Simply closing the reactor improves the electron efficiency of zerovalent iron toward various metal(loid)s removal

The controlled corrosion of zerovalent iron (ZVI) is crucial for the favorable performance of ZVI toward metal(loid)s removal, and dissolved oxygen (DO) plays an important role in the process of ZVI corrosion. However, few efforts have been made to control the concentration of DO in real practice. In this study, we found that the electron efficiency and the specific removal capacity of ZVI toward the removal of four metal(loid)s were increased by 1.2-9.1 times and 1.2-3.6 times, respectively, by simply closing the reactor, while the removal kinetics of metal(loid)s was slightly influenced. The rate constants obtained under open condition were always greater than those obtained under closed condition, and the removal amounts of metal(loid)s by ZVI at the reaction equilibrium under closed condition were nearly equivalent to those under open condition. Compared with the case under open condition, the consumption-redissolution process of DO was decelerated under closed condition, and the rapid corrosion of ZVI was alleviated subsequently. Although closing the reactor is simple, it does contribute much to the favorable electron efficiency of ZVI toward metal(loid)s sequestration and can be easily adopted in real practice. Practitioner points Closing the reactor promoted the selectivity of ZVI towards four metal(loid)s removal. The consumption-redissolution process of DO and corrosion of ZVI were decelerated by closing the reactor. Metal(loid)s were reduced to lower valence by ZVI under closed condition. Effect of DO was different when ZVI was applied to remove different metal(loid)s.

Automated summary

By simply closing the reactor, the electron efficiency and specific removal capacity of ZVI for four metal(loid)s increased significantly, while the removal kinetics was slightly affected. The consumption-redissolution process of DO and corrosion of ZVI were decelerated under closed condition, leading to improved selectivity in metal(loid)s removal.