Gold is recovered from the heap leaching solution, although zinc displacement or ion exchange resin adsorption can also be used, but larger scale heap leaching is still more simple and effective than activated carbon adsorption. The Renault Research Center of the US Mining Bureau is also studying the method of direct electrowinning of gold from heap leaching liquid.
The activated carbon adsorption of gold in the noble liquid is usually carried out by using 2 to 5 adsorption columns (or tanks) in series. The carbon column with a diameter of 0.6m and a height of 1.8m can be welded with carbon steel plates of 5 to 6.5mm. Each column is filled with carbon of about 90kg, accounting for one-third of the column capacity. The column is arranged in a stepwise manner or the liquid is self-flowing by the height difference of the high-position tank, and the carbon is kept in the column in a suspended state by controlling the flow rate of the solution at a certain flow rate from the bottom to the top. In order to prevent the char from flowing away with the solution, a stainless steel screen is installed in the inlet and outlet ports of the column (when -3.327 to 0.991 mm (-6 to +16 mesh) carbon is used, a 0.833 mm (20 mesh) screen is used). The structure of the adsorption column is shown in Fig. 1. When a certain volume of precious liquid is passed and the gold loading of the carbon column 1 is saturated, the column 2 is changed to a column, the original column is replaced with a new carbon and then changed to the last column, and so on.
Figure 1 Carbon column structure
1-lean outlet; 2-screen;
3-discharge port; 4-your liquid inlet; 5--remaining liquid port
When the amount of gold and silver in the noble liquid is high, an appropriate amount of Na 2 S is added according to the amount of silver before carbon adsorption, and about 85% of the silver is precipitated into Ag 2 S, and then carbon adsorption is performed. Na 2 S is added in an amount not in excess should be strictly controlled in order to avoid remaining in the liquid S 2 - Effect of charcoal on gold.
The desorption and gold extraction methods of gold-loaded carbon are the same as those of the carbon slurry method.
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