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

Qualifies for CMS

Qualifies for Certification

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:
  • 3 hours

Course Summary


This is the first course in the six-course Cyanide Management in Mining series. This course assumes knowledge of environmental engineering or mineral processing.

The chemistry of cyanide solutions is unique with its ability to dissolve gold and silver. Cyanide is highly selective with respect to combining with gold and silver; in solution it forms complexes with other metals, such as mercury, zinc, copper, iron, and nickel. The formation of these other metal complexes partially account for the consumption of cyanide in gold extraction circuits and generate solutions that can be difficult to treat and analyze.

Although chemical replacements for cyanide have been investigated for decades, it remains the exclusive extraction reagent or lixiviant of choice for over 90% of the gold recovered. This is due to a combination of availability, effectiveness, economics, and an ability to use and manage cyanide with acceptable risk to humans and the environment.

Cyanide Management in Mining Series

The Cyanide Management in Mining course series provides the learner with the necessary background for developing a cyanide management plan that meets the unique requirements of each operating mine. Due to 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 series consists of the following courses.

  • 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

Course Content

This course consists of 5 viewing sessions of 30–45 minutes each with supporting figures, references, and multiple choice course reviews. Course duration is equivalent to approximately 3 hours of viewing content.

Learning Outcomes

  • Discuss gold dissolution and recovery from cyanide solution.
  • Discuss the solution chemistry of cyanide and metal complexes.
  • Recognize that the chemistry of cyanide and metal complexes must be taken into account when developing a cyanide management plan.

Recommended Background

  • A degree or diploma in environmental engineering or mineral processing.
  • Experience using 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.