Preparation Of Kaolinite Nanotubes

As one of the traditional industrial mineral raw materials, kaolin is widely usedin industry. In order to build the resource-efficient and environment-friendly society,the performance of kaolin and other ore resources products must be improved and thefield of application must be broadened. Halloysite has the good future inenergy-storage material, drug laden, catalyst carrier and so on. However, naturalhalloysite has problems of low reserves, purity, etc, which limits its large-scaleapplication in industrial production. Due to the similar component and structurebetween kaolinite and halloysite as well as the rich reserves of kaolin in China,preparation of kaolinite nanotubes by using kaolin as raw materials was investigatedin this thesis, in order that the kaolinite nanotubes will substitute halloysite in thefuture. The raw kaolin and its pretreatment method were studied firstly. Then, thekaolinite nanotubes were prepared by conventional method (mechanical agitationcooperating with ultrasonic method), two-step solvothermal method and one-stepsolvothermal method, respectively. The obtained samples were characterized by XRD,SEM, DTA-TG, FT-IR and BET. Based on the above research, some results wereobtained as follows:The raw kaolin is mainly compose of kaolinite, as well as a little of quartz andrutile. The kaolinite has the pseudo-hexagonal shapee and the high crystallinity. Itsparticle size is under4μm and mostly about2μm. The specific surface area of rawkaolin is8.08m2/g. Kaolin obtained by centrifugal sedimentation method has theparticle size less than1μm, and its ratio of radius to thickness is small.Intercalation-delamination method was used to prepare platy-like kaolinite, whoseparticle size is less than2μm and the ratio of radius to thickness is large. Specificsurface area of the platy-like kaolinite obtained by two cycles ofintercalation-delamination process reaches8.66m2/g. The platy-like kaolinite isbeneficial to the intercalation of Dimethyl sulfoxide (DMSO), methonal andN-Hexadecyltrimethylammonium Chloride (CTAC) and then the preparation ofkaolinite nanotubes.When kaolinite/methanol composites were prepared by using kaolinte/DMSO composites as precursor and methanol as intercalation molecule, the intercalationratio of methanol increases with the increasing of reaction time. The intercalationratio of solvothermal method (24h,97.9%) is better than that of conventional method(24h,90.2%).Two-step solvothermal method was used to prepare the kaolinite nanotubeswhich had perfect morphology, good uniformity and high rate of production.Two-step solvothermal method means the kaolinite/methanol composites wasprepared by solvothermal method firstly. Then, it was mixed with the CTACmethanol solution, and finally the kaolinite nanotubes were prepared by solvothermalmethod by using the above mixture. When the concentration of CTAC in methanolsolution is1mol/L, the reaction temperature is100oC and reaction time is24h, theas-prepared kaolinite nanotubes by two-step solvothermal method has the outerdiameter of40-80nm, the inner diameter of20-40nm，the length of200-2000nmand the specific surface area of45.44m2/g. When the kaolinite nanotubes wereprepared by one-step solvothermal method, the rate of production of kaolinitenanotuhes increased slightly with the increasement of concentration of CTAC inmethanol solution and the increasement of reaction time. Moreover, the rate ofproduction of kaolinite nanotuhes is far less than that of two-step solvothermalmethod.