Facile synthesis of EDTA-functionalized halloysite nanotubes for the removal of methylene blue from aqueous phase
EDTA-functionalized halloysite nanotubes (EDTA-HNTs) were synthesized by a two-step method. The structures of the EDTA-HNTs were analyzed by Fourier-transform infrared spectra, X-ray diffraction, thermogravimetric analysis, and transmission electron spectroscopy. Then, the EDTA-HNTs were applied as adsorbents for the removal of methylene blue from aqueous phase. Adsorption of methylene blue onto EDTA-HNTs was investigated with respect to adsorbent dose, contact time, initial methylene blue concentration, and temperature. A maximum adsorption capacity of 115.8 mg/g for methylene blue onto EDTA-HNTs at room temperature was achieved. The adsorption kinetics could be described by the pseudo-second-order model. Both the Langmuir and Freundlich models were employed to describe the adsorption isotherms, and the results presented that the equilibrium data obeyed the Langmuir model. Thermodynamic parameters of ΔG0 and ΔH0 verified the spontaneous and exothermic nature of the methylene blue adsorption onto EDTA-HNTs. Moreover, the EDTA-HNTs could be facilely regenerated and efficiently reused, exhibiting a good prospect for the treatment of dye effluents.