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Biodegumming of ramie fiber with pectinases enhanced by oxygen plasma
Accepted Manuscript Biodegumming of ramie fiber with pectinases enhanced by oxygen plasma Ming Shen, Ling Wang, Jia-Jie Long PII:
S0959-6526(15)00321-2
DOI:
10.1016/j.jclepro.2015.03.081
Reference:
JCLP 5349
To appear in:
Journal of Cleaner Production
Received Date: 27 November 2014 Revised Date:
27 January 2015
Accepted Date: 28 March 2015
Please cite this article as: Shen M, Wang L, Long J-J, Biodegumming of ramie fiber with pectinases enhanced by oxygen plasma, Journal of Cleaner Production (2015), doi: 10.1016/j.jclepro.2015.03.081. 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.
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Biodegumming of ramie fiber with pectinases enhanced by oxygen plasma
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Ming Shen, Ling Wang, Jia-Jie Long* College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, China
(b) Oxygen plasma treated
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(a) Without any pretreatment
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Graphical Abstract
(c) Biodegummed with plasma-aided
The resultant word count: 6455 words in whole text files including tables and figure captions. ACCEPTED MANUSCRIPT
Biodegumming of ramie fiber with pectinases enhanced by oxygen plasma
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Ming Shen, Ling Wang, Jia-Jie Long*
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College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, China
*Corresponding author. Tel.:+86 0512 67164993; Fax: 086-0512-67246786 E-mail: [email protected] (Jia-Jie Long) 1
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Abstract
A novel biodegumming process with pectinases for ramie fiber was developed in combination with oxygen plasma, in order to improve the efficiency of enzymes in impurity degradation. The results show that a notable positive influence of oxygen plasma on the biodegumming of ramie was
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achieved, in comparison with a conventional biodegumming process. The fabric weight loss, capillary rise height and whiteness of ramie fabric were evidently improved by employing the oxygen plasma-aided biodegumming process with a half dosage of enzymes, in comparison with a
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conventional experiment at different temperatures, solution pH values and treatment times. An
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optimized plasma-aided biodegumming process for raw ramie fabric was recommended with a temperature of 75℃, a pH value of 8.0 in subjected solution for 60.0 min. Moreover, the role of oxygen plasma on ramie biodegumming was further confirmed by static water contact angle measurement and scanning electron microscopy (SEM) analysis.
1. Introduction
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Key words Ramie fiber; Biodegumming; Impurity removal; Enzyme; Oxygen plasma
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As one of the longest, strongest and oldest natural fibers, Ramie (Boehmeria nivea) is an important material for textile manufacturing, and is very popular with customers in the last decades
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(Xie, 2008; Wei, 2007). Ramie poses essentially advanced properties as an textile material, such as holding shape, less wrinkling, silky luster, special cooling feel, high absorbency, good air permeability, as well as a green, ecological and functional fiber, etc (Zheng etc., 2001; Liu, 1995). Whereas, as a bast fiber, decorticated ramie contains 20-30% gummy materials, mainly consisting of pectins and hemicelluloses, as well as other impurities (Jiang, 2011; Mukhopadhyay etc., 2013). Therefore, prior to industrial utilization, ramie fiber should be sufficiently degummed to remove the gummy materials and separate the spinnable cellulosic component. 2
ACCEPTED Moreover, in recent years, cleaner andMANUSCRIPT ecological pretreatment processes for textile manufacturing have been paid extensive attentions, such as the cleaner process for extraction of silk sericin using infrared (Gupta, et al., 2013), and the degumming of Persian silk by ultrasound and enzymes as a cleaner and environmentally friendly process (Mahmoodi, et al., 2010), as well as the
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usability of ultrasound in scouring of raw wool for thermal energy, water and chemical savings (Bahtiyari and Duran, 2013), etc. Especially, the biodegumming processes with various enzymes for ramie fibers are very popular due to their clean, environmentally friendly, water and energy saving
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advantages, etc., in comparison with the conventionally chemical degumming processes (Zheng etc.,
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2001; Mukhopadhyay etc., 2013). Bruhlmann et al. (1994) reported the isolation and culture of the actinomycetes for production of pectinolytic enzymes and applied to ramie degumming process, they demonstrated that a good correlation between the pectate lyase activity and degumming effect was obtained for good separation of the bast fibers. Moreover, Bruhlmann et al. (2000) also
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investigated the degumming effects of different pectate lyase and other extracellular enzymes on ramie bast fibers, and revealed that the pectinolytic activity of the Amycolata sp. played a role in the ramie substrate degumming. Zheng et al. (2001) selected three strains of alkalophilic bacteria and
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their enzymes for removing residual gum from ramie fibers, and found that pectate lyase and
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xylanase played a role in the degradation of residual gum, in which the residual gum of the fibers decreased to 9.4% after 5.0 h by enzymatic degumming with improved fiber properties. Furthermore, Basu et al. (2009) investigated the production of pectate lyase from immobilized Bacillus pumilus DKS1 cells in calcium –alginate beads, and revealed that high-quality degummed ramie fibers could be prepared by applying the obtained enzymes at the first time. Mukhopadhyay et al. (2013) carried out the ramie degumming process with hydroxyapatite nanoparticle supplemented pectate lyase, and disclosed that raw and decorticated ramie fibers could be better
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ACCEPTED MANUSCRIPT degummed with nanoparticle supplemented pectate lyase than non-supplemented one in weight loss after 24.0 and 48.0 h of processing with an enhancement of fiber tenacity and fineness. However, those biodegumming processes described above are mild or gentle treatments for degradation of the organic polymer impurities with different enzymes; which usually involve a long
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treatment period, such as several hours and even several days (Bruhlmann et al., 1994; Mukhopadhyay et al., 2013). Furthermore, it is not sufficient or adequate to remove the incrusted gummy materials, as well as other impurities, from raw and /or decorticated ramie fibers by
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employing biodegumming treatment only due to its slow and low efficiency. Therefore, mild and
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conventional chemical treatments are necessary and usually applied in practice before or after the biodegumming processes to meet the requests of textile manufacturing (Kapoor et al., 2001). In addition, as well known to all, every enzyme poses unique characteristics and only plays a role for its individual and suitable substrate. Consequently, various enzymes and their synergistic actions are
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necessary for biodegumming processes to biodegrade the different impurities from raw and /or decorticated ramie fibers, which usually result in a higher treatment cost and complex situations in process control.
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Accordingly, it is very important and meaningful to develop some effective alternatives to
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conventionally chemical methods for improving the efficiency of biodegumming processes, with more environmentally friendly and cleaner production during the pretreatment of ramie substrates. Fortunately, low temperature plasma treatment is proved as a promising dry method to improve the efficiency of conventional processes with the reduction of water, chemicals and energy consumptions (Morent et al., 2008). In recent years, more and more applications of low temperature plasma are available for the textile pretreatments in combination with wet chemical processes, such as for the desizing of PVA on cotton with an atmospheric plasma (Cai et al., 2003), for the desizing
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or scouring of grey cotton withACCEPTED low-pressure MANUSCRIPT plasma (Wang et al., 2013), and for removal of different sizing agents on polyester fabrics (Bae et al., 2006), as well as for silk degumming (Long et al., 2008). Briefly, most of the reported applications of low temperature plasma in textile pretreatments
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are mainly combined with wet-chemical processes. However, very few works have been reported about the application of low temperature plasma to improve the efficiency in biodegumming of raw ramie fabric with enzymes, although their combination is very benefit to the cleaner production of
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textile and very desirable in ramie industry.
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The objective of the present work is to develop an effective and more environmentally friendly pretreatment method for ramie fabric degumming by combination of a low-temperature oxygen plasma treatment and a subsequent biodegumming with pectinases. The biodegumming parameters such as temperature, subjected solution pH and treatment time were investigated and optimized.
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Moreover, the plasma and biodegumming treatment effects on ramie substrate were further investigated and confirmed by static water contact angle measurement and scanning electron
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microscopy (SEM) analysis.
2. Experimental section
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2.1 Materials and chemicals
A commercial and raw ramie fabric (a woven, with a fabric weight of 127.2 g m-2) was kindly supplied by Chongqing Fuling Kinde group Co., Ltd. (Chongqing, China) in this study. The raw ramie fabric was cut into a dimension of 30.0 cm ×15.0 cm, and used as received without any other previous treatment. All raw ramie fabric samples were conditioned at 20℃±2℃ and 65%±3% relative humidity for 24.0 h before a measurement or testing. The employed pectinolytic enzyme of Hontonzyme DN (kindly supplied by Qingdao Hai Yin 5
MANUSCRIPT Da chemical co., LTD, China) forACCEPTED biodegumming of ramie fabric was a commercial product, and a mixture of different pectinases mainly containing polygalacturonases and pectinolytic lyases, etc. The toll activity of the employed enzyme of Hontonzyme DN was 300 U mL-1. Other chemicals used in experiments, such as sodium hydroxide, dilute sulfuric acid, penetrating agent JFC, etc.,
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were commercially available products. Pure oxygen gas (with a purity of 99.5% vol. - %) employed in low-temperature plasma treatment was purchased from Suzhou Jinhong gas Co., Ltd. (Jiangsu
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province, China).
2.2 Apparatus and procedures
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2.2.1 Low-temperature plasma treatment
The pretreatment of raw ramie fabric samples by low-temperature oxygen plasma was carried out in the same batch plasma system (HD-1, Suzhou Hongda plasma technology company, China) as described elsewhere (Long et al., 2008), with previously optimized parameters at a pressure of
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40.0 Pa and a discharge power of 250.0 W for 3.0 min. Before a low-temperature oxygen plasma treatment, the raw ramie fabric sample was dryed in an oven at 95℃ for 60 min, and then was hung
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vertically with a sample stand between the two parallel electrodes.
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2.2.2 Biodegumming treatment of ramie fabric samples A conventional biodegumming treatment with pectinolytic enzyme of Hontonzyme DN was performed for removing the gummy impurities of raw ramie fabric samples, as described with a flowchart in Figure 1.
The soaking treatment for samples was carried out in a solution involving 0.5 g L-1 of penetrating agent JFC at 25 ±1℃ for 30.0 min, in order to wet the dry ramie substrate and improve the uniform adsorption and penetration of enzymes into the substrate yarns at the following treatment. The biodegumming treatment was performed in a solution involving 10.0% (o.m.f.; on 6
ACCEPTED MANUSCRIPT the mass of fabric) of Hontonzyme DN at a material to liquor ratio of 1: 40, with temperature varying from 15℃ to 90℃, the pH value from 2.0 to 12.0 and treatment time from 30.0 min to 105.0 min. Theoretically, most of the gummy materials, especially for various pectins could be degraded and removed from the ramie substrate by the biodegumming treatment, as well as for
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other impurities partly. Moreover, a washing procedure was followed with tap water to remove the degraded residual impurities on the ramie fabric for further extraction of the substrate before the sample preparation for testing.
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The biodegumming of the ramie fabric samples after a previous treatment by oxygen plasma in
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this study was carried out in a mild condition and described with a flowchart in Figure 2. The mild biodegumming process for the treated ramie substrate with oxygen plasma was performed by employing half dosage of Hontonzyme DN at 5.0% (o.m.f.) at a shorter time of 50.0 min for most of experiments, and with the same other conditions and treatments as in the
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conventional biodegumming process.
Subsequently, all the samples were well rinsed with distilled warm water again and dried at room temperature. A weight loss, characterized for the total removal of gummy impurities (mainly
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consisting of pectins, as well as other impurities, etc.) from ramie substrate, was evaluated
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according to the equation (1):
Weight loss(%) =
W1 − W2 × 100% W1
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where W1, W2 refer to the conditioned fabric weight before and after a biodegumming treatment, respectively. An average weight loss value was obtained from 3 replicate measurements with a relative deviation of values within 3.0%. 2.2.3 Capillary rise height measurement of ramie fabric samples Capillary rise height is a direct and convenient index for fabric wettability or wickability in 7
ACCEPTED MANUSCRIPT practice. In this work, the capillary rise height measurement was carried out on a ramie fabric strip in warp direction (China textile criteria of FZ/T01071-2008, 2008; which references to ISO9073-6:2000) by employing a capillary rise measurement apparatus (ZBW 04019, Shanghai Luozhong institute, China). The fabric strip was suspended vertically with lower end immersed into
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a thin layer of potassium dichromate aqueous solution (1.0 wt. %) for 1.0 cm. A capillary rise height reading was made at a given time of 30.0 min under ambient temperature. An average height value
2.2.4 Fabric whiteness measurement for ramie samples
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was utilized from 3 replicate measurements with a relative deviation of values within 1.5%.
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A fabric whiteness value (Wr, namely the whiteness of R457) was measured according to China textile criteria of GB/T 17644-2008 (China textile criteria of GB/T 17644-2008, 2008; which is equal to ISO 2470 for ISO whiteness) with four-folded sample on a full-automatic fabric whiteness meter (WSB-3A, Nantong Hongda experiment instruments Co., Ltd., China) by
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employing a simulated D65 light source lamp and a 10˚ visual angle. An average value of 3 measurements was used with a relative deviation of values within 1.0%. The calculation method according to the cited criteria for the whiteness value (R457 or Wr) of fabric is shown as in equation
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(2):
(2)
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R457 (Wr ) = 0.925 × Z 10 + 1.16
where R457 or Wr, Z10 refer to the fabric whiteness value (or R457 whiteness) and the tristimulus value in the CIE 1931 color space, respectively; the subscript of “10” is for the CIE 1964 standard observer. 2.2.5 Tensile testing of ramie fabric samples Tensile testing of ramie fabric samples was performed on an electric and versatile material tensile apparatus (Instron 5900, Instron Co., Ltd., USA) by strip method (China textile criteria of
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MANUSCRIPT GB/T3923.1 -1997, 1997; whichACCEPTED is equal to ISO13934.1). The ramie fabric strip was made to a dimension of 5.0 cm × 35.0 cm in warp direction. The tensile strength of each fabric sample was an average result of four replicate measurements with a relative deviation of the testing results lower than 2.0%.
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2.2.6 Water contact angle measurement for ramie samples A static water contact angle (α, °) for ramie fabric samples was measured by employing the sessile drop method on an OCA 15Pro optical contact anger meter (Dataphysics Co., Ltd., Germany)
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at ambient temperature. Water droplet with a volume of 1.0 µL was dropped carefully onto the
different spots on a same sample was used.
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sample surface for measuring static water contact anger. An average value of 6 measurements at
2.2.7 Investigation of surface morphology for ramie substrate
The investigations of surface morphologies for ramie substrate before and after a treatment by
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oxygen plasma, as well as a subsequent biodegumming treatment in a mild condition, were carried out on a scanning electronic microscopy (SEM) (S-4800, Hitachi, Japan) at an acceleration voltage
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of 3.0 kV with 2000 × magnification. Before investigation, samples were sputtered with gold.
3. Results and discussion
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3.1 Influence of temperature on the plasma-aided biodegumming of raw ramie fabric An influence of treatment temperatures on the mild biodegumming of pretreated ramie fabric by oxygen plasma was investigated with a dosage of the Hontonzyme DN at 5.0% (o.m.f.), a solution pH at 8.0 and a treatment time of 50.0 min at different temperatures. The fabric weight loss, capillary rise height, whiteness and tensile strength were determined for all samples. Simultaneously, a conventional biodegumming process was also performed with a dosage of Hontonzyme DN at 10.0% (o.m.f.), a treatment time of 80.0 min and with other similar conditions as in the mild process. 9
The obtained results are depicted ACCEPTED in Figure 3-6. MANUSCRIPT Figure 3 shows that an increase in the weight loss of raw ramie fabric from the plasma-aided biodegumming process was achieved with the temperature from 15.0℃ to 75.0℃, and then an accelerated decrease in the weight loss was also observed as temperature higher than 75.0℃.
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Moreover, Figure 3 also shows that an increase in the weight loss of raw ramie fabric from the conventional biodegumming process was obtained with temperature from 15.0℃ to 30.0℃, however, no further improvement was observed as treatment temperature up to 90.0℃. In
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comparison with the conventional biodegumming process, a higher efficiency of the plasma-aided
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biodegumming process in fabric weight loss or impurity removal was observed at most of the applied treatment temperatures, although only a half dosage of the pectinases and a shorter treatment time were applied.
The above results indicate that the oxygen plasma treatment played a role in the
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biodegumming of ramie fabric with pectinases and presented a positive effect on the removal of gummy impurities, especially for pectin, etc. In principle, plasma is an ionized gas involving various excited, energetic and discharged species as its definition (Li et al., 1997; Yip et al., 2002).
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Therefore, the reactive and energetic oxygen plasma species could attack the encrusted gummy film
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and other impurities on ramie fibers effectively, and break them by physical and / or chemical etching effects due to chain scission and oxidation, etc. Thus, those etching effects resulted in a readily diffusion of the pectinases into the broken gummy films, and also led to an easy degradation of the broken pectin impurities. For example, some insoluble protopectins could be readily changed into soluble pectins, and a de-esterification of pectins and hydrolytic cleavage of the α-(1, 4)-glycosidic bonds could also be achieved easily, as well as for the swelling, hydrolyzing, dissolving of other natural impurities (Jayani etc., 2005; Wang etc., 2013). However, the accelerated
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ACCEPTED MANUSCRIPT decrease in the weight loss from the plasma -aided biodegumming process with temperature higher than 75.0℃, was probably due to an overhigh and undesirable treatment temperature for the enzymes. In fact, overhigh treatment temperature could readily result in the decrease of the enzymatic reactivity for the removal of gummy impurities from ramie substrate.
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Figure 4 is for the comparison of the plasma-aided biodegumming process and the conventional enzymatic one in the capillary rise height of treated ramie fabric samples at different temperature. It demonstrates that an improvement and similar increase tendencies of the capillary
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rise height of ramie fabrics from both the processes were achieved with the treatment temperature
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from 15.0℃ to 75.0℃, and then a decrease was also obtained as temperature higher than 75.0℃. During the pretreatment for textile manufacturing, the capillary rise height is a convenient and useful indirect indicator for impurity removal efficiency from a pretreatment process, especially for the removal of some hydrophobic impurities, such as pectins, waxes, fats, oils, etc. Consequently, a
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higher result of the capillary rise height usually demonstrates that more hydrophobic impurities were removed from the raw substrate, and a good wettability could be achieved. Therefore, the comparable wettability of the treated raw ramie substrate by the plasma-aided biodegumming
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process in comparison with the control experiments in Figure 4, further discloses that the oxygen
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plasma showed a positive effect on the enzymatic removal of those hydrophobic impurities. It is probably that those impurities were degraded and modified by physical bombardments and / or even chemically oxidized previously by the active oxygen plasma species, which resulting in a benefit for their further degradation by the pectinases in the subsequent biodegumming treatment. Figure 5 depicts the influence of the plasma-aided and conventional biodegumming processes on the ramie fabric whiteness at different temperatures. The obtained curves show that an improvement and a similar increase tendency in fabric whiteness (R457 /Wr) were observed for
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ACCEPTED MANUSCRIPT ramie fabric samples treated by both the biodegumming processes with solution temperature from 15.0℃ to 75.0℃, as well as a decrease in fabric whiteness as temperature higher than 75.0℃. Furthermore, Figure 5 also indicates that, an enhanced bleaching effect on the ramie substrate with higher whiteness was also achieved at all the tested temperatures from the plasma-aided
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biodegumming process in comparison with the convention biodegumming. Figure 6 demonstrates that a slight decrease tendency in fabric tensile strength was obtained with the applied temperatures for both the biodegumming processes. Moreover, a relative lower
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tensile strength of the ramie fabric samples from the plasma-aided biodegumming was also
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observed for all the treatment temperatures. Probably, it was due to the penetration of excited oxygen plasma species into the ramie fiber core and some harsher modifications occurred to the fiber macrochains.
By taking account into the all influences of the treatment temperatures on ramie fabric above,
biodegumming.
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a temperature of 75 ℃ was recommended in further experiments for raw ramie fabric
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3.2 Influence of solution pH on the plasma-aided biodegumming of raw ramie fabric An influence of pH value of subjected solution on the plasma-aided and mild biodegumming
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of ramie substrate was investigated with a dosage of the Hontonzyme DN at 5.0% (o.m.f.), a temperature of 75℃ and a treatment time of 50 min. A conventional biodegumming process was also carried out for comparison with a dosage of Hontonzyme DN at 10.0% (o.m.f.), a treatment time of 80.0 min and with other conditions similar as in the mild process. Figure 7 shows that a slight increase in the fabric weight loss from both the plasma-aided and conventional biodegumming processes was observed with the pH value from 4.0 to 8.0, and then a slight decrease tendency was also obtained as pH value further increased to 12.0, except for a 12
ACCEPTED MANUSCRIPT relative higher value appeared with pH value at 2.0. Furthermore, Figure 7 also reveals that a higher efficiency of the plasma-aided biodegumming in fabric weight loss was achieved at all the subjected solution pH, although a half dosage of the pectinases and a shorter treatment time were involved in comparison with the conventional biodegumming. It seems like that the pH value of the subjected
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solution showed a slight effect on the weight loss of the raw substrate in a wide range. However, the higher value of the fabric weight loss at the pH value of 2.0 was probably due to an additionally chemical hydrolyzation of the impurities in a strong acidic condition. Moreover, the higher
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efficiency in the fabric weight loss from the plasma-aided process further proves the contribution of
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the oxygen plasma in the removal of the gummy impurities during the subsequent mild biodegumming process.
Figure 8 is for the effect of the plasma-aided biodegumming on the capillary rise height of ramie fabric at different solution pH values in comparison with the conventional biodegumming
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process. It shows that a notable improvement and comparable or even higher values of the fabric capillary rise height were achieved from the plasma-aided process compared with the conventional biodegumming as solution pH ranging from 4.0 to 8.0, and then a decrease in both the curves was
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also observed as the solution pH increased further. Moreover, a relative high value of the fabric
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capillary rise height was also obtained with pH value at 2.0. Theoretically, the pH value in the subjected solution usually shows a significant influence on the enzyme activity in the impurity degradation, and each individual enzyme often prefers a different and desirable acidic and / or alkaline solution condition for its highest activity. Accordingly, the results in Figure 8 further demonstrates that a suitable and desirable pH condition for the mixture pectinases of Hontonzyme DN is at 8.0 to keep their highest activities for degrading the hydrophobic impurities, especially for various pectins on the ramie substrate. Therefore, all those resulted in the highest capillary rise
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ACCEPTED MANUSCRIPT height in the curves with pH value at 8.0. Probably, the improvement of the capillary rise height at the pH value of 2.0 was attributed to an additionally chemical hydrolyzation of those hydrophobic impurities in a strong acidic condition. Figure 9 shows that slight and different decrease tendencies in fabric whiteness (R457 /Wr)
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were obtained for the plasma-aided biodegumming process and the conventional one with solution pH value varying from 2.0 to 12.0. Furthermore, a higher fabric whiteness was achieved from the plasma-aided biodegumming process as pH value higher than 4.0. Those indicate that the
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commercial and mixture enzymes of Hontonzyme DN employed in this study also played a role in
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the removal of some natural colorants from the raw substrate, in comparison with the whiteness (R457 /Wr) of 60.5 for the raw ramie fabric without any pretreatment. Probably, it was due to the Hontonzyme DN also involving some enzymatic components with decoloration potential, too. Moreover, Figure 9 also indicates that the oxygen plasma presented a positive effect on the
10.0.
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biodegradation of natural colorants from the substrate, especially for the solution pH from 4.0 to
Figure 10 reveals that a significant decrease in the ramie fabric tensile strength was observed
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as solution pH value decreased from 6.0 to 2.0, as well as a slight decrease with solution pH value
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higher than 10.0 or 8.0 for both the biodegumming processes. Furthermore, as depicted in Figure 10, at most of the subjected solution pH, a little worse deterioration in the ramie fabric strength was observed for the samples treated by plasma-aided biodegumming process than that of the conventional biodegumming. In practice, a soaking procedure with strong acidic solution is usually employed in a wet-chemical pretreatment for raw ramie substrate, in order to hydrolyze and remove some impurities. Therefore, this was also coincident with the improvements in fabric weight loss, capillary rise height and whiteness at a solution pH value as low as 2.0 in Figure 7, 8 and 9.
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ACCEPTED MANUSCRIPT However, the acidic condition also notably catalyzed the hydrolysis of the macrochains of the cellulosic ramie substrate, which resulted in a worse tolerance of the tensile strength of ramie fabric after the treatment in an acidic solution than an alkaline solution as illustrated in Figure 10. The relative lower tensile strength of ramie fabric samples from the plasma-aided biodegumming
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process was also probably due to the oxygen plasma species affects. By consideration of the all influences of the pH on ramie fabric treatment above, a subjected solution pH of 8.0 was suggested in further experiments for the raw ramie fabric biodegumming,
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not only in order to keep the pectinases with a high activity in improving the biodegumming
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efficiency, but also to keep a less affect on the ramie fabric mechanic properties. 3.3 Influence of treatment time on the plasma-aided biodegumming of raw ramie fabric An influence of treatment time on the plasma-aided and the conventional biodegumming of raw ramie fabric samples was investigated at a solution temperature of 75℃, a pH value of 8.0, as
Figure 11-14.
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well as a dosage of the Hontonzyme DN at 5.0% and 10.0% (o.m.f.), respectively, as depicted in
Figure 11 shows that a significant improvement in the fabric weight loss was achieved as
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treatment time ranging from 30.0 min to 60.0 min, and then no any further enhancement was
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observed as treatment time extend to 105.0 min in both the biodegumming processes. Moreover, a higher efficiency in fabric weight loss from the plasma-aided biodegumming process was also obtained at all the treatment times. Theoretically, an appropriate, enough treatment time for substrate is helpful and benefits for the enzymes to degrade the gummy materials and other impurities as full as possible. Consequently, the ramie fabric weight loss was improved in both the biodegumming processes. However, no further improvement in the fabric weight loss as treatment time longer than 60.0 min was probably due to an almost complete removal of the pectin impurities,
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ACCEPTED MANUSCRIPT etc. The higher efficiency in the fabric weight loss at different treatment times from the plasma-aided process was also due to the positive effect of the oxygen plasma pretreatment on the ramie substrate. Figure 12 shows that an improvement and satisfactory capillary rise height results were
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obtained with treatment time from 30.0 min to 50.0 min, and then no evident enhancement was also observed with time prolonged further to 105.0 min for the plasma-aided and the conventional biodegumming processes. Moreover, a relative high value of fabric whiteness was achieved at a
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short treatment time of 30.0 min, and then an almost independent tendency in fabric whiteness was
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obtained with the treatment time as illustrated in Figure 13. Furthermore, better results of fabric whiteness from the plasma-aided biodegumming process than the conventional one were also available with treatment time from 30.0 min to 60.0 min. Those further indicate that an appropriate short treatment time could present an evident effect on the removal of the hydrophobic pectin
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impurities and natural colorants, etc., to improve the wettability and whiteness of the ramie substrate by the mixture enzymes of Hontonzyme DN in both the biodegumming processes. Moreover, the improvement of the wettability and whiteness of the ramie fabric from the
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plasma-aided biodegumming process in comparison with the conventional one was also due to the
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help of the oxygen plasma pretreatment. Figure 14 shows that comparable values and a slight decrease tendency in the ramie fabric tensile strength were observed with the treatment time from 30.0 min to 105.0 min for both the biodegumming processes. It was probably due to the continuous and long time treatment affects on the ramie fibers in the weakly alkaline degumming solution, especially for the conventional biodegumming process. Accordingly, a treatment time of 60.0 min was recommended in the plasma-aided
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ACCEPTED MANUSCRIPT biodegumming process for raw ramie fabric. 3.4 Influence of oxygen plasma and its aided biodegumming on the water contact angle of ramie fabric According to the discussion above, the oxygen plasma played a role in the biodegumming of
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raw ramie fabric with the mixture pectinases for the removal of gummy impurities, etc., as well as for saving the dosage of enzymes and treatment time. In order to investigate and confirm the plasma role further, a static water contact angle (α, °) for ramie fabric samples was measured, as shown in
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Figure 15 (a-c).
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Figure 15a demonstrates that a hemispheric droplet of static water on the raw ramie fabric surface was observed with a contact angle (α,) of 97.7°, which indicates that the raw ramie fabric without any treatment poses a poor wettability due to the gummy impurities on the ramie substrate, especially for the hydrophobic pectins, etc. However, Figure 15b shows that the static water droplet
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was absorbed quickly by the ramie fabric after oxygen plasma pretreatment and only a very small part of water was remained on the surface of the substrate with a contact angle (α,) of 14.5°. This clearly reveals that the wettability of the raw ramie fabric surface could be improved significantly
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by the oxygen plasma treatment. Those was directly due to the physical bombardments and/ or
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chemical modifications onto those hydrophobic impurities by the reactive and energetic plasma species, which is also helpful for the enzymes to adsorb, penetrate into the ramie yarns and accelerate the degradation of the broken impurities. Consequently, higher efficiencies in the fabric weight loss, capillary rise height and whiteness were obtained by employing plasma-aided biodegumming process, even a lower dosage of the pectinases of Hontonzyme DN and a shorter treatment time were involved in comparison with the conventional biodegumming. Figure 15c demonstrates that a complete adsorption of the droplet of water occurred immediately on the
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ACCEPTED MANUSCRIPT plasma-aided and mild biodegummed ramie fabric with a contact angle (α,) of 0.0°, which further proves that a satisfactory removal of the gummy impurities and a high wettability on the raw substrate were achieved by employing the recommended plasma-aided biodegumming process. 3.5 Influence of oxygen plasma and its aided biodegumming on the surface morphology of
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ramie substrate An influence of oxygen plasma treatment and its aided biodegumming on the surface
Hitachi, Japan). The results are shown in Figure 16 (a-c).
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morphology of ramie substrate was also investigated on a scanning electronic microscopy (S-4800,
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Figure 16a shows that the surfaces of the raw ramie fibers without any pretreatment were encrusted by smooth and intact gummy impurity films, and the unique characteristics of ramie fibers, such as the natural stripes and cross sections, were almost invisible due to the impurity covering on the fiber surfaces. However, a notably broken appearance of the ramie surfaces was
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observed with various pittings, groovings and even some fragments on the outer surfaces of the ramie after an oxygen plasma treatment, as shown in Figure 16b. Obviously, the oxygen plasma played a significant role in breaking the intact impurity cover and presented a big contribution to the
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subsequent biodegumming with the enzymes. Figure 16c shows that a clean and smooth ramie fiber
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surface with a magnification of 2000× was achieved by the plasma-aided biodegumming process, although some micro-cracks were also observed probably due to the oxygen plasma effects. Theoretically, the high energetic oxygen plasma species could physically bombard and chemically modify the surface impurities on the ramie fibers, resulting in the broken of the impurity coverings, as well as the change of the surface morphology of the ramie substrate. Moreover, those also make the subsequent biodegumming process benefit from the easy and quick wettability of the substrate surfaces, as well as the easy penetration, diffusion of the enzymes into the broken impurity
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MANUSCRIPT films or the fabric yarns. Finally,ACCEPTED those result in easy enzymatic reactions with various impurity fragments on fiber surfaces. Therefore, the oxygen plasma treatment shows a significant effect on the surface morphology of the ramie substrate, which then results in the significant contribution to
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the subsequent biodegumming process.
4. Conclusions
A novel biodegumming process with the aid of oxygen plasma for ramie substrate was
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successfully developed with pectinases. The results show that a notable positive effect of oxygen plasma on ramie biodegumming with the pectinases was achieved with much less application of the
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enzymes and treatment time. The static water contact angle measurement and SEM investigations further confirm the functions of oxygen plasma in the change of wettability, morphologies and the improvement of the substrate biodegumming. The novel process has potential applications in the
in the textile industry.
Acknowledgement
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pretreatment of raw ramie, grey cotton fabrics, etc., with more environmentally friendly advantages
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The authors acknowledge gratefully the financial supports from the First Phase of Jiangsu
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Universities’ Distinctive Discipline Development Program for Textile Science and Engineering of Soochow University.
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J. Clean. Prod. 41, 283-290.
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Basu, S., Saha, M.N., Chattopadhyay, D., Chakrabarti, K., 2009. Degumming and characterization of ramie fibre using pectate lyase from immobilized Bacillus pumilus DKS1. Lett. Appl. Microbiol. 48, 593–597. Bruhlmann, F., Kim, K.S., Zimmerman, W., Fiechter, A., 1994. Pectinolytic enzymes from
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actinomycetes for the degumming of ramie bast fibers. Appli. Environ. Microbiol. 60 (6), 2107–2112.
Bruhlmann, F., Leupin, M., Erismann, K.H., Fiechter, A., 2000. Enzymatic degumming of ramie
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bast fibers. J. Biotechnol. 76 (1), 43-50.
Cai, Z., Qiu, Y., Zhang, C., Hwang, Y.J., McCord, M., 2003. Effect of atmospheric plasma treatment
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on desizing of PVA on cotton. Text. Res. J. 73, 670–674.
China textile criteria of FZ/T01071-2008., 2008. Textiles – Test method for Capillary effect, Beijing, China.
China textile criteria of GB/T 17644-2008., 2008. Test method for whiteness and chromaticity of
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textile fibers, Beijing, China.
China textile criteria of GB/T3923.1 -1997., 1997. Textiles-Tensile properties of fabrics—Part 1:
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determination of breaking force and elongation at breaking force—strip method, Beijing,
Gupta, D., Agrawal, A., Chaudhary, H., Gulrajani, M., Gupta, C., 2013. Cleaner process for
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extraction of silk sericin using infrared. J. Clean. Prod. 52, 488-494. Jayani, R.S., Saxena, S., Gupta, R., 2005. Microbial pectinolytic enzymes: A review. Process Biochem. 40 (9), 2931–2944. Jiang, M., 2011. On the relationship between ramie fiber quality and textiles quality. China Fiber Inspect. (11), 74-76. Kapoor, M., Beg, Q.K., Bhushan, B., Singh, K., Dadhich, K.S., Hoondal, G. S., 2001. Application of an alkaline and thermostable polygalacturonase from Bacillus sp. MG-cp-2 in degumming of ramie (Boehmeria nivea) and sunn hemp (Crotalaria juncea) bast fibres. Process Biochem. 36, 20
803–807.
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Li, R., Ye, L., Mai, Y.-W., 1997. Application of plasma technologies in fibre-reinforced polymer composites: a review of recent developments. Compos. Part A- Appl. S. 28, 73-86. Liu, Z. C., 1995. The prospect and countermeasures of ramie industry development in China. China’s Fiber Crop. 17(1), 45-46.
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Long, J.-J., Wang, H.-W., Lu, T.-Q., Tang, R.-Ch., Zhu,Y.-W., 2008. Application of low-pressure plasma pretreatment in silk fabric degumming process. Plasma Chem. Plasma P. 28, 701-713. Mahmoodi, N.M., Arami, M., Mazaheri, F., Rahimi, S., 2010. Degradation of sericin (degumming)
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of Persian silk by ultrasound and enzymes as a cleaner and environmentally friendly process. J. Clean. Prod. 18(2), 146-151.
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Morent, R., De Geyter, N., Verschuren, J., De Clerck, K., Kiekens, P., Leys, C., 2008. Non-thermal plasma treatment of textiles. Surf. Coat. Tech. 202, 3427–3449.
Mukhopadhyay, A., Dutta, N., Chattopadhyay, D., Chakrabarti, K., 2013. Degumming of ramie fiber and the production of reducing sugars from waste peels using nanoparticle supplemented
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pectate lyase. Bioresource Technol. 137, 202–208.
Wang, L., Xiang, Z.-Q., Bai, Y.-L., Long, J.-J., 2013. A plasma aided process for grey cotton fabric pretreatment. J. Clean. Prod. 54, 323-331.
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Wei，C. X., 2007. The history, status and future of ramie textile industry in China. Plant Fiber Sci. in
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China, 29, 77-85.
Xie, H., 2008. Chinese ramie and its product criteria. China Fiber Inspect. (3), 20-22. Yip, J., Chan, K., Sin, K. M., Lau, K. S., 2002. Low temperature plasma-treated nylon fabrics, J. Mater. Process. Tech. 123, 5-12. Zheng, L., Du, Y., Zhang, J., 2001. Degumming of ramie fibers by alkalophilic bacteria and their polysaccharide-degrading enzymes. Bioresource Technol. 78 (1), 89-94.
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ACCEPTED MANUSCRIPT Captions to Figures Fig.1 Process flowchart for conventional biodegumming treatment of raw ramie fabric samples with pectinolytic enzyme of Hontonzyme DN
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Fig.2 Process flowchart for oxygen plasma-aided biodegumming of raw ramie fabric samples with pectinolytic enzyme of Hontonzyme DN
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Fig.3 Influence of treatment temperature on the ramie fabric weight loss from the plasma-aided and the conventional biodegumming processes
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Fig.4 Influence of treatment temperature on the fabric capillary rise height from the plasma-aided and the conventional biodegumming processes
Fig.5 Influence of treatment temperature on the fabric whiteness from the plasma-aided and the conventional biodegumming processes
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Fig.6 Influence of treatment temperature on the fabric tensile strength from the plasma-aided and the conventional biodegumming processes
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Fig.7 Influence of solution pH on the ramie fabric weight loss from the plasma-aided and the conventional biodegumming processes
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Fig.8 Influence of solution pH on the fabric capillary rise height from the plasma-aided and the conventional biodegumming processes Fig.9 Influence of solution pH on the fabric whiteness from the plasma-aided and the conventional biodegumming processes Fig.10 Influence of solution pH on the fabric tensile strength f from the plasma-aided and the conventional biodegumming processes Fig.11 Influence of treatment time on the ramie fabric weight loss from the plasma-aided and the
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conventional biodegumming processes Fig.14 Influence of treatment time on the fabric tensile strength from the plasma-aided and the conventional biodegumming processes
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Fig.15 Static water contact angle of the raw ramie fabric surface (a) without any pretreatment, (b)
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oxygen plasma pretreated sample at a pressure of 40.0 Pa and a discharge power of 250.0 W for 3.0 min, (c) the plasma-aided and mild biodegummed ramie fabric with a dosage of the Hontonzyme DN at 5.0% (o.m.f.), a temperature of 75℃ and pH value of solution at 8.0 for 60.0 min Fig.16 SEM images of the raw ramie fabric surface (a) without any pretreatment, (b) oxygen
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plasma treated sample at a pressure of 40.0 Pa and a discharge power of 250.0 W for 3.0 min, and (c) the biodegummed sample with the optimized plasma-aided mild biodegumming process with a
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8.0 for 60.0 min
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dosage of the Hontonzyme DN at 5.0% (o.m.f.), a temperature of 75℃ and pH value of solution at
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Sample preparation for testing
Washed with tap water
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Treated with pectinases of Hontonzyme DN in a biodegumming solution
Soaked in a penetrating agent solution
Fig.1 24
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Treated with half dosages of Hontonzyme DN as in the conventional biodegumming process
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Soaked in a penetrating agent solution
Oxygen plasma treatment
Sample preparation for testing
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Washed with tap water
Fig.2 25
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7.0
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6.0 5.5
–○– Weight loss from plasma-aided biodegumming –Δ– Weight loss from conventional biodegumming
5.0 4.5 30.0
45.0
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15.0
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Weight loss (%)
6.5
60.0
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Temperature (℃)
Fig.3 26
75.0
90.0
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13.0 12.0 11.0
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10.0 9.0
–*– Capillary rise height from plasma-aided biodegumming –▽– Capillary rise height from conventional biodegumming
8.0 7.0 6.0 15.0
30.0
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Capillary rise height (cm)
14.0
45.0
60.0
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Temperature (℃)
Fig.4 27
75.0
90.0
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70.0
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68.0 66.0 64.0
–□– Fabric whiteness from plasma-aided biodegumming –×– Fabric whiteness from conventional biodegumming
62.0 60.0 30.0
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15.0
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Fabric whiteness (R457)
72.0
60.0
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Temperature (℃)
Fig.5 28
75.0
90.0
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800.0
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700.0 650.0
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Tensile strength (N)
750.0
600.0
–+–Fabric tensile strength from plasma-aided biodegumming –◇– Fabric tensile strength from conventional biodegumming
550.0 500.0
30.0
45.0
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15.0
60.0
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Temperature (℃)
Fig.6 29
75.0
90.0
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10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0
–○– Weight loss from plasma-aided biodegumming –Δ– Weight loss from conventional biodegumming
4.0
6.0
8.0 pH
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2.0
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Weight loss (%)
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Fig.7 30
10.0
12.0
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13.0
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12.0 11.0 10.0
–*– Capillary rise height from plasma-aided biodegumming –▽– Capillary rise height from conventional biodegumming
9.0 8.0
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Capillary rise height (cm)
14.0
4.0
6.0 pH
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2.0
Fig.8 31
8.0
10.0
12.0
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74.0
70.0
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68.0 66.0
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Fabric whiteness (R457)
72.0
–□– Fabric whiteness from plasma-aided biodegumming –×– Fabric whiteness from conventional biodegumming
64.0 62.0 60.0 4.0
6.0
pH
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2.0
Fig.9 32
8.0
10.0
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800.0
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700.0 650.0
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Tensile strength (N)
750.0
600.0 550.0
–+–Fabric tensile strength from plasma-aided biodegumming –◇– Fabric tensile strength from conventional biodegumming
500.0
400.0
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450.0
4.0
6.0
8.0 pH
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2.0
Fig.10 33
10.0
12.0
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10.0
8.0
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7.0 6.0
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Weight loss (%)
9.0
–○– Weight loss from plasma-aided biodegumming –Δ– Weight loss from conventional biodegumming
5.0 4.0 3.0 30
40
50
60
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20
70
80
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Treatment time (min)
Fig.11 34
90 100 110
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16.0
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12.0
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10.0 8.0
–*– Capillary rise height from plasma-aided biodegumming –▽– Capillary rise height from conventional biodegumming
6.0 4.0 2.0 20
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Capillary rise height (cm)
14.0
30
40
50
60
70
80
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Treatment time (min)
Fig.12 35
90 100 110
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70.0
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65.0
–□– Fabric whiteness from plasma-aided biodegumming –×– Fabric whiteness from conventional biodegumming
60.0 55.0 50.0 20
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Fabric whiteness (R457)
75.0
30
40
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80
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Treatment time (min)
Fig.13 36
90 100 110
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700.0 650.0
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750.0
600.0
–+–Fabric tensile strength from plasma-aided biodegumming –◇– Fabric tensile strength from conventional biodegumming
550.0
20
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500.0 30
40
50
60
70
80
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Treatment time (min)
Fig.14 37
90 100 110
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(a) α =97.7°
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(b) α =14.5°
(c) α =0°
Fig.15 38
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(a)
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(b)
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(c)
Fig.16 39
ACCEPTED MANUSCRIPT Highlights:
►A novel plasma aided biodegumming process for ramie substrate was developed. ►The biodegumming process involving plasma treatment for ramie fabric was optimized.
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►Enzyme was reduced in half for the plasma-aided process compared to traditional one. ►Better results were achieved with plasma-aided process compared to traditional one.
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►Notable etching effect and wettablity on ramie were obtained from plasma species.
S0959-6526(15)00321-2
DOI:
10.1016/j.jclepro.2015.03.081
Reference:
JCLP 5349
To appear in:
Journal of Cleaner Production
Received Date: 27 November 2014 Revised Date:
27 January 2015
Accepted Date: 28 March 2015
Please cite this article as: Shen M, Wang L, Long J-J, Biodegumming of ramie fiber with pectinases enhanced by oxygen plasma, Journal of Cleaner Production (2015), doi: 10.1016/j.jclepro.2015.03.081. 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.
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Biodegumming of ramie fiber with pectinases enhanced by oxygen plasma
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Ming Shen, Ling Wang, Jia-Jie Long* College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, China
(b) Oxygen plasma treated
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(a) Without any pretreatment
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Graphical Abstract
(c) Biodegummed with plasma-aided
The resultant word count: 6455 words in whole text files including tables and figure captions. ACCEPTED MANUSCRIPT
Biodegumming of ramie fiber with pectinases enhanced by oxygen plasma
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Ming Shen, Ling Wang, Jia-Jie Long*
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College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, China
*Corresponding author. Tel.:+86 0512 67164993; Fax: 086-0512-67246786 E-mail: [email protected] (Jia-Jie Long) 1
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Abstract
A novel biodegumming process with pectinases for ramie fiber was developed in combination with oxygen plasma, in order to improve the efficiency of enzymes in impurity degradation. The results show that a notable positive influence of oxygen plasma on the biodegumming of ramie was
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achieved, in comparison with a conventional biodegumming process. The fabric weight loss, capillary rise height and whiteness of ramie fabric were evidently improved by employing the oxygen plasma-aided biodegumming process with a half dosage of enzymes, in comparison with a
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conventional experiment at different temperatures, solution pH values and treatment times. An
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optimized plasma-aided biodegumming process for raw ramie fabric was recommended with a temperature of 75℃, a pH value of 8.0 in subjected solution for 60.0 min. Moreover, the role of oxygen plasma on ramie biodegumming was further confirmed by static water contact angle measurement and scanning electron microscopy (SEM) analysis.
1. Introduction
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Key words Ramie fiber; Biodegumming; Impurity removal; Enzyme; Oxygen plasma
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As one of the longest, strongest and oldest natural fibers, Ramie (Boehmeria nivea) is an important material for textile manufacturing, and is very popular with customers in the last decades
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(Xie, 2008; Wei, 2007). Ramie poses essentially advanced properties as an textile material, such as holding shape, less wrinkling, silky luster, special cooling feel, high absorbency, good air permeability, as well as a green, ecological and functional fiber, etc (Zheng etc., 2001; Liu, 1995). Whereas, as a bast fiber, decorticated ramie contains 20-30% gummy materials, mainly consisting of pectins and hemicelluloses, as well as other impurities (Jiang, 2011; Mukhopadhyay etc., 2013). Therefore, prior to industrial utilization, ramie fiber should be sufficiently degummed to remove the gummy materials and separate the spinnable cellulosic component. 2
ACCEPTED Moreover, in recent years, cleaner andMANUSCRIPT ecological pretreatment processes for textile manufacturing have been paid extensive attentions, such as the cleaner process for extraction of silk sericin using infrared (Gupta, et al., 2013), and the degumming of Persian silk by ultrasound and enzymes as a cleaner and environmentally friendly process (Mahmoodi, et al., 2010), as well as the
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usability of ultrasound in scouring of raw wool for thermal energy, water and chemical savings (Bahtiyari and Duran, 2013), etc. Especially, the biodegumming processes with various enzymes for ramie fibers are very popular due to their clean, environmentally friendly, water and energy saving
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advantages, etc., in comparison with the conventionally chemical degumming processes (Zheng etc.,
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2001; Mukhopadhyay etc., 2013). Bruhlmann et al. (1994) reported the isolation and culture of the actinomycetes for production of pectinolytic enzymes and applied to ramie degumming process, they demonstrated that a good correlation between the pectate lyase activity and degumming effect was obtained for good separation of the bast fibers. Moreover, Bruhlmann et al. (2000) also
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investigated the degumming effects of different pectate lyase and other extracellular enzymes on ramie bast fibers, and revealed that the pectinolytic activity of the Amycolata sp. played a role in the ramie substrate degumming. Zheng et al. (2001) selected three strains of alkalophilic bacteria and
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their enzymes for removing residual gum from ramie fibers, and found that pectate lyase and
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xylanase played a role in the degradation of residual gum, in which the residual gum of the fibers decreased to 9.4% after 5.0 h by enzymatic degumming with improved fiber properties. Furthermore, Basu et al. (2009) investigated the production of pectate lyase from immobilized Bacillus pumilus DKS1 cells in calcium –alginate beads, and revealed that high-quality degummed ramie fibers could be prepared by applying the obtained enzymes at the first time. Mukhopadhyay et al. (2013) carried out the ramie degumming process with hydroxyapatite nanoparticle supplemented pectate lyase, and disclosed that raw and decorticated ramie fibers could be better
3
ACCEPTED MANUSCRIPT degummed with nanoparticle supplemented pectate lyase than non-supplemented one in weight loss after 24.0 and 48.0 h of processing with an enhancement of fiber tenacity and fineness. However, those biodegumming processes described above are mild or gentle treatments for degradation of the organic polymer impurities with different enzymes; which usually involve a long
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treatment period, such as several hours and even several days (Bruhlmann et al., 1994; Mukhopadhyay et al., 2013). Furthermore, it is not sufficient or adequate to remove the incrusted gummy materials, as well as other impurities, from raw and /or decorticated ramie fibers by
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employing biodegumming treatment only due to its slow and low efficiency. Therefore, mild and
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conventional chemical treatments are necessary and usually applied in practice before or after the biodegumming processes to meet the requests of textile manufacturing (Kapoor et al., 2001). In addition, as well known to all, every enzyme poses unique characteristics and only plays a role for its individual and suitable substrate. Consequently, various enzymes and their synergistic actions are
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necessary for biodegumming processes to biodegrade the different impurities from raw and /or decorticated ramie fibers, which usually result in a higher treatment cost and complex situations in process control.
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Accordingly, it is very important and meaningful to develop some effective alternatives to
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conventionally chemical methods for improving the efficiency of biodegumming processes, with more environmentally friendly and cleaner production during the pretreatment of ramie substrates. Fortunately, low temperature plasma treatment is proved as a promising dry method to improve the efficiency of conventional processes with the reduction of water, chemicals and energy consumptions (Morent et al., 2008). In recent years, more and more applications of low temperature plasma are available for the textile pretreatments in combination with wet chemical processes, such as for the desizing of PVA on cotton with an atmospheric plasma (Cai et al., 2003), for the desizing
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or scouring of grey cotton withACCEPTED low-pressure MANUSCRIPT plasma (Wang et al., 2013), and for removal of different sizing agents on polyester fabrics (Bae et al., 2006), as well as for silk degumming (Long et al., 2008). Briefly, most of the reported applications of low temperature plasma in textile pretreatments
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are mainly combined with wet-chemical processes. However, very few works have been reported about the application of low temperature plasma to improve the efficiency in biodegumming of raw ramie fabric with enzymes, although their combination is very benefit to the cleaner production of
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textile and very desirable in ramie industry.
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The objective of the present work is to develop an effective and more environmentally friendly pretreatment method for ramie fabric degumming by combination of a low-temperature oxygen plasma treatment and a subsequent biodegumming with pectinases. The biodegumming parameters such as temperature, subjected solution pH and treatment time were investigated and optimized.
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Moreover, the plasma and biodegumming treatment effects on ramie substrate were further investigated and confirmed by static water contact angle measurement and scanning electron
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microscopy (SEM) analysis.
2. Experimental section
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2.1 Materials and chemicals
A commercial and raw ramie fabric (a woven, with a fabric weight of 127.2 g m-2) was kindly supplied by Chongqing Fuling Kinde group Co., Ltd. (Chongqing, China) in this study. The raw ramie fabric was cut into a dimension of 30.0 cm ×15.0 cm, and used as received without any other previous treatment. All raw ramie fabric samples were conditioned at 20℃±2℃ and 65%±3% relative humidity for 24.0 h before a measurement or testing. The employed pectinolytic enzyme of Hontonzyme DN (kindly supplied by Qingdao Hai Yin 5
MANUSCRIPT Da chemical co., LTD, China) forACCEPTED biodegumming of ramie fabric was a commercial product, and a mixture of different pectinases mainly containing polygalacturonases and pectinolytic lyases, etc. The toll activity of the employed enzyme of Hontonzyme DN was 300 U mL-1. Other chemicals used in experiments, such as sodium hydroxide, dilute sulfuric acid, penetrating agent JFC, etc.,
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were commercially available products. Pure oxygen gas (with a purity of 99.5% vol. - %) employed in low-temperature plasma treatment was purchased from Suzhou Jinhong gas Co., Ltd. (Jiangsu
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province, China).
2.2 Apparatus and procedures
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2.2.1 Low-temperature plasma treatment
The pretreatment of raw ramie fabric samples by low-temperature oxygen plasma was carried out in the same batch plasma system (HD-1, Suzhou Hongda plasma technology company, China) as described elsewhere (Long et al., 2008), with previously optimized parameters at a pressure of
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40.0 Pa and a discharge power of 250.0 W for 3.0 min. Before a low-temperature oxygen plasma treatment, the raw ramie fabric sample was dryed in an oven at 95℃ for 60 min, and then was hung
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vertically with a sample stand between the two parallel electrodes.
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2.2.2 Biodegumming treatment of ramie fabric samples A conventional biodegumming treatment with pectinolytic enzyme of Hontonzyme DN was performed for removing the gummy impurities of raw ramie fabric samples, as described with a flowchart in Figure 1.
The soaking treatment for samples was carried out in a solution involving 0.5 g L-1 of penetrating agent JFC at 25 ±1℃ for 30.0 min, in order to wet the dry ramie substrate and improve the uniform adsorption and penetration of enzymes into the substrate yarns at the following treatment. The biodegumming treatment was performed in a solution involving 10.0% (o.m.f.; on 6
ACCEPTED MANUSCRIPT the mass of fabric) of Hontonzyme DN at a material to liquor ratio of 1: 40, with temperature varying from 15℃ to 90℃, the pH value from 2.0 to 12.0 and treatment time from 30.0 min to 105.0 min. Theoretically, most of the gummy materials, especially for various pectins could be degraded and removed from the ramie substrate by the biodegumming treatment, as well as for
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other impurities partly. Moreover, a washing procedure was followed with tap water to remove the degraded residual impurities on the ramie fabric for further extraction of the substrate before the sample preparation for testing.
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The biodegumming of the ramie fabric samples after a previous treatment by oxygen plasma in
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this study was carried out in a mild condition and described with a flowchart in Figure 2. The mild biodegumming process for the treated ramie substrate with oxygen plasma was performed by employing half dosage of Hontonzyme DN at 5.0% (o.m.f.) at a shorter time of 50.0 min for most of experiments, and with the same other conditions and treatments as in the
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conventional biodegumming process.
Subsequently, all the samples were well rinsed with distilled warm water again and dried at room temperature. A weight loss, characterized for the total removal of gummy impurities (mainly
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consisting of pectins, as well as other impurities, etc.) from ramie substrate, was evaluated
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according to the equation (1):
Weight loss(%) =
W1 − W2 × 100% W1
(1)
where W1, W2 refer to the conditioned fabric weight before and after a biodegumming treatment, respectively. An average weight loss value was obtained from 3 replicate measurements with a relative deviation of values within 3.0%. 2.2.3 Capillary rise height measurement of ramie fabric samples Capillary rise height is a direct and convenient index for fabric wettability or wickability in 7
ACCEPTED MANUSCRIPT practice. In this work, the capillary rise height measurement was carried out on a ramie fabric strip in warp direction (China textile criteria of FZ/T01071-2008, 2008; which references to ISO9073-6:2000) by employing a capillary rise measurement apparatus (ZBW 04019, Shanghai Luozhong institute, China). The fabric strip was suspended vertically with lower end immersed into
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a thin layer of potassium dichromate aqueous solution (1.0 wt. %) for 1.0 cm. A capillary rise height reading was made at a given time of 30.0 min under ambient temperature. An average height value
2.2.4 Fabric whiteness measurement for ramie samples
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was utilized from 3 replicate measurements with a relative deviation of values within 1.5%.
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A fabric whiteness value (Wr, namely the whiteness of R457) was measured according to China textile criteria of GB/T 17644-2008 (China textile criteria of GB/T 17644-2008, 2008; which is equal to ISO 2470 for ISO whiteness) with four-folded sample on a full-automatic fabric whiteness meter (WSB-3A, Nantong Hongda experiment instruments Co., Ltd., China) by
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employing a simulated D65 light source lamp and a 10˚ visual angle. An average value of 3 measurements was used with a relative deviation of values within 1.0%. The calculation method according to the cited criteria for the whiteness value (R457 or Wr) of fabric is shown as in equation
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(2):
(2)
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R457 (Wr ) = 0.925 × Z 10 + 1.16
where R457 or Wr, Z10 refer to the fabric whiteness value (or R457 whiteness) and the tristimulus value in the CIE 1931 color space, respectively; the subscript of “10” is for the CIE 1964 standard observer. 2.2.5 Tensile testing of ramie fabric samples Tensile testing of ramie fabric samples was performed on an electric and versatile material tensile apparatus (Instron 5900, Instron Co., Ltd., USA) by strip method (China textile criteria of
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MANUSCRIPT GB/T3923.1 -1997, 1997; whichACCEPTED is equal to ISO13934.1). The ramie fabric strip was made to a dimension of 5.0 cm × 35.0 cm in warp direction. The tensile strength of each fabric sample was an average result of four replicate measurements with a relative deviation of the testing results lower than 2.0%.
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2.2.6 Water contact angle measurement for ramie samples A static water contact angle (α, °) for ramie fabric samples was measured by employing the sessile drop method on an OCA 15Pro optical contact anger meter (Dataphysics Co., Ltd., Germany)
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at ambient temperature. Water droplet with a volume of 1.0 µL was dropped carefully onto the
different spots on a same sample was used.
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sample surface for measuring static water contact anger. An average value of 6 measurements at
2.2.7 Investigation of surface morphology for ramie substrate
The investigations of surface morphologies for ramie substrate before and after a treatment by
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oxygen plasma, as well as a subsequent biodegumming treatment in a mild condition, were carried out on a scanning electronic microscopy (SEM) (S-4800, Hitachi, Japan) at an acceleration voltage
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of 3.0 kV with 2000 × magnification. Before investigation, samples were sputtered with gold.
3. Results and discussion
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3.1 Influence of temperature on the plasma-aided biodegumming of raw ramie fabric An influence of treatment temperatures on the mild biodegumming of pretreated ramie fabric by oxygen plasma was investigated with a dosage of the Hontonzyme DN at 5.0% (o.m.f.), a solution pH at 8.0 and a treatment time of 50.0 min at different temperatures. The fabric weight loss, capillary rise height, whiteness and tensile strength were determined for all samples. Simultaneously, a conventional biodegumming process was also performed with a dosage of Hontonzyme DN at 10.0% (o.m.f.), a treatment time of 80.0 min and with other similar conditions as in the mild process. 9
The obtained results are depicted ACCEPTED in Figure 3-6. MANUSCRIPT Figure 3 shows that an increase in the weight loss of raw ramie fabric from the plasma-aided biodegumming process was achieved with the temperature from 15.0℃ to 75.0℃, and then an accelerated decrease in the weight loss was also observed as temperature higher than 75.0℃.
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Moreover, Figure 3 also shows that an increase in the weight loss of raw ramie fabric from the conventional biodegumming process was obtained with temperature from 15.0℃ to 30.0℃, however, no further improvement was observed as treatment temperature up to 90.0℃. In
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comparison with the conventional biodegumming process, a higher efficiency of the plasma-aided
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biodegumming process in fabric weight loss or impurity removal was observed at most of the applied treatment temperatures, although only a half dosage of the pectinases and a shorter treatment time were applied.
The above results indicate that the oxygen plasma treatment played a role in the
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biodegumming of ramie fabric with pectinases and presented a positive effect on the removal of gummy impurities, especially for pectin, etc. In principle, plasma is an ionized gas involving various excited, energetic and discharged species as its definition (Li et al., 1997; Yip et al., 2002).
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Therefore, the reactive and energetic oxygen plasma species could attack the encrusted gummy film
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and other impurities on ramie fibers effectively, and break them by physical and / or chemical etching effects due to chain scission and oxidation, etc. Thus, those etching effects resulted in a readily diffusion of the pectinases into the broken gummy films, and also led to an easy degradation of the broken pectin impurities. For example, some insoluble protopectins could be readily changed into soluble pectins, and a de-esterification of pectins and hydrolytic cleavage of the α-(1, 4)-glycosidic bonds could also be achieved easily, as well as for the swelling, hydrolyzing, dissolving of other natural impurities (Jayani etc., 2005; Wang etc., 2013). However, the accelerated
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ACCEPTED MANUSCRIPT decrease in the weight loss from the plasma -aided biodegumming process with temperature higher than 75.0℃, was probably due to an overhigh and undesirable treatment temperature for the enzymes. In fact, overhigh treatment temperature could readily result in the decrease of the enzymatic reactivity for the removal of gummy impurities from ramie substrate.
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Figure 4 is for the comparison of the plasma-aided biodegumming process and the conventional enzymatic one in the capillary rise height of treated ramie fabric samples at different temperature. It demonstrates that an improvement and similar increase tendencies of the capillary
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rise height of ramie fabrics from both the processes were achieved with the treatment temperature
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from 15.0℃ to 75.0℃, and then a decrease was also obtained as temperature higher than 75.0℃. During the pretreatment for textile manufacturing, the capillary rise height is a convenient and useful indirect indicator for impurity removal efficiency from a pretreatment process, especially for the removal of some hydrophobic impurities, such as pectins, waxes, fats, oils, etc. Consequently, a
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higher result of the capillary rise height usually demonstrates that more hydrophobic impurities were removed from the raw substrate, and a good wettability could be achieved. Therefore, the comparable wettability of the treated raw ramie substrate by the plasma-aided biodegumming
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process in comparison with the control experiments in Figure 4, further discloses that the oxygen
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plasma showed a positive effect on the enzymatic removal of those hydrophobic impurities. It is probably that those impurities were degraded and modified by physical bombardments and / or even chemically oxidized previously by the active oxygen plasma species, which resulting in a benefit for their further degradation by the pectinases in the subsequent biodegumming treatment. Figure 5 depicts the influence of the plasma-aided and conventional biodegumming processes on the ramie fabric whiteness at different temperatures. The obtained curves show that an improvement and a similar increase tendency in fabric whiteness (R457 /Wr) were observed for
11
ACCEPTED MANUSCRIPT ramie fabric samples treated by both the biodegumming processes with solution temperature from 15.0℃ to 75.0℃, as well as a decrease in fabric whiteness as temperature higher than 75.0℃. Furthermore, Figure 5 also indicates that, an enhanced bleaching effect on the ramie substrate with higher whiteness was also achieved at all the tested temperatures from the plasma-aided
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biodegumming process in comparison with the convention biodegumming. Figure 6 demonstrates that a slight decrease tendency in fabric tensile strength was obtained with the applied temperatures for both the biodegumming processes. Moreover, a relative lower
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tensile strength of the ramie fabric samples from the plasma-aided biodegumming was also
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observed for all the treatment temperatures. Probably, it was due to the penetration of excited oxygen plasma species into the ramie fiber core and some harsher modifications occurred to the fiber macrochains.
By taking account into the all influences of the treatment temperatures on ramie fabric above,
biodegumming.
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a temperature of 75 ℃ was recommended in further experiments for raw ramie fabric
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3.2 Influence of solution pH on the plasma-aided biodegumming of raw ramie fabric An influence of pH value of subjected solution on the plasma-aided and mild biodegumming
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of ramie substrate was investigated with a dosage of the Hontonzyme DN at 5.0% (o.m.f.), a temperature of 75℃ and a treatment time of 50 min. A conventional biodegumming process was also carried out for comparison with a dosage of Hontonzyme DN at 10.0% (o.m.f.), a treatment time of 80.0 min and with other conditions similar as in the mild process. Figure 7 shows that a slight increase in the fabric weight loss from both the plasma-aided and conventional biodegumming processes was observed with the pH value from 4.0 to 8.0, and then a slight decrease tendency was also obtained as pH value further increased to 12.0, except for a 12
ACCEPTED MANUSCRIPT relative higher value appeared with pH value at 2.0. Furthermore, Figure 7 also reveals that a higher efficiency of the plasma-aided biodegumming in fabric weight loss was achieved at all the subjected solution pH, although a half dosage of the pectinases and a shorter treatment time were involved in comparison with the conventional biodegumming. It seems like that the pH value of the subjected
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solution showed a slight effect on the weight loss of the raw substrate in a wide range. However, the higher value of the fabric weight loss at the pH value of 2.0 was probably due to an additionally chemical hydrolyzation of the impurities in a strong acidic condition. Moreover, the higher
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efficiency in the fabric weight loss from the plasma-aided process further proves the contribution of
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the oxygen plasma in the removal of the gummy impurities during the subsequent mild biodegumming process.
Figure 8 is for the effect of the plasma-aided biodegumming on the capillary rise height of ramie fabric at different solution pH values in comparison with the conventional biodegumming
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process. It shows that a notable improvement and comparable or even higher values of the fabric capillary rise height were achieved from the plasma-aided process compared with the conventional biodegumming as solution pH ranging from 4.0 to 8.0, and then a decrease in both the curves was
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also observed as the solution pH increased further. Moreover, a relative high value of the fabric
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capillary rise height was also obtained with pH value at 2.0. Theoretically, the pH value in the subjected solution usually shows a significant influence on the enzyme activity in the impurity degradation, and each individual enzyme often prefers a different and desirable acidic and / or alkaline solution condition for its highest activity. Accordingly, the results in Figure 8 further demonstrates that a suitable and desirable pH condition for the mixture pectinases of Hontonzyme DN is at 8.0 to keep their highest activities for degrading the hydrophobic impurities, especially for various pectins on the ramie substrate. Therefore, all those resulted in the highest capillary rise
13
ACCEPTED MANUSCRIPT height in the curves with pH value at 8.0. Probably, the improvement of the capillary rise height at the pH value of 2.0 was attributed to an additionally chemical hydrolyzation of those hydrophobic impurities in a strong acidic condition. Figure 9 shows that slight and different decrease tendencies in fabric whiteness (R457 /Wr)
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were obtained for the plasma-aided biodegumming process and the conventional one with solution pH value varying from 2.0 to 12.0. Furthermore, a higher fabric whiteness was achieved from the plasma-aided biodegumming process as pH value higher than 4.0. Those indicate that the
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commercial and mixture enzymes of Hontonzyme DN employed in this study also played a role in
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the removal of some natural colorants from the raw substrate, in comparison with the whiteness (R457 /Wr) of 60.5 for the raw ramie fabric without any pretreatment. Probably, it was due to the Hontonzyme DN also involving some enzymatic components with decoloration potential, too. Moreover, Figure 9 also indicates that the oxygen plasma presented a positive effect on the
10.0.
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biodegradation of natural colorants from the substrate, especially for the solution pH from 4.0 to
Figure 10 reveals that a significant decrease in the ramie fabric tensile strength was observed
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as solution pH value decreased from 6.0 to 2.0, as well as a slight decrease with solution pH value
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higher than 10.0 or 8.0 for both the biodegumming processes. Furthermore, as depicted in Figure 10, at most of the subjected solution pH, a little worse deterioration in the ramie fabric strength was observed for the samples treated by plasma-aided biodegumming process than that of the conventional biodegumming. In practice, a soaking procedure with strong acidic solution is usually employed in a wet-chemical pretreatment for raw ramie substrate, in order to hydrolyze and remove some impurities. Therefore, this was also coincident with the improvements in fabric weight loss, capillary rise height and whiteness at a solution pH value as low as 2.0 in Figure 7, 8 and 9.
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ACCEPTED MANUSCRIPT However, the acidic condition also notably catalyzed the hydrolysis of the macrochains of the cellulosic ramie substrate, which resulted in a worse tolerance of the tensile strength of ramie fabric after the treatment in an acidic solution than an alkaline solution as illustrated in Figure 10. The relative lower tensile strength of ramie fabric samples from the plasma-aided biodegumming
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process was also probably due to the oxygen plasma species affects. By consideration of the all influences of the pH on ramie fabric treatment above, a subjected solution pH of 8.0 was suggested in further experiments for the raw ramie fabric biodegumming,
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not only in order to keep the pectinases with a high activity in improving the biodegumming
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efficiency, but also to keep a less affect on the ramie fabric mechanic properties. 3.3 Influence of treatment time on the plasma-aided biodegumming of raw ramie fabric An influence of treatment time on the plasma-aided and the conventional biodegumming of raw ramie fabric samples was investigated at a solution temperature of 75℃, a pH value of 8.0, as
Figure 11-14.
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well as a dosage of the Hontonzyme DN at 5.0% and 10.0% (o.m.f.), respectively, as depicted in
Figure 11 shows that a significant improvement in the fabric weight loss was achieved as
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treatment time ranging from 30.0 min to 60.0 min, and then no any further enhancement was
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observed as treatment time extend to 105.0 min in both the biodegumming processes. Moreover, a higher efficiency in fabric weight loss from the plasma-aided biodegumming process was also obtained at all the treatment times. Theoretically, an appropriate, enough treatment time for substrate is helpful and benefits for the enzymes to degrade the gummy materials and other impurities as full as possible. Consequently, the ramie fabric weight loss was improved in both the biodegumming processes. However, no further improvement in the fabric weight loss as treatment time longer than 60.0 min was probably due to an almost complete removal of the pectin impurities,
15
ACCEPTED MANUSCRIPT etc. The higher efficiency in the fabric weight loss at different treatment times from the plasma-aided process was also due to the positive effect of the oxygen plasma pretreatment on the ramie substrate. Figure 12 shows that an improvement and satisfactory capillary rise height results were
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obtained with treatment time from 30.0 min to 50.0 min, and then no evident enhancement was also observed with time prolonged further to 105.0 min for the plasma-aided and the conventional biodegumming processes. Moreover, a relative high value of fabric whiteness was achieved at a
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short treatment time of 30.0 min, and then an almost independent tendency in fabric whiteness was
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obtained with the treatment time as illustrated in Figure 13. Furthermore, better results of fabric whiteness from the plasma-aided biodegumming process than the conventional one were also available with treatment time from 30.0 min to 60.0 min. Those further indicate that an appropriate short treatment time could present an evident effect on the removal of the hydrophobic pectin
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impurities and natural colorants, etc., to improve the wettability and whiteness of the ramie substrate by the mixture enzymes of Hontonzyme DN in both the biodegumming processes. Moreover, the improvement of the wettability and whiteness of the ramie fabric from the
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plasma-aided biodegumming process in comparison with the conventional one was also due to the
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help of the oxygen plasma pretreatment. Figure 14 shows that comparable values and a slight decrease tendency in the ramie fabric tensile strength were observed with the treatment time from 30.0 min to 105.0 min for both the biodegumming processes. It was probably due to the continuous and long time treatment affects on the ramie fibers in the weakly alkaline degumming solution, especially for the conventional biodegumming process. Accordingly, a treatment time of 60.0 min was recommended in the plasma-aided
16
ACCEPTED MANUSCRIPT biodegumming process for raw ramie fabric. 3.4 Influence of oxygen plasma and its aided biodegumming on the water contact angle of ramie fabric According to the discussion above, the oxygen plasma played a role in the biodegumming of
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raw ramie fabric with the mixture pectinases for the removal of gummy impurities, etc., as well as for saving the dosage of enzymes and treatment time. In order to investigate and confirm the plasma role further, a static water contact angle (α, °) for ramie fabric samples was measured, as shown in
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Figure 15 (a-c).
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Figure 15a demonstrates that a hemispheric droplet of static water on the raw ramie fabric surface was observed with a contact angle (α,) of 97.7°, which indicates that the raw ramie fabric without any treatment poses a poor wettability due to the gummy impurities on the ramie substrate, especially for the hydrophobic pectins, etc. However, Figure 15b shows that the static water droplet
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was absorbed quickly by the ramie fabric after oxygen plasma pretreatment and only a very small part of water was remained on the surface of the substrate with a contact angle (α,) of 14.5°. This clearly reveals that the wettability of the raw ramie fabric surface could be improved significantly
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by the oxygen plasma treatment. Those was directly due to the physical bombardments and/ or
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chemical modifications onto those hydrophobic impurities by the reactive and energetic plasma species, which is also helpful for the enzymes to adsorb, penetrate into the ramie yarns and accelerate the degradation of the broken impurities. Consequently, higher efficiencies in the fabric weight loss, capillary rise height and whiteness were obtained by employing plasma-aided biodegumming process, even a lower dosage of the pectinases of Hontonzyme DN and a shorter treatment time were involved in comparison with the conventional biodegumming. Figure 15c demonstrates that a complete adsorption of the droplet of water occurred immediately on the
17
ACCEPTED MANUSCRIPT plasma-aided and mild biodegummed ramie fabric with a contact angle (α,) of 0.0°, which further proves that a satisfactory removal of the gummy impurities and a high wettability on the raw substrate were achieved by employing the recommended plasma-aided biodegumming process. 3.5 Influence of oxygen plasma and its aided biodegumming on the surface morphology of
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ramie substrate An influence of oxygen plasma treatment and its aided biodegumming on the surface
Hitachi, Japan). The results are shown in Figure 16 (a-c).
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morphology of ramie substrate was also investigated on a scanning electronic microscopy (S-4800,
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Figure 16a shows that the surfaces of the raw ramie fibers without any pretreatment were encrusted by smooth and intact gummy impurity films, and the unique characteristics of ramie fibers, such as the natural stripes and cross sections, were almost invisible due to the impurity covering on the fiber surfaces. However, a notably broken appearance of the ramie surfaces was
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observed with various pittings, groovings and even some fragments on the outer surfaces of the ramie after an oxygen plasma treatment, as shown in Figure 16b. Obviously, the oxygen plasma played a significant role in breaking the intact impurity cover and presented a big contribution to the
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subsequent biodegumming with the enzymes. Figure 16c shows that a clean and smooth ramie fiber
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surface with a magnification of 2000× was achieved by the plasma-aided biodegumming process, although some micro-cracks were also observed probably due to the oxygen plasma effects. Theoretically, the high energetic oxygen plasma species could physically bombard and chemically modify the surface impurities on the ramie fibers, resulting in the broken of the impurity coverings, as well as the change of the surface morphology of the ramie substrate. Moreover, those also make the subsequent biodegumming process benefit from the easy and quick wettability of the substrate surfaces, as well as the easy penetration, diffusion of the enzymes into the broken impurity
18
MANUSCRIPT films or the fabric yarns. Finally,ACCEPTED those result in easy enzymatic reactions with various impurity fragments on fiber surfaces. Therefore, the oxygen plasma treatment shows a significant effect on the surface morphology of the ramie substrate, which then results in the significant contribution to
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the subsequent biodegumming process.
4. Conclusions
A novel biodegumming process with the aid of oxygen plasma for ramie substrate was
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successfully developed with pectinases. The results show that a notable positive effect of oxygen plasma on ramie biodegumming with the pectinases was achieved with much less application of the
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enzymes and treatment time. The static water contact angle measurement and SEM investigations further confirm the functions of oxygen plasma in the change of wettability, morphologies and the improvement of the substrate biodegumming. The novel process has potential applications in the
in the textile industry.
Acknowledgement
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pretreatment of raw ramie, grey cotton fabrics, etc., with more environmentally friendly advantages
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The authors acknowledge gratefully the financial supports from the First Phase of Jiangsu
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Universities’ Distinctive Discipline Development Program for Textile Science and Engineering of Soochow University.
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Basu, S., Saha, M.N., Chattopadhyay, D., Chakrabarti, K., 2009. Degumming and characterization of ramie fibre using pectate lyase from immobilized Bacillus pumilus DKS1. Lett. Appl. Microbiol. 48, 593–597. Bruhlmann, F., Kim, K.S., Zimmerman, W., Fiechter, A., 1994. Pectinolytic enzymes from
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ACCEPTED MANUSCRIPT Captions to Figures Fig.1 Process flowchart for conventional biodegumming treatment of raw ramie fabric samples with pectinolytic enzyme of Hontonzyme DN
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Fig.2 Process flowchart for oxygen plasma-aided biodegumming of raw ramie fabric samples with pectinolytic enzyme of Hontonzyme DN
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Fig.3 Influence of treatment temperature on the ramie fabric weight loss from the plasma-aided and the conventional biodegumming processes
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Fig.4 Influence of treatment temperature on the fabric capillary rise height from the plasma-aided and the conventional biodegumming processes
Fig.5 Influence of treatment temperature on the fabric whiteness from the plasma-aided and the conventional biodegumming processes
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Fig.6 Influence of treatment temperature on the fabric tensile strength from the plasma-aided and the conventional biodegumming processes
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Fig.7 Influence of solution pH on the ramie fabric weight loss from the plasma-aided and the conventional biodegumming processes
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Fig.8 Influence of solution pH on the fabric capillary rise height from the plasma-aided and the conventional biodegumming processes Fig.9 Influence of solution pH on the fabric whiteness from the plasma-aided and the conventional biodegumming processes Fig.10 Influence of solution pH on the fabric tensile strength f from the plasma-aided and the conventional biodegumming processes Fig.11 Influence of treatment time on the ramie fabric weight loss from the plasma-aided and the
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ACCEPTED MANUSCRIPT conventional biodegumming processes Fig.12 Influence of treatment time on the fabric capillary rise height from the plasma-aided and the conventional biodegumming processes Fig.13 Influence of treatment time on the fabric whiteness from the plasma-aided and the
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conventional biodegumming processes Fig.14 Influence of treatment time on the fabric tensile strength from the plasma-aided and the conventional biodegumming processes
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Fig.15 Static water contact angle of the raw ramie fabric surface (a) without any pretreatment, (b)
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oxygen plasma pretreated sample at a pressure of 40.0 Pa and a discharge power of 250.0 W for 3.0 min, (c) the plasma-aided and mild biodegummed ramie fabric with a dosage of the Hontonzyme DN at 5.0% (o.m.f.), a temperature of 75℃ and pH value of solution at 8.0 for 60.0 min Fig.16 SEM images of the raw ramie fabric surface (a) without any pretreatment, (b) oxygen
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plasma treated sample at a pressure of 40.0 Pa and a discharge power of 250.0 W for 3.0 min, and (c) the biodegummed sample with the optimized plasma-aided mild biodegumming process with a
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8.0 for 60.0 min
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dosage of the Hontonzyme DN at 5.0% (o.m.f.), a temperature of 75℃ and pH value of solution at
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EP
TE D
M AN U
SC
Sample preparation for testing
Washed with tap water
RI PT
Treated with pectinases of Hontonzyme DN in a biodegumming solution
Soaked in a penetrating agent solution
Fig.1 24
ACCEPTED MANUSCRIPT
Treated with half dosages of Hontonzyme DN as in the conventional biodegumming process
RI PT
Soaked in a penetrating agent solution
Oxygen plasma treatment
Sample preparation for testing
AC C
EP
TE D
M AN U
SC
Washed with tap water
Fig.2 25
ACCEPTED MANUSCRIPT
RI PT
7.0
SC
6.0 5.5
–○– Weight loss from plasma-aided biodegumming –Δ– Weight loss from conventional biodegumming
5.0 4.5 30.0
45.0
TE D
15.0
M AN U
Weight loss (%)
6.5
60.0
AC C
EP
Temperature (℃)
Fig.3 26
75.0
90.0
ACCEPTED MANUSCRIPT
RI PT
13.0 12.0 11.0
SC
10.0 9.0
–*– Capillary rise height from plasma-aided biodegumming –▽– Capillary rise height from conventional biodegumming
8.0 7.0 6.0 15.0
30.0
M AN U
Capillary rise height (cm)
14.0
45.0
60.0
AC C
EP
TE D
Temperature (℃)
Fig.4 27
75.0
90.0
ACCEPTED MANUSCRIPT
RI PT
70.0
SC
68.0 66.0 64.0
–□– Fabric whiteness from plasma-aided biodegumming –×– Fabric whiteness from conventional biodegumming
62.0 60.0 30.0
45.0
TE D
15.0
M AN U
Fabric whiteness (R457)
72.0
60.0
AC C
EP
Temperature (℃)
Fig.5 28
75.0
90.0
ACCEPTED MANUSCRIPT
RI PT
800.0
SC
700.0 650.0
M AN U
Tensile strength (N)
750.0
600.0
–+–Fabric tensile strength from plasma-aided biodegumming –◇– Fabric tensile strength from conventional biodegumming
550.0 500.0
30.0
45.0
TE D
15.0
60.0
AC C
EP
Temperature (℃)
Fig.6 29
75.0
90.0
RI PT M AN U
SC
10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0
–○– Weight loss from plasma-aided biodegumming –Δ– Weight loss from conventional biodegumming
4.0
6.0
8.0 pH
AC C
EP
2.0
TE D
Weight loss (%)
ACCEPTED MANUSCRIPT
Fig.7 30
10.0
12.0
RI PT
ACCEPTED MANUSCRIPT
SC
13.0
M AN U
12.0 11.0 10.0
–*– Capillary rise height from plasma-aided biodegumming –▽– Capillary rise height from conventional biodegumming
9.0 8.0
TE D
Capillary rise height (cm)
14.0
4.0
6.0 pH
AC C
EP
2.0
Fig.8 31
8.0
10.0
12.0
ACCEPTED MANUSCRIPT
RI PT
74.0
70.0
SC
68.0 66.0
M AN U
Fabric whiteness (R457)
72.0
–□– Fabric whiteness from plasma-aided biodegumming –×– Fabric whiteness from conventional biodegumming
64.0 62.0 60.0 4.0
6.0
pH
AC C
EP
TE D
2.0
Fig.9 32
8.0
10.0
12.0
RI PT
ACCEPTED MANUSCRIPT
800.0
SC
700.0 650.0
M AN U
Tensile strength (N)
750.0
600.0 550.0
–+–Fabric tensile strength from plasma-aided biodegumming –◇– Fabric tensile strength from conventional biodegumming
500.0
400.0
TE D
450.0
4.0
6.0
8.0 pH
AC C
EP
2.0
Fig.10 33
10.0
12.0
ACCEPTED MANUSCRIPT
RI PT
10.0
8.0
SC
7.0 6.0
M AN U
Weight loss (%)
9.0
–○– Weight loss from plasma-aided biodegumming –Δ– Weight loss from conventional biodegumming
5.0 4.0 3.0 30
40
50
60
TE D
20
70
80
AC C
EP
Treatment time (min)
Fig.11 34
90 100 110
RI PT
ACCEPTED MANUSCRIPT
16.0
SC
12.0
M AN U
10.0 8.0
–*– Capillary rise height from plasma-aided biodegumming –▽– Capillary rise height from conventional biodegumming
6.0 4.0 2.0 20
TE D
Capillary rise height (cm)
14.0
30
40
50
60
70
80
AC C
EP
Treatment time (min)
Fig.12 35
90 100 110
RI PT
ACCEPTED MANUSCRIPT
SC
70.0
M AN U
65.0
–□– Fabric whiteness from plasma-aided biodegumming –×– Fabric whiteness from conventional biodegumming
60.0 55.0 50.0 20
TE D
Fabric whiteness (R457)
75.0
30
40
50
60
70
80
AC C
EP
Treatment time (min)
Fig.13 36
90 100 110
RI PT
ACCEPTED MANUSCRIPT
SC
700.0 650.0
M AN U
Tensile strength (N)
750.0
600.0
–+–Fabric tensile strength from plasma-aided biodegumming –◇– Fabric tensile strength from conventional biodegumming
550.0
20
TE D
500.0 30
40
50
60
70
80
AC C
EP
Treatment time (min)
Fig.14 37
90 100 110
TE D
M AN U
SC
(a) α =97.7°
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
(b) α =14.5°
(c) α =0°
Fig.15 38
ACCEPTED MANUSCRIPT
SC
RI PT
(a)
EP
TE D
M AN U
(b)
AC C
(c)
Fig.16 39
ACCEPTED MANUSCRIPT Highlights:
►A novel plasma aided biodegumming process for ramie substrate was developed. ►The biodegumming process involving plasma treatment for ramie fabric was optimized.
RI PT
►Enzyme was reduced in half for the plasma-aided process compared to traditional one. ►Better results were achieved with plasma-aided process compared to traditional one.
AC C
EP
TE D
M AN U
SC
►Notable etching effect and wettablity on ramie were obtained from plasma species.