Research PaperHighly reactive and stable nanoscale zero-valent iron prepared within vesicles and its high-performance removal of water pollutants

- NZVI particles were prepared in vesicles by self-assembly of PVV in aqueous THF solution.
- Dried NZVI in vesicles could be stored directly in the air.
- Fresh NZVI could be easily released from the vesicles in water.
- NZVI in vesicles exhibited excellent reactivity in water.

Nanoscale zero-valent iron particles have large specific surface area and high reaction activity, and have been increasingly used for the degradation of environmental contaminants. However, rapid aggregation and deactivation hinder their wide applications. In this work, nanoscale zero-valent iron (NZVI) particles were prepared in vesicles, which were formed by self-assembly of amphiphilic block copolymer poly(1-vinylpyrrolidone-co-vinylacetate) (PVV) in aqueous tetrahydrofuran medium, and characterized with the aid of XRD, FTIR, SEM-EDX, TEM, XPS and DLS techniques. It was found that the NZVI particles were well encapsulated in the vesicles, and they could be stored directly in the air as solids, but the dried NZVI particles could be easily released from the vesicles once they were put in water. These NZVI particles showed some unique features, such as uniform nanometer size distribution (from 70 to 100 nm), vesicle-like morphology, and good dispersion. Activity and stability of the NZVI in vesicles were examined by using Cr(VI) and nitrobenzene as the model pollutants, and compared with the bare NZVI particles synthesized with the same procedures but without PVV. A dramatic difference in activity and stability was observed for the two different NZVI particles. The NZVI in vesicles showed a good chemical stability in the air, and still maintained its high reactivity in water. Such excellent performance might be attributed to the encapsulation of the NZVI by vesicles, which could impede well the strong agglomeration of metal particles in water and prevent metal particles from being oxidized in the air.

166Nanoscale zero-valent iron particles have been prepared in vesicles by self-assembly of PVV block copolymer in aqueous THF solution, which exhibit good stability in the air, and maintain their high reactivity in water due to the encapsulation of particles in the vesicles.