·Various leaching parameters such as particle size cyanide concentration pH and the application of oxygen and lead nitrate have been investigated for the recovery of gold from an ore containing
·SART for copper control in cyanide heap leaching by M Stewart and D Kappes Synopsis Copper cyanide is a common component of cyanide treatable precious metal ores The copper concentration in production heaps can be predicted from laboratory column tests but the exact correlation is not necessarily intuitive
·The most commonly used cyanide salts are KCN and NaCN which are easily soluble in water Cyanide leaching is the dominating process for gold recovery from primary resources due to its simplicity
·The new cyanide concentration is ranging between 500 ppm in the first leach tank and 300 ppm NaCN at the end of the leaching circuit The cyanide consumption of the plant was reduced from to 0
·In a cyanide solution lead nitrate lead sulphide and lead sulphite react with gold to form AuPb 2 Whereas the predominant iron species at the surface of the pyrite after lead pre leaching and cyanidation are as sulphides u E o < Pb 30 20 10 ] I I Pb Iron sulphides Fe oxy forms Pb 110 3 Pb oxy forms Main
·The high oxidizing potentials involved with some lixiviants lead to high By cyanide leaching this residue over 95% of gold can be extracted with solutions containing g/L of KCN
·The application of lead nitrate in combination with oxygen generated the best results Gold extraction of 96% can be obtained with cyanide consumption of kg/t and lime consumption of kg/t in 24 hours A four hour pre leach followed by cyanidation is required free cyanide concentration 480 ppm pH lead nitrate 200 g/t and 16 ppm
5 ·The stability constants of the cyanide complexes with lead silver copper and nickel are less than for ion complexes which release HCN more easily and are therefore more toxic Oelsner et al 2001 The cyano complexes of copper and zinc in WADs are insoluble in water but soluble in ammonia solution Leaching with biogenic cyanide can
·During the cyanide leaching of sulfidic gold ores the sulfide minerals dissolve into the leach solution and produce metastable sulfur species such as sulfide bisulfide polysulfide elemental sulfur and thiocyanate In the tests designed to study the Pb effect on the gold leaching 16 32 and 80 mg/L of lead nitrate [Pb NO 3 2 Fisher
·Introduction to Gold and Silver Leaching The cyanide leaching process is the most important method ever developed for extracting gold from its ores The early development of the process is attributed to a Scotchman John Stewart Mac Arthur in collaboration with the Forrest brothers The method was introduced into South Africa in 1890
·Cyanide has several advantages such as low cost high efficiency and selectivity compared to other compounds such as halides thiosulfate thiourea and thiocyanate which are also capable of
·Thiosulfate leaching Thiosulfate is a non toxic alternative to cyanide and its gold dissolution rates are generally slower than those of cyanide It is more commonly used in large scale mining
·for leaching but the gangue mineralogy in some way interferes with cyanidation process The gangue minerals consume cyanide and oxygen in solution or they re adsorb gold from solution Ores that contain cyanide and oxygen consumers are
·Introduction to Leaching & Adsorption CIL technology is based on the fact that the gold dissolves readily in cyanide solutions in the presence of oxygen and the resultant gold cyanide complex ion molecule is readily Lead nitrate is added to the leach circuit and has the effect of accelerating the gold dissolution
·Large stoichiometric ratios of O 2 /M for the cyanidation of graphite coated gold appears to be a result of the enhanced oxidation of cyanide by oxygen or hydrogen peroxide leading to a cyanide deficiency at the surface and passivation of gold by hydroxide/oxide The presence of excess cyanide or lead II does not override this effect
·For over two hundred years cyanide has served as the primary reagent for gold extraction However due to its high toxicity the use of cyanide poses significant risks Traditional low toxicity leaching reagents have limitations that restrict their widespread industrial application leading to the necessity for the development of new efficient and low toxic gold
·In this article lead oxide was used to increase leaching efficiency and decrease sodium cyanide consumption The mechanism of lead oxide enhanced gold leaching was studied by thermodynamic
·The addition of lead nitrate could have resulted in the passivation of these cyanide consumers resulting in a decrease in the amount of cyanide consumed An increase in the pH range from to 11 resulted in an g/t decrease in cyanide consumption This is probably due to the fact that less cyanide is lost as
hours leaching by the addition of lead nitrate as kg/Mg NaCN consumption decreased or did not change except for the Ovacik ore In the case of the Ovacik ore it slightly increased Keywords lead nitrate gold silver cyanide leaching Introduction Extraction of gold from its ores by cyanide leaching has been the preferred method for
·The rates of oxidation of thioarsenite thioantimonite and sodium sulphide in cyanide solutions of pH 12 in the presence of a small amount of lead nitrate were compared The thioarsenite solution was much more stable than the sodium sulphide solution while the thioantimonite solution was the most stable of all
5 ·The stability constants of the cyanide complexes with lead silver copper and nickel are less than for ion complexes which release HCN more easily and are therefore more toxic Oelsner et al 2001 The cyano complexes of copper and zinc in WADs are insoluble in water but soluble in ammonia solution Leaching with biogenic cyanide can
·for leaching but the gangue mineralogy in some way interferes with cyanidation process The gangue minerals consume cyanide and oxygen in solution or they re adsorb gold from solution Ores that contain cyanide and oxygen consumers are
·The ore with a low sulphide content required a pre leaching of only 1 h with a small quantity of Pb NO3 2 50 g/t and leaching can be performed at 360 ppm NaCN to allow a recovery of % Au and
DOI / Corpus ID 96975419; Leaching and electrochemistry of gold silver and gold silver alloys in cyanide solutions Effect of oxidant and lead II ions
·Gold leaching in the glycine solution is a chemically controlled process in which temperature is an effective parameter Eksteen and Oraby 2015 With the addition of cyanide the dissolution of gold increases significantly from 8% to 59% within 6 h from 24 to 30 h while the dissolution of copper increases from 28 to 31% over the same period
