Cesium adsorption from aqueous solutions onto Japanese oak charcoal III: effects of water-extraction treatment

To remove group 1 and 2 metal ions from Japanese oak ( Quercus serrata Thunb. and/or Quercus crispula Blume) charcoal (OC), a water-extraction treatment was employed. The treatment was repeated 1, 4, 8, or 12 times. The amounts of four metal (sodium, potassium, magnesium, and calcium) ions eluted from non-treated and treated OC were determined using an ion chromatographic apparatus. The effects of water-extraction treatment on the ability of OC to adsorb cesium were investigated using 2.50 × 10 −5 and 2.50 × 10 −6 mol/L aqueous cesium chloride solutions. As for both aqueous solutions, an unexpected result was obtained in that the cesium-adsorption ability of OC decreased suddenly when the repetition of water-extraction treatments exceeded a certain threshold. We explain the results in terms of pH of the sample solutions and the point of zero charge for OC.