A crystallization method with significant industrial potential for the separation and enrichment of silver from crude lead

Abstract

Approximately 60 % of silver is produced through lead smelting systems, where silver is mainly concentrated in crude lead. Silver in crude lead is usually separated and enriched during lead refining processes. However, these methods are disadvantageous owing to their lengthy processes and high energy consumption. In this study, a novel, green, and efficient process for silver separation and enrichment via crystallization was developed. Theoretical analysis showed that the equilibrium distribution coefficient (K0) is less than 1. At 327.50 °C, silver was completely separated in the solid phase, while at 304.10 °C, silver was enriched to 2.5 wt% in the liquid phase. Experimental studies showed that, through crystallization, the silver content in low-silver lead was reduced to 0.0047 wt%, achieving a separation rate of 95.41 %. Concurrently, the silver content in rich-silver lead was enriched to 0.5690 wt% with an enrichment ratio of 7.10, consuming 185 kW·h/t of electricity. The silver content in low-silver lead was found to be lower than the Standard Specification for Refined lead, and the rich-silver lead was used for silver refining. Compared to existing processes, this method can efficiently enrich silver from crude lead in a single step. This study provides a sustainable method for silver recovery from crude Pb, offering advantages such as a short process duration, cleanliness, and ease of industrial implementation and promotion. This study offers important theoretical and technological guidance for the extraction of silver from crude lead, ensuring a secure supply of silver for major national projects.