grafting of chitin by irradiation technique

IRRADIATION GRAFTING OF HYDROPHYLIC MONOMER ONTO CHITIN FOR ION EXCHANGE APPLICATION

Gatot Trimulyadi Rekso

Center for Research and Development of Isotopes and Radiation Technology Jl . Lebakbulus raya No 49, Jakarta 12240, INDONESIA

Fax 62 21 7691607, E-Mail : [email protected]

Abstract: Studies on radiation grafting of hydrophilic monomer onto chitin for ion exchange application were examined . Over the past several years , chitin has been receiving increased attention for its application such as ion exchange . They are utilized scarcely because of problems associated with poor solubility, hidrophilicity and low reactivity. Graft copolymerization induced by irradiation is one of the methods for chitin modification in order to improve its properties such as hydrophilicity and reactivity. The aim of this research is to increasing the ability of chitin as ion exchange for heavy metal adsorbent. The hydrophilic monomers used were acrylic acid and acryl amide. In the present experiment , the pre-radiation per oxidized method was employed . The irradiation of sample was carried out in Co-60 gamma irradiation source at room temperature . The monomers solutions acrylic acid or acryl amide than introduce into irradiated chitin and the graft polymerization was carried out in nitrogen atmosphere. The presentation of grafting has been determined as a variation of monomer concentration and temperature as a function of time of reaction. The grafted chitin obtained was washed and dried in vacuum and the percentage of grafting was measured by gravimetric method . Measuring the capasity of adsorption of grafted chitin to Cr, Cu and Hg metal ion was determined by using AAS and CV AAS. The result shows that using acryl amide give percentage of grafting higher compare with acrylic acid. The presence of monomer grafted onto chitin is demonstrated by FTIR spectrum with the appearing of carbonyl functional group. Chitin grafted with acrylic acid give a higher rate of adsorption of metal ion Cr, Cu and Hg compare grafted with acryl amide. The high rate of adsorption is for metal ion Hg it was found 294.3 mg/g for chit-g-Aac and 257.3 mg/g for Chit-g-Aam.

Keywords : Chitin, irradiation, grafting, ion exchange

INTRODUCTION. In order to solve the environmental problem due to industrial development, many factor have been studied . Generally, both solid and liquid industrial waste can make seriously environmental problems.

The liquid waste with the heavy metal content in the large scale of production can be hazardous to environmental conditions. Separation method of heavy metal using ion exchange adsorbent to adsorb metal ion should be cheap, simple and industrial useful in waste treatment. The natural chelating marine polymer chitin, poly(N-acetyl-D-glucosamine) and its deacetylated derivative chitosan is useful for removing heavy metal ion waste from discharge water . Chitin , the most abundant naturally is undoubtedly one of the most promising and attracting resources present in quantity. Among some interesting properties of chitin , chelating ability arising from its characteristic structure is especially noteworthy. Many researchers have explored the feasibility of this approach. Kurita.K et.,all, conducted experiments with a number of heavy metals.

The adsorption behavior of chitin and its concerns with various degree of deacetylization. This high adsorption capacity was ascribable primarily to its remarkable hydrophilicity in cooperation with the relatively high amino group content. It is indicate that the importance of hydrophlicity and suggest that , in order to develop adsorbents of high capacity , it is make indicate the importance of hydrophilicity essential to make chitin derivatives highly hydrophylic and yet insoluble in water. Chitosan is natural polysaccharide and has the same skeleton structure as cellulose, by a radiation modification such as graft-co polymerization of hydrophilic monomer expected to improve its hidrophilicity.and performance for application as an ion exchange adsorbent. In the field of Radiation Process, free radical formation is the key role of the modification technique. Graft modified of chitosan with hydrophilic functional monomers was suitable method to develop its as ion exchange adsorbent.

In this present study, the purpose of the experiments is to study graft-copolyimerization reactions as well as to study the chemical and the

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physical properties of grafted chitin. Hydrophilic monomers such as acrylic acid, and acryl amide will be employed for these experiments. The functional group of graft –copolymers is expected to be useful in the attaching test of metal ions.

II. EXPERIMENTAL.

Material and Experiment: Chitin extracted from prawn shell (Penaeus Monodon), it was got from Muara Karang , North Jakarta. The were initially washed by water and then dried at 800 C overnight and conditioned at room temperature for 24 hr. Acrylic acid monomer, and white crystalline powder of acryl amide , obtained from E Merck , and other chemicals of reagent grade were used without purification.

Radiation Source : Gamma radiation source of Co-60, IRKA batch irradiator , with irradiation dose rate about 9,0 kGy/hr was employed in these experiments. This radiation source is located at Pasar Jumat, Center for Research and Development of Isotopes and Radiation Technology, Jakarta, Indonesia.

Grafting reaction: In the present experiment, the pre irradiation graft co polymerization method was employed. In this method a sample of chitin powder of about 500 mg , was put into a glass tube, then irradiated in air atmosphere at room temperature. A monomer acryl amide solution was deairated by bubbling with nitrogen gas, then introduced into the pre irradiated sample and the graft polymerization was carried out in a nitrogen atmosphere at certain tempera-ture. The grafted chitin obtained was washed toughly with aquadest and soaked overnight in aquadest, then subjected to sox let extraction with methanol for 8 hours to extract homopolymer. The grafted chitin then was dried in vacuum until they reached a constant weight at 500 C. The percentage

of graft yield was calculated from the difference in weight ;

Graft yield = ( Wg - Wo ) / Wo x 100 %

Where Wo and Wg are the weight before and after grafting.

Measuring off adsorption of metal ions by chitin and its modified : The experiment was done with chitosan with degree of the deacetylization of 78,5 % and modified chitin were Chitin-g-Aac and Chitin-g-Aam with degree of grafting 32,4 % and 45,6 % and modified chitosan were chitosan-g-Aac and Chitosan –g-Aam were got from deacetylated modified chitin. Measuring the rate of adsorption about 100 mg of powder material (chitin,chitosan and it’s modifications) equilibrated with 100 ml 0f solutions ( HgSO4 , CuSO4.5 H2O, K2Cr2O7) 0,1 M, at pH 4,0 and stirred for 60 min. The metal ion uptake concentrated after equilibrating were determined by using AAS and for Hg(II) using CV-AAS.

III. RESULTS AND DISCUSSION

Evidence of grafting : The increase in weight of the extracted grafted sample, as compare with that the original chitin and their FTIR spectra , was used as evidence of grafting. The FTIR spectra of chitin and grafted chitin are shown in Fig 1. It can be seen that a band around at 1660 cm –1 arises from carbonyl absorption of chitin and anew band appear at 3400 cm-1

which correspond to the hydroxyl absorption of grafted chitin with acrylic acid and at 3500 cm -1 is asymmetric stretching of NH2 for grafted chitin with acrylamide.

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Fig 1. The FTIR spectra of the original chitin

Fig 2. The FTIR spectra of chitin grafted with acrylic acid

monomer

Effect of monomer concentration and reaction time. The effect of acrylic acid and acryl amide monomer concentration on the percentage of grafting with reaction period of 1 hr, 2 hr, 3 hr and 4 hr are presented on Figure 2 and 3 . It can be seen that the percentage of grafting is independent of the monomer concentration. Grafting with acryl amide monomer give higher yield percentage of grafting compare with acrylic acid monomer. This may results in enhancement of the monomer diffusion into the

chitin powder and the solubility of the monomer , acryl amide monomer is good soluble in water-methanol solvent . By using acrylic acid or acryl amide concentration above 30 % , high percentage of grafting was obtained. However . the increase in percentage of grafting is followed by increase of homopolymerization, which is difficult to separate.

The result shows that the different on percentage of grafting for reaction period of 3 hr and 4 hr is not significant. It can be concluded that the optimum monomer concentration is 30 % with 3 hr reaction period.

Fig 3. Effect of acrylic concentration on percentage of grafting

Fig 4. Effect of acrylamide concentration on percentage of grafting

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Grafting temperature . The reaction temperature play a great role on the grafting process because this influence on the diffusion of monomer into the matrix polymer of chitin and also on the lifetime of the peroxide radical in the preirradiated chitin. Figure 5 and 6 shows the degree of grafting time curves for the grafting of aqueous of 30 % acrylic acid monomer and 30 % of acrylamide at various temperature reaction

Fig 5. Effec of time reaction on percentage of grafting of acrylic acid at various temperature reaction

Fig 6. Effec of time reaction on percentage of grafting of acrylamide at various temperature reaction

From the figure 5 and 6, it is oblivious that the degree of grafting is largely by the reaction temperature . The higher temperature the higher of degree of grafting obtained. The reason is that the increase in temperature improves the monomer diffusibility as well as the mobility of the monomer. It is recommended that the optimum reaction for this grafting system is 70 0 C more than that the increasing of degree of grafting is not so much, there is a nearly constant value.

The ion exchange adsorption of metals ions by grafted chitin and its derivatives. The adsorption behavior of the resulting grafted chitin with acrylic acid and acryl amide was examined in comparison with the original chitin and chitosan. The results are illustrated in Table 1 .

Tabel 1. The capacity of adsorption of some metal ions ( mg/gr) by chitin, chitosan and

grafted chitin/ chitosan

Materials

The capacity of adsorption ( mg / g)

Hg(II) Cr(VI) Cu(II)

Chitin

Chitosan

Chitin-g-Aac

Chitin-g-Aam

Chitosan-g-Aac

Chitosan-g-AAm

92,6

174,5

294,3

257.3

488,9

464,2

30,6

48,4

109,5

94,8

318,5

325,8

24,4

44,2

180,1

154.6

362,8

398,2

These results clearly show that chitin modified as chitin grafted acryl amide have higher capacity of adsorption for ion metal such Hg, Cr, and Cu. The highest one is for metal ion Hg both grafting with acrylic acid or acryl amide. The chitin modified have an excellent adsorption capacity due to the advantageous location of -OH and –NH2 group in

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the molecule of chitosan to form complex formation and functional group of monomer act as ion exchanger for ions metal.

IV. CONCLUSION

Using acryl amide give percentage of grafting higher compare with acrylic acid.

The presence of monomer grafted onto chitin is demonstrated by FTIR spectrum with the appearing of carbonyl functional group.

The optimal condition of monomer acrylic acid or acryl amide concentration was 30 %, temperature 700 C and reaction period of 3 hours.

Chitin grafted with acrylic acid give a higher capacity of adsorption of metal ion Cr, Cu and Hg compare grafted with acryl amide.

The high rate of adsorption is for metal ion Hg it was found 488,9 mg/g for chitosan-g-Aac and 464,2 mg/g for Chitosan-g-Aam.

References[1]. Goosen, M.F.A., Application of Chitin and Chitosan, Technomic Publishing Company, Inc, Lancaster, Pennsylvania, USA. 1997,.[2] Chapiro, A., Radiation Chemistry of Polymeric System. Willey Inter-science, New York, 1962.[3] Kurita, K; Koyama,Y ; and Taniguchi, A. Journal of Applied Polymer Science. 1986 , 31, 1169 – 1173

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