Separation of indium and other metal values in flash smelter electrostatic precipitator dust using hydrometallurgical leaching methods

Abstract

Indium is designated as a critical mineral by the U.S. Department of Energy commonly used in electronic displays, lead free solders, and photovoltaic panels. Currently, the U.S. is essentially 100% dependent on imports for its refined indium supply. Because of this, efforts to produce refined indium domestically are being pursued. This document describes efforts to improve the capability of Rio Tinto Kennecott Copper, a primary copper producer located in Utah, to produce indium. Two main categories of efforts are included: 1) improvements to the grade of indium in their concentrator’s main output stream and 2) separation of indium from other metal values in their Flash Smelter Electrostatic Precipitator Dust, as well as separation of copper from containments bismuth and arsenic, using a variety of hydrometallurgical leaching methods. Specifically, they are leaching with sulfuric acid at atmospheric pressure and in pressurized conditions, leaching with water, leaching with sulfurous acid, leaching with sodium hydroxide, and sequential leaching with a variety of lixiviants. It was determined that, due to the nature of indium deportment in the ore body, it is not feasible to increase the grade of indium in the Kennecott concentrator. Also, it was determined that of the lixiviants used, none transferred a satisfactory amount of indium to the leachate within the constraints of the conditions tested, but water did provide a separation between indium and copper, and separations between copper and both bismuth and arsenic.