Preparation of Mg–Al layered double hydroxides intercalated with 1,3,6-naphthalenetrisulfonate and 3-amino-2,7-naphthalenedisulfonate and assessment of their selective uptake of aromatic compounds from aqueous solutions

Mg–Al layered double hydroxides (Mg–Al LDHs) intercalated with 1,3,6-naphthalenetrisulfonate (NTS3−) and 3-amino-2,7-naphthalenedisulfonate (ANDS2−) ions were prepared by coprecipitation and were characterized by X-ray diffraction and chemical analyses. Based on X-ray diffraction patterns, the naphthalene rings of NTS3− and ANDS2− were most likely oriented parallel to the brucite-like host layers of the Mg–Al LDH, midway between layers. The prepared Mg–Al LDHs were able to selectively take up aromatics from aqueous solutions, and the order of percentage uptake was as follows: 1,3-dinitrobenzene > nitrobenzene > benzaldehyde > N,N-dimethylaniline > anisole > 1,2-dimethoxybenzene. The differences in the extent of π–π stacking interactions occurring between the benzene rings of the aromatics and the naphthalene ring of the intercalated NTS3− and ANDS2− probably resulted in these differences among the absorbed quantities of the various aromatics.

Uptake of aromatic compounds by Mg–Al layered double hydroxides intercalated with 1,3,6-naphthalenetrisulfonate (NTS3−) probably involves the insertion of the benzene ring of the aromatic compound between the parallel naphthalene units of the intercalated NTS3− and the brucite-like host layers to generate the π–π stacking interactions.Figure optionsDownload as PowerPoint slide