XRD and FTIR Studies of Nanocrystalline Cellulose

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Aug 21, 2017 - the reinforcing agent in a polymer matrix composites [4]. ... strong fiber that has a certain potential as a reinforcing agent in composites.
Journal of Metastable and Nanocrystalline Materials ISSN: 2297-6620, Vol. 29, pp 9-16 doi:10.4028/www.scientific.net/JMNM.29.9 © 2017 Trans Tech Publications, Switzerland

Submitted: 2017-01-17 Revised: 2017-04-04 Accepted: 2017-04-04 Online: 2017-08-21

XRD and FTIR Studies of Nanocrystalline Cellulose from Water Hyacinth (Eichornia crassipes) Fiber Mochamad Asrofi1,a, Hairul Abral2,b*, Anwar Kasim3,c, Adjar Pratoto2,d 1

Doctoral Student of Agricultural Sciences, Faculty of Graduate Studies, Andalas University, 25163 Padang, Indonesia 2

Department of Mechanical Engineering, Andalas University, 25163 Padang, Indonesia

3

Department of Agriculture Technology, Andalas University, 25163 Padang, Indonesia a

[email protected], [email protected], [email protected], d [email protected] *Corresponding author

Keywords: Nanocrystalline cellulose, water hyacinth fiber, XRD, FTIR.

Abstract. The isolation and characterization of nanocrystalline cellulose (NCC) from water hyacinth (WH) fibers were carried out. There are two treatments to obtain NCC from WH fibers by chemical and mechanical treatments. The chemical treatment involved alkalization with NaOH 25% in a highly-pressured tube, acid hydrolysis with 5M HCl, and bleaching with (NaClO2:CH3COOH) in ratio 5:2. The mechanical treatment was performed by using ultrasonic homogenizing at 12000 Rpm for 2 h. The morphological surface was observed by Transmission Electron Microscopy (TEM). TEM reported that the size of NCC was 10–40 nm. Crystallinity index and functional group analysis of the NCC WH fibers were also examined using X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. XRD reported that the crystallinity index increased significantly after chemical and mechanical treatment due to the presents of crystalline area in the WH fibers. The crystallinity index of raw fiber, digester, bleaching, and ultrasonic homogenizing were 7%, 68%, 69%, and 73% respectively. The content cellulose of final product was 68% as measured by the chemical composition test. Meanwhile, FTIR reported that WH fibers after being given chemical treatment lead the functional group change due to removal hemicellulose and lignin. The result of XRD and FTIR were indicated that the sample of NCC WH fibers presents the structure of cellulose crystal type I. Introduction Cellulose is the main component of various fibrous plantations such as cotton, flax, hemp, jute, sisal, and etc. Cellulose is a linear polymer unit of β-(1=>4)-D-glucopyranose (Fig. 1) [1]. The mechanical properties of several natural fibers depend on the type of cellulose structure. There is a number of cellulose types structure namely was (I, II, III, IV, and V) respectively. The type of cellulose structure I is the one of the most prominent due to having good mechanical properties compared to the other type of cellulose structure [2].

Fig. 1. Cellulose chain structure

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Cellulose which is composed with microfibrils has been traditionally defined as crystalline components of cellulose chains having diameters within the range of 3.5-38 nm [3]. Cellulose in the form of nanocrystalline shows prominent properties such as dimension in the nano-scale that provides the high contact surface area. The nano-sized fiber is the new material that can be used as the reinforcing agent in a polymer matrix composites [4]. Nanocrystalline cellulose can be made by through a chemical treatment such as acid hydrolysis which can serve to penetrate the crystalline region of microfibrils. The cellulose can be accessed and achieved in the single crystal formation [4,5]. The cellulose is a crystalline unit of the fibrous plants. XRD characterization in the form of powder is one of a method to determine the crystalline structure of the cellulose sample. This method is usually using peak height method as reported by Johnson [6]. The water hyacinth is one of potential natural fiber containing the cellulose which is considered weeds plant in a water environment. The WH fiber is one of natural fiber material which is not yet maximally used for it has various potency. The availability of WH in Indonesia is abundant and has great potential from the raw materials as well as from the selling value is not so high [7]. It is a strong fiber that has a certain potential as a reinforcing agent in composites. The chemical content of WH fibers is about 60% cellulose, 8% hemicellulose and 17% lignin as reported by Abdel [8]. Several types of research have been reported about the extraction of nanocellulose from fiber plants. The combination of chemical and mechanical treatments was done by Alemdar et al about the isolation of nanocellulose fiber from wheat straw and soy hull as the reinforcement material in bio-composite. They acquired the size of the nanocellulose fiber of wheat straw and soy-hull was about 10-80 nm and 20-120 nm respectively. The XRD reported that the crystallinity index of soyhull and wheat straw increased after being given the chemical treatment was about 77.8% and 69.6% respectively. The FTIR also reported that the amorphous components such as hemicellulose and lignin were removed in the nanocellulose fiber of wheat straw and soy hulls after chemical treatment [1]. Ramesh et. al. has conducted studies about the isolation of nanocellulose from water hyacinth fibers under the cryo-crushing and sonication methods. On the TEM characterization shows that the fiber diameter in the ranges 25-40 nm [9]. However, the characterization was not done yet on the research conducted by Ramesh et. al. as to know the crystalline of each step on both chemical and mechanical treatments. Therefore, in this studies, the novel and simple method were explained namely the ultrasonic homogenizing methods in produce NCC of WH fibers. The characterization of XRD and FTIR were done to know the crystallinity and the functional group change of each treatment respectively. TEM characterization was also carried out to know the size of WH fibers in nanometer area. Materials and Methods Materials. The tree of WH fibers was obtained from water hyacinth plants at the watery and muddy areas in Payakumbuh, West Sumatera, Indonesia. Several treatments were carried out to get WH fibers such as alkalization, acid hydrolysis, and bleaching. Sodium Hydroxide (NaOH) 25%, distilled water, hydrochloric Acid (HCl) 5M, sodium chlorite (NaClO2) and acetate acid (CH3COOH) were supplied from the Faculty of Agrotechnology, Andalas University. Preparation of WH plants. The tree of WH plants was separated from both roots and leaves respectively, then washed to get rid of dirt. The tree of WH plants was dried at room temperature for 3 days and cut into small pieces ± 5 mm. Alkalization. The isolation of WH fibers consists of three procedures namely was alkalization, acid hydrolysis, bleaching and ultrasonic homogenizing respectively. In alkalization, the dried tree of WH plants was boiled using high-pressure reactor. Firstly, NaOH 25% (125 grams), distilled water (7 liters), and the dried tree of WH plants (500 grams) were poured down into a high-pressure reactor under temperature and pressure 130oC and 4 bars respectively. Then, the mixture was stirred and boiled for 30 min and 6 h respectively. After the mixture was boiled for 6 h, we will produce

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soft WH fibers containing PH about 12-13. The WH fibers were neutralized with distilled water up to PH 7 and made into paper. Acid hydrolysis. The 10 grams dried WH fibers in paper form were measured by using analytical balance. Afterward, WH fibers were treated by grinding and wet blending using high rotation under Hakasima HK 7997 brand at 3000 Rpm for 5 min and 20000 Rpm for 5 min respectively. Finally, we produce the WH fibers in pulp form. In acid hydrolysis, The WH pulp fibers were treated with 5M HCl 150 ml and heat up under the temperature and rotation 50oC and 300 Rpm respectively for 12 h. Finally, we produce finer WH fibers than alkalization in a high-pressure reactor. The WH fibers were neutralized with distilled water to remove acid content up to PH 7 Bleaching. In bleaching condition, The WH fibers from acid hydrolysis process were treated by using (NaClO2:CH3COOH) under ratio 5:2 or 125 ml NaClO2 : 30 ml CH3COOH. Then, the mixture was heated under the temperature 50oC for 1.5 h or the product of WH fibers changes into white color. It was indicated that the content of amorphous regions such as hemicellulose and lignin were removed from WH fibers. The WH fibers were neutralized up to PH 7 using distilled water. Ultrasonic homogenizing. The fine WH fibers from bleaching process were re-dispersed with distilled water into chemical glass up to 150 ml. The mixture was treated by using WiseTis Equipment ultrasonic homogenization at 12000 Rpm for 2 h to obtain the suspension of NCC WH fibers. Finally, we produce NCC from WH fibers. Surface morphology observation. The morphology of NCC from WH fibers was measured by using TEM (JEM-1400, JEOL, Department of Chemistry, Gajah Mada University, Indonesia). It was operated at 100 keV. The nanocrystalline cellulose in the liquid suspension was dropped to the copper grid under the support of carbon film and then dried. The dried samples were directly observed by TEM at room temperature. Crystallinity index measurement. The XRD Characterization was carried out by using (PAN analytical Xpert PRO instrument, Padang State University, Indonesia) with the sample in the solid film. The operation voltage and current were 40 kV and 35 mA respectively. The range of diffraction intensity was recorded at (2θ = 10 - 30o). The wavelength radiation was (λ=0,154 nm). The crystallinity index was measured by using a Segal’s method (Eq. 1): Icr = (I200-Iam)/I200

(1)

where I200 is the maximum intensity of peak diffraction at (2θ=22.6o) corresponds with the crystallinity region. Meanwhile, Iam is the intensity of peak diffraction at (2θ=18o) corresponds to the amorphous region. The crystalline size was calculated by using Derby Scherer’s equation (Eq. 2): D = k λ / β Cos θ

(2)

where k is the form factor (0.89) and β is FWHM (Full Width Half Maximum) of maximum intensity (I200) in radian. Functional group determination. FTIR characterization was studied to determine the chemical structure of WH fibers. The spectrum of FTIR in the raw sample, digester, bleached pulp, and ultrasonic homogenizing was recorded by using an instrument (The Perkin-Elmer Frontier) within the range of wave number 600 – 4000 cm-1 under resolution 4 cm-1. The samples were made in powder and mixed with KBr as well as followed with the pressure within the pellet ultra of the thin layer.

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Result and Discussion Chemical composition analysis The chemical composition was carried out to determine the content of cellulose in the samples before (raw fiber) and after become a final product (homogenizing). The content cellulose of before and after become a final product was 40% and 68% respectively. It was indicated that the effect of treatment can increase the cellulose content in the sample due to the removal hemicellulose and lignin. Surface morphology analysis The NCC of WH fibers image (Fig. 2) was indicated by TEM from nano-cellulose in liquid suspension. As shown in (Fig. 2a), nanocrystalline cellulose was formed like a particle and it has a circular form. It still looked clearly an independent particle with a diameter range of 10-40 nm. However, several particles aggregated (Fig. 2b) due to the nanocrystalline cellulose size is very small and the surface hydroxyl of the particle is also easy to form the hydrogen bond which causes a reunion as reported by Hongjia Lu et al [21]. This phenomenon was similar to a previous report [10,21]. Therefore, it is suggested to use of ultrasonic homogenizing to obtain the homogenous NCC diameter of WH fibers.

(a)

(b)

Fig. 2. TEM image: (a) of independent particle like circular form; (b) of aggregated NCC from WH fibers Crystallinity index analysis The samples were characterized in the raw, digester, bleaching, and ultrasonic homogenizing of WH fibers. It can be seen at the (Fig. 3) that the raw fiber has flat diffracting pattern correspond a lot of amorphous regions. Meanwhile, the XRD pattern of digester, bleaching, and ultrasonic homogenizing fiber has the same diffractive pattern. There are two peaks at (2θ = 22.6 o and 16o) which are indicated the crystal structure of cellulose type I. This result was indicated the presence of intra and inter-molecular hydrogen bonding occurring in the cellulose through hydroxyl group that can trigger the formation of crystal order in the cellulose as reported by Sunil et. al. [11]. Index crystallinity of raw, digester, bleaching, and ultrasonic homogenizing of WH fibers were consecutive as follows 7%, 68%, 69%, and 73% respectively. This phenomenon proves that the role of chemical treatment successfully increased the cellulose fiber crystalline due to the removal of hemicellulose and lignin contents during the chemical treatment as reported by Janoobi et.al. [12].

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Fig. 3. XRD pattern of fibers at various stages of treatment Meanwhile, the higher crystalline in the cellulose fiber could also increase the domain size of crystalline fiber may be due to the presence of mechanical treatment such as ultrasonic homogenizing that can lead the diameter was achieved in the nanometer size and the contact surface area of WH fibers slightly increased (Table. 1). This result was a similar report with the Sunil et. al. that the domain size of areca nut husk fibers was slightly increased after being given chemical and mechanical treatments [11]. Table 1. Crystallinity index, crystalline domain size, and d-spacing of fibers at different stages of treatment Fiber treatment stage Raw fiber Digester Bleaching Ultrasonic homogenizing

Crystallinity Index (%) 7 68 69 73

Crystalline domain size (nm) 0.04 3.31 3.43 3.54

d-spacing (nm) 0.40 0.39 0.39 0.39

Functional group analysis In the FTIR characterization, the spectrum of raw, digester, bleaching, and ultrasonic homogenizing of WH fibers was performed. In the (Fig. 4), The raw fiber sample was the one not given any treatment. It has been already discussed that the chemical analysis on the main component of the natural fiber was the cellulose, hemicellulose, and lignin. There were three components which composed of the natural fibers such as ester, an aromatic ketone, and alcohol groups with the amount difference of oxygen contained in the functional groups. In (Fig. 4) shows the FTIR spectrum of all WH fibers sample which is not given treatment and the ones are given treatments showed at the domain of 3500-3200 cm-1 due to the presence of OH stretching vibration of hydrogen bonding in the hydroxyl group. It can be seen the value of wavenumber was getting greater. This phenomenon was attributed to the presence of interaction of hydrogen bonding in the cellulose molecule which is stronger after being given the chemical treatment [11]. Other than that, CH groups appeared a peak in each sample in the wavenumber of 2800 and 3000 cm-1 which indicated the presence of cellulose molecule [12,13]. Due to nature is hydrophilic, all fibers show spectrum at the wavenumber of 1600-1650 cm-1 which correspond the bending vibration of water absorption [11,14]. It can be seen at the (Fig 4.), that the highest water absorption occurred in the raw fiber. This phenomenon was indicated still a lot of amorphous components as reported by Alemdar et. al and Velazquez et. al. [1,15].

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The lignin components presence in the raw of WH fiber on the peak characteristic of 1253, 1322, and 1620 cm-1 which correspond the aromatic skeletal vibration and carbonyl group. This is quite obvious that after the alkalization and bleaching treatments, the spectrum of the three peaks appeared with low intensity. This result was similar to Abraham’s report [16].

Fig. 4. FTIR spectra of fibers at various stages of treatment The peak which appearing at 1620 cm-1 in the spectrum was the raw of WH fibers fiber due to the linkage presence of C=O, one of which is the characteristic group of lignin and lignin/hemicellulose. The alkali treatment can reduce the hydrogen bonding due to the disappearance of the hydroxyl group by the sodium hydroxide reaction (NaOH) [17]. This result decreases -OH concentration, and it also strengthens the degradation of the intensity of the peak ranging 3500 and 3200 cm-1 compared to the fiber without treatment [18]. It can be concluded from the FTIR characterization, that there was a reduction in the quantum of bonding component present in the fiber due to the alkalization and bleaching process. The raw of WH fiber preserves the characteristic at the peak of 1253, 1322, and 1620 cm-1. Primarily, this peak was caused by the hemicellulose component and lignin. The FTIR spectrum of NCC of WH fibers preserves almost similar profile in each wavenumber with digester and bleached pulp treatment. It was indicated the effect of chemical treatment that can lead to cellulose crystal structure of type I as reported by Ibrahim et. al. [19]. However, in this case, the intensity peak of NCC WH fibers is higher than the raw and digester fiber as the reported by Rosli et. al [20]. This was further confirmed by the XRD analysis.

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Summary This study shows that the isolation of nanocrystalline cellulose from water hyacinth fiber was done successfully. Two combination treatment were carried out such as chemical and mechanical treatments. A chemical treatment consists three stage: alkalization, acid hydrolysis, and bleaching process. Meanwhile, a mechanical treatment such as ultrasonic homogenizing. FTIR results show that chemical treatments could successfully be used to remove amorphous regions such as lignin and hemicellulose. This result is an agreement with the XRD’s result that the crystallinity index of raw fiber to bleaching stage slightly increased due to removal a non-cellulosic component. And besides that, the effect of chemical treatment can lead a presence of cellulose crystal structure of type I. The XRD pattern of each sample exhibit significantly different depend on crystallization behaviors. Crystallinity index of raw fiber, bleaching, and ultrasonic homogenizing was 7%, 69%, and 73% respectively. This result was supported by chemical composition analysis that the cellulose content of final product (after homogenizing) increased 70% than non-treatment (raw fiber). The nanocrystalline cellulose after being given treatment such as acid hydrolysis and ultrasonic homogenizing showed a higher crystallinity index due to removal amorphous regions. TEM shows that nanocrystalline cellulose was formed like a particle and it has a circular form with a diameter range of 10-40 nm. All of these that nanocrystalline cellulose from water hyacinth fibers has potential application in various fields especially as reinforcing agent in bionanocomposites. Acknowledgement This research was funded by Directorate General of Higher Education Ministry of National Education, Indonesia, with project name The Research of Master Program Leading to Doctoral Degree for Excellent Students in the year of 2017. References [1] [2] [3] [4] [5] [6] [7] [8] [9]

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