Anti-stacking, recyclable and electron-rich Fe3O4 modified L-glutamic acid functionalized graphene oxide towards Cr(VI) removal by adsorption-reduction behavior

Hexavalent chromium (Cr(VI)) is one of the hazardous pollutants in wastewater because of acute toxicity and superb solubility. Graphene oxide (GO) is the promising adsorbent to handle Cr(VI), however, the drawbacks of easy aggregation, limited adsorption sites, unable valence changes and difficult recyclability hinder its further applications. In this study, Fe 3 O 4 modified L-glutamic acid functionalized graphene oxide (M−Glu/GO) was synthesized for Cr(VI) decontamination by the solvothermal method for effectively offsetting the above shortcomings. From characterization results, M−Glu/GO carried the traits of the relatively bigger surface area, abundant active sites, favorable surface charges and stable magnetic property. Cr(VI) adsorption process by M−Glu/GO was conformed to the pseudo-second order kinetic model with fast adsorption rate ( k 2  = 1.75 × 10 –3 g·mg −1 ·min −1 ) and Freundlich isotherm model with the maximum adsorption capacity of 75.63 mg·g −1 at 308 K, far more exceeding than GO (6.38 mg·g −1 ). Surprisingly, with the help of oxygen-containing groups, amine groups and Fe 3 O 4 with ample electron supplement, M−Glu/GO was capable of transforming partly Cr(VI) into Cr(III), realizing the detoxification. It exhibited practical application potentials with magnetic separation under various water matrices and kept a relative adsorption capacity of 70 % after 8 cycles. Furthermore, six interactions, involving pore filling, hydrophilic interactions, coordination interactions, anion-π interactions, electrostatic interactions and adsorption-reduction, witnessed the satisfied Cr(VI) adsorption by M−Glu/GO. This work paves a feasible way to accelerate the Cr(VI) adsorptive removal, and provides a vivid case for developing recyclable GO-functionalized adsorbents.