Produced water is considered the largest by volume waste stream in the oil and gas industry, requiring intensive treatment before disposal or reuse. Common treatment methods are generally inefficient and requires secondary and tertiary steps to achieve the required specifications for reuse or disposal. In this work composites were developed for removing oil from water using adsorption.
The first material is based on carbon nanotubes and polystyrene (PS-CNT-PU). The material includes a porous matrix polymer, carbon nanotubes grafted to surfaces of the porous matrix polymer, and a hydrophobic polymer grafted to the carbon nanotubes. The polystyrene added in the amounts that formed composites PS-CNT-PU-1, PS-CNT-PU-2, PS-CNT-PU-3 and PS-CNT-PU-5 all of which exhibit different characteristics. PS-CNT-PU was characterized using BET for surface area, FTIR, FE-SEM for surface morphology FE-TEM for surfaces of the multiwall carbon nanotubes. Hydrophobic characteristics were evaluated by measuring the water contact angle on the composite surfaces; the maximum angle recorded was 140.75°. The adsorption capacity was further assessed by submerging the material in various hydrocarbons, the weight gain ratio was calculated to be greater than 4000% when using hexane and over 50 times their original weight.

The second material is based on 9-octadecenoic acid grafted graphene (POG) that was synthesized for oil/water separation. Graphene derived from graphite was adapted with 9-octadecenoic acid to produce 9-octadecenoic acid grafted graphene. The new synthesized materials (POG25, POG50 and POG75) were characterized by using N₂-physisorption and Fourier transform infrared. The BET surface area of POG75 was 288 m²/g while POG50 was 225 m²/g and POG25 was 79 m²/g. These new materials showed fast uptake of the certain quantity of the oil, and this can be clarified by the high hydrophobicity nature of the materials. The most promising results for oil removal from water was POG75, which displayed the highest adsorption capability to organic compounds and the highest BET surface area.
Both composites demonstrate high efficiency and are feasible for large-scale processes in the oil and gas industry, especially for produced water treatment. The recyclability and durability of the composites makes them a good candidate for adsorbent materials to remove oil contaminants from produced water, which will help to reuse produced water in several applications such as flooding and fracturing.

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