萘在土壤上的吸附行为及温度影响的研究

采用批量平衡法研究了多环芳烃萘在塿土耕层土、塿土粘化层土、塿土古土壤、黄壤、紫色土和石灰土上的吸附行为,比较了不同吸附模型方程对实验数据的拟合情况,并探讨了温度对萘在土壤上吸附行为的影响机理及吸附热力学特征。Henry模型、Freundlich模型和deBoer-Zwikker极化模型均能较好地拟合萘的吸附等温线;45℃下的吸附等温线明显地高于25℃的吸附等温线,表现出随温度升高吸附量增大的趋势。Freundlich模型的吸附容量参数Kf和deBoer-Zwikker模型的起始吸附势ε0在两个温度下有极显著的差异;但Freundlich模型的n参数表征了土壤颗粒表面的性质,对温度变化不敏感。在25℃条件下,萘在土壤有机碳上的分配可能是吸附的主要机制,但随着温度增加,吸附机制变得复杂。土壤对萘的吸附是一吸热反应,整个吸附体系中熵增是吸附作用进行的主要驱动力。

Adsorption Process of Naphthalene in Soils and the Effect of Temperature

Adsorption of naphthalene by 6 different soils was examined using batch adsorption equilibrium methods.Henry model,Freundlich model and deBoer-Zwikker model could perfectly fit the adsorption isotherm of naphthalene by soils.The adsorption isotherm by adsorption and relative balance concentration at 45 ℃ were obviously higher than that at 25 ℃,which showed that adsorption capacity increased with the temperature increasing.The adsorption capacity Kf of Freundlich model and the initial adsorption potential of deBoer-Zwikker model had extremely significant difference at two temperature degrees,but the parameter n in Freundlich model was not sensitive to temperature change because it only characterizes the surface property of the soil particles.In 25 ℃ condition,naphthalene distribution between aqueous solution and soil organic carbon was the main adsorption mechanism,but the adsorption mechanism became more complicated as the temperature increasing.The evaluated Gibbs free energy change and enthalpy change indicated the spontaneous and endothermic nature of naphthalene adsorption in soils,and the entropy gain in whole adsorption system was the main adsorption driving force.