Normal Temperature & Pressure Gold Desorption Electrolysis System

【Structure of Normal Temperature and Normal Pressure Desorption Electrolysis System】 
A typical Normal Temperature and Normal Pressure Desorption Electrolysis System consists of the following major components:

1.Desorption section

• Desorption column/tank – contains the loaded activated carbon.
• Heating tank or heater – heats the desorption solution to the required operating temperature.
• Circulation pump – circulates the stripping solution through the carbon bed.
• Solution piping and valves – direct the solution through the desorption circuit.
• Temperature and flow instruments – monitor and control operating conditions.

2.Electrolysis section

• Electrolysis cell – receives the gold-bearing pregnant solution.
• Cathode plates – gold is deposited onto the cathodes.
• Anodes – complete the electrical circuit and support the electrochemical reaction.
• DC rectifier/power supply – supplies controlled direct current to the electrolysis cell.
• Gold sludge collection system – collects the deposited gold-bearing material from the cathodes.

3. Solution circulation section
The system normally includes: pregnant-solution tank, lean-solution/return tank, circulation pump, filters or screens, piping and valves. These components allow the desorption solution to circulate repeatedly between the carbon column and electrolysis unit.
4. Control and auxiliary equipment
Depending on the design, the system may also include: control cabinet, temperature controller, flowmeter, pressure gauges, liquid-level indicators, heating system, safety protection and emergency shutdown devices.
【Working Principle of the Normal-Temperature and Normal-Pressure Desorption Electrolysis System】
The ambient temperature and pressure desorption-electrolysis system is a two-stage process designed to recover gold from gold-loaded activated carbon. The process consists of gold desorption from activated carbon followed by electrowinning of gold from the pregnant solution.

1. Gold Desorption
During the desorption stage, a hot alkaline solution containing a high concentration of OH⁻ and/or CN⁻ is circulated through the desorption column containing gold-loaded activated carbon.
The alkaline solution promotes the desorption of the gold cyanide complex Au(CN)₂⁻ from the activated carbon by shifting the adsorption equilibrium and promoting ion competition within the carbon pores. As a result, the gold complex is released from the activated carbon and transferred into the liquid phase.
The resulting solution, enriched in dissolved gold, is referred to as the pregnant solution.
The desorption process is carried out under atmospheric pressure. Solution circulation is maintained by pumps, eliminating the need for pressurized operation.
2. Gold Electrowinning
The pregnant solution from the desorption column is then directed into the electrowinning cell.
Under the action of a direct-current (DC) electric field, the dissolved gold complex migrates toward the cathode, where gold is electrochemically reduced and deposited as metallic gold. A simplified cathodic reaction can be represented as:
Au(CN)₂⁻ + e⁻ → Au↓ + 2CN⁻
The metallic gold gradually accumulates on the cathode, forming a gold-bearing cathode sludge (gold mud) that can subsequently be collected and refined.
At the anode, oxidation reactions occur, including the generation of oxygen and the regeneration of cyanide species. The depleted solution, or barren solution, is then returned to the desorption circuit for reuse.
3. Continuous Circulation and Gold Recovery
The entire process forms a closed-loop circulation system:
Gold-loaded Activated Carbon → Alkaline Desorption → Pregnant Solution → DC Electrowinning → Gold Sludge → Barren Solution → Desorption
Through the combination of alkaline thermal desorption and direct-current electrowinning, gold is efficiently transferred from activated carbon into solution and subsequently recovered in metallic form.