Electrochemical properties of apatite and other minerals of Zambian phosphate ores in aqueous solution

Abstract

A microelectrophoresis technique was used to study the electrochemical properties of apatite, quartz and hornblende from Chilembwe phosphate ore;and apatite, calcite and magnetite from Kaluwe phosphate ore. The tests were conducted in distilled water and the water near the source of the phosphate ores under study.

The apatite from Chilembwe gave an isoelectric point (i.e.p.) value of pH 6 in distilled water while in Mankwala Dam water the i.e.p. was of pH 4. Quartz and hornblende were negatively charged throughout the entire pH range studied in both cases. Apatite from Kaluwe showed an i.e.p. value of pH 3.8 while calcite and magnetite had i.e.p. values of pH 6.1 and 4.1 in distilled water, respectively. However, in Kaluwe water the i.e.p. of calcite shifted to pH 8.8 resulting in a charge reversal on either side of the i.e.p. There was no marked difference in the i.e.p. values of apatite and magnetite in Kaluwe water from those in distilled water. Comparison of zeta potential-curves for different apatites showed that they exhibit different i.e.p. values because of their variable composition.