Molecular Simulation Study On Adsorption Of Heavy Metal Ions By Clay Minerals

With the rapid development of industry and mining industry,economic prosperity has been promoted,but serious environmental pollution has been exposed.As the material condition of our survival,the polluted condition of soil can not be ignored,and the treatment of its pollution is imminent.How to find an efficient and feasible governance method is an urgent problem.Physical adsorption is widely used as an effective method to control heavy metal pollution in soil,but the following problem is to find a cheap and easily available material to absorb heavy metal pollutants.Clay minerals have gradually come into people's attention because of their wide distribution,high economic benefits and easy to exploit in large quantities.Among the clay minerals in China,kaolinite and montmorillonite are the most widely distributed,and their reserves are also in the forefront of the world.Therefore,this paper chooses kaolinite and montmorillonite as the research object,and adopts materials Studio simulation software,build kaolinite and montmorillonite model,at 268 k,278k,288 k and 298 K,carry out separate adsorption and competitive adsorption of cadmium ion,nickel ion,copper ion,mercury ion and lead ion,study their adsorption capacity and heat by Monte Carlo method,and then use molecular dynamics method to study their concentration distribution function,radial distribution function and self expansion The dispersion coefficient is analyzed.Through the research of this paper,the main conclusions are as follows:(1)Kaolinite and montmorillonite are both exothermic physical adsorption behaviors when adsorbed separately.The adsorption amount and adsorption heat both decrease with the increase of temperature.The adsorption amount and adsorption heat of kaolinite both have lead ion> copper Ions> cadmium ions>nickel ions> mercury ions,and the amount and heat of adsorption of montmorillonite both have copper ions> cadmium ions> lead ions> nickel ions>mercury ions.In the competitive adsorption of heavy metal ions by kaolinite and montmorillonite,the adsorption capacity and adsorption heat of lead ions,copper ions and cadmium ions decrease with increasing temperature,while the adsorption capacity and adsorption heat of nickel ions and mercury ions both With the increase of temperature.And the adsorption amount of montmorillonite in single adsorption and competitive adsorption is larger than that of kaolinite,so the selection of montmorillonite for the adsorption material of heavy metals is better than kaolinite.(2)Through the analysis of the concentration distribution diagram and radial distribution function of kaolinite adsorption and competitive adsorption of heavy metal ions,it can be seen that: when kaolinite is adsorbed alone,before298 K,the adsorption of lead and copper ions in layer t is strong,the adsorption of cadmium ions in layer o is strong,and the reverse occurs at 298 K.The adsorption capacity of t-layer and o-layer to Ni and Hg is weak,and the main distribution is in the middle free layer.In the competitive adsorption of kaolinite,lead and copper ions occupy the favorable adsorption positions in the o layer,while cadmium ions occupy the favorable adsorption positions in the T layer,and nickel and mercury ions occupy the adsorption positions in the middle free layer.During the adsorption process,competitive adsorption effect and adsorption migration phenomenon occur.The adsorption of heavy metal ions by kaolinite depends on Coulomb force and van der Waals force.(3)From the concentration distribution map and radial distribution function of montmorillonite's heavy metal ion alone and competitive adsorption,it can be drawn that when montmorillonite is solely adsorbed,copper ions,cadmium ions and lead ions are mainly adsorbed on the surface of the T layer.Nickel ions and mercury ions are mainly adsorbed in the intermediate free layer,and only a small amount is distributed near the T layer.In competitive adsorption,copper ions,cadmium ions,and lead ions occupy the adsorption position of the T layer,while nickel ions and mercury ions occupy the adsorption position of the intermediate free layer.(4)The conclusion of radial distribution function is consistent with that of adsorption heat.The larger the adsorption heat is,the more stable the structure is and the smaller the self diffusion coefficient is.(5)From the point of view of adsorption capacity and adsorption structure stability,montmorillonite is more suitable for the treatment of heavy metal pollutants.