The ability of various solid adsorbents to adsorb tritium from tritiated water was studied. The tritium removability and adsorption ability of mesoporous silica (MCM-41) were found to be larger than those of conventional microporous zeolites such as mordenite (MOR) and Linde-type A (LTA). The different adsorbents can be arranged in order of tritium removability and tritium adsorption ability as follows: MCM-41 > LTA(5A) > high-silica MOR [approximately equal] low-silica MOR [approximately equal] LTA(4A). The adsorbents can also be arranged in decreasing order of the separation factor () as follows: MCM-41 > LTA(5A) > low-silica MOR [approximately equal] LTA(4A) > high-silica MOR.