Synergistic vacuum distillation separation and recovery of zinc and lead from leaded-brass scrap

Abstract

Growing societal copper reserves have intensified the focus on sustainable recycling. The rising adoption of lead-free brass has displaced leaded brass alloys, redirecting substantial quantities to the recycling markets. Pyrometallurgy remains the dominant copper recovery method. However, it is inefficient in reclaiming critical metals from leaded brass. Vacuum metallurgy offers a transformative alternative, utilizing precise phase separation capabilities and a minimal environmental footprint to overcome these limitations. In this study, we employed the molecular interaction volume model (MIVM) to calculate the thermodynamic parameters of Zn and Pb in copper alloys. Subsequently, we plotted the saturated vapor pressure curves, separation coefficient curves, and vapor-liquid equilibrium diagrams. The results demonstrate that Zn and Pb can be efficiently separated via vacuum distillation under specific conditions, with an optimal temperature range of 1307.85–1435.15 K and a vacuum pressure of 20–39 Pa. Single-factor experiments identified the optimal conditions as 1373 K for 30 min at 20 Pa, achieving volatilization rates of 99.38 % for Zn and 95.09 % for Pb. Our findings further reveal that under these conditions, the condensation temperatures for Zn and Pb were approximately 473–541 K and 575−673 K, respectively. The condensed products exhibit high recoverability and economic value, highlighting the potential of vacuum metallurgy for sustainable metal recycling.