In the electrolysis workshop, copper anode plates undergo a visible dissolution
process—the metal surface gradually becomes uneven and eventually dissolves
completely in the electrolyte. This seemingly wasteful phenomenon is actually the
core mechanism of industrial purification. This article will delve into the chemical
essence, process value, and control strategies of copper anode dissolution, unveiling
the scientific logic behind this process.
The Dissolution Code from an Electrochemical Perspective
The dissolution of copper anodes in electrolytic cells is essentially an oxidation reaction, with the
standard half-reaction equation being:
Cu → Cu²⁺ + 2e⁻
In this process, each copper atom loses two electrons, converting into soluble copper ions that enter
the solution. Three key factors drive the reaction to continue:
Potential difference: An external power source provides a voltage of ≥0.3V to overcome the metal ionization energy
Ion migration: The conductivity of the electrolyte (copper sulfate + sulfuric acid) is >200 mS/cm
Interface activation: A double layer forms on the anode surface, accelerating electron transfer
Theoretical calculations indicate that dissolving 1 kg of copper requires approximately 1700 Ah of
electricity. In actual production, due to the presence of side reactions, the current efficiency typically
remains within the 95%-98% range.
Dissolution control in industrial settings
In electrolytic refining workshops, the dissolution of the anode requires precise control of five parameters:
1. Current density (220-320 A/m²)
Below 220 A/m²: Uneven dissolution, anode residual rate >15%
Above 320 A/m²: Sudden increase in cell voltage, energy consumption per ton of copper increases by 23%
At the optimal value of 280 A/m², anode dissolution thickness can reach 3 mm/day
2. Electrolyte formulation
Cu²⁺ concentration: 42–48 g/L (too low causes impurity precipitation)
H₂SO₄ content: 160–200 g/L (inhibits hydrolysis side reactions)
Temperature: 55–65°C (each 5°C decrease reduces conductivity by 12%)
3. Anode composition
Copper anodes contain 98–99% copper, with impurity control standards:
As < 0.15%: prevents the generation of arsenic trioxide gas
Pb < 0.02%: avoids anode sludge blocking the membrane
S < 0.003%: reduces sulfate scaling
A refinery optimized these three parameters, extending anode lifespan from 18 days to 22 days
and reducing residual anode rate to 8.7%.
Abnormal Dissolution and Process Countermeasures
Common anode dissolution issues and solutions in actual production:
Abnormal Phenomenon Causes Countermeasures
Anode Passivation Formation of CuO/Cu₂O oxide film on the surface Add Cl⁻ to the electrolyte at 20-30 mg/L
Localized Over-Corrosion Uneven current distribution causing pitting corrosion Optimize electrode spacing to 95 mm
Preferential dissolution of impurities Selective oxidation of active metals such as nickel/iron Pre-electrolysis
to remove low-potential metals
Anode sludge agglomeration Aggregation of precious metal particles Enhance electrolyte circulation and filtration
By adopting electrochemical impedance spectroscopy (EIS) for online monitoring, the detection time
for anode abnormalities can be reduced to within 30 minutes.
Industrial Value of the Dissolution Process
The continuous dissolution of copper anodes serves three core functions:
Raw material supply
Each ton of cathode copper consumes 1.03 tons of anode copper
Cu²⁺ generated during dissolution accounts for 92% of the total copper ions in the electrolyte
Impurity separation
Precious metals (Au, Ag) precipitate as anode sludge, with recovery rates of 99.5% and 98%, respectively
Harmful elements (As, Sb) are removed by subsequent processes after entering the solution
Energy balance
The standard electrode potential of the anode dissolution reaction (-0.34V) complements the cathode deposition (+0.34V)
The theoretical cell voltage required is only 0.68 V, significantly lower than other metal electrolysis processes.
A certain smelting project leveraged this characteristic to control direct current energy consumption at
2,200 kWh/t of copper, 15% lower than the industry average.
Innovation in dissolution in green metallurgy
Carbon neutrality goals are driving anodic dissolution technology to evolve in three directions:
1. Intelligent dissolution control
Installation of over 2,000 sensors to monitor anode thickness
AI models dynamically adjust current distribution, extending anode lifespan by 12%
2. Low-carbon energy coupling
Direct input of wind power DC electricity into the electrolytic cell
Reducing AC/DC conversion losses (saving 18 million kWh annually)
3. Circular Economy Model
100% of anode residues are returned to the smelting system
Electrolyte closed-loop circulation saves 97% of water
Platinum group metal recovery rate from anode sludge exceeds 95%
Conclusion: Industrial philosophy in the art of dissolution
The continuous dissolution of copper anodes is, in essence, a meticulously designed material transformation
process in modern metallurgy. From crude copper from mines to chip-grade high-purity materials, this
seemingly “self-sacrificing” process achieves the ultimate purification of metallic materials. Understanding
the underlying logic of anode dissolution is the key to unlocking the door to efficient and clean metallurgy.