| As the country pays more and more attention to the problem of soil pollution,the "Soil Pollution Prevention and Control Action Plan"（"Ten Articles"）has been successfully promulgated and implemented,and the problem of soil pollution has aroused widespread concerns.Among them,the problem of soil organic matter pollution is still one of the urgent problems to be solved,and the problem of soil pollution by polycyclic aromatic hydrocarbons is particularly prominent,which is self-evident to pose the threat to human health and the ecological environment.In recent years,surfactant enhanced remediation technology（SERT）has been regarded as one of the most promising technologies for remediation of polycyclic aromatic hydrocarbons contaminated soil.However,the leaching effect of this technology in clayey soil is not ideal,and the leaching waste liquid also needs to be treated with a suitable method.Therefore,this paper innovatively introduces hydrothermal carbons with strong adsorption capacity in the leaching process in order to achieve competitive adsorption with the soil,promoting the desorption of polycyclic aromatic hydrocarbons in the soil,and reduce the amount of polycyclic aromatic hydrocarbons re-adsorbed by the soil.At the same time,hydrothermal carbons can also be used for the treatment of leaching waste liquid,and the surfactants in the leaching waste liquid can be recycled,satisfying the integrated treatment of polycyclic aromatic hydrocarbons in soil.The main research conclusions are as follows:（1）Rice husk powder was carbonized at 220 ℃ for 4 h to prepare hydrothermal carbon BC,and then it was modified by ferric chloride and glucose,denoted as FBC and GBC.The modification further promoted the distribution of acidic functional groups on the surface of the hydrothermal carbons,enhanced the aromaticity of the hydrothermal carbons,and increased the number and types of surface functional groups.The pore structures of three hydrothermal carbons were mainly mesopores,and the specific surface area was FBC>GBC>BC.（2）In the leaching experiment of phenanthrene and pyrene contaminated soil by surfactants,when the surfactant concentration was 40 g/L,the liquid-solid ratio was30:1,the leaching time was 120 min,the leaching temperature was 25 °C,and the number of rinsing was 2 times,the rinsing effect was the best.The dissolved organics in the leaching wastewater were mainly humic acids and microbial by-products.Among them,the dissolved organic matters content in the wastewater produced by Tween 80 was the highest.（3）After the addition of hydrothermal carbons in the surfactant-enhanced leaching process,the proportion of phenanthrene and pyrene in the soil and the leaching solution decreased,and the content of phenanthrene and pyrene in the hydrothermal carbons increased,indicating the pollutants in the leaching solution and soil were transferred to the hydrothermal carbons.Comprehensive consideration of economic benefits and leaching effects,GBC was the best experimental material,when GBC content was 5%,p H=6（SDBS as leaching agent）or p H did not change（Tween 80 as leaching agent）,the dissolved organic matter HA content was 5%,the total elution rate of phenanthrene and pyrene could reach more than 90%.（4）The adsorption effect of modified hydrothermal carbons GBC and FBC was slightly higher than that of BC.The optimal dosage of three hydrothermal carbons was 6 g/L,and the adsorption equilibrium was reached within 24 hours,whose equilibrium adsorption capacity was GBC>FBC>BC.Studies on adsorption kinetics and adsorption isotherms showed that the adsorption of phenanthrene and pyrene by hydrothermal carbons was the result of uneven surface and monolayer adsorption,mainly chemical adsorption.Surfactant reuse experiments have proved the feasibility of the reuse operation after the leaching waste liquid was treated,but it was necessary to manually add surfactants or take other measures to ensure the efficient leaching of the surfactant after multiple reuses. |
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