Study On Sorption-desorption Behaviors Of Chlorinated Olefins On Different Soil Compositions

Sorption-desorption plays an important role in the transport and the fate of chlorinated hydrocarbons in soil.TCE and PCE were selected as the target contaminants in this paper.Two types of natural soil with different organic carbon content and four types of soil with most of the low aggregation of "soft carbon" pre-treated by hydrogen peroxide or with all of organic carbon removed by high temperature ignition from the original soil,were adopted as adsorbents,the effects of parameters(organic carbon content and composition,minerals,the initial PCE concentration)on TCE or PCE sorption-desorption behavior were examined.In addition,the differences of the sorption-desorption behavior and sorption-desorption hysteresis size of the single solute system(TCE or PCE)and the binary-solute system(TCE and PCE)was also compared.The results showed that all the soil sorption-desorption isotherm was non-linear within the experimental range and the H2O2-treated samples exhibited the higher nonlinear sorption isotherms than that of the original soils.Target contaminants adsorption capacity was increased with the increase of the organic carbon content and desorption quantity is not only related to the organic carbon content,and organic carbon structure and mineral microporous also has a certain relationship.Both organic carbon and minerals play an important role in sorption-desorption of the target contaminants,organic carbon plays a major role,but the role of minerals can not be ignored.In addition,sorption and desorption of the target contaminants in soil organic carbon and minerals was related to the initial concentration.In binary-solute systems,the affinity of soil samples to PCE greater than TCE,TCE desorption is easy,and the desorption of PCE is controlled by the promotion function of TCE and the restrictive of hard carbon and mineral microporous.All soil samples have shown a certain degree of desorption hysteresis and the H2O2-treated samples exhibited the higher desorption hysteresis;The exist of PCE decresed the hysteresis index of TCE and the higher of the PCE concentration,the smaller desorption hysteresis of the TCE.