Nanoscale zerovalent iron (nZVI) particles represent an important material for diverse environmental applications because of their exceptional electron donating properties, which can be utilized, eg, for reduction, catalysis, adsorption and degradation of a broad range of pollutants. The synthesis and assembly of nZVI using biological and natural sustainable resources is an attractive option for alleviating environmental contamination worldwide. In this review, various green synthesis pathways for generating nZVI particles are summarized and compared with conventional chemical and physical methods. In addition to describing the latest environmentally benign methods for the synthesis of nZVI, their properties and interactions with diverse biomolecules are discussed, especially in the context of environmental remediation and catalysis. Future prospects in the field are also considered.

1. Sustainable synthesis of nanoscale zerovalent iron particles for environmental
remediation
Yukti Monga,[a]† Pawan Kumar,[b]† Rakesh K. Sharma,[a]* Jan Filip,[b] Rajender S. Varma,[b]
Radek Zbořil,[b]* and Manoj B. Gawande[b][c]*
ChemSusChem 2020, DOI: 10.1002/cssc.202000290

2. Figure 1. Some advantages of bio-based methods.

3. Figure 2. The core–shell model of nZVI and schematic representation of the reaction
mechanisms. Adapted from references [18, 22].

4. Figure 3. Comparison of different methods for synthesis of iron nanoparticles and their
advantage and disadvantage.

5. Figure 4. Various capping and reducing agents present in tea- and grape extracts identified
with GC-MS and IR.[39-40]

6. Figure 5. The general scheme of biochar-zerovalent iron (BC-ZVI) derived from corn.
Reprinted from ref. [46] Copyright 2017 American Chemical Society.

7. Figure 6. Schematic representation of interaction of Gram-positive and Gram-negative bacteria
with nano zerovalent iron (nZVI), Fe2+ and Fe3+ ions. Reprinted from ref. [58]; Copyright 2013
Royal Society of Chemistry).

8. Figure 7. a) Schematic depiction of chitosan-modified nanoparticles.[72] b) Schematic diagram
of amino acid-mediated synthesis of surface modified Fe0 nanoparticles.

9. Figure 8. Reductive degradation mechanism for the removal of Orange II by core–shell
structured Fe NPs. (Adapted from ref. [84] Copyright 2015 Elsevier).

10. Figure 9. Schematic illustration of ultrasound-assisted cavitations and dye degradation mechanism
by nZVI-containing system. Reprinted from ref. [85] Copyright 2017 Elsevier b). Degradation
pathway for malachite green (MG) and methylene blue (MB) on nZVI. (Adapted from ref. [85])

11. Figure 10. The schematic diagram for the removal mechanism of Cr(VI) by nZVI particles.
(Adapted from ref. [104] Copyright 2017 Elsevier)

12. Figure 11. The mechanism for the enhanced Cr(VI) removal by nZVI particles with bio-
amended iron corrosion: bio-induced iron corrosion, bio-reduction of Fe(III), growth of the
positive corrosion, reduction of Cr(VI) to Cr(III), reactive sites passivated by Cr(III) precipitates.
Reprinted from ref. [105] Copyright 2016 Elsevier.