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How does activated carbon work ?
A: Activated carbon works by a process of adsorption. This is an attraction of a molecule to the carbon’s vast internal surface by weak forces, known as London forces. The molecule is held in place and cannot be removed, unless the process conditions change, for example heating or pressure. This can be useful as an activated carbon can be used to concentrate material on its surface, that can be later stripped and recovered. The use of activated carbon for gold recovery is one common example of this.
In some cases, the activated carbon is chemically treated to remove pollutants and in this case the resulting reacted compound is generally not recovered.
Activated carbon surface is also not completely inert, and a variety of catalytic processes can be achieved using and taking advantage of the extended internal surface area available.
What forms can activated carbon applied in ?
A: Activated carbon can be manufactured commercially in granular, pelletised and powdered forms. Different sizes are defined for different applications. For example, in air or gas treatment, the restriction to flow is import, and so coarse particles are used to minimise pressure loss. In liquid treatment, where the removal process is slower, then finer particles are used to improve the rate, or kinetics, of the purification process.
What is meant by activated carbon ?
A: Activated carbon is a processed natural material that is high in carbon content. For example, coal, wood or coconut are perfect raw materials for this. The resulting product has a high porosity and can adsorb molecules of pollutants and trap them, thus purifying air, gases and liquids.
How can activated carbon be used ?
A: How an activated carbon is used depends very much on the application duty, and its form. For example, powdered activated carbon (PAC) is used to treat drinking water, by simply adding the required amount directly to the water and then separating the resulting coagulation matter (as well as other solids) before sending the treated water to the network. The contact with the organics present results in adsorption of them and the purification of the water.
Granular carbons (or extruded pellets) are used in fixed filter beds, with the air, gas or liquid passing through it with a determined residence (or contact) time. During this contact the unwanted organics are removed and the treated effluent is purified.
How is activated carbon made ?
A: Activated carbon is commercially manufactured from coal, wood, fruit stones (mainly coconut but also walnut, peach) and derivatives of other processes (gas raffinates). Of these coal, wood and coconut are the most widely available.
The product is manufactured by a thermal process, but in the case of raw materials such as wood, a promoter (such as an acid) is also used to develop the required porosity.
Downstream processes crush, screen, wash and/or grind the multitude of products to the client’s requirements.
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