Separable and reactivated magnetic mZVAl/nFe3O4 composite induced by ball milling for efficient adsorption-reduction- sequestration of aqueous Cr (VI)

Destruction of the dense oxide layer on the surface of pristine or re-passivated micro zero-valent aluminum (mZVAl) can rejuvenated its reduction activity, which is beneficial to the removal of aqueous pollutants. To rejuvenated the reduction activity of mZVAl and rapidly recovery passivated mZVAl, in this study, a novel mZVAl/nFe(3)O(4) composite with high activity and magnetic properties was synthesized by ball milling (BM). Compared with pristine mZVAl and nFe(3)O(4) , more than 95% of Cr(VI) could be removed in 30 min at 3.0 g/L mZVAl/nFe(3)O(4) dosage over a wide range of pH (3.00-11.00). The removal of Cr(VI) conformed to the pseudo first-order adsorption kinetic model, and the equilibrium adsorption data was in accordance with the Langmuir adsorption isotherm model. The maximum absorption (8.14 mg/g) was related to the BM parameters (the weight ratio of mZVAl/nFe(3)O(4) , BM speed and BM time). Accord to the effect of co-existing ions on the removal efficiency of Cr(VI), it was proved that the significance of the adsorption process was a prerequisite step for Cr(VI) reduction. Based on X-ray photoelectron spectroscopy (XPS) and the valence analysis of aqueous Cr, the Cr(VI) removal mechanism by mZVAl/nFe(3)O(4) was also unraveled, in addition to achieving Cr(VI) reduction, also achieves the sequestration of total Cr under neutral environment. Furthermore, the reusability of mZVAl/nFe(3)O(4) was limited by the accumulation of (hydr)oxide on its surface, but can be easily rejuvenated by BM again with a small amount of nFe(3)O(4) . In conclusion, mZVAl/nFe(3)O(4) composite are a promising green material to reductive remove Cr(VI) from near-neutral wastewater.