Flocculation Behavior And Mechanism Of A Polysaccharide Produced By Halomonas Sp. V3a'

Bioflocculants are an important kind of the crude macromolecular flocculant. Compared with inorganic and organic flocculants, bioflocculants are biodegradable and nontoxic and no secondary pollution. Halomonas sp.V3a'was a mutant strain of Halomonas sp.V3a, which was isolated from deep-sea mud.The contents of this research include:examining the flocculating activity of polysaccharide HBF-3 produced by Halomonas sp.V3a'on kaolin clay suspension; exploring the flocculation mechanism of HBF-3 on kaolin clay suspension and studying its application in Congo red removal.Based on previous study, we know that HBF-3 was a polysaccharide produced by deep-see Halomonas sp.V3a', its molecular weight was approximately 2.3 x 105, including amino and carboxyl. Its monosaccharide components were mainly composed of rhamnose, glucuronic acid, glucose, mannose and trehalose. In order to effectively utilize deep-sea bioflocculants, a series of experiments was conducted to investigate the properties of HBF-3. HBF-3 in the concentration of 4 mg/L showed a peak flocculating activity of 95.9% in 5 g/L kaolin clay suspension. It appears that HBF-3 was an effective flocculant over wide pH (3.0-11.0) and temperature (5℃-40℃) rangesExploring the flocculation mechanism could help us to well understand the role of bioflocculants in wastewater treatment and to improve the efficiency of actual wastewater treatment. The measured zeta-potentials during the flocculation process, as well as the bonding type of flos, and the surface profile of flocs revealed by scan electron micrograph suggest that bridging flocculation was the main flocculation mechanism of the studied HBF-3. HBF-3 promoted the efficient formation of flocs through chemical bridging and charge neutralization. The bivalent cation Ca2+ could compress the double layer of kaolin particles, weaken the static repulsive force among kaolin particles, and shorten the distance between kaolin particles and the bioflocculant. Individual bioflocculant molecules and kaolin particles formed kaolin-bioflocculant complexes through ionic interactions of the bivalent cation Ca2+. The application of HBF in Congo red removal was also explored, the result showed that removal of Cong red was 83.7% in 100 mg/L HBF-3.The polysaccharide HBF-3 produced by Halomonas sp.V3a'showed well flocculating performance in kaolin clay suspension. Compared with the original strain, Halomonas sp.V3a'was less dependent on salt, could be cultured under normal temperature and easier to produce uniformly and reliably by fermentation processes. So, it will be a promising bioflocculant in industrial processing.