Study On The Sulfidation Behavior And Mechanism Of Smithsonite In The Chlorine-ammonium Component System

With the depletion of zinc sulfide resources and the increasing demand for zinc,the extraction of metallic zinc from low-grade zinc oxide ores has become one of the important research topics at home and abroad.The sulfide-xanthate flotation method has good prospects in the separation of zinc oxide ore because it is less affected by slime.Sulfidation is a key step in zinc oxide flotation.How to effectively promote the sulfidation of zinc oxide minerals and obtain stable artificial zinc sulfide surface is the key to"sulfide-xanthate flotation"zinc oxide ore.The purpose of this master's thesis is to promote the formation of stable zinc sulfide components on the surface of smithsonite,improve the hydrophobicity of mineral surface,and provide theoretical basis and technical support for the industrial application of sulfide-xanthate flotation technology.In this paper,smithsonite?-74+38um?is taken as the research object.Firstly,the sulfide-flotation experiments of pure smithsonite minerals in different component solution systems are carried out,and the main factors of flotation experiments are determined.Then,through smithsonite dissolution test,Visual MINTEQ calculation,transition state calculation and minimum energy path search,the zinc and sulfur components of smithsonite-water solid-liquid interface and solution system are studied.Migration and transformation.Based on the double sulfidation mechanism of"ion exchange"and"metal sulfide precipitation adsorption",a model of ammonium component catalytic sulfidation of smithsonite surface was proposed.Finally,through the combination of XRD,TOF-SIMS and XPS,the properties of zinc sulfide precipitates,the sulfide surface properties of smithsonite and the influence of ammonium components on the sulfidation of smithsonite were studied.Based on the above results,the recovery of sulfide-flotation of smithsonite in sodium chloride-ammonia water and ammonium chloride system is 10%²0%higher than that in deionized aqueous solution system.Under the optimum test conditions,the highest flotation recovery of smithsonite is 74.52%.In the top adsorption configurations of Zn and C,the hydration film hinders the chemical adsorption of HS^-on the surface of smithsonite?001?.NH₄Cl can promote the dissolution of smithsonite.The addition of sodium sulfide promotes the migration of zinc and sulfur ions to the surface of smithsonite,thus reducing the concentration of zinc(C_ZnT)in the solution system.The addition of NH₄Cl and NH₃·H₂O promoted the transfer of zinc and sulfur ions to the surface of smithsonite.When solid phase formation is considered,NH₄⁺ions and Zn²⁺ions with increased concentration in solution promote the deep transformation of ZnS?aq?,Zn₂S₃^2-ions and Zn₄S₆^4-ions to sphalerite,and more sphalerite precipitation is formed.The adsorption of sphalerite precipitation on the surface of smithsonite strengthens the sulfidation of smithsonite.Density functional theory?DFT?studies on sulfurization of smithsonite catalyzed by NH₃groups show that the energy barrier of Zn?OH?₂+HS^-?ZnS reaction needs to be overcome as high as 90.46 kcal/mol;when Zn?OH?₂ complexes with NH₃-H₂O,the formation of Zn?NH₃?₄²⁺ions will be preferential;under the catalysis of NH₃ groups,the total energy barrier of the reaction pathway of Zn?OH?₂+HS^-?ZnS will be reduced to 65.31 kcal/mol.By reducing the energy barrier and reaction path of the reaction between Zn?OH?₂ and HS^-to form zinc sulfide,the NH₃ group shows catalytic action,which is the main reason for the sulfidation of smithsonite surface catalyzed by ammonium component.The minimum energy path of the reaction of Zn?OH?₂+HS^-?ZnS indicates that the step fracture of O-Zn bond and H-S bond is the main way of sulfidation on the surface of smithsonite without NH₃ group,and the energy barrier needed to be overcome is higher.In the presence of NH₃ group,the formation of zinc-ammonia-hydroxyl complex promotes the dehydroxylation of Zn?OH?₂,and significantly reduces the energy barrier of dehydroxylation.At the same time,in the presence of NH₃ group,the energy barrier overcome by S atom migrating from HS^-to Zn atom to produce ZnS is lower than that without NH₃ group,so it plays a catalytic role.The addition of NH₃·H₂O and NH₄Cl can promote the formation of zinc sulfide components on mineral surface.The thickness of sulfides formed on the mineral surface after the interaction of smithsonite with sodium sulfide is about 15.32 nm,and the thickness of sulfides formed on the mineral surface is 29.2nm and 26.66 nm after the addition of NH₃·H₂O and NH₄Cl,respectively.Before and after the surface treatment of smithsonite with zinc sulfide precipitate,the concentration of S atom increased to 1.6%,and that of zinc atom increased from18.2%to 24.2%.The zinc sulfide components formed on the surface of smithsonite treated with Na₂S are composed of zinc monosulfide and zinc polysulfide.The addition of NH₃·H₂O increases the sulfur content on the surface of smithsonite and transforms monosulfide into polysulfide,which promotes the sulfidation of smithsonite,thus helping to improve the hydrophobicity of smithsonite surface.