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 (NTS^3-) and 3-amino-2,7-naphthalenedisulfonate (ANDS^2-) 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 NTS^3- and ANDS^2- 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 NTS^3- and ANDS^2- probably resulted in these differences among the absorbed quantities of the various aromatics.