The Challenge
The copper electrorefining process transforms raw copper anodes into ultra-high-purity cathodes through electrochemical deposition in sulfuric acid solution. However, impurities from the mining process—particularly bismuth (Bi³⁺) and antimony (Sb³⁺)—create serious operational challenges.
Process Disruption: These metallic impurities cause short circuits between anodes and cathodes, generating:
- Low-quality cathode deposits failing purity standards (>99.999% required)
- Interrupted electrorefining operations requiring cell shutdowns
- Reduced production efficiency and throughput
- Increased operational costs from process interruptions
Extreme Operating Conditions: The electrorefining environment presents unique purification challenges:
- pH ≤ 2.0: Extreme acidity that deactivates most chelating resins
- 200 g/L H₂SO₄: High sulfuric acid concentration
- 41 g/L Cu²⁺: High copper concentration that must remain largely untouched
- High altitude: 2,850 meters (9,350 feet) above sea level operation
- Temperature: 60°C operating temperature in electrolytic cells
Technical Requirements: The mining company needed a purification solution that could:
- Reduce Bi³⁺ and Sb³⁺ concentrations to <0.05 g/L
- Operate effectively at pH ≤ 2.0 with high sulfuric acid content
- Minimize copper removal from the electrolyte
- Process high volumes continuously (2,400+ m³/day)
- Integrate with existing electrorefining operations
- Support regeneration and reuse of reagents
Traditional ion exchange resins lose selectivity at such extreme pH levels, making this application particularly challenging.
The Solution
ResinTech's Technical Department recommended SIR-500, a specialized polystyrene macroporous chelating weak acidic cation resin functionalized with aminophosphonic acid chelating groups. Unlike conventional resins, SIR-500 exhibits enhanced selectivity specifically under extreme acidity conditions.
Unique Selectivity Profile:
Under normal acidic conditions (pH 3.0-7.0):
Pb²⁺ > Cu²⁺ > Zn²⁺ > Mg²⁺ > Ca²⁺ > Ni²⁺ >> Na⁺
Under extreme acidity (pH ≤ 2.0):
Sb³⁺, Sn⁴⁺, In³⁺, Bi³⁺, Sb⁵⁺, Fe³⁺ > Cu²⁺, Al³⁺ > Pb²⁺ > Cd²⁺, Fe²⁺ > Mn²⁺ > Co²⁺ > Ni²⁺, Zn²⁺ > Ca²⁺, Mg²⁺ >> Na⁺
This pH-dependent selectivity shift makes SIR-500 ideal for targeting bismuth and antimony while minimizing copper removal in highly acidic copper sulfate electrolytes.
Superior Complexing Capacity:
- Antimony: 8.7 g/L complexing capacity
- Bismuth: 1.68 g/L complexing capacity
- These exceptional capacities enable extended operational cycles and efficient impurity removal
System Configuration:
The installed purification system features:
- Three columns: Each containing 5,000 liters (176.55 ft³) of SIR-500
- Parallel operation: Two columns operate simultaneously while third regenerates
- Flow rate: 50 m³/h (220 gpm) per column
- Daily capacity: 2,400 m³ (634,000 gallons)
- Cycle time: 6-8 hour operational cycles
- Expandability: Three additional columns planned to double capacity to 4,800 m³/day
Regeneration & Sustainability:
SIR-500 regenerates with 20% hydrochloric acid, followed by neutralization with 20% sodium hydroxide and reconversion to H⁺ form. The mining company's HCl recovery plant reclaims the regenerant, creating a closed-loop system that:
- Cuts primary reagent costs significantly
- Reduces environmental footprint in the Atacama Desert region
- Maximizes process efficiency through reagent reuse
- Recovers valuable metals from the regenerant stream
The Results
The industrial testing and full-scale implementation demonstrated exceptional performance across 30 consecutive operational cycles, with the system consistently meeting all purification targets.
Impurity Removal Performance:
Antimony Reduction:
- Initial concentration: 0.3 g/L
- After 1 hour: 0.03 g/L (90% reduction)
- After 4 hours: 0.03 g/L (maintained)
- After 8 hours: 0.06 g/L (80% reduction)
Bismuth Reduction:
- Initial concentration: 0.1 g/L
- After 1 hour: 0.005 g/L (95% reduction)
- After 4 hours: 0.008 g/L (92% reduction)
- After 8 hours: 0.01 g/L (90% reduction)
Iron Reduction:
- Initial concentration: 0.1 g/L
- Consistently maintained below 0.01 g/L throughout 8-hour cycles
Copper Preservation:
- Initial concentration: 41 g/L
- After 8 hours: 36.7 g/L (minimal 10.5% removal)
- Copper remains largely in solution for electrorefining process
Operational Excellence:
Extended Cycle Performance: The system exceeded initial 6-hour projections, operating effectively for 8-hour cycles across 30 consecutive days without performance degradation.
Production Impact:
- Eliminated short circuits in electrolytic cells
- Enabled consistent production of >99.999% pure copper cathodes
- Improved overall electrorefining process efficiency
- Reduced operational interruptions and cell maintenance
Environmental Benefits:
- HCl regenerant recovery reduces chemical consumption
- Closed-loop system minimizes waste generation
- Metal recovery from regenerant stream adds value
- Reduced environmental impact in sensitive Atacama Desert ecosystem
Regenerant Recovery Composition:
The HCl regenerant after stripping contains valuable metals:
- Copper: 3 g/L (recovered)
- Antimony: 9 g/L (concentrated for recovery)
- Bismuth: 2 g/L (concentrated for recovery)
- Iron: 1 g/L (removed from main process)
These concentrated metals can be recovered as valuable byproducts, offsetting operational costs.
Why SIR-500 Outperforms Conventional Resins
ResinTech SIR-500's aminophosphonic acid functional groups provide decisive advantages for extreme acidity applications:
pH-Dependent Selectivity:
Most chelating resins lose effectiveness below pH 3.0. SIR-500's selectivity actually enhances at pH ≤ 2.0, making it uniquely suited for sulfuric acid-rich copper electrorefining applications.
High Capacity Under Harsh Conditions:
The resin maintains exceptional complexing capacity for antimony (8.7 g/L) and bismuth (1.68 g/L) even in 200 g/L sulfuric acid solutions—conditions that would destroy conventional resins.
Copper Selectivity Control:
While SIR-500 has affinity for copper at normal pH, its selectivity profile at extreme acidity prioritizes antimony and bismuth removal, minimizing unwanted copper loss from the electrolyte.
Regenerability:
The resin fully regenerates with hydrochloric acid, enabling indefinite reuse while producing a concentrated metal stream suitable for recovery operations.
Macroporous Structure:
The robust macroporous polymer matrix withstands the physical and chemical stresses of continuous operation in harsh industrial conditions at high altitude.
Strategic Impact & Future Expansion
The successful implementation at this Chilean mining operation validates SIR-500 as the premier solution for copper electrorefining purification worldwide.
Capacity Expansion Underway:
Based on initial success, the mining company is adding three additional columns to double daily capacity to 4,800 m³, supporting increased production targets while maintaining ultra-high copper purity standards.
Operational Advantages Realized:
- Predictable performance: Consistent removal across 30+ cycles
- Extended cycles: 8-hour operation exceeds initial 6-hour projections
- Process reliability: Eliminates short circuit interruptions
- Quality assurance: Enables consistent >99.999% cathode purity
- Cost efficiency: Regenerant recovery maximizes ROI
Industry Applications:
This technology applies to copper mining and refining operations globally, particularly for:
- Large-scale copper electrorefining facilities
- High-purity copper production requirements
- Operations facing impurity-related production challenges
- Facilities seeking to optimize electrolyte quality
- Companies prioritizing sustainability through reagent recovery
Competitive Positioning:
The mining company now produces copper cathodes that consistently meet the most stringent purity specifications, supporting premium pricing and preferred supplier status in global copper markets.
Conclusion
The Chilean copper mining operation successfully implemented ResinTech SIR-500 to solve critical impurity challenges in their electrorefining process. Key achievements include:
- >99.999% copper purity consistently maintained in cathode production
- 90%+ removal of antimony and bismuth impurities preventing short circuits
- 2,400 m³/day capacity with expansion to 4,800 m³/day planned
- Extended cycle life exceeding initial projections by 33%
- Sustainable operations through HCl regenerant recovery and reuse
- Metal recovery from concentrated regenerant streams adding value
The project demonstrates SIR-500's unique capabilities under extreme acidity conditions—solving purification challenges that conventional ion exchange resins cannot address. ResinTech's specialized resin technology enables copper mining operations to achieve ultra-high purity standards while maximizing operational efficiency and environmental sustainability.
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