Study On The Interaction Mechanism Of Alumina/silicon Minerals-Bubbles And Regulation Of Adhesion Behavior In The Flotation System

The bauxite flotation process is actually a separation process between the valuable mineral（diaspore）and gangue minerals（kaolinite,illite,pyrophyllite,etc.）.Investigating the interaction mechanism between Al/Si minerals and bubbles（interaction probability,interaction force,and interaction process,etc.）,as well as discussing the regulation methods to strengthen the difference in adhesion behavior between Al-mineral-bubbles and Si-minerals-bubbles,can reveal the deep mechanism of the difference in floatability of Al-Si minerals and provide a theoretical basis for strengthening the floatation separation of Al-Si minerals.First,the composition and surface properties of diaspore,kaolinite,illite,and pyrophyllite mineral samples were analyzed.The IEP order of the four minerals is diaspore>kaolinite>illite>pyrophyllite,and the order of natural hydrophobicity is pyrophyllite>illite>diaspore>kaolinite.The differences in surface active sites and surface properties of the four minerals determine their differences in the adsorption properties of cationic dodecylamine（DDA）collector and anionic sodium oleate（NaOL）collector as well as their flotability in these two collector solutions.Second,the interaction probability between Al/Si minerals and bubbles was studied.Single-mineral flotation tests showed that the capture probability and rate of intermediate-sized particles of four minerals are substantially greater than these of fine-sized and coarse-sized particles.The classical probability model theory calculation showed that there is a best matching range between the mineral particle size and the bubble size that maximizes the capture probability.The larger the particle size,the larger the bubble size required to achieve the best match.Third,the interaction force（energy）between Al-Si minerals and bubbles was studied.The test results of the real-time micro-force test system showed that the addition of collectors can increase the detachment force between Al/Si minerals and bubbles.The greater the detachment force,the longer the separation process between bubbles and minerals takes;the greater the detachment force,the greater the stretched and deformed degree of bubble and the greater the contact area of the bubble in the mineral plane just before its separation from the mineral plane.E-DLVO theoretical calculations show that the Al-Si mineral particles and bubbles may be weakly adhered in the acidic solution without the addition of the collector,but no adhesion occurs in the alkaline solution.Electrolyte concentration,collector adsorption behavior,collector concentration,mineral particle size,bubble size,and pulp pH all affect the interaction between Al/Si minerals and bubbles.Fourth,the key parameters in the interaction process between Al-Si minerals and bubbles were analyzed.The induction time test showed that the minerals flotation recovery decreased with the increase of induction time,and the induction time can be used as a very sensitive parameter to predict flotation recovery.The test of the formation time of stable three-phase contact perimeter（TPCL）showed that the more hydrophobic the mineral,the shorter the time that bubbles form TPCL on the mineral plane and the less collisions the bubbles have with the plane before they are captured.The time for bubbles to form TPCL on the plane of the four minerals was shortened after the collector was added,and the t _TPCL was slightly shortened with the immersing time.The test of the liquid film drainage rate showed that without addition of collector,the more hydrophobic the minerals,the faster the drainage rate.A kinetic model was established between the film drainage rate and the adsorption of the reagents.It was found that the higher the concentration of the collector,the faster the drainage rate,and the faster the adsorption rate of the collector molecules on the mineral surfaces.There are differences in the adsorption rate of collector molecules between valuable and gangue minerals,so the floatability differences between valuable and gangue minerals can be enhanced by controlling the stirring time of the collector.Finally,methods for regulating the difference in adhesion behavior between Al mineral-bubbles and Si minerals-bubbles were explored.Increasing the roughness of the mineral surface can effectively enhance the adhesion between minerals and bubbles.Therefore,in actual flotation,increasing the surface roughness of the target mineral and reducing that of the non-target minerals selectively by grinding can be used to increase the floatability difference between the two.The depress mechanism of sodium hexametaphosphate（SHMP）on Al-Si minerals in DDA and NaOL solutions is different:in the reverse flotation,excess SHMP can be used to effectively depress the adhesion between diaspore and bubbles and the depress degree of adhesion between silicate minerals and bubbles is not substantially increased;in the direct flotation,the use of a small amount of SHMP can effectively suppress the adhesion between the silicate minerals and the bubbles and the suppress degree of adhesion between the diaspore and the bubbles is suppressed to a less extent.Sulfuric acid pretreatment can reduce the liquid film drainage rate and the adsorption rate of DDA on the diaspore surface,while the impact on the three silicate minerals was the opposite,which favors the reverse flotation separation of Al and Si minerals.The GCS model connected the minerals zeta potential and the active sites density on the mineral surface was established.Model fitting showed that the sulfuric acid pretreatment changed the active site density of Al-Si minerals.The regulation mechanism of sulfuric acid pretreatment was explained from the perspective of the interface active site.