Effects of temperature and heating method on the performance of Ti/Ru0.25Ir0.25Ti0.50O2 anodes applied toward Bisphenol S removal

Abstract One of the challenges faced by environmentally-related electrochemical techniques and which limit their industrial application is the lack of efficient and economically viable electrodes. This paper reports the development and application of a microwave-assisted hybrid heating method for the production of mixed metal oxide (MMO) anodes aiming at obtaining low-cost, highly catalytic, and durable anodes with reduced production time. The Ti/Ru0.25Ir0.25Ti0.50O2 electrodes were prepared by the Pechini method using two calcination temperatures (350 and 400°C) and two heating mechanisms (conventional in an electric furnace and hybrid heating using microwaves). The electrodes developed were applied toward the electrochemical degradation of Bisphenol S (BPS); this is the first report involving the application of MMO electrodes for BPS removal in the literature. The calcination temperature and type of heating influence the electrodes physical and electrochemical characteristics, as well as the film compositions and catalytic activities. With the exception of the anode produced in the furnace at 400°C (CM-400), which exhibited a crack-free compact surface, the oxide film layers covered the Ti substrates entirely, displaying a typical “cracked mud” morphology. The morphological characteristics of CM-400 contributed toward obtaining low voltammetric charge (88 mC) and high resistivity (194 Ω) for the film. In contrast, the electrode developed by microwave-assisted hybrid heating at 350°C was produced in a relatively shorter time (4.6-fold), presented the lowest charge transfer resistance (24 Ω), the highest voltammetric charge (240 mC), and the highest stability (with 51 h – accelerated life test). Overall, the electrodes produced in furnace were slightly more efficient when applied toward the electrochemical removal of BPS; to be precise, the electrode calcined at 400 °C showed total BPS removal in 10 min at 100 mA cm–2. About 20% of TOC removal was obtained in 60 min of electrolysis; this is the highest TOC rate reported for BPS under such short treatment time. Thus, the anodes developed are found to be suitable and highly promising for the electrochemical removal of BPS from water.