Thorium interaction with the silanol group, water, and nitrate in the pores of silica gel

• Published in: Journal of colloid science 1963-01, Vol.18 (9), p.878-885
• Main Authors: Stanton, Jimmy, Maatman, Russell W
• Format: Article
• Language: English
• ISSN: 0095-8522
• DOI: 10.1016/0095-8522(63)90080-1

Solvation of Th +4 is observed by measuring the exclusion of Th(C1O 4) 4 from 50% of the pore volume of a high surface area silica gel under conditions of no cation exchange. Competition between Th +4 ions for water molecules increases as the concentration is increased from 0 to 0.4 M. Enough water of hydration is removed from Th +4 hydrate by HC1O 4 to increase the pore volume availability to 100% in 8 M HC1O 4. If HNO 3 replaces HC1O 4 at 6–8 M acid, the size of the thorium species increases markedly, presumably owing to Th +4-NO 3 − interaction. If, however, HNO 3 replaces HC1O 4 at 1.5–2.7 M acid, any Th +4-NO 3 − interaction merely replaces Th +4-H 2O interaction and a size change is not observed. The thermodynamic values for the exchange Th +4 + 4 SiOH ⇌ Th(OSi) 4 + 4 H + are: ΔF 0 298 = 8.3 kcal., ΔH 0 = 11.0 kcal., ΔS 0 298 = 9.1 e.u.