Facile synthesis of graphene nanosheets on wastewater sediments for high efficient adsorption of methylene blue.

[Display omitted] • Wastewater sediments were used to synthesize large surface area GNS. • The metal elements (Fe, Mn, Ca) in the catalyst greatly enhanced the GNS yield. • The maximum adsorption capacity of methylene blue by GNS was 1092.1 mg/g. • Decolorization rates (>98.5 %) were achieved for the simulated textile wastewater. Development of high performance adsorbents through the recovery of waste resources for wastewater treatment is a sustainable strategy for environment protection. Here, graphene nanosheet (GNS) adsorbent with extremely high surface area of 1149.7 m2/g was synthesized by one-step chemical vapor deposition using catalysts derived from wastewater for the first time. The obtained catalyst was mainly composed of MgO and a small amount of Fe 2 O 3 , MnO 2 and CaO, and the presence of these metal oxides in the catalyst improved the catalytical activity of MgO, leading to the enhanced yield of GNS. The GNS yield was 144 % higher than that of GNS synthesized on commercial MgO. The possible growth mechanism of GNS was discussed. The adsorption of methylene blue (MB) on GNS was then systematically investigated, and GNS demonstrated excellent adsorption capacity and extremely fast adsorption rate for MB at a wide pH range (2–12) and different temperatures (293–313 K). GNS has achieved a high removal efficiency of ∼ 99.0 % in 20 min, and its maximum adsorption capacity was 1092.1 mg/g. The adsorption kinetic and isotherms by GNS were also studied. The adsorption results were closely fitted by Langmuir isotherm model and pseudo-second-order kinetic model. The adsorption of MB on GNS involved multiple adsorption mechanisms, including electrostatic interactions, hydrogen bonding, and π-π stacking interaction. Based on the regeneration experiment, the GNS demonstrated good reusability, retaining a removal efficiency of 95 % after 5 cycles. Finally, high decolorization rates (98.5–99.9 %) were obtained using GNS in the treatment of simulated textile wastewater. This study provided a sustainable method for wastewater treatment by low cost and efficient adsorbents benefitted from the effective utilization of wastewater resources. [ABSTRACT FROM AUTHOR]