Abstract: In this study, corn straw biochar was modified to micro-nano-engineered nitrogenous biochar (NBC), and the comparative analysis of the performance of NBC with iron modified biochar (FeBC) and thiol modified biochar (SBC) on Pb²⁺ adsorption in aqueous solutions was conducted. These modified biochars were characterized by SEM and BET, and the Pb²⁺ adsorption behavior of NBC was analyzed by batch adsorption experiments. To better understand the mechanisms of Pb²⁺ adsorption by NBC, a sequential desorption test was performed and the changes of biochar function groups before and after he adsorption were analyzed. The results show that, after modification, the aromaticity was enhanced and hydrophilicity and polarity were weakened, the specific surface area and total pore volume of NBC was increased by 6.30 and 2.68 times, respectively, as compared with the unmodified biochar. The adsorption capacity of the three modified biochar for Pb²⁺ was in the order of NBC > FeBC > SBC. The isothermal adsorption by NBC was better fitted to the Langmuir model, and its maximum adsorption capacity reached to 148.25 mg·g^-1, which was 1.68 and 1.93 times higher than that of FeBC and SBC, respectively. The adsorption kinetics of NBC well fits the pseudo-second order model (R²=0.952 4). Additionally, there are rod-like deposits in pores after the adsorption of Pb²⁺ by NBC. The sorption of Pb²⁺ by biochars likely occurred through greater cation exchange, precipitation, cation-π interactions and complexation. The sequential desorption test results indicate that the contribution of NBC to the adsorption modes of Pb²⁺ was ranked hydrogen bonding (57.98%) > cation exchange (29.98%) > complexation (11.95%) > physical adsorption (0.10%). Therefore, the micro-nano-engineered nitrogenous biochar has good adsorption effect on Pb²⁺ in solution, and could be a promising adsorbent for recovering Pb²⁺ from waste water.

Key words: micro-nano-engineered nitrogenous biochar, modified, lead, adsorption