Adsorpiton And Desorption Of Octachlorodipropyl Ether In Selected Soils

In order to find out the environmental effects of OCDPE.Adsorption/desorptiondynamics and isotherm of OCDPE in four typical soils with different physicochemicalproperties from Changsha Hunan Tianjin Hefei Anhui Ying tan Jiangxi were conducted byusing oscillatory equilibrium methods and the main results showed as the follows.1. Adsorption and desorption dynamics process of OCDPE in four tested soils.The adsorption and desorption dynamics process of OCDPE in the tested soils aredivided into rapid allocated and slow gap filling phase and reached to the equilibriumwithin12h.The adsorption percentage and strength of OCDPE on the soils increased withthe increasing of the organic content in the soils.2. Adsorption and desorption behavior of OCDPE in the tested soilThe adsorption capacities increased with the increasing amount and equilibriumconcentration of OCDPE added. The adsorption isotherms of OCDPE on all soils could bedescribed by Freundlich and Linear equation very well. The Freundlich coefficient valuesfor on the soils varying greatly from31.94L/kg134.62L/kg372.64L/kg and413.99L/kgmg/L on red earth moisture soil Yellow-cinnamon soi and paddy soil respectively,and Komrange of1867.8-13845.8,suggesting that OCDPE sorption abilityof was strong in paddysoil and it had less risk to pollute groundwater, The transfer ability of OCDPE was strongin red earth,which had more risk to pollute ground water, according to McCall,s classifica-tion system．Adsorption free energy (△G0)of OCDPE on red earth moisture soil paddysoiland Yellow-cinnamon soi was-4.46-5.22-5.65-5.76Kcal/mo l,respectively,showingthat the adsorption largely resulted from the physical adsorption,The adsorption processwas spontaneous exothermic reaction.The adsorption coefficients were found to be betterrelated to the content of organic matter (OM%) and cation exchange capacity (CEC) thanclay content and pH value.It was very difficult to desorb while OCDPE was adsorbed in the soil. The desorptionisotherms also conformed well to the Freundlich and Linear equation well.The kfrangedfrom85.14L/kg340.00L/kg592.35L/kg and792.41L/kg and under the same conditionsOCDPE adsorbed in paddy soil was desorbed more difficult than that in red soil. Theapparent adsorption-desorption hysteresis was found with the average hysteresis index (HI)0.610.780.82in Changsha Hunan, Hefei Anhui, Yingtan Jiangxi soils. The soils have the desorption hysteresis on OCDPE is relavant with the organic content in the soils. Therewas a positive correlation between adsorption and desorption.4. The adsorption capacities under different soil conditionOrganic matter played a significant role in adsorption of OCDPE. The kfwas66.3716.98113.9544.53L/kg in the four OM-removed soils respectively indicating that: theadsorption capacities decreased sharply with the organic matter removed from thesoils.CaCl2as a background electrolyte.The adsorption capacities decreased with theincreasing of concentration of CaCl2. At the tested pH interval of5～9, there were noobvious effects of pH values on OCDPE adsorption.5. The effect of several environmental substances on the adsorption capacitiesSeveral environmental substances including anionic surfactant sodium dodecylbenzene sulfonate (SDBS), nonionic surfactant Tween80and NH4NO3as a chemicalfertilizer were selected to see their influence on the adsorption dynamics of OCDPE inJiangxi red earth. The results showed that OCDPE adsorption capacity could be changedby those environmental substances. The presence of Tween80and SDBS can decreaseslightly the adsorption of OCDPE by comparison with the measured in Tween80andSDBS free solution. While the distribution coefficient (Kd) decrease from34.64to4.93and8.01when NH4NO3was added, indicating that the presence of NH4NO3can sharplydecrease the adsorption of OCDPE by comparison with the measured in the NH4NO3freesolution.