Dissolution Characteristics Of Carbonate Minerals In Magnesite Ore And Its Influence On Floatability Of Minerals

Magnesite resource in China has a dominant position.The main target mineral in the ore is magnesite,and the gangue mineral containing calcium is dolomite.Magnesite and dolomite are both carbonate minerals,and the flotation separation of them is difficult due to their similar floatability.The effective separation of magnesite and dolomite has become one of the key and difficult points of magnesite purification.Magnesite and dolomite have different dissolution characteristics,leading to the difference of surface properties after dissolution.It is possible to improve the flotation separation effect of magnesite and dolomite via enlarging the difference of floatability based on the characteristics of dissolution and floatability.It has theoretical and practical significance to study the dissolution characteristics of carbonate minerals in magnesite ores and their effects on the floatability of minerals.The dissolution characteristics of magnesite and dolomite were studied.The dissolution test is conducted with the parameters of distilled water,p H,dosage of adjusting agent sodium hexametaphosphate,dosage of collector LKD and different conditions（stirring speed,temperature,time,etc.）.The dissolution characteristics of magnesite and dolomite were studied with modern detection methods.The results showed that the calcium and magnesium ions dissolved from magnesite and dolomite increased with the increase of slurry concentration,stirring speed and stirring time within the range of test conditions;With the increase of p H value,the calcium and magnesium ions dissolved from magnesite and dolomite decrease;With the increase of the dosage of sodium hexametaphosphate,the calcium and magnesium ions dissolved from magnesite and dolomite first decreased and then increased;With the increase of the amount of LKD,the calcium and magnesium ions dissolved from magnesite and dolomite increase first and then decrease;With the increase of temperature,the calcium and magnesium ions dissolved from magnesite and dolomite increase first and then decrease;Under the same dissolution conditions,the solubility of dolomite is greater than that of magnesite,so the magnesium ions dissolved from dolomite are more than that from magnesite;SEM-EDS results show that some calcium and magnesium ions are adsorbed on the mineral surface after the dissolution of magnesite and dolomite;The results of atomic force microscope show that under the same conditions,the dissolution depth and width of dolomite are larger than those of magnesite,indicating that magnesite and dolomite are not synchronized in the dissolution process;The infrared spectrum analysis shows that the absorption peak of CO₃^2-antisymmetric stretching vibration at 1448 cm^-1 has changed,indicating that the surface of the mineral has changed after dissolution.The solvation model of magnesite and dolomite was established.The solvation model of magnesite and dolomite under neutral,acidic,neutral and alkaline conditions was established under COMPASSⅡforce field.The results show that water molecules are adsorbed on the surface of magnesite and dolomite;The H atom in the water molecule will form hydrogen bond with the O atom exposed on the surface of magnesite and dolomite;While the surface of magnesite and dolomite adsorbs water molecules,some magnesium and calcium ions will dissolve out and enter into the aqueous solution,and calcium and magnesium ions on the mineral surface of the acid solvation model will basically dissolve out.The dissolution of carbonate minerals and the influence of dissolved components on their floatability are studied.Determine the change of mineral floatability after dissolution through flotation test;The flotation behavior and change rule of minerals in the presence of Mg²⁺,Ca²⁺,Fe³⁺and the dissolution of magnesite and dolomite are studied,and the appropriate conditions for the separation of magnesite and dolomite are obtained.In LKD system,the amount of flotation collector LKD for magnesite and dolomite is 80 mg/L,the p H is between 6-7,and the amount of sodium hexametaphosphate is 20 mg/L.At this time,the recovery rate of magnesite is 45.04%and that of dolomite is 68.40%.The floatability of magnesite and dolomite decreased after acid dissolution,but the floatability of magnesite decreased and the floatability of dolomite increased under the conditions of slurry concentration,sodium hexametaphosphate dosage,collector LKD dosage,stirring speed,stirring time and temperature;After dissolution in distilled water and flotation,the floatability difference between the two minerals is obvious.At this time,the recovery rate of magnesite is 37.26%and that of dolomite is 71.60%.After adding Mg²⁺and Ca²⁺,the flotation recovery of magnesite and dolomite after dissolution is lower than that when they are not dissolved.After adding Fe³⁺,the recovery of magnesite is higher than that of undissolved magnesite,and the recovery of dolomite is lower than that of undissolved magnesite;When the dissolution rate is large,the recovery rate of magnesite is higher than that of dolomite,which indicates that the addition of Mg²⁺and Ca²⁺has little influence on the flotation of dolomite after dissolution under different dissolution rates,but has great influence on magnesite.With the increase of Mg²⁺dosage,the recovery of magnesite and dolomite after dissolution decreases slowly.With the increase of the amount of Ca²⁺and Fe³⁺,the recovery of magnesite increases,while the recovery of dolomite slowly decreases.In the sodium oleate system,the flotation of magnesite and dolomite finally determined that the amount of sodium oleate as the collector is 140 mg/L,p H is 11,and the amount of sodium hexametaphosphate is 10 mg/L.At this time,the recovery rate of magnesite is67.34%and that of dolomite is 48.09%.The recovery of magnesite and dolomite decreased with the increase of dissolution rate.After adding Mg²⁺,the recovery of magnesite and dolomite after dissolution is lower than that when they are not dissolved.After adding Ca²⁺,the recovery of magnesite and dolomite after dissolution is higher than that when they are not dissolved.After adding Fe³⁺,the recovery of magnesite and dolomite after dissolution has little change.The artificial mixed ore test shows that the flotation after mineral dissolution in LKD system can improve the calcium removal effect of magnesite.With the increase of sodium oleate dosage,the effect of calcium removal is not ideal.The influence mechanism of magnesite and dolomite dissolution on flotation was studied.IR and SEM-EDS analysis results show that magnesite and dolomite have physical adsorption with collector LKD after they are dissolved and interact with collector LKD.The results of mineral electrokinetic potential analysis show that the zeta potential value changes after the interaction of magnesite and dolomite with the collector LKD and dissolved components(Mg²⁺,Ca²⁺)before and after dissolution,indicating that the collector LKD has adsorption mainly by electrostatic action and hydrogen bond action on the surface of magnesite and dolomite before and after dissolution.The results of XPS analysis show that before and after the dissolution of magnesite and dolomite,they interact with the collector（LKD）and dissolved components(Mg²⁺,Ca²⁺),and Nitrogen element are detected,indicating that the collector has adsorbed on the surface of magnesite and dolomite.The element narrow zone spectrum shows that the collector LKD has adsorption on the surface of magnesite and dolomite through electrostatic attraction and hydrogen bond.The simulation results show that the collector LKD has a strong effect on the dolomite surface.