Determination of the Fe3+/$${\varvec{\Sigma}}$$Fe Ratio in Synthetic Lead Silicate Slags Using X-Band CW-EPR

The oxidation balance is arguably one of the most important parameters during pyrometallurgical processes. In many cases, iron is the most abundant multivalent element present in silicate slags. Within these molten oxide mixtures, the oxygen balance is dominated by the relative fractions of Fe3+ and Fe2+ present. Measuring the concentration of ferrous and ferric iron in quenched slags can provide useful information about the oxidation state of the liquid slag at the moment of freezing. These measurements are not always straightforward, especially in lead-rich slags, as present in modern secondary smelting processes. Building on previous work, this article aims towards a practical and reliable methodology for determining the Fe3+ concentration in lead-rich silicate slags using continuous wave electron paramagnetic resonance (CW-EPR). The method is demonstrated for different Fe3+/ $$\Sigma $$ Fe ratios and a basic model is proposed that relates the slag composition to the EPR spectrum, optimized for a high-lead ternary PbO–SiO2–Fe2O3 slag.