INTERFACIAL PROPERTIES OF CELESTITE AND STRONTIANITE IN AQUEOUS-SOLUTIONS

The present study addressed the investigation of the basic fundamental s of the behaviour of celestite (SrSO4), strontianite (SrCO3) and calc ite (CaCO3) in aqueous solutions in the presence and absence of sodium oleate. The results showed that the isoelectric point (IEP((aq))) of aqueous suspensions of strontianite and calcite takes place at pH 8 an d 8.2, respectively; from thermodynamics, the IEP((aq)) of the mineral s takes place at pH 8 and 8.3, respectively. Similarly, a thermodynami c analysis of the celestite-aqueous solution equilibrium open to the a tmosphere showed celestite transforms to strontium carbonate in alkali ne slurries (pH greater than or equal to 7.75). This phenomenon is due to the chemical reaction of celestite with the carbonate ion that for ms in the solution as a result of the dissolution of the atmospheric C O2. The results of the mineral-aqueous solution equilibrium, electroki netic and infrared spectroscopy studies appear to confirm such a super ficial transformation. The electrokinetic studies showed the isoelectr ic point (IEP) of celestite and strontianite takes place at pH 5.4 and 7.4, respectively. The floatability of the minerals was investigated in the pH range 5 to 11 and varying the concentration of sodium oleate from 10(-6) to 10(-4) M. The results showed that celestite floatabili ty had a maximum in the pH range 7 to 9; at higher pH values its float ability tended to decrease as a result of its surface transformation t o strontium carbonate. The floatability of strontianite and calcite wa s substantially lower than that of celestite and tended to increase wi th the pH (pH greater than or equal to 7) and concentration of sodium oleate. It is proposed that in alkaline slurries sodium oleate was ads orbed on the celestite, strontianite and calcite surfaces by a chemiso rption mechanism.