THE FLOCCULATION OF AQUEOUS SUSPENSIONS OF TITANIA INDUCED BY SURFACE NUCLEATION OF CALCIUM PHOSPHATES#

# This paper is dedicated to professor Care J. van Oss on the occasion of his 75th birthday

ABSTRACT

Titanium oxide aqueous suspensions have been destabilized by a novel mechanism; the nucleation of octacalcium phosphate on the particle surfaces, using the constant composition technique. The results suggest that the potential energies resulting from the electric double layers around the titania particles play only secondary roles in the flocculation, in that a decrease in ζ-potential of titania colloids from −47 mV to −13 mV does not in itself cause the titania suipension to flocculate, in contrast to the predictions of the classical DLVO theory. However, in the process of hucleation of the moderately hydrophobic octacalcium phosphate phase (γ^- _sequals;19.7 mJ m^-2) onto titania particle surfaces, the latter become more hydrophobic with values ranging from 52 to 23.4 mJ m-2, This change is sufficient to cause the particles to flocculate since the energies of attraction result from hydrophobic interactions (90%) and van der Waals forces (10%).

Notes

# This paper is dedicated to professor Care J. van Oss on the occasion of his 75th birthday

Additional information

Notes on contributors

Ŵeénju Wu

To whom correspondence should be addressed