Surface complexation at calcium mineral-water interfaces

Sammanfattning: Surface reactions occurring at solid-water interfaces in calcium mineral-ligands systems have been studied. Both hydrous apatite and fluorite surfaces show clear amphoteric properties. An ion exchange process between lattice ions of F- on fluorite and OH- ions in bulk solution is discovered. The surface adsorption of Alizarin Red S and sodium oleate are determined. Surface chemical reaction models are established based on acidbase potentiometric titrations, solubility, adsorption and zeta-potential measurements in 0. 1 mol dm-3 ionic media at 25'C. Experimental data are evaluated using the computer program FITEQL assuming a constance capacitance model for the electric double layer. Surface complexes identities are obtained from FT-IR, FT-Raman, and UV/visible spectroscopy studies. A series of surface equilibrium constants in the system are presented. The correlation between surface complex formation and mineral flotation is discussed.