Optimal condition for modification of chitosan: a biopolymer for coagulation of colloidal particles

doi:10.1016/S0043-1354(99)00211-0

Water Research

Volume 34, Issue 3, 15 February 2000, Pages 1057-1062

https://doi.org/10.1016/S0043-1354(99)00211-0 Get rights and content

Abstract

Chitosan, an acetylated derivative of chitin, is a biodegradable cationic polymer. Chitosan can be a promising substitute for alum in the coagulation process, because of its potential feasibility in coagulation without posing any health threat as the residual aluminium and other synthetic polymers do. In this study, various pretreatment conditions were tested in search of the optimum chitosan modification. Batch tests with synthetic source water suggest that the optimal pretreatment condition to prepare modified chitosan coagulant is deacetylation by 45% alkali solution for 60 min, followed by dissolution in 0.1% hydrochloric acid.

Introduction

In conventional water treatment systems, alum has been the most widely used coagulant because of its proven performance, cost-effectiveness, relative ease of handling and availability. Recently, much attention has been drawn on the extensive use of this coagulant. Besides the large amount of sludge produced, high level of aluminium remained in the treated water has raised concern on public health (Driscoll and Letterman, 1995). McLachlan (1995) discovered that intake of large quantity of alum salt may cause Alzheimer disease. To minimise the detrimental effect accompanied with the use of alum, polymers are added either with alum or alone and have gradually gained popularity in water treatment process. Synthetic polyelectrolytes generally produce sludge of better dewatering characteristics and facilitate better filtration. However, their long-term effects on human health are not well understood.

Chitin, a cellulose-like biopolymer, is widely distributed in nature, especially in marine invertebrates, insects, fungi and yeasts. Its deacetylated derivative, chitosan, is a linear cationic polymer of high molecular weight, readily soluble in acidic solutions. It is also biodegradable, non-toxic, and has been used in the coagulation of suspended solids from various food processing wastes (Knorr, 1983). Since chitosan is effective in coagulation without any known disadvantage, it can be a promising substitute for synthetic products (Kawamura, 1991). Chitosan has been applied in the coagulations of bentonite and koalinite particles in our laboratory (Huang and Chen, 1996). The preliminary studies suggested that chitosan can be a potent coagulant for the surface water treatment. When investigating the adsorption of chitosan on kaolin, Domard et al. (1989) showed that the adsorption can be described by the Langmuir equation and that the greatest adsorption was achieved when the chitosan was fully deacetylated. The objective of this study is to search for the optimum condition for chitosan pretreatment by evaluating the coagulation efficiencies of chitosan prepared from different conditions.

Section snippets

Chitosan preparation

Chitin isolated from a crab shell was crushed to a powder form and then deacetylated by NaOH (45%, w/w) at 100°C. The product was rinsed several times with deionized water until the pH of the chitosan suspension reached 7, followed by drying at 80°C for 48 h. Chitosan was dissolved in acetic acid and hydrochloric acid of various concentration by stirring at room temperature or mildly heated until completely dissolved to make 1% stock solution.

Synthetic source water

Given amount of bentonite powder, product of Hayashi

Selection of acid solvent for chitosan

Chitosan is virtually insoluble in water under normal conditions. It can dissolve in carboxylic acid solutions, in which acetic acid (HAc) has been a most common solvent for chitosan. However, this organic solvent might increase the organic content of suspensions, which were coagulated by chitosan. In this study, therefore, we selected one of inorganic acids, hydrochloric acid (HCl), as an alternative solvent to evaluate the coagulation capacity of HCl-prepared chitosan.

First of all, Chitosan

Conclusion

Batch tests with synthetic turbidity water were performed to evaluate the coagulation efficiency of chitosan prepared with different concentrations of acetic acid and hydrochloric acid and various degree of alkali treatment. The results recommend that the optimal pretreatment condition to prepare modified chitosan coagulant is deacetylation by 45% alkali pretreatment for 60 min and dissolution by 0.1% hydrochloride solvent.

Acknowledgements

This work was partially funded by the National Science Council, ROC. The authors wish thank Dr. Li Chin-Fung, National Taiwan University, for the supply of crab chitin and Dr. Chung Ying-Chien, National Science Council, for the information of chitosan preparation.

References (9)

W Wang et al.
Determination of the Mark–Houwink equation for chitosan with different degrees of deacetylation
Int. J. Biol. Macromol.
(1991)
Dentel S. K., Abu-Orf M. M. and Griskowitz, N. J. (1993) Guidance Manual for Polymer Selection in Wastewater Treatment...
A Domard et al.
Adsorption of chitosan and a quaternized derivative on kaolin
J. Appl. Polymer Sci.
(1989)
C.T Driscoll et al.
Factors regulating residual aluminium concentrations in treated waters
Environmetrics
(1995)

There are more references available in the full text version of this article.

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Technical noteOptimal condition for modification of chitosan: a biopolymer for coagulation of colloidal particles

Abstract

Introduction

Section snippets

Chitosan preparation

Synthetic source water

Selection of acid solvent for chitosan

Conclusion

Acknowledgements

Int. J. Biol. Macromol.

Adsorption of chitosan and a quaternized derivative on kaolin

J. Appl. Polymer Sci.

Factors regulating residual aluminium concentrations in treated waters

Environmetrics

Technical note
Optimal condition for modification of chitosan: a biopolymer for coagulation of colloidal particles