有机膨润土对吡虫啉的吸附

Adsorption characteristics of organobentonite towards imidacloprid

缓释剂的使用是提高农药效率和减少环境污染的有效策略。以四甲基氯化铵、十二烷基三甲基氯化铵和十六烷基三甲基氯化铵为改性剂制备系列有机膨润土,研究其对吡虫啉的等温吸附,分析吡虫啉在有机膨润土的吸附机理和影响因素。结果显示,与未改性膨润土相比,有机改性膨润土极大增强了膨润土对吡虫啉的吸附性能。吡虫啉分子具有较强的极性,无论是短碳链有机膨润土还是长碳链有机膨润土,暴露的硅氧烷表面相对于碳氢基团具有更强的吸附作用,延长季铵盐改性剂的碳链长度增强了有机膨润土对吡虫啉的吸附系数,但是降低了标碳化吸附系数。季铵盐载量对有机膨润土吸附性能的影响与其在膨润土的负载机理有关,载量小于1.0 CEC时,季铵盐主要以离子交换方式吸附到膨润土层间域,增加季铵盐用量可增强有机膨润土对吡虫啉的吸附能力。随着载量的进一步增加,超过可交换阳离子总量的季铵盐以分子形式进入膨润土层间域,降低了膨润土层间域的疏水性及其对吡虫啉的吸附能力。

The use of controlled release formulation （CRF） is one of the best strategies to reduce the use and impact of pesticides in the environment. To provide the fundamental information for the preparation of CRF of imidacloprid by employing bentonite as matrix of low cost, tetramethylammonium chloride, dodecyhrimethylammonium chloride and hexadecyhrimethylammonium chloride were used as modifying agents to prepare organobentonite with different loading levels and the isothermal adsorption of imidacloprid was investigated. Compared with the raw bentonite, the adsorption ity of organobentonite towards imidacloprid was greatly enhanced and was found to be related structural feature of the adsorbent and adsorbate. Owning to the polarity of imidacloprid, the carbon surface of both short-and long-chain organobentonite was less effective than the capacto the hydroexposed siloxane surface in the adsorption process. Although the adsorption coefficient of organobentonite increased, the organic carbon content normalized adsorption coefficient decreased with increasing carbon chain of modifying agents. The adsorption of imidacloprid was found to be related to the surfactant loading level and the loading process on bentonite. An increase of quaternary ammonium loading less than the cationic exchange capacity, via electrostatic interaction, increased the adsorption capacity of organobentonite. At higher loading ire interlayer, leading to a decrease in hydro to imidacloprid. level, the molecule form surfactant entered the bentonphobicity of the interlayer organic phase and its affinity to imidacloprid.