In recent the decades, Silica nano colloids have received a lot of attention due to their high specific surface area in versatile applications such as catalysis, surface modification, casting, polishing, etc. Among different synthesis methods, ion exchange technique using sodium silicate precursor is more suitable for industrial applications due to the used simple equipment and cheap raw materials. In this current study, the diluted sodium silicate is passed through a cation-exchange resin bed (Putrolite C100) and active silicic acid is collected. Then, silicic acid is titrated by potassium hydroxide (KOH) solution at different temperatures. Synthesis parameters such as temperature, titration rate and KOH concentration are among the parameters affecting the formation silica colloids. In the current study, the effect of synthesis temperature between 25°C and 100°C on the formation of nano colloidal silica synthesised by ion exchange method was investigated. Moreover, silica nanoparticles (average particle size of 50nm) were dispersed to KOH solution to act as seeds for the formation of silica nanoparticles. The synthesized nano silica colloidals were characterized by Dynamic Light Scattering analysis (DLS), Scanning Electron Microscopy (SEM), Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES) and Fourier-transform infrared spectroscopy (FTIR). The observations revealed that the average particle size of the synthezied nono colloidal silica was affected by the synthesis temperature. The ICP-OES test results presented that after the ion exchange process, the amount of sodium ions in the obtained silicic acid compared to the initial sodium silicate was significantly decreased, showing 99% reduction. According to the FTIR results, the chemical composition of the silicic acid and silica colloids were confirmed. Moreover, the collected silicic acid became to a gel state after 7 days while did not change chemically, if the formation of silica colloidal was delayed. This inferred that silicic acid was not stable at low pH values due to the rapid polymerization.
