As a high-end technology in the field of precious metal
refining, electrolytic gold refining is the ultimate solution
for obtaining gold with a purity of ≥99.99%. In
semiconductor manufacturing, aerospace science and
technology and financial reserves and other fields with
stringent requirements for material purity, this technology
realizes a leapfrog improvement in gold purification
efficiency and quality through precise electrolysis
control and innovative process design.
First, the scientific principles of electrolytic
gold refining and equipment innovation
Electrochemical purification mechanism
Electrolytic gold refining is based on the selective dissolution and
deposition characteristics of metals in the electric field. With crude
gold casting plate as the anode, high purity gold plate as the
cathode, in the chloride electrolyte system to apply DC electric
field. Gold (Au) at the anode is preferentially oxidized to Au³⁺
into solution, while impurities such as silver (Ag) and copper (Cu)
are segregated in the form of anodic sludge due to the high
oxidation potential. On the cathode surface, gold crystals with a
purity of 99.99% or more are deposited directionally, realizing
the hierarchical separation of impurity elements.
Innovative Application of FRPP Electrolyzer
The fiberglass-reinforced polypropylene (FRPP) electrolyzer
combines resistance to strong acid corrosion (10% hydrochloric
acid) with high mechanical strength. Its double-layer hollow
structure design and built-in titanium alloy cooling coil can
precisely control the temperature of the electrolyte in the
range of 45-55℃, with a temperature fluctuation of ≤±0.5℃.
Compared with the traditional PVC tank, the service life is
extended by more than 3 times, and the risk of metal ion
infiltration is eliminated.
Optimization of key process parameters
Electrolyte system: gold chloride (HAuCl₄) concentration
of 80-120g / L, free hydrochloric acid 3-5%
Current density: 200-350A/m², pole plate spacing 50-80mm
Tank voltage: 0.3-0.8V, deposition cycle 72-144 hours
Second, the whole process analysis
and technological innovation
1. Raw material pretreatment and anode preparation
Crude gold raw material is melted by high-frequency induction
furnace (1200℃), and potassium nitrate is added to oxidize and
remove more than 90% of base metal. The molten metal is
injected into titanium alloy molds and cast into anode plates
with a thickness of 15-20mm, and the surface is wrapped
with 300-mesh polypropylene fiber bags. The design can
effectively intercept 99.5% of the anode sludge and prevent
silver, lead and other impurities from polluting the electrolyte.
2. Precise control of electrolysis process
Anode protection technology: Mechanical scraping system
is automatically triggered when the anode sludge accumulates
up to 3mm in the bag to ensure the uniformity of current distribution.
Pulse current deposition: adopting 10-100Hz pulse frequency,
the cathode gold grain size is refined to 5-10μm, and the
density is increased by 25%.
Electrolyte regeneration system: through the nano-ceramic
membrane filtration device, real-time removal of suspended
impurities, gold ion recovery rate of over 99.8%.
3. Cathode treatment and product refining
The deposited gold plate is ultrasonically cleaned with
ultrapure water (resistivity ≥18MΩ-cm) to remove the
electrolyte residue on the surface. High-frequency remelting
(1600 ℃) is carried out under argon protection, casting into
1kg gold ingots in accordance with the London Bullion
Market Association (LBMA) standards. The total amount
of 41 impurity elements is ≤50ppm by Glow Discharge
Mass Spectrometry (GDMS).
Technical Advantages and Industry
Breakthroughs
1. Improvement of purity and efficiency
The purity of cathode gold is stabilized at 99.995%-99.999%,
and the content of selenium (Se), tellurium (Te) and other
hard-to-remove impurities is ≤1ppm.
The current efficiency reaches 96%-98%, and the unit energy
consumption is reduced to 2.5-3.2kWh/kg, which is 40%
more energy-saving than the traditional process.
The recovery rate of precious metals in anode sludge is over
99.5%, and the enrichment of platinum group metals is
5-8 times higher.
2. Environmental protection and safety breakthrough
Fully enclosed electrolysis system is equipped with three-stage
acid mist absorption tower, NOx emission concentration <5mg/m³.
Electrolysis waste liquid is treated by ion exchange resin, the
heavy metal content is <0.1ppm, reaching Class I water
quality standard.
Intelligent emergency power-off system can cut off the
current within 0.1 second, eliminating the risk of chlorine leakage.
3. Intelligent process innovation
DCS control system monitors 18 process parameters in
real time and adjusts current and temperature automatically.
Machine vision system identifies cathode deposition
morphology and dynamically optimizes plate spacing
and current density.
Blockchain traceability platform records the whole process
data, realizing digital certification of gold quality.
Frontier Applications and Future Trends
1. Advanced Material Preparation
Semiconductor 6N grade (99.9999%) gold target: controlled
by ultra-clean electrolysis environment, sodium (Na),
potassium (K) content ≤ 0.1ppb
Aerospace-grade bonding wire: crystal-controlled electrolysis
technology improves the ductility of gold wire by 30% and
reduces the wire breakage rate to 0.01 times/million meters.
2. Circular economy model innovation
E-waste purification: the recovery rate of gold from used
chips has increased from 75% to 99.2%.
Closed-loop regeneration of precious metals: the cost of
recovering trace gold from industrial catalysts has
been reduced by 60%.
3. Green Technology Breakthrough
Ionic liquid electrolysis system: operating at room
temperature, energy consumption reduced by 50%,
no acidic exhaust emissions
Microbial electrochemical technology: utilizing
electro-producing bacteria to reduce gold ions,
realizing the integration of biometallurgy and electrolysis process.
V. Quality system and sustainable development
Quality control nodes of the whole process
Raw material side: Laser Induced Breakdown Spectroscopy
(LIBS) analyzes 32 elements in 0.5 seconds.
Process end: online X-ray fluorescence meter (XRF) detects
the composition of electrolyte every hour.
Finished product: ultrasonic flaw detection + hot isostatic
pressure treatment to eliminate internal defects of gold ingots
Zero Emission Technology Path
Electrolysis waste gas: condensation recovery of
hydrochloric acid, waste heat for solution preheating
Wash wastewater: reverse osmosis membrane concentration
50 times and then reused for anode cleaning
Solid waste: microwave roasting of anode sludge to extract
precious metals, and the residue is made into environmentally
friendly building materials.
With the advancement of the White Paper on Carbon Neutral
Precious Metals Smelting, electrolytic gold refining is evolving
towards a zero-carbon process. The application of photovoltaic
DC power supply system and hydrogen heating technology
reduces carbon emissions per unit of gold by 80%. This
cutting-edge technology, which integrates materials science,
electrochemistry and intelligent manufacturing, will continue
to drive the gold refining industry toward an efficient, clean
and high-value future.