Characteristics and mechanisms of sorption of organic contaminants onto sodium dodecyl sulfate modified Ca-Al layered double hydroxides

A series of calcium aluminum layered double hydroxides (LDHs) modified with sodium dodecyl sulfate (SDS) (Ca /Al-SDSLDHs) were synthesized by co-precipitation, and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and elemental analysis. The Ca /Al-SDS-LDHs enhanced sorption of nitrobenzene and naphthalene from water compared with inorganic LDH (Ca /Al-Cl-LDH). The sorption isotherms for sorption of organic contaminants onto the Ca /Al-SDS-LDHs were linear for the concentration range tested, which implies that the sorption mechanism is mainly by partition. The sorption of naphthalene onto Ca /Al-SDS-LDH was apparently stronger than that of nitrobenzene, but this order reversed after eliminating the hydrophobic effect of these two contaminants. Because naphthalene is non-polar and nitrobenzene is polar, the results indicate that the Ca /Al-SDS-LDHs were selective for polar organic contaminants.