The Study Of High Purity Silica Sol

A new process of high purity silica sol has been presentsed which adopted ion exchange method to product high purity silicon dioxide(mother liquor) from Waterglass. One growth experiment of silicon dioxide can be carry on by silica sol liquor dropwise technique,We can obtain alkaline silica product with a certain particle size and hing-purity. The Secondary growth experiments of silicon particles can be carryed out by hydrolyzing silicon powder under the catalyst,silica product with large diameter and high-purity can be obtained after purification and concentration. These two different size specifications high-purity silica can be applied to different areas.The effects of different types of cation and anion resin, velocity when dilute sodium silicate and poly acid solution flow through the resin bed and the concentration of sodium silicate on the purity and average particle size of poly acid solution and colloidal silica sol prepared, have been studied by single factor experiments. Experimental results show:Using 732 strong-acid styrene cation exchange resin and 717 anion exchange resin, the initial concentration of dilute sodium silicate solution5%, flux was 0.45ml/cm2·min and 0.30ml/cm2·min when dilute sodium silicate solution and poly acid solution flow through the resin bed.Purificating mother liquor,the average particle size of silica sol 3.4～4nm, the metal ion concentration 6.05×10-6g/g, pH value 9.5, concentration of SiO2 4%, with good stability that does not gelate under 110℃10 days. The effects of factors on the first colloid particles growth was also been studied,such as the reaction stirring rate, reaction time, dropping rate of mother liquor silica, the ratio with the additive and base of silica sol, the concentration of base silica sol. Through the range and variance analysis, the optimum conditions was determined.The reaction stirring rate 100r/min, reaction temperature 95℃,reaction time7h, the concentration of base silica sol 4.5%, the concentration of mother liquor silica 4%,dropping rate of mother liquor silica 0.555 ml/cm2-min, the ratio with the additive and base of silica sol 20:1. the average particle size of silica sol 7.7～8.3nm, uniform distribution,the metal ion concentration 6.05×10-6g/g, pH value 9.5, concentration of SiO2 35%, with good stability that does not gelate under 110℃10 days.The study discuss the process conditions of the effects on the second colloid particles growth by investigating the methods and conditions of pretreating elemental silicon powder, the particle size,added amount and type of elemental silicon powder, the types and added amount of catalyst, the concentration of base solution, reaction time and temperature.The optimum conditions was thermal pretreating elemental silicon powder 1h, adding 150 mesh elemental silicon powder 25g, the base silica concentration 8%,150ml,the mass fraction of the catalyst 10%,the amount 12ml, reaction time 7h,temperature of 80℃. The average particle size of silica sol 19～22nm, uniform distribution,the metal ion concentration 8.60×10-6g/g, pH value 9.5, concentration of SiO2 35%, with good stability that does not gelate under 110℃10 days.