A New Approach to Accessing Gold in Arsenopyrite

"Arsenic released from the lithosphere by mining and metallurgical activities is a growing global environmental concern. Dundee sustainable technologies (“DST”) has developed a processing technology to sequester arsenic by means of vitrification. This method can effectively sequester arsenic trioxide without the need to oxidize from As (III) to As (V). Arsenic oxide is incorporated within a silica glass matrix that is stable as per the Toxicity Leaching Characteristic Procedure (“TCLP”) or EPA Method 1311. In this paper, the conventional treatment of arsenopyrite, commonly referred to as “two-stage roasting”, is discussed along with the options traditionally available for the remediation of the arsenic trioxide by-product. The drawbacks limiting the adoption of this processing flowsheet are discussed and a new processing route is presented for the treatment of arsenopyrite. This new flowsheet outputs an auriferous aluminosilicate highly amenable to gold extraction (> 96%) while eliminating the sulfur dioxide production associated with the second-stage roasting of pyrrhotite and ultimately uses vitrification as a definitive sequestration solution to arsenic trioxide.INTRODUCTION Faced with the depletion of conventional gold ores, the gold industry has witnessed a trend towards the exploitation of arsenical deposits. Arsenic is a naturally occurring metalloid often found in mineralogical association with gold. Many northern Canadian regions, from the Northwest Territories to Northern Manitoba, Northern Ontario and the Abitibi region are facing significant arsenic challenges. Projects are deemed uneconomic or prevented from going into operations due to the costs associated with handling arsenic material and there are penalties imposed to complex concentrates by smelters. In addition, Canadian mining operations have left an environmental legacy of gold tailings with grades typically of up to 9 grams per tonne with no processing solution as they also contain significant arsenic contamination at grades of up to 20%. Table 1 presents a list of Canadian deposits known to contain arsenic."