Study On The Influence Mechanism Of Dissolved Ions On The Surface Properties And Floatability Of Fluorapatite And Dolomite

The fluorapatite and dolomite in the calcium magnesium phosphate rock are calcium salt minerals,which are easy to dissolve in the flotation process to produce Ca²⁺,Mg²⁺,PO₄^3-,F^-and other lattice ions.After adding the inhibitor H₂SO₄ in the flotation,SO₄^2-is also introduced;especially under acidic conditions,the dissolution rate of mineral surface is accelerated and the ion concentration increases rapidly.In addition,due to the poor hard water resistance of fatty acid collectors,the dissolved ions in the pulp will affect the adsorption of collectors on the mineral surface,thus affecting the surface properties and flotation behavior of minerals.Therefore,the effects of dissolved ions on the surface properties and floatability of fluorapatite and dolomite were studied,and the adverse effects and mechanism of dissolved ions on flotation were identified,which laid a foundation for targeted removal of harmful ions in flotation backwater.In this paper,the effects of Ca²⁺,Mg²⁺,SO₄^2-,PO₄^3-and F^-on the flotation behavior of dolomite and fluorapatite were studied by single mineral flotation and actual ore flotation tests.The flotation foam and mineral particle agglomeration were observed.The contact angle,Zeta potential,adsorption density,X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy（SEM）,surface tension,density functional theory（DFT）calculation and molecular dynamics simulation（MDS）were used to reveal the microscopic mechanism of dissolved ions affecting the surface properties and floatability of dolomite and fluorapatite.The main results are as follows:（1）Single mineral flotation tests showed that Ca²⁺,Mg²⁺,SO₄^2-and PO₄^3-would reduce the floatability of dolomite and fluorapatite,especially for dolomite,when the dosage of H₂SO₄ and GJBW were 200 mg/L and 100 mg/L,respectively.The high concentration of dissolved ions will reduce the number of mineralized foams,polarize the foam size,fail to form a stable foam layer,and weaken the particle agglomeration in the slurry,resulting in a decrease in the floating rate.F-has little effect on the floatability of dolomite and fluorapatite.The effect of ion interaction on the flotation of calcium magnesium phosphate ore shows that the coexistence system of dissolved ions Ca²⁺/Mg²⁺,Ca²⁺/SO₄^2-,Mg²⁺/SO₄^2-,Mg²⁺/PO₄^3-,SO₄^2-/PO₄^3-will reduce the grade and recovery of P₂O₅ in flotation concentrate and increase the content of Mg O in concentrate.（2）Dissolved ions will adsorb on the mineral surface to change its surface electrical properties and surface wettability.Ca²⁺and Mg²⁺will increase the zeta potential of dolomite and fluorapatite surface,while SO₄^2-and PO₄^3-will reduce the zeta potential of mineral surface.Under natural conditions,dissolved ions do not affect the surface wettability of dolomite and fluorapatite.However,after adding the collector GJBW,Ca²⁺,Mg²⁺,SO₄^2-,PO₄^3-will reduce the contact angle of dolomite and fluorapatite,resulting in a decrease in hydrophobicity,thereby reducing the floating rate.The adsorption density test further shows that Ca²⁺,Mg²⁺,SO₄^2-,PO₄^3-will reduce the adsorption density of the collector GJBW on the surface of dolomite and fluorapatite,especially dolomite.Ca²⁺and Mg²⁺have a certain precipitation effect on the collector GJBW,and the precipitation effect of Ca²⁺on the collector is higher than that of Mg²⁺.（3）The collector GJBW can effectively reduce the surface tension of the pure water,and the dissolved ions will not affect the surface tension of the aqueous solution,but Ca²⁺,Mg²⁺,PO₄^3-will increase the surface tension of the collector GJBW solution and weaken its surface activity.XPS analysis shows that Ca²⁺will react with SO₄^2-in the solution to form Ca SO₄ precipitate and adhere to dolomite surface.Mg²⁺may generate part of Mg SO₄,but Mg SO₄ has a large solubility and is unstable dolomite surface.In the acidic system,PO₄^3-can react with dissolved Ca²⁺to form Ca（H₂PO₄）₂,which weakens the adsorption of collector.（4）DFT calculations show that fatty acids（caproic acid）can be stably adsorbed on dolomite（104）surface and fluorapatite（001）surface by chemical adsorption and hydrogen bonding.Ca²⁺can be adsorbed on the surface of dolomite and fluorapatite by combining with O（surf）,and O（surf）has obvious relaxation phenomenon.With Ca²⁺as the medium,caproic acid can interact with O（surf）to form a stable adsorption configuration.The O of caproic acid and O（surf）on the surface of dolomite and fluorapatite can formσbond and weakπbond with Ca²⁺,respectively,and produce more weakπbonds on the surface of fluorapatite.Mg²⁺cannot bond with O（surf）on the surface of dolomite and fluorapatite,and is mainly adsorbed on the mineral surface in the form of van der Waals force.（5）The adsorption of SO₄^2-will reduce the active sites on the mineral surface and weaken the adsorption effect of Na OL on the surface of dolomite,thus inhibiting the flotation of dolomite and fluorapatite.Both PO₄^3-and H₂PO₄^-inhibited the adsorption of Na OL on dolomite and fluorapatite surfaces.H₂PO₄^-inhibited the adsorption of Na OL on dolomite surface more strongly,while PO₄^3-inhibited the adsorption of NaOL on fluorapatite surface strongly.