preparation and characterization of colloidal silica in alkaline and constant range of ph

in this study, alkaline colloidal silica was prepared by titration of an alkaline solution such as sodium silicate with silicic acid in constant range of ph  .this constant range of ph was achieved by using concentrated soduim silicate solutions as ph adjusting solutions during titration.the sodium silicate solutions  having a variety of concentrations were passed  through ion-exchange resin to prepare the silicic acid solutions. various effective  parameters on the method were investigated. in this research, the results show the mean particle size and surface area of prepared colloidal  silica are influenced by formation temperature, titration rate, silicic acid and alkaline solutions concentration. low titration rate of slicic acid, high formation temperature and low concentration of silicic acid and alkaline solution would help the particle growth to form the larger particle size of colloidal silica.