Relationship between aggregated structures and dispersibility of layered double hydroxide nanoparticles ca. 10nm in size and their application to ultrafast removal of aqueous anionic dye

Layered double hydroxides (LDHs) are anion-exchanging materials applicable to removal of harmful anionic species from water. Here, we report novel highly dispersible LDH nanoparticles (LDHNPs) which can remove methylorange (MO), a model anionic pollutant, quite rapidly. The LDHNPs are prepared by using tris(hydroxymethyl)aminomethane. The LDHNPs aggregate into sheet-like structure by face-to-face association or house-of-cards structure by edge-to-face association. The removal of MO by the LDHNPs with the house-ofcards structure reaches 95% of equilibrium level within only 5 s, which is much faster than the sheet-like aggregates and conventional large LDHs by at least two orders of magnitude. Therefore, it is found that the structural control of aggregates is critical to the dispersibility of LDHNPs and the ultrafast removal of anionic dye.