Adsorption Of VOCs In Soil Gas By Metal Organic Framework Materials And Use For Risk Assessment

The Johnson-Ettinger?J&E?model has been widely used to calculate the health risk of volatile organic compounds?VOCs?in contaminated sites on the human body.However,the theory and practice have proved that the risk and repair targets calculated by this model are too conservative,resulting in excessive repair and capital waste.In this paper,the international advanced model Dual-Equilibrium Desorption?DED?model is used to modify the health risk of the J&E model.At the same time,the selected metal organic skeleton material?MOFs?is used as an adsorbent to adsorb and measure the content of the VOCs content in the soil gas phase?soil pollutants in water,soil and gas three phase?.Calculate the risk in order to obtain the best soil conditions suitable for the two models?J&E and JE-DED?,so as to guide the actual site risk assessment.Therefore,the following research work has been completed in this paper1.Using terephthalic acid,dimethylimidazole and fumaric acid as ligands,metal ions such as Cr³⁺,Zr⁴⁺,and Zn²⁺were selected to synthesize MIL-101,ZIF-8,UIO-66,and MOF-801.It was characterized by infrared analysis,elemental analysis,XRD,nitrogen adsorption-desorption isotherm,and thermogravimetric analysis.In addition,expanded graphite was also prepared.2.A series of MOFs and expanded graphite,spherical activated carbon,HiSiv1000 and HiSiv3000 molecular sieves were used to perform adsorption studies on the target analytes.The best adsorption material MIL-101 was selected and used to adsorb and determine the content of VOCs in soil gas.In order to follow-up calculations measured soil gas health risk level.3.Measure the trichloroethylene concentration in the soil of Beijing fluvo-aquic soil and Heilongjiang black soil by MIL-101 adsorption and calculate the risk.The risk results calculated with the J&E and JE-DED models indicate:?1?Compared with the J&E prediction results,JE-DED and based on The measured soil gas risk results are more consistent;Black soil with high organic matter content is more consistent than fluvo-aquic soil with low organic matter content;?2?For both soils,the J&E model calculation results are too conservative.4.The study of benzene soil gas was conducted.The risk values calculated by the J&E model and the JE-DED model were compared with those calculated based on the measured benzene concentration in the soil gas.In addition to the conclusion consistent with the above experiment,it was also obtained.The following conclusions:?1?The higher the hydrophilicity of VOCs,the more conservative the health risks calculated by J&E model;?2?The organic matter content and VOCs solubility are two important factors affecting the accuracy of J&E and JE-DED prediction results,the higher the content of soil organic matter,The smaller the solubility of VOCs,the better the consistency of JE-DED and the risk results based on measured soil gas calculations.Based on the above conclusions,a JE-DED model was used to assess the risk of a contaminated site in Central South China,and a reasonable remediation target was formulated to save hundreds of millions of treatment costs for the repair of contaminated sites.The research on the prediction of the risk of soil gas VOCs concentration and the determination of the remediation goal shows that the risk evaluation based on the JE-DED model can avoid the problem of J&E calculation being too conservative to a certain extent,and can reflect the degree of site pollution more realistically and objectively and avoid excessive repair.The waste of resources provides a theoretical and practical basis for the future application of the JE-DED model in site health risk assessment.