EFFECfS OF DISSOLVED MINERAL SPECIES ON THE ELECfRO- KINETIC BERA VIOR OF CALCITE AND APATITE

The interfacial behavior of salt-type minerals such as calcite and apatite is governed to a large extent by their electrochemical properties which in turn are governed by pH and concentration of dissolved mineral species. In mixed mineral systems, the interfacial behavior of various minerals is often quite different from what might be expected on the basis of their individual properties. Predictions for flotation separation based on single mineral tests often fail in these systems mainly owing to the interactions between dissolved mineral species. The effect of dissolved mineral species of the calcite-apatite system is investigated in this study using the electrokinetic technique. The electrochemical, dissolution and spectroscopic properties of each mineral were markedly altered by the supernatants of the other mineral. Most interestingly, under the test conditions, the isoelectric point of each mineral in the supernatant of the other was observed to be similar to the supernatant mineral source. It is clear that, under these conditions, a flotation separation scheme designed on the basis of the surface properties of the single minerals is not likely to perform satisfactorily. Tests in inorganic solutions have shown that surface reaction and/or bulk precipitation could be responsible for the observed shifts. Surface chemical alterations predicted from theoretical considerations using species distribution diagrams are correlated with the experimental results.