1 research outputs found
Theoretical Study of p<i>K</i><sub>a</sub> Values for Trivalent Rare-Earth Metal Cations in Aqueous Solution
Molecular
acidity of trivalent rare-earth metal cations in aqueous
solution is an important factor dedicated to the efficiency of their
extraction and separation processes. In this work, the aqueous acidity
of these metal ions has been quantitatively investigated using a few
theoretical approaches. Our computational results expressed in terms
of p<i>K</i><sub>a</sub> values agree well with the tetrad
effect of trivalent rare-earth ions extensively reported in the extraction
and separation of these elements. Strong linear relationships have
been observed between the acidity and quantum electronic descriptors
such as the molecular electrostatic potential on the acidic nucleus
and the sum of the valence natural atomic orbitals energies of the
dissociating proton. Making use of the predicted p<i>K</i><sub>a</sub> values, we have also predicted the major ionic forms
of these species in the aqueous environment with different pH values,
which can be employed to rationalize the behavior difference of different
rare-earth metal cations during the extraction process. Our present
results should provide needed insights not only for the qualitatively
understanding about the extraction and separation between yttrium
and lanthanide elements but also for the prediction of novel and more
efficient rare-earth metal extractants in the future