Heterogeneous Electro-Fenton Process Using a Cathode of Carbon Felt Impregnated with Iron for the Degradation and Biodegradability Enhancement of Sulfamethazine

The objective of this study was to develop a carbon felt impregnated with iron (III) sulfate (CF-Fe) for its use both as a cathode and reusable heterogeneous catalyst source in the Fenton reaction for the elimination of sulfamethazine (SMT). The CF-Fe cathode was characterized with Scanning electron microscopy-energy dispersive spectrometric (SEM-EDS) and X-ray diffraction (XRD). The results of morphology characterization with SEM-EDS revealed that the raw CF displayed a rod-like morphology with a clean and smooth surface. After the impregnation of CF with iron (III) sulfate, the surface of CF-Fe became rough and porous while retaining the raw CF structure well. Furthermore, some solid particles were clearly observed on the FC-Fe, suggesting that the iron species were loaded onto the CF-Fe surface, which contained 57.20% w of iron. The XRD indicated that iron species were successfully embedded in the CF. The effect of the current intensity and injected compressed air flow on the production of hydrogen peroxide (H2O2) was investigated. From the obtained results, it is shown that the highest concentrations of H2O2 are produced at I = 50 mA and 0.2 L min-1 compressed air flow rate. The effect of current intensity on the degradation and mineralization rate of SMT was investigated by varying the current intensity from 20 to 100 mA. At the optimal current applied (50 mA), the total degradation of SMT and a maximum of 70.2% mineralization were achieved after 120 min electrolysis. In addition, the biodegradability of the solutions electrolyzed under several experimental conditions was performed. The results revealed that the BOD5/COD ratio increased from 0 to 0.42 after 120 min when the solutions were electrolyzed at 100 mA; while, when the electrolysis was performed at 50 mA no biodegradability was observed. Finally, the stability of the CF-Fe cathode was evaluated during six consecutive cycles. The results showed that the total degradation of SMT was achieved in less than 120 min of treatment and remained the same even after six cycles. However, a significant decrease in the mineralization rate was observed, since the mineralization rate decreased from 70 to 36% after six cycles, due to the leaching of iron at the cathode, as demonstrated by the results of the evolution of total iron in solution. In view of the results obtained, the heterogeneous electro-Fenton process using CF-Fe cathode is promising to treat the SMT containing wastewater. Development of a carbon felt electrode impregnated with iron (III) sulfateUse of the electrode both as a cathode and as a reusable heterogeneous catalyst source in the Fenton reaction for sulfamethazine (SMT) removalEvaluation of the biodegradability of electrolyzed solutions for various EF experiments.