Study On The Migration Law And Purification Method Of Pollutants In Unsaturated Soil Under The Action Of Water Flow

In this paper,by carrying out indoor static adsorption-desorption experiments,the adsorption-desorption experiments of three heavy metal ions in silt were carried out,and the nonlinear adsorption-desorption model,Freundlich model and Langmuir model were used for fitting.Microscopic characterization of silt particles.In order to further study the migration process of pollutants in unsaturated soil under the action of heavy metal ions,a one-dimensional short soil column pollutant migration test was used to investigate the influence of heavy metal pollutant concentrations and types on the distribution of soil moisture content and the effect of different heavy metal pollutant migration capabilities.difference.Finally,based on the migration test of unsaturated soil pollutants,the purification mechanism of graphene oxide was studied,and the conclusions were as follows:(1)Compared with the Freundlich model and the Langmuir model,the nonlinear adsorption-desorption model can better fit the static adsorption-desorption experimental law,and the nonlinear adsorption-desorption model fitting parameters have different effects on temperature,heavy metal ion concentration,and heavy metal ion species.The parameter change law is consistent with the parameter change law of the two traditional models.The adsorption equilibrium constant of the nonlinear adsorption-desorption model increases with the increase of temperature,and the desorption equilibrium constant decreases with the increase of temperature,indicating that the increase of temperature improves the adsorption performance of silt and inhibits the adsorption of silt.desorption performance.The order of the adsorption strength of the three heavy metal ions is: Pb(II)> Cu(II)> Cd(II),which is just the opposite of the order of their nonlinear characteristics.The nonlinear adsorption-desorption model can better describe the adsorption-desorption process in the strongly adsorbed silt.(2)The microstructure of the silt loaded with heavy metals was analyzed,and the test showed that the adsorption of heavy metals by the silt was not only related to the specific surface area,but also closely related to the mineral composition and functional groups in the silt.The adsorption of heavy metal lead ions is related to the hydrolysis reaction of silt mineral components kaolinite,calcite,dolomite,plagioclase and quartz.The adsorption of heavy metal copper ions is related to the silt mineral components calcite,illite,albite and kaolinite.The adsorption of heavy metal cadmium ions is related to the mineral components albite and kaolinite,and the silicate minerals in the silt also participate in the adsorption reaction.The zeta potential of the silt loaded with heavy metals is lead ion,copper ion,and cadmium ion in turn,which is consistent with the size of the deposition amount in the static adsorption-desorption test of different heavy metals.(3)Under the condition of constant temperature control,the species and concentration of pollutant ions play an important role in the migration and diffusion of pollutants in unsaturated soil.Under the same concentration,the penetrability of the heavy metal lead ion is greater,the copper ion is the second,and the cadmium ion is the worst;under the same heavy metal ion,the greater the ion concentration,the greater the penetration to the soil column.The deposition and distribution law of heavy metal pollutants in the soil column under the condition of constant water head is lead ion >copper ion > cadmium ion,which is consistent with the adsorption order of heavy metal adsorption by silt.The concentration distribution law of the soil column filtrate is:cadmium ion> copper ion> lead ion.(4)The zeta potential of graphene oxide is higher than the zeta potential of silt,so graphene oxide can be used as an adsorbent to deprive heavy metals deposited in silt,but the complexity of the porous medium and the wide particle size distribution of graphene oxide make it difficult for purification.During the soil process,graphene oxide is deposited in the soil,resulting in the deposition effect of porous media,and the deposition of heavy metal pollutants somewhere in the soil increases.