Abstract
Chitosan is a biodegradable cationic polymer that may be a potential substitute for aluminum salts in water treatment systems. In our study, we compared the coagulation performances of chitosan with those of coagulant mixtures of chitosan and aluminum sulfate and chitosan and poly-aluminum chloride, respectively. The coagulation efficiency was evaluated in terms of coagulant dosage, solution pH, settling velocity of flocs, floc diameter, and water turbidity. The optimum dosages for acid-soluble and water-soluble chitosan required for removal of a bentonite suspension (100 NTU) were only 1.25 and 1.50 mg/l, respectively, at a respective efficiency of 99.2% and 95.8%. The optimal dosage range for water-soluble chitosan was broader than that for acid-soluble chitosan. The coagulation of bentonite decreased with increasing pH when acid-soluble chitosan was the coagulant. In contrast, the coagulation efficiency of bentonite was not affected at pH 5–9 when water-soluble chitosan was the coagulant. The mixing of chitosan with alum or PAC in a 1:1 mass ratio significantly improved the coagulation process in terms of preventing the occurrence of re-stabilization. The highest floc settling velocity occurred at a dosage of 5–6 mg/l of the coagulant mixtures, which was also the highest coagulation efficiency. Given the relatively high cost of chitosan and the good coagulation performance of the coagulant mixtures, we suggest that a 1:1 mass ratio of chitosan mixed with alum or PAC may be an alternative method to the use of pure chitosan in water treatment systems.
Similar content being viewed by others
References
Ahmad, A. L., Sumathi, S., & Hameed, B. H. (2005). Residual oil and suspended soild removal using natural adsorbents chitosan, bentonite and activated carbon: A comparison study. Chemical Engineering Journal, 108, 179–185.
Ahmad, A. L., Sumathi, S., & Hameed, B. H. (2006). Coagulation of residue oil and suspended solid in palm oil mill effluent by chitosan, alum and PAC. Chemical Engineering Journal, 118, 99–105.
Chatterjee, T., Chatterjee, S., & Woo, S. H. (2009). Enhanced coagulation of bentonite particles in water by a modified chitosan. Chemical Engineering Journal, 48, 414–419.
Chen, C. Y., Chen, C. C., & Chung, Y. C. (2007). Removal of phthalate esters by α-cyclodextrin-linked chitosan bead. Bioresource Technology, 98, 2578–2583.
Chung, Y. C., Kuo, C. L., & Chen, C. C. (2005). Preparation and important functional properties of water-soluble chitosan produced through Maillard reaction. Bioresource Technology, 96, 1473–1482.
Divakaran, R., & Pillai, V. N. S. (2001). Flocculation of kaolinite suspensions in water by chitosan. Water Research, 35, 3904–3908.
Divakaran, R., & Pillai, V. N. S. (2004). Mechanism of kaolinite and titanium dioxide flocculation using chitosan—Assistance by fulvic acids? Water Research, 38, 2135–2143.
Droppo, I. G. (2001). Rethinking what constitutes suspended sediment. Hydrological Processes, 15, 1551–1564.
Huang, C. P., Chen, S. C., & Pan, J. R. (2000). Optimal condition for modification of chitosan: A biopolymer for coagulation of colloidal particles. Water Research, 34, 1057–1062.
Huang, C. P., & Chen, Y. (1996). Coagulation of colloidal particles in water by chitosan. Journal of Chemical Technology and Biotechnology, 66, 227–232.
Pan, J. R., Huang, C., Chen, S., & Chung, Y. C. (1999). Evaluation of a modified chitosan biopolymer for coagulation of colloidal particles. Colloids and Surfaces, 147, 359–364.
Pontius, F. W. (2000). Regulation for aluminium in drinking water. Journal of the American Waterworks Association, 92, 18–22.
Renault, F., Sancey, B., Badot, P. M., & Crini, G. (2009). Chitosan for coagulation/flocculation processes—An eco-friendly approach. European Polymer Journal, 45, 1337–1348.
Roussy, J., Van Vooren, M., Dempsey, B. A., & Eric Guibal, E. (2005). Influence of chitosan characteristics on the coagulation and the flocculation of bentonite suspensions. Water Research, 39, 3247–3258.
Roussy, J., Van Vooren, M., & Guibal, E. (2004). Chitosan for the coagulation and flocculation of mineral colloids. Journal of Dispersion Science and Technology, 25, 663–677.
Stauber, J. L., Florence, T. M., Davies, C. M., Adams, M. S., & Buchanan, S. J. (1999). Bioavailability of Al in alum treated drinking water. Journal of the American Waterworks Association, 91, 84–93.
VanDuin, P. J., & Hermans, J. J. (1959). Light scattering and viscosities of chitosan in aqueous solutions of sodium chloride. Journal of Polymer Science, 36, 295–304.
Willem, T. B., & Lee, V. (2000). Temporal variation of floc size and settling velocity in the Dollard estuary. Continental Shelf Research, 20, 1495–1511.
Acknowledgments
The work was supported by Grant from the National Science Council.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Chen, CY., Chung, YC. Comparison of Acid-Soluble and Water-Soluble Chitosan as Coagulants in Removing Bentonite Suspensions. Water Air Soil Pollut 217, 603–610 (2011). https://doi.org/10.1007/s11270-010-0613-8
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11270-010-0613-8