Silica fume wet purified preparation of spherical nano-silica
|School||Kunming University of Science and Technology|
|Keywords||Silica fume Eliminating impurities Spherical Nano-silica Wet method|
The application of Nano-silica in all kinds of fields is getting sophisticated. As the range of use is expanding, the shortage of the Nano-silica has become a problem. The spectrum of material used in the conventional preparation technology is very narrow, so that many researchers devote their time in finding new materials. Silica fume, which is discarded in the extraction process of industrial grade silicon and silicon steel, is used as a new material to produce silica in this paper. The practice is a successful exploration in recycling secondary sources and finding a new way to produce silica.The process flow is depicted as follow. Silica fume is first baked to eliminate carbon under 550℃and heat insulation for 5h, and then silica fume is put into HCl solution to get rid of some other impurities and to change surface properties of the particles, while silica fume settles to the bottom because of gravitation. Separate the particles and the fluid. The particles are further washed in HF solution to dissolve the glass outer casing which is generated while silica fume is produced. Then the particles after washing are delivered to alternant acid leaching in HCl and H2SO4 solutions, which is the body part of the experiment. In the end, dry the leached residue to produce samples.Dictation technologies, such as XRD, XRF, SEM and ICP, are used to research the microscopic structure and phase component of material and products, as well as the purification of the products and the mechanism of eliminating impurities.As how purification of silica fume arc affected by factors, such as temperature, reaction time, concentration of solutions and stirring rate, are systematically discussed in the paper, the best experiment scheme is developed according to efficiency of purification and practicable conditions. The optimal condition is 60℃,600r/min stirring rate,2h reaction time and liquid-solid ratio is 50:1.Nano-silica of high purity is produced through acid leaching, while the nanometer grade size of silica fume is reserved and most of the impurities are removed. The remove rate of impurities is Fe:63.1%, Al:55.3%, Ca:88.2, Mg: 84.4%, K:82.5%, P:93.06% respectively. Spherical Nano silica of 98.3% is gained ultimately. SiO2 is increased by 5.22% than raw material.