One-step preparation of Fe/N co-doped porous biochar for chromium(VI) and bisphenol a decontamination in water: Insights to co-activation and adsorption mechanisms

One-Step Synthesis of Nitrogen-Doped Porous Biochar Based on N-Doping Co-Activation Method and Its Application in Water Pollutants Control

“…Through the diffusion of the gas, the surface of the biochar develops various wrinkles and pores. The NH 3 released during the pyrolysis process combines with the -OH group in lignocellulose (the main component of BB) to form C-NH2, and further generate C=N-C [ 20 ]. Eventually, these nitrogenous groups form various N-bond configurations including pyrrolic-N, pyridinic-N, and graphite-N.…”

“…In common with many biomass materials [ 34 , 35 , 38 , 39 ], the bands at around 1047–1159 cm −1 represented the tensile vibrations of C-O from alcohols, phenols, acids, or esters. After N-doping co-activation, a new vibration peak appeared at 1690 cm −1 , which indicated that the C=N was formed on N-BBB [ 20 ].…”

“…The high-resolution N1s spectra of ITGB and MITGB both had peaks at 397.41–37.42 and 399.33–399.38 eV, corresponding to pyridinic-N and pyrrolic-N, respectively [ 38 , 39 , 40 ]. In addition, N-BBB had a unique peak corresponding to graphite-N at 403.53 eV [ 20 ], indicating that the N-doped co-activation method had indeed successfully doped N into N-BBB.…”

“…Conversely, when the pH was higher than 6 (particularly 8), the protonation of the dye was gradually weakened, and the biochars with negative active sites on the surface were not conducive to the adsorption of anionic dyes due to electrostatic repulsion, which reduced the adsorption amount of MO. Cr 6+ also possessed various forms at different pH levels [ 4 , 5 , 20 ], where it exists as HCrO 4 − and Cr 2 O 7 2− when the pH is lower than 6.5, and as Cr 2 O 7 2− and CrO 4 2− when the pH is higher than 6.5. With the increase in pH, the adsorption capacities of both BBB and N-BBB decreased, and the maximum adsorption capacities were at a pH value of 2.…”

“…As an effective strategy to improve biochar performance, nitrogen doping (N-doping) technology has been applied in environmental remediation, such as adsorption, catalysis, and electrochemistry [ 18 , 19 ]. N hetero-atoms provide more binding sites on the biochar surface, which enhances the hydrophilicity and adsorption capacity of the compound by forming a more stable complex with pollutants [ 20 ]. At the same time, the N-doping method can adjust part of the electronic structure in the carbon skeleton, and further improve the reactivity of the biochar [ 21 ].…”