[2M18-20] Dissolution/Preciptation

5:40 PM - 5:55 PM JST(8:40 AM - 8:55 AM UTC)

[2M20] Effects of Temperature and Inner Pores of Solid Phase on the Precipitation of Supersaturated Silicic Acid in the Presence of Aluminum

*Yutaro Kusaka¹, Taiji Chida¹, Tsugumi Seki¹, Yuichi Niibori¹ (1. Tohoku Univ.)

Keywords:

High-level radioactive waste,Supersaturated silicic acid,Aluminum,Precipitation,Temperature dependence,Solid phase particle size,Geological disposal,Colloid migration,Internal pores,Natural barriers

In geological disposal safety assessments, silicic acid precipitation in varying pH fields around disposal sites can delay radionuclide migration by blocking groundwater flow paths. This study examined the effects of temperature and solid phase internal pores on silicic acid precipitation in the presence of Al. Using porous amorphous silica with varying particle sizes, we set the initial silicic acid concentration at 8 mM and Al ion concentration at 0.14 mM, investigating temperature dependence from 15 to 40°C. Results showed increased precipitation and rate constants at higher temperatures, with Al potentially inhibiting surface precipitation. Larger particle sizes reduced apparent precipitation rate constants, indicating limited internal pore utilization. Overall, precipitation rate constants remained around 10^-10 m/s, suggesting effective flow path blockage even with Al presence.