adsorption capacity =amount of adsorbate adsorbed in mg)/(amount of adsorbent used for adsorption expressed in gm). 

So, the flow rate multiplied with the time of adsorption process will give the volume or the mass of the gas to be adsorbed. So you have the density then you can get the mass of the adsorbate from the volume calculated above.

You know the capacity

You have the mass of the adsorbate

Then you can calculate the mass of the adsorbent using the equation in the first line

i am agreeing with the previous comment. just concern with conversion of mole fraction in the feed stream and molar or mass density

May be these links will be useful:

https://www.researchgate.net/publication/264351893_Early_construction_and_operation_of_highly_contaminated_water_treatment_system_in_Fukushima_Daiichi_Nuclear_Power_Station_I_-_Ion_exchange_properties_of_KURION_herschelite_in_simulating_contaminated_w?ev=prf_high

https://www.researchgate.net/publication/263287678_Characterization_and_storage_of_radioactive_zeolite_waste?ev=prf_high

Article Early construction and operation of highly contaminated wate...

Article Characterization and storage of radioactive zeolite waste