Adsorption of naphthalene and phenanthrene on dodecylpyridinium-modified bentonite

Eight organoclays were prepared from sodium-rich bentonite and dodecylpyridinium chloride loading levels of 0.25–2.00 times the cation exchange capacity (CEC). The organoclays were characterized by the specific surface area, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Adsorption of DPC onto bentonite and of PAHs from the aqueous solution on the organoclays were studied in batch experiments. DPC was adsorbed in excess of the CEC. The adsorption isotherms of PAHs onto the organoclays were linear, indicating partition as the main mechanism of PAH adsorption. As the amount of DPC increased from 0.25 to 1.25 times the CEC, the increased basal spacing and partition medium promoted PAH adsorption. When the amount of DPC was higher than 1.25 times the CEC, PAH adsorption was limited by densely packed dodecylpyridinium chains in the interlayer space.