Facile preparation of modified Fe-graphene hydrogel with enhanced removal of perfluorooctanoic acid

In a facile one-step hydrothermal process, Fe-graphene hydrogel FC1 was prepared through the reaction of graphene and iron ions, besides that, FC2 to FC5 were prepared with the addition of ethylene glycol (EG), EG+NaClO, EG+ ascorbic acid (VC)+NaClO and EG+VC respectively. EG showed to promote the assembly process of graphene hydrogels. The structure of the hydrogel FC4 had the lowest degree of agglomeration and the most porous structure among the samples, indicating that the graphene and iron oxides could support each other with the addition of VC and NaClO. The iron crystals in FC1 and FC5 were alpha-FeOOH, in FC2 and FC3 were alpha-FeOOH and Fe3O4, while in FC4 were Fe3O4 and Na3FeO4. The perfluorooctanoic acid (PFOA) removal by FC1 to FC5 through Fenton reaction were 73.61%, 75.2%, 84.35%, 89.9% and 75.44% respectively. The PFOA removal through adsorption by FC4 was 41.5%. PFOA removal by FC4 could reach equilibrium in 120 min. Based on the Langmuir model, FC4 had higher maximum adsorption capacity (218.4 mg/g) for PFOA than FC1 (158.3 mg/g). The Fe-graphene hydrogels had excellent removal performance in a wide pH range, and the removal rates were retained well over 5 cycles.

Automated summary

Fe-graphene hydrogels were prepared through a facile hydrothermal process, with different additives optimizing their structure and enhancing PFOA removal efficiency. Among the samples, FC4 showed the best removal efficiency for PFOA and exhibited superior adsorption capacity.