Removal of oil from oil–water emulsions using thermally reduced graphene and graphene nanoplatelets

The application of thermally reduced graphene (TRG) and graphene nanoplatelets (GNP) for the removal of emulsified and dissolved oil from oil–water emulsions has been investigated under different process parameters; namely, initial oil concentration, adsorbent dosage and salinity. Batch equilibrium studies have been performed at low oil concentrations (25–200 ppm), achieving an adsorption capacity = 1550 mg oil/g for TRG and 805 mg oil/g for GNP. Batch kinetic studies were performed to assess the rate of removal and over 90% removal was achieved in less than 10 min. Fixed bed column adsorption studies obtained bed capacities of 1100 mg oil/g for TRG and 850 mg oil/g for GNP. Regeneration studies revealed that both adsorbents could still adsorb over 94% of the full bed capacity after three adsorption–regeneration cycles. Increasing the emulsion salinity up to 20,000 ppm NaCl enhanced the adsorption capacities and removal efficiency, but further increases in salinity had no additional effect on capacity.