Sonophotocatalysis of oxalic acid solution

Sonophotocatalysis of oxalic acid was performed in various atmospheric conditions. Sonophotocatalysis means a coupled reaction of sonolysis and photocatalysis. CO(2), CO and H(2) were obtained. The yield of CO(2) was twice larger than the sum of yields of photocatalysis and sonolysis in an Ar atmosphere. Namely, synergistic effect was observed. Further improvement was observed after pre-sonication. Hydrogen peroxide produced during sonication is a key material for the synergistic effect. In surroundings including O(2), however, synergistic effect could not be observed. The role of ultrasonic waves on the sonophotocatalysis of organic compounds was investigated.     

Treatment of dye wastewater by using photo-catalytic oxidation with sonication

The degradation of Acid Orange 52 in aqueous solutions was investigated by using three processes (photocatalysis, sonolysis, and photocatalysis with sonication). In the case of photocatalysis, although the concentration of Acid Orange 52 decreased to 35% in 480 min, the color of the solution was not disappeared. In the case of sonolysis, it was decomposed completely in 300 min, but the total organic carbon concentration decreased down by only about 13% in 480 min. In the case of photocatalysis with sonication, the concentration of Acid Orange 52 reached to 0 in 240 min and the total organic carbon concentration decreased by about 87% in 480 min. These results indicate that the ultrasonic irradiation enhanced the photocatalytic degradation. The addition of chloride ion (50 ppm) into Acid Orange 52 solution decreased the decomposition efficiency for photocatalysis. In the cases of sonolysis and photocatalysis with sonication, the decomposition efficiency did not change significantly by the addition of chloride ion. These results indicate that chloride ion disturbs the photocatalysis of dye, but the decomposition of dye using the irradiation of ultrasound is not influenced by chloride ion. From these results, it is considered that the photocatalysis with sonication is most effective for the decomposition of dye in the three processes in this study.     

Controllable irregular phenomenon induced by Ag atomic segregation on the melting of (AgPd)561 bimetallic clusters

Here focusing on the very new experimental finding on carbon nanomaterials for solid-state electron mediator applications in Z-scheme photocatalysis, we have investigated different graphene-based nanostructures chemisorbed by various types and amounts of species such as oxygen (O), nitrogen (N) and hydroxyl (OH) and their electronic structures using density functional theory. The work functions of different nanostructures have also been investigated by us to evaluate their potential applications in Z-scheme photocatalysis for water splitting. The N-, O?CN-, and N?CN-chemisorbed graphene-based nanostructures (32 carbon atoms supercell, corresponding to lattice parameter of about 1?nm) are found promising to be utilized as electron mediators between reduction level and oxidation level of water splitting. The O- or OH-chemisorbed nanostructures have potential to be used as electron conductors between H₂-evolving photocatalysts and the reduction level (H⁺/H₂). This systematic study is proposed to understand the properties of graphene-based carbon nanostructures in Z-scheme photocatalysis and guide experimentalists to develop better carbon-based nanomaterials for more efficient Z-scheme photocatalysis applications in the future.     

Degradation of methyl tert-butyl ether in water: effects of the combined use of sonolysis and photocatalysis

The degradation of methyl tert-butyl ether (MTBE) in water was kinetically investigated in a O(2)/Ar 80:20 atmosphere employing either sonolysis at 20 kHz, or photocatalysis on TiO(2) (with 315 nm< lambda(irr) <400 nm), or simultaneous sonolysis and photocatalysis (i.e. sonophotocatalysis), as degradation techniques. In all investigated conditions, MTBE concentration decreased according to a first order rate law; under ultrasound the degradation rate was stirring-dependent. The time profile of the reaction intermediates gave information on the reaction paths prevailing under the different experimental conditions. The energy consumption of the employed degradation techniques was also evaluated, which might be decisive for their practical application.     

脉冲放电等离子体/TiO2协同体系中氧自由基的光谱分析

基于脉冲放电等离子体/TiO2的协同作用效果,研究利用脉冲放电过程中产生的紫外光效应,建立以玻璃珠负载的TiO2膜作为光催化剂的脉冲放电等离子体/TiO2协同体系,并从氧自由基(·O)光谱分析的角度说明脉冲放电等离子体/TiO2光催化的协同作用机理.研究结果表明,·O主要在777 um处形成特征发射光谱,对应跃迁为3p...     

Sonochemical preparation of high surface area MgAl2O4 spinel

High surface area MgAl(2)O(4) has been synthesised by a sonochemical method. Two kinds of precursors were used, alkoxides and nitrates/acetates and in both cases nanostructured MgAl(2)O(4) was obtained. The effect of the addition of a surfactant during the sonication, cetyl trimethyl ammonium bromide, was also investigated. In the case of alkoxides precursors the as-made product is a mixture of hydroxides of aluminium and magnesium, while with nitrates/acetates a gel is obtained after sonication, containing the metal hydroxides and ammonium nitrate. Heating at 500 degrees C transforms the as-made products into MgAl(2)O(4) spinel phase. The surface area is up to 267m(2)/g after treatment at 500 degrees C and 138m(2)/g at 800 degrees C.     

Effect of ultrasound in enantioselective hydrogenation of 1-phenyl-1,2-propanedione: comparison of catalyst activation, solvents and supports

The enantioselective hydrogenation of 1-phenyl-1,2-propanedione was carried out over Pt/Al2O3, Pt/SiO2, Pt/SF (silica fiber), Pt/C catalysts modified with cinchonidine under ultrasonic irradiation. The initial rate, regioselectivity and enantioselectivity were investigated for different catalyst pretreatments, solvents and ultrasonic powers. The ultrasound effects were very catalyst dependent. The sonication significantly enhanced enantioselectivity and activity of the Pt/SF (silica fiber) catalyst. For the other Pt supported catalysts the reaction rate, enantioselectivity and regioselectivity increased moderately. The choice of solvent influenced the impact of ultrasound effect, namely in mesitylene, which has the lowest vapor pressure, the highest ultrasound enhancement was observed. The effect of sonication on catalysts surface was studied by transmission electron microscopy and scanning electron microscopy (SEM). No significant change in the metal particle size distribution due to sonication was observed. However, in the case of the Pt/SF catalyst, acoustic irradiation induced morphological changes on the catalyst particle surface (SEM), which might be the cause for enhancement of the initial reaction rate and enantioselectivity.     

Degradation of organic water pollutants through sonophotocatalysis in the presence of TiO(2)

The degradation of 2-chlorophenol and of the two azo dyes acid orange 8 and acid red 1 in aqueous solution was investigated kinetically under sonolysis at 20 kHz and under photocatalysis in the presence of titanium dioxide particles, as well as under simultaneous sonolysis and photocatalysis, i.e. sonophotocatalysis. The influence on the degradation and mineralisation rates of the initial substrate concentration and of the photocatalyst amount was systematically investigated to ascertain the origin of the synergistic effect observed between the two degradation techniques. The evolution of hydrogen peroxide during kinetic runs was also monitored. Small amounts of Fe(III) were found to affect both the adsorption equilibria on the semiconductor and the degradation paths. Ultrasound may modify the rate of photocatalytic degradation by promoting the deaggregation of the photocatalyst, by inducing the desorption of organic substrates and degradation intermediates from the photocatalyst surface and, mainly, by favouring the scission of the photocatalytically and sonolytically produced H(2)O(2), with a consequent increase of oxidising species in the aqueous phase.     

Study of the Photocatalytic Antimicrobial Activity of Nanocomposites Based on TiO2–Al2O3 under Action of LED Radiation (405 nm) on Staphylococci

Optics and Spectroscopy - We study the photocatalytic activity of nanocomposites based on θ-phase alumina (Al2O3) with different TiO2 concentrations for heterogeneous photocatalysis and...     

Synthesis and characterization of dispersions of ZnCrO4 prepared in AOT stabilized water/heptane microemulsion

Dispersions of zinc chromate (ZnCrO₄) were prepared in H₂O/AOT (sodium bis(2-ethylhexyl sulfosuccinate))/n-heptane water-in-oil (W/O) microemulsion medium with various water pool sizes and precursor concentration both without and with sonication. The formation of ZnCrO₄ in the microemulsion was verified by XRD and FTIR measurements. The absorbance of the dispersions formed in different water pool sizes was studied. Their dimension in the microemulsion medium was determined by the dynamic light scattering method. Enthalpy of formation of ZnCrO₄ in W/O microemulsion medium was measured by isothermal titration calorimetry (ITC). The dimension and morphology of the formed ZnCrO₄ colloidal particles examined by transmission electron microscopy (TEM) were strongly dependent on the water pool size, precursor concentration and sonication.     

Sonochemical preparation of pure t-LaVO4 nanoparticles with the aid of tris(acetylacetonato)lanthanum hydrate as a novel precursor

Herein a simple and fast method is introduced for the synthesis of lanthanum orthovanadate (LaVO₄) nanoparticles under ultrasound irradiation. The effect of tris(acetylacetonato)lanthanum hydrate ([La(acac)₃·3H₂O]) and La(OAc)₃ as two different precursors on the morphology and phase purity of LaVO₄ was investigated. To optimum the particle size of the products, sonication time and the kind of surfactants have been changed. The as-synthesized products were characterized by XRD, FT-IR, SEM, TEM, and EDS. Based on the obtained results, it was found that the size and shape of the sonochemically formed LaVO₄ nanoparticles were dramatically dependent on the sonication time, type of surfactant and lanthanum precursor. According to the XRD results, it was observed that pure tetragonal phase lanthanum orthovanadate (t-LaVO₄) could be obtained only by using [La(acac)₃·3H₂O] as precursor under ultrasound irradiation for 30 min. On the other hand, monoclinic phase lanthanum orthovanadate (m-LaVO₄) with poor crystallinity has been produced by vigorous stirring at room temperature without sonication.     

State of the art and recent advances in the ultrasound-assisted synthesis,exfoliation and functionalization of graphene derivatives

Sonochemistry, an almost a century old technique was predominantly employed in the cleaning and extraction processes but this tool has now slowly gained tremendous attention in the synthesis of nanoparticles (NPs) where particles of sub-micron have been produced with great stability. Following this, ultrasonication techniques have been largely employed in graphene synthesis and its dispersion in various solvents which would conventionally take days and offers poor yield. Ultrasonic irradiation allows the production of thin-layered graphene oxide (GO) and reduced graphene oxide (RGO) of up to 1 nm thickness and can be produced in single layers. With ultrasonic treatment, reactions were made easy whereby graphite can be directly exfoliated to graphene layers. Oxidation to GO can also be carried out within minutes and reduction to RGO is possible without the use of any reducing agents. In addition, various geometry of graphene can be produced such as scrolled graphene, sponge or foam graphene, smooth as well as those with rough edges, each serving its own unique purpose in various applications such as supercapacitor, catalysis, biomedical, etc. In ultrasonic-assisted reaction, deposition of metal NPs on graphene was more homogeneous with custom-made patterns such as core-shell formation, discs, clusters and specific deposition at the edges of graphene sheets. Graphene derivatives with the aid of ultrasonication are the perfect catalyst for various organic reactions as well as an excellent adsorbent. Reactions which used to take hours and days were significantly reduced to minutes with exceedingly high yields. In a more recent approach, sonophotocatalysis was employed for the combined effect of sonication and photocatalysis of metal deposited graphene. The system was highly efficient in organic dye adsorption. This review provides detailed fundamental concepts of ultrasonochemistry for the synthesis of graphene, its dispersion, exfoliation as well as its functionalization, with great emphasis only based on recent publications. Necessary parameters of sonication such as frequency, power input, sonication time, type of sonication as well as temperature and dual-frequency sonication are discussed in great length to provide an overview of the resultant graphene products.     

新型复合电极对偶氮染料分子的光催化降解

介绍了具有合成H2 O2 和光催化性能的双功能新型复合电极 ,并用X射线衍射、扫描电镜等方法进行了表征 .双功能复合电极是将TiO2 光催化剂负载在活性碳 (AC)和具有合成H2 O2 性能的新型载体空气电极上形成的 .在复合电极作阴极的光反应器中 ,·OH和TiO2 光催化剂的存在实现了光化学氧化与光催化氧化在同一电极 /溶液界面上的联合作用 .实验结果表明 ,复合电极对提高偶氮染料分子活性艳红 (K 2BP)的氧化降解速度起了重要作用 ,仅反应 3min ,脱色率可达 4 9% ;反应 80min ,偶氮染料分子COD去除率可达 4 7% .     

Effects of dissolved gas species on ultrasonic degradation of (4-chloro-2-methylphenoxy) acetic acid (MCPA) in aqueous solution

Sonochemical degradation of MCPA ((4-chloro-2-methylphenoxy) acetic acid) in dilute aqueous solutions was studied using ultrasound with a frequency of 500 kHz. The effect of gas atmosphere on MCPA degradation was investigated in nitrogen (N(2)), air (O(2)/N(2)), oxygen (O(2)), argon (Ar) and Ar/O(2) (60/40% v/v) atmospheres. For sonochemical degradation of MCPA in N(2), air (O(2)/N(2)), O(2) and Ar atmospheres, the rate enhancement of MCPA decomposition by sonolysis was found to be more effective in an O(2)-enriched atmosphere compared to Ar atmosphere. It was considered that a higher amount of oxidants was formed in a higher O(2) partial pressure, which accelerated MCPA decomposition in a radical reaction system. On the other hand, both dechlorination and total organic carbon (TOC) removal rates were higher in Ar atmosphere, compared to those in O(2)/N(2) atmosphere. It was found that, MCPA was most effectively decomposed by sonication in Ar/O(2) (60/40% v/v) atmosphere, with higher rates of decomposition, dechlorination and TOC removal.     

Kinetics of nitrous acid formation in nitric acid solutions under the effect of power ultrasound

Sonochemical nitrous acid formation was investigated in 0.1-4.0 mol dm(-3) aqueous nitric acid solutions under the effect of power ultrasound with 20 kHz frequency. HNO2 steady-state concentration was obtained under long-time sonication; the excess HNO2 formed is decomposed and evoluted from the solution as NO and NO2 gases. The HNO2 steady-state concentration and the HNO2 initial formation rate depend linearly on the HNO3 concentration and acoustic intensity (1.8-3.5 W cm(-2)) and decrease with rising temperature in the range 21-50 degrees C. The HNO2 formation rate depends on the type of saturating gas as follows: Ar > N2 > He > air. NO and O2 are the major gaseous products of HNO3 sonication. The NO2 accumulation of in the gas phase is observed only when the decomposition of HNO2 formed becomes noticeable. The gaseous products formation rates depend on the HNO3 concentration, acoustic intensity and the type of saturating gas. The mechanism of HNO2 sonochemical formation is assumed to be the thermal decomposition of HNO3 in the gaseous vicinity of collapsing bubbles or in the overheated liquid reaction zone surrounding the cavitational bubbles.     

磁载光催化剂ZnO/ SiO2/γ-Fe2O3的光催化性能

本文采用液相沉积法制备出了纳米SiO2/γ-Fe2O3复合粒子,在其表面负载ZnO, 从而得到了易于磁性固液分离的磁载光催化剂ZnO/SiO2/γ-Fe2O3, 并通过XRD和TEM等测试技术对样品进行了表征。以可溶性染料亚甲基兰等为降解对象, 研究了磁载光催化剂ZnO/SiO2/γ-Fe2O3在紫外光下的光催化活性。结果表明, 在γ-Fe2O3和ZnO之间包覆一层无定形SiO2可使催化剂降佳率由20.76%提高到95.63%,并且该磁载光催化剂对染料有较好的降解效果, 在三次循环使用后仍能保持较好的光催化性能.     

Sonophotocatalysis in advanced oxidation process: A short review

Sonophotocatalysis involves the use of a combination of ultrasonic sound waves, ultraviolet radiation and a semiconductor photocatalyst to enhance a chemical reaction by the formation of free radicals in aqueous systems. Researchers have used sonophotocatalysis in a variety of investigations i.e. from water decontamination to direct pollutant degradation. This degradation process provides an excellent opportunity to reduce reaction time and the amount of reagents used without the need for extreme physical conditions. Given its advantages, the sonophotocatalysis process has a futuristic application from an engineering and fundamental aspect in commercial applications. A detailed search of published reports was done and analyzed in this paper with respect to sonication, photocatalysis and advanced oxidation processes.     

纳米TiO2光催化氧化活性嫩黄废水

以TiCl4为原料,采用可控水解法制备了TiO2光催化剂。以活性嫩黄为模拟污染源,紫外灯为光源,考察了溶液pH值、催化剂用量、反应时间和催化剂循环次数等对纳米二氧化钛光催化降解活性嫩黄的影响。实验结果表明,pH 5.5,催化剂投加量为2.0g/L,光催化反应时间为60min时,色度及化学需氧量（COD）去除率均较高。TiO2光催化剂重复使用在5次以内,其催化活性基本不变。     

Ultrasound assisted PTC catalyzed saponification of vegetable oils using aqueous alkali

A few vegetable oils were saponified using aqueous KOH and different PTCs at room temperature in the presence of ultrasound. The extent of saponification was studied using the saponification value as a reference. Optimizations of various parameters such as time, selection of PTC, quantity of PTC, quantity of KOH and quantity of water were carried out using soyabean oil as a sample oil under sonication with stirring. To study the effect of ultrasound, the saponification was also carried out at 35 +/- 2 degrees C under different conditions, namely stirring, sonication, stirring and sonication, and heating at 100 degrees C. It was found that the heterogeneous liquid-liquid phase saponification of different vegetable oils using aq. KOH/CTAB was remarkably accelerated at 35 +/- 2 degrees C in the presence of ultrasound along with stirring.     

Inactivation of Escherichia coli by ultrasonic irradiation

Ultrasonic inactivation of Escherichia coli XL1-Blue has been investigated by high-intensity ultrasonic waves from horn type sonicator (27.5 kHz) utilizing the "squeeze-film effect". The amplitude of the vibration face contacting the sample solution was used as an indication of the ultrasonic power intensity. The inactivation of the E. coli cells by ultrasonic irradiation shows pseudo first-order behavior. The inactivation rate constant gradually increased with increasing amplitude of the vibration face and showed rapid increase above 3 microm (p-p). In contrast, the H2O2 formation was not observed below 3 microm (p-p), indicating that the ultrasonic shock wave might be more important than indirect effect of OH radicals formed by ultrasonic cavitation in this system. The optimal thickness of the squeeze film was determined as 2 mm for the E. coli inactivation. More than 99% of E. coli cells was inactivated within 180-s sonication at the amplitude of 3 microm (p-p) and 2 mm of the thickness of the squeeze film.