Efficient Cu(II) removal with boronated zero-valent iron via inhibition of oxygen adsorption and enhanced electron transfer

Abstract

The inhibition of electron transfer by the iron oxide passivation layer and the competition of oxygen for electrons limited the efficiency of heavy metal removal by zero-valent iron reduction. Herein we synthesized micron zero-valent iron modified with boric acid by mechanical ball milling, and demonstrated its enhanced copper ions removal performance. Compared to pristine ZVI, B-ZVI is approximately 2.6 times more efficient in the removal of copper. Interestingly, copper removal was significantly inhibited under air atmosphere for pristine ZVI. However, for B-ZVI, copper removal efficiency was almost insignificantly different between air and argon atmosphere conditions. Furthermore, the modification of ZVI with boric acid promoted the Cu(II) reduction proportion. Boronated modification effectively inhibited oxygen competition for electrons in removing heavy metals by zero-valent iron, which was conducive to the improvement of the heavy metal removal efficiency and the electron utilization of zero-valent iron. This study elucidated the importance of surface modification on the reactivity of micron-sized zero-valent iron and provided an efficient heavy metal removal strategy with zero-valent iron for environmental remediation.