Experimental and DFT investigation on N-functionalized biochars for enhanced removal of Cr(VI).

In this study, N-functionalized biochars with varied structural characteristics were designed by loading poplar leaf with different amounts of urea at 1:1 and 1:3 ratios through pyrolysis method. The addition of urea significantly increased the N content of biochar and facilitated the formation of amine (-NH-, -NH), imine (-HCNH), benzimidazole (-CHN), imidazole (-CHN), and pyrimidine (-CHN) groups due to substitution reaction and Maillard reaction. The effect of pH on Cr(VI) removal suggested that decrease in solution pH favored the formation of electrostatic attraction between the protonated functional groups and HCrO.