Sorption behaviour of Am on marl groundwater colloids

The sorption of americium on marl colloids is studied in a comprehensive way. In Na-HCO3 groundwater conditions, americium in the concentration range 3×10−11–3×10−10 M sorbs onto groundwater colloids. In these tests, the colloid concentration is rather high, i.e. Ccoll 1.7±1.3 mg l−1 for sizes 50–5000 nm or Ncoll (1.7±0.1)×1011 l−1 for sizes larger than 100 nm. These colloids are mainly chlorite and smectite/illite with an average size smaller than 500 nm. For the groundwater (pH 8.6, [Na+] [HCO3−] 2×10−2 M), Kd values in the range 1–3×106 ml g−1 are measured. These values are compared with experimental and modelled values reported earlier in the literature.