| At present,the problem of heavy metal pollution in groundwater is becoming increasingly serious.Barrier wall technology is a rising risk control technology in recent years.By setting barriers to block pollutants in polluted areas,barrier walls can effectively prevent the diffusion of pollution in groundwater.Currently,it is not common to study the composition of the wall materials of the barrier wall.In this paper,the soil-sepiolite barrier wall materials were selected as the research object.The main conclusions are as follows:（1）Through the slump,seepage prevention,compression resistance,erosion resistance and compatibility experiments found that:The best soil-sepiolite barrier wall materials ratio is soil:modified sepiolite:cement=75:20:5,moisture content is 35%,the permeability coefficient of the barrier wall is 3.87×10-8cm/s,which meets the USEPA impermeability standard;The optimal curing age is 30 days,and the maximum compressive strength is 288.72k Pa,which meets the design requirements of underground barrier wall;The barrier wall has good corrosion resistance to acidic,alkaline,Pb2+and phenol erosion solutions,and the alkali erosion resistance is stronger;Before and after heavy metal ions penetrate the barrier wall,the permeability coefficient and compressive strength of the barrier wall change little,indicating that the wall material is compatible with the heavy metal contaminated solution.（2）Five typical heavy metals（Pb,Zn,Cu,Cd,Cr）were selected as pollutants to study the barrier performance of wall materials.The experimental results show that:The equilibrium adsorption capacity of five heavy metals in a single heavy metal system of 50 mg/L and 100mg/L is equal;In 200 mg/L,300 mg/L,400 mg/L,500 mg/L single heavy metal system qe(Pb2+)>qe(Cu2+)>qe(Cd2+)>qe(Cr3+)>qe(Zn2+);The adsorption effect of barrier wall materials on single heavy metal ions is very good;The adsorption capacity of five kinds of heavy metals in 50mg/L,100 mg/L and 200 mg/L composite heavy metal systems is proportional to the ion concentration;In 300 mg/L,400 mg/L and 500 mg/L composite heavy metal systems,qe(Pb2+)increases with increasing concentration,while qe(Cr3+)and qe(Zn2+)decrease with increasing ion concentration;The adsorption process is more consistent with Langmuir isothermal adsorption model,indicating that monolayer adsorption is dominant;The results of kinetic fitting were more consistent with the quasi-second-order kinetic model,indicating that the adsorption process was mainly chemical adsorption;The results of the diffusion model show that the adsorption rate is affected by both liquid film diffusion and particle diffusion,and diffusion is not the only factor affecting the adsorption rate.（3）Through SEM,EDS,XRD analysis of the barrier wall materials microstructure and elemental composition found:Sepiolite changed from fibrous to massive after modification,and the specific surface area increased,which was conducive to adsorption;The surface of wall materials become rough after absorbing heavy metal ions;The content of heavy metal ions on the surface of barrier wall materials has increased,it means heavy metal ions are attached to the surface.The paper has 37 figures,13 tables,and 126 references. |
