Gold is an almost non reactive metal but halogens chlorine bromine fluorine and iodine can dissolve it Chlorine is the cheapest and lightest product that can achieve this Bleach is the chemical compound sodium hypochlorite When combined with hydrochloric acid the mixture produces chlorine that dissolves gold from gold ore

Gold leaching is the key stage in process of gold mining There are a few well reputed leaching methods using a variety of different reagents Nowadays the most popular industrial processes include cyanide thiourea and thiosulfate leaching methods

During the past 10 years biotreatment of refractory gold ores which contain finely disseminated gold particles associated with sulfide minerals including arsenopyrite pyrite and pyrrhotite has been developed to an industrial application and several tank leaching operations are being run in South Africa Brazil and Australia 50 54–56

Also the waste alkaline sulfide solutions can be recycled for further gold leaching or further processed with low temperature oxidation to sodium sulfate Na2SO4 This also oxidizes the arsenic to soluble sodium arsenate which can then be precipitated by conventional means using iron compounds

This mechanism leads to adsorption of polysulfides and sulfate ions on the gold surface By controlling pH and oxygen concentration this effect can be reduced The high thiourea concentration in conducted trials facilitate the reagent decomposition Unlike the thiosulfate system the passive layer is soluble and enables further gold leaching

Bacterial Leaching of Copper Ores Several types of bacteria capable of living in an acid environment have been isolated from copper mine waters The foremost of these are of the genus Thiobacillus T Thiobacillus bacteria are acidophilic aerobic chemolithotrophs which grow most rapidly at a pH in the range of 2 3 T ferrooxidans derive their energy by oxidizing ferrous iron elemental

for copper leaching is 0 1 kg NaCN t If the quantity of copper extracted increases to 300 g t then the cyanide requirement increases to 0 7 kg NaCN t Viewed another way since the 3 moles of cyanide that are complexed with each mole of copper in the leach solution are effectively inactive as far as gold leaching is concerned the Maricunga

Thiourea Leaching In order to compare gold dissolution from the ore with and without pretreatment for another lixiviant the system of thiourea ferric sulfate was chosen Figure 9 shows the results for gold leaching at SC NH2 2 0 of 0 15 M 11 4 g L and Fe 3 0 of 0 02 M 1 12 g L and pH 2

This investigation was published in 2010 as Order 4088 Chloride to Sulfate Mass Ratio CSMR Changes from Water Treatment and its Impact on Lead Leaching in Potable Water WaterRF then extended that project to examine effects of CSMR and galvanic corrosion on lead leaching to potable water after partial lead service line replacements

Sulfate roasting and thiosulfate leaching were used to recover metals Three sulfate promoters sulfur iron sulfate or pyrite were used Sulfur presented best results on the recovery of Ag Cu and Zn A comparison of gold recovery with cyanide or sodium thiosulfate was performed Thiosulfate is efficient in the recovery of gold

Presence of Ferric Iron in the Leaching Solvent – Ferric sulfate was found to be essential for oxidizing sulfide minerals and when used in conjunction with acid on the oxide minerals was found to substitute for acid and thereby reduce the ultimate consumption of acid A good example of the use of ferric sulfate as a substitute for acid is

Also the waste alkaline sulfide solutions can be recycled for further gold leaching or further processed with low temperature oxidation to sodium sulfate Na 2 SO 4 This also oxidizes the arsenic to soluble sodium arsenate which can then be precipitated by conventional means as scorodite or ferrihydride using iron compounds

The leaching rates of the two systems were similar in the first 5 h In the case of the system without lead nitrate the gradual dissolution of stibnite decreased the gold leaching kinetics after the 5 h point The gold extraction gap between the two systems increased with time

Alternative lixiviants to cyanide for leaching gold ores 517 to the halide systems the stability of gold in solution and the lack of a suitable recovery option appear to restrict them as a simultaneous leaching and recovery process For sulfide ores containing a combination of base precious and platinum group metals these processes may be

Chloride–hypochlorite oxidation and leaching of refractory sulfide gold concentrate 63 Fig 1 The Pourbaix diagram of Fe–S at Fe – 10 4 M S 10– M and 25 C the chlorine species regions are also marked Marsden and House 2005 Fig 2

Heap leaching is an industrial mining process used to extract precious metals copper uranium and other compounds from ore using a series of chemical reactions that absorb specific minerals and re separate them after their division from other earth materials Similar to in situ mining heap leach mining differs in that it places ore on a liner then adds the chemicals via drip systems to the

May 19 2011· I have some questions about thiosulfate leaching Has anyone here actually used thiosulfate for leaching gold ore and had positive results that can be repeatable as a real leaching process sulfate not AR or cyanide Safety is the key issue and my main concern

ALKALINE OXIDATIVE LEACHING OF GOLD BEARING ARSENOPYRITE ORES By P Bhakta 1 J W Langhans Jr 1 and K P V Lei2 ABS rRACT The U S Bureau of Mines developed an alkaline oxidative pretreatment leaching procedure to increase the recovery of gold from arsenopyrite FeAsS ores The best solution compositions for

In the present paper a kinetic study of gold leaching in alkaline sulfide solutions is presented For the gold leaching system both a complexing lixiviant and an oxidant are required to effect dissolution It will be shown that sulfide is an effective lixiviant and the polysulfides are effective oxidants 2 EXPERIMENTAL

Bioleaching is the extraction of metals from their ores through the use of living organisms This is much cleaner than the traditional heap leaching using cyanide Bioleaching is one of several applications within biohydrometallurgy and several methods are used to recover copper zinc lead arsenic antimony nickel molybdenum gold silver and cobalt

A Method for Leaching or Dissolving Gold from Ores or Precious Several reagents are known to leach native gold from gold bearing ores It has been known for more than a century burette 14 Reducing reactant for precipitating gold such as iron II sulfate and oxalic acid

Project Target 2 – Gold ore with nuisance copper Gold ores with elevated or nuisance copper levels are difficult to process by conventional cyanide heap leaching as the copper causes high cyanide consumption As well as the direct cyanide cost this increases the cost of detoxifying effluent solutions

In situ leaching ISL also called in situ recovery ISR or solution mining is a mining process used to recover minerals such as copper and uranium through boreholes drilled into a deposit in situ In situ leach works by artificially dissolving minerals occurring naturally in a solid state For recovery of material occurring naturally in solution see Brine mining