Degradation mechanism of losartan in aqueous solutions under the effect of gamma radiation
Introduction
Among important pharmaceutical products, with great interest, we can cite antibiotics, anti-inflammatories, anti-epileptics, anti-depressants, anti-hypertensive, diuretics, analgesics, and psycho-stimulants (Deblonde et al., 2011; Gros et al., 2010; Utrilla Rivera et al., 2013). Over the last few years, their consumption has increased significantly and in particular the anti-hypertensives products (Hiltunen et al., 2015). In fact, all over world, up to one billion persons have suffered from hypertension according to the last World Health Organization's (WHO) estimation. In its reports, the WHO also predicts this number would be rising up to 1.5 billion by the end of 2020 (Padmanabhan et al., 2012). Pharmaceutical products are considered as emerging contaminants (ECs) acting as disturbances of endocrine systems and have disastrous effects on development of wildlife as well as the aquatic system (Martínez-Pachón et al., 2018; Tegze et al., 2019; Tejada et al., 2014; Wang et al., 2016; Zhang et al., 2015, 2019). In addition, most of these compounds are not completely metabolized after their consumption. They are to be excreted out of the body via urine and feces (Jurado et al., 2012). Since these pollutants are massively released in environment in non-focused form, they have been turned to be a serious source of concern (Rosal et al., 2010; Utrilla Rivera et al., 2013). The deficient suppression of these ECs by conventional techniques implies that alternative or complementary treatments have to be proposed and tested in order to effectively eliminate these contaminants (Martínez-Pachón et al., 2018). Amongst these treatments, Advanced Oxidation Processes (AOPs) have been demonstrated as a promising alternatives for treating contaminated water by pharmaceutical emerging compounds. The goals behind the use of such AOPs are the improvement of the quality of effluent, and in some cases, the reuse of the treated water (De la Cruz et al., 2012; Martínez-Pachón et al., 2018). The common product of all mentioned methods is the hydroxyl radical production (•OH). These very reactive radical can be produced by different ways and known to be a powerful oxidizing species. By generating CO2 and H2O as final products, they could lead to a complete mineralization of pollutants through their chemical oxidation. Among these advanced, we mention oxidation process like photo-fenton (De la Cruz et al., 2012, 2013; Martínez-Pachón et al., 2018, Rosal et al., 2012), electro-fenton (Alizadeh Fard and Barkdoll, 2018), ozonation (Wang et al., 2012), sonolysis (Serna-Galvis et al., 2019), electrochemical oxidation (Salazar et al., 2016; Zaouak et al.; 2013, 2014, 2015), as well as using ionizing radiations techniques (Jiménez-Becerril et al., 2016; Reinholds et al., 2017; Zaouak et al., 2018, 2019, 2020). In this context, some previous studies were proposed the application of ionizing radiation as a promotional degradation treatment method applied to the water-dissolved pharmaceutical pollutants, such as amoxicillin, doxycycline and ciprofloxacin (Alsager et al., 2018), morphine and codeine (Kantoğlu and Ergum, 2015), ketoprofen and ibuprofen (Illés et al., 2012; Zheng et al., 2011), paracetamol (Cruz-González et al., 2016), chloramphenicol (Hong and Altorfer, 2001), carbamazepine (Wang and Wang, 2018), sulfamethoxazole (Zhuan and Wang, 2020). To our knowledge, there has been no work concerning the removal of antihypertensive drugs from aqueous solutions by application of ionizing radiation (Salazar et al., 2016).
Thus, in this study, we had selected one of the most popular among the antihypertensive drug family, the losartan (LOS) also named [2-butyl-4-chloro-1-[[2-(1H-tetrazol-5-yl) [1,1-biphenyl]-4-yl] methyl]-1H-imidazole-5-methanol] belongs to sartan class (Salazar et al., 2016). As others medications, losartan has side effects such as loss of appetite, vomiting or diarrhea, rapid heartbeat, mood changes, nausea, increased thirst, muscle cramps, headache, dizziness … (Salazar et al., 2016). In recent studies, losartan and other antihypertensive drugs have been found in many wastewaters (Klosterhaus et al., 2013; Pereira et al., 2016). Some research studies on losartan treatment were carried out such as, photo-degradation (Martínez-Pachón et al., 2018), electro-chemical degradation (Salazar et al., 2016) and sonolysis (Serna-Galvis et al., 2019).
In this paper, we had interested to study the degradation of losartan in aqueous solutions. Samples of losartan in aqueous solutions have been irradiated with the Tunisian gamma radiation facility with doses varying from 0.5 kGy to 4 kGy at a dose rate of 47.62 Gy/min. After irradiation, UV–Visible spectroscopy technique has been applied in order to performed the kinetic study. COD, TOC and pH measurements have been also examined as a function as absorbed dose. The identification of by products during treatment was made leading the establishment of degradation mechanistic scheme of losartan.
Section snippets
Losartan
Fig. 1 shows the chemical structure of losartan “LOS” which is also named 2-Butyl-4-chloro-1-[[2'-(1H-tetrazol-5-yl)-1,1′-biphenyl-4-yl] methyl] imidazole-5-methanol]. LOS was purchased from Sigma. The molecular formula of the drug is C22H23ClN6O with 422.91 g mol−1 molecular weight.
Irradiation methodology
Aqueous solutions of LOS were irradiated by a Cobalt 60 gamma source. All irradiation processes were performed at ambient temperature in the inner area of the gamma irradiator facility. The dose rate was determined
Losartan concentration as function as irradiation dose
The examination of losartan UV–Visible absorption spectra indicates two absorption peaks located at λ = 230 and 320 nm. The decrease in the concentration of losartan as a function of dose was monitored at its maximum absorbance band of λ = 230 nm to avoid any interferences absorption from degradation products.
Fig. 2 shows that the losartan concentration decreases during treatment and reaches 5.6 ppm at approximately 4 kGy. Under our experimental conditions, gamma rays interact with water
Conclusion
This work reports the degradation of gamma radiation from losartan which can be considered as an emerging organic pollutants and the most widely antihypertensive drugs used in the world. Such organic pollutants are not readily biodegradable. The results showed that gamma radiation treatment was quite efficient for degradation of losartan solutions. Both % COD and TOC removals were influenced by the applied doses and reaches respectively 97% and 93% after 4 kGy radiation dose. Thus, it can be
Author statement
AMIRA ZAOUAK: Conceptualization, Methodology, writting JELASSI HAIKEL:Data curves, Writing- draft preparation. NOOMEN AHLEM: mechanistic schema, Investigation.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This research study has been achieved with the financial support of the Tunisian Ministry of Higher Education and Scientific Research through the research laboratory funding (LR16CNSTN02).
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