Leaching and removal of arsenic with waste acids from arsenic pre-removed dusts discharged from furnaces for pyrometallurgical refining of copper

Abstract

ABSTRACT Dusts from furnaces for pyrometallurgical refining of copper (Cu) in which arsenic (As) was pre-removed through the use of vacuum carbothermal reduction methods could be used as raw materials. After treating the As pre-removed dusts through oxidative leaching using waste acids, the process of neutralizing and precipitating As and iron (Fe) in the leaching solution was investigated, as well as the precipitation and stabilization process of As and Fe residues. The results show that the leaching rate of Cu, Zn, and As from such dusts can reach 98.98%, 97.46%, and 95.22%, respectively, after leaching operation with waste acids under a liquid–solid ratio of 8:1, a leaching temperature of 80°C, an airflow rate of 300 ml/min, and a leaching time of 120 min. When the molar ratio of Fe to As (n(Fe)/n(As)) is 1.50 in the solution after advanced oxidization, and the final pH value of neutralization is 2.0, the precipitation rate of As and Cu in the residues as ferric arsenates is 93.65% and 2.2%, respectively. As and Fe are neutralized and precipitated, which allows Cu to enter the solution, while As enters the residues. After being transformed, the unstable As and Fe residues can be stockpiled as nontoxic, stable waste.