Introduction to Gold Electrowinning Process

Gold-Electrowinning-Equipment-Plant

Gold electrowinning is an electrochemical process in which gold ions (Au⁺ or Au(CN)₂⁻) dissolved in solution are reduced and deposited as metallic gold onto cathode surfaces using direct current electricity.

In most gold processing circuits, electrowinning is used to recover gold from:

• Carbon-in-leach (CIL) or carbon-in-pulp (CIP) elution solutions

• Heap leach pregnant solutions (often combined with carbon adsorption)

• Intensive cyanidation circuits for gravity gold concentrates

The deposited gold is later removed from the cathodes, dried, and smelted to produce doré bars.

A typical gold electrowinning circuit includes the following steps:

1. Gold Leaching and Adsorption

Gold-bearing ore is leached using a cyanide solution. Dissolved gold is then adsorbed onto activated carbon (CIP/CIL) or collected directly in solution.

2. Carbon Elution (If Applicable)

Loaded carbon is treated in an elution system to strip gold into a high-grade pregnant electrolyte solution.

3. Electrowinning

The gold-rich solution is pumped into electrowinning cells, where direct current causes gold to plate onto cathodes.

4. Cathode Harvesting

Gold-bearing cathodes (steel wool or mesh) are periodically removed from the cells.

5. Smelting and Refining

Collected cathode sludge is dried, fluxed, and smelted to produce gold doré.

The electrowinning process relies on electrolysis:

• Cathode (reduction):
  Gold ions gain electrons and are reduced to metallic gold.
  Au(CN)₂⁻ + e⁻ → Au + 2CN⁻

• Anode (oxidation):
  Oxidation reactions occur, typically involving oxygen evolution.

The efficiency of gold electrowinning depends on factors such as:

• Gold concentration in solution

• Electrical current density

• Solution temperature and chemistry

• Cell design and cathode material

1. Electrowinning Cells

Electrowinning cells are rectangular tanks constructed from steel, fiberglass, or polypropylene. They are designed to ensure:

• Uniform current distribution

• Effective solution flow

• Easy cathode removal

Cells can be installed individually or in modular banks for scalable capacity.

2. Cathodes

Common cathode materials include:

• Stainless steel wool

• Mild steel mesh

• Expanded metal plates

Steel wool cathodes are widely used due to their high surface area, which improves gold deposition efficiency.

3. Anodes

Anodes are typically made from:

• Stainless steel

• Lead alloy

• Mixed metal oxide (MMO) materials

They are selected for corrosion resistance and long service life.

4. Rectifier (DC Power Supply)

The rectifier converts AC power into controlled DC current. Key parameters include:

• Adjustable voltage and amperage

• Stable current output

• Energy efficiency

5. Ancillary Systems

Additional equipment may include:

• Solution pumps and piping

• Heat exchangers

• Flow control and monitoring instruments

Optimizing electrowinning performance requires careful control of several parameters:

• Gold concentration: Higher concentrations improve recovery rates

• Current density: Excessive current can reduce efficiency and increase power consumption

• Solution temperature: Typically maintained between 40–60°C

• Electrolyte composition: Free cyanide and pH must be controlled

• Residence time: Adequate contact time ensures high gold recovery

Gold electrowinning offers several operational and economic advantages:

High Recovery Efficiency

Electrowinning can achieve gold recoveries above 95% when properly designed and operated.

Compatibility with CIP/CIL Circuits

It integrates seamlessly with carbon adsorption and elution systems, making it ideal for modern gold plants.

Lower Chemical Consumption

Unlike Merrill–Crowe, electrowinning does not require zinc dust or extensive clarification systems.

Automation and Operational Simplicity

Electrowinning systems are easy to automate, reducing labor requirements and operational risk.

Compact Footprint

Electrowinning cells require less space compared with precipitation and filtration systems.

Gold electrowinning is widely used in:

• CIP and CIL gold processing plants

• Heap leach gold recovery circuits

• Small to medium-scale gold mines

• Gravity gold intensive leaching systems

• Tailings reprocessing and gold recovery projects

Its flexibility makes it suitable for both greenfield projects and plant upgrades.

When designing or investing in a gold electrowinning system, key factors include:

• Throughput and gold production targets

• Integration with upstream leaching and elution systems

• Power supply reliability and energy costs

• Ease of maintenance and cathode handling

• Supplier experience and after-sales support

A properly engineered electrowinning system can significantly reduce operating costs and improve overall gold recovery.

Gold electrowinning is a proven, efficient, and cost-effective gold recovery technology widely adopted in modern gold processing plants. With high recovery rates, low operating complexity, and strong compatibility with CIP/CIL circuits, it remains a cornerstone process for gold producers worldwide.

For mining investors and plant operators, selecting the right gold electrowinning equipment and process design is essential to maximizing gold recovery, minimizing operating costs, and ensuring long-term project success.