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This work aims to explain the effect of common salt on absorbance spectra and solubility of textile direct dyes, which is important in analysing and reusing wastewater of dyeing process.

Several textile dyes such as Direct red 243, Direct yellow 86 and Direct blue 201 solutions with and without NaCl salt were used to study the effect of common salt on solubility of textile direct dyes. Several methods such as derivative spectrophotometry, principal component analysis and colorimetric techniques were used to analyse the absorbance spectra of dye solution.

The obtained results indicate that the effect of common salt on absorbance spectra and solubility of textile direct dye depends on the chemical structure of dyes. The NaCl salt significantly affects the solubility of Direct red 243 (red dye) and Direct yellow 86 (yellow dye) which have Azo compounds containing four SO₃ functional groups. But the NaCl salt does not change the solubility of Direct blue 201 (Blue dye) which has Azo compound containing two SO₃ functional groups. Also, the NaCl salt decreases the accuracy of dye concentration prediction.

During reusing wastewater of dyeing process, the amount of dyes has been evaluated via absorbance spectra of dye solution.

This work explains the effect of common salt on solubility of textile direct dyes and the accuracy of dyes concentration prediction.

Colorfastness properties of dyed degummed and dyed stannic chloride weighted silk fiber were studied as a function of exposure to sunlight in air, washing with soap solution and spotting with alkalis.

Improved multi-voltine variety of degummed silk fibers was weighted with the treatment of stannic chloride at the varying pH level. Maximum weighting of silk fiber was achieved at the optimum SnCl₄ concentration, pH of the solution, time and temperature. The degummed (un-weighted) and weighted silk fibers were then dyed with Direct Blue 1 and Direct Red 28 dyes at the optimized dying conditions.

The role of base (Na₂CO₃) on dyeing of weighted silk fiber with Direct Red 28 was found very influential. The loss in tenacity of degummed silk fiber was higher than that of SnCl₄ weighted silk fiber when they were exposed to sunlight in air.

The colorfastness of weighted dyed silk was comparatively higher than that of un-weighted dyed silk.

While aiming to create methods for fibre recycling, the question of colours in waste textiles is also in focus; whether the colour should be kept or should be removed while recycling textile fibre. More knowledge is needed for colour management in a circular economy approach.

The research included the use of different dye types in a cotton dyeing process, the process for decolourizing and the results. Two reactive dyes, two direct dyes and one vat dye were used in the study. Four chemical treatment sequences were used to evaluate colour removal from the dyed cotton fabrics, namely, HCE-A, HCE-P-A, HCE-Z-P-A and HCE-Y-A.

The objective was to evaluate how different chemical refining sequences remove colour from direct, reactive and vat dyed cotton fabrics, and how they influence the specific cellulose properties. Dyeing methods and the used refining sequences influence the degree of colour removal. The highest achieved final brightness of refined cotton materials were between 71 and 91 per cent ISO brightness, depending on the dyeing method used.

Only cotton fibre and three different colour types were tested.

With cotton waste, it appears to be easier to remove the colour than to retain it, especially if the textile contains polyester residues, which are desired to be removed in the textile refining stage.

Colour management in the CE context is an important new track to study in the context of the increasing amount of textile waste used as a raw material.

Dyeing and printing are important steps in textile manufacturing. After the process completion, these dyes are released in the effluent. These dyes impart an unacceptable appearance but are also toxic to the soil and water bodies. The present research has been carried out to study the rate of photocatalytic degradation of an azo dye, namely, CI Direct Green 26, using titania nanoparticles under ultra violet (UV) irradiation as a function of temperature and time. Azo dyes account for the majority of all dyestuffs are produced and extensively used in the textile, paper, food, leather, cosmetics and pharmaceutical industries. Titania nanoparticles have been found to successfully degrade these dyes in the presence of UV light. The purpose of the present paper was to study the photodegradation of azo dyes using titania nanoparticles at different temperatures and time periods.

Titania nanoparticle concentration of 0.1% (w/v) was dispersed in distilled water by sonication for 1 h in sonication bath. The of rate of degradation of Direct Green 26 dye in the titania nanoparticle dispersion, under UV-A exposure was studied at different temperatures ranging from 25°C to 65 °C for time periods ranging from 1 h to 6 h. Photocatalytic degradation tests were performed in a specially designed UV reactor chamber. Raman spectroscopy of Titania nanoparticles, dye and titania/dye mixture before and after UV exposure was carried out using Confocal Laser Dispersion Raman Microscope (Renishaw, UK) with 785 nm excitation laser.

Titanium dioxide is an efficient photocatalyst for decolourisation of direct dye. The photodegradation of the direct Green dye was found to follow the pseudo first-order reaction. The Arrhenius activation energy was found to be 24.8 kJ/mol with A value of 0.0013 for the photocatalytic degradation of the dye. Raman spectroscopy also confirmed the adsorption of dye on titania nanoparticle and its complete degradation on exposure to UV light.

This research highlights the application of titania nanoparticles for the effective degradation of dye in the effluent from textiles, clothing, paper and any kind of dyeing process. Azo dyes account for the majority of all dyestuffs are produced and extensively used in the textile, paper, food, leather, cosmetics and pharmaceutical industries. Titania nanoparticles have been found to successfully degrade these dyes in the presence of UV light which can be very beneficial for the effluent treatment plants in textile and other industries.

Azo dyes are one of the harmful pollutants released in textile waste water. The degradation and removal of the coloured waste in the textile effluent is an important environmental concern and needs to be investigated. The research is one of the first to investigate and understand the mechanism of the degradation of an azo dye in the presence of titania nanoparticles by Raman spectroscopy.

This study aims to deal with the dyeing of nylon-/cotton-blended fabric in one bath using direct and acid dyes.

The cellulose in cotton/nylon-blended fabric was chemically modified using 3-chloro-2-hydroxypropyl tri-methyl ammonium chloride (CHPTAC) as cationizing agent to impart positive charge on the cellulose. The modified and unmodified blended fabrics were dyed in a single bath with direct and acid dyes under various concentrations of 0.5, 1, 2, 4 and 6 per cent on the weight of fabric by exhaust method. The dyeing of modified and unmodified fabrics was characterized through the properties such as K/S and colorfastness to washing, rubbing and light.

The modified fabric exhibited higher color yield, comparable rubbing fastness and good washing fastness.

The dye uptake was maximum in a single-bath dyeing process of nylon-/cotton-blended fabrics without electrolyte addition, which minimizes the impact of dyes on environment.

The purpose of this paper is to investigate the possible application of recycled wool‐based nonwoven material (RWNM) for removal of different dyes that are used in textile dye houses.

The sorption kinetics, the influence of initial dye concentration, pH and temperature are analyzed. Basic, reactive, direct and metal complex dyes are studied.

The sorption properties are highly influenced by the type of the dye owing to differences in their chemical structure and thus, the mechanism of binding to wool. Modification of material with chitosan and hydrogen peroxide improves the sorption capacities and sorption rates but no general trend can be established. Consequently, the sorption behaviour is analyzed separately for each type of the dye.

The results indicate that RWNM can be used as an efficient, low‐cost sorbent for decolorisation of effluents.

With an increasing awareness of environmental pollution and health hazards associated with synthesis, processing and use of synthetic dyes, there is a worldwide interest in natural dyes for textiles. This paper presents a comparative study of natural dyes and direct dyes in terms of eco-friendliness and their various colour-fastness properties. It also reveals that natural dyes can be used safely as they contain metals and formaldehyde within the Okotex limits and do not contain amines. The fastness properties of natural dyes are found to be satisfactory.

The purpose of this paper is to show how to remove some dyestuffs, as pollutants, from their aqueous solutions.

To achieve the goal, a water soluble hyperbranched poly (ester‐amide) (HBP) was synthesised using the melt polycondensation method by the reaction of maleic anhydride (MA) and diisopropanol amine (DIPA) at 140°C at a molar ratio of 1:1.3 MA: DIPA, respectively. This HBP was incorporated in the preparation of an effective microcrystalline cellulose (MCC)/dimethyloldihydroxyethylene urea (DMDHEU)/HBP adduct by crosslinking HBP with DMDHEU in presence of MCC. Furthermore, the prepared adduct was characterised by investigation its infra red and then utilised in the removal of three anionic dyestuffs from aqueous solutions, namely Irgalan Blau 3GL (an acid dye), SIRIUS Blau S‐BRR (a direct dye) and Levafix Brill Orange P‐GR (a hydrolysed reactive dye).

The results obtained revealed that the optimum conditions for preparing MCC/DMDHEU/HBP adduct are [HBP], 90 g/l; [DMDHEU], 200 g/l; LR, 1/3.3; [NC₄LH], 20 g/l; a time of 30 min and a temperature of 160°C. Moreover, the results also showed that the extent of removal of such dyestuffs from their aqueous solutions by the prepared adduct follows the order: reactive dye>acid dye>direct dye, it is more pronounced at lower than at higher pH values and the removal of each dye by that adduct follows a first‐order reaction.

Other substrates such as chitosan can be used to prepare more effective adducts.

Hyperbranched polymers can be used effectively to prepare ion exchangers capable of removing the pollutants of dyestuffs from their aqueous solutions.

The aforementioned prepared HBP is a novel hyperbranched polymer and could be applied in the removal of many other pollutants.

The purpose of this paper is to compare light fastness assessments by exposure of fabric dyes with various dyes in daylight and an artificial xenon arc lamp.

Cotton fabric dyed with 66 reactive, vat, azoic and direct dyes dyed in different depths were exposed to daylight and Xenon arc lamp for assessment of light fastness by standard methods. The light fastness rating and fading hours by the two methods were analysed and compared statistically.

The correlation between the corresponding light fastness rating (LFR) measured in Xenotest and daylight is quite high (0.93). The logarithmic correlation coefficients between fading hour (FH) and LFR in Xenotest and daylight are 0.95 and 0.88, respectively. For Xenotest, the assessed LFRs are same as those predicted from geometric progression up to LFR of 5.5, and thereafter, the former is higher. On the other hand, in the case of daylight, the assessed LFR is lower. Assessments for three successive seasons showed high repeatability in case of Xenotest and moderate repeatability in case of daylight. Assessments for three successive seasons showed high repeatability in case of Xenotest and moderate repeatability in case of daylight.

The exposure conditions in daylight cannot be controlled or standardised, whereas the exposure in Xenon arc lamp in the accelerated fading instrument can be strictly controlled. These differences in exposure control may affect the repeatability of experimental findings.

Inconsistent ratings may be because of little deterioration of samples during storage, as well as seasonal variation of daylight.

There are no direct social implications.

The researches on the comparison of the two light fastness assessment methods have not been reported in any recent publication to the best our knowledge.

In recent years, the textile industry has been required to develop new methods and technologies through introduction of some new materials in various processes rather than employing the same conventional chemicals. The aim of this research was to investigate the changes induced on the cotton fibre by the nanoclay treatment using a pre‐treatment method.

The fibres were dyed with basic and direct dyes after the nanoclay pre‐treatment. Technical measurements were studied including Fourier‐transform infrared spectroscopy (FTIR), UV‐visible spectrophotometer, differential scanning calorimetry (DSC), thermal degradation analysis (TGA), scanning electron microscopy (SEM), moisture regain measurement (MRM), tensile strength test (TST), reflectance spectroscopy (RS) and fastnesses evaluation.

The intensity of the major peaks in FTIR spectra of the nanoclay treated sample is in favour of the chemical changes of the cellulose functional groups. Basic dyes showed a higher dyeability on the clay pre‐treated samples compared to raw materials. The results of the colour measurements showed that the more concentration of the clay mineral was used, the darker the colour of the dyed sample was. Some interesting results were obtained in the research.

The nanoclay and a dispersing agent used in the present context were used as received. Besides, the type of the dispersing agent is important for preparation of a colloidal dispersion of nanoclay.

The method developed in this research provides a simple and practical solution for improving the dyeability of cotton with direct and basic dyes.

The method for enhancing the dyeability of cotton is novel and can be used in cotton processing with new properties.