Anaerobic reduction of a sulfonated azo dye, Congo Red, by sulfate-reducing bacteria

The capacity for anaerobic decolorization of a sulfonated azo dye, Congo Red, by a strain of a sulfate-reducing bacterium was evaluated. After optimizing the growth rate of the bacteria on a simple carbon source and terminal electron acceptor pair, lactate and sulfate, respectively, the effect of the dye concentration on their growth rate was analyzed. The decolorization rate was affected by the dye concentration in the growth medium. The azo-bond cleavage mechanism of reductive decolorization with the formation of benzidine was consistent with the results, as this metabolite was identified by high-performance liquid chromatography. Several fractions of the culture medium, including lysed cell extracts, were examined for the capacity to reduce the azo dye. This reduction capacity was found in the culture medium in which the cells had previously grown. The results showed that the mechanism of reductive decolorization of this sulfonated azo dye was extracellular and nonenzymatic, consistent with the production of sulfide anion by the microorganisms while growing on lactate and sulfate. The sulfide anions were the cause of the reduction leading to the disappearance of color in the medium. To increase the rate of decolorization, the presence of ferrous ion was also necessary together with the lactate and sulfate substrates.     

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.     

Extraction-chromatographic determination of sulfonated azo dyes in aqueous solutions

The extraction of sulfonated azo dyes E102, E110, E122, E124, and E129 from aqueous solutions using hydrophilic solvents and their mixtures in the presence of a salting-out agent (ammonium sulphate) has been studied. Some regularities of extraction have been revealed. The composition of the mobile phase has been optimized and a procedure has been proposed for the identification and determination of the dyes in aqueous solutions by thin-layer chromatography in concentrations of 0.1–0.01 μg/L. An office scanner and a personal computer have been used to process the results of the separate determination of the dyes.     

Isostructural potassium and thallium salts of sterically crowded triazenes: a structural and computational study

Because of their similar cationic radii, potassium and thallium(I) compounds are usually regarded as closely related. Homologous molecular species containing either K(+) or Tl(+) are very rare, however. We have synthesized potassium and thallium salts MN3RR' derived from the biphenyl- or terphenyl-substituted triazenes Tph2N3H (1a), Dmp(Mph)N3H (1b), Dmp(Tph)N3H (1c), and (Me4Ter)2N3H (1d) (Dmp=2,6-Mes 2C6H3 with Mes=2,4,6-Me3C6H2; Me4Ter=2,6-(3,5-Me2C6H3)2C6H3; Mph=2-MesC6H4; Tph=2-TripC6H4 with Trip=2,4,6-(i)Pr3C6H2). The potassium complexes 2a- d were obtained in almost quantitative yield from the reaction of 1a- d with potassium metal in n-heptane. Metalation of 1a- d with TlOEt afforded the thallium triazenides 3a- d in high yields. All new compounds have been characterized by (1)H and (13)C NMR spectroscopy, elemental analysis, and X-ray crystallography and for selected species by melting point (not 3b), IR spectroscopy (2a, 2d, 3a, 3c, 3d), and mass spectrometry (2a, 3c). In the solid-state structures of monomeric 2a and 3a, quasi-monomeric 2b, 3b, 2c, and 3c, and dimeric 2d and 3d additional metal-eta (n)-pi-arene-interactions to the flanking arms of the biphenyl- and terphenyl groups in the triazenide ligands of decreasing hapticity n are observed. Remarkably, all homologous potassium and thallium complexes crystallize in isomorphous cells. For 2a and 3a, the nature of the M-N and M...C(arene) bonding was studied by density functional theory calculations.     

Electrochemical and structural characterization of sulfonated polysulfone

We describe the synthesis, as well as the electrochemical and structural characterization, of sulfonated polysulfone intended for use in PEM fuel cells. Starting from a commercial polysulfone, we assessed the performance of these prepared ionomers using synthesis protocols compatible with industrial production. The efficiency of the trimethylsilyl chlorosulfonate and chlorosulfonic acid reagents in the sulfonation process was confirmed by ¹H NMR, FTIR, elemental analysis, chemical titration and thermal analysis (DSC and TGA). Chlorosulfonic acid was the most effective sulfonation reagent. However, based on SEC-MALLS, this reagent induced degradation of the backbone that is detrimental to the thermomechanical stability and lifespan of the membranes. The electrical characterization of the membranes was undertaken using impedance spectroscopy in contact with different HCl aqueous solutions at various temperatures. The activation energies, which ranged from 8.2 to 11 kJ/mol, were in agreement with the prevailing proton vehicular mechanism.     

Influence of experimental conditions on the liquid secondary ion mass spectra of sulfonated azo dyes

Two monosulfonated and eight disulfonated azo dyes of varying relative molecular mass were examined by liquid secondary ion mass spectrometry (LSIMS). The effects of matrix, concentration, primary beam energy, and mode of operation were addressed in order to optimize sample ionization, whilst minimizing interference from matrix ions. Seven matrices were investigated: glycerol, thioglycerol, 3-nitrobenzyl alcohol, diethanolamine, 2-hydroxyethyl disulfide, a 1:1 (v/v) mixture of 2-hydroxyethyl disulfide and thioglycerol, and a 1 : 3 (v/v) mixture of dithioerythritol and dithiothreitol. Of these matrices, 3-nitrobenzyl alcohol produced LSIMS spectra that exhibited the most intense sample ions and the least inteiference from matrix ions. Minimum concentrations of 0.4 μg/μl and 4 μg/μl (dye in matrix) were necessary to produce useful full-scan spectra for monosulfonated azo dyes and disulfonated azo dyes, respectively; maximum sample ion intensities were obtained with concentrations ranging from 20 μg/μl to 60 μg/μl. A primary ion beam (cesium) of 10 to 15 kV produced the greatest secondary ionization efficiency, and a negative-ion analysis mode produced more useful spectra than those obtained in the positive-ion mode.     

Transport phenomena of sulfonated dyes into cellulose membrane: Effects of urea on parallel diffusion of mono azo dyes

 Effects of urea on transport phenomena of sulfonated azo dyes with different aggregation constants into water-swollen cellulose membrane have been studied at 25–55 °C. The results were analyzed on the basis of a parallel transport theory of surface and pore diffusion. Addition of urea decreased equilibrium adsorption of the dyes onto cellulose and increased the surface and pore diffusivities for the parallel diffusion model of the dye with high aggreg-ation constant. Temperature dependence of the effects was also discussed. Received: 30 November 1996 Accepted: 7 April 1997     

Determination of sulfonated azo dyes in river water samples by capillary zone electrophoresis

A method based on capillary zone electrophoresis coupled with photodiode-array detection has been developed to determine several sulfonated dyes, including a sulfonated dye (acid yellow 1), and the sulfonated azo dyes acid orange 7, acid orange 12, acid orange 52, acid red 26, acid red 27 and acid red 88. A CElect-FS75 CE column is used. The electrophoresis buffer contains a 1:5 dilution of 10 mM phosphoric acid and tetrabutylammonium hydroxide buffer (pH 11.5), and 25 mM of triethylamine, the final pH being 11.55. The detection limits for the seven dyes ranged from 0.1 to 4.53 microg/ml. Spiked river water samples (100 ml), containing different concentration levels (0.025-0.150 microg/ml) of the dyes were analyzed after acidification (pH 3) and pre-concentration in disposable SPE Oasis HLB, 1 ml cartridges.     

Quininium mandelates--a systematic study of chiral discrimination in crystals of diastereomeric salts

The selectivity profile for the resolution of mandelic acid by quinine is dominated by structures comprising (QUIN(+))(MAND(-)) salts with Z' = 3 which contain (R)-, (R)- and (S)-mandelate anions.     

Sodium salts of sulfonated poly(phenylene ethers) as polysoaps

Polysoaps are of interest because, unlike most polyelectrolytes, their aqueous solutions become more viscous and often form gels upon the addition of salt. A new kind of polysoap was made by sulfonating phenylene oxide polymers that have a pendant alkyl group containing at least 14 carbon atoms on every phenylene unit. Copolymers made from a mixture of 2,6-dimethylphenol and 2-methyl-6-tetradecylphenol have the same composition as the monomer mixture. Tetradecyl substituents in the copolymer act as internal plasticizing agents and, by varying the number of substituents, a gradation in physical properties of the unsulfonated copolymer from rigid solid to heavy oil is possible.     

The synthesis and first full structural elucidation of a benzotriazole azo dye

Although azo dyes containing benzotriazole are of interest as substrates for surface enhanced resonance Raman scattering, SERRS, little is known of their molecular structure due to their poor crystal growth properties. We recently synthesised a highly crystalline dihydroquinoline via an unusual condensation reaction and we report herein that the azo‐benzotriazole dye subsequently formed was sufficiently crystalline to allow structural elucidation using synchroton radiation. It was found that this benzotriazole dye exists as the unexpected 6‐isomer and the structure of the dihydroquinoline moiety changes markedly on coupling due to increased delocalisation.     

Characterization of sulfonated azo dyes and aromatic amines by pyrolysis gas chromatography/mass spectrometry

Sixteen sulfonated and unsulfonated azo dyes as well as eleven sulfonated and unsulfonated aromatic amines were analyzed and qualitatively characterized by means of pyrolysis gas chromatography/mass spectrometry at different temperatures. Aniline and aminonaphthalene were found to be the dominant pyrolysis products of sulfonated aromatic amines and dyes. Azo dye and dye class specific key compounds such as benzidine, vinyl-p-base and 4-aminoazobenzene could be identified by pyrolysis gas chromatography/mass spectrometry of commercial acid, cationic, direct, reactive and solvent dyes. 500 degrees C was the optimal pyrolysis temperature for most of the pyrolyzed compounds. The method was applied to a dried sample of a textile wastewater concentrate from a dyeing process. Reactive azo dyes of the group of Remazol dyes and anthraquinone dyes could be identified as the major compounds of the sample. The finding of caprolactam (a printing additive) suggests that the wastewater contained effluent from a process of heat-activated printing with reactive dyes. p-Chloraniline, a banned aromatic amine, was identified. Chemical reduction of the wastewater sample prior to pyrolysis resulted in the release of volatile aromatic amines and aided the classification of several products of pyrolysis.     

Partially sulfonated polyaniline: conductivity and spectroscopic study

Polyaniline and set of copolymers of aniline with orthanilic acid (OA) were prepared by oxidation of monomers with ammonium peroxydisulfate. Amount of OA in mixture of comonomers was varied from 0 to 10%. The higher amount of OA resulted in decrease of conductivity and increased steepness of temperature dependence of conductivity. The X-ray photoelectron spectroscopy showed content of self-doping groups in surface layer slightly higher than expected from the feed ratio of comonomers. Shifts of positions of bands of ring stretching vibrations towards their position in polyaniline base and shift of the band of protonated units Q=NH⁺–B or B–NH^+?–B in the FTIR spectra observed with increasing amount of OA have shown increase of electron localization in copolymers. Finally, Raman spectroscopy proved that sulfonic groups act as structural defects in polymer’s geometry. Polarons are expected to be localized on short isolated segments between the structural defects.     

Electrospray mass spectrometry: a study on some aqueous solutions of metal salts

Aqueous metal salt solutions were used as models to probe the origin of the species observed in the electrospray mass spectrum. A qualitative or semiquantitative correlation among different species was observed between electrospray responses and calculated equilibrium aqueous solution concentrations. Quantitative correlations were obtained, however, when ions that were identical in charge and similar in type were selected for comparison. In these experiments the ions experienced very similar electrospray-related processes and their effects on the responses were canceled in a comparison of these ions. Consequently, the relative abundances of these ions in the electrospray mass spectrum closely matched the calculated relative abundances in aqueous solution. Our results suggest that the basic principle that determines ionic distribution in the electro spray mass spectrum in aqueous solution chemistry.     

Structural characterization of sulfonated azo dyes using liquid secondary ion mass spectrometry/tandem mass spectrometry

Eight monosulfonated and disulfonated azo dyes were analyzed using liquid secondary ion mass spectrometry/tandem mass spectrometry, in the negative ion mode, under low-energy collision conditions (110–150 eV). Many structurally characteristic fragment ions were obtained, several of which have not been reported previously using other mass spectrometric techniques. Among the structurally important ions observed were those due to loss of SO₂, SO₃ and various aromatic substituents, such as NO₂ and NHCOCH₃. Losses of N₂ were also proposed. In addition, product ions due to cleavage at the azo linkage were observed, and also SO₃^? and HSO₃^? ions. Several of the azo cleavage product ions detected did not contain sulfonate groups. Possible pathways for the formation of product ions are proposed. The structural information obtained should help to better characterize and identify sulfonated azo dyes in the future.     

Study of the casting of sulfonated polyimide ionomer membranes: structural evolution and influence on transport properties

A casting process has been studied for charged polymers: the sulfonated polyimide ionomer membrane. The formation of the membrane has been followed by X-ray reflectivity as a function of temperature. The effect of equivalent weight has been also investigated. The thickness loss presents two regimes: the first one is linear vs time indicating that the models developed for noncharged polymer may be suitable for ionomers in the early period of drying. The second one corresponds to the loss of X-ray reflectivity signal. Moreover, the X-ray reflectivity signal seems to be correlated to the characteristic time of the sample drying. In complement, we have studied the influence of casting on the properties of the dried ionomer membranes. The transport coefficients of N(CH(3))(4)(+) ions confined in two kinds of membranes that were differently cast were measured. The results show that shearing the ionomer solution during casting may lead to an enhancement of the anisotropy of structure and of transport. Moreover, we have studied the effect of both interfaces on the ion transport properties through the dried membranes.     

Caput mortuum: spectroscopic and structural studies of an ancient pigment

The use of a pigment variously described as caput mortuum, usta or ostrum to provide a deep purple colour in ancient wall-paintings was highly prized, despite the technical difficulties associated with its application. With the Raman spectroscopic characterization of pigments in ancient frescoes and wall-paintings becoming more widespread, it is timely to consider the identification of this material either as a generic haematite alone or in admixture with contemporary blue pigments. Here, Raman and infrared spectroscopic, X-ray diffractometric and scanning electron microscopic structural studies have been undertaken to characterize caput mortuum and to identify a specimen of Roman wall-painting dating from the 3rd century.