Why does a teaspoon of activated carbon have a surface area larger than a soccer field

Activated carbon has over 2,500 commercial product applications. Most wastewater treatment plants use carbon to purify the water and air leaving the facility. But you won't find their characteristics and properties in a "formal" education. You learn about them on the job.

Activated carbon is an inert solid adsorbent material commonly used to remove a variety of dissolved contaminants from water and process gas phase streams. It is made from virtually all carbon-containing raw materials, including coconut shells and members of the coal family, as many readers already know.

Adsorption is the accumulation of a gas or liquid on the surface of a liquid or solid substrate, as opposed to absorption, in which an invasive substance enters the volume or volume of the substrate.

Activated carbon is porous, inexpensive and easy to use as an adsorbent, providing a large surface area to remove contaminants. It has a greater useful surface area per gram than any other material available for physical adsorption. In fact, a teaspoon of activated carbon has a surface area larger than a soccer field.

Physical Phenomena

Due to its rare properties, activated carbon has the exceptional ability to trap water-soluble contaminants, including substances that promote taste, odor, color and toxicity. Removal is based on surface interactions between the contaminants and the surface of the carbon graphite sheet through the phenomenon of adsorption.

These contaminant-carbon surface interactions occur through van der Waals forces and induced dipole interactions. Activated carbon graphite flakes induce neutral organic molecules into intramolecular dipoles. The induced dipoles cause the molecules to attract each other and stick together, so they precipitate out of solution in the nanoscale pores or adsorption spaces of the carbon. This is called premature condensation and is promoted by activated carbon.

Activated carbon manufacturers use different raw materials and process parameters to provide a variety of pore size distributions. Proper pore structure selection is critical to address the aqueous and gas phases of activated carbon.

Powdered Activated Carbon

Powdered, micron-sized activated carbon particles are milled from millimeter-particle activated carbon and exhibit faster kinetics and greater contaminant removal capacity than larger particle size carbon.

Powdered activated carbon can be used for sporadic contaminant events that contaminate municipal influent water, such as algal blooms and industrial spills. The powder can be added to the clarification process settling unit to remove these contaminants using activated carbon. It can also protect fixed activated carbon beds from sudden influent contamination.

If a plant lacks the infrastructure to use granular activated carbon, or if there is not enough granular carbon between the influent and effluent to economically remove sporadic contaminants, the plant can use powder instead. Disposable powder activated carbon is used as a batch treatment to remove contaminants to an acceptable specified maximum contaminant level (MCL), but not necessarily to zero or undetected contamination.