Papers by Keyword: Ultrasonic Irradiation

Abstract: The objective of this study was to evaluate the ability of ultrasonic irradiation to remove ammonia-nitrogen in synthetic solution by considering the factors including initial concentration, pH and irradiation time. Ultrasonic bath was used to provide a constant effective power, frequency and temperature of 150 W, 37 kHz and 60°C, respectively during sonication. It was revealed that the removal efficiency of ammonia-nitrogen improved at lower concentration with basic water environment and extended irradiation time. Based on this judgement, optimization is carried out by using response surface methodology (RSM) of Box Behnken design to develop a quadratic regression model in order to analyze the interactions between the three factors and their effects on the removal efficiency. Optimum removal achieved from the model was found to be 82.26% at 10 mg/L of initial concentration with pH of 11 and sonication for 30 minutes. Verification of the quadratic regression model is done by comparing with the experimental work conducted within the experimental domain.

Abstract: In the present work, spent LiCoO₂ was processed to remove impurities by ultrasound with the aim to renovate its electrochemical characteristics. The composition and amount of organic materials remained in the LiCoO₂ particle surface were characterized by GC-MS, FT-IR and TGA, respectively. The morphology and particle sizes of PVDF (Polyvinylidene fluoride) was analyzed by SEM. Experimental results show that ultrasonic cavitation could be effectively used to remove organic substance stuck on LiCoO₂ surface. At room temperature, the spent LiCoO₂ was successfully remove impurities, including EC (Ethylene carbonate) and PVDF, with ultrasound applied for 12 h. It can be considered that most of the PVDF (82.0 wt.%) has decomposed under ultrasonic irradiation. Furthermore, the EC has completely decomposed under such ultrasonic irradiation.

Abstract: In this work, a chemically grown ZnO rod – like structure is produced via precipitation and post – sonication treatment based on the hydrolysis of zinc iodide (ZnI₂) and diethanolamine (DEA). ZnO rod – like structures with aspect ratio of 3 to 4(diameter of 235 nm and 800 nm in length) was observed from the TEM micrograph.The as-synthesized ZnO wurtzite structure was compared to sample without ultrasonic irradiation treatment to study the effect of bubble implosion on the formation of the particle. In contrast to particles treated with ultrasonic irradiation, micron sized and agglomerated particles were observed in sample without the treatment. The mechanism related to acoustic cavitations and the formation of rod – like structure is explained. The XRD results show polycrystalline structure on both samples. The optical property of ZnO was evaluated using room temperature UV - Visible absorption spectroscopy. The result showed an absorption peak at 381 nm in wavelength.

Abstract: Great interests in metallic oxides have emerged because of the possibility to modify the properties of these materials for different applications such as catalysis or sensors. In this work, CuO, ZnO and CuO-ZnO nanoparticles were prepared by a novel sol-gel route under ultrasonic condition using triethanolamine as an emulsifying surfactant. Fine powders were obtained when the pH of the sols were increased to 13 using NaOH. Particle sizes of the produced oxide materials were in the range of 3-4 nm, 40-50 x 100-150 nm (diameter x length) and 100-200 nm for CuO, ZnO and CuO-ZnO, respectively. The molar ratio of triethanolamine to metal nitrate precursors was set at 2:3. TEM micrographs of these particles were obtained to elucidate the morphology of the nanoparticles. Experimental results show that the band gap energies (E_g) for CuO, ZnO and CuO-ZnO were found to be 2.71, 3.35 and 2.82 eV, respectively.

Abstract: In this paper, poly [(2-methoxyl-5-octyloxy) Phenylene Vinylene] (MO-PPV) was synthesized by Gilch route under ultrasonic irradiation. The molecular structure, thin film and luminescence property examined through FT-IR, SEm, AFM, UV-Vis spectroscopy and fluorescent spectroscopy, the results showed that the ‘cavitations effect’ caused by the ultrasonic irradiation not only accelerate the reaction speed but also reduce structural defects of the polymer thin film, the synthesized MO-PPV is free of gelatins which is harmful for the polymer’s thin films act as active layer in polymer light-emitting diodes (PLED).

Abstract: Lithium trivanadate (LiV₃O₈) powders have many attractive characteristics such as high specific energy density, good rate capacity and long cycle life due to their unique crystal structure and outstanding structure stability as cathode material for rechargeable lithium batteries. LiV₃O₈ crystallites were synthesized under different conditions via a combined ultrasonic irradiation and sol-gel method. The as-prepared LiV₃O₈ powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) absorption spectra. The thermal decomposition process was investigated using thermogravimetric (TG) and differential scanning calorimetry (DSC). The effects of molar ratios of metal ion/citric acid and calcinations temperature on phases and microstructure of the powders were investigated. Results indicate that calcinations temperatures have significant influence on the particle morphology, particle size and particle size distribution of the powders. The pure and rod-like LiV₃O₈ powders with an average size of 0.2-1 μm are obtained at 350 and 400 °C. With the increase of calcinations temperature, the powders exhibit preferred growth orientation along (100) planes. The crystallites obtained at 550 and 600 °C are composed by LiV₃O₈ with a small amount of Li_0.3V₂O₅ phase, both of which exhibit tabular morphologies with an average size of 2-10 μm.

Abstract: Effect of ultrasonic intensity on the degradation of phenol solution is investigated by changing the nominal ultrasonic power, ultrasonic frequency and the position of reactor. The actual ultrasonic intensity (I) that reaches reactor is measured by ultrasonic power measuring meter. It can be found that the ultrasonic intensity varies with ultrasonic parameters. With the nominal power input improving from 60 W to 150 W, the ultrasonic intensity rises from 0.21 W•cm-2 to 1.06 W•cm-2 and the degradation rate of phenol solution (η) increases from 21.7% to 43.7%. However, when I reaches the highest value of 1.71 W•cm-2 at the frequency of 100 kHz, η decreases to the lowest value of 21.5%. The ultrasonic intensity distribution is uneven in the ultrasonic bath and η increases with an increase of I in the vertical direction. The ultrasonic degradation of phenol solution is affected by ultrasonic intensity, but η doesn’t definitely increase with an increase of ultrasonic intensity.

Abstract: The actual acoustic intensity (I) that reaches membrane is measured by ultrasonic power measuring meter. I is altered by changing the height of membrane (H), the nominal ultrasonic power, or ultrasonic frequency in ultrasonic cleaner. The evolution of the property of polymeric membrane exposed to ultrasonic irradiation is followed by the calculation of membrane damage factor (R). Effect of acoustic intensity on the extent of membrane damage is investigated. The results show that the polytetrafluoroethylene (PTFE) membrane is comparatively resistant under ultrasonic irradiation, the polypropylene (PP) membrane is less resistant, but the nylon 6 (N6) membrane can be damaged seriously by ultrasound. When ultrasonic frequency is 45 kHz, I decreases from 1.04 W•cm-2 to 0.10 W•cm-2 as H rises from 3 cm to 9 cm; I increases from 1.04 W•cm-2 to 1.33 W•cm-2 as the nominal ultrasonic power rises from 200 W to 400 W, and R increases as I rises. When the nominal ultrasonic power is 200 W, I rises from 1.04 W•cm-2 to 1.45 W•cm-2 as ultrasonic frequency increases from 45 kHz to 100 kHz, but R generally remains stable when ultrasonic frequencies are 80 kHz and 100 kHz. Membranes are resistant under ultrasonic irradiation when ultrasonic frequencies are 80 kHz and 100 kHz.

Abstract: The control parameters of the removal of Chlorella pyrenoidosa, which was irradiated by low frequency ultrasonic, is optimized by using single factor experiments and response surface methodology (RSM). First of all, the approximate ranges of the ultrasonic frequency, the ultrasonic power and the irradiation time were estimated with single factor experiments for the further experiments. And then the optimized values of the three control parameters were determined, which were analyzed by using central composite design (CCD) and RSM. The results showed that the removal rate of chlorophyll-a could reach to 64.1% after the irradiation for 6.34min by using ultrasonic of 77.7 kHz and 250W. Ultrasonic technology can remove Chlorella pyrenoidosa cells in water quickly and effectively, so as to achieve the purpose of water purification.

Abstract: Eu(DBM)₃•phen complexes have been Successfully synthesized by the sonication of an Ethanol solution of europium chloride and dibenzoylmethanide (DBM) in the presence of 1,10-phenanthroline(phen). The properties of the Eu(DBM)₃•phen complexes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform Infrared spectroscopy (FT-IR) and fluorescence spectrometry (FS). Reaction conditions, such as ultrasonic power and the concentration of complexing reagent, were found to have close relation with the morphologies of final products. The formation mechanism of Eu(DBM)₃•phen complexes with ultrasonic irradiation is discussed in the context.