The most common method is the washing with acid solutions (HCl, HNO3...). However, you must be careful with the particle size. Dust dissolution becomes more complicated as particle diameter increases and then Place the activated carbon in a strainer and rinse it thoroughly with cold water. This will help remove any loose particles or dust that may have accumulated during storage.

https://www.researchgate.net/publication/11259588_Removal_of_NiII_from_Aqueous_Solution_by_Adsorption_Onto_Hazelnut_Shell_Activated_Carbon_Equilibrium_Studies

https://www.researchgate.net/publication/318156646_Activated_carbons_prepared_from_hazelnut_shells_walnut_shells_and_peanut_shells_for_high_CO2_adsorption

Emil Aliyev its a nice thoughtful question where yes you are absolutely correct about the activated carbon granules can accumulate dust and impurities over time, reducing their effectiveness. To dedust activated carbon granules, follow these steps:

first can be Sieving: Pass the granules through a mesh sieve or a fine-mesh strainer to remove any lumps and large particles.

Next it can be Air blowing: Gently blow compressed air through the granules to loosen and remove surface dust.

Similarly after airblowing it can be Vibration: Place the granules in a container and vibrate it gently using a vibrating screen or a plate vibrator to dislodge dust particles.

followed by Centrifugation: Spin the granules in a centrifuge to separate dust and impurities from the granules.

and this can also be removed by Rinsing with water: If the activated carbon is water-resistant, rinse it with distilled water to remove any remaining impurities.

and finally one has to look into the Drying: Dry the granules in a low-temperature oven (150°F - 200°F) or under sunlight to remove any moisture.