Guangxin Zhang

Characterization and improved solar light activity of vanadium doped TiO2/diatomite hybrid catalysts

V-doped TiO2/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol-gel method. The diatomite was responsible for the well dispersion of TiO2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO2/diatomite hybrids showed red shift in TiO2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO2 bandgap due to V(4+) ions substituted to Ti(4+) sites. The 0.5% V-TiO2/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO2/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V(4+) ions incorporated in TiO2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO2 to produce superoxide radicals ˙O2(-), while V(5+) species presented on the surface of TiO2 particles in the form of V2O5 contributed to e(-)-h(+) separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability.

A comparative study of different diatomite-supported TiO2 composites and their photocatalytic performance for dye degradation

AbstractThree kinds of diatomites as catalyst carriers were adopted to prepare supported TiO2 catalysts by a typical hydrolysis–deposition method. The prepared composites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption–desorption, scanning electron microscopy transmission electron microscopy, UV–vis diffuser reflectance, and chemical oxygen demand. The photocatalytic properties of composites were determined using rhodamine B, methyl orange, and methylene blue as target pollutants under UV light irradiation. A comparative study on the photocatalytic properties of composite catalysts was carried out. It is indicated that the catalytic performance of TiO2/diatomite is significantly influenced by the physicochemical properties of diatomite supports. Compared with pure TiO2, the TiO2/diatomite composites exhibited smaller crystalline size of TiO2 and better dispersibility, which induced higher specific surface area and better photo-degradation efficiency. The hig...

Synthesis of novel ternary heterogeneous BiOCl/TiO2/sepiolite composite with enhanced visible-light-induced photocatalytic activity towards tetracycline

In this study, the novel ternary heterogeneous BiOCl/TiO2/sepiolite composite with enhanced visible-light-induced photocatalytic activity was synthesized via the hydrolysis precipitation method followed by a calcination crystallization process. The as-prepared samples were characterized by X-ray diffraction (XRD), UV-VIS diffused reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL), respectively. Compared with bare BiOCl and TiO2, the ternary heterogeneous structure in BiOCl/TiO2/sepiolite significantly improved the visible-light-induced photocatalytic performance towards tetracycline (TC), and also contributed to the separation efficiency and recyclability of the photocatalyst. In addition, the influence of the mass ratio of BiOCl in the composites was also discussed, and the optimal mass ratio is identified as 50% (mBiOCl/(mTiO2 + mBiOCl). Furthermore, TC degradation by-products were further detected by HPLC-MS/MS, and a possible degradation pathway was proposed. Besides, ESR (Electron spin resonance) results indicated that the main active radical species were photo-induced holes (h+) and superoxide radical (O2-) in the TC degradation process. Hence, the enhanced photocatalytic activity of the prepared ternary composite was mainly attributed to the remarkable synergistic effect within the BiOCl/TiO2/sepiolite ternary heterogeneous system, resulting in the superior adsorption activity, the outstanding visible-light response performance and the efficient separation of the photogenerated electron-hole pairs. It is speculated that the novel ternary heterogeneous BiOCl/TiO2/sepiolite composite would have a broad application prospect in the field of wastewater treatment.