Retention of neodymium by dolomite at variable ionic strength as probed by batch and column experiments

• Published in: Journal of environmental radioactivity 2018-10, Vol.190-191 (C), p.89-96
• Main Authors: Emerson, H.P., Zengotita, F., Richmann, M., Katsenovich, Y., Reed, D.T., Dittrich, T.M.
• Format: Article
• Language: English
• Subjects: Actinide analogs; Actinoid Series Elements - chemistry; Adsorption; BET; Brunauer Emmett Teller; Calcium Carbonate - chemistry; Carbonates; Department of Energy; DOE; Dolomite; Electron microprobe analysis; EMPA; Energy research and development administration well 6 brine; ERDA-6; Generic weep brine; GWB; ICP-MS; ICP-OES; Incorporation; Inductively coupled plasma mass spectrometer; Inductively coupled plasma optical emission spectrometer; Lanthanide; Magnesium - chemistry; Models, Chemical; Neodymium; Neodymium - chemistry; Osmolar Concentration; Performance assessment; Polytetrafluoroethylene; PTFE; Scanning electron microscope with energy dispersive x-ray spectroscopy; SEM-EDS; Sorption; Time resolved laser fluorescence spectroscopy; TRLFS; Waste Isolation Pilot Plant; WIPP; X-Ray Diffraction; XRD
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2018.05.007

The results presented in this paper highlight the complexity of adsorption and incorporation processes of Nd with dolomite and significantly improve upon previous work investigating trivalent actinide and lanthanide interactions with dolomite. Both batch and mini column experiments were conducted at variable ionic strength. These data highlight the strong chemisorption of Nd to the dolomite surface (equilibrium Kd's > 3000 mL/g) and suggest that equilibrium adsorption processes may not be affected by ionic strength based on similar results at 0.1 and 5.0 M ionic strength in column breakthrough and equilibrium batch (>5 days) results. Mini column experiments conducted over approximately one year also represent a significant development in measurement of sorption of Nd in the presence of flow as previous large-scale column experiments did not achieve breakthrough likely due to the high loading capacity of dolomite for Nd (up to 240 μg/g). Batch experiments in the absence of flow show that the rate of Nd removal increases with increasing ionic strength (up to 5.0 M) with greater removal at greater ionic strength for a 24 h sampling point. We suggest that the increasing ionic strength induces increased mineral dissolution and re-precipitation caused by changes in activity with ionic strength that lead to increased removal of Nd through co-precipitation processes. •Sorption and incorporation of neodymium into dolomite with variable ionic strength.•Long term miniature column saturation experiments with dolomite and neodymium.•Batch kinetics experiments for neodymium sorption to dolomite with variable ionic strength.