First Mining Drc-Zambia 2023 First Mining Drc-Zambia July -August 2023 digital magazine | Page 35

FEATURE

FEATURE

Electrowinning systems for mineral processing applications

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 nonferrous metals , subsequently undergoing further treatment via chemical precipitation or reuse within industrial processes .
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 highpurity 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 capitalsensitive 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 extractionelectrowinning SX-EW is typically
... Continues on page 35
www . fmdrc-Zambia . com 33