Lead removal from brass scrap by fluorine-free compound separation
Taking complexity of process technology, economical and environmental reasons as well as time impact into account, removal of lead based on intermetallics formation and subsequent separation proves to be the most balanced approach. The hitherto used aggregation agent sodium fluoride does serve as a suitable additive in European countries. Therefore, fluorine-free compound separation is evaluated. Thermochemical modelling of Cu-Zn-Pb-Ca-O system identifies ideal process conditions, namely, charging calcium with an amount of 1.5 wt-% at 930°C. Experiments carried out at stated parameters reveal comprehensive formation of Pb-Ca compounds, chemically similar to the stoichiometric intermetallic phase Ca5Pb3. Thus, the results prove the technological feasibility of lead removal from molten brass scrap using fluorine-free compound separation.