An efficient simultaneous degradation of sulfamethoxazole and trimethoprim by photoelectro-Fenton process under non-modified pH using a natural citric acid source: study of biodegradability, ecotoxicity, and antibacterial activity.

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 × 10-5 mol/L) and trimethoprim (TMP-6.89 × 10-5 mol/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 × 10-5 mol/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 45 min and 90 min, 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 45 min 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.

Electrochemical treatment of real petrochemical effluent: current density effect and toxicological tests.

This work aims to investigate the electrochemical treatment of petrochemical industry effluents (from the northwest region of Brazil) mediated by active chlorine species electrogenerated at ruthenium-titanium oxide supported in titanium (Ti/Ru0.3Ti0.7O2) and boron doped diamond (BDD) anodes by applying 15 and 45 mA cm-2. Chemical oxygen demand (COD) determinations and toxicity analyses were carried out in order to evaluate the process extension as well as the possible reuse of the wastewater after treatment. Toxicity was evaluated by assessing the inhibition of lettuce (Lactuca sativa) stem growth, seed germination, and the production of nitrite (NO-2) and nitrate (NO-3) species. Results clearly showed that the best COD reduction performances were reached at the BDD anode, achieving almost 100% of removal in a short time. Degradation of nitrogen-organic compounds generated NO-2 and NO-3 which act as nutrients for lettuce. Toxicity results also indicated that the electrogenerated active chlorine species are persistent in the effluent after the treatment, avoiding the stem growth, and consequently affecting the germination.

The synergic persulfate-sodium dodecyl sulfate effect during the electro-oxidation of caffeine using active and non-active anodes.

It has previously been established during the elimination of organic matter that the addition of sodium dodecyl sulfate in solution is an important condition in the electrochemical oxidation approach that allows to increase the production of persulfate, enhancing the efficacy of the treatment. This outcome was observed when using the anodic oxidation with boron doped diamond (BDD), the extra production of persulfate was achieved after the SDS-sulfate released in solution and it reacts with hydroxyl radicals electrogenerated at BDD surface. However, this effect was not already tested by using active anodes. For this reason, the effect of sodium dodecyl sulfate (SDS) during the electrochemical treatment of caffeine was investigated by comparing non-active and active anodes performances. A significant decrease on the oxidation efficiency of caffeine was observed by using Ti/IrO2-Ta2O5 anode at high current density when SDS was added to the solution. Conversely, at BDD anode, the presence of SDS enhanced the degradation efficiency, depending on the applied current density. This behavior is mainly due to the degradation of SDS molecules, which allows to increase the amount of sulfate in solution, promoting the production of persulfate via the mechanism involving hydroxyl radicals when BDD is used. Meanwhile, no oxidation improvements were observed when Ti/IrO2-Ta2O5 anode was employed, limiting the caffeine oxidation. Results clearly showed that the surfactant concentration had little influence on the degradation efficiency, but this result is satisfactory for the BDD system, since it demonstrates that effluents with complex matrices containing surfactants could be effectively degraded using the electrooxidation technique. Degradation mechanisms were explained by electrochemical measurements (polarization curves) as well as the kinetic analysis. Costs and energy consumption were also evaluated.

Role of sulfate, chloride, and nitrate anions on the degradation of fluoroquinolone antibiotics by photoelectro-Fenton.

Taking ciprofloxacin (CIP) as a fluoroquinolone antibiotic model, this work explores the role of common anions (sulfate, nitrate, and chloride) during the application of photoelectro-Fenton (PEF) at natural pH to degrade this type of compound in water. The system was composed of an IrO2 anode, Ti, or gas diffusion electrode (GDE) as cathode, Fe2+, and UV (254 nm). To determine the implications of these anions, the degradation pathway and efficiency of the PEF sub-processes (UV photolysis, anodic oxidation, and electro-Fenton at natural pH) were studied in the individual presence of the anions. The results highlight that degradation routes and kinetics are strongly dependent on electrolytes. When chloride and nitrate ions were present, indirect electro-chemical oxidation was identified by electro-generated HOCl and nitrogenated oxidative species, respectively. Additionally, direct photolysis and direct oxidation at the anode surface were identified as degradation routes. As a consequence of the different pathways, six primary CIP by-products were identified. Therefore, a scheme was proposed representing the pathways involved in the degradation of CIP when submitted to PEF in water with chloride, nitrate, and sulfate ions, showing the complexity of this process. Promoted by individual and synergistic actions of this process, the PEF system leads to a complete elimination of CIP with total removal of antibiotic activity against Staphylococcus aureus and Escherichia coli, and significant mineralization. Finally, the role of the anions was tested in seawater containing CIP, in which the positive contributions of the anions were partially suppressed by its OH radical scavenger action. The findings are of interest for the understanding of the degradation of antibiotics via the PEF process in different matrices containing sulfate, nitrate, and chloride ions.

Selecting the best AOP for isoxazolyl penicillins degradation as a function of water characteristics: Effects of pH, chemical nature of additives and pollutant concentration.

To provide new insights toward the selection of the most suitable AOP for isoxazolyl penicillins elimination, the degradation of dicloxacillin, a isoxazolyl penicillin model, was studied using different advanced oxidation processes (AOPs): ultrasound (US), photo-Fenton (UV/H2O2/Fe2+) and TiO2 photocatalysis (UV/TiO2). Although all processes achieved total removal of the antibiotic and antimicrobial activity, and increased the biodegradability level of the solutions, significant differences concerning the mineralization extend, the pH of the solution, the pollutant concentration and the chemical nature of additives were found. UV/TiO2 reached almost complete mineralization; while ∼10% mineralization was obtained for UV/H2O2/Fe2+ and practically zero for US. Effect of initial pH, mineral natural water and the presence of organic (glucose, 2-propanol and oxalic acid) were then investigated. UV/H2O2/Fe2+ and US processes were improved in acidic media, while natural pH favored UV/TiO2 system. According to both the nature of the added organic compound and the process, inhibition, no effect or enhancement of the degradation rate was observed. The degradation in natural mineral water showed contrasting results according to the antibiotic concentration: US process was enhanced at low concentration of dicloxacillin followed by detrimental effects at high substrate concentrations. A contrary effect was observed during photo-Fenton, while UV/TiO2 was inhibited in all of cases. Finally, a schema illustrating the enhancement or inhibiting effects of water matrix is proposed as a tool for selecting the best process for isoxazolyl penicillins degradation.

Evaluation of water matrix effects, experimental parameters, and the degradation pathway during the TiO2 photocatalytical treatment of the antibiotic dicloxacillin.

The photocalytic degradation of dicloxacillin (DXC) using TiO2 was studied in synthetic and natural waters. The degradation route and the effect of different experimental variables such as pH, applied power, and the initial concentrations of DXC and the catalyst were investigated. The best performances were achieved at a natural pH 5.8 and using 2.0 g L(-1) of TiO2 with 150 W of applied power. The photodegradation process followed Langmuir-Hinshelwood kinetics. The water matrix effect was evaluated in terms of degradation efficiency in the presence of organic compounds (oxalic acid, glucose), Fe(2+) ion and natural water. An increase in degradation was observed when ferrous ion was part of the solution, but the process was inhibited with all evaluated organic compounds. Similarly, inhibition was observed when natural water was used instead of distilled water. The extent of degradation of the process was evaluated following the evolution of chemical oxygen demand (COD), antimicrobial activity (AA), total organic carbon (TOC) and biochemical oxygen demand (BOD5). Total removal of DXC was achieved after 120 min of treatment and 95% mineralization was observed after 480 min of treatment. Additionally, the total removal of antimicrobial activity and a high level of biodegradability were observed after the photocalytical system had been operating for 240 min.

Enhancement and inhibition effects of water matrices during the sonochemical degradation of the antibiotic dicloxacillin.

The sonochemical degradation of dicloxacillin (DXC) was studied in both synthetic and natural waters. Degradation routes and the effect of experimental conditions such as pH, initial DXC concentration and ultrasonic power were evaluated. Experiments were carried out with a fixed frequency (600kHz). The best performances were achieved using acidic media (pH=3) and high power (60W). The degradation process showed pseudo-first order kinetics as described by the Okitsu model. To evaluate water matrix effects, substrate degradation, in the presence of Fe(2+) and organic compounds such as glucose and 2-propanol, was studied. A significant improvement was achieved with Fe(2+) (1.0mM). Inhibition of the degradation process was observed at a relatively high concentration of 2-propanol (4.9mM), while glucose did not show any effect. Natural water showed an interesting effect: for a low concentration of DXC (6.4µM), an improvement in the degradation process was observed, while at a higher concentration of DXC (0.43mM), degradation was inhibited. Additionally, the extent of degradation of the process was evaluated through the analysis of chemical oxygen demand (COD), antimicrobial activity, total organic carbon (TOC) and biochemical oxygen demand (BOD5). A 30% removal of COD was achieved after the treatment and no change in the TOC was observed. Antimicrobial activity was eliminated after 360min of ultrasonic treatment. After 480min of treatment, a biodegradable solution was obtained.

Borra de café colombiano (Coffea arabica) como fuente potencial de sustancias con capacidad antirradicales libres in vitro / Colombian spent coffee grounds (Coffea arabica) as a potential source of substances with free radicals capacity in vitro

Introducción: Coffea arabica L., además de su importancia comercial, también se considera una planta medicinal, porque presenta propiedades biológicas diversas, pero por su comercialización como bebida genera muchos subproductos. La borra es uno de estos, que se obtiene por la preparación de la bebida, contiene una concentración significativa de compuestos polifenólicos y, por tanto, la recuperación de estas sustancias a partir de un residuo sin valor, sería potencialmente útil para la industria farmacéutica y alimentaria. Objetivos: recuperar compuestos fenólicos a partir de la borra de café y darle un valor agregado a un residuo de origen vegetal, como fuente de componentes con capacidad antirradicales libres in vitro. Métodos: la borra de café previamente secada se sometió a extracciones sólido-líquido usando diferentes sistemas de solventes. Se evaluaron las propiedades antioxidantes in vitro usando los métodos del catión radical del ácido 2,2´-azino-bis (3-etilbenzotiazoline-6-sulfónico) y del radical 1,1-difenil-2-picrilhidracilo. Se usó cromatografía líquida de alta resolución acoplada a espectrometría de masas para la caracterizaron de los principales componentes. Resultados: todos los extractos obtenidos mostraron buena capacidad antioxidante, con el extracto de etanol:agua como el mejor, seguido del extracto de metanol acidulado. Sin embargo, la capacidad antioxidante de la fracción en diclorometano del extracto etanol:agua resultó menor que la presentada por la taza de café. Se identificaron los ácidos clorogénico, isoclorogénico y feruloilquínico como los principales componentes de la borra de café. Conclusiones: todos los extractos presentaron buena capacidad protectora contra radicales libres. La borra de café, considerada un desecho obtenido del procesamiento industrial, se puede convertir en materia prima para la recuperación de sustancias antioxidantes; lo cual genera grandes expectativas sobre su posible uso en la industria farmacéutica y alimentaria, y le da al café un valor agregado importante.

Introduction: besides its commercial importance, Coffee arabica L. is also considered a medicinal plant due to its various biological properties, but its marketing produces a large amount of residues. Spent coffee grounds are one of these residues, which are obtained after the preparation of the drink and contain a significant concentration of polyphenolic compounds. Therefore, the recovery of these substances costless residual will be potentially useful for food and pharmaceutical industry. Objectives: to recover polyphenolic compounds from spent coffee grounds and to give an added value to a vegetable waste as a source of substances with free radicals capacity in vitro. Methods: dehydrated spent coffee grounds were subjected to solid-liquid extraction using different solvent systems. Antioxidant properties were evaluated in vitro using the radical monocation 2,2´-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and the stable free radical 2-2-diphenyl-1-picrylhydrazyl (DPPH). Liquid chromatography coupled to mass spectrometry was applied to characterize the main compounds. Results: all the extracts obtained showed a good antioxidant capacity with ethanol-water extract, followed by acidulated methanol extract. However, the antioxidant capacity of the ethanol-water extract was lower than coffee beverage. Chlorogenic, isochlorogenic and feruloylquinic acids were identified as the main compounds present in spent coffee grounds. Conclusions: all extracts showed a significant protection effect against free radicals; spent coffee ground, which is considered an undesirable solid waste from industrial processing, could be an add-value raw material in the recovery of antioxidant substances which generates great expectations about its possible use in the pharmaceutical and food industry and gives coffee an important added value.

Comparación entre el estado de maduración del fruto de café (Coffee arabica L.), el contenido de antocianinas y su capacidad antioxidante / Comparison between the level of maturation of the coffee fruit (Coffee arabica L.), and the contents of anthocyanins and their antioxidant capacity

Introducción: la piel o pericarpio del café que define su estado de madurez y calidad, es prácticamente lignocelulosa y no tiene ningún valor comercial, no obstante podría considerarse como una fuente importante de compuestos antioxidantes, sobre todo de antocianinas. Objetivos: comparar el potencial antioxidante del pericarpio del fruto de café en diferentes estados de maduración con respecto al contenido de antocianinas. Métodos: la piel del fruto del café liofilizada en cinco estados de maduración se sometió a extracciones sólido-líquido con metanol acidulado; se determinó el contenido de antocianinas por el método diferencial de pH y el potencial antioxidante se evaluó sobre la base de los métodos de DPPH (catión radical a-a-difenil-ß-picrilhidrazilo), ORAC (oxygen radical absorbance capacity) y FRAP (ferric reducing/antioxidant power). Resultados: la muestra de granos sobremaduros presentó un contenido de antocianinas 63,14 mg cianidin-3-glucósido/L. Este valor resulta de 2 a 18 veces mayor con respecto a los otros estados de maduración. No obstante, el estado "pintón" fue el que mostró una mayor capacidad antioxidante (³ 2-5 veces), en todos los métodos evaluados, lo cual sugiere una mayor presencia de otros componentes con actividad antioxidante durante esta etapa de maduración. Conclusiones: todos los extractos presentaron buena capacidad antioxidante, por lo tanto, aquellos frutos que no sean empleados para la industria de consumo de café pueden ser usados como fuente de antioxidantes, independiente de su estado de maduración.

Introduction: the maturity and quality of the coffee beans is defined by the color of its outer and often edible layer (pericarp), and this tissue is mainly lignocellulose without any commercial value; however it could be considered as a source of important antioxidant compounds, mostly anthocyanins. Objectives: to compare the antioxidant potential of the pericarp of the coffee bean at different states of maturation in terms of the content of anthocyanins. Methods: lyophilized and powered pericarp of Coffee arabica on different stages of maturation underwent solid-liquid extractions with acidulated methanol and total anthocyanins content was determined by pH differential method; the antioxidant potential was evaluated by using DPPH (radical cathion a-a-diphenyl-ß-picrylhydrazyl, ORAC (oxygen radical absorbance capacity) and FRAP (ferric reducing/antioxidant power) tests. Results: the sample from over-matured coffee beans showed a content of anthocyanins equal to 63.14 mg cyanidin-3-glucoside/L, which is 2 to 18 times higher than that of other maturation states. Nevertheless, the "pintón" stage demonstrated the highest antioxidant capacity (³ 2-5 times) in all the evaluated methods. This indicates the presence of additional components with antioxidant power during this maturation stage. Conclusions: all the extracts showed significant antioxidant capacity, therefore, the undesired fruits to coffee industry may be used as a source of antioxidant compounds regardless of their maturity stage.