Elimination of the Adverse Effect of Calcium Ion on the Flotation Separation of Magnesite from Dolomite

The separation of magnesite from dolomite was studied by flotation tests, X-ray photoelectron spectroscopy (XPS), and zeta potential measurements in the presence of calcium ion (Ca2+) dissolved from dolomite. Sodium oleate (NaOL) was used as collector, and sodium carbonate (Na2CO3) and sodium hexametaphosphate (SH) were used as regulators. The results showed that SH had a good selective inhibition ability in pure mineral flotations of magnesite and dolomite. While in the presence of Ca2+ dissolved from dolomite, magnesite and dolomite were both inhibited by SH. The separation of magnesite from dolomite cannot be realized because Ca2+ can adsorb on the surface of magnesite in the form of CaCO3 and change the surface properties of magnesite. Thus, the magnesite flotation was depressed. When the sequence of reagent addition was changed to add SH prior to Na2CO3, a complex was made by Ca2+ reacting with SH, which avoided the adsorption of Ca2+ on the magnesite surface and prevented the changing of the magnesite's surface properties. Then, after adjusting the solution pH with Na2CO3, the flotation separation of magnesite from dolomite could be achieved.