Effects of sulfate ligand on uranyl carbonato surface species on ferrihydrite surfaces

Understanding uranium (U) sorption processes in permeable reactive barriers (PRB) are critical in modeling reactive transport for evaluating PRB performance at the Fry Canyon demonstration site in Utah, USA. To gain insight into the U sequestration mechanism in the amorphous ferric oxyhydroxide (AFO)-coated gravel PRB, U(VI) sorption processes on ferrihydrite surfaces were studied in 0.01 M Na₂SO₄ solutions to simulate the major chemical composition of U-contaminatedgroundwater (i.e., [SO₄^2-]~13 mM L^-1) at the site. Uranyl sorption was greater at pH 7.5 than that at pH 4 in both air- and 2% pCO₂-equilibrated systems. While there were negligible effects of sulfate ligands on the pH-dependent U(VI) sorption (