Electrolytic gold refining is a key process in the field of precious
metals refining, which efficiently extracts gold with a purity of
99.99% or more from gold-containing raw materials through
electrochemical methods. This technology is widely used in the
recycling of resources such as gold smelting by-products,
electronic waste, jewelry processing waste, etc., which is both
environmentally friendly and economical, and has become an
important pillar of the global circular economy and green
metallurgy. In this paper, we will discuss the technical process,
innovation breakthroughs and industrial value of electrolytic r
efining of gold, and reveal its core role in the efficient utilization of resources.
I. Raw Material Sources and Process Framework
of Electrolytic Gold Refining
Diversified Raw Material System
Gold-containing raw materials processed by electrolysis mainly include:
Mining by-products: cyanide tailings of gold mines, copper/lead
electrolysis anode sludge (containing 0.5%-5% of gold), and crude
gold ingots from gold smelting (purity of 80%-95%);
Electronic Waste: Used circuit boards, CPU chips, connectors
(containing 0.01%-0.3% of gold);
Industrial and Civil Waste: Failed catalysts, innovative breakthroughs,
and industrial value. and civil waste: failed catalysts, gold-plated devices,
jewelry processing scraps (containing 1%-90% gold);
other resources: medical equipment, aerospace alloy waste, etc..
These raw materials need to be pre-treated (crushing, sorting, smelting)
and transformed into anode plates suitable for electrolysis, usually with a
gold content of 70% or more to ensure the efficiency of electrolysis.
Core process: three-step refining method
The core steps of gold electrolysis refining include:
Pre-treatment and anode preparation: raw materials are melted at high
temperature (1200-1300℃) to remove organic matter and low melting
point metals, and then molded into crude gold anode plates (gold content ≥80%);
Electrolysis purification: in gold chloride electrolyte (HAuCl₄
concentration 80-150g/L, pH 1- 2), pass through direct current into the
electrolyte. 2), direct current (current density 200-500A/m²) is passed,
the anode crude gold is dissolved, and high purity gold is deposited at
the titanium cathode;
Anode reaction: Au → Au³⁺ + 3e-
Anode reaction: Au → Au³⁺ + 3e-
Cathode reaction: Au³⁺ + 3e- → Au
cathodic reaction: Au³⁺ + 3e- → Au
Tail liquid recycling and waste residue treatment: electrolytic waste liquid
recovers the residual gold ions through adsorption on activated charcoal
or chemical reduction, and the waste residue extracts the platinum,
palladium and other accompanying precious metals through sorting, so
as to realize full quantitative utilization of resources. Full quantitative
utilization of resources.
Technical advantages and process innovation
Ultra-high purity and recovery efficiency
Electrolysis can directly produce 99.99%-99.999% national standard
1# gold ingot, which is significantly higher than the traditional fire
refining (purity of 99.9%). Taking the anode sludge containing 30%
gold as an example, the gold recovery rate is over 99%, and the
energy consumption of electrolysis is about 50-80kWh per kg of
gold, which reduces the processing cost by more than 35%
compared with that of cyanidation method.
Breakthrough in Adaptability to Complex Raw Materials
For raw materials containing impurities such as silver, copper,
nickel, etc., the industry innovatively adopts:
Step-by-step electrolysis process: the first electrolysis prioritizes
the extraction of silver, and the second electrolysis purifies gold;
Pulse Reverse Current Technology: inhibits the growth of dendrites,
and reduces the risk of cathode short-circuiting;
Electrolyte Additives: add citric acid or polyvinylpyrrolidone (PVP) to
improve the densification and glossiness of the gold deposited layer.
Green Process Upgrade
The problem of chlorine gas escaping from the traditional electrolysis
process is solved by the following technologies:
Confined Electrolyzer: integrated gas absorption device, converting
chlorine gas into hydrochloric acid for reuse;
Cyanide-free Electrolysis System: adopting thiosulphate or iodide
electrolyte, avoiding the risk of cyanide contamination;
Zero Waste Liquid Discharge System: membrane separation technology
recovers the precious metal ions, and the purified water is recycled
for use in electrolysis process.
Application Scenarios and Industrial Value
The core refining link of gold mining industry
In the gold smelting plant, the electrolysis method can purify the crude
gold ingot (purity 85%-90%) to over 99.99% in one step, and the daily
processing capacity of a single production line can reach 50-100kg of
gold. Annual processing 10 tons of gold smelter, for example, electrolysis
refining link value-added over 200 million yuan.
E-waste “urban mine” development
The world produces more than 50 million tons of electronic waste every year,
containing about 300 tons of gold (accounting for 10% of the supply of
mineral gold). Through electrolysis refining, 1 ton of used cell phones can be
extracted about 300 grams of gold, recycling costs only 40% of the primary
mining. The EU's Circular Economy Action Plan for gold electrolysis technology
supports 20% of its gold demand from renewable sources.
Gold Supply Chain Hub for High-end Manufacturing
High-purity gold produced by electrolysis is widely used in high-end fields
such as semiconductor bonding wires, aerospace plating, and precision
instruments. According to industry statistics, more than 80% of the gold
used in the electronics industry relies on electrolytic refining raw materials,
and its added value is 4-6 times higher than that of crude gold.
IV. Technical Challenges and Future Trends
Precise control of micro-impurities
Semiconductor industry requires gold purity up to 99.9999% (6N level),
which requires the development of:
Ultra-clean electrolyte filtration system: nano-sized filter membrane
(≤ 0.01 μm) to remove suspended particles;
On-line mass spectrometry monitoring: real-time detection of iron,
copper and other trace impurities (≤ 1ppm).
Low-carbon technology innovation
The industry is advancing:
Green power-driven electrolysis: photovoltaic/hydrogen power supply,
reducing the carbon footprint of a single ton of gold by 60%;
Bio-metallurgical pre-treatment: decomposition of gold-containing
sulphides by using sulphurophilic bacteria, reducing energy consumption
for smelting by 30%;
AI Intelligent Control System: dynamic optimization of current density
and electrolyte composition, improving energy efficiency by 15%.
Distributed Refining Mode
For small electronic recycling enterprises, develop modular electrolysis
device (processing capacity 1-5kg/day) to realize local refining of materials
containing more than 0.1% gold and reduce logistics and centralized
processing costs.
Conclusion
Electrolysis gold refining technology has constructed a sustainable closed
loop of “mining-use-recycling” by efficiently transforming the precious
metal resources in industrial by-products and urban wastes. As the global
demand for high-purity gold grows (with an expected shortfall of 800 tons
by 2030) and environmental regulations are tightened, the electrolysis
process will continue to be upgraded in the direction of high efficiency,
low carbon and intelligence, and will become an irreplaceable core link
in the gold supply chain. It is expected that electrolytic refining of gold
will account for 30% of the global supply by 2035, providing a strategic
guarantee for green manufacturing and resource security.