ACTIVATED CARBONS
FOR WASTEWATER TREATMENT

Activated carbon, also called activated charcoal, is a form of carbon processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions.

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Due to its high degree of micro porosity, one gram of activated carbon has a surface area in excess of 3,000 m2 as determined by gas adsorption. An activation level sufficient for useful application may be obtained solely from high surface area. Further chemical treatment often enhances adsorption properties.

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Depending on the source material, and the processing methods used to produce activated carbon, the physical and chemical properties of the end product can differ significantly. This creates a matrix of possibilities for variation in commercially produced carbons, with hundreds of varieties available. Because of this, commercially produced activated carbons are highly specialized to achieve the best results for a given application.

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Despite such variation, there are three main types of activated carbon:

 

  1. Powdered Activated Carbon (PAC)

Normally, activated carbons (R 1) are made in particulate form as powders or fine granules less than 1.0 mm in size with an average diameter between 0.15 and 0.25 mm. Thus they present a large surface to volume ratio with a small diffusion distance. This kind of activate carbon is typically used in liquid-phase adsorption applications and offer reduced processing costs and flexibility in operation.

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  2. Granular Activated Carbon (GAC)

Granular activated carbons generally range in particle sizes of 0.2 mm to 5 mm and can be used in both gas and liquid phase applications. Granular activated carbon (GAC) has a relatively larger particle size compared to powdered activated carbon and consequently, presents a smaller external surface. These carbons are suitable for adsorption of gases and vapours, because gaseous substances diffuse rapidly. Granulated carbons are used for air filtration and water treatment, as well as for general deodorization and separation of components in flow systems and in rapid mix basins. 

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  3. Extruded Activated Carbon (EAC)

Extruded activated carbons are a cylindrical pellet product ranging in size from 1 mm to 5 mm. EACs are a heavy-duty activated carbon as a result of the extrusion process. Extruded activated carbon (EAC) combines powdered activated carbon with a binder, which are fused together and extruded into a cylindrical shaped activated carbon block with diameters from 0.8 to 130 mm. These are mainly used for gas phase applications because of their low pressure drop, high mechanical strength and low dust content. Also sold as CTO filter (Chlorine, Taste, Odour).

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PROPERTIES OF ACTIVATED CARBON

 

When selecting an activated carbon for a particular application, a variety of characteristics should be considered. YASA ET professionals can guide you in choosing the right activated carbon for your needs.

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Pore Structure - The pore structure of activated carbon varies and is largely a result of the source material and the method of production. The pore structure, in combination with attractive forces, is what allows adsorption to occur.

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Hardness/Abrasion - Hardness/abrasion is also a key factor in selection. Many applications will require the activated carbon to have a high particle strength and a resistance to attrition (the breakdown of material into fines). Activated carbon produced from coconut shells has the highest hardness of activated carbons.

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Adsorptive Properties - The absorptive properties of the activated carbon encompass several characteristics, including adsorptive capacity, the rate of adsorption, and the overall effectiveness of activated carbon. Depending on the application (liquid or gas), these properties may be indicated by a number of factors, including the iodine number, surface area, and Carbon Tetrachloride Activity (CTC).

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Apparent Density - While apparent density will not affect the adsorption per unit weight, it will affect the adsorption per unit volume of the activated carbon.

 

Moisture - Ideally, the amount of physical moisture contained within the activated carbon should fall within 3-6%.

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Ash Content - The ash content of activated carbon is a measure of the inert, amorphous, inorganic, and unusable part of the material. The ash content will ideally be as low as possible, as the the quality of the activated carbon increases as ash content decreases.

 

pH Value - The pH value is often measured to predict potential change when activated carbon is added to liquid.

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Particle Size - Particle size has a direct effect on adsorption kinetics, flow characteristics, and filterability of the activated carbon.

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YASA ET

ACTIVATED CARBON APPLICATIONS

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The ability to adsorb components from a liquid or gas lends itself to thousands of applications across a multitude of industries, so much so, in fact, that it would likely be easier to list applications in which activated carbon is not used. The primary uses for activated carbon are listed below. 

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Water Purification

Activated carbon can be used to pull contaminants from water, effluent or drinking. Water purification has a number of sub-applications, including the treatment of municipal wastewater, in-home water filters, treatment of water from industrial processing sites, groundwater remediation, and more. Activated carbons are currently used in most of YASA ET projects, specifically as components of multi-media filtration systems.

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Air Purification

Similarly, activated carbon can be used in the treatment of air. This includes applications in face masks, in-home purification systems, odour reduction/removal, and the removal of harmful pollutants from flue gases at industrial processing sites.

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Food & Beverage

Activated carbon is widely used throughout the food and beverage industry to accomplish a number of objectives. This includes decaffeination, removal of undesirable components such as odour, taste, or colour, and much more.

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ACTIVATED CARBON REACTIVATION

 

One of the many advantages of YASA ET activated carbon is its ability to be reactivated. While not all activated carbons are reactivated, those that are provide cost savings in that they do not require the purchase of fresh carbon for each use.

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Regeneration is typically carried out in a rotary kiln and involves the desorption of the components that had previously been adsorbed by the activated carbon. Once desorbed, the once-saturated carbon is again considered active and ready to act as an adsorbent again.