Cesium adsorption from aqueous solutions onto Japanese oak charcoal I: effects of the presence of group 1 and 2 metal ions

To understand the mechanisms of adsorption of cesium ions onto charcoal from aqueous solution, adsorption isotherms were analyzed in terms of initial cesium concentration in aqueous solution. Aqueous cesium chloride solutions (CsCl concentration: 2.50 × 10−4 or 2.50 × 10−5 mol/L) were used as samples for the adsorption study. Japanese oak charcoal and activated charcoal passed through a 60-mesh sieve were adopted as adsorbents. Japanese oak charcoal displayed higher ability to adsorb cesium ions than activated charcoal. We examined the blocking effects of group 1 and 2 metal ions on the adsorption of cesium ions, because most charcoal or biochar probably contains considerable amounts of group 1 and 2 metals. The group 1 and 2 metals of lithium, sodium, potassium, magnesium, calcium, and strontium were added to 2.50 × 10−5 mol/L cesium chloride solution. A remarkable finding was that group 1 metal ions, which are monovalent cations, prevent cesium ions from attaching to Japanese oak charcoal much more strongly than group 2 metal ions, which are divalent cations.