On the behaviour of doped SnO2 anodes stabilized with platinum in the electrochemical degradation of reactive dyes

In this paper the electrochemical characterisation of Ti/SnO2–Sb–Pt anodes prepared by thermal decomposition is researched using different techniques. These results were also compared to those obtained for the Ti/SnO2, Ti/SnO2–Sb and deactivated Ti/SnO2–Sb–Pt anodes. SECM technique confirmed the increase of electroactivity observed with the antimony doping and a little amount of platinum. In contrast, deactivated Ti/SnO2–Sb–Pt anodes showed a drastic decrease in electroactivity. SEM and EDX analyses were also employed to evaluate the differences observed among these anodes. These results corroborated the high service life of Ti/SnO2–Sb–Pt anodes being very useful for wastewater treatment. COD, HPLC, UV–vis and potential control measurements were also used to verify the viability of these anodes to degrade and decolourise wastewater solutions containing a reactive dye: C.I. Reactive Orange 4. With this purpose, different oxido-reduction electrolyses were carried out in presence of either 0.1 M Na2SO4 or 0.1 M NaCl as electrolyte. Although the use of NaCl gave the best results in decolourisation rate, the oxidation efficiency was practically the same independently of what type of electrolyte was used. It was also found that treated solutions presented oxidation-resistant intermediates as final products in all cases.