Exfoliated graphite for sorption of liquid hydrocarbons from the water surface: Effect of preparation conditions on sorption capacity and water wettability

Exfoliated graphite (EG) is a promising macroporous sorbent for oils and liquid hydrocarbons on water surfaces. The preparation of EG includes a synthesis of graphite intercalation compounds, expandable graphite and its thermal exfoliation. The structure of the initial graphite intercalation compound (GIC) has a significant influence on the structure of exfoliated graphite and its sorption properties: sorption capacity and selectivity of water/octane sorption. Thus, the aim of this work was to investigate the relationship between the structure of EG based on 1st stage, 2nd stage, 3rd stage, 4th stage GICs and EG sorption properties and water wettability. The influence of the GIC stage number on the EG sorption and surface properties is studied. EG obtained from 1st stage GIC at 1000 °C is characterized by a higher sorption capacity toward octane than EG from 4th stage GIC. The selectivity of octane/water sorption reduces when decreasing the GIC stage number from 4 to 1. The high sorption of water can be explained by a higher surface area of EG and the presence of remaining oxygen groups on the edges of graphite crystallites in the EG structure. The EG structure was investigated by XRD, SEM, nitrogen adsorption–desorption method, FTIR and Raman spectroscopy.