3D graphene sponge biomass-derived with high surface area applied as adsorbent for nitrophenols

Abstract

The present work used wood sawdust as a carbon precursor to produce 3D graphene sponge material, a carbon material with an added value, successfully used as an adsorbent for removing o-nitrophenol and p-nitrophenol from aqueous effluents. The resulting material’s structural, morphological, textural, and chemical characteristics (WS-Graphene) were evaluated. Textural analysis revealed a high surface area (∼3000 m2g−1) and high total pore volume (1.38 cm3 g−1). Raman, infrared and X-ray diffraction techniques evidenced the presence of a few layers of graphene, with some fraction of defects. Transmission electron microscopy confirmed the presence of a 3D-packed structure for the graphene. These WS-Graphene characteristics favored its application as an adsorbent for removing o-nitrophenol and p-nitrophenol pollutants. The adsorption process of both nitrophenols was extremely rapid and reached the equilibrium time in less than 5 min when the concentration of both adsorbates was fixed at 700 mg L−1. Furthermore, the maximum adsorption capacity (Qmax) values were 1842 mg g−1 (o-nitrophenol) and 879.6 mg g−1 (p-nitrophenol) at 30 °C. These results confirm that the WS-Graphene adsorbent acts as a 3D sponge. Langmuir’s isothermal was the best-fitted model for both nitrophenols in aqueous solution. The o-nitrophenol adsorption onto WS-Graphene might follow pseudo-second-order as well as general-order, while the adsorption of p-nitrophenol might follow only the general-order model. Thermodynamic studies revealed a spontaneous and endothermic adsorption process. The WS-Graphene adsorbent presents a high percentage (∼97 %) of removing the mixture of pollutants in effluents, showing an excellent adsorption capacity and making it a potential material to remove industrial wastewater.