Deep Eutectic Solvent Assisted Facile and Efficient Synthesis of Nitrogen-Doped Magnetic Biochar for Hexavalent Chromium Elimination: Mechanism and Performance Insights

Dual-modification of biochar through magnetization and nitrogen-doping greatly enhances the removal performance for Cr(VI). In this study, a novel green deep eutectic solvent (DES) produced by complexing of FeCl 3 and urea was adopted for the first time to assist the facile and efficient preparation of nitrogen-doped magnetic biochar (NMBC) by using peanut shell (PS) as raw stock. The results indicated that FeCl 3 /urea-based DES could act as fine iron and nitrogen sources in the formation of NMBC, and moreover, catalyzed the pyrolysis process and promoted the pore development. The synthesized NMBC could capture Cr(VI) by both physisorption and chemisorption, including pore-filling, electrostatic attraction, ion-exchange, reduction and surface complexation, with removal capacity for Cr(VI) outperforming that of many other reported materials. The present study provides a new idea for the facile and efficient magnetization as well as nitrogen-doping decoration of biochar for Cr(VI) decontamination from water.