Research On The Synergy And Its Mechanisms Of Step-by-step Flotation And Dispersing Flotation For Carbonate-containing Refractory Iron Ores

There is rich resource of carbonate-containing iron ores in our country with a deposit more than 5 billion tons,in which 1 billion tons locates in Anshan,Liaoning.Siderite and ankerite are the primary carbonate minerals in carbonate-containing iron ores,which causes difficulties in flotation separation.One of the main reasons of separation difficulties is the sliming of carbonate-containing iron ores after superfine grinding.Thus mineral particles tend to adhere to and cover on each other easily,resulting in similar surface characteristics and floatability of various minerals.Though the valuable minerals have been liberated,it is still extremely difficult to separate them.Based on this,in this dissertation the synergy and its mechanisms of step-by-step flotation and dispersing flotation for carbonate-containing refractory iron ores has been studied,which will be theoretically and practically meaningful for improving the carbonate-containing iron ore resource utilization.In this paper,siderite,hematite and quartz are the research objects,and the floatability of minerals with different particle sizes and the influence of regulators and pH value on flotation separation of minerals have been studied.Furthermore,the influence of hematite and quartz of different particle size on the siderite flotation of different particle size have been researched in starch and sodium oleate flotation system.Meanwhile,separation tests of siderite in binary minerals system and ternary minerals system and application of the synergetic method of step-by-step flotation and dispersing flotation in Donganshan mixed magnetic separation concentrate have been studied.Moreover,the characteristics of flotation products have been analysed by XRD,SEM and EDS analysis.Finally,the mechanisms of the synergy of step-by-step flotation and dispersing flotation have been discussed on the base of flotation solution chemistry and E-DLVO theory by zeta-potential analysis and contact angle measurements.The study on floatability of minerals and the influence of starch and pH value showed that the floatability of siderite and hematite were the best,and that of quartz was the worst in sodium oleate flotation system.The inhibition effect of starch on minerals of various particle size was different in sodium oleate and starch flotation system,and the difference of floatability between siderite with-18?m particle size and hematite and quartz with various particle sizes was obvious within the pH range of 9?11.In sodium oleate and starch flotation system,the results of research on the influence of hematite and quartz with various particle sizes on the flotation of siderite with-18?m particle size showed that the recovery of siderite with particle size of-18?m was improved by hematite of-74+18?m but reduced to a large extent by hematite of-18?m within the pH range of 5?10.And hematite with particle size of-45pm was entrained easily into flotation concentrate by siderite with particle size of-18?m so that its recovery was increased.The recovery of siderite with particle size of-18?m was reduced by quartz with various particle size of-18?m,-45+18?m and-74+18?m under alkaline conditions while the recovery of quartz with particle size of-74?m was increased by siderite with particle size of-18?m.The results of research on flotation separation of siderite with particle size of-18?m showed that proper dispersant can improve the slurry environment and flotation.With citric acid as a dispersant in the dosage of 20mg/L,the separation effect of siderite was better.In the ternary system of siderite with particle size of-18?m,hematite with the particle size of-74?m and quartz with the particle size of-74?m,with citric acid as dispersant,an iron concentrate with siderite content of 31.16%andrecovery of 60.07%,hematite content of 56.14%and recovery of 20.97%,quartz content of 5.87%and recovery of 2.95%separately was obtained.The synergetic method of step-by-step flotation and dispersing flotation was carried out on the mixed magnetic separation concentrate of carbonate-containing refractory iron ore from Dong Anshan.The experiment results indicated that citric acid helped to improve the dispersion of pulp,which weakened inclusions of hematite in siderite concentrate,preventing the decrease of TFe recoveries in hematite concentrate to a certain extent and thus improved the flotation index.An iron concentrate with Fe grade of 66.47%and Fe recovery of 71.71%was obtained on optimum reagent condition through one rougher-one cleaning-three scavenges closed-circuit process.Compared with the closed-circuit flotation process of step-by-step flotation,the synergetic method have ensured the TFe grade close to the premise,and obtained 2.24%higher TFe recovery.The research on the mechanism of the synergy of step-by-step flotation and dispersing flotation showed that after citric acid was added,the zeta potential of siderite,hematite and quartz decreased due to more adsorption of L3-on their surface within the pH range of 9?11,which also enhanced the strength of hydration layer and hydrophilicity on the mineral surface,and enlarged the electrostatic repulsive force between particles.All of the total E-DLVO energy between siderite,hematite and quartz were positive,so the force between them was repulsive.When adding citric acid into the flotation system,the repulsive force between minerals is larger than that without citric acid.So it could be concluded that citric acid can promote the dispersion of particles of those three minerals.Siderite flotation was chosen as the first step of step-by-step flotation,and the dispersing technique was introduced with citric acid as dispersant,which caused the increases of the electrostatic repulsion between particles and some steric hindrance.Meanwhile,the increase of the surface hydrophilicity of mineral particles would produce hydration,facilitating the dispersion of pulp to reduce agglomeration and covering between particles.Therefore,less hematite ore was entrained in the flotation processing of siderite,which avoided the loss of hematite to a certain extent,and thus the final recovery of iron concentrate was enhanced.Siderite was selected out in priority in the first step to reduce its detrimental effects on the reverse flotation of hematite in the second step.The addition of dispersant in the first step could also help to reduce the non-selective aggregation and covering among minerals that was harmful to the reverse flotation of hematite.All of the above mentioned were conducive to reverse flotation of hematite and the finally obtained better flotation index.