Title

The Effects of Different Coagulation Conditions on the Aggregation Mechanism of Colloidal Haematite

RIS ID

55750

Publication Details

Ng, K. W.K., Amal, R., Raper, J. & Waite, T. 1993, 'The Effects of Different Coagulation Conditions on the Aggregation Mechanism of Colloidal Haematite', Process Industries Power the Pacific Rim: Sixth Conference of the Asia Pacific Confederation of Chemical Engineering; Twenty-first Australasian Chemical Engineering Conference; Official Proceedings of Combined Conference 1993, Institution of Engineers, Australia, Barton, ACT, pp. 75-81.

Abstract

In this work, both photon correlation spectroscopy and forward light scattering are used to measure the kinetics of haematite (α-Fe{2}O{3}) aggregation and flocculation which is induced by alum (Al{2} (SO{4}){3} 18H{2}O). At pH 3, the aggregation is induced by double layer compression and charge neutralisation. The critical coagulation concentration at pH 3 is about 85 ppm of alum. At pH 7, the flocculation is induced by either sweep flocculation and/or adsorption destabilisation. Aggregation kinetics induced by sweep flocculation is fast and by adsorption destabilisation is slow. The oxy-hydroxide flocs formed are fragile and can be broken up with continuous agitation to an equilibrium size which depends on the shear force applied. The oxy-hydroxide flocs can be characterised by a fractal dimension of 2.2 which is independent of the shear force applied.