One-Step Preparation of Magnetic Co/N-Containing Carbon for Efficient Chromium Removal: Performance and Mechanism.

Magnetic nitrogen-containing carbon (Co/NC) is prepared by one-step carbonization of ZIF-67, reducing the pore blockage caused by the extra addition of magnetic particles and element doping. Co/NC-800-2 has a relatively high specific surface area, abundant nitrogen-containing functional groups, and sufficient magnetization intensity, achieving a Cr(VI) adsorption capacity of 85.46 mg·g at 30 °C. The Cr (VI) adsorption process is a spontaneous endothermic reaction and conforms to both the quasi-second-order kinetic and Langmuir models, simultaneously. Through spectral analysis and simulation calculations, the interaction mechanism between Co/NC-800-2 and chromium salt is mainly determined to be electrostatic adsorption, redox reaction, and chelation. Otherwise, Co/NC-800-2 demonstrates good reusability, maintaining 90.08% of the initial adsorption capacity after five cycles, while also possessing structural stability and good magnetic separation performance. Overall, the Co/NC prepared by one-step carbonization of ZIF-67 shows promising application prospects for chromium removal from wastewater.