Fosfitos aplicados em pós-colheita reduzem o mofo-azul em maçãs 'Fuji' e 'Gala'

O mofo-azul (Penicillium expansum) é uma podridão pós-colheita comum em maçãs (Malus domestica). O uso de substâncias menos ofensivas ao ambiente, como o fosfito (ácido fosforoso), é uma das alternativas de controle dessa doença. Visou-se, então, a avaliar neste estudo a eficiência de fosfito-K (40% de P2O5 e 30% de K2O) e fosfito-CaB (10,7% de P2O5, 3,89% de Ca e 0,5% de B) no controle do mofo-azul em maçãs 'Fuji' e 'Gala'. Os testes foram delineados em blocos ao acaso com seis repetições de 20 frutos cada. Os frutos foram desinfestados em hipoclorito de Na (1%) por três minutos, lavados em água esterilizada, feridos (1mm de diâmetro e de profundidade) com agulha em quatro pontos eqüidistantes, imersos nos tratamentos por 15 minutos e armazenados a 15-20ºC. Nas suspensões contaminadas com Penicillium expansum (10² conídios.mL-1), foram adicionadas as seguintes substâncias: benomil (150 mg.L-1), fosfito-K (0,5 a 1,5 mL.L-1) e fosfito-CaB (1,5 a 3,0 mL.L-1). As maçãs 'Fuji' e 'Gala' imersas em água com fosfito-CaB (1,5 mL.L-1), fosfito-K (0,5-1,5 mL.L-1) ou benomil (150 mg.L-1) foram menos afetadas pelo mofo-azul. A aplicação de fosfito-K (1,5 mL.L-1) ou benomil (150 mg.L-1) nos frutos foi mais eficiente do que os demais tratamentos no controle do mofo-azul.

Estudo eletroquímico do azul de metileno adsorvido sobre sílica gel quimicamente modificada com óxido de nióbio

Methylene blue (AM) was immobilised on surface of the silica gel modified with niobium oxide. This material was incorporated in a carbon paste electrode, which showed a redox couple in a potential of E= -113 mV vs SCE in KCl solution at pH 7.0. The formal potential, in 0.5 mol L-1 KCl at pH 7.0, shifted about 290 mV towards more positive values compared to those observed for AM solubilized in aqueous solution. The dependence on the formal potential with solution pH between 2 and 7 was much lower than those observed for AM solubilized in aqueous solution.

Una cálida luz azul

Comentarios libres a los textos de Steffan Hessel sobre el 15M

Azul de metileno imobilizado na celulose/TiO2 e SiO2/TiO2: propriedades eletroquímicas e planejamento fatorial

The electrochemical properties of methylene blue immobilized on cellulose/TiO2 and mixed oxide SiO2/TiO2 matrices were investigated by means of cyclic voltammetry. The electron mediator property of the methylene blue was optimized using a factorial design, consisting of four factors in two levels. The experimental observations and data analyses on the system indicate that the lowest peak separation occurs for Sil/TiOAM, 1.0 mol L-1 KCl solution and 20 mV s-1 scan rate, while values of current ratio closest to unity were found for Cel/TiOAM independent of electrolyte concentration, 0.2 or 1.0 mol L-1, and scan rate, 20 mV s-1 or 60 mV s-1.

O emprego de quitosana quimicamente modificada com anidrido succínico na adsorção de azul de metileno

The adsorption capacity of alpha-chitosan and its modified form with succinic anhydride was compared with the traditional adsorbent active carbon by using the dye methylene blue, employed in the textile industry. The isotherms for both biopolymers were classified as SSA systems in the Giles model, more specifically in L class and subgroup 3. The dye concentration in the supernatant in the adsorption assay was determined through electronic spectroscopy. By calorimetric titration thermodynamic data of the interaction between methyene blue and the chemically modified chitosan at the solid/liquid interface were obtained. The enthalpy of the dye/chitosan interaction gave 2.47 ± 0.02 kJ mol-1 with an equilibrium constant of 7350 ± 10 and for the carbon/dye interaction this constant gave 5951 ± 8. The spontaneity of these adsorptions are reflected by the free Gibbs energies of -22.1 ± 0.4 and -21.5 ± 0.2 kJ mol-1, respectively, found for these systems. This new adsorbent derived from a natural polysaccharide is as efficient as activated carbon. However 97% of the bonded dye can be eluted by sodium chloride solution, while this same operation elutes only 42% from carbon. Chitosan is efficient in dye removal with the additional advantage of being cheap, non-toxic, biocompatible and biodegradable.

Remoção de azul de metileno de solução aquosa usando zeólitas sintetizadas com amostras de cinzas de carvão diferentes

Batch sorption experiments were carried out to remove methylene blue from its aqueous solutions using zeolites synthesized from fly ashes as an adsorbent. The adsorbents were characterized by XFR, XRD and SEM. Nearly 90 min of contact time are found to be sufficient for the adsorption of dye to reach equilibrium. Equilibrium data have been analyzed using Langmuir and Freundlich isotherms and the results were found to be well represented by the Freundlich isotherm equation. Adsorption data were fitted to both Lagergren first-order and pseudo-second-order kinetic models and the data were found to follow pseudo-second-order kinetics.

Síntese e caracterização de nanopartículas de óxido de ferro suportadas em matriz carbonácea: remoção do corante orgânico azul de metileno em água

In this work were prepared composites of iron oxide and carbonaceous materials in two different weight proportions (Carbon/Fe 1/1 and 1/2). The physico-chemical properties of the composites were determined by temperature programmed reduction (TPR), adsorption/dessorption of N2, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and pulse titration H2. The XRD and XPS analysis showed a cubic iron oxide phase, identified as maghemite, formed over the carbon surface. The particle size of maghemite showed to be within 10-30 nm. Carbon/Fe 1/2 was the most active in MB removal kinetics and ESI-MS studies showed that MB removal by both composites leads to oxidized intermediates.

Adsorção do corante azul de metileno em partículas de argilominerais: análise dos tamanhos das partículas

Interactions of cationic dye methylene blue (MB) with clay particles in aqueous suspension have been extensively studied. As already known, the number of natural negative charges on the clay modifies significantly the particle sizes dispersed in water and therefore the nature of the interaction with the dye. This work evaluated with UV-Vis spectroscopy method how the clay particle sizes weighted on the adsorption and rearrangement of the dye molecules in aqueous system. The results obtained from light-scattering measurements confirmed that larger particles are found in suspensions containing the high-charged clays as the visible absorption band related to the MB aggregates (570 nm) on these suspensions prevailed.

Determinação de peróxido de hidrogênio em antisséptico bucal usando um microdispositivo contendo partículas de Azul da Prússia

A simple flow-injection amperometric procedure using a three-electrode-integrated sensor for the determination of H2O2 in antiseptic mouthwash is reported. This method involves the use of a working composite electrode modified with Prussian Blue (PB) particles that was easily adapted as detector in FIA. The best amperometric response was observed for a composite containing 30% of graphite modified with PB particles (GAP) and 70% of pure graphite (GR). The proposed method presents a linear response in the range of 10 to 200 μmol L-1. The detection and quantification limits were 0.8 and 2.6 μmol L-1, respectively.

Remoção dos corantes azul brilhante, amarelo crepúsculo e amarelo tartrazina de soluções aquosas utilizando carvão ativado, terra ativada, terra diatomácea, quitina e quitosana: estudos de equilíbrio e termodinâmica

This work compared activated carbon, activated earth, diatomaceous earth, chitin and chitosan to removal acid blue 9, food yellow 3 and FD&C yellow nº 5 dyes from aqueous solutions with different pH values (2-10). In the best process condition for each dye, equilibrium studies were carried out at different temperatures (from 298 to 328 K) and Langmuir, Freundlich, Redlich-Peterson, Temkin and Dubinin-Radushkevich models were fitted with experimental data. In addition, entropy change, Gibbs free energy change and enthalpy change were obtained in order to verify the thermodynamic adsorption behavior.

Degradação fotoeletroquímica do corante azul QR 19 em solução aquosa

In this work the degradation capacity of a photo-electrocatalytic system was evaluated, mainly regarding the effect of the electrolyte solution on the degradation capacity toward a reactive textile dye. In the presence of NaCl the photo-electrochemical process shows high degradation efficiency, permitting almost total color removal in treatment of about 5 min. In view of the low degradation efficiency observed for the photocatalytic process it is possible to assume that the high degradation efficiency of the process is a function of electrochemical generation of oxidant active chlorine species, which are subsequently transformed to higher oxidant radical forms.

Desenvolvimento e avaliação de eletrodos de difusão gasosa (EDG) para geração de H2O2 in situ e sua aplicação na degradação do corante reativo azul 19

This work reports the development of GDE for electrogeneration of H2O2 and their application in the degradation process of Reactive Blue 19 dye. GDE produced by carbon black with 20% polytetrafluoroethylene generated up to 500 mg L-1 of H2O2 through the electrolysis of acidic medium at -0.8 V vs Ag/AgCl. Reactive Blue 19 dye was degraded most efficiently with H2O2 electrogenerated in the presence of Fe(II) ions, leading to removal of 95% of the original color and 39% of TOC at -0.8 V vs Ag/AgCl.

Adsorção do corante Reativo Azul 19 em solução aquosa por lama vermelha tratada quimicamente com peróxido de hidrogênio

Adsorption of Reactive Blue 19 dye onto activated red mud was investigated. Red mud was treated with hydrogen peroxide (LVQ) and heated at both 400 ºC (LVQ400) and 500 ºC (LVQ500). These samples were characterized by pH, specific surface area, point of zero charge and mineralogical composition. Adsorption was found to be significantly dependent on solution pH, with acidic conditions proving to be the most favorable. The adsorption followed pseudo-second-order kinetics. The Langmuir isotherm was the most appropriate to describe the phenomenon of dye removal using LVQ, LVQ400 and LVQ500, with maximum adsorption capacity of 384.62, 357.14 and 454.54 mg g-1, respectively.

EFEITO DO DIOXIDO DE CARBONO SOBRE A ESTABILIDADE DA FASE Ca2Fe2O5 APLICADA NO PROCESSO DE DEGRADAÇÃO FOTOCATALITICO DO AZUL DE METILENO

Solid samples containing a Ca2Fe2O5 phase were synthesized using the Pechini method. The samples were characterized using X-ray diffraction, thermogravimetric analysis, differential thermal analysis, X-ray fluorescence, nitrogen adsorption/desorption isotherms, and scanning electron microscopy. The stability of the Ca2Fe2O5 phase was evaluated in the photocatalytic degradation of methylene blue (MB) in aqueous solution in the presence of bubbling gas (air, N2, or CO2). The presence of CO2 is known to suppress MB degradation. After the photocatalytic test, changes were observed in the crystalline phase of all systems. These results suggest the low stability of the Ca2Fe2O5 phase in aqueous systems and the significant effect of CO2 on the photocatalytic activity of the Ca2Fe2O5 phase.