高岭土表面润湿性的分子动力学研究

Study on molecular dynamics of surface wettability of kaolinite

黏土矿物的润湿性对于岩土工程、石油工程和土壤科学等领域的研究都至关重要。高岭土作为典型的黏土矿物,在宏观实验中通常被认为具有疏水性,但在扫描电镜下观测到其表面有铝氧面和硅氧面两种结构,因此采用分子动力学方法计算了水分子吸附在高岭土两种表面时的接触角,从微观分子尺度揭示了高岭土的润湿性机理。计算结果表明:水分子吸附在铝氧面时形成的是多层水分子结构,接触角为0°,具有极强的亲水性;水分子吸附在硅氧面时形成的是类半球体结构,接触角为104°,具有疏水性;润湿性差异可由固液界面分子作用的差异解释。研究结果在一定程度上丰富了高岭土浮选化学理论,并可以为其在工业领域的应用提供一定的理论基础。

The wettability of clay minerals is crucial in the fields of geotechnical engineering,petroleum engineering and soil science.Kaolinite,a typical clay mineral,is usually exhibits hydrophobic in macroscopic experiments.However,it was found under scanning electron microscope that its surface was divided into two structures,aluminum-oxygen surface and silicon-oxygen surface.Therefore,in this paper molecular dynamics method was employed to study and calculate the contact angle when water molecules were adsorbed on the two surfaces of kaolinite,and the mechanism of kaolinite wettability from microscopic molecular scale were presented.The results show that the water molecules adsorbed on the aluminum-oxygen surface formed a multilayer water molecule structure with a contact angle of 0°,which was extremely hydrophilic,while the water molecules adsorbed on the silica-oxygen surface formed a hemisphere-like structure with a contact angle of 104°,which was hydrophobic.The difference of wettability can be contri-buted to the differences in molecular interaction at the solid-liquid interface.The results of the study enrich the theory of kaolinite flotation chemistry to a certain extent and provide some theoretical basis for its preparation in the industrial field.