Nanostructured carbon materials for enhanced nitrobenzene adsorption: Physical vs. chemical surface properties

The influence of physical and chemical surface properties on the adsorption of nitrobenzene, a major organic contaminant in wastewater, was investigated using a wide range of graphene-based materials. These included carbon blacks and activated carbons as well as nanostructured materials such as graphitic nanoribbons (GNRs) and graphene-like structures derived from rice husk (RHC). The surface of GNRs was also modified by oxidation with hydrogen peroxide under UV irradiation (yielding Ox-GNRs). For the understanding of the importance of electrostatic and dispersive interactions, the uptake of nitrobenzene was measured in solutions at controlled pH conditions. The Langmuir and Freundlich parameters were found to be dependent on both surface physics and chemistry. To elucidate this influence, the adsorption of H₂O/D₂O was performed on selected samples. The edge surfaces of nanoporous carbons appear to exert dominant interactions with polar molecules such as nitrobenzene. At the same time, while the presence of micropores is the most important factor for adsorption at low concentration, the meso- and macropores become more important at higher nitrobenzene concentrations. The novelty of this study resides in the use of complementary techniques to understand the adsorption on traditional carbon materials as a guide for the optimization of novel, graphene-like nanostructured adsorbents.