Results 1 - 10 of 844
Results 1 - 10 of 844. Search took: 0.025 seconds
|Sort by: date | relevance|
[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] 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] 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] 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] White rot fungi have exclusive capacity to decolorize synthetic azo dyes. five different fungal strains namely s. commune ibl-01 (sc), p. ostreatus ibl-02 (po) p. chrysosporium ibl-03 (pc), t. versicolor ibl-04 (tv) and g. lucidum ibl-05 (gl) were used for the decolorization of synthetic dyes effluent. p. ostreatus ibl-02 showed maximum decolorization of synthetic textile effluent, so it was selected for the optimization of experimental factors. different physico-chemical parameters were optimized using pleutorus ostreatus ibl-02 (po), for the maximum de-colorization of synthetic dyes effluent. under optimum conditions, p. ostreatusibl-02 (po) decolorized the synthetic dyes effluent by 92.7%. effect of various amendments like carbon and nitrogen sources on the decolorization and mineralization of synthetic dyes effluent by pleutorus ostreatus ibl-02 was also studied. ligninolytic enzymes at the end of each experiment were studied to find their role in decolorization and mineralization of synthetic dyes effluent. uv-visible spectral analysis was used to indicate the decolourization of treated dyes effluent sample. a diminution in spectral line height displaying absorption maxima designated decolorization (%) while a move of spectral line to the uv-region depicted the degradation of synthetic dyes effluent. (author)
[en] This novel comparative study tended to disclose how the molecular structures present in seven azo dyes including two types of azo dyes (i.e., naphthol type azo dyes - Reactive Black 5 (RB 5), Reactive Blue 171 (RB 171), Reactive Green 19 (RG19), Reactive Red 198 (RR198), Reactive Red 141 (RR141) and non-naphthol type azo dyes - Direct Yellow 86 (DY86), Reactive Yellow 84 (RY84)) affected color removal capability of Aeromonas hydrophila. Generally speaking, the decolorization rate of naphthol type azo dye with hydroxyl group at ortho to azo bond was faster than that of non-naphthol type azo dye without hydroxyl group, except of RG19. The azo dyes with electron-withdrawing groups (e.g., sulfo group in RR198, RB5 and RR141) would be easier to be decolorized than the azo dyes with the electron-releasing groups (e.g., -NH-triazine in RB171 and RG19). In addition, the azo dyes containing more electron-withdrawing groups (e.g., RR198, RB5 and RR141) showed significantly faster rate of decolorization. The azo dyes with electron-withdrawing groups (e.g., sulfo group) at para and ortho to azo bond (e.g., RR198, RB5 and RR141) could be more preferred for color removal than those at meta (e.g., DY86 and RY84). The former azo dyes with para and ortho sulfo group provided more effective resonance effects to withdraw electrons from azo bond, causing azo dyes to be highly electrophilic for faster rates of reductive biodecolorization. However, since the ortho substituent caused steric hindrance near azo linkage(s), azo dyes with para substituent could be more favorable (e.g., SO2(CH2)2SO4- in RR198 and RB5) than those with ortho substituent (e.g., sulfo group at RR141) for decolorization. Thus, the ranking of the position for the electron-withdrawing substituent in azo dyes to escalate decolorization was para > ortho > meta. This study suggested that both the positions of substituents on the aromatic ring and the electronic characteristics of substituents in azo dyes all significantly affected the performance of biodecolorization of A. hydrophila.