نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم خاک، دانشکده کشاورزی، دانشگاه ارومیه، ارومیه، ایران.
2 گروه علوم خاک، دانشکده کشاورزی، دانشگاه ارومیه، ارومیه، ایران
3 گروه علوم خاک، دانشکده کشاورزی، دانشگاه ارومیه، ارومیه ایران
4 گروه علوم درمانگاهی، دانشکده دامپزشکی، دانشگاه ارومیه، ارومیه، ایران،
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Antibiotics as emerging pollutants, potentially affect the environment and human health and their entry into the environment has created great concerns. To study the ciprofloxacin hysteresis phenomenon in the soil, the adsorption process was done with different concentrations of ciprofloxacin (0–1 mmol L-1) on a calcareous soil system. Then, the reversibility of the adsorption process was assessed through desorption experiments of ciprofloxacin-loaded soil samples. The concentration of ciprofloxacin was determined using high-performance liquid chromatography-tandem mass spectrometry (HPLC–MS/MS). The experimental data were analyzed using the Langmuir, Freundlich, and Redlich-Peterson isotherms. The results demonstrated the experimental data followed the Redlich-Peterson isotherm model due to the lowest value of error (SE= 0.24) and the highest value of correlation coefficient (R²=0.99). The exponent value of this equation (g) was less than one, so the adsorption surfaces are heterogeneous. Ciprofloxacin adsorption increased with increasing initial concentrations. The highest adsorption and desorption efficiency of ciprofloxacin was obtained at concentration 1 mmol L-1, 96% and 2%, respectively. The hysteresis index was 0.89 indicating low reversibility of the adsorption process or hysteresis phenomenon. The strong bind of the ciprofloxacin to the soil components leads to less degradability in soil and forms stable residues in the soil environment.
کلیدواژهها [English]
Study of the Ciprofloxacin Hysteresis Phenomenon in Soil
EXTENDED ABSTRACT
Antibiotics are used to prevent or treat bacterial infections and to promote growth on a global scale. Antibiotics are not completely metabolized in the body and a high percentage of them (between 17% and 90%) is excreted unchanged. The direct application of animal manure is one of the principal sources of antibiotic contamination of agricultural soils. In the soil environment, antibiotics may be subject to different processes, including transformation, degradation, sorption, desorption, uptake by plants, runoff and transport into groundwater. Ciprofloxacin is one of the most widely used antibiotics in the worldwide. It is a serious threat to human health due to its long half-life (about 10 years) and its resistance to degradation. Thus this study focused on the adsorption/desorption behavior of the ciprofloxacin and determination of the hysteresis index in a calcareous soil.
Surface soil (0–20 cm) used in these experiments was collected from an agricultural field in Western Azerbaijan province in 2021 and the physiochemical properties of the soil such as texture, EC, pH, organic carbon (OC%) and calcium carbonate equivalent were measured. Seven initial concentrations of ciprofloxacin (purity>98%) (0- 1 mmol L−1) were prepared and 20 mL 0.01M CaCl2 solution was added to 1 g dried soil. All the samples were shaken and centrifuged to reach equilibrium, then the supernatant was taken and filtered before HPLC analysis. After taking the supernatants, the same aliquot of 20 mL 0.01M CaCl2 was added to each remaining soil sample for desorption experiments. The equilibrium concentration adsorbed on the soil was fitted by the Langmuir, Freundlich, and Redlich-Peterson equations. The reversibility of the adsorption process was also calculated using parameters 1/n adsorption and 1/n desorption of the Freundlich equation.
The adsorption isotherms of the ciprofloxacin were indicated that Redlich-Peterson three-parameter model is suitable to depict the adsorption behaviors of ciprofloxacin (R2= 0.99) in contaminated soil. The parameters values of the isotherm equations were high, suggesting that the ciprofloxacin has a stronger tendency to be adsorbed in the calcareous soil and potentially persist for extended periods. In this study, the exponent g of the Redlich-Peterson equation, was found 0.13 indicating that the equation is similar to Freundlich model. The results also suggested that the sorption of ciprofloxacin intensified by increasing initial concentration. Approximately 2% of the total amount of adsorbed antibiotics desorbed from soil. So that the hysteresis index was obtained 0.89 and the adsorption process was only partially reversible.
Hysteresis index of adsorption and desorption isotherms of the ciprofloxacin was positive, which indicates the strong bind of the ciprofloxacin to the components of calcareous soil. Therefore, these findings highlight limited mobility of ciprofloxacin in calcareous soil systems and lower risk of groundwater contamination. This study contributes substantially to our understanding the adsorption/ desorption behavior of the ciprofloxacin in calcareous soils its fate in the soil environment.