Enhanced acidic dye adsorption onto the dendrimer-based modified halloysite nanotubes

Abstract

In this study, amine-terminated dendritic functional groups were grown on the surface of Halloysite Nanotubes (HNTs) to improve their adsorption tendency towards the anionic dye molecules. HNTs were first silanized by (3-Aminepropyl) triethoxysilane, and then amine dendritic groups were added via divergent synthesis from zero to third generation by repeating the Michael addition of methyl acrylate and amidation of the esters groups with ethylenediamine. In fact, amine groups of APTES act as a core for growing of dendritic structure in divergent synthetic route. Field emission scanning electron microscopy, energy dispersive X-ray spectroscopy analysis, and Fourier transform infrared spectroscopy were used to characterize the modified HNTs. The adsorption of C.I. Acid Red 1 (AR1) and C.I. Acid Red 42 (AR42) was investigated and the effect of initial dye concentration, pH, adsorbent dosage, and temperature was studied. The adsorption isotherm and kinetic data followed the Langmuir and pseudo-second-order equations, respectively. The maximum removal efficiencies of 93–94% were achieved at pH 3 for AR1 and AR42, respectively, while the pure HNTs revealed only 9–13% of removal.

Keyword:

• Halloysite nanotubes
• Dendrimer
• Amine-terminated functional groups
• Equilibrium parameters