Preparation Technology And Flotation Mechanism Of Super Iron Concentrate From Bayan Obo Iron Ore

The Bayan Obo ore deposit is a large polymetallic deposit with symbiosis of iron,rare earth and niobium.The production of super iron concentrate is one of the effective ways to improve the economic benefit of enterprises and promote the upgrading of mineral processing products.Compared with the ordinary iron concentrates,super iron concentrate?TFe>72%,SiO₂<0.25%?is high quality feedstock as the direct reduced iron,powder metallurgy,magnetic materials and the clean steel production except its own price being 4⁵times as high.Especially,the Baiyun Obo ore contains the elements such as RE,Nb,is used to prepare iron and steel products,ceramic material with strong wear resistance,corrosion resistance,which have good comprehensive performance.Therefore,the Bayan Obo ore should be developed as a kind of mineral material and should not be used cheaply.According to the“poor,fine and complex”mineralogical characteristics of Bayan Obo iron ore,the super iron concentrate is prepared by the combined technology of“grinding-magnetic separation-flotation”to improve iron grade and reduce silicon content,so as to realize its high-value utilization.And a new type of compound activator is developed to research the mechanism of flotation activation.By means of XRD,SEM,EDS and chemical detection,the process mineralogy of Bayan Obo iron REO was analyzed.The optimum technological condition for the preparation of super iron concentrate from Bayan Obo iron ore is studied by the combined process of“stage grinding-low intensity magnetic separation-reverse flotation”.The results show that the magnetite concentrate with iron grade of 70.50%,iron recovery of 67.58%and SiO₂ content of 0.35%can be obtained by three stage grinding and low intensity magnetic separation process.Based on this,the influence of three kinds of activator(Ca²⁺,Fe³⁺and Ca²⁺/Fe³⁺compound activator)on desilication effect of the magnetite concentrate?grinding fineness is 0.030mm?93.0%??is mainly investigated by reverse flotation desilication experiment.It show that Ca²⁺/Fe³⁺the best desilication index of compound activator,in optimum roughing experimental conditions(pH=8,sodium dodecyl sulfonate?SDS?collector dosage of 200 g/t and Ca²⁺/Fe³⁺compound activator dosage of 400 g/t),the grade,recovery and SiO₂ content of iron concentrate is 72.05%,96.58%and 0.22%respectively.Then through the“one crude one fine”open-circuit process of reverse flotation desiliconization,the super iron powder is finally obtained with iron grade of 72.15%,recovery of 87.46%and SiO₂ content of 0.21%,which contains trace rare earth,niobium.Based on the flotation desilication process of iron concentrate,the activation mechanism of Ca²⁺,Fe³⁺and Ca²⁺/Fe³⁺on collector SDS flotation of quartz is studied by the flotation test of pure minerals?quartz and magnetite?,solution chemical calculation and Zeta potential,FT-IR,photoelectron spectroscopy?XPS?test methods.The results show that the addition of three activators in a certain pH range significantly inhibits the floatability of magnetite and is beneficial to the flotation of quartz,thus increasing the recovery rate of quartz,and the quartz recovery of Ca²⁺/Fe³⁺activation is higher than that of Ca²⁺or Fe³⁺.The activation mechanism is that the positive potential of quartz is improved by adsorbing of Ca²⁺or Fe³⁺onto its surface,thus enhancing the adsorption of anionic SDS collector on quartz,and Ca?OH?⁺and Fe?OH?₃ precipitate are respectively the main activation factors on the surface of quartz.After being activated by cationic ions(Ca²⁺,Fe³⁺and Ca²⁺/Fe³⁺),quartz interacts with collector,and its surface potential is significantly shifted,indicating that cationic adsorption improves the positivity of quartz surface and enhances the electrostatic adsorption of quartz surface and anionic SDS collector.The dominant components of Ca²⁺and Fe³⁺on quartz surface are Ca?OH?⁺and Fe?OH?₃,respectively,and synergistic effects of Ca²⁺and Fe³⁺make the positive electricity reaching to the strongest.The results of FT-IR analysis showed that in the infrared spectrum of quartz activated by cationic ions and acting with collectors,new stretching vibration absorption peaks of-CH₂-and-CH₃-are found,but there is no wave-number deviation,so physical adsorption takes place on the surface of quartz;while wave-number positive deviation and enhanced absorption peak of Si-O asymmetric stretching vibration absorption peak are found,thus bond energy increases,indicating that chemical adsorption takes place on the surface of quartz.In addition,due to the synergistic effects of Ca²⁺and Fe³⁺,its adsorption behavior includes both single oxygen bond of Ca?OH?⁺and double oxygen bond of Fe?OH?₃,Therefore,the activation ability is stronger than that of using it alone at an appropriate pH value,which is more conducive to activate the flotation of quartz.XPS test also proved that the binding energy of Ca²⁺/Fe³⁺synergistically activated quartz is obviously stronger than that of Ca²⁺or Fe³⁺alone,the chemical shift of Si2s and Si2p moved towards the high binding energy in XPS spectra of Ca²⁺/Fe³⁺synergistically activated quartz is larger,indicating that under the synergy activation the chemical adsorption of Ca²⁺/Fe³⁺and quartz is more stable and more compact,and in quartz surface both stable Fe-base six-member ring chelate compound and Ca-base chain complex are formed,thereby the chemical adsorption and the physical adsorption on the surface quartz are enhanced at the same time.