Reaching beyond the sulfided surface: Doping of copper cation to expand the pH tolerance range for SZVI

Abstract

Sulfidation of zero-valent iron (SZVI) is an important means to greatly inhibit the formation of inert hydr/oxide and improve the overall reactivity in pollutant removal reactions, which is mainly benefiting from the formation of FeSx layer on surface of the zero-valent iron (ZVI). However, FeSx phase can act as reducing reagent in the treatment of pollutants, resulting in inevitable consumption. Considering that, copper cation was introduced to the FeSx phases to prepare copper-doped sulfides with improved durability. In this study, we successfully prepared copper-doped SZVI (Cu-SZVI). The composition and structure have been clearly confirmed by a combination of several techniques, including Raman spectroscopy and X-ray powder diffraction. Cu-SZVI exhibits a superior sequestration reaction to remove Cr(VI) with higher removal capacity of 82.93 mg/g, with the comparison of SZVI (57.54 mg/g) and ZVI (8.23 mg/g). Moreover, Cu-SZVI possesses better operational pH tolerance and longer lifetime of usage, which makes it particularly attractive to large-scale environmental applications. This work proposes a new way to modify SZVI by doping a secondary cation, which can be used to further explore new SZVI materials based on specific needs.