Polysaccharide/Fe(III)-porphyrin hybrid film as catalyst for oxidative decolorization of toxic azo dyes: An approach for wastewater treatment

A hybrid film of chitosan/poly(vinyl alcohol)/cationic Fe(III)-porphyrin (Cht/PVA-FeTMPyP) was synthesized to act as a Fenton-like catalyst to decolorize methyl orange and methyl red azo dyes. The Cht/PVA-FeTMPyP film was characterized by different analytical and microscopy techniques, which indicated that the metalloporphyrin affects different properties of the hybrid film. Batch experiments revealed that the hybrid film exhibits enhanced catalytic activity towards dyes decolorization in the presence of H₂O₂ as compared to the “free” FeTMPyP. Fast decolorization rates as high as 90 min were observed for both azo dyes under mild conditions (pH 7 and room temperature), even at low concentrations of the catalyst in H₂O₂. After the decolorization, FTIR analysis showed that simple molecules are released as by-products. Moreover, the hybrid film performed well in cyclic runs without leaching out iron ions or losing its catalytic activity. All these features associated with its ease handling ranks the Cht/PVA-FeTMPyP hybrid film as a promising heterogeneous Fenton-like catalyst for the decomposition of azo dyes in water.     

Decolorization and partial degradation of selected azo dyes by methanogenic sludge

The toxicity potential and decolorization of three acid azo dyes (Acid Orange 6, Acid Orange 7, and Acid Orange 52) by methanogenic granular sludge from an anaerobic expanded granular sludge bed reactor was assayed. Complete bioreduction was found for all three azo dyes. Sulfanilic acid and 4-aminoresorcinol were detected from the decolorization of Acid Orange 6, sulfanilic acid and 1-amino-2-naphtol were detected from the reduction of Acid Orange 7, and sulfanilic acid and N,N-dimethyl-1,4-phenylenediamine (DMP) were found to be intermediates of Acid Orange 52 degradation. Sulfanilic acid and 1-amino-2-naphtol were persistent in the anaerobic conditions, whereas 4-aminoresorcinol was completely mineralized by anaerobic sludge and DMP was transformed into 1,4-phenylenediamine. Enrichment cultures obtained via consecutive passages on basal medium with only azo dye as a carbon and an energy source seemed to be morphologically heterogeneous. Baculiform and coccus cells were found when viewed under a light microscope. Cocci were joined in chains. Because anaerobic sludge contains sulfate-reducing bacteria and therefore may generate sulfide, azo dyes were tested for chemical decolorization by sulfide to compare rates of chemical and biologic reduction.     

Mixed ligand complexes of benzimidazole and pyrimidine hydroxy azo dyes with some transition metals and glycine,DL-alanine, orDL-leucine

Summary The overall formation constants of ternary complexes of Cu(II), Zn(II), and Cd(II) with glycine (Gly),DL-alanine (Ala), orDL-leucine (Leu) as primary and 2-(o-hydroxyphenylazo)-2-cyanomethyl benzimidazole (ABI) and 5-(o-hydroxyphenylazo) barbituric acid (ABA) as secondary ligands as well as those of the binary systems have been investigated potentiometrically in 40% (v/v) EtOH. The stability of the ternary complexes is compared quantitatively with that of the corresponding binary complexes. The concentration distribution of the species formed in solution was evaluated; they were characterized by means of IR and¹H NMR spectroscopy.

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Ternäre Komplexe von Hydroxyphenylazoverbindungen mit einigen Übergangsmetallen und Glycin,DL-Alanin oderDL-Leucin

Zusammenfassung Die Bildungskonstanten der ternären Komplexe von Cu(II), Zn(II) und Cd(II) mit Glycin (Gly),DL-Alanin (Ala) oderDL-Leucin (Leu) als Primärliganden und 2-(o-Hydroxyphenylazo)-2-cyanomethyl-benzimidazol (ABI) bzw. 5-(o-Hydroxyphenylazo)-barbitursäure (ABA) als Sekundärliganden wurden wurden ebenso wie jene binärer Systeme potentiometrisch in 40% (v/v) Ethanol bestimmt. Die Stabilität der ternären Komplexe wird mit jener der binären verglichen. Die Konzentration der verschiedenen Spezies in Lösung sowie ihre IR- und¹H-HMR-Spektren wurden gemessen.

     

Thienylpyrrole azo dyes: synthesis, solvatochromic and electrochemical properties

The synthesis and the evaluation of solvatochromic and electrochemical properties of new donor-acceptor-substituted thienylpyrrole azo dyes 3 are described. These derivatives exhibit dramatic changes in both their electronic and redox properties in comparison with thienylpyrroles 1. In agreement with the solvatochromic and electrochemical studies of push-pull derivatives 3 the new compounds prepared, may find application in the manufacture of new materials with notable non-linear optical properties.     

Photocatalytic degradation of azo dyes in aqueous solutions under UV irradiation using nano-strontium titanate as the nanophotocatalyst

Research on photocatalytic degradation rate of azo dyes using nano-strontium titanate in photocatalysis process was the main goal of present study. In this regard, the influence of the main operating parameters such a photocatalyst concentration, dye concentration, temperature, pH and the presence of hydrogen peroxide upon dye removal rate under UV irradiation was studied. The absorbance of samples was measured by a UV–Vis spectrophotometer. The structure and morphology of nano-powder were investigated using scanning electron microscopy and crystalline structure by X-ray diffraction spectroscopy. The results reveal that nano-strontium titanate has high and significant photocatalytic activity and in comparison with nano-titanium dioxide was superior photocatalyst.     

Optimization of an analytical procedure for the determination of banned azo dyes in leather

The possibility of improving an existing method, based on supercritical-fluid extraction (SFE) and microwave-assisted extraction (MAE), for the determination of banned azo dyes in leather has been studied. Thus, optimization of experimental conditions in different steps (degreasing, reduction, and extraction) of the analytical procedure was performed. The influence of different variables (reaction time, temperature, and concentration of reducing agent) on the reduction process was evaluated by use of a factorial design. It was found that the concentration of the reducing agent and the interaction between time and temperature were the most influential variables. Consequently, by applying a higher temperature, the reaction time could be halved. The use of acidified water as extraction solvent in MAE was also investigated. Usually 1 mol L^–1 HCl was superior to methanol and buffer in terms of extraction efficiency. In conclusion, the present method gave significantly higher recoveries in comparison with the original method. All dyes were determined indirectly by measuring their corresponding harmful amines, formed after reduction by use of sodium dithionite.     

Synthesis of 6-chloro and 6-fluoro-4-hydroxyl-2-quinolone and their azo disperse dyes

<正>In this study,6-chloro-4-hydroxy-2-quinolone and 6-flouro-4-hydroxy-2-quinolone were synthesized from corresponding dianilides.These compounds were coupled with some diazotized aromatic amines to give the corresponding azo disperse dyes.The structures of the quinolone derivatives and new azo dyes were confirmed by UV-vis,FT-IR,~1H NMR and elemental analysis.     

Standard additio--a way of improving quantification of banned azo dyes in leather

An analytical procedure based on supercritical-fluid extraction and microwave-assisted extraction was applied on six different real leather samples for the determination of banned azo dyes. Determination of the dyes was performed indirectly by measuring their corresponding harmful aromatic amines, formed after reduction. A comparative study between external standard calibration and standard addition using both the dyes as well as the corresponding amines showed that the latter quantification method provided the highest accuracy.     

Straightforward synthesis of bioconjugatable azo dyes. Part 1: Black Hole Quencher-1 (BHQ-1) scaffold

Azo dyes are currently used to quench the fluorescence of energy donors in bioassays through Förster resonance energy transfer (FRET) phenomenon. Common examples of such dark quenchers are DABCYL and the three members of Black Hole Quencher® (BHQ) family. Yet, only carboxylic acid and phosphoramidite derivatives of such azo dyes are presently commercially available. This Letter presents a straightforward synthesis method to novel bioconjugatable quenchers derived from BHQ-1 scaffold and equipped with a reactive group being either azido, terminal alkyne, or maleimide. The potential utility of the ‘clickable’ azido and thiol-reactive derivatives was notably demonstrated through the preparation of the first water-soluble BHQ-1 dye and a FRET-based probe suitable for the detection of urokinase-type plasminogen activator (uPA), a key protease in cancer invasion and metastasis, respectively.     

Extraction and recovery of azo dyes into an ionic liquid

The azo dyes are commonly used in the leather and textile industries as they are quite versatile in nature. However, they are neither totally utilised during the process, nor are they recovered at the end of the process. In fact, in the leather industry, typically about 10–15% of the dye is discharged with the effluent creating both environmental and economic issues. Hence, there is a need to remove the residual dye from the large volume of aqueous effluent. In this study, for the first time, azo dyes employed in the leather industry have been successfully extracted into a neutral ionic liquid, with an extraction efficiency of 98%, potentially providing a method of minimizing pollution of waste-waters. The extraction of the dye into the ionic liquid also provides a potential analytical approach to determination of these dyes.     

Synthesis and two-photon absorption property of novel salen complexes incorporated with two pendant azo dyes

New salen compounds have been developed to possess two pendant azo dye chromophores. The two-photon absorption properties have been observed which result from the chromophores. The additive property has been found to exist as a result of no detrimental dipole-dipole interaction between chromophores.     

Electrically enhanced liquid‐phase microextraction of three textile azo dyes from wastewater and plant samples

An electromembrane extraction procedure coupled with HPLC and visible detection was applied for the extraction of three textile azo dyes as organic salts. The extraction parameters such as extraction time, applied voltage, pH range, and concentration of salt added were optimized. A driving force of 60 V was applied to extract the analytes through 2‐nitrophenyl octyl ether, used as the supported liquid membrane, into a neutral aqueous solution. This method required 20 min extraction time from a neutral sample solution. The proposed microextraction technique provided good linearity with correlation coefficients from 0.996 to 0.998 over a concentration range of 1.0–1000.0 ng/mL. The LODs of dyes were 0.30–0.75 ng/mL, while the reproducibility ranged from 6.7 to 12.9% (n = 6). Also, enrichment factors of 96–162 that corresponded to the recoveries ranging from 48 to 81% were achieved. Finally, the application of this new method was demonstrated on wastewater samples and some plants grown in contaminated environments. Excellent selectivity was obtained as no interfering peaks were detected.     

Straightforward synthesis of bioconjugatable azo dyes. Part 2: Black Hole Quencher-2 (BHQ-2) and BlackBerry Quencher 650 (BBQ-650) scaffolds

A further extension of the efficient synthetic methodology described in Part 1, to the aromatic bis-diazo scaffold of Black Hole Quencher-2 dye is presented. Bioconjugatable derivatives bearing either azido, terminal alkyne, or maleimide reactive group were easily obtained as well as the free-phenol form of BlackBerry® Quencher 650 (BBQ-650®) initially developed by Berry & Associates, Inc. Company. The efficient conjugation ability of azido- and maleimide-quenchers was demonstrated through the facile preparation of the first water-soluble and formylated BHQ-2 dyes and a FRET-based probe suitable for the in vitro/in cellulo detection of a cancer-associated protease namely urokinase-type plasminogen activator.     

Selective recognition and discrimination of water‐soluble azo dyes by a seven‐channel molecularly imprinted polymer sensor array

A seven‐channel molecularly imprinted polymer sensor array was prepared and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, UV‐Vis spectroscopy, and nitrogen physisorption studies. The results revealed that the imprinted polymers have distinct‐binding affinities from those of structurally similar azo dyes. Analysis of the UV‐Vis spectral response patterns of the seven dye analytes against the imprinted polymer array suggested that the different selectivity patterns of the array were closely connected to the imprinting process. To evaluate the effectiveness of the array format, the binding of a series of analytes was individually measured for each of the seven polymers, made with different templates (including one control polymer synthesized without the use of a template). The response patterns of the array to the selected azo dyes were processed by canonical discriminant analysis. The results showed that the molecularly imprinted array was able to discriminate each analyte with 100% accuracy. Moreover, the azo dyes in two real samples, spiked chrysoidin in smoked bean curd extract and Fanta lime soda (containing tartrazine), were successfully classified by the array.     

Analytical control of photocatalytic treatments: degradation of a sulfonated azo dye

The degradation of Methyl Orange (C₁₄H₁₄N₃SO₃Na), chosen as a model sulfonated azo dye, was investigated in aqueous solutions containing suspended polycrystalline TiO₂ particles under irradiation with simulated sunlight. The dye disappearance and the formation of the mineralization end products were monitored; the formation of the main transient intermediates was also examined in detail. Particular attention was devoted to the identification and to the evolution of fragments retaining the chromophoric group. The comparison of data coming from various analytical techniques led to a possible reaction mechanism for the degradation process, giving insight into an aspect of the treatment which has not been considered in previous studies.     

Dependence of fungal biodegradation of PEG/castor oil-based polyurethane elastomers on the hard-segment structure

In the context of protecting of the environment, this work studies the biodegradation of PEG-based polyurethane elastomer films in the presence of the soft rot fungus Chaetomium globosum, determined via the Petri-dish test. Using PEG with high-molecular weight (MW = 1500) as a chain extender led to polyurethane elastomers with lower physical crosslink density and higher swelling rates. The structural modifications in the hard-segment area (CO and N-H peaks) are considerable and were analyzed by FTIR spectroscopy. Biodegradation lowers the final mechanical properties, but increases yield points, especially in the case of polyurethane elastomers crosslinked with castor oil. Polyurethane elastomer samples showed visible degradation proved by the mechanical weakening of the films. Thus, breaking strains decrease from 670-1180% to 500-680% and tensile strengths decreased from 11.5-27.5 MPa to 4-11.5 MPa after 130 days of fungal biodegradation. The changes in the morphology of the polyurethane films surface were analyzed by SEM and have been found to exhibit increasing porous structure and fungal hyphae. The effects of the hard-segment composition of the polyurethane elastomers on the fungal biodegradation behaviour were investigated.     

Improvement of dye-sensitized solar cells' performance via co-sensitization of new azo thiazole organic dyes with ruthenium (II) based N-719 dye

Three novel azo thiazole organic dyes, NA-1–3, have been synthesized and utilized as co-sensitizers in dye-sensitized solar cells (DSSCs). These co-sensitizers were designed with a thiazole ring π-bridge that mediates between the diazo (–N = N–) functional group and carboxylic acid anchoring unit. They possess a rod-like molecular structure and exhibit strong UV–vis absorption near 600 nm. Co-sensitization studies were also conducted with the ruthenium complex N719. The co-sensitized DSSCs showed enhanced short-circuit and open-circuit photocurrents (Jsc) and voltages (Voc), resulting in more efficient photovoltaic performance compared to N719 (PCE 7.25%). Electrochemical impedance spectroscopy (EIS) and incident photon to current efficiency (IPCE) were employed to investigate the underlying reasons for these improvements. It was found that co-sensitization effectively reduced electron recombination, resulting in a higher Voc without compromising photocurrent loss.     

Subcritical water and dynamic sonication-assisted solvent extraction of fluorescent whitening agents and azo dyes in paper samples

Two low-volume solvent continuous extraction methods are applied to the extraction of paper matrices. In the methods reported here, a complex mixture of fluorescent whitening agents (FWAs) and azo dyes (AZOs) used in paper materials intended to come into contact with foodstuffs was extracted by using subcritical water extraction (SWE) and dynamic sonication-assisted solvent extraction (DSASE). Rationale for the work is based upon migration concerns of these groups of analytes from the packaging to the packaged items, thus compromising their subjective and/or objective quality. In SWE, sample was extracted in 21 min with 0.5 mL of water, whereas the DSASE method required 11 min and used 7 mL of water. DSASE was further developed by incorporating an organic modifier in order to change water polarity, thus improving extraction of moderately polar analytes. This way, modified-DSASE used a total organic volume of 0.9 mL which represents a reduction of 200 times in organic solvent consumption (200 mL versus approximately 1.0 mL) and 11 times in extraction time (2h versus 11 min) compared to the existing methods. SWE was able to extract only 9 out of 12 test analytes with average recoveries between 10 and 25% whereas modified-DSASE succeed in extracting all the target analytes with an average recovery of 89%. Complete discussion and explanation concerning these differences are provided in the text.     

Enhancement of the photochromic switching speed of bithiophene azo dyes

A series of heteroaryl substituted bithiophene azo dyes in solution were irradiated with visible light to promote the azo E-Z isomerization and then the kinetics of the thermal Z-E back reaction was studied. The speed of this process is strongly influenced by the nature of the aromatic ring linked to the NN function. While thiazole bithiophene azo dyes exhibit high switching speeds between the two isomers, but limited interconversion, for benzothiazole and substituted thiadiazole bithiophene azo dyes the switching between the two photoisomers can be performed in 3 s with a significant conversion of the trans-isomer to the thermal unstable cis-isomer (19-21%) and therefore a notable variation of the visible spectrum is observed.     

A novel digitally optimized rapid quantification of carcinogenic aryl azo amines from various food matrices by HPTLC-MS

Abstract

A rapid, precise and reproducible high-performance thin-layer chromatography-mass spectroscopy (HPTLC-MS) method was developed and validated for identification and quantification of toxic aryl azo amines from chili oils, pickles and related food matrices using Merck thin-layer chromatography (TLC) silica gel F-254 plates, as a stationary phase adsorbent by CAMAG HPTLC system. Extraction of azo food colors was done using method specified as per ISO standard. The use of tert-butyl-methyl ether as final extraction solvent resulted in minimal sample clean up and high efficiency. Calibration was performed to combat matrix effect. Good linearity levels were observed for the concentrations of aniline, 2, 4-xylidine and 4 aminoazobenzene of 2–14?ppm per band. The limits of detection and quantification found for aniline, 2,4-xylidine and 4-aminoazobenzene were found to be 0.0015, 200, and 400?ppm and limit of quantification (LOQ) values were found to be 0.004, 600, and 1200?ppm, respectively, with a correlation coefficient of 99.94 %. This study thus highlights an economically viable, commercially sustainable yet highly scientific technique of HPTLC-MS methodology with structural elucidation of banned azo amines in food and related products for their identification duly detectable at trace levels in a digitized form, which can enable material integrity-related prediction capacity of suspected food matrices.