Adsorption-solubilization controlled extraction of pyrene from surfactant solutions by graphene oxide

Graphene and its derivatives such as graphene oxide (GO) has attracted increasing attention in water treatment because of its unique physical and chemical properties. Herein, the adsorption performance of GO for a typical polycyclic aromatic hydrocarbon (PAH), pyrene from solutions of either a non-ionic surfactant Tergitol 15-S-7 or an anionic surfactant sodium dodecyl benzene sulphonate (SDBS) is investigated. It demonstrates that the high affinity of GO to pyrene leads to multi-layer adsorption of pyrene, with an adsorption capacity 2 to 3 times of its own weight at a low GO concentration of 3.9 mg/L. Linear two-zone pyrene adsorption isotherms are identified, which should be due to competitive adsorption-solubilization processes of pyrene. Although Tergitol 15-S-7 has a considerably higher solubilization capacity (affinity) for pyrene compared to SDBS, faster adsorption kinetics, larger solid-liquid distribution coefficients, and higher recovery of pyrene from Tergitol 15-S-7 solutions are achieved. The higher affinity of SDBS to GO leads to its competitive adsorption that impairs the adsorption of pyrene by GO. Furthermore, the GO demonstrates excellent adsorption capacity for pyrene even after 5 recycling cycles.