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Adsorption - desorption characteristics of volatile chlorinated hydrocarbons in typical soils of China

Author: MengFanYong
Tutor: LiuRui
School: Shanghai Normal University
Course: Environmental Science
Keywords: Volatile chlorinated hydrocarbons Soil pollution Adsorption equilibrium Adsorption isotherm Soil organic carbon Soil minerals
CLC: X131.3
Type: Master's thesis
Year: 2011
Downloads: 64
Quote: 1
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Abstract


In recent years, the Chinese soil pollution accident-prone, causing widespread concern in the community and government departments. The adsorption of volatile chlorinated hydrocarbons (Volatile chlorinated hydrocarbons, VCHs) one of the main mechanisms of contaminated soil. The adsorption behavior of soil VCHs not only directly impact the soil VCHs concentration distribution, and the impact of migration and transformation of VCHs soil contamination on-site repair capacity and have a significant impact. Therefore, understanding the the adsorption characteristics VCHs soil survey and restoration of contaminated sites has important practical significance. The VCHs soil adsorption - desorption behavior research based on this study, quantitative analytic typical soils of China with common VCHs of gas adsorption equilibrium relationship, to predict the content of pollutants in soil based on soil gas concentrations, simultaneously with continuous ventilation Experimental Study of PCE (tetrachlorethylene, PCE) desorption from the long-term contamination in soil characteristics, provide a theoretical basis for advancing our investigation and control of soil pollution in urban areas. Mainly include the following three parts: (1) static adsorption equilibrium experiments test dry paddy soil the six kinds VCHs gas adsorption equilibrium. The results show that the balance of dry soil adsorption isotherms good fit with the Dubinin-Astakhov equation (R2 gt; 0.95), and the equation parameters and the the soil and VCHs characteristics related. Dubinin-Astakhov equation parameters from soil organic carbon content; found no correlation between the molecular volume of the the beta and VCHs compounds, but with VCHs molecular polarity increases larger trend; E0 soil V lt; average pore diameter was linearly related; W 0 V lt; 10 nm good, but the relationship between specific surface area and soil. Dubinin-Astakhov equation equilibrium adsorption capacity of the dry soil forecast, the predicted and measured values ??fit well (R 2 = 0.98). (2) dynamic adsorption equilibrium experiments testing the moist soil of of four kinds VCHs gas adsorption equilibrium. Moist soil trichlorethylene, tetrachlorethylene, 1,1,1 - trichloroethane adsorption isotherms meet Henry-type adsorption isotherm, and 1,1,2 - trichloroethane is non-linear adsorption . Different soil solid - liquid equilibrium adsorption coefficient (KSW) showed a good linear relationship with soil organic carbon content (α). To predict the equilibrium adsorption capacity of the moist soil, the predicted and measured values ??correlated well (R 2 = 0.98). Directly exposed to the adsorption of the hydrated surface of the soil in the gas phase in the semi-moist soil between the moisture between the dry and wet adsorption can not be ignored, this part of the drying of the soil have similar adsorption mechanism can be by pressure mercury method and BET N < sub> 2 adsorption method to be exposed to the gas phase in the surface of the soil of the ratio γ and the relative soil saturation RS. Thus, the adsorption amount of the semi-moist soil the predictive estimate can be used dry and moist soil. (3) continuous the ventilation experiments analytic PCE contaminated soil from the long-term desorption characteristics. Off-gas PCE concentration decreased with the ventilation time, especially in the ventilation in the initial period of time, the concentration sharply decreased. PCE removal rate during ventilation with contaminated soil particle size distribution and organic carbon content. Part of the PCE after the ventilation, ventilation difficult detachment, this is because adsorbed to the slow diffusion of soil organic carbon, mineral crystals, and the particle layer between the PCE's sake.

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CLC: > Environmental science, safety science > The basic theory for the Environment and Science > Environmental Chemistry > Environmental pollution, chemical > Soil pollution chemistry
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