Halloysite nanotube-magnetic iron oxide nanoparticle hybrids for the rapid catalytic decomposition of pentachlorophenol

- In situ growth of small magnetite nanoparticles at natural clay nanotubes (halloysite).
- Novel, facile synthetic strategy involving a modified wet-impregnation method.
- Efficient catalytic decomposition of pentachlorophenol by magnetite@halloysite hybrids.
- Catalytic efficiency of hybrids significant higher compared to free nanoparticles.
- Hybrids can be reused for multiple catalytic cycles without noteworthy loss of activity.

Halloysite clay are a very attractive class of alumino-silicate based, natural nanotubes possessing high-aspect ratio, significant thermal and mechanical stability, as well as tunable surface chemistry. We report a novel, facile, synthetic approach involving a modified wet-impregnation method for the in situ synthesis of small, magnetite nanoparticles at the surface of natural halloysite nanotubes. In addition to their magnetic properties, the synthesized magnetite-halloysite hybrids are evaluated for the first time against the catalytic decomposition of pentachlorophenol from reaction solutions at room temperature. Their performance was found superior compared to free, self-supported NPs synthesized with previously reported methods. Very interestingly, after their first catalytic evaluation cycle and because of their magnetic properties the hybrids could be easily recovered from their corresponding reaction solution. The halloysite-nanoparticle hybrids are also very promising in terms of sustainability, since we demonstrate that they can be re-collected, cleaned and re-used for multiple catalytic cycles without any significant loss in their catalytic activity.

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