Simultaneous removal of calcium and sulfate ions from flotation water of complex sulfides

•The excess of reactants accelerates the reaction kinetics but does not necessarily make it more efficient.•Monocalcium aluminate provides aluminate ions for precipitation of solids.•pH control is essential to achieve an efficient ion removal process.•The pH defines the stability of the solid products and the concentration of ions in solution.•Stability of the ettringite is also a function of the reaction time.