Sustainable application of Cassia obovata-based chrysophanic acid as potential source of yellow natural colorant for textile dyeing

Bio-mordants: a review

Due to the increasing pressure on environmentally friendly approaches and sustainable production processes, the textile dyeing industry has focused on natural colorants. Thus, the use of bio-mordants, which are biological materials, has become widespread as an alternative to metal salts, most of which are non-ecological, used in the application processes of natural colorants. In natural dyeing, dyers want to use mordant substances in the dyeing processes in order to both expand the color spectrum and improve the fastness properties. Conventional metal salts used in natural dyeing are made up of metallic ions, which, when released into the environment as wastewater effluent at the end of the dyeing process, cause major damage to the ecosystem. Many researchers have thought about using mordants derived from natural sources to address the environmental problem. This article is a review of the investigation of natural mordants used instead of metallic mordants in the process of coloring various textile materials with natural dyestuff sources. It has been determined that many substances, most of them herbal materials, are used as mordants. In this review, mordants, except for conventional metal salts, are examined under three main groups for a better understanding. These groups are as follows: (i) natural or bio-mordants, (ii) oil mordants, and (iii) new-generation and non-vegetable-based mordants. Here, researchers will find an overview of the most recent developments in green mordants as well as application techniques for a variety of mordants.

Application of different concentrations of the natural dye potassium norbixinate (annatto) in polyamide 6.6 fabrics

Polyamide fabrics were dyed with concentrations ranging from 4% to 0.25% (o.w.f.) of the natural dye, potassium norbixinate (annatto). The exhaustion, chromatic coordinates, colouristic intensity (K/S), and fastness to washing and rubbing were evaluated. The natural dye was characterised, and its maximum absorption peaks were identified at 452 nm and 482 nm through UV-vis scanning. Its main chemical groups were identified by FTIR-ATR. All dyeings exhibited high exhaustion percentage, with a maximum of 98.4% for 1% dye concentration. The dyed samples displayed visually appealing orange hues, with a maximum K/S value of 6.9. Most of the fastness test results were rated between 5 and 4/5, remaining within the standards established by most textile industries. Potassium norbixinate exhibited a similar tinctorial behaviour to synthetic acid dyes for polyamide, suggesting ionic chemical reaction interaction between dye and polyamide, highlighting the potential use in the textile industry.

Sustainable appraisal of lac (Kerria Lacca) based anthraquinone natural dye for chemical and bio-mordanted viscose and silk dyeing

The coloring behavior of laccaic acid, a natural red dye derived from lac insects, has been investigated in this work for the dyeing of silk and viscose fabrics while being heated in MW radiation. The extract was made in an aqueous and acidic media and then used to color fabrics under microwave treatment for up to 10 min. For developing new shades, eco-friendly green bio-mordants and, in comparison, chemical mordants were employed at given conditions. The obtained results revealed that the aqueous extract after 4 min of radiation exposure produced a high color strength (K/S  =  17.132) onto silk and the aqueous extract after 6 min of radiation exposure produced better color strength (K/S  =  6.542) onto viscose at selected conditions. The fastness ratings evaluation as per ISO standards demonstrates that bio-anchors have provided good ratings under selected irradiation and dyeing conditions. It is concluded that this environmentally friendly technique has improved the natural coloration process of fabrics as well as addition of green mordants has furnished colorfast shades using lac-derived natural anthraquinone dye.

Anthraquinone Removal from Cassia obtusifolia Seed Water Extract Using Baking, Stir-Frying, and Adsorption Treatments: Effects on the Chemical Composition, Physicochemical Properties of Polysaccharides, and Antioxidant Activities of the Water Extract

Safety issues of the controversial anthraquinones from Cassia obtusifolia seed water extracts (CWEs) limit its application. This work aimed to remove the anthraquinones of CWEs by baking treatment (BT), stir-frying treatment (ST), and adsorption treatment (AT). Effects of these treatments on the chemical composition, physicochemical properties of polysaccharides, and antioxidant activities of CWEs were analyzed and compared. Results indicated that AT exhibited the best removal effect on the total anthraquinone among the three treatments. After AT, the contents of rhein, emodin, aloe-emodin, and aurantio-obtusin of the CWE were below the limit of detection. In addition, AT increased the contents of neutral sugars in CWEs in comparison to BT and ST. None of the treatments had an obvious influence on the structural characteristics of polysaccharides. However, AT decreased the antioxidant activity of CWEs due to their lower anthraquinone content. In summary, AT was considered as an efficient and simple method to remove anthraquinones, while retaining the features of polysaccharides.

Microwave-assisted sustainable exploration of cocklebur leaves (Xanthium strumarium L.) as a novel source of distinct yellow natural colorant for dyeing cotton fabric

During current times, the use of bio-colorants attained public acceptance as a sustainable alternative to synthetic ones which in turn reduced the environmental contamination. The present study focused on the green, safe, and clean technology for the resurgence of natural colorant from cocklebur (Xanthium strumarium L.) leaves and their application to cotton fabric. Natural colorants were extracted by employing an eco-friendly microwave-assisted extraction process using an aqueous and alkaline medium. Dyeing of cotton fabric was carried out using irradiated and unirradiated cotton fabric with irradiated and unirradiated natural dyes of cocklebur leaves. The results of extraction experiments revealed that 4 min microwave-assisted alkaline extract exhibited significantly outstanding color strength onto microwave-treated cotton fabric compared to aqueous one. Further to investigate the optimum dyeing conditions for cotton fabric, various dyeing variables such as dyeing time, dyeing temperature, dye concentration, and exhausting agent were monitored and found a superior result using a dye concentration of 45 ml, for dyeing cotton fabric at 75 °C for 50 min in the presence of 4 g/100 ml of table salt. For improvement in color strength and color fastness properties, the effects of various bio-mordants, such as eucalyptus bark, acacia bark, turmeric rhizome, and onion shells, and chemical mordants (aluminum and copper) on dyed cotton fabric were also evaluated. It was also observed that cotton fabric dyed with alkaline extract of cocklebur leaves using bio-mordants as pre-mordants (4% acacia, 4% eucalyptus, 2% onion) and post-mordants (3% onion, 3% eucalyptus, 4% acacia) exhibited the highest color strength and various hues with acceptable colorfastness properties against light, washing, and rubbing in comparison to chemical mordants. The ISO standard for fastness also revealed that bio-mordanting has enhanced the rating from good to excellent in comparison to chemical mordants. The results provide ample scope for the extraction of yellow natural dye from the cocklebur leaves for eco-friendly coloration of fabrics using bio-mordants.

Assessment of wild turmeric-based eco-friendly yellow natural bio-colorant for dyeing of wool fabric

The current study has been designed to observe the coloring efficacy of wild turmeric-based natural yellowish colorant for wool dyeing under microwave (MW) treatments. Extracts and fabrics have been exposed to MW treatment for up to 10 min. Surface morphology and changes in the fabric's chemical nature before and after radiation have been studied through SEM and FTIR, respectively. The results obtained after a series of experiments show that using 45 mL of aqueous extract (pH = 5) in the presence of 1.5g/100mL of table salt as an exhausting agent at 75°C for 45 min has displayed outstanding color depth (K/S) onto microwave-treated wool fabric. On applying biomordants, it has been found that acacia extract (1.5%), pomegranate (2%), and pistachio extracts (1.5%) before dyeing, whereas acacia (1%), pomegranate (1%), and pistachio extracts (2%) after dyeing, have shown colorfast shades of high strength. Comparatively, salts of Al (1.5%) and Fe (1%), and T.A (2%) before dyeing, while salts of Al (1%) and Fe (1.5%) and T.A (1.5%) after dyeing, have given the best results. Generally, it has been originated that salt of Fe (1.5%) as a post-chemical mordant and pomegranate extract (1.5%) as a post-bio-mordant have displayed wonderful color strength. It very well may be inferred that MW treatment, being naturally protected, has just superior the varying strength of colorants on wool fabric. Adding biomordants has transformed the strategy into a more sustainable one.

Environmental-friendly extraction of Peepal (Ficus Religiosa) bark-based reddish brown tannin natural dye for silk coloration

The present study aims to extract a natural reddish brown colorant from Peepal (Ficus religiosa) for silk dyeing using the microwave radiation process (MW). The colorant was isolated in aqueous and acidic media, and MW treatment for 1, 2, 3, 4, and 5 min has been given to both fabric and extract to observe changes in color intensity. The dye variables have been optimized, and for sustainable shade making process with good fastness, 1.0-5.0 g/100 mL of sustainable chemical and bio-mordants has been employed. It has been found that after microwave treatment for 3 min, under selected conditions, the irradiated aqueous extract has given high color intensity onto silk fabric. The utilization of 3% of Al, 4% of Fe, and 2% of tannic acid (T.A.) as pre chemical mordant whereas 4% of Al, 4% of Fe, and 3% of tannic acid as post chemical mordant have given good color characteristics. In comparison, 4% of acacia and 3% of turmeric and pomegranate while 3% of acacia and turmeric and 4% of pomegranate extracts as post-bio-mordant have given excellent color characteristics. It is concluded that MW treatment has an excellent sustainable efficacy to isolate colorant from Peepal bark for silk dyeing, whereas the inclusion of bio-mordants has not only made the process more sustainable and environmental friendly but also best K/S, and L*a*b* values have been acquired.

Valorization of Juglans regia. L Bark Residues as a Natural Colorant Based on Response Surface Methodology: A Challenging Approach to a Sustainable Dyeing Process for Acrylic Fabrics

The dyeing industry is considered one of the most polluting industries. Thus, several researchers have focused on studying the possibilities of natural textile dyeing. The objective of this paper was to optimize the microwave extraction process for Juglans regia bark residues in order to dye acrylic fabrics. Hence, at first, the following extraction conditions were studied: microwave power, pH, extraction duration and concentration of dry mass. Flavonoid and tannin content was measured each time. Moreover, the obtained extracts were used for dyeing acrylic fibers with microwave assistance, and the corresponding color yield (K/S) was measured. Then, the microwave extraction process already developed was optimized; a response surface design was established using Minitab 19 software. The optimal extraction conditions were found to be: microwave power = 850, pH = 3 and extraction time = 4 min. Finally, dyed and undyed acrylic were characterized by infrared (FTIR) spectroscopy in order to distinguish the effect of this natural dye on the external layer of the acrylic fiber.