In this study, N-doped biochar BZ-9.5AG-30 min was prepared from bamboo by using ZnCl2 as activator and heat treated at 950 °C under NH3 gas flow for the removal of Cr(VI). The adsorbent was characterized by BET, and the amount of introduced nitrogen content and nitrogen species on BZ-9.5AG-30 min was examined by CHN elemental analyzer and X-ray photoelectron spectroscopy, respectively. Herein, the obtained BZ-9.5AG-30 min had a high specific surface area (1,610 m2/g) and high N content (4.52%). The pH of the solution had a great influence on the adsorption process, indicating that the acid condition is conducive to the adsorption process of Cr(VI). Adsorption equilibrium data of Cr(VI) were analyzed by the Langmuir and the Freundlich models. The adsorption equilibrium data were well described by the Langmuir model, and BZ-9.5AG-30 min has excellent adsorption capacity for Cr(VI) (4.31 mmol/g). BZ-9.5AG-30 min showed superior recyclability, and after five times regenerations, the adsorption capacity of BZ-9.5AG-30 min still had 63% of the initial adsorption capacity.

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