The vanadium, niobium, antimony distribution between Na
2O-SiO
2 melts and carbon-saturated iron were measured in the temperatures range from 1 200°C to 1 350°C. Those for vanadium and niobium increased with increasing the Na
2O content in melts. Their temperature dependencies for the typical basic composition are expressed as follows;log(%V)/[%V]=2410/
T+0.187, log(%Nb)/[%Nb]=2360/
T+1.34
The predominant species of vanadium under these conditions changed from V
2+ to V
5+ with increasing the Na
2O content, while those for niobium were Nb
4+ and Nb
5+.
The distribution of antimony decreased with increasing the Na
2O content up to 57 mol%, beyond which it decreased. Antimony species changed from Sb
2+ to Sb
4+ as melts became more basic. Since the distribution ratio is too small in this case, it would be impossible to remove antimony from carbon-saturated iron by the soda ash treatment.
The activity coefficient of SbO
1.5 in Na
2O-SiO
2 melts was calculated by measuring the activity coefficient of antimony in carbon-saturated iron in equilibrium with molten Cu-Sb alloys, which was 0.45 at 1 200°C.
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