Optimum Dyeing Conditions Research Articles

Enhancing dyeability of sustainable polylactic acid fabrics through cross-sectional modification of filaments

Polylactic acid (PLA) fiber, renowned for its renewable and biodegradable nature, is increasingly recognized as a promising alternative to conventional polyethylene terephthalate (PET) polyester fiber in the textile industry. However, the poor dyeability of PLA has limited its widespread industrial application. This study aims to enhance the dyeability of PLA fabrics by modifying the cross-sectional shape of PLA filaments and optimizing the dyeing conditions for disperse dyes. PLA filaments with circular, cruciform, and trilobal cross-sections (designated as PLAO, PLA+, and PLAY, respectively) were fabricated and then knitted into fabrics. Dyeing experiments using three different disperse dyes consistently demonstrate that PLA+ fabrics exhibit the best dyeing performance, followed by PLAY fabrics, with PLAO fabrics showing the lowest effectiveness. These results highlight the significant effect of filament cross-sectional shape on dyeing performance. Further macroscopic and microscopic analyses indicate that profiled PLA+ and PLAY filaments possess higher non-roundness factors and specific surface areas, lower glass transition temperatures, and reduced crystallinity, collectively enhancing their dyeability. In addition, lower fabric luster contributes to achieving deeper color. The study also identifies the optimal dyeing conditions for PLA fabrics with the selected disperse dyes: pH 5.0, dye concentration of 4% owf, dyeing temperature of 110°C, and dyeing time of 30 minutes. Under these optimized conditions, PLA+ and PLAY fabrics exhibit significantly enhanced K/ S values, while dyeing levelness and color fastness across all PLA fabrics remain within acceptable ranges.

Clean production and dyeing of fluorescent yellow dyes based on naphthalic anhydride in supercritical carbon dioxide

Supercritical carbon dioxide (scCO2) was selected as the medium for the synthesis and dyeing of four naphthalimide dyes (Y-1, Y-2, Y-3, and Y-4). They were synthesized through the reaction of 4-bromo-1,8-naphthalene dianhydride with various amines. These dyes demonstrated good photophysical properties and thermal stability, aligning with the prerequisites for scCO2 dyeing. Consequently, the scCO2 dyeing of polyester fabrics using these four dyes was investigated, and the optimal dyeing conditions were established in the range of 1820 MPa, 120130℃, and 8090 min. Surface analysis confirmed the uniform distribution of the dyes on the fabrics, with no significant damage to the fabric structure under the dyeing conditions. Additionally, the dyed fabrics exhibited good color fastness to soap washing and friction with level 4 or above. Overall, the clean preparation and dyeing of naphthalimide dyes hold promise for reducing environmental pollution.

Study of Dyeing With Natural Extract of Butterfly Pea Flowers (Clitoria Ternatea) on Cotton Fabrics

Objective: This study aims to optimize the dye extraction and dyeing variables in cotton fabrics using dried Butterfly Pea flowers (Clitoria ternatea), in order to evaluate its potential as a natural dye in the dyeing of cotton fabrics. Theoretical Framework: This research is presented based on fundamentals related to dyeing with natural dyes, dye extraction and pre-mordanting procedures, as well as studies related to the dyeing of cotton fabrics. Method: This research was carried out by varying the dye extraction temperature and dyeing parameters, which were documented and optimized. The pre-mordanting process was also used with 5 different biomordants, at the end the washing and friction fastness properties of the fabrics dyed with and without the pre-mordanting process were observed. Results and Discussion: The results showed that the best dye removal temperature was 70°C and the optimized dyeing conditions were a temperature of 50°C, time of 60 minutes and pH 3. In general, the use of biommordants did not promote improvements in solidity interactions. Research Implications: The use of natural dye made from Butterfly Pea flowers in dyeing provides a blue color to the cotton fabric, which is difficult to achieve. Originality/Value: The use of natural dye made from Butterfly Pea flowers in dyeing provides a blue color to the cotton fabric, which is difficult to achieve.

Sustainable Bio-Dyeing of Cellulosic-Based Fabrics with Anthocyanins from Black Carrot (Daucus carota L.)

Abstract In this study, anthocyanin-based black carrot (Daucus carota L.) extract was investigated as a natural textile dye on cellulose-based flax and cotton. Sodium alginate and gall oak (Quercus infectoria Olivier) were used as bio-mordants. The optimal dyeing conditions were determined by varying the amounts of these organic bio-mordants. A CIEL*a*b* spectrophotometer was used to measure the color characteristics of the dyed samples. The RP-HPLC-DAD method was used to identify the dye components in all dyed fabrics. Moreover, the dyed fabrics were evaluated for color fastness to washing, light, and rubbing. The mixture of these bio-mordants gave good color efficiency and acceptable colorfastness test results. Consequently, it appeared that black carrot (Daucus carota L.) can be used to color natural fibers. Applying these natural dye sources and bio-mordants may easily produce various colors.

Diversifying color palette of Prangos ferulacea colorants on wool yarns: dual mordant approach for enhanced color, antioxidant, and UV protection properties

Natural dyes have gained significant attention in recent years due to their environmentally friendly characteristics. This research paper focuses on the dyeing of wool yarns with P. ferulacea aerial part extract in conjunction with biomordants and metal mordants. The study focused on optimizing dyeing variables including pH of 2–8, temperature of 65 °C–95 °C, dye concentration of 25%–125% o.w.f., and dyeing time of 15–120 min using a one-factor-at-a-time (OFT) optimization by determining the color depth (K/S) values on wool yarns. The optimized dyeing conditions were a pH of 4, a temperature of 95 °C, a dye concentration of 75.0% (o.w.f.), and dyeing time of 60 min. The color hues, brightness, color intensity, and fastness of the samples varied significantly depending on the kind and nature of the biomordant used. Furthermore, the introduction of metal ions as pretreatment to biomordanted wool yarns exhibited unique characteristics such as the creation of new color shades, the combined enhancement of dye absorption (K/S), and increased color fastness with the most colorfast hues produced by Cr, Cu, and Fe-biomordant combinations. The antioxidant potential of biomordanted wool yarns was evaluated in terms of the inhibition of peroxidation by 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging activity and compared to the un-dyed wool yarns. The two-step mordanting process enhanced the antioxidant activity of dyed wool yarn (up to 99.90%) compared to the unmordanted sample (58.30%) and the negative control sample (5.70%). The ultraviolet protection factor (UPF) values were found in a very good to excellent range, with a rating >40 and maximum protection (UPF = 59.80) provided by Fe-YM mordanting. The findings indicate that this efficient technique enabled us to broaden the spectrum of colors generated by the extract of P. ferulacea aerial parts on wool, while simultaneously guaranteeing outstanding antioxidant and UV protection characteristics.

A study of the effect of organic acids (gallic acid and ascorbic acid) on the coloration and functionalization of wool yarns with Millettia laurentii sawdust natural dye

Wastewater from the textile industry, especially the dyeing sector, is a major contaminant for aquatic ecosystems. Synthetic dye compounds and metal salts from leftover mordant and dyeing baths are washed into rivers, endangering aquatic life and the environment. In regards to the current study’s examination of Millettia laurentii sawdust’s potential as a natural color source, eco-friendly organic acids (gallic acid and ascorbic acid) were studied in conjunction with small amounts of metal salts (aluminum sulfate, stannous chloride, copper sulfate, and ferrous sulfate) for enhancing the color shade palette with simultaneous functionalization (antimicrobial and UV-protection) of wool yarns. The effects of metal salts up to ecologically permissible concentration limits on the dyeing and functional properties were assessed in combination with organic acids. The study focused on optimizing dyeing variables including pH (2–8), temperature (65–95 °C), dye concentration (25–125% o.w.f.), and dyeing time (15–90 min) using a one-factor-at-a-time (OFT) optimization by determining the color depth (K/S) values on the wool yarns. The optimized dyeing conditions were pH of 4, temperature of 95 °C, dye concentration of 75.0% (o.w.f.), and dyeing time of 60 min. The color characteristics (CIEL*a*b*c*ho) and fastness (Wash, rub, and light) properties are evaluated comparatively against control dyed wool yarns using standard methods. The antimicrobial activity of control dyed and mordanted dyed wool yarns was evaluated in terms of the percentage microbial reduction of bacterial colonies. Metal salts especially ferrous sulfate in conjunction with gallic acid (Fe/GA) provided the highest average color strength (13.50) with a maximum percentage microbial reduction of 96.67%. UV protection ability was assessed by an Australian and New Zealand standards (AS/NZS 4399: 1996) method in terms of UPF values. UV protection levels were significantly improved by using binary combinations of organic acids and metal salts with the maximum protection offered by Fe/GA (97.66) and Sn/GA (97.90). Dyeing outcomes were significantly impacted by the chemical structure of organic acids (gallic acid and ascorbic acid) and the type of metal salts; the research proposes a more environmentally friendly natural dyeing process for the textile industry.

Towards environmental protection and safety coloration process in wool fibers: Role of disperse reactive dyes structure

Traditional wool fibers dyeing uses a huge amount of water and energy, and relies on lots of chemicals, which produces huge amounts of lower-biodegradable wastewater, and poses a great threat to the water environment. Here, to investigate the role of disperse reactive dyes structure on the dyeing properties, a sustainable waterless dyeing of wool fibers was investigated with four synthesized disperse reactive dyes by using supercritical CO2 as a non-aqueous dyeing medium. The effects of dyeing time, pressure, temperature and dye concentration on the dyeing properties were discussed. The results showed that K/S values up to 5.5 under the optimal dyeing condition of 383.15 K, 23 MPa, and 70 min were obtained, indicating shorter reaction time and higher K/S values compared to similar studies. Moreover, excellent colorfastness to soaping and rubbing up to 4–5 was displayed since nucleophilic substitution reaction occurs between the C atom on the triazine group of disperse reactive dyes and -NH2 on the cysteine of fiber macromolecules. This study provides an environmental protection and safety coloration process to produce high-quality wool fiber products by establishing the relationship between structure of disperse reactive dyes and dyeing properties of wool.

Eco-friendly natural dyeing of submicron cotton fabrics

To explore the color diversity and performance of functional submicron cotton fabric dyed with ecological natural dyes, three types of natural dyes sappanwood, madder, and gardenia and orchid, were used to dye the fabric. The optimal dyeing conditions for sappanwood were found to be an insulation temperature of 95°C, a dyeing bath pH of 5.5, and a dyeing time of 60 min, resulting in the highest apparent color value ( K/S). For madder, the optimal conditions were an insulation temperature of 90°C, a dyeing bath pH value of 6, and a dyeing time of 60 min. Similarly, for gardenia and orchid, the optimal conditions were an insulation temperature of 90°C, a dyeing bath pH value of 5, and a dyeing time of 60 min. Based on these preferred dyeing processes, the K/S value, color characteristic value, color fastness, and biodegradability of the three natural dyes were compared and analyzed with synthetic dyes. The results showed that natural dyeing resulted in higher brightness ( L* values), lower color depth ( C* values), lower red-green ( a*) and yellow-blue ( b*) values, similar hues, and lower K/S values compared to synthetic dyeing. The color fastness of the natural dyes was slightly lower than that of chemical dyes by 0.5 grade. Additionally, the average breaking strength, elongation at break, tearing strength, and bursting strength of the fabric increased by 9.34%, 5.69%, 9.75%, and 7.31%, respectively. Furthermore, the biodegradability of the natural dyes was over 93%, significantly higher than that of synthetic dyes. These findings provide a theoretical basis for the production of eco-friendly dyeing of functional submicron cotton fabrics and their textile color applicability.

Synergetic construction of color and multifunction for sustainable lyocell fabric by microbial nano pigment

As a kind of low-carbon, environmentally friendly and high-quality regenerated cellulose fiber derived from nature plant, the promotion and application of lyocell fiber is attracting much attention. In this paper, for the first time, microbial pigment was applied for color and multifunction construction of lyocell fabric. The size change of the pigment nano-particles during the color construction process was explored to verify the dyeing mechanism of nano-suspension system, and the optimal dyeing condition was obtained. In order to improve the dyeing effect and functionality of fabric, 1,2,3,4-butanetetracarboxylic acid (BTCA) was used to realize the anionic modification of lyocell fabric with high strength retention rate. Under optimal color construction condition, the color depth of the modified fabric was 298.5% higher than that of the unmodified one, and the dyed fabric possessed excellent dyeing uniformity and permeability. Moreover, the crosslinking reaction between BTCA and cellulose macromolecules, as well as the pigment deposition inside the fibers were helpful to the fibrillation prevention function of lyocell fibers. Dyed fabrics inherited the antibacterial and ultraviolet absorption properties of prodigiosins. The bacteriostatic rate against Staphylococcus aureus was above than 98.5%, and the UV protection performance was obviously improved. This technology successfully realized the color and multi-functional construction of the lyocell fabric in one step by natural pigment from microorganism.

Enhancing silk dyeing with eco-friendly colorant extracted from Cassia fistula brown pods using green mordants

This research project focuses on the extraction of the natural brown colorant, anthraquinone, from Cassia fistula pods using microwave radiation as a method for dyeing silk fabric. The colorant was isolated in aqueous and acidic mediums before and after microwave radiation for up to 6 min, and subsequently used for dyeing purposes. To achieve new and diverse hues, environmentally friendly chemical mordants (iron salt, aluminum salt, and tartaric acid) and biological mordants (red sumac, pomegranate, and hulela zard) were applied in varying quantities (ranging from 0.5g to 2.5g per 100 mL). Colorfast shades were developed by employing these mordants before and after the dyeing process on silk fabric. The dyeing variables essential for shade development before and after mordant application were determined through the utilization of central composite design for statistical analysis. The results indicated that the optimal conditions for irradiating both silk and extract were 6 min, while dyeing the irradiated silk fabric should be conducted at 75 °C for 45 min using 30 mL of extract irradiated at a pH of 3, with a salt concentration of 1.5g/100 mL. The optimized dyeing conditions also showed maximum level of colorfastness properties of 5 for light, 5 for wash, 5 for dry rubbing and 4/5 for wet rubbing. As a result, the extraction of anthraquinone from Cassia fistula pods using microwave radiation has the potential to be effective and ecologically benign, allowing for the creation of bright and colorfast hues on silk fabric. The results support the development of novel and sustainable dyeing techniques in the textile sector.

Dyeing of cotton/acrylic blend fabric in a single‐bath‐single‐stage method using indigo dye

AbstractIn this study, an attempt has been made to dye cotton/acrylic blend fabrics in a single‐bath‐single‐stage method considering today's growing market for such blended products. Yarn‐blend cotton/acrylic fabric was produced and dyed at 3% shade using indigo dye in the exhaust method to optimise the dyeing conditions by varying the amount of reducing agent, pH, and dyebath temperature. The colour yield of both the acrylic part and cotton components of the blend was influenced by pH levels. Meanwhile, the temperature played a notable role in determining the colour yield of the acrylic portion. Optimised dyeing conditions were obtained at pH 6 and 120°C for the acrylic part, whereas pH 11 and 90°C temperature were obtained for the cotton part. These conditions involved the use of sodium dithionite (15 g/L) as a reducing agent and sodium hydroxide as an alkali. While the yarn‐blend fabrics exhibited a unique shadow dyeing effect, solid dyeing results were achieved with fibre‐blend fabrics, underscoring the versatility of this single‐bath‐single‐stage method. To assess the overall dyeing performance, comprehensive evaluations including bursting strength measurements, assessments of fastness to washing, perspiration, and rubbing were conducted, all of which provided valuable insights into the durability and colour retention of the yarn‐blend fabrics. This research not only addresses the demand for cotton/acrylic blend fabrics in today's market but also demonstrates an efficient and innovative single‐bath‐single‐stage dyeing approach using indigo dye, which holds promise for the textile industry's future sustainability and product diversity.

Textiles Dyeing with Pomegranate (Punica granatum) Peel Extract Using Natural Mordant

ABSTRACT Agricultural waste represents a potential source of raw materials as natural dyes. The peel from pomegranate (Punica granatum) is a waste product, it is used in the textiles industry as dye. The objective of the study is to improve dyeing properties of pomegranate peel dyed silk fabric. We analyzed the pigment composition of pomegranate peel extract through ultraviolet-visible and Fourier-transform infrared (FTIR) spectroscopy; evaluated natural mordants and metallic mordants on fabrics dyed with pomegranate peel extracts by testing the K/S value, color characteristics, and color fastness; examined the morphology of dyed fabrics before and after color fixing treatment by scanning electron microscopy. The major pigment component in pomegranate peel is ellagic acid. An orthogonal array experiment revealed that the optimum dyeing conditions were pH 9, 60°C 60 min for silk fibers. Under the natural mordant, the K/S value of dyed fabric could acquire maximum (8.70). Moreover, the K/S value and color fastness of dyed fabrics could be further enhanced to 11.74 and level 5 by color-fixing treatment of natural gum rosin. Overall, the dyed silk samples with pomegranate peel represented good dyeing properties with natural mordant and natural color-fixing agent of gum rosin.

Synthesis of novel carbene dyes and investigation of their dyeing properties and reaction mechanism for various fabrics

Week interactions between traditional dye molecules and synthetic fibers requires addition of numerous chemical additives during the dyeing process, resulting in the generation of a significant amount of printing and dyeing wastewater, thereby causing environmental pollution. Herein, three novel carbene dyes containing diazirine were rationally designed, whose decomposition into carbenes at 145 °C subsequently forms covalent bonds with the C–H bonds present in the fibers. The structure-property relationships of the dyes were analyzed based on the results of density functional theory (DFT) calculations. Additionally, the calculations of Yoshida correlations demonstrated that all three dyes exhibit non-explosive properties, thereby indicating their feasibility for large-scale production. The dyeing process of polyester (polyethylene terephthalate/PET), polypropylene (PP), aramid, spandex, and polyester/spandex (P/S) blended fabrics was performed using a non-aqueous solvent dyeing method without the addition of any additives, and the optimal dyeing and color fixation conditions were determined. The samples dyed with carbene dyes displayed similar K/S values compared to conventionally dyed samples, higher color fixation rates, and improved blended dyeing effects, and the reaction mechanism between the carbene dyes and the fibers was elucidated, which proved the versatility and environmental friendliness of the novel carbene dyes and non-aqueous solvent dyeing method. Furthermore, it is noteworthy that all of these dyed fabrics exhibited exceptional color fastness, highlighting the immense potential of the novel carbene dyes in promoting green production in the textile industry.

Plant colorants for natural hair coloration: Dyeing optimization and photostability assessment

There is a growing interest in using naturally-occurring plant colorants as alternative to the toxic synthetic colors for hair coloration. However, poor color reproducibility and color fastness on the human hair remain a constant problem for natural hair dyeing. This study presents a systematic investigation into the dyeing performances of dye extracts of four hair dye plants (henna, walnut husks, sappanwood and Chinese gallnuts) for hair coloration with the focus on their photostability on the dyed human hair and the underlying mechanisms. First, the optimal dyeing conditions for each of the four plant colorants were obtained on yak hairs by assessing the effects of different dyeing variables (i.e. metallic mordants, mordant concentrations, mordanting methods and pHs) on color strength and CIE coordinates. Then, the plant colorants with ferrous mordant as the most influential metallic mordant to produce dark colors were investigated in terms of dyeability and photostability on human bleached hairs and natural gray hairs. The results demonstrated that the photosensitivity of naturally dyed human hairs is related to the nature of both hair dye colorant and the dyeing substrate. ESR measurement and fluoresce probing of hydroxyl radicals in hair fibers revealed that dyeing human hairs with natural plant colorants can inhibit, to varying extents, the photogeneration of oxidative radicals in human hairs, which may in turn provide the dyed human hairs with certain photo-protecting effects.

Catechin-rich reddish-brown dye from cocoa (Theobroma cacao L) leaf for functionalizing herbal-anchored wool fabrics

Colorists are seriously worried about the long extraction time, low color yield and colorfastness of natural dye obtained via conventional extraction techniques. In this study, microwave (MW)-aided extraction technique was exploited as an alternative method to the conventional extraction technique. The cocoa leaf extraction parameters were varied for obtaining optimal extraction conditions. Likewise, dyeing and mordanting parameters were varied for achieving dyed wool fabric with preferred tint strength (K/S) and colorfastness. The colorimetric properties of MW-aided cocoa leaf extract (CL) dyed wool fabrics were compared to those of the conventional extract dyed fabrics. The antioxidant, antibiotic and ultraviolet protection properties (UPP) of un-dyed, MW-irradiated CL dyed and mordanted wool fabrics were evaluated for healthcare functional properties. MW-irradiation enhanced the dye yield by 33.82%, reduced the extraction time by 90% and increased tint yield by 44%. The optimal dyeing conditions were liquor ratio 1:20, pH 6, 45 min dyeing time and temperature of 65 °C. Post-mordanting with 5% Fe2+ and 9% Al3+ as chemical-mordants enhanced K/S and colorfastness of the dyed fabric from good to very good, while 3% neem and 7% moringa bark extract as herbal-anchors improved the dyed fabrics’ K/S and colorfastness from good to excellent. Dyeing enhanced the poor antioxidant and antibiotic properties of MW-irradiated fabrics to excellent, which was further boosted after mordanting process. All the fabrics possess desired UPP. Desired healthcare functional properties of MW-assisted CL dyed wool fabrics after fifth laundry cycle established CL extract as a potential future sustainable colorant for producing healthcare wears.

Optimization of the process parameters for dyeing silk fabric with a fungal pigment using RSM

This study explores the extraction and application of a sustainable dye derived from Talaromyces purpurogenus fungi for dyeing silk fabric. The fungal dye imparted a vibrant red shade to silk, offering a promising alternative to synthetic dyes. The dyeing process was optimized using the Box and Behnken Design of RSM software, focusing on dye pH, dyeing temperature, and dyeing time. Silk fabric was dyed using an HTHP dyeing machine, and its performance was assessed in terms of colour strength, percent absorption, light fastness, rubbing fastness, and washing fastness. SEM imaging and FT-IR spectroscopy were employed to investigate the interaction between the dye and silk fabric. The optimized dyeing process resulted in silk fabric with a satisfactory red shade, demonstrating favorable fastness ratings at pH 5. The optimal dyeing conditions included a dye pH of 5, dyeing temperature of 82 °C, and dyeing time of 55 minutes, with an optical density of 10 and MLR of 1:30. Silk fabric exhibited maximum dye absorption capacity at pH 5, while maintaining excellent washing and rubbing fastness properties. However, the light fastness of the dyed silk fabric was relatively poor. Microscopic examination revealed a rough surface texture. Overall, this study highlights the potential of T. purpurogenus fungal dye as a sustainable alternative for silk fabric dyeing, while emphasizing the importance of addressing challenges such as improving light fastness through surface treatment and further exploring dyeing techniques.

Optimization of Process Conditions of Cotton Fabric Dyeing with Nettle Leaf Extract for Antibacterial Application Using Central Composite Design

ABSTRACT In this study, all conditions of the natural dyeing process of cotton fabric with antibacterial efficiency, extracted from the leaves of the nettle were optimized using a central composite design. The optimized dyeing conditions are: concentration of 16.943 g, temperature of 50 °C, time of 40 min, and the color strength obtained at optimum condition was 1.53. The Nettle natural dye is applied to cotton fabrics by the Pad-Dry-Cure method for imparting antibacterial properties to the textile product for apparel applications. Biomordants were applied on scoured cotton fabric in the pre-mordanting process of dyeing. Color characteristics of the dyed fabrics were measured by CIE L*a*b* value using a spectrophotometer. Gram-positive (S. aureus) and gram-negative (E. coli) bacterial assessments were performed quantitatively using the AATCC-100 test method. The results provided evidence that the treated fabric exhibits higher antibacterial efficiency of gram-positive and gram-negative bacteria by 96.5–98% reduction compared to the control samples, respectively. The one having the highest antibacterial activity was washed 15 times under the same conditions and samples were taken after 1, 5, 10, and 15 washes. They retained nearly 91% S. aureus and 94% E. coli activity up to 10 launderings against the two bacteria.

Single box dyeing of denim yarns under nitrogen protection with high indigo concentration

In the era of “double carbon,” green short process preparation of denim textiles will become more and more popular, and dyeing is an essential step in this process. In order to improve dye utilization and energy efficiency, a high-concentration indigo single box dyeing method based on nitrogen (N2) protection has been studied. The optimal dyeing conditions were obtained. The dyeing mechanism was revealed by evaluating the stability of the dyeing solution and dye distribution in the dyed yarns. Various dyeing properties, chemicals, energy consumption, and dyeing wastewater were measured and compared with conventional slasher dyeing. It has been shown that N2 protection effectively avoids the oxidation of soluble leuco-indigo and improves the stability of the leuco dyeing bath. In addition, the dyes diffused more deeply into the fiber in the dyeing box under a micro-positive pressure environment, enhancing the dyeing efficiency and depth. The proposed technique exhibited better dye utilization and excellent color fastness. Dyeing wastewater was more chemical and biodegradable, relieving wastewater treatment. Generally, cleaner dyeing not only reduces the consumption of energy, water, and chemicals, but also saves 46.8% of the economic cost compared with traditional slasher dyeing, indicating that the proposed technology is interesting for industrial application.

Ecofriendly hair dye extraction from wastewater pericarp processing by-products of water caltrop (Trapa quadrispinosa): Optimization and evaluation

As an alternative approach for toxicological effects of synthetic hair dyes, water caltrop (Trapa quadrispinosa) pericarp pigment extracted by 50% ethanol at 40 °C for 30 min was used as an ecofriendly and natural hair dye. Water caltrop pericarp (WCP) of seven regions were experimented to develop eco-friendly dyes intended for application in alternative chemical synthesis hair dyeing products. The results showed that the highest content of polyphenol was extracted from WCP in Jiaxing, which was used as a follow-up study. The optimization method was mordant dyeing first and then dyeing. Optimal dyeing conditions were identified as 4% Fe3+ at 25 °C with a total dyeing time of 65 min, and WCP hair dye showed better resistance to washing. The results of SEM and DSC showed that WCP hair dye could replace synthetic hair dyes and has some restorative function for damaged hair. This study provides a valuable reference for the development of more environmentally friendly hair dyes.

Agricultural crop of Scrophularia striata as a new dye for eco-friendly dyeing and bioactive finishing of handwoven piles

Today, great efforts were carried out to introduce sustainable colorants with low cost and high efficiency to protect the environment as much as possible. In this study, an agricultural crop (Scrophularia striata) was introduced as a new source of natural colorant for the dyeing wool yarns. The response surface method was used to deduce optimum dyeing conditions and to investigate the interactive effects of main dyeing parameters. Obtained results show that the total flavonoid and polyphenolic contents of the hydroalcoholic extract of S. striata were estimated to be equal to 44.37 mg quercetin equivalent/g of extract and 98.47 mg gallic acid equivalent/g of extract, respectively, thereby suggesting S. striata to be an ecological and low-cost novel dye for woolen coloration process. A statistically predictive model of the dyeing procedure was developed to correlate the operating variables and the dependent factors. The results also reveal that the dyed samples at the optimized dyeing condition show relatively high colorfastness and noticeable antibacterial properties against Gram-positive and negative bacteria. This means that the extract of S. striata could be considered a natural dye for the wool dyeing process with remarkable antibacterial performance and low energy consumption and environmental impact. Hence, the introduced colorant in the present work seems to be of potential use for a value-adding green waste management.