Activated carbon is often used to adsorb molecules, and adsorption determines the applicability, while adsorption is related to the pore size distribution of various carbon types. Take the steam-activated peat-based, lignite-based and coconut-shell-based powdered activated carbon as examples:
Peat-based activated carbon has micropores and mesopores for various applications; lignite-based charcoal has more mesopores and larger mesopores, providing excellent accessibility; mainly in coconut shell-based charcoal Holes, only for low molecular removal.
Chemically activated activated carbon is very porous, mostly in the microporous and mesoporous range, however, compared to water vapor activated activated carbon, chemically activated activated carbon has a less hydrophobic surface and more negative charge.
Activated carbon filtration principle:
The adsorption capacity of activated carbon has a certain relationship with the level of water temperature and the quality of water. The higher the water temperature, the stronger the adsorption capacity of activated carbon; if the water temperature is above 30 °C, the adsorption capacity reaches the limit and there is a possibility of gradual decrease. When the water quality is acidic, the adsorption capacity of activated carbon for anionic substances is relatively weakened; when the water quality is alkaline, the adsorption capacity of activated carbon for cationic substances is weakened. Therefore, the pH of the water is unstable, which will also affect the adsorption capacity of activated carbon.
The principle of adsorption of activated carbon is: a balanced surface concentration is formed on the surface of the particles, and the impurities of the organic substances are adsorbed into the activated carbon particles, and the initial adsorption effect is high. However, after a long period of time, the adsorption capacity of activated carbon will be weakened to varying degrees, and the adsorption effect will also decrease. If the water in the aquarium is turbid and the organic content in the water is high, the activated carbon will soon lose its filtering function. Therefore, activated carbon should be cleaned or replaced regularly.
The size of the activated carbon particles also has an effect on the adsorption capacity. In general, the smaller the activated carbon particles, the larger the filtration area. Therefore, the powdered activated carbon has the largest total area and the best adsorption effect, but the powdered activated carbon easily flows into the aquarium with water, which is difficult to control and is rarely used. Granular activated carbon is not easy to flow due to particle formation, and impurities such as organic matter in water are not easily blocked in the activated carbon filter layer, and its adsorption capacity is strong, and it is convenient to carry and replace.
The adsorption capacity of activated carbon is proportional to the time of contact with water. The longer the contact time, the better the water quality after filtration. Note: The filtered water should flow out of the filter layer slowly. The new activated carbon should be cleaned before the first use, otherwise black ink will flow out. Before the activated carbon is installed in the filter, it should be spread with 2~3 cm thick sponge at the bottom and top to prevent the penetration of large particles such as algae. After 2~3 months of activated carbon, if the filtration effect is reduced, it should be exchanged. New activated carbon and sponge layers should be replaced regularly.
Take extruded and broken granular activated carbon as an example:
Peat-based extruded activated carbon can be made into a variety of different pore size distribution varieties. Microporous-based varieties are mainly used for gold recovery in gas phase applications. Most of the microporous and mesoporous varieties are used in liquid phase applications, such as adsorption of small molecules and macromolecular impurities in water purification.
Broken coal-based carbon combines micropores and mesopores for a variety of applications. The lignite-based or coconut-shell-based granular activated carbon has the same microporous and mesoporous structure as the powdered charcoal.
What are the performance indicators of activated carbon?
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 a very important role in the selection and application of activated carbon.
The main physical performance indicators are: shape, appearance, specific surface area, pore volume, specific gravity, mesh number, particle size, wear resistance, and floating rate.
The main chemical performance indicators are: PH value, ash, moisture, ignition point, uncarbide, sulfide, chloride, cyanide, sulfate, acid soluble, alcohol soluble, 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, sulfur penetration capacity, water capacity, Ethyl chloride vapor protection time, ABS value, etc.
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