Effect of Calcination Conditions on the Properties and Photoactivity of TiO2 Modified with Biuret

A simple wet impregnation-calcination method was used to obtain a series of novel non-metal doped TiO2 photocatalysts. Biuret was applied as C and N source, while raw titanium dioxide derived from sulfate technology process was used as TiO2 and S source. The influence of the modification with biuret and the effect of the atmosphere (air or argon) and temperature (500–800 °C) of calcination on the physicochemical properties and photocatalytic activity of the photocatalysts towards ketoprofen decomposition under simulated solar light was investigated. Moreover, selected photocatalysts were applied for ketoprofen photodecomposition under visible and UV irradiation. Crucial features affecting the photocatalytic activity were the anatase to rutile phase ratio, anatase crystallites size and non-metals content. The obtained photocatalysts revealed improved activity in the photocatalytic ketoprofen decomposition compared to the crude TiO2. The best photoactivity under all irradiation types exhibited the photocatalyst calcined in the air atmosphere at 600 °C, composed of 96.4% of anatase with 23 nm crystallites, and containing 0.11 wt% of C, 0.05 wt% of N and 0.77 wt% of S.

Synthesis of Glycerol Carbonate from Glycerol and Dimethyl Carbonate Catalyzed by Solid Base Catalyst Derived from Waste Carbide Slag

Na2CO3 was loaded onto waste carbide slag (CS) by impregnation-calcination method to prepare the solid base catalyst, which was used to synthesize glycerol carbonate (GC) by the transesterification of glycerol with dimethyl carbonate (DMC). The prepared catalysts were characterized by a scanning electron microscope (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Brunner−Emmet−Teller (BET) techniques. The catalyst 15 wt.% Na2CO3-CS-800, which was prepared by impregnating CS to the Na2CO3 solution with the concentration of 15 wt.% weight of CS and calcined at 800°C for 3 hours, showed an excellent catalytic ability. When it was applied in the catalytic synthesis of GC, 98.1% glycerol conversion and 96.0% GC yield were achieved in 90 mins at 75°C with the catalyst dosage of 3 wt.% to total reactants and the DMC to glycerol molar ratio of 5. More importantly, the loading of Na2CO3 can effectively improve the reusability of catalyst. The 15 wt.% Na2CO3-CS-800 can still achieve 83.6% glycerol conversion and 80.5% GC yield after five-time reuse. Meanwhile, under the same reaction conditions, the CS-800, which was obtained by calcining CS at 800°C for 3 hours, experienced significant activity reduction with only 15.2% glycerol conversion and 14.1% GC yield after five-time reuse. FTIR and XRD characterization revealed that CO32- might play a key role in preserving active catalytic CaO component by forming protective CaCO3 shell on the catalyst surface.

Microcystis@TiO2 Nanoparticles for Photocatalytic Reduction Reactions: Nitrogen Fixation and Hydrogen Evolution

Solar-driven photocatalysis has been known as one of the most potential technologies to tackle the energy shortage and environmental pollution issues. Utilizing bio-pollutants to prepare functional materials has been considered as a green option. Herein, we used Microcystis aeruginosa as a bio-template to fabricate a Microcystis@TiO2 photocatalyst using a calcination method. The as-prepared Microcystis@TiO2 showed prominent ability as well as favorable stability for photocatalytic reduction reactions including hydrogen evolution and nitrogen fixation. Under light illumination, Microcystis@TiO2 calcined at 550 °C exhibited optimal photo-reduced activity among all samples, with the highest hydrogen evolution (1.36 mmol·g−1·h−1) and ammonia generation rates (0.97 mmol·g−1·h−1). This work provides a feasible approach to prepare functional materials from disposed pollutants.

Synthesis of Z-scheme g-C3N4/V2O5photocatalyst with high activity under visible light

Direct Z-scheme g-C3N4/V2O5 photocatalysts were prepared through a sonication-assisted calcination method. The obtained samples were characterised by X-ray diffraction (XRD),Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis-DRS), Scanning electron microscope (SEM), andPhotoluminescence spectroscopy (PL). Oxidations of tetracycline hydrochloride (TC) were employed to evaluate the photocatalytic activities of the obtained g-C3N4/V2O5materials. Different weight ratios (5, 10, 15, and 20%) of g-C3N4/V2O5 loaded composites were prepared, in which a 15% (CV-15) loaded composite was found to show optimal catalytic performance for the reaction. The degradation conversation of TC has achieved approximately 79.67% in CV-15 after a 2-hour reaction. g-C3N4/V2O5 photocatalystwas more active than the individual g-C3N4 and V2O5 materials, which could be attributed to the efficient separation of photogenerated electron-hole pairs shown in the photocatalytic mechanism of TC degradation.

Preparation of novel porous Al2O3-SiO2 nanocomposites via solution-freeze-drying-calcination method for the efficient removal of uranium in solution

In this work, the efficient extraction of uranium in solution using Al2O3-SiO2-T was reported. Kinetics and isotherm models indicated that the removal process of uranium onAl2O3-SiO2-T accorded with pseudo-second-order kinetic model and Langmuir isotherm model, which showed that the adsorption process was a uniform mono-layer chemical behavior. The maximum adsorption capacity of Al2O3-SiO2-T reached 738.7 mg g-1, which was higher than AlNaO6Si2 (349.8 mg g-1) and Al2O3-SiO2-NT (453.1 mg g-1), indicating that the addition of template could effectively improve the adsorption performance of Al2O3-SiO2 to uranium. Even after five cycles of adsorption-desorption, the removal percentage of uranium on Al2O3-SiO2-T remained 96%. Besides, the extraction efficiency of uranium on Al2O3-SiO2-T was 72.5% in simulated seawater, which suggested that the Al2O3-SiO2-T was expected to be used for uranium extraction from seawater. Further, the interaction mechanism between Al2O3-SiO2-T and uranium species was studied. The results showed that the electrostatic interaction and complexation played key roles in the adsorption process of Al2O3-SiO2-T to uranium.

Enhanced photoelectrochemical performance of NiO-doped TiO2 nanotubes prepared by an impregnation–calcination method

To improve the photocatalytic activity of TiO2, a series of NiO–TiO2 nanotubes (NTbs) is prepared by impregnating TiO2 nanotubes in a solution of NiCl2·6H2O at different concentrations. Self-organized TiO2 nanotubes are prepared by a two-step anodization process. Scanning electron microscopy images show that large particle agglomerates are formed for higher precursor concentrations, and X-ray energy-dispersive spectroscopy results indicate that the atomic percentages of Ni in the NiO–TiO2 NTbs prepared with precursor concentrations of 100 and 300 mM are 1.95% and 4.23%, respectively. Electronic lifetime measurements show that the recombination rate of photogenerated electron–hole pairs is lower for NiO–TiO2 NTbs compared to that of TiO2. Specifically, the recombination rate of the sample prepared at 50 mM is the lowest, which is associated with the longest electron lifetime. Compared to unmodified TiO2 nanotubes, NiO–TiO2 NTbs exhibit improved results for the photocatalytic degradation of rhodamine B.

The Pozzolanic Activity of the Sediment Treated by the Flash Calcination Method

The dredged sediment has been positioned for years as alternative materials in the construction field. However, it is often necessary to apply a treatment to improve their reactivity and performance. This article aims to study the pozzolanic reactivity of fluvial sediment treated by flash calcination method at different temperatures 650 °C, 750 °C, and 800 °C. The physico-chemical, mineralogical, and environmental characteristics were studied for treated (flash-calcined sediment) and raw sediment. The pozzolanic reactivity of the flash-calcined sediments was estimated with Frattini’s test, isothermal calorimetry test, lime consumption analysis and compressive strength then compared to metakaolin which is considered as the reference. The results of the compressive strength of mortars show the detrimental effect of raw sediment on the development of resistance. Contrary to the raw sediment, the treatment of the sediments by flash calcination activates the pozzolanic reactivity of the clay phases and considerably improves the contribution of the sediments to the development of resistance and the porous structure. Moreover, the sediment calcined at 750 °C gives better properties than those obtained at 650 °C and 800 °C. The result demonstrates the feasibility of using calcined sediments as a pozzolanic mineral addition in a cementitious material.

Characteristic and photocatalytic performance of magnetic photocatalyst β-Bi2O3/MnxZn1−xFe2O4 synthesized by hydrothermal and calcination method

A magnetic photocatalyst [Formula: see text]-Bi2O3/Mn[Formula: see text]Zn[Formula: see text]Fe2O4 (Bi2O3/MZF) was fabricated by hydrothermal and calcination method, and characterized by XRD, FTIR, XPS and SEM, BET and VSM. The photocatalytic efficiency was measured by the degradation experiment of Rhodamine B (RhB). The degradation rate of the optimum sample Bi2O3/MZF (10 wt.%) could reach 96.8% after 3 h under visible light, and was improved significantly compared with pure [Formula: see text]-Bi2O3 due to the larger pore size (11.76 nm) and specific surface area (17.87 m2 ⋅ g[Formula: see text]. Meanwhile, the Bi2O3/MZF (10 wt.%) could be recovered under the external magnetic field due to its high magnetization saturation (9.22 emu ⋅ g[Formula: see text]. After reusing three times, the Bi2O3/MZF could still maintain the excellent photocatalytic activity and structural stability.