Photodegradation of benzene,toluene, ethylbenzene and xylene by fluidized bed gaseous reactor with TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> photocatalysts

The photodegradation of BTEX (benzene, toluene, ethylbenzene and xylene) in a photocatalytic fluidized bed reactor with TiO₂/SiO₂ was investigated. The TiO₂ film was prepared using the sol-gel method and coated onto silica-gel powder. The effects of the superficial gas velocity and SiO₂ size on the photodegradation of BTEX were examined in a fluidized bed reactor. At steady-state operation, above 79, 79, 99, 98, and 98% removal efficiencies were achieved for benzene, toluene, ethylbenzene, m, p-xylene and o-xylene, respectively, under optimal conditions (2.0 U _mf of superficial gas velocity and 1.43 of height/diameter ratio). The reaction product such as CO₂ was detected and intermediate products such as benzaldehyde, malonic acid, acetaldehyde, and formic acid were identified from the photocatalytic reaction. Also, small amounts of benzoic acid and benzyl alcohol were found through analyzing the intermediate species adsorbed on the photocatalysts. The experimental results can lead to the development of an efficient photocatalytic treatment system that utilizes solar energy and TiO₂/SiO₂ photocatalysts.     

Synthesis of LLDPE/TiO<Subscript>2</Subscript> nanocomposites by in situ polymerization with zirconocene/dMMAO catalyst: effect of [Al]/[Zr] ratios and TiO<Subscript>2</Subscript> phases

This article reveals the dependence of crystalline phases in titania on the intrinsic activity during in situ polymerization of ethylene/1-hexene using the zirconocene/dMMAO catalyst to produce LLDPE/TiO₂ nanocomposites. First, the TiO₂ nanoparticles having different crystalline phases were employed as the nanofillers by impregnation with dMMAO to obtain dMMAO/TiO₂. Then, copolymerization of ethylene/1-hexene using zirconocene catalyst was performed in the presence of dMMAO/TiO₂. It was found that the catalytic activity derived from the anatase TiO₂ (A) was about four times higher than that obtained from the rutile TiO₂ (R). This was likely due to higher intrinsic activity of the active species present on the TiO₂ (A). In addition, increased [Al]_dMMAO/[Zr]_cat ratios apparently resulted in enhanced activities for both TiO₂ (A) and TiO₂ (R). However, the TiO₂ (R) showed less deactivation upon increased [Al]_dMMAO/[Zr]_cat ratios. This can be attributed to strong interaction between dMMAO and TiO₂ (R) as proven by the TGA measurement. The microstructure of the LLDPE/TiO₂ obtained was found to be random copolymer for both TiO₂ (A) and TiO₂ (R).     

Facile Synthesis and Tensile Behavior of TiO<Subscript>2</Subscript> One-Dimensional Nanostructures

High-yield synthesis of TiO₂ one-dimensional (1D) nanostructures was realized by a simple annealing of Ni-coated Ti grids in an argon atmosphere at 950 °C and 760 torr. The as-synthesized 1D nanostructures were single crystalline rutile TiO₂ with the preferred growth direction close to [210]. The growth of these nanostructures was enhanced by using catalytic materials, higher reaction temperature, and longer reaction time. Nanoscale tensile testing performed on individual 1D nanostructures showed that the nanostructures appeared to fracture in a brittle manner. The measured Young’s modulus and fracture strength are ~56.3 and 1.4 GPa, respectively.     

Electrochemical treatment of ammonia in wastewater by RuO<Subscript>2</Subscript>–IrO<Subscript>2</Subscript>–TiO<Subscript>2</Subscript>/Ti electrodes

This study investigated the removal of ammonia in wastewater by an electrochemical method using titanium electrodes coated with ruthenium and iridium (RuO₂–IrO₂–TiO₂/Ti) with low chlorine evolution over-voltage. The effects of operating parameters, including chloride ion concentration, current density and initial pH, were also investigated. The results were evaluated primarily by considering the efficiency of the elimination of NH₄⁺-N. The removal of ammonia by electrochemical oxidation mainly resulted from the indirect oxidation effect of chlorine/hypochlorite produced during electrolysis. The direct anodic oxidation efficiency of ammonia was less than 5%, and the current efficiency was less than 10%. The ammonia removal followed pseudo-first-order kinetics. The electrochemical process can be applied successfully as a final polishing step, or as an alternative method to biological nitrification. The process seems to be most beneficial for small coastal cities     

Degradation kinetics of recalcitrant organic compounds in a decontamination process with UV/H<Subscript>2</Subscript>O<Subscript>2</Subscript> and UV/H<Subscript>2</Subscript>O<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> processes

In this study, degradation aspects and kinetics of organics in a decontamination process were considered in the degradation experiments of advanced oxidation processes (AOP),i.e., UV, UV/H₂O, and UV/H₂O,/TiO₂ systems. In the oxalic acid degradation with different H₂O₂ concentrations, it was found that oxalic acid was degraded with the first order reaction and the highest degradation rate was observed at 0.1 M of hydrogen peroxide. Degradation rate of oxalic acid was much higher than that of citric acid, irrespective of degradation methods, assuming that degradation aspects are related to chemical structures. Of methods, the TiO₂ mediated photocatalysis showed the highest rate constant for oxalic acid and citric acid degradation. It was clearly showed that advanced oxidation processes were effective means to degrade recalcitrant organic compounds existing in a decontamination process.     

Combustion of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript>/Al thermit mixtures in steel tubes

Explored was the combustion of Fe₂O₃/TiO₂/Al thermit mixtures in steel tubes upon variation in green composition and with special emphasis on the dependence of combustion temperature T _c and burning velocity U on reaction heat Q. Special attention was given to incompleteness of combustion for compositions with low Q.     

Some characteristics of heat-resisting concretes modified by SiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript> nanoparticles

Nanoparticles of SiO₂ or TiO₂ have been added in the preparation of heat-resisting concretes of two types. The major technical and chemical characteristics have been determined. Features have been found in some of the technological operations in making the concretes of both types, and also aspects of the physicomechanical properties. Higher chemical stability has been found for heat-resisting concrete containing TiO₂ nanoparticles in an NaOH solution.     

Effect of TiO<Subscript>2</Subscript> loading on the activity of V/TiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> in the catalytic oxidehydrogenation of ethylbenzene with carbon dioxide

TiO₂-Al₂O₃ mixed oxides with different compositions ranging from 40wt-% to 95wt-% of TiO₂ were prepared by sol-gel method and impregnated with different amounts of VO _x . Supports and catalysts were characterized by X-ray diffraction (XRD), physisorption, temperature preprogrammed reduction (H₂-TPR), and ammonia temperature programmed desorption (NH₃-TPD). TiO₂ content in the support had obvious effect on the crystal structure, texture characteristic, acid property, and catalytic activity in dehydrogenation of ethylbenzene (EB) with carbon dioxide. The highest catalytic activity was acquired when the TiO₂ content was 50 wt-%.     

Li<Subscript>2</Subscript>Cu<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> + SiO<Subscript>2</Subscript>/Ti compositions for the catalytic afterburning of diesel soot

Two methods were used to obtain a catalytically active oxide coating on the surface of titanium for the catalytic afterburning of diesel soot: plasma electrochemical formation of an oxide film on the surface of titanium and extraction pyrolytic deposition of the Li₂Cu₂(MoO₄)₃ compound. The Li₂Cu₂(MoO₄)₃/TiO₂ + SiO₂/Ti compositions synthesized by the single-step extraction pyrolytic treatment of the oxidized surface of titanium ensured a high burning rate of soot of ∼300°C. The subsequent deposition of Li₂Cu₂(MoO₄)₃ lowers the activity of the catalyst, due probably to the growth of molybdate phase crystallites and the filling of open oxide film pores. Double lithium-copper molybdate is able to reduce appreciably the concentration of CO in the oxidation products of soot. The advantages of these methods are the possibility of forming high-cohesion durable coatings on surfaces of any complexity, the simplicity of their implementation, and high productivity and low cost. The obtained results can be recommended for use in developing methods for creating composite coatings on catalytic soot filters.     

Synthesis and Electrochemical Performance of Spheroid LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> in the Electrolyte Modified by Ethylene Sulfate and Methylene Methanedisulfonate

In this study, spheroid LiNi_1/3Co_1/3Mn_1/3O₂ (NCM111) cathode material were synthesized using LiOH with Ni_0.5Co_0.2Mn_0.3(OH)₂ precursor by a simple solid-state reaction, and characterized by X-ray diffraction and scanning electron microscopy. Electrochemical behavior of NCM111 was investigated by electrochemical impedance spectroscopy (EIS) combining with cyclic voltammogram (CV) and charge/discharge test in the 1 M LiPF₆-EC:EMC electrolyte with ethylene sulfate (DTD) and methylene methanedisulfonate (MMDS) additives either singly or in combination with high cutoff voltage of 3.0–4.5 V at room temperature of 25 °C or elevated temperature of 55 °C. It was found that DTD additive can increase the initial coulombic efficiency of NCM111, and the spheroid NCM111 can obtain the maximum initial discharge capacity of 177.81 mAh/g with the 2 wt% DTD, and keep 92.29% capacity retention after 80 cycles. The MMDS additives would decrease the initial discharge capacity of the NCM111, and enhance significantly long cycle life of the NCM111 with the capacity retention of 99.23% over 80 cycles at high voltage of 4.5 V. The additive combination 2 wt% DTD?+?1 wt% MMDS was an optimal additive combination, demonstrating the 102.2% capacity retention over 80 cycles at room temperature and the 94.2% capacity retention over 70 cycles at elevated temperature of 55 °C. EIS results revealed that the additive blend of 2 wt% DTD?+?1 wt% MMDS can drastically lower the kinetics impedance and suppress the growth rate of R _ct for the NCM111 electrode.     

Synthesis and characterization of porous TiO<Subscript>2</Subscript> with wormhole-like framework structure

A fast and reliable synthetic route for preparing contaminant-free porous TiO₂ with a wormhole-like framework and close packed macropores is demonstrated based on a sol-gel process involving acid hydrolysis of an alkoxide in the presence of a cationic surfactant. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements have been used to characterize the porous structure and the crystallinity. The XRD patterns, TEM and scanning electron microscopy (SEM) images confirm that these materials have disordered wormhole-like topology with close-packed nearly hexagonal macropores. The mesopore diameters and surface area of titanium dioxide, evaluated from the N₂-sorption isotherms, indicate average pore diameters of about 7 and 6 nm and surface areas of about 100 and 335 m²/g, for as-prepared and calcined samples at 400°C.     

Uniform color coating of multilayered TiO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> films by atomic layer deposition

Thin film optics, based on light interference characteristics, are attracting increasing interest because of their ability to enable a functional color coating for various applications in optical, electronic, and solar industries. Here, we report on the dependence of coloring characteristics on single-layer TiO₂ thicknesses and alternating TiO₂/Al₂O₃ multilayer structures prepared by atomic layer deposition (ALD) at a low growth temperature. The ALD TiO₂ and Al₂O₃ thin films were studied at a low growth temperature of 80°C. Then, the coloring features in the single-layer TiO₂ and alternating TiO₂/Al₂O₃ multilayers using both the ALD processes were experimentally examined on a TiN/cut stainless steel sheet. The Essential Macleod software was used to estimate and compare the color coating results. The simulation results revealed that five different colors of the single TiO₂ layers were shown experimentally, depending on the film thickness. For the purpose of highly uniform pink color coating, the film structures of TiO₂/Al₂O₃ multilayers were designed in advance. It was experimentally demonstrated that the evaluated colors corresponded well with the simulated color spectrum results, exhibiting a uniform pink color with wide incident angles ranging from 0° to 75°. This article advances practical applications requiring highly uniform color coatings of surfaces in a variety of optical coating areas with complex topographical structures.     

Assessment of Microwave/UV/O<Subscript>3</Subscript> in the Photo-Catalytic Degradation of Bromothymol Blue in Aqueous Nano TiO<Subscript>2</Subscript> Particles Dispersions

In this study, a microwave/UV/TiO₂/ozone/H₂O₂ hybrid process system, in which various techniques that have been used for water treatment are combined, is evaluated to develop an advanced technology to treat non-biodegradable water pollutants efficiently. In particular, the objective of this study is to develop a novel advanced oxidation process that overcomes the limitations of existing single-process water treatment methods by adding microwave irradiation to maximize the formation of active intermediate products, e.g., OH radicals, with the aid of UV irradiation by microwave discharge electrodeless lamp, photo-catalysts, and auxiliary oxidants. The results of photo-catalytic degradation of BTB showed that the decomposition rate increased with the TiO₂ particle dosages and microwave intensity. When an auxiliary oxidant such as ozone or hydrogen peroxide was added to the microwave-assisted photo-catalysis, however, a synergy effect that enhanced the reaction rate considerably was observed.     

Synthesis and Cytotoxicity of Y<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanoparticles of Various Morphologies

As the field of nanotechnology continues to grow, evaluating the cytotoxicity of nanoparticles is important in furthering their application within biomedicine. Here, we report the synthesis, characterization, and cytotoxicity of nanoparticles of different morphologies of yttrium oxide, a promising material for biological imaging applications. Nanoparticles of spherical, rod-like, and platelet morphologies were synthesized via solvothermal and hydrothermal methods and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), light scattering, surface area analysis, thermogravimetric analysis (TGA), and zeta potential measurements. Nanoparticles were then tested for cytotoxicity with human foreskin fibroblast (HFF) cells, with the goal of elucidating nanoparticle characteristics that influence cytotoxicity. Cellular response was different for the different morphologies, with spherical particles exhibiting no cytotoxicity to HFF cells, rod-like particles increasing cell proliferation, and platelet particles markedly cytotoxic. However, due to differences in the nanoparticle chemistry as determined through the characterization techniques, it is difficult to attribute the cytotoxicity responses to the particle morphology. Rather, the cytotoxicity of the platelet sample appears due to the stabilizing ligand, oleylamine, which was present at higher levels in this sample. This study demonstrates the importance of nanoparticle chemistry on in vitro cytotoxicity, and highlights the general importance of thorough nanoparticle characterization as a prerequisite to understanding nanoparticle cytotoxicity.     

Preparation and Characterization of Mesoporous MoO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> Composite with High Surface Area by Self-Supporting and Ammonia Method

Abstract  

A mesoporous MoO₃/TiO₂ composite was prepared from titanate derivative by consecutive self-supporting and ammonia method. All samples were characterized by X-ray Diffraction, N₂ adsorption–desorption, Raman Spectra and Field-Emission Scanning Electron Microscopy. The results showed that mesoporous MoO₃/TiO₂ composite had a higher surface area (173 m²/g) and a better MoO₃ dispersion than that prepared by traditional impregnation (90 m²/g). As for hydrodesulfurization tests, mesoporous MoO₃/TiO₂ composite in this case presented a better catalytic performance, attributed to its high surface area and good dispersion of MoO₃. It can be found that self-supporting played a key role in preparing mesoporous MoO₃/TiO₂ composite with high surface area. Additionally, aqueous ammonia could effectively dissolve excess MoO₃, which helped to obtain mesoporous MoO₃/TiO₂ composite with better dispersion of MoO₃.