Graphene oxide aerogels co-functionalized with polydopamine and polyethylenimine for the adsorption of anionic dyes and organic solvents

Abstract Polydopamine (PDA) and polyethylenimine (PEI) co-functionalized graphene oxide (GO) aerogel (PPGA) is rapidly synthesized at room temperature by a facile method. Glutaraldehyde acting as crosslinking agent accelerates rapid crosslinking of PDA-coated GO sheets with PEI, and three-dimensional hydrogel is formed within 3 min. The structure of PPGA is characterized by Field emission scanning electron microscope, Fourier transform infrared spectra, X-ray photoelectron spectroscopy, and zeta potential analysis. The obtained PPGA shows efficient adsorption toward anionic dyes (202.8 mg/g for Methyl orange and 196.7 mg/g for Amaranth) and organic solvents. Furthermore, the dye adsorption behaviors, including kinetics, isotherms, and thermodynamics, are systematically investigated. The adsorption process of methyl orange onto PPGA can be well depicted with the pseudo-second-order kinetic model and Langmuir isotherm model. Thermodynamic analysis shows that the adsorption is a spontaneous and endothermic process of entropy increment. Adsorption mechanism indicates that the removal of dye is mainly attributed to the hydrogen bonding between hydrogen atoms of nitrogen-containing functional groups in PPGA and oxygen atoms of anionic dye. The adsorption capacity for the chosen organic solvents ranges from 28.7 to 63.5 mg/mg depending on the densities of the solvents. This work may provide an inspiration for the researchers who are devoted to rapid fabrication of hydrogels with excellent adsorption ability.