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The destruction of cyanide in gold tailings is a crucial part of metallurgical recovery of gold.

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Many jurisdictions have strict regulations controlling the destruction of cyanide and metal cyanide in tailings prior to discharge into the environment. Additionally, the cost of treating cyanide can represent an important part of the total operating costs incurred during gold recovery. A bankable, cost-effective solution to cyanide destruction is a major consideration from the early planning stages of a gold metallurgical plant.

SGS is respected as a technological leader in the destruction of cyanide. We provide globally recognized bankable and cost-effective solutions to cyanide destruction while ensuring compliance with local regulations. SGS offers a number of different processes for cyanide destruction. Our metallurgists consider several factors before recommending the best option for your particular application:

  • Environmental regulations that specify the allowable concentration limits in the tailings
  • The unique chemical composition of the tailings from your operation
  • Detoxification techniques in relation to their ability to treat certain species
  • Reagent consumption and cost

SGS has extensive experience with the several most effective methods of cyanide destruction. Our experts work with you to select the method that is most appropriate for your operations. The advantages and limitations for our most commonly used methods are listed below. Please see the asset Cyanide Destruction for advantages and limitations of other common processes.

Alkaline Chlorination
Advantages Limitations
  • Relatively simple to operate
  • Fast kinetics
  • Strong oxidant
  • No copper catalyst required
  • Non-selective, high reagent consumption
  • Requires high pH (pH 11) to ensure rapid and complete hydrolysis of highly toxic cyanogen chloride gas
  • Ferrocyanide is not destroyed, only partially oxidized to ferricyanide
  • May leave residual chlorine in solution
Hydrogen Peroxide
Advantages Limitations
  • Relatively simple to operate
  • No production of toxic gases
  • More selective toward CN’WAD than chlorination
  • Incorporates cost-effective ferrous sulfate in the process
  • High reagent consumption
  • Requires copper in solution as a catalyst Tends to leave some residual copper in solution
  • Cyanate hydrolyzes to ammonia
  • Ferrocyanide is not destroyed, but precipitates as a base metal ferrocyanide complex
SO2
Advantages Limitations
  • Low reagent cost
  • Efficiently oxidizes CN’WAN
  • Sulfite salts may be used in the process
  • Allows for the use of zinc sulfate
  • Relatively difficult system to operate
  • Requires copper in solution as a catalyst
  • Tends to leave some residual copper in solution
  • Requires vigorous mixing and longer retention time
  • Cyanate hydrolyzes to ammonia
  • Ferrocyanide is not destroyed, but precipitates as a base metal ferrocyanide complex
  • Copper may redissolve in high chloride environment

SGS can offer expert advice in all aspects of cyanide leaching, recovery and destruction. Contact us early in your project to discuss possible solutions to the use, recovery and destruction of cyanide in your tailings to ensure that you can satisfy environmental regulations and ultimately improve your bottom line.