Heap leach is a method developed by Henin and Lindstrom to process low-grade ore on a large scale with small production cost so that the levels below the cut-of grade can still be economical. Heap leach is the process of leaching of low grade gold rocks thrown, then the solution containing the metal particles are screened and separated by electrolysis. Heap leach done repeatedly and on a large scale.
There are several steps that are used in processing gold ores using heap leaching system

HEAP LEACHING Processing System

Heap leaching process was developed as a mineral processing low-grade metal that is more efficient and minimal cost. Compared with conventional cyanidation process of the mineral leaching process with stirred tank Heap leaching has several advantages in the form of designs that use a very simple, operating costs are also minimal, and in requiring less investment, because the heap leaching recovery is around 60% to 80 %. In large-scale process technology was first used and applied to the mining of gold ore at Carlin Nevada USA in 1970. This process has really made ​​a lot of mines that can easily take on geological resources that have a low grade and transforming them into the category of proven ore. Ore value as low as 0.01 oz Au can be processed by heap leaching system is economically.

The Difference Between Gold ore with a minerals Pyhrite

Physical appearance is almost similar to the gold ore PHYRITE, markasit, and chalcopyrite seen from the color, but can be distinguished from its soft, high density, and golden appearance. Gold associated with quartz, phyrite, arsenopyrite, and Silver.The physical properties of gold is very stable, not corrosive or weathered and rarely had a compound with other chemical elements. Electrical and thermal conductivity is very good, malleable so it can be formed and also be ductile. Gold is the most high-density metals.

People often think phyrite as a golden appearance, which resembles gold glitter. Occasionally someone asks, if pyrite is gold? Or is this auriferous pyrite?.

GOLD Content In Precipitates Aqua Regia.

In decision precipitates in aqua regia solution that has been contained gold metal content is required several stages.And eventually precipitated from these precipitates can be dissolved to be made in a metallic gold.
Some stages are used in the decision are as follows :
  • To neutralize the residual HNO, add urea [CO (NH2) 2] to the Aqua Regia which has been filtered.
it will get a reaction :
6 HNO3 + 5CO(NH2 ) 2 = 8N2 + 5CO2 + 13H2O   
The trick Urea enter little by little until the reaction finished white bubbles. From this reaction would make nitric acid to neutral pH conditions and changed from 0.1 to pH 1.0. 
  • After the reaction is complete then Enter Sodium Bisulphite and observe the reaction.In theory, every single gram of gold requires 1.89 grams of Sodium Bisulphite. However, it should be added more, about 1.5 times longer.
Then the reaction is :

2HAuCl 4 + 2NaHSO3 = 2Au + 4HCl + Na2 SO4 + SO2
  • Wait about 30 minutes, until no precipitate (sludge) that appear brownish-black color. And then dispose of the liquid solution slowly to the remaining precipitate only way destilled filtered and then rinsed with water. Sodium Bisulfide If not then there are several alternative reagents that can be used as a substitute such as Sodium Sodium Bisulphite Metabisulfide (SMB), oxalic acid, sulfur, and Sulphur Dioxide or Copperas (Ferrous Sulphate)
  • Then pour it gently - the land of ammonia solution (30 ml Aqua ammonia has been dissolved into 100 ml mineral water) to precipitate until the pH reached 8.It will get a Gold Fulminating sediment.Remember fulminant sediment is very dangerous, not to dry because it has the nature of the High Explosive.  
  • Wash the precipitate to remove excess ammonia. Wash several times until the pH reaches close to 7
  • Then rinse the sediment precipitates made ​​in one and then in the process of melting metal to form gold.  
  • Related Articles PROCESS SMELTING GOLD 

READ MORE >>> Gold Precipitation Methods