Effects Of Surface Defect Structure Of Iron Oxide Minerals On The Adsorption Of Flotation Reagents And The Regulation Mechanism

Iron oxide mineral resources are an important source of strategic metal iron and play an important supporting role in the development of the national economy and the construction of national defense and military industries.Iron oxide minerals in China are mainly low-grade refractory resources,which need to be enriched before further metallurgical utilization.Flotation is the most effective and important method for the processing and utilization of refractory oxide minerals.Due to the cleavage and collision of minerals in the grinding process before flotation,numerous of defect structures will be generated on the surface of mineral particles.The surface defect atoms possess stronger reaction activity because of their stronger residual bonding ability and coordination unsaturated.Mineral flotation is an interfacial reaction process,and mineral surface defects,as key active sites,have a significant impact on the surface structure and properties,which in turn affect the adsorption behavior and action mechanism of reagents,and ultimately affects the floatability of minerals.Mineral flotation is based on the coordination and binding of collectors at atomic sites on the mineral surface to realize the hydrophobic floating of minerals.The essence is that the coordination adsorption of collectors on mineral surfaces at an atomic scale.In this work,taking the typical iron oxide minerals hematite and goethite and gangue quartz as the research objects,the effects of the typical point defect structures of the minerals surface on the adsorption of flotation reagents and regulation mechanism were studied by experimental methods and first-principles quantum chemical calculations.The main research findings and innovation results are as follows:（1）The surface hydroxylation behavior of hematite,goethite and quartz is thermodynamically favorable,and the hydroxylation ability of quartz is the strongest,followed by goethite and hematite.For the stable fully hydroxylated structure,the orientation of the Fe-OH structure formed on the hematite（012）surface is roughly the same,the H and O atoms of the Fe-OH structure form hydrogen bonds with each other and appear alternately in the same direction of the plane.While the H and O atoms of the Fe-OH structure on the goethite（010）surface form horizontal hydrogen bonds with each other,the O atoms in the Fe-OH structure form vertical hydrogen bonds with the H atoms on the goethite surface,which makes the goethite surface form a three-dimensional hydrogen bond network.The orientations of all silanol（Si-OH）structures on the quartz（101）surface are completely consistent,and there is no obvious hydrogen bond structure between them.（2）In theoretical calculation,the Fe and Si atoms around O vacancy have high activity and show good affinity for collector sodium oleate,depressant sodium humate,water molecule and OH^-on the O vacancy surface.On the perfect surface,quartz shows better adsorption performance for oxygen-containing adsorbates than iron oxide.On the hydroxyl surface,the existence of the hydroxyl layer on the mineral surface depresses the direct adsorption of oxygen-containing adsorbates on the mineral surface,but enhances the adsorption of the activator Ca²⁺.（3）The collaborative researches of experimental analyses and theoretical DFT calculations show that OL^-is an effective collector component for the flotation separation of iron oxide and quartz.In the absence of Ca²⁺,OL^-cannot be directly adsorbed on the mineral surface.The reason is that the presence of the hydroxyl layer on the mineral surface depresses the direct action of the collector.In the presence of Ca²⁺,the selective adsorption of Ca²⁺ions on the quartz surface creates adsorption sites for the interfacial adsorption of the collector sodium oleate,which realizes the efficient flotation separation of quartz and iron oxide minerals.