Absence Of Ultrasound Irradiation Research Articles

Prilezhaev epoxidation of oleic acid in the presence and absence of ultrasound irradiation

AbstractBACKGROUNDEpoxidation of double bonds in vegetable oils provide valuable green intermediates for the chemical industry. The epoxidation of oleic acid with hydrogen peroxide according to the Prilezhaev principle was studied experimentally in a multiphase laboratory‐scale batch reactor operated isothermally at 50 °C and atmospheric pressure. A solid cation exchanger (Amberlite IR‐120) was used as the solid catalyst to enhance the slow step in the Prilezhaev process: the in situ formation of the epoxidation agent, peracetic acid, from hydrogen peroxide and acetic acid. A rotating basket stirrer was used to suppress the external mass transfer limitations and to guarantee a turbulent random flow in the vicinity of the catalyst particles. Kinetic experiments demonstrated the catalytic effect of the cation exchanger. Several experiments were performed in the presence and absence of ultrasound irradiation at different amplitudes.RESULTSThe exposure of ultrasound irradiation on the multiphase reaction mixture impaired the conversion of the double bonds and the yield of the epoxide, compared to a reference experiment conducted under silent conditions. Catalyst characterization by scanning electron microscopy and the determination of the acid sites in recycled catalyst samples confirmed that the main reason for deactivation was leaching and/or neutralization of the sulfonic acid groups from the solid catalyst matrix.CONCLUSIONSThe application of ultrasound at different input powers resulted in lower reaction yields compared to the silent reference experiment. This observation was attributed to deactivation of the catalyst caused by leaching and/or neutralization of the sulfonic groups promoted by ultrasound exposure. © 2021 Society of Chemical Industry (SCI).

Ultrasound assisted synthesis of reduced graphene oxide (rGO) supported InVO4-TiO2 nanocomposite for efficient hydrogen production

Herein, a ternary nanocomposite, comprising metal oxide (InVO4 and TiO2) photocatalysts supported on rGO sheets was prepared via the hydrothermal method in the presence and absence of ultrasound irradiation. The photocatalytic performance of the prepared rGO/InVO4-TiO2 nanocomposites was evaluated for H2 evolution activity from water splitting with glycerol as a sacrificial agent. Interestingly, a synergistic effect (6-fold) was observed with rGO/InVO4-TiO2 nanocomposite prepared with the help of ultrasound compared to the samples prepared without ultrasound. The optimized nanocomposite (rGO/InVO4-TiO2) exhibited a maximum H2 evolution of 1669 μmol h−1, a ∼13-fold enhancement compared to the bare TiO2. This remarkable enhancement is mainly due to the synergistic effect induced by ultrasonic irradiation along with the shifting of the optical band gap of TiO2 from 3.20 eV to 2.80 eV by loading of InVO4 and rGO and also strong chemical bonding between metal (Ti) and C through Ti–C bond formation, as identified by UV–vis DRS spectra and XPS spectra, respectively. Moreover, a significant quenching of PL emission intensity and smaller radius arc of the Nyquist plot in the EIS were observed when the rGO and InVO4 were loaded in TiO2, indicating the efficient charge carriers separation and transfer in the presence of rGO sheet, resulting in enhanced photocatalytic activity. Thus, application of ultrasound has played significant and important roles in substantially enhancing hydrogen evolution along with rGO and InVO4 acting as support and co-catalyst, respectively.

Ultrasound-assisted electrodeposition of Cu3Se2 nanosheets and efficient solar cell performance

This study is devoted to the synthesis of nanostructured copper selenide (Cu3Se2) thin films through electrodeposition and evaluation of the effect of ultrasonication on the structural, optical, and photovoltaic properties of the deposited films. According to the X-ray (XRD) diffraction patterns, the films are composed of tetragonal Cu3Se2 structures while ultrasonication increases the crystallite sizes and intensifies the diffraction peaks. In addition, ultrasonication increases the lattice parameter and strain of the crystal lattice. Based on the field emission scanning electron microscopy (FESEM) images, the samples electrodeposited in the presence and absence of ultrasound irradiation are both sheet-like while their sheet thicknesses are 66 and 121 nm, respectively. In addition, with respect to the photoluminescence (PL) spectra of the films, applying ultrasonication increases the intensity of their emission bands and shifts the bands towards lower wavelengths. So that, the absorption spectra exhibit the increase of band gap energy by irradiating ultrasound waves during the synthesis of the nanosheets. The highest value of Voc, Isc, and efficiency are obtained 0.47 V, 2.38 mA/cm2, and 1.11% for the sample synthesized using ultrasonication, respectively. Finally, ultrasound irradiation applies compressive stress on the electrodeposited structures, influences the thickness and morphology of the deposited films and enhances the photovoltaic properties of the solar cells fabricated using the ultrasound-assisted Cu3Se2 layer.

Numerical simulation of heat transfer and phase change during freezing of potatoes with different shapes at the presence or absence of ultrasound irradiation

As novel processes such as ultrasound assisted heat transfer are emerged, new models and simulations are needed to describe these processes. In this paper, a numerical model was developed to study the freezing process of potatoes. Different thermal conductivity models were investigated, and the effect of sonication was evaluated on the convective heat transfer in a fluid to the particle heat transfer system. Potato spheres and sticks were the geometries researched, and the effect of different processing parameters on the results were studied. The numerical model successfully predicted the ultrasound assisted freezing of various shapes in comparison with experimental data of the process. The model was sensitive to processing parameters variation (sound intensity, duty cycle, shape, etc.) and could accurately simulate the freezing process. Among the thermal conductivity correlations studied, de Vries and Maxwell models gave closer estimations. The maximum temperature difference was obtained for the series equation that underestimated the thermal conductivity. Both numerical and experimental data confirmed that an optimum condition of intensity and duty cycle is needed for reducing the freezing time, as increasing the intensity, increased the heat transfer rate and sonically heating rate, simultaneously, that acted against each other.

Sono-dispersion of TiO2 nanoparticles over clinoptilolite used in photocatalytic hydrogen production: Effect of ultrasound irradiation during conventional synthesis methods

Hydrogen evolution via water splitting was investigated over the sonochemically synthesized TiO2-clinoptilolite photocomposites. To this aim, a series of photocatalysts containing 10wt% titania were prepared by impregnation and solid state dispersion (SSD) methods in the presence and absence of ultrasound irradiation. The samples were characterized by XRD, FESEM, EDX, BET, FTIR, PL and UV–vis techniques and tested for the water splitting. The characterization results indicated that ultrasound irradiation endowed the photocatalysts with uniform morphology, higher surface area and more homogenous dispersion. In addition, the analyses also exhibited less population of particle aggregates, a strong titania-support interaction and lower electron-hole pairs recombination rate. These features were more prominent when ultrasound was employed during SSD method. The TiO2/Clinoptilolite photocatalyst prepared by the ultrasound assisted SSD method (TiO2/CLT(US)), had more uniform active sites dispersion, high separation efficiency of electron–hole pairs and as a consequence, high surface density of active sites. The highest photocatalytic activity, 569.88μmol/gTiO2·h, was obtained for the TiO2/CLT(US) sample which was about 8 times more than that of P-25 as a reference sample. Furthermore, the TiO2/CLT(US) photocomposite as optimal photocatalyst showed sufficient reusability, making it a good choice for photocatalytic water splitting applications.

Kinetics Analysis and Effects of Various Factors on Removing Iron from Silica Sand Under Ultrasound-Assistance

The kinetics of leaching silica sand in hydrochloric acid solution under conventional stirring and ultrasound-assisted conditions was studied. Acid concentration, temperature, stirring speed, ultrasound frequency and particle size had significant effects on the leaching rate while the influence of ultrasound power was negligible. The leaching kinetics followed the shrinking core model with product layer diffusion control as the rate-controlling step for the conventional stirring and ultrasound-assisted leaching process. The apparent activation energies in the presence and absence of ultrasound irradiation was determined to be 43.6 and 67.5 kJ/mol respectively. The presence of ultrasound not only increases the diffusion rate of mass but also promotes chemical reaction.

Optimization of ultrasound-assisted oxidative desulfurization of high sulfur kerosene using response surface methodology (RSM)

An experimental investigation was conducted on the ultrasound-assisted oxidative desulfurization of non-hydrotreated kerosene. The influences of various operating parameters including oxidant-to-sulfur molar ratio (n o/n s), formic acid-to-sulfur molar ratio (n acid/n s), the ultrasound power per fuel oil volume, sonication time, and temperature on the sulfur removal of kerosene have been investigated. Response surface methodology based on Box–Behnken design has been employed. 95.46 % sulfur removal of kerosene has been achieved in the sonication time of 10.5 min under the optimal oxidation conditions (i.e., n o/n s = 15.02, n acid/n s = 107.8, and the ultrasound power per fuel oil volume of 7.6 W/mL) followed by liquid–liquid extraction. More than 90 % sulfur removal of kerosene has been achieved in about 3.5 min of sonication followed by the liquid–liquid extraction. 70.2 % sulfur removal of kerosene has been achieved in the same operating conditions after 3.5 min of oxidation followed by the liquid–liquid extraction in the absence of ultrasound irradiation. The effects of the number of extraction stages on the desulfurization and recovery of kerosene have been also investigated.

A Green Ultrasound Synthesis, Characterization and Antibacterial Evaluation of 1,4-Disubstituted 1,2,3-Triazoles Tethering Bioactive Benzothiazole Nucleus.

The synthesis of N-(benzo[d]thiazol-2-yl)-2-(4-substituted-1H-1,2,3-triazol-1-yl)acetamides 5a–r via the 1,3-dipolar cycloaddition reaction between 2-azido-N-(benzo[d]thiazol-2-yl)acetamide derivatives 3a–c and different alkynes were performed in the presence and absence of ultrasound irradiation. The synthesis was carried out using t-BuOH/H2O (1:1, v/v) as reaction solvents and CuSO4·5H2O/sodium ascorbate as the catalyst. The copper catalyst was implemented to provide the regioselective 1,4-disubstituted 1,2,3-triazoles 5a–r. Significant reductions in reaction times with comparably higher yields were observed when the reactions were carried out under ultrasound irradiation. The structures of the newly synthesized 1,2,3-triazoles were elucidated by IR, NMR, MS, and elemental analyses. They were also screened for their antimicrobial activity against three gram-positive (Streptococcus pneumonia, Bacillus subtilis, and Staphylococcus aureus), three gram-negative (Pseudomonas aeuroginosa, Escherichia coli, and Klebsiella pneumonia), and two fungal strains (Aspergillus fumigates and Candida albicans). Most of the tested compounds displayed promising antimicrobial activities at a Minimum Inhibition Concentration (MIC) of 4–16 μg/mL.

Waste fish oil (WFO) esterification catalyzed by sulfonated activated carbon under ultrasound irradiation

In the present research work, esterification reaction of waste fish oil (WFO) catalyzed by sulfonated activated carbon under ultrasound irradiation was studied. The application of this catalyst, in addition to the elimination of purification process, leads to the green biodiesel production. The influences of various operating variables such as catalyst loading (1–12 wt%), methanol to oil molar ratio (6–15), and ultrasonic power (100–400 W) on the esterification conversion have been investigated. Response surface methodology (RSM) based on Box–Behnken design (BBD) has been employed. 88% conversion for the esterification reaction has been obtained under the best conditions (i.e., catalyst loading of 11.4 wt%, ultrasonic power of 296.09 W, and methanol to oil molar ratio of 14.85). An accurate mathematical correlation has been developed for the prediction of the esterification conversion. 56% conversion for the esterification reaction has been obtained in the same operating conditions in the absence of ultrasound irradiation.

Effect of high frequency ultrasound on micromixing efficiency in microchannels

In the present work, an investigation on the effect of high frequency ultrasound wave on micromixing in the studied microchannels was carried out. Three types of microchannels with different shapes are examined. A 1.7MHz piezoelectric transducer (PZT) was employed to induce the vibration in these microchannels through an indirect contact. A method based on the Villermaux–Dushman reaction was employed to study the micromixing in these microchannels. The segregation intensity was determined for layouts with and in the absence of ultrasound irradiation. Further, the effect of ultrasound waves, in various flow rates and initial concentrations of acid, on the segregation index (XS) and micromixing time (tm) was investigated. The experimental results showed that the ultrasound waves have a significant influence on product distribution and segregation index at various flow rate ratios. The data obtained in all cases showed that the segregation index was reduced when the flow rate ratios were increased. Also the results demonstrate that in spite of a low energy consumption of PZT, the relative segregation index improved up to 18–36% at various flow rate ratios.

Ultrasound-assisted enzymatic hydrolysis of cassava waste to obtain fermentable sugars

This work evaluates ultrasound-assisted enzymatic hydrolysis of cassava waste using α-amylase and amyloglucosidase to obtain fermentable sugars. The influence of solid to liquid ratio and the concentrations of α-amylase and amyloglucosidase on the amount of fermentable sugars released was assessed in the presence and absence of ultrasound irradiation by means of a central composite rotational design. The results showed that the concentration of fermentable sugars released ranged from 21.3 to 83.1 g l −1 and from 32.8 to 116.1 g l −1 , in the absence and presence of ultrasound, respectively. The specific total reducing sugar (TRS) production (expressed as g of TRS per g of dry cassava waste) ranged from 0.18 to 0.27 for hydrolysis in the water bath and from 0.26 to 0.36 g g −1 in the ultrasound bath. The TRS concentration obtained using ultrasound for a sample with solid to liquid ratio of 0.16 was around 80 g l −1 , and without ultrasound the similar concentration was only obtained for solid to liquid ratios higher than 0.34. This demonstrates that ultrasound technology can be useful for process intensification due to its positive effects on sugar yield.

Effect of ultrasound-assisted irradiation on the activities of α-amylase and amyloglucosidase

Abstract This work is focused on the evaluation of the effects of ultrasound irradiation on the activity of α-amylase and amyloglucosidase. A central composite rotational design was carried out for each of the enzymes to evaluate the effects of temperature and pH on the activities in the presence and absence of ultrasound irradiation. The activation energy was also determined for both enzymes in the presence and absence of ultrasound irradiation. The results obtained for α-amylase and amyloglucosidase indicated that the ultrasound alters the behavior of enzymes, since they responded differently to alterations of pH and temperature in the presence of ultrasound comparing with effects in the absence. For temperatures up to 50 °C the activities of enzymes were always higher in the presence of ultrasound irradiation than in the absence. The activation energy of both enzymes in the presence of ultrasound was considerably reduced. The ultrasound showed to be a promising alternative to improve the enzyme activity, presenting potential for industrial application in enzyme reactions.

Evaluation of activity of a commercial amylase under ultrasound-assisted irradiation

The main objective of this work was to evaluate the effects of ultrasound irradiation on the activity of a commercial amylase. A central composite design was carried out to assess the effects of temperature and pH on the enzyme activity in the presence and absence of ultrasound irradiation. The activation energy, the influence of treatment time as well as the substrate concentration on enzyme activity were also determined in the presence and absence of ultrasound irradiation. The results demonstrated that the effect of temperature was less pronounced in the presence of ultrasound, resulting in a decreasing of about 80% in the activation energy in comparison with the value obtained in the absence. The enzyme showed activities about 3 times higher for temperatures up to 40°C in the presence of ultrasound. The pH negatively affected the activity in the presence of ultrasound, whereas in the absence a positive effect was verified. The ultrasound irradiation is a promising technology to be used in enzymatic reaction due to its positive effects on enzyme activity.

Ethanol Separation through Ultrasonic Atomization under Controlled Pressure

An aqueous solution of ethanol was ultrasonically atomized, and the mist was recovered to obtain concentrated ethanol solution. The atomization vessel was vacuumed, and the recovery vessel was pressurized for enhancing mist generation and recovery. Batch operation was carried out with and without pressure control, and the results obtained were compared. The amounts of produced and recovered mist increased dramatically upon pressure control. The ethanol concentration in the collected liquid was higher in the presence of ultrasound irradiation than in its absence. It was suggested that production of very fine ethanol-rich droplets was facilitated at reduced pressures, and the recovery was enhanced at elevated pressures.The effect of pressure in the atomization vessel on the amount of mist production and the ethanol concentration in the collected liquid was examined in the presence and absence of ultrasound irradiation. Without ultrasound irradiation, only evaporation would occur. Comparison of the results obtained with and without ultrasound irradiation indicated that the formation of fine droplets affected ethanol separation. The amount of mist collected was 1.4 times the amount of vapor. The ethanol concentration in the collected mist exceeded that in the collected vapor by 5 mol%. The results also suggested that the formation of fine droplets affected the ethanol separation degree by ultrasonic atomization.

Mineralization enhancement of a recalcitrant pharmaceutical pollutant in water by advanced oxidation hybrid processes

Degradation of the biorecalcitrant pharmaceutical micropollutant ibuprofen (IBP) was carried out by means of several advanced oxidation hybrid configurations. TiO 2 photocatalysis, photo-Fenton and sonolysis – all of them under solar simulated illumination – were tested in the hybrid systems: sonophoto-Fenton (FS), sonophotocatalysis (TS) and TiO 2/Fe 2+/sonolysis (TFS). In the case of the sonophoto-Fenton process, the IBP degradation (95%) and mineralization (60%) were attained with photo-Fenton (FH). The presence of ultrasonic irradiation slightly improves the iron catalytic activity. On the other hand, total removal of IBP and elimination of more than 50% of dissolved organic carbon (DOC) were observed by photocatalysis with TiO 2 in the presence of ultrasound irradiation (TS). In contrast only 26% of mineralization was observed by photocatalysis with H 2O 2 (TH) in the absence of ultrasound irradiation. Additional results showed that, in the TFS system, 92% of DOC removal and complete degradation of IBP were obtained within 240 min of treatment. The advanced oxidation hybrid systems seems to be a promising alternative for full elimination/mineralization for the recalcitrant micro-contaminant IBP.

Synthesis of morphologically controlled lanthanum carbonate particles using ultrasound irradiation

Lanthanum carbonate particles, which can be used as precursors to lanthanum oxide, have been synthesised from lanthanum nitrate and urea in the presence and absence of ultrasound irradiation. The use of ultrasound irradiation was found to have a remarkable effect on the morphology of the lanthanum carbonate particles formed. Needle-shaped particles were found to be formed in the presence of ultrasound irradiation, whereas spherical carbonate particles were produced in the absence of ultrasound irradiation. Characterization by powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, FT-IR spectroscopy, as well as elemental analysis was carried out on the materials synthesised. The effect of heating on the chemistry and the morphology of the carbonate particles was also investigated. The carbonate particles were found to be completely converted into lanthanum oxide at ca. 725 °C. In the case of the needle-shaped lanthanum carbonate particles, the shape was found to be deformed to a small extent on heating, whereas a larger degree of deformation was observed for the spherical lanthanum carbonate particles.