The reduction of zinc from slags by an iron-carbon melt

Abstract

An experimental investigation was undertaken to study the mechanism of reduction of zinc from slags in the presence of a carbon-saturated iron melt. Batch tests were performed at 1400 °C, and the variation of the zinc and iron concentration in the slag during reduction was determined by sampling the slag at intervals during the test. In graphite crucibles, zinc in slags containing iron was reduced faster than zinc in iron-free slags, both when an iron bath was present and when it was absent. Zinc was reduced faster from slags containing iron when an iron bath was present than when an iron bath was absent. The dominant mechanism of reduction of zinc from slags containing iron appears to be the reaction of Zn2+ ions with Fe2+ ions to form zinc vapor and Fe3+ ions. When an iron bath is present, the Fe3+ ions are reduced back to Fe2+ predominantly by reaction with iron from the bath. Mass transfer of Fe3+ ions in the slag appears to be the rate-controlling step. Reduction of iron from slag by carbon occurred in parallel with the reduction of zinc, and whether there was a net increase or decrease of iron in the slag depended on the relative rates of production and consumption of iron. Lead and copper in the slag were reduced to low levels. The lead volatilized and the copper dissolved in the alloy.