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heap leaching with ore concentration low price

heap leaching with ore concentration low price

How to Process Gold Ores by Heap Leaching amp; Carbon Adsorption ...

The basic principle of the cyanidation process is that weak alkaline cyanide solutions have a preferential dissolving action on the gold and silver contained in an ore. The reaction generally accepted for several decades as representing the dissolution of gold by cyanide solution is 4Au + 8CN + O2 + 2H2O 4Au2 + 4 OH .. Recent research on the mechanism of cyanidation, however, indicates this reaction proceeds in two stages. Most of the gold dissolves by the reaction 2Au + 4CN + O2 + 2H2O 2Au2 + H2O2 + 2 OH and a small but significant proportion dissolves via reaction 1. The gold dissolution rate is dependent on the concentration of NaCN and the alkalinity of the solution, the optimum pH being 10.3. For efficient leaching, the gold should occur as free, fine size, clean particles in an ore that contains no cyanicides or impurities that might destroy cyanide or otherwise inhibit the dissolution reaction. An adequate s...

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The manner of gold occurrence and its association with the gangue minerals dictate whether or not the ore can be processed by the cyanide heap leach method. From a metallurgical standpoint, gold ores may be roughly classified as simple oxide ores containing fine particles of native gold in a quartz or limestone gangue, simple sulfide ores in which the gold is associated with minor amounts of pyrite or arsenopyrite, placer or alluvium material, complex or refractory ores in which the gold bearing mineral species are not readily soluble in cyanide solution, complex base metal ores in which the precious metals are important economic constituents, and base metal ores in which the precious metals are of minor value and are byproducts of treatment. Of these, only the simple oxide and sulfide ores and certain placers are suitable for heap leaching. These materials must possess the following characteristics: Gold and silver values are leachable by cyanidation, in October 1976 published its recommendations designed to protect the health of employees working with cyanide salts. The publication, Criteria for a Recommended Standard Occupational Exposure to Hydrogen Cyanide and Cyanide Salts NaCN, KCN, and Ca2 can be purchased from the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402. Employe...

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Recently, efforts have been directed toward the development of lower cost gold processing procedures that will improve the economics of treating lower grade ores and deposits too small to warrant construction of conventional mill facilities. The Bureau of Mines developed a more efficient process for recovering gold and silver from laden activated carbon. Factors that can affect the performance of the modified strip solution include temperature, and concentrations of NaOH and ethanol. The strip solution, which is water containing 1 wt pct NaOH and 20 vol pct ethanol, is heated to 80° C and circulated through a bed of loaded carbon to desorb precious metals and cyanide ions. The precious metals arc recovered by electrolysis, and the depleted electrolyte is recycled to the carbon desorption column. Five to six hours of simultaneous stripping and electrowinning will desorb up to 99 pct of the precious metal values carried by the activated carbon. A flow diagram for the process is shown...

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