EMISSION MOSSBAUER STUDIES OF CO-57(2-119(5+) ADSORBED ON GAMMA-FE2O3AND NIFE2O4 SURFACES() AND SB)

Surface chemical states of Co-57(2+) and Sb-119(5+) ions adsorbed on g amma-Fe2O3 and NiFe2O4 were studied in the presence of the aqueous pha se using the magnetic interaction between the substrates and Fe-57(2+) or Sn-119(4+) arising from the adsorbed species. Two chemical forms w ere observed for the Co-57(2+) adsorbed on gamma-Fe2O3; one giving a p eak in the high-field region and another giving a broad distribution i n the lower fields, which were attributed to Co-57(2+) at surface B si tes of the spinel structure of gamma-Fe2O3 and Co-57(2+) species weakl y bonded to the substrate, respectively. In case of the NiFe2O4 substr ate, the latter species was dominant and was converted to the former b y heating. Most of the Sb-119(5+) ions adsorbed on the gamma-Fe2O3 and NiFe2O4 particles were found to have a certain magnetic interaction w ith the magnetically ordered ions of the substrates.