Effect of selected ligands on the U(VI) immobilization by zerovalent iron

Summary

Theeffect ofCl^-, CO₃ ^2-, EDTA, NO₂ ^-, NO₃ ^-, PO₄ ^3-, SO₄ ^2-, and humic substances (HS)on the U(VI)co-precipitation from aqueous solutions by zerovalent iron (ZVI) was investigated in the neutral pH range.Batch experiments without shaking were conducted for 14 days mostly with five different ZVI materials (15 g/l), selected ligands (10mM) and an U(VI) solution (20 mg/l, 0.084mM). Apart from Cl^-, all tested ligands induced a decrease ofU(VI)coprecipitation. This decrease is attributed to the surface adsorption and complexation of the ligands at the reactive sites on the surface of ZVI and their corrosion products. The decrease ofU(VI)removal was not uniform with the five ZVI materials. Generally, groundwater with elevated EDTA concentration could not be remediated with the ZVI barrier technology. The response of the system on the pre-treating by two ZVI materials in 250mM HCl indicated that in situ generated corrosion products favor an irreversible U(VI) uptake. Thus for the long term performance of ZVI barrier, the iron dissolution should continue in such a way that fresh iron oxide be always available for U(VI) coprecipitation.