In electronic waste, jewelry processing residues and mineral concentrates, the symbiosis of gold and
copper is common. The differences in the physical and chemical properties of the two metals have
given rise to a variety of separation technologies, and the choice of process directly affects the
economic efficiency of precious metal recovery and resource utilization. This paper will systematically
explain the mainstream gold and copper separation technology principles and innovation direction.
Strategic value of gold and copper separation industry
Resource Economy Dimension
The world produces more than 2 million tons of copper-based waste containing gold and silver every
year, of which the gold content can be up to 5-300 grams / ton. High-efficiency separation technology
can increase the recovery rate of precious metals to more than 99%, and create an additional added
value of 30,000-80,000 yuan per ton of electronic waste.
Demand for industrial upgrading
The demand for high purity gold (99.99%) in 5G communication and semiconductor industry is increasing
by 12% annually, and the traditional separation process is difficult to meet the purity requirements.
The new technology can control the copper residue below 5ppm and reach the gold standard for IC
bonding line.
Environmental Benefit Calculation
Bio-leaching method instead of cyanidation process, per kilogram of gold separation wastewater
emissions reduced by 90%, heavy metal sludge generation reduced by 75%, treatment cost savings
of 40%.
Comparison of five mainstream separation technologies
1. Electrolytic refining method
Process principle: the use of gold, copper electrode potential difference (Au ³ ⁺ / Au +1.5V, Cu ² ⁺ / Cu +0.34V),
in the mixed electrolyte preferential precipitation of gold
Technical parameters: current density 200-300A/m², electrolyte temperature 55-65℃, gold purity up to 99.99%.
Applicable scenes: anode sludge, electroplating waste liquid and other materials with gold content＞1%.
2. Nitric acid selective dissolution
Reaction equation: 3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 4H₂O + 2NO↑
Control Points: Maintain the concentration of 30%-40%, temperature 80-90 ℃, copper dissolution rate> 99.5%
Slag treatment: After dissolution, the filtrate grade of gold is increased to 60%-85%, and it enters the refining process.
3. Chloride system separation
Innovative process: adopt HCl/Cl₂ mixed medium to realize selective chlorination of copper (Cu→CuCl₂), and keep
gold in metallic state.
Efficiency breakthrough: dynamic redox potential control (ORP 800-1000mV), the separation time is reduced to 4 hours.
Environmental advantage: the waste gas is absorbed by lye to generate sodium hypochlorite, realizing the recycling
of chlorine.
4. Pyrolysis process
Temperature gradient control: silicate slagging agent is added at 1200℃ in the molten state, and copper is preferentially
oxidized into the slag phase.
Improvement of purity: vacuum distillation device is introduced to improve the purity of gold ingot from 99.5% to 99.99%.
Optimization of energy consumption: Oxygen-enriched combustion technology reduces fuel consumption by 35%.
5. Biochemical leaching
Strain selection: At. ferrooxidans reacts specifically with metal sulfides.
Process flow: Copper is converted to Cu²⁺ into solution, gold is enriched in the form of monomers
Environmental benefits: pH stabilized at 1.5-2.5, no cyanide pollution, RoHS compliant
Environmental Treatment and Resourcefulness System
Exhaust gas treatment module
Nitrogen oxides: three-stage alkali spraying + selective catalytic reduction (SCR), emission concentration <50mg/m³
Chlorine gas: two-stage packing tower absorption, conversion efficiency>99%, by-product hydrochloric acid
reuse to leaching process
Wastewater closed-loop system
Copper ion recovery: electrowinning method to extract Cu²⁺ in solution, copper cathode purity up to 99.9%.
Water purification: Combined ion exchange resin, copper content in effluent <0.1mg/L, reaching GB8978
level 1 standard.
Solid waste value-added path
Leaching slag: fire smelting to extract residual precious metals, tailings made of microcrystalline glass raw materials
Sludge: high-pressure filtration dewatering (water content <15%), stabilized with heavy metals for roadbed materials.
Three major directions of technological upgrading
1. Microfluidic separation system
Development of millimeter-scale reaction channel, reagent consumption is reduced by 90%, and the separation
speed is increased by 5 times.
Gold particle grading and trapping device, realizing precise control of 0.1-10μm particle size.
2. Supercritical fluid technology
Selective extraction of gold compounds using supercritical CO₂-carrying complexing agent.
No solvent residue, product purity directly meets LBMA (London Bullion Market Association) standards.
3. Intelligent control platform
On-line XRF analyzer monitors solution concentration in real time and automatically adjusts oxidant dosage.
Digital twin model predicts metal recovery deviation <±0.8%.
Core parameters for process selection
Raw material characteristics: gold-copper ratio, particle size distribution, symbiotic mineral species
Economic threshold: when the treatment capacity is more than 500kg/day, the electrolysis method is preferred;
the chemical method is applicable to small batch.
Environmental compliance: obtain hazardous waste business license and ISO14064 certification.
Energy consumption standard: comprehensive energy consumption of tons of material <150kW-h, reaching
the second level of clean production.
Conclusion
The innovation of gold and copper separation technology is essentially the deep integration of resource economics
and environmental science. From hydrometallurgy to bio-extraction, from large-scale production to precise recycling,
modern processes are reshaping the precious metal recycling system. Choosing a technology route that matches
the material characteristics and meets the requirements of sustainable development will become the key pivot
point for enterprises to build core competitiveness. In the future, the combination of intelligent control system
and green chemical reagents is expected to push the separation of precious metals to a new stage
of “zero pollution and full recovery”.