Mutual effect of U(VI) and phosphate on the reactivity of nanoscale zero-valent iron (nZVI) for their co-removal

Abstract

Nanoscale zero-valent iron (nZVI) has been widely considered as a promising permeable barrier material for remediating U(VI)-contaminated waters. Little information is available regarding co-removal of U(VI) and oxyanion contaminants by nZVI, yet in the majority of areas polluted by U(VI), co-existence of phosphate is found to be common especially in eutrophic water. Herein, the mutual influence of U(VI) and phosphate on the effectiveness of nZVI in co-removing U(VI) and phosphate is investigated by macroscopic and microscopic approach. The results indicate that nZVI can effectively co-remove U(VI) and phosphate and the processes intensively depend on the solution pH and the additional order due to the formation of nZVI-U(VI)-phosphate complexes and will change the morphology of nZVI through the formation of a new phase. Furthermore, the maximum removal capacity of nZVI increases by 21.63% at pH 6.0 for U(VI) ions and by 34.28% at pH 7.0 for phosphate when both U(VI) and phosphate are present simultaneously. In short, the co-presence of U(VI) and phosphate has a great impact on the reactivity and morphology of nZVI. The findings will be beneficial to broaden the potential feasibility of nZVI in simultaneous radionuclide and phosphate pollution cleanup.