Gold cyanide processing gold extraction method

Gold cyanide processing gold extraction method
Gold cyanide processing gold extraction method, the basic principle of gold cyanidation method, gold cyanide leaching six factors, methods to extract gold from cyanide leaching solution List
Cyanide gold extraction is one of the main methods to extract gold from gold ore. Cyanide to explain the mechanism of gold dissolution is not the same, most of that in the case of gold cyanide solution at the presence of oxygen to generate a gold complex can be dissolved. The basic reaction is:
 4Au + 8KCN + 2H2O + O2 → 4KAu (CN) 2 + 4KOH
Generally considered the gold is dissolved cyanide occurs in two steps:
   2Au + 4KCN + O2 + 2H2O → 2Au (CN) 2 + H2O + 2KOH

2Au + 4KCN + H2O2 → 2KAu (CN) 2 + 2KOH
Surface gold in cyanide solution to dissolve gradually from outside to inside. The oxygen concentration in the solution with the gold dissolution speed.
Factors cyanide gold leaching rate when there are: the concentration of cyanide and oxygen, pH value of the pulp, the raw material properties of gold minerals, leaching temperature, slime content, pulp density and leach time.
Leaching cyanide concentration is generally 0.03% to 0.08% with increasing the dissolution rate of gold cyanide concentration was straight up to the maximum. Then rise slowly, when the cyanide concentration of 0.15%, the unrelated gold dissolution rate and cyanide concentration, or even decline (due to cyanide hydrolysis).
Gold dissolution rate increased with oxygen concentration increases, the use of oxygen-rich solution can be enhanced or high-pressure inflatable cyanide to dissolve gold.
Ability to dissolve gold and silver cyanide reagent is: ammonium cyanide> cyanide calcium> sodium> potassium cyanide. Potassium cyanide most expensive, most currently used sodium cyanide, cyanide consumption depends on the nature of the material and operational factors, often 20 to 200 times the theoretical amount.
Material properties affect the leaching rate of gold. Although cyanidation gold extraction is the main method, but some gold-bearing mineral raw materials should not be used directly cyanidation process, if the ores of copper, arsenic, antimony, tin, sulfur, phosphorus, magnetite, marcasite, etc. will greatly increase cyanide consumption or consumption of pulp in the oxygen content is high component. Lower gold extraction rate, high carbon-containing ore, gold has been dissolved carbon will absorb the loss and with the tailings. Pre-roasting or flotation methods on harmful impurities can be removed.
Hydrolysis of cyanide is: KCN + H2O ← → KOH + HCN ↑, therefore volatile toxic HCN; lime cyanide hydrolysis weakened the reactor to the left direction, reduce chemical loss of cyanide. Lime and acids as well as the role of the pulp and precipitation of harmful ions, and the dry dissolve gold at the best conditions, commonly used as a protective lime base. Lime added in an amount to make the pulp pH value of 11 to 12 is appropriate, when the pulp pH value is too high for gold dissolution disadvantage.
Gold particles size mainly affects cyanide time, coarse gold (> 74 microns) was dissolved slower speed. Therefore, before using cyanide amalgamation, re-election or pre-flotation recovery of coarse gold it is reasonable to. In the grinding process, to fine gold particles fully monomer dissociation is still improving gold leaching rate of more to factor.
When the content of cyanide sludge and slurry concentration component directly affects the rate of diffusion. Pulp concentration should be less than 30 to 33%. Pulp sludge concentration for a long time should be less than 22 to 25 percent, but under the concentration should be too low, otherwise increase cyanide consumption.
Cyanidation time depends on material properties, cyanide and cyanide way conditions. Usually cyanide leaching stirring often more than 24 hours, sometimes for more than 40 hours, we need 72 hours when the hoof and gold cyanide, cyanide leaching percolation takes more than five days.

The method of extracting gold from cyanide leaching solution List
Mention gold from cyanide leach solution methods more, if CIP (CIP), carbon leaching (CIC), magnetic carbon method (MCIP) or resin exchange process can go solid-liquid separation operations. Usually cyanide slurry solid-liquid separation to get your solution (gold solution). From your liquid gold extraction methods are zinc substitution precipitation, activated carbon adsorption, ion exchange resin adsorption method or electrolytic deposition method. Metal zinc wire or zinc powder from the solution by precipitation of gold is a commonly used method of substitution. Before entering your fluid replacement precipitate jobs clarified to remove the sludge and suspended solids, because these impurities to precipitate the next replacement job is harmful.
The basic principle is that gold precipitated zinc substitution: in your liquid zinc will dissolve in the solution leaving the gold precipitates out your liquid ion Au (CN) 2- and Zn role reaction is usually written as:
   2KAu (CN) 2 + 3Zn + 4KCN + 2H20 ← → 2Au ↓ + 2K2Zn (CN) 4 + K2Zn02 + H2 ↑
There must be sufficient cyanide and alkali solution when the zinc substitution, or else gold dissolved oxygen in the solution will have been precipitated leaving the zinc oxide powder was redissolved into Zn (OH) 2 precipitation:
                                    Zn + 1 / 2O2 + H2O ← → Zn (OH) 2 ↓
There solution K2Zn (CN) 4 will be broken down into cyanide zinc precipitate insoluble:
K2Zn (CN) 4 + Zn (OH) 4 ← → 2Zn (CN) 2 ↓ + 2KOH
These zinc hydroxide and zinc cyanide as a white precipitate will be housed in a thin film formed on the surface of metallic zinc, zinc substitution effect and prevented from expensive solution for gold. The conventional settling tank by adding a small amount of lead acetate and lead nitrate and better contribute to the dissolution of zinc replacement precipitate gold. Expensive solution containing soluble sulfide, mercury, copper and other impurities are replaced hinder gold precipitation.