关键词: 电化学氧化, 土霉素降解, Fe₃O₄磁性纳米颗粒, 稳定性

Abstract:

The purpose of this study is to optimize the electrochemical degradation of oxytetracycline (OTC) in water using a low cost and simple preparation method. In this paper, the Fe₃O₄ magnetic nanoparticles were used as catalysts to activate the electrochemical oxidation system of peroxydisulfates (PDS) which acted as electrolytes to provide active free radicals in order to improve the degradation of OTC under the condition of applying current. As one of the tetracycline antibiotics (TCs), OTC is one of the most used antibiotics in the world, therefore, it is necessary to study the effective degradation of OTC. By means of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and other characterization methods, it was proved that the Fe₃O₄ magnetic nanoparticles at about 150 nm were successfully prepared by a simple hydrothermal method. Firstly, it is suggested that the application of electric current and the presence of Fe₃O₄ magnetic nanoparticles are necessary for the effective degradation of OTC. Secondly, the optimal reaction experiment confirmed an excellent OTC degradation ability by combination of Fe₃O₄ magnetic nanoparticles and current. The optimal reaction conditions were as follows: the concentration of PDS was 4.0 mmol·L^-1, the initial pH value of the solution was 7, and the current density j was 30 mA·cm^-2. When the dosage of Fe₃O₄ magnetic nanoparticles was 0.1 g·L^-1 and the initial OTC concentration was 70 mg·L^-1, the degradation rate of OTC could reach 88.75% within 60 min and the rate constant of the first-order kinetics simulation curve could reach 0.06069. In addition, the variation of UV-vis characteristic peak of OTC during the degradation process revealed that the change of OTC concentration was not due to simple physical adsorption, but through the complete degradation of active free radicals. In addition, after the continuous circulation of Fe₃O₄ magnetic nanoparticles for 5 times, the degradation rate of OTC could still reach more than 68%, proving that Fe₃O₄ magnetic nanoparticles have good catalytic stability. The presence of Fe₃O₄ magnetic nanoparticles and the application of electric current could promote the formations of SO₄^·- and ^·OH, respectively. The radical quenching experiments showed that both SO₄ ^·- and ^·OH were active free radicals degraded by antibiotics. This work uses a low-cost catalyst to enhance an electrochemical degradation of OTC. The experimental operation is simple, the degradation rate is fast, and the energy consumption is low. It is promising to practical applications.

Key words: electrochemical oxidation, oxytetracycline degradation, Fe₃O₄ magnetic nanoparticles, stability