Analysis of Adsorption Mechanism of Cobalt on the Crud by Emission Mossbauer Spectroscopy

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Effect of pretreatment with Mg^<2+>, Ca^<2+>, Sr^<2+>, or Zn^<2+> ions on adsorption of cobalt ions on gamma-Fe_2O_3 and Fe_3O_4 crud was studied at 102ﾟC in a vibrating-type autoclave which was purchased by this scientific research. Absorption state of cobalt on curd was also investigated by emission Mossbauer spectroscopy and the following conclusions were derived : (1) When Mg^<2+> ions having high octahedral site preference in bulk sample were adsorbed on crud prior to cobalt ions adsorption, Mg^<2+> ions were adsorbed on octahedral site on crud surface, and reaction of crud with cobalt ions having high octagedral site preference was retarded. (2) When Sr^<2+> or Ca^<2+> ions having high tetrahedral site preference in bulk were adsorbed on crud prior to cobalt ions adsorption, cobalt ions were adsorbed only on octahedral sites on crud. (3) When Zn^<2+> ions having the highest tetrahedral site preference in bulk are adsorbed on crud prior to cobalt ions adsorption, it is expected that Zn^<2+> ions are adsorbed on tetrahedral sites on crud and cobalt ferrite is formed at the highest level. However, the experimental result pretreated with Zn^<2+> ions was the same as that without pretreatment. This fact can be explained by small distribuion ratio of Zn^<2+> ions between crud and solution.