Preparation Of Kaolinite Nanotube And Study On The Mechanism Of Emulsion Stabilization

Pickering emulsion is an environment-friendly emulsion,which has the ad-vantages of long stabilization period and good thermal stability.It has been widely applied in the fields of food,pharmaceuticals,oil recovery,wastewater treatment.Recently,it aroused the concern that using the clay minerals as emulsifiers to stabilize Pickering emulsions.Clay minerals are a cheap resource which can get easily,and because of their anisotropy and surface chemistry,it is a good choice to using them to develop the new Pickering emulsion.According to the effect of layered clay minerals on emulsion stability,besides forming a three-dimensional network and a house of cards structure in the continuous phase,those particles can also form the single-layer particle film.The film with high-density can effectively hinder the coalescence be-tween the droplets,which leads to a decrease in the moving speed of the solid parti-cles at water/oil interface.In the end,the stability of the emulsion improved.Kaolinite is a well-known and commonly used layered clay mineral formed by stacking silox-ane tetrahedron（SiO₄）and aluminum octahedron（Al₂（OH）₄）.It is composed of Al–O octahedral sheets and Si–O tetrahedral sheets by the proportion of 1:1.However,the size of lamellar structure of the kaolinite is non-uniform,so it is difficult to form a high-density particle film on the emulsion water/oil interface.Due to the mismatch of the octahedral sheet and tetrahedral sheet,the lamellar-structured kaolinite can turn into nanotube structure through the method called modification-intercalation-liquid.Although the size of kaolinite is not uniform nanotube,which derived from kaolinite is known for its regularity and the uniform nano-size,contributes to improve the emulsion stability.The main conclusions are presented as follows:Through the method of modification-intercalation-liquid,the interlayer space of kaolinite reached nearly 4 nm by inserting and replacing dimethyl sulfoxide,methanol and cetyltrimethylammonium chloride sequentially.During the methanol eluting pro-cess of kaolinite-cetyltrimethylammonium chloride intercalation composite,the kao-linite nanosheets（Ksheet）,kaolinite nanosheet-tube（Ksheet-tube）,and kaolinite nanotubes（Ktube）which have different morphologies can be obtained by contrlling the ultrasonic and the frequency of methanol eluting.The Ksheet mainly exhibits a single lamellar morphology,which is similar to the morphology of the raw kaolinite,while the stacking between the lamellar layers is not as serious as the raw kaolinite.the Ksheet-tube mainly exhibits the connection state of the nanotube and nanosheets;in the Ktube,the sheet structure kaolinite is completely transformed into a tubular structure,with the inner and outer diameters about 20 nm and 40 nm respectively,so the morphology and size of the kaolinite nanotubes are more uniform.In this work,nano-scale kaolinite nanotube was prepared and used as an emulsi-fier to stabilize the Pickering emulsion.Emulsion stability was investigated by meas-uring the creaming index,viscosity,droplet size,and the distribution structure of the emulsifier at the water/oil interface.The result shows that the emulsion droplet size was 60?μm and the viscosity of the emulsion continuous phase reached 3470 mPa·S.The creaming index was 76%and maintained 36%after centrifugation at 2000?r/min.Besides,the kaolinite nanotube has nano particle-size which can produce small and uniform emulsion droplets.The kaolinite nanotube had a larger specific surface area and was easy to adsorb at the water/oil surface which can reduce the emulsion demul-sification caused by the interfacial tension.Furthermore,the kaolinite nanotube can sembled a regular and tight at water/oil interface.And the dense and ordered sin-gle-layer solid particle film can prevented the coalescence between the droplets effec-tively.