Thorium(IV) and neptunium(V) uptake from carbonate containing aqueous solutions by HDTMA-modified natural zeolites
Panagiotis Misaelides1, David Fellhauer2, Xavier Gaona2, Marcus Altmaier2, Horst Geckeis2
1 Department of Chemistry, Aristotle University, 54124 Thessaloniki, Greece
2 Institute for Nuclear Waste Disposal (INE), Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021 Karlsruhe, Germany
The 232Th-uptake ([Th(IV)]0 = 9.7 × 10-5 M) from carbonate solutions ([CO32- ]tot = 0.25 M, 9.0<pHc<10.8) by raw and HDTMA-modified HEUtype zeolitic-, chabazitic- and phillipsitic-tuffs was investigated. The strong uptake by the HDTMA-tuffs at pHc ~9 was assigned to the Th(CO3)56- and ThOH(CO3)45- predominance. The sorption coefficients (Rd) decreased with increasing pHc indicating carbonate competition. Enhanced Rd values for pHc>10.5 are likely due to ThO2(am)-precipitation. The 237Np-uptake ([Np(V)]0 = 2.6 × 10-5 M) from carbonate solutions ([CO32-]tot = 0.25 and 3.0 × 10 -4 M) by raw and HDTMA-modified HEU-type zeolitic tuff and pulverized pure heulandite crystals was studied under Ar-atmosphere at 6<pHc<11. The Rd values for both elements indicated the modified tuffs potential to remove tetravalent- and pentavalent actinides from environmental matrices.
Journal of Radioanalytical and Nuclear Chemistry
Volume 31, pages 1665-1671, 2017