Stable graphene oxide/poly(ethyleneimine) 3D aerogel with tunable surface charge for high performance selective removal of ionic dyes from water

Graphene oxide (GO) with oxygen-containing functional groups views a promising adsorbent to remove cationic pollutants from water. To achieve high removal efficiency of both anionic and cationic pollutants and overcome recycling difficulty of GO, positively charged poly(ethyleneimine) (PEI) was associated with GO to fabricate GO/PEI (GP) 3D aerogels. Surface charges of the constructed GP aerogels were tuned from positive to negative within a wide range via changing solution pH. The constructed GP aerogels were stable in acidic and basic aqueous environments, and even in organic solvents (such as methanol, acetonitrile, methylbenzene, acetone and N, N-dimethyl formamide), which are easily recovered. Anionic methyl orange (MO) and cationic methylene blue (MB) were utilized as model pollutants to investigate the adsorption capability of the GP aerogels. The GP aerogels showed high adsorption capacity for anionic MO (331.0 mg/g) at pH 2.0 while for cationic MB (249.6 mg/g) at pH 10.5. The electrostatic attraction force and p-p interaction dramatically improved the adsorption capacity of the charge-tunable GP aerogels against both anionic and cationic dyes. In addition, the GP aerogels were able to selectively separate anionic and cationic dyes in designed aqueous environments. These aerogels may be used as versatile sorbents for various charged pollutants removal due to tunable surface charges.