As the porosity of ZSM-5 is key for its adsorption capacity , thermal, as well as chemical modification, are commonplace to increase mesoporosity and hence adsorption capacity . However, the adsorption ability of ZSM-5 has not received sufficient examination thus far . The adsorption of heavy metals may improve by chemical modification of the zeolite via ion exchange or wet impregnation . The chemical modification can enhance the performance, selectivity, and functionality of the zeolite compared to the raw unmodified form .