Abstract:

Fundamental study of diffusion and adsorption of nanoparticles under shear flow provides a theoretical basis for designing more efficient processes for separations and transportations. In this work, the mechanism of chelating particles (ChP) trapping contaminant particles (CoP) in hydrocyclone was addressed. By constructing simple yet meaningful theoretical models, the effects of shear flow on adsorptions were investigated. Rotational speed only strengthened adsorption, whereas adsorption direction was determined by intrinsic characteristics of adsorbents and solvent. Besides, the capture time of CoP was dominated by the diffusion process of CoP in the solvent, towards which a simple equation for estimating diffusion time was derived. Diffusion time was inversely proportional to the 4/3 power of ChP concentration but directly proportional to the averaged volume of a single Cop. Current theoretical study provided guidance for improving efficiency of separating contaminants.

Key words: rotation effect, adsorption, molecular contaminants, diffusion, time, model

摘要：

剪切流场中粒子扩散、吸附的微观机理探索为提高分离、传递等典型化工过程的效率提供理论依据。针对旋流分离过程中低浓度污染物纳米颗粒在剪切流场中被螯合剂大颗粒(又称吸附大颗粒)吸附及扩散过程构建近似理论模型, 研究了污染物颗粒扩散及螯合剂捕集吸附与剪切流速度的关系。结果表明, 剪切流的存在对于颗粒的吸附过程起到强化的效果, 剪切流速度越大效果越强, 而吸附的方向(朝向或远离吸附大颗粒)只取决于吸附大颗粒及溶液的特性, 此外低浓度污染物纳米颗粒被捕集吸附的过程主要与颗粒的扩散有关。推导了扩散时间的简洁解析表达式, 扩散时间与吸附大颗粒浓度的4/3次方呈反比, 与粒子的体积大小呈正比。剪切流对吸附的影响及捕集吸附时间的估算, 为物理化学吸附结合旋流分离处理污染物等技术开发提供理论指导。

关键词: 自转, 吸附, 污染物, 扩散, 时间, 模型