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BIOGEOCHEMICAL, HEALTH, AND ECOTOXICOLOGICAL PERSPECTIVES ON GOLD AND GOLD MINING - CHAPTER 11

Cyanide mối nguy hiểm cho thực vật và động vật từ khai thác mỏ vàng và các vấn đề nước liên quan Có độc tính cao natri xyanua (NaCN) là sử dụng ngày càng được cộng đồng khai thác mỏ quốc tế để trích xuất vàng và các kim loại quý khác thông qua việc xay xát cao cấp quặng và lọc đống quặng cấp thấp. Quá trình tập trung vàng bằng cách sử dụng cyanide được phát triển ở Scotland vào năm 1887 và được sử dụng gần như ngay lập tức trong các lĩnh vực vàng Witwatersrand của nước. | CHAPTER 11 Cyanide Hazards to Plants and Animals from Gold Mining and Related Water Issues Highly toxic sodium cyanide NaCN is used increasingly by the international mining community to extract gold and other precious metals through milling of high-grade ores and heap leaching of low-grade ores. The process to concentrate gold using cyanide was developed in Scotland in 1887 and used almost immediately in the Witwatersrand gold fields of the Republic of South Africa. Heap leaching with cyanide was proposed by the U.S. Bureau of Mines in 1969 as a means of extracting gold from low-grade ores. The gold industry adopted the technique in the 1970s soon making heap leaching the dominant technology in gold extraction Da Rosa and Lyon 1997 . The heap leach and milling processes which involve dewatering of gold-bearing ores spraying of dilute cyanide solutions on extremely large heaps of ores containing low concentrations of gold or milling of ores with the use of cyanide and subsequent recovery of the gold-cyanide complex have created a number of serious environmental problems affecting wildlife and water management. This chapter reviews the history of cyanide use in gold mining with emphasis on heap leach gold mining cyanide hazards to plants and animals water management issues associated with gold mining and proposed mitigation and research needs. 11.1 HISTORY OF CYANIDE USE IN GOLD MINING About 100 million kg cyanide CN are consumed annually in North America of which 80 is used in gold mining Eisler et al. 1999 Fields 2001 . In Canada more than 90 of the mined gold is extracted from ores with the cyanidation process which consists of leaching gold from the ore as a gold-cyanide complex and recovering the gold by precipitation. The process involves the dissolution of gold from the ore in a dilute cyanide solution and in the presence of lime and oxygen according to the following reactions Hiskey 1984 Gasparrini 1993 Korte and Coulston 1998 1 2Au 4NaCN O2 2H2O 2NaAu CN 2 .