Ultrasonic Reactor Research Articles

Mapping of a Stirred Ultrasonic Reactor Operated in Recirculation Mode Using a Cavitation Activity Meter and Validation Using Dye Degradation

Mapping of a Stirred Ultrasonic Reactor Operated in Recirculation Mode Using a Cavitation Activity Meter and Validation Using Dye Degradation

Optimisation and numerical simulation of ultrasonic reactor in hydrometallurgical process

ABSTRACT In this paper, COMSOL Multiphysics software is used to carry out simulations to visualise the distribution of the acoustic field and sound pressure in the reaction cavity for different ultrasonic frequencies, powers, reaction cavity shapes, ultrasonic horn diameters and ultrasonic horn action depths. The results indicate the ultrasonic frequency affects the uniformity of the acoustic field distribution, and the ultrasonic power affects the magnitude of the sonic pressure. Taking into account that the sonic pressure is not less than the cavitation threshold, the sound field is evenly distributed, and it is energy-saving and environment-friendly. The optimal simulation conditions are obtained. In a 500 mL cylindrical reaction chamber, the ultrasonic frequency and power are 25 kHz and 130 W, respectively. The diameter of the ultrasonic horn is 34 mm, and the depth of action is 30 mm. Under these conditions, the maximum sound pressure reaches 1.08 × 106 Pa.

Multifrequency Ultrasound-Based Predictive Method for Biodiesel Production

Fossil fuel price continuous growth invites to look for alternative solutions to fuel for internal combustion engines. One of the most accepted options is biodiesel. In the present study, the multifrequency ultrasound-assisted synthesis of Sinapis alba oil biodiesel has been tested. For this purpose, an ultrasonic probe working at 20 kHz and an ultrasonic reactor with interchangeable transducers of discrete frequencies (195 kHz, 578 kHz, 861 kHz and 1136 kHz) have been used. For the probe, a multi-response optimisation has been carried out, setting methanol-to-oil molar ratio at 5.5:1. Optimal results were provided by 1.42 percentage weight (wt%) of catalyst after approx. 10 min of ultrasonication. In case of transducers, oil-to-biodiesel conversion needed an ultrasonication time of 15 min. Overall, when ultrasound frequency increases, oil-to-biodiesel conversion slightly improves. In conclusion, this work provides a predictive method to produce biodiesel under ultrasonication conditions, at different frequencies, in batch mode. Resulting biodiesel meets European standard requirements.

Thermodynamics analysis of fins integration in sono-PCM reactor: Sonic power influence

This research presents a novel approach of integrating fins into a sonochemical phase change material (PCM) reactor to tackle the challenge of low PCM thermal conductivity, with a focus on cooling the ultrasonic reactor. Through comprehensive numerical simulations using a Fluent-based CFD code, we analyze the thermal performance of the sono-PCM system with and without fins under varying power densities (45.5 and 85.6 kW/m3) and operating times (up to 1 h). Our results highlight the remarkable advantage of fins in accelerating the heat transfer and melting process, reducing the time for a 50% PCM melt by 28.1 and 45.2% for power densities of 45.5 and 85.6 kW/m3, respectively. Enthalpy analysis further confirms the efficiency of the fins, demonstrating a reduction of ∼19% in water enthalpy after 1 h for both power densities. Moreover, the presence of fins significantly enhances the heat recovery by the PCM, leading to 20.1 and 73.2% increase in PCM enthalpy for power densities of 45.5 and 85.6 kW/m3, respectively. These enhancements are attributed to the increased surface area of contact provided by fins, which facilitate efficient heat dissipation within the bulk PCM. This study not only provides crucial insights into PCM systems with fins but also opens up avenues for advanced thermal energy management strategies, revolutionizing heat storage and transfer processes across various engineering applications.

Ultrasonic reactor set-ups and applications: A review

Sonochemistry contributes to green science as it uses less hazardous solvents and methods to carry out a reaction. In this review, different reactor designs are discussed in detail providing the necessary knowledge for implementing various processes. The main characteristics of ultrasonic batch systems are their low cost and enhanced mixing; however, they still have immense drawbacks such as their scalability. Continuous flow reactors offer enhanced production yields as the limited cognition which governs the design of these sonoreactors, renders them unusable in industry. In addition, microstructured sonoreactors show improved heat and mass transfer phenomena due to their small size but suffer though from clogging. The optimisation of various conditions of regulations, such as temperature, frequency of ultrasound, intensity of irradiation, sonication time, pressure amplitude and reactor design, it is also discussed to maximise the production rates and yields of reactions taking place in sonoreactors. The optimisation of operating parameters and the selection of the reactor system must be considered to each application’s requirements. A plethora of different applications that ultrasound waves can be implemented are in the biochemical and petrochemical engineering, the chemical synthesis of materials, the crystallisation of organic and inorganic substances, the wastewater treatment, the extraction processes and in medicine. Sonochemistry must overcome challenges that consider the scalability of processes and its embodiment into commercial applications, through extensive studies for understanding the designs and the development of computational tools to implement timesaving and efficient theoretical studies.

Intensification of α-amylase activity using ultrasound and its application for food waste hydrolysis

The current research aims to study the ultrasound assisted intensification of activity of commonly applied amylase enzyme, under varying parameters like power, frequency, duty cycle, temperature and enzyme concentration. Two ultrasonic reactor configurations as bath and horn are used for comparing the efficacy of reactor configuration. The initial activity of native amylase was found as 5.77 U/g at optimum temperature of 35° C and pH 7. Under US bath treatment, α amylase attained maximum activity of 7.498 U/g at best treatment conditions of 120 W power, 30% duty cycle and 15 minutes of exposure time. In the case of US horn, application of 60 W power, 30% duty cycle, and 5 minutes of exposure increased the enzyme activity to 6.907 U/ g. Set of treatment approaches explored for obtaining highest yield of reducing sugars revealed the best approach of ultrasonic treatment of food waste followed by ultrasonic bath intensified amylase hydrolysis, yielding maximum amount of reducing sugars as 8.14 g/L in only 15 min. Overall the work elucidated the role of ultrasound in intensifying the enzyme activity as well as food waste hydrolysis maximizing the utilization of sustainable resource.

Coffee brewing sonoreactor for reducing the time of cold brew from several hours to minutes while maintaining sensory attributes

This research designed and developed an ultrasonic reactor for a fast and on demand production of cold brew coffee, remarkably reducing the brewing time from 24 h to less than 3 min. The technology was engineered by utilizing resonance to induce ultrasonic waves around the walls of the brewing basket of an espresso machine. The sound transmission system comprised a transducer, a horn and a brewing basket. This arrangement transformed the coffee basket into an effective sonoreactor that injected sound waves at multiple points through its walls, thereby generating multiple regions for acoustic cavitation within the reactor. Furthermore, acoustic streaming induced greater mixing and enhanced mass transfer during brewing. The design was accomplished by modeling the transmission of sound, and acoustic cavitation. Brew characterization and chemical composition analysis was performed, considering factors such as pH, acidity, color, and the composition of caffeine, fatty acids, and volatiles. The efficiency of the extraction increased by decreasing the basket loading percentage (BLP). For instance, sonicating at 100 W doubled the extraction yield and caffeine concentration, from 15.05 % to 33.44 % at BLP = 33 %, and from 0.91 mg/mL to 1.84 mg/mL at BLP = 67 %, respectively. The total fatty acids increased from 1.16 mg/mL to 9.20 mg/mL, representing an eightfold increase, at BLP = 33 %. Finally, a sensory analysis was conducted to evaluate appearance, aroma, texture, flavor, and aftertaste, which demonstrated that coffee brewed for 1 and 3 min in the sonoreactor exhibited almost undistinguishable properties compared to a standard 24 h brewing without ultrasound.

Sintesis Biodiesel Dari Minyak Jelantah Dalam Reaktor Ultrasonik

Waste cooking oil is considered promising alternative to biodiesel production as substitute for diesel fuel becauce it it is environmentally friendly, biodegradable, non-toxic, and renewable energy source. This study aims to obtain the optimum operating conditions of ultrasonic reactors in biodiesel production using Response Surface Methodology (RSM) method. RSM with CCD was used to determine effect of transducer distance (1-5 cm) and reaction time (5-20 minutes) on biodiesel yield, to determine optimal operating conditions and to optimize biodiesel yield. In this study, waste cooking oil was transesterified into biodiesel with ultrasonic waves to intensify reaction. Transesterification waste cooking oil was carried out in a sodium hydroxide catalyst using methanol. Solution inserted into the erlenmeyer with the transducer distance and reaction time to determined by RSM. Once the reaction time was reached, mixture of biodiesel and glycerol was separated in separate funnel. Biodiesel obtained was then washed and evaporated the remaining solvent. Biodiesel yield was obtained under 88.33% under optimal conditions of 1 cm transducer distance with reaction time 20 minutes. Reaction time was the most important parameter based on the ANOVA test. The properties biodiesel produced including kinematic viscosity, density, acid number, methyl ester contents and monoglicerida have met the requirements of standards SNI 7182: 2015.

Acoustic cavitation for agri-food applications: Mechanism of action, design of new systems, challenges and strategies for scale-up

Acoustic cavitation, an intriguing phenomenon resulting from the interaction of sound waves with a liquid medium, has emerged as a promising avenue in agri-food processing, offering opportunities to enhance established processes improving primary production of ingredients and further food processing. This comprehensive review provides an in-depth analysis of the mechanisms, design considerations, challenges and scale-up strategies associated with acoustic cavitation for agri-food applications. The paper starts by elucidating the fundamental principles of acoustic cavitation and its measurement, delving then into the diverse effects of different parameters associated with, the acoustic wave, mechanical design and operation of the ultrasonic system, along with those related to the food matrix. The technological advancements achieved in the design and set-up of ultrasonic reactors addressing limitations during scale up are also discussed. The design, engineering and mathematical modelling of ultrasonic equipment tailored for agri-food applications are explored, along with strategies to maximize cavitation intensity and efficiency in the application of brining, freezing, drying, emulsification, filtration and extraction. Advanced US equipment, such as multi-transducers (tubular resonator, FLOW:WAVE®) and larger processing surface areas through innovative designing (Barbell horn, CascatrodesTM), are one of the most promising strategies to ensure consistency of US operations at industrial scale. This review paper aims to provide valuable insights into harnessing acoustic cavitation's potential for up-scaling applications in food processing via critical examination of current research and advancements, while identifying future directions and opportunities for further research and innovation.

Heat management in sonochemical reactor using fins-PCM integrated system: Unveiling the influence of the sonicated volume

With the purpose of enhancing the heat management in the ultrasonic reactor, the present innovative research aims at the exploration of the thermal behavior of sonochemical reactor integrated with fins and phase change material (PCM), focusing on the influence of different liquid heights (LH). The performance of this combination (i.e., sonicated water, fins, and PCM) is investigated for the first time with consideration of the water volume variation. The interplay between fins, liquid height and heat transfer efficiency is explored through detailed numerical analysis of temperature profiles, PCM melt fractions, and enthalpy distributions. The numerical investigation has been conducted using a validated CFD model implemented in ANSYS Fluent® software. The results highlight the significant role of fins in accelerating the PCM melting process and improving heat transfer within the reactor. Notably, fins facilitates efficient conductive heat transfer during the early stages of melting. At t = 1000 s, PCM melt percentages of 22.2 %, 32.6 % and 30 % were attained with fins, compared to 15 %, 18 % and 22 % (without fins), for LH = 5.1, 10.2 and 15.3 cm, respectively. Therefore, LH = 10.2 cm showcased a 43.5 % improvement at this specific time point (1000 s). Moving forward to t = 2000 s, the most favorable melting performance is achieved with LH = 15.3 cm, resulting in a melting percentage increase to 66 % (with fins) compared to 44 % (without fins). Besides, the inclusion of fins results in significant increases of 32.56 % (5.1 cm), 57.6 % (10.2 cm) and 14.4 % (15.3 cm) in PCM enthalpy, while water temperature declined by approximately 4 K for LH = 5.1, 10.2 and 15.3 cm. These outcomes indicate clearly the importance of fins in improving the heat transfer from the irradiated water to the surrounding PCM in the annular space of the reactor.

Designing of ultrasonic reactor using machine learning

Ultrasonic reactors consist of transducers that emit high-frequency acoustic waves, with designs varying based on their intended application. One such application is extraction, achieved through the cavitation effect generated by the pressure gradients produced by the ultrasound field within the medium. The cavitation effect depends on several physical parameters of the ultrasonic reactor, such as the driving frequency, acoustic energy, liquid medium, transducer attachment locations, and size and shape of the reactor. The proper design of an ultrasonic reactor is complex due to the numerous parameters that affect the distribution of ultrasonic energy, which must be concentrated and distributed in a specific way to extract effectively. To simplify the design process, this study utilizes an artificial neural network (ANN) to predict the physical dimensions and transducer locations of a square duct-shaped ultrasonic reactor with transducers attached to its sides based on the desired spatial energy distribution. The algorithm was developed using data from 1365 reactor configurations, which were numerically generated using COMSOL Multiphysics. The study tested two main models of ANNs, one using intensity profile as input and the other using power profile as input, and the results showed that each ANN had its advantages.

Effect of in situ ultrasonic wave and influent ammonia nitrogen fluctuation on stability of aerobic granular sludge

ABSTRACT This study elucidates the impact of fluctuating influent conditions and in situ ultrasonic wave exposure on the stability of aerobic granular sludge (AGS) in the treatment of simulated wastewater emanating from rare earth mining operations. During a stable influent period spanning from Day 1 to Day 95, the seed granules underwent an initial disintegration followed by a re-granulation phase. The secondary granulation was achieved on Day 80 and Day 40 for the ultrasonic reactor (R1) and the control reactor (R2), respectively. Notably, granules formed in R1 exhibited a more porous structure compared to those generated in R2. Subsequently, when the ammonia nitrogen in the influent oscillated between 100 and 500 mg/L during Days 96-140, both reactors yielded compact and densely structured granules. Nitrogen removal profiles were comparable between the two reactors: the removal efficiencies for ammonia nitrogen and total inorganic nitrogen escalated from 95% and 80%, respectively, during Days 1-95, to 95% and 90%, respectively, post-Day 140. A suite of performance metrics indicated that steady-state granules from R1 outperformed those from R2 across several parameters. Specifically, the nitrification/denitrification rates, and relative abundance of denitrifying bacteria were all higher in granules from R1. Conversely, the relative abundance of nitrifying bacteria was comparable between granules from both reactors. However, R1 granules demonstrated lower sludge concentration and smaller average particle size than their R2 counterparts. In conclusion, the AGS system demonstrated robust resilience to fluctuating ammonia nitrogen, and the application of ultrasonic waves significantly enhanced granular activity while achieving in situ sludge reduction.

Mapping of 20 L capacity ultrasonic reactor using cavitation activity meter and dye degradation

Mapping of a novel 20 L capacity ultrasonic (US) reactor having a total of 44 transducers was done by measuring the local cavitation intensity using a cavitation activity meter at different horizontal planes and subsequent validation based on dye degradation. A fixed frequency of 33 kHz and temperature of 30 °C was used during the mapping performed at two different power levels of 250 W and 400 W. In addition, the mapping of specific plane 2 was also performed with transducers operating on walls 1 and 3, while switching the transducers on walls 2 and 4 off and vice versa so as to establish the role of using multiple transducers. Degradation of RO4 dye was also measured at the plane 2 at various powers as 250 W, 400 W, and 1000 W. The degradation of the RO4 dye directly correlated to the cavitation intensity measured at the various location inside the US reactor. The average cavitation intensity was 265.38, 317.25, 185, and 300.5 Cavins for power dissipations of 250 W, 400 W, 250 W (wall 1 and 3 transducers in operation), and 400 W (wall 2 and 4 transducers in operation), respectively. Correspondingly, the average degradation was 10.35 %, 13.03 %, 5.52 %, and 8.9 % for same sequence of operational power and transducers. The investigation amply illustrated dependency of the cavitational activity on the location, power dissipation, and operating mode elucidating important design related information useful for scale up of sonochemical reactors.

Flow and temporal effects on the sonolytic defluorination of perfluorooctane sulfonic acid

The removal of per- and polyfluoroalkyl substance (PFAS) pollution from the environment is a globally pressing issue, due to some PFAS’ recalcitrant, bioaccumulative, and carcinogenic nature. Destruction via ultrasonic waves (sonolysis) is a promising contender for industrialisation due to; moderate power consumption, applicability to several PFAS and sample types, and limited by-products. Liquid flow rate through an ultrasonic reactor can affect the size, shape, and spatial distribution of ultrasonic cavities and hence their chemical activity. Such effects have not been studied during PFAS sonolysis, and temporal effects have not been studied much beyond the reactant concentration. Here, the effects of varying recirculating flow rate on the ultrasonic defluorination of perfluorooctane sulfonic acid (PFOS) and implications for industrial scale up are presented. Under the ultrasonic power (200 W L−1, 2.27 W cm−2) and frequency (410 kHz) used, flow rates of 79 and 214 ml min−1 enhanced defluorination up to 14 % during 30 min of treatment. However, these effects were temporal and most significant in the initial minutes of treatment. This indicated a dynamic bubble size distribution which stabilised after around 15 min. Defluorination rates of PFOS were compared with measured potassium iodide dosimetry, calorimetry, sonoluminescence (SL), and sonochemiluminescence (SCL). Flow rates which enhanced defluorination correlated moderately with enhanced SCL and negatively impacted SL, calorimetry, and dosimetry. Effects were attributed to perturbed cavity surfaces, leading to asymmetric cavity collapse, and the possibility of enhanced solvated electron production/interaction. SL, SCL, dosimetry, and calorimetric measurements were also temporal, and each showed different times to equilibrate. Flow rates of 439 and 889 ml min−1 returned all sonochemical measurements to the levels without flow, likely due to continued collapse temperature quenching by furthered bubble asymmetry. Flow also enhanced reactor cooling, which is significant for industrial temperature control. The pump energy consumed was small (≈1.9 %) compared to that of the amplifier and chiller, hence, PFOS defluorination was more cost-effective using flow. However, the effect may be limited for the longer treatment times needed for environmental remediation.

Unveiling the Potential of Cavitation Erosion-Induced Heavy Crude Oil Upgrading

The application of ultrasonic waves in the processing of hydrocarbons is a new promising technology that has developed rapidly in recent years. However, the acoustic-induced cavitation erosion phenomenon is poorly studied. In this paper, a comparison study of cavitation erosion was carried out in water and oils with different viscosities produced from Ashal’cha and North Komsomol using an ultrasonic reactor operating at an industrial frequency of 20 kHz. The acoustic spectra obtained from hydrophones during the ultrasonic treatment of fluids can be characterized by using subharmonics of the main frequency and a continuous white noise level. Moreover, the cavitation erosion of aluminum foil under various ultrasound irradiation times and power levels was thoroughly investigated. It has been found that the process of ultrasonic cavitation has a less erosive impact on metal foil in oil due to its high viscosity. In addition, the formation of microflows in the oil phase, which also intensify the erosion process, is hindered. Cavitation erosion in the Ashal’cha oil sample exhibited a higher intensity compared to that in the North Komsomol oil sample. It was found that upon increasing ultrasound intensity in the case of the viscous (Ashal’cha) oil sample, cavitation stability was disrupted. In turn, this led to a reduction in the collapse energy of the cavitation bubbles. The results we obtained enable the assessment of cavitation erosion in crude oil and could be used to improve methodologies for monitoring and optimizing cavitation processes in crude oil.

Improving properties of bilge water’s treatment sludge in a port reception facility by novel continuous ultrasonic reactor

ABSTRACT The main problem faced by facilities dealing with bilge water treatment is the generation of a high sludge amount, which has significant contents of oil and hazardous substances. The presence of petroleum and petroleum-derived organic oil, which ranges from 10 to 20% in bilge water with varying characteristics not only poses challenges in treating the bilge water but also complicates the management of the bilge water treatment sludge. Hence, this study aims to improve the characteristics of treatment sludge generated after bilge water treatment at one of Turkey’s largest port waste reception facilities (PRF), consisting of a combined process involving ultrasound and a filter press. When the filter press was used to reduce the water content in the sludge cake to approximately 65%, a similar water content of about 65% was achieved by employing ultrasound as a pre-treatment, even when the initial sludge contained 95–98% water. Additionally, the application of ultrasound before the filter press did not have a significant impact on the values of total organic carbon (TOC) and loss on ignition (LOI). However, the value of dissolved organic carbon (DOC) decreased by 45% when subjected to sonication for 60 minutes at a density of 100 W/L. Furthermore, when ultrasound was applied as a pre-treatment, an increase in the sonication duration resulted in improvements of 10% and 22% in the parameters of total dissolved solids (TDS) and chloride, respectively, which were influenced by different levels of ultrasonic power. Briefly, such research has been novelly conducted on the management of bilge water treatment sludge. Ultrasound, which is often preferred in sludge dewatering applications, was applied to this type of sludge for the first time, and the studies were conducted in a pilot-scale facility and a real PRF field. In conclusion, the partially promising results of this study will provide a new alternative and a pioneering guide for the treatment of bilge water sludge.

A hybrid RSM-GA-PSO approach on optimization of process intensification of linseed biodiesel synthesis using an ultrasonic reactor: Enhancing biodiesel properties and engine characteristics with ternary fuel blends

The depletion of fossil fuels necessitates the development of sustainable and energy-efficient techniques for biodiesel production. In recent years, cavitation reactors have emerged as a viable alternative to conventional biodiesel synthesis methods due to their superior conversion rates and shorter processing times. These reactors possess a high surface-to-volume ratio and facilitate efficient heat and mass transfer. This study aims to optimize the production of biodiesel from linseed oil using a novel ultrasonic cavitation reactor through a hybrid approach. In order to achieve this, an L50 orthogonal array with five factors and three levels was developed using a Box-Behnken design based on response surface methodology (RSM). These factors included the molar ratio (4:1, 6:1, and 8:1), ultrasonic power (100, 125, and 150 W), temperature (25, 35, and 45 °C), time (3, 6, and 9 min), and ultrasonic frequency (25, 30, and 35 kHz). The parameters were optimized using RSM-based desirability, genetic algorithm (GA), and particle swarm optimization (PSO) approaches. The results indicated that the RSM-based optimization approach outperformed the other methods. The optimal combination of parameters obtained through RSM consisted of molar ratio of 6.58:1, ultrasonic power of 133.65 W, temperature of 37.44 °C, time of 7.71 min, and pulse frequency of 26.29 kHz. This combination resulted in a biodiesel yield of 95.25%. Furthermore, this study explored the impact of different linseed oil methyl ester, octanol, and diesel blends (B10, B20, B30, B10 (O-10), and B20 (O-10)) on engine performance and emission characteristics. The B20 (O-10) blend exhibited significant potential for simultaneously reducing emissions and enhancing engine performance. When used as engine fuel, the B20 (O-10) blend increased brake thermal efficiency (BTE) by 0.848%, decreased brake specific fuel consumption (BSFC) by 0.607%, and decreased CO, HC, and NOx emissions by 18.75%, 6.55%, and 0.72%, respectively, compared to pure diesel at rated power.

Synthesis of activated carbon/magnetite nanocatalyst for sono-Fenton-like degradation process of 4-chlorophenol in an ultrasonic reactor and optimization using response surface method

Effective removal of 4-chlorophenol, a toxic and persistent organic pollutant, from wastewater is of utmost importance for environmental preservation and human well-being. The aim of this study is to design a new reactor for the quasi-Fenton process to increase the degradation efficiency of 4-chlorophenol using ultrasonic waves. For this purpose, activated carbon/magnetite nanocatalyst was synthesized using active carbon obtained from used tires and Fe3O4 nanoparticles prepared by the chemical coprecipitation method. The characterization of the active carbon/magnetite nanocatalyst showed a specific surface area of 172.46 m2g−1, and the size of the nanocatalyst was 10 nm. In addition, FTIR, EDX and XRD analyses were also investigated to identify the nanocatalyst. Evaluation of mechanical and chemical resistance confirmed the stability of the nanocatalyst. The degradation process of 4-chlorophenol was optimized using the RSM method. The experimental findings indicated that the optimal operating conditions for maximizing 4-chlorophenol removal efficiency were found to be pH 3, temperature 42 °C, nanocatalyst dose 2 gL−1, hydrogen peroxide concentration 25.58 mM ultrasonic power 320 W, and reaction time of 78 min. The validity of these optimal conditions was further confirmed through real-world experiments, resulting in remarkable removal efficiencies of 97.32 % and 93.47 % for 4-chlorophenol concentrations of 250 and 500 mgL−1, respectively.

Synthesis of Biginelli Compounds using Microwave-Assisted Methods

Abstract: Biginelli adducts, also known as dihydropyrimidin-2(1H)-ones/-thiones (DHMPs), ex-hibit versatile biological activities. Among them, monastrol has gained significant popularity as an inhibitor of kinesin-5 (Eg5), a motor protein crucial for spindle bipolarity. The inhibitory effect of monastrol on Eg5 accounts for its promising anticancer properties, along with its well-estab-lished role as an anti-inflammatory agent and calcium channel inhibitor. Since its first report in 1893, the Biginelli reaction has been extensively studied from various angles, including the scope of reagents used, the incorporation or omission of catalysts and solvents, and the application of innovative techniques like mechanochemical and ultrasonic reactors. Among these methods, mi-crowave irradiation (MWI) has shown remarkable promise, aligning with the principles of green chemistry by offering solvent-free conditions, eco-friendly catalysts, and accelerated reaction times, ultimately leading to higher yields with a reduced environmental impact. In this mini-re-view, we shed light on the literature surrounding the synthesis of Biginelli adducts using MWI and highlight how this heating method can significantly enhance the preparation of this important class of bioactive compounds. By exploring the benefits of MWI, we aim to contribute to the advancement of greener and more efficient synthetic routes for bioactive substances.

The sono-PCM reactors: A new approach for recovering the heat dissipated from ultrasonic reactors using a phase change material

To keep sonochemical reactors at a constant temperature, cryothermostat systems (equipped with a pump, cooling fluids and tubing) are commonly used. The cryothermostat serves a dual purpose, supplying both heating and cooling as needed to keep the temperature stable. However, this device is an energy consumer, especially when the sonochemical reaction is carried out over an extended period of time (hours to days). As a result, alternative systems are required to reduce the operating cost of sonosystems. The present work introduces a new approach of incorporating phase change materials (PCMs) for the recovery and storage of heat dissipated from ultrasonic reactors (i.e. the sono-PCM reactor approach). The purpose of the project is to go as far as replacing the circulating fluid-based cooling system with a small PCM unit capable of absorbing the generated heat flux and storing it in the form of latent heat (with phase change). The analysis was made on sonicated water (300 mL) in a standing wave ultrasonic reactor operating at 300 kHz, where the dissipated heat flux was measured calorimetrically. After that, using a computational fluid dynamics (CFD) model (implemented in ANSYS Fluent® software), the energetic performance of the PCM unit was assessed by tracking the system (i.e. the sono-PCM reactor) response (i.e. average and spatial evolutions of temperature, enthalpy, total energy, velocity and PCM-melting kinetics) to the imposed acoustic energy. Paraffin RT31 was selected as PCM because of its suitable characteristics such as low melting point (27–31 °C) and high thermal energy storage capacity (165 kJ kg−1). Despite the relatively low thermal conductivity of the used PCM (0.2 W m− 1 °C − 1), promising results have been obtained in terms of thermal energy management and storage using a phase change material (PCM) instead of a water-cooling system.