Green miles in dyeing technology: metal-rich pumpkin extracts in aid of natural dyes

To reduce environmental pollution, it is essential to use green processes in dyeing and meet its requirements. Most natural dyes have a low affinity to be used in the dyeing process. To refine this limitation, the mordanting flow is necessary for many dyeing cases. Pumpkin extract as a natural, metal-rich source can be used as a bio-mordant in green dyeing of natural yarns such as wool. Two natural dyes native to Iran, Reseda luteola and madder, were employed in this study. The effectiveness of bio-mordant presence on yarns was evaluated by FTIR-ATR test from mordanted and mordanted-dyed wool samples. The study of K/S (color strength) content of dyed samples showed that increasing the dye concentration increases the amount of K/S. Fastness performance of wool dyed with pumpkin alternated from good to excellent depending on natural dye type and concentration, due to the formation of complex structures.


Introduction
Patents evidence that varieties of materials, methods, and systems are born every day for the HITECH incentives. The orientation of technological developments towards sustainability needs reflected more level headedly in the future picture of advanced systems enlivened by the scientists working in the era of energy-harvesting materials. To come across requirements for a cleaner planet, green materials and technologies are developing too quickly, but still there are unsolved problems associated with materialization, mainly because of the materials used in manufacture of energy-harvesting devices not being either efficient or environmental friendly. Dyeing process with green colorants has received a great deal of attention in recent decades. Because of their renewability and biodegradability, natural dyes are crucial elements in textile, food, and drug coloration nowadays (Rather et al. 2016;Adeel et al. 2020). Though natural dyes can be derived from different sources such as invertebrates and minerals, plants are the commodity natural dyes used in this sense (Shen et al. 2014;Mehrparvar et al. 2016a, b). Nevertheless, only a few among natural dyes could be directly applied in coloring procedure because of their low affinity towards textile fibers-what demands mordanting as compliment to dyeing process (Hadder et al. 2014;Hosseinnezhad et al. 2021a, b). A mordant principally ties textile fibers with dyes by a coordination complex to compensate for the lack of affinity, but a few natural dyes yield good fastness properties; hence, optimizing dyeing process remained an unsolved problem (Indi et al. 2016).
Examples of natural dyes examined on dyeing are Emblica officinalis used in dyeing silk and cotton fabrics in the presence of different kinds of nature-inspired dyes that resulted in acceptable fastness properties when pre-mordanting was utilized (Prabhu et al. 2011); gallnut (Quercus infectoria olive) extract used in dyeing wool that resulted in a proper depth of shade and good fastness in the presence of alum mordant (Shahid et al. 2012;Hosseinnezhad et al. 2018); Manjistha, annatto, ratanjot, and babool extracts used in dyeing wool showing good hue of dyed fabrics and washing fastness (Chattopadhyay et al. 2013); Red Calico leaf extracts used in dyeing wool that resulted inacceptable fastness as well as an extraordinary antibacterial character featured by a high-strength fiber, and gamma irradiation declined the amount of bio-mordant and dyeing time (Ahmad Khan et al. 2014); mulberry (Morus rubra) extracts used in dyeing cotton fabrics under different conditions showing good fitness properties ; and pomegranate extracts used in dyeing silk showing higher fastness properties rather than metal salts (Hosseinnezhad et al. 2017); and particularly attempts being made by Rather and coworkers in using acacia nilotica (babul) in conjunction with Kerria lacca (Rather et al. 2019), gallnut, pomegranate, and babool in bio-mordant-aided green dyeing of wool and silk. Adeel et al. utilized coconut coir (Cocos nucifera) containing tannin as a source of natural colorants for coloration of bio-mordanted silk under the influence of ultrasonic radiations at various dyeing conditions. It is found that ultrasonic waves have excellent potential to isolate the colorant followed by dyeing and environmentally friendly mordanting at optimal conditions, but also, the usage of herbal-based plant anchors, i.e., bio-mordants, has made the natural dyeing process more sustainable and clean (Adeel et al. 2022).
We believe that the abovementioned bio-mordants with good dyeing performance can be categorized in a general class of tannin-rich compounds, denoted as first-generation bio-mordants. Still, there is another class of bio-mordants (metal-rich compounds), say second-generation natural mordant, which should be underlined for their excellent fastness and unconditional yarn affinity brought about from their metal-rich structure (Fig. 1).
In this work, we introduce pumpkin extract as the first member of the metal-rich bio-mordants for dyeing wool yarns. Evaluation of various natural sources showed that pumpkin can be used as a suitable option to present the metal naturally in dyeing. As a result, in this study, pumpkin extract was used to dye wool yarns with two colors of madder and Reseda luteola. Through a chronological procedure, we first extracted pumpkin bio-mordant and applied it separately, in dyeing of wool yarns with madder and Reseda luteola. The color and fastness performance of two types of wool yarns dyed in the presence of pumpkin extracts are evaluated with and without mordanting, and the results are compared with previous studies related to tannin-based natural mordants.

Materials and instruments
All the materials employed in this work were of analytical grades unless otherwise specified. Natural dyes (Reseda and madder) and pumpkin as mordant were obtained from underbrush grown in the north and center of Iran. The scoured 100% wool yarns (215 tex/fourfold) was purchased from Toos Co., Ltd., Mashhad, Iran, and was soaked in distilled water and then treated with a non-ionic detergent (Lotensol Hansa) solution containing 2 g/L of soap and soda ash at 80 °C for 60 min to remove starch and other stiffening agents.
The FTIR spectra were gathered on a spectrometer (Perkin Elmer, USA) equipped with a ZnSe crystal. It was used to qualitatively assess any change in the main Fig. 1 A brief comparison between two groups of natural mordants characteristic group absorption bands in the mordanting wool yarns and dyed wool yarns. The FTIR ATR spectra were recorded using a single reflection horizontal ATR accessory with a ZnSe crystal fixed at an incident angle of 45°. To achieve the colorimetric characteristics, the reflectance spectra of dyed yarns were collected using the GretagMacbeth 7000A spectrophotometer. ISO105-C10, ISO105-B02, and ISO105-X12 were selected to study wash, light, and rubbing fastness of dyed samples, respectively.

Extraction procedure
The dried samples of pumpkin were ground in a mixer and stored in glass bottle at room temperature (25-27 °C). The fine powder of pumpkin (50 g) was extracted with 200 mL of ethanol on shaker for 20 h. The residue was extracted three more times to complete the extraction. The total extract was heated to boil and was allowed to stand overnight and filtered again. The clear filtrate was concentrated under vacuum using Rota evaporator, and the semi-solid mass obtained on concentration was diluted with distilled water. The precipitate obtained was dried in an oven and collected in powder form: λ max = 482 nm; FTIR (KBr) (Cm −1 ): 3617: OH str., 3093: CH str. Ar., 1611, 1483: C = C str. Ar. The madder and Reseda extraction process was performed similar to the pervious study (Kozlowski, 2012;Cerrato et al. 2002;Mehrparvar et al. 2016a, b).

Mordanting procedure
Pre-mordanting methods were applied in this study to prepare mordanting yarns with natural extraction and mineral mordant. For this end, wool yarns were treated with a pumpkin or myrobalan extraction at 30% and alum 5% and mixture of pumpkin 15% and alum 2% concentrations of weight of fabric (owf).
The washed wool yarns were added to the mordant solution and then the temperature was increased to 90 °C in 30 min and held for 45 min. Mordanted yarns were drained with water to remove weakly adsorbed mordants.

Dyeing of wool yarns
The dyeing process was performed in a bath with L.R. 40:1. In the pre-mordanting method, extracted dye was added to the bath at 40 °C and stirred for 5 min; then, the mordanted yarns are added to the bath. But, in the meta-mordanting method, the dye and the mordant were added to the bath together and stirred for 5 min.
Dyeing was carried out by raising the dye bath temperature from 40 to 100 °C at a heating rate of 2 °C min −1 , holding it at this temperature for 60 min and cooling down at 100 °C at a rate of 3 °C min −1 . Afterward, the dyed yarn was washed and analyzed.

Results and discussion
Various methods are used to prepare natural extracts. Selecting the correct method to draw the highest yield with the best quality is very important. Today, environmental concerns are on the rise and need to be addressed. In this research, solvent method has been used for extraction. Madder, Reseda, and pumpkin extraction efficiencies were 23%, 33%, and 27%, respectively. The possibility of copper presence in pumpkin extract was evaluated by two methods: FTIR and atomic absorption (Fig. 2a). The sharp peak at 575 cm −1 corresponds to pumpkin extracted, indicating Cu symmetric stretching. The atomic absorption spectrum of the sample extracted from the pumpkin skin ( Fig. 2b) indicates the presence of 265 mg/L of copper in the sample. The density and humidity of the sample are 4.56 g/cm 3 and 17%, respectively.
The FTIR technique was employed to investigate the properties of mordanted and dyed yarns. The peak at 3400 cm −1 correspond to madder and Reseda luteola extracted, indicating OH symmetric stretching, and peak at 1717 cm −1 indicates C = O ketone stretching vibration. The peptide bonding as the fundamental group of the polypeptide chain is presented in the FTIR spectra of wool yarns (Hosseinnezhad et al. 2022). The peptide bonds (Fig. 3), containing three different types of amines, have been reported in many papers (Jahan and Datta, 2015;Chairat et al. 2007;Kozlowski 2012;Sakhai and Bennett 2008). The researcher reported amid I, II, and III in the peptide bonding (Ebrahimi and Gashti, 2015;Sakhai and Bennett, 2008). The washed wool yarns displayed absorption peaks of 3302 cm −1 (NH str.), 1637 cm −1 (C = O str., amide I), 1519 cm −1 (N-H str., amide II), and 1230 cm −1 (C-N str. amide III). The presences of a hydroxyl group in the spectrum of mordanted and dyed yarns are of the utmost importance in the spectrum of washed yarns (Sanjay et al. 2017). The absorption of the spectrum of washed and mordanted and dyed yarns have an important difference, which is related to the presence of hydroxyl peak in mordanted and dyed spectrum. The absorption hydroxyl peak of mordanted and dyed yarns was observed at 3367 cm −1 and 3318 cm −1 , respectively. The results indicated the presence of a strong bonding on the yarns.
The use of mordant in the dyeing process has an undeniable effect on increasing color stability and yield (Riaz et al 2021). Mordant application alters and enhances dye and yarn interactions. In the presence of metal mordant, metal complexes are formed on the surface of the yarns, which increases the color strength. The amount of K/S of dyeing samples is illustrated in Table 1. The increase of natural dye concentration (either madder or Reseda) from 10 to 20, and then 40% boosted color strength, is apparent from the figure. The results show that the amount of K/S for Reseda luteola-dyed samples is higher than the madder-dyed samples. All peaks related to the CN group in the FTIR test results of the dyed samples have been removed (Rather et al. 2016(Rather et al. , 2018. The pumpkin extract to dyeing bath gives rise to a higher K/S value for wool with respect to the natural yarns dyed in the absence of pumpkin. Second-generation bio-mordants used in this work also helped delving into the depth of dyeing in aid of mineral components present in pumpkin extracts. There is evidence that metal ions contribute to formation of complex with dye molecules leading to enhanced fixation and affinity of dyed fibers/fabrics-what   Yin et al. 2017). In another study, babul extract was employed as tannin-based mordant in wool dyeing with K/S about 4.14 (Kozlowski, 2012). Employing of gallut (tannin-rich) in pre-and post-mordanting techniques resulted in the K/S values of 16.09 and 14.66, respectively (Yusuf et al. 2017). This is an indication of the fact that dyeing in the presence of tannin-based first-generation bio-mordant gives the K/S values relatively lower than that of metal-rich pumpkin ones.

Conclusion
One of the main problems of many industries is the production of wastewater and environmental pollution. Therefore, this is one of the most important issues regarding the reduction of pollution. Use of natural materials (dyes and mordants) reduces wastewater pollution. In this study, the dyeing properties of wool yarns were evaluated using the two natural dyes of madder and Reseda. Madder, Reseda, and pumpkin extraction efficiencies were 23%, 33%, and 27%, respectively. Wool yarns were chosen for dyeing because wool is widely used and important yarns in the handmade carpet industry. FTIR techniques were used to investigate the extracts obtained and to identify the changes in the yarns. Examination of the amount of the K/S value showed that by increasing the concentration of the dye, the amount of K/S increased. The latest ISO standards were followed to evaluate the fastness properties. The wash, light, and rub fastness of dyed yarns were good, moderate, and good, respectively.