THE ROLE OF MICELLAR STRUCTURES IN SHEAR FLOCCULATION .1. FLOCCULATION OF QUARTZ WITH ALKYLAMINE SURFACTANTS

In a collaborative study between the US Bureau of Mines and the Depart ment of Chemistry at the University of Alabama, research has been cond ucted to study the role surfactants play in shear flocculation. The sh ear flocculation of silica by amine surfactants was studied as a funct ion of surfactant alkyl chain length. A six-carbon amine chloride did not produce shear flocculation. At twelve carbons and above, the avera ge particle size increased steadily with chain length. Zeta potential measurements show that particle aggregation is due to shear flocculati on and not electrostatic coagulation produced by charge neutralization by adsorbed surfactant. The presence of air bubbles was observed to a lter the rate and degree of particle aggregation, and to cause flee fl otation. The presence of surfactant aggregates in the shear flocculati on process was confirmed by electron paramagnetic resonance (EPR) spec troscopy using a spin-labeled analog of cetyl-trimethylammonium bromid e. Analysis of the EPR spectra clearly indicates that surfactant aggre gation increases during shear flocculation. The EPR results were found to be consistent with both enhanced bilayer formation, and with displ acement of the surfactant equilibrium due to inclusion of surfactant w ithin the particle aggregates.