Activated carbon, with its well-developed pore structure, is an expert at adsorbing pollutants. However, its adsorption capacity is not unlimited. Once it reaches "adsorption saturation", its efficiency will drop significantly, and it may even become completely ineffective. Timely judgment of saturation status is the key to ensuring treatment effectiveness and avoiding resource waste. The following introduces several commonly used judgment methods:
Performance degradation monitoring: The most direct signal
Observe the treatment effect: This is the most commonly used and intuitive method. If pollutants that could originally be effectively removed by activated carbon (such as odors, colors, and specific chemical substances) start to "penetrate" the treatment system and are clearly detected at the outlet, or their concentrations increase significantly, this is a strong signal of adsorption saturation. For instance, if the water from a water purifier has an unpleasant smell, or if the odor rebounds at the outlet of industrial waste gas after treatment.
Changes in appearance and physical properties (for reference) :
Color change: New activated carbon is usually dark black and lustrous. Saturated activated carbon may become lighter in color, gray, lose its luster, and even be stained with the color of the adsorbed substances (such as changing color after adsorbing dyes) due to the adsorbed substances.
Weight increase: Activated carbon that has adsorbed a large amount of substances will have a significantly heavier weight than new carbon. In fixed-bed or small-scale applications, regularly taking out a small amount of samples for weighing and comparison can serve as an auxiliary basis for judgment (the influence of moisture needs to be considered).
Pore clogging sensation: Saturated activated carbon particles may appear denser, more moist or sticky due to the clogging of pores by adsorbates.
Penetration test (more accurate)
Set up detection points (such as gas detectors, water quality analyzers) downstream of the activated carbon bed. When the concentration of the target pollutant reaches the preset critical value at the outlet (usually 5%-10% of the inlet concentration), it is considered that "penetration" has occurred at this point, indicating that the activated carbon at this location is saturated or close to saturation. If the entire bed layer is completely penetrated, it means that replacement is needed.
Laboratory analysis (the most accurate but costly)
Samples are sent to a professional laboratory. The weight loss caused by the desorption of adsorbates is measured by thermogravimetric analysis (TGA), or the total amount of adsorbates is determined by solvent extraction. The adsorption capacity is accurately calculated and compared with the theoretical or initial value of new carbon.
A comprehensive consideration is needed to determine the saturation of activated carbon. Closely monitoring the decline in processing effect during daily operation is the most core and practical method. Combining the observation of appearance changes with a simple weight comparison can provide auxiliary information. For high-demand or large-scale industrial applications, conducting penetration tests or regular laboratory analyses can provide more scientific and reliable basis. Regular monitoring and timely replacement of saturated activated carbon are essential to ensure its continuous and efficient performance as an "environmental guardian".
https://www.naturecarbon.com/honeycomb-activated-carbon/gas-phase-activated-carbon.html
