Recovery of Copper by Solvent Extraction: what is the process?

Image courtesy: Cyprium Metals Limited

Introduction

Solvent extraction (SX) is a widely used hydrometallurgical technique for recovering copper from various sources, including ores and industrial waste. This process involves the selective separation of copper ions from aqueous solutions using organic solvents.

Process Overview

The SX process typically consists of several key stages:

1. Leaching: Copper ore is treated with an acidic solution (commonly sulfuric acid) to dissolve copper ions, creating a copper-rich leach solution.
2. Extraction: The leach solution is mixed with an organic solvent containing extractants (e.g., ketoximes) that selectively bind to copper ions, forming a metal-extractant complex.
3. Stripping: The loaded organic phase is treated with a stripping solution (often concentrated sulfuric acid) to release the copper ions back into the aqueous phase.
4. Electrowinning: The stripped solution undergoes electrowinning to produce pure copper metal.

Key Techniques and Innovations

• Extractants: Various extractants are used, such as LIX reagents, which have been optimized for efficient copper recovery. For example, LIX 64 is known for its rapid kinetics and high selectivity for copper over iron.
• Efficiency: Recent studies indicate that SX can achieve over 96% recovery of copper in a single extraction step, with nearly complete recovery possible through multiple stages. The use of 2 M sulfuric acid for stripping can yield up to 99% recovery of copper
• Biological Methods: Innovative approaches include using sulfate-reducing bacteria to precipitate copper as covellite nanoparticles, enhancing recovery rates from stripping solutions.

Applications and Economic Impact

SX is particularly advantageous for low-grade ores and secondary materials, where traditional methods may be economically unfeasible. Approximately 25% of global copper production now utilizes solvent extraction, highlighting its significance in modern metallurgy. In Chile, the largest producer of copper, SX processes are projected to account for 50% of production soon.

Challenges and Future Directions

While SX offers numerous benefits, challenges remain, such as managing the degradation of extractants and optimizing the process for varying ore compositions. Ongoing research aims to refine these methods further, potentially integrating more sustainable practices and enhancing the purity of recovered metals.

Conclusion

In summary, solvent extraction stands as a critical technology in the recovery of copper, combining efficiency with economic viability in the face of evolving industry demands.