نوع مقاله : مقاله پژوهشی
نویسندگان
گروه مهندسی محیط زیست، دانشکده مهندسی عمران و محیط زیست، دانشگاه تربیت مدرس. تهران، ایران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Introduction: Advanced oxidation processes (AOPs) have emerged as efficient strategies for eliminating persistent organic pollutants from wastewater due to their superior capability in degrading chemically persistent organic compounds. Tetracycline, owing to its high chemical and environmental stability, is recognized as one of the most challenging pharmaceutical contaminants in aquatic systems, with its presence contributing to the proliferation of antibiotic-resistant bacteria and posing substantial ecological risks. This study aimed to investigate the role of reactive species and the effect of various scavengers in the degradation of tetracycline, utilizing an Electro-Fenton system based on MIL-100(Fe) catalyst and persulfate as the oxidant.
Material and methods: Experiments were performed in a 1-L cylindrical glass reactor equipped with four graphite electrodes spaced 5 cm apart. MIL-100(Fe) was synthesized and employed as a heterogeneous catalyst for persulfate activation. The effects of operational parameters, including tetracycline concentration, pH, catalyst dosage, persulfate concentration, and electric current, were evaluated using the one-factor-at-a-time (OFAT) method. The degradation performance was assessed through tetracycline removal, COD and TOC reduction, mineralization current efficiency (MCE), average oxidation state (AOS), and energy consumption (EC). Methanol, tert-butanol, and catalase were applied as scavengers to determine the contribution of sulfate radicals, hydroxyl radicals, and hydrogen peroxide, respectively. Kinetic analyses were conducted using pseudo-zero-order, pseudo-first-order, and pseudo-second-order models.
Results and discussion: The optimum operating conditions were obtained at tetracycline concentration of 50 mg/L, pH 5, persulfate dosage of 200 mg/L, catalyst dosage of 400 mg/L, and current intensity of 400 mA. Under these conditions, tetracycline removal reached 83.8%, while COD and TOC removals were 46.57% and 38.26%, respectively. The MCE and AOS values were determined as 67% and 0.538, indicating effective mineralization and progressive oxidation of intermediates. Radical scavenging experiments revealed that sulfate radicals, hydroxyl radicals, and hydrogen peroxide contributed 36.80%, 20.47%, and 27.89% to tetracycline degradation, respectively, highlighting the dominant role of sulfate radicals generated through persulfate activation. Kinetic investigations demonstrated that the degradation process followed a pseudo-second-order model with a rate constant of 0.0010 L·mg⁻¹·min⁻¹. The presence of methanol, tert-butanol, and catalase significantly reduced the reaction rate constants to 0.00009, 0.00036, and 0.00028 L·mg⁻¹·min⁻¹, respectively.
Conclusion: The Electro-Fenton/persulfate system employing MIL-100(Fe) exhibited high efficiency for tetracycline degradation through the synergistic generation of sulfate and hydroxyl radicals. Sulfate radicals were identified as the predominant reactive species, while hydroxyl radicals and hydrogen peroxide played complementary roles in the oxidation process. The results demonstrate that the MIL-100(Fe)-assisted Electro-Fenton process is a promising and sustainable approach for the treatment of antibiotic-contaminated wastewater and has considerable potential for future large-scale applications.
کلیدواژهها [English]
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