Magnetic iron oxide chestnutlike hierarchical nanostructures: preparation and their excellent arsenic removal capabilities.

To obtain adsorbents with high As(V) removal capacity and quick magnetic separation simultaneously, we have fabricated maghemite (γ-Fe(2)O(3)) and magnetite (Fe(3)O(4)) chestnutlike hierarchical nanostructures (CHNs) with strong ferromagnetic property by annealing the Fe(2)O(3) chestnutlike amorphous core/γ-phase shell hierarchical nanoarchitectures (CAHNs) at different temperatures in a nitrogen atmosphere. Compared to the Fe(2)O(3) CAHNs, the saturated magnetization of the as-obtained γ-Fe(2)O(3) CHNs is enhanced over 10 times, while the As(V) removal capacity is maintained 74% and reaches 101.4 mg·g(-1). Both of the as-obtained γ-Fe(2)O(3) and Fe(3)O(4) CHNs can be separated simply and rapidly from treated water by magnetic separation after As(V) adsorption treatment. The As(V) adsorption process of the as-obtained γ-Fe(2)O(3) CHNs obeys well the Freundlich isotherm model rather than the Langmuir one, suggesting that a multilayered adsorption occurs on the surface of the γ-Fe(2)O(3) CHNs. Taking advantages of the high adsorption capacity, fast adsorption rate and quick magnetic separation from treated water, the γ-Fe(2)O(3) CHNs developed in the present study is expected to be an efficient magnetic adsorbent for As(V) removal from aqueous solutions.