Acidic Dispersion of Fused SiO2 Particles

The acidic dispersion behavior of fused SiO2 particles was investigated and compared to two fumed SiO2 particles. In contrast, the fused SiO2 particles have a larger particle size, broader size distribution, and lower surface area. Fluoride adsorption was used to study surface activity, and acid–base titration was used to study surface charge in 10−1 to 10−3 M NaCl solutions over the pH range of 2–7.5. Each of the three SiO2 particles exhibited similar titration behavior, with the fused SiO2 particles displaying a higher intrinsic pKa2 value of 7.0 as compared to 6.8 and 6.1 for the two fumed SiO2 particles. Rheological experiments designed to test for dispersion and agglomeration/ gellation at 3 and 6 wt% solids loading in 10−3 M NaCl solutions adjusted to pH 2, 4, and 6 showed the fused SiO2 particles to be more stable in suspension, exhibiting lower viscosity results for all test conditions. Results show that the fused SiO2 particles tested in this report display superior dispersion properties as compared to conventional fumed SiO2 particles for slurry applications under acidic conditions.