What Is Granular Activated Carbon, and How Does It Work?

Granular activated carbon is a specific preparation of activated carbon, or activated charcoal. It has been used as a purification agent since antiquity. Activated carbon was used for drinking water filtration in ancient India, and as a multi-use purifier in ancient Egypt. In modern times, it was introduced to Europe’s sugar refining industry in the early 19th century. Today, activated carbon in various forms, including granular, is used in a wide range of industrial, commercial, and home applications to remove contaminants.

What Is Activated Carbon?

All forms of activated carbon are produced in the same way. Organic material with a high level of naturally occurring carbon, such as wood, peat, or coal is slowly heated in a low- or no-oxygen environment. This draws out water and impurities without allowing the material to burn. The resulting product is known as char.

The char is then treated through a variety of chemical and physical processing methods to vastly increase its surface area and create a network of submicroscopic pores. The finished product, known as activated carbon, has a remarkable ability to attract and bind a variety of compounds. Activated carbon can be impregnated with various chemicals to improve its binding ability against targeted compounds.

How Does Activated Carbon Work?

All preparations of activated carbon work through a process known as adsorption. In absorption, compounds are evenly distributed throughout the absorbent product, like a sponge soaking up water. In adsorption, however, the compounds bind only to the surface molecules, creating a film.

Carbon molecules are naturally attractive. That is, they actively seek out other molecules with which they can bond. The immense surface area and highly porous nature of activated carbon allow the adsorbed compounds to penetrate the material fully, seeking out all available binding points.

Chemical reactions also take place, changing some offensive compounds into less objectionable variations. Although activated carbon is not effective against all compounds, it does have the ability to bond with compounds in all three phases: liquid, solid, and gas.

What Is Granular Activated Carbon?

Granular activated carbon (GAC) consists of particles that are too large to pass through an 80-mesh sieve. Unlike smaller powdered activated carbon (PAC), granular activated carbon can be used alone rather than solely within a processing machine such as a gravity filter. GAC can also be mixed with a binder and extruded to create evenly sized cylindrical pellets known as extruded activated carbon (EAC).

Both GAC and EAC are sold in a range of sizes designed for specific applications. Choosing the right GAC or EAC for your project depends on a complex balance of factors including size, surface area, and possible “head loss”—a loss of flow pressure due to the friction of passing through a filter.

What Are the Best Applications for Granular Activated Carbon?

Granular activated carbon can be used in a wide range of applications, depending on the size that you select and whether you are using GAC or EAC. Both forms have a high diffusion rate and are particularly good at adsorbing vapors and gases. GAC is frequently used for water treatment and deodorization applications, while EAC’s low dust content makes it ideal for gas phase applications.

Granular activated carbon can remove most, though not all, organic compounds. However, it is a poor choice for most inorganic compounds, which are usually present in ionized form in water, creating strong bonds that are tough for the granular activated carbon to break. Various impregnations are available to strengthen the GAC or EAC’s ability to adsorb those compounds.

Choosing the right form of activated carbon can be complex. Even if you have narrowed down your preference to GAC or EAC, it is important to select the size that best targets the compounds you want to remove. Professional guidance is the best way to ensure that you purchase the product that is right for you.

Are you interested in purchasing activated carbon for a specific application? Do you require expert guidance in choosing the right impregnation for your needs? With more than 70 years of experience in the activated carbon industry, Oxbow Activated Carbon is proud to provide the most diverse line of activated carbon products on the market today. We provide both standard and custom impregnations, spent carbon disposal and reactivation, and numerous other specialized services. We pride ourselves on our individualized customer service, and we look forward to becoming your one-stop shop for all your activated carbon needs.
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