The dispersion properties of precipitated calcium carbonate suspensions adsorbed with alkyl polyglycoside in aqueous medium

The zeta potentials and dispersion properties of precipitated calcium carbo nate suspensions adsorbed with alkyl polyglycosides in aqueous medium were investigated. Within the investigated pH ranges, the adsorption curves of a lkyl polyglycosides on calcium carbonates show sigmoidal shapes, and the ze ta potential decreases as the amount of adsorption increases. At positively charged surfaces of low pH, the adsorption amounts were greater than those at negatively charged surfaces, indicating that alkyl polyglycosides were negatively charged in aqueous solutions. At low concentrations of alkyl pol yglycosides, the dispersion stabilities of suspensions were very poor and s howed no linearity with zeta potentials over the entire range of pHs, which may be attributed to the onset of hydrophobic interaction between particle s due to the adsorption of surfactant molecules. This destabilization conti nued until monolayer coverage by the surfactant layer was complete. Based o n the classical DLVO theory, there may be a strong hydrophobic interaction between particles. Beyond monolayer adsorption, the dispersion stability in creases, probably by the formation of hemimicelle or admicelle. Therefore, it is believed that ionization of alkyl polyglycosides and admicelles of su rfactants on particle surface plays a key role in the stability of dispersi ons and the abrupt increase in adsorption, (C) 2000 Academic Press.