Application of oxide fine-mesh electrodes composed of Sb-SnO2 for the electrochemical oxidation of Cibacron Marine FG using an SPE filter-press reactor

Oxide fine-mesh electrodes composed of tin dioxide doped with antimony (OFM-Sb-SnO2), which had different percentages of Sb, were prepared using the thermal decomposition method on a stainless steel fine-mesh support for application in a solid polymer electrolyte (SPE) filter-press reactor. The electrochemical oxidation of Cibacron® Marine FG (CMFG) was carried out during recirculation through a plug-flow reactor, using electrolyte-free dye solutions. An influence of the Sb content on the electrochemical oxidation of CMFG was verified. The highest combustion rate of CMFG was obtained using an electrode containing 6.57 mol% Sb. Studies were carried out as a function of the initial dye concentration (IDC) and the applied current density (j) for this particular electrode composition. It was verified that the decolourisation and mineralisation reactions were affected considerably by IDC and j. In trying to interpret the experimental findings, an electrode mechanism was proposed for the irreversible parallel reactions comprising the oxygen evolution reaction (OER) and the advanced oxidation process (EAOP). The instantaneous current efficiency (ICE) for the mineralisation reaction was calculated for the different cases using the average mass-transport coefficient (〈kL〉) and the initial limiting current (jL0) values. The energy consumption (EC) was also calculated for the mineralisation reaction. It was confirmed that ICE and EC are strongly affected by IDC and j. Analysis of the reactor voltage (U) under galvanostatic conditions revealed that the OFM-Sb-SnO2 electrode (6.57 mol% Sb) is more stable when the OER is partially suppressed during the electrochemical oxidation of CMFG.