Overview
The copper hydrometallurgical process begins with crushing and grinding the raw copper oxide ore to achieve a fine particle size, making the copper minerals accessible for leaching. The ore is then mixed with an acidic solution in the leaching stage, where sulfuric acid dissolves the copper into a solution. After leaching, the copper-rich solution undergoes solvent extraction (SX), where copper is separated from impurities and transferred to an organic solvent. The copper is stripped from the organic phase into a highly concentrated aqueous solution. Finally, the purified solution enters the electrowinning (EW) stage, where copper ions are plated onto cathodes as high-purity metallic copper, completing the process from raw ore to cathode copper.
1. Ore Crushing and Grinding
The first critical step in copper hydrometallurgy is crushing and grinding the raw ore. The purpose of this stage is to reduce the size of the copper oxide ore and expose the copper minerals to improve subsequent leaching efficiency.
- Crushing: The raw copper oxide ore is delivered from the mine and fed into crushers, where it is broken down into smaller pieces. This primary crushing reduces the ore to a manageable size for further processing.
- Grinding: The crushed ore is further processed in grinding mills, such as ball mills, to achieve a finer particle size. This step ensures that the copper-containing minerals are sufficiently liberated from the gangue (non-copper bearing material), optimizing the ore’s surface area for leaching.
- Slurry Formation: After grinding, the finely crushed ore is mixed with water and sulfuric acid, forming a slurry that can easily flow into the next processing stage.
2. Leaching: Dissolving Copper from Ore
Leaching involves dissolving copper from its ore by using sulfuric acid. The aim is to convert the copper into a soluble form that can be extracted in later steps.
- Slurry Formation: The ground ore is mixed with a raffinate solution (a recycled acidic solution) in large leaching tanks, where it is continuously agitated.
- Chemical Reaction: Sulfuric acid is added to the slurry, which reacts with the copper oxide in the ore, forming a copper sulfate solution. The reaction typically occurs at room temperature and can last up to 4 hours.
- High Leach Efficiency: The leaching process achieves high recovery rates of 92-94% for copper. The pH of the solution is controlled between 1.5 and 2.0 to maintain optimal conditions for copper dissolution.
- Solid-Liquid Separation: After leaching, the copper-laden solution is separated from the solid residues (leached ore) using a thickening process. The resulting copper-rich solution is then moved to the solvent extraction phase.
3. Solvent Extraction: Purifying Copper Solution
Once the copper is dissolved in the leachate, the solution still contains impurities that need to be removed. Solvent extraction (SX) is the next step, where copper is selectively transferred from the aqueous solution into an organic solvent.
- Extraction Phase: The copper-laden leachate is mixed with an organic solvent containing an extractant (such as Lix984N). Copper ions transfer from the aqueous phase into the organic phase, leaving impurities behind in the aqueous raffinate.
- Stripping Phase: The organic solvent, now loaded with copper, is then “stripped” with a highly acidic solution (lean electrolyte). This process moves the copper ions back into an aqueous phase, making them ready for electrowinning.
- Clarification and Phase Separation: Multiple stages of phase separation and clarification are used to ensure the clean separation of the organic and aqueous phases. This purified solution is now ready for electrowinning.
4. Electrowinning: Producing Pure Cathode Copper
Electrowinning (EW) is the final stage of the hydrometallurgical process, where copper is plated onto cathodes through an electrolytic process, resulting in high-purity cathode copper.
- Electrolysis Setup: The copper-rich electrolyte is fed into electrowinning cells equipped with stainless steel cathodes and lead anodes. An electric current is passed through the solution.
- Copper Deposition: Copper ions in the solution are reduced at the cathode, depositing as a layer of pure metallic copper. The electrowinning process usually takes 6-8 days to accumulate enough copper on the cathodes.
- Stripping and Washing: Once the copper has sufficiently plated onto the cathodes, the cathodes are removed, and the copper is stripped off, washed, and prepared for sale as cathode copper.
- Recycling the Barren Solution: The electrolyte, now depleted of copper (referred to as barren electrolyte), is recycled back to the solvent extraction process, where it can be reused to strip copper from the organic phase.
Closing the Loop: Solution Recycling and Waste Management
To ensure the process is efficient and environmentally sustainable, there are several recycling loops:
- The raffinate from solvent extraction is sent back to the leaching stage to be reused as part of the leaching solution for fresh ore.
- The barren electrolyte from electrowinning is returned to the SX process to strip copper from the organic solvent, maintaining a continuous loop.
Additionally, the solid residues from the leaching process are neutralized with lime before being deposited in tailing ponds, preventing environmental damage.
Sichuan Precision Technologies (PRS) stands out as a leader in designing and implementing the solvent extraction and electrowinning (SX-EW) process within the copper beneficiation landscape. Our expertise enables us to create tailored solutions that optimize efficiency and recovery rates, ensuring that our clients achieve the highest quality cathode copper. As a trusted EPC service provider, we offer comprehensive support throughout the entire project lifecycle, from initial design to final commissioning. Partner with PRS to leverage our innovative technologies and extensive industry experience, and together we can drive your copper production ambitions to new heights.
