Armaghane Danesh Bimonthly Journal (Apr 2022)
Photocatalytic Degradation of Gentamicin Antibiotics Using Fe3O4 / SiO2 / TiO2 Nanocomposites Synthesized in Aqueous Solutions in the Presence of Sunlight
Abstract
Background & aim: In recent years, the production of sewage and effluents containing pharmaceutical compounds and the subsequent entry of these compounds into nature is one of the major threats to the environment. Among these medicinal compounds, we can mention antibiotics, which are a large group of medicinal substances. Gentamicin is one of the aminoglycosides, after use, most of them are excreted from the user's body without absorption and enter the environment. Therefore, the purpose of this study was to determine and photocatalytically degrade the antibiotic gentamicin using Fe3O4 / SiO2 / TiO2 nanocomposite synthesized in aqueous solutions in the presence of sunlight. Methods: The present experimental study was conducted in 2018. The initial concentrations of the antibiotic gentamicin (5, 15, 25, 35 and 45 mg/liter), the effect of pH (5, 4, 6, 7 and 8), retention time (10, 35, 60, 85 and 110 minutes) and nano-particle dose (75, 150, 225, 300 and 375 mg/liter) and in the presence of sunlight were investigated. The number of experiments based on the design method of the central compound design method was 34. In order to obtain the removal kinetics, 20 experiments were considered. Therefore, the total number of samples was equal to 54 samples. All experiments were performed in a one-liter reactor at laboratory temperature (24 degrees Celsius) with three repetitions. Identification and determination of the amount of gentamicin antibiotic was done by reverse phase high performance liquid chromatography method. The collected data were analyzed using Design Expert and SPSS software and statistical tests of analysis of variance and Excel 2019. Results: Removal of gentamicin using Fe3O4 / SiO2 / TiO2 catalyst in the presence of sunlight under optimal conditions (initial pH equal to 6.91, gentamicin 15.30 mg/L, catalyst 299.80 mg and time equal to 83.86 minutes) in about 13 81.0% and the mineralization efficiency of gentamicin antibiotic was also shown as 42.1%. The results of the kinetic study showed that the data follow the pseudo-first-order kinetic model well. The efficiency of the process decreased with the use of sulfate and chloride ions as radical scavengers. Also, the reusability of the photocatalyst in removing gentamicin decreased from 81.13 in the first cycle to 80.7 and 57.8% in the fifth cycle, respectively. Conclusion: The results of the present study indicated that the photocatalytic process of Fe3O4 / SiO2 / TiO2 exposed to natural sunlight can be an efficient process in the field of removing the antibiotic gentamicin from aqueous solutions.