Abstract
The reaction of precipitation of amorphous silicon dioxide from aqueous solution of sodium silicate and sulfuric acid has been studied. The factors affecting the precipitation process of the sodium silicate solution such as sodium silicate concentration and addition of anionic surfactant (sodium dodecyl sulfate, SDS) on particle size, size distribution and degree of agglomeration of the precipitated silica were examined. The precipitation of silica from the produced sodium silicate solution was carried out using sulfuric acid at pH 7. Scaning electron microscope (SEM), transmission electron microscope (TEM) and Dynamic light scattering (DLS) have been used for characterization of the produced nano-silica. The surface area of silica was tested by oil absorption method according to ASTM standard. Results showed that the particle size of the precipitated silica gel was decreased with increasing Na2SiO3 and SDS concentrations and Particle size of about 44nm can be achieved at 20% Na2SiO3 and 200ppm SDS. But with decreasing particle size, degree of agglomeration also increased.
Highlights
Producing of fine and uniform precipitated silica is of interest in scientific and technological point of view
Production of precipitated silica nano particles from sodium silicate solution with sulfuric acid at pH7 is according to the Eq No
The effect of two variables on the particle size of precipitated silica was studied and the results are presented in Table
Summary
Producing of fine and uniform precipitated silica is of interest in scientific and technological point of view. Concentration of reactive substances has a great effect on the particle size and size distribution of precipitated silica. According to the Bogush and Zukoski’s model [1, 4], which describes the particle growth of silica in sol precipitation, stable silica particles are formed and grown via the aggregation of primary particles that are nucleated in a supersaturated solution. The particle size and distribution change significantly according to the solvent, solution pH, and reactant concentrations, all of which affect the nucleation and aggregation of the primary particles. A multi-modal particle size distribution can be obtained by modifying the particle nucleation and growth processes via varying the reactant concentrations. Surfactants are often applied to the solprecipitation process to control the size and uniformity of silica particles. A uniform particle size originates from the molecular interaction with the surfactant provides the driving force for particle aggregation [7,8,9]
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