Oily wastewater has caused serious environmental and biological issues, to overcome this problem, various materials have developed. In this perspective, herein, we report the preparation of a nanoporous carbon aerogel (NPCA)@carbon (C) NPs aerogel through a core-shell growth method. It is interesting to note that in this study, we introduce a new procedure to remove δ-Al2O3 NPs without using any alkaline media. In the other word, NPCA is not only a great candidate to use as a template for growing the NPCA@carbon (C) NPs aerogel, but also has an excellent ability to remove the formed δ-Al2O3 NPs only by heat treatment, which is the first example in this area, to the best of our knowledge. Importantly, the integration of two layers of carbon in one particle at the nanometer level in the structure of NPCA@C NPs aerogel leads to achieving a structure with an average size of 13–51 nm, hierarchical porous structures, low density (3.7 mg/cm3), high porosity (99.83%), large specific surface area (946.75 m2/g) and superhydrophibicity underoil behavior. The as-prepared aerogel was found to be an excellent sorbent to rapidly separate both surfactant-free and surfactant-stabilized water-in-oil emulsions by gravity with high separation efficiencies up to 99.9% and, the filtration fluxes up to ~ 4000 L m− 2 h− 1. Notably, the aerogel mentioned above exhibited excellent separation performance even after 40 recycle runs without a discernible decrease in its separation efficiency (99.94%).

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