Abstract
The revival of natural dyes has once again revolutionized the globe with its aesthetic charm and sustainable behavior. In this study using central design and MW treatment for a selection of dyeing conditions, the binary mixture from walnut and henna as an anthraquinone source of dye has been appraised for silk. Using an extract of 5 pH from binary powder (3 g + 3 g) at 70°C for 65 min having 3 g/100 mL of salt has given better yield (K/S = 6.20), which was enhanced after MW treatment up to 6 min (K/S = 6.66). Color fastness was formed by using Fe+2 (pre 3%, post 1%, meta 2.5%), Al+3 (pre 1.5%, post 3%, meta 1%), and Tannic Acid (pre 3%, post 1%, meta 3%) as inorganic mordants onto silk. In comparison, using bio sources, extracts of clove (pre 3%, post 1%, meta 3%), cinnamon (pre 2%, post 1.5%, meta 2.5%), myrobalan (pre 2%, post 2.5%, meta 1%) and red sumac (pre 3%, post 1%, meta 3%) has given colorfast shades also. The ISO standards for colorfastness to light washing and rubbing have shown good to excellent results that reveal the potential of MW treatment, eco-friendly mordanting process, and statistical tool addition for process optimization.
Introduction
The global scenario is changing day by day due to the inclusion of advanced technologies for the betterment of the community and ecosystem. Global heat, destruction of agri-land and death of global beauty all are due to many anthropogenic or industrial activities. Many factors for such causes are under key observation, where pollution through the industrial sector is the hot topic under pen. 1 Many industries are playing their role in destroying eco-balance, where textile and its allied sectors have the key roles. 2 Many dyes produced require carcinogenic intermediates, which during the finishing step elute in the form of effluents that directly affect fertile land, community and water ecosystem, and practicing. 3 Similarly, fabric processing from yarn to printing also requires many hazardous chemicals that are passed out either in the form of solid waste and gaseous or liquid effluents. A lot of by-products in the effluent load are untreatable and the moieties when come in contact with the water channels, affect their quality to be used for domestic and land activity. 4 Similarly, domestic water when polluted with such effluents if drunk causes various waterborne diseases. And the freshwater streams when mixed with such waste polluted stuff rise or lower their quality parameters. 5 Thus, these causes have compelled the globe to rush toward natural alternatives.
Sustainability is the demand of the current era because sustainable, green and eco-friendly products are not only harmless but also if needed easily degradable. 6 Under green chemistry, the 12 principles of sustainable development goals are now on the desk of researchers, traders, and stakeholders, and new products have been developed and practiced under these green approaches. 7 Many sustainable products are present but for the textiles and all allied fields, plant-based dyes and pigments have the special place. 8 These dyes are from renewable sources, easily biodegradable, and need mild conditions for their isolation and applications. Mostly these plant colorants are part of the medication system 9 and possess biological characteristics such as antimicrobial, antibacterial, antiviral, and anti-fungal, etc. that are beneficial for the people. 10 The cultural heritage declined by the introduction of synthetic dyes but the polluted, carcinogenic, and pollution effects of such dyes have led to the revival of the art of classic dyeing and printing. People who are health conscious, art lovers, and artisans are now demanding these colorants. However, such colorants are facing two major issues such as low colorant amount from waste sources and after application their poor shade stability. 11
Previously the colorants were isolated from plant waste using classic methods. These methods include boiling, soaking, stirring, maceration, Soxhlet, etc., 12 where all these methods take a long process time and heating, solvent consumption and costs. Sometimes bi-methods are required for isolation, which also causes severe loss of economy and energy. Now modern tools have been found, where MW (microwave) treatment is the cheapest, the highly effective, and the uniform and leveled heating source for natural dyeing. 13 This method causes mass transfer (colorant) into the medium through solid-liquid interaction by a special mode of action 14 and tunes the fabric surface for raising its sorption to give high strength.
To overcome the issue of stable shade, the addition of metal salts and some organic acids is done. 15 However, the electrolytes of heavy metals have been found highly toxic and are considered replaced. 16 Now some bio-organic moieties (bio-mordants) have been introduced as possible alternatives to toxic chemical anchors. These plants are bio-active when interacting with fabric before and after dyeing developing stable colorfast new tints but also have a good chance to shed their biological characteristics onto fabric which is beneficial for people. 17
Thus, keeping given the benefit, the current study has been designed to apply the binary mixtures of dyes from anthraquinone source of natural dyes such as henna and walnut onto silk using MW treatment and statistical method. Henna (Lawsonia inermis L) has lawsone that is responsible for the coloring of the fabric. Moreover, henna leaf extract has antimicrobial activity, UV protection and mosquito repellency as well.18,19 Walnut (Juglone regia) contains juglone (Figure 1(a)–(d)) that has antibacterial, antifungal, and antioxidant properties along with the coloring properties for fabric such as wool, silk, cotton, etc. 20 Silk is polyamide fabric that needs particular medium for dyeing with plant extracts, where the fabrics having amido linkage play their role for binding with dye.
Walnut powder (a), juglone (b), henna powder (c) and Lawson (d).
Materials and Methods
Material Selection
Dried henna leaves (L. inermis L) and small walnut bark (J. regia) chips after grinding finely were sieved and stored for the isolation process. Pre-treated silk (70 g/m2) on washing with neutral soap in lukewarm water was made ready for dyeing. Eco-friendly sources of biomolecules, that is, clove, cinnamon, myrobalan and red sumac as bio-mordant and Al-salt (potash alum), Iron-salt, and Tannic acid as chemical mordant have been selected for developing colorfast shades.
Extraction Process
Extraction of dyes from binary mixtures (1:1) of plant wastes (henna and walnut) was carried out on boiling for 60 min with 100 mL of distilled water. To select the optimum amount of binary powder for colorant extraction with variable ratios, 2 g (1 + 1), 4 g (2 + 2), 6 g (3 + 3), 8 g (4 + 4), and 10 g (5 + 5) boiled with 100 mL of distilled water, filtered and used for further dyeing. For the selection of levels of dyeing parameters central composite design was used and analysis of variance was used to check the significance of the color parameters. 21 Each experiment was performed separately and the results were analyzed using two-way ANOVA. The parameters include dye bath pH 3–7, time 25–65 min, temperature 50°C–90°C, and salt amount 1–5 g/100 mL. The detailed design has been given in Table 1. The relationship between response variable and input variable(s) has been modeled by following equation
where,
Color strength of silk fabric dyed with binary extract using central composite design.
Selection of MW Treatment
The extract from henna and walnut before mixing (RBM), after mixing (RAM) and radiation after dyeing (RAD) were given by MW source up to 10 min using irradiator of 700 W with 50 Hz frequency. Each experiment was performed separately using a binary mixture of 5 pH, having 3 g/100 mL of salt for dyeing of silk at 70°C for 65 min keeping the dye bath to fabric ratio of 25:1. The purpose was to see how MW rays affect the extraction mixture, which was found in terms of K/S after dyeing.
Mordanting Process
Green mordanting is a vital step to overcome the fastness issue related to plant dyes for silk. Three chemical green electrolytes (salts of Al+3 and Fe+2 and Tannic acid = 1–3 g/100 mL) and four bio-mordants (clove, cinnamon, myrobalan and red sumac = 1–3 g/100 mL) have been selected and employed. For the preparation of chemical mordant, 1–3 g of electrolytes of Al+3, Fe+2 and tannic acid were dissolved in 100 mL of lukewarm water by occasion stirring and 25 mL from each set was used before, during, and after dyeing at 80°C for 55 min. Bio-mordants were first extracted from clove, cinnamon, myrobalan, and red sumac by boiling 1–3 g/100 mL of water for 45 min. After filtration, from each set, 25 mL was used to bio-coat the fabric before, during, and after dyeing at optimum levels for 65 min at 70°C.
Dyed Fabric Analysis
Antioxidant activity of the fabrics and extracts was found using DPPH by following already documented method. 22 The dyed fabrics obtained from isolation, dyeing, and mordanting were tested in the CIE Lab system using Data Color SF 600 through the Kubelka equation and tonal appearances were observed using the CMC equation computed in datacolotr SF 600 (USA). For washing ISO 103 CO3 was followed where standard soap solution was prepared and mordanted dyed fabrics were washed. After washing the color staining (CS) and color change (CC) were observed at a gray scale. For rubbing (dry and wet), the mordanted fabrics were crocked by 10 turns following ISO 105 X12. After crocking the stained fabric was assessed at a gray scale. For light fastness, the mordanted fabrics were clamped, where half of the samples were exposed to light (Xenon source) by following ISO 105 B02. The ratings of all tests were assessed to observe the role of treatment given during isolation and dyeing.
Results and Discussion
Isolation of anthraquinone-based natural colorant from crude plant material is the prime step for the dyeing of proteinous fabric. The role of dyeing parameters individually or in combination is always seen as promising because leveled dyeing can be achieved at selected conditions. In this study, a central composite design was employed as a design strategy, the importance of every parameter was assessed through a two-way analysis of variance (two-way ANOVA). Initially from Table 1, it has been found that binary-extract of henna (lawsone) and walnut (juglone) obtained from 6 g (3 + 3 ratio) of 5 pH having 3 g/100 mL of table salt as exhauster when employed at 70°C for 65 min, the dyed silk fabric has shown excellent yield up to K/S = 6.20 value. A low amount of dye source does not give a high yield, where up to 10 g of binary powder may give other molecular moieties along with colorant, which, on dyeing has affected the shade strength. However, using 6 g of binary powder, that is, 3 g of henna and 3 g of walnut on boiling followed by dyeing has resulted in high yield. The medium of dye bath particularly using proteinous fabric is of great importance. For silk, using an acidic dye bath, the amido linkage works well and gets protonated. The protonated amides site helps make firm interaction with –OH and -C=O of binary colorant (anthraquinone) to give a dark shade. By raising the pH of the dye bath toward alkalinity, the color strength decreases due to weak ionic interaction between dye and fabric. 23 Hence, at 5pH, the dyeing of silk with binary anthraquinone extract has given a stable shade. Particular temperature for silk dyeing using natural colorants is the important parameter because low temperature does not cause significant sorption. At 70°C, the equilibrium of the dye bath may be achieved and even dyeing with dark shade is observed. The same situation was found in our studies where contact levels for dyeing of silk with binary colorants have been found promising. For low contact time the colorant mainly remains at the surface due to poor fixation, whereas for long-time dyeing, colorant molecules are sorbed onto fabric in the form of clusters and fail to diffuse into voids of silk fibers. 24 In both cases, after washing, a lot of unfixed colorants are wiped away and on assessment, the low-quality shade is found. However, contact of binary colorant with silk for 65 min at 70°C develops a high-quality shade of excellent strength. Salt (3 g/100 mL) in natural dyeing gives better exhaustion toward silk if colored at 70°C for 65 min with binary extract of 5 pH. The low salt amount does not cause better exhaustion, where the selected amount causes promising development of the atmosphere for the interaction of colorant with silk through interactive forces. 25 Over the salt amount (>3 g/100 mL) gives high exhaustion, where the binary colorant molecules are aggregated at the surface due to bulk size unabsorbed, and upon washing loose bond molecules are stripped to give less depth. Hence, 3 g/100 mL of table salt gives leveled exhaustion of binary extract toward fabric to give high yield. Using two-way interaction, the contact variables, that is, dyeing time (65 min) in the presence of temperature (70°C) has been found highly significant (p = 0.00). Similarly, dyeing time (65 min) in the presence of salt (3 g/100 mL) has also been found highly significant (p = 0.00). Similarly, the role of the heating variable (70°C) in the presence of dye bath pH (5pH) has been observed significant (p = 0.06) also. It shows that powder, time, temperature, salt, and pH are linearly playing a significant role in the response. The currently used second-order polynomial model was found effective since the insignificant value of lack of fit (0.625) was found. The model was found to be highly significant as the F-value was high (47.63) with a smaller probability value (0.000). The findings presented in Table 2 indicate highly reliable laboratory results, as reflected by the low standard deviation (0.163089). The value of R2 (99%) is highly good, which shows that dyeing variables selected for the bio-coloration of silk with a binary mixture of henna and walnut as anthraquinonoid based natural source has been found promising to get desired results. Most color parameters contribute strongly to the response variable (K/S). Significant interaction effects were observed for powder × time, powder × pH, time × temperature, time × salt, and temperature × pH. Quadratic effects of powder, temperature, and salt were also influential (i.e., the curvature of their individual response trends, showing that their impact on K/S is not strictly linear but changes at different levels of the variable Figures 2 and 3). Overall, nearly all color parameters play a meaningful role in predicting the response, which is further supported by the main-effects and interaction plots. Thus the joint role of one factor in the presence of another has also been found significant and reveals that dyeing of silk at 70°C for 65 min using a binary colorant solution of 5 pH having 3 g/100 mL of salt should be done for achieving the desired color results.
Assessment of results for silk dyeing at selected conditions using binary extract from henna and walnut based through two-way analysis of variance (ANOVA).
Plot showing the linear contribution of color parameters.
Three-dimensional surface plot displaying the combined contribution of color parameters.
Using selected dyeing variables, the role of radiation on the binary extract and fabric has been seen. The results in Figure 4 reveal that after dyeing, radiation up to 8 min has shown good strength 6.15 (K/S). The shade developed has been found dark reddish yellow (L* = 47.90; a* = 11.36; b* = 21.64) with good saturation and high hue value of (c* = 24.44, h = 62.31). Similarly, after mixing the binary extracts of henna and walnut, radiation up to 6 min followed by dyeing of silk has given excellent strength up to 6.66 K/S. The shade produced by this treatment is much darker (L* = 46.39) having a good reddish-yellow tone (a* = 12.74, b* = 22.68) with excellent saturation and hue values (c* = 26.02; h = 60.69). In comparison, the radiation treatment of up to 8 min to henna and walnut separately before mixing, followed by the dyeing of silk has given yield strength (K/S) up to 6.61. The dyed fabric obtained is also much darker in shade (L* = 45.43) with a reddish yellow hue (a* = 11.40; b* = 20.48; h = 60.90) and good saturation (c* = 23.44). This good color depth is due to the rapid, uniform action of MW treatment onto extract and fabric. The irradiation of each extract before mixing allows the isolation of more colorants from ruptured cell walls through the mass-transfer mode of action. On mixing the binary – anthraquinone extract after MW treatment for up to 6 min followed by dyeing of silk has developed a shade of high strength. The other significant effect of using MW treatment is the improvement in the sorption potential of silk fabric. Our previous studies showed that MW treatment modifies the surface of the silk fibers by peeling. The scratched surface, when used for dyeing, sorbed more dye up to maximum extent (K/S = 6.66). Figure 5 shows the FT-IR spectra of microwave-treated henna extract. A broad peak at 3367 cm−1 indicates hydroxyl (–OH) stretching, suggesting the presence of phenolic compounds, such as lawsone. The peak at 2926 cm−1 corresponds to aliphatic C–H stretching, indicating hydrocarbons or fatty acids. The peak at 1752 cm−1 signifies C=O stretching, likely from carbonyl groups in Lawsone, contributing to the dyeing properties. Aromatic C=C stretching is indicated around 1639 cm−1 while bending vibrations of methyl groups (–CH3) are suggested by the peak at 1386 cm−1. The peak at 1033 cm−1 represents C–O stretching, suggesting polysaccharides or complex carbohydrates. There are some main shifts in microwave-treated dye at the peaks 3443 cm−1, 1632 cm−1, and 1040 cm−1. Also, Figure 3 presents the FT-IR spectra of the microwave treatd walnutextract. Key peaks include 3444 cm−1 (hydroxyl groups, indicating phenolic compounds and tannins), and 2942 cm−1 (C-H stretching). The bands at 1608 cm−1 at walnut shell spectrum can be attributed to the C=C stretching vibration of aromatic carboxyl groups. Moreover, the broad at 1049 cm−1 at walnut shell spectrum corresponds to C–O vibrations in secondary and primary R–OH groups in alcohol. 26 There are some main shifts in microwave-treated dye at the peaks 3437 cm−1, 1612 cm−1, and 1056 cm−1. These results suggest that microwave treatment does not lead to chemical changes in the characteristic peaks of cellulose units. On observing twofold benefits, it can be seen that MW treatment only causes physical tuning of silk without changing its chemical nature but also adds value in yield strength by stimulation of colorant through the mass transfer of kinetics. 27 Hence for better results, it is revealed that extract and fabric should be MW treated for up to 6 min and dyeing should be done at 70°C for 65 min using irradiated binary extract of 5 pH having 3 g/100 mL of salt.
Dyeing of silk with binary extract of walnut and henna before radiation (RAD), radiation after mixing (RAM) and radiation before mixing (RBM).
Spectral image of henna and walnut extract.
Mordanting in the plant-based coloring process is the essential step to overcome poor shade issues. Mostly these dyes are substantive and need auxiliaries for their firm interaction with stuff. The additive may be natural or synthetic. 27 In our study salts of Al+3, and Fe+2 and tannic acid (TA) have been used before, after and during the dyeing of silk with an anthraquinone-based binary mixture from henna leaves and walnut bark (Figure 6(a)–(c)). These metals interact with the binding area (-OH and -C=O) from binary colorant and with amido group (-C=O and -NH) of silk by coordinate covalent bond to form stable shade, 28 where only the optimum amount of metal anchors can give stable and even shade of high strength. Similarly, the use of tannic acid (TA) with amido linkage of silk and functional groups of colorant through H-bonding produces darker shades of high strength. The results given in Figure 6(a) to (c) show that before dyeing of silk with binary colorant, the coating of silk with 1.5% of Al+3, 3% of Fe+2 salt and 3% of tannic acid (TA) on dyeing with binary extracts at given conditions has given good results. Bio-mordant was started not only to get colorfast new shades but also to replace the toxic chemical mordants. Most of these anchors are herbal based having dual benefits. 29 The potent molecules (organic mordant) after their isolation when used before, after, or during the dyeing of silk develop colorfast new shades. From bio-mordants, the –OH sites or –OH and -C=O sites form H- bonding with –OH (flavonoid) or –OH and -C=O of dye (juglone and lawsone) and amido sites (-CONH) of silk to produce new colorfast shades. 30 The additional bonding also gives variable tone of reddish yellow hue with darker or brighter shades. The results given in Table 3 show that before dyeing of silk with binary extracts of henna and walnut, 3% clove, 2% cinnamon, 3% red sumac and 2.0% myrobalan gave excellent yield. For comparison, if results are observed, then 3% of clove, 2.5% of cinnamon, 3% of red sumac, and 1% of myrobalan, during dyeing of silk with henna and walnut binary extract has given good strength. Overall, if colorfast shades are required then 2% of myrobalan should be used to coat silk before coloration, 2.5% of myrobalan should be used after bio-dyeing of silk and 3% of red sumac should be used during the dyeing of silk with binary henna and walnut extract at given selected conditions. The shade variables (Table 3) reveal that bio-mordanted shades of dyed silk are darker, more reddish yellow in tone, with high chromacity and saturation value. The application of myrobalan before dyeing has given a darker shade (L* = 49.12), with a reddish yellow tone (a* = 11.63, b* = 23.22), having good chromacity (c = 25.97) and high hue value (h = 63.40). The usage of myrobalan after silk dyeing has given a darker shade (L* = 46.01), less reddish (a* = 8.84) and more yellow tone (b* = 23.75), with good chromacity and hue saturation (c* = 25.34, h = 69.60). During dyeing, the inclusion of myrobalan produced a much darker (L* = 53.80), more reddish yellow hue (a* = 9.65, b* = 25.62), having high chromacity and good hue value (c* = 27.38; h = 69.37). Thus, from chemical and bio-mordant extract hue values, darkness in shades and reddish-yellow tones has been raised.
Chemical and bio-mordanting of silk (a) before, (b) after and (c) during of silk with binary henna and walnut extract.
Tonal expression of silk fabric dyed with binary extract before, after and during chemical and bio-mordanting.
The colorfastness properties of mordanted silk dyed with a binary mixture of anthraquinone-based colorant from henna and walnut at selected conditions have been shown in Table 4. For natural dyes, it is essential to be colorfast in terms of light, washing, crocking, perspiration, etc., where the role of mordants either chemical or bio is promising. 31 In this study using selected amounts of chemical mordants for firm binding with –OH and -C=O of colorants (binary mixture) and amido part (-CONH) from silk through coordinate covalent bond has given good and stable shades. 32 Good light fastness at the blue scale is due to stable complex formation where additional resonance by binary site, that is, juglone from walnut and lawsone from henna has added value in resistance toward fading. Similarly soaping also did not affect too much the shade due to dyeing at selected conditions followed by MW treatment and mordanting. Crocking in both dry and wet conditions also has been found good due to colorfast shades/tints. The bio-mordants having –OH group, as well as benzene ring in interaction with fabric and dye, valorized the shade. Hence, eco-friendly chemicals and green bio-mordants have been encouraged to be used at selected dyeing variables for silk using a binary mixture of natural dye sources.
Shade fastness rating of mordanted silk fabric dyed with henna and walnut extracts.
Conclusion
The current green scenario appreciates green products with manifold benefits if formulated under sustainable developmental goals. Natural dyes from plant wastes using sustainable techniques for silk dyeing have always been welcomed due to their aesthetic and eco-friendly nature. The results of the current study showed that if chemical-mordanted or bio-mordanted silk after MW treatment is dyed at selected conditions, attractive colorfast shades are obtained with a binary mixture of natural anthraquinone dyes. The inclusion of statistical methods to find cost, energy, and time-effective dyeing variables, MW treated to sustainable dyeing process and eco-friendly mordants to develop colorfast shades is the new addition in the field of bio-coloration. Using an extract of 5 pH from binary powder (3 g+ 3 g) at 70°C for 65 min having 3 g/100 mL of salt has given better yield (K/S = 6.20), which was enhanced after MW treatment up to 6 min (K/S = 6.66). If such processing is taken, new dye-yielding plants from their green wastes for dyeing of natural and synthetic fibers can be used and made acceptable for the global community with zero or less effluent load. This study has utilized classical response surface design such as central composite design for finding optimal values of the dyeing variables. Furthermore, MW treatment is used to enhance the sorption behavior of fabric using waste plant materials such as fallen leaves, dry flowers and barks.
Footnotes
Acknowledgements
The work is the part of PhD Studies done by Ms. Umaira Bilal. The authors are thankful to College of Home Economics University of Peshawar and Department of Applied Chemistry, Government College University Faisalabad for providing technical and scientific guidance in smooth running of PhD studies.
Author Contributions
Ms. Umaira Bilal is PhD student who has done experiments; Prof. Dr. Shahnaz Parveen Khattak is supervisor who has given guidance in analysis as well as in methodology, where as Dr. Shahid Adeel has given scientific guidance to conduct experiments, mordanting and proper shade development as well as in writing manuscript.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.