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Synthesis of azo and anthraquinone dyes and dyeing of nylon-6,6 in supercritical carbon dioxide
Journal of CO₂ Utilization 38 (2020) 49–58
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Synthesis of azo and anthraquinone dyes and dyeing of nylon-6,6 in supercritical carbon dioxide
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Raju Penthalaa, Gisu Heoa, Hyorim Kima, In Yeol Leeb, Eun Hee Kob, Young-A Sona,* a b
Department of Advanced Organic Materials Engineering, Chungnam National University, 220 Gung-dong, Yuseong-gu, Daejeon, 305-764, South Korea Korea High Tech Textile Research Institute, Yangju, 11410, South Korea
ARTICLE INFO
ABSTRACT
Keywords: Azo dyes Anthraquinone dyes Dyeing Supercritical carbon dioxide Nylon 6,6 fabric
In this work, thiazole based azo dyes (6A and 6B) and anthraquinone dye derivatives (6C, 6D and 6E) were synthesized from commercially inexpensive starting materials.The advantage of the synthesis of these dyes are quite facile and scale-up is feasible, which favors for an industrial dyeing applications. All the dyes were characterized by spectroscopic techniques such as IR, NMR (1H and 13C), HRMS and UV–vis spectroscopy. Preliminary dyeing experiments were carried out with these dye stuffs on nylon 6,6 fabrics to examine the possibility of scaling up supercritical carbon dioxide dyeing to a factory level. All the five dyes (6A-6E) showed good color strength and especially two dyes 6A and 6C exhibited excellent dye fixation. Remarkable results obtained for washing fastness (fading and staining grade of 4–5) and sweat fastness (fading and staining grade of 4–5) for all the dyes (6A-6E). Based on the results, the synthesized dyes could be hopefully applied in near future for the dyeing of nylon 6,6 fabrics on an industrial scale under the ecofriendly and energy-efficient supercritical carbon dioxide medium.
1. Introduction In the traditional dyeing method, water is used for performing dyeing and washing experiments. In order to increase the solubility of the disperse dyes in water media, numerous dispersing agents and surfactants have been used in traditional dyeing method [1–3]. Generally, these experiments produce a large quantity of waste water which is associated with colored compounds and concentrated electrolytes [4]. However, this type of dyeing process is a burden in terms of environmental and economic aspects [5–7]. To reduce the unpredictable damages, industries are looking for new technologies to solve the respective problems by innovative concepts [8,9]. Supercritical fluid dyeing technology is attractive because supercritical fluid is used as a solvent medium instead of water [10–15]. The fluid has unique properties under supercritical conditions. Most of the substances have been identified as supercritical fluids. However, carbon dioxide has been extensively used in the dyeing technology due to its advantageous properties such as nonflammability, nontoxicity, low cost, and ease of use (Tc of 31.1 °C, Pc of 7.38 MPa) [16]. In addition, the viscosity [10−5−10-4 Pa s] and diffusion coefficient [10-8−10-7 m2 s] values are similar to water, which makes it a suitable dyeing medium for dyeing technology [17]. Nylon is in the synthetic textile category. It shows a high tensile ⁎
strength, elasticity and resistance towards chemicals and mechanical stresses [18]. In the textile industry, these fabrics are useful for a considerable amount of applications. Nylon molecules have amino end groups; even though it possesses some nonpolar nature, and nylon is slightly polar when compared to PET. Hence, for the dyeing of nylon 6, 6 fibers, some disperse dyes are also used [19]. However, there have been several studies reported on the dyeing of nylon under supercritical carbon dioxide. Disperse dyes and some hydrophobic reactive dyes were shown to be suitable for the dyeing of nylon under supercritical conditions [20–26].The disperse dyes were physically bound due to their nonpolar nature whereas the reactive dyes were covalently bound with the nucleophilic centers of nylon. Azo and anthraquinone dyes are the most important classes of organic dyes. These classes of dyes are mainly the source for the developments of blue disperse dyes in textile industry. Further these dye derivatives are also used in other various fields like pharmaceutical, food, paper, painting and coating industries [27–29]. In supercritical carbon dioxide dyeing technology, the solubility of dyes is one of the most important parameters for the dye selection. Due to the hydrophobic nature of carbon dioxide, the solubility of dye molecules was increased with less polar substituents and decreased for more polar substituents. Although, several studies have been made on the solubilities of azo and anthraquinone dyes in supercritical carbon dioxide
Corresponding author. E-mail address: [email protected] (Y.-A. Son).
https://doi.org/10.1016/j.jcou.2020.01.013 Received 2 July 2019; Received in revised form 9 January 2020; Accepted 10 January 2020 2212-9820/ © 2020 Published by Elsevier Ltd.
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Scheme 1. Synthesis of azo dye 6A.
(99.6 vol %) was used in this study for the dyeing of nylon fabrics. 1H NMR and 13C NMR spectra were recorded with an AVANCE III spectrometer by using CDCl3 as the solvent and the system was operated at 600 MHz (1H NMR) and 150 MHz (13C NMR). The chemical shift (δ) values were represented in ppm and were downfield from an internal standard, TMS. By using an Agilent 8453 spectrophotometer, the UV–vis absorption spectra were recorded for all the dyes. The reflectance spectra of the dyed fabrics were taken from Shimadzu UV 26,000 spectrophotometer. The MS data were obtained from an AB Sciex 4000 QTRAP, and HRMS were taken from a Bruker micrOTOF-Q spectrometer. The IR spectra were obtained from an ALPHA-P spectrometer. With the help of Electrothermal-IA9100/OA melting point detector, the melting points were taken by visually in a capillary tube method. The thermal analysis of the fabrics was conducted on a PerkinElmer DSC 6000 instrument. The HPLC purity of dyes was taken from Ultimate-3000 ISQ EC high performance liquid chromatography. The conditions in HPLC for mobile phase composition are 0.1 % formic acid in acetonitrile (0.0 %), with a flow rate of 0.3 mL/min. The purity was given by calculating percentage of peak area in relation to the total area of peaks under interests or in relation to the main peak (small impurities determined).1H NMR, 13C NMR, HRMS, FTIR and HPLC spectra were given in supporting information (Fig. S1–S25).
[30–32]. The solubility data of these dyes used as basic important information for the designing of high performance new dyes for the dyeing of nylon fibers in supercritical carbon dioxide. In earlier, our group synthesized various dyes and applied dyeing on polyester and polypropylene fabricsunder aqueous medium [33–35]. Further, in recent we synthesized some extreme hydrophobic anthraquinone disperse dyes and are applied dyeing on PET fabrics under supercritical conditions (Part-I). The results indicated that two favorable characteristics of excellent dye fixation and commercially acceptable fastness data [36]. In accordance with these results, tocontinuation of our work (Part-II) herein, we design some little hydrophobic bright blue disperse dyes developed from thiazole based azo dyes (6A and 6B)and anthraquinonedye derivatives (6C, 6D and 6E).Further, these dyes are applied for the dyeing of nylon 6,6 fabric using the ecofriendly supercritical fluid dyeing technology. Moreover, we also investigated the dye fixation efficiency, color strength, and fastness properties on nylon 6,6 fabrics. 2. Experimental 2.1. Chemicals and materials We purchased aniline, 2-ethylaniline, 3-ethylaniline, 1-bromopropane, 1-bromobutane, 1-heptylamine, and tert-butyl (4-aminobutyl) carbamate from TCI (Tokyo Chemical Industry Co., LTD.) and 2-amino5-nitrothiazole, quinizarin, 4-toluenesulfonyl chloride, and 1,8-dihydroxy-4,5-dinitroanthracene-9,10-dione, sodium nitrite, sodium acetate, sulfuric acid, acetic acid, propionic acid, potassium hydroxide, pyridine, from Alfa Aesar. All these chemicals and reagents are supplied from chemical industries with more than 98 % purity and directly used for the study. Dichloromethane, dimethyl sulphoxide, ethanol, 2methoxyethanol, ethylacetate, diethyl ether and hexane solvents. All of these solvents were HPLC grade, and are purchased from Samchun Pure Chemical Co., Ltd. Thin-layer chromatography (TLC) was performed by using silica gel G60 F254 (Merck) plates. Monitoring of product formation by visualization on TLC with UV light (254 and 366 nm) or with an iodine vapor. Silica gel (70–230 mesh, Fluka) was used for column chromatography. A 100 % scouring, unfinished nylon-6,6 fabric of plain cloth was supplied by Archroma Korea Ltd. Pure carbon dioxide gas
2.2. Synthesis Herein, two azo (6A and 6B) and three anthraquinone dyes (6C, 6D and 6E) were synthesized from previously reported methods with slight modifications [36–38]. In the azo dyes (6A and 6B) synthesis, first two N-protected anilines 3A and 3B were synthesized from compounds 1 and 1A by reacting with 1-bromopropane and 1-bromobutane under basic condition respectively. For the preparation of diazonium salt on 5nitrothiazol-2-amine, the diazotitation reaction was carried out by using sodium nitrite and concentrated sulfuric acid. Due to the weak basicity of 5-nitrothiazol-2-amine, concentrated sulfuric acid was used for the preparation of stable diazonium salt. Further, this diazonium salt subsequently undergoes a coupling reaction with the components 3A and 3B to produce target compounds 6A and 6B, respectively (Schemes 1 and 2). The aqueous 10 % NaOAc solution was used to maintain reaction pH ∼4–5 and also completion of coupling reaction.
Scheme 2. Synthesis of azo dye 6B. 50
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Scheme 3. Synthesis of anthraquinone dye 6C.
the mixture was allowed to cool to room temperature and 10 ml of cold water was added. Then extracted with ethyl acetate (2 × 30 mL). The organic layers were combined and dried with Na2SO4, filtered, the resulting filtrate was concentrated in vacuo. The column chromatography (elution with 3–5 % of ethyl acetate-hexane) rendered pure products 3A and 3B.
For the synthesis of anthraquinone dye 6C, first tosylation reaction was performed on 1,4-dihydroxyanthracene-9,10-dione 7 under basic condition to afford compound 9. Further, this compound 9 was reacted with n-heptylamine under mild reaction conditions to give compound 10 as a red solid. The reaction of this intermediate 10 with tert-butyl (4aminobutyl) carbamate (11) in pyridine under reflux condition to afforded compound 6C as a dark blue solid (Scheme 3). A nucleophilic substitution reaction between 1,8-dihydroxy-4,5-dinitroanthracene-9,10-dione (12) and 2-ethyl aniline or 3-ethyl aniline in 2-methoxyethanol at 120 °C to yielded compounds 6D and 6E respectively (Scheme 4). Here the reactivity of aryl amines was increased with their nucleophilicity due to presence of ethyl groups. The synthesis of azo and anthraquinone dyes utilizes simple and an efficient coupling reaction (6A, 6B), and nucleophilic substitution reactions (6C, 6D and 6E) through the use of readily available and commercially inexpensive starting materials and reagents. These reactions were carried out under relatively mild conditions. Moreover, all the dyes were obtained in a pure form with good yields. The obtained dyes can be used for the dyeing without further column purifications (energy saving), which makes potentially suitable for industrial scale synthesis.
2.3.1. Characterization of N,N-dipropylaniline (3A) Color less liquid; Yield: 89 % (1.57 g); 1H NMR (CDCl3, 600 MHz): δ 7.14 – 7.01 (2H, m, Ar–H), 6.58 – 6.52 (3H, m, Ar–H), 3.15 (4H, t, J = 7.5 Hz, 2 x N–CH2), 1.57 – 1.49 (4H, m, 2 x –CH2–), 0.84 (6H, t, J = 7.5 Hz, 2 x –CH3). ESI-MS: 178 [M+H]+. 2.3.2. Characterization of N,N-dibutyl-3-ethylaniline (3B) Color less liquid; Yield: 81 % (1.88 g); 1H NMR (CDCl3, 600 MHz): δ 7.18 (1H, d, J =8.8 Hz, Ar–H), 6.44 – 6.41 (2H, m, Ar–H), 6.29 –6.25 (1H, dd, J = 8.8, 3.0 Hz, Ar–H), 3.15 (4H, t, J = 7.7, 7.5 Hz, 2 x N–CH2), 2.60 (2H, q, J = 7.5 Hz, Ar–CH2–), 1.50 – 1.43 (4H, m, 2 x –CH2–), 1.31 – 1.23 (4H, m, 2 x –CH2–), 1.14 (3H, t, J = 7.5 Hz, –CH3), 0.87 (6H, t, J = 7.5 Hz, 2 x –CH3). ESI-MS: 234 [M+H]+. 2.4. General experimental procedure for the synthesis of compounds 6A and 6B
2.3. General experimental procedure for the synthesis of compounds 3A and 3B
H2SO4 (5 mL) was placed in a round bottom flask and kept at 0 °C. To this, dry NaNO2 (0.95 g, 13.783 mmol) was slowly added. Then, the mixture temperature was slowly raised to 60−65 °C to generate nitrosylsulfuric acid and stirred for 1 h and cooled to 5 °C. In another round bottom flask, an AcOH:propionic acid mixture (1:1, 20 mL) was placed and kept at 0-5. To this,5-nitrothiazol-2-amine (2 g, 13.783 mmol) was added portion-wise and stirred for 15 min. At 0−5 °C temperature, the nitrosylsulfuric acid was gradually added to the above mixture. The diazotization salt formation was confirmed by TLC (Thin layer chromatography). This diazonium salt solution was used immediately in the next coupling reaction. In a round bottom flask (100 mL), the coupling components 3A and 3B (13.783 mmol) were dissolved in AcOH: H2O (2:1, 15 mL) together with 5 g of sodium acetate (NaOAc) and kept at 5 °C. To this mixture, the diazonium solution was slowly added at 5 °C over 30 min. The reaction mixture pH was maintained ∼4–5 by addition of 10 % aqueous sodium acetate solution. The reaction was stirred at 5 °C for 1 h and at room temperature for 1 h. The resulting precipitates were filtered off and washed with cold and hot water until the elimination of acid.
To a solution of aniline or substituted aniline (10.0 mmol) in DMSO (10 mL), potassium hydroxide (20.0 mmol) and alkyl bromides (30.0 mmol) were added at room temperature. Further the reaction mixture was stirred at 50 °C for 5 h. After completion of the reaction,
Scheme 4. Synthesis of anthraquinone dyes 6D and 6E. 51
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Recrystallized from DMF provided the pure dyes 6A and 6B.
4.47 (1H, brs, H–N–C = O), 3.40 – 3.30 (4H, m, 2 x N–CH2),3.18 – 3.10 (2H, m, N–CH2), 1.76 – 1.67 (4H, m, –CH2–),1.65 – 1.58 (2H, m, –CH2–), 1.44 – 1.35 (11H, m, –CH2–, 3 x –CH3), 1.33 – 1.22 (4H, m,2 x –CH2–), 0.83 (3H, t, J = 7.1 Hz, –CH3); 13C NMR (CDCl3, 600 MHz): δ 182.3 (ArC=O), 182.1 (ArC=O), 155.9 (HN–C=O), 146.2 (ArC–N), 146.0 (ArC–N), 134.5, 134.4, 131.9, 131.8, 125.9, 123.6, 123.4, 109.7, 109.6 (ArC), 42.9 (N–CH2), 42.4 (N–CH2), 40.1 (N–CH2), 31.7 (–CH2–), 29.6 (–CH2–), 29.0 (–CH2–), 28.3 (–CH2–), 27.7 (–CH2–), 27.1 (–CH2–), 26.8 (–CH2–), 22.6 (3 x –CH3), 14.0 (–CH3). HRMS: 507.3085 [M]+. Calculated for C30H41N3O4: 507.3097.Purity: 90 %.
2.4.1. Characterization of4-((5-nitrothiazol-2-yl)diazenyl)-N,N-dipropylaniline (6A) Dark blue solid; Yield: 73 % (3.35 g); mp: 148–150 °C; IR (KBr) (νmax/cm–1): 2960 (=C–H), 2930 (–C–H), 1596 (C = C), 1504 (N = O), 1474 (N = N), 1334 (N–O), 1231 (C–N); 1H NMR (CDCl3, 600 MHz): δ 8.51 (1H, s, HAr–H), 7.90 – 7.80 (2H, m, Ar–H), 6.66 (1H, d, J = 9.5 Hz, Ar–H), 3.36 (4H, t, J = 7.8 Hz, 2 x N–CH2), 1.69 – 1.61 (4H, m, 2 x –CH2–), 0.93 (6H, t, J = 7.5 Hz, 2 x –CH3); 13C NMR (CDCl3, 600 MHz): δ 180.7 (HAr–C), 153.2 (HAr–C), 145.5 (ArC–N), 142.8, 141.6, 111.2 (Ar–C), 52.3 (N–CH2), 19.7 (–CH2–), 10.3 (–CH3). HRMS: 334.1354 [M+H]+. Calculated for C15H20N5O2S: 334.1338. Purity: 98%.
2.7. General experimental procedure for the synthesis of compounds 6D and 6E 1,8-Dihydroxy-4,5-dinitroanthracene-9,10-dione (12) (0.2 g, 0.605 mmol) was placed in 2-methoxy ethanol (10 mL) and 2-ethyl aniline/3-ethyl aniline (1.211 mmol) was added at ambient temperature. The reaction was further refluxed at 125 °C for 6 h. Then the liquor was cooled to room temperature and ethanol was added (5 mL) and kept to stand for 3 h. The formed blue precipitates were filtered and washed with water. The recrystallization was performed in ethanol provided 6D and 6E as pure dyes.
2.4.2. Characterization ofN,N-dibutyl-3-ethyl-4-((5-nitrothiazol-2-yl) diazenyl)aniline (6B) Green solid; Yield: 71 % (3.81 g); mp: 217–219 °C; IR (KBr) (νmax/ cm–1): 2956 (=C-H), 2867 (-C-H), 1599 (C = C), 1504 (N = O), 1475 (N = N), 1349 (N–O), 1244 (C-N); 1H NMR (CDCl3, 600 MHz): δ 8.57 (1H, s, HAr–H), 8.03 (1H, d, J = 9.4 Hz, Ar–H), 6.59 (1H, dd, J = 9.5, 2.8 Hz, Ar–H), 6.54 (1H, d, J = 2.8 Hz, Ar–H), 3.45 (4H, t, J = 7.7 Hz, 2 x N–CH2), 3.04 (2H, q, J = 7.5 Hz, Ar–CH2–), 170 – 1.64 (4H, m, 2 x –CH2–), 1.46 – 1.39 (4H, m, 2 x –CH2–), 1.32 (3H, t, J = 7.7 Hz, –CH3), 1.00 (6H, t, J = 7.7 Hz, 2 x –CH3); 13C NMR (CDCl3, 600 MHz): δ 182.9 (HAr–C), 154.8 (HAr–C), 152.8 (HAr–C–N), 144.1 (ArC–N), 140.5, 121.0, 111.6, 111.2 (Ar–C), 51.3 (N–CH2), 29.7 (Ar–CH2), 25.7 (–CH2–), 20.2 (–CH2–), 16.7 (–CH3), 13.8 (–CH3). HRMS: 390.1983 [M +H]+. Calculated for C19H28N5O2S: 390.1964. Purity: 96 %.
2.7.1. Characterization of 1-((2-ethylphenyl)amino)-4,5-dihydroxy-8nitroanthracene-9,10-dione (6D) Blue solid; Yield: 88 % (0.215 g), mp: 204–206 °C; IR (KBr) (νmax/ cm–1): 2914 (=C-H), 2861 (-C-H), 1583 (C = C), 1540 (N = O), 1359 (N–O), 1251 (C-N), 1165 (C-O); 1H NMR (CDCl3, 600 MHz): δ 12.80 (1H, brs, ArO–H), 12.76 (1H, brs, ArO–H), 11.57 (1H, brs, ArN–H), 7.56 (1H, d, J = 9.0 Hz, Ar–H),7.28 (1H, dd, J = 7.5, 2.4 Hz, Ar–H), 7.23 – 7.17 (4H, m, Ar–H), 7.11 (1H, dd, J = 6.7, 2.0 Hz, Ar–H), 7.09 (1H, d, J = 9.5 Hz, Ar–H),2.55 (2H, q, J = 7.5 Hz, Ar–CH2–), 1.10 (3H, t, J = 7.5 Hz, –CH3); 13C NMR (CDCl3, 600 MHz): δ 189.4 (ArC=O), 177.8 (ArC=O), 163.4 (ArC–OH), 158.7 (ArC–OH), 147.0 (ArC–NO2), 142.1 (ArC–NH), 140.3 (ArC–NH), 135.8, 130.5, 129.7, 129.2, 128.0, 127.4, 126.9, 126.7, 122.3, 115.7, 112.1, 108.2 (ArC), 24.6 (Ar–CH2–), 14.4 (–CH3). HRMS: 405.1034 [M+H]+. Calculated for C27H17N2O6: 405.1087. Purity: 98 %.
2.5. Experimental procedure and characterization of4-(heptylamino)-9,10dioxo-9,10-dihydroanthracen-1-yl 4-methylbenzenesulfonate (10) 9,10-Dioxo-9,10-dihydroanthracene-1,4-diyl bis(4-methylbenzenesulfonate) (9) (2.7 g, 4.922 mmol) in DCM (30 mL),and heptan-1-amine (7.383 mmol) was added at ambient temperature, and stirred for 24 h. TLC indicated consumption of starting material. The reaction crude was directly absorbed with silica and performed column chromatography (elution with13 % ethyl acetate-hexane) rendered a pure red solid (10). Yield: 51 % (1.25 g), mp: 116–118 °C; IR (KBr) (νmax/cm–1): 3463 (NH), 2926 (=C-H), 2854 (-C-H), 1704 (C = O), 1570 (C = C), 1156 (CN); 1H NMR (CDCl3, 600 MHz): δ 9.89 (1H,t, J = 4.5 Hz, N–H), 8.10 (1H, d, J = 7.7 Hz, Ar–H), 7.90 (1H, d, J = 7.7 Hz, Ar–H),7.74 (2H, d, J = 8.2 Hz, Ar–H), 7.65 – 7.61 (1H, m, Ar–H), 7.60 – 7.56 (1H, m, Ar–H), 7.27 (1H, d, J = 9.4 Hz, Ar–H), 7.17 (2H, d, J = 8.2 Hz, Ar–H), 6.92 (1H, d, J = 9.4 Hz, Ar–H), 3.24 (2H, q, J = 6.9 Hz, N–CH2), 2.26 (3H, s, Ar–CH3), 1.69 (2H, qt, J = 7.5 Hz, –CH2–), 1.41 (2H, qt, J = 7.5 Hz, –CH2–), 1.35 – 1.21 (6H, m, –CH2–), 0.83 (3H, t, J = 7.1 Hz, –CH3); ESI-MS: 492 [M+H]+.
2.7.2. Characterization of 1-((3-ethylphenyl)amino)-4,5-dihydroxy-8nitroanthracene-9,10-dione (6E) Blue solid; Yield: 87 % (0.212 g), mp: 219–221 °C; IR (KBr) (νmax/ cm–1): 2919 (=C-H), 2859 (-C-H), 1581 (C = C), 1536 (N = O), 1359 (N–O), 1251 (C-N), 1165 (C-O); 1H NMR (CDCl3, 600 MHz): δ 12.83 (1H, brs, ArO–H),12.74 (1H, brs, ArO–H), 11.68 (1H, brs, ArN–H), 7.56 – 7.52 (2H, m, Ar–H), 7.25 (1H, t, J = 8.0 Hz, Ar–H), 7.21 (1H, d, J = 8.8 Hz, Ar–H), 7.12 (1H, d, J = 9.5 Hz, Ar–H), 7.04 – 7.01 (1H, m, Ar–H), 7.00 – 6.97 (2H, m, Ar–H), 2.60 (2H, q, J = 7.5 Hz, Ar–CH2–), 1.18 (3H, t, J = 7.5 Hz, –CH3); 13C NMR (CDCl3, 600 MHz): δ 189.4 (ArC=O), 177.7 (ArC=O), 163.3 (ArC–OH), 159.0 (ArC–OH), 146.2 (ArC–NO2), 142.1 (ArC–NH), 130.5, 129.5, 129.1, 128.2, 126.7, 125.8, 124.3, 122.4, 121.9, 115.6, 112.2, 108.6 (ArC),28.7(Ar–CH2–), 15.4 (–CH3). HRMS: 405.1032 [M+H]+.Calculated for C27H17N2O6: 405.1087.Purity: 93 %.
2.6. Experimental procedure and characterization of tert-butyl (4-((4(heptylamino)-9,10-dioxo-9,10-dihydroanthracen-1-yl)amino)butyl) carbamate (6C) Compound 10 (1.2 g, 2.443 mmol) was placed in pyridine (20 mL), and tert-butyl (4-aminobutyl)carbamate 11 (2.683 mmol) was added at ambient temperature. Further the mixture stirred at reflux temperature for 16 h. The reaction was monitored by TLC, showed full consumption of starting material (red spot). Then pyridine was evaporated under reduced pressure. The resulting residue was triturated with diethyl ether and hexane (2:1, 12 mL) to afford pure compound 6C. Blue solid; Yield: 53 % (0.615 g), mp: 121–123 °C; IR (KBr) (νmax/cm–1): 3482 (NH), 3350 (N-H), 2928 (=C-H), 2852 (-C-H), 1705 (C = O), 1672 (C = O), 1573 (C = C), 1251 (C-O), 1156 (C-N); 1H NMR (CDCl3, 600 MHz): δ 10.76 – 10.74 (2H, brs, ArN–H), 8.29 – 8.24 (2H, m, Ar–H), 7.63 – 7.59 (2H, m, Ar–H), 7.18 – 7.16 (2H, m, Ar–H), 4.56 –
2.8. Supercritical dyeing procedure Fig. 1 shows the components of the dyeing instrument for supercritical fluid dyeing. It mainly consistsCO2 cylinder, cooling bath, CO2 pressure pump, circulation system, dyeing vessel, temperature control unit, separator and recycling unit. In the dyeing process, first nylon 6,6 fabrics (approximately 5 × 10 cm, 10 g) were wrapped around a rotating warp beam and placed inside the dyeing vessels. In order to remove residual air in the dyeing vessel, gaseous CO2was injected for approximately 2 min. The purified azo and anthraquinone fine dye powders were placed into the stirring unit of the dye stuff vessel. The 52
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Fig. 1. Schematic representation of the lab scale supercritical carbon dioxide dyeing plant.
used concentration of dyes here is 2 %, 3 % and 5 % with respect to the nylon 6,6 fabric weight. The operator was then sealed before starting the dyeing. The carbon dioxide gas was passed from the cylinder to the dyeing system via heat exchanger, cooling bath (−10 to +5 °C) and pressure pump. In the dye stuff vessel, the dyes were pre dissolved by the supercritical carbon dioxide fluid. After 20 min, the dyeing vessel was occupied by the fluid. Then the carbon dioxide circulation system was opened. In the dyeing process, the nylon fabric and supercritical fluid ratio approximately used in this study is 1: 50. After reaching the desired temperature (120 °C) and pressure (25 MPa), the dyeing process started and continued for 1 h. During the dyeing process constant temperature was maintained by temperature control unit. After 1 h, the temperature was slowly reduced to 30 °C. The dye stuff and supercritical carbon dioxide were separated in the separator unit. Further, carbon dioxide gas was purified by passing through a purifier containing molecular sieves and stored in a gas container. After recycling the sufficient amount of carbon dioxide, the pressure was reduced to atmospheric level. Then dyed nylon 6,6 fabrics were retrieved from the dyeing vessel for further analysis. 2.9. Traditional dyeing The traditional dyeing experiment of nylon 6,6 fabrics were performed by using ACE-6000 T model infrared laboratory-scale dyeing machine. First, the nylon 6,6 fabrics (1 g) were treated with 5 g/dm3 carrier, 4 % ammonium sulfate by maintaining the pH 5.5 at 60 °C for 20 min at a liquor ratio of 1:20. Herein, various concentrations of synthesized dyes (6A-6E) 2 %, 3 % and 5 % owf were used in our study. The dyes were dissolved in the solution of (2 g/dm3) an anionic dispersing agent. The dyes being precipitated in fine dispersion and it was added to the dye bath and the temperature was raised at a rate of 2 °C min−1 until a temperature of 120 °C was reached in 45 min. Further the dyeing was continued for 1 h at this temperature. After that, the dyed samples were cooled to room temperature and the fabrics were separated and washed with 2 % of nonionic detergent at 60 °C for 20 min. Then the fabrics were rinsed in water and dried.
Fig. 2. (a) Effect of dye concentration in supercritical condition; (b) Effect of dye concentration in aqueous condition.
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3. Results and discussion 3.1. Effect of dye concentration Herein, the effect of dye concentration on the color strength (K/S) of nylon 6,6 fabric were studied and the corresponding results are given in Fig. 2. The dyeing experiments were performed by using different concentration of dye 2 %, 3 % and 5 % owf (on weight of fabric) for 1 h. According to Kubelka − Munk equation (equation 1), the K/S values are calculated and are well linear with respect to the dye concentration on the dye substrate [4]. The dyed fabrics were immersed in hot acetone solution and extracted the adsorbed dye and measured the concentration of dye solution at a maximum wavelength. By increasing the concentration of all dyes azo (6A, 6B) and anthraquinone (6C, 6D and 6E), the color strength of nylon 6,6 fabric is increased in supercritical as well as in traditional dyeing conditions; From experimental results (Fig. 2a and b), indicate that the azo dyes exhibited more color strength values than the anthraquinone dyes. Since the azo dyes (6A and 6B) are having hydrophobic N,N-propyl and N,N-butyl aniline groups whereas anthraquinone dyes are having little hydrophilic carbamate (6C), hydroxyl, and ethyl aniline groups (6D and 6E). Therefore, azo dyes can be dissolved more easily compared to anthraquinone dyes, which mean that color strength may also be increased for the azo dyes. In super critical carbon dioxide conditions, the increment in the color strength for the azo dyes 6A and 6B is larger from 2 % to 3 % and is smaller from 3 % to 5 %. This is attributed to the azo dyes having strong saturation at low concentrations. The diffusion speed of dye particles may gradually slow down therefore, the absorption of dye by nylon 6,6 fabric is limited and the interaction between the dye and fabric cause color strength values to increase a smaller (from 3 % to 5 %) [23]. The overall results indicate that the color strength was considerably increased in supercritical carbon dioxide conditions when compared to the traditional dyeing. This is attributed to the fact that, the synthesized dyes exhibited good solubility and diffusion under supercritical carbon dioxide dyeing than the traditional dyeing. Moreover, it has been suggested that the supercritical carbon dioxide dyeing system has significant advantages than traditional aqueous dyeing [39]. 3.2. Thermal analysis The thermal analysis results were obtained from the DSC instrument, and the corresponding results are illustrated in Fig.3. From the figure, a little change was observed in the amorphous region (30−90 °C) of the dyed nylon 6,6 fabrics after being treated with high temperature (120 °C). In contrast, we did not observe any changes in the crystal region (250−270 °C) of the dyed fabrics. This is suggested to that there was no damage to the nylon 6,6 fabric under the supercritical carbon dioxide dyeing medium. The heat factor only influenced the fiber properties. Fig. 4 shows the digital photographs of the dyed nylon 6,6 fabric with azo (6A and 6B) and anthraquinone (6C, 6D and 6E) dyes in supercritical CO2.
Fig. 3. Thermal analysis diagram of nylon 6,6 fabrics: (a) undyed nylon fabric; (b) Dyed nylon fabric with compound 6A at 120 °C; (c) Dyed nylon fabric with compound 6C at 120 °C.
extraction), and (K/S)dyed (after dyeing) in equation (2). To measure the (K/S)extracted, the dyed nylon 6,6 fabrics were soaked in acetone solvent at ambient temperature and slowly the temperature was raised to 80 °C for 1 h to yield the dye extracts [40]. After that, the dye extract was set aside and allowed to stand for 10 min to cool to ambient temperature and filtered. The extracted fabrics were separated and dried. The reflectance of these fabrics was measured and substituted in equation (1) and (K/S)extracted was calculated. From Fig.5, the order of the (K/S)dyed values for the synthesized dyes are6A > 6B > 6E > 6D > 6C. The (K/S)dyed values of the azo dyes, are significantly superior than those of anthraquinone dyes. Meanwhile, the dye 6A displayed a higher (K/S)extracted value (19.07), whereas for the dye 6B,the (K/S)extracted value is 13.46. Anthraquinone dyes 6C, 6D and 6E exhibited (K/S)extracted values of5.94, 6.14 and 6.71 respectively. The dye fixation percentage (%F) values of the dyed nylon
3.3. Color strength and dye fixation Table 3 indicated that the color strength (K/S) values of the dyed nylon6,6 fabrics. The experiment was carried out at a temperature of 120 °C and pressure of 25 MPa with 2 % owf dye for 1 h. The K/S values of the dyed nylon 6,6 fabricswere calculated,by using the Kubelka − Munk equation (equation 1), at a maximum absorption wavenumber (λmax). In this equation, K is the absorbance, S is the scattering coefficient, and Rmin is the minimum value of the reflectance curve, which is obtained from a Shimadzu UV-26,000 spectrophotometer by measuring the dyed nylon 6,6 fiber in a reflectance mode, a is constant and q is adsorbed dye on the fabric (mol g−1). Dye fixation (%F) percentage was calculated by substituting color strengths of (K/S)extracted (after 54
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Table 1 Color of dyed nylon 6,6 fabrics. Dye
L*
a*
b*
C*
h
K/S
6A 6B 6C 6D 6E
24.22 24.58 48.67 43.59 42.48
8.40 9.49 0.05 −7.93 −10.35
−27.99 −30.14 −43.66 −24.75 −21.48
29.22 31.60 43.66 25.99 23.84
286.71 287.48 270.07 252.24 244.27
21.43 17.95 6.83 7.31 7.90
3.4. Color assessment The color assessment of the dyed nylon 6,6 fabrics in supercritical carbon dioxide was conducted using a Datacolor 110 spectrometer. Table 1 indicates the CIELAB coordinates which are represented in terms of L*(lightness), chroma (C*), h (hue angle from 0° to 360°), and color-opponent dimensions (a* and b*). A negative value of a* shows the degree of greenness and a positive value of a* shows the degree of redness; similarly, a negative value of b* shows the degree of blueness and a positive value of b* shows the degree of yellowness. Based on the following statements, the synthesized dyes exhibited good levelness, brightness and depth on the nylon 6,6 fabric under optimized conditions. For the dyes 6A-6E, the color lightness value (L*) varied from 24.22–48.67. Dye 6C is lighter than the other compounds. According to the negative values of a*, the color hues for dyes 6D and 6E are shifted to the greenish direction on the red-green axis, whereas for dyes 6A, 6B and 6C, they are shifted to the reddish direction on the red-green axis. According to the negative values of b*, the color hues for all the dyes are shifted to the bluish direction on the yellow-blue axis in our investigations on nylon 6,6 fabric. Based on the color brightness (C*) values, dye 6C is brighter (43.66) and dye 6E is duller (23.84) than the other dyes. The color strength K/S values for the synthesized dyes ranged from 21.43 to 6.83. From Table 1, the azo dyes have higher color strength values than the anthraquinone dyes. Among them, compound 6A exhibits a superior color strength value (K/S 21.43) than the other dyes.
Fig. 4. Digital photographs of dyed nylon 6,6 fabrics with azo (6A, 6B) and anthraquinone (6C, 6D, and 6E) dyes in supercritical CO2.
Fig. 5. (K/S)dyed, and (K/S)extracted, values of dyed nylon 6,6fabrics.
6,6 fabrics ranked in the following order: 6A > 6C > 6E > 6D > 6B. The compound 6A had a low molecular weight and exhibited high solubility. In general, the lower molecular weight dyes having greater solubility in supercritical carbon dioxide. The transport rate of this dye towards the fiber is also very high. Hence, the 6A dye adsorption rate is greater and displayed higher K/S value as well as high dye fixation value. The dyes 6C, 6D and 6E have hydrogen bonding sites (NH−CO and –NH (6C), –NH and −OH (6D and 6E)), which may participate in strong hydrogen bonding interaction with the NHeCO group of the nylon 6,6 fabric. Therefore, these dyes exhibited good dye fixation values. Finally, for the dye 6B, the weak vander Waal forces may be responsible for the adsorption. Hence, it has a lower dye fixation value when compared to the other dyes. In addition to that, the nylon 6,6 fabrics are porous and can have sufficient access of dye molecules by allowing diffusion into these pores. Hence, dye adsorption takes place and good color strength and dye fixation values are exhibited. Our results revealed that the thiazole based azo and anthraquinone dye derivatives are convenient for the dyeing of nylon 6,6 fabrics in a supercritical carbon dioxide medium. The synthesized azo dyes (6A, and 6B) developed froman aminothiazole containing nitro group are given bright blue shades with good color strength values (K/S ∼17-21; 2 % o.w.f.) when compared to the azo dyes derived from carbocyclic analogues (simple aromatic rings like benzene and naphthalene, K/S ∼7-14; 4 % o.w.f) [24]. Since the nitro thiazole ring prized bathochromism and high tinctorial strength relative to their carbocyclic analogues. Moreover, the dye fixation values are also greater for 6A and 6B than the carbocyclic azo dyes [19].
3.5. Color fastness 3.5.1. Wash fastness The wash fastness data issummarized in Table 2. The KS K ISO 105 C06:2014 method was used for the wash fastness test. In this method, the dyed nylon 6,6 fabric (specimen) was washed together with multifiber white fabrics of acetate, cotton, nylon, polyester, acryl and wool. Here, first 4 × 10 cm of the test specimen was stitched with the same size of white multi fabrics. This sample was washed with 0.4 % of detergent at 40 °C for 30 min by using a rotawash. After washing, the samples were rinsed in hot water followed by squeezing with cold water and further dried in air. Then, stitching was removed, and assessed the color change of the specimen and the staining of color on the adjacent Table 2 Fastness properties of dyed nylon 6,6 fabrics with dyes 6A-6E. Wash fastnessa
Dye
6A 6B 6C 6D 6E a b
55
Fading color
Acetate
Cotton
Nylon
Polyester
Acryl
Wool
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
Light fastnessb
2-3 2-3 4-5 3-4 3-4
Rating for wash fastness: > 3 (acceptable); < 2 (not acceptable). Rating for light fastness: > 4 (acceptable); < 2 (not acceptable).
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fabrics by using the international grayscale. All the compounds (6A-E) showed excellent washing fastness ratings for both fading and staining with a grade of 4–5. In our study, these results were probably due to the good dye diffusion and penetration in to the nylon 6,6 fabric.
acetate and nylon was of grade 2–3 in both acid and alkaline media. Most likely, it is due to the high affinity of the hydrolyzed dye 6A and 6B molecules towards acetate and nylon fibers in acid and alkaline conditions during the wash process [43]. It is clear that the synthesized azo and anthraquinone dyes in this work displayed excellent characteristics and coloration activities. In addition, these dyes have commercially satisfactory properties and color fastness results on nylon 6,6 fabric under supercritical carbon dioxide media. Hence, these types of dyes could potentially be applied for coloration in nylon 6,6based textile industries.
3.5.2. Light fastness Light fastness results are given in Table 2. The KS K ISO 105 – B02:2015 xenon arc method was used for the light fastness test. In this experiment, we exposed dyed nylon 6,6 fabrics to light for ∼20 h, and the changes in color was compared with the unexposed sample. By using blue scales, we measured the color changes. From the data, compound 6Cexhibited an excellent grade (4–5), whereas the compounds 6D and 6E (3–4 grade) exhibited good light fastness and other azo compounds 6A and 6B (2–3 grade) showed moderate light fastness. Based on the results, the azo dyes exhibited weak light fastness when compared to the anthraquinone dyes. The light fastness of theseazo dyes is very poor than the light fastness of azo (∼4–5) dyes, having acetamido, amino and hydroxyl groups on phenyl ring and ortho to the azo linkage (intramolecular hydrogen bond between these groups and azo group) [41]. Since our dyes having simple alkyl chains and are not involved in hydrogen bonding. In addition, the synthesized anthraquinone dyes (6C, 6D and 6E) exhibited good light fastness whereas the natural occurring anthraquinone dyes exhibited poor light fastness (∼3) properties [42].
3.6. Color characteristics Azo and anthraquinone dyes are soluble in dichloromethane, acetone, tetrahydrofuran and methanol solvents. Azo dyes form a purple colored solution in dichloromethane and a deep blue colored solution in acetone, tetrahydrofuran and methanol, whereas the anthraquinone dyes are form a deep blue colored solution in all these solvents. To assess the λmax, the synthesized dyes were subjected to spectrophotometric analysis in acetone solvent withinthe range of 400−800 nm. The dyes 6A, 6B, 6D and 6E have single absorption maxima at 583 nm, 599 nm, 606 nm, and 605 nm respectively. The peak wavelength of absorption spectra of 6B is slightly greater than 6A. It is speculated that an electron-donor substituent (-ethyl) on the chromophore caused a bathochromic shift of dye 6B. Due to the structural similarity of 6D and 6E (positional isomers), the absorption spectra almost similar. Moreover, the dye 6C exhibits double absorption maxima
3.5.3. Sweat fastness The results of fastness to perspiration are summarized in Table 3. The KS K ISO 105 – E04:2015 method was used for the determination of sweat fastness. In this experiment, we conducted the evaluation of perspiration resistance of the dyed nylon fabric (test specimen) together with multi-fiber white fabrics of acetate, cotton, nylon, polyester, acryl and wool. The test samples were sewn with multi-fiber fabrics and were dipped into acid or base solutions separately for 30 min, at ambient temperature. After that these samples were removed from acid and base solutions and were placed between two plates by maintaining of ∼ 4.5 kg force. These plates were kept in oven at ∼37 °C for 4 h. The test specimen was detached from multi-fiber white fabrics. The color changes were measured by using the international gray scale for the dyed nylon 6,6 fabrics and staining of undyed fabrics. Table 3 demonstrates that azo (6A and 6B) and anthraquinone (6C, 6D and 6E) dyes have outstanding sweat fastness results towards acid and alkaline media. For all dyes (6A-6E), the fading fastness results reached a grade of 4–5. However, the staining results reached a grade of 4–5 for the anthraquinone dyes (6C-6E). Moreover, azo dye 6B also reached a grade of 4–5 for all adjacent fabrics except acetate and nylon (3–4), whereas the azo dye 6A staining fastness adjacent to acryl and wool was of grade 4, adjacent to PET and cotton was of grade 3–4, and adjacent to Table 3 Sweat fastness data of nylon 6,6 fabrics with dyes 6A-6E. Sweat fastnessa
6A
6B
6C
6D
6E
Acidic
4-5 2-3 3-4 2-3 3-4 4 4 4-5 2-3 3-4 2-3 3-4 4 4
4-5 3-4 4-5 3-4 4 4-5 4 4-5 3-4 4 3-4 4 4-5 4
4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5
Alkaline
a
Fading Acetate Cotton Nylon PET Acryl Wool Fading Acetate Cotton Nylon PET Acryl Wool
Fig. 6. a) UV–vis spectra of 6A and 6B, b) UV–vis spectra of 6C, 6D and 6E in acetone (1 × 10−4 M).
Rating for sweat fastness: 3–5 (acceptable); 1–2 (not acceptable). 56
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at 591 nm and 638 nm (Fig. 6). These bands are typically attributed to amine to quinone intramolecular charge–transfer transitions. The reflectance spectra of dyed nylon 6,6 fabrics were also recorded adopting white standard BaSO4. For dyes 6A, 6B, 6C, 6D and 6E, the reflectance curve minimum value was centered ∼ 583 nm, 599 nm, 651 nm, 620 nm and 616 nm respectively (Fig. S26. Supporting information).
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[34] R. Penthala, R.S. Kumar, H. Kim, G. Heo, Y.A. Son, Synthesis, generic dyeing of nindigo derivatives on unmodified polypropylene; First time application in dyeing technology, J. Nanosci. Nanotechnol. 19 (2019) 7105–7111. [35] R. Penthala, R.S. Kumar, G. Heo, H. Kim, I.Y. Lee, E.H. Ko, Y.A. Son, Synthesis and efficient dyeing of anthraquinone derivatives on polyester fabric with supercritical carbon dioxide, Dyes Pigm. 166 (2019) 330–339. [36] H.R. Maradiya, V.S. Patel, Thiazole based disperse dyes for nylon and polyester fibers, Fiber Polym.2 (2001) 153–158. [37] A.T. Peters, Y.C. Chao, Substituent effects on the colour, dyeing and fastness properties of 4-arylamino-5-nitro-(and amino)-1,8-dihydroxyanthraquinone and 4arylamino-8-nitro-(and amino)-1,5-dihydroxyanthraquinone disperse dyes, J. S. D. C. 104 (1988) 435–441. [38] A. Hou, B. Chen, J. Dai, K. 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4. Conclusion In conclusion, we synthesized azo (6A and 6B) and anthraquinone (6C, 6D and 6E) dye derivatives from inexpensive starting materials by using simple methods. The primary dyeing experiments were performed on nylon 6,6 fabric with these dyes to confirm the possibility of scaling up supercritical carbon dioxide dyeing to the factory level. All the dyes (6A-6E) exhibited good color strength values, and the dye fixation order was 6A > 6C > 6E > 6D > 6B. Further, we discussed the effect of dye concentration, on the color strength values (K/S). Especially for the azo dyes 6A and 6B, a dye concentration of 2 % (owf) gave higher K/S values in supercritical carbon dioxide when compared to 5 % (owf) of dye concentration in aqueous dyeing. The thermal analysis results indicated that the supercritical carbon dioxide did not damage the nylon 6,6 fabric. All the dyes (6A-6E) exhibited excellent results in washing fastness (fading and staining grade of 4–5) and sweat fastness (fading and staining grade of 4–5) and exhibited good to moderate results for light fastness (6C (4–5), 6D, 6E (3–4) and 6A, 6B (2–3)). The obtained results suggest that it would be valuable to develop new reactive disperse dyes containing these backbones (azo and anthraquinone), which could potentially be applied on cotton fabrics under a supercritical carbon dioxide dyeing medium. The corresponding work will be publishing in the future. CRediT authorship contribution statement Raju Penthala: Conceptualization, Investigation, Writing - original draft. Gisu Heo: Investigation, Visualization. Hyorim Kim: Investigation, Visualization. In Yeol Lee: Investigation. Eun Hee Ko: Investigation. Young-A Son: Writing - review & editing, Supervision. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments This work was supported by the nurture project of waterless color industry (10078334) funded by the Ministry of Trade, Industry and Energy (MOTIE) of Korea. References [1] Z.T. Liu, L.L. Zhang, Z.W. Liu, Z.W. Gao, W.S. Dong, H.P. Xiong, Y.D. Peng, S.W. Tang, Supercritical CO2 dyeing of ramie fiber with disperse dye, Ind. Eng. Chem. Res. 45 (2006) 8932–8938. [2] N.A. Ibrahim, N.M.A. Moneim, E.S.A. Halim, M.M. Hosni, Pollution prevention of cotton-cone reactive dyeing, J. Clean. Prod. 16 (2008) 1321–1326. [3] B. Thomas, T. Aurora, Electrochemical reduction in vat dyeing: greener chemistry replaces traditional processes, J. Clean. Prod. 17 (2009) 1669–1679. [4] A.S. Özcan, A. Özcan, Adsorption behavior of a disperse dye on polyester in supercritical carbon dioxide, J. Supercrit. Fluids 35 (2005) 133–139. [5] E. Rosalesm, M.A. Sanromán, M. Pazos, Application of central composite facecentered design and response surface methodology for the optimization of electroFenton decolorization of Azure B dye, Environ. Sci. Pollut. Res. 19 (2012) 1738–1746. [6] K. Enayatzamir, H.A. Alikhani, B. Yakhchali, F. Tabandeh, S. Rodríguez-Couto, Decolouration of azo dyes by phanerochaete chrysosporium immobilised into alginate beads, Environ. Sci. Pollut. Res. 17 (2010) 145–153. [7] P.B.S. Ratna, Pollution due to synthetic dyes toxicity & carcinogenicity studies and remediation, Int. J. Environ. Sci. 3 (2013) 940–955.
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occurringanthraquinone dyes on nylon, Color. Technol. 120 (2004) 205–212. [42] Z. Yan-Qin, W. Xiao-Chen, L. Jia-Jie, Ecofriendly synthesis and application of special disperse reactive dyes in waterless coloration of wool with supercritical carbon dioxide, J. Clean, Prod. 133 (2016) 746–756.
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Synthesis of azo and anthraquinone dyes and dyeing of nylon-6,6 in supercritical carbon dioxide
T
Raju Penthalaa, Gisu Heoa, Hyorim Kima, In Yeol Leeb, Eun Hee Kob, Young-A Sona,* a b
Department of Advanced Organic Materials Engineering, Chungnam National University, 220 Gung-dong, Yuseong-gu, Daejeon, 305-764, South Korea Korea High Tech Textile Research Institute, Yangju, 11410, South Korea
ARTICLE INFO
ABSTRACT
Keywords: Azo dyes Anthraquinone dyes Dyeing Supercritical carbon dioxide Nylon 6,6 fabric
In this work, thiazole based azo dyes (6A and 6B) and anthraquinone dye derivatives (6C, 6D and 6E) were synthesized from commercially inexpensive starting materials.The advantage of the synthesis of these dyes are quite facile and scale-up is feasible, which favors for an industrial dyeing applications. All the dyes were characterized by spectroscopic techniques such as IR, NMR (1H and 13C), HRMS and UV–vis spectroscopy. Preliminary dyeing experiments were carried out with these dye stuffs on nylon 6,6 fabrics to examine the possibility of scaling up supercritical carbon dioxide dyeing to a factory level. All the five dyes (6A-6E) showed good color strength and especially two dyes 6A and 6C exhibited excellent dye fixation. Remarkable results obtained for washing fastness (fading and staining grade of 4–5) and sweat fastness (fading and staining grade of 4–5) for all the dyes (6A-6E). Based on the results, the synthesized dyes could be hopefully applied in near future for the dyeing of nylon 6,6 fabrics on an industrial scale under the ecofriendly and energy-efficient supercritical carbon dioxide medium.
1. Introduction In the traditional dyeing method, water is used for performing dyeing and washing experiments. In order to increase the solubility of the disperse dyes in water media, numerous dispersing agents and surfactants have been used in traditional dyeing method [1–3]. Generally, these experiments produce a large quantity of waste water which is associated with colored compounds and concentrated electrolytes [4]. However, this type of dyeing process is a burden in terms of environmental and economic aspects [5–7]. To reduce the unpredictable damages, industries are looking for new technologies to solve the respective problems by innovative concepts [8,9]. Supercritical fluid dyeing technology is attractive because supercritical fluid is used as a solvent medium instead of water [10–15]. The fluid has unique properties under supercritical conditions. Most of the substances have been identified as supercritical fluids. However, carbon dioxide has been extensively used in the dyeing technology due to its advantageous properties such as nonflammability, nontoxicity, low cost, and ease of use (Tc of 31.1 °C, Pc of 7.38 MPa) [16]. In addition, the viscosity [10−5−10-4 Pa s] and diffusion coefficient [10-8−10-7 m2 s] values are similar to water, which makes it a suitable dyeing medium for dyeing technology [17]. Nylon is in the synthetic textile category. It shows a high tensile ⁎
strength, elasticity and resistance towards chemicals and mechanical stresses [18]. In the textile industry, these fabrics are useful for a considerable amount of applications. Nylon molecules have amino end groups; even though it possesses some nonpolar nature, and nylon is slightly polar when compared to PET. Hence, for the dyeing of nylon 6, 6 fibers, some disperse dyes are also used [19]. However, there have been several studies reported on the dyeing of nylon under supercritical carbon dioxide. Disperse dyes and some hydrophobic reactive dyes were shown to be suitable for the dyeing of nylon under supercritical conditions [20–26].The disperse dyes were physically bound due to their nonpolar nature whereas the reactive dyes were covalently bound with the nucleophilic centers of nylon. Azo and anthraquinone dyes are the most important classes of organic dyes. These classes of dyes are mainly the source for the developments of blue disperse dyes in textile industry. Further these dye derivatives are also used in other various fields like pharmaceutical, food, paper, painting and coating industries [27–29]. In supercritical carbon dioxide dyeing technology, the solubility of dyes is one of the most important parameters for the dye selection. Due to the hydrophobic nature of carbon dioxide, the solubility of dye molecules was increased with less polar substituents and decreased for more polar substituents. Although, several studies have been made on the solubilities of azo and anthraquinone dyes in supercritical carbon dioxide
Corresponding author. E-mail address: [email protected] (Y.-A. Son).
https://doi.org/10.1016/j.jcou.2020.01.013 Received 2 July 2019; Received in revised form 9 January 2020; Accepted 10 January 2020 2212-9820/ © 2020 Published by Elsevier Ltd.
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Scheme 1. Synthesis of azo dye 6A.
(99.6 vol %) was used in this study for the dyeing of nylon fabrics. 1H NMR and 13C NMR spectra were recorded with an AVANCE III spectrometer by using CDCl3 as the solvent and the system was operated at 600 MHz (1H NMR) and 150 MHz (13C NMR). The chemical shift (δ) values were represented in ppm and were downfield from an internal standard, TMS. By using an Agilent 8453 spectrophotometer, the UV–vis absorption spectra were recorded for all the dyes. The reflectance spectra of the dyed fabrics were taken from Shimadzu UV 26,000 spectrophotometer. The MS data were obtained from an AB Sciex 4000 QTRAP, and HRMS were taken from a Bruker micrOTOF-Q spectrometer. The IR spectra were obtained from an ALPHA-P spectrometer. With the help of Electrothermal-IA9100/OA melting point detector, the melting points were taken by visually in a capillary tube method. The thermal analysis of the fabrics was conducted on a PerkinElmer DSC 6000 instrument. The HPLC purity of dyes was taken from Ultimate-3000 ISQ EC high performance liquid chromatography. The conditions in HPLC for mobile phase composition are 0.1 % formic acid in acetonitrile (0.0 %), with a flow rate of 0.3 mL/min. The purity was given by calculating percentage of peak area in relation to the total area of peaks under interests or in relation to the main peak (small impurities determined).1H NMR, 13C NMR, HRMS, FTIR and HPLC spectra were given in supporting information (Fig. S1–S25).
[30–32]. The solubility data of these dyes used as basic important information for the designing of high performance new dyes for the dyeing of nylon fibers in supercritical carbon dioxide. In earlier, our group synthesized various dyes and applied dyeing on polyester and polypropylene fabricsunder aqueous medium [33–35]. Further, in recent we synthesized some extreme hydrophobic anthraquinone disperse dyes and are applied dyeing on PET fabrics under supercritical conditions (Part-I). The results indicated that two favorable characteristics of excellent dye fixation and commercially acceptable fastness data [36]. In accordance with these results, tocontinuation of our work (Part-II) herein, we design some little hydrophobic bright blue disperse dyes developed from thiazole based azo dyes (6A and 6B)and anthraquinonedye derivatives (6C, 6D and 6E).Further, these dyes are applied for the dyeing of nylon 6,6 fabric using the ecofriendly supercritical fluid dyeing technology. Moreover, we also investigated the dye fixation efficiency, color strength, and fastness properties on nylon 6,6 fabrics. 2. Experimental 2.1. Chemicals and materials We purchased aniline, 2-ethylaniline, 3-ethylaniline, 1-bromopropane, 1-bromobutane, 1-heptylamine, and tert-butyl (4-aminobutyl) carbamate from TCI (Tokyo Chemical Industry Co., LTD.) and 2-amino5-nitrothiazole, quinizarin, 4-toluenesulfonyl chloride, and 1,8-dihydroxy-4,5-dinitroanthracene-9,10-dione, sodium nitrite, sodium acetate, sulfuric acid, acetic acid, propionic acid, potassium hydroxide, pyridine, from Alfa Aesar. All these chemicals and reagents are supplied from chemical industries with more than 98 % purity and directly used for the study. Dichloromethane, dimethyl sulphoxide, ethanol, 2methoxyethanol, ethylacetate, diethyl ether and hexane solvents. All of these solvents were HPLC grade, and are purchased from Samchun Pure Chemical Co., Ltd. Thin-layer chromatography (TLC) was performed by using silica gel G60 F254 (Merck) plates. Monitoring of product formation by visualization on TLC with UV light (254 and 366 nm) or with an iodine vapor. Silica gel (70–230 mesh, Fluka) was used for column chromatography. A 100 % scouring, unfinished nylon-6,6 fabric of plain cloth was supplied by Archroma Korea Ltd. Pure carbon dioxide gas
2.2. Synthesis Herein, two azo (6A and 6B) and three anthraquinone dyes (6C, 6D and 6E) were synthesized from previously reported methods with slight modifications [36–38]. In the azo dyes (6A and 6B) synthesis, first two N-protected anilines 3A and 3B were synthesized from compounds 1 and 1A by reacting with 1-bromopropane and 1-bromobutane under basic condition respectively. For the preparation of diazonium salt on 5nitrothiazol-2-amine, the diazotitation reaction was carried out by using sodium nitrite and concentrated sulfuric acid. Due to the weak basicity of 5-nitrothiazol-2-amine, concentrated sulfuric acid was used for the preparation of stable diazonium salt. Further, this diazonium salt subsequently undergoes a coupling reaction with the components 3A and 3B to produce target compounds 6A and 6B, respectively (Schemes 1 and 2). The aqueous 10 % NaOAc solution was used to maintain reaction pH ∼4–5 and also completion of coupling reaction.
Scheme 2. Synthesis of azo dye 6B. 50
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Scheme 3. Synthesis of anthraquinone dye 6C.
the mixture was allowed to cool to room temperature and 10 ml of cold water was added. Then extracted with ethyl acetate (2 × 30 mL). The organic layers were combined and dried with Na2SO4, filtered, the resulting filtrate was concentrated in vacuo. The column chromatography (elution with 3–5 % of ethyl acetate-hexane) rendered pure products 3A and 3B.
For the synthesis of anthraquinone dye 6C, first tosylation reaction was performed on 1,4-dihydroxyanthracene-9,10-dione 7 under basic condition to afford compound 9. Further, this compound 9 was reacted with n-heptylamine under mild reaction conditions to give compound 10 as a red solid. The reaction of this intermediate 10 with tert-butyl (4aminobutyl) carbamate (11) in pyridine under reflux condition to afforded compound 6C as a dark blue solid (Scheme 3). A nucleophilic substitution reaction between 1,8-dihydroxy-4,5-dinitroanthracene-9,10-dione (12) and 2-ethyl aniline or 3-ethyl aniline in 2-methoxyethanol at 120 °C to yielded compounds 6D and 6E respectively (Scheme 4). Here the reactivity of aryl amines was increased with their nucleophilicity due to presence of ethyl groups. The synthesis of azo and anthraquinone dyes utilizes simple and an efficient coupling reaction (6A, 6B), and nucleophilic substitution reactions (6C, 6D and 6E) through the use of readily available and commercially inexpensive starting materials and reagents. These reactions were carried out under relatively mild conditions. Moreover, all the dyes were obtained in a pure form with good yields. The obtained dyes can be used for the dyeing without further column purifications (energy saving), which makes potentially suitable for industrial scale synthesis.
2.3.1. Characterization of N,N-dipropylaniline (3A) Color less liquid; Yield: 89 % (1.57 g); 1H NMR (CDCl3, 600 MHz): δ 7.14 – 7.01 (2H, m, Ar–H), 6.58 – 6.52 (3H, m, Ar–H), 3.15 (4H, t, J = 7.5 Hz, 2 x N–CH2), 1.57 – 1.49 (4H, m, 2 x –CH2–), 0.84 (6H, t, J = 7.5 Hz, 2 x –CH3). ESI-MS: 178 [M+H]+. 2.3.2. Characterization of N,N-dibutyl-3-ethylaniline (3B) Color less liquid; Yield: 81 % (1.88 g); 1H NMR (CDCl3, 600 MHz): δ 7.18 (1H, d, J =8.8 Hz, Ar–H), 6.44 – 6.41 (2H, m, Ar–H), 6.29 –6.25 (1H, dd, J = 8.8, 3.0 Hz, Ar–H), 3.15 (4H, t, J = 7.7, 7.5 Hz, 2 x N–CH2), 2.60 (2H, q, J = 7.5 Hz, Ar–CH2–), 1.50 – 1.43 (4H, m, 2 x –CH2–), 1.31 – 1.23 (4H, m, 2 x –CH2–), 1.14 (3H, t, J = 7.5 Hz, –CH3), 0.87 (6H, t, J = 7.5 Hz, 2 x –CH3). ESI-MS: 234 [M+H]+. 2.4. General experimental procedure for the synthesis of compounds 6A and 6B
2.3. General experimental procedure for the synthesis of compounds 3A and 3B
H2SO4 (5 mL) was placed in a round bottom flask and kept at 0 °C. To this, dry NaNO2 (0.95 g, 13.783 mmol) was slowly added. Then, the mixture temperature was slowly raised to 60−65 °C to generate nitrosylsulfuric acid and stirred for 1 h and cooled to 5 °C. In another round bottom flask, an AcOH:propionic acid mixture (1:1, 20 mL) was placed and kept at 0-5. To this,5-nitrothiazol-2-amine (2 g, 13.783 mmol) was added portion-wise and stirred for 15 min. At 0−5 °C temperature, the nitrosylsulfuric acid was gradually added to the above mixture. The diazotization salt formation was confirmed by TLC (Thin layer chromatography). This diazonium salt solution was used immediately in the next coupling reaction. In a round bottom flask (100 mL), the coupling components 3A and 3B (13.783 mmol) were dissolved in AcOH: H2O (2:1, 15 mL) together with 5 g of sodium acetate (NaOAc) and kept at 5 °C. To this mixture, the diazonium solution was slowly added at 5 °C over 30 min. The reaction mixture pH was maintained ∼4–5 by addition of 10 % aqueous sodium acetate solution. The reaction was stirred at 5 °C for 1 h and at room temperature for 1 h. The resulting precipitates were filtered off and washed with cold and hot water until the elimination of acid.
To a solution of aniline or substituted aniline (10.0 mmol) in DMSO (10 mL), potassium hydroxide (20.0 mmol) and alkyl bromides (30.0 mmol) were added at room temperature. Further the reaction mixture was stirred at 50 °C for 5 h. After completion of the reaction,
Scheme 4. Synthesis of anthraquinone dyes 6D and 6E. 51
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Recrystallized from DMF provided the pure dyes 6A and 6B.
4.47 (1H, brs, H–N–C = O), 3.40 – 3.30 (4H, m, 2 x N–CH2),3.18 – 3.10 (2H, m, N–CH2), 1.76 – 1.67 (4H, m, –CH2–),1.65 – 1.58 (2H, m, –CH2–), 1.44 – 1.35 (11H, m, –CH2–, 3 x –CH3), 1.33 – 1.22 (4H, m,2 x –CH2–), 0.83 (3H, t, J = 7.1 Hz, –CH3); 13C NMR (CDCl3, 600 MHz): δ 182.3 (ArC=O), 182.1 (ArC=O), 155.9 (HN–C=O), 146.2 (ArC–N), 146.0 (ArC–N), 134.5, 134.4, 131.9, 131.8, 125.9, 123.6, 123.4, 109.7, 109.6 (ArC), 42.9 (N–CH2), 42.4 (N–CH2), 40.1 (N–CH2), 31.7 (–CH2–), 29.6 (–CH2–), 29.0 (–CH2–), 28.3 (–CH2–), 27.7 (–CH2–), 27.1 (–CH2–), 26.8 (–CH2–), 22.6 (3 x –CH3), 14.0 (–CH3). HRMS: 507.3085 [M]+. Calculated for C30H41N3O4: 507.3097.Purity: 90 %.
2.4.1. Characterization of4-((5-nitrothiazol-2-yl)diazenyl)-N,N-dipropylaniline (6A) Dark blue solid; Yield: 73 % (3.35 g); mp: 148–150 °C; IR (KBr) (νmax/cm–1): 2960 (=C–H), 2930 (–C–H), 1596 (C = C), 1504 (N = O), 1474 (N = N), 1334 (N–O), 1231 (C–N); 1H NMR (CDCl3, 600 MHz): δ 8.51 (1H, s, HAr–H), 7.90 – 7.80 (2H, m, Ar–H), 6.66 (1H, d, J = 9.5 Hz, Ar–H), 3.36 (4H, t, J = 7.8 Hz, 2 x N–CH2), 1.69 – 1.61 (4H, m, 2 x –CH2–), 0.93 (6H, t, J = 7.5 Hz, 2 x –CH3); 13C NMR (CDCl3, 600 MHz): δ 180.7 (HAr–C), 153.2 (HAr–C), 145.5 (ArC–N), 142.8, 141.6, 111.2 (Ar–C), 52.3 (N–CH2), 19.7 (–CH2–), 10.3 (–CH3). HRMS: 334.1354 [M+H]+. Calculated for C15H20N5O2S: 334.1338. Purity: 98%.
2.7. General experimental procedure for the synthesis of compounds 6D and 6E 1,8-Dihydroxy-4,5-dinitroanthracene-9,10-dione (12) (0.2 g, 0.605 mmol) was placed in 2-methoxy ethanol (10 mL) and 2-ethyl aniline/3-ethyl aniline (1.211 mmol) was added at ambient temperature. The reaction was further refluxed at 125 °C for 6 h. Then the liquor was cooled to room temperature and ethanol was added (5 mL) and kept to stand for 3 h. The formed blue precipitates were filtered and washed with water. The recrystallization was performed in ethanol provided 6D and 6E as pure dyes.
2.4.2. Characterization ofN,N-dibutyl-3-ethyl-4-((5-nitrothiazol-2-yl) diazenyl)aniline (6B) Green solid; Yield: 71 % (3.81 g); mp: 217–219 °C; IR (KBr) (νmax/ cm–1): 2956 (=C-H), 2867 (-C-H), 1599 (C = C), 1504 (N = O), 1475 (N = N), 1349 (N–O), 1244 (C-N); 1H NMR (CDCl3, 600 MHz): δ 8.57 (1H, s, HAr–H), 8.03 (1H, d, J = 9.4 Hz, Ar–H), 6.59 (1H, dd, J = 9.5, 2.8 Hz, Ar–H), 6.54 (1H, d, J = 2.8 Hz, Ar–H), 3.45 (4H, t, J = 7.7 Hz, 2 x N–CH2), 3.04 (2H, q, J = 7.5 Hz, Ar–CH2–), 170 – 1.64 (4H, m, 2 x –CH2–), 1.46 – 1.39 (4H, m, 2 x –CH2–), 1.32 (3H, t, J = 7.7 Hz, –CH3), 1.00 (6H, t, J = 7.7 Hz, 2 x –CH3); 13C NMR (CDCl3, 600 MHz): δ 182.9 (HAr–C), 154.8 (HAr–C), 152.8 (HAr–C–N), 144.1 (ArC–N), 140.5, 121.0, 111.6, 111.2 (Ar–C), 51.3 (N–CH2), 29.7 (Ar–CH2), 25.7 (–CH2–), 20.2 (–CH2–), 16.7 (–CH3), 13.8 (–CH3). HRMS: 390.1983 [M +H]+. Calculated for C19H28N5O2S: 390.1964. Purity: 96 %.
2.7.1. Characterization of 1-((2-ethylphenyl)amino)-4,5-dihydroxy-8nitroanthracene-9,10-dione (6D) Blue solid; Yield: 88 % (0.215 g), mp: 204–206 °C; IR (KBr) (νmax/ cm–1): 2914 (=C-H), 2861 (-C-H), 1583 (C = C), 1540 (N = O), 1359 (N–O), 1251 (C-N), 1165 (C-O); 1H NMR (CDCl3, 600 MHz): δ 12.80 (1H, brs, ArO–H), 12.76 (1H, brs, ArO–H), 11.57 (1H, brs, ArN–H), 7.56 (1H, d, J = 9.0 Hz, Ar–H),7.28 (1H, dd, J = 7.5, 2.4 Hz, Ar–H), 7.23 – 7.17 (4H, m, Ar–H), 7.11 (1H, dd, J = 6.7, 2.0 Hz, Ar–H), 7.09 (1H, d, J = 9.5 Hz, Ar–H),2.55 (2H, q, J = 7.5 Hz, Ar–CH2–), 1.10 (3H, t, J = 7.5 Hz, –CH3); 13C NMR (CDCl3, 600 MHz): δ 189.4 (ArC=O), 177.8 (ArC=O), 163.4 (ArC–OH), 158.7 (ArC–OH), 147.0 (ArC–NO2), 142.1 (ArC–NH), 140.3 (ArC–NH), 135.8, 130.5, 129.7, 129.2, 128.0, 127.4, 126.9, 126.7, 122.3, 115.7, 112.1, 108.2 (ArC), 24.6 (Ar–CH2–), 14.4 (–CH3). HRMS: 405.1034 [M+H]+. Calculated for C27H17N2O6: 405.1087. Purity: 98 %.
2.5. Experimental procedure and characterization of4-(heptylamino)-9,10dioxo-9,10-dihydroanthracen-1-yl 4-methylbenzenesulfonate (10) 9,10-Dioxo-9,10-dihydroanthracene-1,4-diyl bis(4-methylbenzenesulfonate) (9) (2.7 g, 4.922 mmol) in DCM (30 mL),and heptan-1-amine (7.383 mmol) was added at ambient temperature, and stirred for 24 h. TLC indicated consumption of starting material. The reaction crude was directly absorbed with silica and performed column chromatography (elution with13 % ethyl acetate-hexane) rendered a pure red solid (10). Yield: 51 % (1.25 g), mp: 116–118 °C; IR (KBr) (νmax/cm–1): 3463 (NH), 2926 (=C-H), 2854 (-C-H), 1704 (C = O), 1570 (C = C), 1156 (CN); 1H NMR (CDCl3, 600 MHz): δ 9.89 (1H,t, J = 4.5 Hz, N–H), 8.10 (1H, d, J = 7.7 Hz, Ar–H), 7.90 (1H, d, J = 7.7 Hz, Ar–H),7.74 (2H, d, J = 8.2 Hz, Ar–H), 7.65 – 7.61 (1H, m, Ar–H), 7.60 – 7.56 (1H, m, Ar–H), 7.27 (1H, d, J = 9.4 Hz, Ar–H), 7.17 (2H, d, J = 8.2 Hz, Ar–H), 6.92 (1H, d, J = 9.4 Hz, Ar–H), 3.24 (2H, q, J = 6.9 Hz, N–CH2), 2.26 (3H, s, Ar–CH3), 1.69 (2H, qt, J = 7.5 Hz, –CH2–), 1.41 (2H, qt, J = 7.5 Hz, –CH2–), 1.35 – 1.21 (6H, m, –CH2–), 0.83 (3H, t, J = 7.1 Hz, –CH3); ESI-MS: 492 [M+H]+.
2.7.2. Characterization of 1-((3-ethylphenyl)amino)-4,5-dihydroxy-8nitroanthracene-9,10-dione (6E) Blue solid; Yield: 87 % (0.212 g), mp: 219–221 °C; IR (KBr) (νmax/ cm–1): 2919 (=C-H), 2859 (-C-H), 1581 (C = C), 1536 (N = O), 1359 (N–O), 1251 (C-N), 1165 (C-O); 1H NMR (CDCl3, 600 MHz): δ 12.83 (1H, brs, ArO–H),12.74 (1H, brs, ArO–H), 11.68 (1H, brs, ArN–H), 7.56 – 7.52 (2H, m, Ar–H), 7.25 (1H, t, J = 8.0 Hz, Ar–H), 7.21 (1H, d, J = 8.8 Hz, Ar–H), 7.12 (1H, d, J = 9.5 Hz, Ar–H), 7.04 – 7.01 (1H, m, Ar–H), 7.00 – 6.97 (2H, m, Ar–H), 2.60 (2H, q, J = 7.5 Hz, Ar–CH2–), 1.18 (3H, t, J = 7.5 Hz, –CH3); 13C NMR (CDCl3, 600 MHz): δ 189.4 (ArC=O), 177.7 (ArC=O), 163.3 (ArC–OH), 159.0 (ArC–OH), 146.2 (ArC–NO2), 142.1 (ArC–NH), 130.5, 129.5, 129.1, 128.2, 126.7, 125.8, 124.3, 122.4, 121.9, 115.6, 112.2, 108.6 (ArC),28.7(Ar–CH2–), 15.4 (–CH3). HRMS: 405.1032 [M+H]+.Calculated for C27H17N2O6: 405.1087.Purity: 93 %.
2.6. Experimental procedure and characterization of tert-butyl (4-((4(heptylamino)-9,10-dioxo-9,10-dihydroanthracen-1-yl)amino)butyl) carbamate (6C) Compound 10 (1.2 g, 2.443 mmol) was placed in pyridine (20 mL), and tert-butyl (4-aminobutyl)carbamate 11 (2.683 mmol) was added at ambient temperature. Further the mixture stirred at reflux temperature for 16 h. The reaction was monitored by TLC, showed full consumption of starting material (red spot). Then pyridine was evaporated under reduced pressure. The resulting residue was triturated with diethyl ether and hexane (2:1, 12 mL) to afford pure compound 6C. Blue solid; Yield: 53 % (0.615 g), mp: 121–123 °C; IR (KBr) (νmax/cm–1): 3482 (NH), 3350 (N-H), 2928 (=C-H), 2852 (-C-H), 1705 (C = O), 1672 (C = O), 1573 (C = C), 1251 (C-O), 1156 (C-N); 1H NMR (CDCl3, 600 MHz): δ 10.76 – 10.74 (2H, brs, ArN–H), 8.29 – 8.24 (2H, m, Ar–H), 7.63 – 7.59 (2H, m, Ar–H), 7.18 – 7.16 (2H, m, Ar–H), 4.56 –
2.8. Supercritical dyeing procedure Fig. 1 shows the components of the dyeing instrument for supercritical fluid dyeing. It mainly consistsCO2 cylinder, cooling bath, CO2 pressure pump, circulation system, dyeing vessel, temperature control unit, separator and recycling unit. In the dyeing process, first nylon 6,6 fabrics (approximately 5 × 10 cm, 10 g) were wrapped around a rotating warp beam and placed inside the dyeing vessels. In order to remove residual air in the dyeing vessel, gaseous CO2was injected for approximately 2 min. The purified azo and anthraquinone fine dye powders were placed into the stirring unit of the dye stuff vessel. The 52
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Fig. 1. Schematic representation of the lab scale supercritical carbon dioxide dyeing plant.
used concentration of dyes here is 2 %, 3 % and 5 % with respect to the nylon 6,6 fabric weight. The operator was then sealed before starting the dyeing. The carbon dioxide gas was passed from the cylinder to the dyeing system via heat exchanger, cooling bath (−10 to +5 °C) and pressure pump. In the dye stuff vessel, the dyes were pre dissolved by the supercritical carbon dioxide fluid. After 20 min, the dyeing vessel was occupied by the fluid. Then the carbon dioxide circulation system was opened. In the dyeing process, the nylon fabric and supercritical fluid ratio approximately used in this study is 1: 50. After reaching the desired temperature (120 °C) and pressure (25 MPa), the dyeing process started and continued for 1 h. During the dyeing process constant temperature was maintained by temperature control unit. After 1 h, the temperature was slowly reduced to 30 °C. The dye stuff and supercritical carbon dioxide were separated in the separator unit. Further, carbon dioxide gas was purified by passing through a purifier containing molecular sieves and stored in a gas container. After recycling the sufficient amount of carbon dioxide, the pressure was reduced to atmospheric level. Then dyed nylon 6,6 fabrics were retrieved from the dyeing vessel for further analysis. 2.9. Traditional dyeing The traditional dyeing experiment of nylon 6,6 fabrics were performed by using ACE-6000 T model infrared laboratory-scale dyeing machine. First, the nylon 6,6 fabrics (1 g) were treated with 5 g/dm3 carrier, 4 % ammonium sulfate by maintaining the pH 5.5 at 60 °C for 20 min at a liquor ratio of 1:20. Herein, various concentrations of synthesized dyes (6A-6E) 2 %, 3 % and 5 % owf were used in our study. The dyes were dissolved in the solution of (2 g/dm3) an anionic dispersing agent. The dyes being precipitated in fine dispersion and it was added to the dye bath and the temperature was raised at a rate of 2 °C min−1 until a temperature of 120 °C was reached in 45 min. Further the dyeing was continued for 1 h at this temperature. After that, the dyed samples were cooled to room temperature and the fabrics were separated and washed with 2 % of nonionic detergent at 60 °C for 20 min. Then the fabrics were rinsed in water and dried.
Fig. 2. (a) Effect of dye concentration in supercritical condition; (b) Effect of dye concentration in aqueous condition.
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3. Results and discussion 3.1. Effect of dye concentration Herein, the effect of dye concentration on the color strength (K/S) of nylon 6,6 fabric were studied and the corresponding results are given in Fig. 2. The dyeing experiments were performed by using different concentration of dye 2 %, 3 % and 5 % owf (on weight of fabric) for 1 h. According to Kubelka − Munk equation (equation 1), the K/S values are calculated and are well linear with respect to the dye concentration on the dye substrate [4]. The dyed fabrics were immersed in hot acetone solution and extracted the adsorbed dye and measured the concentration of dye solution at a maximum wavelength. By increasing the concentration of all dyes azo (6A, 6B) and anthraquinone (6C, 6D and 6E), the color strength of nylon 6,6 fabric is increased in supercritical as well as in traditional dyeing conditions; From experimental results (Fig. 2a and b), indicate that the azo dyes exhibited more color strength values than the anthraquinone dyes. Since the azo dyes (6A and 6B) are having hydrophobic N,N-propyl and N,N-butyl aniline groups whereas anthraquinone dyes are having little hydrophilic carbamate (6C), hydroxyl, and ethyl aniline groups (6D and 6E). Therefore, azo dyes can be dissolved more easily compared to anthraquinone dyes, which mean that color strength may also be increased for the azo dyes. In super critical carbon dioxide conditions, the increment in the color strength for the azo dyes 6A and 6B is larger from 2 % to 3 % and is smaller from 3 % to 5 %. This is attributed to the azo dyes having strong saturation at low concentrations. The diffusion speed of dye particles may gradually slow down therefore, the absorption of dye by nylon 6,6 fabric is limited and the interaction between the dye and fabric cause color strength values to increase a smaller (from 3 % to 5 %) [23]. The overall results indicate that the color strength was considerably increased in supercritical carbon dioxide conditions when compared to the traditional dyeing. This is attributed to the fact that, the synthesized dyes exhibited good solubility and diffusion under supercritical carbon dioxide dyeing than the traditional dyeing. Moreover, it has been suggested that the supercritical carbon dioxide dyeing system has significant advantages than traditional aqueous dyeing [39]. 3.2. Thermal analysis The thermal analysis results were obtained from the DSC instrument, and the corresponding results are illustrated in Fig.3. From the figure, a little change was observed in the amorphous region (30−90 °C) of the dyed nylon 6,6 fabrics after being treated with high temperature (120 °C). In contrast, we did not observe any changes in the crystal region (250−270 °C) of the dyed fabrics. This is suggested to that there was no damage to the nylon 6,6 fabric under the supercritical carbon dioxide dyeing medium. The heat factor only influenced the fiber properties. Fig. 4 shows the digital photographs of the dyed nylon 6,6 fabric with azo (6A and 6B) and anthraquinone (6C, 6D and 6E) dyes in supercritical CO2.
Fig. 3. Thermal analysis diagram of nylon 6,6 fabrics: (a) undyed nylon fabric; (b) Dyed nylon fabric with compound 6A at 120 °C; (c) Dyed nylon fabric with compound 6C at 120 °C.
extraction), and (K/S)dyed (after dyeing) in equation (2). To measure the (K/S)extracted, the dyed nylon 6,6 fabrics were soaked in acetone solvent at ambient temperature and slowly the temperature was raised to 80 °C for 1 h to yield the dye extracts [40]. After that, the dye extract was set aside and allowed to stand for 10 min to cool to ambient temperature and filtered. The extracted fabrics were separated and dried. The reflectance of these fabrics was measured and substituted in equation (1) and (K/S)extracted was calculated. From Fig.5, the order of the (K/S)dyed values for the synthesized dyes are6A > 6B > 6E > 6D > 6C. The (K/S)dyed values of the azo dyes, are significantly superior than those of anthraquinone dyes. Meanwhile, the dye 6A displayed a higher (K/S)extracted value (19.07), whereas for the dye 6B,the (K/S)extracted value is 13.46. Anthraquinone dyes 6C, 6D and 6E exhibited (K/S)extracted values of5.94, 6.14 and 6.71 respectively. The dye fixation percentage (%F) values of the dyed nylon
3.3. Color strength and dye fixation Table 3 indicated that the color strength (K/S) values of the dyed nylon6,6 fabrics. The experiment was carried out at a temperature of 120 °C and pressure of 25 MPa with 2 % owf dye for 1 h. The K/S values of the dyed nylon 6,6 fabricswere calculated,by using the Kubelka − Munk equation (equation 1), at a maximum absorption wavenumber (λmax). In this equation, K is the absorbance, S is the scattering coefficient, and Rmin is the minimum value of the reflectance curve, which is obtained from a Shimadzu UV-26,000 spectrophotometer by measuring the dyed nylon 6,6 fiber in a reflectance mode, a is constant and q is adsorbed dye on the fabric (mol g−1). Dye fixation (%F) percentage was calculated by substituting color strengths of (K/S)extracted (after 54
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Table 1 Color of dyed nylon 6,6 fabrics. Dye
L*
a*
b*
C*
h
K/S
6A 6B 6C 6D 6E
24.22 24.58 48.67 43.59 42.48
8.40 9.49 0.05 −7.93 −10.35
−27.99 −30.14 −43.66 −24.75 −21.48
29.22 31.60 43.66 25.99 23.84
286.71 287.48 270.07 252.24 244.27
21.43 17.95 6.83 7.31 7.90
3.4. Color assessment The color assessment of the dyed nylon 6,6 fabrics in supercritical carbon dioxide was conducted using a Datacolor 110 spectrometer. Table 1 indicates the CIELAB coordinates which are represented in terms of L*(lightness), chroma (C*), h (hue angle from 0° to 360°), and color-opponent dimensions (a* and b*). A negative value of a* shows the degree of greenness and a positive value of a* shows the degree of redness; similarly, a negative value of b* shows the degree of blueness and a positive value of b* shows the degree of yellowness. Based on the following statements, the synthesized dyes exhibited good levelness, brightness and depth on the nylon 6,6 fabric under optimized conditions. For the dyes 6A-6E, the color lightness value (L*) varied from 24.22–48.67. Dye 6C is lighter than the other compounds. According to the negative values of a*, the color hues for dyes 6D and 6E are shifted to the greenish direction on the red-green axis, whereas for dyes 6A, 6B and 6C, they are shifted to the reddish direction on the red-green axis. According to the negative values of b*, the color hues for all the dyes are shifted to the bluish direction on the yellow-blue axis in our investigations on nylon 6,6 fabric. Based on the color brightness (C*) values, dye 6C is brighter (43.66) and dye 6E is duller (23.84) than the other dyes. The color strength K/S values for the synthesized dyes ranged from 21.43 to 6.83. From Table 1, the azo dyes have higher color strength values than the anthraquinone dyes. Among them, compound 6A exhibits a superior color strength value (K/S 21.43) than the other dyes.
Fig. 4. Digital photographs of dyed nylon 6,6 fabrics with azo (6A, 6B) and anthraquinone (6C, 6D, and 6E) dyes in supercritical CO2.
Fig. 5. (K/S)dyed, and (K/S)extracted, values of dyed nylon 6,6fabrics.
6,6 fabrics ranked in the following order: 6A > 6C > 6E > 6D > 6B. The compound 6A had a low molecular weight and exhibited high solubility. In general, the lower molecular weight dyes having greater solubility in supercritical carbon dioxide. The transport rate of this dye towards the fiber is also very high. Hence, the 6A dye adsorption rate is greater and displayed higher K/S value as well as high dye fixation value. The dyes 6C, 6D and 6E have hydrogen bonding sites (NH−CO and –NH (6C), –NH and −OH (6D and 6E)), which may participate in strong hydrogen bonding interaction with the NHeCO group of the nylon 6,6 fabric. Therefore, these dyes exhibited good dye fixation values. Finally, for the dye 6B, the weak vander Waal forces may be responsible for the adsorption. Hence, it has a lower dye fixation value when compared to the other dyes. In addition to that, the nylon 6,6 fabrics are porous and can have sufficient access of dye molecules by allowing diffusion into these pores. Hence, dye adsorption takes place and good color strength and dye fixation values are exhibited. Our results revealed that the thiazole based azo and anthraquinone dye derivatives are convenient for the dyeing of nylon 6,6 fabrics in a supercritical carbon dioxide medium. The synthesized azo dyes (6A, and 6B) developed froman aminothiazole containing nitro group are given bright blue shades with good color strength values (K/S ∼17-21; 2 % o.w.f.) when compared to the azo dyes derived from carbocyclic analogues (simple aromatic rings like benzene and naphthalene, K/S ∼7-14; 4 % o.w.f) [24]. Since the nitro thiazole ring prized bathochromism and high tinctorial strength relative to their carbocyclic analogues. Moreover, the dye fixation values are also greater for 6A and 6B than the carbocyclic azo dyes [19].
3.5. Color fastness 3.5.1. Wash fastness The wash fastness data issummarized in Table 2. The KS K ISO 105 C06:2014 method was used for the wash fastness test. In this method, the dyed nylon 6,6 fabric (specimen) was washed together with multifiber white fabrics of acetate, cotton, nylon, polyester, acryl and wool. Here, first 4 × 10 cm of the test specimen was stitched with the same size of white multi fabrics. This sample was washed with 0.4 % of detergent at 40 °C for 30 min by using a rotawash. After washing, the samples were rinsed in hot water followed by squeezing with cold water and further dried in air. Then, stitching was removed, and assessed the color change of the specimen and the staining of color on the adjacent Table 2 Fastness properties of dyed nylon 6,6 fabrics with dyes 6A-6E. Wash fastnessa
Dye
6A 6B 6C 6D 6E a b
55
Fading color
Acetate
Cotton
Nylon
Polyester
Acryl
Wool
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5
Light fastnessb
2-3 2-3 4-5 3-4 3-4
Rating for wash fastness: > 3 (acceptable); < 2 (not acceptable). Rating for light fastness: > 4 (acceptable); < 2 (not acceptable).
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fabrics by using the international grayscale. All the compounds (6A-E) showed excellent washing fastness ratings for both fading and staining with a grade of 4–5. In our study, these results were probably due to the good dye diffusion and penetration in to the nylon 6,6 fabric.
acetate and nylon was of grade 2–3 in both acid and alkaline media. Most likely, it is due to the high affinity of the hydrolyzed dye 6A and 6B molecules towards acetate and nylon fibers in acid and alkaline conditions during the wash process [43]. It is clear that the synthesized azo and anthraquinone dyes in this work displayed excellent characteristics and coloration activities. In addition, these dyes have commercially satisfactory properties and color fastness results on nylon 6,6 fabric under supercritical carbon dioxide media. Hence, these types of dyes could potentially be applied for coloration in nylon 6,6based textile industries.
3.5.2. Light fastness Light fastness results are given in Table 2. The KS K ISO 105 – B02:2015 xenon arc method was used for the light fastness test. In this experiment, we exposed dyed nylon 6,6 fabrics to light for ∼20 h, and the changes in color was compared with the unexposed sample. By using blue scales, we measured the color changes. From the data, compound 6Cexhibited an excellent grade (4–5), whereas the compounds 6D and 6E (3–4 grade) exhibited good light fastness and other azo compounds 6A and 6B (2–3 grade) showed moderate light fastness. Based on the results, the azo dyes exhibited weak light fastness when compared to the anthraquinone dyes. The light fastness of theseazo dyes is very poor than the light fastness of azo (∼4–5) dyes, having acetamido, amino and hydroxyl groups on phenyl ring and ortho to the azo linkage (intramolecular hydrogen bond between these groups and azo group) [41]. Since our dyes having simple alkyl chains and are not involved in hydrogen bonding. In addition, the synthesized anthraquinone dyes (6C, 6D and 6E) exhibited good light fastness whereas the natural occurring anthraquinone dyes exhibited poor light fastness (∼3) properties [42].
3.6. Color characteristics Azo and anthraquinone dyes are soluble in dichloromethane, acetone, tetrahydrofuran and methanol solvents. Azo dyes form a purple colored solution in dichloromethane and a deep blue colored solution in acetone, tetrahydrofuran and methanol, whereas the anthraquinone dyes are form a deep blue colored solution in all these solvents. To assess the λmax, the synthesized dyes were subjected to spectrophotometric analysis in acetone solvent withinthe range of 400−800 nm. The dyes 6A, 6B, 6D and 6E have single absorption maxima at 583 nm, 599 nm, 606 nm, and 605 nm respectively. The peak wavelength of absorption spectra of 6B is slightly greater than 6A. It is speculated that an electron-donor substituent (-ethyl) on the chromophore caused a bathochromic shift of dye 6B. Due to the structural similarity of 6D and 6E (positional isomers), the absorption spectra almost similar. Moreover, the dye 6C exhibits double absorption maxima
3.5.3. Sweat fastness The results of fastness to perspiration are summarized in Table 3. The KS K ISO 105 – E04:2015 method was used for the determination of sweat fastness. In this experiment, we conducted the evaluation of perspiration resistance of the dyed nylon fabric (test specimen) together with multi-fiber white fabrics of acetate, cotton, nylon, polyester, acryl and wool. The test samples were sewn with multi-fiber fabrics and were dipped into acid or base solutions separately for 30 min, at ambient temperature. After that these samples were removed from acid and base solutions and were placed between two plates by maintaining of ∼ 4.5 kg force. These plates were kept in oven at ∼37 °C for 4 h. The test specimen was detached from multi-fiber white fabrics. The color changes were measured by using the international gray scale for the dyed nylon 6,6 fabrics and staining of undyed fabrics. Table 3 demonstrates that azo (6A and 6B) and anthraquinone (6C, 6D and 6E) dyes have outstanding sweat fastness results towards acid and alkaline media. For all dyes (6A-6E), the fading fastness results reached a grade of 4–5. However, the staining results reached a grade of 4–5 for the anthraquinone dyes (6C-6E). Moreover, azo dye 6B also reached a grade of 4–5 for all adjacent fabrics except acetate and nylon (3–4), whereas the azo dye 6A staining fastness adjacent to acryl and wool was of grade 4, adjacent to PET and cotton was of grade 3–4, and adjacent to Table 3 Sweat fastness data of nylon 6,6 fabrics with dyes 6A-6E. Sweat fastnessa
6A
6B
6C
6D
6E
Acidic
4-5 2-3 3-4 2-3 3-4 4 4 4-5 2-3 3-4 2-3 3-4 4 4
4-5 3-4 4-5 3-4 4 4-5 4 4-5 3-4 4 3-4 4 4-5 4
4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5
4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5 4-5
Alkaline
a
Fading Acetate Cotton Nylon PET Acryl Wool Fading Acetate Cotton Nylon PET Acryl Wool
Fig. 6. a) UV–vis spectra of 6A and 6B, b) UV–vis spectra of 6C, 6D and 6E in acetone (1 × 10−4 M).
Rating for sweat fastness: 3–5 (acceptable); 1–2 (not acceptable). 56
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at 591 nm and 638 nm (Fig. 6). These bands are typically attributed to amine to quinone intramolecular charge–transfer transitions. The reflectance spectra of dyed nylon 6,6 fabrics were also recorded adopting white standard BaSO4. For dyes 6A, 6B, 6C, 6D and 6E, the reflectance curve minimum value was centered ∼ 583 nm, 599 nm, 651 nm, 620 nm and 616 nm respectively (Fig. S26. Supporting information).
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4. Conclusion In conclusion, we synthesized azo (6A and 6B) and anthraquinone (6C, 6D and 6E) dye derivatives from inexpensive starting materials by using simple methods. The primary dyeing experiments were performed on nylon 6,6 fabric with these dyes to confirm the possibility of scaling up supercritical carbon dioxide dyeing to the factory level. All the dyes (6A-6E) exhibited good color strength values, and the dye fixation order was 6A > 6C > 6E > 6D > 6B. Further, we discussed the effect of dye concentration, on the color strength values (K/S). Especially for the azo dyes 6A and 6B, a dye concentration of 2 % (owf) gave higher K/S values in supercritical carbon dioxide when compared to 5 % (owf) of dye concentration in aqueous dyeing. The thermal analysis results indicated that the supercritical carbon dioxide did not damage the nylon 6,6 fabric. All the dyes (6A-6E) exhibited excellent results in washing fastness (fading and staining grade of 4–5) and sweat fastness (fading and staining grade of 4–5) and exhibited good to moderate results for light fastness (6C (4–5), 6D, 6E (3–4) and 6A, 6B (2–3)). The obtained results suggest that it would be valuable to develop new reactive disperse dyes containing these backbones (azo and anthraquinone), which could potentially be applied on cotton fabrics under a supercritical carbon dioxide dyeing medium. The corresponding work will be publishing in the future. CRediT authorship contribution statement Raju Penthala: Conceptualization, Investigation, Writing - original draft. Gisu Heo: Investigation, Visualization. Hyorim Kim: Investigation, Visualization. In Yeol Lee: Investigation. Eun Hee Ko: Investigation. Young-A Son: Writing - review & editing, Supervision. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments This work was supported by the nurture project of waterless color industry (10078334) funded by the Ministry of Trade, Industry and Energy (MOTIE) of Korea. References [1] Z.T. Liu, L.L. Zhang, Z.W. Liu, Z.W. Gao, W.S. Dong, H.P. Xiong, Y.D. Peng, S.W. Tang, Supercritical CO2 dyeing of ramie fiber with disperse dye, Ind. Eng. Chem. Res. 45 (2006) 8932–8938. [2] N.A. Ibrahim, N.M.A. Moneim, E.S.A. Halim, M.M. Hosni, Pollution prevention of cotton-cone reactive dyeing, J. Clean. Prod. 16 (2008) 1321–1326. [3] B. Thomas, T. Aurora, Electrochemical reduction in vat dyeing: greener chemistry replaces traditional processes, J. Clean. Prod. 17 (2009) 1669–1679. [4] A.S. Özcan, A. Özcan, Adsorption behavior of a disperse dye on polyester in supercritical carbon dioxide, J. Supercrit. Fluids 35 (2005) 133–139. [5] E. Rosalesm, M.A. Sanromán, M. Pazos, Application of central composite facecentered design and response surface methodology for the optimization of electroFenton decolorization of Azure B dye, Environ. Sci. Pollut. Res. 19 (2012) 1738–1746. [6] K. Enayatzamir, H.A. Alikhani, B. Yakhchali, F. Tabandeh, S. Rodríguez-Couto, Decolouration of azo dyes by phanerochaete chrysosporium immobilised into alginate beads, Environ. Sci. Pollut. Res. 17 (2010) 145–153. [7] P.B.S. Ratna, Pollution due to synthetic dyes toxicity & carcinogenicity studies and remediation, Int. J. Environ. Sci. 3 (2013) 940–955.
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