Explore the vast range of titles available.

Conventional extraction of natural dyes requires more energy and time. This research investigated a rapid and low-cost extraction method for red yeast rice, utilizing a pressurized extraction process with a coffee maker machine. The application of the extract for dyeing cotton fabrics was also investigated. The effects of extraction time, particle size, and temperature on the color value (CVU/gds) were investigated. The particle size varied at 16, 18, and 20 mesh, the extraction temperature varied at 85, 90, and 95 °C, while the extraction time varied at 3, 6, and 9 s. The dyeing process variables studied were reapplication and dilution of the extract solution. Reapplication was varied at the 1st, 2nd, and 3rd dyeing, while dilutions were varied by 1, 2, and 3 times. The highest color value is 15.3105 CVU/gds, obtained at a 20 mesh particle size and 85 °C of extraction. At a significance level of  = 0.05, reapplication up to 3 times had no significant effect on color strength (K/S); the K/S of 0.1813 decreased to 0.1521. At the same time, the dilutions significantly decreased the K/S, resulting in a K/S of 0.0129. The wet and dry rubbing fastness test was rated from very good to excellent (4.5–5), whereas the washing fastness test was rated as poor (1–1.5). The subsequent study should investigate the extraction process using higher pressure and organic solvents, as well as determine suitable mordants and higher temperatures for fabric dyeing.

The textile industry is developing rapidly in China. It generates large volumes of cotton dyeing pretreatment wastewater (CDPW). CDPW contains high concentrations of pollutants characterized by their strongly alkaline and recalcitrant nature for microbial degradation. This project aimed to evaluate the performance of a microbial electrolysis cell (MEC) coupled with anoxic/oxic (A/O) system (MEC-A/O) in treating CDPW, as well as analyze changes in microbial diversity. The results indicated that the effect of biological treatment in an electrolytic cell to treat CDPW was optimal at the voltage of 0.6V. The chemical oxygen demand (COD) removal efficiency under optimum conditions was 69.13%, higher than that of the A/O system alone (48.93%). Within a certain range, applied voltage was able to enhance microbial activity, increase the sludge concentration and enlarge the sludge particle size. At the same time, the applied voltage could effectively increase the abundance and the diversity of Bacteria and Archaea, as well as accelerate the degradation of pollutants.

Textile industry uses large quantities of different dyes to fulfill the rapidly growing demand for the dyed textile products, resulting in more dye consumption, greater dye discharge as textile dyeing effluent, and higher cost. To decrease the dyes consumption, this research evaluates the performance of novel ozone-based dyeing processes for cotton fabric. So far, reported ozone-based processes for textile involve the usage of high ozone intensity for removing impurities, discoloration of solution, color fading in denim and other fabrics. This research is a first effort, which concentrates on the performance enhancement of the exhaust dyeing process for cotton fabrics through the application of controlled and lower amount of ozone. In this research, ozone dosage is controlled through ozone generator knob to only 0.5 g/h (10%), 1 g/h (20%), 1.5 g/h (30%), 2 g/h (40%), and 2.5 g/h (50%). In contrast, ozone dosage reaches up to 60 g/h in cotton bleaching. This research evaluates the four ozone-based dyeing processes for cotton fabrics using two primary reactive dyes and two primary direct dyes under different concentrations of ozone. Effect of ozonation was evaluated for both direct and reactive dyes at four stages, namely during dyeing, dry ozonation before dyeing, pre-wet ozonation before dyeing, and ozonation after dyeing. Results showed that K/S value of the optimized ozone-based processes was better than the conventional exhaust process. For instance, K/S value for benchmarked conventional dyed sample was 2.147 for reactive yellow, and it was 3.271 (33.5% higher) for the “ozonation after dyeing” process. Similar trends were observed for many other trials, resulting in higher K/S value. In addition, the fastness properties of the optimized processes were comparable with the conventional exhaust process. FTIR and SEM analysis were also performed on selective ozone dyed fabrics.

The influence of caustic mercerization (CM) and liquid ammonia (LA) treatments on the properties of reactively dyed cotton fabrics were schematically studied. The cotton fabrics were dyed using different commercial reactive dyes such as Reactive Red 2 (R2), Reactive Blue 21 (B21), and Reactive Orange 5 (O5) via industrial dyeing procedures. The dyed fabrics were then treated using 260 g·L−1 of caustic soda solution at 23 °C for 180 s and pure LA at −40 °C for 3 min in slack and tension conditions. The dyeing properties of the fabrics such as dye removal percentage, color strength, color uniformity, reflectance, and fastness properties (washing, rubbing, hot pressing and light) were examined. The changes in tensile strength, elongation, bending property, decomposition temperature, crystal structure, and surface morphology of the samples were also investigated using a tensile strength tester, thermogravimetric analyzer (TGA), scanning electron microscope (SEM), and an X-ray diffractometer (XRD). Results revealed that the fabric dyed with O5 showed the best stability in CM and LA treatment, and the color strength and color uniformity of the dyed fabrics increased extensively after both treatments, while the reflectance of the fabrics decreased. The washing and rubbing fastness of the fabrics were also improved, which was mainly attributed to the diffusion of the dye molecules inside the fibers and enhanced bonding between fiber and dye molecules. The fastness to hot pressing and light was unaffected and all the samples retained fastness rating between 4 and 5 after being post-treated with the CM and LA, respectively. The tensile strength of the fabrics improved from 287 to 291 and 301 N, and the elongation at break increased from 11 to 21.5 and 26% after CM and LA treatment in slack conditions, respectively. Additionally, the tensile strength of the fabrics improved from 287 to 312 and 330 N, and the elongation at break increased from 11 to 12% after applying tension during both treatments. However, the total bending length and total flexural rigidity of the samples slightly increased after both the treatments either treated with or without tension, which was mainly attributed to the orientation of the cellulose microfibril angle along the fiber axis. The surface morphology and X-ray diffraction examination revealed that the treated samples consisted of smooth rod-like structure and the cellulose I allomorph was converted to cellulose II and cellulose III after CM and LA treatments. This developed treatment method could have application potential within the textile wet-processing industry, as it could be used to improve the dyeing properties and mechanical properties of cotton fabrics.Graphic abstract

Ecofriendly exploration of Arjun bark ( Terminalia arjuna ) is a herbal natural colorant for cotton dyeing. This is because the demand for natural dyes has been increased worldwide due to their therapeutic usage and other food, textiles, agriculture, engineering, and medical applications. Therefore, this study has been carried out due to the isolation of colorant from Arjun bark in an acidified methanolic medium after exposure to ultrasonic rays up to 60 min. Additionally, using bio-mordants, it has been found that the application of 10% of Zeera ( Cuminum cyminum ) extract as meta-bio-mordant, 3% of Ilaichi ( Elettaria cardamomum ) extract as meta-bio-mordant, and10 % of Harmal ( Peganum harmala ) and Neem ( Azadirachta indica ) extract as meta-bio-mordants has given excellent color strength. These bio-mordants have not only made the coloration process more eco-friendly, viable, and greener, but also improved color strength with various tonal effects from red to reddish brown shades. Thus, it has been found that ultrasonic treatment as an environment-friendly tool has not only enhanced the color strength of natural colorant isolated from Arjun bark onto the cotton fabric under mild conditions. Graphical abstract

The interest in pH-sensitive textile sensors is growing in the global market. Due to their low-cost production, mechanical stability, flexibility, air-permeability, washability, and reusability, they are more suitable than electronic sensor systems. The research tailored the pH-sensitive textile by applying the pH indicator methyl orange to the cotton fabric during conventional dyeing. Adsorption of methyl orange dye to cotton fabric is hindered due to electrostatic repulsive forces between dye anions and negatively charged cotton fibre. To overcome this problem, chemical modification of cotton fabric using a commercial product was performed. The pH sensitivity of the dyed fabric was spectrophotometrically evaluated. In addition, the colour fastness of dyed cotton fabric to washing, light, hot pressing and rubbing was investigated according to valid SIST EN ISO standards. The research results show that the pH-responsive cotton fabric was successfully developed. The chemical modification of cotton fabric is crucial for the increased adsorption of methyl orange dye. The halochromic effect was not only perceived spectrophotometrically but also with the naked eye. The developed halochromic cotton fabric showed poor colour fastness to light and good colour fastness to hot pressing and rubbing, while no significant improvement in colour fastness to washing was observed, even though the fabric was after-treated with a cationic fixing agent. Higher adsorption of the methyl orange dye to the cotton fabric during the dyeing process leads to less wastewater pollution after dyeing with unfixed dye and, thus, a reduction in wastewater treatment costs.

The application of plant dyes in the textile industry has been very limited due to their limited sources, incomplete color space, and narrow color gamut, etc. Therefore, studies of the color properties and color gamut of natural dyes and the corresponding dyeing processes are essential for completing the color space of natural dyes and their application. In this study, water extract from the bark of Phellodendron amurense (P. amurense) was used as a dye. Dyeing properties, color gamut, and color evaluation of dyed cotton fabrics were studied, and optimal dyeing conditions were obtained. The results showed that the optimal dyeing process was pre-mordanting with liquor ratio at 1:50, P. amurense dye concentration at 5.2 g/L, mordant concentration (aluminum potassium sulfate) at 5 g/L, dyeing temperature at 70 °C, dyeing time of 30 min, mordanting time of 15 min, and pH 5. Through the optimization of the dyeing process, a maximum color gamut range was obtained with lightness L* value from 74.33 to 91.23, a* value from −0.89 to 2.96, b* value from 4.62 to 34.08, chroma C* value from 5.49 to 34.09, and hue angle h° value from 57.35° to 91.57°. Colors from light yellow to dark yellow were obtained, among which 12 colors were identified according to the Pantone Matching Systems. The color fastness against soap-washing, rubbing, and sunlight on the dyed cotton fabrics all reached grade 3 level or above, further expanding the applicability of natural dyes.

The dyeing process commonly deteriorates the luster of pre-mercerized cotton fabric, so post-mercerization processes are regularly applied to compensate for this. Herein, the influence of combining pre-mercerization with CS (caustic solution) or LA (liquid ammonia) and post-mercerization with CS or LA on the morphological structure, dyeing performance, tensile strength, and stiffness of woven cotton fabric was investigated. The crystallinity index values greatly decreased from 73.12 to 51.25, 58.73, 38.42, and 40.90% after the combined mercerization processes of LA–LA, CS–CS, LA–CS, and CS–LA, respectively. Additionally, the CS–LA- and LA–CS-treated samples exhibited a mixture of cellulose II and cellulose III allomorphs. The combined mercerization processing of cotton fabric resulted in slightly worse thermal stability. The LA and CS pre-mercerization processes increased the dye exhaustion, although the former decreased the dye fixation rate while the latter increased it by 4% for both dyes. The color strength of the dyed cotton fabric increased after both post-mercerization processes. Moreover, the fabric stiffness and mechanical properties showed an increasing trend due to the combined mercerization efforts.

From sustainable chemistry and engineering perspectives, water and energy consumption are arguably the main issues in the textile industry. Thus, a silicone reverse emulsion dyeing system is developed to dye cellulosic textile with reactive dye. When the amount of dye is the same, the color depth of dyed cotton fiber is 13.82 and the fixation of dye is 87.76% in the silicone reverse emulsion dyeing system. In traditional water-based dyeing system, the color depth of dyed cotton fiber and the fixation of dye is only 9.31, 56.63% respectively. The silicone reverse emulsion dyeing technology does not consumes salts, but it can improve the dye fixation by 31.13%, and decreases the dye discharge by 72.41%. For the hydrolysis of bifunctional reactive dye, the main hydrolysis reaction is the individual hydrolysis of monochlorotriazine or vinyl sulfone at the prophase of hydrolysis. After 30 min, the additional β-hydroxyethyl sulfone and hydroxyl triazine dye are hydrolyzed to dihydroxyl dye. To confirm the hydrolytic reaction energy of dye in different dyeing system, the optimization of molecular structure, the hydrolysis reaction gap and the distribution of electron density on the dye were investigated using density functional theory. The hydrolytic reaction energy gap of bifunctional reactive dye is higher in silicone reverse emulsion dyeing system than that in traditional aqueous dyeing system, resulting the hydrolysis of dye is difficult in silicone oil emulsion dyeing system. The electron density is distributed almost entirely on the carbon–carbon double bond and triazine group in the HOMO of the dye, resulting in the LUMO of dyes can attacked by HOMO of hydroxyl anion. These successful investigations of the dyeing performance and the hydrolysis mechanism of dye explain that reactive dye can keep a long reactivity to fiber and effectively reduce the number of washing times, which greatly reduces the discharge of dyeing waste water.

The revival of cultural heritage in a form of natural colorants for textile dyeing is gaining popularity due to their soothing nature and bright shades. The present study was conducted to explore the coloring potential of harmala ( Peganum harmala ) seeds and to improve color strength of dye using microwave radiations followed by a mordanting process. The results showed that harmala plant seeds could be an excellent source of natural dyes for cotton dyeing if the irradiated acidified methanolic extract (RE, 4 min) is used to dye un-irradiated fabric (NRC) at 85 °C for 45 min using a dye bath of pH 9.0 having salt concentration of 7 g/100 mL. Alum (1%) as pre-mordants and iron (7%) as post-mordants have improved the color strength in chemical mordanting more than other mordants employed. The bio-mordants employed reveal that 10% of acacia as pre-bio-mordants and 7% of acacia as post-bio-mordants are effective amounts to obtain high color strength. Suggested ISO standards for colorfastness illustrate that bio-mordanting has given more excellent rating as compared to chemical mordants. It is concluded that harmala seeds have a great potential to act as a source of natural colorant for cotton dyeing under the influence of microwave radiation.