Ultrasound-assisted bleaching: Mathematical and 3D computational fluid dynamics simulation of ultrasound parameters on microbubble formation and cavitation structures

Synergist effect of thermosonication and NaCl on inactivation of Staphylococcus aureus and Shigella flexneri in lettuce: The effect of acoustic field and reaction kinetics

The study aimed to investigate the effect of thermosonication (TS; 37 KHz, 300 W; 30, 40, 50, and 60 °C for 10 min) and NaCl (12 % w/v) on the inactivation of Staphylococcus aureus and Shigella flexneri in lettuce, as well as to examine the kinetics of inactivation and the thermodynamic behaviors of the process. Computational Fluid Dynamics (CFD) simulations were employed to analyze the acoustic pressure field, velocity contours, and streamlines. The results showed that NaCl addition had the least impact on inactivation compared to TS and combined NaCl + TS. Increasing the temperature led to higher inactivation of both bacteria, with a more significant effect at 60 °C. Thermosonication treatment had a more consistent effect on inactivation compared to the addition of NaCl. When exposed to thermosonication, the population of S. aureus and S. flexneri could be reduced by 5.1 to 6.9 log CFU/g and 5.5 to 7.4 log CFU/g, respectively, at temperature levels of 30 and 60 °C. Additionally, no significant relationship between entropy reduction and type of microorganisms was observed. The samples that were treated only with NaCl had higher energy absorption than the other samples.

Application and development of ultrasound in industrial crystallization

Crystallization is an important process that affects the properties of final products and is essential in nearly all chemical processing industries. In recent years, ultrasonic technology has received widespread attention due to its ability to enhance crystallization yield, improve crystal morphology and shape, and regulate the particle size and distribution of crystal products. It holds promising prospects for industrial crystallization. In this work, the ultrasonic cavitation effect and ultrasonic crystallization mechanism are described, and the influence of ultrasound on the crystallization effect of products is analysed and discussed. In addition, the application status of ultrasonic reactors and ultrasonic crystallization processes is introduced in detail, and the change trend from laboratory to industrialization is analyzed. Finally, the challenges and opportunities facing the industrialization of ultrasonic crystallization in future developments are discussed. The purpose of this work is to make the selective promotion or inhibition of ultrasound more helpful for industrial crystallization.

Insights into kinetic, isotherm, and thermodynamic of ultrasound mode- and amplitude-dependent carotenoid and chlorophyll degradation or/and adsorption

Experimental data were analyzed to investigate the underlying adsorption or degradation mechanism of carotenoids and chlorophylls over the bleaching of sunflower oil through different amplitudes of horn and bath ultrasound (ultrasound-assisted bleaching; UAB), temperature, time, and bleaching clay. Quantifying the color removal efficiency in both batch and continuous systems, along with the corresponding process time and energy consumption, is paramount for evaluating the energy-related performance of the treatment method. The adsorption of pigments onto activated bentonite was notably rapid and effective when ultrasound was employed. In both bleaching processes, the adsorption kinetics of carotenoids and chlorophyll exhibited a pseudo-second-order behavior. At the same time, a pseudo-first-order equation provided a better fit for the control conditions. Moreover, intra-particle diffusion contributed to the adsorption mechanism, although it was not the only rate-limiting step in the adsorption of pigments on the clay. It is hypothesized that carotenoid and chlorophyll adsorption occur through physisorption in control conditions, while chemical reactions play a role in pigment removal under sonication. The Freundlich isotherm yielded precise estimates of the adsorption equilibrium data for carotenoid and chlorophyll during ultrasonic bleaching, suggesting a multilayer adsorption mechanism under ultrasound exposure. The thermodynamic study found that pigment adsorption was feasible, spontaneous, and endothermic. According to the results, horn and bath ultrasound, especially at higher voltages, can remarkably remove carotenoid and chlorophyll from sunflower oil compared to the traditional bleaching process.

A comparative study on bath and horn ultrasound-assisted modification of bentonite and their effects on the bleaching efficiency of soybean and sunflower oil: Machine learning as a new approach for mathematical modeling

In this study, the effect of high-power bath and horn ultrasound at different powers on specific surface area (S BET), total pore volume (V total), and average pore volume (D ave) of bleaching clay was examined. After subjecting the bleaching clay to ultrasonication treatment, the SBET values demonstrated an escalation from 31.4 ± 2.7 m2 g-1 to 59.8 ± 3.1 m2 g-1 for HU200BC, 143.8 ± 3.9 m2 g-1 for HU400BC, 54.4 ± 3.6 m2 g-1 for BU400BC, and 137.5 ± 2.8 m2 g-1 for BU800BC. The mean pore diameter (D ave) declined from 29.7 ± 0.14 nm in bleaching clay to 11.3 ± 0.13 nm in HU200BC, 8.3 ± 0.12 nm in HU400BC, 16.7 ± 0.14 nm in BU400BC, and 9.6 ± 0.12 nm in BU800BC. Therefore, horn ultrasound-treated bleaching clay significantly increased S BET and V total, indicating improved adsorption capacity. Moreover, to establish the relationship between bleaching parameters, seven multi-output ML regression models of Feedforward Neural Network (FNN), Random Forest (RF), Support Vector Regression (SVR), Multi-Task Lasso, Ridge regression, Extreme Gradient Boosting (XGBoost), and Gradient Boosting are used, and compared with response surface methodology (RSM). ML has revolutionized the understanding of complex relationships between ultrasonic parameters, oil color, and pigment degradation, providing insights into how various factors such as temperature, ultrasonic power, and time can influence the bleaching process, ultimately enhancing the efficiency and precision of the treatment. The XGBoost model showed outstanding performance in predicting the target variables with a high R 2-train up to 1, R 2-test up to .983, and a minimum mean absolute error (MAE) of 0.498. The lower error between the predicted and experimental values implies the superiority of the XGBoost model to predict outcomes rather than RSM. It represents the suitability of bath ultrasound as a mild condition for low-pigmented oil bleaching. Finally, the Bayesian optimization method in conjunction with XGBoost was used to optimize the amount of bleaching clay and energy consumption, and its performance was compared with RSM. It was observed that the consumption of bleaching clay was reduced by approximately 60% for sunflower oil and 30%-35% for soybean oil.

Ultrasound-assisted starch hydrolyzing by alpha-amylase: Implementation of computational fluid dynamics, acoustic field determination, and rheology modeling

The study aimed to optimize the ultrasonic-assisted modification (UAM) of corn and potato starch by assessing the influence of ultrasound geometry, power, and frequency on the fluid flow for sonicated starch to achieve porous starch with a higher degree of hydrolyzing by α-amylase. This assessment was conducted through mathematical modeling and 3D computational fluid dynamics (CFD) simulations. The ultrasonic pressure field is determined by the solution of the non-linear Westervelt equation in the frequency domain. Then, the obtained field is utilized to simulate the dissipated power and flow field characteristics. According to the results obtained from the Rapid Visco Analyzer (RVA), it was observed that the peak and final viscosity of hydrolyzed sonicated starch were less than hydrolyzed native starch. This decrease in viscosity indicates a breakdown of the starch structure, leading to a more fluid-like consistency. The shear rate and shear stress data are used for rheology modeling. The fluid's viscosity is represented based on three models of Herschel-Bulkley, Casson, and Power law (Ostwald-de Waele). The magnitude of yield shear stress at low shear rates, the shear-thinning behavior, and the nearly Newtonian fluid nature at high shear rates are extracted from the viscosity models. The surfaces of the starch granules were analyzed using scanning electron microscopy (SEM) revealed that sonication treatments caused damage, cracks, and porosity on the surfaces of the starch granules which were prone to amylolytic enzymes. This indicates that the structural integrity of the granules was compromised and facilitated enzyme penetration. This study proposes that ultrasonication can be utilized to produce damaged starch, which is susceptible to hydrolysis by α-amylase. This approach holds the potential for reducing enzyme consumption in various industries.

Investigation of ultrasound-assisted starch acetylation by single- and dual- frequency ultrasound based on rheology modelling, non-isothermal reaction kinetics, and flow/acoustic simulation

To achieve wheat starch acetylation (AC) with a high degree of substitution (DS), the acetylation process was carried out using various ultrasonication frequencies, including 25 kHz, 40 kHz, and 25 + 40 kHz. In the second step, wheat starch's ultrasound-assisted acetylation (UAA) is simulated using various approaches including the rheology models, non-isothermal reaction kinetics, and flow/acoustic modelling. The computational fluid dynamics (CFD) simulation solves the non-linear acoustic governing equation to determine the flow field and the amount of delivered ultrasound energy. The acetylated starch increased peak and final viscosity, with the highest values observed for the 25 + 40 kHz frequency than other single frequencies (25 kHz and 40 kHz). The viscosity of the starch is specified based on the experimental data using Herschel-Bulkley, power law, and Casson rheology models. According to differential scanning calorimetry (DSC) analysis, the gelatinization parameters and enthalpy of gelatinization (ΔHgel), were found to be lower in acetylated starches at the frequency of 25 + 40 kHz compared to those at frequencies of 25 kHz and 40 kHz, as well as native starches (NS). Moreover, the gelatinization process is examined by implementing the non-isothermal reaction kinetics to obtain the activation energy and reaction order. Based on the results obtained, implementing sonication at 25 kHz reduces the activation energy by 70.3 % compared to native starch. However, the same parameter is obtained to be 69.9 % and 67.1 % for the application of 40 and 25 + 40 kHz transducers, respectively. Additionally, during the sonication treatment, the yield shear stress increases between 24.1 and 31.8 %, based on the applied frequency. Morphology analysis determined by scanning electron microscopy (SEM) revealed that the surfaces and small granules underwent more damage in acetylated starches at frequencies of 25 kHz and 40 kHz. However, in acetylated starches at 25 + 40 kHz, the larger granules were more affected than the smaller ones.

High-power ultrasound bleaching technique for canola oil (Brassica napus L.): Pigments removal and quality parameters

Canola seeds (Brassica napus L.) are among the most commonly used seeds in Mexico for vegetable oil production. This is based on the high yield and content of polyunsaturated and monounsaturated fatty acids. During oil bleaching, it is important to maintain fatty acids in their cis configuration because of the health concerns associated with trans-fatty acid consumption. In this sense, the industrial processing parameters employed for this purpose present some limitations, such as high temperatures and long times, which may change the cis configuration to trans. In addition, the amount of bleaching clay employed for this process could be a source of contamination because it is disposed of after treatment. Therefore, the aim of this study was to develop a bleaching process for canola oil using high-power ultrasound (US). US processing was applied to nine treatments with different processing times (60, 75, and 90 min), clay percentages (1, 2, and 3%), and temperatures (60 and 80 °C) to determine the concentrations of chlorophyll a and b (µg chlo/100 g oil), carotenes (µg β-carotene/100 g oil), color (L*, a*, b*, C*, and h°), iodine value (g I2/100 g oil), and finally carrying out a spectroscopic analysis (ATR-FTIR and Raman). A conventional bleaching treatment (100 °C for 180 min, 3% bleaching clay) was used as a control. The results revealed that US treatments with 2% clay at 60 °C for 60 and 90 min eliminated most of the chlorophyll compounds (98%). However, in terms of carotenes reduction, these identical treatments exhibited a similar tendency to that of the control (approximately 30% decrease). These findings also affected the sample color, in which US treatments revealed chromatic coordinates that indicated yellow tones with chroma values that were more intense than those in the control samples. In terms of the iodine value, such treatments fulfilled the international standards for vegetable oils (90-100 g I2/100 g oil). Finally, the spectroscopic study revealed no trans configurations or the presence of different chemical compounds after US treatment, because neither of them presented typical peaks for those molecular configurations. In this regard, US can be a useful methodology for bleaching vegetable oils, helping to reduce time, and bleaching clay with similar pigment reduction results.

Ultrasonic Synthesis of Nanochitosan and Its Size Effects on Turbidity Removal and Dealkalization in Wastewater Treatment

A detailed study on the synthesis of chitosan nanoparticles under ultrasonication is reported in this paper. By using this simple technique, chitosan particles in nanometer range can be easily prepared without using any harmful and expensive chemicals. The results show that increasing the ultrasonic irradiation time and ultrasonic wave amplitude are the key factors for producing discrete chitosan nanoparticles with narrow particle size distribution. The resulting nanoparticles show superior turbidity removal efficiency (75.4%) and dealkalization (58.3%) in wastewater treatment than the bulk chitosan solid (35.4% and 11.1%, respectively), thus offering an eco-friendly and promising approach for treating wastewater via the coagulation/flocculation process.

The potential use of ultrasound-assisted bleaching in removing heavy metals and pigments from soybean oil using kinetic, thermodynamic and equilibrium modeling

In this research, the sorption behavior (kinetic, isotherm, and thermodynamic modeling) of heavy metals (Cu (II) and Fe (II)) and pigments (carotenoid and chlorophyll) onto activated bentonite clay was investigated for soybean oil under industrial (IBM) and ultrasonic bleaching method (UBM). A nonlinear fitting approach was used to determine the best-fit isotherm and kinetic models by two statistical criteria including the coefficient of determination (R²) and chi-square (χ²). The adsorption of metal ions and pigments onto activated bentonite clay under UBM was quite well by the pseudo-first-order model. In both bleaching methods, the equilibrium adsorption data follows the Toth isotherm model, presenting the sorption occurrence tends to be on a heterogeneous surface. The results indicated that the adsorption thermodynamics was endothermic in nature and the process was spontaneous between 35 and 65 °C.

Analysis of ultrasound-assisted convective heating/cooling process: Development and application of a Nusselt equation

In this study, the convective heating/cooling process assisted by US irradiation is analyzed with the aims of developing a new convective heat transfer correlation. Heat transfer experiments were conducted with different copper machined geometries (cube, sphere and cylinder), fluid velocities (0.93-5.00 × 10^-3 m/s), temperatures (5-60 °C), and US intensities (0-6913 W/m²) using water as heat transfer fluid. The Nusselt (Nu) equation was obtained by assuming an apparent Nu number in the US-assisted process, expressed as the sum of contributions of the forced convection and cavitation-acoustic streaming effects. The Nu equation was validated with two sets of experiments conducted with a mixture of ethylene glycol and water (1:1 V/V) or a CaCl₂ aqueous solution (30 g/L) as immersion media, achieving a satisfactory reproduction of experimental data, with mean relative deviations of 17.6 and 17.8%, respectively. In addition, a conduction model with source term and the proposed correlation were applied to the analysis of US-accelerated heating kinetics of dry-cured ham reported in literature. Results demonstrated that US improves heating of ham slices because of the increased heat transfer coefficients and the direct absorption of US power by the foodstuff.

Sonication treatment of pomegranate juice containing Saccharomyces cerevisiae and Byssochlamys fulva: Thermodynamic and predictive modeling after treatment and during shelf life

The effect of ultrasound treatment (100 W, 30 kHz; 50 and 100% amplitudes) on inactivation of Saccharomyces cerevisiae and Byssochlamys fulva in pomegranate juice and shelf life of the juice during storage at different temperatures (5, 15 and 30 °C) for 30 days was modeled using predictive and thermodynamics models. The Baranyi and square root type models were implemented to determine the growth rate of microorganisms. It was predicted that the minimum growth temperature (T_min) of B. fulva increased by increasing sonication amplitude, however, the T_min of S. cerevisiae was not function of sonication amplitude. The predicted shelf life was shown to be in good agreement with the measured sensorial shelf life. Increasing the temperature from 5 to 35 °C, reduced the shelf life from 17.5 to 3.5 days for B. fulva and from 15 to 5 days for S. cerevisiae. Moreover, for B. fulva, the activation energy (E_a) decreased from 43.4 to 27.5 kJ/mol by increasing the amplitude, while no significant change was observed for S. cerevisiae. Besides, thermodynamics properties of the shelf life such as enthalpy (ΔH++), entropy (ΔS++) and Gibbs free energy (ΔG++)  were proven to be suitable measures to determine the microbial spoilage reaction.

Establishing an ultrasound-assisted activated peroxide system for efficient and sustainable scouring-bleaching of cotton/spandex fabric

This study presents a high-efficient and cost-effective ultrasound-assisted strategy for one-bath one-step scouring and bleaching of cotton/spandex fabric using sodium percarbonate (SPC) and tetraacetylenediamine (TAED) couple. SPC plays both roles of pH regulator and H₂O₂ donor to initiate the peracetic acid (PAA) release from TAED. The significance and interaction effects of operating parameters (TAED concentration, temperature and time) on the WI (Whiteness Index) of fabrics were investigated through a central composite design. The bleaching mechanism was studied by exploring the relationship between WI and PAA and hydroxyl radical (HO·) concentrations. The mechanical and dyeing performances of treated fabrics were also evaluated. Results show that temperature exerted a significant impact on WI followed by TAED concentration and time. The PAA concentration decreased and HO· concentration increased upon the temperature rise. Both PAA and HO· were significant to upgrade WI and ultrasound was effective in enhancing their bleaching efficiency. The fabric treated only with 15 mmol/L TAED and 10 mmol/L SPC at 40 °C for 40 min under ultrasound could achieve a WI of 68.6 (43% higher than greige fabric), which was almost equivalent to that of the fabric treated at 60 °C without ultrasound. This verifies the contribution of ultrasound technology in reducing bleaching temperature for energy-saving purpose. Moreover, the treated fabric displayed less than 5% tensile strength loss, having a marginal impact on the apparel performance. The wettability of fabric was greatly improved leading to a good dyeing performance. Encouraging results demonstrate the high efficiency of the ultrasound-assisted pre-treatment process of cotton/spandex fabric, which contributes to the sustainable production of textiles.

Effect of Different Green Extraction Methods and Solvents on Bioactive Components of Chamomile (Matricaria chamomilla L.) Flowers

Chamomile (Matricaria chamomilla L.) dried flowers contain a group of interesting biologically active compounds such as sesquiterpenes, flavonoids, coumarins, vitamins, phenolic acids and glucosides. Therefore, the aim of the present study was to characterize the composition in bioactive compounds (specialized metabolites) present in water and ethanol extracts of chamomile flowers, together with monitoring the impact of different extraction techniques (conventional vs. ultrasound-assisted extraction (UAE)) on the parameters under investigation. UAE treatment significantly decreased the extraction time of bioactive compounds from herbal material. Polyphenolic compounds content and antioxidant capacity were significantly higher in UAE extracts. Moreover, solvent type had a significant impact on the specialized metabolites content, while the highest vitamin C and polyphenols content were recorded in 50% ethanol (v/v) extracts. Optimization of basic extraction factors: solvent type, temperature and technique is crucial for obtaining the extracts with the highest content of specialized metabolites and antioxidant capacity.