1. INTRODUCTION:

X-Ray Diffraction (XRD) technique is a prominent and nondestructive tool, used for the crystallographic structure determination of any material. When incident beam of X-rays fall on any material, atomic planes of a crystal cause interference of an incident beam of X- rays, as they leave the crystal and produce X-ray Diffraction (XRD) pattern.¹ During X-ray diffraction, every substance gives a pattern; which is specific for a given substance and depends up on the scattering angles of x-rays by the material. Planes of compounds act as three-dimensional diffraction gratings for X-ray wavelengths similar to the spacing of planes in a crystal lattice. The interaction of the incident X-rays with the sample produces constructive interference (and a diffracted ray) when conditions satisfy Bragg's Law ²as shown in equation (i)-

………………………… ( i )

Where n= Order of Reflection; d= Plane spacing;

This law relates the wavelength of electromagnetic radiation (λ) to the diffraction angle (θ) and the lattice spacing in a crystalline sample (d). By scanning the sample through a range of 2θangles, all possible diffraction directions of the lattice should be attained due to the random orientation of the powdered material. The diffracted X-rays are then detected by X-ray diffractometer to generate the XRD pattern.

Crystallinity index (CI) of any material, which is a quantitative indicator of crystallinity³have been measured by using several methods like Solid-state 13C NMR, infrared (IR) spectroscopy, Raman spectroscopy including XRD technique⁴. In current study CI is calculated using XRD data and applying Segal’s method⁵ of maximum peak height determination by following relationship-

…………. (ii)

Where CI is Crystallinity Index; I₀₀₂ is maximum intensity of the principle peak of crystalline form; and I_am is minimum intensity for amorphous form. Generally CI of any lignocellulosic material depends on the ratio of cellulose, hemicelluloses, lignin etc. any physic-chemical treatment may alter the ratio of cellulose, lignin, hemicellulose, etc.⁶ which may be clearly seen in the XRD patterns. In the present study, CI of alkali/acid treated soya hulls is calculated with the help of equation (ii) using Segal’s peak height method.

2. MATERIALS AND METHOD:

2.1 Chemicals:

Sodium hydroxide pellets (anhydrous), ≥ 98%(Fluka), Orthophosphoric acid, ACS reagent, ≥85 wt. % in H2O(Sigma-aldrich), L-Ascorbic acid reagent grade(Sigma-aldrich), Oxalic acid reagent grade(Sigma-aldrich), Doubly distilled Water, Soya hull wastes.

2.2 Method:

Soya hulls are agro-industrial wastes generated at soya-oil manufacturing units and are collected from local small scale industry of Kota, Rajasthan, India. Washed soya hulls are oven dried at 60^oC for 24 hours, crushed in a kitchen blender and sieved through 120 mesh to get powered form. Four types of chemical treatments are carried out by using 05 g powdered soybean hulls, first sample alkali treated soya hulls ASH is prepared by performing alkali treatment with 2% sodium hydroxide while acid treatments are given using 0.5 M acid solutions of phosphoric acid, oxalic acid, and ascorbic acid, to prepare PASH, OASH, and AASH respectively. X-ray diffraction studies are carried out (Rigaku Ultima-X-ray diffractometer with Cu-Kα, λ = 0.1542 nm) to identify the crystalline nature of the soya hull materials. The maximum intensity of the principle peak of 200 (I₀₀₂, 2θ= 22°) and the intensity of diffraction of 110 peaks (I_am, 2θ=16°) was noted and calculation for the crystallinity index (CI) were performed using Segal’s method, I₀₀₂ denote highest intensity for crystalline form and I_am denotes the amorphous material. XRD patterns obtained are shown in fig.2.

3. RESULT AND DISCUSSIONS:

X-Ray diffraction pattern of native cellulose contains sharp as well as defused bands as shown in fig. 1.⁴Sharp bands correspond to orderly arranged crystalline regions and defused bands correspond to amorphous regions. Crystalline structure is formed due to regular arrangement of atoms. Cellulose contains both crystalline and amorphous phases, arranged randomly. When beam of X-Ray passed through the sample, some of the regularly arranged atoms reflect the X-ray beam constructively and produced enhance intense patterns.

Fig. 1 XRD Pattern of Native Cellulose

X-Ray analysis of alkali/acid treated soya hulls is shown in fig. 2, evidently an increase in ordered crystalline cellulose content is seen and was achieved by the solubilization of the amorphous cellulose, hemicellulose and lignin etc. present in soya hulls-

Fig. 2 XRD Pattern of Acid/Alkali Treated Soya-hulls

Many researchers reported that acid treatment tends to increase CI ^3,6,8 and same has been observed by us as for treated soya hulls are depicted in the Table1 -

Table 1 Values of CI for Lignocellulsic Materials

S. No.

Material

Crystallinity index (CI %)

Reference

Raw material

NaOH-treated

16%

50%

CML-1T

CML-2T

CML-3T

63.82%

43.10%

61.42%

Raw Fibers

Alkali Treated Fibers

Bleached Fibers

Acid Hydrolysis Fibers

25%

54%

57.5%

60.3%

Alkali treated Soya hulls (ASH)

Phosphoric acid treated Soya hulls (PASH)

Oxalic acid treated Soya hulls (OASH)

Ascorbic acid treated Soya hulls (AASH)

22.65%

54.82%

70.39%

76.16%

This Study

4. CONCLUSION AND FUTURE ASPECTS:

Crystallinity Index of lignocellulosic materials depends upon the cellulose, lignin, hemicellulose, etc. contents of material any physicochemical treatments may alter the ratio of cellulose, lignin, hemicellulose, etc. for instance acid hydrolysis treatments given to soya-hulls lead to increase the cellulosic contents of materials and remove amorphous lignin, hemicellulose etc. the values of CI showed vast variations from 22.65% to 76.16%. Hence calculating CI using XRD patterns may lead to give useful information about cellulose contents of lignocellulosic materials and provide also the impact of any physical or chemical treatment applied. This study reveals that organic acids like ascorbic acid and oxalic acid which are more eco-friendly can work better to increase CI and cellulose content of any lignocellulosic waste biomaterials like soya hulls for the application in the field of nanocomposites material synthesis for wide range of applications viz. drug delivery, food packaging, wastewater treatment, etc. at reasonable cost with eco-friendly techniques.

5. DECLARATION OF COMPETING INTEREST:

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

6. ACKNOWLEDGEMENTS:

The authors are thankful to Head, Department of Chemistry University of Kota for XRD analysis and execution of data. SV and PS are thankful to SERB- DST New Delhi for financial support under ASEAN-India CRD scheme (CRD/2018/000062).

REFERENCES:

1. V. Pecharsky, and P. Zavalij, Fundamentals of Powder Diffraction and Structural Characterization of Materials, 2nd Ed.; Springer Science, 2009, https://drxaplicacionesmx.files.wordpress.com/2009/10/pecharsky_fundamentals-of-powder-diffraction-and-structural-characterization-of-materials.pdf

2. Britannica, T. Editors of Encyclopaedia. "Bragg law." Encyclopedia Britannica, December 30, 2016. https://www.britannica.com/science/Bragg-law

3. Mariño M, Lopes da Silva L, Durán N, Tasic L., Enhanced materials from nature: nanocellulose from citrus waste, Molecules,2015;20(4):5908-5923. https://doi.org/10.3390/molecules20045908

4. Nicoleta Terinte, Roger Ibbett and Kurt Christian Schuster, Overview on native cellulose and microcrystalline cellulose structure studied by x-ray diffraction (waxd): comparison between measurement techniques 2011, lenzinger berichte 89 2011, 118-131.

5. L. Segal, J. J. Creely, A. E. Jr. Martin, and C. M. Conrad. An Empirical Method for Estimating the Degree of Crystallinity of Native Cellulose using X-ray Diffractometer, Tex. Res. J. 29,1959, 786-794.

6. Shweta and Jha Bioresour. Synthesis and characterization of crystalline carboxymethylated lignin– TEOS nanocomposites for metal adsorption and antibacterial activity. Bioprocess. (2016) 3:31

7. Anuj Kumar, Yuvraj Singh Negi, Veena Choudhary, and Nishi Kant Bhardwaj, Characterization of Cellulose Nanocrystals Produced by Acid-Hydrolysis from Sugarcane Bagasse as Agrowaste. Journal of Materials Physics and Chemistry 2, no. 1 (2014): 1-8. doi: 10.12691/jmpc-2-1-1.

8. Zain NFM, Yusop SM, Ahmad I. Preparation and Characterization of Cellulose and Nanocellulose From Pomelo (Citrus grandis) Albedo. J Nutr Food Sci, (2015), 5: 334. https://www.longdom.org/open-access/preparation-and-characterization-of-cellulose-and-nanocellulose-2155-9600-5-334.pdf

Received on 05.04.2022 Modified on 01.05.2022

Asian J. Research Chem. 2022; 15(3):225-227.

DOI: 10.52711/0974-4150.2022.00040