EFFECTS OF SURFACTANTS ON PARTICLE ADHESION - II - INTERACTIONS OF MONODISPERSED COLLOIDAL HEMATITE WITH GLASS-BEADS IN THE PRESENCE OF 1-DODECYLPYRIDINIUM CHLORIDE

The kinetics of deposition of colloidal hematite particles on glass be ads in the presence of a cationic surfactant, 1-dodecylpyridinium chlo ride (DPC), at pH 4.0 and 10.5 was studied using the packed column tec hnique. At the high pH, the surfactant adsorbed both on particles and beads, which influenced the attachment process; depending on condition s either monolayer or multilayer deposition was observed. At pH 4.0, o nly a monolayer of hematite formed at all surfactant concentrations us ed. At this pH value, the DPC adsorbed little on particles but signifi cantly on beads, making a part of the collector surface inaccessible f or the particle attachment. A modification of the multilayer adhesion theory was proposed which allows one to account for the latter effect. The kinetics of particle release from the monolayer, by rinsing the l oaded column with 10(-2) mol dm(-3) NaOH solutions, was also investiga ted. It was shown that the detachment rate was insensitive to the amou nt of surfactant present in the dispersions used for the deposition. ( C) 1998 Elsevier Science B.V.