Remediation of U(VI)-contaminated water using zero-valent iron

We investigated the possibility of U(VI) reduction by zero-valent iron (Fe- 0). We conducted batch experiments with granular iron and solutions contain ing 0.25 and 9.3 mg L-1 U(VI) at 24 degrees C. The solution pH ranges betwe en 2 and 9. In all experiments uranium removal was complete within several hours to several days regardless of the pH value. The reduced uranium preci pitated as poorly crystallized hydrated uraninite, UO2.nH(2)O. The reductio n of U(VI) to U(IV) by Fe-0 was found to be the principal mechanism of U re moval from the solution. Other mechanisms such as U(VI) sorption on the new ly formed Fe(III) hydroxides are insignificant. These results show that zer o-valent iron can be used to remediate U-contaminated waters from uranium m ines and mill tailings sites, the pH of which usually ranges between 2 and 9. ((C) Academie des sciences / Elsevier, Paris).