Electrostatic Separation of Precious Metals
Precious metals such as gold, silver and platinum usually occur as ores. These mineral ores contain a number of other impurities that have to be removed to extract the pure form of the metal. Extraction of precious metals traditionally consists of four steps, namely, reduction of particle size, separation using particle size, flotation and electrostatic separation. Electrostatic separation basically evolved from extensive research with other minerals. The procedure was then found to be of great use in the extraction of precious metals.
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The Principle
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Electrostatic separation is a type of physical separation that uses the physical difference between the particles like the size, specific gravity or electric charge to separate two different particles. It is seen that many minerals and metals have a general behavior of being attracted or repelled when charged. This property of metals is used for separating them from impurities and extracting the pure form of the metal and forms the basic principle of electrostatic separation.
The Process
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This process uses dry ore particles that are broken into smaller sizes, and 250 mesh size particles are chosen and separated from impurities. This dry ore is electrostatically charged by passing a high velocity arc through the ore. This creates two oppositely charged particles. An oppositely charged collector is used to remove the impurities. This process gives the pure form of the metal and is very widely used for extracting precious metals.
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Advantage Over Other Methods
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Heating and chemical processes can bring about physical changes in precious metals that may affect the quality of the metal. These metals naturally conduct heat and get hot faster. But charging metals just prior to separation gives specific control of the amount of electrostatic charge used. Such controlled electrostatic charging may have very little or no effect on the property of the metal.
Benefits
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Electrostatic separation is an important technique suitable for the processing of minerals. For example, electrostatic beneficiation is commonly used at coal mines to remove particulate matters e.g., ash from mined coal. It also has application during coal preparation to enrich the value of raw coal. Electrostatic separation is an important subject with respect to the recovery of other valuable materials e.g., separates the sulfides from the quartz as well as the cleaning/sanitizing of some food products (e.g., beverages and drinks).
Facts
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The extraction of precious metals from their ores is done using the process of physical separation or electrostatic separation. This method has very low effect in changing the basic quality of the metal. Being precious, these metals cannot be extracted using chemicals, which may lead to a change in their chemical constitution. Some chemicals also have the property of changing color of the metal. These metals are known for their color and hence such risks are unacceptable.
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References
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