What Are the Classifications of Activated Carbon?

Activated carbon is commonly used in the pretreatment of ultrapure water systems, adsorbing and filtering out organic colloids, residual chlorine, and iron ions from raw water. So, what are the different types of activated carbon?

I. Based on the raw materials used in its production, activated carbon can be divided into:

1. Wood-based activated carbon: This can be further divided into wood charcoal (made from sawdust), bamboo charcoal (made from bamboo), fruit shell charcoal (made from walnut shells or apricot kernels), and coconut shell charcoal (made from coconut shells). Coconut shell charcoal or fruit shell charcoal are commonly used in pure water equipment.

2. Coal-based activated carbon (made from anthracite, with Ningxia coal considered to be of higher quality).

3. Bone charcoal (made from animal bones). 4. Silver-loaded activated carbon: Generally made from coconut shell activated carbon, it is impregnated with silver using a special process. The silver content is usually 0.1%–0.3%. It slowly releases silver ions (Ag+) into water. Silver ions have bactericidal properties, so silver-loaded activated carbon, in addition to the adsorption function of ordinary activated carbon, also inhibits bacterial growth.

II. According to different forms of activated carbon, it can be divided into:

1. Powdered activated carbon (PAC). Powdered activated carbon is actually granular activated carbon with a finer particle size. Due to its small particle size and large specific surface area, its adsorption effect is superior to commonly used granular activated carbon.

2. Granular activated carbon (GAC). The smaller the particles, the better the adsorption effect, but the water resistance (inlet and outlet pressure difference) is greater, and it is also easier for carbon to leak. Therefore, water purifier manufacturers should choose particles with appropriate particle size.

3. Activated carbon fiber felt (ACF): Depending on the raw materials, there are two types: one is made from viscose-based fiber filaments, processed into cloth, and then carbonized, activated, and treated at high temperatures; the other is made from polyacrylonitrile-based fibers, processed into felt, and then pre-oxidized, carbonized, activated, and treated at high temperatures. The average pore size of the former is 17–26 Å, and that of the latter is 10–20 Å.

4. Sintered activated carbon filter cartridges (CTO), also known as carbon rod filter cartridges or compressed activated carbon filter cartridges, are made by adding a binder (such as PE resin) to granular activated carbon, sintering, and extruding. The outer layer of the carbon core is often covered with white polypropylene (PP) non-woven fabric. Sintered activated carbon filter cartridges have both adsorption and filtration functions (average pore size 3–20 μm), but their filtration function is lower than that of PP melt-blown filter cartridges, and their adsorption function is lower than that of granular activated carbon filter cartridges.