Natural dye from Croton urucurana Baill. bark: Extraction, physicochemical characterization, textile dyeing and color fastness properties

Dyes and Pigments 173 (2020) 107953

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Natural dye from Croton urucurana Baill. bark: Extraction, physicochemical characterization, textile dyeing and color fastness properties Patricia Muniz dos Santos Silva a, *, Ticiane Rossi Fiaschitello a, Rayana Santiago de Queiroz b, ^nio Fernando Montemor d, Harold S. Freeman c, Silgia Aparecida da Costa a, Patricia Leo d, Anto Sirlene Maria da Costa a a

School of Arts, Sciences and Humanities, University of S~ ao Paulo, S~ ao Paulo, 03828-000, SP, Brazil Laboratory of Technical Textiles and Protection Products, Institute for Technological Research of S~ ao Paulo State, S~ ao Paulo, 05508-901, SP, Brazil College of Textiles, North Carolina State University, Raleigh, NC, USA d Laboratory of Industrial Biotechnology, Bionanomanufacturing Center, Institute for Technological Research of S~ ao Paulo State, S~ ao Paulo, 05508-901, SP, Brazil b c

A R T I C L E I N F O

A B S T R A C T

Keywords: Natural dyeing Natural extract Cotton Wool Full factorial design Wastewater analysis

Natural dyes have become an alternative option of interest for textile dyeing. The selection of native species as a natural dye can make its use feasible and enhance local biodiversity. In the present study, the extract of Croton urucurana Baill. bark, which is native to Brazil, was investigated as a natural textile dye. The extract showed a reddish-brown color and the presence of tannins. The extract was characterized by physicochemical methods and optimization of the dyeing process was determined by factorial design 23. The dyed fabrics were evaluated for color fastness to light, wash, rubbing and perspiration. They showed colors between beige and reddish-brown and had good fastness properties. Antibacterial activity assessment was performed on the extract and fabrics and UV protection was evaluated in the fabrics. The wastewater generated from the dyeing process was also characterized. It exhibited high biochemical oxygen demand and chemical oxygen demand, in addition to a large amount of dissolved iron and aluminum, when these metals were used as a mordant in the dyeing process. On balance, the extract of C. urucurana has the potential to be employed as a textile dye.

1. Introduction Environmental concerns and awareness have favored the develop­ ment of sustainable products and processes that are less impacting to the environment and human health [1]. In the context of the textile chain, many processes and products used have been questioned and reeval­ uated due to social and environmental damages associated with them, and new alternatives for production and consumption have been explored by designers and researchers [2]. Since natural dyes are generally less allergenic and toxic than synthetic dyes and generate wastewater that can be treated by biodegradation, this family of color­ ants has been increasingly contemplated as an environmentally less impactful alternative to certain synthetic dyes, especially certain azo dyes that release aromatic amines that are carcinogenic, presenting a risk of cancer to users of articles dyed with these dyes, as well as causing allergy [3,4]. Thus, they have restricted use in some countries [5]. Knowing the potential of vegetable-based substrates for natural dye

extraction is important to enabling their use and value from native species. In addition, this may be a differentiated competitive strategy for companies in the textile sector to meet niche markets in which con­ sumers are concerned about environmental aspects in textiles and be willing to pay more for products that are less harmful to the environ­ ment [2,6]. Thus, in recent years research on natural dyes has been increasing, contributing to the recovery of traditional knowledge and the dissemination of information on natural dyeing techniques, aligning traditional knowledge with scientific research. In addition, the number of companies that use these dyes for textile dyeing has increased. The search for new sources of natural dyes has included an exami­ nation of the dyeing behaviour, antifungal activity, and ultraviolet protection properties of Pterocarya fraxinifolia extracts. P. fraxinifolia was found to be suitable for dyeing wool, a source of antifungal com­ pounds, and the juglone component exhibited protection activity against solar UV rays [7]. It has also been shown that extracts of eggplant skins can be used to dye Iranian wool pre-mordanted with Fe2þ, Sn2þ, Cu2þ,

* Corresponding author. E-mail address: [email protected] (P.M.S. Silva). https://doi.org/10.1016/j.dyepig.2019.107953 Received 6 June 2019; Received in revised form 6 September 2019; Accepted 3 October 2019 Available online 5 October 2019 0143-7208/© 2019 Elsevier Ltd. All rights reserved.

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Cr6þ and Al3þ mordants. Colorimetric properties were evaluated with a reflectance spectrophotometer and wash and light fastness properties were measured using standard test methods [8]. Similarly, extracts of dried and powdered pistachio hulls were used to dye wool yarns pre-mordanted with Cu, Cr and Al salts. The Taguchi statistical method involving an L18 orthogonal array (seven factors in three levels) was employed to evaluate the effects of different parameters on the dyeing process. The colorimetric properties of the dyed yarns were evaluated in CIELAB system. A stepwise process for dyeing pre-mordanted wool yarns for carpet fibers was reported [9]. In another study, Whitfieldia lateritia leaves were extracted with 1% alkali and the extract used for dyeing cotton fabric with an alum and tannic acid mixed mordant. Results from spectroscopic and color fastness assessments suggested that Whitfieldia lateritia contained flavonoids, polyphenols and tannins, and dyed cotton fabric in the presence or absence of a mordant. However, the mordant afforded better color fastness on cotton [10]. Studies involving dyeing fibers other than cotton have been under­ taken. In this regard, bentonite-type nano clay was used as an alternative to traditional mordants in the application of natural dye madder to wool. Analysis of the resultant dyeings using methods such as FT-IR and UV–Vis spectroscopy, DSC and TG analysis, and fastness testing indi­ cated chemical changes in the polypeptide functional groups in the wool structure. Further, madder exhibited higher dye uptake on clay-pre­ treated samples compared with untreated wool and the color strength of dyeing on wool improved with an increasing clay levels in the pre­ treatment baths [11]. Extracts of dried Delphinium Zalil flowers con­ taining quercetin were used for dyeing silk yarns. It was reported that pre-mordanting increased dye uptake levels and that the resultant dye­ ings possessed good light fastness [12]. Regarding synthetic fibers, nylon 6 fabric pre-treated with Al3þ, tannic acid, and Sn2þ mordants has been dyed using extracted polyphenolic dyes from henna leaves, pomegranate rind, and Pterocarya fraxinifolia leaves. FT-IR spectral analysis was used to characterize the interaction between the mordants and the dyes. As expected, the mordants increased color strength and improved the fastness properties on nylon and it was suggested that the metal mordants can be effectively replaced with tannic acid [13]. Brazil has great potential for use of native plant species, since it has the most diverse flora in the world [14]. To consolidate the use of native plant species, it is important to combine: i) availability of raw material; ii) knowledge of traditional communities; iii) development of research and technology; iv) interactions with government and society to pro­ mote the sustainable use of these raw materials; v) the marketplace [15, 16]. Of the products of the local flora, the bark of trees possesses great social and cultural importance and economic value and are used for different purposes [17]. Barks also have potential for the extraction of natural dyes for textile dyeing. The use of this type raw material (extract) as a dye in Brazil is reported by Garcia [18], Maureau, Fonseca and Altafin [19] and Ferreira [20]. In addition, studies with the barks of certain species have already been carried out by researchers such as Bechtold, Mahmud-Ali and Mussak [21], Pisitsak et al. [22] and Pun­ rattanasin et al. [23]. Tree bark consists of all tissues surrounding and external to its vascular exchange and consists generally of polysaccharides (cellulose and hemicellulose), pectic substances, lignin, tannin, polyesters of crosslinking, low molecular mass phenolic compounds, fatty acids and resins [24]. The composition will vary with the species, the part of the tree, the geographic location, the climate and the soil conditions [24]. The main classes of extracted chromophores in the bark are phenolic compounds, such as flavonoids, stilbenes and tannins [25]. Tannins are the group most widely used as a natural dye, being traditionally extracted with water [24,25]. They consist of water soluble and high molar mass polyphenols containing an aromatic ring structure with hydroxyl sub­ stituents [26,27]. There are two main types of tannins: hydrolysable tannins (yellowish colors) and condensed tannins (reddish colors) [26, 28]. The hydrolyzable tannins can be grouped into galotannins and ellagitannins and form gallic acid and ellagic acid, respectively, when

Table 1 Geographical coordinates of the trees used in this research. Conservation unit

Trees

Juquery State Park

1 2 1 2 3 4 5

Experimental Station of Itapetininga

Geographical coordinate Latitude

Longitude

23� 20.1130 S 23� 20.1130 S 23� 40.6560 S 23� 40.6510 S 23� 40.6520 S 23� 40.6490 S 23� 40.6430 S

46� 41.4580 W 46� 41.4610 W 48� 01.0460 W 48� 01.0520 W 48� 01.0520 W 48� 01.0540 W 48� 01.0550 W

hydrolyzed [26]. The condensed tannins are oligomeric and polymeric proanthocyanidins, consisting of coupled flavan-3-ol units, such as catechin and epicatechin [24,29]. Studies show that barks containing high tannin have potential for use as natural dyes [30]. The tannins can form effective bonds with proteins because of their hydroxyl groups and play an important role in dyeing with cellulosic fibers, because it allows a better fixation of the dye [24, 27]. This is because tannins, together with metal salts, form metal tan­ nates, which in turn forms insoluble lakes with natural dyes, resulting in better color fastness [27]. Among the native trees of Brazil that are popularly used for natural dyeing is the Croton urucurana Baill. (known as “sangra d’� agua” in Brazil), of the Euphorbiaceae family [19,31]. The specie is distributed in all Brazilian states and are suitable for multiple uses [31,32]. The wood can be used for hydraulic and external works, construction of canoes, carpentry and joinery; the tree can be used in afforestation, in mixed plantations in degraded riparian areas, and as a hedge; their flowers are melliferous [31,33]. Its trunk exudes a red resin upon being wounded. Other species that produce red resin, also known as Dragon’s blood, have already been used as natural dye [34]. The C. urucurana resin has different components with antibacterial and analgesic properties [34]. The extract of its bark also has antibacterial properties [35,36]. The objective of the present work was to evaluate the Croton uru­ curana Baill. bark extract as natural textile dye. The aqueous extract obtained was characterized by physicochemical methods and optimi­ zation of dyeing conditions was investigated using a full factorial design methodology with the independent variables: temperature, time and concentration of extract. Color fastness to light, wash, rubbing and perspiration of the dyed fabrics from optimized dyeing conditions with and without mordants were analyzed. The wastewaters of dyeing were characterized by physicochemical methods. In view of previous reports indicating that C. urucurana has different components exhibiting antibacterial and analgesic properties [34–36], the extract of C. urucurana Baill bark was also examined antibacterial properties in the present study. 2. Material and methods 2.1. Bark – gathering and processing Bark samples were collected from C. urucurana specimens in con­ ~o Paulo, Brazil: Juquery State Park servation units of the State of Sa (Franco da Rocha) – Identification of the species carried out by MSc. Osny Tadeu de Aguiar; Experimental Station of Itapetininga (Itapeti­ ninga) – Identification of the species carried out by Dra. Cristina de Marco Santiago. The barks were collected from the trunk by the bark board removal method [17]. The geographical coordinates of the specimens were determined with the application GPS Status 8.0.170 – PRO for Android (Table 1). The barks were washed under running water with the aid of a brush and dried in an oven at 40 � C until constant mass. Subsequently, the barks were milled with 10 mesh granulometry. 2

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Table 2 Independent variables and their actual values used in factorial design. Independent variable

Symbol

Unit

Level

Temperature Time Concentration of extract

A B C

�

C min %

40 20 10

1

Table 3 Physicochemical properties of the C. urucurana bark extract.

0

1

69 40 55

98 60 100

pH

Total (%) solids content

5.39

1.63

Color L*

a*

b*

30,23

8,31

6,76

were prepared from the extract (1.63% solids) without dilution (100%) and at dilutions of 2 mL extract to 20 mL bath (10%) and 11 mL extract to 20 mL bath (55%). The pH of all baths was adjusted to 5 using solu­ tions of acetic acid (HOAc) and sodium hydroxide (NaOH), both at 1 M concentration. The pH of all dyebaths was adjusted to 5, because the pH of the extract is near to this value (Table 3). The exhaust dyeing process was performed on the Mathis HT ALT-I equipment. For each combina­ tion of temperature (40, 69 and 98 � C) and time (20, 40 and 60 min) the equipment was programmed to generate a dyeing curve. After dyeing, the samples were washed in running water and dried at 80 � C. The dyed samples were evaluated by a HunterLab UltraScan PRO spectrophotometer, by total reflectance, in the CIELAB space, with illuminant D65 at 10� observer angle and 400–700 nm scan. Data was analyzed using EasyMatch QC software. The coordinates of color (L*, a* and b*) and the color strength values (K/S) were determined at 400 nm.

2.2. Aqueous extraction The barks were immersed in distilled water for 24 h (weight ratio of 1:10) in a 500 mL flat-bottomed flask. The extraction was carried out on a hot plate, with the flask connected to a reflux condenser. The extrac­ tion was carried out at boiling temperature of the water for 1 h. The extract was filtered through polyester voile fabric. 2.3. Characterization of the extract The pH of the extract was measured in triplicate with a pH meter. The total solids content was measured in triplicate with a Mettler Toledo HB43-S moisture analyzer. The color in the CIELAB space was read by total reflectance using a spectrophotometer with illuminant D65 at 10� observer angle and 400–700 nm scan. A quartz transmission cell was used. Data was read by EasyMatch QC software. L* is the lightness and varies from white (100) to black (0); a* is the red-green variation, when it is positive the color varies for red, when negative, for green; b* is the yellow-blue variation, when positive the color varies from yellow, when negative, to blue.

2.4.1. Optimization of dyeing conditions A 23-statistical experimental design (three independent variables at two levels) including replication with central point was used to deter­ mine the optimized conditions for the textile dyeing with natural dye extract of C. urucurana to obtain a higher color strength (K/S). The in­ dependent variables viz., temperature (A), time (B) and concentration of extract (C), were coded at two levels as 1 and 1 and are given in Table 2. The experimental design was generated by the statistical soft­ ware Dell Statistica 13.2. Three replications were performed at the central point. A total of 11 experiments were performed in triplicate. Data analyses was performed using results obtained (response vari­ ables) for color strength (K/S) from the reflectance values determined on dyed fabrics at 400 nm. Data were treated by analysis of variance (ANOVA) and multiple regression analyses, for the development of mathematical models that represented the individual and interaction effects of the independent variables on the color strength. The prediction of the models was performed with 95% significance.

2.3.1. UV–Vis spectroscopy UV–visible spectral analysis of the extract was carried out using an Ultrospec 1100 pro spectrophotometer (Amersham Biosciences). The UV–visible spectrum was obtained in 245–455 nm wavelength range with a 1 cm quartz cuvette. The dilution used was 1 ml of extract to 100 ml of water. Deionized water as the reference was used. 2.3.2. Lyophilization procedures C. urucurana aqueous extract (50 mL) was placed in a 50 mL volume high density polyethylene bottle. The sample frozen at 80 � C was placed to a freeze dryer Thermo Modulyo D at 47 � C for 71 h.

2.4.2. Mordanting To establish the influence of the mordant on the color fastness properties a meta-mordanting procedure was used. Dyeing was per­ formed under the optimized dyeing conditions, using the extract and mordant aluminum potassium sulfate (KAl(SO4)2⋅12H2O, alum) and ferrous sulfate (FeSO4⋅7H2O) (6% owf).

2.3.3. Fourier transform infrared spectroscopy (FT-IR) Pressed pellets were prepared with the freeze-dried extract and KBr. The FT-IR spectra were recorded with a Thermo Fisher Scientific Nicolet iS10 spectrophotometer, with 32 scans in spectral range of 4000–400 cm 1 at a resolution of 4 cm 1. 2.3.4. Thermal analyses The thermal analyses were carried out in freeze-dried extract as well as in cotton and wool fabrics before and after dyeing with C. urucurana extract in optimized dyeing condition, according to item 2.4. Ther­ mogravimetric (TG) analyses were carried out on a Mettler Toledo TGA/ DSC 1 STARe System apparatus under nitrogen atmosphere (50 mL min 1), at a heating rate of 10 � C min 1 and a temperature range between 25 and 600 � C. Differential scanning calorimeter (DSC) mea­ surements were performed on a Mettler Toledo DSC822e apparatus under nitrogen atmosphere (50 mL min 1), at a heating rate of 10 � C min 1 and a temperature range between 25 and 350 � C. The TG and DSC curves were analyzed in the STARe SW 12.10 thermal analysis software.

2.5. Color fastness assessment Color fastness of dyed fabrics were evaluated for their light, wash, rubbing and perspiration fastness properties, according to standard test methods ISO 105-B02:1994 (method 1, exposure cycle A1), ISO 105C06:2010 (method A1S), ISO 105-X12:2016 and ISO 105-E04:2013, respectively. 2.6. UV protection properties UV protection of the cotton and wool fabrics before and after dyeing with C. urucurana extract was evaluated according to standard test method AATCC TM 183:2014. The UPF value for label and the UVprotection category was determined according to standard test method ASTM D 6630:2019.

2.4. Dyeing procedure Samples of 100% cotton woven fabric (203 g m 2) and 100% wool woven fabric (215 g m 2) were prepared with 1 g each. The bath ratio used in the dyeing process was 20:1. Aqueous dye baths (20 mL each) 3

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Fig. 2. Absorption spectrum of C. urucurana bark extract following a 1 to 100 dilution.

Fig. 1. Images of the C. urucurana (a) bark and (b) aqueous extract.

2.7. Antibacterial activity assessment Cotton fabrics dyed under optimal conditions with and without aluminum potassium sulfate and ferrous sulfate mordants, along with the aqueous extract and freeze-dried extract of C. urucurana, were evaluated for antibacterial activity. The untreated fabric samples and fabric samples which went through the same dyeing conditions, but only with the use of water (mock dyeing) and with the application of both mordants only were evaluated too. In this assay, freeze-dried extract (0.1 g) was suspended in 1.0 mL of deionized water and a non-toxic filter paper disc was soaked in this suspension. The assessment was conducted according to standard test method AATCC TM 90:2016. The antimi­ crobial potential of the fabrics and the extract was evaluated by the halo test against Staphylococcus aureus ATCC 6538 and Klebsiella pneumoniae ATCC 4352. 2.8. Wastewater analyses

Fig. 3. FT-IR spectra of C. urucurana extract.

The wastewaters from dyeing under optimized conditions before and after mordant treatments were evaluated. A multiparameter Aquaread AP 800 Aquameter probe was used to measure the pH, turbidity, and total dissolved solids. Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) were determined according to Standard Methods for the Examination of Water and Wastewater [37] by method n� 5210 B and method n� 5220 D, respectively. The analysis of dissolved aluminum and iron levels was carried out in an CCD simultaneous ICP-OES Varian Vista MPX spectrophotometer and performed in triplicate. Initially, the samples were calcined and dissolved in aqua regia 1:1 (7.5 mL of HCl, 3.5 mL of HNO3 and 10 mL of ultrapure water). The samples were then filtered through filter paper 40 and the filtrate diluted to 50 mL with ultrapure water. The spectrophotometer was calibrated, and the samples were read.

3.1.1. UV–Vis spectroscopy Determination of the absorption properties of the extract afforded the results shown in Fig. 2, where it can be seen that the principal ab­ sorption lies in the UV region, specifically at 275 nm. The observed absorption properties provided a basis for examining the UV-protection properties of textiles dyed with the extract. The phenolic compounds exhibit intense absorption in the UV region of the spectrum [38]. Phenols and phenolic acids show absorption bands between 250 and 290 nm while flavones and flavonols exhibit two ab­ sorption bands of approximately at about 250 and 350 nm [38]. The principal absorption of the present extract may be associated with the presence of phenolic systems. 3.1.2. Fourier transformed infrared spectroscopy (FT-IR) An FT-IR spectrum derived from the freeze-dried bark extract con­ tains characteristic bands at 1616 and 3386 cm 1 (Fig. 3). The intense and relatively broad band centered at 3386 cm 1 is probably due to –OH groups from polyphenols, such as flavonoids and tannins [39–41] and from associated (H-bonded) water molecules [42]. Similarly, the intense, sharp band at 1616 cm 1 is consistent with the presence of a substituted benzene system. Representative structures for the hydroxyl-rich flavonoids and tannin moieties are given in Fig. 4. Strong peaks in the 1620 to 1610 cm 1 suggest the presence of condensed tannins [41]. The high intensity of this peak is consistent with a high degree of polymerization [41]. According with Foo [43], bands in the region between 1540 and 1520 cm 1 are commonly attributed to the stretching of an aromatic ring. In this case,

3. Results and discussion 3.1. Physicochemical evaluations Fig. 1 shows images of the C. urucurana bark and aqueous extract used in this study. From the results presented in Table 3 it is possible to observe that the bark extract has acidic pH. Visually the extract was reddish-brown in color. Based on CIELAB values the extracts have red (cf. a*) and yellow (cf. b*) character. Since the coordinate a* and b* are closer to the achromatic point (0), the red and yellow colors are less saturated, that is, it has grayer. The value of L* is low, which indicates that the extract is dark.

4

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Fig. 4. Flavonoid (left) and tannin (right) type compounds in C. urucurana bark extract.

Fig. 5. TG curves from C. urucurana extract and cotton and wool fabrics.

gallocatechin and catechin can be differentiated, since gallocatechin has three hydroxyl groups on aromatic ring B and gives twin peaks around 1535 and 1520 cm 1, while catechin has two hydroxyl groups and gives a single peak near 1520 cm 1 [43]. In addition, the hydroxylation of ring B also produces peaks around 780 and 730 cm 1, where the out-of-plane deformations of the hydrogen atoms of the aromatic rings are absorbed, being more accentuated between 780 and 770 cm 1 for procyanidins (catechins) and in 730 cm 1 for the prodelfinidines (gallocatechins) [42]. In the spectrum it is possible to observe a peak near 1520 cm 1 (1521 cm 1) and a peak at 778 cm 1, which suggests the presence of catechin type condensed tannin in this extract. A peak was observed around 1452 and 1446 cm 1 (1448 cm 1) which corresponds to the vibration of elongation of aromatic rings [41]. Peaks around 1509 cm 1, indicate the existence of aromatic rings and C–H in the samples, which may be associated with the presence of lignin [44]. Peaks in 1300 to 800 cm 1 are related to C–O stretching and may indicate the presence of cellulose and hemicellulose [40,41]. The most informative bands for the presence of aromatic compounds are in the 900 and 675 cm 1 region and are related to deformation outside the plane of the C–H connections [40]. Peaks in this region can also be attributed to the presence of tannin in the evaluated extract [41].

Table 4 Results from TG analysis of the C. urucurana bark extract. Mass loss events

Tinitial (� C)

Tfinal (� C)

Loss of mass (%)

1� 2� 3� 4�

29.15 129.37 226.92 438.34

129.37 227.35 438.34 605.25

4.19 10.23 28.37 9.10

loss in the first event (4.19%) may be associated with desorption of water and evaporation of other volatile components. The total mass loss � ski [45], when was 51.9%. According to Wesołowski and Konieczyn samples of plants are evaluated by thermal analyzes, the observed decomposition is a physicochemical phenomenon involving various organic and inorganic compounds, and it is therefore not feasible to associate the loss of mass with the decomposition of a specific compo­ nent present in the sample. Although the author refers to the analysis of plants and not natural extracts, tree bark extracts also have different components, due to the presence of multiple components that are easily extracted with water [24,25,27]. Thus, it is possible to infer that the freeze-dried extract of C. urucurana has a complex composition and that the observed mass loss is associated with loss of mass from different components. The TG curves of the cotton and wool fabrics without and with dyeing showed mass loss events between 25 to 150 � C and 150–600 � C, which are summarized in Table 5.

3.1.3. Thermal analysis The thermogravimetric profile of the extract (Fig. 5) shows the presence of four mass loss events, which is summarized in Table 4. Mass 5

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fiber [49]. In Fig. 5, a large loss of mass of the wool samples in the range of 200–350 � C. This event may be related to thermal degradation of keratin, which occurs around 230 � C [50]. Regarding the behaviour of the dyed fabrics, it is possible to infer that the dyeing did not generate a significant change in the thermal degradation properties of the sub­ strates, because the mass loss curves of the dyed substrates presented a very similar profile to the non-dyed substrates. This indicates that the loss mass, in these cases, is mainly occurring due to the composition of the substrates. As regards to the analysis using DSC (Fig. 6), in Table 6 the

Table 5 Results from TG analysis of cotton and wool fabrics before and after dyeing. Substrate

Mass loss (%)

Cotton Dyed cotton Wool Dyed wool

25–150 � C

150–600 � C

Total

3.78 4.14 8.42 8.02

80.84 85.89 66.16 64.95

84.62 90.03 74.58 72.97

The first mass loss presented in Table 5, between 25 and 150 � C, may indicate water desorption of the fabrics, since both wool and cotton are hydrophilic [46]. It is possible to observe in Fig. 5 that in the range 320 and 370 � C there is a large loss of mass in the cotton samples, which may be related to the thermal degradation of the cellulose, which occurs around 350 � C [47,48]. At temperatures below 300 � C, cellulosic dam­ age occurs in its amorphous region, however, between 300 and 380 � C there is a significant mass loss, this being the main stage of pyrolysis of the cellulosic fibers, occurring generally in the crystalline region of the

Table 6 Results from DSC analysis of C. urucurana extract and wool fabrics. Event

Sample

Peak temperature (� C)

ΔH (J.g

Endothermic Exothermic Endothermic

Extract Extract Wool Dyed wool

54.8 299.9 80.7 66.7

151.0 704.8 197.5 307.9

1

)

Fig. 6. DSC curves from C. urucurana extract and cotton and wool fabrics. Table 7 Composition of the runs of the factorial design and experimental responses. Substrate

Run

Independent variables

Responses – Color strength (K/S) Repetition

A Cotton

Wool

1 2 3 4 5 6 7 8 9 10 11 1 2 3 4 5 6 7 8 9 10 11

1 1 1 1 0 0 0

1 1 1 1 0 0 0

B 1 1 1 1

1 1 1 1

1 1 1 1 0 0 0 1 1 1 1 0 0 0

C 1 1 1 1

1 1 1 1

1 1 1 1 0 0 0 1 1 1 1 0 0 0

1 1 1 1

1 1 1 1

I

II

III

0.18 0.83 0.20 0.82 0.39 1.56 0.48 1.84 0.70 0.72 0.76 0.72 0.91 0.60 0.98 1.35 3.55 2.00 5.24 1.25 1.25 1.22

0.19 0.77 0.20 0.88 0.40 1.56 0.47 1.79 0.70 0.71 0.71 0.70 0.88 0.61 0.97 1.36 3.54 1.81 5.26 1.17 1.21 1.25

0.19 0.79 0.18 0.83 0.38 1.50 0.46 1.90 0.76 0.71 0.74 0.66 0.94 0.62 0.96 1.40 3.56 1.86 5.47 1.22 1.20 1.23

Average

Standard deviation

0.186667 0.796667 0.193333 0.843333 0.390000 1.540000 0.470000 1.843333 0.723333

0.005774 0.030551 0.011547 0.032146 0.010000 0.034641 0.010000 0.055076 0.023979

0.693333 0.910000 0.610000 0.970000 1.370000 3.550000 1.890000 5.323333 1.222222

0.030551 0.030000 0.010000 0.010000 0.026458 0.010000 0.098489 0.127410 0.026822

Note – The mean and standard deviation values for the center point include the nine results obtained from the three runs: 9, 10 and 11. 6

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the heat flow around 300 � C, which may be related to the onset of for­ mation of an exothermic peak of heat. Peaks around 350 and 370 � C are associated with the degradation of hemicellulose, cellulose and lignin [52,53]. This result corroborates what was observed in the TG analyzes. If DSC analyzes comprised a higher temperature range, exothermic peaks could have been observed in cotton fabric analyzes. Two endothermic peaks were observed in the wool fabrics evaluated (Fig. 6). The first endothermic peak corresponds to the first mass loss evident in the TG curves. Xu et al. [54] observed an endothermic peak around 80 � C when evaluating wool fibers by DSC. This peak is close to that obtained in the analysis of the undyed wool fabric, therefore referring to the evaporation of water [54]. The undyed wool fabric had a slightly displaced peak compared to dyed wool fabric, occurring in 66.7 � C. A second event occurred around 230 � C, where a significant mass loss was observed in the TG curves. Xu et al. [54] related the peaks at 230 � C to the cleavage of cystine, ionic and hydrogen bonds and changes in the matrix and microfibrillar regions of wool fiber. In the DSC curves of the wool fabrics, it is possible to observe an overlap of endo­ thermic and exothermic events, since immediately after the endothermic peak around 230 � C, an exothermic peak begins, and its end is probable to occur after 350 � C. This overlap of events makes it difficult to deter­ mine the integration limits for the enthalpy calculation. Thus, it was not calculated for the second peak observed in the DSC curves of the wool fabrics.

Table 8 Variance analysis of dyeing of cotton and wool with C. urucurana bark extract. Substrate

Term

SS

df

MS

F-value

p-value

Cotton

A B C AB AC BC ABC Error Total A B C AB AC BC ABC Error Total

1.853704 0.071504 5.367604 0.040837 0.598504 0.026004 0.012604 0.040971 8.011733 30.03844 1.93234 14.36854 2.01260 9.51300 0.73150 0.46204 3.20094 62.25941

1 1 1 1 1 1 1 25 32 1 1 1 1 1 1 1 25 32

1.853704 0.071504 5.367604 0.040837 0.598504 0.026004 0.012604 0.001639

1131.112 43.631 3275.259 24.919 365.201 15.867 7.691

0.000000 0.000001 0.000000 0.000038 0.000000 0.000517 0.010337

30.03844 1.93234 14.36854 2.01260 9.51300 0.73150 0.46204 0.12804

234.6061 15.0919 112.2211 15.7188 74.2984 5.7132 3.6086

0.000000 0.000666 0.000000 0.000542 0.000000 0.024693 0.069077

Wool

temperature peaks and the enthalpy of the extract and of the wool fabrics are given. For the extract, a peak was observed at 54.8 � C, which may be related to the evaporation of water and volatile components of the sample. In TG analysis it was observed that the first loss of mass in both extracts occurred approximately between 30 and 120 � C and may therefore encompass this endothermic peak. The extract showed a broad DSC peak around 300 � C, which may be related to the decomposition of a wide variety of secondary metabolites, mainly phenolic [51]. As the plant extracts are composed of a mixture of substances in the plant matrix, their peaks are difficult to reproduce and their impurity level directly affects the enthalpy obtained and the width of the peak [51]. In TG analysis, the cotton fabrics gave a large mass loss between 320 and 370 � C. In the DSC curve, it was possible to observe an increase in

3.2. Optimization of dyeing conditions Table 7 show the color strength (K/S) results at the wavelength of 400 nm for cotton and wool fabrics dyed with C. urucurana bark extract. It is possible to observe that the values of color strength for both fabrics were higher when the variables were at level 1 (98 � C, 60 min and concentration of the extract was 100%). Table 8 show the ANOVA from dyed cotton and wool fabric. The p-

Fig. 7. Pareto chart showing the estimated effects of independent variables and their interactions on response factor, in (a) cotton dyeing and (b) wool dyeing. A – Temperature; B – Time; C – Concentration of extract. 7

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Fig. 8. Surface plots of (a) dyed cotton and (b) dyed wool.

value <0.05 indicated that the model terms were significant (95% confidence level). By multiple regression analysis on the experimental data, the models for the predicted responses could be expressed in the form of coded values by Eq. (1), to cotton fabric, and Eq. (2), to wool fabric. K/S ¼ 0.757 þ 0.278A þ 0.054B þ 0.473C þ 0.041AB þ 0.158AC þ 0.033BC þ 0.023ABC, with R2 ¼ 0.995 and R2 adj ¼ 0.993

However, there is a distinction between cotton and wool dyeing. For cotton dyeing, the most influential factor is the concentration of the extract, while for wool dyeing, the temperature is the most important. This shows that for the dyeing of the cotton fabric, the change in con­ centration has a more significant influence on the value of the color strength. However, the color strength of wool fabric tends to change much more with temperature variation. The time has a lower effect on the color strength than the variables temperature and concentration and the interaction between them, indicating to be the variable with less influence in the increase of the color strength of the dyed fabrics. In addition, it is possible to observe that the interaction between the three studied variables presents less influence than the isolated variables and the second order interactions in the coloristic force. In dyeing the wool fabric with both extracts the interaction between these three factors is not significant. In the surface plots (Fig. 8) it is possible to observe that with increase

(1)

K/S ¼ 1.726 þ 1.119A þ 0.284B þ þ 0.774C þ 0.289AB þ 0.629AC þ 0.174BC þ 0.139ABC, with R2 ¼ 0.948 and R2 adj ¼ 0.934 (2) It is possible to observe in the Pareto chart (Fig. 7) the variables or interactions that have greater influence on the color strength of the dyed fabrics. The temperature and concentration of the extract, as well as the interaction between these two variables, are the most significant, indi­ cating that they are the most important for the response variable. 8

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Dyes and Pigments 173 (2020) 107953

Fig. 9. Resulting colors in the wool and cotton fabrics by dyeing with the extract of C. urucurana without and with mordants. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

3.3. Dyeing under optimized conditions

Table 9 Color reading in CIELAB space for cotton and wool fabrics dyed with C. urucurana bark extract. Substrate

Mordant

L*

a*

b*

ΔE*

K/S

Cotton

– KAl(SO4)2 FeSO4 – KAl(SO4)2 FeSO4

61.69 63.31 48.46 47.02 55.78 40.79

14.22 12.27 2.64 19.64 15.69 2.05

17.90 16.28 5.56 18.40 19.29 5.91

38.71 36.01 46.06 45.28 35.73 47.88

1.62 1.41 2.54 4.80 3.49 5.31

Wool

Fig. 9 shows the resulting colors in the wool and cotton fabrics by dyeing with the extract of C. urucurana without and with mordants. The CIELAB color coordinates and color strength (K/S) of the dyed fabrics under the optimized conditions are presented in Table 9. It was possible to observe that the colors of the wool fabrics were more intense than those of the cotton fabrics. Lightness values (L*) were lower for wool fabrics than for cotton fabrics under all conditions. As for the colors, it was possible to observe that the values of the coordinates a* and b* were higher for the fabrics dyed only with the extract and with the alum mordant, indicating that these fabrics obtained more red and yellow character. The coordinates a* and b* of the iron mordant dyed cotton and wool fabrics are close to the achromatic point (0.0), showing that the colors resulting from dyeing with that mordant are less saturated, thus having a higher amount of gray. In addition, the lightness of the colors dyed with this mordant is lower than those of the dyed fabrics in other conditions, which corroborates with the literature, which in­ dicates that iron salt mordants make the colors darker [59]. As for the color difference (ΔE*) between the dyed fabrics and the undyed cotton and wool fabrics, it was possible to observe that the ironmordant dyed fabrics had the highest values. Concerning the coloristic strength (K/S), it was possible to observe that the lowest values were for cotton fabrics. The highest values of color strength were observed in the wool fabrics dyed only with the extract and with the iron mordant. In order to perform dyeing under optimized conditions with the use of mordants, the meta-mordanting was selected, once pre- and postmordanting require a separate dyeing bath, where the substrate will be treated with the mordant, thus necessitating a greater amount of water and energy. The meta-mordanting process enables natural dyeing to be performed with just one bath. By reducing the stages of dyeing, it is considered a more economical process [59]. Owing to the absence of direct affinity between most natural dyes and cotton fibers, mordants are used to help link these dyes to cellulose chains. The typical dye–fiber interactions involve coordination bonds illustrated in Fig. 10, for linking a flavonoid dye to cellulose in cotton fibers using a metal ion (e.g. Al3þ, Fe2þ). These interactions are also essential to obtaining good fastness to light and water exposures.

of the values of the variables - temperature, concentration and time there is the increase of the color strength, for all the dyeing. Thus, it is possible to determine that the best dyeing with C. urucurana bark extract in cotton and wool fabrics was at 98 � C, 60 min and 100% of extract concentration. The results obtained with the present study agree with the results of studies found in the literature on the dyeing of textile substrates with tree bark extracts [23,55,56]. Nevertheless, based on the graphs (Fig. 8) and results obtained, it is possible to verify that, for the variable time being the least significant, if it were reduced to 40 min, both for the dyeing of the cotton and wool fabric, the color strength obtained would be comparable to the color strength obtained under best dyeing conditions. Coupled with this change, the decrease in tempera­ ture for dyeing the cotton fabric to 80 � C and adjusting the concentration of the extract for the dyeing of wool to 80% would also allow the resulting color strength to be comparable to the color strength obtained under the best conditions dyeing, constituting more economical pro­ cesses. In addition, other changes could result in medium color strength values, which may be useful and economical depending on the final application of the dyed fabric. Greater color intensity was observed on dyed wool fabric compared to dyed cotton fabric. The presence of amino and carboxyl groups in wool’s molecular structure provide bonding sites for natural dye mole­ cules [57]. It is known, for instance, that 1 mol of tannin can bind to 12 mol of protein substrates [58]. This helps account for the affinity of the present tree bark extract for wool, as the bark is rich in tannin and this is extracted into water [24,25,27]. 9

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caused by the alkaline detergent solution [60]. The grades of color fastness to rubbing (Table 10) varied from 4 to 5 to 5 for the dry test and 2–3 to 4–5 for the wet test. For the wool fabric, the mordants aided in increasing color fastness. As for the cotton fabric, the grades were, in general, kept. For color fastness to perspiration (Table 11) the grades of color change varied from 2 to 3 to 4–5 for alkaline perspiration, while for acid perspiration, the grades varied from 3 to 5. As for the grades of color staining, with exception of the dyed cotton fabrics without mordant, all samples obtained grades between 4 and 5 and 5. 3.5. UV protection properties The UV protection factor (UPF) of the cotton and wool fabrics before and after dyeing with C. urucurana extract is shown in Table 12. It was observed that there was a significant increase in UPF of the fabrics after dyeing. According to ASTM D 6630:2019, the cotton and wool fabrics without dyeing cannot be classified as UV protective since they have a UPF value for label less than 15. The presence of an aryl-hydroxyl group ortho to the carbonyl group in flavonoid compounds contributes to colorfastness to light, through

Fig. 10. Representation of natural dye–mordant interactions on cotton, where Met is a metal ion.

3.4. Color fastness The grades of color change to light (Table 10) ranged from 2 to 3 (“poor to fair”) to 5 (“very good”). With the exposure to the light, the fabrics tended to become weaker and yellower. In wool dyeing, the mordants increased the color fastness. In cotton dyeing, the aluminum mordant decreased the color fastness when compared with the cotton fabric without dyeing. Color staining to the wash of the dyed fabrics (Table 10) was rating as “very good” (5) for all the fibers of the multifiber fabric, under all conditions evaluated. The color change was between 2-3 and 4–5. The use of the alum mordant increased the grades of color fastness of both fabrics. In the cotton fabric the iron mordant maintained the grades of the non-mordanted fabric, while in the wool fabric the grade was rating as “poor to fair” (2–3). Some fabrics tended to become redder after washing. In these cases, a bathochromic change in the absorption spectrum of the dye molecules may have occurred due to their ionization

Table 12 UV protection properties of the cotton and wool fabrics before and after dyeing. Substrate

Mordant

UPF value

UPF value for label

UV-protection category

Non-dyed cotton Dyed cotton

–

8.50

–

–

– KAl (SO4)2 FeSO4 –

213.0 126.6

50þ 50þ

Excellent Excellent

172.8 17.0

50þ –

Excellent –

– KAl (SO4)2 FeSO4

118.8 57.2

50þ 40–50

Excellent Excellent

151.9

50þ

Excellent

Non-dyed wool Dyed wool

Table 10 Color fastness to light, wash and rubbing. Substrate

Mordant

Light

Wash

Rubbing

Color change Cotton Wool

3–4 W 2–3 W, Y 3–4 W 2–3 W, Y 3–4 W 5W

– KAl(SO4)2 FeSO4 – KAl(SO4)2 FeSO4

4 4–5 R 4R 3–4 R 4 2–3 R

Color staining

Wet

Dry

CA

CO

PA

PES

PAC

WO

Warp

Weft

Warp

Weft

5 5 5 5 5 5

5 5 5 5 5 5

5 5 5 5 5 5

5 5 5 5 5 5

5 5 5 5 5 5

5 5 5 5 5 5

4–5 5 5 4–5 4–5 4–5

4–5 5 4–5 4–5 4–5 4–5

4 4 4 2–3 4–5 3–4

4 4 3–4 2–3 4 3–4

CA – Acetate; CO – Cotton; PA – Polyamide; PES – Polyester; PAC – Acrylic; WO – Wool; W – Weaker; Y – Yellower; R – Redder. Table 11 Color fastness to perspiration. Substrate

Mordant

Alkaline Color change

Cotton Wool

– KAl(SO4)2 FeSO4 – KAl(SO4)2 FeSO4

3 3–4 2–3 4–5 4–5 4

Acid Color staining

Color change

CA

CO

PA

PES

PAC

WO

4 4–5 5 4–5 5 5

3–4 4–5 4–5 4–5 4–5 4–5

3–4 4–5 5 4–5 4–5 5

3–4 4–5 5 5 5 5

3–4 4–5 5 4–5 5 5

4 4–5 5 4–5 5 5

CA – Acetate; CO – Cotton; PA – Polyamide; PES – Polyester; PAC – Acrylic; WO – Wool. 10

4–5 3–4 3 5 4–5 3–4

Color staining CA

CO

PA

PES

PAC

WO

4–5 4–5 5 4–5 5 5

3–4 4 4–5 4–5 4–5 4–5

3–4 4–5 4–5 4–5 4–5 5

4 4–5 5 4–5 5 5

4 4–5 4–5 5 5 5

4 4–5 4–5 4–5 5 5

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Despite the present results obtained, previous studies have shown that the C. urucurana bark extract has antibacterial activity. Peres et al. [35] showed the antibacterial activity of the C. urucurana bark extract obtained with water and ethanol against the bacteria Staphylococcus aureus and Salmonella typhimurium. In the study by Oliveira et al. [36], latex and bark extracts obtained with hexane, dichloromethane, ethyl acetate, 75% ethanol and chloroform were evaluated for antibacterial activity. The bacterial strains evaluated were: Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pyogenes, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmo­ nella typhimurium e Shigella flexneri. Latex showed activity toward all bacteria except E. coli, for which it was inactive. All bark extracts showed antibacterial activity against S. aureus. Only chloroform and ethyl acetate extracts showed activity toward the bacterium K. pneumoniae. Simionatto et al. [62] examined the antimicrobial ac­ tivity of the essential oils from stem bark C. urucurana obtained by hydrodistillation for 4 h using a modified Clevenger-type apparatus, followed by exhaustive extraction of the distillate with hexane. The results reveal that the crude essential oil of C. urucurana bark inhibited the growth of all microorganisms and that S. epidermidis and E. coli (MIC ¼ 1.25 mg mL 1) were the most sensitive, while B. subtilis and C. albicans were the most resistant microorganisms (MIC ¼ 10 mg mL 1). Furthermore, the microbial growth inhibition increases to 70–90% when alum and copper sulfate are used for mordanting in textile dye [63]. However, the antimicrobial activity is completely lost when ferrous sulfate is used [63]. In this study, no antibacterial activity was observed in fabric even with the use of alum mordant.

Fig. 11. UV light induced IPT, as exhibited in the flavonoid Morin.

intramolecular proton transfer (IPT) in the excited state – a nondestructive mechanism for dissipating the energy of absorbed UV light. This process is illustrated in Fig. 11. As previous reported, flavo­ noids typically absorb UV light in the 280–315 nm region to afford UV-B protection [12]. Bearing in mind that the flavonoid (morin) in the pre­ sent study is isomeric with quercetin in the previous study, probably for this reason the C. urucurana extract offers UV protection on the cotton and wool fabrics. In addition, dyeing fabrics in dark colors improve their UV protection properties [61]. As can be seen from Fig. 9, the colors resulting from the dyeing of cotton and wool with the C. urucurana bark extract were deeper colors, which may have helped to considerably increase the protection factor of these fabrics. 3.6. Antibacterial activity assessment Results from this assessment indicated the absence of antibacterial properties before and after dyeing cotton, as illustrated in Fig. 12 (against S. aureus) and in Fig. 13 (against K. pneumoniae), and in the aqueous extract and freeze-dried extract, as illustrated in Fig. 14.

3.7. Wastewater analysis From the data obtained by the wastewater analysis (Table 13), it can be observed that, according to the criteria determined by the Brazilian

Fig. 12. Assessment of antibacterial properties against Staphylococcus aureus during the various stages of dyeing cotton using C. urucurana without and with mordants. 11

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Dyes and Pigments 173 (2020) 107953

Fig. 13. Assessment of antibacterial properties against Klebsiella pneumoniae during the various stages of dyeing cotton using C. urucurana without and with mordants.

Regarding the quantity of wastewater solids, CONAMA defines that the quantity of sedimentable materials in 1 h test in Imhoff cone should be determined, being the limit of 1 mL L 1 [64]. However, it was possible to observe, from the total dissolved solids (TDS) test, that the amount of TDS in the wastewaters is high, mainly due to its high organic load, arising from different components present in the extract and possibly from residues of textile fibers. The parameters for turbidity in wastewater, according to CONAMA [65], will depend on the body of water in which the wastewater will be released. For freshwater bodies, depending on the class, the turbidity should be up to 40 or 100 NTU [65]. It is possible to verify that the turbidity of the analyzed wastewater was well above this value. In some cases, the turbidity was above the capacity of the equipment (4000 NTU) or the equipment could not register. The high turbidity value of these wastewaters is related to the high presence of suspended solids in them, mainly organic compounds. According to Sperling [66], BOD of textile wastewater can vary from 200 to 5000 mg L 1, depending on the textile process evaluated. For textile dye wastewater, Sperling [66] indicates that the BOD concen­ tration varies from 2000 to 5000 mg L 1. According to Table 12, it is possible to observe that the BOD of the wastewater ranged from 221 to 4055 mg L 1, being close to the value found in the literature. In addition, it was possible to observe that the BOD of the evaluated wastewater exceeded the limits determined by CONAMA, which establishes the limit of 120 mg L 1 [64]. According to Ammayappan and Jose [67] the ratio of the BOD to COD concentration in the natural dye wastewater is approximately 1:2. This shows that these wastewater are highly biodegradable and treat­ able in treatment plants [67]. This relationship was observed for all evaluated wastewaters, indicating that they can be treated by biological processes so that they could be released into receiving bodies. As for dissolved metals, Brazilian legislation determines the

Fig. 14. Assessment of antibacterial properties against Staphylococcus aureus and Klebsiella pneumoniae in the aqueous extract and freeze-dried extract; (1) negative control, (2) positive control.

National Environment Council (CONAMA) for the pH of wastewater to be released into receptor bodies, only wastewater containing iron sulfate did not reach the allowed limit, which should be between 5 and 9 [64]. 12

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Table 13 Characteristics of the wastewater from dyeing cotton and wool substrates with C. urucurana bark extract. Substrate

Mordant

pH

Turbidity (NTU)

TDS (mg L

Cotton

– KAl(SO4)2⋅12H2O FeSO4⋅7H2O – KAl(SO4)2⋅12H2O FeSO4⋅7H2O

5.92 5.72 4.49 6.36 6.05 4.86

3580 þ n 2673 þ n

1086 1996 1660 1153 2020 1557

Wool

1

)

BOD (mg L 4055.0 221.0 293.0 212.0 2340.0 266.0

1

)

COD (mg L 1)

Iron (mg L 1)

Aluminum (mg L 1)

7128.2 408.0 511.2 390.0 3963.6 482.7

– – 409 – – 495

– 126 – – 118 –

NTU – Nephelometric Turbidity Units; TSD – Total Dissolved Solids; BOD – Biochemical Oxygen Demand; COD – Chemical Oxygen Demand; “n” – The equipment could not register the value; “þ” – The equipment extrapolated the capacity of 4000 UNT.

maximum quantity of 0.1 or 0.2 mg L 1 for aluminum, depending on the class of freshwater body where the wastewater will be released [65]. For iron, the maximum quantity is 15.0 mg L 1 for discharge of wastewater [64]. The values obtained from the analyzed samples are well above the values determined by the legislation, which indicates the need to treat these wastewaters for these metals. For future studies, it is important to evaluate the wastewater generated in the pre- and post-mordanting processes, which may lead to a most efficient method for the mordants to bond with the fibers, reducing their amount in the wastewater.

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4. Conclusions The C. urucurana bark extract was found to be a potential natural dye source for textile dyeing. From the analysis of the extract, the presence of tannins, lignin, cellulose and hemicellulose were observed. The 23statistical experimental design was effective to obtain an optimized dyeing method. The R2 values of 0.995 (cotton) and 0.948 (wool) indicated a good fit of the models with experimental data. The optimum dyeing process of the evaluated cotton and wool fabrics involved a temperature of 98 � C, a time of 60 min and the 100% of the extract, and the method did not affect the fabrics thermal degradation properties. Colors were obtained from beige to reddish brown on dyed fabrics, and in general, good color fastness ratings were obtained. Dyeing signifi­ cantly increased the protection factor of dyed fabrics. However, the C. urucurana extract and dyed fabrics did not show antibacterial activity. Further, wastewater analysis indicated that dyebaths would benefit from treatment for suspended organic materials and dissolved metals before being released into receptor bodies. Declaration of competing interest We have no conflicts of interest to disclose. Acknowledgements The authors acknowledge the Institute for Technological Research of S~ ao Paulo State (IPT), the Foundation to Support Institute for Techno­ logical Research of S~ ao Paulo State (FIPT) and Coordination for the Improvement of Higher Education Personnel (CAPES), for the financial support of this research. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.dyepig.2019.107953. References [1] Haws KL, Winterich KP, Naylor RW. Seeing the world through GREEN-tinted glasses: green consumption values and responses to environmentally friendly products. J Consum Psychol 2014;24:336–54. https://doi.org/10.1016/j. jcps.2013.11.002. [2] Niinim€ aki K, Hassi L. Emerging design strategies in sustainable production and consumption of textiles and clothing. J Clean Prod 2011;19:1876–83. https://doi. org/10.1016/j.jclepro.2011.04.020.

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