УДК 544.024.1


The films of chitosan for use in processes of water purification


Solodovnik T.V., Dzіhora Y.V., Kravchenko S.O., Egorova O.V.

Cherkassy State Technological University,

Cherkassy, Ukraine


It is known that aminopolysaccharide chitosan and its derivatives are becoming more widely used in various industries. Chitosan has many beneficial properties.

Chitosan is a biocompatible, non-toxic and is laid out in an environment characterized by valuable regenerating and healing properties. Chitosan absorbs heavy metal ions, dyes, petrochemicals and oil from water. Chitosan has been successfully used in medicine, food and chemical industry and biotechnology [1]. Chitosan membranes and films used for drinking water.

Other authors have shown the use of polymeric chitosan films as ion-exchange for alkaline and acidic solutions [2-4]. The polymeric nature and high chemical activity of chitosan determine prospects of films based on it in water treatment technology and aqueous solutions.

The disadvantages of increased use of films and membranes based on chitosan in sorption processes is their lack of stability and solubility in aqueous solutions.

The study of physical - chemical properties of chitosan films to improve their properties and increase stability when used in aqueous solutions of unstable pH is a very pressing issue.

The aim of this work is to study the effects of heat treatment and forming films on their structure and solubility.

To produce films using chitosan with a degree of deacetylation 87%. Chitosan was obtained from mycelial fungi Aspergillus niger biomass – waste of biotechnological production of citric acid by the method [5]. The content of linked chitosan films acid and amino content was determined by potentiometer titration [6]. We used a combined glass electrode. Measurement of pH was carried out with an accuracy of ± 0,01.

The process of curing the films were performed in the temperature range from 20 to 75°C for 10 to 72 hours. The film of chitosan was heated in an oven at 115°C for 1 to 3 hours. The kinetics swelling investigated the gravimetrically on an analytical balance. To create the proper environment using buffers with pH: 1.1; 5.5; 6.86.

The films of chitosan in S-form and H-form was analyzed using IR spectroscopy (Specord IR-75). The samples were cut into small pieces before grinding with KBr powder in the ratio of approximately 2:100 of sample to KBr. Explanation spectra were performed using the program MicroCAL Origin v.6.10.

It is established that an increase in temperature during curing films acid content-solvent (CH3COOH) freshly formed samples decreases (Table 1). There is a decrease acid-solvent and with increasing duration of the process. Established that virtually unchanged degree of substitution for amide and amino groups in chitosan structure. Thus it is proved that the curing process is not accompanied by chitosan films amidation reaction (Fig.1). As can be seen from Table 1, at high temperatures (115oС) on chitosan films observed reduction of acid-solvent and increasing the number of amide groups in the structure of chitosan. The results show that the action of temperature on the film of chitosan polymer cross-linking occurs through amidation reaction.

Table 1Terms curing chitosan films, composition of the films before and after exposure to temperatures* (аccording potentiometric titration)

Terms curing films

To exposure to temperature

to heat treatment

After exposure to temperature

after heat treatment

Т,

°С

τ, hours


W%(CH3COOH), %

W%(N), %

**

W%(CH3COOH), %

W%

(N),

%

**

20

72

36.1

7.3

0.87

0

0

18.0

5.08

0.64

0.23

0.26

50

20

25.0

7.8

0.87

0

0

14.8

3.97

0.51

0.36

0.41

75

10

18.9

7.8

0.85

0.02

0.02

10.95

4.3

0.55

0.32

0.37

               * Heat treatment was performed at 115 ° C for 3 hours

** Increase from baseline of chitosan

It is proved that the transfer film with a S- form H- form accompanied by intense absorption band 1635 cm-1 in the IR spectrum, which is characteristic of amino groups. Гnder heat in the infrared spectra of films of chitosan (S-form), a decrease of intensity of absorption bands of Аmide I (1633, 1630 cm-1) and there is an intense absorption band Аmide II (1550 cm-1 ).

For films of chitosan in H- form  observed accumulation of amide groups (1550 cm-1, 1495 cm-1). This confirms amidation reaction that occurs during the thermal impact on the chitosan film.

In the stretching vibration of hydroxyl and amino groups (2980-2350 cm-1) by the action of the temperature distribution is the intensity of the absorption maximum in the offset area smaller wavelengths.

Established that under the influence of temperature decreases the degree of swelling of chitosan films in the S- form and H- form.

Іt is proved that under the influence of temperature in the macromolecules of chitosan, a decrease in the number of amino groups and reduce the ability of ionized molecules participate in conformational transformations.

The process amidation and organization of the structure, which reduces the solubility of chitosan films.

The results are in good agreement with data obtained by other authors [7].

Conclusions:

1. Іt was established that the increase in temperature and duration of curing films of chitosan leads to reduction of solvent-acid (CH3COOH) in freshly formed films. The amidation reaction does not occur.

2. It is proved that heat treatment of chitosan films reduces solubility. This can be explained by substitution of amino groups (NH2-) to amide (NHСО-). There is a formation of chains of chitin chitosan structure. As well as the polymer crosslinking occurs through amidation reaction.

3. Discussed in the ways of modifying chitosan films demonstrate feasibility of their application for films with improved properties. Chitosan films after thermal modification can be used in different sectors of the economy, and especially in the manufacturing processes of water purification.


References:

1. Muzzarelli R.A.A. In:Chitin. – London: Pergamon press Ltd., 1977. – 143 p.

2. Hirano S., Tokura S. (1982) Chitin and Chitosan. Proceedings of the second international conference on chitin and chitosan. Sapporo. 254 p.

3. Singh D. K., Ray A. R. (1998) Characterization of grafted chitosan films. Carbohydrate polymers. 36 (2), рр.51–55.

4. Begin A., Van Calsteren M.R. (1999).  Antimicrobial films produced from chitosan Carbohydrate polymers. 26(1), рр. 63–67.

5. Ukrainian patent 79581 А, MKP С08В 37/08. The method of chitosan extraction from mycelial fungi Aspergillus niger biomass. Stolyarenko H.S., Solodovnik T.V., Kurilenko U.M., Egorova O.V (Ukraine). Applied 05.11.12, Published 25.04.2013, Bulletin №8.

6. Zotkin M.A., Vihoreva GA., Smotrina T.V., Derbenev M.A. (2004). Thermal modification and study of the structure of chitosan films. Fibre Chem. 36(1), рр.16-20.

7. Kim, C.H., Park, H.S., Gin, Y.J., Son, Y.S., Lim, S.H., Choi, Y.J., Park, K.S. and Park, C.W. (2004) Improvement of the biocompatibility of chitosan dermal scaffold by rigorous dry heat treatment. Macromol. Res., 12(4), рр. 367–373.