Natural Dyeing of Cellulose and Protein Fibers with the Flower Extract of Spartium Junceum L

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Article Natural Dyeing of Cellulose and Protein Fibers with the Flower Extract of Spartium junceum L. Plant

Zorana Kovaˇcevi´c 1 , Ana Sutlovi´c 1 , Ana Matin 2 and Sandra Bischof 1,*

1 Department of Textile Chemistry and Ecology, Faculty of Textile Technology, University of Zagreb, 10000 Zagreb, Croatia; [email protected] (Z.K.); [email protected] (A.S.) 2 Department of Agricultural Technology, Storage and Transport, Faculty of Agriculture, University of Zagreb, 10000 Zagreb, Croatia; [email protected] * Correspondence: [email protected]; Tel.: +385-1-4877-351

Abstract: In this study, the natural dye was extracted from Spartium junceum L. (SJL) flowers and applied on cellulose (cotton) and protein (wool) fabric. Fabrics were pre-mordant with alum prior to the dyeing process. Considering the global requirements on zero waste and green policy, the dyeing process was intended to be as much as possible environmentally friendly but still effective. Therefore, mordant concentration was optimized due to the reduction of the negative impact. The efficiency of the dyeing process was investigated by examination of fabrics’ color characteristics and colorfastness to washing properties. In this paper, we have proved that the extracted dye from Spartium junceum L. is an acidic dye (mordant dye) which is more applicable for the treatment of wool fabrics. In this paper, it was proved that phytochemicals responsible for coloring are part of the flavonoids group. The UV absorption spectra of extracted dye show 4 bands in the region of λmax 224, 268, 308 and 346 nm which are ascribed to bands characteristic for flavonoids. Wool fabric pre-mordant with 3% alum and dyed shows great chromatic (C*) properties where C* value is in a Citation: Kovaˇcević,Z.; Sutlović,A.; range from 47.76 for unwashed samples to 47.50 for samples after 5 washing cycles and color hue Matin, A.; Bischof, S. Natural Dyeing (h◦) is in a range 82.13 for unwashed samples to 81.52 for samples after 5 washing cycles. The best of Cellulose and Protein Fibers with result regarding the colorfastness properties is shown by the wool sample treated with 3% alum the Flower Extract of Spartium after 5 washing cycles (total difference in color (Delta E*) = 0.87). These results confirm that metal junceum L. Plant. Materials 2021, 14, (Al) from alum mordant make strong chemical bonds with wool substrate and dye since Delta E* 4091. https://doi.org/10.3390/ values decrease in comparison to Delta E* values of the cotton samples treated the same way. The ma14154091 results revealed it is possible to reduce the concentration of mordant up to 3% and obtain satisfactory results regarding the colorfastness. Nevertheless, future research will go in the direction of replacing Academic Editor: Steve Eichhorn synthetic mordant with a more environmentally friendly one.

Received: 29 June 2021 Accepted: 19 July 2021 Keywords: Spartium junceum L.; natural dye; mordant dye; cellulose fibers; protein fibers; wool Published: 22 July 2021 dyeing; flavonoids; colorfastness to washing

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- 1. Introduction iations. Since an interdisciplinary approach is desirable within the science community, this research comprises several specific objectives, which seeks to find new solutions for a better understanding of the investigated topic. The wide availability of indigenous Mediterranean plants directs research towards sustainable development and circular economy. Further- Copyright: © 2021 by the authors. more, utilization of widely available biomass for natural dye production will be applied Licensee MDPI, Basel, Switzerland. in the dyeing of protein and cellulosic textile materials with emphasis on the aspects of This article is an open access article textile care. distributed under the terms and Spartium junceum L. (SJL) or Spanish broom is a Mediterranean plant, which has conditions of the Creative Commons been used as a textile raw material since ancient times. Its greatest use was in fiber Attribution (CC BY) license (https:// production but it was also well known for its flowers which are blooming between May creativecommons.org/licenses/by/ and July [1]. It is interesting that the SJL plant as a raw material resource was mostly 4.0/).

Materials 2021, 14, 4091. https://doi.org/10.3390/ma14154091 https://www.mdpi.com/journal/materials Materials 2021, 14, 4091 2 of 18

used in the period of poverty between the great wars but afterward was abandoned. Although, it is native to southern Europe and the Mediterranean area, including North Africa, Turkey and the Middle East it becomes an aggressive invader in many tropical, subtropical and temperate regions of the world. For example, in the USA, the Canary Islands, the Azores, Argentina, Bolivia, Peru, Uruguay, South Africa and the Dominican Republic SJL is considered an invasive, noxious weed [2,3]. Nowadays, SJL is applied again as a renewable raw material which could have numerous possibilities of usage for the production of fibers, yarns, fabrics, ropes, baskets, composite materials reinforced with SJL fibers [1], decorative and artistic items, painting canvas, oils, perfumes, and natural dyes by following the concept of circular economy [4] and zero waste model. Aqueous extracts prepared from the flowers were used as herbal medicine in the treatment of gastric ulcers in Turkish folk medicine, against herpes simplex virus type 1 in recent times [5] and in yellow dye production [6,7]. Regardless of the fact that natural dyes were successfully used for fabric dyeing in ancient times, the discovery of synthetic dyes in the 19th century significantly improved and facilitated the dyeing process by achieving cheaper dyes. Due to increased awareness of the environmental and health hazards and cognition of toxicity and carcinogenicity of synthetic dyes products, most commercial dyers have started to search up again for renewable and sustainable natural dyes derived from the plant, animal and mineral sources in accordance with EU regulations. REACH (EC No. 1907/2006) and Ecolabel (EC No. 66/2010) regulations provide restrictions on the usage of dyes that are considered dangerous to human health [8,9]. EU Directives must be implemented by the EU member states in their national legislation and monitored by the national authorities. Natural dyes show two main advantages compared to synthetic dyes: synthesis processes within natural materials performed by nature without environmental pollution and biodegradability of natural materials, thus not affecting hazardous effluent upon degradation in the environment [10]. The limitation of natural dyes upon the synthetic one is their reproduction of color since the quality of natural dyes depends on the climate, plant genus, region, etc. [10,11]. The dyeing of textile materials is influenced by dyeing parameters such as fiber structure, temperature, time and pH of the dye bath and dye molecule characteristics. The efficiency of dyes on textile materials depends on the stability of the dyes/fiber complex. Cellulose fibers show poor affinity and substantivity according to natural dyes causing difficulties in the dyeing process. Protein fibers, on the contrary, show better affinity to natural dyes since they have ionic groups in their structure and get stronger bonds with natural dyes possessing ionic groups in dye structure [12,13]. Natural dyes can be classified based on their chemical structure, origin, method of application and color. Based on the chemical structure they belong to classes of indigoids, anthraquinonoids, ketones, imines, betalains, anthocyanidins, flavonoids, carotenoids or chlorophylls. Based on their method of application they can be classified as mordant dyes, direct dyes, vat dyes, acid dyes, basic dyes and disperse dyes [14,15]. According to the literature [16] flavonoids (water soluble polyphenols) give yellow color to SJL flowers. Chemically flavonoids are divided into flavones, flavonols, isoflavones, flavanones, chalcones and arones. The SJL plant’s dried flowers contain luteolin and quercetin dyes. Lu- teolin is part of the flavones subclass, which are UV absorbing flavonoids, while quercetin is part of the flavonols subclass. Today, in addition to aqueous extraction, modern methods are used for the extraction of pigments from plant sources, e.g., microwaves [17], ultrasound [18], supercritical CO2 [19]. These methods are used for qualitative analysis, however, in the application of these components in the field of microbiology and green synthesis, aqueous extraction is still preferred. Quercetin and luteolin belong to the mordant dyes class [20], which is equally suitable for both vegetable and animal fibers [21]. In most ways, mordant dyes show soft, pastel and lustrous shades soothing to the human eye but one of their main drawbacks is little affinity for textile substrates causing poor colorfastness to washing, rubbing, sweat and sunlight [22]. Mordant dyes are acid dyes and have an anionic character, therefore requiring mordants in their formulations to fix dyes on fibers and improve the quality and fabric’s color brightness [20–23]. Mordants can Materials 2021, 14, 4091 3 of 18 Materials 2021, 14, x FOR PEER REVIEW 3 of 20

be natural (tannic acid, citric acid, clay, bark extracts, etc.) or synthetic (various metallic salts,be natural such as(tannic alum, acid, stannous citric chloride,acid, clay, copper bark extracts, sulfate, ferrousetc.) or sulfate,synthetic etc.) (various [23]. Metallic metallic mordantssalts, such are as usuallyalum, stannous used for chloride, fabrics pretreatment copper sulfate before, ferrous the dyeingsulfate, process. etc.) [23 Different]. Metallic metalmordants mordants are usually impact used various for coloration fabrics pretreatment effects with thebefore same the natural dyeing dye. process. The final Different color experiencemetal mordants does not impact depend various only on coloration a dye but effects is also affectedwith the by same the typenatural and concentrationdye. The final ofcolor mordant. experience In this does paper, not we depend haveused only alum,on a dye metallic but is salt also of affected potassium by aluminumthe type and sulfate con- dodecahydratecentration of mordant. (KAl(SO 4In)2 x12this Hpaper2O). It, we is a have widely used used alum, mordant metallic for cottonsalt of and potassium wool fibers alu- whichminum show sulfate the dodecahydrate lowest negative (KAl(SO ecological4)2 x12 impact H2O). among It is a otherwidely metallic used mordant mordants for [ 24cotton]. It isand recommended wool fibers which to add show approx. the 12%lowest of alumnegative on theecological weight impact of the fabricamong [25 other] but metallic in this paper,mordants we have[24]. investigatedIt is recommended the color to add enhancement approx. 12% of pre-mordantof alum on the fabrics weight with of the a much fabric lower[25] but amount in this of paper alum, (3we to have 5%) andinvestigated color changes the color of such enhancement fabrics after of the pre washing-mordant process. fabrics Studieswith a much about lower SJL dye’s amount colorfastness of alum (3 to to washing 5%) andare color very changes rare in of the such literature. fabrics after In this the paper,washing the process. possibility Studies of the about usage SJL of the dye’s aqueous colorfastness extract from to washing the SJL flowersare very as rare a natural in the dyeliterature. for the In cellulose this paper, and proteinthe possibility fabrics wasof the evaluated. usage of Thethe noveltyaqueous of extract this work from is the in theSJL directflowers contribution as a natural towards dye for thethe principlescellulose and of aprotein circular fabrics economy was evaluated. where each The part novelty of the of plantthis work is successfully is in the direct utilized contribution for the production towards the of principles fibers and/or of a circular technical economy textiles, where so as each for thepart extraction of the plant of naturalis successfully dyes. utilized for the production of fibers and/or technical textiles, so as for the extraction of natural dyes. 2. Experimental 2.1.2. Experimental Materials 2.1. MaterialsTwo different textile fabrics were used in the experiment: cotton and wool fabrics with characteristic parameters presented in Table1. Two different textile fabrics were used in the experiment: cotton and wool fabrics withTable characteristic 1. Technical characteristicparameters presented parameters in of Table used fabrics. 1.

Table 1. Technical characteristic parameters of used fabrics.Density (cm−1) Label Composition Producer Weave Weight (g/m2) WarpDensity Weft (cm−1) Label Composition Producer Weave Weight (g/m2) C 100% Cotton Cateksˇ d.o.o., Cakovec,ˇ Croatia Plain 26Warp 25 Weft 191.45 W 100% WoolC Tekstilpromet 100% Cotton d.d., Zagreb,Čateks Croatia d.o.o., Čakovec, Plain Croatia 22Plain 26 22 25 118.16191.45 W 100% Wool Tekstilpromet d.d., Zagreb, Croatia Plain 22 22 118.16

SpartiumSpartium junceum junceumL. L. ﬂowers flowers were were picked picked near near the the town town of of Šibenik Šibenik (Figure (Figure1). 1).

FigureFigure 1. 1.Collecting Collecting of ofSpartium Spartium junceum junceumL. L. ﬂowers flowers in in May May 2021. 2021.

2.2.2.2. NaturalNatural DyeDye ExtractionExtraction SpartiumSpartium junceumjunceum L.L. flowersflowers werewere usedused asas anan herbal herbal source source for for biological biological pigment pigment extraction.extraction. TheThe dyedye waswas extractedextracted byby boilingboiling flowersflowers in in distilled distilled water water at at material-liquor material-liquor ◦ ratioratio (MLR)(MLR) 1:2.7,1:2.7, at 100 °CC for for 1 1 h. h. After After the the fir firstst extraction extraction process process,, the thedye dye solution solution was

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was filtered and evaporated water was adjusted with distilled water to a volume of 3 L. Extraction process was repeated twice by using residual flowers after the first extraction.

2.2.1. Determination of pH Values The pH values of dye solutions were measured by pH meter MA 5736, Metrel (Iskra), Slovenia with the glass-electrode method. Prior to the measurement pH meter was cali- brated in the solution of pH 3, pH 5 and pH 7 buffers.

2.2.2. Determination of the Crude Dye Yield The mass of the crude dye was determined by the evaporation method. To do this, 100 mL of the extracted and ﬁltered dye solution was placed in the Petri dish and heated in the oven at 105 ± 2 ◦C for 24 h. Crude solid dry material weight after evaporation was calculated on the volume of 3 L. The solid and dried dye was weighed, and the percentage of crude dye was calculated using Equation (1) in relation to the original weight of plant material used for extraction.

Wcd = (Wae)/Wbe) ∗ 100, (1)

where Wcd–percentage yield of crude dye (%); Wae–crude solid dry material weight after evaporation (g); Wbe–dry material weight before extraction (g).

2.2.3. FT-IR Spectroscopy Fourier transform infrared (FT-IR) spectra were obtained with a Perkin Elmer Spec- trum 100 FT-IR spectrometer using ATR (attenuated total reﬂection) method. The analyses were carried out at room temperature and ambient humidity. All spectra were registered from 4000 cm−1 to 380 cm−1, with a resolution of 4 cm−1. The background was collected at the beginning of the measurement. Each spectrum was collected from an average of 4 scans.

2.2.4. UV-VIS Spectrophotometry The absorption spectra of the dye solutions were measured using a UV-Vis spectrophotometer, UV-2600, Shimadzu Europe, Germany at a wavelength from 200 to 800 nm.

2.3. Fabric Treatment 2.3.1. Pre-Mordanting Process Pre-mordanting of cotton and wool fabrics was applied by using potassium aluminum ◦ sulfate dodecahydrate KAl(SO4)2 × 12 H2O. MLR ratio was 1:40, at 50 C for 30 min with mordant concentrations of 3% and 5% on the weight of the fabric. After mordanting, fabrics were air dried.

2.3.2. Dyeing Process Cotton and wool fabrics were dyed in water extract of Spartium junceum L. ﬂowers by exhaustion method with MLR 1:40, at 90 ◦C for 60 min. Dyeing was performed with and without mordanting process using dye solution after the ﬁrst extraction. Afterward, the fabrics were thoroughly washed in cold water, followed by hot soaping with Kemopon 30, CHT Bezema, Switzerland and cold rinsing.

2.3.3. Washing Process The washing process was carried out at MLR 1:20, at 60 ◦C for 30 min, through 5 cycles using the apparatus Turbomat P4502, Mathis, Switzerland. The washing bath was made with 2.5 g/L ECE-2 colorfastness test detergent, without using phosphate, ISO 105-C08/C09. Washed fabrics were dried between the washing cycles. Colorfastness to washing was tested by colorimetric evaluations. Materials 2021, 14, 4091 5 of 18

2.3.4. Color Measurement The color coordinates of dyes were determined on spectrophotometer Datacolor 850, Switzerland under illuminant D65, using d/10◦ geometry. The coordinates used to determine color values are “L*” for lightness, “a*” for redness (positive value) and greenness (negative value), “b*” for yellowness (positive value) and blueness (negative value), “C*” for chroma and “h◦” for hue angle in the range of 0◦ to 360◦. The changes in coloration of unwashed and washed samples were characterized by the difference in lightness “dL*”, hue “dH*”, chroma “dC*” and the total difference in color “Delta E*”. Delta E (∆E*) was calculated by the following Equation (2):

∆E* = [(∆L*)2 + (∆a*)2 + (∆b*)2]1/2, (2)

where ∆L* = L* washed–L* unwashed; ∆a* = a* washed–a* unwashed; ∆b* = b* washed– b* unwashed. Color strength (K/S) was calculated by the Kubelka-Munk Equation (3):

K/S = (1 − R)2/2R, (3)

where K is the absorption coefficient, S is the scattering coefficient and R is the remission value (reflectance of the dyed fabric) at Lmax. The color coordinates were measured before and after the 1st, 3rd and 5th washing cycle.

3. Results and Discussion 3.1. Sample Labeling Samples labels were deﬁned according to material composition, dye extraction, pre- mordanting and washing process:

C/W_E_Me_Wx,

where C/W stands for ﬁber type (C for cotton and W for wool fabric), E stands for the extraction process of dye solutions (1E for 1st extraction, 2E for 2nd extraction and 3E for 3rd extraction), Me is mordant concentration (from 0 to 5% on the weight of the fabric) and Wx is number of washing cycles (from 0 to 5 cycles).

3.2. Analysis of Dye Extract 3.2.1. pH Values of Aqueous Dye Solutions All the investigated solutions show pH values around 5 indicating the acidic range. 1st extraction (1E) shows pH 5.4 at 21.3 ◦C, 2nd extraction (2E) shows pH 5.5 at 20.6 ◦C and 3rd extraction (3E) shows pH 5.6 at 22.9 ◦C. Acidic dye solutions are most often anionic in nature and are suitable for the dyeing of protein ﬁbers and polyamide as well [26,27].

3.2.2. Crude Dye Yield Crude dye yield is an indicator of the total extracted pigments from the plant source. It signiﬁcantly depends on the characteristics of the plant (climate, harvesting time, etc.) and on the extraction process parameters (pH, temperature, time) as well. The highest amount of extracted pigment which can be objectively assessed from the Table2 and visually from Figure2 is obtained after 1st extraction.

Table 2. Crude dye yield in the investigated dye solutions.

Dye Solutions Mass of the Crude Dye (g) Crude Dye Yield (%) 1E 52.8 4.8 2E 25.98 2.4 3E 12.48 1.1 Materials 2021, 14, 4091 6 of 18 Materials 2021, 14, x FOR PEER REVIEW 6 of 19

(a) (b)

FigureFigure 2. Evaporated 2. Evaporated residue residue of (a of) 1st (a )extraction 1st extraction dye solution dye solution (1E) and (1E) (b and) 3rd ( extractionb) 3rd extraction dye solu- dye tionsolution (3E). (3E).

Table 2.Natural Crude dye dyes yield of in plant the inve origin,stigated most dye commonly solutions. from the flavonoid group, have been shownDye Solutions to have good solubility Mass inof the acidic Crude media Dye (g) since glycosides Crude are Dye resistant Yield (%) to acid hy- drolysis1E resulting in better pigment52.8 extraction [6,12,16,28,29]. Alkaline 4.8 media is used in the extraction2E of compounds, which25.98 contain phenolic groups [29,30]. Therefore, 2.4 flavonoid derivatives3E are most often detected12.48 in the acidic extract. In this paper, 1.1 a relatively small amount of crude dye yield was obtained after 1st acidic extraction (4.8%), which is further reducedNatural by dyes 50% of in plant each origin, subsequent most dyeingcommonl process.y from Thethe flavonoid results after group, crude have dye been yield showncalculation to have indicate good solubility the unprofitability in acidic ofmedia using since 2E and glycosides 3E dye solution, are resistant therefore to acid multiple hy- drolysisextractions resulting of the in collectedbetter pigment plant areextraction not recommended [6,12,16,28,29]. for furtherAlkaline research. media is Asused can in be theseen extraction from Figure of compounds,2, 3E dye solution which contain is inadequate phenolic so groups 1E dye [29,30]. solution Therefore, was applied flavonoid in this derivativesexperiment. are This most was often also detected confirmed in the by VISacidic spectrophotometric extract. In this paper, analysis a relatively of the extracts. small amount of crude dye yield was obtained after 1st acidic extraction (4.8%), which is further reduced3.2.3. UV-VIS by 50% Spectrophotometryin each subsequent dyeing process. The results after crude dye yield cal- culationThe indicate UV absorption the unprofitability spectra ofof Spartiumusing 2E junceumand 3E dyeL. dyesolution, solutions therefore after multiple 1 cycle of extractionsextraction of (1E) the arecollected shown plant in Figure are not3. Itrecommended shows 4 bands for in further the region research. of λ maxAs 224,can be 268, seen308 from and Figure 346 nm 2, which 3E dye are solution ascribed is inadequate to benzoyl so and 1E cinnamoyl dye solution bands was characteristicapplied in this for experiment.flavonoids This [31]. was Flavonoids also confirmed are comprised by VIS spectrophotometric of two benzene rings analysis linked viaof the a heterocyclic extracts. pyrane ring visible as a band at 224 nm which correlates well with the literature [12,32]. In 3.2.3.the UV-VIS paper published Spectrophotometry by Amat, A. et al., the UV absorbance band of luteolin was measured Materials 2021, 14, x FOR PEER REVIEW 7 of 20 in acidicThe UV media absorption and found spectra to be of 348 Spartium nm which junceum is in lineL. dye with solutions our measurements after 1 cycle [ 33of]. ex- The peak at 268 nm is characteristic of flavonols, the subclass of flavonoids whose representative traction (1E) are shown in Figure 3. It shows 4 bands in the region of λmax 224, 268, 308 and 346is nm quercetin which [are34]. ascribed to benzoyl and cinnamoyl bands characteristic for flavonoids [31]. Flavonoids are comprised of two benzene rings linked via a heterocyclic pyrane ring visible as a band at 224 nm which correlates well with the literature [12,32]. In the paper published by Amat, A. et al., the UV absorbance band of luteolin was measured in acidic media and found to be 348 nm which is in line with our measurements [33]. The peak at 268 nm is characteristic of flavonols, the subclass of flavonoids whose representative is quercetin [34].

Figure 3. The UV absorption spectra of dye solution 1E. Figure 3. The UV absorption spectra of dye solution 1E.

The absorbance spectra of Spartium junceum L. dye solutions after 3 cycles of extraction are shown in Figure 4. As can be seen, the dye solution from the first extraction shows

the highest absorption intensity at 400 nm wavelength in the visible area, which proved the presence of the highest amount of extracted pigments. According to the literature [16], Spartium junceum L. flowers contain luteolin and quercetin dyes responsible for its yellow color. Flavonoids like luteolin and quercetin are expected to have the highest absorbance in the yellow area (from 390 to 450 nm) [12].

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The absorbance spectra of Spartium junceum L. dye solutions after 3 cycles of extraction are shown in Figure4. As can be seen, the dye solution from the ﬁrst extraction shows the highest absorption intensity at 400 nm wavelength in the visible area, which proved Materials 2021, 14, x FOR PEER REVIEW 8 of 20 the presence of the highest amount of extracted pigments. According to the literature [16], Spartium junceum L. ﬂowers contain luteolin and quercetin dyes responsible for its yellow color. Flavonoids like luteolin and quercetin are expected to have the highest absorbance in the yellow area (from 390 to 450 nm) [12].

FigureFigure 4. 4. TheThe VIS VIS absorption absorption spectra spectra of 1 1stst extraction (1E),(1E), 2nd2ndextraction extraction (2E) (2E) and and 3rd 3rd extraction extraction (3E). (3E). 3.2.4. FT-IR Spectra of Crude Dye Materials 2021, 14, x FOR PEER REVIEW 9 of 20 3.2.4. FTThe-IR color Spectra of SJL of flowersCrude D isye directly connected to the presence of flavonoids, which are mainly present in yellow colored parts of plants [15,16]. FTIR technique was applied for The color of SJL flowers is directly connected to the presence of flavonoids, which are possible differentiation of flavonoids subclasses presented in examined crude dye [12,28]. mainly present in yellow colored parts of plants [15,16]. FTIR technique was applied for FTIR spectra of crude dye after the first extraction are presented in Figure5. possible differentiation of flavonoids subclasses presented in examined crude dye [12,28]. FTIR spectra of crude dye after the first extraction are presented in Figure 5.

FigureFigure 5.5. TheThe transmissiontransmission FTIRFTIR spectraspectra ofof thethe ﬁrstfirst extractionextraction (1E)(1E) crudecrude dye.dye.

ThisThis spectrumspectrum cancan bebe divideddivided intointo sixsix regions:regions: 1.1. 40004000–2500:–2500: associatedassociated withwith thethe stretching stretching vibrations vibrations of OHof OH functional functional group group of phe- of −1 −1 phenolsnols (3300 (3300 cm cm) and) and aromatic aromatic CH CH and and CH CH2 stretching2 stretching vibrations vibrations of of alkenes alkenes (2849(2849 and 2922 cm −1)1 )[[35];35]; 2.2. 24992499–1800:–1800: this region didn’t show any applicable spectral information; 3. 1799–1630: assigned to double bond stretching vibrations (band at 1711 cm−1 corresponding to C = O stretch of ketone, and band at 1643 cm−1 corresponding to carbonyl group characteristic for flavones, i.e., for luteolin [36,37]; 4. 1629–1400: assigned to C = C stretching of the aromatic ring (1603 cm−1 and 1513 cm−1); 5. 1399−1200: associated with C–OH deformations vibrations of phenols (1398 cm−1 and 1369 cm−1) and C–O stretching vibrations of aromatic ethers in phenols (1237 cm−1) and C–O stretching band due to pyranose structure (1202 cm−1) [38]; 6. 1199–700: assigned to C–O stretching vibrations (1063 and 1042 cm−1), C−OH stretching vibrations characteristic for flavanols, i.e., for quercetin (1013 cm−1) and out of plane CH deformation vibrations of the functional groups mainly from carbohydrates (region from 900 to 700 cm−1) [12,28,39,40]. The spectral area from 1799 and 700 cm−1 is called the ‘’fingerprint region’’ and is notable for the large number of infrared bands and is very important to characterize the sample’s chemical structure.

3.3. Analysis of Fabrics after Pre-Mordanting, Dyeing and Washing 3.3.1. Color Measurement K/S values of cotton and wool fabrics are presented in Figures 6 and 7. Figure 6 shows the effect of different mordant concentrations on dyed and undyed cotton fabrics. It is also visible that different aluminum mordant concentration does not significantly affect the K/S value. Vankar, P.S. et al. [31] stressed out that alkaline pH allows the strongest affinity of Al3+ metal to natural dye than acidic pH. Consequently, such low color strength is due to poor metal bonding with cellulose substrate and natural dye. Furthermore, Glogar, M.I. et al. presented in their paper [41] how the sample surface affects color strength as well. Smooth fabrics like cotton produce lower K/S compared to fabrics with a rougher surface (e.g., wool).

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3. 1799–1630: assigned to double bond stretching vibrations (band at 1711 cm−1 corresponding to C = O stretch of ketone, and band at 1643 cm−1 corresponding to carbonyl group characteristic for flavones, i.e., for luteolin [36,37]; 4. 1629–1400: assigned to C = C stretching of the aromatic ring (1603 cm−1 and 1513 cm−1); 5. 1399−1200: associated with C–OH deformations vibrations of phenols (1398 cm−1 and 1369 cm−1) and C–O stretching vibrations of aromatic ethers in phenols (1237 cm−1) and C–O stretching band due to pyranose structure (1202 cm−1)[38]; 6. 1199–700: assigned to C–O stretching vibrations (1063 and 1042 cm−1),C−OH stretching vibrations characteristic for flavanols, i.e., for quercetin (1013 cm−1) and out of plane CH deformation vibrations of the functional groups mainly from carbohydrates (region from 900 to 700 cm−1) [12,28,39,40]. The spectral area from 1799 and 700 cm−1 is called the ‘’fingerprint region” and is notable for the large number of infrared bands and is very important to characterize the sample’s chemical structure.

3.3. Analysis of Fabrics after Pre-Mordanting, Dyeing and Washing 3.3.1. Color Measurement K/S values of cotton and wool fabrics are presented in Figures6 and7. Figure6 shows the effect of different mordant concentrations on dyed and undyed cotton fabrics. It is also visible that different aluminum mordant concentration does not signiﬁcantly affect the K/S value. Vankar, P.S. et al. [31] stressed out that alkaline pH allows the strongest afﬁnity of Al3+ metal to natural dye than acidic pH. Consequently, such low color strength is due to poor metal bonding with cellulose substrate and natural dye. Furthermore, Glogar, M.I. Materials 2021, 14, x FOR PEER REVIEWet al. presented in their paper [41] how the sample surface affects color strength10 asof well.20 Smooth fabrics like cotton produce lower K/S compared to fabrics with a rougher surface (e.g., wool).

6 K/S 4

2 1.0241 1.0451 1.0631 0.5280 0.5078 0.5286 0

Figure 6. K/S values of cotton samples which are untreated (C_0x), treated only with mordants Figure 6. K/S values of cotton samples which are untreated (C_0x), treated only with mordants (C_3%Al_0x(C_3%Al_0x and and C_5%Al_0x) C_5%Al_0x) or dyed or dyed with with (C_1E_3%Al_0x (C_1E_3%Al_0x and and C_1E_5%Al_0x) C_1E_5%Al_0x) and and without without mor- mordantsdants (C_1E_0%Al_0x). (C_1E_0%Al_0x).

FigureFigure 7 shows7 shows the the effect effect of ofdifferent different mordant mordant concentrations concentrations on on dyed dyed and and undyed undyed wool fabrics. The undyed wool substrate shows slightly yellow color. It was observed wool fabrics. The undyed wool substrate shows slightly yellow color. It was observed that that by increasing the alum concentration up to 3% and 5% on undyed wool substrates, by increasing the alum concentration up to 3% and 5% on undyed wool substrates, the the color strength was decreased by 7.91% and 15.73% indicating poor bonding between color strength was decreased by 7.91% and 15.73% indicating poor bonding between wool wool and metal ions. Metal ions from alum mordant cause linking between dye and wool and metal ions. Metal ions from alum mordant cause linking between dye and wool sub- substrate by forming covalent bonding between functional groups of the dye molecule strate by forming covalent bonding between functional groups of the dye molecule (OH, (OH, C = O) and protein ﬁber (NH2, COOH). Dyed wool fabrics treated with 3% and C = O) and protein fiber (NH2, COOH). Dyed wool fabrics treated with 3% and 5% alum mordant show an increase in K/S value compared to dyed wool fabric without mordant for 34.87% and 63.21%, respectively.

Materials 2021, 14, 4091 9 of 18 Materials 2021, 14, x FOR PEER REVIEW 11 of 20

5% alum mordant show an increase in K/S value compared to dyed wool fabric without mordant for 34.87% and 63.21%, respectively.

12 11.3700

10 9.3954

8 6.9663

6 K/S

2 0.4284 0.3945 0.3610 0

Figure 7. K/S values of wool samples which are untreated (W_0x), treated only with mordants Figure 7. K/S values of wool samples which are untreated (W_0x), treated only with mordants (W_3%Al_0x and W_5%Al_0x) or dyed with (W_1E_3%Al_0x and W_1E_5%Al_0x) and without (W_3%Al_0x and W_5%Al_0x) or dyed with (W_1E_3%Al_0x and W_1E_5%Al_0x) and without mordants (W_1E_0%Al_0x). mordants (W_1E_0%Al_0x). A huge difference between cotton and wool fabrics regarding the color strength is relatedA huge to thedifference charge ofbetween the dye cotton and fabric. and wool In this fabrics research, regarding the acidic the color dye was strength extracted is relatedfrom to the theSpartium charge junceumof the dyeL. flowersand fabric. which In hasthis anresearch, anionic the character acidic dye and was negative extracted charge. fromCotton the Spartium fabric has junceum a negative L. flowers charge which as well. has an Since anionic the same character charges and repelnegative each cha other,rge. it Cottonwas apparentfabric has that a negative cotton charge fabric with as well. current Since conditions the same charges would notrepel show each sufficient other, it was color apparentstrength that compared cotton to fabric the wool with fabric current which conditions is positively would charged not and show therefore sufficient much color more strengthprone to compared fiber/mordant/dye to the wool crosslinking fabric which [42 is– 45 positively]. charged and therefore much more proneTable to3 presents fiber/mordant/dye that pre-mordant crosslinking and undyed [42–45 cotton]. samples show a minor decrease inTable lightness, 3 presents chroma that and pre hue-mordant for 0.19%, and 11.47% undyed and cotton 1.19%, samples respectively show for a minor sample de- pre- creasemordant in lightness, with 3% chroma alum. and hue for 0.19%, 11.47% and 1.19%, respectively for sample pre-mordant with 3% alum. Table 3. Color coordinates of cotton samples dyed with SJL aqueous extract with and without Tablemordants 3. Color before coordinates washing. of cotton samples dyed with SJL aqueous extract with and without mordants before washing. Samples L* a* b* C* h Samples L* a* b* C* h − C_0xC_0x 97.2797.27 3.333.33 −11.2011.20 11.68 11.68 286.54 286.54 − C_3%Al_0xC_3%Al_0x 97.0997.09 2.352.35 −10.0710.07 10.34 10.34 283.14 283.14 − C_5%Al_0xC_5%Al_0x 96.8296.82 2.342.34 −9.939.93 10.20 10.20 283.27 283.27 − C_1E_0%Al_0xC_1E_0%Al_0x 90.09 90.09 1.73−1.73 17.5217.52 17.60 17.60 95.65 95.65 C_1E_3%Al_0xC_1E_3%Al_0x 90.02 90.02 −2.10−2.10 20.4520.45 20.55 20.55 95.86 95.86 C_1E_5%Al_0xC_1E_5%Al_0x 90.01 90.01 −2.05−2.05 21.3021.30 21.39 21.39 95.49 95.49

TheyThey also also show show a decrease a decrease in lightness, in lightness, chroma chroma and hue and for hue 0.46%, for 12.67% 0.46%, and 12.67% 1.14%, and respectively1.14%, respectively for sample for pre sample-mordant pre-mordant with 5% alum, with both 5% alum, regarding both the regarding reference the samples reference C_0x.samples Subjective C_0x. Subjectivevisual assessment visual assessment of dyed cotton of dyed samples cotton matches samples the matches objective the objectivemeas- urementmeasurement and give ands light gives yellow lightyellow color. These color. Thesesamples samples show showno significant no signiﬁcant differences differences in huein (h° hue is (hin◦ theis in rang thee rangefrom 95.49 from to 95.49 95.86) to 95.86)and lightness and lightness values values(L* is in (L* the is range in the from range 90.01from to 90.0190.09). to Dyed 90.09). cotton Dyed sample cotton without sample withoutprevious previous mordanting mordanting shows the shows highest the light- highest nesslightness value (L* value = 90.09) (L* = 90.09)and the and lowest the lowest chroma chroma value value (C* (C*= 17.60) = 17.60) within within series series of ofdyed dyed samples.samples. The The increase increase in inchroma chroma value value is isnoticeable noticeable for for dyed dyed cotton cotton samples, samples, which which are are prepre-mordant-mordant with with 3% 3% and and 5% 5% alum forfor 16.76%16.76% and and 21.53%, 21.53%, respectively, respectively, regarding regarding the the dyed dyedcotton cotton sample sample without without previous previous mordanting mordanting (C_1E_0%Al_0x). (C_1E_0%Al_0x). According According to to thethe paperpa- perpublished published by by Repon, Repon, M.R. M.R. etet al.al. pre pre-mordanting-mordanting of of cotton cotton fabric fabric with with 5% 5% alum alum shows shows slightly positive impact on color saturation of dyed cotton fabric but negative impact on

Materials 2021, 14, 4091 10 of 18

slightly positive impact on color saturation of dyed cotton fabric but negative impact on the environment since Al3+ metal from alum mordant shows lower exhaustion on material surface due to its lower coordination number [11]. Table4 presents that pre-mordant and undyed wool samples show a minor decrease in lightness and chroma for 0.36% and 7.85%, respectively, while a minor increase in hue for 1.17%, for sample pre-mordant with 3% alum regarding the reference sample W_0x occurs.

Table 4. Color coordinates of wool samples dyed with SJL aqueous extract with and without mordants before washing.

Samples L* a* b* C* h W_0x 90.45 −1.04 12.83 12.87 94.62 W_3%Al_0x 90.12 −1.18 11.80 11.86 95.73 W_5%Al_0x 91.24 −1.18 11.68 11.74 95.76 W_1E_0%Al_0x 71.70 5.01 38.42 38.74 82.56 W_1E_3%Al_0x 70.91 6.54 47.31 47.76 82.13 W_1E_5%Al_0x 69.96 7.98 51.02 51.64 81.11

Wool sample pre-mordant with 5% alum shows an increase in lightness and hue for 0.87% and 1.20%, respectively and a decrease in chroma for 8.78%, regarding the reference sample W_0x. Dyed wool samples show higher intensity in coloration than cotton samples which is assessed by subjective visual method and confirmed objectively by color coordinate measurements. Comparing cotton and wool dyed samples noticeable decrease in lightness (L* was approx. 90 for cotton and 70 for wool samples) and hue (h◦ was approx. 95 for cotton and 82 for wool samples) occurs while at the same time increase in chroma values (C* was approx. 20 for cotton and 46 for wool samples) happens. Haji, A. et al. have shown in their research paper mechanism of attachment of quercetin to wool structure assisted with the addition of alum mordant. One molecule of mordant binds the protein fiber while at the same time holding one or two molecules of dye with it, causing an increase of the affinity between wool fiber and dye and its color yield as well [46]. Similar to cotton, dyed wool sample without previous mordanting shows the highest lightness value (L* = 71.70) and the lowest chroma value (C* = 38.74) within series of dyed samples. Samples which are dyed and pre-mordant with 5% alum show lowest lightness value (L* = 69.96) and highest chroma (C* = 51.64). The impact of multiple washing cycles on the color fastness of cotton and wool dyed fabrics was monitored through an objective color measurement technique. Colorfastness to washing is an important factor since most dyed fabrics are frequently washed after their usage. Results were presented in Tables5–18.

Table 5. Change in color coordinates of the cotton sample without mordants after 1st, 3rd and 5th washing cycle (compared with C_0x).

Samples dL* dC* dH* dE* C_1x −0.17 −0.46 0.25 0.55 C_3x −0.36 −0.78 0.33 0.92 C_5x −0.29 −0.23 0.19 0.42

Table 6. Change in color coordinates of the cotton sample treated with 3% Al mordants after 1st, 3rd and 5th washing cycle (compared with C_3%Al_0x).

Samples dL* dC* dH* dE* C_3%Al_1x −0.03 1.06 0.80 1.33 C_3%Al_3x 0.09 1.19 0.75 1.41 C_3%Al_5x 0.13 1.48 0.69 1.64 Materials 2021, 14, 4091 11 of 18

Table 7. Change in color coordinates of the cotton sample treated with 5% Al mordants after 1st, 3rd and 5th washing cycle (compared with C_5%Al_0x).

Samples dL* dC* dH* dE* C_5%Al_1x 0.24 1.51 0.74 1.70 C_5%Al_3x 0.32 1.55 0.79 1.77 C_5%Al_5x 0.40 1.67 0.71 1.86

Table 8. Change in color coordinates of cotton samples dyed with SJL aqueous extract without mordants after 1st, 3rd and 5th washing cycle (compared with C_1E_0%Al_0x).

Samples dL* dC* dH* dE* C_1E_0%Al_1x 3.78 −18.36 −7.41 20.15 C_1E_0%Al_3x 4.64 −15.08 −18.69 24.46 C_1E_0%Al_5x 5.12 −14.15 −20.61 25.52

Table 9. Change in color coordinates of cotton samples dyed with SJL aqueous extract with 3% Al mordants after 1st, 3rd and 5th washing cycle (compared with C_1E_3%Al_0x).

Samples dL* dC* dH* dE* C_1E_3%Al_1x 3.45 −18.87 −5.39 19.93 C_1E_3%Al_3x 4.32 −17.13 −16.09 23.90 C_1E_3%Al_5x 5.00 −15.61 −19.79 25.70

Table 10. Change in color coordinates of cotton samples dyed with SJL aqueous extract with 5% Al mordants after 1st, 3rd and 5th washing cycle (compared with C_1E_5%Al_0x).

Samples dL* dC* dH* dE* C_1E_5%Al_1x 3.37 −19.38 −4.38 20.15 C_1E_5%Al_3x 4.42 −17.90 −16.68 24.87 C_1E_5%Al_5x 4.84 −17.07 −18.78 25.84

The difference in the sensation of color after washing was presented by Delta E* values. Table5 shows there are no significant differences among washed and unwashed samples since Delta E* is lower than 2 which is an indicator that the differences are within the tolerance limits. Tables6 and7 show that metal (Al) from alum mordant binds well and firmly to the cotton material, especially when applied in higher concentrations (5%). Comparing only the best results from Tables6 and7 (samples after 1 washing cycle) with an untreated cotton sample from Table5 (Delta E* = 0.55) it can be seen that Delta E* has increased and amounts 1.33 and 1.70, respectively. Table8 shows high colorfastness to washing (after 1st washing cycle) of cotton dyed samples without pre-mordant (Delta E* = 20.15). Delta E* higher than 2 indicates that differences in coloration are visible with the naked eye and are outside the tolerance limits. A higher number of washing cycles influences Delta E* values indicating a greater color change of sample after 5 washing cycles (Delta E* = 25.52). Results of pre-mordant and dyed cotton material are presented in Tables9 and 10. It is noticeable that metal (Al3+) from alum mordant does not make strong chemical bonds with dye since Delta E* values increase regarding the higher concentration of alum and higher number of washing cycles, as well. This is also confirmed with differences in lightness and hue values, which directly affect Delta E*. The difference in lightness value (dL*) has the smallest influence on the total difference in coloration (dE*). The dL* values are under 5.00 while differences in hue (dH*) are increasing with a higher number of washing cycles and are in the range of approx. 16.00 to 20.00 indicating a noticeable change in samples’ color. MaterialsMaterials 2021 2021, 14, 14, x, xFOR FOR PEER PEER REVIEW REVIEW 1212 of of 19 19 MaterialsMaterialsMaterials 2021 20212021, ,14,, 1414, ,x,, x xxFOR FORFORFOR PEER PEERPEERPEER REVIEW REVIEWREVIEWREVIEW 121212 of ofof 19 1919

ResResResultsultsults of ofof pre-mordant pre-mordantpre-mordant and andand dyed dyeddyed cotton cottoncotton material materialmaterial are areare presented presentedpresented in inin Tables TablesTables 9 9 9and andand 10. 10.10. It ItIt 3+3+3+ isisisis noticeable noticeablenoticeablenoticeable that thatthatthat metal metalmetalmetal (Al (Al(Al(Al3+3+3+) ))from fromfrom alum alumalum mordant mordantmordant does doesdoes not notnot make makemake strong strongstrong chemical chemicalchemical bonds bondsbonds withwithwith dye dyedye since sincesince Delta DeltaDelta E* E*E* values valuesvalues increase increaseincrease rega regaregardingrdingrding the thethe higher higherhigher concentration concentrationconcentration of ofof alum alumalum and andand higherhigherhigher number numbernumber of ofof washing washingwashing cycles, cycles,cycles, as asas well. well.well. This ThisThis is isisis also alsoalsoalso confirmed confirmedconfirmedconfirmed with withwithwith differences differencesdifferencesdifferences in ininin light- light-light-light- nessnessness and andand hue huehue values, values,values, which whichwhich directly directlydirectly affect affectaffect Delt DeltDeltaa aE*. E*.E*. The TheThe difference differencedifference in inin lightness lightnesslightness value valuevalue (dL*) (dL*)(dL*) hashashas the thethe smallest smallestsmallest influence influenceinfluence on onon the thethe total totaltotal differen differendifferencecece in inin coloration colorationcoloration (dE*). (dE*).(dE*). The TheThe dL* dL*dL* values valuesvalues are areare underunderunder 5.00 5.005.00 while whilewhile differences differencesdifferences in inin hue huehue (dH*) (dH*)(dH*) are areare in inincreasingcreasingcreasing with withwith a a ahigher higherhigher number numbernumber of ofof washing washingwashing cyclescyclescycles and andand are areare in inin the thethe range rangerange of ofof approx. approx.approx. 16.00 16.0016.00 to toto 20.00 20.0020.00 indicating indicatingindicating a a anoticeable noticeablenoticeable change changechange in inin sam- sam-samples’ples’ples’ color. color.color.

TableTableTable 9. 9.9. Change ChangeChange in inin color colorcolor coordinates coordinatescoordinates of ofof cotton cottoncotton samples samplessamples dyed dyeddyed with withwith SJL SJLSJL aqueous aqueousaqueous extract extractextract with withwith 3% 3%3% Al AlAl mordantsmordantsmordants after afterafter 1st, 1st,1st, 3rd 3rd3rd and andand 5th 5th5th washin washinwashingg gcycle cyclecycle (compared (compared(compared wi wiwithththth C_1E_3%Al_0x). C_1E_3%Al_0x).C_1E_3%Al_0x).C_1E_3%Al_0x). SamplesSamples dL*dL* dC*dC* dH*dH* dE*dE* SamplesSamplesSamples dL*dL*dL* dC*dC*dC* dH*dH*dH* dE*dE*dE* C_1E_3%Al_1xC_1E_3%Al_1x 3.3.4545 −18.−18.8787 −5.39−5.39 19.19.9393 C_1E_3%Al_1xC_1E_3%Al_1xC_1E_3%Al_1x 3.3.3.454545 −−18.−18.18.878787 −−5.39−5.395.39 19.19.19.939393 C_1E_3%Al_3xC_1E_3%Al_3x 4.4.3232 −17.−17.1313 −16.09−16.09 23.23.9090 C_1E_3%Al_3xC_1E_3%Al_3xC_1E_3%Al_3x 4.4.4.323232 −−17.−17.17.131313 −−16.09−16.0916.09 23.23.23.909090 C_1E_3%Al_5xC_1E_3%Al_5x 5.5.0000 −15.61−15.61 −19.79−19.79 25.25.7070 C_1E_3%Al_5xC_1E_3%Al_5xC_1E_3%Al_5x 5.5.5.000000 −−15.61−15.6115.61 −−19.79−19.7919.79 25.25.25.707070

TableTableTable 10. 10.10. Change ChangeChange in inin color colorcolor coordinates coordinatescoordinates of ofof cotton cottoncotton sample samplesamples ssdyed dyeddyed with withwith SJL SJLSJL aqueous aqueousaqueous extract extractextract with withwith 5% 5%5% AlAlAl mordants mordantsmordants after afterafter 1st, 1st,1st, 3rd 3rd3rd and andand 5th 5th5th wa wawashingshingshing cycle cyclecycle (compare (compare(compareddd with withwith C_1E_5%Al_0x). C_1E_5%Al_0x).C_1E_5%Al_0x). SamplesSamples dL*dL* dC*dC* dH*dH* dE*dE* SamplesSamplesSamples dL*dL*dL* dC*dC*dC* dH*dH*dH* dE*dE*dE* C_1E_5%Al_1xC_1E_5%Al_1x 3.3.3737 −19.−19.3838 −4.38−4.38 20.20.1515 C_1E_5%Al_1xC_1E_5%Al_1xC_1E_5%Al_1x 3.3.3.373737 −−19.−19.19.383838 −−4.38−4.384.38 20.20.20.151515 C_1E_5%Al_3xC_1E_5%Al_3x 4.4.4242 −17.−17.9090 −16.68−16.68 24.24.8787 C_1E_5%Al_3xC_1E_5%Al_3xC_1E_5%Al_3x 4.4.4.424242 −−17.−17.17.909090 −−16.68−16.6816.68 24.24.24.878787 C_1E_5%Al_5xC_1E_5%Al_5x 4.4.8484 −17.07−17.07 −18.78−18.78 25.25.8484 C_1E_5%Al_5xC_1E_5%Al_5xC_1E_5%Al_5x 4.4.4.848484 −−17.07−17.0717.07 −−18.78−18.7818.78 25.25.25.848484

VisualVisualVisual assessment assessmentassessment of ofof colorfastn colorfastncolorfastnessessess to toto washing washingwashing can cancan be bebe seen seenseen in inin Table TableTable 11. 11.11. In InIn the thethe first firstfirst part partpart Materials 2021, 14, 4091 12 of 18 ofofof Table TableTable 11, 11,11, undyed undyedundyed cotton cottoncotton samp sampsamplesleslesles were werewerewere presented presentedpresentedpresented and andandand the thethethe effect effecteffecteffect of ofofof washing washingwashingwashing on ononon its itsitsits dis- dis-dis-dis- colorationcolorationcoloration is isis almost almostalmost negligible. negligible.negligible.

TableTableTable 11. 11.11. Visual VisualVisual assessment assessmentassessment of ofof colorfastness colorfastnesscolorfastness to toto washing. washing.washing. TableTableTable 11. 11.11. Visual VisualVisual assessment assessmentassessment of ofofof colorfastness colorfastnesscolorfastnesscolorfastness to to toto washing. washing. washing.washing. WashingWashing Cotton Cotton without without Mordant Mordant Cotton Cotton 3% 3% Mordant Mordant Cotton Cotton 5% 5% Mordant Mordant WashingWashingWashing Cotton Cotton Cotton without withoutwithout Mordant MordantMordant Cotton Cotton Cotton 3% 3%3% Mordant MordantMordant Cotton Cotton Cotton 5% 5%5% Mordant MordantMordant Washing Cotton without Mordant Cotton 3% Mordant Cotton 5% Mordant

0x0x 0x0x0x 0x

5x5x5x 5x5x5x5x

MaterialsMaterialsMaterials 2021 20212021,, ,14,, 1414,, ,x,x, x x xFORFOR FORFORFOR PEERPEER PEERPEERPEER REVIEWREVIEW REVIEWREVIEWREVIEW 131313 of ofof 19 1919

WashingWashingWashing WashingWashing Dyed Cotton without Mordant Dyed Cotton 3% Mordant Dyed Cotton 5% Mordant

0x0x0x 0x

5x5x5x 5x5x

DyedDyedDyed cotton cottoncotton samples samplessamples were werewere presented presentedpresented in inin the thethe se sesecondcondcond part partpart of ofof Table TableTable 11. 11.11. Discoloration DiscolorationDiscoloration of ofof Table 12. Change in color coordinates of the wool sample without mordants after 1st, 3rd and 5th samplessamplessamples after afterafter the thethe washing washingwashing process processprocess is isis significant significantsignificant especially especiallyespecially since sincesince the thethe color colorcolor change changechange is isis quite quitequite washing cycle (compared with W_0x). noticeablenoticeablenoticeable after afterafter 5 55 washing washingwashing cycles. cycles.cycles. TableTableTable 12 1212 shows showsshows that thatthat there therethere are areare significant significantsignificant differences differencesdifferences among amongamong washed washedwashed samples samplessamples after afterafter 3 33 TableTableSamples 12 12 shows shows that that there there are dL*are significant significant differences differences dC* among among dH* washed washed samples samples dE* after after 3 3 andandand 5 55 washing washingwashing cycles cyclescycles and andand unwashed unwashedunwashed samples. samples.samples. Delta DeltaDelta E* E*E* is isis lower lowerlower than thanthan 2 22 for forfor wool woolwool untreated untreateduntreated W_1x −0.96 0.79 −0.03 1.24 samplessamplessamples after afterafter 1st 1st1st washing washingwashing cycle cyclecycle (Delta (Delta(Delta E* E*E* = == 1.24 1.241.24)) )which whichwhich is isis an anan indicator indicatorindicator that thatthat the thethe differences differencesdifferences samplessamples after afterW_3x 1st 1st washing washing cycle cycle− (Delta 1.51(Delta E* E* = = 1.24 1.24)2.02 )which which is is an an indicator indicator−0.38 that that the the differences differences 2.55 areareare within withinwithin W_5xthe thethe tolerance tolerancetolerance limits. limits.limits. − 1.59 2.50 −0.48 3.00

TableTableTable 12. 12.12. Change ChangeChange in inin color colorcolor coordinates coordinatescoordinates of ofof the thethe wool woolwool samp sampsamplelele without withoutwithout mordants mordantsmordants after afterafter 1st, 1st,1st, 3rd 3rd3rd and andand 5th 5th5th washingwashingTablewashing 13. cycle cyclecycleChange (compared (compared(compared in color with coordinateswithwith W_0x). W_0x).W_0x). of wool sample treated with 3% Al mordants after 1st, 3rd and 5th washing cycle (compared with W_3%Al_0x). SamplesSamplesSamples dL*dL*dL* dC*dC*dC* dH*dH*dH* dE*dE*dE* W_1xSamplesW_1xW_1x −−0.96−0.960.96 dL*0.0.0.79 dC*7979 −−0.03− dH*0.030.03 1.1. dE*1.242424 W_3xW_3xW_3x −−1.51−1.511.51 2.2.2.020202 −−0.38−0.380.38 2.2.2.555555 W_3%Al_1x 0.22 0.75 0.01 0.78 W_5xW_5xW_5x −−1.59−1.591.59 2.2.2.505050 −−0.48−0.480.48 3.3.3.000000 W_3%Al_3x −1.09 2.45 −0.40 2.71 W_3%Al_5x −1.64 3.58 −0.80 4.02 TablesTablesTables 13 1313 and andand 14 1414 show showshow that thatthat metal metalmetal (Al) (Al)(Al) from fromfrom alum alumalum mordant mordantmordant binds bindsbinds well wellwell and andand firmly firmlyfirmly to toto thethethe wool woolwool material, material,material, especially especiallyespecially when whenwhen applied appliedapplied in inin higher higherhigher concentrations concentrationsconcentrations (5%). (5%).(5%). Comparing ComparingComparing onlyonlyonly the thethe best bestbest results resultsresults from fromfrom Tables TablesTables 13 1313 and andand 14 1414 (samples (samples(samples after afterafter 1 11 washing washingwashing cycle) cycle)cycle) with withwith the thethe un- un-un- treatedtreatedtreated wool woolwool sample samplesample from fromfrom Table TableTable 12 1212 (Delta (Delta(Delta E* E*E* = == 1.24) 1.24)1.24) it itit can cancan be bebe seen seenseen that thatthat Delta DeltaDelta E* E*E* has hashas de- de-de- creasedcreasedcreased by byby 100% 100%100% and andand amounts amountsamounts 0.78 0.780.78 and andand 0.74, 0.74,0.74, respectively. respectively.respectively.

TableTableTable 13. 13.13. Change ChangeChange in inin color colorcolor coordinates coordinatescoordinates of ofof wool woolwool sample samplesample treated treatedtreated with withwith 3% 3%3% Al AlAl mordants mordantsmordants after afterafter 1st, 1st,1st, 3rd 3rd3rd andandand 5th 5th5th washing washingwashing cycle cyclecycle (compared (compared(compared with withwith W_3%Al_0x). W_3%Al_0x).W_3%Al_0x).

SamplesSamplesSamples dL*dL*dL* dC*dC*dC* dH*dH*dH* dE*dE*dE* W_3%Al_1xW_3%Al_1xW_3%Al_1x 0.220.220.22 0.0.0.757575 0.010.010.01 0.0.0.787878 W_3%Al_3xW_3%Al_3xW_3%Al_3x −−1.09−1.091.09 2.2.2.454545 −−0.40−0.400.40 2.2.2.717171 W_3%Al_5xW_3%Al_5xW_3%Al_5x −−1.64−1.641.64 3.3.3.585858 −−0.80−0.800.80 4.4.4.020202

TableTableTable 14. 14.14. Change ChangeChange in inin color colorcolor coordinates coordinatescoordinates of ofof wool woolwool sample samplesample treated treatedtreated with withwith 5% 5%5% Al AlAl mordants mordantsmordants after afterafter 1st, 1st,1st, 3rd 3rd3rd andandand 5th 5th5th washing washingwashing cycle cyclecycle (compared (compared(compared with withwith W_5%Al_0x). W_5%Al_0x).W_5%Al_0x).

SamplesSamplesSamples dL*dL*dL* dC*dC*dC* dH*dH*dH* dE*dE*dE* W_5%Al_1xW_5%Al_1xW_5%Al_1x −−0.46−0.460.46 0.0.0.585858 0.080.080.08 0.740.740.74 W_5%Al_3xW_5%Al_3xW_5%Al_3x −−1.47−1.471.47 1.1.1.696969 −−0.04−0.040.04 2.2.2.242424 W_5%Al_5xW_5%Al_5xW_5%Al_5x −−1.84−1.841.84 2.2.2.606060 −−0.23−0.230.23 3.3.3.191919 Materials 2021, 14, 4091 13 of 18

Table 14. Change in color coordinates of wool sample treated with 5% Al mordants after 1st, 3rd and 5th washing cycle (compared with W_5%Al_0x).

Samples dL* dC* dH* dE* W_5%Al_1x −0.46 0.58 0.08 0.74 W_5%Al_3x −1.47 1.69 −0.04 2.24 W_5%Al_5x −1.84 2.60 −0.23 3.19

Table 15. Change in color coordinates of wool sample dyed with SJL aqueous extract without mordants after 1st, 3rd and 5th washing cycle (compared with W_1E_0%Al_0x).

Samples dL* dC* dH* dE* W_1E_0%Al_1x −1.03 1.60 −1.46 2.39 W_1E_0%Al_3x −0.35 −0.90 −1.52 1.80 W_1E_0%Al_5x 0.56 −3.22 −1.55 3.61

Table 16. Change in color coordinates of cotton samples dyed with SJL aqueous extract with 3% Al mordants after 1st, 3rd and 5th washing cycle (compared with W_1E_3%Al_0x).

Samples dL* dC* dH* dE* W_1E_3%Al_1x −1.58 7.14 −1.31 7.43 W_1E_3%Al_3x −0.62 4.71 −0.98 4.85 W_1E_3%Al_5x 0.65 −0.27 −0.51 0.87

Table 17. Change in color coordinates of wool sample dyed with SJL aqueous extract with 5% Al mordants after 1st, 3rd and 5th washing cycle (compared with W_1E_5%Al_0x).

Samples dL* dC* dH* dE* W_1E_5%Al_1x −2.13 8.68 −1.37 9.04 W_1E_5%Al_3x −1.28 8.80 −1.01 8.94 W_1E_5%Al_5x −0.08 3.25 −0.29 3.27

Visual assessment of colorfastness to washing can be seen in Table 11. In the first part of Table 11, undyed cotton samples were presented and the effect of washing on its discoloration is almost negligible. Dyed cotton samples were presented in the second part of Table 11. Discoloration of samples after the washing process is significant especially since the color change is quite noticeable after 5 washing cycles. Table 12 shows that there are significant differences among washed samples after 3 and 5 washing cycles and unwashed samples. Delta E* is lower than 2 for wool untreated samples after 1st washing cycle (Delta E* = 1.24) which is an indicator that the differences are within the tolerance limits. Tables 13 and 14 show that metal (Al) from alum mordant binds well and firmly to the wool material, especially when applied in higher concentrations (5%). Comparing only the best results from Tables 13 and 14 (samples after 1 washing cycle) with the untreated wool sample from Table 12 (Delta E* = 1.24) it can be seen that Delta E* has decreased by 100% and amounts 0.78 and 0.74, respectively. Table 15 shows better colorfastness to washing of wool dyed samples without pre- mordant (Delta E* = 2.39) in comparison to the cotton sample treated under the same conditions. Delta E* higher than 2 indicates that differences in coloration are visible with the bare eye and are outside the tolerance limits. Results of pre-mordant and dyed wool material are presented in Tables 16 and 17. It is interesting that wool samples treated with mordant show a decrease in Delta E* values regarding a higher number of washing cycles. MaterialsMaterialsMaterials 2021 2021 20212021, 14,, , 14 1414, x,, , x xFORx FOR FORFOR PEER PEER PEERPEER REVIEW REVIEW REVIEWREVIEW 15151515 of of ofof 19 19 1919 MaterialsMaterialsMaterialsMaterials2021 20212021 20212021,,,,14 1414,,, 14,14,,, 4091 xxx,,, xxFORFORxFOR FORFORFOR PEERPEERPEER PEERPEERPEER REVIEWREVIEWREVIEW REVIEWREVIEWREVIEW 1415151515 of ofof ofof 18 1919 1919

TableTableTableTable 18. 18.18.18. Visual VisualVisualVisual assessment assessmentassessmentassessment of ofofof colorfastness colorfastnesscolorfastnesscolorfastness to to toto washing. washing.washing.washing. TableTableTableTable 18. 18. 18.18.Visual Visual VisualVisual assessment assessment assessmentassessment of of ofof colorfastness colorfastness colorfastnesscolorfastness to to toto washing. washing. washing.washing. WashingWashingWashingWashing Wool Wool Wool Wool without without withoutwithout Mordant Mordant MordantMordant Wool Wool Wool Wool 3% 3% 3%3% Mordant Mordant MordantMordant WoolWoolWoolWool 5% 5% 5%5% Mordant Mordant MordantMordant WashingWashing Wool without Mordant Wool Wool 3% Mordant WoolWool 5% 5% Mordant Mordant

0x0x0x0x 0x0x0x0x 0x

5x5x5x5x 5x5x5x5x

WashingWashingWashingWashing Dyed Dyed Dyed Dyed Wool Wool WoolWool without without withoutwithout Mordant Mordant MordantMordant Dyed Dyed Dyed Dyed Wool Wool WoolWool 3% 3% 3%3% Mordant Mordant MordantMordant Dyed Dyed Dyed Dyed Wool Wool WoolWool 5% 5% 5%5% Mordant Mordant MordantMordant WashingWashing Dyed Dyed Wool Wool without without Mordant Mordant Dyed Dyed Dyed Wool Wool Wool 3% 3% Mordant Mordant Dyed Dyed Wool Wool 5% 5% Mordant Mordant

0x0x0x0x 0x0x0x0x 0x

5x5x5x5x 5x5x5x5x

DiscolorationDiscolorationDiscolorationDiscoloration of of ofof woolen woolen woolenwoolen samples samples samplessamples after after afterafter the the thethe wa wa wawashingshingshingshing process process processprocess is is isis significantly significantly significantlysignificantly lower lower lowerlower than than thanthan The best result is shown in Table 16 by the sample treated with 3% alum after 5 wash- waswaswaswas the thethethe case casecasecase with withwithwith cotton cottoncottoncotton samples. samples.samples.samples. According AccordingAccordingAccording to tototo Li, Li,Li,Li, Y.V. Y.V.Y.V.Y.V. et etetet al. al.al.al. if ifif ifthe thethethe natural naturalnaturalnatural dye dyedyedye is isisis bonded bondedbondedbonded ing cycles (Delta E* = 0.87). These results confirm that metal (Al) from alum mordant withwithwithwith mordant mordantmordantmordant forming formingformingforming a a aastable stablestablestable dye-metal dye-metaldye-metaldye-metal complex complexcomplexcomplex then thenthenthen the thethethe water waterwaterwater solubility solubilitysolubilitysolubility of ofofof the thethethe dye dyedyedye is isisis make strong chemical bonds with wool substrate and dye since Delta E* values decrease lowerlowerlowerlowerlowerlower andand andandandand thethe thethethethe colorcolor colorcolorcolorcolor isis isisisis lessless lesslesslessless likelylikely likelylikelylikelylikely toto totototo bleedbleed bleedbleedbleedbleed outout outoutoutout onon onononon washingwashing washingwashingwashingwashing processprocess processprocessprocessprocess [50].[50]. [50].[50].[50].[50]. LightnessLightness LightnessLightnessLightnessLightness valuevalue valuevaluevaluevalue inlower comparison and the to color Delta is E*less values likely of to the bleed cotton out sampleson washing treated process in the [50]. same Lightness way. These value waswaswaswas decreasing decreasingdecreasingdecreasing while whilewhilewhile increasing increasingincreasingincreasing mordant mordantmordantmordant co cococoncentrationncentrationncentrationncentration (L* (L*(L*(L* from fromfromfrom 71.70 71.7071.7071.70 for forforfor unmordant unmordantunmordantunmordant resultswas decreasing correlate well while with increasing the research mordant of Haji, co A.ncentration [47] and Pour, (L* R.A.from [ 4871.70] who for have unmordant shown samplesamplesamplesample to tototo 69.96 69.9669.9669.96 for forforfor the thethethe sample samplesamplesample treated treatedtreatedtreated with withwithwith 5% 5%5%5% alum) alum)alum)alum) providing providingprovidingproviding darker darkerdarkerdarker shades shadesshadesshades of ofofof wool woolwoolwool thatsamplesample optimization to to 69.96 69.96 for offor metalthe the sample sample mordants treated treated concentrations with with 5% 5% alum) alum) and providing usage providing of lower darker darker concentration shades shades of of wool canwool fabricsfabricsfabricsfabrics which whichwhichwhich are areareare in ininin contrast contrastcontrastcontrast to tototo increasing increasingincreasingincreasing the thethethe L* L*L*L* value valuevaluevalue when whenwhenwhen increasing increasingincreasingincreasing the thethethe number numbernumbernumber of ofofof improvefabricsfabricsfabrics which colorfastnesswhichwhich are areare in inin contrast tocontrastcontrast washing. to toto increasing Althoughincreasingincreasing cottonthe thethe L* L*L* samplesvalue valuevalue when whenwhen did not increasing increasingincreasing show significant the thethe number numbernumber differ- of ofof washingwashingwashingwashing cycles cyclescyclescycles (L* (L*(L*(L* from fromfromfrom 70.91 70.9170.9170.91 for forforfor unwashed unwashedunwashedunwashed and andandand with withwithwith 3% 3%3%3% alum alumalumalum pre-mordanted pre-mordantedpre-mordantedpre-mordanted sample samplesamplesample to tototo enceswashingwashingwashing among cycles cyclescycles various (L* (L*(L* from fromfrom mordant 70.91 70.9170.91 for concentrations, forfor unwashed unwashedunwashed and andand wool with withwith samples 3% 3%3% alum alumalum show pre-mordanted pre-mordantedpre-mordanted that the concentration sample samplesample to toto 71.5671.5671.5671.56 for forforfor the thethethe same samesamesame sample samplesamplesample after afterafterafter 5 555washing washingwashingwashing cycles) cycles)cycles)cycles) providing providingprovidingproviding a aaalittle littlelittlelittle bit bitbitbit lighter lighterlighterlighter shades. shades.shades.shades. of71.5671.5671.56 mordant for forfor the thethe has same samesame a significant sample samplesample after after effectafter 5 5 5washing on washingwashing the obtained cycles) cycles)cycles) resultsproviding providingproviding and a on a alittle littlelittle the bit dyeing bitbit lighter lighterlighter effects shades. shades.shades. as well as colorfastness properties. Lightness values are dependent on both mordant concentra- 3.3.2.3.3.2.3.3.2.3.3.2. FT-IR FT-IRFT-IRFT-IR Spectra SpectraSpectraSpectra of ofofof Dye DyeDyeDye Wool WoolWoolWool Fabrics FabricsFabricsFabrics tion3.3.2.3.3.2.3.3.2. and FT-IR FT-IRFT-IR number Spectra SpectraSpectra of washingof ofof Dye DyeDye Wool WoolWool cycles Fabrics FabricsFabrics [49]. Higher mordant concentration influences lower FTIRFTIR spectra spectra of of reference reference (unmordant, (unmordant, undy undyeded and and unwashed) unwashed) and and dyed dyed wool wool fabrics fabrics lightnessFTIRFTIRFTIR value spectra spectraspectra while of ofof reference areferencereference higher (unmordant, number (unmordant,(unmordant, of washing undy undyundyeded cyclesed and andand unwashed) shows unwashed)unwashed) a slightly and andand dyed dyed higherdyed wool woolwool lightness fabrics fabricsfabrics −1−−−111 value.areareareare presented presentedpresentedpresented Considering in ininin Figure FigureFigureFigure only wool8. 8.8.8. Spectra SpectraSpectraSpectra samples of ofofof all pre-mordant allallall samples samplessamplessamples show showshow withshow absorption 3% absorptionabsorptionabsorption alum and peaks peakspeakspeaks dyed, at atatat its3276 327632763276 L* valuecm cmcmcm−1−− − 1as-11as- is as-as-as-as- −1−−−111 insignedsignedsignedsigned the range to tototo the thethethe from NH NHNHNH 70.91stretching stretchingstretchingstretching for unwashed vibrations, vibrations,vibrations,vibrations, samples 1631 163116311631 cm cm tocmcm− 71.561−− − 1assigned1assigned1 assignedassignedassignedassigned for samples toto totototo amide-Iamide-I amide-Iamide-Iamide-Iamide-I after (C(C (C(C 5(C(C washing======OO OOOO stretching),stretching), stretching),stretching),stretching),stretching), cycles −1−− −111 −1−− −111 (Table1515151515151515 cm 4 cmcmcm).−1 All−− −assigned111 assignedassignedassigned the dyed to tototo amide-II samples amide-IIamide-IIamide-II (NH show (NH(NH(NH bending bendingbending colorbending coordinates and andandand CN CNCNCN stretching) stretching)stretching)stretching) in a red-yellow and andandand 1075 107510751075 zone. cm cmcmcm− The1−− −assigned111 assigned assignedassigned a* is −1−− −111 increasing,tototototo CNCN CNCNCN stretchingstretching stretchingstretchingstretching while andand b* andandand is NHGNHG decreasingNHGNHGNHG bendingbending bendingbendingbending with ofof ofofof amide-III higheramide-III amide-IIIamide-IIIamide-IIIamide-III numbers [51].[51]. [51].[51].[51].[51]. TheThe TheTheTheThe of peakpeakwashing peakpeakpeakpeak atat atatatat 13911391 1391139113911391 cycles, cmcm cmcmcmcm−1 except−− −isis111 is isisis assignedassigned assignedassignedassignedassigned for the toto totototo −1−− −111 thethethethe amino aminoaminoamino acid acidacidacid (COO-) (COO-)(COO-)(COO-) functional functionalfunctionalfunctional group. group.group.group. A AAA peak peakpeakpeak at atatat 1233 123312331233 cm cmcmcm−1− is1 isisis assigned assignedassignedassigned to tototo CH CHCHCH2 2and22 andandand CH CHCHCH3 333 samplethethethe amino aminoamino treated acid acidacid with(COO-) (COO-)(COO-) 5% functional alumfunctionalfunctional where group. group.group. is visible A AA peak peakpeak aminor at atat 1233 12331233 increase cm cmcm−−is11 isisis assignedin assignedassignedassigned b* value—from to tototo CH CHCHCH2 22and2 andandand 51.02 CH CHCHCH3 333 Materials 2021, 14, 4091 15 of 18

for the unwashed sample to 54.19 for sample after 5 washing cycles. Hue angle shows the highest values for unwashed samples and for the sample treated with 3% alum. Visual assessment of colorfastness to washing for wool fabrics was performed as well and presented in Table 18. The effect of the washing process on its color change is visible

Materials 2021, 14, x FOR PEER REVIEWwithin L* value which shows lighter shades with regard to higher mordant concentration17 of 20 (L* from 90.45 for unmordant to 91.24 for the sample treated with 5% alum) and darker shades with regard to a higher number of washing cycles (L* from 90.45 for unwashed wool without a mordant sample to 88.86 for the same sample after 5 washing cycles). DiscolorationDiscoloration ofof woolenwoolen samplessamples after the wa washingshing process is is significantly signiﬁcantly lower lower than than waswas thethe casecase withwith cottoncotton samples.samples. According to Li, Y.V. Y.V. et al. if the natural dye dye is is bonded bonded withwith mordantmordant formingforming aa stablestable dye-metaldye-metal complex then the water solubility of of the the dye dye is is lowerlower andand the the color color is is less less likely likely to to bleed bleed out out on on washing washing process process [50 ].[50]. Lightness Lightness value value was decreasingwas decreasing while while increasing increasing mordant mordant concentration concentration (L* from (L* 71.70 from for 71.70 unmordant for unmordant sample tosample 69.96 to for 69.96 the samplefor the treatedsample withtreated 5% with alum) 5% providing alum) providing darker shadesdarker shades of wool of fabrics wool whichfabrics are which in contrast are in contrast to increasing to increasing the L* value the L* when value increasing when increasing the number the ofnumber washing of cycleswashing (L* cycles from 70.91(L* from for unwashed70.91 for unwashed and with and 3% alumwith 3% pre-mordanted alum pre-mordanted sample to sample 71.56 forto the71.56 same for samplethe same after sample 5 washing after 5 cycles)washing providing cycles) providing a little bit a lighterlittle bit shades. lighter shades.

3.3.2.3.3.2. FT-IRFT-IR SpectraSpectra ofof DyeDye WoolWool FabricsFabrics FTIRFTIR spectraspectra ofof reference (unmordant, undyed and unwashed) and dyed dyed wool wool fabrics fabrics areare presentedpresented inin FigureFigure8 .8. Spectra Spectra ofof all all samples samples show show absorption absorption peaks peaks at at 3276 3276 cm cm−−11 assignedassigned toto thethe NHNH stretchingstretching vibrations,vibrations, 16311631 cmcm−−1 assignedassigned to to amide-I amide-I (C (C = = O O stretching), stretching), 15151515 cmcm−−1 assignedassigned to to amide-II (NH bending and CNCN stretching)stretching) andand 10751075 cmcm−−1 assignedassigned toto CNCN stretchingstretching andand NHG bending of of amide-III amide-III [51]. [51]. The The peak peak at at 1391 1391 cm cm−1 −is1 assignedis assigned to −1 −1 tothe the amino amino acid acid (COO-) (COO-) functional functional group. group. A peak A peak at 1233 at 1233 cm cmis assignedis assigned to CH to2 and CH2 CHand3 CHbending.3 bending. Dyed Dyed samples samples showed showed a little a little bit bitlower lower intensity intensity of of peaks peaks characteristic characteristic for for amide-Iamide-I andand amide-IIamide-II comparedcompared to untreateduntreated wool indicating the involvement of of amine amine functionalfunctional groupsgroups withinwithin the the wool, wool, alum alum and and dye dye molecules molecules [ 45[45].]. Untreated Untreated wool wool shows shows a peaka peak at at 1515 1515 cm cm−1−1(peak (peak characteristiccharacteristic forfor amide-II) which closely corresponds corresponds to to the the peak peak atat 15131513 cmcm−−1 ofof investigated investigated dye dye solution. solution. An An increase increase of of intensity intensity of of a a very very weak weak band band at at 11251125 cmcm−−1 whichwhich is is assigned assigned to to amide-II amide-II due due to to CN CN stretch stretch is is visible visible in in the the pre-mordant andand dyeddyed woolwool spectraspectra indicatingindicating the effect of alum mordant. Peak Peak visible visible in in an an untreated untreated woolwool samplesample atat 506506 cmcm−−1 isis assigned assigned to to the the S-S S-S bond. bond. In In pre-mordant pre-mordant and and dyed dyed samples samples thisthis peakpeak hasn’thasn’t beenbeen detecteddetected sincesince thethe areaarea fromfrom 500–600 500–600 cmcm−−1 showedshowed several several peaks peaks of of minorminor intensityintensity characteristiccharacteristic for sulfate absorptionabsorption and Al-O stretching vibration vibration from from alumalum mordantmordant (539(539 andand 565565 cmcm−−11) )[[48,52,53].48,52,53].

FigureFigure 8.8.FTIR FTIR spectraspectra of of wool wool fabrics, fabrics, where where W_0x W_0x is is reference reference fabric, fabric, W_1E_5%Al_0x W_1E_5%Al_0x is pre-mordantis pre- withmordant 5% alum, with dyed5% alum, and dyed unwashed and unwashed wool fabric wool and fabric W_1E_5%Al_5x and W_1E_5%Al_5x is the same is samplethe same as sample previous as previous but after 5 washing cycles. but after 5 washing cycles. 4. Conclusions The paper proved that the extracted dye from Spartium junceum L. is an acidic dye (mordant dye) that is successfully used for the treatment of protein fibers. Cellulose fibers can also be dyed with acidic dye, but optimization of conditions is required. Dyed wool samples show higher intensity in coloration than cotton samples. Wool samples that are dyed and pre-mordant with 5% alum show the lowest lightness value (L* = 69.96) and highest chroma (C* = 51.64) regarding the other dyed samples. Discoloration of wool samples after the washing process is significantly lower than was the case with cotton

Materials 2021, 14, 4091 16 of 18

4. Conclusions The paper proved that the extracted dye from Spartium junceum L. is an acidic dye (mordant dye) that is successfully used for the treatment of protein fibers. Cellulose fibers can also be dyed with acidic dye, but optimization of conditions is required. Dyed wool samples show higher intensity in coloration than cotton samples. Wool samples that are dyed and pre-mordant with 5% alum show the lowest lightness value (L* = 69.96) and highest chroma (C* = 51.64) regarding the other dyed samples. Discoloration of wool samples after the washing process is significantly lower than was the case with cotton samples. The best results were achieved with wool samples treated with 3% alum where Delta E* after 5 washing cycles was 0.87 and within the tolerance limits. A further conclusion is in the possibility to reduce the concentration of mordant to 3% to obtain satisfactory results regarding colorfastness. Otherwise, approx. 15% of mordant is added, and this significant reduction favors potentially increased negative environmental impact. This research shows wide practical application due to the aspects of circular economy, textile care and environmental friendliness. According to the zero waste model, this research is focused on the total utilization of the SJL plant. The majority of the SJL plant usage has been successfully processed in our previous research. The least used part of the SJL plant is found out to be a valuable source of raw material for natural dye production. Such dyes show better affection to protein fibers and consequently better color fastness, which enables its application for dyeing the textile materials suitable for multi-cycle washing. Positive results gained after reduction of alum mordant concentration influence usage of SJL natural dye in a more environmentally friendly manner and allow its response to the stringent requests of various EU regulations. Nonetheless, future research will go in the direction of replacing a synthetic mordant with a more environmentally friendly mordant. Furthermore, these findings lead us to the interdisciplinary approach and wider research on the usage of energy crop cultures which are investigated within the BIOCOMPOSITES project, such as Miscanthus x giganteus, Sida hermaphrodita or Arundo donax, as a valuable resource for dyes extracted from their leaves, while at the same time facilitates their eventual application in practice.

Author Contributions: Conceptualization, Z.K. and A.S.; methodology, Z.K. and A.S.; software, Z.K.; validation, Z.K., A.S.; formal analysis, Z.K.; investigation, Z.K.; resources, Z.K.; data curation, Z.K.; writing—original draft preparation, Z.K.; writing—review and editing, A.S., A.M. and S.B.; visualization, Z.K.; supervision, A.S. and S.B; project leader, S.B.; All authors have read and agreed to the published version of the manuscript. Funding: The research was funded by the European Regional Development Fund within K.K.01.1.1.04.0091 project “Design of Advanced Biocomposites from Renewable Energy Sources” (BIOCOMPOSITES). Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Data available in a publicly accessible repository. Acknowledgments: The research was performed on equipment purchased by K.K.01.1.1.02.0024 project “Modernization of Textile Science Research Centre Infrastructure” (MI-TSRC). Conﬂicts of Interest: The authors declare no conﬂict of interest.

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