Removal of humic substances by chitosan

Abstract

Results from laboratory tests, conducted to study different aspects regarding the removal of humic substances by the environmentally friendly cationic biopolymer chitosan, are presented. Chitosan was shown to be an efficient remover of the high molecular weight humic substances, significantly reducing the colour and UV absorbance in typical humus-rich Norwegian surface waters with low particle content. By adding small amounts of Fe3+ together with a reduced dose of chitosan, it was possible to significantly improve the removal of the medium molecular weight humic substances. The highest charged (low Fa) chitosans were the most efficient coagulants, indicating that charge neutralisation was the triggering mechanism for the coagulation. Surface charge measurements of coagulated raw water gave strong indications in the same direction. However, net positive surface potentials of flocs after neutralisation indicated that excess chitosan participated in the build-up of flocs, suggesting that bridging or electrostatic patch flocculation could be important mechanisms during flocculation. However, the molecular weight of chitosan had no significant influence on the maximum removal of the humic substances.

The Merits of the High-temperature Combustion Method for Determining the Amount of Natural Organic Carbon in Surface Freshwater Samples

“…Co-addition of Chitosan and iron chloride, however, has shown similar treatment results as the metal-based coagulants alone, but at a significantly lower total coagulant addition , Vogelsang et al 2004. The coagulating effect of Chitosan on NOM is due to a combination of charge neutralisation and inter-particle bridging (Vogelsang et al 2004). Due to the potential problems of residual NOM, as indicated above, a better characterisation of the properties and stability of the remaining organic matter (OM) after coagulation with Chitosan is needed.…”

“…On the other hand it is found to leave a higher proportion of the medium molecular weight organic matter in the treated water than the metal-based coagulants (Vogelsang et al 2004). Co-addition of Chitosan and iron chloride, however, has shown similar treatment results as the metal-based coagulants alone, but at a significantly lower total coagulant addition , Vogelsang et al 2004. The coagulating effect of Chitosan on NOM is due to a combination of charge neutralisation and inter-particle bridging (Vogelsang et al 2004).…”

“…Chitosan has previously been shown to be an efficient colour remover. Based on the study of Vogelsang et al (2004) it is shown that the Chitosan treatment preferably removes the largest molecular weight organic matter measured by size exclusion chromatography. On the other hand it is found to leave a higher proportion of the medium molecular weight organic matter in the treated water than the metal-based coagulants (Vogelsang et al 2004).…”

“…The organic matter content of the water was designed to reflect the humus rich waters often used as raw water source for the production of drinking water. This synthetic humic material was chosen over natural humic matter for two reasons: 1) to represent an initial pilot experiment performed under controlled and reproducible conditions, and 2) to be integrated into a larger project on Chitosan coagulation treatment initiated by The Norwegian Institute for Water Research (NIVA) and comparable to other experiments in this project already using this artificial standard (Vogelsang et al 2004).…”

Flocculation of Organic Matter and Aluminum in Water Using Chitosan-inorganic Coagulant

“…Studies on the use of chitosan in conjunction with inorganic coagulants such as alum and ferric chloride [2] and application of chitosan in the flocculation of mineral suspensions such as montmorillonite, bentonite and kaolinite and organic solutions such as dyes, humic acid [3][4][5][6][7][8][9] have been reported. Applications for flocculation of silt in river water [10] , latex particles [11][12] and bacteria [13][14][15] are also described in the literature.…”