Heterogeneous photocatalysis of moxifloxacin at a pilot solar compound parabolic collector: Elimination of the genotoxicity.

Photocatalysis has been applied for the elimination or reduction concentration of emerging pollutants in water. One of them, is the moxifloxacin (MOX), a fluoroquinolone that have a potential to develop resistant bacteria and have been present toxicity. The MOX achieves the environment due to inefficient wastewater treatment and incorrect disposal. Aiming to find a sustainable solution for photocatalytic process, compound parabolic concentrator (CPC) reactors have been proposed. In this sense, the present study investigates the application of CPC reactor for the degradation of MOX using sunlight and artificial light (UV-A lamp). In addition, the acute toxicity for L. sativa seeds and A. cepa bulbs, as well as the MOX cytotoxicity and genotoxicity for A. cepa root were investigated before and after treatment. The MOX degradation was around 65% using the sunlight and 44% with the artificial light. This difference was due to the kind of incident radiation (direct and diffuse), as well as the type of radiation (visible and/or ultraviolet) used in the processes. For L. sativa the acute toxicity was eliminated after MOX treatment using sunlight. A. cepa root length increased before the treatment and reduced significantly after it, what can indicate hormesis occurrence. MOX cytotoxicity was not observed. In contrast, genotoxicity assays showed high frequency of chromosomal aberrations for MOX solution, indicating elevated genotoxicity that was eliminated after solar treatment. The transformation products of MOX after CPC reactor solar treatment did not show cytotoxicity and genotoxicity in A. cepa and acute toxicity in L. Sativa. The results indicates that photocatalysis in a CPC solar reactor is efficient for MOX toxicity removal in the treated solutions.

Green Nanocoatings Based on the Deposition of Zirconium Oxide: The Role of the Substrate.

Herein, the influence of the substrate in the formation of zirconium oxide monolayer, from an aqueous hexafluorozirconic acid solution, by chemical conversion and by electro-assisted deposition, has been approached. The nanoscale dimensions of the ZrO2 film is affected by the substrate nature and roughness. This study evidenced that the mechanism of Zr-EAD is dependent on the potential applied and on the substrate composition, whereas conversion coating is uniquely dependent on the adsorption reaction time. The zirconium oxide based nanofilms were more homogenous in AA2024 substrates if compared to pure Al grade (AA1100). It was justified by the high content of Cu alloying element present in the grain boundaries of the latter. Such intermetallic active sites favor the obtaining of ZrO2 films, as demonstrated by XPS and AFM results. From a mechanistic point of view, the electrochemical reactions take place simultaneously with the conventional chemical conversion process driven by ions diffusion. Such findings will bring new perspectives for the generation of controlled oxide coatings in modified electrodes used, as for example, in the construction of battery cells; in automotive and in aerospace industries, to replace micrometric layers of zinc phosphate by light-weight zirconium oxide nanometric ones. This study is particularly addressed for the reduction of industrial waste by applying green bath solutions without the need of auxiliary compounds and using lightweight ceramic materials.

Parâmetros operacionais na remoção biológica de nitrogênio de águas por nitrificação e desnitrificação simultânea / Operating parameters on biological nitrogen removal of water by simultaneous nitrification and denitrification

RESUMO O nitrogênio é um dos contaminantes mais importantes presentes nas águas residuais. As alternativas tecnológicas mais usuais para o tratamento de águas contendo esse composto lançam mão do ciclo bioquímico do nitrogênio, o qual se sustenta em dois processos, a nitrificação e a desnitrificação. Dentre os parâmetros que influenciam na remoção de nitrogênio, podemos citar a concentração de oxigênio dissolvido, relação carbono/nitrogênio, temperatura, pH entre outros. Este trabalho apresenta uma revisão sobre a remoção biológica de nitrogênio das águas e os principais parâmetros que influenciam na sua remoção, dando ênfase ao processo de nitrificação e desnitrificação simultânea.

ABSTRACT Nitrogen is one of the most important contaminants present in wastewater. The most common alternative technologies for the treatment of waters containing this compound lay hold of the biochemical cycle of nitrogen, which is based on two processes, nitrification and denitrification. Among the parameters that influence the removal of nitrogen, we can mention the concentration of dissolved oxygen, carbon/nitrogen ratio, temperature, pH, and other relationships. This paper presents an overview of the biological nitrogen removal of water and the main parameters that influence the removal, emphasizing the simultaneous nitrification and denitrification process.

The effect of sanitary landfill leachate aging on the biological treatment and assessment of photoelectrooxidation as a pre-treatment process.

The sanitary landfill leachate is a dark liquid, of highly variable composition, with recalcitrant features that hamper conventional biological treatment. The physical-chemical characteristics of the leachate along the landfill aging, as well as their effects on the efficiency of the conventional treatment, were evaluated at this paper. The feasibility of photoelectrooxidation process as an alternative technique for treatment of landfill leachates was also determined. Photoelectrooxidation experiments were conducted in a bench-scale reactor. Analysis of the raw leachate revealed many critical parameters demonstrating that the recalcitrance of leachate tends to increase with time, directly influencing the decline in efficiency of the conventional treatment currently employed. The effects of current density and lamp power were investigated. Using a 400 W power lamp and a current density of 31.5 mA cm(-)(2), 53% and 61% efficiency for the removal of ammoniacal nitrogen and chemical oxygen demand were respectively achieved by applying photoelectrooxidation process. With the removal of these pollutants, downstream biological treatment should be improved. These results demonstrate that photoelectrooxidation is a feasible technique for the treatment of sanitary landfill leachate, even considering this effluent's high resistance to treatment.

Polyaniline emeraldine salt in the amorphous solid state: polaron versus bipolaron.

The polaronic and bipolaronic forms of polyaniline emeraldine salt (PAni-ES) in the amorphous solid state have been simulated using classical molecular dynamics (MD) and hybrid quantum mechanical/molecular mechanical-molecular dynamics (QM/MM-MD) approaches. It should be remarked that the electronic state of PAni-ES has been theoretically investigated in the gas phase, solution phase, and crystalline state, but this is the first study in the amorphous solid state, which is the most typical for this conducting polymer. MD simulations were carried out using force-field parametrizations explicitly developed for polaronic and bipolaronic models. QM/MM-MD calculations were performed using a quantum mechanical zone defined by four repeat units. In addition of the structural and electronic characteristics of the two forms of PAni-ES, MD and QM/MM-MD simulations indicate that the bipolaronic is the most stable state of amorphous PAni-ES. Complementary studies have been carried out using different experimental techniques. Although the morphology and topography of doped and undoped PAni are very similar, comparison of their UV-vis spectra supports the preference toward the bipolaronic form of PAni-ES.

Water absorbed by polyaniline emeraldine tends to organize, forming nanodrops.

Interactions, in terms of both binding energies and microscopic organization, of water molecules absorbed by hydrophilic polyaniline emeraldine base have been investigated using quantum mechanical calculations, molecular dynamics simulation, FTIR spectroscopy, and (1)H NMR. From an enthalpic point of view, water molecules interact more favorably with imine nitrogen atoms than with amine ones, even though the latter are entropically favored with respect to the former because of their two binding sites. Quantum mechanical results show that interaction energies of water molecules reversibly absorbed but organized individually around a binding site range from 3.0 to 6.3 kcal/mol, which is in good agreement with activation energies of 3-5 kcal/mol previously determined by thermodynamic measurements. The irreversible absorption of water to produce C-OH groups in rings of diimine units has been examined considering a three steps process in which water molecules act as both acidic and nucleophilic reagent. Although calculations predict that the whole process is disfavored by 5-8 kcal/mol only, FTIR and (1)H NMR detected the existence of reversibly absorbed water but not of C-OH groups. Both the binding energies and the structural information provided by molecular dynamics simulations have been used to interpret the existence of two types of physisorbed water molecules: (i) those that interact individually with polymer chains and (ii) those immersed in nanodrops that are contained within the polymeric matrix. The binding energies calculated for these two types of water molecules are fully consistent with the thermodynamic activation energies previously reported.