Preparation and Performance of Tannin-Based Flocculants
The hydroxyl groups of conifer tree tannins can be readily converted to quaternary ammonium ether derivatives having a N-content as high as 4 percent and reagent incorporation of about 90 percent. While such a cationic tannin is an effective flocculant, its performance can still be improved by crosslinking reactions of the A-ring with formaldehyde or epichlorohydrin. The flocculation ability of cationic tannins can readily be evaluated in the laboratory by a conventional jar test or by a photometric dispersion analyzer, which records the relative floc sizes. Many times the best flocculation behavior of the cationic tannin in a real wastewater treatment situation is achieved by a combination dosage, which contains cationic tannin as an inexpensive charge neutralizer of the colloidal particles and a more costly macromolecular linear polymer as a bridging agent.
KeywordsCellulose Formaldehyde Sludge Lignin Turbidity
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