This work investigates the influence of calcium (Ca), sodium (Na) and bicarbonate (HCO(3) over bar) on the uptake of uranium (U) onto nanoscale zero-valent iron particles (nZVI). Solutions tested contained U at 1 mg/L, NaHCO3 ranging from 0 to 100 mg/L and CaCl2 or NaCl ranging from 625 to 719 mg/L to normalise the ionic strength. Mine water containing a similar concentration of U (1.03 mg/L) and HCO(3) over bar at 845 mg/L was also tested as a natural analogue. All solutions were stored in sealed glass jars in the open laboratory with headspace comprising ambient air. Results demonstrate Ca, Na and HCO(3) over bar as having no significant inhibitive influence on the efficacy of nZVI for initial U removal from solution, with >= 95.7% uptake recorded for all systems studied after 0.5 h reaction. Similar U retention (>97.1%) was recorded throughout the entire 672 h experiment for all solutions with Ca absent. In contrast, partial U desorption in the latter stages of the experiment was recorded for all solutions with Ca present, with 87.3%, 85.2% and 84.7% removal recorded after 672 h for solutions containing 0, 10 and 100 mg/L HCO(3) over bar, respectively, and 10.9% removal recorded for the mine water. Maximum U removal onto nZVI was recorded as directly proportional to HCO(3) over bar concentration for solutions with Ca absent, however, no trend was identified for the Ca-bearing solutions. Overall results demonstrate Ca as having a significant inhibitive influence on the long-term retention (e.g. >48 h) of U on nZVI, which is independent of HCO(3) over bar concentration when also present at <100 mg/L. (C) 2015 Elsevier B.V. All rights reserved.