Introduction to indicators of activated carbon
11 Feb.,2025
Activated carbon has three important indicators, which determine the efficiency of activated carbon.The performance indicators of activated carbon products can be divided into physical performance indicators, chemical performance indicators, adsorption performance indicators.Different indicators represent different properties of activated carbon, and they all play an important role .
The performance indicators of activated carbon products can be divided into physical performance indicators, chemical performance indicators, and adsorption performance indicators. Three performance indicators play an important role in the selection and application of activated carbon.
The main physical performance indicators include: shape, appearance, specific surface area, pore volume, specific gravity, mesh number, particle size, wear resistance, floating rate, etc.
The main chemical performance indicators are: PH value, ash content, moisture, ignition point, uncarbonized matter, sulfide, chloride, cyanide, sulfate, acid-soluble matter, alcohol-soluble matter, iron content, zinc content, lead content, arsenic content, Calcium and magnesium content, heavy metal content, phosphate, etc.
The main adsorption performance indicators are: methylene blue adsorption value, iodine adsorption value, phenol adsorption value, carbon tetrachloride adsorption value, caramel adsorption value, quinine sulfate adsorption value, saturated sulfur capacity, penetration sulfur capacity, water capacity, Ethyl chloride vapor protection time, ABS value, etc.
Activated carbon adsorption capacity index
1.Iodine value (iodine adsorption value)
Refers to the amount of iodine absorbed per gram of activated carbon when the remaining (equilibrium) concentration of iodine in the solution is 0.02N/L. The unit of iodine value is mg/g. The diameter of the iodine molecule is only 0.335nm, so the iodine value is mainly used to characterize the degree of development of activated carbon micropores and the ability of activated carbon to adsorb small molecules.
Detection method: Take a certain amount of activated carbon sample and fully contact and oscillate with the iodine standard solution of known concentration. After filtering (centrifugal separation), remove a certain amount of iodine clear solution and use it with sodium thiosulfate of known concentration. Titration. Find the amount of iodine adsorbed per gram of activated carbon.
Standard distinction: Iodine value is the most likely indicator to cause disputes. The iodine value test results of the coal-based charcoal national standard, the wood-based charcoal national standard, the American standard, and the Japanese standard are all different. Among them, the iodine value test results of the coal-based charcoal 2008 national standard and the American standard ASTM The results are consistent.
2.Methylene blue value
Refers to the number of milligrams of methylene blue absorbed when 1.0g of carbon and a methylene blue solution with a concentration of 1.0mg/L reach equilibrium. Commonly used units are mg/g and ml/0.1g. Unit conversion formula: 1ml/0.1g = 15mg/g, such as methylene blue value 8ml/0.1g = 120mg/g.
The molecular diameter of methylene blue is larger than that of iodine molecules, and the methylene blue value is usually used to characterize the number of pores in activated carbon. In practical applications, the methylene blue value is also commonly used to represent the decolorization ability of activated carbon. The higher the methylene blue value, usually the better the decolorization performance is under the same unit weight.
Testing method: Weigh a certain amount of ground and dried activated carbon sample and mix it thoroughly with the prepared methylene blue solution of known concentration for absorption. After filtering, use a spectrophotometer to measure the absorbance of the filtrate at a wavelength of 6655m. Compare it with the absorbance of the copper sulfate standard color solution (aqueous solution with a mass fraction of 0.4%), and adjust the amount of methylene blue solution added until the difference in absorbance reading between the measured sample filtrate and the copper sulfate standard color solution is no more than ±0.02 until. Calculate the mass of methylene blue adsorbed per gram of activated carbon.
Standard distinction: The unit of methylene blue for coal-based activated carbon is usually mg/g, and ml/0.1g for wood-based activated carbon.
3. Caramel decolorization rate
Refers to the decolorization ability of activated carbon on caramel test liquid. The caramel decolorization rate is usually used to evaluate the ability of sugar activated carbon to decolorize sugar liquid. The caramel decolorization rate indicates the degree of macropore development of the activated carbon. In practical applications, usually only wood powder charcoal will be tested for caramel decolorization rate, and charcoal made of other materials will rarely be tested for caramel decolorization rate indicators.
Detection method: Under certain test conditions, the porosity of activated carbon is used to decolorize the caramel test liquid. The ratio of the remaining caramel liquid concentration after decolorization to the original concentration of the caramel liquid is the caramel decolorization rate.
4. Molasses value
Refers to the ability of activated carbon to decolorize molasses solution. The molasses value also indicates the degree of development of macropores of activated carbon. There is currently no testing standard for molasses value in China. The American Calgon standard is generally used for testing. In China, only briquette carbon with a high molasses value is tested. Other carbons are tested. Molasses values are not routinely tested.
5. Carbon tetrachloride adsorption value/carbon tetrachloride adsorption rate CTC
Refers to the adsorption ratio of activated carbon to carbon tetrachloride. Under specific temperature conditions, mix the carbon tetrachloride steam through the activated carbon. After a period of time, weigh it and repeat this step until the weight remains constant and the activated carbon adsorption is saturated. The total amount of carbon tetrachloride adsorbed by the activated carbon is Carbon tetrachloride adsorption value of activated carbon.
The unit of carbon tetrachloride adsorption rate is %. CTC is mainly used to evaluate the gas phase adsorption capacity of activated carbon and is the main testing method for quality control of gas phase carbon.
Testing method: Put the activated carbon sample to be tested into an oven with a temperature of 150 degrees and dry it for 2 hours. Cool to room temperature, load the sample into the measurement tube in 2-3 times, the height of the carbon layer is about 10cm, weigh the filled sample tube and record the reset, connect it to the instrument, and place it vertically for 25± 1 degree constant temperature water bath. Then control the dry air with an air flow specific speed of (0-50±0.01) L/(min·cm2) to pass through the CCl4 generating bottle in the ice water bath until the CCl4 vapor concentration stabilizes at (25±10) mg/L; let this concentration Pass CCl4 through each measuring tube. After ventilating for 60 minutes, take out the measuring tube, wipe it clean and weigh it. Weigh it every 15 minutes until saturated adsorption.