A superfast hexavalent chromium scavenger: Magnetic nanocarbon bridged nanomagnetite network with excellent recyclability.

In this work, a nanocarbon bridged nanomagnetite network (NC-NMN) is developed through the electrospinning of epichlorohydrin functionalized polystyrene (f-PS), followed by the direct calcination of f-PS and ferric nitrate, which is capable of superfast removing hexavalent chromium (Cr(VI)) from polluted water within only 15 s benefiting from its gridding framework, with an adsorption rate constant of 1.64 g mg-1  min-1 according to the pseudo-second-order kinetics. The well-fitted Langmuir isotherm model indicates a monolayer adsorption for Cr(VI) on NC-NMN. The thermodynamic parameters including negative ΔG° and positive ΔH° demonstrate that the Cr(VI) adsorption on NC-NMN is spontaneous and endothermic. The Cr(VI) adsorption retention, which is only 3.8%, is achieved for NC-NMN after five cycles, exhibiting a prominent stability and an excellent recyclability. X-ray photoelectron spectroscopy (XPS), zeta potential and energy-filter transmission electron spectroscopy (EFTEM) results illustrate that both the electrostatic attraction and the network structure of NC-NMN are responsible for the superior Cr(VI) adsorption performance. This work intends to provide a new method for designing the novel structure materials for polluted water treatment.