Oxalate Modification Dramatically Promoted Cr(VI) Removal with Zero-Valent Iron

Abstract

In this study, we demonstrated that oxalate modification could promote the Cr­(VI) removal performance of zerovalent iron (ZVI) and increase the removal rate constant by about 20 times. This dramatic enhancement of Cr­(VI) removal was attributed to the binding of oxalate groups on the surface of ZVI in a monodentate mononuclear configuration. The surface structure of oxalate-modified zerovalent iron (OA-ZVI) and the Cr­(VI) adsorption behaviors on ZVI and OA-ZVI were carefully investigated. The theoretical results revealed that this oxalate modification favored Cr­(VI) adsorption on the ZVI surface with a much lower adsorption energy and also accelerated electrons transfer from the iron core to the surface, which could produce more surface Fe­(II) to easily reduce Cr­(VI) via a single electron transfer pathway, greatly promoting the reduction removal of Cr­(VI). More importantly, OA-ZVI still remained at a high Cr­(VI) removal activity even after six cycles of use for both simulated and real Cr­(VI)-containing wastewaters, revealing its excellent continuous Cr­(VI) removal ability for practical application. This study provides an environmental-benignity surface modification method of ZVI and also highlights the importance of surface functional groups on the Cr­(VI) removal property of ZVI.

Oxyanion-modified zero valent iron with excellent pollutant removal performance

“…Oxyanions can form stable iron complexes with Fe( ii )/Fe( iii ), 40–43 and thus be able to change the structure and properties of ZVI for efficient pollutant removal. 38,44–54 Moreover, oxyanions used in oxyanion modification are more abundant and environmentally benign than those species used for other modification methods, like bimetallic modification and sulfidation, 25 allowing for tuning the properties of ZVI to remove different target pollutants with less environmental risks. Thus, oxyanion modification becomes one of the most cost-effective approaches with great potential to enhance the decontamination performance of ZVI.…”

“…Thus, oxyanion modification becomes one of the most cost-effective approaches with great potential to enhance the decontamination performance of ZVI. This Feature Article endeavors to summarize the recent progress of oxyanion-modified zero valent iron (OM-ZVI) developed in our group, including oxyanion-modified microscale ZVI (OM-mZVI) 44,45,47 and nanoscale ZVI (OM-nZVI). 38,46 We focus on the synthesis, characterization, enhanced pollutant removal performance, and structure-property relationships of OM-ZVI, including phosphate-modified nZVI, 46 phosphorylated nZVI, 38 oxalate-modified mZVI, 45 oxalated mZVI, 47 and strained-mZVI with interstitial B doping.…”

“…This Feature Article endeavors to summarize the recent progress of oxyanion-modified zero valent iron (OM-ZVI) developed in our group, including oxyanion-modified microscale ZVI (OM-mZVI) 44,45,47 and nanoscale ZVI (OM-nZVI). 38,46 We focus on the synthesis, characterization, enhanced pollutant removal performance, and structure-property relationships of OM-ZVI, including phosphate-modified nZVI, 46 phosphorylated nZVI, 38 oxalate-modified mZVI, 45 oxalated mZVI, 47 and strained-mZVI with interstitial B doping. 44 Finally, we highlight the challenges and possibilities regarding the design and development of OM-ZVI for its practical applications in pollution control and environmental remediation.…”

Simultaneous Sequestration of Humic Acid-Complexed Pb(II), Zn(II), Cd(II), and As(V) by Sulfidated Zero-Valent Iron: Performance and Stability of Sequestration Products

“…Given the critical role of the oxide/passive films in the performance of ZVI, a diversity of strategies for enhancing ZVI reactivity have been developed based on manipulating the properties of oxides . For example, acid washing, H 2 pretreatment, ultrasonication, weak magnetic fields, phosphorylation, , and so forth are all reported to be able to accelerate ZVI corrosion either by disrupting the intrinsic oxide coating or modulating the spatial distribution of secondary authigenic iron (hydr)­oxides. Recently, by incorporating sulfur into ZVI and thus constructing an iron sulfide (FeS x ) shell on the ZVI surface, sulfidation pretreatment was proposed as an alternative approach to enhancing the performance of ZVI and has gained increasing interest since its inception. − As a semiconductor, FeS x has higher electron conductivity than that of iron oxides, which can thus facilitate electron transfer and ZVI corrosion under oxic conditions. ,, Besides the improved ZVI reactivity, the presence of reduced sulfur species (e.g., S 2– ) in sulfidated ZVI (S-ZVI) was also found to be able to provide an additional metal sequestration route by forming insoluble metal sulfide precipitates .…”

“…Given the critical role of the oxide/passive films in the performance of ZVI, a diversity of strategies for enhancing ZVI reactivity have been developed based on manipulating the properties of oxides. 12 For example, acid washing, 18 H 2 pretreatment, 19 ultrasonication, 20 weak magnetic fields, 21 phosphorylation, 22,23 and so forth are all reported to be able to accelerate ZVI corrosion either by disrupting the intrinsic oxide coating or modulating the spatial distribution of secondary authigenic iron (hydr)oxides. Recently, by incorporating sulfur into ZVI and thus constructing an iron sulfide (FeS x ) shell on the ZVI surface, sulfidation pretreatment was proposed as an alternative approach to enhancing the performance of ZVI and has gained increasing interest since its inception.…”