Free-Standing Sodium Titanate Ultralong Nanotube Membrane with Oil-Water Separation, Self-Cleaning, and Photocatalysis Properties

Abstract

In this work, a free-standing sodium titanate ultralong nanotube membrane for multifunctional water purification has been prepared. For obtaining this free-standing membrane with good tenacity, one-dimensional (1D) sodium titanate ultralong nanotubes with a diameter of about 48 nm and length of hundreds of micrometers were prepared from TiO₂ nanoparticles by a stirring hydrothermal method, which can be easily assembled into 2D membranes by facile vacuum filtration. After modified with methyltrimethoxysilane (MTMS), the free-standing membrane with hydrophobic surface possesses oil-water separation, self-cleaning and photocatalytic functions at the same time, which is favorable for the recovery of membrane and decontamination of various pollutants including oils, dust, and organic dyes from water. Furthermore, this membrane also exhibits excellent alkaline, acid, and corrosive salt resistance. This free-standing sodium titanate membrane with multifunction has potential applications in efficient wastewater purification and environmental remediation.

Keywords: Free-standing; Oil-water separation; Photocatalysis; Self-cleaning; Sodium titanate ultralong nanotubes.

Fig. 1

a XRD pattern, b SEM, c TEM, and d HRTEM of Na₂Ti₃O₇ ultralong nanotubes

Fig. 2

SEM images of Na₂Ti₃O₇ nanotubes synthesized by hydrothermal method with 0 rpm (a) and 300 rpm (b)

Fig. 3

SEM images of cross-section of F-30 (a, b), F-45 (d, e), F-60 (g, h), and F-75 (j, k). TEM images of top view of F-30 (c), F-45 (f), F-60 (i), and F-75 (l). The insets are the optical images of corresponding membranes

Fig. 4

The plot of thickness versus the weight of the membrane

Fig. 5

a Optical photo of the F-60 membrane dropped with carbon tetrachloride (left side, stained by methyl red) and water (right side, stained by methylene blue). b Effect of aging time of MTMS on the contact angle of the modified F-60 membrane

Fig. 6

a Oil/water separation device and process, b separation efficiencies for immiscible oil/water mixtures containing different water phase by the modified F-60 membrane

Fig. 7

Digital images of self-cleaning process

Fig. 8

Optical picture of the membrane after oil/water separation and self-cleaning (a) and the optical pictures of this membrane irradiated under UV-light for 10 min (b), 20 min (c), and 30 min (d). e Degradation efficiency of methyl red solution without photocatalyst under irradiation of UV-light. Inset is the optical photo of methyl red solution irradiated at different times

Fig. 9

a Contact angle of the membrane after UV-light irradiation and b FTIR spectra of pure membrane