The Surface State Of Dolomite And Its Wettability

Dolomite is one of the main gangue minerals of low-grade phosphate ore.Its chemical composition is Ca Mg(CO3)2.The high Mg O content in phosphate ore will have serious adverse effects on the subsequent wet-process phosphoric acid.Therefore,it needs to be removed.miscellaneous.Flotation is the main effective method for the enrichment of low-grade phosphate ore.It is a physical and chemical process based on the difference in wettability of mineral surfaces to achieve mineral separation.The useful minerals of dolomite and phosphate rock are the same as calcium-containing minerals,which have similar surface physicochemical properties,which makes it difficult to separate the flotation.In the industry,the reverse flotation process under acidic conditions is generally used,and the apatite is inhibited by sulfuric acid or phosphoric acid,and the dolomite is floated by the fatty acid collector.Studying the surface state of dolomite and its wettability is of great significance for enriching the flotation theory of phosphate rock and guiding the flotation and enrichment of low-grade phosphate ore.In this study,the gangue mineral dolomite associated with phosphate ore was studied.The electronic structure properties of dolomite were calculated based on density functional theory.The content and distribution of dolomite surface elements were determined by time-of-flight secondary ion mass spectrometry.The three-dimensional morphology of CO2 nanobubbles generated on the dolomite surface under acidic conditions was observed by atomic force microscopy.CO2 was studied by captivity measurement of contact angle,particle-bubble induction time measurement,pure mineral flotation test and molecular dynamics simulation.The effect of nanobubbles and collector sodium oleate on the surface wettability of dolomite reveals the surface state and wetting mechanism of dolomite from a microscopic point of view.The main conclusions are as follows:(1)Dolomite is an insulator with a forbidden band width of 4.96 e V.Both the Mg6 and Ca atoms in the dolomite electronic structure are electron donors,the Mg atoms lose electrons in the 3s and 2p orbits,and the Ca atoms lose electrons in the 3s and 4d orbitals.The maximum value of C-O bond layout in the Dolomite Mulliken bond layout is 0.87,which is the covalent bond.The interaction between atoms is the strongest and most stable;the population value of Mg-O is-0.65 is the ion bond.The population value of Ca-O is 0.12 as an ionic bond.The Ca-O bond length is 2.36 ?,the Mg-O bond length is 2.11 ?,and the Ca-O bond length is long and easy to break.Ca,Mg and O atoms have higher charge density and higher activity,which is a site where drug adsorption is more likely to occur during flotation.The main exposed surface of dolomite is {104} cleavage surface,the surface of dolomite is rough,the specific surface area of-150+75 ?m granular dolomite particles is 0.36 m2/g,and the Ca content of dolomite surface is higher than that of Mg element.(2)The dissolution of dolomite surface under acidic conditions,CO2 nanobubbles were observed,the height ranged from 2.91 nm to 63.48 nm,and the nanobubble density was 0.92/m2.Under acidic conditions,the contact angle of dolomite increased from 8°to 19°under natural conditions,and the adhesion work increased from 0.71 m J/m2 to 3.96 m J/m2.Dolomite particles-bubble induction times in solutions with p H = 9 and p H = 4 were 1300 ms and 700 ms,respectively.When p H=2,the dolomite particles react violently with the solution,and microbubbles on the surface of the particles will carry the dolomite particles continuously floating.The molecular dynamics simulation showed that the droplet contact angle was 17° when the CO2 molecular layer was present on the dolomite surface,and the droplet contact angle of the dolomite surface without the CO2 molecular layer was 5°.The dolomite surface without the CO2 molecular layer has a higher water molecular density than the dolomite in which the CO2 molecular layer is present.(3)The adsorption site of sodium oleate and the surface is a Ca atom.The adsorption energy of sodium oleate and dolomite is 301.95 k J/mol,which is greater than the adsorption energy of water of 109.75 k J/mol and H+ adsorption of 5.90 k J/mol,indicating that sodium oleate can overcome the adsorption of water molecules or hydrogen ions on the surface of mineral.In the presence of sodium oleate,thedolomite contact angle increases from 13 ° in the natural state to 88 °.With the increase of p H=2 to p H=12,the dolomite contact angle decreased from 98°to 52°,the adhesion work decreased from 30.08 m J/m2 to 11.74 m J/m2,and the floating rate decreased from 94.82% to 62.80%.