Study On Formation Mechanism And Passive Treatment Technology Of Typical Heavy Metals In Mine Water

Coal is the most important energy resource in Chinese energy structure for a long time.However,intensive coal mining will produce abundant mine water.If mine water is discharged directly,it will lead to water resources waste and surrounding environment pollution.Reclamation of mine water is the key to ecological environment protection and water utilization.However,heavy metals especially Fe Mn and Zn in mine water from most mining areas exceed specified criterion,this hinders the reuse of mine water.Hence,studying formation and treatment technology of typical heavy metals in mine water is conducive to the mine water recycle and green exploitation.In this thesis,formation mechanism and treatment technology of typical heavy metals were studied based on the speculative knowledge of hydrogeology,environmental engineering,geochemistry,mineralogy as well as the analysis technology of X-ray diffraction(XRD),scanning electron microscopy with an energy dispersive spectrometer(SEM-EDS),three dimensional excitation-emission matrix(3DEEM),fourier infrared spectroscopy(FI-IR),Raman spectrum(RS).In addition,a series of experiments including step by step chemical extraction tests,water-rock interaction simulation tests and batch oscillating tests were carried out.Firstly,we concluded the content and distribution of typical heavy metals in mine water of China.Secondly,regarding Mindong mine as a research area,we studied the sources of typical heavy metals,release rules,influence factors and changes of speciation and valence state of typical heavy metals from coal and rock and treatment technology.The conclusions are as follows:(1)Typical heavy metals in mine were defined,and they were divided into four concentration levels according to concentration.Based on this,we concluded the content and distribution of typical heavy metals in mine water in China and analyzed forming reasons of typical heavy metals,preliminarily.(2)Regarding Mindong mine as a research area,we identified the natural and man-made sources of typical heavy metals.And aquifer ? and coal seam are natural sources while mining machinery leaking is man-made source.Contribution rate of aquifer ? and coal seam contributed 77.64% and 22.36% to typical heavy metals of mine water,respectively,based on chemical mass balance elicitor-receptor model.(3)Coal and rock samples were collected to detect heavy metals content and occurrence,then,we carried out the water-rock interaction experiment.The results indicate that release of typical heavy metals is affected by content and mode of occurrence of typical heavy metals.However,among forms of heavy metals,only carbonate bounded and exchangeable form can dissolve easily.In addition,release rules of typical heavy metals from coal and rock are described using spike function and exponential function,respectively.The difference of release rule is related to humic acid dissolution of coal.(4)Water-rock interaction experiments under different conditions including pH,temperature,Eh,grain size were carried out.The results show that when the pH reduces,temperature rises or grain size decreases,Solution release of typical heavy metal increases.In addition,the effect of pH on release of typical heavy metals is related to mineral species.As the Eh increases,the dissolution of carbonate minerals increase while it of sulfide mineral decreases.(5)We built kinetic equations according to Solution release of typical heavy metals under different conditions.The results indicate that with temperature increasing or pH decreasing,dissolution rate accelerates.Besides changes of typical heavy metal form and valence state were revealed by hydrogeochemistry simulation using PHREEQC.(6)The batch permeability experiments were conducted to study passive treatment,and coal ash ceramsite,humus,cocoanut active charcoal were selected as adsorbing material.Then adsorption mechanism and optimum adsorption condition of materialswere researched.Besides,when the mixture ratio of coal ash ceramsite,humus,cocoanut active charcoal is 8:1:1,removal rate of typical heavy metals reachs the maximum.