| Oxidation reaction behaviors of Cu(OH)₂ and Fe(OH)₂ coprecipitates by oxygen in aqueous solution were investigated in relation to the variation of initial Cu/Fe ratio, R (2(OH)-/SO₄^(2-)) value and temperature. When increase the Cu/Fe ㏖ ratio, initial pH decreased and final pH increased. Oxidation behavior monitored by ORP (Oxidation Reduction Potential) showed 2 distinct stages. The 1st stage was due to the oxidation from Fe(OH)₂ to Fe₃O₄, and the 2nd stage resulted from the transformation Cu(OH)₂ to CuO. In any conditions, temperatures ranging 50 to 80℃ and R value 1.0 to 1.4, Cu-ferrite did not formed. The final oxidation product was Fe₃O₄ covered with CuO. At Temp. 150℃, Cu/Fe= 0.5 and R=1.1, reaction product was CuO and Cu-ferrite. The Composition of Cu-ferrite was Cu_(0.65)Fe_(2.35)O₄ and its saturation magnetization was 28 emu/g. |
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