The Know-How or Experience is on gold-loaded carbon elution and pregnant solution electrolysis, for direct production of  gold alloy. It is maily learning for small scale gold mine,  which adopting carbon in pulp plant or heap leaching, which adopting  active carbon adsorption process. It will help the small scale gold mine to get the pure gold after process the loaded carbon.

1, Technical Principle

The gold and silver in the gold-loaded activated carbon precipitated from the carbon into pregnant solution after heating and washing by desorption liquid configured with sodium cyanide (NaCN) and sodium hydroxide (NaOH) in the desorption column, and the pregnant solution was deposited on the cathode into gold powder due to the action of direct current in the electrolytic cell.

 

2, What equipment will be adopted

 

It is simple to adopt normal pressure and temperature elution and electrowinning plant to make the gold-loaded carbon regeneration, and get the gold electrolytic deposition.

The equipment includes desorption column, electric heater, heat exchanger, electrowinning cell, desorption liquid storage tank, circulation pump, rectifier control cabinet and so on. The rectifier control cabinet can be used for DC output, electric heating constant temperature control and circulation pump control. The safety valve can operate and return the desorption liquid when the temperature is over and the pressure is over. Desorption liquid circulation pump has: desorption liquid configuration, desorption liquid circulation and other functions.

Electrowinning cell.  It is made of polypropylene plate and can withstand the temperature of 80℃. A total of 15 anodes are made of stainless steel plates with a size of 500×550 mm. A total of 14 cathodes are made of φ0.13 stainless steel microfilaments or carbon fibers.

Capacity: 500~2000Kg/batch

 

3, How to install elution and electrowinning plant

3.1, Overhead scheme: If the height of the workshop allows the carbon hopper to be at a reasonable elevation, the equipment can be 60-70 cm high, the equipment is flattened, and the 3-phase 4-wire AC power supply is connected after fixing, that is, the four terminals of ABCN.

3.2, Flat scheme: If the height of the workshop does not allow, the equipment could be placed flat on the ground, a 1.8m square pit 60-70cm deep is built under the ground of the desorption column in order to recover the carbon and surface water after desorption.

3.3, The ground of the equipment should be well impermeable and leak-proof, and the ground can be treated with anti-corrosion if it is acceptable.

3.4,  after the power supply, should try the positive and negative rotation of the acid pump

3.5, the desorption column is connected as one assembly, and the fastening screws should be symmetrical.

 

4, How to Operate

4.1, operating conditions

Desorption time: 44 hours (starting from 95℃)

Desorption solution concentration: NaCN not less than 2% NaOH not less than 1%

Desorption temperature: 95℃

Desorption voltage: 1.5-3V (DC)

Electrolytic current: 320A

Electrolyte flow rate: 3.6t/h

Initial dosage: NaCN , NaOH

 

4.2, Operating steps

4.2.1  Inspection

After the elution and electrowinning plant is installed, fill the desorption liquid storage tank with clean water and open the pump for cycle to check whether the elbows, flanges, valves and other joints leak, and whether the electric heating and electric control are sensitive and normal.

4.2.2  Gold loaded carbon loading 

The gold-loaded carbon added into the desorption column must be cleaned with water, and the carbon must not contain mineral slime, wood chips and other debris. After the carbon loading is completed, the top carbon inlet should be tightened with a blind plate. After checking the discharge valve of the desorption column, no mineral slime or carbon particles are discharged, and the carbon loading is considered to be complete.

4.2.3  Reagent Dosing  (the example is on the basis for processing 500kg/batch)

Weigh sodium cyanide (NaCN) 80kg, sodium hydroxide (NaOH)40kg into the desorption liquid storage tank , rinse the agent with clean water, if the storage tank is full of water, the agent is not completely dissolved, you can open the circulation pump with bypass water to dissolve the regent , open the through valve after the agent is completely dissolved.

4.2.4  Desorption

After opening the relevant valve, the desorption liquid circulation pump is opened. When the desorption liquid is circulated back to the electrolytic cell, the electric heater can supply electricity for heating. When the desorption temperature reaches 95℃, the electrolytic cell is sent to DC and the current, voltage is adjusted to the appropriate data. Since the desorption temperature reaches 95℃ continuous desorption and electrowinning more than 44 hours, this elution and electrowinning ends.

4.2.5  Stop the equipment

First stop the electrolytic power supply, then power off the heater, and then stop the circulation pump operation. After closing the valve of the inlet pipe at the front end of the electrolytic cell, the drain valve of the electrolytic cell is slightly opened to make the lean liquid in the electrolytic cell slowly flow back to the storage tank.

The lean liquid and cooling rinse water in the desorption column should also be pumped back to the adsorption tank, and the lean carbon cooled in the desorption column should be discharged from the carbon discharge port, the poor carbon is washed by water, pickling (5% HC1) and then washed by water, and can be returned to the adsorption section after screening.

4.2.6  Gold Powder Treatment

After the elution and electrowinning, open the electrolytic cell and remove the cathode plate (the plate can also be removed once after multiple desorption and electrowinning). The steel wool loaded with gold is rinsed in clean water, and the steel wool after elution of gold mud is re-loaded into the cathode, loaded into the electrolytic cell, ready for next use.

The gold mud is sieved to remove impurities, dried and smelted to get the finished gold ingots.

In order to improve the fineness of gold, gold mud can also be added acid , silver seperation, washing, drying, smelting to obtain gold ingots with higher fineness.

pure gold powder

pure gold by Aqua Regia Gold Refining Plant