模拟有机-矿质体中不同吸附域对TCE的吸附影响

为研究无机矿物与有机质相互作用形成复合体对有机污染物的吸附行为影响,制备了蒙脱土-腐植酸复合体以及混合体模拟土样,分别代表蒙脱土与腐植酸之间有相互作用和无相互作用,并运用批实验的方法,针对不同有机质与无机矿物质量比(C/M)的有机-矿质复合体及混合体开展了三氯乙烯(TCE)吸附实验研究.结果表明,TCE在不同C/M的有机-矿质复合体和混合体中的吸附符合Freundlich等温吸附模型.采用纯蒙脱土及腐植酸的吸附方程叠加计算获取无相互作用模拟土样的固相吸附量计算值,计算值均小于复合体和混合体的实际固相吸附量,表明复合体中蒙脱土与腐植酸吸附域之间存在相互作用,导致腐植酸性质改变,使复合体的吸附能力增强,而混合体由于等温吸附实验过程中有水的参与,也可能在一定程度上形成了复合体.随着C/M的增大,有机-矿质复合体和混合体对TCE的吸附能力增强.当 C/M小于0.08时,复合体中蒙脱土与腐植酸发生较为充分的相互作用,导致腐植酸性质改变,增强了复合体对TCE的吸附能力,因而复合体对TCE的吸附能力明显强于混合体;当C/M大于0.08时,复合体中后续叠加在补丁上的有机质保留了源腐植酸的特性,这部分有机质将掩盖变性有机质的吸附影响,因而复合体与混合体对TCE的吸附能力基本相当.TCE初始浓度影响分析表明,当C/M固定时,随着TCE初始浓度(C0)的增大,非线性叠加模型的固相吸附量计算值与实测值的差值(?Qe)呈增大趋势,分析认为复合体中的变性有机质较其他组分对TCE具有更强的亲和力,随着C0的增加,变性有机质的吸附贡献率增大,因此导致?Qe的增大.

The effects on the trichloroethylene sorption behaviors caused by the interactions between different sorption domains in model organic-mineral complexes

In order to research the sorption behavior effect of the complexes on organic pollutants, organic matters/minerals (C/M) montmorillonite-humic acid complexes and mixtures soil samples with different ratios were prepared to represent interactions and non-interactions between montmorillonite and humic acid respectively. A series of batch experiments were carried out to determine the sorption behavior of trichloroethylene (TCE) on the organic-mineral complexes and mixtures. Results showed that the adsorption isotherms of TCE fit the Freundlich adsorption model. By using the superposition of adsorption equation of montmorillonite and humic acid, the theoretical value of the adsorbed TCE amount in solid phase was calculated to represent the soil samples which were made up by non-interactions between montmorillonite and humic acid. The theoretical value of the adsorbed TCE amount in solid phase were all smaller than the actual values in the adsorption of complexes and mixtures, indicating that there were interactions between the two sorption domains in the complexes, which lead to some change in the properties of humic acid. And this enhanced the adsorption capability of complexes. At the same time, mixtures transformed into complexes to some extent, due to the participation of water in the process of isothermal adsorption. The adsorption capability of complexes and mixtures on TCE was enhanced with the increasing of C/M. The adsorption capability of complexes was higher than the mixtures when the C/M was lower than 0.08. This suggested that the changing of humic acid properties enhanced the adsorptioncapability of complexes. However, when the C/M was higher than 0.08, more organic matter were added on the patch, which would keep the original characteristics. This part of humic acid would cover up the influence taken by those denatured humic acid. Therefore, the adsorption capability of complexes and mixtures were almost the same. When the C/M of the complexes was fixed, the difference ?Qe, which calculated from the theoretical value of nonlinear superposition mode and the actual value, increased with the initial aqueous-phase solute concentration (C0) of TCE. This suggested that denatured humic acid had higher affinity for TCE than other components in the complexes. The sorption contribution of denatured humic acid increased with the increasing of C0.