes because they interact very weakly with physisorbed BDD( OH) produced by reaction (1) and promote a much greater O 2 -overpotential than other conventional anodes like Pt, DSA and PbO 2 [19,22,23,36,37], enhancing the mineralization of azo dyes due to the efficient removal of ultimate generated carboxylic acids [31,32,38].…”