Effect of Me2+(Me2+=Ni2+, Zn2+) on Precipitation Reaction in Fe(NO3)3-Me(NO3)2-HNO3 Solutions
1995 Volume 103 Issue 1196 Pages 351-356
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1995 Volume 103 Issue 1196 Pages 351-356
Effect of Me2+(Me2+=Ni2+, Zn2+) on the formation of precipitation in the Fe(NO3)3-Me(NO3)2-HNO3 solutions was determined on the basis of the potentiometric titration curve. By comparison of the titration curves obtained from Fe(NO3)3-Me(NO3)2 solutions with those of Me(NO3)2 solutions, it was found that the pH values of the plateau in the titration curve and its variation against the amount of added alkali depended on the nature of the respective cation. In the Fe(NO3)3-Ni(NO3)2 solution system, Ni2+ only reacted with Fe3+ untill the molar ratio of Ni2+ to Fe3+ in the precipitates becomes 2:1, but the reaction between Ni2+ and Ni2+ preferentially proceeded to produce Ni(OH)2 when the amount of Ni2+ in the precipitates increased further. In the Fe(NO3)3-Zn(NO3)2 solution system, Zn2+ reacted with Fe3+ to produce amorphous precipitate but the reaction between Zn2+ and Zn2+ simultaneously occurred to produce Zn5(NO3)2(OH)8⋅2H2O irrespective to the amount of Zn2+ in the precipitates. These precipitates were aged at 25 and 75°C. The precipitates obtained at 25°C were heat-treated at 500°C for 2h. The amount of crystalline McFe2O4 in these samples varied between the Fe(NO3)3-Ni(NO3)2 and the Fe(NO3)3-Zn(NO3)2 solution systems. By the aging and heating treatments, only Ni(OH)2 or NiO crystallized in the former system, whereas both ZnFe2O4 and ZnO crystallized in the latter system when the amounts of Me2+ in the precipitates increased.
