Cyanide Management in Mining - 1: Chemistry of Free and Complexed Cyanide
Cyanide Management in Mining - 1: Chemistry of Free and Complexed Cyanide

Cyanide Management in Mining - 1: Chemistry of Free and Complexed Cyanide

Areas of Study: Environment and Community

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The Cyanide Management in Mining courses attempt to provide the user with the background for development of a cyanide management plan that meets the unique requirements of each operating mine. This course, the first in a series of six, discusses the unique chemistry of cyanide solutions in the context of gold and silver extraction

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  • Audience Level:
  • Professional
  • Enrollment:
  • Required
  • Duration:
  • 4 hours

Course Summary


The cyanidation process for the extraction of gold and silver from ore has been employed since 1898 when it was first used in New Zealand and Africa and soon after in the United States. It is a very efficient process capable of extracting gold in amounts of less than one percent of an ounce from a ton of rock with over 90% efficiency.

Because of the environmental risks, a cyanide management plan is of critical importance to a mining operation. The lack of such a plan, in some cases, has contributed to adverse environmental incidents involving cyanide. The United Nations Environment Programme (UNEP) is developing an international code for the management of cyanide. Implementation and adherence to this code, augmented by experienced scientific and engineering judgment, will help reduce both the number and severity of environmental incidents involving cyanide.

The "Cyanide Management in Mining" courses attempt to provide the user with the necessary background for development of a cyanide management plan that meets the unique requirements of each operating mine. The full complement of courses in the series includes:

  • Chemistry of Free and Complexed Cyanide
  • Analysis of Cyanides
  • Geochemical Properties and Environmental Fate of Cyanide
  • Toxicity and Environmental Properties of Cyanide
  • Water Management and Discharge Strategies
  • Treatment Technologies for Cyanide and Related Compounds
"Chemistry of Free and Complexed Cyanide" is the first in the series of six courses. The chemistry of cyanide solutions is unique, which is responsible for its ability to dissolve gold and silver. Although cyanide is highly selective with respect to combining with gold and silver, in solution it nonetheless forms complexes with other metals, such as mercury, zinc, copper, iron and nickel. It is the formation of these other metal complexes that not only partially accounts for the consumption of cyanide in gold extraction circuits but also generates solutions that can be difficult to treat and analyze.

This course comprises six viewing sessions, each of 30 - 60 minutes duration, plus supporting figures, tables and references, and an interactive review that confirms achievement of the learning objectives.

Learning Outcomes

  • Discuss gold dissolution and recovery from cyanide solution.
  • Discuss the solution chemistry of cyanide and metal complexes.
  • Apply the knowledge gained to development of a cyanide management plan.

Recommended Background

  • A degree or diploma in environmental engineering or mineral processing.
  • Experience of gold or silver extraction with cyanide.

Dr. Terry Mudder

Dr. Mudder has over three decades of experience in the investigation of the analysis, chemistry, fate, monitoring, toxicity, and treatment of cyanide- and metals-containing wastes, and is considered the leading international expert on environmental issues related to cyanide in mining.

In 2000, he was one of the original participants invited to Paris to formally discuss the creation of an international code for the management of cyanide in the gold mining industry sponsored by the United Nations Environmental Program. Later he served as the technical advisor to the International Cyanide Management Institute (ICMI).

Dr. Mudder has been instrumental in developing and applying innovative chemical, physical, and biological treatment processes, for which he has received patents as well as national and international awards, including the prestigious Philip Morgan Medal of the Water Environment Federation. In 2013, he was inducted into the International Mining Technology Hall of Fame for his biotechnology and environmental engineering contributions to the mining industry over the past three decades.

For twenty years, he co-owned TIMES Limited with his wife Dr. Karen Hagelstein, an environmental science and engineering consulting firm based out of Wyoming, USA. Since 2014 he has been consulting on a sole proprietor basis. He was formally a partner, office manager, and corporate consultant for SRK Consulting, an international mining consulting firm. Prior to consulting, he served as Chief Environmental Engineer and Chief Research Chemist at the Homestake Mine in South Dakota, USA, where he along with James Whitlock developed the first full-scale process for the microbial degradation of cyanide in mining wastewater.

Dr. Mudder has served as adjunct professor, thesis advisor, and quest lecturer at several colleges and universities in Australia, Canada, and the United States. He has received the prestigious Guy March Medal from his Alma Mata, the South Dakota School of Mines and Technology, as an outstanding alumnus. He has also served as technical advisor to aboriginal groups, various industries, international governments, and NGOs including the World Bank, the International Finance Corporation, and the United Nations Environmental Program (UNEP).

He has worked on scores of mining projects, authored nearly one hundred publications, and been involved with numerous short courses on acid mine drainage, rehabilitation, and cyanide. As a leading expert on cyanide in mining in the world, he has co-authored many manuals, pamphlets, and books, including the CDs entitled The Chemistry and Treatment of Cyanidation Wastewaters, The Cyanide Monograph, and The Cyanide Compendium.

Dr. Mudder holds B.S. and M.S. degrees in Chemistry, and a Ph.D. in Environmental Science and Engineering.

Mike Botz M.S., P.E.

Mr. Mike Botz is president and owner of the consultancy Elbow Creek Engineering, Inc. and is a registered professional chemical engineer. Mr. Botz holds a BS degree in Chemical Engineering from Montana State University and an MS degree in Chemical Engineering from Purdue University. As a Senior Process Engineer, Mr. Botz has over ten years of experience related to the evaluation, testing, design, cost estimating, construction, commissioning and troubleshooting of industrial water treatment plants. In addition, Mr. Botz is also highly experienced with industrial gas cleaning systems for removing chemical contaminants and particulate matter. Projects completed by Mr. Botz have spanned North America, Latin America, Europe, Australia, Africa and Asia and have ranged in scope from conceptual evaluations through pilot testing, full-scale facility construction and plant commissioning. In addition to industrial project work, Mr. Botz has provided course instruction to academic, government and industry groups, and has presented research findings at numerous industry professional societies. Mr. Botz is active in the Society for Mining, Metallurgy and Exploration (SME), the American Water Works Association (AWWA) and the American Institute of Chemical Engineers (AIChE) through presenting papers and chairing technical sessions. Mr. Botz has authored and co-authored numerous publications in regard to the management and treatment of industrial waters and gases. Mr. Botz was also co-author of the books The Cyanide Monograph and the Chemistry and Treatment of Cyanidation Wastes, both published through Mining Journal Books Limited in London.