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Abstract  

The adsorption of the organic anionic dye Congo red (CR) by montmorillonite saturated with Na+, Cs+, Mg2+, Cu2+, Al3+ and Fe3+ was investigated by XRD of unwashed and washed samples after equilibration at 40% humidity and after heating at 360 and at 420°C. The clay was treated with different amounts of CR, most of which was adsorbed. Clay samples, untreated with CR, after heating showed collapsed interlayer space. Unwashed and washed samples, which contained CR, before heating were characterized by three peaks or shoulders, labeled A (at 0.96-0.99 nm, collapsed interlayers), B (at 1.24-1.36 nm) and C (at 2.10-2.50 nm). Peak B represents adsorbed monolayers of water and dye anions inside the interlayer spaces. Peak C represents interlayer spaces with different orientations of the adsorbed water and organic matter. Diffractograms of samples with small amounts of dye were similar to those without dye showing peak B whereas diffractograms of most samples with high amounts of dye showed an additional peak C. Heated unwashed and washed samples were also characterized by three peaks or shoulders, labeled A' (at 0.96 nm), B' (at 1.10-1.33 nm) and C' (at 1.61-2.10 nm), representing collapsed interlayers, and interlayers with charcoal composed of monolayers or multilayers of carbon. When the samples were heated from 360 to 420°C some of the charcoal monolayers underwent rearrangement to multilayers. In the case of Cu the charcoal decomposed and oxidized. The present results show that most of the adsorbed dye was located inside the interlayer space.

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Abstract  

The efficiency of color removal from aqueous Congo Red dye (CR) solution has been investigated in TiO2 suspensions irradiated with artificial UV light. Batch photocatalytic tests were carried out by varying the amount of TiO2 and the irradiation time using the same initial CR concentration. The experimental results indicated that the decolorization rate follows pseudo first-order kinetics with respect to CR concentration. The doses of TiO2 were 0.25, 0.5 and 1.0 g L−1 and the wavelength of incident ultraviolet light was predominantly 254 nm. CR adsorption on the surface of TiO2 is also investigated and described.

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Acta Biologica Hungarica
Authors: Márta Kotormán, Alexandra Varga, Phanindra Babu Kasi, and János Nemcsók

. Dec , R. , Babenko , V. , Dzwolak , W. ( 2016 ) Molecules of Congo red caught hopping between insulin fibrils: a chiroptical probe of the dye-amyloid binding dynamics . RSC Advances 6 , 97331 – 97337 . 7

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Acta Biologica Hungarica
Authors: Márta Kotormán, Zita Kelemen, Phanindra Babu Kasi, and János Nemcsók

. E. , Jacob , R. F. , Mason , R. P. ( 1999 ) Quantifying amyloid beta-peptide (Abeta) aggregation using the Congo red-Abeta (CR-abeta) spectrophotometric assay . Anal. Biochem. 266 , 66 – 76 . 18

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producer; (3) 2 × ODc < OD ≤ 4 ×ODc = moderate biofilm producer; and (4) 4 × ODc < OD = strong biofilm producer [ 15 ]. Congo red agar method (CRA) It is a qualitative method used for screening biofilm formation. As described

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Abstract  

In the present work a study was made for determining colour intensities using as luminous non-monochromatic source the Cherenkov emission produced in the walls of a glass capillary which acts as luminous source itself inside of a coloured solution to be evaluated. The reproducibility of this method has been compared with the spectrophotometric assay; the relative errors of both analytical methods have been calculated for different concentrations of congo red solution in the range of minimal error, according to Ringbom's criterion. The sensitivity of this analytical method has been studied for the two β-emitters employed:90Sr/90Y and204Tl.

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Abstract  

Iron (Fe3+) loaded TiO2 nanocatalysts were prepared by the photochemical reduction process. These supported nanocatalysts were characterized by X-ray diffraction (XRD), surface area (BET) measurements, scanning electron microscopy SEM with energy dispersive X-ray (EDX-elemental mapping) analysis and atomic force microscopy (AFM) with adhesion force measurements. XRD and BET results showed adsorption of iron species on the surface of the TiO2 support. AFM and SEM images revealed obvious variations in the surface morphology of the support after loaded with Fe3+ ions. Photocatalytic activities of the supported nanocatalysts were examined for decolorization and degradation processes of Congo red (CR) under UV irradiation. Fe3+ ions improved the performances of the supported nanocatalysts by suppressing the electron–hole recombination reactions. Effects of Fe3+ ion content and initial CR concentration were investigated. A tentative model was proposed for the photocatalytic degradation of CR.

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Summary Thermo-XRD-analysis is applied to identify whether or not the adsorbed organic species penetrates into the interlayer space of the smectites mineral. In this technique an oriented smectite sample is gradually heated to temperatures above the irreversible dehydration of the clay, and after each thermal treatment is diffracted by X-ray at ambient conditions. In the thermal treatment of organo-clays, under air atmosphere at temperatures above 250°C, the organic matter is in part oxidized and charcoal is formed from the organic carbon. In inert atmosphere e.g. under vacuum above 250°C the organic matter is pyrolyzed and besides small molecules, charcoal is formed. If the adsorbed organic compound is located in the interlayer space, the charcoal is formed in that space, preventing the collapse of the clay. A basal spacing of above 1.12 nm suggests that during the adsorption the organic compound penetrated into the interlayer space. Thermo-XRD-analyses of montmorillonite complexes with anilines, fatty acids, alizarinate, protonated Congo red and of complexes of other smectites with acridine orange are described. To obtain information about spacings of the different tactoids that comprise the clay mixture, curve-fitting calculations on the X-ray diffractograms were adapted.

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