複雑硫化鉱の製錬 (第2報)

弱還元性雰囲気中における硫酸塩および酸化第二鉄の挙動について

抄録

Studies were made on behaviors of lead sulfate and ferric oxide in the roasting with a weakly reducing atmosphere, furthermore, behaviors of artificially produced magnetite to dilute sulfuric acid were investigated.
A reaction product of lead sulfate with the reducing gases containing CO, CO₂ and N₂ (PCO/PCO₂=1/9, 2-8% CO) at 600°C was basic lead sulfate PbO %middot; EPbSO₄ final reaction products at 650°C and 700°C were metallic lead which was formed by equations (1) and (2).
2PbSO₄+CO=PbO · PbSO₄+CO₂+SO₂…(1)
PbO · PbSO₄+3CO=2Pb+3CO₂+SO₂…(2)
The reaction velocity equation for the reaction (1) obtained by this study is
P/Mri (1-³√1-x)=Kt
K is proportional, within a range of these experiments, to P^0.84_CO, andanenergy of activation of the reaction (1) is 7.9 kcal/mol. Therefore it is considered that the velocity-controlling step in the reaction (1) is a diffusional process of the reducing gas or the reacted gaseous products through a diffusional layer between the formed PbO · PbSO₄ layer and unreacted PbSO₄.
The sarrie velocity equation is applicable for the reduction of ferric oxide to magnetite and an energy of activation of the reduction is 9. 4 kcal/mol.
Artificially produced magnetite at relatively lower temperature (500°-700°C) is very soluble in dilute sulfuric acid, for instance, 10.4% of the magnetite was dissolved with 0.4N H₂SO₄ solution. Magnetite which was formed in a reducing atmosphere containing 0.7% of SO₂ is more soluble. 31.6% of the magnetite was dissolved with the same solution and the magnetite contained 6.3% of sulfur, but iron sulfide was not detected in the magnetite by an X-ray diffraction method.