FLOCCULATION OF BENTONITE SUSPENSIONS WITH CATIONIC GUAR

Cationic guar gums of varying molar mass and charge density were synth esized and tested as flocculants for bentonite suspensions. The gums w ere fragmented using ammonium persulphate as a degrading agent, follow ed by precipitation of the products with ethanol. Cationic charge was added to the guar molecule by reacting it with 2,3-epoxypropyltrimethy lammonium chloride. Flocculant performance was assessed by determining the extent of polymer adsorption, by measuring both residual turbidit ies of the resulting supernatants and the changes in the particles' el ectrophoretic mobility (EM). Increasing the flocculant charge density causes the optimal flocculation concentration (OFC), as well as the ef ficient flocculant concentration range, to be reduced. Above this rang e restabilization occurs. The OFC (for highly modified guar) is also t he concentration at which the particles' EM is zero. It was found that decreasing the molecular weight of the guar (at the same charge densi ty) increases the OFC and decreases the electrophoretic mobility of th e clay particles in the overdose range.