Effect of coal ash on sonochemical degradation of phenol in water

The influences of coal ash on the degradation of phenol in water were investigated under the stirring or ultrasonic irradiation conditions. Phenol solution (10mg/L, 100mL) was sonicated at 200 kHz and 200 W with or without coal ash (53-106 microm in particle size and concentration of 0.0-1.5 wt%). It was found that the sonochemical degradation of phenol in the presence of coal ash was faster than that in the absence of coal ash, and the optimum amount of coal ash was a maximum at 0.4-0.6 wt%. It was confirmed that the phenol degradation did not occur by the addition of hydrogen peroxide and nitric acid under the stirring conditions. The sonochemical degradation with coal ash was depressed by the addition of tertiary butyl alcohol as a radical scavenger. These results indicated that the coal ash accelerated the phenol degradation due to the increase in the amount of hydroxyl radicals under the ultrasonic irradiation. Since the coal ash used had a porous and uneven surface, which was observed by SEM, it was assumed that the coal ash led to the increase in the nucleation site for cavitation bubble due to its surface roughness.     

The effect of pH on sonochemical degradation of hydrazine

The degradation of hydrazine (N(2)H(4)) with concentrations of 0.1 and 1.0 mmol/L was investigated as a function of pH under the stirring (300 rpm) and ultrasonic irradiation (200 kHz, 200 W) conditions. It was found that the hydrazine degradation depended greatly upon pH under the ultrasonic irradiation condition, while it did not take place over the whole pH range (0.8-9) under the stirring condition. The hydrazine degradation was suppressed by the addition of tertial butyl alcohol (t-BuOH) known as a scavenger of OH radicals. This result suggested that OH radicals played an important role in the hydrazine degradation. The pH dependence of the hydrazine degradation was discussed in terms of a dissociating form of hydrazine depending upon pH and the effect of OH radicals.     

燃煤底灰-微波法降解亚甲基蓝的研究

燃煤底灰中含有丰富的金属,这些金属在微波作用下可以对有机物进行有效降解,燃煤底灰-微波法降解亚甲基蓝溶液主要是通过羟基自由基来降解有机物的。底灰中的金属及稀有金属可以作为深度氧化有机物的催化剂,可降低处理成本、减少环境污染。考查了燃煤底灰用量、H₂O₂用量、以及微波时间对亚甲基蓝降解效率的影响,并测定了亚甲基蓝溶液处理前后的紫外可见光谱。结果表明,亚甲基蓝在燃煤底灰与H₂O₂微波条件下降解率接近100%。燃煤底灰的用量增加可以加快反应进程,增加亚甲基蓝的降解;H₂O₂的增加可以提供更多的·OH,加快反应进程,但当增加到一定量后,对反应进程的影响减弱;微波时间的加长可以提高反应温度,促使亚甲基蓝完全降解。对于0.125 g·L-1的亚甲基蓝,加入1.0 g燃煤底灰、5 mL H₂O₂在中温微波下反应4 min即可全部降解。     

光谱法研究纳米二氧化硅(SiO_2)催化超声波照射对牛血清白蛋白(BSA)的损伤

利用紫外-可见(Uv-Vis)光谱和荧光光谱研究了超声波照射激活纳米二氧化硅(SiO2)粒子对牛血清白蛋白(BSA)分子的损伤,并考查了超声波照射时间、纳米SiO2粉末加入量、溶液酸度和超声波照射功率等因素对BSA分子损伤程度的影响.结果表明,对于体系温度为(37.0±0.2)℃和浓度为1.0×10-5mol·-1的BSA溶液,UV-Vis光谱显示,随着超声波照射时间,纳米SiO2粉末加入量,溶液pH值和照射功率的增大呈现出越来越明显的增色效应.然而,BSA溶液的荧光光谱却随着上述因素的增大呈现出越来越明显的猝灭现象.此外,还初步探讨了超声波照射激活纳米siO2粒子对BSA分子损伤的机理,认为是声致发光或高热激发使纳米siO2粒子产生·OH自由基,进而损伤溶液中的BSA分子.这一研究结果对声催化方法应用于临床治疗肿瘤以及纳米药物的开发具有一定的指导意义.     

Sonocatalytic facilitation of hydroxyl radical generation in the presence of TiO2

The generation of hydroxyl (OH) radicals was investigated during ultrasonic irradiation and in the presence of TiO(2). The effect of TiO(2) on an ultrasonic system's oxidation power was evaluated by examining the oxidation of salicylic acid. The generation of the salicylic acid derivatives, 2,3-dihydroxybenzoic acid (DHBA) and 2,5-DHBA, was measured by high-performance liquid chromatography coupled with electrochemical detection under different experimental conditions. The presence of TiO(2) enhanced the generation of DHBA during ultrasonic irradiation, thus indicating a higher oxidation power in the ultrasonic system. Al(2)O(3) also increased the generation of DHBA during irradiation; however, the effect of TiO(2) was found to be higher than that of Al(2)O(3). The addition of OH radical scavengers such as dimethylsulfoxide (DMSO), methanol and mannitol significantly suppressed the production of DHBA, and DMSO was found to have the highest suppressive effect among all scavengers. The effects of dissolved gases on the generation of OH radicals were further studied, and their power was found to be in the order Xe > Ar > O(2) > N(2). The degassing of the irradiation solution completely suppressed the generation of OH radicals. These results indicate that the presence of TiO(2) accelerates the generation of OH radicals during ultrasonic irradiation, and that the process may be mediated through the induction of cavitation bubbles in irradiating solutions.     

Sonochemical degradation of chlorophenols in water

Sonochemical degradation of dilute aqueous solutions of 2-, 3- and 4-chlorophenol and pentachlorophenol has been investigated under air or argon atmosphere. The degradation follows first-order kinetics in the initial state with rates in the range 4.5-6.6 microM min-1 under air and 6.0-7.2 microM min-1 under argon at a concentration of 100 microM of chlorophenols. The rate of OH radical formation from water is 19.8 microM min-1 under argon and 14.7 microM min-1 under air in the same sonolysis conditions. The sonolysis of chlorophenols is effectively inhibited, but not completely, by the addition of t-BuOH, which is known to be an efficient OH radical scavenger in aqueous sonolysis. This suggests that the main degradation of chlorophenols proceeds via reaction with OH radicals; a thermal reaction also occurs, although its contribution is small. The addition of appropriate amounts of Fe(II) ions accelerates the degradation. This is probably due to the regeneration of OH radicals from hydrogen peroxide, which would be formed from recombination of OH radicals and which may contribute a little to the degradation. The ability to inhibit bacterial multiplication of pentachlorophenol decreases with ultrasonic irradiation.     

Ultrasonically initiated emulsion polymerization of styrene in the presence of Fe2+

Ultrasonically initiated emulsion polymerization of styrene was carried out in the presence of Fe(2+). The addition of a small amount of Fe(2+) markedly enhanced the polymerization rate of styrene. In the presence of 50 microM Fe(2+), the conversion of monomer in the reaction time of 60 min was 2.4 times as high as that in the absence of Fe(2+). The increase in the polymerization rate was due to higher concentration of hydroxyl (*OH) radicals generated via Fenton reaction of Fe(2+) with hydrogen peroxide (H(2)O(2)), which was proved by a lower amount of H(2)O(2) in Fe(2+) aqueous solution compared with that in pure water during ultrasonic irradiation. However, the addition of excessive Fe(2+) had no further accelerating effect on the polymerization rate due to the reduction of *OH radicals by Fe(2+). So it is an effective way to add an appropriate amount of Fe(2+) to accelerate ultrasonically initiated emulsion polymerization of styrene.     

Sonochemical and photosonochemical degradation of 4-chlorophenol in aqueous media

The degradation of 4-chlorophenol (4-CP) in aqueous media by 516 kHz ultrasonic irradiation was investigated in order to clarify the degradation mechanism. The degradation of concentrated 4-CP solution by means of ultrasound, UV irradiation and their combined application was also studied. The obtained results indicate that *OH radical are the primary reactive species responsible for 4-CP ultrasonic degradation. Very little 4-CP degradation occurs if the sonolysis is carried out in the presence of the *OH radical scavenger tert-butyl alcohol, also indicating that little or no pyrolysis of the compound occurs. The dominant degradation mechanism is the reaction of substrate with *OH radicals at the gas bubble-liquid interface rather than high temperature direct pyrolysis in ultrasonic cavities. This mechanism can explain the lower degradation rate of the ionic form of 4-CP that is partly due to the rapid dissociation of *OH radicals in alkaline solutions. The sonochemical destruction of concentrated 4-CP aqueous solution is obtained with low rate. Coupling photolysis with ultrasound irradiation results in increased efficiency compared to the individual processes operating at common conditions. Interestingly, the photosonochemical decomposition rate constant is greater than the additive rate constants of the two processes. This may be the result of three different oxidative processes direct photochemical action, high frequency sonochemistry and reaction with ozone produced by UV irradiation of air, dissolved in liquid phase because of the geyser effect of ultrasound streaming. Additionally, the photodecomposition, at 254 nm, of hydrogen peroxide produced by ultrasound generating *OH radical can partly explain the destruction enhancement.     

Sonochemical synthesis of monodispersed magnetite nanoparticles by using an ethanol–water mixed solvent

The magnetite nanoparticles were synthesized in an ethanol–water solution under ultrasonic irradiation from a Fe(OH)₂ precipitate. XRD, TEM, TG, IR, VSM and UV/vis absorption spectrum were used to characterize the magnetite nanoparticles. It was found that the formation of magnetite was accelerated in ethanol–water solution in the presence of ultrasonic irradiation, whereas, it was limited in ethanol–water solution under mechanical stirring. The monodispersibility of magnetite particles was improved significantly through the sonochemical synthesis in ethanol–water solution. The magnetic properties were improved for the samples synthesized under ultrasonic irradiation. This would be attributed to high Fe²⁺ concentration in the magnetite cubic structure.     

Ultrasonic coal-wash for de-sulfurization

Coal is the one of the world's most abundant fossil fuel resources. It is not a clean fuel, as it contains ash and sulfur. SOx as a pollutant are a real threat to both the ecosystem and to human health. There are numerous de-sulfurization methods to control SO(2) emissions. Nowadays, online flue gas de-sulfurization is being used as one such method to remove sulfur from coal during combustion. The biggest disadvantage associated with this method is formation of by-products (FGD gypsum). A way for effective usage of FGD gypsum has not yet been found. This will lead to acute and chronic effects to humans as well as plants. Power ultrasound can be used for the beneficiation of coal by the removal of sulfur from coal prior to coal combustion. The main effects of ultrasound in liquid medium are acoustic cavitation and acoustic streaming. The process of formation, growth and implosion of bubbles is called cavitation. Bulk fluid motion due to sound energy absorption is known as acoustic streaming. In addition, coupling of an acoustic field to water produces OH radicals, H(2)O(2), O(2), ozone and HO(2) that are strong oxidizing agents. Oxidation that occurs due to ultrasound is called Advanced Oxidation Process (AOP). It converts sulfur from coal to water-soluble sulphates. Conventional chemical-based soaking and stirring methods are compared here to ultrasonic methods of de-sulfurization. The main advantages of ultrasonic de-sulfurization over conventional methods, the mechanism involved in ultrasonic de-sulfurization and the difference between aqueous-based and solvent-based (2N HNO(3), 3-volume percentage H(2)O(2)) de-sulfurization are investigated experimentally.     

Ultrasonic waste-water treatment: incidence of ultrasonic frequency on the rate of phenol and carbon tetrachloride degradation

Organic compounds in aqueous solution submitted to an ultrasonic irradiation behave differently according to their physical and chemical properties. In this work, hydrogen peroxide formation and the degradation rate of phenol and carbon tetrachloride have been studied at different frequencies: 20, 200, 500 and 800 kHz. Whatever the frequency, it is easier to decompose CCl₄ than phenol by means of ultrasonic wave. It is shown that the rates of reactions involving hydroxyl radicals (hydrogen peroxide formation and phenol degradation) have a maximum value at 200 kHz. The best yield observed at 200 kHz for the phenol degradation may be the result of better HO radicals availability outside of the bubble of cavitation. The degradation rate for carbon tetrachloride which decomposes into the bubble of cavitation increases with frequency. Calculating the reaction rate for one ultrasonic period shows that the efficiency of one ultrasonic cycle decreases as frequency increases.     

Synthesis and sonocatalytic property of rod-shape Sr(OH)2·8H2O

A novel rod-shape sonocatalyst Sr(OH)₂·8H₂O was prepared by a facile precipitation method, and characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy and UV–vis absorption spectroscopy. Comparative sonocatalytic degradation experiments were carried out in different conditions under ultrasonic irradiation by using rhodamine B (RhB) as the model substrate, indicating that Sr(OH)₂·8H₂O was highly sonocatalytic. Total organic carbon experiment demonstrated Sr(OH)₂·8H₂O with mass mineralization of organic carbon. The effects of catalyst amount, initial RhB concentration and ultrasonic energy of degradation were investigated, and the sonocatalyst could be reused 5 times without significant loss of activity. Furthermore, the potent degrading capability was ascribed to ultrasonic cavitation producing flash light/energy which generated radicals (e.g., OH) with high oxidation activity.     

Spatiotemporal measurement using L-band ESR-CT system for water sonolysis in the presence of 1-Hydroxy-2,2,5,5-tetramethyl-3-imidazoline-3-oxide

When using ESR to measure the radicals generated by ultrasound, it is necessary to extract a solution and place it in the ESR system. To avoid this process, we incorporated an ultrasonic reaction cell in an L-band ESR-CT system, producing a system that allows the detection of the concentration of radicals during ultrasonic irradiation. This system was used to measure the time and space dependences of OH radicals generated by ultrasonic irradiation. When a 10 ml aqueous solution of 1-hydroxy-2,2,5,5-tetramethyl-3-imidazoline-3-oxide (HTIO) was irradiated with ultrasound, it was found that the generation of radicals was clearly shown in a CT image after a period of 10 min. It was also found that continued irradiation resulted in an increased concentration of radicals. In addition to this system, an X-band ESR system was also used to measure the concentration of OH radicals generated, and the results of both systems were then compared. Both results are very similar, showing that the proposed system, which was realized by incorporating an ultrasonic irradiation cell in the L-band ESR-CT system, operated properly. Because this system allows the measurement of sonochemical reactions in an opaque cell or an opaque solution such as blood and industrial wastewater, it is a very useful measurement system for achieving the applying of sonochemistry to the medical engineering field.     

Facile sonochemical synthesis of novel pyrazolyne derivates at ambient conditions

Claisen–Schmidt condensation reaction of 4-acetamidoacetophenone with aromatic aldehydes under ultrasonic irradiation affords acetylaminochalcones (yields: 71–90%) which also under ultrasonic irradiation and in the presence of sodium acetate and acetic acid aqueous undergo facile and clean cyclocondensation with hydrazine to afford 3-(4-acetamidophenyl)-5-(aryl)-1-H-pyrazolines. The pyrazolines were obtained in good to excellent yields (81–89%), and were characterized by conventional spectral data. The work-up is simple and the results obtained indicate that, unlike classical heating, ultrasonic irradiation results in higher yields, shorter reaction times (1.5–2.3 h) and milder conditions.     

Investigation on the sonocatalytic degradation of acid red B in the presence of nanometer TiO2 catalysts and comparison of catalytic activities of anatase and rutile TiO2 powders

Here, the nanometer anatase and rutile titanium dioxide (TiO(2)) powders were introduced to act as the sonocatalysts during the ultrasonic degradation of azo dye-acid red B which was chosen as model compound. The ultrasound of low power was used as an irradiation source to induce TiO(2) particles performing catalytic activity. It was found that the processes of sonocatalytic degradation were different between nanometer anatase TiO(2) and nanometer rutile TiO(2). For nanometer anatase TiO(2) catalyst, the acid red B was mainly oxidated by the holes on the surface of nanometer anatase TiO(2) particles, so that the decolorization and degradation happened at the same time. For the nanometer rutile TiO(2) catalyst, the acid red B was mainly oxidated by the *OH radicals from the ultrasonic cavitation, so that the decolorization of azo bond takes place primarily, and then the degradation of naphthyl ring does. The intermediates of acid red B in the presence of nanometer anatase and rutile TiO(2) powders have been monitored by UV-vis spectra and high performance liquid chromatography (HPLC), respectively. All experiments indicated that the degradation effect of acid red B in the presence of nanometer anatase TiO(2) powder was obviously better than that in the presence of nanometer rutile TiO(2) powder. Hence, the method of sonocatalytic degradation for organic pollutants in the presence of nanometer anatase TiO(2) powder is expected to be promising as an advisable choice for the treatment of organic wastewaters in future.     

Kinetics of ultrasonic degradation of phenol in the presence of TiO2 particles

The degradation of phenol by ultrasonic irradiation in the presence of TiO2 was investigated in complete darkness. The effects of amount of TiO2 and the combination of TiO2 addition with gas (air or oxygen) supply on the degradation kinetics of phenol and the formation of the reaction products were examined. The degradation rate of phenol increased with the amount of TiO2. As the dissolved oxygen concentration increased by supplying oxygen, the degradation rate of phenol also increased. A kinetic model for the disappearance of phenol was proposed. The model takes into account the OH radical formation by direct water degradation, indirect degradation by oxygen atom and indirect degradation by TiO2 catalysis. The calculated results explained well the fact that a higher amount of TiO2 and dissolved oxygen concentration gave faster disappearance rate.     

Ultrasound assisted enzyme catalyzed transesterification of waste cooking oil with dimethyl carbonate

This work reports the production of biodiesel with waste cooking oil and dimethyl carbonate in solvent free system through transesterification by immobilized enzyme (Novozym 435) under the influence of ultrasound irradiation. The experiments were conducted in an ultrasonic water bath under three different conditions i.e. ultrasonic irradiation (UI) without stirring, UI coupled with stirring and only stirring to compare their overall effects on fatty acid methyl esters (FAME) conversion. As compared with the conventional stirring method, where FAME conversion was 38.69% at 4 h, the UI without stirring significantly enhanced the conversion of enzymatic transesterification to 57.68% for the same reaction time. However the reaction rate was further increased under the condition of ultrasonication coupled with stirring and resulted into higher conversion of 86.61% for the same reaction time. Effects of reaction parameters, such as temperature, ratio of DMC/oil, speed of agitation and enzyme loading on the conversion were investigated. Furthermore, repeated use of Novozym 435 showed gradual decline in both conversion as well as enzyme activity.     

Preparation of zinc tungstate nanomaterial and its sonocatalytic degradation of meloxicam as a novel sonocatalyst in aqueous solution

Zinc tungstate (ZnWO₄) was previously used as a photocatalyst. In this paper, for the first time as an sonocatalyst, the performance of ZnWO₄ for sonocatalytic degradation of meloxicam (MEL) under ultrasonic irradiation were studied. Firstly, ZnWO₄ nanomaterials were synthesized at different acidity (pH = 5, 6, 7, 8, 9) via the hydrothermal method. Utilizing SEM, XRD and EDS techniques to characterize composition and morphology of each product, the same crystal forms, but different morphologies (nano-sheet, nano-microspheres or nano-rod) of ZnWO₄ could be obtained. Secondly, the sonocatalytic activities of ZnWO₄ on degradation of MEL were studied. It was found that the degradation ratio varied with the synthetic pH values, with ZnWO₄ under synthetic pH = 6 exhibiting the best sonocatalytic performance (75.7%). While being synthesized at this pH value, ZnWO₄ nano-microspheres had the largest BET surface area (27.068 m²/g), the smallest particle size (40–60 nm) so as to provide more active sites on its surface, which were able to produce more reactive oxygen species (ROS) and holes under ultrasonic irradiation. These ROS and holes had a positive effect on the degradation of MEL into CO₂, H₂O and inorganic. Thirdly, various influential factors including ultrasonic power intensity, ultrasonic time, catalyst addition dosage, initial concentration of MEL solution and reusability of catalyst were also explored. Under the condition of 10 mg/L MEL concentration, 20 mg catalyst dosage, 120 min irradiation time, 0.278 W/cm² ultrasonic power intensity, the degradation ratio on MEL reached 75.7%. Finally, the presence of hydroxyl radical (OH) and singlet molecular oxygen (¹O₂) in the reaction was confirmed by adding ROS scavenger. The experimental results suggested that ZnWO₄ nanoparticle could be used not only as an effective photocatalyst, but also, under the condition of ultrasonic irradiation, a promising sonocatalyst for degradation of organic pollutants in aqueous media.     

Individual and combined effects of ultrasound, ozone and UV irradiation: a case study with textile dyes

Comparative degradation of azo dyes by 520 kHz ultrasonic irradiation and its combinations with ozone and/or ultraviolet light (UV) was investigated using a probe dye C.I. Acid Orange 7. Operation parameters such as ultrasonic power density, ozone flow, UV intensity, and type and injection mode of the bubbling gas were optimized based on the rate of absorption decay in the visible and UV bands as estimated by regression analysis of absorption-time data. At equivalent initial dye concentrations and contact times, individual effects of UV irradiation, ultrasound and ozone were "no effect", "bleaching", and "bleaching/organic carbon degradation", respectively. UV irradiation, however, was found to induce a catalytic effect when applied in combination with either ultrasound or ozone schemes; and the overall degradation process was most rapid under simultaneous operation of the three in the presence of a continuous flow of a gas mixture made of argon and oxygen. The synergy observed in combined schemes was attributed to enhanced ozone diffusion by mechanical effects of ultrasound, and the photolysis of ultrasound-generated H(2)O(2) to produce hydroxyl radicals.     

Spectroscopic study on the sonodynamic and sonocatalytic damage of anthraquinone derivants to bovine serum albumin under ultrasonic irradiation

In this work, three anthraquinone derivants (Alizarin: 1,2-dihydroxy-9, 10-anthraquinone, Alizarin–DA: 1,2-dihydroxy-9, 10-anthraquinone-3-aminomethyl-N, N-diacetic acid and Alizarin–DA–Fe: 1,2-dihydroxy-9, 10-anthraquinone-3-aminomethyl-N, N-diacetate-Ferrous(III)) were used to study the sonodynamic and sonocatalytic damage of bovine serum albumin (BSA) molecules according to the hyperchromic effect of UV–vis spectra and quenching effect of intrinsic fluorescence. Meanwhile, some influencing factors such as ultrasonic irradiation time, anthraquinone derivants concentration and ionic strength on the damage of BSA molecules were also considered. The results show that the synergetic effect of anthraquinone derivants and ultrasonic irradiation can efficiently damage the BSA molecules. Finally, some special radical scavengers were used to determine the kind of generated reactive oxygen species (ROS) in the presence of three anthraquinone derivants under ultrasonic irradiation. The results show that the ROS, at least, including singlet oxygen (¹O₂) and hydroxyl radicals (OH) are generated during the sonodynamic and sonocatalytic processes. It is wished that this paper could offer some valuable references for the application of anthraquinone derivants in sonodynamic therapy (SDT) and sonocatalytic therapy (SCT) for tumor treatment.