Impact of thermal modification of carbon felt on the performance of oxygen reduction reaction and mineralisation of dye in on-line electro fenton system

Carbon felt (CF) is frequently used as an electrode in various processes of oxygen reduction reactions (ORR) and water treatment. Therefore, it is critical to increasing the performance of this material in ORR. In this study, the effect of the thermal modification, which is a simple and low-cost process, was examined. For testing the hydrogen peroxide generation efficiencies and the mineralisation of Acid Orange 7 (AO7) dye, the modified CF electrodes (under 0-900 degrees C and N-2 atmosphere for 1 hour) were used as cathodes with Ti/RuO2-IrO2-TiO2 as anode and saturated calomel electrode (SCE) as a reference electrode. In addition, to find the optimum Electro-Fenton (EF) process parameters, the potential of the cathode (0.8-3.0 V), pH (3.0-9.0), Fe2+ concentration (0.2-1.0 mM) and electrolyte (sodium sulphate) concentration (10-500 mM) were investigated. The highest efficiencies in dye and TOC removal were achieved at 0.8 V, 50 mM of electrolyte concentration with 0.3 mM of Fe2+ by using CF modified at 900 degrees C as 96.26% at 10 min and 91.83% at 120 min, respectively. Besides, the modification process was increased the electroactive surface area (41.70%) and crystallite size (22.69%) of the electrode. Thus, more effective treatment was achieved. Thanks to the modification, the electrical energy and electrochemical energy saving are approximately 23.87% and 70.22%, respectively. On the other hand, a kinetic study was conducted with a large number of data coming from the on-line analysis system, which is different from most systems in the literature. At the end of the kinetic study, it was revealed that EF systems could not be explained by a single kinetic equation. It was found that the EF system has two different rate equations (first order and pseudo first order) with high correlation coefficients (R-2 = 0.9965 and 9920).