New method for efficient removal of Cr(VI) by recoverable magnetic nitrogen-doped carbon aerogel microspheres: Kinetics and mechanism

•The nZVI and N co-doped magnetic carbon aerogel composites were synthesized.•nZVI@NCA900 displayed high Cr(VI) removal capacity of 266.79 mg·g−1 at 318 K.•Cr(VI) can be reduced to Cr(III) by nZVI and N-containing functional groups.•Simulation results by DFT prove that N-doped show positive effect.•The nZVI@NCA could provide magnetism after several adsorption and desorption cycles.