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Tight ceramic ultrafiltration membranes have been proven to exhibit good rejection performance for reactive dye wastewater at high temperatures because of their high thermal and chemical resistance. However, the application of ceramic membranes for the treatment of cationic dye wastewater is challenging because of their surface charge. In this study, a ceramic membrane is modified by grafting aminosilane (KH-551) to enhance the positive charge of the membrane surface. The rejection performance of the charged modified ceramic membrane toward the methylene blue solution is significantly improved. The modification substance is bonded to the ceramic membrane surface via covalent bonding, which imparts good thermal stability. The modified ceramic membrane exhibits stable separation performance toward the methylene blue solution. Overall, this study provides valuable guidance for the adjustment of the ceramic membrane surface charge for treating industrial cationic dye wastewater.

Manufactured synthetic substances have been generally utilized as dyes by the material enterprises. Since a lot of various dyes are utilized by material ventures, wastewater released out of them represents a danger to the environmental factors. These dyes go into the encompassing water bodies as hued wastewater, except if debased appropriately. Miniature creatures can change over shaded colors to non-hued fluid under characterized natural conditions. In this examination, degrading dye capacity for blended consortia (Bacterial and parasitic) of Pseudomonas putida and Phanerocheate chrysosporium is read for manufactured color Reactive Red 198. Results show that blended consortia of Pseudomonas putida and Phanerocheate chrysosporium has a proficiency of 91% in decolorization and 87% in COD evacuation inside 3 days of dynamic condition.

This study analyzed the influence of operational conditions on the Direct Contact Membrane Distillation for synthetic effluents containing reactive and disperse dyes. Results of the permeate flux demonstrated different behavior of the process according to the class of dye. It was found a higher dependence of feed temperature to reactive dye and the analysis of temperature gradient between feed and permeate demonstrated the possibility of operation with higher temperatures in both streams to increase the permeate flux for both dyes. Feed flow rate influenced more the process with reactive dye, while the permeate flow rate determined this behavior for disperse dye. Energy factors showed that the gain output rate and energy efficiency enhanced with the increase of feed temperature, and the energy efficiency increased only with the permeate flow rate (and not with feed flow rate). The water distillation recovery rate was 97.3 % for reactive and 98.7 % for disperse dye; the color rejection of the dyes was over 98 %. These results indicated the adequate functionality of the process for water recovery of textile wastewater, providing an adequate permeate for possible reuse.

Reactive dyes have been identified to be highly hazardous pollutants because they were shown to be more toxic towards mammals than general organic compounds and organic dyes. Accordingly, for the first time, meso-architectured mercapto-modified siliceous hollow quasi-capsules (SH-SHQC) were prepared by a facile, ultrasonic-assisted, and one-step synthesis protocol. Adsorptive removal of rhodamine B (RhB) and methylene blue (MB) onto SH-SHQC in a batch system has been investigated. Isotherm results agreed very well with the Langmuir equation for both dyes. The maximum adsorption capacity of SH-SHQC for RhB and MB was determined with the Langmuir equation and was found to be 147.06 and 119.05 mg g−1 at 298 K, respectively (pH: 6.0 for RhB and 7.0 for MB; adsorbent dosage: 15.0 mg; the volume of the dye solution: 40.0 mL). Among different kinetic models, the pseudo-first-order equation was better fitted since experimental data agreed very well with theoretical data. SH-SHQC was shown to be a promising adsorbent for adsorptive removal of reactive dyes from aqueous solutions. To date, there has been no report on the adsorption of reactive dye cations by meso-architectured mercapto-modified siliceous hollow quasi-capsules prepared by an ultrasonic-assisted, one-pot, and sol-gel synthesis method.

One of the main drawbacks of heterogeneous photocatalysis is the high consumption of electrical energy generated by conventional lamps. This study proposes a methodology to find the best distribution of light emitting diodes (LEDs), i.e., the least amount of elements, and the optimum distance between them in order to substitute conventional lamps in photocatalytic processes, and a performance analysis in terms of energetic efficiency, using for this the Electric energy per order (EEO) Figure-of-merit and the cost results for the degradation of the textile reactive dye Orange PX-2R by means of UV/TiO2 process, using conventional lamps and different geometrical patterns of LED arrays. The obtained experimental results show that it is possible to replace sources of high-energy consumption by UV-LED arrays adapted to the specific needs for a given photocatalytic reactor obtaining suitable oxidation results, and the rate of decolorization obtained is similar to the results obtained with conventional lamps; however the UV-LEDs require 70% less electrical energy (178 vs 628 kWh/m3/order) than UV-lamps. Consequently, the use of UV-LEDs enables to degrade 3.5 times more dye with the current energy consumption of UV lamps. Finally, the proper choice for an array can generate additional energy savings.

In this study, the copper nanoparticles (Cu NPs) reactivity for degradation of the reactive dye black 5 (RP5), picric acid (PA) and 2,4-D herbicide was evaluated. The RP5 degradation occurred by oxidative via, through hydroxyl radicals generated in situ, with active participation of Cu(I) and H2O2. The use of catalase confirmed the hydrogen peroxide formation in situ. Reduction degradation via electron transfer was also possible. On the other hand, PA had low degradation efficiency (less than 20%) under any conditions studied (similar to those used for RP5). High degradation efficiency for 2,4-D was achieved by the association of the Cu NPs/H2O2. Thus, the behavioral model of Cu NPs has been proven. This behavioral difference of the chemical species to be degraded in relation to the behavior of the Cu NPs was studied, evaluating its redox behavior by voltammetric analyzes. This study aided in the understanding and selection of the chemical species that can be degraded by these NPs.

High chemical oxygen demand (COD) and a strong color, which primarily originates from desizing and dyeing operations, are two major removal objectives in textile wastewater treatment. In this study, crosslinking-induced precipitation via the covalent bonding between –OH groups of PVA and vinyl sulfone groups of reactive dyes is proposed to simultaneously remove poly(vinyl alcohol) (PVA) and reactive dyes. Due to the nucleophilic addition reaction under an alkaline condition, PVA polymers can be efficiently crosslinked by dye molecules and destabilized in the presence of alkali and Na2SO4. Additionally, due to the high coagulation efficiency under the alkaline conditions, MgSO4 was used as a coagulant to facilitate the removal of the residual color after precipitation. After a two-step process, whereby coagulation was followed by crosslinking-induced precipitation, the maximum efficiencies of the removal of COD, PVA, and color attained 88.9%, 86.3%, and 99.2%, respectively, when the PVA monomer/RB5 mole ratio was 400. We hope that this technically feasible, highly efficient, and cost-effective process provides a basis for the practical application of the simultaneous treatment of desizing and dyeing wastewater.

This study presents a new approach to enhance reactive dye uptake and functional finishing of wool yarns via simple grafting with synthesized chitosan-acrylamide (Ch-Ac) hybrid. To this, Ch-Ac was synthesized and characterized with fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. Then, Ch-Ac was grafted on wool, characterized with FTIR, SEM, and weight gain analysis and dyeability with two commercial reactive dyes. Results showed that Ch-Ac treated wool could be dyed at lower temperatures (ca. 40 °C), times (ca. 30 min), and amount of reactive dye (2% owf) as compared to raw wool. Also, deeper shades not obtainable in conventional dyeing could be attained using Ch-Ac treated wool. In addition, Ch-Ac treatment imparted very good radical scavenging and excellent antibacterial activity against gram-negative (E. coli) and gram-positive (S. aureus) bacteria. Color fastness results confirmed that Ch-Ac treatment had no adverse effect on durability of dyes against washing, light, rubbing and perspiration. The results of this study clearly indicated that Ch-Ac can be used in eco-friendly functional finishing of wool with enhanced reactive dye uptake, minimized residual dye in wastewater, saving in consumption of chemicals, energy, and time of dyeing.

In this work, a new method for facile synthesis of covalently colored polyurethane latex was developed. A series of blue dye monomers were synthesized via one-step reaction of a reactive dye and amino compounds, and then employed as chain extenders to react with polyurethane prepolymer in the emulsification process to prepare the covalently colored polyurethane latexes. The chemical structures and the properties of dye monomers and the corresponding polymers were investigated, and the UV–Vis spectra of covalently colored polyurethane featured fairly consistent with dye monomers with maximum absorption wavelength at 620 nm and 580 nm, since the chemical structure of chromophore maintained unchanged. The conversion of dye monomer reached more than 92% with 1.0 wt% dye content, whereas the conversion decreased with the increase of the dye amount and the adding time. Compared with the noncovalently latex film, the light fastness of the covalently colored latex film was greatly promoted due to the chemical bonding of chromophores with polymer matrix.

Synthesized iron-nickel (Fe–Ni) bimetallic nanoparticles (NPs) were utilized for the colour removal of C. I. Reactive Blue 21 (RB21) dye. NPs agglomeration was prevented using polyvinyl pyrrolidone (PVP) as a capping agent. The NPs were characterized by nanoparticle size analysis, TEM , XRD and EDX. The operational conditions like pH, NPs concentration and initial dye concentration for decolourization were optimized using mathematical modelling, and its kinetics were studied. Influence of the presence of alkali and salt on dye decolourization was also investigated. Decolourization products were analysed by using FTIR and GCMS analysis. 93.46% of dye decolourization was obtained and a reduction in COD, BOD values was achieved along with minimal sludge generation.

A model is proposed to explain the manner by which the uptake of reactive dyes on cellulosic fibres is promoted by the addition of NaCl or Na2SO4 to the dyebath. The theoretical model invokes the concept of interstitial water in dyeing and suggest that increased dye uptake occurs because the added inorganic electrolyte promotes dye aggregation which reduces the solubility of the dye in the dyebath, so that the inherent preference of the highly soluble dye to favour the aqueous phase shifts towards the fibre phase. It is proposed that the same model can account for the promotion of direct dye uptake imparted by the reduction in the liquor ratio utilised for dyeing. As such, added inorganic electrolyte and reduced liquor ratio are considered to exert a combinatorial promotional effect on reactive dye uptake.

Reverse micelles using nonionic poly(ethyleneglycol) (PEG)-based surfactant as building block were introduced to encapsulate reactive dye for cotton dyeing. The morphological transition of reactive dyes from well-dispersive spherical form into highly agglomerated form via various surfactant-to-co-surfactant molar ratios and surfactant-to-water molar ratios have been preliminary investigated. The dyeing properties of cotton has been analyzed in terms of dispersion of reverse micelle structure from transmission electron microscopy, identification of chemical signatures of dye-cotton interaction from Raman spectroscopy, color strength and relative levelness. The reverse micellar structures under both highly dispersed and agglomerated forms are in good agreement with color strength and levelness data. The optimization of surfactant conditions can be considered as major parameters for investigating the quality of cotton dyeing including color strength and levelling conditions.

In this study, SBA-15 mesoporous silica was synthesized and functionalized with cross-linked polyacrylic acid and used to remove Reactive Orange 16 (RO16) from aqueous media. X-ray diffraction (XRD), filed emission scanning electron microscope (FE-SEM), fourier transform infrared spectrometer (FT-IR), thermo gravimetry analysis (TGA) and BET method were used to study the characteristics of the resulting nanocomposite (SBA-15/CPAA). The effective parameters on dye removal, including pH, contact time, temperature and adsorbent dosage were investigated and optimized. The optimum condition was: pH = 2, adsorbent dosage of 0.03 g and contact time of 60 min at 25 °C. Uv–Vis spectrophotometer was used to determine the amount of residual dye in solution. Multilayer Perceptron (MLP), Redial Basis Function (RBF) and Group Method of Data Handling (GMDH) models have been applied for predicting adsorption value according to the amount of pH, dosage, temperature, concentration and contact time. Comparison of these models revealed that the MLP model was more accurate than the other two models.

This study investigates an alternative green strategy based on non-toxic and readily biodegradable chlorocholine chloride/urea deep eutectic solvents (DESs), which act both as functionalization agents and solvents that allow for the cationization of cellulose monoliths to form novel adsorbents for removal of anionic reactive dye from water. Cellulose monolith was produced by deacetylation of cellulose acetate monolith which was fabricated via thermally induced phase separation (TIPS) method using binary solvents of DMF and 1-hexanol. Cationization of cellulose monolith was confirmed by SEM, FTIR, elemental analysis, TGA and BET surface area analysis. For the flow-through applications, the permeability and mechanical properties were also analysed in this study. The cationized cellulose monoliths were employed to remove acid red 70 dye from aqueous solutions in dynamic adsorption experiments. Results showed exceptional affinity for adsorption of acid red 70 dye due to the charge-induced adsorption aided by quaternary ammonium groups. A high adsorbed percentage of 83% could be obtained at initial concentration of 70 ppm. Moreover, the adsorbed dye could be easily desorbed. Combining their ultrafast adsorption kinetics with excellent properties of high adsorption capacity and rapid adsorption/desorption rates remained during the five consecutive cycles, the DES-modified cellulose monolith has large potential for effluent treatment applications.

Synthetic dyes especially reactive dye that are usually discharged into the wastewater are considered as toxic and harmful to the aquatic organisms and human. Various methods have been introduced to remove the reactive dyes. In this study, a green synergistic extractant has been formulated in the vegetable oil to enhance the extraction efficiency of liquid-liquid extraction (LLE) process for the Orange 3R removal. Several types of extractants were investigated as the extractant and synergist extractant to increase the extraction performance such as acidic, basic and neutral extractants. Interestingly, the results showed that Aliquat 336 and D2EHPA have shown their potentialities as an extractant and a synergist extractant, respectively. Both extractants were formulated in the cooking palm oil as a diluent at the concentrations of 0.1 M Aliquat 336 and 0.08 M D2EHPA. Using the aforementioned optimum conditions, about 90% of the Orange 3R has been successfully extracted with the highest synergistic coefficient (SC) of 67.2. In the meantime, the back extraction study have indicated that NaOH was capable of working as a potential stripping agent where almost 100% of dyes were successfully stripped out from the loaded organic-dye phase into the stripping phase. In conclusion, the green synergist formulation has offered a great prospective for the Orange 3R extraction via LLE process.

Coagulation-flocculation (CF) is an essential process for water and wastewater treatment plants. Whilst compared with the conventional coagulants, the freshly generated magnesium hydroxide (FGMH) is environmental friendly within its coagulative and adsorptive jellied sediment. However, decoloration of dye wastewater using FGMH has not been well understood yet. In this paper, operating variables such as initial pH, coagulant dosage, agitation speed and duration were examined for efficient reactive dye removal. The flocs breakage and regrowth capacity after slow agitation of original CF phase were monitored for mechanism analysis. The mechanism analysis showed that the charge neutralization was the predominance during coagulation, and the precipitate enmeshment and adsorption bridging dominated the flocculation stage. In comparison with the initially formed flocs, though the regenerated flocs were considerably smaller after the second rapid agitation, the bridging interaction of loose flocs could absorb the small residual particles during the slow agitation stage.

Bimetallic iron-copper nanoparticles (Fe-Cu-NPs) were used for decolorization of C. I. Reactive Black effluent. NPs were capped using polyvinylpyrrolidone (PVP) to prevent them from agglomeration. The NPs were characterized by particle size analysis, TEM, EDX, XRD, and zeta potential. Decolorization parameters such as pH, dye concentration, nanoparticle concentration and duration of treatment were evaluated to determine the optimum reaction parameters using response surface modeling, and the kinetic study was also undertaken. Effect of the presence of salt and alkali in the effluent was also evaluated. Reaction products formed during dye decolorization were investigated by GCMS, FTIR, and SEM. These analyses indicated that chromatogenous groups from the dye decompose which leads to dye decolorization. Recycling of NPs was also analyzed. There was 97.86% reduction in dye along with the COD, and BOD lowering was achieved with minimal sludge generation.

Green synthesis of manganese oxide nanoparticles (NPs) was carried out by sol-gel method using Acacia Concinna fruit extract for removal of reactive dye. The effect of calcination temperature on its morphology was investigated. α-MnO2 and Mn3O4 NPs were synthesized at 400 °C and 900 °C respectively and were characterized by PXRD, SEM, TEM, FTIR, BET, Raman and TGA. As-synthesized MnO2 NPs were investigated for the adsorption of Reactive Blue 21 (RB-21) dye. The effect of pH, adsorbent dose, agitation speed, initial dye concentration and temperature on dye removal was explored. pHpzc was calculated from zeta potential study showing positive surface charge below pH 3.18 resulting in electrostatic force of attraction between adsorbate and adsorbent. Both linear and non-linear regression approaches were utilised for the fitting of kinetic models and adsorption isotherms. Adsorption data follows a pseudo second order kinetics and fits well with the Freundlich isotherm model. Thermodynamic parameters such as ΔHo, ΔSo and ΔGo were determined. The dye removal efficiency, in case of MnO2 NPs at pH 3.0 was obtained to be 98% whereas for Mn3O4, no such dye adsorption was observed. The mechanism of adsorption was studied theoretically confirming π-π interaction and H-bonding between the MnO2 and RB dye molecules.

The traditional grass cloth, which has a long history in China, is primarily constructed of raw ramie yarns. In this study, the dye adsorption of three reactive dyes (Reactive Red 2, Reactive Blue 194, and Reactive Orange 5) onto raw ramie yarns indicated that the high-temperature type of reactive dye was more suitable for dyeing raw ramie yarn. The adsorption kinetics for the sorption of Reactive Orange 5 onto raw and degummed ramie yarns was studied by applying pseudo-first-order and pseudo-second-order kinetics and the intraparticle diffusion model. The kinetics study revealed that adsorption primarily followed the pseudo-second-order model in the case of both yarns, and the adsorptions were spontaneous and exothermic. The adsorption isotherms were studied by applying Langmuir and Freundlich isotherm models and found that the Freundlich isotherm model was better fitted. The dyeing performance of Reactive Orange 5 on raw ramie fiber was investigated and compared with that of the degummed ramie yarn. The dyed fiber surface and cross-section were investigated using an optical microscope to understand the structural characteristics. The influences of different dyeing conditions and soap washing on gummy substance removal were also investigated. The tensile strength, stiffness, and colorfastness were also evaluated after raw ramie yarn washing. After the dyeing and soaping processes, gummy substances in the fiber were removed, and notably, they did not affect the water absorbency, tensile strength, and stiffness of ramie yarn.

The concept of natural organic matter of anthropogenic origin is introduced and its characteristics and interaction with chemical pollutants are investigated by adopting several distinct analytic methodologies. Scanning electron microscopy indicates that the used sample of anthropogenic organic matter (AOM) has an amphiphilic nature, which allows its supramolecular organization in water. Fourier transform infrared spectroscopy, in turn, gives a clear indication about the presence of polysaccharide markers, lipidic and amidic fractions, and suggests the absence of free organic acid. AOM sample and AOM mixed with dye sample were examined by the three-dimensional excitation-emission matrix fluorescence spectra and the nuclear magnetic resonance mono-dimensional spectra. The results highlighted the interactions occurring between the AOM and the reactive dye, selected as a representative chemical pollutant. Electron Spin Resonance confirms that the used AOM is able to completely include the dye in its structure. Overall, the obtained results indicate that the fate, transport, and toxicity of pollutants in the environment can be drastically influenced by the presence of AOM.

Nanofiltration (NF) has attracted increasing interest for dye and NaCl fractionation in textile industry. However, it typically shows high rejections to divalent salts (i.e., Na2SO4), compromising to effectively purify dye from dye/Na2SO4 mixtures, which is crucial in digital ink-jet printing. This study used a tight ceramic ultrafiltration (UF) membrane (MWCO of 2410 Da) to desalinate diverse reactive dye species with molecular weights from 626.6 to 1205.4 Da. The UF membrane showed considerably high rejections to all the reactive dyes (> 98.12%) and nearly complete salt transmission (rejections

In the paper, a one-step inkjet printing technology with reactive dye ink and cationic compound ink for cotton fabric was reported. Cationic ink of 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (CHPTAC) and reactive dye ink were printed simultaneously on the sized cotton fabric, and then the sample was steamed. Response surface methodology (RSM) was used to investigate the influences of steam conditions on the K/S value and dye fixation rate. The K/S value, dye fixation rate, staining of the white ground and colorfastness of cotton fabrics treated with different inkjet printing methods were compared. X-ray photoelectron spectrometer (XPS) analysis and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrum confirmed the reaction of CHPTAC to cotton treated by one-step inkjet printing technology. And a suggested reaction process of the one-step inkjet printing method was proposed through Gaussian calculation.

Generally the exhaust dyeing process utilizes a large amount of energy, time and high liquor ratio. On the contrary, the microwave irradiation can be used for the exhaust dyeing that consumes less energy and less time. In this research, the environmental friendly technique, the microwave irradiation, is used to dye cotton fabric at lower liquor ratio through the exhaust dyeing process and it is compared with the conventional dyeing method. The exhaustion percentage, fixation percentage, and color strength values have been measured and a suitable recipe is obtained. It is found that the microwave technique facilitates the process by minimizing the dyeing time and maximizing the exhaustion percentage, fixation percentage, and color strength values. Furthermore, the microwave technique is considered as a green technique and higher exhaustion and fixation percentages indicate that there is comparatively less residue dye in the effluent. XRD and SEM tests also performed to analyze whether the microwave has affected the morphological structure but from the results, there is not a considerable difference observed. Finally, the colorfastness tests have been carried out and compared with the conventionally dyed samples and the results are almost the same for both techniques. Hence the microwave technique is providing almost the same quality product by using less time with the environment friendliness.

To enhance dye fixation rate in pad-steam dyeing, a preliminary research was carried out to examine that the effect of the water content in water-ethanol mixed medium on reactive dyeing of cotton fabrics. The fabric temperature and dyeing properties as affected by the water content were investigated. Based on the results, a batch procedure was incorporated in the pad-steam dyeing to enhance the interactions between reactive dye and cellulosic fibers. The dyeing properties, chemicals and energy consumption of the pad-batch-steam process and conventional pad-steam process were also evaluated. The results show that reducing the water content could expedite fabric heating and improve dyeing properties significantly. The batching time of 60 min, 20 g/L of sodium carbonate and steaming time of 2.0 min were appropriate for dyeing cotton fabric with 25 g/L of C.I. Reactive Violet 5. Compared with conventional pad-steam dyeing, the color strength and dye fixation rates of dyed fabrics using pad-batch-steam dyeing process were maximum increased by 21.4% and 16.1%, respectively. The proposed dyeing process saved 13.7% dye, 33.3% sodium carbonate, 33.3% steam and 28.5% industrial electricity. The pad-batch-steam dyeing process has significant potential for enhancing dye fixation rate and reducing the dyeing effluent, which is a major step towards cleaner dyeing of cotton fabrics.

Ceria (CeO2) nanoparticles were synthesized by the precipitation method without use of any organometallic precursors. Photocatalytic degradation of reactive dyes such as Reactive Green 19 (RG19), Reactive Orange 84 (RO84), Reactive violet 1 (RV1) and Reactive Yellow 81 (RY 81) were investigated in a batch reactor catalysed by CeO2. XRD characterization confirmed cubic phase of CeO2 with 19 nm crystallite size, which was supported by SEM and TEM analyses. The band gap of synthesized CeO2 was found to about 3.05 eV from the Kubelka-Munk function analysis of UV-diffuse reflectance spectra. Synthesized CeO2 showed the effective catalytic activity towards the photocatalytic removal of reactive dyes under visible light. Photocatalytic activity was studied to identify the effect of reaction parameters such as catalyst loading, initial dye concentration and pH of dye solutions for the removal of reactive dyes. >95% removal of reactive dyes, reactive green-19, reactive orange-84 and reactive yellow-81, was found under solar irradiation, while in case of reactive violet-1 > 99.9% removal was obtained. Highest activity was found at neutral pH and at 1.5 g/L loading. The photogenerated holes were the most active species responsible for the degradation of reactive dyes. Thus, CeO2 photocatalyst shows great potential for passive solar degradation of reactive dye effluents.

Effort was made to understand the role of major constituents of coconut fibres i.e., lignin, hemicelluloses and cellulose, on its absorption of different ionic dyes. Composition and functional groups of raw coconut fibre were changed by progressive removal of lignin, and hemicelluloses. Differently treated fibres were analyzed through FTIR, TGA, composition analysis and were dyed with anionic (acid, reactive) and cationic (basic) dyes separately. Absorption performance was assessed by surface and core colour uptake. Progressive removal of lignin resulted in reduction of uptake of anionic (acid and reactive) dyes, while increase in uptake of cationic (basic) dye. Treatment causing removal of hemicelluloses improved uptake of basic dye due to structural swelling. Increase in α-cellulose (29.9%), favours uptake of reactive dye to a higher extent. Loss of lignin occurred in case of both delignification and hemicelluloses removal treatments to the extent of 6.3% and 11.9% respectively, consequently uptake of acid dyes reduced. It may be concluded that treatment causing higher removal of hemicelluloses are beneficial and loss of lignin is disadvantageous for absorption of dyes.

In the current work, 2,2’-(butane-1,4-diylbis(oxy))dibenzaldehyde cross-linked magnetic chitosan nanoparticles (Fe3O4@CS-BAL) were successfully synthesized as the new magnetic adsorbent through crosslinking modification of magnetic chitosan nanoparticles (Fe3O4@CS) using 2,2’-(butane-1,4-diylbis (oxy))dibenzaldehyde (BAL) as a crosslinker at room temperature. The chemical structure, surface properties and morphology of the synthesized nanoparticles were characterized by Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD) and Scanning electronic microscope (SEM), Thermogravimetric analysis (TGA) and N2 adsorption-desorption isotherms. The 2,2’-(butane-1,4-diylbis(oxy))dibenzaldehyde-modified magnetic chitosan nanoparticles (Fe3O4@CS-BAL) were used as an effective adsorbent for removal of an anionic reactive dye, Reactive red 239 (RR239) from aqueous solutions by batch adsorption procedure. The effects of various experimental parameters such as adsorbent dosage, pH, contact time and initial dye concentration on the RR239 adsorption onto the Fe3O4@CS-BAL were investigated and optimized. The Langmuir and Freundlich adsorption models were used to describe adsorption isotherms and constants. The equilibrium results revealed that the adsorption behavior of the RR239 dye on the Fe3O4@CS-BAL nanoparticles fitted well with the Langmuir model. On the basis of the Langmuir analysis, the maximum adsorption capacity (qm) of the Fe3O4@CS-BAL for RR239 was found to be 200 mg/g. The experimental results showed that the Fe3O4@CS-BAL could be remove more than 99% of investigated dye within the first 2 min of contact time. Therefore, the Fe3O4@CS-BAL adsorbent can be successfully applied as an efficient and low-cost adsorbent for removal of anionic reactive dyes from aqueous solutions.

Magnetic palladium (Pd)-magnetite (Fe3O4)-flyash composite particles have been recently utilized for the removal of industrial azo reactive dyes from the aqueous solutions. The mechanism of dye-removal involves advanced oxidation process (AOP) such as the activation of costlier and hazardous oxidizer such as hydrogen peroxide (H2O2). The process also requires further backing-up with the adsorption treatment of activated carbon (AC) to control the enhanced chemical oxygen demand (COD) level of treated aqueous solution which not only increases the number of steps involved in the dye-removal process but also results in the generation of large amount of sludge. There is an urgent need to replace H2O2 with an efficient, cost-effective, and non-hazardous oxidizer which can resolve the aforementioned issues in the present dye-removal application. In this investigation, we utilize the magnetic Pd-Fe3O4-flyash composite particles for the decoloration of aqueous solutions containing industrial azo reactive dye such as Corafix Red ME4B via synergistic activation of persulfate anions (S2O82−) involving the catalytic and thermal contributions. In contrast to the activation of H2O2, the synergistic activation of S2O82− anions is noted to significantly reduce the COD level almost in a single step which reduces the dependency on the post adsorption treatment of AC. Moreover, the regeneration of AC in the present dye-removal application has also been demonstrated using the synergistic activation of S2O82− anions. The latter, hence, appears to be an efficient, cost-effective, and non-hazardous approach for the removal of organic synthetic-dyes from aqueous solutions by using the magnetic Pd-Fe3O4-flyash composite particles as catalyst.

Recently, antibacterial textiles have gained interest from scientists due to their potential to provide protection and high-quality life to people. In this study, zwitterionic poly(sulfobetaine methacrylate) (pSBMA) brushes were grafted onto cotton fabrics via reactive dye intermediate reaction and surface-initiated atom transfer radical polymerization (SI-ATRP) technology. Two bacterial species (Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli) was used for bacterial attachment experiments. The capability of resisting nonspecific protein adhesion, short-term bacterial attachment (24 h) and long-term biofilm formation (120 h) of pSBMA-grafted cotton fabrics were studied. The results suggested that the pSBMA-grafted cottons exhibited an excellent non-fouling performance. Different from the studies on two-dimensional surfaces, our study provides an insight into the long-term biofilm resisting properties of porous textiles grafted with zwitterionic polymers.

The current approach focuses on studying the leverage of nanosilver (AgNPs) incorporation on the dyeing process of viscose fibers by blue reactive dye. Nanosilver was straightway incorporated into viscose fibers using sodium citrate as nanogenerator. Owing to AgNPs incorporation, color of fibers was turned to greenish-blue and darker greenish color was observed with low Ag content (

One dimensional MgO nanofibres with high photocatalytic activity were fabricated using the electrospinning method via a polyvinyl alcohol (PVA)/magnesium precursor based system and the dye degradation efficacy of MgO nanofibres was compared with MgO nanospheres. Optimum electrospinning parameters including suitable magnesium precursors were investigated and the formation of MgO nanofibres were confirmed with scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) mapping. Furthermore, the crystalline lattice structure and surface roughness of fabricated nanofibres were evaluated using transmission electron microscopic-electron diffraction mode (TEM-SAED) and atomic force microscopy (AFM), respectively. Fabricated MgO nanofibres exhibited excellent photocatalytic degradation activity against widely used model reactive dye, Reactive Yellow (RY). In contrast to MgO nanospheres, electrospun MgO nanofibres completely degraded the reactive dye under UV irradiation. These photocatalytic MgO nanofibres show a great potential to be used in efficient treatment of industrial dye effluents.

Adsorption process using Surfactant-impregnated Activated Carbon (SIAC) was studied to remove reactive dye from an aqueous solution. The study on additional of cleavable cationic surfactant on the adsorption of Reactive Blue 4 (RB4) dye onto activated carbon was investigated using palm-based esterquat (PBE) surfactant. The effect of surfactant concentration on dye removal was discussed to assess the efficiency of adsorption process for both direct and isolated impregnation method. Results obtained from this study shows that the best RB4 dye removal obtained was 39.67% at PBE concentration of 128 mg/L in 5 hours contact time by direct impregnation method while by isolated impregnation method, the RB4 dye removal achieved was 84.19% in 7 hours contact time at PBE concentration of 38 mg/L. It was observed that adsorption of RB4 dye was greatly enhanced by modification of AC with cleavable cationic surfactant impregnated by indirect method compared to direct method.

This research work is an attempt to evaluate the role of micellar flocculation (MF) for the treatment of dye-contaminated water. Solubilization of dye by organized assemblies of anionic surfactants and its subsequent complexation with the metal cations during flocculation has been found as the active phenomena in this treatment methodology. Base soap (BS) being a mixture of anionic surfactants along with the salt of the divalent cation (Ca2+) was employed to capture and separate the reactive dye, reactive red 195 (RR-195), in the form of flocs at optimized concentrations of soap, dye, and flocculant. The effect of contact time, temperature, pH, and electrolyte has also been investigated to figure out the optimum conditions necessary to perform this adsorptive removal. The surface characteristics of adsorbent and favorability of adsorption were evaluated with the help of different isotherm models i.e., Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin. Furthermore, kinetic and thermodynamic calculations were performed for a better understanding of the nature of the said removal. Herein, the results reveal that this removal process is spontaneous, favorable, and exothermic. The excellent removal of RR-195 (≈99%) through micellar flocculation suggests that it’s an economical, sustainable, and efficient approach for the treatment of industrial effluent containing dyes.

In the process of fabric dyeing production, the color samples are usually obtained from the users first, and then the color-matching personnel conducts proofing according to the color of the samples. Therefore, the efficiency of color matching is low, and many fabric color-matching technologies emerge. In this work, we designed a series of dyeing schemes, and built three single reactive dye databases by dyeing cotton knitted fabrics with Levafix Red, Levafix Blue and Levafix Amber in the pad-dry-pad-steam (PDPS) process, respectively. Furthermore, three prediction models were established based on PSO-LSSVM, which took the color parameter L∗, a∗ and b∗ value of the dyed fabrics as model input and dye concentration as model output. The color parameter L∗, a∗ and b∗ values of the fabrics dyed at the dye concentration predicted from the PSO-LSSVM models are consistent with actual measured values of the tested cotton fabrics. All evaluation indexes show that the Ep of PSO-LSSVM models are above 96%, possessing a high accuracy of dye recipe prediction and strong dye specificity, which can be used in actual dyeing color matching.

High performance cotton fabrics with color, luster and wrinkle resistance are manufactured by three steps. The coloration, wrinkle resistance and luster finishing consume a large number of resources, and generate a huge amount of colored wastewater. The present research reports a cleaner process for dyeing, wrinkle resistance and luster finishing of cotton fabrics. Cotton fabrics were dyed at 35 °C for 15 h with multifunctional reactive dye solutions of high concentrations. Scanning electron microscope images show the fiber cross sections became circular like the mercerized cotton fibers, and the fabrics exhibited nice luster and wrinkle resistant ability. For fabrics with light and middle color, a certain amount of 1,3,5-triacryloyhexahydro-1,3,5-triazine was added into the dye liquor to make the fiber cross section become circular and to make the wrinkle recovery angle reach more than 260° to obtain good wrinkle resistant ability. When the padded fabrics were steamed at 102 °C for 3 min instead of fixing at 35 °C for 15 h, the wrinkle recovery angle also reached 266°. The breaking strength of dyed fabrics decreased with increasing the dye and 1,3,5-triacryloyhexahydro-1,3,5-triazine concentrations. The enhancement of wrinkle resistance of dyed fabrics is due to the crosslink effect of the dye molecules with cellulose macromolecules. This one-step process will save a significant amount of energy and water, and reduce the effluent discharged.

Molecular separation using nanostructured materials have attracted much attention recently for various applications. Different classes of materials have been used among which metal organic framework (MOF) and layered double hydroxide (LDH) have been recently developed due to their superior structure in separation, specifically adsorption process. In this work, we have studied removal of dye from water using a nanocomposite of MOF/LDH. The method of investigation is development of an artificial intelligence-based model for prediction of the adsorption process. The adsorption data have been obtained for removal of a dye (orange II reactive dye) from water at different conditions. The model was proposed using artificial neural network for simulation of the adsorption output which was considered to be equilibrium concentration in the solution (Ce). Indeed, the equilibrium concentration of solute was assumed as the main output in developing the model, while two inputs were postulated including the pH and adsorbent dosage. The model was built considering two hidden layers in the neural network. The validation and training steps were carried out and statistical analysis indicated excellent agreement between the simulated and measured data possessing high coefficient of determination (R2 greater than 0.999). The model revealed to be a high-performance model for simulation of dye removal using adsorption process with high accuracy.

This investigation was aimed at studying reactive orange 16- (RO-16) dye biodegradation by the Antarctic yeast Candida sake 41E. Dye decolorization reached 94.3% (an initial 100 mg.l−1) within 48 h in a stirred-tank bioreactor at a specific decolorization rate of 0.09 mg.RO-16.g−1.h−1. The presence of reactive dye in the medium did not affect yeast growth. A specific growth rate (μ) of 0.09 h−1 and biomass yield (Yx/s) of 0.23 CmolX.CmolS−1 were obtained. Reversed-phase ultrahigh-performance-liquid-chromatography–mass-spectrometry analysis was performed to investigate the by-products generated during the biodegradation. Five yeast-catalyzed reaction products of RO-16 were identified and a biodegradation pathway for this azo dye thus proposed. In addition, the toxicity of the dye and by-products generated was assessed with Lactuca sativa L. seeds, confirming the phytotoxicity of RO-16 and its decrease after 48 h of treatment with C. sake 41E.

The textile industry widely uses reactive dyes to obtain cotton fabrics having good resistance to color removal despite frequent washing. This level of dye usage generates substantial volumes of wastewater containing significant quantities of residual dye requiring treatment before discharges from commercial dyeing operations to public waterways. As part of a study aimed at recycling/reusing rather than discharging reactive dye wastewater, well-known dyes Reactive Yellow 176, Reactive Red 241, and Reactive Blue 221 were used in dyeing cotton fabric, and the generated wastewater samples were decolorized with H2O2 catalyzed by UV light. The efficiency of UV/H2O2 decolorization for trichromic wastewater was determined by UV-Vis monitoring at 550 nm, wherein it was found that more than 91% of color removal in trichromic wastewater occurred at pH 4. The reuse of wastewater was investigated by a total of three sequential cycles of wastewater treatments. The quality of cotton dyed with reused wastewater was assessed through color measurements using CIELAB, fastness to light, and wash fastness testing. Results showed that MCT/VS-based reactive dye wastewater arising from UV/ H2O2 treatment could be used for two subsequent dyeing cycles without compromising the quality of the color of the dyed cotton fabrics. The proposed treatment can also save water and salt, enhancing the economy of the dyeing process.

Herein, we reported the improvements of wicking properties and dyeability of the jute-cotton blended (40:60) fabrics due to the effect of low-pressure glow discharge (LPGD) air plasma under selected exposure times. The microscopic features, functional groups, wettability, contact angles, wetting area, wicking rates, and reflectance values of the jute-cotton blended fabrics were analyzed using numerous experimental techniques. The scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques were used to investigate the morphological and compositional modifications of plasma-treated jute blended cotton fabrics. The compositional analysis confirmed various functional groups such as –OH, C–O, and COO− on the surface of jute blended cotton fabrics. The average pore radii and diffusion coefficient were calculated by using the modified Lucas-Washburn equation. The plasma-treated fabrics were shown to have an average pore radius of 0.93, 1.46, 2.26, and 4.8 μm under treatment time of 5,10,15, and 20 min. Nearly 50% reduction of contact angle was observed after a plasma treatment time of 20 min. The absorption to scattered ratio, K/S (determined using Kubel-Munk model) of the colored fabrics with 5 min pre-treated plasma was 6.47, although it was raised up to 8.51 after 20 min of pre-treatment. A reactive dye, Bezaktiv Red S–3B, was used for the dyeability test, and our findings showed that the dyeability and the wettability of the fabric were substantially enhanced with the treatment time of LPGD air plasma. Among the samples, only 10 min plasma pre-treated colored fabric exhibited a color difference of less than one compared to the standard one., Highlights • The wicking properties and dyeability of the jute-cotton blended (40:60) fabrics were studied. • 50% reduction of contact angle was observed after a plasma treatment time of 20 min. • The presence of –OH, C–O, and COO− functional groups on the surface of jute blended cotton fabrics was seen. • The absorption to scattered ratio, K/S of the fabrics was increased with the increase in plasma treated times. • The dyeability and wettability of the fabric enhanced with the treatment times of LPGD air plasma., Plasma treatment; Jute-cotton blended; Contact angle; Average pore radii; Wettability; Dyeability.

The poly[2-hydroxy-3-(1-naphthyloxy)propyl] methacrylate [poly(NOPMA)] was used as a novel adsorbent for the removal of Remazol Brilliant Blue R (RBBR) known as a reactive dye. Physico-chemical properties of polymer were analyzed by FT-IR and SEM before and after dye adsorption. The Langmuir and Freundlich isotherms were used to explain the adsorption equilibrium, and when it was compared with each other it was seen that the adsorption process was well explained by the Langmuir isotherm model and showing a monolayer adsorption capacity for RBBR of 238.10 mg/g. Kinetic models known as pseudo-first-order, pseudo-second-order and intra-particle diffusion model were utilized to analyze the mechanism of adsorption, and results indicated that was an adsorption kinetic suitable with the pseudo-second-order. The thermodynamic parameters (∆ H o , ∆ S o , ∆ G o ) indicated that the adsorption process was spontaneous and endothermic. To optimize the study conditions, the effects of the concentration of RBBR, adsorbent amount and contact time on the adsorption were investigated by response surface methodology (RSM). According to RSM results, maximum RBBR removal was reached at the optimum initial dye concentration of 60.85 mg/L, adsorbent dosage of 0.04 g/50 mL and contact time of 59.91 min.

A novel, green and Ecofriendly method for photocatalitic stripping of fixed Reactive Red X-3B dye on cotton substrate was developed at the first time by employing a nano-TiO 2 /UV system in a self-built photoreactor. The effects of photocatalitic stripping parameters such as the initial pH value of working solution, temperature and stripping duration, on color stripping efficiency and fabric tensile strength were investigated. Moreover, the photocatalitic stripping of the fixed reactive dye on cotton substrate in the nano-TiO 2 /UV system was further explored by Attenuated total reflection-Fourier transform infrared spectrometry (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). The results show that the fixed Reactive Red X-3B dye on cotton could be photocatalitically stripped or decolorized efficiently by employing the nano-TiO 2 /UV system with a dipped stripping manner in which the substrate was immersed into working solution. The tested stripping parameters of temperature and treatment duration presented notably positive effects on the color stripping efficiency, while an inappropriate control of all the parameters could result in a deterioration of the tensile strength of the substrate. Furthermore, a heterogeneous photocatalitic color stripping mechanism was also supposed for the fixed Reactive dye molecules on cotton substrate in nano-TiO 2 /UV system with the dipped stripping manner.

The dyeing ability of the dichlorotriazine dye on cotton fiber in siloxane media was investigated using a water/oil emulsion system. Compared with traditional water base dyeing, a deeper color depth of fabric and 90% fixation rate of dye could be achieved without using salts in siloxane reverse micro-emulsion system. The hydrolysis mechanism of dichlorotriazine dye, which deeply affects the dyeing performance, was analyzed using high performance liquid chromatography and mass spectrometric methods. In siloxane reverse micro-emulsion dyeing system, the lower hydrolysis of dye is probably due to the grasping water ability of surfactant, the reaction between fiber and dye, and the dye aggregation under a high concentration of dye. Furthermore, the hydrolysis model shows that the hydrolysis rate constants in traditional water base was about three to four times faster than the one in siloxane reverse micro-emulsion system. The dye hydrolysis mechanism in siloxane reverse micro-emulsion system in this study could successfully guide the siloxane reverse micro-emulsion dyeing technology.

Rice bran is a major by-product of the rice milling industry and is abundant in Taiwan. This study proposed a simple method for modifying rice bran to make it a low-cost adsorbent to remove reactive blue 4 (RB4) from aqueous solutions. The effects of independent variables such as dye concentration (100–500 ppm), adsorbent dosage (20–120 mg) and temperature (30–60 °C) on the dye adsorption capacity of the modified rice bran adsorbent were investigated by using the response surface methodology (RSM). The results showed that the dye maximum adsorption capacity of the modified rice bran adsorbent was 151.3 mg g−1 with respect to a dye concentration of 500 ppm, adsorbent dosage of 65.36 mg, and temperature of 60 °C. The adsorption kinetics data followed the pseudo-second-order kinetic model, and the isotherm data fit the Langmuir isotherm model well. The maximum monolayer adsorption capacity was 178.57–185.19 mg g−1, which was comparable to that of other agricultural waste adsorbents used to remove RB4 from aqueous solutions in the literature. The thermodynamics analysis results indicated that the adsorption of RB4 onto the modified rice bran adsorbent is an endothermic, spontaneous monolayer adsorption that occurs through a physical process.

Azo dyes, possessing a primary aromatic amino group, on diazotisation in presence of cotton followed by treatment with soda ash at 60–65 °C were found to ‘reactively’ dye cotton with varying degrees of fixation depending on the chemical structure of the azo dye. Evidence of dye-fibre reaction is indirectly inferred from poor to fair colour values obtained in absence of added soda ash. Dyed cotton retained significant colour even after three treatments with boiling dimethyl formamide (DMF). Coloured cellulose precipitated when a solution of dyed cotton in 85% w/w phosphoric acid was diluted with dimethyl sulfoxide (DMSO). The phosphoric acid-DMSO mixture was colourless. These two tests prove the existence of a dye-fibre covalent bond. A new class of reactive dyes without an externally attached reactive system is therefore, in principle, available. It will have the advantage of reduced raw material and manufacturing costs.

In this study, papermaking sludge was used as the raw biomass material to produce the lignin-based flocculant (LBF) by grafting quaternary ammonium groups and acrylamide. LBF was used as a coagulant aid with polyaluminum chloride (PAC) to treat reactive and disperse dyes wastewater. Effects of dosing method, pH, hardness and stirring speed on the coagulation behavior and floc properties were studied. Results showed that the superior coagulation efficiency and recovery factor were achieved by PAC+LBF compared with PAC and LBF+PAC. The primary mechanisms of LBF in the treatment of disperse and reactive dye solutions were charge neutralization and bridging effect, respectively. In the dual-coagulation, the impact of pH on the coagulation efficiency was weak during pH range of 5-9. Moderate hardness could enhance the floc properties due to the decrease of electrostatic repulsion and the chelation of Ca(II) and LBF. Besides, flocs coagulated by PAC+LBF had a stronger anti-crush ability.

The electrochemical behavior of different carbon-based electrodes with and without nanoparticles of platinum electrochemically dispersed on their surface has been studied. Among others, reduced graphene oxide based electrodes was used to determine the best conditions for the decolorization/degradation of the reactive dye C.I. Reactive Orange 4 in sulfuric medium. Firstly, the electrochemical behavior was evaluated by cyclic voltammetry. Secondly, different electrolyses were performed using two cell configurations: cell with anodic and cathodic compartments separated (divided configuration) and without any separation (undivided configuration). The best results were obtained when reduced graphene oxide based anodes were used. The degree of decolorization was monitored by spectroscopic methods and high performance liquid chromatography. It was found that all of them followed pseudofirst order kinetics. When reduced graphene oxide-based electrodes coated with dispersed platinum by alternate current methods electrodes were used, the lowest energy consumption and the higher decolorization kinetics rate were obtained. Scanning Electronic Microscopy was used to observe the morphological surface differences., The authors wish to thank the Spanish Agencia Estatal de Investigacion (AEI) and European Union (FEDER funds) for the financial support (contract MAT2016-77742-C2-1-P). A.I. del Rio is grateful to the Spanish Ministerio de Ciencia y Tecnologia for her FPI fellowship. J. Molina is grateful to the Conselleria d'Educacio, Formacio i Ocupacio (Generalitat Valenciana) for the Programa VALi+D Postdoctoral Fellowship (APOSTD/2013/056). C. Garcia is grateful to the Conselleria d'Educacio, Formacio I Ocupacio (Generalitat Valenciana) for her Geronimo Forteza fellowship. The authors wish to acknowledge to Chemviron Carbon who kindly donated the 265 ZORFLEX (R) activated carbon fabric.

Reactive dye is one of the most applicable dyes in textile industries which its release to the water bodies creates a concern for environmentalists. Here, in this data article a bone-char (BC) ash decorated with MgO-FeNO3 for removing reactive black 5 (RB5) dye in a catalytic ozonation process (COP) system. Operational parameters data such as initial RB5 concentration, pH, catalyst dosage, and reaction time were optimized using Taguchi method. The optimal conditions for initial RB5 concentration, pH, catalyst dosage, and reaction time were determined 10 mg/L, 10, 0.1 g/L, and 15 min, respectively. Data of Taguchi optimization tests indicated that the initial RB5 concentration had a significant influence on RB5 removal efficiency (54.03%) during the catalytic ozonation process, and reaction time had lower contribution (2.04%). Keywords: Reactive black 5, MgO- FeNO3, Bone-char ash, Catalytic ozonation, Taguchi, Optimization

In this study firstly we aimed at introducing the effects of ultrasound and sonochemistry in surface modification of polyester fibers. For this purpose, surface modification of polyester fibers was achieved by ultrasound, and contact angle and water spreading time measurements were used to confirm the treatment efficiency. Hydroxylation of terephthalate was occurred by hydroxyl radicals formed during water sonolysis, forming functional groups on polyester surface, as confirmed by XPS analysis, improving the wettability. Creation of hydroxyl groups under sono surface modification was further assessed by dyeing the samples with reactive dye. Secondly, we investigated the durable nano-sono-finishing of polyester fibers by nano TiO2 particles under ultrasonic bath. Washing durability of the sono-synthesized TiO2 nanoparticles was evaluated confirming the effective role of sonochemical technique in polyester surface modification. Thirdly, the self-cleaning activity of sono-synthesized nano TiO2 treated samples toward degradation of Methylene Blue stain was superior to coating of fabric with commercial nano TiO2 using identical procedure.

Azo dyes are important groups of chromospheres having a particular structure in color-contaminated wastewater. In the present study, Reactive Red 198 (RR198) dye was chosen as a model of azo dyes group. Electrocoagulation technique as an effective and environmental-friendly process for wastewater treatment was applied. Hence; to determine the extent of decolorization process, the main different parameters such as pH (4-11), contact time (80 min), initial concentrations (25-400 mg/L), current density (1.9-23.1 mA/cm2), distance between gaps (1-4 cm), and effect of supporting electrolytes were evaluated. Results show that optimum conditions were 20 min of operation time, 1 cm distance between electrodes, pH equal to 4 and optimum initial concentration of dye equal to 100 mg/L as well as NaCl was identified as the best electrolyte. Under these optimum conditions and also at both aeration and non-aeration operating conditions decolorization efficiency was more than 90%. The results also demonstrated that total organic carbon removal efficiency as (TOC), during 120 min of contact time was about 80.95%. XRF analyses show that a large portion of deposited sludge (58.282%) was aluminum oxide.

Salt-free reactive dyeing is the need of hour in textile reactive dyeing industries to overcome the problems posed by salt usage. A cationic agent (CA) namely 3-chloro-2-hydroxypropyl trimethylammonium chloride was used to cationize the cotton fabric. At present cold pad batch method is used to fix the cationic agent to fabrics. In the present work, exhaust method of application of cationic agent to knitted cotton goods at an industrial level is proposed. The reaction mechanism and effect of materials to liquor ratio, the molar ratio of NaOH to cationic agent, the temperature on dyeing performance are discussed in detail. The cationization process was optimized based on the colour strength of the cationized cotton fabric dyed with the Black GDNN reactive dye at 7% shade which is widely used for knitted fabric processing in India. Various analytical tools such as Fourier transform infrared spectroscopy and field emission electron microscope with energy dispersive X-ray analyser were used to characterize the efficiency of the cationization process. The change occurring in molecular and supermolecular level due to the cationization process is discussed in detail.