DEPENDENCE OF SHEAR-FLOCCULATION ON SURFACE COVERAGE AND ZETA-POTENTIAL

The dependence of shear-flocculation on surface coverage and zeta potential is elucidated using a model system of fluorite/scheelite/oleate. The experiments carried out are (1) shear-flocculation, (2) oleate adsorption/abstraction, (3) flotation of the shear-flocs, (4) zeta potential, and (5) turbidity. Analyses of the results show that at a sufficiently high, constant shear both an increase in surface coverage and a decrease in zeta potential lead to the increase in amount of shear-flocculating. Manipulation of these two factors permits the turbidity to be reduced from as high as 450 NTU (θ(surface coverage) = ∼.5; ζ (zeta potential) = ∼-40 mV) to as low as 40 NTU (θ= ∼1.2; ζ= ∼ -29 mV) in the case of scheelite. With fluorite turbidity drop is from 120 NTU (θ= ∼1; ζ= ∼ -40 mV) to 20 NTU (θ= ∼1.5; ζ= ∼ -19 mV). A very close relationship exists between the turbidity measurements and the amount shear-flocculating in percentage. The total flotation of the shear-flocs is possible at apparent surface coverages corresponding to a partly formed bilayer. © 1990.