苯噻酰草胺在海泡石和凹凸棒石中的吸附行为

Adsorption of mefenacet on sepiolite and attapulgite

吸附是农药在土壤环境中行为和归宿的重要过程,农药在土壤矿物上的吸附直接影响其在土壤中的迁移、转化和生物利用等过程。了解农药在土壤中的吸附,对于预测和评价农药对土壤、地下水存在的潜在危害,开展土壤修复具有十分重要的意义。本研究通过批量平衡试验,研究了苯噻酰草胺在海泡石和凹凸棒石中的吸附行为及机理。结果表明:苯噻酰草胺在海泡石和凹凸棒石中的吸附分为快速反应阶段和慢速平衡阶段,吸附平衡时间约为6 h。其吸附动力学曲线符合准二级动力学方程,线性方程和Freundlich吸附等温方程能较好地描述其在海泡石和凹凸棒石中的吸附行为,海泡石对苯噻酰草胺的吸附容量高于凹凸棒石。傅立叶变换红外光谱(FTIR)和X-射线衍射(XRD)分析显示:苯噻酰草胺在海泡石和凹凸棒石中的吸附不仅发生在其表面层,还进入了其内层。机理分析推测:苯噻酰草胺主要是通过氢键、电荷转移和电荷-偶极键形式吸附在黏土矿物中。

Adsorption is an important process in governing the fate of pesticides in soil system. Adsorption on minerals was shown to control the transport, transformation and biological processes of pesticides. It was also of great significance in evaluating the potential effects on soil and groundwater and developing soil chemical remediation. In this study, sepiolite and attapulgite were selected as absorbent. Batch equilibrium experiments were performed to study the adsorption characteristics and adsorption mechanisms of mefenacet on sepiolite and attapulgite. It was indicated that the adsorption process of mefenacet on the two clay minerals could be divided into two phases ： rapid adsorption stage and slow adsorption equilibrium stage, and equilibrium phase was 6 h. Its adsorption behavior could be described by Pseudo-second-order kinetics. The adsorption isotherms of mefenacet on the two clay minerals were well fitted by Linear equation and Freundlich equation. The adsorption capacity of mefenacet on sepiolite was larger than on attapulgite. FTIR spectroscopy and XRD analysis indicated that mefenacet could enter the interlayer of sepiolite and attapulgite. Hydrogen bonds, charge transfer and charge-dipole might exist between mefenacet and sepiolite or attapulgite.