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aria-controls="toc-Application-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Application subsection</span> </button> <ul id="toc-Application-sublist" class="vector-toc-list"> <li id="toc-Effect_of_dissolved_oxygen" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Effect_of_dissolved_oxygen"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Effect of dissolved oxygen</span> </div> </a> <ul id="toc-Effect_of_dissolved_oxygen-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Pre-aeration_and_ore_washing" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Pre-aeration_and_ore_washing"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Pre-aeration and ore washing</span> </div> </a> <ul id="toc-Pre-aeration_and_ore_washing-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Recovery_of_gold_from_cyanide_solutions" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Recovery_of_gold_from_cyanide_solutions"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Recovery of gold from cyanide solutions</span> </div> </a> <ul id="toc-Recovery_of_gold_from_cyanide_solutions-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Cyanide_remediation_processes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Cyanide_remediation_processes"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Cyanide remediation processes</span> </div> </a> <ul id="toc-Cyanide_remediation_processes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Effects_on_the_environment" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Effects_on_the_environment"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Effects on the environment</span> </div> </a> <ul id="toc-Effects_on_the_environment-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Alternatives_to_cyanide" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Alternatives_to_cyanide"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Alternatives to cyanide</span> </div> </a> <ul id="toc-Alternatives_to_cyanide-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Legislation" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Legislation"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Legislation</span> </div> </a> <ul id="toc-Legislation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" 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href="https://fa.wikipedia.org/wiki/%D8%B3%DB%8C%D8%A7%D9%86%DB%8C%D8%AF%D8%A7%D8%B3%DB%8C%D9%88%D9%86_%D8%B7%D9%84%D8%A7" title="سیانیداسیون طلا – Persian" lang="fa" hreflang="fa" data-title="سیانیداسیون طلا" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Cyanuration" title="Cyanuration – French" lang="fr" hreflang="fr" data-title="Cyanuration" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Pr%C3%B3iseas_ciain%C3%ADde" title="Próiseas ciainíde – Irish" lang="ga" hreflang="ga" data-title="Próiseas ciainíde" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%B8%E0%A4%BE%E0%A4%AF%E0%A4%A8%E0%A4%BE%E0%A4%87%E0%A4%A1_%E0%A4%B5%E0%A4%BF%E0%A4%A7%E0%A4%BF" title="सायनाइड विधि – Hindi" lang="hi" hreflang="hi" data-title="सायनाइड विधि" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Cianurazione_dell%27oro" title="Cianurazione dell'oro – Italian" lang="it" hreflang="it" data-title="Cianurazione dell'oro" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Az_arany_ci%C3%A1nl%C3%BAgz%C3%A1sa" title="Az arany ciánlúgzása – Hungarian" lang="hu" hreflang="hu" data-title="Az arany ciánlúgzása" 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searchaux" style="display:none">Technique for extracting gold from low-grade ore</div> <p><b>Gold cyanidation</b> (also known as the <b>cyanide process</b> or the <b>MacArthur–Forrest process</b>) is a <a href="/wiki/Hydrometallurgy" title="Hydrometallurgy">hydrometallurgical</a> technique for extracting <a href="/wiki/Gold" title="Gold">gold</a> from low-grade <a href="/wiki/Ore" title="Ore">ore</a> through conversion to a water-soluble <a href="/wiki/Coordination_complex" title="Coordination complex">coordination complex</a>. It is the most commonly used <a href="/wiki/Leaching_(chemistry)" title="Leaching (chemistry)">leaching</a> process for <a href="/wiki/Gold_extraction" title="Gold extraction">gold extraction</a>.<sup id="cite_ref-Ullmann_1-0" class="reference"><a href="#cite_note-Ullmann-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Cyanidation is also widely used in <a href="/wiki/Silver" title="Silver">silver</a> extraction, usually after <a href="/wiki/Froth_flotation" title="Froth flotation">froth flotation</a>.<sup id="cite_ref-KO_2-0" class="reference"><a href="#cite_note-KO-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>Production of <a href="/wiki/Reagent" title="Reagent">reagents</a> for mineral processing to recover gold represents 70% of cyanide consumption globally. While other metals, such as <a href="/wiki/Copper" title="Copper">copper</a>, <a href="/wiki/Zinc" title="Zinc">zinc</a>, and silver, are also recovered using cyanide, gold remains the primary driver of this technology. <sup id="cite_ref-Ullmann_1-1" class="reference"><a href="#cite_note-Ullmann-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The highly <a href="/wiki/Toxic" class="mw-redirect" title="Toxic">toxic</a> nature of <a href="/wiki/Cyanide" title="Cyanide">cyanide</a> has led to controversy regarding its use in gold mining, with it being banned in some parts of the world. However, when used with appropriate safety measures, cyanide can be safely employed in gold extraction processes.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> One critical factor in its safe use is maintaining an alkaline pH level above 10.5, which is typically controlled using <a href="/wiki/Lime_(material)" title="Lime (material)">lime</a> in industrial-scale operations. Lime plays an essential role in gold processing, ensuring that the pH remains at the correct level to mitigate risks associated with cyanide use.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=1" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In 1783, <a href="/wiki/Carl_Wilhelm_Scheele" title="Carl Wilhelm Scheele">Carl Wilhelm Scheele</a> discovered that gold dissolved in <a href="/wiki/Aqueous_solution" title="Aqueous solution">aqueous solutions</a> of cyanide. Through the work of <a href="/wiki/Peter_Bagrationi" class="mw-redirect" title="Peter Bagrationi">Bagration</a> (1844), Elsner (1846), and <a href="/wiki/Michael_Faraday" title="Michael Faraday">Faraday</a> (1847), it was determined that each gold atom required two cyanide ions, i.e. the <a href="/wiki/Stoichiometry" title="Stoichiometry">stoichiometry</a> of the soluble compound. </p> <div class="mw-heading mw-heading3"><h3 id="Industrial_process">Industrial process</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=2" title="Edit section: Industrial process"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Jsmacarthur-X-007r.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/37/Jsmacarthur-X-007r.jpg/170px-Jsmacarthur-X-007r.jpg" decoding="async" width="170" height="251" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/37/Jsmacarthur-X-007r.jpg/255px-Jsmacarthur-X-007r.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/37/Jsmacarthur-X-007r.jpg/340px-Jsmacarthur-X-007r.jpg 2x" data-file-width="1148" data-file-height="1694" /></a><figcaption><a href="/wiki/John_Stewart_MacArthur" title="John Stewart MacArthur">John Stewart MacArthur</a> developed the cyanide process for gold extraction in 1887.</figcaption></figure> <p>The expansion of gold mining in the <a href="/wiki/Witwatersrand" title="Witwatersrand">Rand</a> of South Africa began to slow down in the 1880s, as the new deposits found tended to contain <a href="/wiki/Pyrite" title="Pyrite">pyritic ore</a>. The gold could not be extracted from this compound with any of the then available chemical processes or technologies.<sup id="cite_ref-Gray_5-0" class="reference"><a href="#cite_note-Gray-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> In 1887, <a href="/wiki/John_Stewart_MacArthur" title="John Stewart MacArthur">John Stewart MacArthur</a>, working in collaboration with brothers Robert and William Forrest for the <a href="/wiki/Charles_Tennant" title="Charles Tennant">Tennant Company</a> in <a href="/wiki/Glasgow" title="Glasgow">Glasgow</a>, Scotland, developed the MacArthur–Forrest process for the extraction of gold from gold ores. Several patents were issued in the same year.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> By suspending the crushed ore in a cyanide solution, a separation of up to 96 percent pure gold was achieved.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> The process was first used on the <a href="/wiki/Witwatersrand" title="Witwatersrand">Rand</a> in 1890 and, despite operational imperfections, led to a boom of investment as larger gold mines were opened up.<sup id="cite_ref-Recent_Advances_in_Gold_Metallurgy_8-0" class="reference"><a href="#cite_note-Recent_Advances_in_Gold_Metallurgy-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Gray_5-1" class="reference"><a href="#cite_note-Gray-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>By 1891, Nebraska pharmacist <a href="/wiki/Gilbert_S._Peyton" class="mw-redirect" title="Gilbert S. Peyton">Gilbert S. Peyton</a> had refined the process at his <a href="/wiki/Mercur,_Utah" title="Mercur, Utah">Mercur Mine</a> in Utah, "the first mining plant in the United States to make a commercial success of the cyanide process on gold ores."<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> In 1896, Bodländer confirmed that oxygen was necessary for the process, something that had been doubted by MacArthur, and discovered that <a href="/wiki/Hydrogen_peroxide" title="Hydrogen peroxide">hydrogen peroxide</a> was formed as an intermediate.<sup id="cite_ref-Recent_Advances_in_Gold_Metallurgy_8-1" class="reference"><a href="#cite_note-Recent_Advances_in_Gold_Metallurgy-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> Around 1900, the American metallurgist <a href="/wiki/Charles_Washington_Merrill" title="Charles Washington Merrill">Charles Washington Merrill</a> (1869–1956) and his engineer Thomas Bennett Crowe improved the treatment of the cyanide leachate, by using vacuum and zinc dust. Their process is the <a href="/wiki/Merrill%E2%80%93Crowe_process" title="Merrill–Crowe process">Merrill–Crowe process</a>.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Chemical_reactions">Chemical reactions</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=3" title="Edit section: Chemical reactions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Dicyanoaurate(I)-3D-balls.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Dicyanoaurate%28I%29-3D-balls.png/220px-Dicyanoaurate%28I%29-3D-balls.png" decoding="async" width="220" height="55" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Dicyanoaurate%28I%29-3D-balls.png/330px-Dicyanoaurate%28I%29-3D-balls.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Dicyanoaurate%28I%29-3D-balls.png/440px-Dicyanoaurate%28I%29-3D-balls.png 2x" data-file-width="1100" data-file-height="274" /></a><figcaption><a href="/wiki/Ball-and-stick_model" title="Ball-and-stick model">Ball-and-stick model</a> of the aurocyanide or dicyanoaurate(I) complex anion, [Au(CN)<sub>2</sub>]<sup>−</sup><sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup></figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Gold_heap_leaching.jpeg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Gold_heap_leaching.jpeg/220px-Gold_heap_leaching.jpeg" decoding="async" width="220" height="145" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Gold_heap_leaching.jpeg/330px-Gold_heap_leaching.jpeg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/df/Gold_heap_leaching.jpeg/440px-Gold_heap_leaching.jpeg 2x" data-file-width="728" data-file-height="480" /></a><figcaption>Cyanide leaching "heap" at a gold mining operation near <a href="/wiki/Elko,_Nevada" title="Elko, Nevada">Elko, Nevada</a></figcaption></figure> <p>The chemical reaction for the dissolution of gold, the "Elsner equation", follows: </p> <dl><dd>4<span class="nowrap"> </span>Au + 8<span class="nowrap"> </span>NaCN + O<sub>2</sub> + 2<span class="nowrap"> </span>H<sub>2</sub>O → 4<span class="nowrap"> </span>Na[Au(CN)<sub>2</sub>] + 4<span class="nowrap"> </span>NaOH</dd></dl> <p><a href="/wiki/Potassium_cyanide" title="Potassium cyanide">Potassium cyanide</a> and <a href="/wiki/Calcium_cyanide" title="Calcium cyanide">calcium cyanide</a> are sometimes used in place of sodium cyanide. </p><p>Gold is one of the few metals that dissolves in the presence of cyanide ions and oxygen. The soluble gold species is <a href="/wiki/Dicyanoaurate" class="mw-redirect" title="Dicyanoaurate">dicyanoaurate</a>.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> from which it can be recovered by adsorption onto activated carbon.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Application">Application</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=4" title="Edit section: Application"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Ore" title="Ore">ore</a> is <a href="/wiki/Comminution" title="Comminution">comminuted</a> using grinding machinery. Depending on the ore, it is sometimes further concentrated by <a href="/wiki/Froth_flotation" title="Froth flotation">froth flotation</a> or by <a href="/wiki/Mineral_processing#Gravity_concentration" title="Mineral processing">centrifugal (gravity) concentration</a>. Water is added to produce a slurry or <i>pulp</i>. The basic ore slurry can be combined with a solution of <a href="/wiki/Sodium_cyanide" title="Sodium cyanide">sodium cyanide</a> or <a href="/wiki/Potassium_cyanide" title="Potassium cyanide">potassium cyanide</a>; many operations use <a href="/wiki/Calcium_cyanide" title="Calcium cyanide">calcium cyanide</a>, which is more cost effective. </p><p>To prevent the creation of toxic <a href="/wiki/Hydrogen_cyanide" title="Hydrogen cyanide">hydrogen cyanide</a> during processing, slaked lime (<a href="/wiki/Calcium_hydroxide" title="Calcium hydroxide">calcium hydroxide</a>) or soda (<a href="/wiki/Sodium_hydroxide" title="Sodium hydroxide">sodium hydroxide</a>) is added to the extracting solution to ensure that the acidity during cyanidation is maintained over <a href="/wiki/PH" title="PH">pH</a> 10.5 - strongly basic. <a href="/wiki/Lead(II)_nitrate" title="Lead(II) nitrate">Lead nitrate</a> can improve gold <a href="/wiki/Tank_leaching" title="Tank leaching">leaching</a> speed and quantity recovered, particularly in processing partially oxidized ores. </p> <div class="mw-heading mw-heading3"><h3 id="Effect_of_dissolved_oxygen">Effect of dissolved oxygen</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=5" title="Edit section: Effect of dissolved oxygen"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Oxygen" title="Oxygen">Oxygen</a> is one of the <a href="/wiki/Reagent" title="Reagent">reagents</a> consumed during cyanidation, accepting the electrons from the gold, and a deficiency in <a href="/wiki/Oxygen_saturation" title="Oxygen saturation">dissolved oxygen</a> slows leaching rate. Air or pure oxygen gas can be purged through the pulp to maximize the dissolved oxygen concentration. Intimate oxygen-pulp contactors are used to increase the partial pressure of the oxygen in contact with the solution, thus raising the dissolved oxygen concentration much higher than the saturation level at <a href="/wiki/Atmospheric_pressure" title="Atmospheric pressure">atmospheric pressure</a>. Oxygen can also be added by dosing the pulp with <a href="/wiki/Hydrogen_peroxide" title="Hydrogen peroxide">hydrogen peroxide</a> solution. </p> <div class="mw-heading mw-heading3"><h3 id="Pre-aeration_and_ore_washing">Pre-aeration and ore washing</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=6" title="Edit section: Pre-aeration and ore washing"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In some ores, particularly those that are partially sulfidized, <a href="/wiki/Aeration" title="Aeration">aeration</a> (prior to the introduction of cyanide) of the ore in water at high pH can render elements such as iron and sulfur less reactive to cyanide, therefore making the gold cyanidation process more efficient. Specifically, the oxidation of iron to <a href="/wiki/Iron_(III)_oxide" class="mw-redirect" title="Iron (III) oxide">iron (III) oxide</a> and subsequent <a href="/wiki/Precipitation_(chemistry)" title="Precipitation (chemistry)">precipitation</a> as <a href="/wiki/Iron_hydroxide" class="mw-redirect" title="Iron hydroxide">iron hydroxide</a> minimizes loss of cyanide from the formation of ferrous cyanide complexes. The oxidation of <a href="/wiki/Sulfur" title="Sulfur">sulfur</a> compounds to sulfate ions avoids the consumption of cyanide to <a href="/wiki/Thiocyanate" title="Thiocyanate">thiocyanate</a> (SCN<sup>−</sup>) byproduct. </p> <div class="mw-heading mw-heading2"><h2 id="Recovery_of_gold_from_cyanide_solutions">Recovery of gold from cyanide solutions</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=7" title="Edit section: Recovery of gold from cyanide solutions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In order of decreasing economic efficiency, the common processes for recovery of the solubilized gold from solution are (certain processes may be precluded from use by technical factors): </p> <ul><li><a href="/wiki/Carbon_in_pulp" title="Carbon in pulp">Carbon in pulp</a></li> <li><a href="/wiki/Electrowinning" title="Electrowinning">Electrowinning</a></li> <li><a href="/wiki/Merrill%E2%80%93Crowe_process" title="Merrill–Crowe process">Merrill–Crowe process</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Cyanide_remediation_processes">Cyanide remediation processes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=8" title="Edit section: Cyanide remediation processes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The cyanide remaining in tails streams from gold plants is potentially hazardous. Therefore, some operations process the cyanide-containing waste streams in a detoxification step. This step lowers the concentrations of these cyanide compounds. The INCO-licensed process and the <a href="/wiki/Peroxymonosulfuric_acid" title="Peroxymonosulfuric acid">Caro's acid</a> process oxidise the cyanide to <a href="/wiki/Cyanate" title="Cyanate">cyanate</a>, which is not as toxic as the cyanide ion, and which can then react to form carbonates and ammonia: <sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p> <dl><dd><span class="chemf nowrap">CN<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> + [O] → <span class="chemf nowrap">OCN<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span></dd> <dd><span class="chemf nowrap">OCN<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> + 2 <span class="chemf nowrap">H<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">2</sub></span></span>O</span> → <span class="chemf nowrap">HCO<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">3</sub></span></span></span> + <span class="chemf nowrap">NH<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">3</sub></span></span></span></dd></dl> <p>The Inco process can typically lower cyanide concentrations to below 50 mg/L, whereas the Caro's acid process can lower cyanide levels to between 10 and 50 mg/L, with the lower concentrations achievable in solution streams rather than slurries. Caro's acid – peroxomonosulfuric acid (H<sub>2</sub>SO<sub>5</sub>) - converts cyanide to cyanate. Cyanate then hydrolyses to ammonium and carbonate ions. The Caro's acid process is able to achieve discharge levels of Weak Acid Dissociable" (WAD) cyanide below 50 mg/L, which is generally suitable for discharge to tailings. Hydrogen peroxide and basic chlorination can also be used to oxidize cyanide, although these approaches are less common. Typically, this process blows compressed air through the tailings while adding <a href="/wiki/Sodium_metabisulfite" title="Sodium metabisulfite">sodium metabisulfite</a>, which releases SO<sub>2</sub>. <a href="/wiki/Lime_(material)" title="Lime (material)">Lime</a> is added to maintain the pH at around 8.5, and <a href="/wiki/Copper_sulfate" title="Copper sulfate">copper sulfate</a> is added as a catalyst if there is insufficient copper in the ore extract. This procedure can reduce concentrations of WAD cyanide to below the 10 ppm mandated by the EU's Mining Waste Directive. This level compares to the 66-81 ppm free cyanide and 500-1000 ppm total cyanide in the pond at <a href="/wiki/Baia_Mare" title="Baia Mare">Baia Mare</a>.<sup id="cite_ref-Baia_Mare_report_16-0" class="reference"><a href="#cite_note-Baia_Mare_report-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Remaining free cyanide degrades in the pond, while cyanate ions hydrolyse to ammonium. Studies show that residual cyanide trapped in the gold-mine tailings causes persistent release of toxic metals (e.g. mercury ) into the groundwater and surface water systems.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Effects_on_the_environment">Effects on the environment</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=9" title="Edit section: Effects on the environment"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/List_of_gold_mining_disasters" title="List of gold mining disasters">List of gold mining disasters</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Chemung_mine-sodium_cyanide.jpeg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Chemung_mine-sodium_cyanide.jpeg/220px-Chemung_mine-sodium_cyanide.jpeg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Chemung_mine-sodium_cyanide.jpeg/330px-Chemung_mine-sodium_cyanide.jpeg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Chemung_mine-sodium_cyanide.jpeg/440px-Chemung_mine-sodium_cyanide.jpeg 2x" data-file-width="1600" data-file-height="1200" /></a><figcaption>Sodium cyanide drum at the abandoned Chemung Mine in <a href="/wiki/Masonic,_California" title="Masonic, California">Masonic, California</a></figcaption></figure> <p>Despite being used in 90% of gold production:<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> gold cyanidation is <a href="/wiki/Controversy" title="Controversy">controversial</a> due to the toxic nature of cyanide. Although aqueous solutions of cyanide degrade rapidly in sunlight, the less-toxic products, such as cyanates and thiocyanates, may persist for some years. The famous disasters have killed few people — humans can be warned not to drink or go near polluted water, but cyanide spills can have a devastating effect on rivers, sometimes killing everything for several miles downstream. The cyanide could be washed out of river systems and, as long as organisms can migrate from unpolluted areas upstream, affected areas can soon be repopulated. Longer term impact and accumulation of cyanide in riparian or limnological benthos and environmental fate is less clear. According to Romanian authorities, in the <a href="/wiki/Some%C8%99" title="Someș">Someș</a> river below <a href="/wiki/Baia_Mare" title="Baia Mare">Baia Mare</a>, the plankton returned to 60% of normal within 16 days of the spill; the numbers were not confirmed by Hungary or Yugoslavia.<sup id="cite_ref-Baia_Mare_report_16-1" class="reference"><a href="#cite_note-Baia_Mare_report-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Famous cyanide spills include: </p> <table style="margin:auto;" class="wikitable"> <tbody><tr> <th style="text-align:left;">Year </th> <th style="text-align:left;">Mine </th> <th style="text-align:left;">Country </th> <th style="text-align:left;">Incident </th></tr> <tr> <td>1985–1991 </td> <td><a href="/wiki/Summitville_mine" title="Summitville mine">Summitville</a> </td> <td>US </td> <td>Leakage from leach pad </td></tr> <tr> <td>1980s–present </td> <td><a href="/wiki/Ok_Tedi_Mine" title="Ok Tedi Mine">Ok Tedi</a> </td> <td>Papua New Guinea </td> <td><a href="/wiki/Ok_Tedi_environmental_disaster" title="Ok Tedi environmental disaster">Unrestrained waste discharge</a> </td></tr> <tr> <td>1995 </td> <td>Omai </td> <td>Guyana </td> <td>Collapse of tailings dam </td></tr> <tr> <td>1998 </td> <td><a href="/wiki/Kumtor_Gold_Mine" title="Kumtor Gold Mine">Kumtor</a> </td> <td>Kyrgyzstan </td> <td>Truck drove over bridge </td></tr> <tr> <td>2000 </td> <td><a href="/wiki/Baia_Mare" title="Baia Mare">Baia Mare</a> </td> <td>Romania </td> <td>Collapse of containment dam (see <a href="/wiki/2000_Baia_Mare_cyanide_spill" title="2000 Baia Mare cyanide spill">2000 Baia Mare cyanide spill</a>) </td></tr> <tr> <td>2000 </td> <td>Tolukuma </td> <td>Papua New Guinea </td> <td>Helicopter dropped crate into rainforest<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>2018 </td> <td>San Dimas </td> <td>Mexico </td> <td>Truck leaked 200 liters of cyanide solution into the Piaxtla River in Durango<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </td></tr> <tr> <td>2024 </td> <td>Eagle Mine </td> <td>Canada (Yukon) </td> <td>Heap Leach failure, cyanide spill into surrounding waterways, ecological damage and company bankruptcy </td></tr></tbody></table> <p>Such spills have prompted fierce protests at new mines that involve use of cyanide, such as <a href="/wiki/Ro%C5%9Fia_Montan%C4%83" class="mw-redirect" title="Roşia Montană">Roşia Montană</a> in Romania, <a href="/wiki/Lake_Cowal" title="Lake Cowal">Lake Cowal</a> in Australia, <a href="/wiki/Pascua_Lama" title="Pascua Lama">Pascua Lama</a> in Chile, and Bukit Koman in Malaysia. </p> <div class="mw-heading mw-heading2"><h2 id="Alternatives_to_cyanide">Alternatives to cyanide</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=10" title="Edit section: Alternatives to cyanide"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Although cyanide is cheap, effective, and biodegradable, its high toxicity & increasingly poor impact on a mine's political and social license to operate, has incentivized alternative methods for extracting gold. Other extractants have been examined including <a href="/wiki/Thiosulfate" title="Thiosulfate">thiosulfate</a> (S<sub>2</sub>O<sub>3</sub><sup>2−</sup>), <a href="/wiki/Thiourea" title="Thiourea">thiourea</a> (SC(NH<sub>2</sub>)<sub>2</sub>), iodine/iodide, ammonia, liquid mercury, and alpha-<a href="/wiki/Cyclodextrin" title="Cyclodextrin">cyclodextrin</a>. Challenges include reagent cost and the efficiency of gold recovery, although some chlorination process using sodium hypochlorite (household bleach) have shown promise in terms or reagent regeneration. These technologies are at a pre-commercialisation stage and compare favourably to equivalent cyanidation methods, including gold recovery percentage. Thiourea has been implemented commercially for ores containing stibnite.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> Yet another alternative to cyanidation is the family of glycine-based <a href="/wiki/Lixiviant" title="Lixiviant">lixiviants</a>.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Legislation">Legislation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=11" title="Edit section: Legislation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Gold_cyanidation_ban" title="Gold cyanidation ban">Gold cyanidation ban</a></div> <p>The US states of <a href="/wiki/Montana" title="Montana">Montana</a><sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> and <a href="/wiki/Wisconsin" title="Wisconsin">Wisconsin</a>,<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> the <a href="/wiki/Czech_Republic" title="Czech Republic">Czech Republic</a>,<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Hungary" title="Hungary">Hungary</a>,<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> have banned cyanide mining. The <a href="/wiki/European_Commission" title="European Commission">European Commission</a> rejected a proposal for such a ban, noting that existing regulations (see below) provide adequate environmental and health protection.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> Several attempts to ban <a href="/wiki/Gold_cyanidation_in_Romania" title="Gold cyanidation in Romania">gold cyanidation in Romania</a> were rejected by the Romanian Parliament. There are currently protests in Romania calling for a ban on the use of cyanide in mining (see <a href="/wiki/2013_Romanian_protests_against_the_Ro%C8%99ia_Montan%C4%83_Project" class="mw-redirect" title="2013 Romanian protests against the Roșia Montană Project">2013 Romanian protests against the Roșia Montană Project</a>). </p><p>In the EU, industrial use of hazardous chemicals is controlled by the so-called <a href="/wiki/Seveso_II_Directive" class="mw-redirect" title="Seveso II Directive">Seveso II Directive</a> (Directive 96/82/EC,<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> which replaced the original <a href="/wiki/Directive_82/501/EC" title="Directive 82/501/EC">Seveso Directive</a> (82/501/EEC<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> brought in after the 1976 dioxin disaster. "Free cyanide and any compound capable of releasing free cyanide in solution" are further controlled by being on List I of the <a href="/w/index.php?title=Directive_80/68/EEC&action=edit&redlink=1" class="new" title="Directive 80/68/EEC (page does not exist)">Groundwater Directive</a> (Directive 80/68/EEC)<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> which bans any discharge of a size which might cause deterioration in the quality of the groundwater at the time or in the future. The Groundwater Directive was largely replaced in 2000 by the <a href="/wiki/Water_Framework_Directive" title="Water Framework Directive">Water Framework Directive</a> (2000/60/EC).<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> </p><p>In response to the <a href="/wiki/2000_Baia_Mare_cyanide_spill" title="2000 Baia Mare cyanide spill">2000 Baia Mare cyanide spill</a>, the <a href="/wiki/European_Parliament" title="European Parliament">European Parliament</a> and the Council adopted <a href="/w/index.php?title=Directive_2006/21/EC&action=edit&redlink=1" class="new" title="Directive 2006/21/EC (page does not exist)">Directive 2006/21/EC</a> on the management of waste from extractive industries.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> Article 13(6) requires "the concentration of weak acid dissociable cyanide in the pond is reduced to the lowest possible level using <a href="/wiki/Best_available_techniques" class="mw-redirect" title="Best available techniques">best available techniques</a>", and at most all mines started after 1 May 2008 may not discharge waste containing over 10ppm WAD cyanide, mines built or permitted before that date are allowed no more than 50ppm initially, dropping to 25ppm in 2013 and 10ppm by 2018. </p><p>Under Article 14, companies must also put in place financial guarantees to ensure clean-up after the mine has finished. This in particular may affect smaller companies wanting to build gold mines in the EU, as they are less likely to have the financial strength to give these kinds of guarantees. </p><p>The industry has come up with a voluntary "<i>Cyanide Code</i>"<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> that aims to reduce environmental impacts with third party audits of a company's cyanide management. </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=12" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-Ullmann-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-Ullmann_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Ullmann_1-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFRuboKellensReddySteier2006" class="citation encyclopaedia cs1">Rubo, Andreas; Kellens, Raf; Reddy, Jay; Steier, Norbert; Hasenpusch, Wolfgang (2006). "Alkali Metal Cyanides". <i><a href="/wiki/Ullmann%27s_Encyclopedia_of_Industrial_Chemistry" title="Ullmann's Encyclopedia of Industrial Chemistry">Ullmann's Encyclopedia of Industrial Chemistry</a></i>. 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Yarar, Colorado School of Mines, Tailings and Mine Waste '02, Swets & Zeitlinger, <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/90-5809-353-0" title="Special:BookSources/90-5809-353-0">90-5809-353-0</a>, pp. 197 (<a rel="nofollow" class="external text" href="https://books.google.com/books?id=PPTL9-lM78AC&dq=world+cyanide+consumption&pg=PA197">Google Books</a>).</span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text">BBC News, <a rel="nofollow" class="external text" href="http://news.bbc.co.uk/1/hi/world/asia-pacific/687913.stm">BBC: "Cyanide seeps into PNG rivers"</a>, March 23, 2000.</span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text">Wilson, T. E. <a rel="nofollow" class="external text" href="https://www.lapoliticaeslapolitica.com/2018/04/after-cyanide-spill-can-first-majestic.html">La politica es la politica: "After cyanide spill, can First Majestic clean up its act?"</a> April 21, 2018.</span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLa_BrooyLingeWalker1994" class="citation journal cs1">La Brooy, S.R.; Linge, H.G.; Walker, G.S. (1994). "Review of gold extraction from ores". <i>Minerals Engineering</i>. <b>7</b> (10): <span class="nowrap">1213–</span>1241. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1994MiEng...7.1213L">1994MiEng...7.1213L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0892-6875%2894%2990114-7">10.1016/0892-6875(94)90114-7</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Minerals+Engineering&rft.atitle=Review+of+gold+extraction+from+ores&rft.volume=7&rft.issue=10&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1213-%3C%2Fspan%3E1241&rft.date=1994&rft_id=info%3Adoi%2F10.1016%2F0892-6875%2894%2990114-7&rft_id=info%3Abibcode%2F1994MiEng...7.1213L&rft.aulast=La+Brooy&rft.aufirst=S.R.&rft.au=Linge%2C+H.G.&rft.au=Walker%2C+G.S.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGold+cyanidation" class="Z3988"></span></span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.mpsinnovation.com.au/">"Glycine lixiviants"</a>. <i>Mining and Process Solutions</i><span class="reference-accessdate">. Retrieved <span class="nowrap">23 April</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Mining+and+Process+Solutions&rft.atitle=Glycine+lixiviants&rft_id=https%3A%2F%2Fwww.mpsinnovation.com.au%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGold+cyanidation" class="Z3988"></span></span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.meic.org/mining/cyanide_mining/ban-on-cyanide-mining/i-137">The Citizens Initiative banning of cyanide mining in the State of Montana, US</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071021031827/http://www.meic.org/mining/cyanide_mining/ban-on-cyanide-mining/i-137">Archived</a> October 21, 2007, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span> </li> <li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://docs.legis.wisconsin.gov/2001/related/proposals/sb160.pdf">2001 Senate Bill 160</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20061010052437/http://www.legis.state.wi.us/2001/data/SB-160.pdf">Archived</a> 2006-10-10 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> regarding the use of cyanide in mining.</span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://nl.newsbank.com/nl-search/we/Archives?p_product=NewsLibrary&p_multi=BBAB&d_place=BBAB&p_theme=newslibrary2&p_action=search&p_maxdocs=200&p_topdoc=1&p_text_direct-0=0F97DD15035650A1&p_field_direct-0=document_id&p_perpage=10&p_sort=YMD_date:D&s_trackval=GooglePM">"Czech Senate bans use of cyanide in gold mining"</a>. Nl.newsbank.com. 2000-08-10<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-01-03</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Czech+Senate+bans+use+of+cyanide+in+gold+mining&rft.pub=Nl.newsbank.com&rft.date=2000-08-10&rft_id=http%3A%2F%2Fnl.newsbank.com%2Fnl-search%2Fwe%2FArchives%3Fp_product%3DNewsLibrary%26p_multi%3DBBAB%26d_place%3DBBAB%26p_theme%3Dnewslibrary2%26p_action%3Dsearch%26p_maxdocs%3D200%26p_topdoc%3D1%26p_text_direct-0%3D0F97DD15035650A1%26p_field_direct-0%3Ddocument_id%26p_perpage%3D10%26p_sort%3DYMD_date%3AD%26s_trackval%3DGooglePM&rfr_id=info%3Asid%2Fen.wikipedia.org%3AGold+cyanidation" class="Z3988"></span></span> </li> <li id="cite_note-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-27">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://greenpeace.hu/hirek/p1/rkezdo/i202">Zöld siker: törvényi tilalom a cianidos bányászatra!</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110721105032/http://greenpeace.hu/hirek/p1/rkezdo/i202">Archived</a> July 21, 2011, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text">International Mining - <a rel="nofollow" class="external text" href="https://im-mining.com/2010/07/06/european-commission-rejects-proposed-ban-on-using-cyanide-in-extractive-industry/">European Commission rejects proposed ban on using cyanide in extractivism|extractive industry</a>, July, 2010</span> </li> <li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:31996L0082">Council Directive 96/82/EC of 9 December 1996 on the control of major-accident hazards involving dangerous substances.</a> For the modifications see the consolidated version.</span> </li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:31982L0501">Council Directive 82/501/EEC of 24 June 1982 on the major-accident hazards of certain industrial activities.</a> Not in force.</span> </li> <li id="cite_note-31"><span class="mw-cite-backlink"><b><a href="#cite_ref-31">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:31980L0068">Council Directive 80/68/EEC of 17 December 1979 on the protection of groundwater against pollution caused by certain dangerous substances.</a> Not in force.</span> </li> <li id="cite_note-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-32">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:32000L0060">Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (the <i>Water Framework Directive</i>).</a> For the modifications see the consolidated version.</span> </li> <li id="cite_note-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-33">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:32006L0021">Directive 2006/21/EC of the European Parliament and of the Council of 15 March 2006 on the management of waste from extractive industries.</a> For the modifications see the consolidated version.</span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text">ICMI <a rel="nofollow" class="external text" href="https://cyanidecode.org/">cyanidecode.org</a> International Cyanide Management Code For The Manufacture, Transport, and Use of Cyanide In The Production of Gold</span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Gold_cyanidation&action=edit&section=13" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 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href="https://commons.wikimedia.org/wiki/Category:Gold_mining" class="extiw" title="commons:Category:Gold mining">Gold mining</a></span>.</div></div> </div> <ul><li><a rel="nofollow" class="external text" href="http://www.abc.net.au/science/news/enviro/EnviroRepublish_351793.htm">Efforts at a cleaner process</a></li> <li><a rel="nofollow" class="external text" href="https://www.yestech.com/tech/gold1.htm">Yestech</a> A different commercial method that does not use toxic cyanide</li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20121021155525/http://www.earthworksaction.org/files/publications/cyanideuncertainties.pdf">Cyanide Uncertainties</a> (PDF)</li> <li><a rel="nofollow" class="external text" href="https://refreshscience.com/how-gold-is-extracted-by-cyanidation-process/">How gold is extracted by cyanidation process</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist 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assay</a> <a href="/wiki/Non-ferrous_extractive_metallurgy" title="Non-ferrous extractive metallurgy">Non-ferrous extractive metallurgy</a></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Mineral_processing" title="Mineral processing">Mineral processing</a><br /><small>(by physical means)</small></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Extraction</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Geological_survey" title="Geological survey">Geological survey</a></li> <li><a href="/wiki/Natural_resource" title="Natural resource">Natural resources</a></li> <li><a href="/wiki/Ore" title="Ore">Ore</a> <ul><li><a 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title="Comminution">Comminution</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Stamp_mill" title="Stamp mill">Stamp mill</a></li> <li><a href="/wiki/Arrastra" title="Arrastra">Arrastra</a></li> <li><a href="/wiki/Crusher" title="Crusher">Crusher</a> <ul><li><a href="/wiki/Mill_(grinding)#Autogenous_mill" title="Mill (grinding)">AG mill</a></li> <li><a href="/wiki/Mill_(grinding)#SAG_mill" title="Mill (grinding)">SAG mill</a></li> <li><a href="/wiki/Mill_(grinding)#Pebble_mill" title="Mill (grinding)">Pebble mill</a></li></ul></li> <li><a href="/wiki/Ball_mill" title="Ball mill">Ball mill</a> <ul><li><a href="/wiki/Mill_(grinding)#Rod_mill" title="Mill (grinding)">Rod mill</a></li> <li><a href="/wiki/IsaMill" title="IsaMill">IsaMill</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Sizing</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ore_sorting" class="mw-redirect" title="Ore sorting">Ore sorting</a></li> <li><a href="/wiki/Vanning" title="Vanning">Vanning</a></li> <li><a href="/wiki/Hydrocyclone" title="Hydrocyclone">Hydrocyclone</a></li> <li><a href="/wiki/Trommel_screen" title="Trommel screen">Trommel</a></li> <li><a href="/wiki/Cyclonic_separation" title="Cyclonic separation">Cyclonic separation</a></li> <li><a href="/wiki/Gyratory_equipment" title="Gyratory equipment">Gyratory equipment</a></li> <li><a href="/wiki/Mechanical_screening" title="Mechanical screening">Mechanical screening</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Ore_concentrate" title="Ore concentrate">Concentration</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Froth_flotation" title="Froth flotation">Froth flotation</a></li> <li><a href="/wiki/Jameson_cell" title="Jameson cell">Jameson cell</a></li> <li><a href="/wiki/Gold_panning" title="Gold panning">Panning</a></li> <li><a href="/wiki/Jig_concentrators" title="Jig concentrators">Jig concentrators</a></li> <li><a href="/wiki/Mineral_processing#Gravity_concentration" title="Mineral processing">Gravity Concentration</a></li> <li><a href="/wiki/Magnetic_separation" title="Magnetic separation">Magnetic separation</a> (<a href="/wiki/Magnetation_(iron_ore)" title="Magnetation (iron ore)">Magnetation</a>)</li> <li><a href="/wiki/Rocker_box" title="Rocker box">Rocker box</a></li> <li><a href="/wiki/Drywasher" title="Drywasher">Dry washing</a></li> <li><a href="/wiki/Buddle_pit" title="Buddle pit">Buddle pit</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Pyrometallurgy" title="Pyrometallurgy">Pyrometallurgy</a><br /><small>(by heat)</small></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Smelting" title="Smelting">Smelting</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ferrous_metallurgy" title="Ferrous metallurgy">Iron smelting</a></li> <li><a href="/wiki/Lead_smelting" title="Lead smelting">Lead smelting</a></li> <li><a href="/wiki/Zinc_smelting" title="Zinc smelting">Zinc smelting</a></li> <li><a href="/wiki/Flash_smelting" title="Flash smelting">Flash smelting</a></li> <li><a href="/wiki/ISASMELT" title="ISASMELT">ISASMELT</a> furnace</li> <li><a href="/wiki/Refractory" title="Refractory">Refractory linings</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Refining_(metallurgy)" title="Refining (metallurgy)">Refining</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cupellation" title="Cupellation">Cupellation</a></li> <li><a href="/wiki/Parkes_process" title="Parkes process">Parkes process</a></li> <li><a href="/wiki/Bottom-blown_oxygen_converter" title="Bottom-blown oxygen converter">Bottom-blown oxygen converter</a></li> <li><a href="/wiki/Poling_(metallurgy)" title="Poling (metallurgy)">Poling</a></li> <li><a href="/wiki/IsaKidd_refining_technology" title="IsaKidd refining technology">IsaKidd process</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Calcination" title="Calcination">Calcination</a></li> <li><a href="/wiki/Roasting_(metallurgy)" title="Roasting (metallurgy)">Roasting</a></li> <li><a href="/wiki/Liquation" title="Liquation">Liquation</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Hydrometallurgy" title="Hydrometallurgy">Hydrometallurgy</a><br /><small>(by aqueous solution)</small></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Leaching_(metallurgy)" title="Leaching (metallurgy)">Leaching</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Lixiviant" title="Lixiviant">Lixiviant</a></li> <li><a href="/wiki/Heap_leaching" title="Heap leaching">Heap leaching</a></li> <li><a href="/wiki/Dump_leaching" title="Dump leaching">Dump leaching</a></li> <li><a href="/wiki/Tank_leaching" title="Tank leaching">Tank leaching</a></li> <li><a href="/wiki/In_situ_leach" title="In situ leach">In situ leaching</a></li> <li><a href="/wiki/Newbery%E2%80%93Vautin_chlorination_process" title="Newbery–Vautin chlorination process">Gold chlorination</a></li> <li><a class="mw-selflink selflink">Gold cyanidation</a></li> <li><a href="/wiki/Bayer_process" title="Bayer process">Bayer process</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Amalgam_(chemistry)" title="Amalgam (chemistry)">Amalgamation</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Patio_process" title="Patio process">Patio process</a></li> <li><a href="/wiki/Pan_amalgamation" title="Pan amalgamation">Pan amalgamation</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Electrometallurgy" title="Electrometallurgy">Electrometallurgy</a><br /><small>(by electricity)</small></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Electrolysis16" scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Electrolysis" title="Electrolysis">Electrolysis</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Electrowinning" title="Electrowinning">Electrowinning</a></li> <li><a href="/wiki/Hall%E2%80%93H%C3%A9roult_process" title="Hall–Héroult process">Hall–Héroult process</a></li> <li><a href="/wiki/Castner_process" title="Castner process">Castner process</a></li> <li><a href="/wiki/Downs_cell" title="Downs cell">Downs cell</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Co-products</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Tailings" title="Tailings">Tailings</a></li> <li><a href="/wiki/Gangue" title="Gangue">Gangue</a></li> <li><a href="/wiki/Slag" title="Slag">Slag</a></li> <li><a href="/wiki/Clinker_(waste)" title="Clinker (waste)">Clinker</a></li> <li><a href="/wiki/Chat_(mining)" title="Chat (mining)">Chat</a></li> <li><a href="/wiki/Bauxite_tailings" class="mw-redirect" title="Bauxite tailings">Red mud</a></li> <li><a href="/wiki/Stamp_sand" title="Stamp sand">Stamp sand</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" 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