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Optimization of natural anthocyanin efficient extracting from purple sweet potato for silk fabric dyeing
Accepted Manuscript Optimization of natural anthocyanin efficient extracting from purple sweet potato for silk fabric dyeing
Yunjie Yin, Jiru Jia, Ting Wang, Chaoxia Wang PII:
S0959-6526(17)30360-8
DOI:
10.1016/j.jclepro.2017.02.134
Reference:
JCLP 9060
To appear in:
Journal of Cleaner Production
Received Date:
08 July 2016
Revised Date:
17 February 2017
Accepted Date:
18 February 2017
Please cite this article as: Yunjie Yin, Jiru Jia, Ting Wang, Chaoxia Wang, Optimization of natural anthocyanin efficient extracting from purple sweet potato for silk fabric dyeing, Journal of Cleaner Production (2017), doi: 10.1016/j.jclepro.2017.02.134
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ACCEPTED MANUSCRIPT Highlights
1.
Aqueous two-phase system was used to extract natural colorant anthocyanin.
2.
To enhance mass-transfer, ultrasound was used to assist the ATPS extraction.
3.
The dyed silk fabric presented excellent K/S value and color fastness.
ACCEPTED MANUSCRIPT Optimization of natural anthocyanin efficient extracting from purple sweet potato for silk fabric dyeing Yunjie Yin, Jiru Jia, Ting Wang, Chaoxia Wang* Key Laboratory of Eco-Textile, Ministry of Education, School of Textiles & Clothing, Jiangnan University, Wuxi 214122, China Corresponding author: Prof. Chaoxia Wang; E-mail: [email protected] Abstract The main objective of this study is to extract natural colorant anthocyanin from purple sweet potato powder via ultrasound-assisted ammonium sulfate/ethanol aqueous two-phase system, and this method can avoid the serious environment pollution during the preparation and use process of synthetic dye, reduce the solvent and simplify the abstraction procedures. The extracted natural colorant anthocyanin was used to dye silk fabric in a relatively ecological approach. Based on the single-factor extracting experiment, central composite designresponse surface methodology was employed to optimize the ultrasound-assisted aqueous two-phase system extracting conditions including ultrasound temperature, ultrasound time and dosage of purple sweet potato powder. The binomial model was highly significant and applied to fit the experimental data, due to its higher related coefficient. Via optimizing, a dosage of 1.60 g purple sweet potato powder was dispersed in ultrasound bath at 52.48 °C for 48.19 min. In the case of extracting conditions, 191.09 mg.L-1 natural colorant anthocyanin was produced in the upper ethanol-rich phase of the aqueous two-phase system. The color strength value of the silk fabric treated with mordant dyeing method was 4.5, and increased by 40.6% compared to that of the direct dyeing method. The dry and wet rubbing fastness using mordant dyeing method were 4-5 and 4 grade, respectively. The change and stain washing fastness using mordant dyeing method were 3-4 and 4-5 grade, respectively. This study demonstrates that developed natural colorant extracted from plant could be successfully employed as an effective and eco-friendly alternative cleaner to replace synthetic colorant gradually using in textile dyeing industry. Keywords: aqueous two-phase system; ultrasound-assisted extraction; anthocyanin; dyeing property; silk fabric 1. Introduction 1
ACCEPTED MANUSCRIPT The textile industry is the largest consumer of colorants. During the dyeing process, a large percentage of the synthetic colorants does not bind or absorbed to the fibers, and they are left in the waste stream. The residual colorants are released into the environment during dyeing process, making the effluent highly colored and aesthetically unpleasant (Bafana et al., 2011). The effluent from textile industries carries a large number of colorants and other additives which are added during the dyeing process (Rahimi et al., 2013). Also, during the synthetic process of synthetic colorant, many kinds of solvents and chemical intermediates are used, and the toxic chemicals bring serious pollution and harm to environment and our bodies (Gupta and Suhas, 2009). Natural colorant, differing from synthetic colorant, usually comes from plant sources - roots, berries, bark, leaves and wood (Devi and Karuppan, 2015). The resources of natural colorant are multiple. Hou, et al. (Hou et al., 2013) report a novel application of using abundant, cheap and readily available agricultural byproduct orange peel as a new natural dye with strong ultraviolet absorbance, and used to dye wool fabrics. The dyed fabric could impart textiles with remarkable UV-protection properties. Ismal, et al. (Ismal et al., 2014) extracted a novel natural dye from outer green shell of almond fruit using chemical solvent free extraction, small amount of metallic mordant, natural mordant, auxiliary free dyeing and washing. They evaluated biomordant versus metal mordant and to reveal the substitution of the prevalent metal mordant for biomordant as renewable natural sources. Natural colorant is biodegradable and ecological (Ali et al., 2009). Anthocyanin is a biodegradable natural colorant which not only creates desirable colors, but also imparts some potential health benefits including anti-ultraviolet rays and insects resistance (Lee and Choung, 2011). Extensive studies have indicated that the major natural colorant in purple sweet potatoes is anthocyanin, which is a special water-soluble polyphenol compound and performs good heating stability compared to other sources of anthocyanin (Liu et al., 2014). Purple sweet potato anthocyanin exists in the form of anthocyanidin including proteins, polysaccharides and organic acids (Li et al., 2013). 2
ACCEPTED MANUSCRIPT The extraction of natural colorant anthocyanin can be carried out using the traditional organic solvent method, but the traditional solvent extraction is very time-consuming and requires relatively large quantities of solvents, such as ethanol and methanol (Rouskova et al., 2011). The consuming of enormous solvents does not conform to the requirements of ecological and environmental protection in modern factories (Zhang et al., 2014). Nowadays, various improved extracting methods have been developed for natural colorant extraction, such as microwave-assisted extraction (Yang and Zhai, 2010), enzymatic extraction (Passos et al., 2009) and supercritical fluid extraction (Cao and Ito, 2003; Liu et al., 2013). However, the cost related to the investment, operation and maintenance of some extractions have limited their application at large scale. Therefore, the development of simple, efficiency and relatively “green” extracting method becomes more attractive. Response surface methodology (RSM) is a collection of statistical and mathematical technique which is useful in many engineering applications for improving and optimizing processes, for analyzing the interactions between the response and the independent variables, and for predicting the response. Simic, et al (Simic et al., 2016) extracted polyphenolic compounds from the chokeberries (Aronia melanocarpa) using RSM and artificial neural network (ANN). The set of the optimal operational conditions, for example extraction time, solvent and energy consumption, which gave the maximum yield of total polyphenolic content, were concluded easily. Sinha et al. (Sinha et al., 2016) reported that the natural yellow-brown colorant extracted from the bark of Terminalia arjuna might be an alternative source of synthetic dyes for the potential dyeing cotton fiber, and the dye uptake as well as surface color strength of dyed cotton were studied in batch experiments and optimized by using response surface methodology. In recent decades, the aqueous two-phase system (ATPS) has been applied to extracting field. ATPS is usually composed of two or more polymers, a polymer and a salt, or two surfactants including quaternary ammonium surfactants and anionic surfactants (Shao et al., 2013). Short chain alcohol and inorganic salt also can form an aqueous two-phase system. This type of ATPS offers several advantages, 3
ACCEPTED MANUSCRIPT including low cost, high efficiency and simple scale-up (Guo et al., 2012). Generally, ATPS is used as a separation step to obtain molecules from a previously prepared aqueous solution (Ahmad et al., 2008; Wu et al., 2014). The technology has been used to extract quantities of natural small molecule from herbs and other natural dyes (Shen et al., 2007; Zhi and Deng, 2006). Some reports indicated that using ultrasound-assisted exacting or ammonium sulfate/ethanol aqueous twophase system could improve the extraction efficiency, but the increase was not remarkable (Pina and Hatton, 2008; Shao et al., 2013). The authors combined both of the ultrasound-assisted exacting and ammonium sulfate/ethanol aqueous two-phase system method, and tried to improve the extraction efficiency. Specifically, in this study, a small number of ammonium sulfate/ethanol ATPS was used as a solvent to extract anthocyanin from purple sweet potatoes. To enhance mass transfer, ultrasound was used to assist the ATPS extraction. The extracted natural colorant anthocyanin was dissolved to dye the silk fabric. The effects of ultrasound temperature, ultrasound time and dosage of purple sweet potato powder on the anthocyanin concentration were investigated. And central composite design-response surface methodology was utilized to optimize the ultrasound-assisted ATPS extracting conditions. The color strength (K/S value) and dyeing fastness, including rubbing and washing were evaluated. 2.
Experimental
2.1 Chemicals and materials Purple sweet potato (Ningzishu No.1) gained from a local supermarket were sliced and oven-dried at 60 °C until the moisture content remained constant. Dried samples were smashed to powder using the FZ102 micro electric grinder (Tianjing Taisite Instrument Co., Ltd. China) and passed through 60-mesh sieve. Ammonium sulfate, ethanol and AlCl3 were obtained from Sinopharm Chemical Reagent Co., Ltd. (China) and analytically pure. Silk taffeta fabric (16.5 g.m ) was supplied by Wuxi Huiling Silk Co., Ltd (China). -2
4
ACCEPTED MANUSCRIPT 2.2 Extraction of purple sweet potato anthocyanin An ammonium sulfate/ethanol ATPS was prepared according to the previous research (Wu et al., 2011). Ammonium sulfate was weighed and dissolved in deionized water. A certain volume of absolute ethanol was added to make the mass fraction of ammonium sulfate 20% (w/w) and ethanol 30% (w/w). The contents were vortex-mixed and allowed to phase-separate to form ATPS, which consisted of an upper ethanol-rich phase and a lower salt-rich phase. A predetermined quantity of purple sweet potato powder was added into 20 g ammonium sulfate/ethanol ATPS which was prepared as the above method. Ultrasound dispersion was carried out using the SK3200LH ultrasound crasher (Shanghai Precision Instrument Co., Ltd. China) with fixed power (20 kHz). The ultrasound time and ultrasound temperature were controlled, respectively. After extraction, the extraction was filtered and the filtrate was placed until the two phases were completely separated. For further purification, the upper phase solution enriched natural colorant anthocyanin was centrifuged at 9000 rpm for 15 min using the TG16-WS high-speed centrifuge (Shanghai Luxiangyi Centrifuge Instrument Co., Ltd. China). The effect parameters, such as ultrasound temperature, ultrasound time and dosage of purple sweet potato powder, extracting from purple sweet potato colorant were characterized by the concentration of natural colorant anthocyanin which enriched in the upper phase solution. The basic chemical structure of exacted anthocyanin is shown in Fig. 1. OH OH
HO
O
OH OH
Fig. 1 Basic chemical structure of anthocyanin 2.3 Dyeing process for silk fabric 5
ACCEPTED MANUSCRIPT The dyeing experiments were carried out with silk fabric using metal-mordanting technique. A small quantity of mordant AlCl3 (3 g.L-1) was dissolved in colorant extraction. The wetted silk fabrics were impregnated into the dyeing solution at a liquor ratio of 1:50 in infra-red dyeing machine with the temperature gradient 3 °C.min-1. The dyed fabrics were washed and dried at room temperature. 2.4 Determination of the anthocyanin concentration The pH differential method was used to determine the total anthocyanin content enriched in the upper phase of ammonium sulfate/ethanol ATPS (Hosseinian et al., 2008). Two different standard buffer solutions were prepared, The one was prepared using 1 mol.L-1 sodium acetate, 1 mol.L-1 hydrochloric acid and distilled water (10:6:9, v: v: v, pH = 4.5) and the other using 0.2 mol.L-1 potassium chloride and 0.2 mol.L-1 hydrochloric acid (25:67,v:v, pH = 1.0). The upper phase solution of ultrasound-assisted ATPS extraction of anthocyanin was centrifuged and then diluted with two prepared buffer solutions above, respectively. The diluted solutions were left undisturbed for 6 h. The absorbance of each diluted solution was measured at 500 nm and 700 nm against distilled water as blank using the UV2802S UV-Vis spectrophotometer (Shanghai Unico Instrument Co., Ltd.). The anthocyanin concentration (Y, mg.L-1) was evaluated using the following definition and expressed as Cy-3glc equivalents:
Y
A MW DF 1000 L
(1)
where A is the absorbance ((A520nm-A700nm)pH=1-(A520nm-A700nm)pH=4.5), and the absorbance at 700 nm is used to eliminate the effect of liquid turbidity. MW is the molecular weight for Cy-3-glc (449.2 g.mol-1), DF is the dilution factor, ε is the extinction coefficient (26,900 L.(cm × mol)-1), and L is the path length (1cm). 2.5 Color and color fastness measurements The color properties of the fabrics were measured by an Xrite-8400 spectrophotometer under the illuminant D65 using a 10° standard observer. The relative color strength, denoted by the K/S value, is determined with the 6
ACCEPTED MANUSCRIPT Kubelka-Munk equations,
K /S
(1 R) 2 2R
(2)
where K is the absorption coefficient, S is the scattering coefficient and R is the fractional reflectance (value from 0 to 1) of the fabric sample at the wavelength of minimum reflectance (Yin et al., 2008; Zhao et al., 2014). The K/S value is proportional to the color strength of the fabric sample. Rubbing fastness was performed by rubbing the dyed fabric with dry and wet standard rubbing clothes in 10 cycles using a Y571 rubbing fastness tester (Electron Instrument Co., Ltd., Laizhou, China), respectively. The stains of the clothes cloths were measured by an X-Rite 8400 spectrophotometer according to AATCC 82007 standard. The washing fastness was tested according to the ISO 105-C10:2010 (E) standard (Yin et al., 2016). The samples were washed using 3 g.L-1 soap at 40 °C for 30 min by a 12-A washing fastness tester supplied by Wenzhou Darong Textile Instrument Co., Ltd. (China). 2.6 Experimental design and statistical analysis A five-level three-factor central composite design was chosen for optimization with respect to three independent variables including ultrasound temperature, ultrasound time and dosage of purple sweet potato powder. The response variable was the concentration of natural colorant anthocyanin in the upper phase, and the optimal conditions determined by single-factor experiment were at the central point. The factors and levels of central composite design are shown in Table 1. The experimental data were analyzed using the Design-Expert version 8.0.6.1 and fitted to multiple linear model and binomial model (Sinha et al., 2012). The quality of model fit was expressed by the correlation coefficient R2, and its statistical significance was confirmed using the p value. Analysis of variance and response surface methodology were carried out after selecting the most accurate model. Table 1 Factors and levels of central composite design 7
ACCEPTED MANUSCRIPT
3.
Factors
Symbol
Ultrasound temperature (°C)
Levels -1.732
-1
0
1
1.732
A
32.7
40
50
60
67.3
Ultrasound time (min)
B
23
30
40
50
57
Powder dosage (g)
C
1.05
1.20
1.40
1.60
1.75
Results and discussion
3.1 Ultrasound-assisted ATPS extraction The ultrasound-assisted ATPS extraction was carried out at different temperatures (30-70 °C) for 30 min with 1.0 g purple sweet potato powder. The effect of ultrasound temperature on the concentration of natural colorant anthocyanin in the upper phase of ATPS was shown in Fig. 2. The data indicated that the anthocyanin concentration was increased with the temperature until 50 °C, and then gradually decreased. In terms of ultrasound-assisted ATPS extraction, purple sweet potato anthocyanin was mainly concentrated in the upper ethanol-rich phase, whereas the impurities including proteins, polysaccharides and organic acids were mostly enriched in the lower salt-rich phase. During the lower ultrasound temperature stage, the adsorption forces between anthocyanin molecule and impurity were broken with increasing temperature. Anthocyanin molecules moved rapidly, and most anthocyanin transferred into the ethanol-rich phase of ATPS (Mageste et al., 2009). A high ultrasound temperature could increase the penetrability of cell membrane of purple sweet potatoes to facilitate anthocyanin extraction. However, when the ultrasound temperature was above 50 °C, the purple sweet potato starch was easy to gelatinize, and some anthocyanin could be degraded and easily turn into colorless chalcone (Li et al., 2013; Pina and Hatton, 2008).
8
ACCEPTED MANUSCRIPT
Fig. 2 Effect of ultrasound temperature on the anthocyanin concentration To evaluate the effect of ultrasound time on the anthocyanin concentration, ultrasound time in range of 2060 min were performed. The ultrasound-assisted ATPS extraction was carried out at 50 °C with 1.0 g dried purple sweet potato powder. As shown in Fig. 3, the concentration of natural colorant anthocyanin in the upper phase of ATPS was increased with ultrasound duration during the former 40 min, and thereafter increased very slowly. Along with the increased ultrasound time, there was more natural colorant dissolving in the ATPS, so the anthocyanin concentration was high. However, too long heating time could not obviously increase the anthocyanin concentration in the upper phase of ATPS any more. It was because that the ultrasound-assisted ATPS extraction of natural colorant anthocyanin had reached equilibrium via ultrasound for more than 40 min, and extending ultrasound time could not improve the extracting efficiency. So an ultrasound time of 40 min was chosen due to high extracting efficiency and energy saving.
9
ACCEPTED MANUSCRIPT
Fig. 3 Effect of ultrasound time on the anthocyanin concentration Different dosage (0.4-1.6 g) of purple sweet potato powder was placed into the prepared ATPS, and the extracting experiment was carried out at 50 °C for 40 min. Fig 4 showed that the effect of powder dosage on the anthocyanin concentration. In the initial stage, the concentration of natural colorant anthocyanin in the upper phase of ATPS was increased linearly with increasing dosage of purple sweet potato powder, and then kept a gentle increase when the dosage was higher than 1.4 g. The reason was that as increasing the powder dosage, the extracting solvent was fully contacted with purple sweet potato powder, and more colorants were transferred into ATPS. However, the amount of colorants dissolving in ATPS would get to the saturation point, so even with further increase of dosage powder, the concentration of natural colorant anthocyanin the upper phase of ATPS changed slightly.
Fig. 4 Effect of powder dosage on the anthocyanin concentration 10
ACCEPTED MANUSCRIPT 3.2 Modeling of ultrasound-assisted ATPS extraction Based on the single-factor extracting experiment, a five-level three-factor central composite design according to Table 1 was implemented in order to optimize the ultrasound-assisted ATPS extracting conditions of natural colorant anthocyanin. The experimental design and response of the central composite were presented. Experimental data according to Table 2 were analyzed using the program Design-Expert version 8.0.6.1 (Sinha et al., 2012), and fitted to multiple linear model and binomial model. After application of Design-Expert version, the regression models of the purple sweet potato anthocyanin extraction can be described in Table 3. The quality of the model fit was expressed by the correlation coefficient R2, and its statistical significance was confirmed using the p value. The closer the value of R2 to 1, the higher the quality of the model fit. When the p value for the model was at the 5% level (P<0.05), the regression model is accepted. Otherwise, the p value for lack of fit was higher than 0.05 (Guo et al., 2013). Table 2 Experimental design and response of the central composite No
A (°C)
B (min)
C (g)
Y (mg L-1)
1
40
30
1.20
115.49
2
60
30
1.20
118.03
3
40
50
1.20
146.90
4
60
50
1.20
152.29
5
40
30
1.60
164.65
6
60
30
1.60
177.68
7
40
50
1.60
185.93
8
60
50
1.60
189.42
9
32.7
40
1.40
103.75
10
67.3
40
1.40
134.84
11
50
23
1.40
106.61
12
50
57
1.40
163.65
13
50
40
1.05
119.30
14
50
40
1.75
184.34
15~20
50
40
1.40
165.62
11
ACCEPTED MANUSCRIPT In Table 3, the p values of the models (one for 0.0003, another for 0.0019) were all lower than 0.05, so both models might be accepted and could adequately account for the variation observed. However, the R2 value (0.8737) of binomial fitting model was closer to 1, compared to the R2 value (0.6863) of multiple linear fitting model. The binomial fitting model was more appropriate and used to predict the anthocyanin concentration in the upper phase of ATPS. Results of the analysis variance of binomial fitting model for the anthocyanin concentration were presented in Table 4. The binomial fitting model, ultrasound time (B), powder dosage (C) and quadratic term of ultrasonic temperature (A2) showed highly significant influence (P<0.01) on the anthocyanin concentration. Table 3 Multiple linear and binomial fitting equations Regression models
Correlation
Fitting equations
coefficient
Y=-80.37001+0.55928A+1.41062B
Multiple linear model
+106.29378C
P value
0.6863
0.0003
0.8737
0.0019
Y=-577.04661+11.60597A+9.63400B+ Binomial model
204.62503C-8.36250×10-3AB+0.53687AC2.04063BC
-0.11464A2-0.061855B2-15.55357C2
Table 4 Analysis variance of binomial fitting model for the anthocyanin concentration Sum of
Degrees of
squares
freedom
12159.11
A
Source of variation
Mean square
F-value
P value
9
1351.01
7.69
0.0019
437.91
1
437.91
2.49
0.1456
B
2785.77
1
2785.77
15.85
0.0026
C
6327.09
1
6327.09
35.99
0.0001
AB
5.59
1
5.59
0.03
0.8620
AC
9.22
1
9.22
0.05
0.8234
BC
133.25
1
133.25
0.76
0.4044
A2
2069.85
1
2069.85
11.78
0.0064
B2
602.60
1
602.60
3.43
0.0938
C2
6.10
1
6.10
0.04
0.8560
Residual error
1757.83
10
175.78
Total
13916.94
19
Model
12
ACCEPTED MANUSCRIPT 3.3 Effects of extracting conditions on the anthocyanin concentration Response surface methodology was used to investigate the interaction between the variables on the concentration of natural colorant anthocyanin in the upper phase of ATPS (Swamy et al., 2014). The response surface plots constructed according to the binomial fitting equation with one fixed independent variable were discussed. In Fig. 5, an increase in the anthocyanin concentration was observed with increasing ultrasound time at a fixed ultrasound temperature, and the anthocyanin concentration increased with increasing ultrasound temperature. The effect showed that both ultrasound time and ultrasound temperature affected the anthocyanin concentration. Fig. 6 presented the effect of powder dosage and ultrasound temperature on the anthocyanin concentration. The concentration increased significantly with the increase of powder dosage at a fixed ultrasound temperature, whereas, the plot showed relatively flat as increasing ultrasound temperature at a fixed powder dosage. It indicated that the powder dosage had a remarkable effect on the concentration, but the ultrasound temperature showed a less effect. The plot based on powder dosage and ultrasound time (Fig.7) showed a marked increase in anthocyanin concentration when increasing the powder dosage at a fixed ultrasound time; while increasing the ultrasound time, the anthocyanin concentration was also increased. It indicated that both the powder dosage and ultrasound time had significant effects on the anthocyanin concentration. The results observed from the response surface plots were accordance with the variance analysis of binomial fitting equation as shown in Table 4. The reason of the anthocyanin concentration increase with the powder dosage was that the extracting solvent was fully contacted with more purple sweet potato powder, and more colorant was transferred into ATPS. The reason of the anthocyanin concentration increase with the ultrasound time was that with the increase of ultrasound time, there was more anthocyanin to dissolve in the solvent, and a high anthocyanin concentration was obtained.
13
ACCEPTED MANUSCRIPT
Fig. 5 Response surface plot showing the effect of ultrasound temperature and time
Fig. 6 Response surface plot showing the effect of powder dosage and temperature
Fig. 7 Response surface plot showing the effect of ultrasound time and powder dosage On the basis of model fitting and variance analysis, the program Design-Expert version 8.0.6.1 was used to optimize the conditions of the ultrasound-assisted ATPS extraction of natural colorant anthocyanin from purple sweet potato. The optimal ultrasound-assisted ATPS extracting conditions were dosage of 1.60 g of purple sweet potato powder, ultrasound temperature of 52.48 °C and ultrasound time of 48.19 min. In the case of extracting 14
ACCEPTED MANUSCRIPT conditions, 191.09 mg.L-1 natural colorant anthocyanin was obtained in the upper ethanol-rich phase of ATPS. Mageste et al. (Mageste et al., 2012) used the similar ATPS demonstrated the possible use for the extraction of the natural dye norbixin, due to the high value found in the dye partition coefficient in such systems. From developing mathematical models and response surfaces optimization, they obtained a qualitative conclusion that increases in the concentrations of polymer and electrolyte typically promoted increases in the value of norbixin partition coefficient. Whereas, a more precise optimization condition to extract natural colorant was summarized in this experiment. Also, the abstraction procedures were simplified, and the ultrasound-assisted technology in the extracting process reduced the solvent in this process. There was no polluting solvent and chemicals using in the colorant extracting process, and it conformed to the requirements of ecological and environmental protection. 3.4 Dyeing properties of silk fabric Table 5 The dyeing K/S value and fastness of the silk fabrics with extracted natural colorant anthocyanin Rubbing fastness (grade) Dyeing methods
Washing fastness (grade)
K/S Value Dry
Wet
Change
Stain
Direct dyeing
3.2
4
3
2
4-5
Mordant dyeing
4.5
4-5
4
3-4
4-5
The extracted natural colorant anthocyanin was used to dye silk fabric, and the K/S value and the fastness were discussed (Table 5). In the dyeing process, the K/S value of the silk fabric with extracted natural colorant anthocyanin was 3.2 via the direct dyeing method, while using mordant dyeing method, the K/S value was 4.5. The increasement of the mordant dyeing was 40.6% compared to that of the direct dyeing method. Besides, the dry and wet rubbing fastness using mordant dyeing method were 4-5 and 4 grade, respectively, increasing by half and one grade compared to the rubbing fastness of fabric treated with direct dyeing method, respectively. The change and stain washing fastness using mordant dyeing method were 3-4 and 4-5 grade, respectively, and 15
ACCEPTED MANUSCRIPT the washing change fastness was increased by 1.5 grade compared to the washing fastness of fabric treated with direct dyeing method. The small quantity of aluminum ion in the mordant could combined with anthocyanin from purple sweet potato and silk via –OH in anthocyanin and -NH2, -NH-, -C=O, -COOH, –OH in silk (Fig. 8), so the natural colorant anthocyanin could be fixed onto the silk and the fastness was improved, significantly. For the high reaction activity in mordant process, there was nearly no aluminum ion in the residual dyeing solution. After mordant process, although some natural colorant anthocyanin was in the residual dyeing solution, which would drain into environment, the natural colorant anthocyanin was easily degraded in nature condition, and where was no additional environmental pollution.
Fig. 8 Al3+ mordant mechanism between silk and natural colorant anthocyanin 4.
Conclusions The present study revealed the feasibility of using central composite design-response surface methodology
to optimize the eco-friendly ultrasound-assisted ammonium sulfate/ethanol aqueous two-phase system extraction of anthocyanin from purple sweet potato powder. The extracted natural colorant was used to dye silk fabric. Based on single-factor extracting experiment, central composite design-response surface methodology results showed that the binomial model was highly significant and applied to fit to experimental data, due to its higher related coefficient compared to the multiple linear model. Via optimizing, the extracting process was 16
ACCEPTED MANUSCRIPT selected as powder dosage 1.60 g, ultrasound temperature 52.48 °C and ultrasound time 48.19 min. Under these conditions, 191.09 mg.L-1 natural colorant anthocyanin was obtained in the upper phase of aqueous two-phase system. The color strength value increasement of the silk fabric treated with mordant dyeing method was 40.6% compared to that of the direct dyeing method. The dry and wet rubbing fastness using mordant dyeing method were 4-5 and 4 grade, respectively. The change and stain washing fastness were 3-4 and 4-5 grade, respectively. It can be concluded that use of eco-friendly ultrasound-assisted ammonium sulfate/ethanol aqueous two-phase system is very promising concept as an alternative method that may help to reduce the reliance on solvent and simplify the exact procedures, and the natural colorant anthocyanin extraction from plant and dyeing fabric presents a good potential to produce environmental friendly textile material for safe use in textile industry. In view of these attractive properties and environmental protection, the natural dye from purple sweet potato powder can be applied as commercial natural colorant and has a significant potential market. Acknowledgements The authors are grateful for the financial support of the National Natural Science Foundation of China (51403083), the China Postdoctoral Science Foundation (1064130201160130), the Fundamental Research Funds for the Central Universities (JUSRP51724B and JUSRP51514) and the International Joint Research Laboratory for Advanced Functional Textile Materials of Jiangnan University. References Ahmad, A.L., Derek, C.J.C., Zulkali, M.M.D., 2008. Optimization of thaumatin extraction by aqueous twophase system (ATPS) using response surface methodology (RSM). Separation And Purification Technology. 62, 702-708. Ali, S., Hussain, T., Nawaz, R., 2009. Optimization of alkaline extraction of natural dye from Henna leaves and its dyeing on cotton by exhaust method. Journal of Cleaner Production. 17, 61-66. 17
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ACCEPTED MANUSCRIPT Li, X.Y., Ma, H.Y., Huang, H.L., Li, D.F., Yao, S., 2013. Natural anthocyanins from phytoresources and their chemical researches. Natural Product Research. 27, 456-469. Liu, X., Yang, D.L., Liu, J.J., Xu, K., Wu, G.H., 2014. Modeling of supercritical fluid extraction of flavonoids from Calycopteris floribunda leaves. Chemical Papers. 68, 316-323. Liu, X.L., Mu, T.H., Sun, H.N., Zhang, M., Chen, J.W., 2013. Optimisation of aqueous two-phase extraction of anthocyanins from purple sweet potatoes by response surface methodology. Food Chemistry. 141, 3034-3041. Mageste, A.B., de Lemos, L.R., Ferreira, G.M.D., da Silva, M.D.H., da Silva, L.H.M., Bonomo, R.C.F., Minim, L.A., 2009. Aqueous two-phase systems: An efficient, environmentally safe and economically viable method for purification of natural dye carmine. Journal of Chromatography A. 1216, 7623-7629. Mageste, A.B., Senra, T.D.A., da Silva, M.C.H., Bonomo, R.C.F., da Silva, L.H.M., 2012. Thermodynamics and optimization of norbixin transfer processes in aqueous biphasic systems formed by polymers and organic salts. Separation And Purification Technology. 98, 69-77. Passos, C.P., Silva, R.M., Da Silva, F.A., Coimbra, M.A., Silva, C.M., 2009. Enhancement of the supercritical fluid extraction of grape seed oil by using enzymatically pre-treated seed. Journal of Supercritical Fluids. 48, 225-229. Pina, F., Hatton, T.A., 2008. Photochromic soft materials: Flavylium compounds incorporated into pluronic F127 hydrogel matrixes. Langmuir. 24, 2356-2364. Rahimi, S., Ehrampoush, M.H., Ghaneian, M.T., Reshadat, S., Fatehizadeh, A., Ahmadian, M., Ghanizadeh, G., Rahimi, S., 2013. Application of TiO2/UV-C Photocatalytic Process in Removal of Reactive Red 198 Dye from Synthetic Textile Wastewater. Asian Journal of Chemistry. 25, 7427-7432. Rouskova, M., Heyberger, A., Triska, J., Krticka, M., 2011. Extraction of phytosterols from tall oil soap using 19
ACCEPTED MANUSCRIPT selected organic solvents. Chemical Papers. 65, 805-812. Shao, M.Y., Li, N., Shi, J.Y., Jiang, C.F., Lei, L., Zhang, H.Q., Yu, A.M., 2013. Ionic liquid-based ultrasoundassisted aqueous two-phase extraction of the pyrethroid insecticides in tea drinks. Analytical Methods. 5, 2529-2535. Shen, S.F., Chang, Z.D., Liu, J.H., Sun, X., Hu, X., Liu, H.Z., 2007. Separation of glycyrrhizic acid and liquiritin from Glycyrrhiza uralensis Fisch extract by three-liquid-phase extraction systems. Separation and Purification Technology. 53, 216-223. Simic, V.M., Rajkovic, K.M., Stojicevic, S.S., Veliclovic, D.T., Nikolic, N.C., Lazic, M.L., Karabegovic, I.T., 2016. Optimization of microwave-assisted extraction of total polyphenolic compounds from chokeberries by response surface methodology and artificial neural network. Separation And Purification Technology. 160, 89-97. Sinha, K., Aikat, K., Das, P., Datta, S., 2016. Dyeing of Modified Cotton Fiber with Natural Terminalia arjuna Dye: Optimization of Dyeing Parameters Using Response Surface Methodology. Environmental Progress & Sustainable Energy. 35, 719-728. Sinha, K., Das Saha, P., Datta, S., 2012. Extraction of natural dye from petals of Flame of forest (Butea monosperma) flower: Process optimization using response surface methodology (RSM). Dyes and Pigments. 94, 212-216. Swamy, G.J., Sangamithra, A., Chandrasekar, V., 2014. Response surface modeling and process optimization of aqueous extraction of natural pigments from Beta vulgaris using Box-Behnken design of experiments. Dyes and Pigments. 111, 64-74. Wu, X.Y., Liang, L.H., Zou, Y., Zhao, T., Zhao, J.L., Li, F., Yang, L.Q., 2011. Aqueous two-phase extraction, identification and antioxidant activity of anthocyanins from mulberry (Morus atropurpurea Roxb.). 20
ACCEPTED MANUSCRIPT Food Chemistry. 129, 443-453. Wu, Y.C., Wang, Y., Zhang, W.L., Han, J., Liu, Y., Hu, Y.T., Ni, L., 2014. Extraction and preliminary purification of anthocyanins from grape juice in aqueous two-phase system. Separation and Purification Technology. 124, 170-178. Yang, Z.D., Zhai, W.W., 2010. Optimization of microwave-assisted extraction of anthocyanins from purple corn (Zea mays L.) cob and identification with HPLC-MS. Innovative Food Science & Emerging Technologies. 11, 470-476. Yin, Y.J., Huang, R.H., Zhang, W., Zhang, M., Wang, C.X., 2016. Superhydrophobic-superhydrophilic switchable wettability via TiO2 photoinduction electrochemical deposition on cellulose substrate. Chemical Engineering Journal. 289, 99-105. Yin, Y.J., Wang, C.X., Wang, C.Y., 2008. An evaluation of the dyeing behavior of sol-gel silica doped with direct dyes. Journal of Sol-Gel Science and Technology. 48, 308-314. Zhang, B., Wang, L., Luo, L.F., King, M.W., 2014. Natural dye extracted from Chinese gall - the application of color and antibacterial activity to wool fabric. Journal of Cleaner Production. 80, 204-210. Zhao, Q., Feng, H., Wang, L.J., 2014. Dyeing properties and color fastness of cellulase-treated flax fabric with extractives from chestnut shell. Journal of Cleaner Production. 80, 197-203. Zhi, W.B., Deng, Q.Y., 2006. Purification of salvianolic acid B from the crude extract of Salvia miltiorrhiza with
hydrophilic
organic/salt-containing
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21
system
by
counter-current
ACCEPTED MANUSCRIPT Table Captions
Table 1 Factors and levels of central composite design Table 2 Experimental design and response of the central composite Table 3 Multiple linear and binomial fitting equations Table 4 Analysis variance of binomial fitting model for the anthocyanin concentration Table 5 The dyeing K/S value and fastness of the silk fabric with extracted natural colorant anthocyanin
Figure Captions
Fig. 1 Basic chemical structure of anthocyanin Fig. 2 Effect of ultrasound temperature on the anthocyanin concentration Fig. 3 Effect of ultrasound time on the anthocyanin concentration Fig. 4 Effect of powder dosage on the anthocyanin concentration Fig. 5 Response surface plot showing the effect of ultrasound temperature and time Fig. 6 Response surface plot showing the effect of powder dosage and temperature Fig. 7 Response surface plot showing the effect of ultrasound time and powder dosage Fig. 8 Al3+ mordant mechanism between silk and natural colorant anthocyanin
22
Yunjie Yin, Jiru Jia, Ting Wang, Chaoxia Wang PII:
S0959-6526(17)30360-8
DOI:
10.1016/j.jclepro.2017.02.134
Reference:
JCLP 9060
To appear in:
Journal of Cleaner Production
Received Date:
08 July 2016
Revised Date:
17 February 2017
Accepted Date:
18 February 2017
Please cite this article as: Yunjie Yin, Jiru Jia, Ting Wang, Chaoxia Wang, Optimization of natural anthocyanin efficient extracting from purple sweet potato for silk fabric dyeing, Journal of Cleaner Production (2017), doi: 10.1016/j.jclepro.2017.02.134
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Highlights
1.
Aqueous two-phase system was used to extract natural colorant anthocyanin.
2.
To enhance mass-transfer, ultrasound was used to assist the ATPS extraction.
3.
The dyed silk fabric presented excellent K/S value and color fastness.
ACCEPTED MANUSCRIPT Optimization of natural anthocyanin efficient extracting from purple sweet potato for silk fabric dyeing Yunjie Yin, Jiru Jia, Ting Wang, Chaoxia Wang* Key Laboratory of Eco-Textile, Ministry of Education, School of Textiles & Clothing, Jiangnan University, Wuxi 214122, China Corresponding author: Prof. Chaoxia Wang; E-mail: [email protected] Abstract The main objective of this study is to extract natural colorant anthocyanin from purple sweet potato powder via ultrasound-assisted ammonium sulfate/ethanol aqueous two-phase system, and this method can avoid the serious environment pollution during the preparation and use process of synthetic dye, reduce the solvent and simplify the abstraction procedures. The extracted natural colorant anthocyanin was used to dye silk fabric in a relatively ecological approach. Based on the single-factor extracting experiment, central composite designresponse surface methodology was employed to optimize the ultrasound-assisted aqueous two-phase system extracting conditions including ultrasound temperature, ultrasound time and dosage of purple sweet potato powder. The binomial model was highly significant and applied to fit the experimental data, due to its higher related coefficient. Via optimizing, a dosage of 1.60 g purple sweet potato powder was dispersed in ultrasound bath at 52.48 °C for 48.19 min. In the case of extracting conditions, 191.09 mg.L-1 natural colorant anthocyanin was produced in the upper ethanol-rich phase of the aqueous two-phase system. The color strength value of the silk fabric treated with mordant dyeing method was 4.5, and increased by 40.6% compared to that of the direct dyeing method. The dry and wet rubbing fastness using mordant dyeing method were 4-5 and 4 grade, respectively. The change and stain washing fastness using mordant dyeing method were 3-4 and 4-5 grade, respectively. This study demonstrates that developed natural colorant extracted from plant could be successfully employed as an effective and eco-friendly alternative cleaner to replace synthetic colorant gradually using in textile dyeing industry. Keywords: aqueous two-phase system; ultrasound-assisted extraction; anthocyanin; dyeing property; silk fabric 1. Introduction 1
ACCEPTED MANUSCRIPT The textile industry is the largest consumer of colorants. During the dyeing process, a large percentage of the synthetic colorants does not bind or absorbed to the fibers, and they are left in the waste stream. The residual colorants are released into the environment during dyeing process, making the effluent highly colored and aesthetically unpleasant (Bafana et al., 2011). The effluent from textile industries carries a large number of colorants and other additives which are added during the dyeing process (Rahimi et al., 2013). Also, during the synthetic process of synthetic colorant, many kinds of solvents and chemical intermediates are used, and the toxic chemicals bring serious pollution and harm to environment and our bodies (Gupta and Suhas, 2009). Natural colorant, differing from synthetic colorant, usually comes from plant sources - roots, berries, bark, leaves and wood (Devi and Karuppan, 2015). The resources of natural colorant are multiple. Hou, et al. (Hou et al., 2013) report a novel application of using abundant, cheap and readily available agricultural byproduct orange peel as a new natural dye with strong ultraviolet absorbance, and used to dye wool fabrics. The dyed fabric could impart textiles with remarkable UV-protection properties. Ismal, et al. (Ismal et al., 2014) extracted a novel natural dye from outer green shell of almond fruit using chemical solvent free extraction, small amount of metallic mordant, natural mordant, auxiliary free dyeing and washing. They evaluated biomordant versus metal mordant and to reveal the substitution of the prevalent metal mordant for biomordant as renewable natural sources. Natural colorant is biodegradable and ecological (Ali et al., 2009). Anthocyanin is a biodegradable natural colorant which not only creates desirable colors, but also imparts some potential health benefits including anti-ultraviolet rays and insects resistance (Lee and Choung, 2011). Extensive studies have indicated that the major natural colorant in purple sweet potatoes is anthocyanin, which is a special water-soluble polyphenol compound and performs good heating stability compared to other sources of anthocyanin (Liu et al., 2014). Purple sweet potato anthocyanin exists in the form of anthocyanidin including proteins, polysaccharides and organic acids (Li et al., 2013). 2
ACCEPTED MANUSCRIPT The extraction of natural colorant anthocyanin can be carried out using the traditional organic solvent method, but the traditional solvent extraction is very time-consuming and requires relatively large quantities of solvents, such as ethanol and methanol (Rouskova et al., 2011). The consuming of enormous solvents does not conform to the requirements of ecological and environmental protection in modern factories (Zhang et al., 2014). Nowadays, various improved extracting methods have been developed for natural colorant extraction, such as microwave-assisted extraction (Yang and Zhai, 2010), enzymatic extraction (Passos et al., 2009) and supercritical fluid extraction (Cao and Ito, 2003; Liu et al., 2013). However, the cost related to the investment, operation and maintenance of some extractions have limited their application at large scale. Therefore, the development of simple, efficiency and relatively “green” extracting method becomes more attractive. Response surface methodology (RSM) is a collection of statistical and mathematical technique which is useful in many engineering applications for improving and optimizing processes, for analyzing the interactions between the response and the independent variables, and for predicting the response. Simic, et al (Simic et al., 2016) extracted polyphenolic compounds from the chokeberries (Aronia melanocarpa) using RSM and artificial neural network (ANN). The set of the optimal operational conditions, for example extraction time, solvent and energy consumption, which gave the maximum yield of total polyphenolic content, were concluded easily. Sinha et al. (Sinha et al., 2016) reported that the natural yellow-brown colorant extracted from the bark of Terminalia arjuna might be an alternative source of synthetic dyes for the potential dyeing cotton fiber, and the dye uptake as well as surface color strength of dyed cotton were studied in batch experiments and optimized by using response surface methodology. In recent decades, the aqueous two-phase system (ATPS) has been applied to extracting field. ATPS is usually composed of two or more polymers, a polymer and a salt, or two surfactants including quaternary ammonium surfactants and anionic surfactants (Shao et al., 2013). Short chain alcohol and inorganic salt also can form an aqueous two-phase system. This type of ATPS offers several advantages, 3
ACCEPTED MANUSCRIPT including low cost, high efficiency and simple scale-up (Guo et al., 2012). Generally, ATPS is used as a separation step to obtain molecules from a previously prepared aqueous solution (Ahmad et al., 2008; Wu et al., 2014). The technology has been used to extract quantities of natural small molecule from herbs and other natural dyes (Shen et al., 2007; Zhi and Deng, 2006). Some reports indicated that using ultrasound-assisted exacting or ammonium sulfate/ethanol aqueous twophase system could improve the extraction efficiency, but the increase was not remarkable (Pina and Hatton, 2008; Shao et al., 2013). The authors combined both of the ultrasound-assisted exacting and ammonium sulfate/ethanol aqueous two-phase system method, and tried to improve the extraction efficiency. Specifically, in this study, a small number of ammonium sulfate/ethanol ATPS was used as a solvent to extract anthocyanin from purple sweet potatoes. To enhance mass transfer, ultrasound was used to assist the ATPS extraction. The extracted natural colorant anthocyanin was dissolved to dye the silk fabric. The effects of ultrasound temperature, ultrasound time and dosage of purple sweet potato powder on the anthocyanin concentration were investigated. And central composite design-response surface methodology was utilized to optimize the ultrasound-assisted ATPS extracting conditions. The color strength (K/S value) and dyeing fastness, including rubbing and washing were evaluated. 2.
Experimental
2.1 Chemicals and materials Purple sweet potato (Ningzishu No.1) gained from a local supermarket were sliced and oven-dried at 60 °C until the moisture content remained constant. Dried samples were smashed to powder using the FZ102 micro electric grinder (Tianjing Taisite Instrument Co., Ltd. China) and passed through 60-mesh sieve. Ammonium sulfate, ethanol and AlCl3 were obtained from Sinopharm Chemical Reagent Co., Ltd. (China) and analytically pure. Silk taffeta fabric (16.5 g.m ) was supplied by Wuxi Huiling Silk Co., Ltd (China). -2
4
ACCEPTED MANUSCRIPT 2.2 Extraction of purple sweet potato anthocyanin An ammonium sulfate/ethanol ATPS was prepared according to the previous research (Wu et al., 2011). Ammonium sulfate was weighed and dissolved in deionized water. A certain volume of absolute ethanol was added to make the mass fraction of ammonium sulfate 20% (w/w) and ethanol 30% (w/w). The contents were vortex-mixed and allowed to phase-separate to form ATPS, which consisted of an upper ethanol-rich phase and a lower salt-rich phase. A predetermined quantity of purple sweet potato powder was added into 20 g ammonium sulfate/ethanol ATPS which was prepared as the above method. Ultrasound dispersion was carried out using the SK3200LH ultrasound crasher (Shanghai Precision Instrument Co., Ltd. China) with fixed power (20 kHz). The ultrasound time and ultrasound temperature were controlled, respectively. After extraction, the extraction was filtered and the filtrate was placed until the two phases were completely separated. For further purification, the upper phase solution enriched natural colorant anthocyanin was centrifuged at 9000 rpm for 15 min using the TG16-WS high-speed centrifuge (Shanghai Luxiangyi Centrifuge Instrument Co., Ltd. China). The effect parameters, such as ultrasound temperature, ultrasound time and dosage of purple sweet potato powder, extracting from purple sweet potato colorant were characterized by the concentration of natural colorant anthocyanin which enriched in the upper phase solution. The basic chemical structure of exacted anthocyanin is shown in Fig. 1. OH OH
HO
O
OH OH
Fig. 1 Basic chemical structure of anthocyanin 2.3 Dyeing process for silk fabric 5
ACCEPTED MANUSCRIPT The dyeing experiments were carried out with silk fabric using metal-mordanting technique. A small quantity of mordant AlCl3 (3 g.L-1) was dissolved in colorant extraction. The wetted silk fabrics were impregnated into the dyeing solution at a liquor ratio of 1:50 in infra-red dyeing machine with the temperature gradient 3 °C.min-1. The dyed fabrics were washed and dried at room temperature. 2.4 Determination of the anthocyanin concentration The pH differential method was used to determine the total anthocyanin content enriched in the upper phase of ammonium sulfate/ethanol ATPS (Hosseinian et al., 2008). Two different standard buffer solutions were prepared, The one was prepared using 1 mol.L-1 sodium acetate, 1 mol.L-1 hydrochloric acid and distilled water (10:6:9, v: v: v, pH = 4.5) and the other using 0.2 mol.L-1 potassium chloride and 0.2 mol.L-1 hydrochloric acid (25:67,v:v, pH = 1.0). The upper phase solution of ultrasound-assisted ATPS extraction of anthocyanin was centrifuged and then diluted with two prepared buffer solutions above, respectively. The diluted solutions were left undisturbed for 6 h. The absorbance of each diluted solution was measured at 500 nm and 700 nm against distilled water as blank using the UV2802S UV-Vis spectrophotometer (Shanghai Unico Instrument Co., Ltd.). The anthocyanin concentration (Y, mg.L-1) was evaluated using the following definition and expressed as Cy-3glc equivalents:
Y
A MW DF 1000 L
(1)
where A is the absorbance ((A520nm-A700nm)pH=1-(A520nm-A700nm)pH=4.5), and the absorbance at 700 nm is used to eliminate the effect of liquid turbidity. MW is the molecular weight for Cy-3-glc (449.2 g.mol-1), DF is the dilution factor, ε is the extinction coefficient (26,900 L.(cm × mol)-1), and L is the path length (1cm). 2.5 Color and color fastness measurements The color properties of the fabrics were measured by an Xrite-8400 spectrophotometer under the illuminant D65 using a 10° standard observer. The relative color strength, denoted by the K/S value, is determined with the 6
ACCEPTED MANUSCRIPT Kubelka-Munk equations,
K /S
(1 R) 2 2R
(2)
where K is the absorption coefficient, S is the scattering coefficient and R is the fractional reflectance (value from 0 to 1) of the fabric sample at the wavelength of minimum reflectance (Yin et al., 2008; Zhao et al., 2014). The K/S value is proportional to the color strength of the fabric sample. Rubbing fastness was performed by rubbing the dyed fabric with dry and wet standard rubbing clothes in 10 cycles using a Y571 rubbing fastness tester (Electron Instrument Co., Ltd., Laizhou, China), respectively. The stains of the clothes cloths were measured by an X-Rite 8400 spectrophotometer according to AATCC 82007 standard. The washing fastness was tested according to the ISO 105-C10:2010 (E) standard (Yin et al., 2016). The samples were washed using 3 g.L-1 soap at 40 °C for 30 min by a 12-A washing fastness tester supplied by Wenzhou Darong Textile Instrument Co., Ltd. (China). 2.6 Experimental design and statistical analysis A five-level three-factor central composite design was chosen for optimization with respect to three independent variables including ultrasound temperature, ultrasound time and dosage of purple sweet potato powder. The response variable was the concentration of natural colorant anthocyanin in the upper phase, and the optimal conditions determined by single-factor experiment were at the central point. The factors and levels of central composite design are shown in Table 1. The experimental data were analyzed using the Design-Expert version 8.0.6.1 and fitted to multiple linear model and binomial model (Sinha et al., 2012). The quality of model fit was expressed by the correlation coefficient R2, and its statistical significance was confirmed using the p value. Analysis of variance and response surface methodology were carried out after selecting the most accurate model. Table 1 Factors and levels of central composite design 7
ACCEPTED MANUSCRIPT
3.
Factors
Symbol
Ultrasound temperature (°C)
Levels -1.732
-1
0
1
1.732
A
32.7
40
50
60
67.3
Ultrasound time (min)
B
23
30
40
50
57
Powder dosage (g)
C
1.05
1.20
1.40
1.60
1.75
Results and discussion
3.1 Ultrasound-assisted ATPS extraction The ultrasound-assisted ATPS extraction was carried out at different temperatures (30-70 °C) for 30 min with 1.0 g purple sweet potato powder. The effect of ultrasound temperature on the concentration of natural colorant anthocyanin in the upper phase of ATPS was shown in Fig. 2. The data indicated that the anthocyanin concentration was increased with the temperature until 50 °C, and then gradually decreased. In terms of ultrasound-assisted ATPS extraction, purple sweet potato anthocyanin was mainly concentrated in the upper ethanol-rich phase, whereas the impurities including proteins, polysaccharides and organic acids were mostly enriched in the lower salt-rich phase. During the lower ultrasound temperature stage, the adsorption forces between anthocyanin molecule and impurity were broken with increasing temperature. Anthocyanin molecules moved rapidly, and most anthocyanin transferred into the ethanol-rich phase of ATPS (Mageste et al., 2009). A high ultrasound temperature could increase the penetrability of cell membrane of purple sweet potatoes to facilitate anthocyanin extraction. However, when the ultrasound temperature was above 50 °C, the purple sweet potato starch was easy to gelatinize, and some anthocyanin could be degraded and easily turn into colorless chalcone (Li et al., 2013; Pina and Hatton, 2008).
8
ACCEPTED MANUSCRIPT
Fig. 2 Effect of ultrasound temperature on the anthocyanin concentration To evaluate the effect of ultrasound time on the anthocyanin concentration, ultrasound time in range of 2060 min were performed. The ultrasound-assisted ATPS extraction was carried out at 50 °C with 1.0 g dried purple sweet potato powder. As shown in Fig. 3, the concentration of natural colorant anthocyanin in the upper phase of ATPS was increased with ultrasound duration during the former 40 min, and thereafter increased very slowly. Along with the increased ultrasound time, there was more natural colorant dissolving in the ATPS, so the anthocyanin concentration was high. However, too long heating time could not obviously increase the anthocyanin concentration in the upper phase of ATPS any more. It was because that the ultrasound-assisted ATPS extraction of natural colorant anthocyanin had reached equilibrium via ultrasound for more than 40 min, and extending ultrasound time could not improve the extracting efficiency. So an ultrasound time of 40 min was chosen due to high extracting efficiency and energy saving.
9
ACCEPTED MANUSCRIPT
Fig. 3 Effect of ultrasound time on the anthocyanin concentration Different dosage (0.4-1.6 g) of purple sweet potato powder was placed into the prepared ATPS, and the extracting experiment was carried out at 50 °C for 40 min. Fig 4 showed that the effect of powder dosage on the anthocyanin concentration. In the initial stage, the concentration of natural colorant anthocyanin in the upper phase of ATPS was increased linearly with increasing dosage of purple sweet potato powder, and then kept a gentle increase when the dosage was higher than 1.4 g. The reason was that as increasing the powder dosage, the extracting solvent was fully contacted with purple sweet potato powder, and more colorants were transferred into ATPS. However, the amount of colorants dissolving in ATPS would get to the saturation point, so even with further increase of dosage powder, the concentration of natural colorant anthocyanin the upper phase of ATPS changed slightly.
Fig. 4 Effect of powder dosage on the anthocyanin concentration 10
ACCEPTED MANUSCRIPT 3.2 Modeling of ultrasound-assisted ATPS extraction Based on the single-factor extracting experiment, a five-level three-factor central composite design according to Table 1 was implemented in order to optimize the ultrasound-assisted ATPS extracting conditions of natural colorant anthocyanin. The experimental design and response of the central composite were presented. Experimental data according to Table 2 were analyzed using the program Design-Expert version 8.0.6.1 (Sinha et al., 2012), and fitted to multiple linear model and binomial model. After application of Design-Expert version, the regression models of the purple sweet potato anthocyanin extraction can be described in Table 3. The quality of the model fit was expressed by the correlation coefficient R2, and its statistical significance was confirmed using the p value. The closer the value of R2 to 1, the higher the quality of the model fit. When the p value for the model was at the 5% level (P<0.05), the regression model is accepted. Otherwise, the p value for lack of fit was higher than 0.05 (Guo et al., 2013). Table 2 Experimental design and response of the central composite No
A (°C)
B (min)
C (g)
Y (mg L-1)
1
40
30
1.20
115.49
2
60
30
1.20
118.03
3
40
50
1.20
146.90
4
60
50
1.20
152.29
5
40
30
1.60
164.65
6
60
30
1.60
177.68
7
40
50
1.60
185.93
8
60
50
1.60
189.42
9
32.7
40
1.40
103.75
10
67.3
40
1.40
134.84
11
50
23
1.40
106.61
12
50
57
1.40
163.65
13
50
40
1.05
119.30
14
50
40
1.75
184.34
15~20
50
40
1.40
165.62
11
ACCEPTED MANUSCRIPT In Table 3, the p values of the models (one for 0.0003, another for 0.0019) were all lower than 0.05, so both models might be accepted and could adequately account for the variation observed. However, the R2 value (0.8737) of binomial fitting model was closer to 1, compared to the R2 value (0.6863) of multiple linear fitting model. The binomial fitting model was more appropriate and used to predict the anthocyanin concentration in the upper phase of ATPS. Results of the analysis variance of binomial fitting model for the anthocyanin concentration were presented in Table 4. The binomial fitting model, ultrasound time (B), powder dosage (C) and quadratic term of ultrasonic temperature (A2) showed highly significant influence (P<0.01) on the anthocyanin concentration. Table 3 Multiple linear and binomial fitting equations Regression models
Correlation
Fitting equations
coefficient
Y=-80.37001+0.55928A+1.41062B
Multiple linear model
+106.29378C
P value
0.6863
0.0003
0.8737
0.0019
Y=-577.04661+11.60597A+9.63400B+ Binomial model
204.62503C-8.36250×10-3AB+0.53687AC2.04063BC
-0.11464A2-0.061855B2-15.55357C2
Table 4 Analysis variance of binomial fitting model for the anthocyanin concentration Sum of
Degrees of
squares
freedom
12159.11
A
Source of variation
Mean square
F-value
P value
9
1351.01
7.69
0.0019
437.91
1
437.91
2.49
0.1456
B
2785.77
1
2785.77
15.85
0.0026
C
6327.09
1
6327.09
35.99
0.0001
AB
5.59
1
5.59
0.03
0.8620
AC
9.22
1
9.22
0.05
0.8234
BC
133.25
1
133.25
0.76
0.4044
A2
2069.85
1
2069.85
11.78
0.0064
B2
602.60
1
602.60
3.43
0.0938
C2
6.10
1
6.10
0.04
0.8560
Residual error
1757.83
10
175.78
Total
13916.94
19
Model
12
ACCEPTED MANUSCRIPT 3.3 Effects of extracting conditions on the anthocyanin concentration Response surface methodology was used to investigate the interaction between the variables on the concentration of natural colorant anthocyanin in the upper phase of ATPS (Swamy et al., 2014). The response surface plots constructed according to the binomial fitting equation with one fixed independent variable were discussed. In Fig. 5, an increase in the anthocyanin concentration was observed with increasing ultrasound time at a fixed ultrasound temperature, and the anthocyanin concentration increased with increasing ultrasound temperature. The effect showed that both ultrasound time and ultrasound temperature affected the anthocyanin concentration. Fig. 6 presented the effect of powder dosage and ultrasound temperature on the anthocyanin concentration. The concentration increased significantly with the increase of powder dosage at a fixed ultrasound temperature, whereas, the plot showed relatively flat as increasing ultrasound temperature at a fixed powder dosage. It indicated that the powder dosage had a remarkable effect on the concentration, but the ultrasound temperature showed a less effect. The plot based on powder dosage and ultrasound time (Fig.7) showed a marked increase in anthocyanin concentration when increasing the powder dosage at a fixed ultrasound time; while increasing the ultrasound time, the anthocyanin concentration was also increased. It indicated that both the powder dosage and ultrasound time had significant effects on the anthocyanin concentration. The results observed from the response surface plots were accordance with the variance analysis of binomial fitting equation as shown in Table 4. The reason of the anthocyanin concentration increase with the powder dosage was that the extracting solvent was fully contacted with more purple sweet potato powder, and more colorant was transferred into ATPS. The reason of the anthocyanin concentration increase with the ultrasound time was that with the increase of ultrasound time, there was more anthocyanin to dissolve in the solvent, and a high anthocyanin concentration was obtained.
13
ACCEPTED MANUSCRIPT
Fig. 5 Response surface plot showing the effect of ultrasound temperature and time
Fig. 6 Response surface plot showing the effect of powder dosage and temperature
Fig. 7 Response surface plot showing the effect of ultrasound time and powder dosage On the basis of model fitting and variance analysis, the program Design-Expert version 8.0.6.1 was used to optimize the conditions of the ultrasound-assisted ATPS extraction of natural colorant anthocyanin from purple sweet potato. The optimal ultrasound-assisted ATPS extracting conditions were dosage of 1.60 g of purple sweet potato powder, ultrasound temperature of 52.48 °C and ultrasound time of 48.19 min. In the case of extracting 14
ACCEPTED MANUSCRIPT conditions, 191.09 mg.L-1 natural colorant anthocyanin was obtained in the upper ethanol-rich phase of ATPS. Mageste et al. (Mageste et al., 2012) used the similar ATPS demonstrated the possible use for the extraction of the natural dye norbixin, due to the high value found in the dye partition coefficient in such systems. From developing mathematical models and response surfaces optimization, they obtained a qualitative conclusion that increases in the concentrations of polymer and electrolyte typically promoted increases in the value of norbixin partition coefficient. Whereas, a more precise optimization condition to extract natural colorant was summarized in this experiment. Also, the abstraction procedures were simplified, and the ultrasound-assisted technology in the extracting process reduced the solvent in this process. There was no polluting solvent and chemicals using in the colorant extracting process, and it conformed to the requirements of ecological and environmental protection. 3.4 Dyeing properties of silk fabric Table 5 The dyeing K/S value and fastness of the silk fabrics with extracted natural colorant anthocyanin Rubbing fastness (grade) Dyeing methods
Washing fastness (grade)
K/S Value Dry
Wet
Change
Stain
Direct dyeing
3.2
4
3
2
4-5
Mordant dyeing
4.5
4-5
4
3-4
4-5
The extracted natural colorant anthocyanin was used to dye silk fabric, and the K/S value and the fastness were discussed (Table 5). In the dyeing process, the K/S value of the silk fabric with extracted natural colorant anthocyanin was 3.2 via the direct dyeing method, while using mordant dyeing method, the K/S value was 4.5. The increasement of the mordant dyeing was 40.6% compared to that of the direct dyeing method. Besides, the dry and wet rubbing fastness using mordant dyeing method were 4-5 and 4 grade, respectively, increasing by half and one grade compared to the rubbing fastness of fabric treated with direct dyeing method, respectively. The change and stain washing fastness using mordant dyeing method were 3-4 and 4-5 grade, respectively, and 15
ACCEPTED MANUSCRIPT the washing change fastness was increased by 1.5 grade compared to the washing fastness of fabric treated with direct dyeing method. The small quantity of aluminum ion in the mordant could combined with anthocyanin from purple sweet potato and silk via –OH in anthocyanin and -NH2, -NH-, -C=O, -COOH, –OH in silk (Fig. 8), so the natural colorant anthocyanin could be fixed onto the silk and the fastness was improved, significantly. For the high reaction activity in mordant process, there was nearly no aluminum ion in the residual dyeing solution. After mordant process, although some natural colorant anthocyanin was in the residual dyeing solution, which would drain into environment, the natural colorant anthocyanin was easily degraded in nature condition, and where was no additional environmental pollution.
Fig. 8 Al3+ mordant mechanism between silk and natural colorant anthocyanin 4.
Conclusions The present study revealed the feasibility of using central composite design-response surface methodology
to optimize the eco-friendly ultrasound-assisted ammonium sulfate/ethanol aqueous two-phase system extraction of anthocyanin from purple sweet potato powder. The extracted natural colorant was used to dye silk fabric. Based on single-factor extracting experiment, central composite design-response surface methodology results showed that the binomial model was highly significant and applied to fit to experimental data, due to its higher related coefficient compared to the multiple linear model. Via optimizing, the extracting process was 16
ACCEPTED MANUSCRIPT selected as powder dosage 1.60 g, ultrasound temperature 52.48 °C and ultrasound time 48.19 min. Under these conditions, 191.09 mg.L-1 natural colorant anthocyanin was obtained in the upper phase of aqueous two-phase system. The color strength value increasement of the silk fabric treated with mordant dyeing method was 40.6% compared to that of the direct dyeing method. The dry and wet rubbing fastness using mordant dyeing method were 4-5 and 4 grade, respectively. The change and stain washing fastness were 3-4 and 4-5 grade, respectively. It can be concluded that use of eco-friendly ultrasound-assisted ammonium sulfate/ethanol aqueous two-phase system is very promising concept as an alternative method that may help to reduce the reliance on solvent and simplify the exact procedures, and the natural colorant anthocyanin extraction from plant and dyeing fabric presents a good potential to produce environmental friendly textile material for safe use in textile industry. In view of these attractive properties and environmental protection, the natural dye from purple sweet potato powder can be applied as commercial natural colorant and has a significant potential market. Acknowledgements The authors are grateful for the financial support of the National Natural Science Foundation of China (51403083), the China Postdoctoral Science Foundation (1064130201160130), the Fundamental Research Funds for the Central Universities (JUSRP51724B and JUSRP51514) and the International Joint Research Laboratory for Advanced Functional Textile Materials of Jiangnan University. References Ahmad, A.L., Derek, C.J.C., Zulkali, M.M.D., 2008. Optimization of thaumatin extraction by aqueous twophase system (ATPS) using response surface methodology (RSM). Separation And Purification Technology. 62, 702-708. Ali, S., Hussain, T., Nawaz, R., 2009. Optimization of alkaline extraction of natural dye from Henna leaves and its dyeing on cotton by exhaust method. Journal of Cleaner Production. 17, 61-66. 17
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system
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counter-current
ACCEPTED MANUSCRIPT Table Captions
Table 1 Factors and levels of central composite design Table 2 Experimental design and response of the central composite Table 3 Multiple linear and binomial fitting equations Table 4 Analysis variance of binomial fitting model for the anthocyanin concentration Table 5 The dyeing K/S value and fastness of the silk fabric with extracted natural colorant anthocyanin
Figure Captions
Fig. 1 Basic chemical structure of anthocyanin Fig. 2 Effect of ultrasound temperature on the anthocyanin concentration Fig. 3 Effect of ultrasound time on the anthocyanin concentration Fig. 4 Effect of powder dosage on the anthocyanin concentration Fig. 5 Response surface plot showing the effect of ultrasound temperature and time Fig. 6 Response surface plot showing the effect of powder dosage and temperature Fig. 7 Response surface plot showing the effect of ultrasound time and powder dosage Fig. 8 Al3+ mordant mechanism between silk and natural colorant anthocyanin
22