Controllable shell corrosion of coated nanoscale zero valent iron induces long-term potentiation of its reactivity for uranium removal

Environmental remediation approaches by nanoscale zero valent iron (nZVI) based on its reductivity: a review

The fast rise of organic and metallic pollution has brought significant risks to human health and the ecological environment. Consequently, the remediation of wastewater is in extremely urgent demand and has received increasing attention. Nanoscale zero valent iron (nZVI) possesses a high specific surface area and distinctive reactive interfaces, which offer plentiful active sites for the reduction, oxidation, and adsorption of contaminants. Given these abundant functionalities of nZVI, it has undergone significant and extensive studies on environmental remediation, linking to various mechanisms, such as reduction, oxidation, surface complexation, and coprecipitation, which have shown great promise for application in wastewater treatment. Among these functionalities of nZVI, reductivity is particularly important and widely adopted in dehalogenation, and reduction of nitrate, nitro compounds, and metal ions. The following review comprises a short survey of the most recent reports on the applications of nZVI based on its reductivity. It contains five sections, an introduction to the theme, chemical reduction applications, electrolysis-assisted reduction applications, bacterium-assisted reduction applications, and conclusions about the reported research with perspectives for future developments. Review and elaboration of the recent reductivity-dependent applications of nZVI may not only facilitate the development of more effective and sustainable nZVI materials and the protocols for comprehensive utilization of nZVI, but may also promote the exploration of innovative remediation approaches based on its reductivity.

How does the biochar-supported sulfidized nanoscale zero-valent iron affect the soil environment and microorganisms while remediating cadmium contaminated paddy soil?

In previous studies, iron-based nanomaterials, especially biochar (BC)-supported sulfidized nanoscale zero-valent iron (S-nZVI/BC), have been widely used for the remediation of soil contaminants. However, its potential risks to the soil ecological environment are still unknown. This study aims to explore the effects of 3% added S-nZVI/BC on soil environment and microorganisms during the remediation of Cd contaminated yellow-brown soil of paddy field. The results showed that after 49 d of incubation, S-nZVI/BC significantly reduced physiologically based extraction test (PBET) extractable Cd concentration (P < 0.05), and increased the immobilization efficiency of Cd by 16.51% and 17.43% compared with S-nZVI and nZVI/BC alone, respectively. Meanwhile, the application of S-nZVI/BC significantly increased soil urease and sucrase activities by 0.153 and 0.446 times, respectively (P < 0.05), improving the soil environmental quality and promoting the soil nitrogen cycle and carbon cycle. The results from the analysis of the 16S rRNA genes indicated that S-nZVI/BC treatment had a minimal effect on the bacterial community and did not appreciably alter the species of the original dominant bacterial phylum. Importantly, compared to other iron-based nanomaterials, incorporating S-nZVI/BC significantly increased the soil organic carbon (OC) content and decreased the excessive release of iron (P < 0.05). This study also found a significant negative correlation between OC content and Fe(II) content (P < 0.05). It might originate from the reducing effect of Fe-reducing bacteria, which consumed OC to promote the reduction of Fe(III). Accompanying this process, the redistribution of Cd and Fe mineral phases in the soil as well as the generation of secondary Fe(II) minerals facilitated Cd immobilization. Overall, S-nZVI/BC could effectively reduce the bioavailability of Cd, increase soil nutrients and enzyme activities, with less toxic impacts on the soil microorganisms.