2,4-二氯苯酚在黄土中的吸附-解吸行为研究

本以自制的模拟系统研究了溶液浓度、离子强度、pH值和常见金属离子对2，4-二氯苯酚在黄土中迁移行为的影响，并对实验数据用Freudlich和Langmuir经验公式进行了拟合。结果表明，2，4-二氯苯酚在黄土中的吸附／解吸过程包括两个阶段：渗滤液浓度在初始阶段降低迅速，在第二阶段变化缓慢逐渐达到平衡。用分布活性模型能很好地解释这一结果。在实验条件下，离子强度对迁移行为影响不显。在实验的pH范围内，随着pH的升高，吸附量降低，相应的解吸量加大；与碱金属离子Mg^2 、Ca^2 相比，过渡金属离子Zn^2 、Mn^2 和Cd^2 的存在能显促进黄土对2，4-二氯苯酚的滞留能力。但滞后因子尺始终较低，表明天然黄土对如2，4-二氯苯酚这样的水溶性有机物染物的滞留能力较差。在对被这类有机物污染的土壤进行修复过程中，有机物对地下水可能造成的影响是必须予以考虑的因素。

SIMULATED STUDY OF INFLUENCE OF ABSORPTION AND DESORPTION OF 2,4-DICHLOROPHENOL ON LOESS SOIL

The paper aims to present the author's research on the influence of the compound concentration, ionic strength, pH value, and the divalent metal cations on the adsorption-desorptions of 2,4-dichlorophenol and the transitive behavior of the natural loess soil by means of the author's self-made simulation system. The adsorption data have also been analyzed in accordance with Langmuir and Freundlich equations. The analysis result shows that the equilibrium times are shortened with the lowering retardation factors. With the lowering of the retardation factor (R) all the time, the retardant capability of natural loess soil to the water-solubility organic contaminants has also become lower. The process of remediation of contaminated soil reveals that it is necessary to take into the above influential factors on the groundwater. To this end, the author further analyzed the influence of physicochemical parameters by using column reactors filled with a natural loess soil. The analysis proves that the adsorption and desorption curves of 2,4-dichlorophenol in the soil consist of two parts: the first sharp part and the second diffuse part. At the same time, the observed adsorption-desorption breakthrough curves are proved to be asymmetrical. This can be explained by using the Distributed Reactivity Model. And finally, no evident influence was found of the ionic strength on the retention of 2,4-dichlorophenol. Nevertheless, it is influenced by the pH and the heavy metal cations. As is shown, the equilibrium adsorption decreases and desorption increases with the increase of pH. Since the neutral forms have higher hydrophobic property than the negative forms, they are absorbed more easily. While existence of zinc, manganese, cadmium of transitional metals can significantly accelerate the retardant capability of 2,4-dichlorophenol in natural loess soil, magnesium, calcium of alkali metals can not.