The coagulation kinetics of polyaluminum chloride (PACl) and alum applied to kaolin clay suspensions were compared in batch experiments. Increasing aluminum (Al) dosages reduced the time required for particles destabilization and increased the rate at which the number of primary particles decreased. PACl worked faster than alum. Photometric dispersion analysis showed that increasing Al dosages decreased the tune required for floc to form. Again, this rate was faster with PACl than with alum. Increasing the Al dosage accelerated the flocculation rate because it increased collision-attachment efficiency and increased paniculate volume. The rates of particle destabilization, reduction of destabilized primary particles, and agglomeration varied with mixing intensity and water temperature. Although lower temperatures slowed the particle destabilization rate, similar effects on the flocculation rate could be avoided by maintaining a constant G value. PACl was less sensitive to changes in pH, implying that PACl performed better than alum in cold water.
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