Effects of the cation and Si/Al ratio on CH3I adsorption by faujasite zeolites

•CH3I capture by zeolites is influenced by the cation nature and its speciation.•Ag/Y and Cu/Y display the highest CH3I adsorption capacities and I/M ratio.•Undesirable I2 release was evidenced during CH3I retention by Cu/Y at 100 °C.•The state of silver is controlled by the Si/Al ratio and Ag content.•Dispersed Ag+ species are more efficient than nanoparticles for CH3I adsorption.