Synthesis of titanate nanotubes/layered double hydroxides/graphene oxide composites and applications for the removal of methylene blue, methylene green 5, and acid red 1 from aqueous solutions

A multifunctional adsorption material composite was developed for removal of cationic and anionic dyes. The composite adsorbent was derived from titanate nanotubes (TNTs), layered double hydroxides (LDHs) and gra-phene oxide (GO) abbreviated as TLG. TLG including TNTs, LDHs, and GO with a weight ratio of 1:1:1were produced through Hummer method and a hydrothermal process. The properties of TLG are characterized by scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, nitrogen adsorption/ desorption isotherms, X-ray photoelectron spectroscopy, and zeta potentia.The selected dyes including catonic methylene blue (MB), methylene green (MG5), and anionic acid red 1 (AR1). The adsorption experiments were performed in solutions with pH values of 2, 6, and 9. The properties of composite adsorbent demonstrated that the synthesized material possesses the characteristics of TNT, LDHs and GO. The amount of cationic dye adsorbed increased with increasing pH, while the amount of anionic dye adsorbed increased with decreasing pH.The maximum adsorption capacities of MB, MG5, and AR1 on TLG are 322 mg/g, 526 mg/g, (pH 9) and 124 mg/g (pH 2), respectively. T he primary adsorption mechanism was ion exchange between the TNTs or LDHs and dyes, while van der Waals forces between GO and the dyes were regarded as minor adsorption mechanisms.

Automated summary

A multifunctional adsorption material composite, TLG, consisting of titanate nanotubes (TNTs), layered double hydroxides (LDHs), and graphene oxide (GO), was developed for the removal of cationic and anionic dyes. The properties of TLG were characterized using various techniques, and the adsorption experiments showed that the amount of cationic dye adsorbed increased with increasing pH, while the amount of anionic dye adsorbed increased with decreasing pH. The primary adsorption mechanism was ion exchange, and van der Waals forces were considered minor adsorption mechanisms.