Adsorption mechanism of emerging and conventional phenolic compounds on graphene oxide nanoflakes in water.

Emerging contaminants (ECs) such as bisphenol A (BPA), 4-nonylphenol (4-NP) and tetrabromobisphenol A (TBBPA) have gained immense attention worldwide due to their potential threat to humans and environment. Graphene oxide (GO) nanomaterial is considered as an important sorbent due to its exceptional range of environmental application owing to its unique properties. GO was also considered as one of ECs because of its potential hazard. The adsorption of organic contaminants such as phenolic ECs on GO affects the stability of GO nanoflakes in water and the fate of organic contaminants, which would cause further environmental risk. Therefore, the adsorption behaviors of emerging and common phenolic compounds (PCs) including phenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 4-NP, BPA and TBBPA on GO nanoflakes and their stability in water were studied. The adsorption equilibrium for all the compounds was reached <10h and was fitted with Langmuir and Freundlich isotherms. In addition to hydrophobic effect, adsorption mechanisms included π-π bonding and hydrogen bonding interactions between the adsorbate and GO, especially the electrostatic interactions were observed. Phenol has the highest adsorption affinity due to the formation of hydrogen bond. GO has a good stability in water even after the adsorption of PCs in the presence of a common electrolyte, which could affect its transport with organic contaminants in the environment. These better understandings illustrate the mechanism of emerging and common PC interaction with GO nanoflakes and facilitate the prediction of the contaminant fate in the aquatic environment.