RESUMO

Pentachlorophenol is a pesticide widely known for its harmful effects on sewage, causing harm to the environment. In previous studies, our group identified adsorption as a crucial factor in catalytic ozonation processes, and subsequent observations revealed the catalyst's role in reducing toxicity during degradation. In this research, we quantified organochlorine intermediates and low molecular weight organic acids generated under optimal pH conditions (pH 9), with and without the catalyst. Additionally, we assessed the reactivity of these intermediates through theoretical calculations. Our findings indicate that the catalyst reduces the duration of intermediates. Additionally, the presence of CO2 suggests enhanced mineralization of pentachlorophenol, a process notably facilitated by the catalyst. Theoretical calculations, such as Fukui analysis, offer insights into potential pathways for the dechlorination of aromatic molecules by radicals like OH, indicating the significance of this pathway.

RESUMO

INTRODUCTION: Candida albicans and Aspergillus fumigatus are two important agents of Healthcare-associated infections. This study aimed to evaluate the antifungal activity of ozone (O3) gas produced by two commercial devices against cultures of these two species. METHODOLOGY: Sterile plastic plates were inoculated with C. albicans and A. fumigatus and placed on a countertop at three distances (30 cm, 1 m, and 2 m) and three positions in relation to the wall (near, middle, and away), considering the source of O3. Plates were exposed to O3 for one hour and incubated. After incubation, the counting of colony-forming units was performed. As a control, an inoculated plate was incubated, without being exposed to O3. Tests were carried out with two different devices (namely, Mod.I and Mod.II), with the air conditioner on and off, in triplicate. RESULTS: Both devices showed antifungal activity. Mod. I presented better results, due to a higher flow rate. The best activity was on plates at 30 cm, middle position. Contrarily, on plates at 2m, near the wall, the inhibition activity was lower. The best results were obtained with the air conditioner off. Candida albicans was more sensitive to O3 than A. fumigatus. CONCLUSIONS: This method of decontamination by O3 gas shows potential due to its fast and easy execution. The establishment of new protocols for hygiene and hospital disinfection using this approach should be considered, which may reduce environmental contamination by fungi and, consequently, the burden of fungal infections.

Assuntos

RESUMO

In this research, the decomposition of toxic organics from pulp and paper mill effluent by the sequential application of ozonation and biodegradation was studied. Ozonation, as a pre-treatment, was executed to transform the initial pollutants into less toxic compounds (such as organic acids of low molecular weights). Biodegradation was executed during three days with acclimated microorganisms that were able to complete the decomposition of the initial organic mixture (raw wastewater) and to achieve a higher degree of mineralization (85-90%). Experiments were performed under three different conditions: (a) only ozonation of the initial contaminants, (b) only biodegradation of residual water without previous treatment by ozone and (c) ozonation followed by biodegradation performed by acclimated microorganisms. In the case of 72 h of biodegradation, the mineralization efficiency reached 85% and 89% after 30 and 60 min of ozonation, respectively. The no significant difference in this parameter coincided with the calculated generalized microorganisms' consortia specific growing rate µmax that was reduced from 2.08 × 10-3 h-1 to 6.05 × 10-4 h-1 when the ozonation time was longer. The identification of the organics composition by gas chromatography with mass detector (GC-MS) before and after treatments confirmed that the proposed combined process served as a more efficient alternative to secondary and tertiary treatments (mineralization degree between 60 and 80% in average) of the paper industry wastewater.

RESUMO

This study aims the development of photoelectrodes to be incorporated in a photoelectrocatalytic ozonation (PECO) process for tertiary treatment of urban wastewaters, targeting the removal of contaminants of emerging concern (CEC). PECO tests were performed using urban wastewater after secondary treatment fortified with Cefadroxil (CFX, C16H17N3O5S), as target model CEC. Three Nitrogen and Carbon doped TiO2 (CN-TiO2) electrodes were synthesized by anodizing at 50, 70, and 90 V, and calcined. These materials were characterized by X-Ray diffraction and Rietveld refinement, Scanning Electron Microscopy, Diffuse Reflectance Spectroscopy, X-ray photoelectron spectroscopy, chronoamperometry, and electrochemical impedance spectroscopy, to correlate defects with photoactivity. All photoanodes considerably reduced their main bandgaps by the incorporation of C and N species, to enable absorption capacities in the UV region using a Xe lamp. The lowest oxygen vacancy content and largest crystallite size were found for CN-TiO2-70, favoring the reduction of bulk defects that could act as recombination of charge carriers. Therefore, oxygen vacancies affect more the TiO2 photoactivity compared to the crystallite size or the light absorption capacity, confirming that a lower content of vacancies in the material bulk and surface doping significantly influence the activity as detected by Rietveld refinement, DRS, and XPS. The electrochemical techniques confirm that the highest photocurrent was obtained for CN-TiO2-70, whence this photoanode was chosen to carry out the CFX degradation. A point defect model simulating Nyquist plot reveals that the photoactivity depends on the speed to diffuse oxygen vacancies through the TiO2 coating. All abatement processes were followed by high-performance liquid chromatography, and Total Organic Carbon (TOC). At neutral and alkaline conditions, CFX is eliminated to levels below the analytical detection limit after 90 min of treatment (TOC removals of 87 and 91%, respectively), indicating that the coupling between the CN-TiO2-70 photocatalyst and ozone is effective in eliminating the contaminant due to parallel routes forming •OH species. Lower CFX degradation observed at acidic pH (TOC removal of 70%) is assigned to the difficulty of oxidizing protonated CFX species.

Assuntos

RESUMO

This paper proposes the study of a solar-based photocatalytic ozonation process for the degradation of salicylic acid (SA) using a novel S-scheme ZnO/Cu2O/CuO/carbon xerogel photocatalyst. The incorporation of CuO and Cu2O aims to enhance charge mobility through the formation of p-n heterojunctions with ZnO, whereas the carbon xerogel (XC) was selected due to its eco-friendly nature, capacity to stabilize S-scheme heterojunctions as a solid-state electron mediator, and ability to function as a reducing agent under high temperatures. The characterization of the composites demonstrates that the presence of the XC during the calcination step led to the reduction of a fraction of the CuO into Cu2O, forming a ternary semiconductor heterojunction system. In terms of photocatalysis, the XC/ZnO-CuxO 5% composite achieved the best efficiency for salicylic acid degradation, mainly due to the stabilization of the S-scheme charge transfer pathway between the ZnO/CuO/Cu2O semiconductors by the XC. The total organic carbon (TOC) removal during heterogeneous photocatalysis was 80% for the solar-based process and 68% for the visible light process, after 300 min. The solar-based photocatalytic ozonation process was highly successful regarding the degradation of SA, achieving a 75% increase in the apparent reaction rate constant when compared to heterogeneous photocatalysis. Furthermore, a 78% TOC removal was achieved after 150 min, which is half the time required by the heterogeneous photocatalysis to obtain the same result. Temperature, salinity, and turbidity had major effects on the efficiency of the photocatalytic ozonation process; the system's pH did not cause any major performance variation, which holds relevance for industrial applications.

Assuntos

RESUMO

COVID-19 is a global health threat with a large number of confirmed cases and deaths worldwide. Person-to-person transmission through respiratory droplets and contact with aerosol-infected surfaces are the main ways in which the virus spreads. However, according to the updated literature, the new coronavirus (SARS-CoV-2) has also been detected in aqueous matrices, with the main route of transmission being feces and masks from patients diagnosed with the disease. Given the emergence of public health and environmental protection from the presence of lethal viruses and bacteria, this review article aims to report the major challenges associated with the application of ozonation in water contaminated with viruses and bacteria, in order to clarify whether these communities can survive or infect after the disinfection process and if it is efficient. Available data suggest that ozonation is able to increase the inactivation effect of microorganisms by about 50% in the logarithmic range, reducing infectivity. In addition, the evidence-based knowledge reported in this article is useful to support water and sanitation safety planning and to protect human health from exposure to cited contaminants through water.

Assuntos

RESUMO

BACKGROUND: The ozonation of grains in a closed system at low pressure is a strategy with the potential for treating packaged products. Research is necessary to characterize the reaction kinetics of ozone in this type of injection system so that it is possible to design chambers and determine the ozone concentrations suitable for commercial-scale applications. The objective of this study was therefore to characterize the low-pressure ozone injection system in relation to the physical properties of the grains and determine possible changes in their quality. Samples (5 kg each) of common beans, cowpea beans, corn, popcorn kernels, paddy rice, and polished rice were exposed to ozone in a 70 L hypobaric chamber. Initially, the internal pressure of the chamber was reduced to 500 hPa. Then, ozone was injected at a concentration of 32.10 g m-3 at a volumetric flow rate of 1 L min-1 until reaching a pressure of 1000 hPa. To relate the decomposition of ozone to the grains that were being evaluated, different physical properties were determined, and quality analysis was conducted. RESULTS: Ozone gas half-life outside and inside the package depended on the grain type. Ozone decomposition was quickest in polished rice and slowest in common beans. The half-life of the different grains ranged from 17.8 to 52.9 and 16.4 to 52.9 min, outside and inside the package, respectively. Considering the physical properties, specific surface (Ss), surface area (SA), and sphericity (φ) exhibited a significant correlation with the decomposition rate constant (k) of ozone. However, the variables volume (V), permeability (K), porosity (ε), and specific mass (ρ) showed no correlation with k. CONCLUSION: The physical properties of grain influenced the reaction kinetics of ozone gas during the low-pressure injection process. Ozone gas injection at low pressures did not alter the quality attributes of the grains under study. © 2022 Society of Chemical Industry.

Assuntos

RESUMO

Encephalic vascular accident, or stroke, is the most common pathology of the central nervous system in humans, the second leading cause of death and physical and cognitive disabilities, in developing countries. It presents as an ischemic (more common) or hemorrhagic form. Ozone therapy has been shown to be effective in neuromodulation, neuroprotection, and nerve regeneration. The present study aimed to evaluate the effect of targeted mild ozone after inducing cerebral ischemia in vitro. Neuroblastoma lineage cells (SH-SY5Y) and canine amniotic membrane stem cells were subjected to 24 hours of hypoxia in an incubator culture chamber. The cells were evaluated by MTT assay, colorimetric assay spectrophotometry, fluorescence microscopy, and flow cytometry. Treatment with low concentrations of ozone (2-10 µg/mL), indicated a possible neuroregenerative effect at low concentrations, correlated with lower levels of apoptosis and oxidative stress compared to cells not subjected to hypoxia. High concentrations of ozone (18-30 µg/mL) promoted an increase in rate of apoptosis and cell death. We developed a novel protocol that mimics ozone therapy for ischemic stroke, using ozonized culture medium after hypoxia induction. Although more studies are needed, we conclude that ozone has a dose-dependent hormetic effect and can reverse the effect of ischemia in vitro at low concentrations.

Assuntos

RESUMO

Ozone has been successfully employed in water treatment due to its ability to oxidize a wide variety of refractory compounds. In order to increase the process efficiency and optimize its economy, the implementation of heterogeneous catalysts has been encouraged. In this context, the use of cheap and widely available natural materials is a promising option that would promote the utilization of ozone in a cost-effective water treatment process. This review describes the use of natural clays, zeolites and oxides as supports or active catalysts in the ozonation process, with emphasis on the structural characteristics and modifications performed in the raw natural materials; the catalytic oxidation mechanism; effect of the operating parameters and degradation efficiency outcomes. According to the information compiled, more research in realistic scenarios is needed (i.e., real wastewater matrix or continuous operation in pilot scale) in order to transfer this technology to the treatment of real wastewater streams.

Assuntos

RESUMO

Contamination of foods by mycotoxins is a reality. However, emerging technologies such as ozonization can be used to reduce the levels of these contaminants. Thus, the aim of this study was to evaluate the effects of using ozone at different period and application times during the soaking step of parboiling process. Samples were analyzed for qualitative and quantitative analysis of mycotoxins, swelling power and solubility, head rice yield, protein solubility, cooking time, texturometric profile, colorimetric profile and defective grains. The results showed tha parboiled rice grains treated with ozone present significant reduction of mycotoxins contamination, regardless of the time and period of application and the mycotoxin evaluated. Regardig to technological properties, the samples treated with ozone in the final 3 h and for 5 h of soaking presented higher head rice yield, luminosity and hardness, with decreases in cooking time, percentage of defective grains and soluble protein.

Assuntos

RESUMO

Ozonation process was used for leachate treatment from a landfill located in Rio de Janeiro, Brazil. The influence of pH and ozone concentration on COD (Chemical Oxygen Demand), TOC (Total Organic Carbon), Absorbance at 254 nm (ABS254nm), and True color was evaluated through RCCD (Rotatable Central Composite Design) experimental design, resulting in mathematical models that were statistically analyzed in Statistica and Design Expert software. The removals obtained was up to 26.1%, 29.9%, 56.9%, and 97.9% for COD ([COD]0=3,323 mg/L), TOC ([TOC]0=1,275 mg/L), ABS254nm (ABS0=32.2), and True color ([True color]0=3,467 mgPt-Co/L), respectively. Statistical and variance analysis of the experimental data revealed that one quadratic model obtained in Statistica was valid, ABS254nm reduction. However, by applying the Design Expert software, modified models were generated to predict the behavior of all dependent variables. Thus, the optimum point for the best response after ozonation of the landfill leachate was at the highest pH and the lowest ozone dose (9 and 2.2 mgO3/m3, respectively). Toxicity toward Allivibrio fischeri bacteria was abated at the same time that it decreased the impact of the effluent to Danio rerio fish (from 125 UT to 62 UT) on the treated leachate.

Assuntos

RESUMO

Free gossypol is a toxic compound which naturally occurs in cottonseed and its derivates, affecting animal and possibly human health. Consequently, alternatives for gossypol destruction must be evaluated. This work evaluated the emerging technology of ozone processing for free gossypol destruction in cottonseed meal. Ozonation was carried out in the actual cottonseed meal and also a model system, designed to describe the involved mode of action. The model system consisted of glass pearls beads covered with free gossypol. Ozonation was performed in two ways: as a static process, i.e., without homogenising the sample after placing them in the reactor, and also homogenising it. Ozone degraded free gossypol in all the systems, but reaching different levels. Free gossypol reduction was higher in the model system than the cottonseed meal, and higher in the homogenised processing than the static one: cottonseed meal in homogenised (56%) and static (25%); model system homogenised (98%) and static (80%). The obtained differences suggest a problem of gas penetration in the solid particles, the effect of unexposed surfaces due to contact areas, and the reaction with other organic molecules further than the target. Ozonation is a promising technique for gossypol degradation in cottonseed meal, but additional strategies are needed to optimise the ozonation process and evaluate toxicological aspects.

Assuntos

RESUMO

This work presents a bibliographic review of the literature regarding the simultaneous removal of contaminants of emerging concern (CECs) and disinfection in domestic wastewater matrices. These two responses are usually evaluated independently, as most attention has been centered on the discussion over the removal of CECs in the last 10 years. However, the simultaneous removal of CECs and pathogens from wastewater has been recently brought to the spotlight, especially considering the removal of antibiotics and antibiotic-resistant bacteria. Aiming at a reproducible and nonbiased methodology, a combination of the construction of a bibliometric portfolio with systemic analysis was performed with peer-reviewed manuscripts published between 2008 and 2019 in five distinct databases. Several keyword combinations were necessary to achieve a relevant portfolio according to strict criteria. As a result, five highly cited papers and authors were selected. Among the advanced oxidation processes (AOPs) explored for simultaneous removal of CECs and disinfection in these papers, detailed results have been elucidated mainly for ozonation. Thus, revealing the broad range of questions that have yet to be investigated in depth for new technologies such as irradiated solar processes. In addition, there is a lack of information associated with simultaneous assessment of CEC removal and disinfection in real samples and in wastewater matrices originated from different secondary treatment technologies in diverse locations.

Assuntos

RESUMO

Diethyl phthalate (DEP) is a pollutant which can be found on soils as a result of its widespread application in plastic industry. Soil contaminated with DEP requires the application of different chemical methods to attain its remediation. Among these methods, ozonation has proven to be effective against toxic soil pollutants. The presence of metal oxides in soil is a possible source of catalytic effect. In this study, it was analyzed the catalytic effect of goethite (α-FeOOH), hematite (α-Fe2O3), and gibbsite (γ-Al(OH)3) in combination with O3 to achieve DEP decomposition. The DEP elimination efficiency by ozonation on the sand increased according to the following order: without catalyst < γ-Al(OH)3 < α-Fe2O3 < α-FeOOH. Among these three oxides, goethite has the highest OH groups density. The reaction of OH groups and O3 favors the formation of oxidant species, such as O2•- and OH•. The effect of the moisture content, the catalyst concentration, and the type of soil (sand and calcined soil) were also studied. The latter had a significant influence on the total organic carbon (TOC) removal. The mineralization degree was 84% in the O3-soil system, while only 40% was obtained with O3-sand (α-FeOOH) in dry sand after 8 h of treatment. Calcined soil promoted the increase of TOC removal due to the presence of different metal oxides, which were active centers for O3 decomposition. The toxicity tests of the three reaction systems (O3-sand, O3-sand (α-FeOOH), and O3-soil) were evaluated on lettuce seed germination before and after DEP ozonation.

Assuntos

RESUMO

The efficiency of nanoscale zero-valent iron (nZVI) for the recalcitrant organic pollutants degradation has been frequently reported. However, some disadvantages such as low hydraulic conductivity, rapid passivation and consequent loss of reactivity have motivated researchers to study immobilized forms. In this work, calcium alginate beads incorporated with nZVI were prepared, characterized and applied in a catalytic ozonation system of Reactive Red 195 dye (RR195). In order to avoid shearing the calcium alginate beads, an Air lift reactor operated with Air/O3 cycles in an 8 mg L-1 concentration was used. The RR195 treatability tests conducted with a dye concentration of 25 mg L-1, 50 g L-1 of nZVI-Alg beads and an Air/O3 feed flow of 1 L min-1, revealed significant process efficiency, which was not limited only to the dye discoloration. Total discoloration levels were observed in 30 min of treatment and reductions in 97 % of organic matter in 90 min of treatment, measured through the chemical oxygen demand. The typical absorptions of aromatic compounds reduction (λmax =290 nm) and the acute toxicity reduction (Artemia Saline bioassay), contribute to the Alg-nZVI/O3 system potential for the application in the treatment of liquid effluents contaminated with dyes.

RESUMO

Current studies tend to combine different advanced treatment technologies to reduce costs and increase efficiency. The objective of this work was to assess the combination of ozonation and UV/H2O2 with activated carbon adsorption for the removal of effluent quality parameters and micropollutants from secondary effluent samples. The experiments were carried out using the following configurations: O3 + GAC + O3 (1); O3 + GAC + UV/H2O2 (2); UV/H2O2 + GAC + O3 (3); UV/H2O2 + GAC + UV/H2O2 (4). Configurations 1, 3 and 4 were the most efficient for organic matter removal, while configuration 1 had the lowest cost on laboratory scale. An additional ultra-filtration membrane unit (UF) was tested at the end of configuration 1, which was optimized in terms of ozone doses for the removal of three organophosphate micropollutants in ultrapure water (TNBP, TCIPP and TPHP at 10 µgL-1). The best cost-effective configuration of this treatment train was the one using 1 mg L-1 of ozone before and after GAC, which achieved around 100% of micropollutants abatement. The role of each treatment to the final micropollutant removal was also discussed, being the first ozone treatment responsible for about 15% removal of the mixture of contaminants, while GAC was responsible for an additional 80% removal. The complete treatment train reached almost 100% of contaminants removal (under detection limit of the method), as well as added security to the system. The achieved results were also compared to international reuse legislations, proving that the combination of O3 and GAC was an interesting option to achieve enough quality for some reuse purposes.

RESUMO

Resumo Objetivo: Avaliar a ação antimicrobiano do gás ozônio (O3) em superfícies e ar ambiente climatizado artificialmente. Métodos: Estudo experimental/laboratorial e transversal realizado em dez salas de um laboratório de pesquisa em microbiologia médica, com risco de segurança biológica classe 2. As superfícies demarcadas do chão, parede e bancada foram avaliadas, quanto à presença ou ausência de micro-organismos, a partir de coletas feitas com swab umedecido em água destilada estéril, antes e após a exposição do gás O3 gerado por dois equipamentos distintos. Após este procedimento, o swab foi inoculado na superfície do meio de cultura Brain Heart Infusion Agar DIFCO® (BHI), seguindo-se a incubação a 35ºC por 24 horas. Para a análise microbiológica do ar, uma placa com BHI foi exposta aberta por uma hora, antes e após o tratamento do gás O3, sendo incubadas segundo os mesmos critérios. Resultados: A atividade antimicrobiana do gás O3 gerado por ambos os equipamentos foi constatada para todas as áreas investigadas, com registros de redução do número de Unidades Formadoras de Colônias. O potencial de inibição antimicrobiana dos aparelhos se manteve próximo para os critérios de análise adotados, com destaque para as áreas de chão e bancada. Considerando-se todas as salas e percentuais de inibição microbiana, frente aos dois equipamentos, os resultados foram: chão (100%), bancada (90%), parede (50%) e ar, 70%. Conclusão: Os equipamentos geradores de gás O3 apresentaram potencial antimicrobiano para medida de controle de microrganismos presentes em superfícies e ar ambiente climatizado artificialmente, sendo um sanitizante factível para utilização.

Resumen Objetivo: Evaluar la acción antimicrobiana del gas ozono (O3) en superficies y en el aire interior climatizado artificialmente. Métodos: Estudio experimental/de laboratorio y transversal realizado en diez salas de un laboratorio de investigación en microbiología médica, con riesgo de seguridad biológica clase 2. Se evaluaron las superficies delimitadas en el piso, pared y mesa en cuanto a la presencia o ausencia de microorganismos, a partir de muestras recolectadas con hisopo humedecido en agua destilada estéril, antes y después de la exposición del gas O3 generado por dos máquinas distintas. Luego de este procedimiento, el hisopo fue inoculado en la superficie del medio de cultivo Brain Heart Infusion Agar DIFCO® (BHI), y después incubado a 35 °C por 24 horas. Para el análisis microbiológico del aire, se expuso una placa con BHI abierta durante una hora, antes y después del tratamiento del gas O3, y luego se incubó con los mismos criterios. Resultados: Se constató la actividad antimicrobiana del gas O3 generado por ambas máquinas en todas las áreas investigadas, y se registró una reducción del número de unidades formadoras de colonias. El potencial de inhibición antimicrobiana de los dispositivos se mantuvo próximo a los criterios de análisis adoptados, con énfasis en el área del piso y mesa. Considerando todas las salas y porcentajes de inhibición microbiana, con las dos máquinas, los resultados fueron: piso (100 %), mesa (90 %), pared (50 %) y aire (70 %). Conclusión: Las máquinas generadoras de gas O3 presentaron potencial antimicrobiano como medida de control de microorganismos presentes en superficies y aire interior climatizado artificialmente, lo que lo convierte en un desinfectante factible para ser usado.

Abstract Objective: Assess the antimicrobial action of ozone gas (O3) on surfaces and artificially cooled ambient air. Methods: Cross-sectional experimental/laboratory study carried out in ten rooms of a medical microbiology research lab, with class 2 biosafety risk. The demarcated surfaces on the floor, wall and counter were assessed in relation to the presence or absence of microorganisms, based on collections done with swabs dampened in sterile distilled water, before and after exposure to ozone gas produced by two different generators. After this procedure, each swab was inoculated on the surface of a Brain Heart Infusion Agar DIFCO® (BHI) culture, followed by incubation at 35ºC for 24 hours. For the microbiological analysis of the air, a petri dish with BHI was openly exposed for one hour, before and after treatment with O3 gas, and were incubated according to the same criteria. Results: The antimicrobial activity of the O3 gas produced by both generators was checked in all the areas investigated, with records indicating a decrease in the number of colony-forming units. The antimicrobial inhibition potential of the generators was close to the analysis criteria adopted, particularly for the floor and counter areas. Based on all the rooms and microbial inhibition percentages, in relation to the two generators, the results were: floor (100%), counter (90%), wall (50%) and air (70%). Conclusion: The O3 generators had antimicrobial potential as a procedure for controlling microorganisms present on surfaces and in artificially cooled ambient air, constituting a feasible sanitizer.

Assuntos

RESUMO

Advances generated in medicine, science, and technology have contributed to a better quality of life in recent years; however, antimicrobial resistance has also benefited from these advances, creating various environmental and health problems. Several determinants may explain the problem of antimicrobial resistance, such as wastewater treatment plants that represent a powerful agent for the promotion of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG), and are an important factor in mitigating the problem. This article focuses on reviewing current technologies for ARB and ARG removal treatments, which include disinfection, constructed wetlands, advanced oxidation processes (AOP), anaerobic, aerobic, or combined treatments, and nanomaterial-based treatments. Some of these technologies are highly intensive, such as AOP; however, other technologies require long treatment times or high doses of oxidizing agents. From this review, it can be concluded that treatment technologies must be significantly enhanced before the environmental and heath problems associated with antimicrobial resistance can be effectively solved. In either case, it is necessary to achieve total removal of bacteria and genes to avoid the possibility of regrowth given by the favorable environmental conditions at treatment plant facilities.

Assuntos

RESUMO

The carbamazepine (CBZ) abatement is herein evaluated using catalytic ozonation at different NiO concentrations as catalyst: 100, 300, and 500 mg L-1, revealing its total destruction after 5 min of reaction either by conventional or catalytic ozonation. The NiO incorporation in the reactor does not increase the destruction rate, but the catalyst presence enhances the partial mineralization of the contaminant by conversion into oxalic and formic acids and the removal of total organic carbon (TOC) associated with the formation of oxidant species such as hydroxyl radical. Evidence for this behavior is the accumulation rate of the above acids which rise proportionally to the NiO concentration. The highest NiO concentration (500 mg L-1) reached a maximum TOC removal of 79.2%, which exceeds by 50% the outcome of the conventional treatment. The accumulation-decomposition profiles of oxalic and formic acids suggest the occurrence of simultaneous reaction mechanisms (hydroxyl radicals and complex formations) on the catalyst during CBZ ozonation. According to XPS analysis, the presence of nitrogen species in the NiO-ozonated was attributable to byproducts of CBZ decomposition. The toxicity bioassay based on Lactuca sativa seeds demonstrate that ozonated samples attained similar plant germination than the reference substance (water) after 120 min of treatment. This result is comparable with or without the catalyst presence, indicating the formation of non-toxic accumulated byproducts at the end of the ozonation reaction.

Assuntos

RESUMO

1,4-Dioxane is a synthetic cyclic ether traditionally used as a chlorinated solvent stabilizer. It is a small molecule and recalcitrant compound that is difficult to remove by conventional processes and in this regard, there is a need for the development of new technologies. In this study, an innovative CuO-coated ceramic membrane (CM) reactor system that can be used to oxidize 1,4-dioxane dissolved in surface water by catalytic ozonation was developed. The effect of the thickness of the CuO deposited on the ceramic membrane surface on the permeability, fouling resistance, 1,4-dioxane removal, and toxicity was evaluated. The efficiency of the hybrid ozonation coupled to the use of a CuO-coated CM in 1,4-dioxane removal and the antifouling properties were assessed from TOC and 1,4-dioxane removal kinetics data. Reusability in four cycles was also tested. The performance of the CuO-coated CM remained stable during the four cycles of the reusability test. The ceramic membrane coated with CuO particles coupled with ozonation is appropriate for 1,4-dioxane degradation in the aqueous phase (45% efficiency, rate constant increased by a factor of 2.98 compared with the uncoated-hybrid process) and fouling removal (60 min to recovery the permeate flux).

Assuntos