Effect of Secondary FE-Phases


Effect of Secondary FE-Phases

Arnold, T.; Krawczyk-Bärsch, E.; Brandt, F.; Bosbach, D.; Bernhard, G.

The influence of the formation of secondary iron phases on the sorption behavior of U(VI) on chlorite was investigated in batch sorption experiments with two different types of chlorites: an unaltered chlorite from Flagstaff Hill (CCa-2) and a hydrothermally altered chlorite from Grimsel/Switzerland. The easily extractable ions have not been removed in the CCa-2 chlorite and it therefore tends to form secondary phases. In contrast, the hydrothermally altered chlorite is relative resitant to weathering as discussed in Arnold et. al. [1] and therefore does not tend to form secondary phases. The batch sorption experiments were carried out under ambient temperature and pressure using a solid concentration of 0,5 g chlorite in 40 mL 0,1 M NaClO4 solution. The higher sorption capacity of the unaltered CCa-2 chlorite of more than 20 % of the initially added 1´10-6 M U(VI) compared to the hydrothermally altered chlorite is especially striking in the pH region from 6,5 to 8,5 and was attributed to the generation of secondary Fe and Al phases forming during the two months period of the batch sorption experiments. As a consequence of the formation of a new phase additional mineral surface area is generated [2] which serves as a substrate for further uranium sorption. It is well known that Fe-oxyhydroxide particles show a very high affinity for sorbing U(VI) [3]. Our results clearly show that newly-forming secondary phases may increase the sorption capacity of primary minerals. The Diffuse Double Layer Model (DDLM) was applied to model the U(VI) sorption on the two chlorites including the newly-formed secondary phases.

  • Lecture (Conference)
    Migration 03, Korea Sept. 2003

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Publ.-Id: 5336