Cyanide in the rivers and groundwater of El Salvador. And water soluble aurocyanide metallic complex ions.
Where there is gold mining there is cyanide:
Gold Cyanide Solution
(Leaching Gold With Cyanide)
Since the 1890's, cyanide has been used to recover gold from gold bearing ores. And today, over 115 years later, most of the worlds gold is recovered with cyanide playing a large part in the beneficiation of the yellow precious metal. Chemically, it is a rather simple reaction:
4 Au + 8(NaCN) +O2 + 2 H2O = 4 NaAu(CN)2 + 4 NaOH
That presumes that the only elements are the gold, Sodium Cyanide and water. However, as any geologist will tell you, no two ores are the same, and their chemical composition will vary greatly throughout the ore body. These "extra" elements in the mineral compounds will often play havoc with a chemical reaction, as illustrated above.
August 3, 2010
Pac Rim CAFTA Challenge of Salvadoran Environmental, Mining Safety Policies Given Go-Ahead by Tribunal
Initial Win for Corporation in Trade Agreement Attack on Environmental Policy Poses Complications for Obama Administration as It Tries to Revive Korea FTA
WASHINGTON, D.C. – An international tribunal’s decision to allow a controversial suit against El Salvador under the 2005 Central America Free Trade Agreement (CAFTA) will fuel demands by many in Congress that the Obama administration alter the foreign investor terms in three North American Free Trade Agreement (NAFTA)-style trade pacts inherited from the George W. Bush administration and new pacts under negotiation, Public Citizen said today.
Reading the fine print in CAFTA:
The case is being prosecuted under extremely controversial CAFTA provisions that grant foreign investors expansive new rights to sue governments in foreign tribunals over regulations or government actions that conflict with the pacts’ special rights for foreign investors and that could undermine their future expected profits. These terms are included in all three of the Bush-signed but unapproved trade agreements with Panama, Colombia and Korea that the Obama administration inherited.
Hmmm, the "special rights" for foreign investors...
The aggrieved suing party is Pacific Rim Mining Corporation, Canadian-based multinational firm, which would like to establish a massive gold mine with cyanide ore processing in the basin of El Salvador’s largest river, Rio Lempa. The people of El Salvador had concerns about the mine's health and environmental implications, and rightfully so. Despite this, Pacific Rim never completed the feasibility study necessary to obtain an operating permit for the "El Dorado" project. A subsidiary of Pacific Rim, based in the Cayman Islands (where else?), was incorporated in December of 2007, to be reincorporated in Nevada under the name Pac Rim Cayman LLC (where else?). The sole purpose of this newly cloned corporate entity was apparent four months later when it sent a letter to the Salvadoran government threatening a CAFTA claim.
The fait accompli:
In July 2008, the firm ceased exploratory drilling at El Dorado. In December 2008, the firm formally launched a CAFTA claim.
Sadly, gold prices are soaring and El Salvador has been besieged with the filing of 29 permits for new mines.
For more info check out:
As noted above, when one stirs up a broth of 4 Au + 8(NaCN) +O2 + 2 H2O = 4 NaAu(CN)2 + 4 NaOH there are many notable permutations:
Copper is definitely worth mentioning, since copper minerals will dissolve in cyanide solutions, and cause a increased use of cyanide, the copper-cyanide complexes formed by the dissolution will tend to inhibit the dissolution of gold in the cyanide solution. Zinc, the element used to precipitate gold from solution, if present in the ore, will bond with the cyanide to form a zinc cyanide compound. Another element that plays with the cyanide chemistry is nickel. Nickel, however does not interfere with the gold going into solution, but rather the precipitation of the gold from the cyanide solution.
Arsenic and antimony do present a larger problem, by reacting with the cyanide and using up all of the excess oxygen, leaving little or no oxygen to effect the dissolution of gold. Carbonaceous gold ores can have the carbon adsorb the gold onto its surface, and as a result will not be recovered from the pregnant solution.
Leaching gold from sulfide ores is difficult, at best. Generally, the recovery for cyanide leaching of sulfide or refractory ores is no better than 30%, which is not a worthwhile venture.
The use of alkalies such as calcium oxide, will prevent the decomposition of cyanide in solution to form hydrogen cyanide gas. It reduces the volume of cyanide required to leach the gold or silver. In addition, hydrogen cyanide is highly toxic to people. So, the few dollars spent on adding a cheap calcium oxide to the ore or solution, prior to leaching is worth the money spent. Most cyanide leaching is carried out at a alkaline pH of between 10 and 11, depending upon lab testing of individual ores and the optimum leaching/chemical use rates.
Lovely to contemplate, is it not? I am especially moved by the interplay of cyanide, arsenic and antimony, all notable toxins.