Application Basic Research On De-inhibition And Activation Of Fine Cassiterite Flotation Under Reduction Syste

Tin is a strategic metal in China,mainly used in the three traditional fields of solder,tin chemical products,and tin-plated plates.It is also widely used in high-precision fields such as catalytic,sensing,photoelectric,and energy storage materials.Tin belongs to China’s advantageous resources,but with the continuous mining of tin ore,the resources of easy-to-select high-quality tin ore are decreasing year by year,and the selected refractory tin ore resources are characterized by low grade,fine crystallization,complex associated components have become an important way to obtain tin.Flotation is the most important method to solve the efficient utilization of complex mineral resources,and fine-grained cassiterite flotation is also a research hotspot in tin beneficiation.Through research and practice,it is found that ferric ion has an activating effect only in a low and narrow concentration range,and then the inhibiting effect on cassiterite flotation increases with the increase of ferric ion concentration,while ferrous ion has an activating effect on cassiterite flotation in a wide range of concentrations.Based on this,this thesis aims to solve the problem of the differential effect of Fe³⁺and Fe²⁺on cassiterite flotation and research the mechanism of de-inhibiting activated cassiterite flotation.In this work,the cassiterite pure minerals and tin ore were studied by flotation tests,VASP quantitative calculations,solution chemistry calculations,LEIS,To F-SIMS,XPS,FESEM-EDS,FTIR,zeta potential,and other analytical methods.The flotation behavior and law of iron ion activation and de-inhibition activation cassiterite were studied by flotation experiments.The changes in cassiterite surface components,interfacial properties,and microscopic morphology under different conditions were identified by various analytical characterization methods,as well as the chemical composition of the solution,mineral structure characteristics,and surface adsorption revealed by the combined calculations.The flotation mechanism of cassiterite activated by ferrous ions generated in the grinding process and artificially added was elucidated.And innovatively proposed the conversion between Fe³⁺and Fe²⁺by reduction to realize the de-inhibition activation technology of the cassiterite flotation process.It provides theoretical support for the cassiterite flotation mechanism of iron ion activation and de-inhibition activation.The main research conclusions and innovations of this dissertation are listed as follows:1.The treatment of cassiterite by iron grinding medium can activate cassiterite flotationThe flotation test found that the cassiterite ground by stainless steel has better floatability than that ground by ceramics.The laser particle size analysis test ruled out the difference between the two due to the particle size factor.ICP-OES and chemical elemental analysis found that the slurry solution and flotation concentrate obtained from stainless steel ground cassiterite samples had higher iron content.Zeta potential combined with solution chemistry calculations indicates that the stainless steel-treated cassiterite surface adsorbs dissolved iron ions from the solution.During the FESEM-EDS test,it was found that the surface of the stainless steel ground cassiterite was rougher and more clearly imaged than the ceramic ground cassiterite,proving that the surface iron content was also higher.The XPS results showed that the surface of stainless steel ground cassiterite not only had an increased Fe content,but also an increased percentage of Fe²⁺,and the reaction of Fe²⁺with SHA was found to have stronger reactivity and stability than Fe³⁺.Therefore,the adsorption of iron ions on the surface of cassiterite not only weakens the electrostatic repulsion between the negatively charged cassiterite and anions on the surface but also increases the active sites for salicylic hydroxamic acid（SHA）collector adsorption on the cassiterite surface,which plays the role of activating cassiterite.2.In-depth study of the effect of Fe²⁺and Fe³⁺on cassiterite flotation,and found that Fe²⁺activates cassiterite betterFlotation tests show that Fe³⁺can activate cassiterite only at low concentration and in a narrow concentration range,and the inhibition of cassiterite increases with the increase of Fe³⁺concentration,while Fe²⁺has a strong activation effect on cassiterite and has an activation effect on cassiterite in a wide concentration range.The adsorption capacity test showed that the adsorption capacity of SHA was significantly improved after Fe²⁺activated the cassiterite surface.The Zeta potential combined with the solution composition diagram shows that the adsorption of positively charged Fe²⁺and Fe（OH）⁺on the cassiterite surface increases the number of active sites for SHA adsorption on the cassiterite surface.XPS and FTIR results confirmed that Fe²⁺activates cassiterite by interacting with terminal oxygen atoms on the surface of cassiterite,and redox reactions and displacement reactions occur between Fe²⁺and Sn⁴⁺.SHA relies on chemisorption on the cassiterite surface,and the anionic SHA^-reacts more readily with Fe species to form Fe-SHA complexes.Therefore,under the SHA flotation system,Fe²⁺can be used as a green activator for activated cassiterite.3.Developed a reductive SN de-inhibition activator under neutral conditions to achieve de-inhibition and activation of cassiterite flotationThe flotation test shows that the de-inhibiting activator SN can eliminate the inhibitory effect of Fe³⁺on cassiterite flotation,and can further activate cassiterite flotation.The results of the adsorption experiment,Zeta potential test,FTIR analysis,and XPS analysis show that the high concentration of Fe³⁺will reduce the adsorption amount of SHA on the surface of cassiterite,but adding SN can eliminate the inhibitory effect of Fe³⁺on cassiterite,instead,it can activate cassiterite promotes the adsorption of SHA.In addition,Fe（OH）_3（s）colloid adsorbed on the surface of cassiterite is the main reason for inhibiting cassiterite flotation,while SN can reduce Fe³⁺to Fe²⁺,eliminating the inhibition of Fe（OH）₃ on cassiterite flotation,and then activate the cassiterite in the form of Fe²⁺species.Therefore,the theoretical study of de-inhibition activation of the cassiterite flotation process is realized.4.Quantitative calculation and analysis test and actual mine verification to construct a theoretical study of de-inhibition activation cassiterite flotationVASP quantitative calculations revealed that Fe³⁺is adsorbed as Fe（OH）₃ on the raised terminal oxygen on the exterior of cassiterite crystals,while Fe²⁺is adsorbed as Fe²⁺,Fe（OH）⁺and Fe（OH）₂ not only on the raised terminal oxygen on the exterior of the crystals but also on the Sn and O atomic sites in the concave valley of the crystal surface,the latter having more adsorption sites and higher adsorption stability.To F-SIMS tests verified the results of VASP quantification calculations,discovered Fe OH⁺,Fe OSn⁺,and Fe Sn⁺fragments,revealing that Fe species can be adsorbed on the terminal and bulk oxygen sites of cassiterite crystals.In addition,a new adsorption mode between metal ions and metal active sites was proposed for the first time,which provides a revolutionary addition to the flotation activation theory.LEIS study revealed that Fe²⁺activated cassiterite surface promoted SHA adsorption and increased the resistance value of mineral surface,while Fe³⁺was adsorbed in the form of Fe（OH）₃ colloid to form a thick hydrated film on the cassiterite surface,resulting in a significant increase in the resistance value of the cassiterite surface.which hinders the adsorption of SHA on the mineral surface.The addition of SN reduces Fe³⁺to Fe²⁺,which avoids the production of Fe（OH）₃ hydrophilic film on the mineral surface,and the adsorption of Fe²⁺species also effectively reduces the impedance value of the mineral surface,forming the"switch effect"theory.And the preliminary exploration and verification of de-inhibition and activation flotation experiments were carried out with Yunxi Datun oxidized tin ore as an example,and propose a new technology of economical,green,and efficient activated cassiterite flotation.