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Microcrystalline α-ZnMoO4 catalyst for degradation of Reactive Black 5 by self-made open air atmospheric pressure pulsating corona plasma reactor was synthesized by electrodeposition, followed by thermal treatment. The effect of electrodeposition current density on the catalyst’ characteristics was examined by SEM, EDX, FTIR XRD and TG. The catalyst enhanced plasma decolourization rate by 7.5 times. The role of the catalyst in the consumption of plasma generated H2O2 and in dye degradation was examined in details for the first time to the best of our knowledge; the catalyst enhanced the generation of ⋅OH radical, a principle dye degradation reagent, by enhancing decomposition of plasma–generated H2O2. The catalyst’ excitation mostly proceeded by the strikes of plasma–generated active species accelerated by electric field, which transferred their energy to the catalyst, causing the creation of electron – holes pairs which attacked H2O2. Decolourization followed pseudo – first order kinetics. Decolourization rate increases with the increase of discharge current density and reactor input voltage. The ratio between cylindrical reactor cell’s diameter and the liquid level in it didn’t affect the decolourization rate. Relatively high energy yield of 1.86 gkWh−1 was achieved for 50% decolourization. TOC removal was 85.4% after 180 min of the treatment.

The present chapter briefly outlines some basic information about cellulosic fibers, history and chemistry of reactive dye development, different types of reactive dyes, method of application, ecological aspects of reactive dyes, unconventional dyeing methods for reactive dyes, sustainability challenges in the reactive dyes, current technologies for improvement of sustainability of reactive dyes, and feasibilities for improvement. Reactive dyes are a major class of dyestuffs used for the dyeing of cellulosic materials such as cotton and viscose. As the name implies, these dyes have the tendency to chemically react with hydroxyl group of cellulosic materials and form covalent bond, thereby producing good fastness properties to the dyed materials. These dyes produce brilliant colors with reasonable fastness properties, and for that reason they are the most preferred dye for dyeing of cellulosic materials. Cellulosic fiber-based clothing materials are expected to gain further importance due to the ocean plastic problem due to the release of nonbiodegradable microfibers released from synthetic fibers such as polyester and acrylic. Reactive dyes constitute more than 80% of the dyes that are used for dyeing cellulosic materials. Considering the sustainability of reactive dyeing of cellulosics, there are major issues such as requirement of huge amount of salt and alkali for exhaustion and fixation, formation of hydrolyzed dye during dyeing, and poor wet rubbing fastness. These issues lead to high dyeing cost coupled with higher effluent load during dyeing with increased treatment cost. The present chapter outlines the abovementioned challenges in the reactive dyeing of cellulosics and elucidates practical solutions to overcome them.

Herein we report the development of easily separable, Fe3O4 loaded chitin nanomaterial (MCH NM) via simple Co-precipitation route, as a promising adsorbent for removal of Reactive Blue 13 (RB13) dye from aqueous solution in visible light (λ ≥ 420 nm). This nanomaterial was characterized using distinctive physicochemical techniques; MCH NM show band gap energy of 2.257 eV, evaluated by Tauc's plot using UV–visible spectroscopy. MCH NM show excellent swelling property due to the tendency of the polymer chains to reach elongated configurations at equilibrium beyond which an elastic retractive force prevents further expansion. The mechanism of dye-adsorbent interaction is described on the basis of zero-point charge and zeta potential techniques. Batch adsorption studies on MCH NM show excellent adsorption activity of 199.02 mg/g in 22 min towards RB13 dye, maximum value ever reported for any reactive dye. Equilibrium adsorption data and adsorption kinetics were well fitted into Langmuir isotherm model and pseudo second order model predicting chemically rate controlled monolayer adsorption. Thermodynamic studies demonstrate that the adsorption process is spontaneous and exothermic.

Textile dyeing is a hazardous and toxic process. While traditionally it has been managed through effluent treatment, new approaches focused upon improving the dyeing process are gaining relevance. In this work, we sought to obtain, for the first time, an eco-friendly chitosan-nanoparticle based textile dyeing method. To that end, yellow everzol and navy blue itosperse loaded chitosan nanoparticles were produced and their capacity to dye textiles and cytotoxicity towards human skin cells were evaluated. The results obtained showed that it was possible to obtain nanoencapsulated dyes through ionic gelation with an average entrapment efficacy above 90 %. Nanoparticles presented a positive surface charge and sizes between 190 and 800 nm with yellow everzol NPs occurring via ionic interactions while navy blue itosperse NPs were formed through hydrogen bonds. Furthermore, the produced dye NPs presented no cytotoxicity towards HaCat cells and presented staining percentages reaching 17.60 % for a viscose/wool blend.

An analysis is provided of the various models that have been proposed to account for the manner by which added NaCl or Na2SO4 promotes the uptake of reactive on cellulosic fibres. Although conventionally, mathematical interpretations of isothermal equilibrium dye adsorption data are employed to describe the mechanism by which reactive dye adsorption occurs, such an approach does not satisfactorily explain why reactive dyes display inherently low uptake on cellulosic fibres in the absence of added inorganic electrolyte, nor does it explain why added inorganic electrolyte is so effective in promoting dye uptake.

The colour strength of 2% omf dyeings, as well as the extents of both exhaustion and fixation, achieved for three commercial grade reactive dyes on cotton, were promoted by the addition of 50 gl-1 NaCl at each of seven liquor ratios (1:50, 1:20, 1:10, 1:6, 1:3, 1:2 and 1:1.5). The depth of shade of dyeings obtained in the absence of added electrolyte using a 1:1.5 liquor ratio were of similar magnitude to those secured using a 1:10 liquor ratio in the presence of 50 gl-1 NaCl. The promotion of dye uptake imparted by both added electrolyte and reduced liquor ratio was interpreted in terms of their effects on the substantivity of the reactive dyes towards the cotton substrate. It was concluded that the two, ostensibly different actions of adding electrolyte such as NaCl or Na2SO4 to a reactive dye dyebath and reducing the liquor ratio used for dyeing have the same result, namely that of promoting dye aggregation in the dyebath which reduces the aqueous solubility of the anionic dye, which, in turn, results in the inherent preference of the dye to favour the aqueous phase shifting towards the fibre phase. The results show that it is possible to dye cotton using commercial grade reactive dyes in the complete (ie 100%) absence of added inorganic electrolyte. The dyeings obtained were of realistic depths of shade and displayed excellent levels of wash fastness.

The biosorbent was obtained from municipal solid waste (MSW) of the Mostaganem city. Before use the MSW was dried in air for three days and washed several times. The sorption of yellow procion reactive dye MX-3R onto biomass from aqueous solution was investigated as function of pH, contact time and temperature. The adsorption capacity of MX-3R was 45.84 mg/g at pH 2–3 and room temperature. MX-3R adsorption decreases with increasing temperature. The Langmuir, Freundlich and Langmuir–Freundlich adsorption models were applied to describe the related isotherms. Langmuir–Freundlich equation has shown the best fitting with the experimental data. The pseudo first-order, pseudo second-order and intra-particle diffusion kinetic models were used to describe the kinetic sorption. The results clearly showed that the adsorption of MX-3R onto biosorbent followed the pseudo second-order model. The enthalpy (Δ H° ), entropy (Δ S° ) and Gibbs free energy (Δ G° ) changes of adsorption were calculated. The results indicated that the adsorption of MX-3R occurs spontaneously as an exothermic process.

Textile dyeing processes are among the most environmentally unfriendly industrial processes because they produce colored wastewaters that are heavily polluted with synthetic dyes. The investigation presented here focuses on the steel industrial wastewater (SIWW) FeCl3 rich as an original coagulant to remove the synthetic textile wastewater. The effects of relevant parameters—namely; coagulant dosage, initial pH of reactive dye solutions, and dye concentration—have been investigated with regard to decolorization and COD reduction by using response surface methodology (RSM). These experiments were carried out as a central composite design (CCD) consisting of 16 experiments determined by the 23 full factorial designs with six axial points and two center points. A model has been obtained for decolorization, COD reduction, and relevant parameters by means of variance analysis and the model obtained was optimized. The efficiencies of decolorization and COD reduction for Reactive Orange 16 were accomplished under optimum conditions as 98% and 90%, respectively.

The present study reports the results of the ultrafiltration with a ceramic membrane of model solutions containing NaCl and a reactive dye, which simulate textile wastewaters. The effect of salt concentration (1, 2.5 and 4 g/L NaCl) and transmembrane pressure (1, 2, and 3 bar) on the evolution over time of both permeate flux and solutes rejection was tested. Membrane fouling was also investigated in terms of analysis of resistances-in-series, determining the contribution of both reversible and irreversible fouling under any condition tested. More severe flux decline and a slight reduction in color rejection were observed under higher pressure. Furthermore, it was demonstrated that the membrane performance was significantly worsened in the presence of salt, according to permeate flux, dye rejection and the values of the different resistances. Higher flux decline and total resistance together with lower color removal were observed when adding NaCl to the solution. These results were attributed to membrane charge and repulsion-attraction phenomena. It was then suggested that electrostatic interactions between the solutes and the membrane materials have an important role in the ultrafiltration performance, as well as influencing the kind of fouling affecting the membrane., This research was financially supported by the Spanish Ministerio de Ciencia e Innovacion (MICINN) through the Project ref. CTM2009-13048. The authors of this work would also thank the Spanish Ministerio de Educacion for the award of a F.P.U. grant (Ref. AP2009-3509).

The electrochemical treatment of wastewaters from textile industry is a promising technique for substances which are resistant to biodegradation. This paper deals with the electrochemical decolourisation/degradation of synthetic solutions containing a reactive dye, C.I. Reactive Orange 4. Oxidation, reduction and oxido-reduction processes were evaluated using Ti/SnO 2-Sb-Pt and stainless steel electrodes as anode and cathode, respectively. Electrolyses were performed at galvanostatic conditions in a filter press reactor. Decolourisation and degradation were followed by means of total organic carbon (TOC), chemical oxygen demand (COD) measurements and high performance liquid chromatography (HPLC). A higher mineralisation rate for oxidation was found whilst oxido-reduction process gave more oxidised species. The kinetics of decolourisation was of pseudo-first order in all cases. The reduction process was the slowest process to decolourise. Gas chromatography-mass spectrometry (GC-MS) was employed to investigate the main intermediate compounds, confirming the presence of 2-amino-1, 5-naphthalenedisulphonic acid (2A15NDS) in solution. When this compound was generated, it was gradually degraded during the oxidation and oxido-reduction processes indicating the feasibility and durability of Ti/SnO 2-Sb-Pt electrodes. However, during the electrochemical reduction process, this compound was continuously generated but it was not degraded. © 2011 Elsevier B.V., The authors would like to acknowledge the Spanish Ministry of Science and Innovation (MICINN) and European Union (FEDER funds) for the financial support (CTM2007-66570-C02-02 and CTM2010-18842-C02-02). A. I. del Rio thanks the Spanish Ministry of Science and Innovation (MICINN) for her F.P.I. grant awarding. J. Molina is grateful to the Conselleria d'Educacio (Generalitat Valenciana) for his FPI grant awarding.

[EN] Textile wastewaters are characterized by high organic matter concentration and colour presence. Conventional treatments do not remove completely the colour since the aerobic bacteria cannot degrade the azo-bond of the reactive dyes. However, their elimination is a requirement for wastewater reuse. In this study, it is proposed the reuse of textile wastewater as process water by a hybrid process combining a sequencing batch reactor (SBR) process with nanofiltration (NF) membranes. The aim is to evaluate the colour removal yield in the SBR and to study the influence of the addition of NF retentate on the SBR feed. The laboratory SBR was operated in cycles of 20h and was fed with a solution containing a mixture of three reactive dyes: Remazol Yellow RR, Remazol Blue RR and Remazol Red RR. Every day colour and COD removal efficiencies were determined. The NF retentate was stored in order to mix it with the synthetic wastewater for the SBR feed. Colour removal yield ranged from 85 to 90% for the red and blue dyes and from 70 to 75% for the yellow one when the SBR feed was only the textile synthetic wastewater. However, when the SBR feed was the mixture of 50% synthetic wastewater and 50% of NF rejection the colour removal efficiency was reduced between 10 and 15%., This work was supported by Generalitat Valenciana - Conselleria de Empresa, Universidad y Ciencia (Ref. GV06/393).

Recycling and reuse of wastewater after purification will reduce the environmental pollution as well as fulfill the increasing demand of water. Adsorption-based water treatment process is very popular for dye-house wastewater treatment. The present study deals with treatment of wastewater contaminated by reactive dye. TiO2 is used as adsorbent and the spent adsorbent has been regenerated by Advanced Oxidation Process (AOP), without using any other chemicals. TiO2 adsorbs dye molecules and then those dye molecules have been oxidized via a photocatalytic reaction in presence of UV irradiation. Kinetics of dye adsorption and photocatalytic oxidation reaction has been developed in this study. Photocatalyst adsorbent (TiO2) has been reused several times after regeneration. The activity of catalyst decreases after each cycle; due to poisoning cause by intermediate by-products. Kinetic of this catalyst deactivation has been incorporated with L–H model to develop the photocatalytic reaction kinetic model.

The possibility to use cotton as a matrix for controlled release systems was studied by covalently attaching a model compound, specifically the reactive dye Remazol Brilliant Blue R to its surface. Afterwards the fabric was coated with a commercial cellulase. The release of the dye, obtained by the hydrolysis of cotton fibres in sweat buffer, was monitored. The reducing sugars concentration increased for both fabrics (with and without the dye covalently fixed) while the increase in the absorbance was only attained for the dyed cotton, as expected. These results confirm the viability of using cotton as a natural matrix for controlled released systems while presenting a promising approach to immobilize covalently other substances in cotton garments, like fragrances, which could be released by the action of human sweat.

The use of dynamic membranes formed in situ by deposition of a colloidal suspension on a porous support as a pretreatment of membranes is an attractive method to reducing irreversible membrane fouling. A polyethersulfone, PVDF, membrane with a neutral load, hydrophilic character and a cut-off of 30,000 Dalton was studied after treatment with hydrophilic polymers, such as polyetylenoglycol and polyvinyl alcohol. The selectivity and permeability of the membrane without treatment and of the dynamic membranes formed with hydrophilic polymers were measured with a solution of a reactive dye, Black Remazol B, at different pH values. Simultaneously, fouling of the membrane was controlled. It was observed that for identical conditions permeate flux is higher with membranes treated with solutions of hydrophilic polymer and irreversible fouling decreased with the treatment of the membranes.

A two stage sequential Fenton's oxidation followed by aerobic biological treatment train was used to achieve decolorization and to enhance mineralization of azo dyes, viz. Reactive Black 5 (RB5), Reactive Blue 13 (RB13), and Acid Orange 7 (AO7). In the first stage, Fenton's oxidation process was used while in the second stage aerobic sequential batch reactors (SBRs) were used as biological process. Study was done to evaluate effect of pH on Fenton's oxidation process. Results reveal that pH 3 was optimum pH for achieving decolorization and dearomatization of dyes by Fenton's process. Degradation of dye was assessed by COD reduction and reduction in aromatic amines (naphthalene chromophores) which was measured by reduction in absorbance at 200 nm. More than 95% of color was removed with Fenton's oxidation process in all dyes. In overall treatment train 81.95, 85.57, and 77.83% of COD reduction was achieved in RB5, RB13, and AO7 dyes, respectively. In the Fenton's oxidation process 56, 24.5, and 80% reduction in naphthalene group was observed in RB5, RB13, and AO7, respectively, which further increased to 81.34, 68.73, and 92% after aerobic treatment. Fenton's oxidation process followed by aerobic SBRs treatment sequence seems to be viable method for achieving significant degradation of azo dye., © Elsevier

The commercial azo dye C.I. Reactive Orange 4 in its reactive and hydrolysed forms can be efficiently photodegraded, using commercial samples of TiO2 as a photocatalyst. With UV light, aqueous solutions containing only dye and no dyebath additives are decolorised slightly more rapidly with Riedel-de-Häen TiO2 than with Degussa P-25 TiO2 . The rate of decolorisation increases markedly with increasing pH. Sunlight is also very effective as a light source. On the other hand, comparison experiments involving UV irradiation of hydrolysed and unhydrolysed Reactive Orange 4 in a simulated spent dyebath showed Degussa P-25 TiO2 to be significantly the more efficient catalyst, giving more than 90% decolorisation after 20 minutes., PRAXIS XXI/2/2.1/44/94. FEDER.

Advanced oxidation processes (AOPs) for the treatment of model wastewater containing organic dye were investigated. C.I. Reactive Red 45 (RR45) was chosen as a representative of the azo type of dyes that cover more than half of the dyes available commercially, as well as a representative of the monochlorotriazine group of reactive dyes, consumption of which is continuously growing worldwide. The aim of the present paper is comparative evaluation of the efficiency and feasibility of applying high voltage pulsed electrical discharge (Corona), as well as Fenton and Peroxone processes to the destructive treatment of RR45. The effect of HY, NaY and Naβ zeolite on decolorization and degradation in those processes is discussed.

WOS: 000223160200017 Poly(hydroxyethyl methacrylate), pHEMA, and a composite pHEMA/chitosan networks were synthesized in the membrane form via UV initiated photo-polymerisation in the presence of an initiator alpha,alpha'-azoisobutyronitrile. Reactive Yellow 2 (RY-2) was covalently immobilised as a dye-ligand onto both membranes. The polarity and surface energy of the investigated membranes were determined by contact angle measurement. The incorporation of chitosan in the pHEMA networks produced more hydrophilic surface, as indicated by contact angle analysis. The binding characteristics of lysozyme, gamma-globulins, human serum albumin (HSA) and bovine serum albumin (BSA) to pHEMA-RY-2 and pHEMA/chitosan-RY-2 affinity membranes have been investigated from aqueous solution and their dye-ligand free forms were used as control systems. When chitosan was incorporated in the pHEMA network as a cationic polymer led to higher adsorption capacity for the lysozyme. Selective adsorption behaviour was also observed in the case of pHEMA/chitosan-RY-2 membrane for the lysozyme. The non-specific adsorptions of the lysozyme on the pHEMA and pHEMA/chitosan membranes were about 1.9 and 7.2 mg/ml, respectively. These were negligible for all others investigated proteins. The lysozyme adsorption data was analysed using the first-order and the second-order models. The first-order equation in both affinity membrane systems is the most appropriate equation to predict the adsorption capacities of the adsorbents. The adsorption isotherms well fitted the combined Langmuir-Freundlich model. A theoretical analysis has been conducted to estimate the thermodynamic contributions (changes in enthalpy, entropy and Gibbs free energy) for the adsorption of lysozyme to both dye-ligand immobilised membranes. The adsorption capacities of both dye-ligand immobilised membranes increased with increasing the temperature while decreased with increasing the NaCl concentration. Both affinity membranes are stable when subjected to sanitization with sodium hydroxide after repeated separation-elution cycles. (C) 2004 Elsevier B.V. All rights reserved.

Al-Cu pillared clays were prepared by direct introduction of Al-Cu pillaring solution into the dilute bentonite suspension. Al-Cu pillared clays had d001 spacing of about 18 and had surface area of about 140m2/g or higher. Al-Cu pillared clays showed excellent activity toward the catalytic wet peroxide oxidation of reactive dyes. Complete removal of reactive dyes could be achieved within 20min at atmospheric pressure and 80°C which are extremely milder operation condition when compared with the conventional catalytic wet oxidation process. The pillared clays were also stable against the leaching out of Cu.

Dyes containing a carboxylic acid group had been shown to react with wool and polyamide fibres when activated with ethyl chloroformate (Parts I and II). One of the dyes, 3-aminobenzoic acid →N,N-dimethylaniline, was, in this work, activated with other chlorofirmates, so as to improve the dyeing conditions. Benzyl chloroformate was found to be a good substitute since it is not as volatile as ethyl chloroformate, which suggests that it will be easier to apply in practical dyeing conditions. The yield of the reaction with cyclohexylamine is similar to the one obtained with ethyl chloroformate, suggesting that the fixation of the dye on wool or polyamide will be much the same. The fastness results are also equivalent., FCT-Fundação para a Ciência e Tecnologia

Recent developments in biotechnology have given positive indications that biosorption, whereby biomaterials in their native or modified states, may be used as alternatives to conventional adsorbent media. This paper investigates one such alternative, i.e., of using fungal biomass as an adsorbent medium. Specifically this work concentrates on the capacity of certain biomass types to remove synthetic dye and metal ions from aqueous solution. Various biomass types were screened with the filamentous fungus Rhizopus oryzae 26668 proving to be the most effective biosorbent. The dye used was the reactive dye Levadix® Brilliant Red E-4B A. The metal ions used were copper and cadmium. The dye and metal ions were adsorbed singly from solution onto granulated dried biomass. The biosorptive behaviour was analysed using the Freundlich and Langmuir Isotherm models. It was found that both of the models fitted the biosorption well suggesting adsorption by a hybrid mechanism onto a heterogeneous surface. Modification of the biosorptive performance by the application of various pre-treatments was also assessed. It was found that autoclaving the biomass, reacting it with 0.1 M NaOH, a chitin enrichment process, and saturation with Ca2+ ions all enhanced the biosorptive performance of Rhizopus oryzae 26668. Other work carried out in support of these findings included porosity measurement, surface area and infra-red analysis, and scanning electron microscopy. IR analysis of the biosorbent suggests that biosorption is by means of a physical adsorption. Porosity and surface area measurement suggest that autoclaving increases surface and monolayer volume, these findings support the increased dye uptake shown by the autoclaved biomass. The treatment with NaOH increases the biosorptive capacity by exposing the chitin/chitosan complex of the fungal cell wall. Scanning electron micrographs are also presented which show the surface of the biomass to have an open porous and heterogeneous structure.

A strategy is outlined for the removal of reactive dye colour from textile wastewaters using bacteria, capable of dye degradation, attached to environmentally-acceptable cellulose copolymeric supports. A mixed population of bacteria have been isolated from dyehouse effluent and tested on ten different reactive azo dyes. All of the tests resulted in the removal of the original colour and the production of unidentified, colourless or differently coloured, species within the time-scale provided. Immobilisation of these bacterial colonies onto characterised cellulosic supports, as a route to enhance their dye degrading activity, is described.

Summary The effects of dyeing on the porosity of samples of charcoal cloth and cotton fabric have been examined from nitrogen adsorption isotherms. So too has the effect on the cotton fabric of mercerisation, a treatment which causes dimensional changes to the constituent fibres. On application from 1% sodium chloride solution, increased contents of dye in the charcoal cloth progressively block the micropores and reduce mesopore area; but treatment with sodium chloride solution alone increases microporosity. Mercerisation of the cotton fabric enhances the mesoporous nature of the surface. The effect on porosity of treatment with a reactive dye is less clear-cut; it is tentatively suggested that application of the dye narrows the mesopores.

Publisher Summary A reactive textile dye in solution can function as a competitive inhibitor for the substrate, coenzyme, or effector of a variety of proteins, often with an affinity greater than that exhibited by the competitive molecule. Both free and immobilized reactive dyes are available individually and as kits from a variety of suppliers at modest cost. The chemical structure of reactive dyes facilitates their rapid covalent coupling with porous matrices without recourse to prior chemistry, activation reagents, or spacer arms. The screening procedure can be completed rather expeditiously, requiring only a small amount of a crude protein extract, a general assay for protein such as the Lowry or Bradford colorimetric procedure, a specific assay for the protein of interest, and a supply of free or immobilized reactive dyes. The simplest screening procedure involves purchase of a kit of immobilized dyes currently available from at least two suppliers, Amicon and Sigma. Optimal conditions for elution of the desired protein from the positive immobilized dye should now be screened. Each screening should begin by application of sufficient crude extract to the positive immobilized dye to not to overload the column while supplying sufficient desired protein to facilitate reliable quantitative measurement upon its elution.