Application of Graphene Based Nanoadsorbents in Produced-water Treatment for Removal of Dissolved Oil

Co-produced water is the largest waste stream produced during oil and gas production. It contains a mixture of hydrocarbons, suspended and dissolved solids, inorganic substances and production chemicals. Current technology... [ view full abstract ]

Co-produced water is the largest waste stream produced during oil and gas production. It contains a mixture of hydrocarbons, suspended and dissolved solids, inorganic substances and production chemicals. Current technology such as hydrocyclones and API gravity can remove suspended and dispersed oil from produced water down to 40 ppm. However, reducing oil content to few ppms is required to enable any beneficial use of produced water or to meet the recent strict environmental regulations for disposal of produced water. Therefore, post-treatment of produced water to remove emulsified and dissolved oil to acceptable levels is required. In this presentation, we test using different graphene based nanomaterials, including graphene nanoplatelet (GNP), graphene oxide (GO), thermally reduced graphene (TRG), and graphene-iron oxide nancomposite (G-Fe3O4) as adsorbents for removal of diesel from water. The nanomaterials are characterized by Scanning electron microscope (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photospectroscopy (XPS), Thermal Gravimeteric analysis (TGA), and Brunnauer-Emmett-Teller (BET) surface area measurement. The initial diesel concentration was varied between 25-200 ppm, the diesel to adsorbent ratio ranged between 50 and 8000 mg/g, and the salinity (NaCl) was between 0 and 100,000 ppm. The concentration of diesel is measured using Total Organic Carbon (TOC). Our batch and column experiment results indicated that graphene based material has very rapid removal of diesel and more than 90% removal can be achieved in less than 5 min. More interestingly, the removal efficiency and the adsorption capacity increase significantly with salinity for all the adsorbents. The results were analyzed in light of the various adsorption isotherm. Our results indicate that graphene based nanomaterials are capable of reducing the oil content of high salinity produced water to less than 5 ppm. Moreover, different approaches for the regeneration of the graphene materials are tested and will be discussed.