Abstract
In this work, the use of natural organic wastes (orange and lemon peels) as sources of citric acid was evaluated along with the application of the photoelectro-Fenton (PEF) system under non-modified pH as a novel alternative to degrade a complex mixture of pharmaceuticals: sulfamethoxazole (SMX-7.90 × 10-5mol/L) and trimethoprim (TMP-6.89 × 10-5mol/L). The system was equipped with a carbon felt air diffusion cathode (GDE) and a Ti/IrO2 anode doped with SnO2 (DSA). A 3.6 × 10-5mol/L solution of commercial citric acid was used as a reference. The pharmaceuticals' evolution in the mixture was followed by high-performance liquid chromatography (HPLC). The addition of natural products showed an efficient simultaneous degradation of the antibiotics (100% of SMX and TMP at 45min and 90min, respectively) similar to the performance produced by adding the commercial citric acid to the PEF system. Moreover, the addition of natural products allowed for an increment of biodegradability (100% removal of TOC by a modified Zahn Wellens test) and a decrease in ecotoxicity (0% in the bioassay with D. Magna) of the treated solutions. The antibacterial activity was eliminated after only 45min of treatment, suggesting that the degradation by-products do not represent a significant risk to human health or the environment in general. Results suggest that, because of the efficient formation of Fe-citrate complexes, the PEF could be enhanced by the addition of natural organic wastes as a sustainable alternative ecological system for water contaminated pharmaceuticals. Additionally, the potential of reusing natural organic wastes has been exposed, contributing to an improved low-cost PEF by decreasing the environmental contamination produced by this type of waste.
Highlights
Antibiotics are powerful medications used to treat or prevent bacterial infections
Considering pH 3.0 as the recommended condition to performed Fenton-based process since the Fenton reaction is most favorable at acidic media (Gozzi et al 2017; Nogueira et al 2017; Brillas 2020), the addition of citric acid for the degradation of SMX and TMP can be analyzed during the photoelectro - Fenton (PEF) treatment
This research demonstrated the efficiency of the PEF system with citric acid present in orange peel extract in the simultaneous degradation of the antibiotics SMX and TMP
Summary
Antibiotics are powerful medications used to treat or prevent bacterial infections. In the correct way, antibiotics consumption can save human and animal lives, but in an incorrect way (unnecessary situations, incorrect doses, premature interruption of the treatment and the use of bad quality drugs), causes the failure of the antibiotic. In the specific case of sulfamethoxazole and trimethoprim (SMX - TMP), they are the main prescribed antibiotics for patients with bronchitis and infections symptoms caused by Staphylococcus and Streptococcus bacteria, since they inhibit the synthesis of tetrahydrofolate and subsequently the DNA acting as bactericidal and bacteriostatic compounds (Suárez Olivares 2011; Página de créditos 2015; Daza et al 2017) This high consumption increases their appearance in wastewaters, such as those of Bogotá D.C treatment plant (WWTP-Salitre), in which concentrations of 0.63 μg/L for SMX and 0.32 μg/L for TMP where quantified in the influent, while the effluent showed concentrations of 0.64 μg/L for SMX and 0.34 μg/L for TMP (Botero-Coy et al 2018). This because both drugs act synergistically blocking successive steps of folate metabolism in bacteria, which is necessary for the production of cell wall proteins, puric and pyrimidine bases of DNA, thereby acquiring maximum antibacterial activity, which is usually bactericidal and bacteriostatic (Sass 2017; Montiel A. 2018)
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