Study On The Mechanism Of Enhanced Flotation Separation Of Arsenopyrite And Pyrite By Atmospheric Pressure Low-temperature Plasma Pretreatment

Being deleterious impurity,arsenic needs to be removed in the process of flotation as far as possible to avoid affecting the m etallurgical processes and polluting the environment.The core of the conventional flotation separation of arsenopyrite from pyrite lies in the choice of depressants.However,pyrite and arsenopyrite have similar physicochemical properties on mineral surfa ce and the reagent adsorption characteristics,which have added to the difficulty in flotation separation.No matter what type of depressant is applied,it can also depress pyrite and arsenopyrite simultaneously.Low-temperature plasma has been proved to be an effective and powerful method in the selective surface modification of minerals.However,plasma modification on mineral surface can only be carried out at low presser or near-vacuum system so far.In addition,none of the retrieved literature has considered the effects of low-temperature plasma modification on the flotation separation of pyrite from arsenopyrite.In view of the above problems,arsenopyrite and pyrite were utilized as the research object minerals in this study to carry out the following research work:1.An experimental system was set up to investigate mineral surface modification using low-temperature plasma through atmosphere dielectric barrier discharge(DBD).The effects of different discharge gases(such as oxygen,air,nitrogen,and ammonia)and discharge parameters on the flotation separation of pyrite from arsenopyrite were initially investigated,as a result,the objective existence of plasma modification aging was revealed.In addition,the effects of parameters on plasma discharge characteristics were also calculated by one-dimensional numerical simulation.Moreover,the spatial evolution of physical parameters,including the reduced electric field intensity,electron density,electron temperature,and mean electron energy,was also investigated.2.The impacts of low-temperature plasma modification on the surface properties of arsenopyrite and pyrite were analyzed.Notably,differences in the surface properties between the plasma-modified arsenopyrite and pyrite in terms of t he mineral existence within the aqueous solutions were examined using thermodynamic calculations.In addition,X-ray photoelectron spectroscopy(XPS)analysis was adopted to demonstrate the changes and differences in the surface chemical composition between arsenopyrite and pyrite with or without plasma modification.It was revealed that selective surface modification was achieved through introducing the [O] reactive species onto the mineral surfaces,together with the "damage-induced chemical reaction".Moreover,a novelty view that,sulfate was the dominant factor to improve the hydrophilicity of arsenopyrite surface after oxygen-free plasma modification,was put forward.3.The effects of low-temperature plasma modification on the collector adsorption behaviors were also examined.Results of XPS analysis,Fourier transform infrared spectroscopy(FTIR)analysis,inductively coupled plasma mass spectroscopy(ICP-MS)and Zeta potential measures showed that,the adsorption of xanthate onto the arsenopyrite surface only took place in the strongly acidic pulp solution,but had little effect on the adsorption of collector onto the plasma-modified pyrite surface in the neutral or strong alkaline medium.Furthermore,the difference in collector adsorption between the arsenopyrite and pyrite surfaces after plasma modification was revealed.4.The effects of low-temperature plasma modification on the crystal structure and surface morphology of minerals were investigated.X-ray diffraction(XRD)and XPS analyses were utilized to analyze the crystal structure of minerals,which suggested no formation of new crystalline phase after plasma modification.In addition,the change in surface roughness before and after plasma modification was also examined based on the atomic force microscope(AFM)images.Moreover,the effects of plasma etching on the hydrophilicity of arsenopyrite and pyrite were explored by means of scanning electron microscope-energy disperse spectroscopy(SEM-EDS)analysis and XPS depth-profiling.Besides,the etching mechanisms under different discharge gases were also put forward.The mineral floatability was affected by both the surface roughness and the surface oxidation degree in the defect area.Furthermore,the plasma etching-induced selective modification mechanism on the mineral surfaces was also established.The current research provides a new exploration for the flotation separation of pyrite from arsenopyrite.Importantly,the modification mechanisms of plasma on the mineral surfaces are established from the aspects of surface properties,collector adsorption behaviors and selective etching,which is of great theoretical significance to realize the high-efficiency flotation separation of pyrite from arsenopyrite.