Activated Carbon

Broad spectrum removal filter media—overview

Activated carbon is utilized for many water and air filtration applications because it can remove a broad spectrum of contaminants. Activated carbon is utilized in municipal, industrial and hazardous waste streams.

Organic, Inorganic Contaminants

Activated carbon is utilized to remove organic contaminants and some inorganic contaminants. It is generally a non-specific adsorbent. Table 1 is to be utilized as a measure of whether activated carbon is an effective technology. The ratings are based upon current available information and expert judgement.

Activated carbon can adsorb almost all organic compounds to some degree. The effectiveness of activated carbon is related to the chemical composition, molecular structure, and which carbon is being utilized. Activated carbon can be made from coal, coconut shell, wood, bone and peat. The division of pores (macropores, transitional pores and micropores) is different for each product. It is an excellent adsorbent due to its large surface area and the fact that the diverse surfaces can take on many different types of contaminants. The surface area of a carbon is created by activating the base product in a manner to create pores. The effectiveness of the carbon and which carbon delivers best results is based upon the particular site and the contaminants to be removed.

In most water treatment applications the activated carbon will utilize physical adsorption of the contaminants. Physical adsorption is the process of the impurities being held onto the surface area by weak forces. Activated carbon can also utilize chemical adsorption when the forces are strong and happen at active sites on the surface.

Limits

Activated carbon does have limitations. Compounds that have low molecular weight and high purity are usually not recommended for activated carbon. For example, water streams with high solids, oil and grease can cause fouling of the activated carbon.

Another limitation is that the activated carbon does become spent over time and new carbon must be put in its place. The spent carbon must then be disposed of in an appropriate manner. The up side is that the activated carbon may be reactivated or discharged. In most cases the spent carbon is not hazardous; however, if you are unsure about your carbon being non-hazardous or hazardous, it is always best to have it tested.

Due to activated carbon’s ability to be utilized for a variety of contaminants, it is sometimes utilized for applications where another type of filter media or system may be more effective.

Conclusion

Activated carbon is a proven technology that has been around for many years. It is utilized in a wide variety of applications and now comes in many different forms. When looking at a particular application in which a wide array of organic contaminants are found, it may be smart to look at activated carbon first. wqp

About the Author Rick Ciminello is president of CEI - Carbon Enterprises Inc., Circleville, Ohio. He can be reached at 800.344.5770, or by e-mail at rick@ceifiltration.com.

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