Ultrasound-assisted Processes Research Articles

Processing of Magnesium-Based Metal Matrix Nanocomposites by Ultrasound-Assisted Particle Dispersion: A Review

Magnesium-based metal matrix nanocomposites (MMNCs) are an important topic in the development of lightweight structural materials, because their optimized properties are of great interest to the automotive and aerospace industries. Moreover, components with functional properties will also be manufactured from Mg-MMNCs in the future. With a large surface to volume ratio, nanoparticles in the magnesium matrix have an immense effect on mechanical properties, even at low concentrations. The mechanical properties of these materials can be tailored using ceramic nanoparticles, which have been available at a very low cost for a number of years. However, the particle concentration, chemical composition, particle size, and process parameters must be attuned to the respective alloy, in order to influence the resulting properties. When using very small particles, a major problem is to homogeneously distribute the particles in the melt. Due to their large surface area, strong van der Waals forces act to hold the particles together in clusters. At the same time, wettability of the particles with a magnesium melt is very poor. Ultrasonic stirring processes have proven their effectiveness in the de-agglomeration and dispersion of nanoparticles. This review presents ultrasound-assisted processes for the production of these materials and describes some properties of the resulting Mg-MMNCs.

Closed loop cavitation control – A step towards sonomechatronics

In the field of sonochemistry, many processes are made possible by the generation of cavitation. This article is about closed loop control of ultrasound assisted processes with the aim of controlling the intensity of cavitation-based sonochemical processes. This is the basis for a new research field which the authors call “sonomechatronics”. In order to apply closed loop control, a so called self-sensing technique is applied, which uses the ultrasound transducer’s electrical signals to gain information about cavitation activity. Experiments are conducted to find out if this self-sensing technique is capable of determining the state and intensity of acoustic cavitation. A distinct frequency component in the transducer’s current signal is found to be a good indicator for the onset and termination of transient cavitation. Measurements show that, depending on the boundary conditions, the onset and termination of transient cavitation occur at different thresholds, with the onset occurring at a higher value in most cases. This known hysteresis effect offers the additional possibility of achieving an energetic optimization by controlling cavitation generation.Using the cavitation indicator for the implementation of a double set point closed loop control, the mean driving current was reduced by approximately 15% compared to the value needed to exceed the transient cavitation threshold. The results presented show a great potential for the field of sonomechatronics. Nevertheless, further investigations are necessary in order to design application-specific sonomechatronic processes.

EXECUTIVE STUDY OF HYDROSTATIC PRESSURE EFFECTS ON SLUDGE PRETREATMENT BY SONICATION

The effect of hydrostatic pressure on sludge disintegration was studied for the first time using pressurized nitrogen in different operating conditions: sludge types, specific energy input ES, power input PUS, probe size, temperature T, and frequency FS. Optimum pressures (> 1 bar) were found as a function of acoustic intensity due to an increase in both cavitation threshold and cavitation intensity when increasing hydrostatic pressure. Under convenient hydrostatic pressure, the effect of US intensity IUS on DDCOD was much higher than that at atmospheric pressure. The most effective isothermal sonication would be high PUS, low FS, convenient excess pressure, and adequate total solid concentration, i.e. 360 W (35 mm diameter probe), 12 kHz, 3.25 bar, and 28 gTS/L, respectively according to our equipment possibilities. Besides, positive effects of pressure associated with high power adiabatic US were also achieved. The major result was that the optimum pressure depends on P­US, IUS (or probe size), and T, but not on ES, FS, nor sludge type. In general, sludge disintegration efficacy was significantly improved by sonication at the optimum pressure, especially at low ES, leading to a potential of energy input savings in sludge sonication pretreatment, but also in most of ultrasound assisted processes.

The Optimized Concentration and Purity of Spirulina platensis C-Phycocyanin: A Comparative Study on Microwave-Assisted and Ultrasound-Assisted Extraction Methods

Microwave-assisted (MAE) and ultrasound-assisted (UAE) extraction methods to efficiently extract the C-phycocyanin (C-PC) from the blue-green algae, Spirulina platensis, were compared. The results showed that the linear and interaction effects of two parameters of extraction time and buffer pH on C-PC concentration and purity ratio were significant. The C-PC concentration was enhanced by increasing extraction time up to 7 and 25 min for UAE (2.84 mg/mL) and MAE (4.54 mg/mL) processes, respectively. The extraction time significantly had more effect than the buffer pH value on the purity ratio. The highest purity ratio of C-PC in UAE (0.65) and MAE (1.27) technologies was obtained in buffer pH values of 6.0 and 7.0, respectively. The C-PC extracted from the MAE system significantly had higher concentration and purity than that obtained using the UAE procedure. Thus, MAE as an efficient method can be applied to extract heat-sensitive C-PC from S. platensis in an industrial scale. Practical Applications C-phycocyanin (C-PC) is a blue-colored photosynthetic accessory pigment in all cyanobacteria that has high antioxidant activity to enhance the prolonged induction period for fats or oils by preventing peroxidation of unsaturated fatty acids. Finding a proper and novel extraction method is necessary to obtain high-quality C-phycocyanin for using in different food formulations. Optimization of experimental conditions can thus provide selection of a fast and cost-saving process in the extraction of this functional ingredient.

How to design silent control experiments for ultrasound-assisted oil sands extraction and upgrading: A computational study

Abstract The major concern in estimating sonochemical yield and efficiency in ultrasound-assisted processes is in defining a “silent” control experiment, without cavitation effects. To estimate the potential benefit of the ultrasonic treatment as compared to conventional heating, we propose that the effects should be compared at the same power input, when the energy in a silent experiment is dissipated as heat. Our calculations of possible temperature increase under the silent conditions for oil sands extraction and upgrading showed necessity of such approach.

ChemInform Abstract: Sonochemistry: What Potential for Conversion of Lignocellulosic Biomass into Platform Chemicals?

AbstractReview: [100 refs.

Assessment of biorefinery process intensification by ultrasound technology

In the present work, on the basis of literature data, correlations for ultrasound-assisted dissolution of lignin and hemicelluloses from lignocellulosic raw material were defined in Aspen Plus® as function of applied power and duration of the ultrasound treatment. The dissolution yield of these biomass components was represented against the applied acoustic energy, taking into account the volume of solvent–solid treated in each case, making possible the calculation of ultrasonic power consumption in a simulated biorefinery pretreatment process. The proposed ultrasound-assisted process was techno-economically evaluated in terms of process yield and utility requirements. Furthermore, energy and exergy analyses were performed in order to assess the profitability of the simulated ultrasound-assisted biomass fractionation processes.

Multicomponent Reactions and Ultrasound: A Synergistic Approach for the Synthesis of Bioactive Heterocycles

During past decades, significant advancement in the field of ultrasound assisted processes revealed that this method is broadly applicable to a variety of research fields allied to organic synthesis. Emblematically, employing this technique as key step, a great number of multicomponent reactions have been developed for the creation of an assortment of heterocyclic compounds. In this review, we attempt to give an overview about the use of multicomponent reaction under ultrasound irradiation for synthesis of various heterocyclic compounds. Keywords: Bioactive heterocycles, multicomponent reaction, synergistic approach, ultrasound.

Microbial inactivation by ultrasound for enhanced food safety

Inactivation of foodborne pathogens by power ultrasound provides an alternative to traditional thermal processing modalities, with potential for minimizing food-quality degradation. To enhance efficacy, ultrasonic treatment is often combined with other physical or chemical lethal factors, which serve to shorten treatment time and improve quality retention. The inactivation mechanisms, thermodynamic aspects, and kinetic modeling of ultrasonic microbial inactivation will be discussed. The critical issue of how to achieve a relatively uniform acoustic field distribution during treatment will be investigated by computer simulation and verified with microbial inactivation tests. Inactivation of foodborne pathogens in liquid foods, and surface decontamination of fresh produce and nuts, will be used as examples demonstrating the potential of ultrasound-assisted processes. Lastly, the effect of sonication treatment on food product quality and quality retention will be examined.

Ultrasound-assisted MnO2 catalyzed homolysis of peracetic acid for phenol degradation: The assessment of process chemistry and kinetics

The combination of peracetic acid (PAA) and heterogeneous catalyst (MnO2) was used for the degradation of phenol in an aqueous solution in the presence of ultrasound irradiation (US). As a relevant source of free radicals (e.g. OH), peracetic acid was comprehensively studied by means of electron spin resonance (ESR) spin trapping (ST) techniques with the subsequent identification of free radicals by simulation based fitting (SBF) technique. The radical reaction mechanism, where hydroxyl radical was a primary product of OO bond rupture of PAA, was established taking into account radical reactions, occurring during sonolysis. The potential barriers and the reaction heat were determined by basic density function theory (DFT) calculations to estimate whether the proposed radical pathway is possible. The assessment and optimization of the process parameters for MnO2/PAA/US system to eliminate phenol was accomplished with experimental design. Fractional factorial design (FFD) was executed to relate the removal efficiency of phenol with process parameters such as catalyst and PAA concentrations, the presence of ultrasound and the reaction time. The comparative kinetic study of silent and ultrasound-assisted processes revealed the significant difference between these two processes that was mainly attributed to the complex radical system formed during PAA homolysis.

Impact of Immersion Depth of Ultrasonic Horn on Acoustic Field Distribution Using Thermoelectric Probe

Ultrasonic cavitation is at the origin of kinetics and yield improvement of ultrasound-assisted chemical processes. Character of ultrasonic field plays a potential role in choosing the best conditions for ultrasound-assisted chemical processes. In this paper, acoustic field distribution was measured with a thermoelectric probe in a 500mL flask filled with distilled water. A 40kHz ultrasonic horn was used and the temperature signal was measured at different locations, including axial and radial directions along the horn. The immersion depth of ultrasonic horn was investigated with ultrasonic power at 250W and 300W. We concluded that at the same power, when the immersion depth was 3cm, the intensity reached maximum.

Ultrasonic cavitation induced water in vegetable oil emulsion droplets – A simple and easy technique to synthesize manganese zinc ferrite nanocrystals with improved magnetization

In the present investigation, synthesis of manganese zinc ferrite (Mn 0.5Zn 0.5Fe 2O 4) nanoparticles with narrow size distribution have been prepared using ultrasound assisted emulsion (consisting of rapeseed oil as an oil phase and aqueous solution of Mn 2+, Zn 2+ and Fe 2+ acetates) and evaporation processes. The as-prepared ferrite was nanocrystalline. In order to remove the small amount of oil present on the surface of the ferrite, it was subjected to heat treatment at 300 °C for 3 h. Both the as-prepared and heat treated ferrites have been characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), TGA/DTA, transmission electron microscopy (TEM) and energy dispersion X-ray spectroscopy (EDS) techniques. As-prepared ferrite is of 20 nm, whereas the heat treated ferrite shows the size of 33 nm. In addition, magnetic properties of the as-prepared as well as the heat treated ferrites have also been carried out and the results of which show that the spontaneous magnetization ( σ s) of the heat treated sample (24.1 emu/g) is significantly higher than that of the as-synthesized sample (1.81 emu/g). The key features of this method are avoiding (a) the cumbersome conditions that exist in the conventional methods; (b) usage of necessary additive components (stabilizers or surfactants, precipitants) and (c) calcination requirements. In addition, rapeseed oil as an oil phase has been used for the first time, replacing the toxic and troublesome organic nonpolar solvents. As a whole, this simple straightforward sonochemical approach results in more phase pure system with improved magnetization.

Towards cleaner degreasing method in industries: ultrasound-assisted aqueous degreasing process in leather making

Studies on ultrasound-assisted processes are gaining importance due to its effectiveness and facilitating green method in processing. Degreasing of skin/hide prior to tanning process is an important unit operation. Presence of large amounts of natural fat at the interior of skin/hide matrix makes degreasing process a challenging one. Conventionally, organic solvent and/or detergent based degreasing process are employed leading to environmental problems. In the present paper, the use of power ultrasound in aqueous degreasing process has been studied and compared with different degreasing systems. Glutaraldehyde pre-tanning has also been employed for carrying out the degreasing process at ultrasonic bath temperature. The results indicate that there is a significant increase in the degreasing efficiency due to the application of ultrasound. About 2-fold increase in fat removal has been observed due to the use of ultrasound as compared to control under the given process conditions. Comparing the degreasing efficiencies of the solvent with aqueous based ultrasonic processes, about 80% of the solvent degreasing efficiency could be obtained for aqueous degreasing process. This novel ultrasonic process helps in making aqueous degreasing process a viable option, which is eco-friendly even dispensing with temperature control measures.