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In the present work, attempts of reducing a graphene oxide powder using a low temperature hydrogenation disproportionation desorption and the recombination process (L-HDDR) has been carried out. A lower processing temperature in large scale production is significant when costs are concerned. Graphite oxide was prepared using a modified Hummers’ method dispersed in ethanol and exfoliated using ultrasonication to produce Graphene Oxide (GO). Investigations have been carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results of L-HDDR processing graphene oxide powder, using unmixed hydrogen at 400°C and relatively low pressures (

Traditional methods to incorporate metals into graphene oxide (GO) usually require toxic reagents or high temperatures. This study proposes an innovative and sustainable method to incorporate silver (Ag) into graphene oxide using electron beam and evaluate its antibacterial activities. The method is based on green synthesis, without toxic reagents or hazardous wastes, and can be carried out at room temperature, in short reaction times. To synthesize the Ag/rGO nanocomposite, a water/isopropanol solution with dispersed graphene oxide and silver nitrate was submitted to a dose range from 150 to 400 kGy. The product was characterized by thermogravimetry analysis, X-ray diffraction and transmission electron microscopy. The antibacterial activity of Ag/rGO was observed against Gram-negative Escherichia coli by plate count method and atomic force microscopy. The results showed that concentrations as low as 100 μg/mL of produced Ag/rGO were enough to inactivate the cells.

Graphene oxide (GO) can be partially reduced to graphene-like sheets by removing the oxygen-containing groups and recovering the conjugated structure. In this work, the thermal reduction of GO powder has been carried out using back pumping vacuum pressures and investigated employing X-ray diffraction analysis. The experimental results of estimating the number of graphene layers on the reduced powder at various temperatures (200 – 1000 °C) have been reported. Electrical changes have been produced in a graphene oxide with the vacuum reduction process. This study has shown that the ideal processing temperature for reducing graphene oxide nanomaterial was about 400 °C. It has also been shown that at 600 °C the number of layers in the reduced nanomaterial increased. The internal series equivalent resistance (ESR) has been improved substantially with the vacuum thermal treatment even at temperatures above 400 °C. ESR was reduced from 95.0 to about 13.8 Ω cm2 with this processing. These results showed that the process can be applied to the reduction of graphene oxide to produce supercapacitor nanomaterials. The advantage of employing this method is that the processing is a straightforward and low cost thermal treatment that might be used for large amount of nanocomposite material.

Graphene has attracted significant interest because of its excellent electrical properties. However, a practical method for producing graphene on a large scale is yet to be developed. Graphene oxide (GO) can be partially reduced to graphene-like sheets by removing the oxygen-containing groups and recovering the conjugated structure. GO can be produced using inexpensive graphite as the raw material via cost-effective chemical methods. High vacuum and temperature (10−7 mbar and 1100°C, respectively) conditions are well-known to enable the preparation of reduced powder at the laboratory scale. However, a large-scale high vacuum reduction system that can be routinely operated at 10−7 mbar requires considerable initial capital as well as substantial operational and maintenance costs. The current study aims at developing an inexpensive method for the large-scale reduction of graphene oxide. A stainless steel vessel was evacuated to backing-pump pressure (10−2 mbar) and used to process GO at a range of temperatures. The reduction of GO powder at low vacuum pressures was attempted and investigated by X-ray diffraction and Fourier transform infrared spectroscopy. The experimental results of processing GO powder at various temperatures (200–1000°C) at relatively low pressures are reported. The microstructures of the processed materials were investigated using scanning electron microscopy and chemical microanalyses via energy dispersive X-ray analysis.

Graphene (G) has been attracted great interest for its excellent electrical properties. However, the large-scale production of graphene is presently unfeasible. Graphene oxide (GO) can be (partly) reduced to graphene-like sheets by removing the oxygen-containing groups with the recovery of a conjugated structure. It can be produced using inexpensive graphite as raw material by cost-effective chemical methods. Although hydrogen (mixed with argon) at high temperature (1100°C) has been employed to reduce GO powder, the hydrogenation disproportionation desorption and recombination (HDDR) process in particular was unreported for this purpose. In the present work, attempts of reducing GO powder using the HDDR process have been carried out and investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The experimental results of processing graphene oxide powder using unmixed hydrogen at moderate temperatures (about 850°C) and relatively low pressures (

Food allergies have been increasing all over the world. Egg is an important component in the food industries and the second most common cause of food allergy, shortly after milk. In the wine industry, egg white is applied as a fining agent for tannin removal. In this study, a sandwich-based immunoassay for ultrasensitive detection of ovalbumin (OVA) in wine samples was developed. The assay involves the use of magnetic beads (MBs) decorated with a polyclonal anti-OVA antibody (Ab2) and horseradish peroxidase (HRP), used as label for the quantification in a disposable electrochemical microfluidic device (DEμD) here developed. The Ab2-MB-HRP prepared was applied to capture, separate, and pre-concentrate OVA from wine samples. In the DEμD, OVA was immune-magnetically captured (OVA-Ab2-MB-HRP), producing a sandwich structure (GO-Ab1-OVA-Ab2-MB-HRP) on the electrode's surface. This arrangement results in an ultrasensitive device, achieving the ultralow limit of detection of 0.2 fg mL−1 OVA. Five samples of wines were analyzed by using the immuno-magneto-assay which presents excellent accuracy compared with enzyme-linked immunosorbent assay (ELISA).

The radionuclide 55 Fe was determined in sam- ples of radioactive wastes from the water cleanup system of the IEA-R1 nuclear research reactor. In order to validate the results, the 55 Fe activity concentration was measured in eight waste samples and in six simulated samples con- taining the most important interfering radionuclides. A simple method was employed to separate and purify 55 Fe from other radionuclides present in these samples, com- bining co-precipitation with ammonium hydroxide and purification with anionic ion-exchange resin, which enables 55 Fe to be quantified either by liquid scintillation counting (LSC) or by X-ray spectrometry using a low-energy ger- manium spectrometer (LEGe). Both measurement methods were used so that the separation and purification process could be confirmed by comparison of spectra with and without the utilization of anionic ion-exchange resin. Activity and interferences were compared in the results obtained from LSC and LEGe measurement methods.

Ion-exchange resins and activated charcoal beds are employed for purification of the cooling water that is pumped through the core of pool type nuclear research reactors. Once expended, these media are replaced and become radioactive wastes that contain low concentrations of long-lived fission and activation products, uranium isotopes and transuranium elements. Determination of the radioactive inventory is of paramount importance in the management of such radioactive wastes, which, besides high-energy photon emitters that can be identified and quantified directly by gamma-ray spectrometry, also contain pure alpha, pure beta and low-energy photon emitters whose quantitative determination require radiochemical separation. These later are collectively known as difficult to measure (DTM) radionuclides. A characterization program embracing the DTM radionuclides is currently in progress for spent ion-exchange resins and activated charcoal beds that were definitively withdrawn from the water cleanup system of the IEA-R1 nuclear research reactor. Radiochemical methods used in the characterization program include separations with specific anionic resins, chromatographic extractions and co-precipitation, which enabled the measurement of the activity concentrations of 90Sr, 234U, 235U, 238U, 238Pu, 239+240Pu, 241Pu, 241Am and 244Cm. An enhanced retention of uranium and transuranium elements was observed in the activated charcoal compared to the ion-exchange resins as a result of the tendency of actinides to undergo hydrolysis in aqueous solutions.

The present study investigated the influence of 241Am on microbial growth and the degradation of organic waste. Leachate samples collected in a lysimeter were periodically analyzed for bacterial growth, under both aerobic and anaerobic conditions. 241Am inhibited bacterial growth, and the degradation of organic matter was delayed in comparison with the control. Minimal inhibitory concentration assays and survival curves revealed that it inhibits the growth of Pseudomonas putida F1. The assay also revealed that 241Am is more toxic than 238U, Zn2+ and Cd2+. This study further led to the finding of four new radionuclide-tolerant bacterial strains: Flavobacterium spp., Pseudomonas gladioli, Chryseobacterium indologenes and Ochrobactrum anthropi. The survival curves of P. gladioli, C. indologenes revealed that these bacteria are resistant to metal as consortia.

The differentiation between the like and unlike isomers of the title compound, achieved by combined use of ¹H NMR spectroscopy, spectral simulation and Molecular Mechanics, correlated by means of the Altona Equation (a generalized version of the Karplus Equation), is reported herein. Apresenta-se aqui a diferenciação entre os isômeros like (igual) e unlike (diferente) do 3,4-di(p-anisil)adipato de dimetila, que foi efetuada pelo uso combinado de espectroscopia de RMN de ¹H, simulação espectral e Mecânica Molecular, correlacionados pelo uso da Equação de Altona, uma versão generalizada da Equação de Karplus.

Polyacrylonitrile (PAN) polymers are used as precursors for carbon fiber production. This process requires an oxidative stabilization step, which can be studied by differential scanning calorimetry (DSC). In this sense, thermal behavior of PAN based terpolymers by different polymerization processes, compositions and itaconic acid concentrations in the reaction media were investigated. The obtained results showed that the addition of itaconic acid and methyl acrylate as comonomers resulted a lower heat flow during the process comparing to the PAN homopolymer. It suggested that these comonomers aid the oxidative stabilization stage for all studied process. The redox system polymerization at 40°C resulted in a lower heat flow. Itaconic acid decreases slightly initial and peak temperatures of the terpolymer and heat flow until concentration of 3y. The cyclization temperature decreases when MAis incorporated into the terpolymer compared to the MMA terpolymer and increases when MAA is the acidic monomer. Among terpolymers the AN/MA/AA polymer showed the best thermal behavior for carbon fiber producing.

A heavy-metal resistant bacterial consortium was obtained from a contaminated river in Sao Paulo, Brazil and utilized for the design of a fixed-bed column for the removal of copper. Prior to the design of the fixed-bed bioreactor, the copper removal capacity by the live consortium and the effects of copper in the consortium biofilm formation were investigated. The Langmuir model indicated that the sorption capacity of the consortium for copper was 450.0 mg/g dry cells. The biosorption of copper into the microbial biomass was attributed to carboxyl and hydroxyl groups present in the microbial biomass. The effect of copper in planktonic cells to form biofilm under copper rich conditions was investigated with confocal microscopy. The results revealed that biofilm formed after 72 h exposure to copper presented a reduced thickness by 57% when compared to the control; however 84% of the total cells were still alive. The fixed-bed bioreactor was set up by growing the consortium biofilm on granular activated carbon (GAC) and analyzed for copper removal. The biofilm-GAC (BGAC) column retained 45% of the copper mass present in the influent, as opposed to 17% in the control column that contained GAC only. These findings suggest that native microbial communities in sites contaminated with heavy metals can be immobilized in fixed-bed bioreactors and used to treat metal contaminated water.

Radioactive lightning rods (RLR) were manufactured and installed in Brazil for almost two decades, before they were prohibited in 1989. Structures protected by this type of lightning preventers included residential buildings, schools, commercial and industrial facilities, among others. It is estimated that about 3.4 TBq of 241Am were used by manufacturers, and a total of 75,000 pieces with a mean activity of about 46 MBq were in the market. While only a fraction of the total has been recovered, the almost twenty thousand pieces already collected at the Nuclear and Energy Research Institute (IPEN) had their sources successfully separated from the remaining recyclable metal scrap and are now encapsulated in lead containers for final disposal.

Aims: To investigate the diversity and the catabolic capacity of oil-degrading Klebsiella strains isolated from hydrocarbon-contaminated sediments in San- tos-Sao Vicente estuary systems in Brazil. Methods and Results: Klebsiella strains obtained from the estuary were charac- terized using 16S rRNA gene sequencing and BOX-PCR patterns, testing their catabolic capacity to degrade toluene, xylene, naphthalene and nonane, and identifying the catabolic genes present in the oil-degrading strains. Results show that Klebsiella strains were widespread in the estuary. Twenty-one isolates from the Klebsiella genus were obtained; 14 had unique BOX patterns and were further investigated. Among four distinct catabolic genes tested (todC1, ndoB, xylE and alkB1), only the todC1 gene could be amplified in two Klebsiella strains. The biodegradation assay showed that most of the strains had the ability to degrade all of the tested hydrocarbons; however, the strains displayed different efficiencies. Conclusions: The oil-degrading Klebsiella isolates obtained from the estuary were closely related to Klebsiella pneumoniae and Klebsiella ornithinolytica. The isolates demonstrated a substantial degree of catabolic plasticity for hydrocar- bon degradation. Significance and Impact of the Study: The results of this study show that several strains from the Klebsiella genus are able to degrade diverse hydrocar- bon compounds. These findings indicate that Klebsiella spp. can be an impor- tant part of the oil-degrading microbial community in estuarine areas exposed to sewage.

Biocatalysis constitutes an important tool in organic synthesis, especially for the preparation of chiral molecules of biological interest. A series of aliphatic and aromatic aldehydes and two ketones were reduced using plant cell preparations from Manihot esculenta and Manihot dulcis roots. The reduced products were typically obtained in excellent yields (80-96%), and with excellent enantiomeric excess (94-98%), except for vanillin. Esters, a nitrile, and an amide were also examined, but were not reduced. Preliminary conversion rate studies are reported. This is the first attempt to perform the biotransformation of carbonyl compounds using Manihot species.

Volatile compound biodegradation analysis usually requires the time-consuming step of extraction of the analytes from the matrix using organic solvents or costly radioactive-compounds. Thus, it is desirable to have a simple and fast technique to generate a good evaluation of bacterial biodegradation. The goal of this research was to develop a methodology on the basis of static headspace-gas chromatography/mass spectrometry (HS-GC/MS) to evaluate the level of volatile contaminant biodegradation. The effects of the following parameters were studied: temperature and time of equilibration. The biodegradation experiments were carried out with bacteria inoculation in mineral media in presence of volatile hydrocarbon compounds (toluene, p-xylene, nonane and naphthalene). Autoclaved inoculates were used as control and reference sample. The optimal headspace conditions were observed when the vials were heated at 80 degrees C for 20 min, the syringe at 81 degrees C and an injection volume of 0.4 mL was used. This methodology has the advantage of being relative free from matrix effects.

The present work describes the electrochemical oxidation of methyl cinnamate ring methoxylated derivatives in neutral or basic methanolic solution. In the electrochemical studies cyclic voltammetry and preparative electrolyses under controlled potential or current conditions in divided or undivided cells were used. The influence of current density, cell type, electrode material, solvent, substrate and base concentration was investigated for methyl 4-methoxycinnamate.The products result from aromatic ring and side chain methoxylation, however, nuclear methoxylation products were observed in higher yields when the number of methoxy groups in the aromatic ring was increased. The structure of the products is dependent on the work-up procedures. Este trabalho descreve a oxidação eletroquímica do 4-metóxi-cinamato de metila e de outros ésteres metílicos do ácido cinâmico di- e tri- metoxilado, em solução metanólica neutra ou alcalina. Nos estudos eletroquímicos foram empregadas voltametria cíclica, bem como eletrólises preparativas a potencial ou corrente controlados, em celas de um ou dois compartimentos. A influência de parâmetros tais como densidade de corrente, tipo de cela, material do eletrodo, solvente, concentração do substrato e base foi investigada para o 4-metóxi-cinamato de metila. Os produtos observados foram resultantes de metoxilações nucleares e/ou na cadeia lateral, entretanto com o aumento do número de metoxilas no anel aromático foram observados principalmente produtos referentes à metoxilação no anel aromático. As estruturas dos produtos também dependem do tipo de procedimento empregado no seu isolamento.

Wavelength dispersive X-ray fluorescence spectrometry (WDXRF) is a suitable technique for the characterization of contaminated mining sites, providing a quick and reliable screening for areas of significant contamination. This study established and validated a non-destructive methodology for quantitative simultaneous determination of major and minor constituents in soil and sediments by WDXRF, which was further applied to quantify soil and sediment samples from Osamu Utsumi uranium mine (Caldas, Minas Gerais, Brazil). Elements such as Ce, La, Nd, Mn and U were found in more concentrated levels in the calcium diuranate deposit (DUCA), whereas Fe and Al were found at higher levels in the soil samples corresponding to sites where accentuated leaching processes have occurred. Comparatively, the levels of U and rare-earth elements were found in significantly higher levels in the sediments retrieved from the mine’s pit as a result of acid mine drainage. These findings are believed to be useful as an initial environmental assessment for the decommissioning process of the mine.