Synthesis and characterization of silica nanoparticles from clay

• Silica content in bentonite clay was increased after thermal and acid treatments.
• Sodium silicate prepared with two different concentrations of silica rich clay.
• Three size ranges of silica nanoparticles produced at low concentrations of clay.
• Bimodal silica particles produced at high concentration of cosolvent.
• Concentration of clay and acid has direct effect on particle size.

We report a method to synthesize silica nanoparticles from bentonite clay. A series of thermal and acid treatment processes was performed on bentonite clay to lower the alumina and increase the silica content. The obtained silica rich clay was treated in two different concentrations (10 wt% and 40 wt%) with sodium hydroxide solution to form sodium silicate solutions (SSS). One type of SSS was hydrolyzed with three different concentrations (5 M, 10 M and 15 M) of nitric acid in the presence of ethanol as cosolvent while the other SSS was hydrolyzed with nitric acid in the presence of three different quantities (10 ml, 20 ml and 30 ml) of ethanol as cosolvent. A range of silica particle sizes from nanometer to micrometer was obtained by varying the contents of silica rich clay, HNO3, and ethanol. It was observed that the concentration of silica rich clay and HNO3 had a direct effect on the particle size. The increase in the quantity of ethanol from 10 ml to 20 ml produced bimodal particles of nanometer and micrometer size, which maintained at 30 ml. Inductively coupled plasma optical emission spectroscopy, atomic absorption spectroscopy, X-ray fluorescence, scanning electron microscopy and X-ray diffraction were utilized to characterize the clay, SSS and nanoparticles.

Synthesis of silica particles from bentonite clay.Figure optionsDownload as PowerPoint slide