N-Doped Biochar from Lignocellulosic Biomass for Preparation of Adsorbent: Characterization, Kinetics and Application

Medulla tetrapanacis is composed of a lignocellulosic biopolymer and has a regular porous structure, which makes it a potential biomass material for preparing porous N-doped biochar. Herewith, N-doped Medulla tetrapanacis biochar (UBC) was successfully prepared by modification with urea and NaHCO3 under pyrolysis at 700 degrees C. The nitrogen-containing groups were efficiently introduced into biochar, and the micro-pore structures of the UBC were developed with sizeable specific surface area, which was loaded with massive adsorption sites. The adsorption kinetics and isotherms of the UBC conformed to pseudo-second-order and Langmuir model. The superior adsorption capacities of the UBC for methylene blue (MB) and congo red (CR) were 923.0 mg/g and 728.0 mg/g, and the capacities for Cu2+ and Pb2+ were 468.5 mg/g and 1466.5 mg/g, respectively. Moreover, the UBC had a stronger affinity for Cr3+ and Fe3+ in multiple metal ions and retained at a preferable adsorption performance for dyes and heavy metals after five cycles. Precipitation, complexation, and physical adsorption were the main mechanisms of the UBC-adsorbing metal ions and dyes. Thus, lignocellulosic biochar has great potential for removing dyes and heavy metals in aqueous solutions.

Automated summary

In this study, N-doped Medulla tetrapanacis biochar (UBC) with developed micro-pore structures and massive adsorption sites was successfully prepared. It exhibited superior adsorption capacities for methylene blue, congo red, Cu2+, and Pb2+, and retained preferable adsorption performance for dyes and heavy metals after multiple cycles. This research indicates that lignocellulosic biochar has great potential for removing dyes and heavy metals in aqueous solutions.