As a key process for modern precious metal purification and
resource recycling, silver electrolytic refining plays an irreplaceable
role in industrial waste treatment, electronic waste recycling
and jewelry processing. In the face of the continuous growth
of global demand for silver resources and increasingly stringent
environmental protection requirements, electrolytic refining
technology has become the core link of the silver recycling
industry chain by virtue of its high purity output, low pollution
emissions and multi-scenario applicability.
Electrolytic refining process principle
and raw material suitability
Silver electrolytic refining is based on the characteristics of
electrochemical dissolution and selective deposition of metals,
and realizes the precise separation of silver and other metals
through the construction of electrolytic system. Under the action
of DC electric field, the silver in the silver-containing anode plate
enters into the electrolyte in the form of ions, while copper,
lead, gold and other impurities are retained in the anode mud
or electrolyte due to the difference in oxidation potential, and
finally silver with a purity of 99.95% or more is directed to
precipitate at the cathode. The process is highly adaptable to
the raw material and can handle diversified and complex
materials with silver content of 15%-90%.
Raw material pre-treatment requires customized solutions
depending on the source:
Metallurgical anode sludge (copper/lead electrolysis by-product):
Dole alloy needs to be separated from base metals by nitric acid
leaching, and the silver content is enriched to more than 80%
before casting into anode.
E-waste: Remove non-metallic components such as plastics and
ceramics through high temperature melting, and precious
metal alloys are crushed and screened before entering the
electrolysis system.
Cyanide gold sludge: hydrochloric acid is used to remove cyanide
treatment, and gold and silver alloys are smelted by silver-splitting
furnace to prepare electrolytic anodes.
Jewelry waste: directly melting and casting into anode plate with
silver content ≥92%, with electrolyte additives to remove
platinum, palladium and other trace impurities.
Electrolysis system construction and
process flow
The electrolysis tank is made of PVC or PP anticorrosive material,
equipped with titanium-based ruthenium-plated anode frame and
stainless steel cathode plate. The electrolyte system is usually
silver nitrate-nitric acid system, with the concentration of silver
ions 80-150g/L, free nitric acid 0.5-2mol/L, and gelatin or sodium
lignosulfonate is added as grain refiner. The temperature is
maintained at 35-45℃, the current density is set at 250-400A/m²,
and the tank voltage is stabilized in the range of 1.8-2.5V.
Staged process control points:
Anode dissolution stage:
The anode plate is gradually dissolved in 72-120 hours, and the cathode
silver layer grows at a rate of 0.1-0.3mm/day. Real-time monitoring of
electrolyte silver ion concentration, maintain chemical balance by
replenishing silver nitrate. Regular scraping of anode mud (containing
gold and platinum group metals) to avoid short circuit risk.
Cathode deposition management:
Mechanical stripping is carried out when the silver layer thickness
reaches 3-5mm, and the deposited silver is ultrasonically cleaned
to remove the electrolyte residue on the surface. Adopting periodic
current reversal technology (cycle 30-60 seconds) can effectively
inhibit the growth of dendrites and enhance the density of silver
layer by more than 15%.
Waste liquid recycling:
Electrolysis waste liquid enters the extraction system after three-stage
filtration, and copper, nickel and other metals are recovered
through replacement, with a nitric acid reuse rate of over 95%.
The terminal waste liquid containing less than 5ppm of silver is
neutralized and discharged according to the standard.
Technical Advantages and Comprehensive
Utilization of Resources
Compared with fire refining, the purity of electrolytic process
has significant advantages:
The purity of cathode silver can reach 99.99%, and the content
of selenium, tellurium and other hard-to-remove impurities is
less than 10ppm.
Platinum, palladium and other precious metals are enriched in
anode mud by 3-5 times, and the recovery rate is over 98%.
The silver recovery rate in e-waste is increased from 75% in the
traditional process to more than 96%.
In terms of environmental benefits, the closed electrolysis system
reduces NOx emissions by 80% and wastewater generation by
70% compared with the wet process. Intelligent control system
realizes precise optimization of current efficiency (92%-96%)
and energy consumption (2.8-3.5kWh/kg Ag), and the
comprehensive cost per unit of silver production is
reduced by 25%.
Multi-metal synergistic recovery system:
After the anode mud is separated from gold and silver by
hydrochloric acid leaching, the residue enters the platinum
group metal extraction process
Copper in the electrolyte is recovered by electrowinning, and
copper cathode with a purity of 99.7% can be directly used
as an industrial raw material.
Palladium and rhodium in waste circuit boards are selectively
adsorbed by ion exchange resin to realize ppm-level trace
metal recovery.
Technology innovation and industry
application expansion
High-frequency pulse electrolysis technology breaks through
the traditional DC limitations, and by adjusting the pulse
frequency (50-1000Hz) and duty cycle, the cathode silver
grain size is refined to 5-10μm, and the ductility of the
product is increased by 30%. After the adoption of this
technology by a recycled silver enterprise, the specific
surface area of silver powder reaches 4.5m²/g, which
meets the particle size requirements of 3D printing silver paste.
New electrolyte system research and development:
Silver sulfamate electrolyte works under pH=8 conditions,
avoiding the generation of nitric acid mist, suitable for
environmentally sensitive areas
Ionic liquid electrolysis system can operate at room temperature,
reducing energy consumption by 40% and increasing silver
deposition rate by 20%.
Carbon nanotube reinforced cathode substrate increases the
bonding strength of the deposited layer by 50% and
reduces the loss of silver layer flaking.
In the field of electronics industry, electrolytic silver has realized
the breakthrough of 6N grade (99.9999%) ultra-high purity.
Through ultrafiltration membrane purification technology
and clean room electrolysis environment control, the oxygen
content of silver target material is stabilized at less than 5ppm,
which meets the requirements of semiconductor coating
process. Silver powder for photovoltaic silver paste adopts
ultrasound-assisted electrolytic deposition technology,
with the particle size distribution D50 controlled at
0.8-1.2μm, and the sintering shrinkage reduced to
less than 2%.
Quality Control and Sustainable Development
Establish a digital monitoring system for the whole process:
The raw material end adopts LIBS laser spectroscopy technology,
which completes the qualitative analysis of 32 elements within 0.1 second
The electrolysis process is implanted with IoT sensors, tracking
18 parameters in real time, including temperature, pH value,
metal ion concentration, etc.
Finished silver ingots are inspected by XRD for crystal structure
and EDX for surface composition to ensure no segregation defects.
Circular economy model innovation:
Modularized mobile electrolysis unit can complete direct purification
of silver concentrate at the mine site, reducing transportation loss by 60%.
Docking with urban mineral recycling network to establish a
closed-loop system of “e-waste - electrolytic purification -
high-value materials”.
The introduction of biological reduction technology reduces the
cost of recovering trace silver from electrolysis waste liquid by 70%.
With the promotion of the Global Silver Sustainability Initiative,
the electrolytic refining process is moving towards the goal of
zero wastewater discharge and 100% precious metal recovery.
The integration of plasma electrolysis, microbial electrochemistry
and other cutting-edge technologies will drive the silver
recycling industry into a new stage of green and efficient
development.