An innovative green process for separating and enriching tellurium from lead anode slime via vacuum gasification

Abstract

Lead anode slime, which is produced by electrolytic refining of refined Pb, is a significant source of the rare metal Te. However, traditional methods for treating lead anode slime are characterized by complex processes, hazardous waste discharge, high energy consumption, repeated reduction and oxidation, and inefficient separation of Te. Therefore, a novel, green, and efficient vacuum gasification process for Te separation and enrichment was developed in this study. The optimal gasification temperature and time of Te volatilization were investigated using two-step, high-temperature and low-temperature vacuum distillation experiments; the system pressure was maintained at 5–15 Pa for both steps. Te (96.07%) in lead anode slime was separated using high-temperature vacuum gasification at 1173 K for 60 min and low-temperature vacuum gasification at 723 K for 45 min, yielding Te-rich volatiles with a 4.80% tellurium content. Te was enriched more than 16 times. Te existed as Te and TeO2 in the tellurium-rich volatiles, making the volatiles an excellent raw material for further tellurium purification. This two-step vacuum gasification process provides theoretical guidance for effective and sustainable recovery of Te from lead anode slime with no waste gas or water, which meets the need for cleaner production methods in the metallurgical industry.