Chitosan Complexes Eliminate Chloroform and Carbon Tetrachloride in Drinking Water

Yuan Yihua a,b , Jia Demina, Chen Xin b,Pang Yulian b

(a) Department of Macromolecular Science, School of Materials Science and Engineering, South China University of Technology, Guangzhou.510640, P. R. China,

(b) Department of Chemistry and Chemical Engineering, Foshan University, Foshan.528000 , P. R. China

E-mail: fsxuyuan@fosu.edu.cn

Abstract

This paper introduced the preparation methods of

chitosan and its complex. It focuses on drinking water treatment, eliminating products causing by chlorine disinfect (Chloroform, Carbon tetrachloride). The results showed that all the chitosan granule, chitosan- activated carbon complex and activated carbon had certain adsorption ability to the chloroform and carbon tetrachloride. Before 40 min, the adsorption rate was 80% or so, but at 60 min, the adsorption rate suffered a decline apparently, or even occurred the negative adsorption. 1. Introduction

Chlorination is the widely adopted method to deal with the disinfection of drinking water at present[1]. It is difficult to produce the drinking water that conform to the water quality standard (of drinking water) by adopting the conventional disposal methods, while the supply water that produced by conventional disposal method would be with the exquisite flavor or would make the mouth feel discomfort. The organic matter in the water is the fore body to sterilize the outgrowth which affected the security of the water.

In the investigation of drinking water sterilized by chlorine in 80 main cities of America, Symons found that the drinking water generally had possessed haloform with a rather high consistency[2]. And in our country, great amount of haloform could also be discovered in the general survey of drinking water. CHCl3 was one of the main compositions of haloform and CHCl3 has been classified as one of the emphasis detection index of drinking water because of it’s

owning of carcinogenesis, teratogenesis. In our country, chlorinating disinfections still the economic and effective way to deal with the water at present [3]. In nowadays, how to decrease and eliminate the halogenated hydrocarbon in the drinking water is the crux to increase the quality of drinking water [4, 5].

The adoption of chitosan in the disposal of water has become more and more universal at abroad in recent years [6, 7]. This article would take the chitosan and activated carbon to be the raw materials and compound them into chitosan complexes according to certain proportion and adopted the chitosan complexes to eliminate the chloroform and carbon tetrachloride in the drinking water. 2. Experimental 2.1 Apparatus and materials 2.1.1 Materials

Chitosan: (C6H11NO4)n whose degree of deacetylation was calculated to be 85.4% from the amino contents[8], was prepared according to the procedure reported previously by N-deacetylation of chitin from shrimp shells[9].

Hydrochloric acid: chemically pure, C.P. with the molecular weight of 36.46 and the content should be 36%-38% Guangzhou city Donghong Chemical Plant.

Sodium hydroxide: chemically pure, C.P. with the molecular weight of 40.00 and the content should be equal to 95% or larger. Zhongshan city Shiqi Chemical Plant.

Chloroform: liquid state, analytical reagent, (A.R.) with the molecular weight of 119.38, and the content

2008 International Conference on BioMedical Engineering and Informatics

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2008 International Conference on BioMedical Engineering and Informatics

978-0-7695-3118-2/08 $25.00 © 2008 IEEEDOI 10.1109/BMEI.2008.186

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should be 99.5% or larger. Guangzhou medical station Chemical Reagent Company.

Carbon tetrachloride: liquid state, analytical reagent, (A.R.) with the molecular weight of153.89, and the content should be 99.5% or larger. Guangzhou medical station Chemical Reagent Company.

2.1.2 Apparatus

Electro thermal constant-temperature dry box: HG202-2 model, produced by Nanjing Experiment Apparatus Factory.

Centrifuge：L04－2 model with the 0-4000 revolutions per minute. Beijing medical use Centrifuge plant

Gas chromatograph: HP5890 Ⅱ model American Hewlett-Packard Company (HEWLETT PACKARD)

Chromatographic column: HP-624

2.2 The preparation method of chitosan- activated carbon complexes

5 grams of chitosan were weighed, and dissolved with 250 milliliters 36% hydrochloric acid (10 milliliters 36% hydrochloric acid was weighed, then put into the 1000 milliliters volumetric flask, and diluted to the specific graduation by distilled water and shook up), then the chitosan and the 250 milliliters 36% hydrochloric acid were stirred continuously until the chitosan had been dissolved into glutinosity solution, when stirring continuously, 20 grams powdery activated carbon was added, stirred it continuously until it turned into the glue. And then with the unceasing stir, the sodium hydrate aqueous solution of Baumé degree with a density of 48 was added slowly (1 gram 96% activated carbon was weighed, and dissolved with 10 milliliters distilled water ), and stopped adding the activated carbon when it appeared as neuter or slight alkalinity. Laid it aside, until it precipitated, then filtrated, separated it and scrubbed it by water, then after it had been dried to certain degree, grinding it by mortar and turned it into granular, and then drying the granular again, the chitosan- activated carbon complexes could be produced at last[10]. 2.3 The preparation method of chitosan granular

2 grams of chitosan were weighed, then 100 milliliters 0.36% hydrochloric acid were adopted to dissolve it (the preparation method was the same as above-mentioned) and kept stirring it until the chitosan solution dissolved into glutinosity solution. With the unceasing stir, added the sodium hydrate aqueous

solution of Baumé degree with a density of 48 slowly( the preparation method was the same as above-mentioned) stopped adding sodium hydrate when it appeared as neuter or slightly as alkalinity. Laid it aside, until it precipitated, then filtrated, separated it and scrubbed it by water, then after certain degree of drying, grinding by mortar and turned it into granular, and then after it had been dried to certain degree, the chitosan- granular could be produced. 3. The apply of chitosan-activated carbon complexes in the disposal of drinking water 3.2 Experiment Procedure 3.2.1 1498.5mg/ml chloroform solutions was made.

Then the 1 milliliter suction pipette was adopted to displace 1 milliliter chloroform whose density should be 1.4985m g/ml, and put it into the 1000 milliliters volumetric flask, diluted it with distilled water until the capacity of the solution reached the designated graduation of the volumetric flask, and shook it up, then kept in reserve.

Table 1 The effect of absorbents on chloroform

3.2.2 159.4 g/ml carbon tetrachloride solution was made. The 0.1 milliliter suction pipette was adopted to displace 0.1 milliliter carbon tetrachloride whose density should be 1.594 g/ml, and put it into another 1000 milliliters volumetric flask, diluted it with distilled water until the capacity of the solution reached the designated graduation of the volumetric flask, and shook it up, then kept in reserve.

Table 2 The effect of absorbents on carbon tetrachloride

Time/min chitosan

chitosan- activated carbon

complexes

activated carbon

20 -0.027 0.839 0.842 40 -0.028 0.825 0.847 60 -0.0107 0.124 0.826 120 0.686 0.835 0.158 180 0.707 0.742 0.738

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3.2.3 Another 0.1 milliliter suction pipette was adopted to displace 0.4 milliliters 159.4mg/ml carbon tetrachloride that had been made up as above-entioned. Put it into the 2000 milliliters volumetric flask, applied 2 milliliters suction pipette to displace 2 milliliters chloroform with the density of 1498.5 mg/ml that had been made up as above-mentioned, and laid it in the same 2000 milliliters volumetric flask, diluted it with distilled water until the capacity of the solution reached the designated graduation of the volumetric flask, and shook it up, then kept in reserve. In this way, the mixed solution was obtained and the density of the chloroform and carbon tetrachloride were 1498.5 mg/ml and 31.88 g/l respectively.

3.2.4 A 50 milliliters suction pipette and the 25 milliliters suction pipette were adopted respectively to displace 175 milliliters mixed solution that had been made up as above-mentioned, then put them into different reagent bottles, and numbered them, then added the different adsorbent of 20 milliliters in different reagent bottle respectively (including chitosan granule, chitosan-activated carbon composite and activated carbon), and limited the adsorption time to be 20min, 40min, 60min, 120min and 180min respectively (the adsorption times of the three adsorbent were the same). 3.2.5 Centrifugalized the miscible liquids that had finished the adsorption by centrifuge with 3600 revolutions per minute. The centrifugalization time /duration should be 60 seconds or so. After finishing the centrifugalization, then put the clear liquid into the sample plasma bottle and stuffed it with rubber cork, and marked every sample plasma bottle according to the numbers of the reagent bottle, then waited to be tested. 3.2.6 Centrtifugalized the chloroform and Carbon tetrachloride miscible liquids that had never been adsorbed by centrifuge, then the clear liquid was put

into the sample plasma bottle and stuffed with rubber cork, then marked as the standard liquid, and waited to be tested. 3.3 According to the experiment procedure of 3.2, the same experiment is done on the blank water sample. The quantity of the water were the same to be 175 milliliters.The same kind and the same quantity -20 milliliters of the adsorbent while the adsorption time/ duration were 20 min, 60 min and 120 min respectively.

Table 3 The effect of absorbents on chloroform in the blank water

Time/min chitosan

chitosan- activated carbon

complexes

activated carbon

20 -0.981 0.245 0.255

60 -1.936 0.226 -0.095

120 -2.608 -3.184 -0.625

Table 4 The effect of absorbents on carbon

tetrachloride in the blank water

Time/min chitosan

chitosan- activated carbon

complexes

activated carbon

20 -2.691 0.242 0.88

60 -2.672 0.154 0.814

120 -3.116 -2.865 0.535

3.4 The condition and result of the test 3.4.1 The condition of the test The temperature of entrance of sample: 1500C The temperature of the colum: 35℃（1min.）to 60℃ The amount and manner：400μL The speed of gas：N2: 8.5 ml/min The detector and the temperature: ECD，250℃ 3.4.2 The result of the test

The density of the chloroform and carbon tetrachloride in the mixed solution (made up according to the experiment procedure) were 1498.5 mg/l and 31.88m g/l respectively.

The results indicated that: (1) all the chitosan granule, chitosan- activated carbon complexes and activated carbon had certain adsorption ability to the chloroform and carbon tetrachloride. Before 40 min, the adsorption rate was 80% or so, but at 60 min, the

Time/min chitosan

chitosan- activated carbon

complexes

activated carbon

20 0.392 0.851 0.867

40 0.516 0.856 0.888

60 0.397 0.469 0.875

120 -1.806 -1.034 0.459

180 -1.616 -1.485 -0.815

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adsorption rate suffered a decline apparently, or even occurred the negative adsorption.

(2) The water sample test results of the distilled water showed that each kind of adsorbent would all occur the negative adsorption in different degree that means with a longer usage time，the adsorbent would release the contamination, such as chloroform and carbon tetrachloride that might resulted from the adoption of hydrochloric acid to eliminate the inorganic salt of shrimp when preparing the chitosan, therefore, the chloride ion might remain in the chitosan, apart from this, under the affection of ultraviolet light and enzyme, the chloride ion might combine with the chitosan which generated the chloroform and carbon tetrachloride that remained in the inner of the adsorbent. In this way, having a longer adsorption time /duration, the chloroform and carbon tetrachloride would be released from the interior of the chitosan which would also increase the content of the chloroform and carbon tetrachloride.

(3) The reduction rate of the activated carbon could be achieved to be 80% or above, when adopted as the adsorbent to eliminate the contaminant, such as chloroform and carbon tetrachloride, however, there would also emerge another problem if the time was too long. 4. References [1] Zhou Dazuo, the biological water treatment of the

polluted source of water, Shanghai environment science 1997.16,40: 23-25

[2] Yue Shunlin, The development of bio-chlorination in

disposal research of water supply, The water supply in cities and towns 1997,(8), 4-10

[3] Bull RJ, Birnaum LS.,Water Chlorination: essential

process or cancer hazard., Fundam Appl Toxicol, 1995, 28(2):155

[4] Yu Huifang, Ma Zheng, Zhang Zhengliang, The

disposal technology process of drinking water, Environment Protection, 1999,(5):13-17

[5] Rittmann BruceE. Etal. ,Civil Engineering,New

York,1996,6(7) [6] Huang Junli, Li Haibo, Gan Weifang and etc., The

research of the typical organic which caused mutation in drinking water, Environmental Science, 1998. 19 (1): 54

[7] Chen Liang, Chen Donghui, The application of chitosan

flocculant in the water disposal, Disposal of industrial water, 2000. 20(9): 4-7

[8] Sun Jialong, Ban Weiping, Zhang Yunzhan., The

exploration of chitosan preparation technology, J Dalian Light Industry College 2000. 19,1: 1-3

[9] Peng Lifeng, The preparation and application in the

wastewater disposal of chitosan, Chemistry/ Chemical World. 1999(4): 176-179

[10] Z hang Wenfu, Zhang Li, Zhong Shu, 40 kinds

manufacture technologies of chemical industry products ,Jindun Press. 1992.(12): 103-108

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