Strength of Flocs Formed from Aluminium Sulfate Hydrolysis Product Particles

The kinetics of aggregation of aluminium sulfate hydrolysis product particles (AS HPP) formed in two model waters with different pH and alkalinity values, at different shear conditions in a flow system has been studied. The effect of the hydrolyzing salt dose, ionic strength of the solution and the mode and rate of stirring the system on the growth, destruction and regrowth of HPP aggregates has been investigated. The comparison of the results obtained with our previous data on the electrokinetic potential and hydration of AS HPP [7] testifies that the aluminium sulfate hydrolysis product particles formed in a model water with parameters that facilitate appearance of small particles with relatively high charge and zeta-potential values, low degree of hydration and interaction of primary particles predominantly in the primary minimum (water II: pH 7.5, alkalinity 1 mmol/l, average particle radius 6–7 nm, ζ =26–29 mV), are more stable and possess higher ability for reconstruction after their destruction during intensive stirring, than aggregates built of particles with lower charge, higher initial particle size and hydration, aggregating in the secondary minimum (water I: pH 9.3, alkalinity 3 mmol/l, average particle radius 10–11 nm, ζ =16–18 mV).