Electrowinning systems for mineral processing applications

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Electrowinning is a widely employed technology in modern industries, including metal recovery, mining, refining, and wastewater treatment. The origins of electrowinning can be traced back to 1807 when Humphry Davy, an English chemist, first introduced this electrolytic process. However, it took 66 years for the commercial adoption of electrowinning by the Balbach and Sons Refining and Smelting Company, propelling it to become the second largest metal processing company in the United States.

Aqueous electrowinning relies on an electrolyte as an electrically conductive solution. These electrolytes consist of positively charged ions (cations) and negatively charged ions (anions). Upon applying a direct current (DC) voltage to the solution, cations migrate towards the cathode, while anions move towards the anode.

In aqueous electrowinning, the electrolyte solution contains dissolved metals that require recovery. Another similar process, known as electrorefining, is specifically employed in refining applications to enhance metal purity. Both processes deposit metals at the cathode and serve to purify non-ferrous metals like copper and silver.

A conventional electrowinning unit generally comprises a tank, rectifier, and pump. Inside the tank, cathodes and anodes are arranged, while the pump fills the tank with an electrolytic solution. The electrowinning rectifier supplies electrical current to the cathodes and anodes, creating an electric potential that drives the migration of cations towards the cathode. Gradually, the positively charged ions deposit onto the cathodes, resulting in the formation of a metal deposit. It is worth noting that as metal accumulates on the cathode, the deposition rate from the solution decreases, leading to a slowdown in the plating process. Once the metal deposition rate becomes insufficient for electroplating, the cathodes containing pure metal deposits are collected. In the context of wastewater treatment, the solution (wastewater) is effectively purified or significantly cleansed of non-ferrous metals, subsequently undergoing further treatment via chemical precipitation or reuse within industrial processes.

electrowinning emew cell

In recent years, electrowinning technology has advanced with the introduction of cylindrical cells featuring high flow rates (vortex electrowinning). These advancements have addressed challenges associated with depletion zones, enabling the production of high-purity metals, even in the presence of impurities. Electrometals was the pioneering company to develop and commercialize the first cylindrical electrowinning cell, known as emew. The adoption of vortex electrowinning has expanded the scope of electrowinning beyond metal refining, finding applications in recycling, waste and wastewater treatment, and even in high-tech industries such as semiconductors.

The emew Group offers modular technology packages that are specifically designed and produced for mining projects and capital-sensitive endeavors. These packages are highly suitable for various types of ores, including:

  • Copper oxide ores
  • Complex, polymetallic ores
  • High-grade silver and silver/gold ores

The modular nature of these technology packages allows for efficient and rapid production initiation, enabling quick cash flow generation. Additionally, the low minimum initial investment requirement ensures quick start up and a smooth expansion process in the future.

Heap leaching is a widely employed method across the globe for extracting copper from low-grade oxide deposits. Solvent extraction-electrowinning SX-EW is typically used to recover copper. However, as with any hydrometallurgical process, it is necessary to bleed a portion of the electrolyte to control impurities in the circuit.

In the case of (SX-EW) operations, the impurity bleed removed often flows to the raffinate pond, which adversely affects the efficiency of the leaching process in the heap. According to Fick’s Law, this practice hampers leaching performance due to increased cationic load (copper in the bleed solution) and reduced acid to the heap leach. However, by directly recovering copper cathode from the bleed stream using emew electrowinning before it enters the raffinate pond, several benefits can be obtained:

  • Up to a 10% improvement in copper recovery from the heap
  • A reduction of 15-30% in copper levels in the raffinate
  • Lower consumption of fresh acid
  • Reduced working capital requirements
  • Increased production of copper cathode

The utilization of emew electrowinning technology to recover high-grade, marketable copper cathode from SX-EW bleed streams results in decreased copper levels returning to the heap, thereby enhancing leach efficiency and improving overall copper recovery from the heap. Incremental copper production at very low marginal cost.

Furthermore, as the heap approaches the end of its operational life, it becomes crucial to recover the maximum amount of copper units to ensure profitability and successful decommissioning. The unique emew electrowinning technology enables the recovery of more soluble copper units from spent heap leach ores than any other electrowinning technology available.

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