Abstract:

Cationic guar gums of varying molar mass and charge d. were synthesized and tested as flocculants for bentonite suspensions. The gums were fragmented using ammonium persulfate as a degrading agent, followed by pptn. of the products with ethanol. Cationic charge was added to the guar mol. by reacting it with 2,3-epoxypropyltrimethylammonium chloride. Flocculant performance was assessed by detg. the extent of polymer adsorption, by measuring both residual turbidities of the resulting supernatants and the changes in the particles' electrophoretic mobility (EM). Increasing the flocculant charge d. causes the optimal flocculation concn. (OFC), as well as the efficient flocculant concn. range, to be reduced. Above this range restabilization occurs. The OFC (for highly modified guar) is also the concn. at which the particles' EM is zero. It was found that decreasing the mol. wt. of the guar (at the same charge d.) increases the OFC and decreases the electrophoretic mobility of the clay particles in the overdose range. [on SciFinder(R)]