Influence of colloids produced by the weathering of rock material on uranium(VI) behaviour


Influence of colloids produced by the weathering of rock material on uranium(VI) behaviour

Zänker, H.; Weiß, S.

There is a mechanism of secondary mineral colloid generation straight at the water-rock interfaces by the weathering of the rock material. It is of importance in the unsaturated zone as for instance in mine waste rock piles. Here we demonstrate the influence of iron-rich colloids generated by this mechanism on the behaviour of uranium(VI). The weathering of phyllite from an abandoned uranium mine in waters poor in cations and anions (“rainwater”) was simulated. The colloids produced by the weathering of this phyllite were able to keep large fractions (up to 90 %) of the uranium(VI) in a colloid-borne form in the pH region of 5.0 to 7.5. In the absence of colloids, this U(VI)) would have been truly dissolved in this pH region. The consequences of this colloid influence on uranyl speciation in natural oxic waters depend on the specific conditions in a geological environment. In a mine waste rock pile both, situations where the iron-rich colloids increase U(VI) mobility by preventing UO22+ attachment at interfaces and situations where the colloids immobilize U(VI) by scavenging, colloid aggregation, colloid deposition, formation of crusts etc., are possible

Keywords: Colloids; Weathering; Transport of Uranium(VI); Mine waste rock piles

  • Lecture (Conference)
    36th Journées des Actinides, 01.-04.04.2006, Oxford, Great Britain

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Publ.-Id: 8014