1. Specific surface area
The larger the specific surface area, the stronger the adsorption capacity of activated carbon. Specific surface area refers to the total surface area per unit mass of activated carbon, usually measured in square meters per gram (m²/g). The specific surface area of activated carbon is usually between 500 and 1500 m²/g.
2. Pore size distribution
The pore size distribution determines what size molecules the activated carbon can adsorb. Activated carbon contains three main types of pores:
Micropores (<2 nm): adsorb small molecules of gas and dissolved organic matter.
Mesopores (2-50 nm): adsorb larger molecules, such as organic dyes and hydrocarbons.
Macropores (>50 nm): adsorb very large molecules and act as fast mass transfer channels.
3. Iodine value
The iodine value is the amount of iodine adsorbed by activated carbon in a 0.02N 12/KL aqueous solution. The iodine value is related to the surface area of pores with a diameter greater than 10A, and the iodine value can be understood as an indicator of the total pore volume.
4. Molasses value
The molasses value is a method of measuring the relative decolorization ability of activated carbon in boiling molasses solution. The molasses value is interpreted as the surface area of pores with a diameter greater than 28A. Because molasses is a mixture of multiple components, this parameter must be tested strictly according to the instructions. The molasses value is obtained by treating molasses solution with an activated carbon standard and a sample of the activated carbon to be tested, and calculating the ratio of the optical density of the filtrate.
5. Bulk weight
Bulk weight is a method of measuring the mass of a specific amount of carbon. The activated carbon is gradually added to a graduated barrel to 100cc and its mass is measured. This value is used to calculate the amount of activated carbon required to fill a specific adsorption device. Simply put, bulk weight is the weight of activated carbon per unit volume.
6. Granular density
Granular density is the weight of granular carbon per unit volume, excluding the spaces between particles and cracks greater than 0.1 mm. Granular density is determined by displacement with mercury.
7. Carbon tetrachloride
The carbon tetrachloride value is an indicator of total pore volume and is measured by passing a saturated zero degree Celsius CCI4 gas stream through a 25 degree carbon bed. The weight of adsorbed CCI4 is measured at regular intervals until the weight change of the sample becomes negligible.
8. Methylene blue
The methylene blue value is the number of milligrams of methylene blue absorbed by 1.0 gram of carbon in equilibrium with a 1.0 mg/liter methylene blue solution.
9. Hardness
Hardness is a measure of the mechanical strength of activated carbon. The change in weight is expressed as a percentage. More specifically, the hardness value is the resistance of the granular activated carbon to the decaying motion of a steel ball in the RO-TAP instrument. The hardness value is calculated by using the weight of the carbon on the sieve after the carbon has been in contact with the steel ball.
10. Abrasion Value
Abrasion value is a measure of the resistance of activated carbon to abrasion. This test measures the change in MPD, expressed as a percentage. The abrasion value of granular activated carbon describes the resistance of the particles to decrease during treatment. It is calculated by measuring the ratio of the average diameter of the final particles to the average diameter of the original particles after the carbon sample is exposed to steel balls in a RO_TAP machine.
11. Butane Value
The butane value is the amount of butane adsorbed per unit weight of activated carbon after saturated air with butane is passed through a carbon bed at a specific temperature and a specific pressure.
12. Ash
Activated carbon contains inorganic materials, usually aluminum and silicon. Ash is the residue left after the ground carbon is burned at 954 degrees Celsius for 3 hours. From a technical point of view, ash is the fraction of mineral oxides in activated carbon. It is usually defined as the weight percentage after a certain amount of sample has been oxidized.
13. Moisture
Moisture is a measure of how much water the carbon contains. Moisture is measured by boiling activated carbon in a xylene solution using a Dean-Stark trap and condenser. To test for moisture, water is condensed and trapped in the arm-shaped container to be measured. The water content of activated carbon can also be measured by the change in weight of the activated carbon after drying at 150 degrees Celsius for 3 hours. Moisture is the percentage of weight of water adsorbed in the activated carbon.
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