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Reactive dyes are pernicious pollutants in textile effluent, which are to be treated passably before discharging into the environment. In the present study, a potential dye degrading bacterial strain Pseudomonas guariconensis was isolated from paddy rhizosphere and was characterized by 16S rRNA gene sequencing. The biodegradation ability of the strain was evaluated by time-based study with immobilized bacterial cells in calcium alginate biocarrier matrix and also with free cells. The results indicated that the strain exhibited maximum degradation of 91% when immobilized in the biocarrier matrix. The enzymatic study revealed the production of oxidoreductase enzymes. The degraded products were identified as 2-amino-3-phenylpropanoic acid and benzoquinone by gas chromatography-mass spectroscopy (GC-MS) analysis, and a degradative pathway was derived based on the enzymatic profile. A packed bed column was designed using P. guariconensis VITSAJ5 immobilized in calcium alginate beads as a biosorbent for the removal of Reactive Red 120. The immobilized bacterial cells exhibited 87% uptake of RR120, whereas the nonimmobilized bacterial cells exhibited a maximum uptake of 37%. The phytotoxicity analysis by seed germination assay revealed an enhanced plumule and radicle length, indicating the nontoxic byproducts after the treatment of Reactive Red 120 by VITSAJ5 compared to the untreated Reactive Red 120 solution. PRACTITIONER POINTS: Current study is the first report on Pseudomonas guariconensis capable of degrading reactive dyes (Reactive Red 120) It was observed that the degradation potential was maximum when cells were immobilized with Ca-Ag biocarrier matrix Breakdown metabolism of Reactive Red 120 was derived through pathway prediction Employing immobilized bacteria in a packed bed column found to possess a prominent biosorption ability on the matrix enhancing the degradation process Toxic reactive dye was converted into nontoxic compounds, evidenced by phytotoxicity studies.

Chloropyrimidine-based reactive dyes are reported as well suited to textile printing; however, nucleophilic aromatic substitution of chloropyrimidines with amino-containing chromophores is slow and often suffers from poor yields. In this study, a novel and simple method was developed for the synthesis of chloropyrimidine-based reactive dye under microwave irradiation. In addition, the dye was also synthesised by conventional heating for comparison, which took both the reaction time and yield into account. The progress of the synthesis reactions concerned were monitored using capillary electrophoresis and the purity of the dye obtained was assessed by thin-layer chromatography. The structure of the synthesised trichloropyrimidine dye was confirmed by Fourier Transform–infrared spectroscopy and elemental analysis. It was found that the reaction rate of the nucleophilic aromatic substitution carried out under microwave irradiation was 4-fold faster than that carried out under conventional heating, although the enhancement in product yield was modest. These results suggest that microwave irradiation is an effective technique for the synthesis of chloropyrimidine-based reactive dyes. The synthesised chloropyrimidine dye was formulated into an ink and applied onto a wool fabric by ink-jet printing. The printed fabrics were steamed at 102°C for 5-25 minutes at 5-minute intervals. Good K/S and rate of dye fixation were obtained, both of which improved with increasing steaming time. The prints obtained exhibited reasonably good light and wash fastness properties.

To achieve textile dyeing and functional finishing in one process, a bleach-resistant reactive dye precursor to anti-bacterial N-halamine was synthesised by reacting a type of dichlorotriazine reactive dye with 4-amino-2,2,6,6-tetramethylpiperidine. The synthesised compound, which can be transformed to an N-halamine molecule by exposure to dilute bleach solution, was used to dye cotton fabrics. After exposure to a dilute sodium hypochlorite solution, dyed cotton fabrics showed excellent anti-bacterial properties against Staphylococcus aureus and Escherichia coli O157:H7, facilitating a ca. 6-log reduction in bacteria within a short period of contact. Compared with the dichlorotriazine reactive dye, the reactive dye precursor demonstrated comparable dyeing properties including exhaustion and fixation values. No differences in rub fastness, wash fastness or bleach fastness were detected between fabrics dyed with, respectively, dichlorotriazine reactive dye and the reactive dye precursor to N-halamine.

An ionic liquid, choline hydroxide, was synthesised and used in a mixed alkali system for fixation of homobifunctional reactive dyes. Its molecular structure was confirmed using FTIR, 1H NMR, and 13C NMR spectroscopy. Response surface methodology was employed to optimise the dyeing conditions for reactive dyes using a sodium carbonate–choline hydroxide mixed alkali system. A Box–Behnken design with three variables, namely sodium carbonate concentration, choline hydroxide concentration, and fixation time, was used to design the experimental runs. Analysis of variance was used to estimate the statistical parameters and to evaluate the quality of the statistical model fit. The quality and model terms were evaluated using Fisher's F-test, the coefficient of determination, and probability values. The interactive effect of operating variables on the response (K/S) was studied using three-dimensional response surface plots. The results obtained from the solutions of highest desirability were found to be comparable with conventionally used alkali systems, namely sodium carbonate alone and sodium carbonate–sodium hydroxide mixed alkali. The ionic liquid choline hydroxide could be effectively used along with sodium carbonate for fixation of reactive dyes, with the advantage of reductions in pollution load, total dissolved solids, and chemical oxygen demand.

A new anthraquinonoid disperse reactive dye containing a dichlorotriazine reactive group was successfully synthesised on the basis of the Ullmann reaction in a ligand-free system by employing a copper(i) iodide as catalyst, in combination with a subsequent condensation reaction. The parameters of the cross-coupling reaction between 1-chloroanthraquinone and 2,5-diaminotoluene sulphate were investigated and optimised, such as the molar ratio of the reactants, the dosage of potassium carbonate and copper(i) iodide, the reaction temperature, and the reaction time. The results demonstrate that the dosage of potassium carbonate and the reaction time had significant impacts on the yield of the dye precursor, and an optimum synthesis process was also recommended. Moreover, the achieved dye was successfully characterised and confirmed from chemical structure and colour characteristics by employing Fourier transform infrared analysis, nuclear magnetic resonance spectroscopy, UV-vis absorption spectroscopy, elemental analysis, and liquid chromatography–mass spectrometry (LC-MS). Furthermore, a successful application of the obtained dye was achieved, with satisfactory coloration properties on silk and wool.

Benzenesulfonic acid-doped polyaniline nanorods were synthesized by oxidative polymerization of aniline and were subsequently used for the decolorization of simulated reactive dye bath effluent. Transmission electron micrograph showed that the size of the nanorods varied from 60 to 90 nm. Fourier transform infrared pattern of nanorods indicate that sulfonic acid was successfully doped on polyaniline nanorods. Under optimized conditions, sulfonic acid doped polyaniline nanorods decolorized 78% of simulated reactive dye bath effluent. The modified Freundlich model and modified pseudo-first-order model showed satisfactory fit for dye decolorization. The crystalline nature of the nanorods was modified after adsorption of dyes. The results of the study indicate that benzenesulfonic acid doped polyaniline could be used for the treatment of textile wastewaters. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1383–1389, 2017

Solar‐driven vapor generation is a promising method to mitigate freshwater shortage and water contamination. However, most of the current highly efficient solar evaporators suffer from low robustness, tedious preparation procedures, and high cost. In this study, an easy‐to‐manufacture, low‐cost, and high‐reliability solar‐driven evaporator is designed using a black cotton towel with a hollow conical shape. The reactive dye molecules diffuse into the cotton and form strong covalent bonds with the fiber after dyeing, which firmly fixes light‐absorbing materials on the substrate. The looped pile structure of towels and hierarchical structure of yarns enable the evaporator enlarged surface area. The hollow conical shape of the cotton towel can effectively suppress the heat loss to the environment without compromising light absorption. The 3D vapor generator exhibits an evaporation rate of 1.40 and 1.27 kg m−2 h−1 for pure water and saline water, respectively. Meanwhile, this towel‐based solar‐driven evaporator exhibits a promising antifouling property as well as superior reusability and provides a reliable pathway in dealing with realistic waters, such as seawater and dyeing sewage. Therefore, the low‐cost, solar‐driven water evaporation system offers a complementary approach for high‐efficiency vapor generation and water purification in practical application.

A series of padded cotton fabrics with various water contents were obtained through vacuum dehydration. The effects of the water content on the fabric temperature variation during steaming, the colour properties, and the dye fixation rate (%F) were investigated. Dye distribution in the dyed cotton fibres was assessed. The influences of steaming time and sodium carbonate concentration on K/S value and %F of the dyed fabrics with low water content were also evaluated. The results indicate that reducing the water content of the padded cotton fabric to around 25.0% prior to steaming was favoured for reactive dyeing. The temperature of the wet fabric rose rapidly, the K/S value and %F were enhanced, and in addition the dye penetration into the dyed cotton fibres was sufficient. However, for padded fabrics with extraordinarily low and high water contents (e.g. 1.4% and 70.9% respectively), both the K/S value and %F were decreased. Furthermore, a white core phenomenon was evident for the fibres of the dyed fabric with a water content of 1.4%. Variation in the L* values was in line with the K/S values as the fabric water content varied. As expected, steaming time and sodium carbonate dosage can also affect reactive dye fixation greatly and should be determined accordingly for dyeing cotton fabric with low water content.

A noticeable amount of dyes may remain in the wastewater downstream of dyeing facilities giving anaesthetic colorations as well as environmental concern. Conventional biological treatment alone cannot guarantee a sufficient decolouration and tertiary treatments have to be necessarily considered. Two oxidation schemes by ozone were considered in this work. A bubble column reactor (as a benchmark, in agreement with industrial applications) and a recycle well-mixed reactor were compared to reach the highest decolouration of standard dyes. In addition, hydrodynamic and ultrasonic cavitation were considered in the recycled well-mixed reactor to intensify its performance. The decolouration analysis was carried out for two dye classes (reactive and disperse), characterized by very different physical and chemical features. It appeared that some benefit was brought by ultrasound cavitation in the case of disperse dye only, while the degradation of the reactive dye was not intensified by the above hydraulic phenomenon. Ozone treatment was protracted to obtain different decolouration degrees of wastewater generated by wool dyeing. The resulting water was tested as a recycled process fluid to prepare fresh dyeing liquors, where devising the minimum decolouration degree became one of the quality specifications for recycling water back to dyeing. This article is protected by copyright. All rights reserved

Three types of layered double hydroxides (LDHs) including Mg-Fe, Mg-Al-Fe, and Mg-Zn-Al-Fe were synthesized by the coprecipitation method. Nanoparticles of the LDH adsorbents were characterized by X-ray powder diffraction (PXRD), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and specific surface area measurement. The size and morphology of nanoparticles were inspected by scanning electron microscopy (SEM). The comparative study was performed to evaluate the effect of cation variety on removal of C.I. Reactive Red 43 dye. Adsorption capacity of LDHs was obtained as: 279.23, 210.4, 150.03 mg/g for 4, 3, and 2 cationic LDH respectively. Batch adsorption experiments were carried out at room temperature (25°C) under various conditions such as contact time, solution pH, and dye concentration (20–60-100 mg/L). Results revealed that adsorption rate increases with increase in contact time as long as equilibration is established and decreases as dye concentration increases. The effect of solution pH was investigated and urban water pH without adjustment was selected as the operational pH. It was found that the adsorption capacity of LDH containing four cations (Mg-Zn-Al-Fe) is higher than that of others which can be attributed to the highest degree of crystallinity and the highest total pore volume (0.059 cm3/g) of this LDH. The kinetic and isotherm studies were performed on four cationic LDH and the results show that adsorption of dye onto LDH fits to the Freundlich equation as well, which confirms multilayer adsorption. Moreover, the regeneration study indicates that the prepared LDH could be used for several cycles. © 2016 American Institute of Chemical Engineers Environ Prog, 2016

Gallinaceous feathers (from Gallus gallus domesticus, strains Cobb 500 and Label) were used as adsorbent for colour removal from a simulated textile effluent containing a wool reactive dye, the Yellow Lanasol 4G (CI Reactive Yellow 39). A brief chemical and physical characterisation of feathers was performed. Equilibrium studies at different selected temperatures, in the range 10–60 °C, were carried out. The equilibrium data were analysed using the Freundlich and Langmuir isotherm models. Adsorption capacity strongly increases with temperature. A maximum adsorption capacity of around 300 mg g 1 was obtained for Gallus gallus feathers, strain Cobb 500, at 60 °C, while for strain Label, 200 mg g 1 was obtained at 50 °C. For each type of feather a generalised model, valid for a given temperature range, was obtained. The isosteric heat of adsorption calculated was positive, so the mechanism involved in the adsorption process should correspond to endothermic chemisorption. This study provides important information concerning the use of gallinaceous feathers without any chemical treatment for colour removal from real textile wastewaters. The results in this study indicated that gallinaceous feathers, when compared with activated carbon, open promising perspectives concerning their utilisation for colour removal from textile effluent discharged at high temperatures; moreover, it would be an alternative for the valorisation of this waste., info:eu-repo/semantics/publishedVersion

Ink dot distribution on cotton fabrics determines the colour performance of reactive dye inkjet printing, and ink drop spreading is one of the important factors influencing the ink dot distribution. In order to reveal the relationship between fabric pretreatment and ink drop spreading, two pieces of cotton fabric were pretreated respectively with sodium alginate and sodium alginate plus high fatty acid derivative solutions. Results indicate that the surface energy of the cotton fabrics was reduced from 73.79 to 69.45 and 58.49 mJ m−2 after the pretreatment with sodium alginate and sodium alginate plus high fatty acid derivative respectively. Correspondingly, the spreading area of cyan ink drops on these fabrics was reduced from 104.9 to 92.5 and 72.3 mm2. Furthermore, on the fabric treated with sodium alginate plus high fatty acid derivative, the strip-like ink dots were narrow and short, which means the dye was concentrated in an area on the fabric surface. Colorimetric values of the inkjet-printed fabrics demonstrated that the high fatty acid derivative would enhance the ability of sodium alginate to control ink droplet spreading, thereby improving the colour performance.

A chitosan/gelatin composite microsphere (CGMS) adsorbent prepared by inverse suspension was used as a reactive dye washing agent. Techniques such as scanning electron microscopy, X-ray diffraction analysis, and atomic force microscopy facilitated the evaluation of the materials. A series of experiments were conducted to assess the effect of variables, i.e. initial pH, temperature, microsphere dosage, and contact time. The wash-off effectiveness increased with increase in temperature and decrease in pH. Results obtained from this study showed that it was possible to reduce the number of wash-off stages and the water consumption. Furthermore, the microspheres had the properties of resistance to hard water and electrolyte as a wash-off agent. The efficiency of the microspheres can rival routine detergent in colour fastness, while the chemical oxygen demand of the wash-off residue of the microspheres amounted to about 1/10 of the chemical oxygen demand of detergent wash-off residue. This research proved that chitosan/gelatin composite microspheres are a potential candidate for use as an adsorbent washing agent for reactive dyes.

The effect of CO2 laser treatment before dyeing (LD) and after dyeing (DL) was compared in terms of colour variation. Two reactive dyes, CI Reactive Blue 19 (RB19) and CI Reactive Black 5 (RB5), were used in three concentrations −0.1, 1, and 5% owf. Morphological changes of the fabrics after laser treatment were observed using a scanning electron microscope. Chemical modification of the laser-treated cotton fabrics was detected using attenuated total reflectance Fourier transform infrared spectroscopy. The difference in colour was evaluated by spectrophotometer; reflectance value, colour yield, CIE L*a*b*, and levelness were determined. The tensile strength of fabrics laser treated before and after dyeing was also measured. The results show that the DL approach has a stronger effect, resembling a fading of colour, yet a higher tensile strength, especially when dye RB5 is used. The LD approach, on the other hand, provides a better colour yield, levelness, and tensile strength when dye RB19 is used.

Nonionic surfactants are widely used in reactive dyeing processes, and the interaction between surfactants and reactive dyes affect the hydrolytic property of reactive dyes. In this study, reactive brilliant blue KN-R (C.I. reactive blue 19) was employed as a model dye, and fatty alcohol polyoxyethylene ether (AEO-9) was selected as a model nonionic surfactant. The interaction was first investigated in aqueous solutions by a UV-spectrophotometry method, then the effect of surfactant concentration on the hydrolytic behavior of KN-R was studied using high performance liquid chromatography method. Below the critical micelle concentration, the surfactant served as dispersant; the hydrolysis of reactive dye was accelerated. However, when the concentration of surfactant was above its critical micelle concentration, the dye was solubilized into the micellar phase, which was revealed from the changes in absorbance intensity and wavelength of the maximum absorbance. This led to slowed hydrolysis of reactive dye. These findings are useful in understanding the effect of concentration of nonionic surfactant on the hydrolysis of vinyl sulfone reactive dyes.

The most widely used dyes for coloration of cotton textiles are from reactive class. However, the large amount of unfixed dye causes color in the wastewater, which is environmentally unacceptable. Decolorization of various commercially important reactive dyes in aqueous solutions was attempted by microbial treatment using the bacteria Proteus vulgaris and Proteus mirabilis, individually as well as in a consortium. Different parameters such as treatment temperature, pH, dye solution concentration, and the seed age of the bacteria were optimized to achieve maximum decolorization. Although both bacteria displayed good growth in a shake culture, the color removal was better in an anoxic static culture. The selected dyes were based on azo and anthraquinone chromophores and complete decolorization under optimized conditions could be achieved at a concentration of 30 mg/L. Good results were obtained also at dye concentrations of 60 and 90 mg/L.

Adsorption characteristics of three clay adsorbents – sepiolite, kaolin and synthetic talc – were investigated to determine their applicability to remove an anionic reactive dye – Reactive Yellow 138:1 – from a water stream. Results showed that synthetic talc had the highest maximum monolayer adsorption capacity of 10.07 mg/g, followed by kaolin (3.73 mg/g) and sepiolite (3.23 mg/g), for the removal of Reactive Yellow 138:1. Synthetic talc and sepiolite removed dyes from aqueous solutions mainly through physical adsorption depending on the surface area. By contrast, the adsorption mechanism of kaolin was strongly influenced by the anion exchange mechanism. Zeta potential analysis revealed that the adsorption capacity of clay adsorbents increased under acidic rather than alkaline conditions, owing to protonation of the clay surface. Moreover, synthetic talc was successfully regenerated by heating at more than 400°C, effectively restoring its original adsorption capacity.

In an earlier paper we have described sulphite-based resist printing using ink-jet procedures. This paper describes an alternative approach to sulphite inactivation of vinylsulphone dyes by using secondary amines to inactivate fluoro-s-triazine dyes while maintaining the reactivity of the vinylsulphone dyes. Monofluoro-s-triazine reactive dyes are padded onto cotton fabrics and then deactivated by ink-jet printing with a suitable secondary amine formulation to produce a white image on a solid ground colour after appropriate fixation and soap-off procedures have been undertaken. A coloured image can be achieved by overprinting the resist-printed areas with a coloured ink formulation containing a β-sulphatoethylsulphone-type reactive dye; such dyes form a β-bis-alkylaminoethylsulphone dye via reaction with the secondary amine. This latter dye ‘unblocks’ during a mildly acidic steaming process to form the reactive vinylsulphone dye, and so, unlike the monofluoro-s-triazine dye, is not deactivated towards subsequent covalent reaction with the cotton substrate.

In this project, an eco-friendly aqueous synthesis method of water-based polymeric dye (WPD) was developed and its potential as a colorant for waterborne polyurethane (WPU) was tested. The WPD was produced by reacting polyethylenimine with commercial reactive dye in the warm alkaline solution. The colored polyurethane membrane was then produced via solution blending of WPD and WPU, followed by air-drying. The results showed that WPD with a wide variety of colors can be easily synthesized by selecting different precursory reactive dyes and can be easily blended with WPU via moderate stirring. The colored PU membranes have good transparency and the logo under them can be clearly observed. Compared with the pure polyurethane membrane, the absorbance of colored polyurethane membrane at the wavelength of maximum absorption increases at least 20.2% even if the content of WPD within the colored polyurethane membrane is as low as 0.16%, implying that our WPD has excellent color strength. Finally, the colored polyurethane membranes have very high colorfastness to water and can be stored in deionized water for 2 weeks without dissolution of WPD. As a result, our developed WPD is a promising and cost-effective colorant for WPU. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44710.

This study examined the reactive dye decolorization activities of sodium dodecyl sulfate (anionic), cetylpyridinium chloride monohydrate cetylpyridinium chloride monohydrate (CPC) (cationic) surfactants, and their influence on fungal growth. The effect of CPC on Remazol Blue (RB) bioremoval by Aspergillus versicolor was investigated in low-cost molasses medium. The optimum pH (3–7) and CPC (0.1–1 mM) concentrations for fungal RB decolorization were achieved in molasses medium with 50 mg/L RB. It was observed that the CPC effectively removed RB due to electrostatic interactions and it was well tolerated by fungus. Maximum decolorization in the presence of CPC occured at pH 6. Increasing the toxic CPC concentrations (0, 0.1, 0.25, 0.5, 1 mM) decreased fungal growth from 5.08 to 2.87, 1.40, 0.21, and 0.07 mg/L dry biomass, respectively, but enhanced fungal decolorization, respectively (63.2, 78.7, 92, 95.75, and 98.9%). As the augmentation of CPC concentration reduced energy costs by reducing effective decolorization period from 96 to 24 h, surfactant stimulated fungal decolorization method may provide highly efficient, inexpensive, and time-saving procedure in treatment of textile effluents.

In this study, starch-montmorillonite/polyaniline (St-MMT/PANI) nanocomposite was synthesized by chemical oxidative polymerization of aniline in the presence of St-MMT nanocomposite dispersion. The prepared ternary nanocomposite was characterized using FTIR, XRD, and SEM techniques. Adsorption properties of the nanocomposite were investigated for removal of reactive blue (RB 194) as a model reactive dye from aqueous solution. Response surface methodology was employed for the modeling of adsorption capacity of the nanocomposite. A second-order empirical relationship between adsorption capacity and independent variables (initial dye concentration, amount of the nanocomposite, and pH of the solution) was obtained. Pareto analysis for identification of the factors effect on the system revealed that initial dye concentration was the most effective parameter. The adsorption capacity value of reactive dye on St-MMT/PANI nanocomposite was 91.74 mg g−1. Further investigations indicated that the adsorption experimental data were well fitted to the Langmuir isotherm and pseudo-second-order kinetic model. POLYM. ENG. SCI., 54:1595–1607, 2014. © 2013 Society of Plastics Engineers

Laccase from the white-rot fungus Pleurotus florida, produced under solid-state fermentation conditions, was used for the decolorization of reactive dye Remazol Brilliant Blue R (RBBR). RBBR was decolorized up to 46% by P. florida laccase alone in 10 min. In the presence of N-hydroxybenzotriazole (HBT), the rate of decolorization was enhanced 1.56-fold. Central composite design of response surface methodology with four variables namely, dye, enzyme, redox mediator concentrations, and time at five levels was applied to optimize the RBBR decolorization. The predicted optimum level of variables for maximum RBBR decolorization (87%) was found to be 52.90 mg L−1 (RBBR), 1.87 U mL−1 (laccase), 0.85 mM (HBT), and 7.17 min (time), respectively. The validation results showed that the experimental value of RBBR decolorization (82%) was close to the predicted one. The disappearance of C–N and C–X groups, and a small shift in N–H groups in Fourier-transform infra red (FTIR) spectroscopy confirms the degradation of RBBR chromophore by laccase enzyme. The phytotoxicity of RBBR was considerably reduced after the treatment with laccase. RBBR decolorization kinetics; Km and Vmax were calculated to be 145.82 mg L−1 and 24.86 mg L−1 min, respectively.

The current commercial application of ink-jet reactive inks to cotton fabrics requires pretreating with pad liquor containing a thickener, urea and alkali prior to printing. In this study, attempts have been made to develop a reactive ink-jet print in a single-phase process by adding an organic salt to the ink formulation and hence removing the need to pretreat fabrics. This approach utilises inks containing both a reactive dye, in this case Procion Red H-E3B, and an organic salt such as sodium formate, sodium acetate, sodium propionate or tri-sodium citrate. The behaviour of a novel reactive ink formulation for ink-jet printing on to cotton fabric was evaluated at different pH vlaues. The results at optimum pH indicated that printed non-pretreated fabrics with ink containing organic salts exhibited a higher level of reactive dye fixation than printed pretreated fabric containing no organic salt ink. The yielded prints demonstrate excellent colour fastness to washing and dry/ wet crocking properties. The light fastness of the printed fabrics was improved by adding an organic salt to the ink formulation. Coloration Technology

BACKGROUND Effluents discharged from tannery industry contain significant amount of chromium and synthetic dyes. Both chromium and dyes can be transformed individually into less toxic forms, but very little is known about their simultaneous treatment. The present study was aimed at isolating bacteria capable of removing toxic hexavalent chromium (CrVI) and reactive black-5 azo dye simultaneously in liquid mineral salt medium (MSM). RESULTS About 150 bacterial isolates were collected from tannery wastewater and sludge through enrichment of the MSM with CrVI (2 mg L−1) and reactive black-5 dye (100 mg L−1) under static (batch) condition. Bacterial strains KI (Pseudomonas putida ) and SL14 (Serratia proteamaculans) were able to reduce simultaneously 93% CrVI and 100% color of reactive black-5 azo dye in 24 h at pH 7.2 and 35 °C in a batch culture. Individually, 100% reduction of CrVI and reactive black-5 dye was achieved in 12 h by strain KI and SL14. CONCLUSION These bacterial strains are one of the most efficient bacteria capable of reducing toxic CrVI and synthetic reactive dye simultaneously and could be used for developing bioreactors to treat tannery effluent prior to its discharge into the environment. © 2012 Society of Chemical Industry

Ozonation of the commercially important, recalcitrant reactive dye intermediate 2-naphthylamine 3,6,8-trisulphonic acid (K-Acid) was investigated. Ozonation performance was examined by following ozone absorption rates and K-Acid, chemical oxygen demand and total organic carbon removals. Mean oxidation states and unidentified organic products were also determined. At pH 3, where direct ozone reactions are dominant, the second-order rate constant between K-Acid and molecular ozone was determined as 20 m−1 s−1 for steady-state aqueous ozone concentration. The competition kinetics approach was also adopted where a reference compound, phenol, and K-Acid were subjected to ozonation. By applying this method, the second-order reaction rate constant was found to be 76 m−1 s−1. Common oxidation products formed during ozonation at pH 3, pH 7 and pH 7 with 1 mm hydrogen peroxide were identified as methoxy-phenyl-oxime, phenol, benzene, benzaldehyde and oxalic acid via high-performance liquid chromatography and gas chromatography/mass spectrometry analyses. Continuous nitrate and sulphate evolution were observed during K-Acid ozonation as a consequence of the abrupt release and subsequent oxidation of its amino and sulphonate groups. The number and amount of reaction products were most intensive for K-Acid ozonation at pH 7 with 1 mm hydrogen peroxide. According to the acute toxicity tests conducted with Vibrio fischeri, ozonation products were not less toxic than the original K-Acid solution that caused only 15% inhibition.

Reactive dye fixation and color yield of a dyed cellulosic fiber significantly depend on the dye diffusion into the fiber polymer system. In case of pad-dyeing processes, dye diffusion exerts a more significant influence on dye fixation and hence color yield. This article proposes a new method for determining the extent of diffusion of reactive dyes into the fiber in pad dyeings using Kubelka-Munk equation. The K/S values are used as in an equation, %D (extent of dye diffusion) = 100 - [(K/S diffusion index)/ (K/S reference) × 100]. The article introduces and explains how to determine the new K/S variables used in this equation. The new method is simple, nondestructive, relatively faster, and applicable to industrial dyehouses, and was validated by a microscopic analysis of dyed fiber cross-section carried out in this work and to the dye manufacturer's recommendations for dyebath-ingredient concentrations.

The effect of dodecyl trimethyl ammonium bromide (DTAB) cationic surfactant on Remazol Blue reactive dye bioremoval properties of a growing Aspergillus versicolor strain in a molasses medium was investigated in a batch system as a function of pH, dye and surfactant concentrations. To determine the optimal pH value in the presence of 0.5 mM DTAB pH 3 to 7 was examined and pH 6 was selected. The dye concentrations of 50, 100, 200, 400 and 800 mg/L were examined with 0.5 mM DTAB and maximum decolorization occurred in 100 mg/L dye (98.8 %). The surfactant concentration of 0.1, 0.5, 1 and 2 mM DTAB was performed in 100 and 800 mg/L dye. The effect of surfactant concentration (0.1 to 2 mM DTAB) in a fungal growth experiment has shown that DTAB inhibited fungal growth. The decolorization was increased from 53.6 % (dry weight: 1.31 g/L) to 100 % (dry weight:0.93 g/L) while the surfactant concentrations were increased from 0.1 to 1 mM. A. versicolor (dry weight: 0.93 g/L) showed its maximum dye removal activity, namely 100 % in 100 mg/L dye with 1 mM DTAB at pH 6 in 3 days. The use of surfactants in biological wastewater treatment process will save energy and lower energy costs (such as the required energy for treat techniques) by shortening the incubation period. The results showed that the A. versicolor strain, which produces laccase enzyme, can effectively decolorize reactive dyes by the enhancement of DTAB. Surfactant enhanced decolorization technology is one of the feasible approaches to remove textile dye from wastewater.

To achieve the goals of saving water and being salt-free in the coloration of cotton fabric with reactive dye, nonionic reverse micelles were prepared and optimised with a surfactant, Triton X-100, n-octanol and isooctane by injecting a small amount of CI Reactive Red 195 aqueous solution. The adsorption, diffusion and fixation of this dye on cotton fabric in Triton X-100 reverse micelle and bulk water were then investigated. The equilibrium and kinetic data of the dye adsorption process were evaluated. The colour strength and fixation rate of cotton fabrics dyed in the micelle and in bulk water were also examined and compared. The results indicated that the amount of dye adsorbed increased with the increasing temperature and the initial dye concentration. The dye adsorption process could be described using the Langmuir isotherm and pseudo-second-order kinetic equations. It was found that CI Reactive Red 195 showed a stronger adsorption property on cotton fabric in Triton X-100 reverse micelle than in bulk water without the addition of sodium chloride. Using Triton X-100 reverse micelle as the dyeing medium offered the reactive dye better diffusion performance within the cotton fibre as compared with bulk water. Moreover, higher fixation of the dyes absorbed on the cotton fibre was achieved when the optimum concentration of sodium carbonate was used as the alkali agent in Triton X-100 reverse micelle.

Insect repellency of fiber is a property which makes the fiber to be of interest in the field of military and health. The insect-repellent substrate could be prepared using either functional finishing or applying an insect-repellent dye. In this article, insect-repellent nylon 6 is obtained using a novel insect-repellent reactive dye containing N,N-diethyl-m-toluamide. To do this, N,N-diethyl-m-toluamide (DEET) was first nitrated at the p-position relative to amide functionality. The nitrated product was reduced in the presence of C2H5OH, SnCl2, and HCl. The produced amine was then condensed with 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride) as a reactive group in below 5°C. The resultant adduct was finally reacted with an amino group present in 6-amino-1-hydroxy naphthalene-3-sulfonic acid (J-acid) to produce 7-(4-chloro-6-(4-(diethylcarbamoyl)-2-methylphenylamino)-1,3,5-triazin-2-ylamino)-4-hydroxynaphthalene-2-sulfonic acid. To synthesis azo dye, sulfanilic acid was diazotized using HCl and NaNO2 and then coupled to the above prepared component to produce insect-repellent reactive dye. An analog dye was prepared via the same route without insect-repellent group making stage. The chemical structures of the novel dyes were characterized using FTIR and 1H-NMR spectroscopy. The spectroscopic properties of the dyes were determined in terms of λmax and emax in aqueous solution. The novel dyes were then reacted with nylon 6 and bonded to it covalently to provide permanent insect-repellent substrate. The insect-repellent efficacy of the reacted nylon 6 was studied using standard methods for Anophele mosquito repellent. The insect-repellent dye reacted nylon 6 showed insect-repellent activity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Discharge printing provides a method of producing either a white or coloured image on a solid ground fabric; unfortunately, the shade range from this process is limited. An alternative approach to discharge printing is resist printing, which provides prints that are almost indistinguishable from those achieved by the discharge printing process and has the advantage of offering a wider shade range. In resist printing, the resist agent prevents fixation of the background colour by chemical (resist agent inhibits dye fixation) or physical (resist agent inhibits dye absorption) processes and so yields a white print. Printing is carried out on grounds that have been pad-dry ‘dyed’ with selected reactive dyes; the dyes must not fix during this process otherwise white grounds are not achievable – subsequently fixation is achieved by steaming after digitally printing the resist agent. In this paper, the resist agent studied is sodium sulphite, which selectively blocks reactive groups in reactive dyes – the ground shade reactive dye must be deactivated in this reaction to produce the resist effect. A coloured print may be achieved by incorporating a suitable reactive dye, of a different class to that used in the ground shade, which is not deactivated by the resist agent, in the resist ink.

Reported herein are the results of an analysis of the compatibility of three methods for quantifying the non-adsorbed forms of reactive dyes, in an exhausted dyebath, of the type monochlorotriazine/β-sulphatoethylsulphone used in dyeing cellulosic fibres (cotton). The first method is based on spectrophotometric analysis and involves measuring the absorbance of the residual dyebath (after the dyeing process), the second is based on colorimetric analysis and involves measuring the reflectance of the dyed fabric and the third is based on high-performance liquid chromatography. The purpose of the latter is to identify and quantify the non-adsorbed dye forms in the residual dyebath. The calculated exhaustion values unequivocally prove the reliability and compatibility of these methods.

This study investigates structural and adsorption properties of the powdered waste shells of Rapana gastropod and their use as a new cheap adsorbent to remove reactive dye Brilliant Red HE-3B from aqueous solutions under batch conditions. For the powder shells characterization, solubility tests in acidic solutions and X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform IR spectroscopy (FT-IR) and thermogravimetric analyses were performed. The results revealed that the adsorbent surface is heterogeneous consisting mainly from calcium carbonate layers (either calcite or aragonite) and a small amount of organic macromolecules (proteins and polysaccharides). The dye adsorptive potential of gastropod shells powder was evaluated as function of initial solution pH (1–5), adsorbent dose (6–40 g L−1), dye concentration (50–300 mg L−1), temperature (5–60°C), and contact time (0–24 h). It was observed that the maximum values of dye percentage removal were obtained at the initial pH of solution 1.2, shells dose of 40 g L−1, dye initial concentration of 50–50 mg L−1 and higher temperatures; the equilibrium time decreases with increasing of dye concentration. It is proved that the waste seashell powder can be used as low cost bioinorganic adsorbent for dyes removal from textile wastewaters.

Adsorption of reactive black 5 (RB5) from aqueous solution onto chitosan was investigated in a batch system. The effects of solution pH, initial dye concentration, and temperature were studied. Adsorption data obtained from different batch experiments were modeled using both pseudo first- and second-order kinetic equations. The equilibrium adsorption data were fitted to the Freundlich, Tempkin, and Langmuir isotherms over a dye concentration range of 45–100 µmol/L. The best results were achieved with the pseudo second-order kinetic and Langmuir isotherm equilibrium models, respectively. The equilibrium adsorption capacity (qe) was increased with increasing the initial dye concentration and solution temperature, and decreasing solution pH. The chitosan flakes for the adsorption of the dye was regenerated efficiently through the alkaline solution and was then reused for dye removal. The activation energy (Ea) of sorption kinetics was estimated to be 13.88 kJ/mol. Thermodynamic parameters such as changes in free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) were evaluated by applying the van't Hoff equation. The thermodynamics of reactive dye adsorption by chitosan indicates its spontaneous and endothermic nature.

The biosorption of reactive red 198 dye using Acalypha indica was investigated in a batch experimental process. The equilibrium dye uptake capacity of A. indica was determined with the influence of various environmental parameters such as sorbent dosage (0.02–0.1 g 100 mL−1), initial pH (1–6), and initial dye concentration (30–110 mg L−1). Batch experiments were carried out for biosorption kinetics and isotherm studies. The results showed that dye uptake capacity was found to increase with decreases in biosorbent dosage. Equilibrium uptake capacity was found to be more at pH value of 2, when compared with all other pH values studied. The equilibrium data was analyzed with the use of Freundlich and Langmuir adsorption isotherm models. The equilibrium data was found to be fitted very well with the Freundlich isotherm model when compared with the Langmuir isotherm model. The kinetic data was analyzed using pseudo-first order and pseudo-second order kinetic models. From the result, it was observed that the kinetic data was found to fit well with the pseudo-second order kinetic model. The surface morphology of the leaves of the A. indica biomass was exemplified by scanning electron microscope. Fourier transform infrared analysis was employed to confirm the existence of an amine group in the A. indica. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.

In this study, the effects of operational parameters such as initial pH, current density, electrolysis time, and initial dye concentrations on the decolorization of Reactive Yellow 135 (RY 135) solutions and the treatment of a textile wastewater by electrocoagulation (EC) with aluminum electrodes were investigated separately. Total organic carbon (TOC) and dye removal ratios were used to measure the treatment efficiency. Energy and electrode consumptions were calculated per m3 of dye solution and per kg of pollutant removed. Amount of sludge produced after EC was also reported per m3 of dye solution. For a complete technical analysis, chemical coagulation experiments with aluminum salts were also carried out. Different direct and indirect cost items including energy, sacrificial electrodes, labor, sludge handling and disposal, maintenance, and depreciation costs have been considered in the calculation of the total operating cost. Under the optimum parameters found in this study, 0.23 $/m3 of total operating cost was acquired with 81% of COD, 85% of TOC, 93.7% of turbidity, and 97.1% of TSS removal efficiencies in treatment of the textile wastewater with EC. 0.11 kWh/m3 of energy and 0.03 kg/m3 of aluminum were consumed while 0.15 kg/m3 of sludge were produced in the process. © 2011 American Institute of Chemical Engineers Environ Prog, 2011

The textile dyeing process requires the consumption of large quantities of water, which includes huge amounts of coloured wastewater. Usually the rinsing of dyed fabric and the treating of the dyeing house wastewater are separated. The two independent processes not only increase the difficulty of wastewater treatment but also increase the costs of the treatment. In this paper, the ozone/tetraacetylethylenediamine active oxidation technology was employed to rinse dyed fabric and to decolorise the rinsing wastewater simultaneously. The effects of the rinsing conditions on the decolorisation ratio and the chemical oxygen demand Cr value of treated wastewater, and the K/S value, colour difference, tensile strength and fastness of dyed samples were investigated. The results indicated that the decolorisation ratio of the rinsing effluent was greater than 80% and the chemical oxygen demand Cr value decreased more than 58% by the ozone/tetraacetylethylenediamine rinsing process compared with that of traditional rinsing processes. Furthermore, the curve of decolorisation kinetics was in good agreement with a pseudo-first-order kinetic model. In addition, the decolorisation mechanism was also discussed after ultraviolet–visible and ultra performance liquid chromatograph–mass spectrometry analyses of the degraded dye molecule.

In this research, the efficiency of electrocoagulation treatment process using aluminum electrodes to treat synthetic wastewater containing Reactive Red198 (RR198) was studied. The effects of parameters such as voltage, time of reaction, electrode connection mode, initial dye concentration, electrolyte concentration, and inter electrode distance on dye removal efficiency were investigated. In addition, electrical energy consumption, electrode consumption, and operating cost at optimum condition have been investigated. The results showed that dye and chemical oxygen demand removals were 98.6 and 84%, respectively. Electrode consumption, energy consumption and operating cost were 0.052 kg/m 3 , 1.303 kWh/m 3 and 0.256 US$/m 3 , respectively. Dye removal kinetic followed first order kinetics. It can be concluded that electrocoagulation process by aluminum electrode is very efficient and clean process for reactive dye removal from colored wastewater.

A novel blue cationic reactive dye (dye 1) based on an azo benzothiazole derivative and possessing an acrylamido reactive group, was synthesised and evaluated on dyeing Coloursafe modified nylon 6.6 at optimum pH. Benzothiazole quaternary dye was chosen as a target as this is known to be very strong chromophically. Evaluation of the technical properties of dye 1 showed that it fixed efficiently to nylon under acidic dyeing conditions. As it was necessary to prove that fixation occurs via a covalent bond, the dyeing properties of a non-reactive cationic dye, (CI Basic Blue 41), on dyeing nylon 6.6 at optimum pH were evaluated. CI Basic Blue 41 was similar in structure to dye 1 and would be capable of forming an ion–ion bond with the fibre. Evaluation of the technical properties of dye 1 proved that, in all cases, its fixation efficiency and build-up properties were far better than that of CI Basic Blue 41.

BACKGROUND: A filamentous fungus Neurospora sitophila was immobilized in Zea mays silk tissue and the prepared system was employed as a new biosorbent for the treatment of reactive dye contaminated solutions. RESULTS: Decolorization potential of the biosorbent system was investigated in batch and continuous mode operations. Design parameters such as pH, biomass dosage, contact time, temperature, dye concentration and flow rate were investigated. Batch mode equilibrium data were analyzed kinetically to determine the rate constants. The process followed the pseudo-second-order kinetic model. The thermodynamics of the biosorption indicated the spontaneous and endothermic nature of the process. Biosorption was well described by the Langmuir isotherm model, with a maximum monolayer biosorption capacity of 105.33 mg g−1. Relatively good dynamic flow decolorization potential was observed for the biosorbent system in synthetic and real wastewater conditions. Flow mode regeneration studies over ten consecutive cycles indicated that the suggested biosorbent maintained consistently high biosorption yield, above 70%. The possible dye-biosorbent interaction mechanism was also confirmed by zeta potential, FTIR, SEM and EDX analysis. CONCLUSION: High biosorption capacity and regeneration potential suggest that the new biosorbent system can be used as an alternative and low-cost biomaterial for the treatment of reactive dye contaminated solutions. Copyright © 2011 Society of Chemical Industry

Laccase (benzenediol, oxidoreducase; Enzyme Commission Number) is a multi-copper oxidase from biomass. Laccase enzyme recycling on molecular oxygen as an electron acceptor can be applied for the decolorisation of synthetic dyes. The decolorisation of 49 commercial reactive dyes using laccase was investigated. The effects of diverse structure surfactants on decolorisation are discussed. The absorption spectra of reactive dyes after a laccase biodegradable reaction were analysed. Reactive dyes based on anthraquinone and azo structures could be decolorised using the enzyme and their chemical structures broken. Reactive dyes based on an anthraquinone structure were easier to decolorise than those based on an azo structure. Surfactants could affect the decolorisation of dyes with an enzyme. The effect of nonionic surfactant on the decolorisation of anthraquinone dyes was the reverse. The cationic surfactant could improve the decolorisation rate of diazo dye. The effect of the anionic surfactant on dye decolorisation was small. Most commercial reactive dyes could be decolorised and biodegraded using a laccase enzyme under mild conditions. Laccase enzyme biotechnology has potential applications in the decolorisation of reactive dye wastewater.