Adsorption of pyrene from aqueous solutions onto sepiolite

Polycyclic aromatic hydrocarbons (PAHs) are commonly referred to a large class of organic compounds, which have been shown to be highly carcinogenic, and to have a significant persistence in an environment for many years. In this study, the adsorption of pyrene, which was chosen as a model PAH due to its specific volatility, miscibility, and relatively soluble properties, onto sepiolite (Turkish origin) was investigated in detail. Pyrene used as a model PAH due to its specific volatility and miscibility characteristics, relatively soluble yet hydrophobic to explore the potential of sepiolite (Turkish origin) to sorb hydrophobic organic compounds from aqueous solution. The microstructure and morphology of sepiolite were characterized by using Elemental analysis, X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscope (FE-SEM), and surface property evaluation by the BET method from nitrogen adsorption isotherms. The results for the adsorption isotherms were closely fitted with the Langmuir model, and the coefficient of determination (R2) was higher than 0.999. The results indicated that the high affinity of pyrene on sepiolite surfaces was dominated by structural channels and large number of Si-OH groups located at the basal surfaces. However, its intracrystalline interactions with pyrene were more favorable than the surface Si-OH groups which could react directly with pyrene to form compounds with true covalent bonds (chemical interactions) between sepiolite and pyrene. Finally, the FE-SEM images initially revealed that after loading with pyrene, fairly straight and rigid fiber arrangement (aggregation of laths to form rods) occurred due to increasing sorption of pyrene onto sepiolite