Kinetics and Mechanisms of Microscale Interfacial Reactions and Structural Evolution during ZnO Dissolution in Multicomponent Oxide Melts

The dissolution mechanism of ZnO in multicomponent oxide melts is pivotal for the co-smelting of primary ores with Zn-bearing secondary resources, as well as for the production and processing of ZnO-containing glasses and ceramics. This study integrated kinetic modeling, in situ interfacial reaction experiments, and melt structure evolution analysis to elucidate the dissolution mechanism of ZnO and assess the impacts of B and Cu on this mechanism. The apparent dissolution rate of ZnO is governed by the interplay of interfacial reactions, precipitation of Zn-bearing solids, and melt-structure evolution. B 2 O 3 expands the liquid phase field and significantly reduces the melting temperature (∼30 °C per 1 wt %). Initially, a Pb/B-rich melt pathway forms and thins the product layer from ∼154 to ∼25 μm. B 2 O 3 depolymerizes the melt, inhibits spinel growth, and accelerates dissolution. In contrast, Cu 2 O generates a dense Cu-rich layer that initially hinders dissolution. As this barrier diminishes, melt depolymerization and spinel growth suppression further accelerate dissolution. Over time, spinel precipitation results in a slight reduction in Zn content in the melt. This study also highlights the amphoteric role of ZnO. With increasing Zn content in the melt, ZnO can switch between acting as a network modifier or acting as a network former. This study lays a theoretical foundation for bath smelting of complex high-zinc feeds and provides a new methodological framework for probing melting mechanisms in multicomponent oxide melts.