Depression mechanism of the zinc sulfate and sodium carbonate combined inhibitor on talc

[Display omitted] •Inorganic depressant for talc consisted by ZnSO4 and Na2CO3 was discussed.•Illustrated depression mechanism of ZnSO4 and Na2CO3 combined inhibitor on talc.•Species distribution of Zn2+ were drawn under different concentrations of Na2CO3.•Formation of ZnCO3(s) was qualified in a certain concentration of Zn2+ and Na2CO3.•The main inhibiting component of the combined inhibitor for talc was ZnCO3(s). Solution chemical calculation, zeta potential measurement and flotation test were introduced to verify the effective inhibiting component and illustrate the inhibition mechanism of ZnSO4 and Na2CO3 as a combined inhibitor for talc. Solution chemical speciation calculations indicated that the formation of solid state Zn(OH)2 occurred in all initial concentration ranges of ZnSO4. The higher the initial concentration was, the lower the pH values were when solid state Zn(OH)2 appeared. The solid state ZnCO3 formed when the initial concentrations of ZnSO4 were higher than 1×10−4mol/L, and the formation was qualified in certain concentration ranges of Na2CO3. Additionally, the ranges extended with the increasing initial concentration of ZnSO4. Along with the results of the zeta potential measurement and flotation test, it demonstrated that the effective inhibiting components of the combined inhibitor were solid state ZnCO3 and Zn(OH)2, while ZnCO3 played a major role. When the combined inhibitor is used for the depression of talc, the addition of Na2CO3 and initial concentration of ZnSO4 should be strictly controlled at a restricted level that is suitable for the formation of solid state ZnCO3. ZnSO4 and Na2CO3 is an effective combined inhibitor for talc in flotation separation of talc and molybdenite.