Spectroscopic Characterization of a Material of Natural Origin before and after Treatment with Different Solvents

Introduction

In Morocco, the sugar industry has known a remarkably developed in recent years, thanks to the important cultivation of sugar cane and sugar beet. The industry of these two plants has produced several by-products; each by-product is valued in several fields. The sugar cane wax is found among the constituents of sugar cane, which is used in the cosmetics and pharmaceutical industry, [1], it is also included in the composition of medicines that lowers cholesterol levels. Thus, the sugar beet molasses is used to produce alcohol, used as spirits or medicine, in the manufacture of perfumes [2,3].

The beet pulp is the second by-product of the sugar beet industry after molasses, and it is mainly used in the feeding cattle [4]. It is a food rich in digestible sugar and generally much appreciated by most animals. The beet pulp can be used as a fermentation substrate or of industrial methanation, as a primary fuel or as an absorbent for heavy metals and other pollutants in water treatment plants. It can also be used as an absorbent in disposable diapers for babies or in pet litters. The use of the pulp as an industrial fermentation substrate by bacteria or fungi allows the production of a wide variety of natural molecules: enzymes, proteins, sugars, natural vanilla flavors. The hydrolysis of the pulp provides many molecules for industrial use.

The galacturonic acid and his polymers derived from the pectin of the beet pulp are used for the manufacture of ecological detergents or surfactants. A derivative of his fermentation, lactic acid, can serve as a basis for producing fully biodegradable plastics [5]. Currently, researchers are also attempting to combine the dry beet pulp with polymers to obtain strong, lightweight building materials [6]. The beet fibers can also be used in the manufacture of insulating felts in the building. It provides the flexibility, elasticity and lightness. Also, other researchers have shown that it is possible to replace the fine sand in concrete or acoustic insulating panels (noise walls along the roads) by the beet pulp, the mixture is made cold with fresh pulp, Which allows a low-cost processing [7].

The production of beet pulp to find a new way of upgrading in the stationery industry [8-13]. It is used to improve the mechanical and optical properties of paper [7].

In this work, we are interested of characterizing the chemical modifications in the structure of this biomaterial before and after treatment, using the following spectroscopic techniques: Infrared (IR), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD).

Materials and Methods

Preparation of the raw beet pulp (RBP)

The raw beet pulp was dried in the air by the action of sunlight and then ground and sieved to obtain homogeneous materials for the experimental designs and the fraction of granularity of very small diameter. The raw beet pulp is designated by the abbreviation RBP.

Preparation of beet pulp treated with the distilled water (BPTDW)

The treatment was carried out several times by contacting an amount of 5 g of the beet pulp crushed and sieved with a sufficient volume of the distilled water. The first treatment is done with hot distilled water under magnetic stirring for 2 hours. This operation involved both the removal of impurities and grinding residues and the evaluation of the soluble fraction, and the resulting material was filtered with filter paper and dried in an oven between 40 and 50°C, to constant mass. The beet pulp treated with the distilled water is referred to by the abbreviation BPTDW.

Preparation of the beet pulp treated by the ethanol (BPTET)

5 g of the beet pulp crushed and sieved and the fraction of granularity very small diameter was treated 5 times with 65% ethanol to remove the residual sugars (sucrose, arabinose, fucose). The first treated was carried out hot until it boiled, it eliminates any trace of enzymatic activity. Subsequently, the material obtained was filtered with a filter paper, and then dried in an oven at 40°C. The beet pulp treated with ethanol is designated by the abbreviation BPTET.

Preparation of beet pulp treated by formaldehyde (BPTFA)

A mass of 5 g of beet pulp crushed and sieved was placed in the mixture of 100 ml of H₂SO₄ at a concentration of 0.1 mol/l and the formaldehyde (36.5%). The mixture obtained was brought to reflux under mild magnetic stirring at 50°C. After 4 h the material obtained was cooled and washed with distilled water to pH=4, filtered with filter paper and dried in an oven at 40°C-50°C, until A constant weight. The beet pulp treated with formaldehyde is referred to as BPTFA.

The treatment of raw beet pulp by formaldehyde in an acid medium consists of crosslinking the biopolymers of the side chains contained in the beet pulp into three-dimensional polymers by creating intermolecular cross-links (formation of bridges).

Analytical techniques

For the characterization of the materials, we used Infrared Spectroscopy (IR) of Bruker type and Tensor 27 model, and X-ray diffraction (XRD) of the Panalytical X Pert³ Powder type, which is carried out at the research center of The Faculty of Science of Kenitra.

Conclusion

The spectroscopic characterization of the beet pulp before, and after chemical treatment with different solvents (distilled water, ethanol and formaldehyde in an acid medium) has been studied. The results obtained give the following conclusions:

The examination of the IR spectrum of this material before treatment shows the existence of several characteristic peaks of several functional groups of cellulose, hemicellulose and pectin. After treatment of this material with the various solvents, the results obtained show that the treatment of BP by these various solvents has a considerable effect on the chemical modification of the structure of this material and especially the treatment with formaldehyde and ethanol.

In the case of the analysis of this material by XRD before and after treatment by the solvents, the results obtained show that this material contains two zones, crystalline zone and amorphous zone. The calculation of Crystallinity Rate (CR) which is at a significant relationship by the surface of the XRD spectra clearly shows that the surfaces of the spectra obtained before and after treatment are different.

The analysis of the morphology obtained from this material by scanning electron microscopy (SEM), shows that, this material contains compact and ordered zones, and disordered and porous zones, containing of fibers characteristic of hemicelluloses. After treatment by the three solvents, it can be concluded that the treatment with distilled water and ethanol has a considerable effect on the removal of some constituents of the original material. On the other hand, treatment of the beet pulp with formaldehyde in an acid medium leads to a compact and ordered material. This is explained by the crosslinking of the side chains of the beet pulp with formaldehyde.

Thus, it can be concluded that the chemical treatment of the beet pulp by the solvents has a considerable effect on the chemical and morphological modification of this material.

References

1. A.K. Taylor, Chem. Innovation, 2000, 45-48.
2. R. Mas, Curr. Ther. Res., 1999, 60, 458-67.
3. R. Van Dijken, Sugar beet and genetic modification. A literature research on sugar beet and the implications of genetic modification. Science Shop for Biology. Department of Molecular Plant Physiology. Utrecht University, 2001, 28p.
4. N.L. Pennington, C.W. Baker, Sugar: A User’s. Guide to sucrose, Avi Book, USA, 1990, 331p.
5. T. Sakai, T. Sakamoto, J. Halleart, E.J. Pectin, Adv. Appl. Microbiol., 1993, 39, 213-294.
6. V.L. Finkenstadt, L.S. Liu, J.L. Willett, J. Polym. Envi., 2007, 15 (1), 1-6.
7. Agra Valor, R. BELHAMRI, V. AGUIÉ, R. BEGUIN, M. DOUILLARD, C.A. MATHLOUTHI, Surfactant and foaming macromolecules extracted from sugar beet. Laboratory of Industrial Physical Chemistry, UMR FARE University of Reims, Plant Walls and Fibers Materials Team, UMRFARE, INRA of Reims, IT Concept, Longessaigne, 2003, 106.
8. M. Maderova, P. Misovec, P. Krkoska, Modification of rheological properties of kraft pulp stock with pectin, Vyskum. Pr. Odboru Papiera Celulozy,1973, 18, 37-40.
9. J.M. Armanet, A. Johansson, J.P. Sachetto,. “Procédé pour simultanément dépectiniser et déshydrater la pulpe brute de betterave sucrière“. Eur. Pat.0139658 Battelle Memorial Institute, 1984.
10. G. Vaccari, G. Mantovani, C. Nicolucci, A. Monegato, Utilization of beet pulp for paper manufacture, XXe general assembly of CITS – Munich 26- 30th June 1995 Int. Sugar J.,1995, 97(1162B), 556-559.
11. P. Chaudhuri, Special cooking process is needed, Pulp and Paper Int., 1993, 35(8), 47- 48.
12. M. Devic, Procédé de fabrication de pulpes végétales blanchies, Eur. Pat.0419385 ELF Atochem SA, 1993.
13. M. Devic, Procédé de blanchiment d’une poudre végétale micronisée, Brevet d'invention Fr Pat 95 00093 ELF Atochem SA, 1995.