Role of Oxidized Debris in Determining the pH-Dependent Adsorption Performance of Graphene Oxide toward Aromatic Pollutants

The latest structural model of graphene oxide (GO) consists of two parts: a large sheet of lightly oxidized graphene (FG) and small highly oxidized debris (ODs). In this article, the role of ODs in regulating the pH-dependent adsorption performance of GO toward aromatic compounds was elucidated using molecular dynamics (MD) simulations and adsorption experiments. The results demonstrate that the adsorption of benzene and bisphenol S (BPS) on GO is regulated by the pH-dependent behavior of ODs, which significantly affects the availability of adsorption sites and the oxygen content of GO. At pH levels below 10, ODs tend to adsorb onto the GO plane, occupying favorable adsorption sites and hindering the adsorption of aromatic compounds, thus allowing FG to demonstrate better adsorption performance toward these compounds. At pH levels above 10, significant stripping of ODs from GO and their recombination with GO lead to GO aggregation and an increase in the adsorption rate. However, the folding of GO sheets that occurs during this aggregation decreases the number of available adsorption sites, which, in turn, reduces the adsorption capacity of GO for larger aromatic compounds. The stripping and recombination of ODs on GO play key roles in regulating the pH-dependent adsorption performance of GO, which should be considered during the development of GO-based adsorbing materials.