Preparation And Characterization On Monodispersed Spherical Silica Particles

Monodispersed spherical silica has been used for templates catalyst carrier, particle filter material, absorption material, as well as the packing material in HPLC including industrial separation column and coating materials due to its large specific surface area, high mechanical strength, good thermal stability and excellent penetration property.A new route to highly purity silica sol prepared by soluble silicate was presented. Firstly, adopted ion exchange method, small particle size silica sol was prepared, and then by adding ammonia solution and adjusting reaction temperature and time, large size particle silica sol was successfully synthesized via hydrothermal treatment. The effects of mass concentration of dilute sodium silicate, flowrate of dilute sodium silicate and pH on the purity, the average particle size and the stability of small particle size silica sol had been studied experimentally. The experimental results show the small particle size silica sol with about 4nm of the average particle size, good stability and the metal ion concentration about 10μg/g, was prepared by selecting the initial mass concentration of dilute sodium silicate 6%, the flow rate of dilute sodium silicate 2.0L/h and the pH value 9.0. The effects of the reaction parameters such as ammonia/silica sol ratio, agitation speed, reaction temperature and time on the growth of particle size were investigated. Based on the particle size and the stability of silica sol, it was found that when the reasonable experimental conditions was the pH value 9.0,agitation speed 300 rpm, reaction temperature 90℃and reaction time 90 min,the enlarged particle size was about 10 nm.Using self-made silica sol as raw material, Large sized, monodispersed spherical silica particles were synthesized by polymer induced colloid aggregation method and seed particle growth method, the effect of seed particle size and distribution, solvent, the additional feed/seed ratio, the introducing timing of the additional feed for particle size growth and the growth times etc., on the final particle size and microstructure of silica were studied by SEM, Laser Particle Sizer etc., devices. The experiment result shows that large sized, monodispersed spherical silica particles with 10μm of average particle size,10.21 nm of pore diameter and more than 383.3m2/g of surface area were synthesized by under the following operational conditions: selecting appropriate seed synthesis condition and generating seed with even particle size, adding 8% weight of acetone as solvent to the seed system, controlling the additional feed/seed weight ratio at 2:1, charging the additional feed at 40 min after the last introduction of formaldehyde, adopting two times of seed particle growth.