| At present,with the increasing attention to ecological environmental protection,a large number of chemical enterprises around the town have moved or closed.Due to long-term industrial production activities and improper environmental management,the sites left by these relocation enterprises are characterized by high pollution and high risk,which have become the focus of the restoration work of polluted sites.Among them,organic pollutants are one of the main sources of pollution in chemical sites.Organic compounds are often widely used in chemical production as raw materials,intermediates and solvents.Their extensive use and discharge make soil and water pollution increasingly serious,threatening ecological security and human health.In particular,persistent organic pollutants(pops)have been shown to be carcinogenic,teratogenic and mutagenic,and are extremely difficult to degrade in the natural environment.In this paper,a commercial artificial natrified bentonite was used as the basic material.Firstly,the engineering properties of bentonite were measured by laboratory test,and then modified by cationic surfactant to prepare organic modified bentonite and characterize its properties.The adsorption mechanism of organic pollutants on organo-modified bentonite and organo-modified bentonite-bentonite mixture was investigated by batch adsorption test.Finally,XRD and sem tests were used to study the microscopic properties of organic modified bentonite after adsorption of organic pollutants.The specific contents and conclusions of this paper are as follows:(1)By measuring the basic characteristics of cationic exchange capacity,expansion index and mineral composition of commercial artificial natrium bentonite.The results showed that the largest cation exchange capacity of commercial sodium bentonite was Na+,followed by Ca2+,and the size of cation exchange capacity was closely related to the expansion index.According to the results of X-ray diffraction test,the mineral content of bentonite is the highest,accounting for about 78.306%,which is higher than that of Wyoming bentonite,whose montmorillonite content is 65%.(2)Hexadecyl trimethylammonium bromide was used as cationic surfactant to perform organic modification on the artifical natrified bentonite,and the batch adsorption test of phenol solution for organo-modified bentonite was conducted.It was found that as the concentration of phenol solution increased,the adsorption capacity of organo-modified bentonite also increased.When the adsorption capacity remained constant,the adsorption reached equilibrium.Then the experimental data were analyzed by the adsorption dynamic model,and it was found that the experimental values were consistent with the quasi-second-order dynamic model.(3)Through batch adsorptivity tests of organo-modified bentonite-bentonite mixtures of different proportions,it was found that when the proportion of organo-modified bentonite-bentonite was 1:1,the adsorption capacity of mixed soil samples reached equilibrium.The adsorption dynamic model of organic modified bentonite-bentonite mixed soil samples with different proportions was analyzed.(4)The 1/3 adsorption equilibrium time was taken as the time interval,and the organomodified bentonite samples with different adsorption time were subjected to sem experiments.Then,image pro plus was used to analyze the apparent porosity of the scanned images.The results showed that the adsorption mechanism of organic modified bentonite was from large pores to small pores,and the adsorption was mainly from small pores in grains.At the same time,X-ray diffraction was performed on organo-modified bentonite samples with the same adsorption time,and the soil layer spacing variation of organo-modified bentonite at different adsorption time was calculated by Bragg law(Bragg law),so as to obtain the microstructure changes of organo-modified bentonite at different adsorption stages. |
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