The hierarchically nitrogenous magnetic porous carbon prepared by ZIF-67 through mesoporous silica-protected calcination for rapid Cr(VI) removal

A novel magnetic composite with hierarchically porous nature is prepared by a facile synthetic strategy for the highly toxic chromium (Cr(VI)) removal. The magnetic NMPC@mSiO2 with defined mesoporous shell is successfully fabricated by one-step carbonization of ZIF-67@mSiO2, which is prepared through a simple one-pot method. Benefiting from the protection of mSiO2 during pyrolysis process, NMPC@mSiO2-800 owns high specific surface area, hierarchically porous structure and increased C–N content. It shows an excellent Cr(VI) removal performance with an adsorption capacity rising to 158.11 mg·g−1 from 78.60 mg·g−1 (NMPC-800). Moreover, the prepared NMPC@mSiO2-800 exhibits antijamming capability for Cl−1/SO42− with a negligible adverse impact on Cr(VI) removal. The kinetic studies show that the Cr(VI) removal on NMPC@mSiO2-800 confirms to pseudo-second-order model equipped with a relatively large adsorption rate constant, revealing the ability to quickly adsorb Cr(VI). The thermodynamic parameters manifest Cr(VI) adsorption is spontaneous and endothermic. Besides, the NMPC@mSiO2-800 can be quickly recovered from the system due to the magnetic porous carbon. Herein, NMPC@mSiO2-800 has a broad application prospect in Cr(VI) removal due to its excellent adsorption capacity, good antijamming ability, high adsorption rate and easy magnetic separation.