RESUMO
The objectives of this study were to determine the viability of removing Orange II (OII) dye by simulated solar photoelectro-Fenton (SSPEF) and to evaluate the stability of a WO2.72/Vulcan XC72 gas diffusion electrode (GDE) and thus determine its best operating parameters. The GDE cathode was combined with a BDD anode for decolorization and mineralization of 350â¯mL of 0.26â¯mM OII by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) at 100, 150 and 200â¯mAâ¯cm-2 and SSPEF at 150â¯mAâ¯cm-2. The GDE showed successful operation for electrogeneration, good reproducibility and low leaching of W. Decolorization and OII decay were directly proportional to the current density (j). AO-H2O2 had a reduced performance that was only half of the SSPEF, PEF and EF treatments. The mineralization efficiency was in the following order: AO-H2O2â¯<â¯EFâ¯<â¯PEFâ¯≈â¯SSPEF. This showed that the GDE, BDD anode and light radiation combination was advantageous and indicated that the SSPEF process is promising with both a lower cost than using UV lamps and simulating solar photoelectro-Fenton process. The PEF process with the lowest j (100â¯mAâ¯cm-2) showed the best performance-mineralization current efficiency.
Assuntos
Compostos Azo/análise , Benzenossulfonatos/análise , Técnicas Eletroquímicas , Peróxido de Hidrogênio/química , Ferro/química , Poluentes Químicos da Água/análise , Eletrodos , Oxirredução , Reprodutibilidade dos Testes , Luz SolarRESUMO
Malacoculture waste (Anomalocardia brasiliana) shellfish shells (ABSS) were evaluated as adsorbents of Nylosan Brilliant Blue (NBB) acid dye. The ABSS were thermally activated at 1,000 °C for 10 h and then characterized by Fourier-transform infrared spectroscopy, analysis of specific surface area (BET), X-ray diffraction (XRD), and scanning electron microscopy. Point of zero charge (PZC) analysis of ABSS verified pHPZC 13.0. The study of kinetics showed that the pseudo-second-order model fit the experimental data best and the system reached equilibrium within 5 min. Adsorption isotherms followed the Langmuir-Freundlich isotherm and ABSS reached an outstanding maximum adsorption capacity of 405 mg·g-1 under the following optimum conditions: pH 12.4, 303 K, 450 rpm, 2.0 g of adsorbent, and 150 µm average particle size. These conditions were obtained after a previous statistical analysis of the variables. Enthalpy and Gibbs energy obtained in the thermodynamics experiments were -23.79 kJ·mol-1 and -4.07 kJ·mol-1, respectively. These parameters confirm that the process is exothermic, spontaneous, and indicative of the physical nature of the adsorption. The adsorption of NBB onto ABSS tended to be more favorable at a lower temperature. Low value of enthalpy suggested that weak binding forces, such as electrostatic interactions, govern the sorption mechanism. ABSS high availability in the environment, its low toxicity and high efficiency make it a promising ecofriendly adsorbent of textile dyes.
Assuntos
Exoesqueleto/química , Benzenossulfonatos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Adsorção , Animais , Benzenossulfonatos/análise , Corantes , Concentração de Íons de Hidrogênio , Cinética , Frutos do Mar , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Poluentes Químicos da Água/análiseRESUMO
A low-cost sensor array system for banana ripeness monitoring is presented. The sensors are constructed by employing a graphite line-patterning technique (LPT) to print interdigitated graphite electrodes on tracing paper and then coating the printed area with a thin film of polyaniline (PANI) by in-situ polymerization as the gas-sensitive layer. The PANI layers were used for the detection of volatile organic compounds (VOCs), including ethylene, emitted during ripening. The influence of the various acid dopants, hydrochloric acid (HCl), methanesulfonic acid (MSA), p-toluenesulfonic acid (TSA) and camphorsulfonic acid (CSA), on the electrical properties of the thin film of PANI adsorbed on the electrodes was also studied. The extent of doping of the films was investigated by UV-Vis absorption spectroscopy and tests showed that the type of dopant plays an important role in the performance of these low-cost sensors. The array of three sensors, without the PANI-HCl sensor, was able to produce a distinct pattern of signals, taken as a signature (fingerprint) that can be used to characterize bananas ripeness.
Assuntos
Grafite/análise , Absorção , Compostos de Anilina/análise , Benzenossulfonatos/análise , Cânfora/análise , Desenho de Equipamento , Etilenos/análise , Frutas , Gases , Mesilatos/análise , Musa , Polímeros/química , Espectrofotometria Ultravioleta/métodos , Ácidos Sulfônicos/análiseRESUMO
An approach to an inhibition bioelectronic tongue is presented. The work is focused on development of an automated flow system to carry out experimental assays, a custom potentiostat to measure the response from an enzymatic biosensor, and an inhibition protocol which allows on-line detections. A Multi-commuted Flow Analysis system (MCFA) was selected and developed to carry out assays with an improved inhibition method to detect the insecticides chlorpyrifos oxon (CPO), chlorfenvinfos (CFV) and azinphos methyl-oxon (AZMO). The system manifold comprised a peristaltic pump, a set of seven electronic valves controlled by a personal computer electronic interface and software based on LabView® to control the sample dilutions into the cell. The inhibition method consists in the injection of the insecticide when the enzyme activity has reached the plateau of the current; with this method the incubation time is avoided. A potentiostat was developed to measure the response from the enzymatic biosensor. Low limits of detection of 10 nM for CPO, CFV, and AZMO were achieved.
Assuntos
Acetilcolinesterase/química , Técnicas Biossensoriais/instrumentação , Drosophila/química , Inibidores Enzimáticos , Inseticidas/análise , Animais , Azinfos-Metil/análogos & derivados , Azinfos-Metil/análise , Benzenossulfonatos/análise , Clorpirifos/análogos & derivados , Clorpirifos/análise , Potenciometria/métodos , SoftwareRESUMO
Fungi of Malassezia genus are known as normal flora in human beings. However, different pathologies due to Malassezia, have been described. Traditionally, early diagnosis was delayed because of the difficulties in culture isolation of these organisms. The aim of this work, is to evaluate the technique of observation microscopy with calcofluor, for identification of Malassezia in both, clinical samples and isolates. In comparison to traditional method of direct examination with lactophenol-blue, calcofluor method offers an advantage because it turns easier the observation of fungal elements and its budding pattern. This technique contributes then, to identify species of Malassezia. The analysis of clinical specimens with calcofluor followed by observation under fluorescence microscopy is a simple and rapid method for the identification, and contribute therefore to the early diagnosis.
Assuntos
Benzenossulfonatos/análise , Dermatite Seborreica/microbiologia , Corantes Fluorescentes/análise , Foliculite/microbiologia , Malassezia/isolamento & purificação , Microscopia de Fluorescência , Tinha Versicolor/microbiologia , Meios de Cultura , Humanos , Ácido Láctico/análise , Malassezia/classificação , Malassezia/ultraestrutura , Micologia/métodos , Fenóis/análise , Coloração e Rotulagem/métodosRESUMO
A study of the voltammetric behaviour of the food colours brilliant blue FCF (C.I. 42090), erythrosine (C.I. 45430) and quinoline yellow (C.I. 47005) in the pH range 2-10 have been carried out by cathodic#10; stripping voltammetry. At pH 4.5 (acetate buffer) with an accumulation potential of 0 V and accumulation time of 30s, the voltammograms presented well-defined reduction peaks at potential - 0.76 V for brilliant blue FCF, - 0.85 V for quinoline yellow and - 0.54 V for erythrosine. Linear calibration graphs were obtained from 8 to 80 microg l(-1) brilliant blue, from 4 to 43 microg l(-1) quinoline yellow and from 10 to 70 microg l(-1) erythrosine. The method has been successfully applied to identify and quantify binary mixtures of these dyes and applied for determining brilliant blue FCF in commercial food products.