RESUMO
Benzimidazoles (BZ) are among the most used drugs to treat parasitic diseases in both human and veterinary medicine. In this study, solutions fortified with albendazole (ABZ), fenbendazole (FBZ), and thiabendazole (TBZ) were subjected to photoperoxidation (UV/H2O2). The hydroxyl radicals generated by the process removed up to 99% of ABZ, and FBZ, in the highest dosage of H2O2 (i.e., 1.125 mmol L-1; 4.8 kJ L-1). In contrast, 20% of initial TBZ concentration remained in the residual solution. In the first 5 min of reaction (i.e., up to 0.750 mmol L-1 of H2O2), formation of the primary metabolites of ABZ-ricobendazole (RBZ), albendazole sulfone (ABZ-SO2), and oxfendazole (OFZ)-was observed. However, these reaction products were converted after the reaction time was doubled. The residual ecotoxicity was investigated using the Raphidocelis subcapitata microalgae and the marine bacteria Vibrio fischeri. The results for both microorganisms evidence that the residual solutions are less harmful to these microorganisms. However, after 30 min of reaction, the treated solution still presents a toxic effect for V. fischeri, meaning that longer reaction times are required to achieve an innocuous effluent.
Assuntos
Aliivibrio fischeri , Microalgas , Benzimidazóis , Fenbendazol , Humanos , Peróxido de HidrogênioRESUMO
This work explored the use of ozonation and photoperoxidation before the microfiltration process to reduce fouling. Produced water was synthesized with salt, viscosifier, and surfactant. The additives influence on membrane fouling was evaluated. Photoperoxidation process led to an overall better performance than ozonation in terms of oil removal and fouling reduction. The maximum oil removal efficiency was 86%, obtained for emulsions with salt after 2 h of treatment (COD: H2O2 ratio 1:1, UV dose of 965 J/m2). The inclusion of chemical additives impaired the oxidative power of hydroxyl radicals leading to a moderate oil removal; however, they were still able to reduce membrane fouling, mainly in oil/water emulsions with viscosifier. Higher salt concentration promoted fouling resistance and also benefited the permeate quality. Cross-flow microfiltration process integrated with photoperoxidation was able to improve the permeate flux from 84 to 182 L/m2.h after 3 h of exposure to UV radiation, resulting in a permeate with less than 10 mg/L of oil content. Graphical abstract.
Assuntos
Peróxido de Hidrogênio , Purificação da Água , Filtração , Membranas Artificiais , Oxirredução , ÁguaRESUMO
Endocrine disruptors represent risks to aquatic ecosystem and humans, and are commonly detected in surface water. Photochemical treatments can be used to remove 17ß-estradiol (E2), but few studies have analyzed the kinetics, intermediates, and 17ß-estradiol degradation pathways in natural matrices. In this study, the photochemical behavior of E2 under ultraviolet irradiation (UVC, 254 nm) associated with oxidants (H2O2 or O3) or photocatalyst (TiO2) was investigated to evaluate the degradation potential and the transformation pathway in a natural surface water matrix. Additionally, computational modeling analyses with Ecological Structure Activity Relationships (ECOSAR) software were performed to predict the toxicity from the E2 and its transformation byproducts. E2 degradation kinetics showed adjusted to the pseudo-first-order kinetic model, being kUV/O3 > kUV/TiO2 > kUV/H2O2 > kUV. Eight transformation byproducts were identified by liquid chromatography with time-of-flight mass spectrometry (HPLC/TOF-MS) in natural surface water samples. These byproducts formed as the result of opening the aromatic ring and adding the hydroxyl radical. The E2 degradation pathway was proposed based on the byproducts identified in this study and in previous studies, suggesting the formation of aliphatic and hydroxylated byproducts. E2 treatment presented both very toxic and not harmful byproducts.
Assuntos
Peróxido de Hidrogênio , Poluentes Químicos da Água , Ecossistema , Estradiol , Humanos , Cinética , Oxirredução , Estresse Oxidativo , Fotólise , Raios UltravioletaRESUMO
Advanced oxidation processes (AOPs) have been highly efficient in degrading contaminants of emerging concern (CEC). This study investigated the efficiency of photolysis, peroxidation, photoperoxidation, and ozonation at different pH values to degrade doxycycline (DC) in three aqueous matrices: fountain, tap, and ultrapure water. More than 99.6% of DC degradation resulted from the UV/H2O2 and ozonation processes. Also, to evaluate the toxicity of the original solution and throughout the degradation time, antimicrobial activity tests were conducted using Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacteria, and acute toxicity test using the bioluminescent marine bacterium (Vibrio fischeri). Antimicrobial activity reduced as the drug degradation increased in UV/H2O2 and ozonation processes, wherein the first process only 6 min was required to reduce 100% of both bacteria activity. In ozonation, 27.7 mg L-1 of ozone was responsible for reducing 100% of the antimicrobial activity. When applied the photoperoxidation process, an increase in the toxicity occurred as the high levels of degradation were achieved; it means that toxic intermediates were formed. The ozonated solutions did not present toxicity.