Abstract
The ε-Keggin [AlO4Al12(OH)24(H2O)12](7+) ion (AlAl12(7+)) is a metastable precursor in the formation of aluminum oxyhydroxide solids. It also serves as a useful model for the chemistry of aluminous mineral surfaces. Herein we calculate the enthalpies of formation for this aqueous ion and its heterometal-substituted forms, GaAl12(7+) and GeAl12(8+), using solution calorimetry. Rather than measuring the enthalpies of the MAl12(7/8+) ions directly from solution hydrolysis, we measured the metathesis reaction of the crystallized forms with barium chloride creating an aqueous aluminum solution monospecific in MAl12(7/8+). Then, the contributions to the heat of formation from the crystallized forms were subtracted using referenced states. When comparing the aqueous AlAl12(7+) ion to solid aluminum (oxy)-hydroxide phases, we found that this ion lies closer in energy to solid phases than to aqueous aluminum monomers, thus explaining its role as a precursor to amorphous aluminum hydroxide phases.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
