GRAPHENE BASED NANOADSORBENTS FOR REMOVAL OF EMULSIFIED AND DISSOLVED OIL FROM HIGH SALINITY CO-PRODUCED WATER

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 the oil content to a 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 very frequently necessary._x000D_ In this thesis, the use of different graphene based nanomaterials, including graphene nanoplatelet (GNP), graphene oxide (GO), thermally reduced graphene (TRG), and reduced graphene oxide-iron oxide nanocomposite (rGO-Fe2O3), has been tested as adsorbents for the removal of emulsified and dissolved diesel oil from water. These graphene nanomaterials have been characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Brunnauer-Emmett-Teller (BET) surface area measurement. Batch and column adsorption experiments have been used to measure the sorption capacity, removal efficiency and the adsorption kinetics for the removal of diesel oil from its water emulsion. Emulsions containing diesel concentration between 25 to 200 ppm were prepared by the probe and bath sonication and their zeta potential and droplet size distribution was examined using ZetaSizer. The effect of salinity on the sorption capacity and removal efficiency has been investigated in a range of salinity (NaCl) from 0 to 100,000 ppm. The concentration of diesel in the emulsion and treated water was measured using Total Organic Carbon (TOC)._x000D_ Batch and column experimental results indicated that the removal of diesel by these graphene based nanomaterials is a very rapid process as more than 90% of the diesel oil removal is achieved in less than 5 minutes. More interestingly, the removal efficiency and the adsorption capacity increase significantly with salinity for all the adsorbents. The results were analyzed with respect to several adsorption isotherms. The isotherm study indicated that the emulsified oil adsorption data for all studied adsorbents were well-described by the Freudlich model. Kinetic analysis showed that the adsorption process follows pseudo-second order kinetics. The graphene based nanomaterials were capable of reducing the oil content of high salinity produced water to below 5 ppm. Breakthrough study was carried and the adsorbent was regenerated using ethanol to investigate the recyclability of the adsorbent materials and to confirm the batch experiment results. It was found that all four nanoadsorbents kept good adsorption capacity after regeneration and reuse for multiples cycles.

Date of Award	2017
Original language	American English
Awarding Institution	HBKU College of Science and Engineering