Nitrogen-rich melamine-based carbon nanosheets prepared via polyvinyl pyrrolidone/ammonia chloride-mediate strategy as an excellent adsorbent for methylene blue adsorption

Abstract The removal of the methylene blue (MB), a cationic azo dye, in water is highly demanded due to its harmful effects on human health. In this study, the nitrogen-doped carbon nano-sheet was prepared as the adsorbent for MB using the efficient one-pot pyrolysis of melamine in the presence of NH4Cl and PVP. During the heat-treatment, the PVP interacted with melamine forming hydrogen-bond, which would not only elevate the melamine deamination process but also prohibit the melamine polymerization, which led to the formation of the layered structure. The addition of NH4Cl in the pyrolysis mixture would favor the formation of crumpled graphene-like-structure. The prepared materials showed a very high adsorption capacity of MB (348.2 mg/g), which is much higher than many other materials. Such a high adsorption capacity was likely due to its unique graphene-like structure, high N doping with a high content of pyridinic N and graphitic N, and large specific surface area. Moreover, the material was successfully recycled with only a slight decrease in the removal efficiency after 5 cycles.