Electrolysis

Gold and silver electrolysis is an advanced hydrometallurgical process used to recover and refine precious metals from leach solutions with extremely high purity. In this method, dissolved Au⁺/Au³⁺ and Ag⁺ ions are selectively reduced and deposited onto cathodes by applying controlled DC electrical current inside an electrochemical cell.

Compared to chemical precipitation, electrolysis offers superior metal purity, higher recovery efficiency, and excellent process control, making it one of the most reliable refining methods for high-value precious metals.

For gold electrolysis, the feed solution is typically a chloro-auric (HAuCl₄) or cyanide-based gold electrolyte produced after leaching and purification stages such as filtration and solvent extraction. The solution is circulated through electrowinning cells equipped with inert anodes (titanium, graphite, or platinized titanium) and stainless steel or titanium cathodes.

Under carefully controlled current density, temperature, and pH conditions, metallic gold deposits uniformly on the cathode surface as a dense, easily stripped layer. The recovered gold typically exceeds 99.999% purity, making it suitable for bullion production or further refining processes.

For silver electrolysis, silver-bearing nitrate or chloride electrolytes are processed in similar electrowinning cells. Silver ions (Ag⁺) are reduced at the cathode to form high-purity metallic silver crystals or sheets. The process can be operated in either batch or continuous mode, depending on production capacity.

Proper electrolyte management, including silver concentration, acidity, and impurity control (Cu, Pb, Zn, etc.), ensures stable operation and prevents contamination of the silver deposit. Typical cathode silver purity exceeds 99.99%.

Modern gold and silver electrowinning systems are fully automated and include solution circulation pumps, rectifiers, current and voltage control units, fume extraction systems, electrolyte filtration, and safety interlocks.

These systems achieve very high metal recovery rates (>99%), low reagent consumption, and minimal environmental emissions, making them ideal for both small-scale precious metal refineries (1–10 kg/day) and large industrial installations (10–1000 kg/day).