The kinetic exchange of alkali ions, from hydroxide or hydroxide/chloride solutions, for H+ in the hydrous oxide was measured by means of titration. At an ionic strength of more than 0.01M (table 127), the rate was controlled by the interdiffusion of the alkali ion and H+ within the oxide. The co-ions seemed to be sorbed to a certain extent, and their effect upon the interdiffusion coefficients appeared to be related to the strength of alkali-OH- interactions near to the pore entrances. The replacement of OH- by Cl- within the oxide led to an enhancement of the exchange rate for Li+ and Na+; especially the former. Essentially no change was observed in the case of K+.
N.Z.Misak, H.F.Ghoneimy, E.I.Shabana, S.S.Shafik: Solid State Ionics, 1991, 48[1-2], 71-7
Table 127
Interdiffusion of Alkali Ions in SnO2
Solution | Ion | D (cm2/s) |
0.01M OH- | Li+ | 2.80 x 10-8 |
0.01M OH- | Na+ | 3.02 x 10-8 |
0.01M OH- | K+ | 3.55 x 10-8 |
0.1M OH- | Li+ | 2.50 x 10-8 |
0.1M OH- | Na+ | 2.60 x 10-8 |
0.01M OH-/0.01M Cl- | Li+ | 3.33 x 10-8 |
0.01M OH-/0.01M Cl- | Na+ | 3.64 x 10-8 |
0.01M OH-/0.01M Cl- | K+ | 3.34 x 10-8 |
0.01M OH-/0.09M Cl- | Li+ | 7.22 x 10-8 |
0.01M OH-/0.09M Cl- | Na+ | 4.66 x 10-8 |
0.01M OH-/0.09M Cl- | K+ | 3.64 x 10-8 |