In the veins of modern industry runs a red metal - electrolytic copper. It is not a direct gift from
the mines, but a magnificent transformation of the rough raw material in the dance of electric
current and chemistry. From the rough anode to the mirror-like cathode, the process called electrolytic
refining is the modern magic that turns stone into gold.
The starting point of raw materials: the appearance of crude copper
The first step of the process begins with the crystallization of pyrometallurgical smelting - rough
copper anode plates. These heavy slabs, copper content is usually about 99%, but hidden gold, silver,
nickel, arsenic, antimony, bismuth and other “uninvited guests”. They are cast to a flat surface, relatively
stable composition, neatly arranged, waiting for the baptism of the current.
Electrolysis tank: the stage of the current
Thousands of electrolysis tanks are connected in series, constituting the core theater of the process.
The tanks are filled with a warm electrolyte - a blue-green solution of copper sulfate (CuSO₄) and sulfuric
acid (H₂SO₄) - and the temperature is usually precisely controlled at 50-60 degrees Celsius. Powerful DC
currents (tens of thousands of amperes) flow through the system, driving the migration and rejuvenation
of the metals.
The Dance of Refinement: Anodic Dissolution and Cathodic Renewal
The anode's curtain call: The current is switched on and the crude copper anode plate begins its journey of dissolution.
The copper atoms on the anode (Cu⁰) lose electrons (oxidize) and dissolve into the electrolyte as copper ions (Cu²⁺):
Cu → Cu²⁺ + 2e-. Those metal impurities that are more reactive than copper (e.g., iron, zinc, nickel) also dissolve. And
gold, silver, platinum group metals, as well as selenium, tellurium and other “stubborn molecules”, due to the difficulty
of oxidation and fall off from the anode, sinking to the bottom of the tank, forming a valuable “anode mud”.
The appearance and growth of the cathode: on the other side of the electrolyzer, the cathode's territory. Here hangs a
very thin pure copper “start pole piece” or special treatment of stainless steel “mother plate”. Copper ions (Cu²⁺) in the
electrolyte are attracted to the cathode, gain electrons (reduction), and are transformed back into metallic copper atoms,
which are deposited layer by layer in a homogeneous and dense layer: Cu²⁺ + 2e- → Cu. The process lasts for several
days (usually 7-14 days), resulting in the growth of a thick, polished copper cathode sheet. The secret lies in the fact that
copper ions are reduced at the cathode at a potential that is “easier” than most impurity ions. As a result, high-purity
copper is precipitated preferentially and efficiently. Trace amounts of additives (e.g. gelatine, thiourea, chloride ions)
play the role of “micro-sculptors”, adsorbing on the cathode surface and finely regulating the direction of crystal growth,
ensuring that the deposited layer is tightly structured and the surface is smooth as a mirror - this is crucial for the
subsequent processing of rolled and drawn copper sheets. This is crucial for subsequent processing such as rolling
and stretching.
Purification of the bloodstream: recycling and regeneration of the electrolyte
The electrolyte is the lifeblood of the process, and it is vital that its composition is stabilized. As anodic dissolution and
cathodic deposition continue:
The concentration of copper ions gradually decreases.
The concentration of harmful impurity ions (e.g. arsenic, antimony, bismuth) rises slowly.
Sulfuric acid concentration rises due to water electrolysis and impurity reactions.
Maintaining the “youthful vigor” of the electrolyte depends on a sophisticated purification cycle:
Withdrawal: A portion of the “aged” electrolyte is continuously withdrawn from the main process.
Purification:
Crystallization: The solution is cooled to crystallize copper sulfate (CuSO₄-5H₂O), which is separated and reused.
Precipitation/Arsenic Salt De-Antimony-Bismuth: Specific reagents are added to precipitate arsenic, antimony, bismuth
and other impurities to form insoluble compounds for removal.
Extraction-Electrowinning: A more advanced technology that utilizes organic solvents to selectively extract copper or other
metals and then recovers them through electrowinning to achieve deep purification and recovery of valuable metals.
Copper Removal: In a specialized electrolyzer, the copper content in the solution is further reduced to produce “black copper”
or “residual electrode”.
Removal of impurities:
Regeneration: The purified solution is replenished with consumed copper (usually by dissolving high-grade copper material
or adding purified and crystallized copper sulphate) and sulphuric acid, adjusted for concentration and temperature, and
re-injected into the main electrolyzer. This is a cyclical process.
Harvest and renewal: the fruits of purity and hidden treasures
Crystallization: High-purity copper cathode: When the copper cathode plate grows to a predetermined thickness, it is lifted
out of the tank. The stripped copper cathode sheet has a characteristic rose-red luster and a flat, dense surface. Its purity is
typically an astonishing 99.99% or more (in accordance with the Grade A copper standard), with key impurities affecting electrical
conductivity (e.g., arsenic, antimony, bismuth) tightly controlled to parts-per-million (ppm) levels. This is the core product of the
process, which can be directly used in the manufacture of high-end wires, foils and precision components.
Treasure at the bottom of the tank: Anode mud: The anode mud collected from the bottom of the tank on a regular basis is a
veritable “treasure bowl of precious metals”. It enriches most of the gold, silver and platinum group metals in the raw materials,
as well as selenium, tellurium and other rare elements. These highly valuable elements are subsequently separated and purified
one by one through complex wet (leaching, replacement, refining) or thermal (smelting, blowing, electrolysis) processes.
Recycled products: By-products generated during the purification process, such as crude nickel sulfate, black copper plate, etc.,
also enter the corresponding recycling process to extract the valuable metals therein, thus maximizing the utilization of resources.
The Soul of the Process: Precision Control and Artisanal Experience
The success of the copper electrolysis process is by no means a mere reaction of energization. It relies on the precise control
of countless key parameters:
Current Density: The amount of current passing per unit cathode area directly affects the deposition rate and crystal structure.
Too high a current can lead to rough deposition or even “plate burning”; too low a current is inefficient.
Electrolyte composition: Copper ion concentration, free acid (sulfuric acid) concentration, additives (gum, thiourea, chloride ion)
concentration must be maintained in the optimal range.
Temperature: Affects ion migration rate, solution viscosity and impurity behavior.
Pole spacing: The distance between the anode and cathode, affecting current distribution and tank voltage.
Cycle rate: Ensures uniformity of electrolyte composition and temperature.
Experienced operators, like the conductor of the orchestra, will observe the cathode deposition status, tank voltage change,
electrolyte color and other subtle signs, combined with on-line monitoring data (e.g., thermometers, flow meters, composition analyzers),
and timely adjust the additives adding amount, circulation speed, etc., to ensure that the whole “symphony orchestra” operates in harmony
and to avoid the emergence of “Long particles” (rough deposition), “burnt plate” (loose and black deposits) and other quality accidents
are avoided.
Pure power to drive the world
High-purity electrolytic copper, which has been “electrified” by a thousand hammers, has become an indispensable “current carrier”
and “heat-conducting vein” for the efficient operation of modern society:
The cornerstone of electric power: high-voltage transmission cables, transformer windings, and generator coils rely on its top-notch
electrical conductivity to minimize energy transmission losses.
The lifeblood of electronics: leadframes for integrated circuits, high-end printed circuit boards (PCBs), and high-speed data cables,
which are the core conductors that enable miniaturization, high-frequency, and high reliability.
Green Power: Photovoltaic battery conductive grid lines, wind turbine windings, electric vehicle drive motor coils and high-voltage
power battery connectors, is a key conductive material for the new energy revolution.
Precision: High-precision instrumentation, high-efficiency heat sinks, and vacuum electronic devices also rely on their excellent
thermal conductivity and stable physicochemical properties.
Evolution of the process: the fusion of green and intelligence
In the face of resource constraints and environmental pressures, the copper electrolysis process continues to
be revolutionized:
Energy saving and consumption reduction: Optimization of electrode structure design (e.g. permanent cathode), application
of more efficient energy-saving rectifier transformers, and enhancement of current efficiency have significantly reduced electricity
consumption per ton of copper.
Environmental protection upgrade: Strengthening the electrolyte closed-loop recycling system to achieve near-zero wastewater
discharge; efficiently capturing and treating acid mist generated in the electrolysis process; harmless treatment and resource
utilization of solid wastes, such as anode sludge and purification slag.
Intelligent control: The application of online sensors, big data analysis platform, advanced process control system (APC) and even
artificial intelligence algorithms makes it possible to monitor and precisely control key parameters of the electrolyte (Cu²⁺, H₂SO₄,
temperature, impurity ion concentration) in real time, which greatly improves the stability of the production, the consistency of
product quality and the overall efficiency. This greatly improves production stability, product quality consistency and overall efficiency.
Resource Recycling: The breakthroughs in efficient and full-component recovery of valuable elements (especially rare metals) in
anode sludge and by-products of purification have greatly enhanced the economic benefits and environmental friendliness of the process.
Conclusion: The industrial cornerstone of current quenching
The copper electrolysis process is a metal purification art driven by electricity, synergized by chemistry and guarded by craftsmen.
It takes the gift of the earth - the rough copper-bearing raw material - and quenches it into crystal-clear, high-purity copper cathode
with excellent performance in a sophisticated array of tanks. This is not only the crystallization of modern metallurgical technology and
engineering wisdom, but also the silent force that supports the information age, energy revolution and sustainable development. Every
passage of electric current injects a purer and stronger “copper” power into modern civilization. With the eternal pursuit of high efficiency,
cleanliness and intelligence, this ancient art of metal refining will surely be revitalized in the wave of Industry 4.0, and continue to light
up the road to the future for human beings.