水稻土及其提取腐植酸组分对邻苯二甲酸二丁酯(DBP)的吸附解吸研究

Sorption and desorption of Di-n-butyl phthalate(DBP)on paddy soils and humic acid

采用批处理试验研究邻苯二甲酸二丁酯(DBP,1~12 mg·L-1)在水稻土及其提取腐植酸组分中的吸附-解吸行为。结果表明,DBP在水稻土及其腐植酸组分中的吸附分别在48 h和24 h内达到平衡,吸附动力学过程均符合拟二级动力学方程(R2>0.997),是涉及表面扩散和颗粒内扩散吸附过程。不同温度条件下(15、25、35℃)吸附等温线均符合Freundlich方程(R2>0.901)。吸附过程属于熵增的自发吸热物理吸附过程,其中腐植酸组分(K_(oc)值为925~7691 m L·g-1)对DBP的吸附性能强于水稻土(K_(oc)值为524~3565 m L·g-1),这与其有机质含量较高有关。解吸实验(25℃)显示,水稻土及其腐植酸组分也符合Freundlich方程(R^2>0.870),其中水稻土对DBP的解吸存在明显滞后现象,但其腐植酸成分对DBP解吸的滞后现象不显著,即其吸附的DBP较易再次释放。

In this study, Di-n-butyl phthalate（DBP）was selected as the target contaminant and humic acid was extracted from the paddy soil. The sorption and desorption of DBP（concentrations from 1 to 12 mg·L-1 in solution）on paddy soil and humic acid were investigated by conducting batch sorption experiments. DBP in supernatant was quantified by high efficiency liquid chromatography. The results showed that the sorption of DBP on paddy soil and humic acid reached the equilibrium within 48 h and 24 h, respectively. The sorption kinetics of DBP followed the pseudo-second-order kinetic models with R2〉0.997. The sorption of DBP was controlled by the boundary layer diffusion and intra-particle diffusion. The DBP sorption isotherms followed the Freundlich models with R2〉0.901 at different temperatures（15, 25, 35℃）. Thermodynamic data showed that DBP sorption in paddy soils and humic acid was a spontaneous physical sorption process. The DBP sorption capacity of humic acid was higher than that of the paddy soil, which was related to the high soil organic matter content of the former.The DBP desorption isotherms also fitted well the Freundlich models with R2〉0.870 at 25 ℃. Obvious desorption hysteresis was found for paddy soil, but not for humic acid. In other words, the adsorbed DBP was more easily released into the environment on humic acid.