Preparation, Properties And Structure Of Alumina Sol

Alumina sol is a colloidal solution, which is positively charged alumina imperceptible particle dispersed in water. Aluminum sol is stable when its pH value is kept between3.5and4.5. Alumina sol has adhesiveness, dispersion, reversible water-soluble, suspended property, positively charged property, adsorption, and many other characteristics. Because of these characteristics, alumina sol is widely used in inorganic fibers and refractory materials, ceramic industry, textile fiber products, industrial cloth, fluff industry, paper-making industry etc.In this thesis, pure aluminum was used as raw material to prepare alumina sol. Firstly, sodium metaaluminate was obtained by the reaction of pure aluminum and sodium hydroxide solution. Then the sodium metaaluminate was mixed with sodium bicarbonate, and amorphous aluminum hydroxide precipitation was prepared in the hydrolysis reaction. After heating the precipitation at a certain temperature for a period of time, the morphous aluminum hydroxide precipitation was transformed into boehmite precipitation. Filtrated the precipitation, then washed the precipitation with deionized water to neutral, dried and milled it. Then pure boehmite powder was obtained. Finally diluted acid was added into boehmite powder to peptize and alumina sol was synthesized when refluxing the mixture.The main influencing factors in the preparation of alumina sol are the heating temperature, the heating time, the type and dosage of peptizer, the period of aging, the aging temperature, etc. single-factor method was adopted after a lot of experiments. Each time only one factor was changed, and the rest several factors was unchanged to conduct a group of experiments. According to the results of the experiments, the influnce of the changed factors in the experiments had been found. And the optimal conditions in the preparation of alumina sol had been concluded.In this study, the optimal preparation conditions was concluded as the following: The heating temperature is85℃. The heating time is2hours. Diluted nitric acid solution was chosen as the best peptizer, and the ratio of acid to aluminum is0.06. The aging temperature is85℃, and the aging time is8h.The solid content of traditional alumina sol is (5-10wt%). When Alumina sol is used in some areas, there are certain requirements on the solid content. The optimal value R(H+/AlOOH molar ratio) is0.06, and the solid content of the aluminum sol is increased at this point. When the solid content is reached12%, the stable period of alumina sol is about68d. In this paper, by adding a cationic surfactant (CTAB), high stability aluminum sol was obtained.In this paper, the preparation of alumina sol was only shown by some research and analysis, when pure aluminum is used as raw material. Further research and exploration are needed for the study of alumina sol.