Yadan Guo

Fe2O3-Pillared Rectorite as an Efficient and Stable Fenton-Like Heterogeneous Catalyst for Photodegradation of Organic Contaminants

An efficient Fe(2)O(3)-pillared rectorite (Fe-R) clay was successfully developed as a heterogeneous catalyst for photo-Fenton degradation of organic contaminants. X-ray diffraction analysis and high-resolution transmission electron microscope analysis clearly showed the existence of the Fe(2)O(3) nanoparticles in the Fe-R catalyst. The catalytic activity of the Fe-R catalyst was evaluated by the discoloration and chemical oxygen demand (COD) removal of an azo-dye rhodamine B (RhB, 100 mg/L) and a typical persistent organic pollutant 4-nitrophenol (4-NP, 50 mg/L) in the presence of hydrogen peroxide (H(2)O(2)) under visible light irradiation (lambda > 420 nm). It was found that the discoloration rate of the two contaminants was over 99.3%, and the COD removal rate of the two contaminants was over 87.0%. The Fe-R catalyst showed strong adsorbability for the RhB in the aqueous solution. Moreover, the Fe-R catalyst still showed good stability for the degradation of RhB after five recycles. Zeta potential and Fourier transform infrared spectroscopy were used to examine the photoreaction processes. Finally, a possible photocatalytic mechanism was proposed.

Hierarchically structured α-Fe2O3/Bi2WO6 composite for photocatalytic degradation of organic contaminants under visible light irradiation

The α-Fe2O3/Bi2WO6 composite with a sphere-like hierarchical structure assembled by nanosheets was synthesized by a one-step hydrothermal route without any templates or surfactants. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectrum (UV–vis DRS), Fourier transform infrared (FT–IR) spectrum, X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmet–Teller (BET) analysis. The BET specific surface area of the hierarchically structured α-Fe2O3/Bi2WO6 composite is 61.7 m2 g−1, which is much higher than that (3.5 m2 g−1) of the pure Bi2WO6. The hierarchically structured α-Fe2O3/Bi2WO6 composite exhibited a strong adsorption capability and a higher visible light photocatalytic activity than the pure Bi2WO6 for the photocatalytic degradation of acid red G dye or Rhodamine B (RhB) dye in aqueous solution under visible-light irradiation (>420 nm). The composite still showed the high photocatalytic activity after four reaction cycles. On the basis of the experimental results and calculated energy band positions, the enhanced photocatalytic activity of the composite can be attributed to the hierarchical structure and the coupling effect of α-Fe2O3 and Bi2WO6 in the composite.

Synthesis, characterization and visible light photocatalytic properties of Bi2WO6/rectorite composites.

Visible light-induced Bi(2)WO(6)/rectorite (BR) composites were prepared by a sol-gel method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectrum, Fourier transform infrared (FTIR) spectrum, X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmet-Teller (BET). The UV absorption edges of the BR-450 catalyst showed a marked red shift as compared to that of the pure Bi(2)WO(6). The photocatalytic activities of the as-prepared samples were evaluated by the photocatalytic degradation of 4BS dye in aqueous solution under visible light irradiation (>420 nm). The results showed that the BR-450 catalyst exhibited a strong adsorption capability and a higher photocatalytic degradation activity than the pure Bi(2)WO(6) for 4BS dye, which could be attributed to the synergetic effects of the adsorbability of rectorite and the photocatalytic property of Bi(2)WO(6) in it.

Facile in situ synthesis of the bismuth oxychloride/bismuth niobate/TiO2 composite as a high efficient and stable visible light driven photocatalyst.

As a strategy of fabricating a heterojunction structure to extend the light response region and improve charge separation efficiency, the BiOCl/Bi(5)Nb(3)O(15)/TiO(2) composites (BiOCl/BiNbO/TiO(2)) were successfully synthesized by a simple method. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, nitrogen adsorption/desorption measurements and UV-vis diffuse reflectance spectra. The results showed that the ternary hybrid of BiOCl-Bi(5)Nb(3)O(15)-TiO(2) exhibited enhanced photocatalytic activity for the degradation of rhodamine B in water and the decomposing of acetone in air to CO(2) under visible light irradiation. The sample with the molar ratio of Bi/Ti=0.032:1 showed the highest efficiency. The enhanced photocatalytic performances of the BiOCl/BiNbO/TiO(2) composites can be attributed to the improved charge separation efficiency derived from the suitable conduction band interaction among the three components, as well as high specific surface area and dual mesoporous structure.

Adsorption of Rhodamine B from aqueous solution onto sepiolite modified by cetyltrimethylammonium bromide

Abstract The sepiolite modified with cetyltrimethylammonium bromide (CTAB/sepiolite), was used as an adsorbent for the removal of Rhodamine B (RhB) from aqueous solutions. The sepiolite and modified sepiolite were characterized by Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller and scanning electron microscopy, respectively. The CTAB/sepiolite exhibited much higher adsorption capacity for the removal of RhB than sepiolite. The effects of the amount of CTAB, contact time, initial RhB concentrations, and pH upon the RhB adsorption were evaluated on the CTAB/sepiolite. The kinetic studies indicated that the adsorption process was fitted well with the pseudo-second-order kinetic model (R 2 > 0.99). The equilibrium data were well described by the Freundlich equation. The results showed that the CTAB/sepiolite is an efficient adsorbent for the removal of organic pollutants from wastewater.

Adsorption of rhodamine B from aqueous solution onto heat-activated sepiolite

The heat-activated sepiolite, which was prepared using sepiolite by thermal treatment at different temperatures, was used as an absorbent for the removal of rhodamine B (RhB) from aqueous solutions. The structure and morphology of the as-prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. The adsorption capacity of RhB onto the heat-activated sepiolite has been examined with pH, adsorbent dosage, contact time, initial dye concentration, and temperature. Kinetic studies showed that the equilibrium was attained within 40 min, and the kinetic data were well described by the pseudo-second-order kinetic model. Besides, the experimental data (R2>0.999) fitted the Freundlich model better than the Langmuir model. The as-prepared sample showed higher adsorption capacity (8.33 mg/g) for the removal of RhB than that of sepiolite, which could be attributed to more adsorption sites caused by appropriate heat treatment. The adsorbent can be well regenerated by calcination at 400 °C for 2 h and regenerated sepiolite did not exhibited significant loss of adsorption activity after five recycles.