THE EFFECTS OF CATIONIC POLYMERS ON FLOCCULATION OF A COAL THICKENER FEED IN WASHERY WATER AS A FUNCTION OF PH

The flocculation of a thickener feed using three cationic polyacrylami de copolymers of high molar mass and different charge densities was st udied at three pHs in washery water. The binding capacities were very dependent on pH but only slightly dependent on the polymeric charge de nsity. The reverse was true for the settling rates. At pH 7, all three polymers were equally effective at clarifying the suspensions, but th ere were marked differences at pH 4 and 9. For the polymers of highest charge density, reducing the pH increased their effectiveness; for th e polymer of lower charge density, changing the pH had little effect o n the residual turbidity. (C) 1997 John Wiley & Sons, Inc.