I. Flores-Aroni
Colorado Schoolod Mines,
United States
Keywords: PGM recovery, froth flotation, refractory smelting materials, flotation collectors, base metals extraction
Summary:
The limited availability of platinum group metals (PGMs) and the challenges in meeting the rising demand for these precious metals in recent years have underscored the need to explore ways to improve recovery, particularly during the concentration stage. In response to this, recycled materials, such as slag and furnace bricks, are being introduced into the concentration circuit. Initial observations from Sibanye-Stillwater's US PGM operations suggest that the platinum and palladium concentrations in materials from the smelting stage, specifically spent Electric Arc Furnace (EAF) and Top Blown Rotary Converter (TBRC) bricks, are significantly higher than those in the primary ores fed into the mills. This finding indicates that processing these materials separately could enhance recovery efficiency. Considering this, this research aims to improve the domestic extraction of PGMs, copper, cobalt, and nickel from refractory material, such as EAF and TBRC spent bricks. These have been found to contain higher concentrations of PGMs compared to the primary ores processed in mills due to the accumulation of PGMs and base metals on the walls of furnaces during the smelting process. The goal of this research is to enhance recovery efficiency through a physical-chemical process of froth flotation. To better understand the flotability of these materials, a series of microflotation experiments were conducted, which tested five different collectors, both individually and in combination, to identify the most effective ones for recovering PGMs and base metals. The microflotation tests were carried out in a 52 mL Partridge-Smith cell with sample sizes of no more than 1 gram. Key factors examined during these tests included froth color and size, flotability, and the content of base metals and palladium in the materials. The results showed varied responses on the flotability and recovery on both materials. However, adjusting the dosage ratio of these collectors was a key factor in increasing the recovery of palladium and base metals. These findings highlight the potential for significantly improving recovery efficiency by optimizing flotation techniques. In conclusion, this research emphasizes the value of refractory smelting material, such as EAF and TBRC spent bricks, as additional sources of PGMs and base metals. By selecting effective collectors and optimizing the flotation process (i.e. particle size, water chemistry, reagent consumption, etc.), the recovery rates of these precious metals could be significantly improved. This approach offers a more sustainable mean of meeting the growing demand for PGMs, copper, cobalt, and nickel.