Direct Synthesis of Reduced Graphene Oxide/TiO2 Nanotubes Composite from Graphite Oxide as a High-Efficiency Visible-Light-Driven Photocatalyst.

Synthesis of reduced graphene oxide/TiO2 nanotubes (rGO/TNTs) composite is being attended. However, the synthesis of rGO/TNTs composite directly from graphite oxide with a greener approach is still challenging. In this study, we directly synthesized rGO/TNTs composite by a simple method from graphite oxide and titanium dioxide nanotube (TNTs) powder without involving any assistant agents. The formation of the graphene oxide (GO) was confirmed by X-ray diffraction (XRD) pattern, transmission electron microscope (TEM) image, Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Besides, photoluminescence analysis (PL) was conducted to determine the defects of materials. The methylene blue (MB) photodegradation efficiency under visible light of rGO/TNTs composite achieved 80% after 180 min. In addition, the key of the photocatalytic mechanism of rGO/TNTs under visible light was systematically investigated via trapping experiments.

Surfactant modified zeolite as amphiphilic and dual-electronic adsorbent for removal of cationic and oxyanionic metal ions and organic compounds.

A hydrophilic Y zeolite was primarily treated with sodium hydroxide to enhance its cation exchange capacity (Na-zeolite). The organo-zeolite (Na-H-zeolite) was prepared by a modification process of the external surface of Na-zeolite with a cationic surfactant (hexadecyltrimethylammonium; HDTMA). Three adsorbents (i.e., pristine zeolite, Na-zeolite, and Na-H-zeolite) were characterized with nitrogen adsorption/desorption isotherms, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, cation exchange capacities, and zeta potential. Results demonstrated that HDTMA can be adsorbed on the surface of Na-zeolite to form patchy bilayers. The adsorption capacity of several hazardous pollutants (i.e., Pb2+, Cu2+, Ni2+, Cr2O72-, propylbenzene, ethylbenzene, toluene, benzene, and phenol) onto Na-H-zeolite was investigated in a single system and multiple-components. Adsorption isotherm was measured to further understand the effects of the modification process on the adsorption behaviors of Na-H-zeolite. Adsorption performances indicated that Na-H-zeolite can simultaneously adsorb the metal cations (on the surface not covered by HDTMA), oxyanions (on the surface covered by HDTMA). Na-H-zeolite also exhibited both hydrophilic and hydrophobic surfaces to uptake organic compounds with various water solubilities (from 55 to 75,000mg/L). It was experimentally concluded that Na-H-zeolite is a potential dual-electronic and amphiphilic adsorbent for efficiently removing a wide range of potentially toxic pollutants from aquatic environments.

Controlled Formation of Silver Nanoparticles on TiO2 Nanotubes by Photoreduction Method.

In this paper, we surveyed the effect of the concentration of AgNO3 solution and the time of photoreduction on the formation of Ag nanoparticles supported on TiO2 nanotubes (Ag/TNTs) were synthesized by photoreduction method. Their morphology and crystal structure were determined by Transmission Electron Microscopy images (TEM), X-ray Diffraction (XRD) and Energy-dispersive X-ray spectroscopy (EDX) data. Results show that the amount of Ag nanoparticles supported on TNTs could be controlled by changing of the illumination time (photoreduction time) and the concentration of AgNO3 solution. Besides, the annealing temperature has a direct influence on the morphology of TNTs. Especially, the nanotubes transformed into nanorods at 500 °C for 2 hours.

The Effect of Acid Treatment and Reactive Temperature on the Formation of TiO2 Nanotubes.

TiO2 nanotubes (TNTs) were synthesized by a hydrothermal method from commercial TiO2 in NaOH followed by HCl washing. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmitting electron microscopy (TEM), and Brunauer-Emmet-Teller (BET) measurements. The untreated acid samples (pH ~ 12) don't appear nanotubes structure, while acid-treated samples until the pH reached around 2 have approximate diameters of nanotubes of 10 nm. The samples reaction temperature at 135 °C appear nanotubes structure while the samples reaction temperature at 150 °C have combination of the nanotubes and the samples treatment temperature at 170 °C appear both nanotubes structure and particles clumping together. The surface area of the TNTs was 83,5 m2/g while the surface area of commercial TiO2 particles was 41 m2/g.