Introduction: Industrial value and challenges of lead purification
As the fourth largest non-ferrous metal used globally, lead accounts for more than 80% of the applications in
storage batteries, radiation protection and other fields. However, the impurity content of recycled lead raw
material is as high as 8%-15% (containing antimony, arsenic, copper, etc.), and the purity of lead produced
by traditional process is only about 99.5%, which is difficult to meet the demand of high-end fields. In this
paper, the depth of the dismantling of fire refining, electrolytic purification and other six core technologies,
and to explore the breakthrough direction of green purification.
Fire refining: modernization and upgrading of the classic process
1. Melt precipitation in addition to copper: the delicate balance of temperature control
Process principle: the use of lead and copper melting point differences (lead 327 ° C vs copper 1083 ° C), in the
330-350 ° C melting pool precipitation of copper slag
Technical parameters:
Reduction of copper content in crude lead from 1.2% to 0.02
Consumption of natural gas 12-15m³ per ton of lead (30% less than traditional reflector furnace)
Innovative program: electromagnetic stirring technology to improve the efficiency of copper removal by 40%,
slag lead content <15%
2. Alkaline refining: efficient removal of arsenic, antimony and tin
Additives Reaction temperature (℃) Removal rate Slag lead content
Sodium nitrate 420-450 Arsenic 95%/Antimony 90% 25%-30
Sodium hydroxide+nitrate 380-400 Tin 98% 18%-22
Environmental breakthrough: closed reactor with tail gas scrubbing tower, arsenic volatilization reduced by 85
3. Vacuum distillation: precious metal recovery and deep purification
Zinc-silver separation: under 10-²Pa vacuum, the evaporation rate of zinc and silver is 1000 times
faster than that of lead.
Purity jump: lead purity from 99.5% to 99.99%, silver recovery > 99%.
Comparison of energy consumption: 40% lower than the traditional electrolysis method, applicable to
the treatment of crude lead containing more than 0.1% silver.
Electrolytic refining: the ultimate solution for high purity
lead production
1. Silicofluoride system electrolysis process
Electrolyte formula:
H₂SiF₆concentration 80-100g/L
Pb²+ ion concentration 80-100g/L
Gelatin additive 0.3-0.5g/L (inhibit dendrite growth)
Current efficiency: 94%-96% (pole plate spacing 60mm, current density 180A/m²)
Cathode quality: surface flatness Ra≤1.6μm, purity up to 99.997
2. Impurity migration control technology
Antimony and arsenic interception: add tartaric acid in the electrolyte to form a stable
complex to inhibit deposition
Removal of copper and nickel: Installation of ion exchange columns to maintain the
concentration of metal impurities <0.005g/L.
Intelligent management:
Online pH sensor automatically adjusts acidity (fluctuation range ±0.2)
Visual recognition system detects cathode crystallization defects in real time.
Hydrometallurgy: new path to green purification
1. Oxygen pressure leaching process
Reaction equation:
PbS + 2H₂SO₄ + O₂ → PbSO₄ + S⁰ + 2H₂O
Technical Advantage:
Sulfur curing rate＞99%, avoid SO₂ emission
Lead leaching rate of 98.5%, simultaneous separation of iron and zinc
Application scenario: processing complex lead-zinc ore (containing Pb 5%-8%, Zn 12%-15%)
2. solvent extraction purification
Extraction system:
Extractant: di(2-ethylhexyl) phosphate (D2EHPA)
Diluent: sulfonated kerosene
Three-stage countercurrent extraction: lead recovery rate of 99.2%, calcium, magnesium impurities
removal rate of > 95%
Environmental benefits: 80% reduction of wastewater generation compared with thermal method
technology attack: four industry pain points to crack the program
1. Antimony-containing lead treatment problems
Molten salt electrolysis: In NaCl-KCl molten salt system, antimony is preferentially oxidized to form Sb₂O₃ slag.
Vacuum distillation coupling: lead-antimony alloy is distilled twice to reduce antimony content from 8% to 50ppm.
2. Micro trace arsenic removal
Sulfide precipitation: add Na₂S to make arsenic precipitated in the form of As₂S₃, residue <1ppm
Electrochemical oxidation: apply 1.8V potential in the anode area to oxidize As³+ to easily adsorbed As⁵+.
3. Waste lead paste regeneration and purification
Desulfurization: Sodium carbonate solution treatment of waste lead paste (PbSO₄→PbCO₃), sulfur resource utilization rate of 92%.
Short process smelting: low-temperature smelting (600 ℃) to obtain lead > 99% of the crude lead, energy
consumption reduced by 50%.
4. Lead fume treatment technology
Super gravity dust removal: rotating packed bed capture efficiency of 99.9%, emission concentration <5mg/m³.
Wet electrostatic precipitator: lead dust removal rate of 99.5%, while the recovery of lead powder purity> 98
Future Trend: Integration of Low Carbonization and Intelligence
1. Hydrogen reduction lead refining test
Hydrogen direct reduction of lead oxide, the reaction temperature from 1200 ℃ to 600 ℃, CO ₂ zero emissions
Pilot line lead purity of 99.95%, tons of lead hydrogen consumption of 45kg
2. Digital twin system application
Real-time simulation of ion concentration field in the electrolyzer, dynamic optimization of current density distribution
Cathode deposition uniformity increased by 30%, DC power consumption reduced to 900kWh/t.
3. Biometallurgy technology breakthrough
Thiobacillus ferrooxidans leaching of lead concentrate with 91% leaching rate and 70% reduction of acid consumption
Biological adsorbent treatment of lead wastewater, lead ion concentration from 200mg/L to 0.05mg/L
Conclusion: technology iteration to promote industrial upgrading
Lead purification technology is experiencing a transition from “crude removal” to “precise purification”. With the maturity
of vacuum distillation, solvent extraction and other technologies, the production cost of 99.999% ultra-high purity lead is
expected to be reduced by 40%. In the new energy storage and electronic packaging demand, driven by the next five
years, high purity lead market size will grow by 25%. Enterprises need to focus on the layout of green processes and
intelligent control systems, to build an efficient resource recycling system.