In the history of metal smelting, copper electrolytic refining
is a milestone in industrial civilization. This technological
innovation, which began in the mid-19th century, revolutionized
the way in which mankind obtains high-purity copper. In the
modern industrial production line, the electrolytic refining
plant is like a precision-run chemical reactor, through
electrolysis will be crude copper raw materials into 99.99%
pure copper cathode, while harvesting the anode mud rich
in precious metals. This seemingly simple electrochemical
process is in fact the crystallization of the cross-fertilization
of multiple disciplines, which perfectly illustrates the deep
excavation of the value of resources by industrial technology.
First, the chemical reaction code of
electrolytic refining
The electrochemical reaction that occurs in the electrolysis tank
is far from being calm as the naked eye can see. When direct current
passes through the copper sulfate solution, the crude copper on the
anode plate starts to undergo oxidation reaction: Cu→Cu²++2e-,
and the copper atoms lose electrons into ions into the solution.
Driven by the electric field, these copper ions migrate through
the electrolyte to the cathode and gain electrons on the stainless
steel cathode plate to be reduced to copper metal: Cu²++2e-→Cu.
This directional migration of metal atoms forms a dense crystal
structure on the cathode surface, which contributes to the
characteristic metallic luster of electrolytic copper.
The current density, as the core parameter of the process, directly
influences the physical properties of the deposited copper. When
the current density is controlled at 280-320 A/m², copper ions
are deposited in a uniform and orderly manner, forming a dense
copper cathode plate. Excessive current density will lead to
dendritic crystallization, producing a rough and porous copper
layer, a structural defect that will seriously affect the subsequent
processing performance. The electrolyte temperature is
maintained at a precise range of 55-65°C to ensure ion migration
efficiency and to avoid the escape of acid mist caused by overheating.
The additive system is the invisible engineer that controls the
crystallization morphology. The synergistic effect of gelatin and
thiourea builds up a precise regulatory network at the microscopic
level. Gelatin molecules are adsorbed on the cathode surface to
form a protective film and inhibit the disordered deposition of
copper ions, while thiourea changes the structure of the bilayer
to promote the growth of copper atoms along the specific crystalline
surfaces in an optimal manner. This molecular level regulation
makes the surface of copper cathode show the characteristic
rose-red metallic luster, and the crystal structure is dense
without defects.
Second, the precious metal treasure in
anode mud
The anode plate undergoes a slow dissolution process during
electrolysis. With the continuous dissolution of crude copper
anode, the originally uniformly distributed trace precious metals
gradually enrich on the anode surface. These dense metal particles
gradually detach from the anode under the effect of electrolyte
convection, and eventually settle at the bottom of the electrolyzer,
forming precious anode mud. For every 1,000 tons of copper
cathode produced, about 0.5-3 tons of anode mud can be
recovered, of which the content of precious metals is as high
as 30%-50%.
The chemical composition of anode mud is like a miniature
sample of the periodic table. In addition to containing 60%-70%
copper oxides, it is also enriched with precious metals such as
gold, silver and platinum group metals, as well as rare elements
such as selenium and tellurium. Modern analysis technology
reveals that 1 ton of anode mud may contain 3000-8000 grams
of silver, 50-200 grams of gold, its value far exceeds the main
product of copper cathode. This kind of “waste material” is
essentially a concentrated carrier of high-value resources.
Precious metal recovery technology continues to break through
the shackles of traditional processes. Modern metallurgical plant
using fire - wet process: first through the Kaldor furnace melting
extraction of gold and silver alloys, and then electrolytic refining
method to separate pure gold and silver. For rare metals such as
platinum and palladium, the advanced technology of solvent
extraction combined with ion exchange is used, and the recovery
rate can reach over 98%. These precious metals are ultimately
processed into electronic contacts, catalysts, jewelry and other
high-end products, to achieve the value of resource utilization
of the gradient.
III. Technical Evolution of Green Smelting
The energy efficiency revolution of the electrolysis system never
stops. The new generation of permanent cathode electrolysis
technology adopts stainless steel mother plate to replace the
traditional initiator plate, which improves the current efficiency
to more than 97% and reduces the electricity consumption of
tons of copper by 15%. The application of bi-directional parallel
power supply technology reduces the overall energy consumption
of the electrolysis workshop by 8%-12%. Intelligent control
system optimizes current distribution in real time and controls
tank voltage fluctuation within ±5mV, which significantly
improves power utilization.
The concept of circular economy is deeply integrated into
the production process. The electrolysis waste liquid is
concentrated by vacuum evaporation, and the recovered
copper sulfate crystals are re-dispensed into the electrolyte
system, realizing the closed-circuit cycle. The waste gas
generated in the anode mud treatment process is purified
by double alkaline washing, and the sulfur recovery rate
exceeds 99%. The wastewater treatment system adopts
membrane separation technology, and the reuse rate of
water reaches more than 95%, truly realizing “zero liquid
discharge”.
Intelligent manufacturing is reshaping the traditional
electrolysis workshop. The digital twin system builds a
virtual electrolyzer, simulating the ion migration and
crystallization process in real time. The machine vision
system automatically detects the cathode deposition
quality, and the AI algorithm dynamically adjusts the
process parameters. This production mode of virtual-reality
integration has increased the pass rate of copper cathode
to 99.98%, and the precision of precious metal recovery
of anode sludge has reached ppm level.
Standing at the threshold of the dual-carbon era and
looking back, copper electrolytic refining technology has
evolved from a mere metal purification process to a
model of resource recycling.