Adsorption of Co2+ and Zn2+ Ions on Hydrous Fe(III), Sn(IV), and Fe(III)/Sn(IV) Oxides.

Thermal analysis has shown that contrary to the case of Zn2+, considerable amounts of water enter in HFO (hydrous ferric oxide), HSO (hydrous stannic oxide), and HMO (hydrous mixed oxide) when Co2+ is adsorbed. A large amount of Co2+ and Zn2+ in all the oxides cannot participate in isotopic exchange, seemingly because of being trapped inside the micropores, a fact hindering oxide capacity determination by isotopic dilution. The % adsorption-pH curves for tracer and 10(-3) M transition metal chloride solutions show a general preference to Zn2+ over Co2+ by all the oxides, in agreement with thermal analysis data.