Treating pharmaceutical wastewater containing tetracycline using an enhanced electro-Fenton system

In this study, the application of a heterogeneous electro-Fenton system based on the metal-organic framework MIL-100(Fe) as a catalyst, combined with persulfate, was investigated for the treatment of pharmaceutical wastewater containing tetracycline. This system utilizes electrochemical advanced oxidation processes driven by sulfate radicals, taking advantage of their broader operational pH range and higher stability compared to hydroxyl radicals. Following the synthesis and structural characterization of MIL-100(Fe), the experiments were conducted in a one-liter glass reactor equipped with four graphite electrodes connected to a DC power supply. The synthetic wastewater was prepared by dissolving 50 mg/L of tetracycline, followed by the sequential addition of 400 mg/L of MIL-100(Fe) catalyst and 200 mg/L of persulfate. The treatment was carried out at room temperature, and the tetracycline concentration was measured using a UV-Vis spectrophotometer at a wavelength of 359 nm throughout the process. Experiments were performed at various tetracycline concentrations (10, 20, 50, 75, and 100 mg/L) and reaction times ranging from 0 to 120 minutes. Using a one-factor-at-a-time (OFAT) method, the optimal operational conditions, including tetracycline concentration of 50 mg/L, catalyst dosage of 400 mg/L, current intensity of 400 mA, persulfate concentration of 200 mg/L, pH of 5, electrode spacing of 5 cm, and reaction time of 90 minutes were identified. Under these conditions, the system achieved a maximum tetracycline removal efficiency of 83.8% with a minimum specific energy consumption of 178 kWh/kg. The findings of this study confirm that the simultaneous use of MIL-100(Fe) and persulfate in an advanced oxidation process provides an efficient, cost-effective, and environmentally friendly approach for the removal of tetracycline from pharmaceutical wastewater. Moreover, the system demonstrated satisfactory performance under near-neutral pH conditions, highlighting its potential for practical applications and its superiority over conventional treatment methods.