| With the continuous development of economic development,urban industrialization and the living standard of the public,the problem of soil pollution has become increasingly serious.This has caused widespread concern in society and government departments.Because TCE has low solubility and high surface tension,its biodegradability is low,and its half-life in soil is about six months to one and a half years.Therefore,Therefore,TCE will enter the soil and groundwater environment and remain in the environment for long-term pollution due to its stability.At the same time,the "triple hazard" of trichloroethylene makes it extremely important to control and eliminate its pollution in the environment.There are many treatments for trichloroethylene pollution.One of the more effective methods is adsorption.Adsorption is a common method used by workers both at home and abroad.And researchers are also seeking to find a kind of adsorbent with high adsorption performance,cheap and environment-friendly.In recent years,biochar has been widely used as a new environmental material for the adsorption of organic pollutants.In this paper,the adsorption properties of trichloroethylene from the extraction of organic matter components,clay minerals,soil and exogenous biochar from natural soils were studied.In this experiment,the structural characteristics and surface characteristics of natural organic components(fulvic acid,humic acid and humin)and homemade biochar were analyzed.The adsorption equilibrium time and isothermal adsorption curve for different adsorption,ie,trichloroethylene,were studied.This paper explored the adsorption mechanism of organic components,clay minerals,Northeast Black Soil and homemade biochar,and discussed the influence of environmental pH and other factors on soil adsorption behavior.The organic matter components of the soil—humic acid(HA),humin(HM)and fulvic acid(FA)were extracted by stepwise extraction method to study the adsorption performance of each component,combined with infrared spectroscopy and scanning electron microscopy.The composition of soil organic matter components and its adsorption mechanism for TCE were initially revealed.The results show,There are large differences in the content of organic components in the soil,ie,HM>FA>HA.The organic components ratios of H/C,O/C and(N+O)/C gradually decreased,ie,FA>HA>HM,indicated that the FA component had the highest fatity and the strongest polarity.The equilibrium time for the adsorption of trichloroethylene for each organic component was 24 hours.The isothermal adsorption curves were in accordance with the Freundlich model.The adsorption performance was HM>HA>FA.The adsorption of trichloroethylene by the organic components was dominated by the polarity.The common five types of clay minerals(kaolinite,montmorillonite,illite,attapulgite,and nano-silica)were used as adsorbents,and the adsorption properties of the five clay minerals on TCE were confirmed by batch adsorption experiments : nano-silica> attapulgite> illite> montmorillonite> kaolinite.The adsorption equilibrium time of each clay mineral was 48 hours,and the isothermal adsorption curves of all clay minerals conformed to the Langmuir model.The adsorption of trichloroethylene by clay minerals was due to the combination of surface adsorption and microporous structure.In addition,the adsorption behavior of TCE in natural black soil and its influencing factors were systematically studied using the batch adsorption test method.The results show that adsorption equilibrium time for adsorption of trichloroethylene in black soil from northeastern China is 48 hours,and the isothermal adsorption curve conforms to the Langmuir model.The pH value and moisture content of the soil have no obvious effect on the adsorption performance.The initial concentration of the solution has a significant influence on the adsorption,meanwhile,the temperature has a certain influence on the adsorption.Adsorption of trichloroethylene into soil is the result of the interaction of organic matter and clay minerals.And this is mainly affected by the role of organic matter distribution.Finally,the self-made biochar was used as the adsorbent material to explore the adsorption of trichloroethylene by biochar.The results showed that the adsorption time of three biochars for TCE was 24 h,and the isothermal adsorption curve was in accordance with the Freundlich model.The adsorption performance was C-550>C-850>C-250.At the same time,combined with elemental analysis and thermogravimetric analysis,the mechanism of TCE adsorption on biomass carbon was explored.The higher the pyrolysis temperature,the higher the biochar has higher aromaticity,contains the least fat components,contains less oxygen-containing functional groups,the more stable the sample structure,the smoother the pore formation process,and the larger specific surface area and micro-dissociation.Hole structure.At the same time,we found that as the pyrolysis temperature of the sample increases,the hydrophilicity of the biochar surface gradually decreases.In the process of biochar adsorption of TCE,the distribution of non-carbonized part and the adsorption of carbonized part are important. |
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