Advanced Mercury Removal from Gold Leachate Solutions Prior to Gold and Silver Extraction: A Field Study from an Active Gold Mine in Peru

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• 作者：Matthew M. Matlock ; Brock S. Howerton ; Mike A. Van Aelstyn ; Fredrik L. Nordstrom ; and David A. Atwood
• 刊名：Environmental Science & Technology
• 出版年：2002
• 出版时间：April 1, 2002
• 年：2002
• 卷：36
• 期：7
• 页码：1636 - 1639
• 全文大小：64K
• 年卷期：v.36,no.7(April 1, 2002)
• ISSN：1520-5851

文摘

Mercury contamination in the Gold-Cyanide Process(GCP) is a serious health and environmental problem.Following the heap leaching of gold and silver ores withNaCN solutions, portions of the mercury-cyano complexesoften adhere to the activated carbon (AC) used toextract the gold. During the electrowinning and retortingsteps, mercury can be (and often is) emitted to the air as avapor. This poses a severe health hazard to plant workersand the local environment. Additional concerns relateto the safety of workers when handling the mercury-laden AC. Currently, mercury treatment from the heap leachsolution is nonexistent. This is due to the fact thatchelating ligands which can effectively work under theadverse pH conditions (as present in the heap leachatesolutions) do not exist. In an effort to economically andeffectively treat the leachate solution prior to passing overthe AC, a dipotassium salt of 1,3-benzenediamidoethanethiol(BDET^2-) has been developed to irreversibly bind andprecipitate the mercury. The ligand has proven to be highlyeffective by selectively reducing mercury levels fromaverage initial concentrations of 34.5 ppm (parts per million)to 0.014 ppm within 10 min and to 0.008 ppm within 15min. X-ray powder diffraction (XRD), proton nuclear magneticresonance (¹H NMR), Raman, and infrared (IR) spectroscopydemonstrate the formation of a mercury-ligand compound,which remains insoluble over pH ranges of 0.0-14.0. Leachatesamples from an active gold mine in Peru have beenanalyzed using cold vapor atomic fluorescence (CVAF)and inductively coupled plasma optical emission spectroscopy(ICP-OES) for metal concentrations before and aftertreatment with the BDET^2- ligand.