Research Of Flotation Behaviors And New Technology On Flaky Graphite

Natural flaky graphite,considered to be one of the most important non-metal ores resources,is widely used in abundant fields.Above all,the splendid progress of graphene applicationstudy in the emerging fields further drives the systematic research of graphite beneficiation.The resource reserves of fine flaky graphite in domestic are particularly large,whereas with poor floatability.How to obtain the high quality of graphite is the significant subject for the beneficiation of fine flaky graphite,which is of important theoretical value for practicalproduction and guiding significance for application.Fine flakes in Shangrao of Jiangxi province and big flakes in Mozambique were used as the actual graphite ore in this paper.For the great difference of the two ores in beneficiation technology and quality of concentrates,the problems such as the relationship between crystal structure and flotation rate,the influence of particle size on flotation rate,gangue entrainment in the concentrate,agglomerate behavior of graphite particles in the flotation process of flaky graphite were of great concern in this study.Single mineral was employed as the research object,to investigate the floatation characteristics,mechanism for the gangue mineral entered into the graphite concentrate and entrainment behavior for the gangue minerals in the floatation process,to analyze the main reason for the poor floatability of fine flaky graphite.Selective agglomeration flotation and direct-reverse flotation were applied in the floatation process of fine flaky graphite in Shangrao of Jiangxi province to improve the technical indicators of concentrate.Characterization techniques,such as XRD,XPS,Zeta potential,UV-vis,laser particle size analyser,etc.were applied to characterize the mineral crystal structure and surface property of graphite,in order to analyze the mechanism of reverse floatation,PAClagglomeration,etc.,systematically.By using the traditional beneficiation technology of graphite with stage grinding and floatation,namely once coarse grinding as well as once roughing,five times regrinding and six times cleaning,the fixed carbon content and recovery of the concentrate from Shangrao ore reached 89.22% and 92.15%,respectively.Nevertheless,the fixed carbon content of the concentrate from Mozambique ore could reach 97.34% with the recovery of 94.23%,only through once coarse grinding and once roughing,twice regrinding as well as three times cleaning.The difference inthe beneficiation technology and technical indicators indicated that the floatability of large flake graphite in Mozambique was much better than that of fine flakes in Shangrao.The main reasons for the huge diversity on floatability between the two ores are shown as follows.1 the oxygenous groups(such as hydroxyl,carboxyl,etc.)existed on the edge of the structure layers of graphite ore from different region could lead to a notable difference in lattice parameters,graphization degree and 3R polymorph content,which simultaneously affected the floatability of graphite directly.The degree of graphitization of fine flaky graphite is lower than that of large flaky graphite,and the floatability is poorer.2 the floatation rate of fine flake graphite was lower than that of large flakes,and the existence of fine flake graphite would significantly decrease the floatation rate of large flakes during the process of fine flake graphite flotation,resulting in worse floatability than that of large flakes.Studies on the flotation properties of flaky graphite and gangue minerals,interactions between mineral particles,and flotation tests of mixture minerals were conducted in the paper.The results demonstrated that the main routes for the gangue minerals entered into the concentrate in the floatation of flaky graphite were entrainment and entrapment.It measured by the Warren method that approximately 7% of gangue minerals entered into the flaky graphite concentrate via entrapment,while the gangue minerals entrained into the flaky graphite concentrate accounted for 93%.The entrainment behavior of gangue minerals in flaky graphite flotation was studied in this paper.The results indicated that the particle size of minerals and slurry concentration significantly influenced the entrainment behavior of gangue minerals.Both the entrainment recovery of gangue minerals and water recovery increased with the slurry concentration,while decreased withthe increase of particle size.Compared to hydrophilic gangue minerals,the influence of hydrophobic graphite on the entrainment was stronger.The entrainment of gangue minerals in mixture flotation was more serious than single mineral flotation.PACl could agglomerate the mica particles in water and enlarge their apparent size with enhanced sedimentation rate.The sedimentation rate was the lowest at pH 7.0 with the PACl concentration of 400mg/L.The fixed carbon content of the concentrate significantly enhanced and the entrained gangues reduced when the PACl was used in the flotation of actual graphite ore.The fixed carbon content of the final concentrate obtained from closed circuit flotation process was 91.81%,with the recovery of 85.69%.The fixed carbon content of the concentrate was 2.06% higher than the traditional flotation process,while the recovery was almost the same.Zeta potential measurements demonstrated that PACl adsorbed on the surface of mica through electrostatic attraction and surface precipitation,which agglomerated the mica particles via charge neutralization.Direct-reverse flotation tests were conducted on flaky graphiteto reduce the entrainment of gangue minerals.Reverse flotation tests were performed with MF as the depressor of graphite and the mixed amines as the collector of gangue minerals.The highest separation efficiency was obtained at pH 8.0 with the MF concentration of 250 mg/L.The results of XPS analysis showed that physical adsorption was mainly responsible forthe interaction between MF and graphite or mica.The fixed carbon content of the final concentrate obtained from direct-reserve flotation closed circuit process of Shangrao graphite ore was 91.81% with the recovery of 85.69%.The fixed carbon content of the concentrate was 2.59% over the traditional flotation process,while the entrainment of mica in concentrate was distinctly fewer than the traditional flotation process.The depression effect on mica entrainment was significant.