Sorption Behavior of Bisphenol A and Triclosan by Graphene: Comparison with Activated Carbon

The sorption behavior of bisphenol A (BPA) and triclosan (TCS) on graphene was investigated and compared with that on activated carbon. The kinetic studies showed that BPA sorption on graphene or activated carbon reached equilibrium within 240 min, whereas TCS sorption on these two materials achieved equilibrium in 60 and 120 min. The maximum sorption capacity (q _m) of BPA on graphene or activated carbon reached approximately 2.0 × 10³ μg/g, which indicated that graphene was not superior to traditional activated carbon for BPA removal. By contrast, the strong partitioning ability of TCS on graphene suggested the potential use of graphene materials to remove TCS from wastewater. Although the pH change from 4.0 to 7.0 did not greatly affect BPA or TCS sorption, the sorption decreased dramatically when the pH was increased from 7.0 to 9.0. This phenomenon should be attributed to the establishment of electrostatic repulsion between anionic BPA (or TCS) molecules and the graphene (or activated carbon) surface under higher pH conditions. The increase of ion (NaCl and CaCl₂) concentrations may lead to substantial increase of BPA sorption on graphene or activated carbon due to the salting-out effect. By contrast, ion concentrations had no significant effect on TCS sorption because of the dominant hydrophobic interaction.