Synthesis of quality silica gel; Optimization of parameters

Silica gels were prepared by acidifying the aqueous solution of sodium silicate. In the investigations, effects of pH, mixing rate, temperature of the reactants and specific gravities of the starting materials were studied. One sample was prepared at temperature of 50 ºC. Self indicating silica gels were also prepared. The silica gels produced were characterized using the standard analytical procedures. Surface area, bulk density, moisture absorptive capacity, water soluble matter, water soluble sulphate, and heat resistance of the prepared samples were determined. Optimum parameters for the preparation of good quality silica gel were found to be sp. gr. of sodium silicate 1.20 and of sulphuric acid 1.10, finishing pH of the hydro sol at 3, mixing time 18-20 min and reaction temperature of 20 0C (room temperature).The quality silica gel produced had bulk density 0.46951 g/cm3, moisture absorptive capacity 32.7% and iodine no. 23.61 and these values were comparable with a good quality commercially available silica gel.