Effect of Slag Composition on the Distribution Behavior of Pb between FetO-SiO2 (-CaO, Al2O3) Slag and Molten Copper

摘要

The distribution behavior of lead between molten copper and FetO-SiO2 (-CaO, Al2O3) slags was investigated at 1473 K and p(O2)=10-10 atm in view of the reaction mechanism of lead dissolution into the slag. Furthermore, the lead capacity of the slag was estimated from the experimental results. The distribution ratio of lead (LPb) decreases with increasing amount of CaO (~6wt%) irrespective of Fe/SiO2 ratio (1.4~1.7). However, the addition of alumina in the slag with Fe/SiO2=1.5 linearly decreases the LPb, whereas there is a minimum value at about 4wt%Al2O3 at Fe/SiO2=1.3. The log LPb continuously decreases with increasing Fe/SiO2 ratio and furthermore, the addition of Al2O3 (5~15wt%) into the silica saturated iron silicate slag (Fe/SiO2 < 1.0) shows the highest Pb distribution ratio. This is mainly due to a decrease in the activity of FeO even at silica saturation condition. The log LPb linearly decreases by increasing the log (Fe3+/Fe2+) values. The Pb distribution ratio increases with increasing content of Cu2O in the slag and the excess free energy of PbO decreases with increasing content of Cu2O. However, in viewpoint of copper loss into the slag, the silica saturated system containing small amounts of alumina is strongly recommended to stabilize PbO in slag phase at low content of Cu2O. The 'lead capacity' was defined in the present study and it shows a linear correlation with the activity of FeO in a logarithmic scale, indicating that the concept of lead capacity is a good measure of absorption ability of lead of iron silicate slags and the activity of FeO can be a good basicity index in the iron silicate slag.