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Carbon filtering is a method of filtering that uses a bed ofactivated carbon to remove impurities from a fluid usingadsorption.
Carbon filtering operates throughadsorption, where pollutants in the fluid to be treated are trapped within the pore structure[1] of a carbon substrate. The substrate consists of many carbon granules, each of which is highlyporous. Consequently, the substrate possesses a large surface area that can trap contaminants. Activated carbon is typically used in filters because it has been treated to have a significantly higher surface area than untreated carbon. One gram of activated carbon has a surface area exceeding 3,000 m² (32,000 sq ft).[2][3][4]
Carbon filtering is commonly used forwater purification,air filtering and industrial gas processing, for example the removal ofsiloxanes andhydrogen sulfide frombiogas. It is also used in a number of other applications, including respirator masks, the purification ofsugarcane, some methods of coffeedecaffeination, and in the recovery of precious metals, especially gold. It is also used incigarette filters and in theEVAP used in cars.[5]
When filtering water, charcoal carbon filters are most effective at removing chlorine, particles such as sediment,volatile organic compounds (VOCs), taste and odor. They are not effective at removing minerals, salts, and dissolved inorganic substances.[6]
Filters containing anadsorbent orcatalyst such ascharcoal (carbon) may also removeodors and gaseous pollutants such asvolatile organic compounds orozone.[7]
Each carbon filter is typically given amicron rating that specifies the size of particle which the filter can remove from a fluid. Typical particle sizes which can be removed by carbon filters range from 0.5 to 50 μm. The efficacy of a carbon filter depends not only on its particle size, but also on the rate of flow of fluid through the filter. For example, if a fluid is allowed to flow through the filter at a slower rate, the contaminants will be exposed to the filter media for a longer amount of time, which will tend to result in fewer impurities.[8]
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