聚羧酸盐分散剂在吡虫啉颗粒表面的吸附特性

通过测定吸附量、吸附层厚度和傅里叶红外光谱研究聚羧酸盐分散剂Tersperse 2700在农药吡虫啉颗粒表面的吸附热力学、动力学、吸附作用力和吸附形态。热力学和动力学研究结果表明:吸附等温线符合Langmuir模型,随温度升高Langmuir常数和饱和吸附量明显降低,由ΔG_ad<0、ΔH_ad<0、ΔS_ad>0可知该吸附为自发、放热、熵增过程,结合吸附层厚度随温度升高而降低的现象可认为高温不利于该吸附进行;吸附动力学符合Lagergren方程,半饱和吸附时间随温度升高而降低表明该吸附速率随温度升高而增加,该吸附过程的表观活化能E_a为12.62 kJ·mol^-1,表明该吸附为物理吸附。吸附作用力和吸附形态研究结果表明:分散剂2700在吡虫啉颗粒表面的吸附作用力以范德华力为主;吸附形态为单层多点式吸附,通过建立假设吸附模型认为分散剂2700以空间位阻效应和静电斥力效应共同维持在吡虫啉颗粒表面的吸附稳定性。

Adsorption of polycarboxylate dispersant onto imidacloprid particle surfaces

The adsorption characteristics of poly-carboxylate dispersant(Tersperse 2700)onto imidacloprid particle surfaces,such as adsorption thermodynamics,kinetics,adsorption force and adsorption conformation,were studied with determining adsorption amounts by remnants of concentration,adsorption layer thickness and Fourier transform infrared spectroscopy.The thermodynamic parameters obtained are as follows:ΔH_ad<0,ΔG_ad<0,ΔS_ad>0,indicating that the adsorption is a spontaneous exothermic process.The adsorption layer thickness decreases as temperature increases.Theoretically,higher temperature is not beneficial to adsorption process.The result of adsorption kinetics shows that the adsorption of dispersant 2700 onto imidacloprid particle surfaces corresponds with Lagergren adsorption rate equation.The adsorption rate increases with temperature and activation energy E_a=12.62 kJ·mol^-1,so the adsorption process is physical adsorption.The result of adsorption force shows that van der Waals force is an important force at different temperatures.The adsorption is monolayer and multi-point.The hypothetical adsorption model shows that the adsorption stability on imidacloprid particle surfaces is maintained by apparent stereo-hindrance effect and electrostatic repulsion produced by dispersant 2700.