The nitrogen-doped graphene-like carbon nanosheets: Confined construction and oxygen-limited oxidation for higher removal efficiency toward organic contaminants

Due to the excellent properties, including large specific surface area, stable structure, and strong adsorbability, mesoporous carbon material has captured a lot of attention and applied to various fields. Here, we proposed a facile approach to synthesize nitrogen-doped graphene-like carbon (NGLC) nanosheets and investigated the performance in wastewater decontamination. In this work, NGLC nanosheets were obtained via the combination of confined synthesis and low-temperature calcination in oxygen-limited condition. Such NGLC nanosheets were composed of several carbon layers with porous structure, which provided a large specific surface area (421.85 m(2) g(-1)). Meanwhile, the NGLC was endowed with abundant active sites, including oxygen-contained groups and nitrogen species, via low-temperature calcination in oxygen-limited conditions. These properties allow the NGLC to be an excellent adsorbent for organic pollution treatment. The maximum adsorption capacities toward cationic dyes, the rhodamine B (RhB) and methylene blue (MB), reached as high as 1272.74 mg g(-1) and 679.55 mg g(-1), respectively, indicating the promising potential for the cationic contaminants treatment. The excellent reusability and wide pH suitability (2-10) were observed by batch adsorption experiments. The kinetic adsorption test showed that 98.97% of RhB could be adsorbed by NGLC-450 after 150 min contact time at 25 degrees C, while the RhB removal efficiencies from bulk polydopamine derived carbon material (denoted as PDA carbon) and NGLC450-Ar (generated at argon atmosphere) were only 17.56% and 62.03%, respectively. The significant difference in adsorption performance implied the importance of confined synthesis with template-assistance and oxygenl-imited oxidation. The adsorption process involved the pore filling & adsorption, electrostatic interaction, and pi-pi interaction, as well as the hydrogen bonding, which was demonstrated by experiment and Fourier transform infrared (FT-IR) & X-ray photoelectron spectroscopy (XPS) analysis.