Factors governing cesium adsorption of charcoals in aqueous solution

Cesium adsorption by commercial charcoals was examined to elucidate the mechanisms for capturing cesium ions in aqueous solution. Changes in the adsorption ability of charcoals due to water extraction (water washing) were investigated to develop practical cesium adsorptives based on charcoal. The commercial charcoals examined included mangrove charcoal (MC) and ubamegashi (Quercus phillyraeoides A. Gray) bincho charcoal (BC). Data from the two charcoals were compared with those of Japanese oak (Quercus serrata Thunb. and/or Quercus crispula Blume) charcoal (OC) reported previously. Aqueous cesium chloride solution (2.50 × 10−5 mol/L) was used as a sample solution for the adsorption study. Charcoal powder was used as an adsorbent after passing through a 60-mesh sieve. The powders were characterized using methods, such as Raman spectroscopy, X-ray fluorescence spectrometry, and infrared photoacoustic spectroscopy. The results indicated that MC, which was manufactured at the lowest possible temperature and had the smallest specific surface area, possessed the greatest ability to adsorb cesium. The MC also had the great cesium-adsorption ability in weak acidic solution and maintained the ability even after lengthy extraction treatments.