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[en] The mediated effects of reduction products of some ortho-hydroxyl substituted azo dyes on biodecolorization were investigated. The results indicated that the addition of reduction products could effectively accelerate dye decolorization by Shigella sp. QRZ-1. The best accelerating effect was obtained with the addition of reduction products of Acid Red 14 (AR14), resulting in an over 3-fold increase in decolorization efficiency of many azo dyes. In sequencing batch reactor experiments, the accelerating effect of reduction products of AR14 was more obvious (1.5-fold) during the startup of the system. When the dye concentration was increased to 500 mg L-1, the accelerated decolorization efficiency was still maintained around 95%. The presence of AR14 in the feed enhanced the decolorization performance of anaerobic sludge, indicating that the strategy may be beneficial for practical application. 1-Naphthol-2-amino-4-sulfonic acid, which is one of the reduction products of AR14, may function as redox mediator to speed up azo dye biodecolorization.
[en] A simple spectrophotometric method was developed for determination of fenoxaprop-p-ethyl herbicide in agricultural samples. The method is based on the acid hydrolysis of fenoxaprop-p-ethyl to form 6-chloro-2,3-dihydro benzoxazol-2-one (CDHB) and ethyl 2-(4-hydroxyphenoxy) propionate (EHPP). The 6-chloro-2,3- dihydro benzoxazol-2-one was used as a coupling reagent in diazotization reaction. The absorbance of the azo dye was measured at 430 nm. The reaction conditions were optimized for hydrolysis as well as for the diazotization reaction. The Beer's law was obeyed over the concentration range of 0.2-25 mu g mL/sup -1/ with molar absorptivity of 1.4 x 104 L mol/sup -1/ cm/sup -1/. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.029 and 0.098 mu g mL/sup -1/, respectively. The method has been successfully applied to the determination of fenoxaprop-p-ethyl I commercial formulations and various agricultural samples. The % recoveries were found in the range of 95-97%. (author)
[en] Few parameters are known to have an effect on the determination of thorium by an azo-based dye such as arsenazo III. In this work, the effect of acid concentration, masking agent and an arsenazo III, iron (Fe3+) interference were studied and discussed
[en] In this work surface relief direct formation during holographic recording in poly (Disperse Red 1 - methacrylate) films was studied. In this material azo-dye Disperse Red 1 is covalently attached to the main polymeric chain making lateral mass transport in the film caused by a presence of light electric field direction modulation very fast and effective. Surface relief grating formation process was induced by 532 nm laser. Read-out was performed by 660 nm diode laser. Diffraction efficiencies kinetics dependence on polarization state of reading and recording beams was studied. Surface relief depth on the films was measured by AFM. Deep surface relief gratings were obtained in Poly (Disperse Red 1 - methacrylate). Films relief can exceed the initial thickness of the sample more than three times. Fabrication of such surface relief gratings is fast and easy. They can find their application in data storage, electro-optical devices, telecommunication. (author)
[en] Synthetic azo dyes are currently used for food coloring more frequently than natural ones and the field of their application is very wide. However, many of them can have detrimental effects on living systems and thus the azo dyes content control in food is very important. Voltammetric azo dyes determination offers many advantages, e.g. high sensitivity, selectivity, speed, low investment and running cost, and low laboriousness. Moreover, these methods are robust, reproducible, user friendly, and compatible with the concept of green analytical chemistry. This review is devoted to the critical comparison of electrochemical sensors and measuring protocols used for voltammetric determination of most frequently used azo dyes in food. Attention is focused on the working electrode and its possible modification which is crucial for successful determination.
[en] Complete text of publication follows. Mechanistic studies were made on ·OH radical and hydrated electron reaction with Sulfanilic Acid Azochromotrop (SPADNS) as model azo dye. SPADNS contains 4,5-dihydroxynaphtalene 2,7-disulfonic acid part and 4-sulfophenylazo group. To establish the details of the reaction mechanism the reactions of two simpler molecules without 4-sulfophenylazo part were also studied: one of them contained one (in position 4, II), the other two (in positions 4 and 5, III) -OH groups. ·OH radicals react with these molecules with radical addition to the naphthalene 2,7-disulfonic acid part. The adduct cyclohexadienyl type radical may decay in radical-radical reactions, or undergoes a (pH dependent) water elimination to naphthoxy radical, radical decay takes place on the ms timescale. ·OH radical addition on the azo bond in dyes has low importance. Degradation efficiencies are 0.6-0.8. The hydrated electron in the case of the two simpler molecules reacts with the rings, while in the case of dye with the azo bond. Electron scavenging is followed by protonation, this reaction in the case of II and III yields cyclohexadienyl, while with the dye hydrazo radical. The efficiency of degradation with II and III is 0.2-0.6, while for the dye it is close to 1.
[en] A simple and rapid method for the spectrophotometric determination of uranium using m- and p-carboxyphenylazo-chromotropic acid is given. The optimum conditions favouring the formation of the two complexes are reported. The molecular structure was found to be 1 : 1 and 1 : 2 of uranium to the m- or the p-compound. Beer's law is obeyed for the ranges 2-16 and 2-18 ppm of uranium in the case of the m- and p-compound respectively. (author)
[en] In this study, TiO2 nanoparticles immobilized on sackcloth fibre were used for the photodegradation of acid dye, and the efficiency of heterogeneous photocatalysts was predicted using the support vector machines model and artificial neural network model. Acid Red 73 was applied as a model compound. The experimental results were determined as the function of key factors such as initial H2O2 concentration, dye concentration, dissolved anions, pH, and time. The obtained results were used for training the models. To find the most suitable and reliable network, different algorithms and transfer functions were tested. The trial and error method was used to find the optimum number of neurons and layers. The root mean squared of error (RMSE), the sum of square error (SSE), and R2 for the models were calculated. Results show that support vector machines and neural network models can effectively learn and model the aforementioned process and predict the efficiency of photodegradation of coloured wastewater. (author)
[en] Two new series of azo reactive dyes containing labile chlorine atoms have been synthesized. The synthetic methodology involved the diazotization of 4-nitro-2-aminophenol (2) and 4-aminobenzene sulfonic acid (7), followed by azo coupling in alkaline medium with 1-amino-8-naphthol-3,6-disulphonic acid (3) and 7-amino-1-hydroxy naphthalene-3-sulfonic acid (8) respectively. The latter on condensation of key intermediates 4 and 9 with 1,3,5-trichlorotriazine afforded the cyanurated dyes (5, 10). A number of separately synthesized novel bis aromatic diamines (1a-i) were coupled with (5 and 10) at room temperature to achieve the targeted dyes 6a-h and 11a-h, respectively. Structures of newly synthesized compounds were confirmed by the spectral and elemental analysis. The dyes were applied on cotton fibers to assess their application properties, and were shown to possess high values of light fastness, wash fastness and rubbing fastness. (author)