四环素在典型土壤中的吸附行为·吸附动力学·热力学特征

Adsorption Behavior and Characteristics of Adsorption Kinetics and Adsorption Thermodynamics of Tetracycline on Typical Soils

[目的]研究四环素在典型土壤中的吸附行为及吸附动力学和热力学特征。[方法]采用平衡振荡法,研究了不同试验条件下3种典型土壤对四环素的吸附效能。[结果]黑土对四环素的吸附能力最高,其对应的饱和吸附量超过85.0 mg/g,黄土次之,而高岭土的吸附效能最低,仅11.6 mg/g。酸性pH条件和较高的土壤有机质含量有利于3种土壤对四环素的吸附,当土壤中有机质去除后整体吸附能力将下降15%。3种土壤对四环素的吸附是一个吸热过程。黑土对四环素吸附过程符合准一级反应动力学方程,而黄土和高岭土对四环素的吸附更符合准二级吸附动力学方程。黄土和高岭土对四环素的吸附满足Langmuir吸附等温式,即认为上述吸附主要归因于单分子层吸附;相对应的常用来表征竞争吸附的Freundlich方程更符合黑土对四环素的吸附。[结论]该研究可为揭示四环素在土壤中的吸附富集机理提供科学依据。

[ Objective ] To study adsorption behavior and characteristics of adsorption kinetics and adsorption thermodynamics of tetracycline on typical soils. [ Method] The effects of different experimental conditions on the adsorption efficiency of tetracycline in three typical soils were studied by equilibrating method. [ Result]The results showed that the adsorption capacity of tetracycline was the highest, and the correspond- ing adsorption capacity was 85.0 mg/g, followed by loess, and the adsorption efficiency of kaolin was the lowest, only 11.6 mg/g. Acidic pH conditions and higher soil organic matter content are favorable for the adsorption of tetracycline in the above three soils, and the overall adsorp- tion capacity will decrease by 15% when the organic matter in soil is removed. The adsorption of tetracycline from the three soils was an endo- thermic process. In addition, the adsorption process of tetracycline in black soil was in accordance with the pseudo first order reaction kinetics equation, while the adsorption of tetracycline on loess and kaolin was more consistent with the quasi-second adsorption kinetics equation. The adsorption of tetracycline on loess and clay satisfies the Langmuir adsorption isotherm, which means that the adsorption was mainly attributed to the adsorption of monomolecular layers. The corresponding Freundlich equation, which was commonly used to characterize the competitive ad- sorption, was more compatible with the adsorption of tetracycline. [ Conclusion ] The study can provide scientific basis for revealing the mecha- nism of tetracycline adsorption and accumulation in soil.