Magnetic few-layers graphene nanocomposites for the highly efficient removal of benzo(a)pyrene from water

Regarding the importance of water pollution by persistent organic pollutants and the need for innovative processes to extract them efficiently, we designed magnetic few-layers graphene-based composite nanomaterials (CNs) for high removal from water of a particularly toxic polycyclic aromatic hydrocarbon (PAH): benzo(a)pyrene (BaP). The CNs were prepared in a one-step polyol solvothermal synthesis process by introducing few-layers graphene coated with tannic acid in the reaction media of iron oxide nanostructures. The synthesis was reproducible and allowed to obtain large amount of magnetic CNs, which can be easily and quickly magnetically removed from aqueous media. The BaP adsorption on CNs was studied for initial BaP aqueous concentration of 1–5000 µg L−1. Very low amount of CNs (5 mg L−1) was sufficient and effective to have a very high and fast BaP adsorption in comparison with previous studies reporting adsorbent amount of 5–1000 mg L−1. Removal efficiencies of 99.95±0.01% in water with 1% of ethanol as co-solvent were reached in minutes. The presence of iron oxide was observed to not affect the adsorption capacity of CNs. The volume percentage of ethanol in the water media influenced the removal efficiency of BaP by the CNs. With 50 vol% of ethanol necessary to obtain an adsorption isotherm, the adsorption follows a Langmuir law with a maximum adsorption capacity qmax=69.45±5.20 mg g−1 and a Langmuir isotherm constant KL=1.92±0.54 L mg−1. These CNs, compared with other BaP and PAHs adsorbents, are clearly very promising for BaP removal from polluted media.

This article is Open Access

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