Isolation and structural characterization of cellulose nanocrystals extracted from garlic straw residues

Published Date
Received 29 January 2016, Revised 18 April 2016, Accepted 21 April 2016, Available online 30 April 2016.

Author
Fatma Kallel. Author links open the author workspace.Opens the author workspaceOpens the author workspacea. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceFedia Bettaieb. Author links open the author workspace.b. Numbers and letters correspond to the affiliation list. Click to expose these in author workspacec. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaced. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceRamzi Khiari. Author links open the author workspace.Opens the author workspaceOpens the author workspaceb. Numbers and letters correspond to the affiliation list. Click to expose these in author workspacec. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaced. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceAraceli García. Author links open the author workspace.c. Numbers and letters correspond to the affiliation list. Click to expose these in author workspacee. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceJulien Bras. Author links open the author workspace.c. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaced. Numbers and letters correspond to the affiliation list. Click to expose these in author workspaceSemia Ellouz Chaabouni. Author links open the author workspace.a. Numbers and letters correspond to the affiliation list. Click to expose these in author workspacef. Numbers and letters correspond to the affiliation list. Click to expose these in author workspace

a

Enzyme Bioconversion Unit (04/UR/09-04), National School of Engineering, Sfax University, P.O. Box 1173-3038, Tunisia

b

University of Monastir, Faculty of Sciences, UR13 ES 63—Research Unity of Applied Chemistry & Environment, 5000 Monastir, Tunisia

c

University of Grenoble Alpes, LGP2, F-38000 Grenoble, France

d

CNRS, LGP2, F-38000 Grenoble, France

e

University of the Basque Country UPV/EHU, Department of Chemical and Environmental Engineering, 20018 San Sebastián, Spain

f

Common Service Unit of Bioreactor Coupled with an Ultrafilter, National School of Engineering, Sfax University, P.O. Box 1173-3038, Tunisia

Highlights

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High aspect ratio cellulose nanocrystals were extracted from garlic straw residues.

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The crystallinity index of the extracted CNCs is found to be 68%.

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Rod-like CNCs have diameters of 6 nm and length 480 nm as revealed by TEM and AFM.

Abstract
The aim of this study was to explore the utilization of garlic straw residues as source for the production of cellulose nanocrystals (CNC). Garlic straw (GS) was first purified using chemical alkali extraction (ATGS) and then bleached (BGS) before the production of cellulose nanocrystals (CNC-GS) by acid hydrolysis (H2SO4). The chemical composition of GS was determined according to TAPPI standards and showed that it is composed by 41% wt cellulose, 18% wt hemicelluloses and 6.3% wt lignin, among other components. Then, the obtained fibers were extracted and characterized by several techniques such as X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The Fourier transform infrared spectroscopy (FTIR) spectra showed changes in the peaks at 1731, 1556 and 1244 cm−1, indicating that the alkali treatment partially removed hemicelluloses and lignin from the fiber surface. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) techniques were used to investigate the morphology of the produced CNC. The crystallinity index of the GS was 37.4%, and it increased to more than 68% after the acid hydrolysis. The garlic straw had better thermal stability than those of the cellulose obtained after the bleaching treatment and of the nanocrystals isolated following acid hydrolysis. The CNC presented a needle-shaped nature, an average diameter and length of 6 nm and 480 nm, respectively, leading to an aspect ratio of approximately 80. These promising results proved revalue of this by-product for the production of CNC and its potential use as reinforcement in the preparation of nanocomposites.

Graphical abstract

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Keywords

Garlic straw

Chemical composition

Morphology behavior

Cellulose nanocrystals

Acid hydrolysis

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http://www.sciencedirect.com/science/article/pii/S0926669016302904