High Efficiency Elution and Electrowinning Plant

Working Principle

1.1 Elution

CN- or OH- dissolved in desorption solution is easier than Au(CN)2- to be absorbed by the activated carbon which causes Au(CN)2- absorbed on loaded carbon is replace by CN- or OH-  and the reversible balance of of gold adsorption is broken. This processing is named as gold desorption (elution, stripping). The reaction formula is below:

Gold is stripped out of loaded carbon by increasing cyanide concentration, alkalinity, temperature, pressure or adding organic solvents, etc. Comparing other methods, it is the lower production cost that temperature and pressure are improved. If the working temperature is 150oC and working pressure is about 5.5 bar, the elution rate is improved by several times and the cycle time is reduced to be fraction of that one of normal pressure cycle. 

1.2 Electrowinning 

Gold exists as Au(CN)2- in the pregnant solution produced in the adsorption circuit. The pregnant solution is sent to the electrowinning cell for electrochemical reactions. The reactions are as below:

Cathode formula:

 Au(CN) 2-+ e → Au+2CN-

Ag(CN) 2-+ e → Au+2CN-

2H2O +2e →    H2+2OH-

Anode formula:

4OH- - 4e → O2+2H2O

CN-+2OH- - 2e → CNO-+H2O

2CNO- +4OH- - 6e → 2CO2+N2+2H2O

When the electrowinning solution temperature grows up, the deposition speed of gold becomes faster and the deposition efficiency is increasing as well.

1.3 Elution - Electrowinning Circuit

Elution and electrowining circuits form a packaged integrated pressure strip (IPS) system which works under high temperature and pressure so the elution circuit cancels the heat exchanger which is used in Zadra system. The pregnant solution ahs high temperature which is favorable to the electrowinning cell.


1. High temperature, high pressure, cyanide-free and elution controlled automatically bring out the advantages of high efficiency, low consumption, and quick cycle.

2. High efficiency: the elution rate can be more than 96% while the gold grade of the loaded carbon reached more than 3000g/t. The grade of barren carbon can be reduced by 3-4 times than that of the conventional system.

3. Quick cycle: the working temperature of the system is 150ºC so that elution is quick and the stripping duration is shorter that total cycle time is about 10 to 13 hours.

4. Low consumption: the elution devices and electrowinning equipment compose a integrated system. The temperature of every section of the whole system is same so that the heat exchanger is no need. The total power consumption is only 1/2-1/4 of the value of the conventional system because heat energy is recycled fully.

5. Cyanide-free: no sodium cyanide is fed to prepare stripping solution to realize low costs and no pollution.

6. Gold recovery: high grade of gold sludge, no reverse electrowinning, easy to collect gold sludge.

7. Automation: special liquid level control unit, temperature control unit and automatic control center.

8. Safety: triple safety protection devices, i.e., self intelligent system, automatic rated pressure release system and safety valves.

9. Long life: the material type of equipment, pipes, valves and instruments is stainless steel.

10. Modular plant: the system is a modular plant which is easy for installation on the site. The small scale elution plant is containerized.