In the modern industrial system, copper has become a core material in electric power, electronics,
new energy and other fields due to its excellent electrical conductivity, thermal conductivity and
ductility. However, the purity of crude copper obtained from natural ores by pyrometallurgical
smelting is limited and cannot meet the demand of high-end applications. Copper electrolytic
refining is the key process to transform crude copper into ultra-high purity copper, which can be
called the “finishing touch” in the modern metallurgical industry.
The beginning of refining: why electrolysis?
The crude copper produced by pyrometallurgical smelting usually contains 0.5%-2% impurities,
including gold, silver, nickel, arsenic, antimony and other elements. These trace elements can
significantly reduce the electrical conductivity of copper - for every 0.01% increase in phosphorus
content, the conductivity drops by as much as 10%; arsenic content of more than 0.1% will make
the copper material brittle increase. Electrolytic refining through the principle of electrochemical
separation, not only can produce high-grade copper cathode with a purity of 99.99% or more, but
also efficiently recovers precious metals, maximizing the value of resources.
Refining Core: Electrochemical Precision Dance
The electrolytic refining system is like a carefully choreographed chemical reaction theater, which mainly
consists of anode plate, cathode plate, electrolysis tank and electrolyte.
Anode Preparation: Crude copper is first melted and cast into anode plates weighing 300-400 kilograms,
with a copper purity of about 98%-99.5%. These anode plates are like a “raw material bank” waiting to be
refined, containing precious metals and impurities to be separated.
Electrolyte mystery: electrolytic tank filled with copper sulfate and sulfuric acid mixed solution, not only is the
current conduction medium, but also the carrier of copper ion migration. The temperature of the solution is
maintained at 50-65℃, and the concentration control is accurate to grams/grades to ensure the stability of
the electrochemical reaction.
Electrochemical separation: After the DC current is passed (tank voltage is usually 0.2-0.3V), copper and active
impurities on the anode plate undergo oxidation reaction and enter the solution in the form of ions. While
gold, silver and other precious metals are difficult to dissolve, precipitated in the form of anode mud - these
seemingly waste black mud, in fact, is a valuable raw material for refining rare metals.
At the cathode, the copper ions in solution preferentially gain electrons and are reduced to metallic copper for
uniform deposition. By controlling the current density (typically 200-300 A/m²), temperature and additive
concentration, it is possible to ensure that the copper cathode crystallizes meticulously and has a flat surface,
resulting in a high-purity copper cathode plate with a thickness of 5-10 mm.
Technology evolution: the permanent cathode process revolution
The traditional electrolysis method requires repeated production of starting electrode sheets, which is
labor-intensive and inefficient. The permanent cathode process is commonly used in modern large-scale
refineries:
Titanium or stainless steel plates are used as the permanent cathode substrate.
Receiving the finished copper cathode through fully automated stripping machines
Continuous and automated production
The annual production capacity of a single production line can reach more than 300,000 tons, and the quality
of copper cathode fully meets the requirements of GB/T 467-2010 standard for Grade A copper.
Resource recycling: a model of green smelting
The modern electrolytic refinery is called a benchmark of circular economy:
Anode sludge treatment: adopting advanced wet-fire combined process, it can recover more than
99% of gold and silver, as well as selenium, tellurium and other strategic metals.
Electrolyte purification: Remove accumulated arsenic, antimony, bismuth and other impurities through
crystallization, extraction and other technologies, and return regenerated copper sulfate to the system
Energy optimization: Waste heat recovery system uses electrolyte heat for other processes, reducing
comprehensive energy consumption by more than 30%.
Wastewater closed-loop: adopting counter-current cleaning-evaporation concentration process,
realizing zero discharge of production wastewater.
Quality control: the pursuit of millimeters
High-end applications have harsh requirements on copper purity. Electronic grade oxygen-free copper
requires an oxygen content of less than 5ppm and a phosphorus content of no more than 0.0005%. Through:
Online X-ray fluorescence analyzer for real-time monitoring of composition
Machine vision system to detect cathode surface defects
Conductivity tester to verify product performance
ensures that every piece of copper cathode meets the purity standard of “four 9s” (99.99%)
or more.
Conclusion: The power of purity drives the future
The journey of transformation from crude copper to high purity copper cathode unites the wisdom
of modern metallurgical technology. Electrolytic refining not only solves the problem of material purity,
but also realizes the unity of economic and environmental benefits through comprehensive resource
recovery. As the demand for high-end copper materials in the new energy industry continues to grow,
this century-old process is still innovating, and with its extremely pure quality, it continues to inject
conductive blood for the progress of human science and technology.