Search

Abstract The N-TiO 2 /g-C 3 N 4 @diatomite (NTCD) composite has been prepared through a simple impregnation method, using titanium tetrachloride as precursor and urea as nitrogen-carbon source. Then the effects of calcination temperature on structure, surface property and photocatalytic activity of the catalysts were investigated. And XRD, TEM, XPS, FTIR and UV–vis diffuse adsorption spectroscopy were used to characterize the obtained powders. The photocatalytic activity of the NTCD was evaluated through the reduction of aqueous Cr (VI) under visible light irradiation (λ > 400 nm). The results demonstrated that the nano-TiO 2 particles ranging from 15 to 30 nm in the crystal of anatase are well deposited on the surface of diatomite in the NTCD-500 which calcined at 500 °C for 2 h. Furthermore, the g-C 3 N 4 with the lay thickness of 0.92 nm was attached to the surface of nano-TiO 2. The N-doped TiO 2 and g-C 3 N 4 doped catalysts could co-enhance response in the visible light region and reduce band gap of NTCD-500 (E g = 3.07 eV). And the NTCD-500 sample exhibited nearly 100% removal rate within 5 h for photocatalytic reduction of Cr (VI) which was higher activity than P25, crude TiO 2 @diatomite and g-C 3 N 4 @diatomite. Graphical abstract Image 1 Highlights • The N-TiO 2 /g-C 3 N 4 @diatomite hybrid photocatalyst was prepared and characterized. • The calcination temperature has significant effect on structure and photocatalytic activity of the catalysts. • The N-TiO 2 /g-C 3 N 4 @diatomite heterostructures exhibit superior Cr(Ⅵ) removal rate under visible light irradiation. • The N-TiO 2 and g-C 3 N 4 work together to enhance the photocatalyst reduction of Cr(Ⅵ). The composite exhibit superior Cr(Ⅵ) removal rate and the calcination temperature has significant effect on structure of the catalysts. [ABSTRACT FROM AUTHOR]

Using the diatomite as the carrier, the nano-TiO 2 /diatomite composite materials (NTID) were synthesized by the hydrolysis deposition of titanium tetrachloride. Thermodynamic behavior of the as-prepared sample was evaluated by thermo gravimetric (TG) and differential scanning calorimetry (DSC). Structures of the composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The photocatalytic property of the composite was investigated through the degradation of Cu 2+ in aqueous solutions. Effects of various parameters such as initial pH, catalyst amount and initial Cu 2+ concentration on the removal of Cu 2+ were investigated to optimize operational conditions. The results indicate that the nano-TiO 2 immobilized on the surface of carrier was crystallized through calcinations at 700 °C. And the phase of TiO 2 is anatase with the average crystallite size of 13 nm. The removal efficiency of 10 mg/L Cu 2+ solution by the composite reaches 96.63% after irradiation for 3 h under UV-light. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diatomite decorated with BiOCl/TiO 2 was prepared for formaldehyde degradation. • Effects of key parameters on the photocatalytic performance was studied. • Optimal pH values, calcination temperature, and mass ration was confirmed. • BiOCl/TiO 2 @diatomite showed excellent performance of formaldehyde degradation. The diatomite decorated with BiOCl/TiO 2 (BiOCl/TiO 2 @diatomite) composites were prepared by supporting BiOCl/TiO 2 heterogeneous junction on the surface of diatomite with precipitation-calcination method. This work systematically studied the effects of terminal pH, calcination temperature, and TiO 2 /BiOCl ratio. Furthermore, the relationship between structure and photocatalytic performance of the composite was investigated. The results demonstrated that composite with optimized performance (84.1% formaldehyde degradation rate of 1.0 g photocatalyst) can be obtained at terminal pH of 6, calcination temperature of 500 °C, and TiO 2 /BiOCl ratio of 55/45. It is indicated that the phase structure, grain size, and porous structure can be significantly affected by the above preparation parameters. In conclusion, the formaldehyde adsorption and degradation properties can be enhanced by the construction of porous structure and heterogeneous junction of composites. Overall, BiOCl/TiO 2 @diatomite composites exhibited excellent formaldehyde degradation performance under visible light due to the multi-layer structure and the combination of TiO 2 and BiOCl on the surface of diatomite. [ABSTRACT FROM AUTHOR]

Highlights: [•] TiO2 nanoparticles/diatomite composite was synthesized and characterized. [•] The composite exhibited a good photocatalytic performance in Cr (VI) reduction. [•] The photocatalyst showed good photocatalytic stability. [•] The composite is a promising material for Cr (VI) photocatalytic reduction. [ABSTRACT FROM AUTHOR]

The TiO 2 /diatomite composite was synthesized through a mild hydrolysis of titanyl sulfate. The prepared composite was characterized by X-ray diffraction, N 2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–vis diffused reflectance spectroscopy. The results demonstrate that the anatase TiO 2 nanopartilces anchored on the surface of diatomite with Ti–O–Si bonds between diatomite and TiO 2 . The photodegradation of gaseous formaldehyde under UV irradiation by the TiO 2 /diatomite composite was studied under various operating conditions, including relative humidity, illumination intensity and catalyst amount, which have significant influence on the degradation process. The TiO 2 /diatomite composite exhibited better photocatalytic activity than pure TiO 2 , which could be attributed to the favorable nanoparticles dispersibility and strong formaldehyde adsorption capacity. In addition, the composite exhibited outstanding reusability over five cycles. The TiO 2 /diatomite composite shows great promising application foreground in formaldehyde degradation. [ABSTRACT FROM AUTHOR]

Novel fluorine doped TiO 2 /diatomite (F-T/DE) composites with visible-light responding activity were fabricated through a facile sol-gel method in this study. The as-synthesized F-T/DE-1.0% (1.0% fluorine content) composite exhibited enhanced photocatalytic activity in degrading rhodamine B (RhB) under visible-light illumination, the reaction rate constant of which was nearly up to 4.4 times and 26.1 times higher than that of F-T-1.0% (fluorine doped TiO 2 with 1.0% content) and pure TiO 2 , respectively. It is indicated that the anatase TiO 2 nanoparticles were firmly and homogeneously loaded on the surface of diatomite and fluorine ions were successfully incorporated into the lattice of TiO 2 . In addition, the construction of composite can effectively promote the generation of oxidative radicals and reduce the recombination probability of photogenerated electron-hole pairs and thus contribute to the enhancement of photoactivity under visible light. The enhanced photocatalytic activity of F-T/DE can be attributed to the fluorine doping induced oxygen vacancies and much more exposed highly active (001) facets, as well as the carrier effect (smaller grain size, well distribution and enhanced adsorption ability). [ABSTRACT FROM AUTHOR]

The highly efficient g-C 3 N 4 /TiO 2 heterojunction was deposited over diatomite supports through an in situ deposition process. The microstructure, morphology and optical properties of the novel g-C 3 N 4 /TiO 2 @diatomite composite were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and UV–visible diffused reflectance spectroscopy (UV–vis DRS). The photocatalytic efficiency of g-C 3 N 4 /TiO 2 @diatomite composite was evaluated by the degradation of rhodamine B and methylene blue under visible light and simulated solar light. It is indicated that the as-synthesized g-C 3 N 4 /TiO 2 @diatomite composite displayed higher photocatalytic performance than pure g-C 3 N 4 and TiO 2 . This enhancement should be ascribed to that diatomite can play as an excellent catalyst carrier to improve the dispersity of g-C 3 N 4 /TiO 2 and increase the reactive sites for dye pollutants degradation. The CN/T@DE-10% exhibited the highest efficiency towards RhB, which was around 2.5 times under visible light and 3.5 times under solar light as much as that of the pure g-C 3 N 4 . In addition, the final removal rates of RhB reach to 96% within 3 h under solar light and 83% within 6 h under visible light, respectively. On the other hand, the g-C 3 N 4 /TiO 2 @diatomite composite can be easily separated from suspension and presents a good durability during five cycles. The outstanding properties of g-C 3 N 4 /TiO 2 @diatomite composite and high photocatalytic efficiency make it promising for the potential application in the dye wastewater treatment. [ABSTRACT FROM AUTHOR]

V-doped TiO 2 /diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol–gel method. The diatomite was responsible for the well dispersion of TiO 2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO 2 /diatomite hybrids showed red shift in TiO 2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO 2 bandgap due to V 4+ ions substituted to Ti 4+ sites. The 0.5% V-TiO 2 /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 TiO 2 /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 TiO 2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO 2 to produce superoxide radicals O 2 – , while V 5+ species presented on the surface of TiO 2 particles in the form of V 2 O 5 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. [ABSTRACT FROM AUTHOR]

TiO 2 /purified diatomite composite materials were prepared through a modified hydrolysis-deposition method under low temperature using titanium tetrachloride as precursor combined with a calcination crystallization process. The microstructure and crystalline phases of the obtained composites prepared under different preparation conditions were characterized by high resolution scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The photocatalytic performance of TiO 2 /purified diatomite composites was evaluated by Rhodamine B as the target pollutant under UV irradiation, and the optimum preparation conditions of composites were obtained. The TiO 2 crystal form in composites prepared under optimum conditions was anatase, the grain size of which was 34.12 nm. The relationships between structure and property of composite materials were analyzed and discussed. It is indicated that the TiO 2 nanoparticles uniformly dispersed on the surface of diatoms, and the photocatalytic performance of the composite materials was mainly determined by the dispersity and grain size of loaded TiO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: Natural porous mineral supported (TiO2/diatomite) photocatalyst was prepared via a modified sol–gel method using titanium (IV) butoxide (TBOT) and diatomite. The effect of TBOT dosage on adsorption capacity and photocatalytic activity for Rhodamine B (RhB) solution was investigated. The morphology and elemental distribution were determined by scanning electron microscopy with attached energy-dispersive X-ray detector. The porous and crystalline structures were characterized using nitrogen adsorption–desorption and X-ray diffraction techniques, respectively. The prepared TiO2/diatomite hybrid catalyst has shown relatively even porous structure and dispersion of TiO2 over the surface. This suggests that the diatomite matrix prevented the agglomeration of TiO2 particles. Initially, the surface area and pore volume of the hybrid catalyst were increased by adding TBOT then decreased for dosages higher than 1.0ml. The crystalline size of TiO2 immobilized on diatomite matrix by sol–gel method was around 20nm. When the experiments were carried out in the absence of diatomite, this value was increased to 33.73nm. The use of diatomite also promoted an increase of the transformation temperature of the crystalline phase anatase to rutile for the TiO2. The as-prepared TiO2/diatomite composite exhibited high photocatalytic activity (96.0% for 0.5h UV-light irradiation) for the degradation of RhB from wastewater as a result of its unique porous structure and optimum TiO2 loading. In addition, it can be easily separated from suspension and possess a good durability. This hybrid material holds great promise in the engineering field for the environmental remediation. [Copyright &y& Elsevier]