Efficient Separation And Its Mechanism Of Strategic Calcium Minerals Based On The Development Of A Ternary-coordination Colloidal Collector

There are difficulties in separation selectivity and high cost among strategic calcium minerals scheelite,fluorite,and common gangue minerals calcite.This study made full use of the advantages of lead nitrate（Pb）,benzohydroxamic acid（BHA）,and sodium oleate（NaOL）,and Pb-BHA-NaOL,a ternary-coordination colloidal collector,was developed based on the interface assembly principle and the difference of crystal surface activity of three calcium minerals.Pb-BHA-NaOL collector possessed high selectivity,strong collection ability,high flotation rate,and low cost.Moreover,the adsorption mechanism of Pb-BHA-NaOL collector on the surfaces of three minerals was systematically explored with the help of various detection methods.At the same time,the combination method was adopted to realize the active desorption and reuse of reagents on mineral surfaces,significantly reducing the cost of flotation reagents.Pb-BHA-NaOL collector was applied to recover the residual tungsten minerals from Shizhuyuan tailings after tungsten minerals flotation at room temperature and Yuanjing tailings after heating and cleaning flotation of scheelite concentrate.Results showed that Pb-BHA-NaOL collector successfully realized the recovery of refractory fine-grained tungsten minerals,highlighting the application range of the collector.The main conclusions of this research are as follows:1.Single mineral flotation tests and flotation kinetics analysis showed that,compared with the traditional reagents,Pb-BHA-NaOL collector had better selectivity,stronger collection capacity and faster flotation rate.Compared with other combination methods,there was a greater difference in floatability among the three minerals to mix Pb,BHA and NaOL in turn and assemble into Pb-BHA-NaOL collector before adding the three reagents to the slurry.When the slurry p H was 9.0,Pb-BHA-NaOL collectors with the molar ratios of 240:120:1,8:8:1,and6:6:1 could realize the selective separation of scheelite and fluorite,fluorite and calcite,scheelite and calcite,respectively.2.Flotation tests of the frother dosage,the determination of in-situ particle size and surface tension of Pb-BHA-NaOL collector showed that NaOL in this collector played the main role in collecting.Furthermore,NaOL also had a dispersion effect,effectively reducing the particle size of the colloidal collector and improving the adsorption efficiency of the three reagents on minerals.Raman and infrared spectra showed that BHA and NaOL in Pb-BHA-NaOL collector reacted with Pb²⁺at different molar ratios.The main produced components were similar,but their contents were quite distinct.3.Calculations of DFT and atomic properties on mineral surfaces showed that the Ca atomic activity on fluorite（1 1 1）,scheelite（1 1 2）,and calcite（1 0 4）surfaces followed the order:fluorite>scheelite>calcite,and the O/F atomic activity followed the order:scheelite>calcite>fluorite.4.Results of solution chemistry calculation,zeta potential,contact angle,reagent adsorption capacity,FTIR,XPS and DFT calculation showed that when the molar ratio of Pb/BHA/NaOL was 240:120:1,the main hydrophobic Pb-BHA⁺and Pb（OH）-BHA complexes in the colloidal collector tended to be adsorbed on the negatively charged scheelite surfaces due to the electrostatic interaction.And Pb atoms in these two complexes formed the Pb-O bond that was more inclined to ionic bond with the O atom on the scheelite（1 1 2）surface.While,the hydrophilic Pb（OH）₃^-species in the colloidal collector was easier to be adsorbed on the positively charged fluorite and calcite surfaces,hindering the adsorption of Pb-BHA⁺and Pb（OH）-BHA on the fluorite and calcite surfaces.These adsorption differences achieved the selective separation of scheelite and fluorite.When the molar ratio of Pb/BHA/NaOL was8:8:1 or 6:6:1,the amount of Pb in this ratio was small,resulting in the reduction of the adsorption capacity of hydrophilic Pb（OH）₃^-species on the surfaces of fluorite and calcite.However,the main hydrophobic Pb-BHA-OL and Pb（OH）-BHA-OL^-complexes in the colloidal collector tended to be adsorbed on fluorite（1 1 1）surface.And the O 2s orbitals of the N-O and C-O groups in the collector were hybridized with the Ca 3p orbitals on fluorite（1 1 1）surface,forming the O-Ca bond that was more inclined to a covalent bond.These adsorption differences realized the selective separation of fluorite and calcite.In addition,although the Pb（OH）-BHA-OL^-complex was negatively charged,the O 2s orbitals of the C-O and H-O groups in the collector were hybridized with the Ca 3p orbitals on scheelite（1 1 2）surface to form the O-Ca bond that was more inclined to covalent bond.These adsorption differences realized the selective separation of scheelite and calcite and improved the separation efficiency of scheelite and fluorite.Compared with Pb-BHA-OL complex,Pb（OH）-BHA-OL^-complex was easier to be adsorbed on the surfaces of fluorite and scheelite,which reflected the"bridging"effect and the role of reducing the reaction energy barrier of hydroxyl groups.5.The Pb-O bond formed by the Pb atom in the Pb-BHA-NaOL collector and the O atom on scheelite surfaces was more inclined to ionic bond and easier to break.Therefore,the active desorption of Pb and BHA on the surfaces of scheelite concentrate was well realized by using the methods of"high alkali+strong stirring"and"high alkali+ultrasonic".Desorption results showed the desorption rates of Pb and BHA were higher than 80%and 65%using these two methods,respectively.Then,the Pb and BHA reagents desorbed by"high alkali+strong stirring"method were reused in flotation operation.The results of single mineral flotation showed that the reuse of desorption solution would save 67%Pb and 75%BHA.6.The tungsten concentrate with the grade of 50.13%and recovery of 42.73%was obtained when Pb-BHA-NaOL collector and the route of“roughing flotation at room temperature and then cleaning flotation using heating"were applied to the recovery of residual tungsten minerals from Shizhuyuan tailings after tungsten minerals flotation at room temperature.At the same time,the reagent desorption and reuse on the coarse tungsten concentrate surfaces before heating and cleaning flotation could reduce the consumption of Pb and BHA by about 20%in tungsten roughing flotation,respectively,and improve the subsequent heating and cleaning operation.In addition,the process also reduced the COD value of the original tailings pulp and improved the following fluorite flotation indexes.The tungsten concentrate with the grade of 11.37%and recovery of 61.07%was obtained when Pb-BHA-NaOL collector was applied to the recovery of residual tungsten minerals from Yuanjing tailings after heating and cleaning flotation of scheelite concentrate.Numbers of the picture,table and reference in this paper are 112,49 and104,respectively.