Unlocking the potential of surface modification with phosphate on ball milled zero-valent iron...

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-ZVI_bm) was prepared with a facile ball milling strategy, and compared with ZVI_bm, the U(VI) removal amount (435.2 mg/g) and efficiency (3.52×10^-3 g·mg^-1·min^-1) of P-ZVI_bm were disclosed nearly 2.0 and 54 times larger than those of ZVI_bm respectively. The identification of products revealed that the adsorption mechanism dominated the removal process for ZVI_bm, while the reactive modified layer strengthened both the adsorption pattern and reduction performance on P-ZVI_bm. 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-ZVI_bm. 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.