Ultrasonic Power Dissipation Research Articles

Investigation on The Effect of Low Frequency Ultrasound on The Crystallization of a Pharmaceutical Compound L+ Ascorbic Acid

One of the most crucial processes in the chemical processing industry is crystallization, which has the major challenge of producing solid products with the required purity and properties. The standard crystallization methods have various processing limitations; hence, research into alternative methods like ultrasonic-assisted crystallization has been at the forefront. The present work investigates the application of low-frequency ultrasound irradiation (40 kHz) for improving the cooling crystallization of ascorbic acid. The impact of ultrasonic irradiation on crystal size, shape, and induction time has been studied, and a comparison with the conventional method has been made. The standing time had a minor effect on particle size on average, while the initial temperature had a far more significant impact. Photographic analysis using image-analysis software indicated that when ultrasound was applied to the saturated solutions, the resulting crystals were smaller and more uniform in size and shape. The resultant crystal grows predominantly in a single direction, resembling thin prisms. The use of ultrasound was also shown to reduce the induction time significantly. This ultrasonic impact is stronger at lower initial temperatures. Indeed, the smallest induction time of 300 s was obtained for sonicated solutions at an initial temperature of 65°C and ultrasonic power of 250 w. When different levels of ultrasonic power dissipation were tested, it was established that the time required for the first nuclei to appear decreased as the power increased. There was, nevertheless, a marginal impact on average crystal size.

Comparison of acoustic and hydrodynamic cavitation based hybrid AOPs for COD reduction of commercial effluent from CETP

The present work investigates the treatment of commercial effluent obtained from Common Effluent Treatment Plants (CETP) using acoustic cavitation (AC) and hydrodynamic cavitation (HC) based hybrid AOPs. Comparison of different hybrid AOPs viz. H2O2, Fe2+/H2O2, Fe2+/H2O2/Air, Fe2+/H2O2/S2O82− and Fe2+/H2O2/S2O82−/Air in combination with both AC and HC has been performed in terms of extent of chemical oxygen demand (COD) reduction and kinetic rate constants. The best results of COD reduction as 95.2% and 97.28% were obtained for AC/Fe2+/H2O2/Air and HC/Fe2+/H2O2/Air systems respectively at Fe2+/H2O2 ratio of 0.1 and pH of 2 within 60 min of treatment under conditions of ultrasonic power dissipation as 150 W, inlet pressure for HC as 4 bar (as applicable depending on process) and temperature of 30 ± 2 °C. Slightly lower efficacy was established for the combination approach involving AC or HC coupled with Fe2+-activated S2O82− and H2O2 yielding COD reduction of 82.9% and 86.93% for the AC/Fe2+/H2O2/S2O82−/Air and HC/Fe2+/H2O2/S2O82−/Air systems respectively at Fe2+/H2O2/S2O82− ratio of 1:40:17.5. Cost estimation on the basis of cavitational yield performed on the AC and HC based treatment systems revealed economical nature of HC based treatment. Kinetic studies were also performed by fitting the experimental data with pseudo first order kinetic model (PFOKM), generalized kinetic model (GKM) and Behnajady-Modirshahla-Ghanbery kinetic model (BMGKM). It was demonstrated that GKM provided best fitting for all the experiments whereas BMGKM was most suitable for Fenton based reactions. It was clearly established that complex CETP effluent can be effectively treated using the combined approaches based on HC with potential for larger scale operation.

Intensified oxalic acid crystallization using ultrasonic reactors: Understanding effect of operating parameters and type of ultrasonic reactor

The present work reports the comparison of the effectiveness of ultrasonic bath and horn for intensifying the cooling crystallization of oxalic acid for the first time. The effect of various parameters such as temperature, crystallization time, irradiation time, ultrasonic frequency and ultrasonic power on the crystal characteristics has been investigated. The average particle size of oxalic acid crystals reduced with an increase in irradiation time and ultrasonic power dissipation. Comparison of crystal characteristics obtained in ultrasonic bath with that obtained in the ultrasonic horn under optimized parameters revealed that the average size in the case of ultrasonic horn and bath were only marginally different. The studies related to the effect of different cooling modes using ultrasonic horn revealed that a narrow size distribution and lower average size of 357.2µm was obtained for the cooling using ice cold water as compared to air cooling where observed mean size was 439.7µm. A narrow particle size distribution was also obtained in the scale-up studies using ultrasound horn with mean size of 96.70µm, which was significantly lower than 161.1µm obtained under conventional approach. Overall significant process intensification benefits have been established for the ultrasound assisted approach for cooling crystallization of oxalic acid.

Acoustic Cavitation as a Novel Approach for Extraction of Oil from Waste Date Seeds

This work deals with the extraction of date seed oil using an acoustic cavitation. The process parameters such as sonication (extraction) time, power dissipation, operating temperature, and solvent to date seed ratio have been optimized on the basis of extracted oil yield. The obtained results have been compared with the frequently used extraction methods (such as maceration and Soxhlet extraction method). The highest extraction efficiency was found at a solvent (hexane) to seed ratio of 5, applied rated power of 30% of 750 W (actual dissipated power is 2.98 W), ultrasound treatment time of 45 min, and at a temperature of 20 °C. It was observed that as ultrasonic power dissipation increases the oil extraction yield also increases and declines with an increase in temperature. These results are attributed to only physical effects of cavitation occuring onto the surface of the date seeds which enhance the permeability of the solvent into the plant tissues due to the formation of cracks, crevices, and microfr...

Intensification of depolymerization of polyacrylic acid solution using different approaches based on ultrasound and solar irradiation with intensification studies

Depolymerization of polyacrylic acid (PAA) as sodium salt has been investigated using ultrasonic and solar irradiations with process intensification studies based on combination with hydrogen peroxide (H2O2) and ozone (O3). Effect of solar intensity, ozone flow and ultrasonic power dissipation on the extent of viscosity reduction has been investigated for individual treatment approaches. The combined approaches such as US+solar, solar+O3, solar+H2O2, US+H2O2 and US+O3 have been subsequently investigated under optimum conditions and established to be more efficient as compared to individual approaches. Approach based on US (60W)+solar+H2O2 (0.01%) resulted in the maximum extent of viscosity reduction as 98.97% in 35min whereas operation of solar+H2O2 (0.01%), US (60W), H2O2 (0.3%) and solar irradiation resulted in about 98.08%, 90.13%, 8.91% and 90.77% intrinsic viscosity reduction in 60min respectively. Approach of US (60W)+solar+ozone (400mg/h flow rate) resulted in extent of viscosity reduction as 99.47% in 35min whereas only ozone (400mg/h flow rate), ozone (400mg/h flow rate)+US (60W) and ozone (400mg/h flow rate)+solar resulted in 69.04%, 98.97% and 98.51% reduction in 60min, 55min and 55min respectively. The chemical identity of the treated polymer using combined approaches was also characterized using FTIR (Fourier transform infrared) spectra and it was established that no significant structural changes were obtained during the treatment. Overall, it can be said that the combination technique based on US and solar irradiations in the presence of hydrogen peroxide is the best approach for the depolymerization of PAA solution.

A novel approach for intensification of enzymatic depolymerization of carboxymethyl cellulose using ultrasonic and ultraviolet irradiations

The present work investigates the application of ultrasonic (US) and ultraviolet (UV) irradiations operated individually or in combination for intensification of enzymatic depolymerization of aqueous solution of carboxymethyl cellulose (CMC) present as sodium salt. The effect of different operating parameters such as reaction temperature, enzyme loading, UV and US power dissipation on the extent of depolymerization have been studied. The effectiveness of treatment approach has been analyzed on the basis of kinetic rate constant, limiting intrinsic viscosity and the time required for the desired extent of intrinsic viscosity reduction. The kinetic rate constant has been found to increase with an increase in the temperature and cellulase loading. The extent of depolymerization increased from 20% to 58.5% with an increase in the operating power of UV from 8W to 32W (irradiation time as 180min) whereas the increase was from 74% to 87% for an increase in ultrasonic power from 60W to 120W (irradiation time of 120min). In the presence of US (60W)+UV (16W)+enzyme (0.05%), the maximum extent of depolymerization of CMC has been observed as 99% with treatment time of 18min. The effect of ultrasonic irradiation on viscosity reduction was established to be more pronounced than the ultraviolet irradiations. The obtained results from FTIR spectra clearly established that no changes in the chemical structure were observed for the treated CMC using combined ultrasound, ultraviolet irradiations with enzyme and native CMC. The work has conclusively established, for the first time, that the combination of ultraviolet and ultrasonic irradiation in presence of cellulase enzyme gives maximum viscosity reduction in CMC polysaccharides as compared to individual approaches.

Ultrasound-assisted improved synthesis of supported V2O5 catalyst and subsequent application for the production of n-hexyl acetate

The present work deals with synthesis of vanadium pentoxide supported on alumina as a heterogeneous catalyst using two approaches as conventional synthesis based on ozonation and intensified approach based on combination of ultrasound with ozonation. Commercially available vanadium sulfate hydrate has been used as a precursor for the catalyst synthesis. The catalyst characterization has been performed in details using particle size, FTIR, SEM, EDX and XRD analysis. It has been observed that the ultrasound assisted approach for catalyst synthesis resulted in reduced particle size and also increased the stability of the synthesized catalyst nanoparticles. The obtained catalyst was further used in the reaction for synthesis of n-hexyl acetate with detailed investigation into the effect of operating parameters. The optimum conditions established for the esterification were molar ratio of alcohol to acid as 6:1, catalyst concentration of 1.5% by weight, temperature as 70°C and ultrasonic power dissipation as 100W with duty cycle of 80% and an irradiation time of 150min. The efficacy of the ultrasound assisted approach for the esterification has also been compared with the conventional approach. The ultrasound assisted operation improved the conversion from 53.33% obtained in the conventional processing to 80.38% with a reduction in operating temperature of the reaction from 100°C for the conventional approach to 70°C for the ultrasound assisted approach. The work has clearly elucidated the beneficial effects that can be obtained by the use of ultrasound in both catalyst synthesis as well as catalytic reactions.

Ultrasound-assisted preparation of ZnO nanostructures: understanding the effect of operating parameters

AbstractThe present work deals with the use of ultrasound atomization for the preparation of zinc oxide nanostructures. The focus of the work is to understand the effect of different operating parameters, such as ultrasonic power dissipation, flow rate, concentration, and surface tension, on the final particle morphology obtained during the synthesis. The prepared nanostructures were observed under scanning electron microscope to understand the morphology of the synthesized nanostructures. It was established that the final characteristics of the nanostructures, in terms of shape and size, can be effectively controlled by controlling flow rate, precursor concentration, surface tension, and ultrasonic power dissipation. The droplet size was found to increase with an increase in the flow rate of an aqueous solution of zinc nitrate, ultrasonic power, and decrease in the loading of surfactant (polyvinylpyrrolidone). The present work has clearly established the utility of ultrasound-assisted synthesis of nanoparticles with clear evidence for obtaining desired characteristics based on controlled application.

Ultrasound Assisted Synthesis of 4-Benzyloxy-3-methoxybenzaldehyde by Selective O-Alkylation of Vanillin with Benzyl Chloride in the Presence of Tetrabutylammonium Bromide

Cavitational reactors are a novel and promising form of multiphase reactors, based on the principle of the release of a large magnitude of energy due to the violent collapse of the cavities, which can be effectively applied for intensification of chemical synthesis. In the present work, 4-benzyloxy-3-methoxybenzaldehyde has been synthesized by selective O-alkylation of vanillin with benzyl chloride using tetrabutylammonium bromide-based phase transfer catalysis in the presence of ultrasonic irradiations. The reactions were performed in a 150 cm3 capacity glass reactor equipped with reflux condenser, and ultrasonic irradiations were introduced using an ultrasonic horn operating at a frequency of 20 kHz with a power rating of 120 W. The effects of different operating parameters such as quantum of aqueous phase, temperature, catalyst loading, ultrasonic power dissipation, and molar ratio of reactants have been investigated with an aim of maximizing the extent of synthesis of 4-benzyloxy-3-methoxybenzaldehyde...

Investigation of induction of air due to ultrasound source in the sonochemical reactors

A detailed investigation into the phenomena of induction of air using a novel arrangement of the ultrasonic horn (tip is located just above the liquid surface) has been made with the quantification of the extent of induction in terms of the air entrainment rate and the gas–liquid mass transfer coefficient for the transfer of air into the system. The measurement of air entrainment rate was found to be quite difficult and hence focus was kept on the quantification in terms of the gas–liquid mass transfer coefficient. The effect of ultrasonic power dissipation and type of the liquid medium (water, sodium chloride and sodium laruyl sulphate [surfactant] solution) on the mass transfer coefficient has been studied and correlations have been developed for the prediction of the same. Comparison with the mechanically agitated surface aerators has enabled us to understand the controlling mechanism in the induction and subsequent distribution of the air i.e. turbulence or convective motion. The present work should open an entirely new field of research in the area of design of sonochemical gas–liquid reactors operating possibly as a combination of gas-inducing reactors and cavitational reactors.