In this world constructed by metal, each piece of ore, each piece of end-of-life products, is a sleeping
treasure. How to accurately dismantle, purify, and return the mixed metal “family” to its place one by
one? This is metal separation - a precision art that combines ancient wisdom and modern technology,
and a silent revolution on resource rebirth and value re-creation. It is not only the cornerstone of
industry, but also the lifeblood of circular economy.
The Source of Separation: From Mines to Urban Deposits
The need for metal separation is ubiquitous:
The “unlocking” ceremony of primary ores: the ores dug out of the ground are a complex “code box” of
metals and rocks, a symbiosis of many metals. Separation is the first step to obtaining pure metals.
The “Phoenix Rising” of scrap metal: End-of-life automobiles, discarded electronic products, industrial
trimmings... These “urban mines” are far more complex and problematic than primary ores, but they also
contain enormous recycling value.
The need to “deconstruct” precision alloys: Sometimes it is necessary to recover key metals from specific
alloys (e.g. nickel, cobalt from high-temperature alloys), or to remove harmful impurities.
The art of deconstruction: the “arsenal” of metal separation
Engineers have an ever-evolving “arsenal” of tools to deal with the wide variety of materials and target metals:
The physical “sieve”: Gravity and magnetism captured with pinpoint accuracy
Gravity sorting: Exploiting the difference in density between metals and veins or between different metals. The
ancient principle of the gold pan has evolved in modern times into jigging machines, shaking tables, spiral chutes,
and centrifugal concentrators. Under the action of water flow, vibration or centrifugal force, the heavy minerals
(such as gold, cassiterite, wolframite) settle faster and realize the enrichment and separation. The effect is
remarkable when processing alluvial gold, tungsten-tin ore, and electronic waste fragments.
Magnetic Separation: The natural property of magnets to attract ferromagnetic metals (iron, cobalt, nickel and
their alloys) is widely used. From weak-field magnetic pulleys separating large pieces of scrap iron, to
high-gradient strong magnetic separators capturing micro-fine grained weakly magnetic minerals (e.g.,
manganese ore, ilmenite), magnetic separation is a highly efficient and clean means of physical separation.
Eddy current sorting: A powerful tool against non-ferrous metals (copper, aluminum, zinc, lead). The high-speed
rotation of the strong magnetic roller produces an alternating magnetic field, so that the conductive metal
particles induced eddy current, which in turn produces a repulsive force, the metal bouncing separation of
non-metals (plastics, rubber, glass) or weakly conductive materials in the mixed stream. Indispensable for the
recovery of non-ferrous metals in waste wires and automotive shredded materials (ASR).
Electrostatic sorting: Utilizes the difference in conductivity of materials in a high-voltage electric field.
Conductive metal particles quickly lose their charge and are separated by electrode rejection, while
non-conductors are adsorbed on the electrode rolls. Commonly used in fine-grained materials (such as
crushed electronic waste powder) in the fine separation of metals and non-metals.
The “Key” to Chemistry: Precise manipulation of dissolution and precipitation
Leaching: Selective dissolution of target metals with acids (sulfuric acid, hydrochloric acid), bases (sodium
cyanide - strictly regulated for gold/silver), salt solutions or microorganisms. E.g. leaching of copper
ores (oxidized ores) with sulphuric acid, leaching of gold/silver with sodium cyanide solution.
Precipitation: The addition of specific chemical reagents to a leach solution to precipitate and separate the
target metal or impurities as a solid compound. For example, adding iron to replace copper (wet copper
refining), adding zinc powder to replace gold (cyanide gold extraction), adding lime precipitation to
remove iron and aluminum.
Solvent extraction (SX): the core separation technology of modern wet process. The use of organic extractant
on specific metal ions “preference”, the target metal from the aqueous phase ‘capture’ to the organic phase,
and then by changing the conditions (such as adjusting the acidity) will be “anti-extraction” back to the new
aqueous phase, to achieve a high level of extraction. By changing the conditions (e.g. adjusting the acidity),
the target metal can be “back-extracted” to the new aqueous phase, realizing the enrichment of high purity
and deep separation of impurities. It is widely used for the separation and purification of copper, cobalt,
nickel, rare earths, uranium, etc.
Ion exchange: the use of ion exchange resin on different metal ions adsorption selectivity difference for
separation and purification. In the water treatment in addition to impurities, trace precious metal recovery,
high purity metal preparation in the role of the key.
Smelting / refining: such as blast furnace refining lead and zinc, the use of the melting point of the metal,
density, and impurities (slag formation) affinity for different separation. Electrolytic refining (copper, lead,
nickel, gold, silver) is the standard route to ultra-high purity metals - impurities are retained in the
anode sludge or electrolyte.
Volatilization/Distillation: Volatile metals such as zinc, mercury, cadmium, etc. can be recovered by
controlling the temperature, vaporizing them and separating them from the hard-to-volatilize
fractions, and then condensing them.
Pyrometallurgy: Separation magic at high temperature.
Hydrometallurgy: “molecular surgery” in aqueous solution.
Biological “touch”: nature's “miner”.
Bioleaching: Specific microorganisms (acidophilic bacteria) oxidize sulphide minerals, releasing the
encapsulated metals (e.g. copper, uranium, gold) into solution. It is suitable for treating low grade
ores, difficult to treat gold ores, and relatively low environmental stress.
Bio-adsorption/accumulation: certain bacteria, fungi, algae can selectively adsorb or enrich metal ions
(such as gold, silver, palladium, uranium) in solution, providing a green way for low concentration metal
recovery or wastewater purification.
Practical: “Precise bomb disposal” in complex materials
Electronic waste (WEEE) “gold” challenge: a piece of waste circuit boards is metal (gold, silver, palladium,
copper, tin, lead, etc.) and non-metallic (plastics, ceramics) of the “thousand-layer cake”.
Physical disassembly: Manual or mechanical removal of large components (batteries, capacitors).
Crushing and Classification: Crushing to the proper size.
Physical sorting “combination punch”: magnetic separation (iron removal) → eddy current (separation of
copper and aluminum) → electrostatic separation (separation of fine-grained metals and non-metals).
Hydrometallurgical “deep processing”: For precious metal-rich powders, acid solubilization (dissolving base
metals) → aqua regia solubilization of gold/silver/palladium → solvent extraction or chemical reduction for
refining and purification. Each step needs to be precisely controlled to maximize recovery and minimize
environmental impact.
End-of-life automobiles “turned into treasure”: Automotive shredded material (ASR) is a mixture of iron,
aluminum, copper, plastics, and rubber.
Pre-processing: Tires, batteries and fluids are dismantled.
Powerful Crushing: Crush the car body.
High-efficiency sorting line: Magnetic separation (sucking away iron and steel, which accounts for the largest
proportion) → Eddy current (bouncing to separate non-ferrous metals such as copper and aluminum) →
Airflow/vibrating screen (separating light materials such as plastics and foams). The recovered metal is so
pure that it can be directly returned to the furnace for smelting.
Green dismantling plants: responsibility and future of separation technology
The rapid development of metal separation technology is driven not only by efficiency and purity, but also by sustainability:
Guardian of sustainable resources: efficiently recovering metals from “urban mines”, significantly reducing dependence
on virgin minerals, energy consumption and carbon emissions.
The “bomb disposal expert” for environmental risks: Proper treatment of exhaust gases (e.g., desulfurization and
denitrification of smelting flue gases), wastewater (deep purification of complex heavy-metal wastewater), and slag
(e.g., safe disposal of cyanide tailings, harmless treatment of toxic dust) generated during the separation process.
Closed loop water system, tailings resource utilization (such as making building materials) is the industry benchmark.
Technology-enabled precision: Sensor technology, artificial intelligence (AI) and automation control are being
introduced into sorting lines, enabling real-time analysis of material composition (e.g., laser-induced breakdown
spectroscopy (LIBS)) and dynamic optimization of sorting parameters, dramatically improving separation precision
and efficiency.
Potential of biotechnology: The development of more efficient and environmentally friendly bioleaching strains
and bioabsorbent materials is opening up new paths for low-environmental impact metal recycling.
Conclusion: the never-ending “gold separation technology”
Metal separation, a seemingly cold technology, is full of creative wisdom and the burden of responsibility.
It is the key bridge connecting the depletion of natural resources and the sustainable development of industrial
civilization, and is the golden hand that turns “waste” into “treasure”. From the roaring crusher to the precise
extraction tank, from the powerful magnetic rollers to the microscopic bacteria, countless separation technologies
are showing their abilities, and together they are weaving a huge network of resource circulation. The relentless
pursuit of higher purity, lower energy consumption, and smaller environmental footprints is driving the
continuous evolution of separation technology. In the future, whether it is to develop minerals from the deep
ocean floor or to build a better circular economy, precise and efficient metal separation technology will be
an indispensable hidden pillar for the sustainable development of human civilization. It is not only an
industrial skill, but also an eternal art of protecting the earth's resources.