Efficient Removal of High Iron Content in Copper Electrolyte: A Green Solution Based on Chelating Resins

This paper addresses the issue of excessive iron content in copper electrolyte systems during hydrometallurgy. Based on actual production data from a copper mine, this paper systematically analyzes the iron distribution characteristics of the electrolyte system and proposes an iron removal process using ion exchange resins. The results demonstrate that the use of chelating resins with specific functional groups can effectively control the electrolyte iron content within the technically specified range of 5-6 g/L, while also meeting process requirements such as no chloride addition and easy regeneration.

1. Process Flow and Iron Distribution Characteristics

1.1 Hydrometallurgical Copper Smelting Process

The study case employed the standard "heap leaching-solvent extraction-electrowinning" process:

Heap leaching: A leachate containing 1.85 g/L Cu, 0.81 g/L Fe²⁺, approximately 22.42 g/L Fe³⁺ (estimated by subtracting Fe²⁺ from total Fe), and 23.23 g/L total Fe was obtained.

Solvent extraction (SX): Produces a lean solution (0.677-0.8 g/L Fe²⁺, 21.91-22.4 g/L total Fe) and a rich electrolyte.

Electrowinning (EW): A circulating electrolyte system containing 35.86-46.84 g/L Cu and 14.24-14.5 g/L total Fe was produced.

1.2 Key Data on Iron Distribution

2. Iron Removal Technology Requirements Analysis

2.1 Current Issues

The iron content of the electrolyte system exceeds the standard (14.24-14.5 g/L), reaching 2.4-2.9 times the target value (5-6 g/L). 1500 m³ of circulating electrolyte requires treatment. Valuable metals such as Co (178-200 mg/L) and Mn (8.5-8.77 mg/L) must be retained.

2.2 Technical Requirements

Treatment Accuracy: Reduce total iron from 14.5 g/L to 5-6 g/L.

Selectivity: Prioritize Fe³⁺ removal (approximately 85%), while retaining Cu²⁺, Co²⁺, and others.

Environmental Performance: Avoid introduction of interfering ions such as Cl⁻.

Economical Performance: The resin must have good regeneration performance (≥500 cycles).

3. Ion Exchange Resin Design

3.1 Resin Selection Recommendations: Iminodiacetic acid chelating resins (such as Lewatit) are recommended. TP-260 features:

Fe³⁺ selectivity (KFe/Cu) reaches 10³-10⁴

Wide pH range (0.5-5.0), suitable for acidic electrolyte environments

Regeneration efficiency >98% (using 5-10% H₂SO₄ solution)

Strong anti-fouling ability (tolerant to organic phase carryover)

3.2 Process Parameter Design

3.3 Expected Results

Single-stage treatment can reduce iron content to below 6 g/L. Cu loss rate <0.5%, Co loss rate <3%. The resin can be used stably for ≥500 cycles (estimated lifespan of 1.5-2 years). The replacement cycle will be assessed based on actual operating conditions.

4. Technical and Economic Analysis

4.1 Investment Estimation

4.2 Operating Costs

Resin Loss: Approximately 0.8%/year (approximately €15,000/year)

Acid Consumption: 0.6 kg H₂SO₄/kg Fe⁺ removed

Energy Consumption: <5 kWh/m³ electrolyte

5. Conclusion

The use of iminodiacetic acid chelating resin to treat high-iron copper electrolyte offers significant technical and economic advantages. This solution not only stably controls the iron content within the process requirement of 5-6 g/L, but also achieves efficient retention of valuable metals and environmentally friendly resin regeneration, providing a reliable technical solution for similar copper smelters. Pilot trials are recommended to further optimize operating parameters.