Vapor-liquid equilibrium of ethanol/ethyl acetate mixture in ultrasonic intensified environment

A vapor-liquid equilibrium (VLE) study was conducted on ethanol/ethylacetate mixture as a preliminary step towards developing an ultrasonic-assisted distillation process for separating azeotropic mixtures. The influence of ultrasonic intensity and frequency on the vapor-liquid equilibrium (VLE) of the mixture was examined using a combination of four ultrasonic intensities in range of 100–400W/cm² and three frequencies ranging from 25–68 kHz. The sonication was found to have significant impacts on the VLE of the system as it alters both the relative volatility and azeotrope point, with preference to lower frequency operation. A maximum relative volatility of 2.32 was obtained at an intensity of 300 W/cm2 and a frequency of 25 kHz coupled with complete elimination of ethanol-ethyl acetate azeotrope. Results from this work were also congruent with some experimental and theoretical works presented in the literature. These findings set a good beginning towards the development of an ultrasonic assisted distillation that is currently in progress.     

The effect of ultrasonic waves on the structure of polyester fibers (PET)

The effect of ultrasonic waves at constant intensity of 20 W/cm² and frequency of 2 × 10⁶ Hz on the microstructure of polyester fibers has been examined. Crystallinity, crystallite size, total orientation, and crystallite orientation have been estimated. It has been found that when subjected to different ultrasonic tests, the degree of fiber orientation decreases and crystalline perfection improves. The changes in crystallinity and crystallite size proved to be particularly difficult to determine with certainty.     

Numerical Analysis and Experimental Validation of Distillation Process for Purification of Tellurium

Numerical analysis was performed on a vacuum distillation process for Te purification. The effects of temperature gradient and Ar gas flow rate and vacuum level on the evaporation behavior of Te were investigated through a series of simulations with a diffusion-coupled convection model. An overall yield of up to 95% of 4 N pure Te was achieved at an average distillation rate of ～5.6 × 10^?4 g · cm^?2 · s^?1 from 2 N pure indigenous Te. The diffusion and condensation factors of impurities were investigated under different distillation conditions such as vacuum degree, temperature and argon flow rate. It was found that the numerical model could be used to predict impurity level during vacuum distillation process of Te and designing and optimization of a larger-scale distillation process also could be possible with a sufficient reliability.     

Effect of input power and feeding concentration on MTBE decomposition using an RF plasma reactor

The toxicology of the widely used oxygenated fuel additive methyl tert‐butyl ether (MTBE) has recently attracted considerable interest in the public sector. In this study, a radio‐frequency (RF) plasma reactor was used to decompose MTBE gas. The effects of two important plasma operational parameters – including power consumption per unit volume of the plasma (W_D, W cm^?3) and MTBE feeding concentration (C_MTBE, %) – for MTBE decomposition were investigated in detail. The results show that the MTBE decomposition efficiency (η_MTBE) increases with increasing W_D and with decreasing C_MTBE. In this study, the results reveal that, in the MTBE/Ar plasma, the η_MTBE was over 99.9%, which occurred at the conditions of for W_D = 0.96W cm^?3, C_MTBE = 3%, 20 Torr of operational pressure and a 100 cm³ · min^?1 total gas flow rate. In particular, the effects of W_D and C_MTBE for the species detected in the effluent gas stream are carefully discussed. In addition, the deposition problem which occurred in the reactor was examined by means of Scanning Electron Microscopy (SEM). © 2002 Society of Chemical Industry     

Effect of ultrasound on the nucleation temperature of water with varied air contents

Abstract

Ultrasonic cavitation is shown to hamper the supercooling required for the nucleation of water. To elucidate the mechanism of nucleation of ice under ultrasonic cavitation, ultrasound waves were applied to supercooled water with oxygen contents of 4.06, 4.48, 4.95, 5.62, and 6.34?mg L^?1. Ultrasonic waves were intermittently applied at temperatures below 0?°C. Nucleation temperatures were measured under different experimental conditions. The maximum nucleation temperature (?3.66?±?0.39?°C) was observed for a water sample containing 4.95?mg L^?1 oxygen, at 319?W power (electric power of ultrasound). At 319?W, the intensity of cavitation in this water sample was less than that at higher power. It is concluded that compared with the effect of pressure produced by cavitation, the effect of heat produced by cavitation is significant during the nucleation of water with high-intensity ultrasonic cavitation.     

污染聚偏氟乙烯中空纤维超滤膜的超声清洗

中空纤维超滤膜污染和清洗影响膜处理废水工艺的经济性及可运行性.研究了平板浸没式超声处理器（40 kHz）与2000 mg·L^-1柠檬酸清洗剂对中石化某水处理厂污染聚偏氟乙烯超滤膜的清洗效果.利用自定义的除垢率和扫描电镜对清洗结果进行表征并用过滤通量来验证.证明超声对超滤膜的清洗效果显著.单根膜清洗除垢率比不加超声时提高了25%,达到80%左右,且没有破坏膜的表面和结构.得到本批污染膜及自制污染膜组件的优化清洗工艺及超声参数为：频率40 kHz、声强2200 W·m^-2、超声处理时间30 min.未使用反向冲清洗,仅切向气流结合超声清洗膜面,清洗后的通量从原来污染组件的0.0368 cm³·cm^-2·min^-1增加到0.1254 cm³·cm^-2·min^-1,恢复到相当于新膜初始通量的72.5%,通量增加率达到241%.进一步证明了超声清洗膜的可行性和有效性.     

Response of a proton exchange membrane fuel cell to a sinusoidal current load

The load-following capability of a proton exchange membrane fuel cell was studied by measuring the cell voltage response to a sinusoidal current load with large amplitude and varying frequency. A mathematical model was developed, incorporating mass transport and capacitive effects as well as the membrane resistance. The model was capable of separating the faradaic and capacitive currents and predicting the observed hysteresis. At frequencies of the sinusoidal current load below 1 Hz, no appreciable hysteresis in the polarisation curve was observed. When increasing the frequency above 1 Hz, a hysteresis appeared at current densities below 0.2 A cm^?2. The model related this hysteresis to capacitive effects. When using air as the cathode feed, hysteresis in the current density range 0.5 A cm^?2 and higher appeared above 1 Hz compared to 100 Hz for pure oxygen. The model revealed that hysteresis observed in this current density range was caused by oxygen transport limitations.     

Preparation and characterisation of carbon-supported palladium nanoparticles for oxygen reduction in low temperature PEM fuel cells

Pd nanoparticles have been synthesised using different reducing agents, including ethylene glycol (EG), formaldehyde and sodium borohydride and their activity for the oxygen reduction reaction (ORR) evaluated. The use of EG led to the best morphology for the ORR and this synthetic method was optimised by adjusting the system pH. Carbon-supported Pd nanoparticles of approximately 7 nm diameter were obtained when reduction took place in the alkaline region. Pd synthesised by EG reduction at pH 11 presented the highest mass activity 20 A g^?2 and active surface area 15 m² g^?1. These synthetic conditions were used in further synthesis. The effect of heat treatment in H₂ atmosphere was also studied; and increased size of the palladium nanoparticles was observed in every case. The Pd/C catalyst synthesised by reduction with EG at pH 11 was tested in a low temperature H₂/O₂ (air) PEMFC with a Nafion^® 112 membrane, at 20 and 40 °C. Current densities at 0.5 V, with O₂ fed to the cathode, at 40 °C were 1.40 A cm^?2 and peak power densities 0.79 W cm^?2, approximately; which compared with 1.74 A cm^?2 and 0.91 W cm^?2, respectively for a commercial Pt/C.     

Ultrasonic Pretreatment Transesterification for Solid Basic-Catalyzed Synthesis of Fatty Acid Methyl Esters

Generally, ultrasound irradiation is required throughout the reaction for fatty acid methyl esters (FAME, namely, biodiesel) production, which is energy-consuming and difficult to scale-up. In order to improve the industrial application of ultrasonic technology, a systematic study of ultrasonic pretreatment solid basic (Na₂SiO₃)-catalyzed transesterification for FAME production from cottonseed oil was carried out, and the effect of ultrasonic waves on the properties of Na₂SiO₃ catalyst was assessed by X-ray diffraction (XRD), Fourier transform Infrared (FTIR) and scanning electron microscopy (SEM) characterization of fresh and collected catalysts. An ultrasonic frequency of 30 kHz, ultrasonic power of 200 W and ultrasonic pretreatment irradiation time of 30 min was determined to guarantee a satisfactory degree of transesterification. The optimum production was achieved in the reaction system at 45 °C with methanol/cottonseed oil molar ratio 5:1, catalyst dosage 3% and stirring speed 350 rpm resulting in a FAME yield of above 97% after 60 min of reaction under mechanical stirring with the ultrasonic pretreatment process. The new process has a shorter reaction time, a more moderate reaction temperature, a less amount of methanol and catalyst than only the mechanical stirring process without essential damage to activity and the structure of catalyst. These results are of great significance for applying the ultrasonic pretreatment method to produce FAME.     

A Silicon Microseparator based Pervaporation Process for Separation of Ethanol/Water Mixtures using a Polymer Membrane

Abstract

The selective removal of water from ethanol through pervaporation was demonstrated in a microchannel device using a commercial membrane. Photolithography and dry etching techniques were employed for fabrication of the microseparator with hydraulic diameters of 30 µm to 80 µm. Experiments conducted at 90°C and 2–3 Torr, with Reynolds Numbers ranging from 8 to 91, resulted in an average water and ethanol permeance of 1.2×10^?3 and 8×10^?5 cm³/cm² · s · cmHg respectively. A mass transfer analysis involving Sherwood correlations was used to calculate the theoretical boundary layer resistance. The comparison of overall mass transfer coefficient with the boundary layer coefficients suggests that the membrane was the dominant resistance for this system.     

Isobaric vapor-liquid equilibrium for methanol+benzene+1-octyl-3-methylimidazolium tetrafluoroborate

Isobaric vapor-liquid equilibrium (VLE) data for {methanol (1)+benzene (2)+1-octyl-3-methylimidazolium tetrafluoroborate (3)} where 3 is an ionic liquid ([OMIM]⁺[BF₄]^?) at atmospheric pressure (101.32 kPa) were measured with a modified Othmer still. The results showed that the ionic liquid studied can transfer the azeotropic point and eliminate the azeotropic phenomena when its concentration is up to x₃=0.30. This means that [OMIM]⁺[BF₄]^? can be used as a promising entrainer in the application of extractive distillation. The measured ternary data were correlated using the NRTL model.     

Electrochemical and sonoelectrochemical processes applied to the degradation of the endocrine disruptor methyl paraben

Methyl paraben is commonly employed as a preservative in pharmaceutical preparations, personal care products and some processed foods. However, the ester constitutes a potential pollutant in aquatic environments and has been classified as an endocrine disruptor. This study describes the degradation of methyl paraben (100 mg L^?1 in 0.05 mol L^?1 aqueous potassium sulfate at pH 5.7) by means of an electrochemical process (employing a boron-doped diamond anode) either alone or coupled with sonolysis. Electrolyses were performed at 25, 30 and 35 ± 1 °C during 120 min using applied constant current densities of 10.8 and 21.6 mA cm^?2. The hybrid sonoelectrochemical processes were conducted under similar conditions with the application of ultrasound at a frequency of 20 kHz and a power intensity of 523 W cm^?2. Although mineralization of methyl paraben could be achieved using either process, in comparison with the electrochemical method, the hybrid technique showed a higher mineralization efficiency (around 60 %) with approximately 50 % removal of total organic carbon, thereby confirming the synergistic effect of sonolysis.     

Electrodeposition and characterization of nickel–copper metallic foams for application as electrodes for supercapacitors

Nickel–copper metallic foams were electrodeposited from an acidic electrolyte, using hydrogen bubble evolution as a dynamic template. Their morphology and chemical composition was studied by scanning electron microscopy and related to the deposition parameters (applied current density and deposition time). For high currents densities (above 1 A cm^?2) the nickel–copper deposits have a three-dimensional foam-like morphology with randomly distributed nearly-circular pores whose walls present an open dendritic structure. The nickel–copper foams are crystalline and composed of pure nickel and a copper-rich phase containing nickel in solid solution. The electrochemical behaviour of the material was studied by cyclic voltammetry and chronopotentiometry (charge–discharge curves) aiming at its application as a positive electrode for supercapacitors. Cyclic voltammograms showed that the Ni–Cu foams have a pseudocapacitive behaviour. The specific capacitance was calculated from charge–discharge data and the best value (105 F g^?1 at 1 mA cm^?2) was obtained for nickel–copper foams deposited at 1.8 A cm^?2 for 180 s. Cycling stability of these foams was also assessed and they present a 90 % capacitance retention after 10,000 cycles at 10 mA cm^?2.     

Effects of ultrasonic irradiation on the viscosity of fuel oils

Fuel oil A, B and C, and a residual oil from vacuum distillation (R-Oil) have been irradiated with 25kHz ultrasonic waves (150W) at 50 °C for 10 h. The observed increases in the kinematic viscosity (Δ v%) are: fuel oil A, 0.3%; fuel oil B, 5.3%; fuel oil C, 17.6%; and R-Oil 5.5%. The value and sign of Δ v are found to change with the sample weight in the flask, l.r. measurements show that ultrasonic irradiation causes the intensities of CH₂ and CH₃ to decrease slightly. The ultrasonic energy appears to be used in the breaking-up and/or coupling of the petroleum molecules.     

IR and Dielectric Analysis of Cellulose and Its Derivatives

Abstract

Infrared (IR) spectra of cellulose, cellulose carbamide, cyanoethyl cellulose, cellulose acetate, and acetylated cyanoethyl cellulose from 400 to 4000 cm^?1 were studied. All cellulose derivatives have lower crystallinity index than cellulose except cellulose carbamide, which is attributed to hydrogen bond strength. Dielectric properties of these derivatives were measured in the range of frequency (0.1–100 kHz). The results showed that cellulose derivatives have lower values and cellulose carbamide has the lowest value. AC conductivity and resistivity values were calculated, and the conduction mechanism beside relaxation was discussed.     

Ultrasound-assisted heat pump drying of pea seed

ABSTRACT

The work is for the purpose of studying the influence of drying temperature and ultrasound on drying kinetics, antioxidant enzymes, and germination performance of pea seeds. The drying experiments were performed at air temperature of 30, 35, and 40°C without ultrasound and with three ultrasonic levels of 28?kHz?+?60?W, 28?kHz?+?100?W, and 40?kHz?+?60?W. The antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) and the toxic substances such as malondialdehyde (MDA) of the dried seeds were determined, and germination percentage (GP), germination index (GI), and mean germination time (MGT) were measured. The result showed that high temperature and ultrasound application had significant (P?<?0.05) enhancing of pea seed drying kinetics, which shortened the drying time and improved the diffusion coefficient from 3.528?×?10^?11 to 5.668?×?10^?11?m²/s. Page model can well describe the drying curves under different experiment conditions. Ultrasound application significantly (P?<?0.05) improved the activities of SOD, POD, and CAT and reduced the MDA content. In addition, high ultrasonic power contributed to the increase in GP and GI and the reduction of MGT of seeds.     

Preparation and wear assessment of ultrasonic electrodeposited Ni–TiN thin films

In this study, pure Ni and Ni–TiN thin films were prefabricated from a reformative Watt nickel bath through ultrasonic electrodeposition (UE) under pulse current (PC) condition. The effects of ultrasonic intensity on surface morphology, microstructure and phase composition were evaluated through scanning electron microscopy (SEM), scanning probe microscopy (SPM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The Vickers hardness, the friction coefficient and the wear resistance of Ni and Ni–TiN thin films were also estimated. All SEM, SPM, and TEM results demonstrated that the Ni-TiN thin film obtained at the ultrasonic intensity of 30?W/cm² had a fine, smooth and homogeneous surface morphology. The root-mean-square roughness (Rms) and arithmetic mean roughness (Ra) of the film with a surface area of 4.096?µm² were 36.813?nm and 22.836?nm, respectively. Also, the mean diameters of Ni grains and TiN nanoparticles were approximately 46.7?nm and 23.2?nm, respectively. The XRD analysis indicated that the XRD patterns of the films prepared with different plating parameters had the same diffraction angle with the Ni phase except the diffraction intensity. Microhardness tests exhibited that the Ni film displayed the minimum microhardness value of 38.6 HV. Moreover, the Ni-TiN film obtained at the ultrasonic intensity of 30?W/cm² acquired the maximum microhardness value of 912.1 HV. The wear behavior assessment demonstrated that the Ni-TiN film prefabricated at the ultrasonic intensity of 30?W/cm² sustained the least weight loss, while the mean friction coefficient was approximately 0.39, thereby displaying the best wear resistance.     

Annealing Effect on Microhardness and Elastic Constants of PMMA

Abstract

The ultrasonic velocities of both longitudinal and shear waves were measured in thermoplastic discs of poly methyl methacrylate (PMMA) as a function of annealing temperatures ranging from 23°C to 95°C (23°C, 45°C, 60°C, 75°C, 80°C, and 95°C). Ultrasonic velocity measurements were taken at 2 MHz ultrasonic frequency using the pulse echo method. From the experimental data, the longitudinal modulus, rigidity, and Young's modulus are derived. Effect of annealing on microhardness of PMMA was studied using ultrasonic pulse echo method as well as mechanical measurements. The critical stress intensity factor was also determined at the same annealing conditions. In all events, the microhardness and the elastic constant are found to be changed at annealed temperature named 80°C.     

The Fabrication and Characterization of Cellulose/Mesoporous Silica Composites Packaging Films with Adjustable Permeability by NMMO Technology

Cellulose-based composites containing various amounts of SBA-15 mesoporous silica were prepared by NMMO-technology, and their morphologies, mechanical properties, permeability for oxygen and water vapor were studied. The investigation suggested that both the modified and unmodified mesoporous silica materials can improve the elongation at break of the cellulose films. However, the incorporation of the mesoporous silica materials can reduce the tensile strength of the films, and the modified one has less effect on that than the unmodified one. The composites films with rational mechanical properties have adjustable oxygen permeability (7.90 × 10^?15–94.6 × 10^?15 cm³ · cm/cm² · s · Pa) and water vapor permeability (7.12 × 10^?13–4.10 × 10^?13 g · cm/cm² · s · Pa).     

Physicochemical properties of hydrolyzed and blended chitin

The molecular structures of chitin and chitin hydrolyzed with sodium hydroxide for different time intervals at 160°C were followed using infrared spectroscopy in the range 200–4000 cm^?1. The frequency and intensity of active groups NHCOCH₃, NH₂, OH, and OCH₃ in chitin, chitosan, cellulose, and lignin, respectively, were calculated and correlated with molecular structural changes. The dielectric constant ?′, dielectric loss ?″, and dissipation factor tan δ for the investigated samples were measured in the frequency range 0.1–100 kHz and interpreted in terms of the molecular structure elucidated from the infrared spectroscopic studies. Also, the effect of blending of cellulose and lignin with chitin on their dielectric properties was investigated. It was found that hydrolysis of chitin improved its insulating properties.