Eco-friendly bio-dyeing of bio-treated nylon fabric using Esfand (P. harmala) based yellow natural colorant

The ongoing age is the time of sustainability, where in the current pandemic scenario, which is getting worse, needs treatment with nature rather than chemical-based products. In this study, microwaves (M.W. rays) treatments as extraction mode for Esfand (P. harmala) have been revived for polyamide (nylon) dyeing. The water solubilized and acid solubilized filtrates and polyamide (nylon fabrics) were treated M.W. rays up to 10 min with an interval of 2 min. Mordanting with chemicals and plant extracts before and after dyeing was done at 60°C–80°C. It has been found the application of M.W. ray treatment for 4 min., to 30 mL of extract of 8 pH containing 4 g/100 mL of Table salt as leveling agent has given desired results when employed at 55°C for 55 min. Statistical analysis of dyeing variables through R.S.M., and two way-Anova shows that the effect of these variables has been observed highly significant. Experimentally it has been observed that the application of extract for dyeing of polyamide (nylon fabric) has given good results when chemical or bio-mordanted at selected conditions. Practically, Esfand seeds has ability for bio-coloration of surface modified polyamide fabric (nylon fabric), and utilization of pomegranate extract as bio-mordant and tannic acid as sustainable chemical mordant has furnished colorfast shades.


Introduction
Herbal-based green products are the part and parcel of the global community. 1,2 Their utilization as the pharmaceuticals has played an essential role in the introduction of world-famous medicines systems such as Chinese, Greek, and Indian Ayurvedic. 3 Because these green products have such potent isolates which contains not only biological characteristics beneficial for the global community but also have the ability to color the matrices such as textile, perfume, flavors, food, pharmaceuticals etc. 4,5 Many plants have been introduced in the world of medicines which has such functional moieties that has the ability to protect the global community from evil diseases such as cholera, flu, plague, dengue, typhoid, swine flu, bird flu, etc., of these plants. 3 Esfand (Peganum harmala L.) commonly known as Harmal belongs to the family of Zygophyllaceae. 6 Its seeds extract (Figure 1(a)) contains specific alkaloids such as harmol, harmaline, and harmine ( Figure 1(b)) which not only have good efficacy to cure various diseases but also exhibit antioxidants, antibacterial, antiviral, anti-tumor, and antiinflammatory effects. [6][7][8] The smoke of its seeds is also said to be antidote for the evil spirits. Its extracts are also used as a possible substitute for Turkey Red Color (TR) to dye fabrics, and to make tattoos and inks. The alkaloids present in extract which act as the source of natural yellow dye for textiles. 9,10 Hence the medicinal-based plants colorants (natural dyes) are found as a possible substitute of carcinogenic synthetic dyes. 11,12 The utilization of harmal seeds have been first time has been explored by our research group onto cotton, silk, wool, and nylon fabrics.
Before discovery of synthetic dyes "Mauveine" by Perkin, these plants were used to color fabrics, houses, bodies, caves etc., but the synthetic dyes have caused their decline due to having variety of cheap and brighter shades. 13,14 With the passage of time, it has been found that their effluent load is untreatable, producing mutagenic and carcinogenic diseases and is destroying the global ecosystem. 15,16 The world protection associations and health conscious people have forced the industrialists to provide sustainable, green, clean, and eco-label products which have not only soothing nature but also act as remedies for diseases. [17][18][19] Previous studies revealed that their effluents could be disposed, recyclable, and even on adding in soil can play as the role of fertilizers. 20 Their extracts, when employed on to the fabric, the dyed fabrics show biological characteristics which are beneficial for humanity. 21,22 These also cover broad spectrum of colors with eye-catching shades. Hence being harmonized with nature, now the classic art of natural dyeing of fabrics, handicrafts, body painting, cosmetics, etc. is on the way. 11,23 However, these colors have some issues such as poor strength and low fastness ratings. 24 Previously, scientists are using conventional methods to improve the colorant strength, and are using chemical mordants to improve fastness ratings. However, these processes are less effective on the basis of cost, time, energy, and labor. 25 Now modern methods such as radiation methods, enzyme methods, supercritical fluid methods etc., are being employed. 24,26 Among these methods radiation methods particularly the utilization of microwaves rays (M.W.) are gaining fame. 27 These rays have ability of leveled, non-contact, and uniform heating to penetrate into the matrix. 28,29 These rays not only extract the colorant with a high strength but also tune the fabric surface to improve its dying behavior. 30,31 As the possible substitute of chemical mordants, now plant-based bio-mordants have been used to improve the fastness ratings with new tints. 32 Nylon (Polyamide) fabric is the elastic man-made fibers that contain polyamide linkage ( Figure  1(c)) as functional points for bonding with colorants.
Hence keeping given advantages of M.W. rays for the extraction with high yield and bio-mordants for improving fastness ratings, this latest research studies have been designed to utilize herbal-based plants that is, harmal as source of natural dye for polyamide fiber (nylon) dyeing. Also, to author's knowledge no such a brief study under M.W., rays on nylon dyeing using Esfand (a common cheap available source of natural dye) has been done so far. Another purpose is to use herbal-based bio mordants and sustainable chemical mordants at 60°C-80°C for getting new shades with good fastness ratings.

Material collection
Using food blender, Esfand seeds (P. harmala) obtained from market were finely grounded and sieved for further Isolation process. Bio-mordants were also treated in same way as discussed above and stored for further shade making process. Nylon (polyamide) fabric was pretreated with neutral soap at 60°C for 30 min. to remove any direct and used for dyeing process.

Dye extraction and irradiation process
Water solubilized extract (aqueous) was prepared by heating fine powder (4 g) at boiling with 100 mL of water. For acid solubilized extract, acidic solution was prepared by mixing 2 mL of conc. HCl with 98 mL of water (2% HCl, V/V), where the rest of extraction process employed was same. Nylon (polyamide) fabric, water (aqueous), and acid solubilized filtrates (acidic) were given MW-rays treatment up to 10 min., with an interval of 2 min. Non treated extracts were employed to dye non-treated (polyamide) nylon fabric at 80°C for 45 min keeping filtrate to (polyamide) nylon fabric ratio (F:N) of 25:1. The rest of experiments displayed in Table 1 were carried out at selected conditions. 33

Optimization of dyeing conditions
On selection of extraction media and M.W. rays time, a plan of 32 experiments was arranged on varying the levels of extract volume, extract pH, and salt concentration contact parameters (dyeing temperature and time). For the purpose, response surface methodology (R.S.M.) as statistical analysis has been utilized to conduct experiments for observing significance of results. The detail of 32 experiments has been displayed in Table 2.

Shade development treatment
In bio-dyeing, treatment of fabric with either salts or natural plant materials (biomolecules) before and after dyeing at given temperature has been done to get colorfast shades. Here, 1-5 g/100 mL of chemical anchors and 1-5 g/100 mL extracts of plants have been utilized at 60°C-80°C before and after dyeing at selected conditions. The process of making colorfast shades has been taken from already published work of Adeel et al. 9 and Habib et al. 34

Evaluation of dyed and un-dyed fabrics
For physic chemical analysis, the nylon fabric before and after M.W. rays treatment for 4 min. was subjected to SEM (SEM-model Tescan; 5kV) and FTIR (Perkin Elmer, USA). The data after assessment was analyzed statistically using table design. All the dyed fabrics were assessed for color analysis through data color (SF 600 USA). The fabrics mordanted at given temperature before and after dyeing were assessed for fastness ratings as per ISO standards for light, washing crocking and dry cleaning.

Selection of extraction and irradiation condition
Exploration of plants having biological and claims characteristics useful for the global health using ecofriendly, green, sustainable techniques is currently the warm topic for all walks of life. 22,35 The results given in Figure 2 Harmine   seed 36,37 The potent molecules interact with medium promisingly through potential mass transfer Kinetics. 29 Upon change of medium ( Figure 2(b)) the acidic extract after exposure to microwave treatment rays for 4 min. has also given good strength onto nylon fabric. In comparison to conventional isolation process the aqueous and acidic extracts (NRE) did not give significant color strength on to unirradiated fabric (NRF). Overall, it can be seen that acidic extract (RE) irradiated for 6 min., has given excellent color strength onto surface tuned fabric (RF). This is because microwave rays are leveled heating source which penetrate the medium at molecular level, and valorize the solid-liquid interaction by transfer of heat in less time to give promising yield. 38 Scratching of surface of nylon (polyamide) fibers before and after M.W. treatment has also been observed (Figure 3(a) and (b)) which has added value in rising tint strength. [39][40][41] The important thing which has been found via FTIR spectra (Figure 4(a) and (b)) is that position of functional peaks of amido-linkage (binding site of nylon) has been remained the same, even after microwave treatment up to 4 min. Hence M.W. rays treatment has not only enhanced color strength in acidic medium but also without altering nylon (polyamide) fabric chemistry has improved its dye uptake potential.

Selection of dyeing parameters
Literature studies show that for biocoloration of nylon (polyamide) fabric, both time and heat plays their roles but M.W. rays treatment has reduced their levels. The results show that at 55°C for 55 min. the dyed fabrics were of high in strength to get excellent results ( Figure 5(a) and (b)).
The addition of Table salt as leveling agent that adds value in bio-coloration by giving maximum evolvation of colorant (at 8 pH) toward fabric from dye bath. The results given in Figure 5(c) shows that the utilization of 4 g/100 mL of Table salt has given good results. Hence M.W. rays treatment has reduced the level which is the proof by their study that this treatment is cost, time, and energy effective in nature 28,29 Statistically for the detailed study of the relationship between the experimental parameters and the K/S value, we initially considered quadratic effects and second order interaction effects of the factors through secondorder polynomial model. We improved the model adequacy and the significance of effects by removing some trials which produced outlier observations and eliminated some insignificant terms from the model (Table 3). It can be seen that the role of extract pH and volume are highly significant (p-value = 0.000) for K/S, where as Time is significant at 5% level of significance and Temperature and Salt are significant at 10% level of significance. This has been improved by statistical analysis also (Table 2).
Hence statistically it has also been found that dyeing variable should also be considered during biocoloration of nylon (polyamide) with harmal extracts.
The color coordinates given in Tables 5 to 7 reveal that mordanting of fabric before dyeing has produced brighter shade with reddish yellow hues. The fabric dyed after application of pomegranate (Pm = 2%) at 60°C is darker (L* = 56.79) having reddish yellow tone (a* = 8.5; b* = 35.66). The fabric dyed before application of Tannic acid (T.A. = 2%) at 70°C is brighter in shade (L* = 77.13) having less reddish yellow tone (a* = 4.56; b* = 26). This high color strength was observed due to formation of coordinate covalent bond by metals with dye onto surface-tuned polyamide (nylon) fabric through metal-dye complex followed by dyeing at optimum temperature. 42,43 Here the reduction power of metal (Al 3 +, Fe 2 +) or -OH of tannic acid as functional site works were to interact with fabric and colorant. Using plant extract, the -OH of quercetin of acacia (Ac), tannin of pomegranate (Pm), curcumin of turmeric (Tm), and catechin of pine nut (Pn) hulls has played their role by forming the additional H-bonding with amido-linkage of polyamide (nylon) and -OH of colorant. [44][45][46] Hence at optimal temperature using M.W. treated extract, the observed amount of mordants have developed not only new tints but also improved color strength with color fast shades (Figure 9(a) and (b)) is showing the suggested interaction of sustainable chemical and bio-mordants with fabric and dye.

Assessment of colorfastness ratings
The colorfastness properties ratings have been assessed at Gray-scale using standard ISO methods. The results given in Tables 5 to 7 reveal that good to excellent fastness ratings have been obtained during dyeing of surface modified polyamide (nylon) fabric with acid solubilized extract of Esfand (harmal). The firm metal complex with dye and additional H-bonding developed by -OH of bio-mordants, conjugation system presents in bio-molecules and microwave treatment to the colorant are possible aspects that have played their role in developing color fastness shades. Upon exposure to heat, light, washing, crocking less color is detached and good to excellent rating is found. 30,47,48 Overall bio-mordants have given better effects. Hence microwave treatment has an excellent potential to isolate colorant from Harmal seeds, and tune to the fabric to reduce dyeing variables. Additionally, bio-mordants as an alternative to their chemical counterparts have made process sustainable ecofriendly and soothing in nature. [49][50][51][52]

Conclusion
The aftereffects of carcinogens have now forced the people to swing toward green sustainable products. Esfand or harmal seeds (P. harmala) as bio-dye source has been valorized under M.W. treatment and plant based antiviral and anti-oxidants molecules as bio-anchors have been utilized to make process more colorfast and sustainable. It has been found the application of M.W. ray treatment for 4 min., to 30 mL of extract of 8 pH containing 4 g/100 mL of Table salt as leveling agent has given desired results when employed at 55°C for 55 min. Statistical analysis of dyeing variables through R.S.M., and two way-Anova shows that the effect of these variables has been observed highly significant. The utilization of pomegranate extract as bio-mordant and tannic acid as sustainable chemical mordant has furnished colorfast shades.  The addition of green and clean processes for the extraction of bio-colors and the application of these sustainable and eco-friendly mordants for improving shade quality has made this act of cultural heritage more value added. For future studies, such new anti-viral, antibacterial, and anti-oxidant based herbal plants should be assessed for their coloring behavior and additionally, plant based herbal mordants should be used to make process more sustainable and ayurvedic.

Acknowledgement
We are thankful to Mr. Zafar Iqbal Manager (R &D) Noor Fatima Fabrics Faisalabad Pakistan and Mr. Muhammad Abbas Chief Executive Harris Dyes and Chemicals Faisalabad Pakistan for providing us the technical guidance at lab scale for smooth running of this M.Phil. Studies. We are also thankful to National Engineering laboratory of Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, China for providing us pre-treated nylon fabric.