Reactivity and Availability of Subnano-Sized Zero-Valent Iron Present in Smectite Interlayers.

Smectite clays have been used in our laboratory as templates to synthesize subnano-sized zero-valent iron. NaBH₄ was utilized to reduce exchangeable Fe cations associated with mineral surfaces to zero-valent iron.  Nitrobenzene was used as a probe molecule to explore the availability and reactivity of zero-valent Fe in the clay interlayers. we detected the existence of dispersive sub-nano-sized ZVI cluster (around 5 Å) in the interlayer and nano-sized ZVI particle (average diameter was about 5 nm)on the cross section and surface of smectite. The sub-nano-sized ZVI has enhanced reductive reactivity comparing to nano-sized ZVI. The results also indicate about 89% of smectite interlayer exchangeable Fe cations were reduced to zero-valent iron, and were available to reduce nitrobenzene to aniline. The results suggest that this innovative technology could be applied in-situ to reduce persistent organic contaminatants in subsurface environment.