Unlocking the potential of surface modification with phosphate on ball milled zero-valent iron reactivity:Implications for radioactive metal ions removal

Abstract

Numerous investigations have illuminated the profound impact of phosphate on the adsorption of uranium, however, the effect of phosphate-mediated surface modification on the reactivity of zero-valent iron (ZVI) remained enigmatic. In this study, a phosphate-modified ZVI (P-ZVIbm) was prepared with a facile ball milling strategy, and compared with ZVIbm, the U(VI) removal amount (435.2 mg/g) and efficiency (3.52×10−3 g·mg−1·min−1) of P-ZVIbm were disclosed nearly 2.0 and 54 times larger than those of ZVIbm respectively. The identification of products revealed that the adsorption mechanism dominated the removal process for ZVIbm, while the reactive modified layer strengthened both the adsorption pattern and reduction performance on P-ZVIbm. DFT calculation result demonstrated that the binding configuration shifted from bidentate binuclear to multidentate configuration, further shortening the Fe-U atomic distance. More importantly, the electron transferred is more accessible through the surface phosphate layer, and selectively donated to U(VI), accounting for the elevated reduction performance of P-ZVIbm. This investigation explicitly underscores the critical role of ZVI's surface microenvironment in the domain of radioactive metal ion mitigation and introduces a novel methodology to amplify the sequestration of U(VI) from aqueous environments.