Electrochemical oxidation ofp-chlorophenol on SnO₂–Sb₂O₅based anodes for wastewater treatment

Abstract

The influence of an IrO 2 interlayer between the Ti substrate and the SnO 2-Sb 2 O 5 coating on the electrode service life and on the efficiency of p-chlorophenol (p-CP) oxidation for wastewater treatment has been investigated. The results have shown that if the loading of the SnO 2-Sb 2 O 5 coating relative to the IrO 2 interlayer loading (c ratio defined by Equation 1) is high (c ¼ 20-30) the service life of the electrode can be increased without modification of the ability of this electrode to perform p-CP oxidation. This suggests that the oxidation of p-CP using a Ti/IrO 2 /SnO 2-Sb 2 O 5 electrode with high c ratio (c > 20) occurs only through the SnO 2-Sb 2 O 5 component of the electrode, with no interference of the IrO 2 interlayer. However, the electrode potential at a given current density is considerably lower in the case of the Ti/IrO 2 /SnO 2-Sb 2 O 5 electrode. In order to explain this decrease in electrode potential we speculate that water is firstly discharged on IrO 2 , which is present in small amounts on the surface, forming hydroxyl radicals at a relatively low potential. These active hydroxyl radicals then migrate (spill over) towards the SnO 2-Sb 2 O 5 coating, where they are physiosorbed and react with p-CP leading to complete combustion.

Anodic oxidation of organic pollutants on a Ti/SnO2–Sb2O4 anode

“…In fact, even when coated with films, the Ti substrate can be oxidized either during the preparation process or when working as an anode, due to film porosity that makes the electrode permeable to oxygen. Therefore, to avoid TiO 2 interlayer formation, which presents high resistivity, many studies have been performed and several proposals have been presented, including the addition of Pt to the SnO 2 film [33][34][35][36], a prior platinization of the Ti substrate followed by SnO 2 deposition [37], an addition of IrO 2 or a isomorphous structure interlayer [7,[38][39][40][41] or a RuO x [41] or Sb 2 O x interlayer [42,43] between the Ti and SnO 2 . All of these procedures increased the lifetime of the electrodes, in some cases up to two orders of magnitude longer [38].…”

Kinetic modelling of the electrochemical mineralization of organic pollutants for wastewater treatment

“…In fact, only electrical energy is consumed for the mineralization of organic pollutants. Besides our contribution in this field [1][2][3][4][5][6][7][8][9][10][11], many other research groups are active in this promising technology [12][13][14][15][16][17][18][19][20][21][22][23][24].…”

Electrocatalytic oxidation of nitrophenols in aqueous solution using modified PbO2 electrodes

“…Electrochemical degradation (ECD) is one of the alternatives for degradation of these compounds, and is suitable for low-volume application and environmental compatibility [4]. In recent years, electrochemical oxidation of aqueous wastes containing non-biodegradable organics such as phenol [5], chlorophenols [6] and aniline [7] has been extensively studied.…”