Novel biodegradable flocculants based on polysaccharides

The waste water and industrial effluent-treatment requires both inorganic and organic flocculants. Among the organic type, polymeric flocculants (synthetic as well as natural) are preferred because of their low dosage, easy handling, inertness to pH changes, production of large cohesive flocs and versatile tailorability. The concern for environmental and ecological issues warrants the use of the biodegradable flocculant in waste water and industrial effluent treatments. Natural polysaccharides such as starch, gums, glues, alginate, etc. function as bridging flocculants. This could be accounted for by the purification and chemical modification. It has been established that by grafting polyacrylamide branches on polysaccharides, the dangling grafted chains have easy approachability to the contaminants. Among the grafted guar gum, xanthan gum, carboxy methyl cellulose and starch, grafted starch flocculates better. Starch consists of amylose (a low molecular weight linear polymer) and amylopectin (a high molecular weight, branched polymer). The grafted amylopectin is found to be a suitable flocculant for various kinds of industrial effluents. Here we summarize the various investigations carried out using flocculants based on polysaccharides.