1. CYANIDE USE IN GOLD PROCESSING;
FEAR, MISCONCEPTION, TRUTH AND ALTERNATIVES
CAMP
Corby G. Anderson, Ph. D., The Center for Advanced Mineral and Metallurgical Processing
Butte, Montana USA
Introduction
The social license for the use of cyanide in gold processing in Montana in the United States is limited by law. One response has been the "International Cyanide Management Code For the Manufacture, Transport, and Use of Cyanide In the Production of Gold" (Code) developed by a multi-stakeholder Steering Committee under the guidance of the United Nations Environmental Program (UNEP) and the then - International Council on Metals and the Environment (ICME). The Code is an industry voluntary program for gold mining companies. It focuses exclusively on the safe management of cyanide and cyanidation mill tailings and leach solutions. Companies that adopt the code must have their mining operations that use cyanide to recover gold audited by an independent third party to determine the status of Code implementation. Those operations that meet the Code requirements can be certified. A unique trademark symbol can then be utilized by the certified operation. Audit results are made public to inform stakeholders of the status of cyanide management practices at the certified operation. The objective of the Code is to improve the management of cyanide used in gold mining and assist in the protection of human health and the reduction of environmental impacts.
Abstract
In many parts of the world including Montana in the United States, the ‘Social License’ to utilize established technologies has come into question. In the case of cyanide use in gold heap leaching, this has become a major focal point for our profession. Currently in the State of Montana, the use of cyanide for gold ores using open pit heap leach technology has been outlawed through the public initiative process. This has largely been predicated on politics and perception rather than from a technical basis. Hence, the larger question looming over process engineering is how to utilize technology for the betterment of our society while addressing barriers of misperception, fear and political agendas. This presentation illustrates the response by the process industries in the form of the International Cyanide Code and alkaline sulfide hydrometallurgy, a cyanide alternative for gold processing.
Alkaline Sulfide Hydrometallurgy
Cyanide Alternative Alkaline
Sulfide Gold Processing
Gold Leaching
2Au + S S2- 2AuS- + 2S2-
Gold Recovery
Ion exchange, solvent extraction, electro winning, cementation.
Waste Solution Treatment
2 O2 + Na2S  Na2SO4
3.5 O NaOH + Na2S2  2 Na2SO H2O
Regeneration and By-Product Formation by Electrodialysis
2NH4OH + Na2SO4 ⇄ 2NaOH + (NH4)2SO4
Thus gold is recovered with alkaline sulfide hydrometallurgy. From waste solutions, caustic is regenerated for the process while by-product ammonium sulfate fertilizer is created.
Summary
This poster has illustrated the established technology of gold heap leaching utilizing cyanide. In some parts of the world, fear, misperception and political agendas have limited the use of this technology. This poster briefly illustrates strategies industry has used to re-establish the social license for this gold processing. This includes the International Cyanide Management Code and the development of cyanide alternatives such as alkaline sulfide hydrometallurgy.
Contact
Corby G. Anderson, Ph.D., Director
Center for Advanced Mineral and Metallurgical Processing
Montana Tech, 1300 West Park Street
Room 221 ELC Building
Butte, Montana USA 59701
Telephone: ; Facsimile:
Web:
Eh – pH Diagrams for the Cyanide Alternative Alkaline Sulfide Gold Processing System.
Cyanide Gold Heap Leach Process