Scalable and cost-effective nanoscale zero-valent iron preparation by combining ball-milling and H2-reduction of micron Fe2O3: modulating crystal plane and reactivity

Nanoscale zero-valent iron (nZVI) is a promising material for pollution remediation, but its practical application is limited by the lack of scaling up preparation method and the high cost of raw materials. In this study, the ball-milling method is used to prepare nanoscale iron oxide prior to high temperature H 2 -reduction, producing ball-milled and then H 2 -reduced nZVI ( BM−RE ZVI). It is demonstrated the strained iron oxide crystals after ball-milling increased the specific surface area, while the high-temperature H 2 -reduction process decreased iron vacancy. In this way, the ball-milling strain and the high-temperature H 2 -reduction together facilitated the exposure of (200) Fe planes (i.e. [100] Fe direction) of the obtained BM−RE ZVI, thereby enhancing reactivity. Compared to commercial nZVI (C-nZVI), BM−RE ZVI was characterized by abundant surface Fe 0 , more reactive crystal planes, and fewer iron vacancies, enabling flexible electron transfer. The reaction rate constants normalized with Fe 0 content ( k Fe 0 ) for removing aqueous Pb, Cr, trichloroethylene (TCE), and florfenicol (FF) increased by 3.3, 2.6, 10.5, and 11.9 times, respectively, as compared to C-nZVI, and the fastest 100 % FF removal was achieved in a real groundwater sample. In addition to its environmental friendliness, BM−RE ZVI was also economically viable according to the environmental friendliness and techno-economic analyses, with an estimated price of 27 k-32 k ¥ ton −1 . These findings provide a new approach for preparing economical and eco-friendly nZVI, which will boost its application in practical pollution remediation