Eco-friendly pretreatment and dyeing processes on green textile fibers

Abstract:
This article reports the studies on pretreatment of natural cellulosic fibers with enzymes and its characterization was investigated in first part. The biotechnology application on natural celluolosic fibers was compared with conventional pretreatment process and found quite compatible. In the second part of studies application of natural dye extracted from curcuma longa L. powder was examined on eco-friendly pretreated cellulosic fibers with different mordants. It was found that dyeing obtained with extract of curcuma longa L. powder in presence  of mordant have better color strength and  moderate to good fastness properties. Further, the efficiency of different mordant were also compared and found that heavy metal mordant can be successfully replaced with natural mordant leading to environmental friendly process of dyeing with curcumin powder.

1 Introduction:
Increasing environmental consciousness throughout the globe has forced technologists and industrialists to adopt safer methods. Textile wet processing consumes lots of water, chemicals, color and auxiliaries and generate high amount of effluent load and eco-standard of final product. Wet processing of textile plays a vital role in controlling the said problems and various approaches have been suggested by many researchers and practiced successfully 1. Application of biotechnology and coloration with natural resources are considered as one of the important aspects in the said areas 2-6. Many enzymes have been developed and practiced commercially in pretreatment of textiles. In ancient time natural colorants were the only sources of textile colorations 1,5,6. With the invention of synthetic dyes in 1856 by W H Perkin from coal tar, the use of natural colors in textile declined tremendously. In spite of some common limitations associated with natural color application on textile fibers, they have been widely adopted in many applications in recent years. Further, potential of natural color usage continuously increases due to their specific advantages like non-toxic, non-carcinogenic, agro-renewable in nature, soothing shades and environmental friendly 7-12.

Cotton and ramie, being natural cellulosic fibers consist heterogeneous non cellulosic impurities, namely, hemicellulose, pectin, lignin, wax etc. Many enzymes have been developed for hydrolysis / decomposition of these non cellulosic components. Very few literatures pertaining to the application of biotechonolgy application on cotton and ramie were available. Further, no systemic and scientific approaches have been made for synergestic application of various enzymes on different components. In the present study, three enzymes of various activities were used in combination for pretreatment of cotton and ramie grey fibers and evaluated and compared with conventional caustic process.  In the second part, optimize dyeing conditions with the most commonly accepted natural color, namely, curcuma longa L. powder was developed on eco-friendly pretreated fibers. The dye was extracted with alcoholic extract, and applied on natural fibers with and without mordant. Fibers dyed with natural colorant were tested for their dyeing efficiency and fastness to various test methods.

2 Experimental:

2.1 Materials:

Cotton fabric in grey form and ramie in decorticated form were procured from Mafatlal Industries Limited, Gujarat and Ramie Research Station, Assam respectively, were pretreated and used in the present study. Curcumin was purchased from the local market, chopped into small pieces and dried in oven at 80oc for 24 h. The dried curcumin was ground to fine powder, filtered through 100 mesh sieve to obtain powder of uniform particle size and stored in air tight container still further use. Enzymes, which are supplied by manufacturer as a commercially grade, were used without further purification (table-1). All the other chemicals used were of laboratory reagent grade.

Table – 1 : Details of enzymes used

2.2 Extraction of dye:

Curcumin chunks, were crushed into powder and filtered through 100 mesh and used for the subsequent extraction. The curcuma longa L. powder (10 gm) was extracted in 100 ml of methanol at 500 C for 1h in soxhlet apparatus. The content was cooled at room temperature and filtered through what man filter paper number 1.The extract was utilized throughout the dyeing experiment.

2.3 Pretreatment of cotton and ramie fibers:

Bio-pretreatment of cotton and ramie fibers were studied with various process parameters earlier and the optimal conditions obtained are reported in table-113,14. After pretreatment the samples were washed thoroughly to neutral pH with distilled water and used for subsequent analysis.

Table – 2 : Pretreatment conditions of cotton and ramie fibers

2.4 Natural color dyeing:

Cotton and ramie fibers, previously pretreated with enzymatic process, were treated with the myrobolan solution (10 %, w/v) at 500C for 30 minutes. After mordanting the samples were dried in air (without washing) to make them ready for subsequent dyeing. Dyeing of curcumin extract was performed by exhaust method at 900C for 60 minutes, using liquor ratio of 1 : 50 on mordanted and unmordanted natural cellulosic fibers at pH of 8. Sodium sulphate (10 gpl) is used as an electrolyte in dye bath. Dyeing was followed by rinsing with water, soaping at 500C with NID (1 gpl), washing and air drying.

2.5 Analytical procedure :

Weight loss percentage, wettability, moisture regain, chemical compositions, tensile properties, whiteness and yellowness indices of the pretreated and raw fibers are determined as per the procedure described earlier14. Dyeing efficiency in terms of percentage exhaustion, colour strength (K/S) and fastness properties were determined as per the prescribed standard procedure15.

3. Results and discussion :

3.1 Enzymatic pretreatment of cotton and ramie fibers :

Cotton and ramie fibers were pretreated with enzymes (E – I to E – III) and compared for their efficiency against conventional process (Table – 3).

Table – 3 : Bio-pretreatment of cotton and ramie fibers

The results indicate that enzymatic pretreatment of cotton and fibers are quite comparable with that obtained with convention. The chemical compositions of both the fibers are heterogeneous in nature and therefore different combinations of enzymes are performed for pretreatment. Weight loss percentage results show that the required impurities are removed effectively from the fibers. Wettability of pretreated cotton and ramie fibers are also found to be improve and as per the required for subsequent dyeing process. Moisture regain values increases on removal of non-cellulosic impurities in case of cotton fiber while decreases in case of ramie fiber. This is because, in case of cotton fibers the major non-cellulosic impurities are present in the primary wall of the fiber and mainly consist fats (form hydrophobic layer). However, in ramie fiber, the non-cellulosic impurities are present mainly in the interior of the fiber strand and consist hemicellulose as the major component (hydrophilic in nature), removal of which decreases moisture regain. Whiteness index of the fibers improve on pretreatment and results are very close to the conventional process. Exactly, similar but opposite trends was observed for yellowness index of the fibers. Tensile strength of the grey fibers is higher and on removal of impurities it decreases. The non-cellulosic components of fibers act as binding material and on removal reduce tensile strength.

3.2 Natural coloration of cotton and ramie fibers:

3.2.1 UV Visible characterization:

It is well known that the solvent exerts a profound influence on the quality and shape of the absorbance curve 16. Different solvents were analysed for UV analysis and methanol satisfied all the conditions relative to peak quality and non interference at the specific wavelength. Curcumin (keto form, figure-1) givesturmeric its characteristics yellow colour. The UV – Visible spectra (figure -2) of methanol extract of curcumin shows the characterized peaks and troughs at 350 – 550 nm with maximum absorbance at 420 nm wavelength.

          Figure – 1 Structure and UV –Visible graph of curcumin colour

3.2.2 Dyeing behavior of curcumin on natural cellulosic fibers:  

From the foregoing experiments it has been observed that enzymatic pretreatment of cotton and ramie fibers are quite compatible with conventional caustic soda process. The previously bio-pretreated fiber samples, in optimal conditions, are dyed in curcumin extract, with and without mordant (myrobolan). Color strength and exhaustion percentage of the dyed samples are determined and summarized in table – 4.

Table – 4 : Color values of curcumin dye extract on cotton and ramie fibers

It can be seen that color strength of cotton fiber (232 %) increases significantly on mordanting in comparison to ramie fiber (181 %). This is because the natural hemicellulose and pectin, being poly carboxyls, present in grey ramie and partially in pretreated ramie supports the dye attachment on the fiber. Further, mordanting increases color strength of cellulosic fibers in general due to the increasing availability of sites on fiber surface. The dye exhaustion percentage on grey cotton and ramie are lower i.e. 10.8 and 26.1 % respectively and on pretreatment increases to 32.3 and 46.4 % respectively. This is because on pretreatment the non-cellulosic impurities being removed and increases the wettability of fiber significantly. Further, on mordanting the dyeing efficiency of cellulosic fibers increases significantly (190 % in cotton and 125 % in ramie). Mordants, required to increase affinity between fiber and certain natural colors. Mordants (mostly metallic salts) anchored to any fiber, chemically combine with certain functional groups present in the natural dye and bound by coordinated/covalent bonds or hydrogen bonds.

The dyeing efficiency of dyed fibers is also evaluated by another important parameters namely, fastness properties (table – 5).The result being expressed in terms of staining of adjacent fiber (cotton). The color change ratting is also almost same to that of staining. Cotton and ramie fibers treated with myrobolan have better washing fastness (ratting 4) compared to untreated (ratting 3). Crock fastness of curcumin on cotton fiber is good (ratting 3/4) but poor on ramie fiber (ratting 3)

Table – 5 : Color fastness of curcumin on cotton and ramie fibers

even after mordanting. Light fastness of the said natural color is found moderate on both the fibers. Poor light fastness can be attributed to the inherent susceptibility of curcumin dye chromphore to photochemical oxidation. In general the overall fastness properties of curcumin after mordanting with myrobolan are said to be of acceptable limit.

4 Conclusions :

The most commonly used natural cellulosic fibers, namely, cotton and ramie fibers, are pretreated with enzymatic process i.e. eco-friendly process. The various characteristics are determined and found that results are quite compatible with that obtained with conventional caustic soda process. Further, the above environmental friendly pretreated fibers are dyed in the most common color i.e. yellow color with curcumin extract with natural mordant. The dyeing results are also energetic in terms of color strength and dye exhaustion after mordanting with myrobolan. Most of the fastness properties of curcumin dye are poor, but somewhat compatible when the fiber is treated with mordant.

It is possible to preserve Green Status of natural cellulosic fibers after their wet processing. Such products have high valued in designed wear particularly in fashion market. Further, research will be made by the same authors to analyze its more value added applications like, microbial, UV protection etc.

5. References :

1 S R Shah & J N Shah, J of Adv Mgt. Tech. & Engg. Sc., March (2012 ) 135.
2. R Araujo, M Casal & A Cavaco-paulo, Biocatalyst & Biotransformation, 26 (5) (2008) 332.
3. P Shyem Sundar, S Kaur, N Karthikeyan & K Prabhu, Ind Text J., May (2007) 33.
4. K Mojsov, Int Congress “enginerring, Ecology & Materials in Processing Industry” at
Jahornia, March 9th – 11th (2011) 230.
5. S R Shah & J N Shah, Res. J of Rec.Sc., May (2013 ) 35.
6. S R Shah & J N Shah, Res. J of Rec. Sc., July (2013 ) 1.
7. R B Chavan, Colourage, April (1995) 27.
8. S R Shah & B H Patel, Bangl. Text. Today, June (2013) 31.
9. M L Gulrajani, Colourage, July (1999) 19.
10. A Samanta & P Agarwal, Ind. J. of Fib. & Text. Res., Dec (2009) 384.
11. N ithriya, J. Basic Appl. Sci. Res., March (2013) 5.
12. S R Shah & B H Patel, Asian Dyer, Dec (2012) 31.
13. S B Guha & S R Shah, J of Text Asso., Jan (2001) 215.
14. S D Bhattacharya & S R Shah, The Indian Text J., May (2009) 16.
15. A Samanta, A Konar & S Chakraborti, Ind. J. of Fib. & Text. Res., Mar (2011) 63.
16. K Sharma, S S Agrawal & M Gupta, Int J of Drug Dev & Res., Vol 4 (2012) 375.