ADSORPTION OF CO2+ AND ZN2+ IONS ON HYDROUS FE(III), SN(IV) AND MIXEDFE(III) SN(IV) OXIDES .1. CHARACTERISTICS OF THE HYDROUS OXIDES, APPARENT CAPACITY AND SOME EQUILIBRIA MEASUREMENTS/

Hydrous ferric oxide (HFO), stannic oxide (HSO) and mixed ferric/stann ic oxide (HMO), obtained by precipitation with ammonia from metal chlo ride solutions, were all found to be microporous. Analysis (X-ray, inf ra-red, thermal) has shown that HFO and HMO are amorphous, whereas HSO is microcrystalline. It also showed that all the samples are oxides c ontaining adsorbed H2O molecules and surface OH groups. In addition, i t revealed that HMO is not a simple mixture of HFO and HSO, a conclusi on which was also supported by the data on porous texture, intrinsic s urface ionization constants, pH(PZC) and apparent capacity. For all th e oxides, the apparent Zn2+ capacity is generally higher than the Co2 capacity, in agreement with a stronger interaction of Zn2+ with O2- o r OH- On the surface. Equilibria measurements point to the adsorption of both Co2+ and Zn2+ on all oxides with the release of two protons.