When a circuit board carrying discarded electronic components enters a dissolution tank, or when precious
metal scrap is gradually dissolved in a chemical reagent, a precise journey of metamorphosis has already begun.
In the field of precious metal recovery and refining, gold electrolysis technology plays an irreplaceable central role.
It is like a skilled alchemist, with precise current control, will dissolve in the solution of gold ions back to high purity
of the monomaterial gold, to realize from the “waste” to the gorgeous transformation of high-purity gold.
Demystifying the core: gold “rebirth” in the electrolysis cell
The core of gold electrolysis lies in the electrolysis cell. Imagine a special container containing a solution of dissolved
gold (electrolyte, such as chloroauric acid solution). Two key electrodes are placed inside the cell:
Anode: Usually made of crude gold or an alloy material to be refined. When energized, the gold (and some of the
impurity metals) on the anode undergoes an oxidation reaction, loses electrons, and dissolves into the electrolyte
as ions (e.g., Au³⁺).
Cathode: Made from thin sheets of high purity gold or stainless steel. Gold ions (Au³⁺) in solution gain electrons on
the surface of the cathode, undergo a reduction reaction, and are redeposited as pure gold.
The central driver of this process is direct current. Under the action of an electric field, positively charged gold ions (Au³⁺)
migrate toward the cathode and are reduced, while the anode provides a steady stream of gold ions into solution. It is
worth noting that other metal impurity ions in solution, due to their different precipitation potentials, are difficult to be
effectively deposited at the cathode under standard electrolytic conditions, thus realizing the efficient separation of gold
from most impurities.
Key equipment: building the cornerstone of refining
An efficient and stable gold electrolysis system cannot be achieved without the coordinated operation of key equipment:
Electrolyzer: As the core reaction vessel, it needs to have excellent corrosion resistance (against strong acid environment) and
insulation performance. The design of the tank should take into account the uniformity of the current distribution, which is
crucial for the uniformity and purity of the gold deposited at the cathode.
Rectifier power supply: Provide stable and controllable DC power. The power supply needs to have precise voltage and
current regulation to optimize electrolysis efficiency and ensure deposition quality. Too high a current density can result
in loose deposits and impurities, while too low a current density is inefficient.
Electrode system:
Anode: Coarse gold anode plate needs to ensure relatively uniform composition, its purity directly affects the electrolysis
efficiency and cathode gold quality.
Cathode: The starting cathode (mother plate) must be highly pure (e.g. more than 99.99% pure gold sheet), and its surface
finish directly affects the stripping ease and appearance of deposited gold.
Electrolyte Circulation and Temperature Control System: The electrolyte needs to be continuously circulated and filtered to
remove solid impurities, such as anode sludge, and to maintain the purity of the solution. Temperature control is also important,
usually within a specific range (e.g., 50-70°C) to maintain optimum ionic activity and deposition rate. Some processes also
require periodic replenishment of the gold ion concentration and adjustment of the acidity (pH).
The refining process: from charging to harvesting high purity gold
The standard gold electrolytic purification operation is a rigorous process:
Pretreatment and loading: Crude gold material is melted, cast and rolled into compliant anode plates. Thoroughly clean and
treat the cathode mother plate. The anodes and cathodes are loaded into the electrolyzer at specific intervals to ensure good
contact and current path.
Preparation and injection of electrolyte: Use high-purity chemical reagents (such as hydrochloric acid, chloroauric acid) to
prepare electrolyte that meets the requirements, and inject it into the electrolytic tank after filtering.
Energize Electrolysis: Start the rectifier power supply and accurately set and maintain the optimum current density (typically
in the range of 1-10 A/dm²) based on parameters such as anode composition, area, and target deposition rate. This step is
particularly critical as voltage, current, temperature and electrolyte condition are continuously monitored.
Process Maintenance: Regular sampling and analysis of electrolyte composition to replenish depleted gold ions and acids,
remove anode sludge, and maintain electrolyte cleanliness and stability. Continuous monitoring of equipment operating
parameters.
Cathode Gold Harvesting: When the cathode has reached a predetermined thickness of deposited gold (may take days to
weeks), electrolysis is stopped. Remove the cathode and wash thoroughly to remove electrolyte residue. Carefully strip the
deposited gold flakes.
Post-processing: The stripped cathode gold flakes may be further purified and cleaned by acid washing, water washing
and drying. Finally, it is melted and cast into a standard gold ingot (e.g., 1 kg) and subjected to rigorous compositional
analysis (fire assay or ICP spectrometry is commonly used) to confirm purity of 99.99% or higher (e.g., 99.999%).
Application and Value: Turning Stone into Gold, Empowering the Cycle
The application value of gold electrolysis technology is broad and far-reaching:
A core process in gold refineries: the most mainstream and reliable method worldwide for purifying raw materials such as coarse
gold, amalgamated gold, and old gold jewelry to international standards for high purity ingots (e.g., London Bullion Market
Association (LBMA) standards).
The “Golden Key” of E-waste Recycling: Recovering gold-containing solutions from electronic waste such as used circuit boards
(PCBs), connectors, CPUs, etc., and ultimately relying on electrolysis technology to enrich and purify dispersed gold into
high-value products is a key link in the resourceful utilization of e-waste.
Quality Assurance for Jewelry Industry: Provide high purity and stable quality raw gold for jewelry manufacturing.
Industrial catalyst regeneration: Used for the recovery and purification of failed gold-containing catalysts in the industrial
sector (e.g. petrochemical catalysts) to realize resource recycling.
Important support for sustainability: By efficiently recycling gold resources from urban mines, we can significantly reduce
our dependence on primary gold mining and lower our environmental footprint, which is a vivid practice of the concept
of circular economy and sustainable development in the field of precious metals.
Looking to the future: greener, leaner, smarter
As technology continues to advance, gold electrolysis technology also continues to evolve:
Green Chemistry Promotion: Research and development of more environmentally friendly electrolyte systems (e.g.,
low-cyanide or cyanide-free systems), reduction of the use of strong acids and alkalis, and optimization of waste liquid
treatment technology to reduce environmental risks.
Efficiency and Purity Improvement: Explore new electrode materials (e.g., titanium-based coated electrodes), optimize
pulse current or cyclic commutation current technology, in order to obtain denser and purer deposited gold, and
further improve current efficiency and energy utilization.
Automation and Intelligence: Integration of more advanced sensors, online analyzers and process control systems
to achieve real-time monitoring of the electrolysis process, automatic optimization of parameters and remote
management, to improve production stability and product quality consistency.
Gold electrolysis technology, a subtle process that combines electrochemistry, metallurgy and material science, is
not only the cornerstone of modern gold refining, but also the core link between resource recovery and high-value
utilization. It allows the “treasures” hidden in waste materials to be efficiently and environmentally rejuvenated, and
continues to contribute brilliant and enduring value to industrial development and social progress. In the pursuit of
sustainable development, the optimization and innovation of this technology will undoubtedly continue to play an
indispensable role.