Search Results (61)

This study investigates the use of potassium-modified silicalite-1 as a catalyst for the transesterification of glycerol to glycerol carbonate (Glyc. Carbonate) with dimethyl carbonate (DMC). Silicalite-1, typically inactive due to the absence of extra-framework cations, was modified with potassium compounds (fluoride, chloride, and hydroxide), which create basic sites by interacting with structural defects formed through silicon removal. This modification significantly enhances the catalyst’s performance in glycerol transesterification. The reaction was conducted in both conventional batch reactor and ultrasound-assisted systems, including an ultrasonic bath and an ultrasonic probe, either within the bath or directly in the reactor. The direct ultrasound probe application yielded the most remarkable results, achieving a 96% Glyc. Carbonate yield at 70 °C in just 15 min—dramatically surpassing the batch reactor, which reached approximately 5%. These findings highlight the synergistic effect of potassium modification and ultrasound-assisted transesterification, offering a highly efficient and sustainable approach for glycerol valorization. Full article

The chemical industry faces major challenges despite recent progress in the transition to more environmentally friendly processes. Sustainable industrial chemistry relies on the optimization of protocols and downstream processes such as extraction, purification, and drying. Process intensification, which includes non-conventional techniques and continuous manufacturing, has emerged as a key strategy to improve efficiency and environmental impact. Technologies such as ultrasound, microwaves, mechanochemistry, and reactive extrusion offer improved performance but face scalability and proprietary barriers. Flow chemistry offers additional benefits, including smaller reactors, lower energy consumption (from 40 to 90%), and increased safety through continuous, automated reactions. However, implementing these methods requires overcoming engineering, economic, and regulatory hurdles. Biphasic catalysis and sonochemical activation in liquid–liquid systems are promising approaches for scalable reactions under mild conditions. The pharmaceutical industry, a major source of waste, has shown resistance due to high validation costs and complex regulations. Fortunately, international regulatory institutions have introduced programs to facilitate the introduction of advanced technologies. Future perspectives emphasize the integration of modular, intensified processes with digitalization and smart manufacturing. Collaborative, transdisciplinary research will be crucial for accelerating commercialization and addressing sustainability challenges in chemical production. Full article

Sludge management is a very relevant aspect in the operation of Wastewater Treatment Plants (WWTPs). In activated sludge systems, it is common to have daily (or continuous) monitoring of total suspended solids in the aeration tank (MLSS). If such control is not properly performed, it can cause solids to wash out in the secondary sedimentation tank or significantly impact BOD (Biochemical Oxygen Demand) and nitrogen removal. There are many commercially available systems which can provide real-time monitoring of solids (mainly optical or ultrasound sensors). Even though commercially available (usually with a high cost), there are still issues related to the use of such sensors. The most important one is the progressive accumulation of solids, which cause measurement errors. In this work, the authors investigated the application of a low-cost US sensor for MLSS (mixed-liquor suspended solids) monitoring in two full-scale activated sludge WWTPs. The tested sensor was similar to a previously described device, which had been previously employed in a pilot-scale UASB reactor in Brazil. The main differences were related to an integrated treatment and acquisition system which allowed real-time treatment of the US wave as well as data acquisition at a predefined time. The values generated by the sensor were compared with a commercial optical sensor installed in the same WWTP and double-checked with periodic gravimetric tests. The results at a Leeuwarden WWTP showed that the measurements of the US sensor, the optical sensor, and gravimetric test did not present significant differences during the test period at a significance level of 5%. Absolute errors were on average 0.04% (US sensor) and 0.03% (optic sensor) of MLSS compared to the gravimetric test. Although the use of the tested US sensor for monitoring solids in WWTP is promising, there are still several improvements that need to be made to the sensor. These include implementing a more precise calibration frequency, establishing a cleaning routine, and preventing sensor fouling. Furthermore, the sensor still needs a more thorough cost–benefit analysis, which would help assess the practicality of implementing this technology in various WWTPs. Full article

The increasing pollution of water bodies, due to the constant release of highly toxic and non-biodegradable organic pollutants, requires innovative solutions for environmental remediation and wastewater treatment. In this study, the effectiveness of different Advanced Oxidation Processes (AOPs) for the purification of water contaminated with Rhodamine B (RhB) dye at a concentration of 5 mg/L were investigated and compared. Using the classical ozonation strategy as a benchmark treatment, the research showed over 99% degradation of RhB within 4 min in a laboratory-scale batch setup with a capacity of 0.2 L. In contrast, a “chemical-free” process exploiting ultrasound (US) technology achieved a 72% degradation rate within 60 min. Further experiments were conducted using a pilot-scale rotor-stator hydrodynamic cavitation (HC) reactor on a 15 L solution leading to 33% of RhB removal in the presence of hydrogen peroxide (H₂O₂) at 75 mg/L. However, the use of an innovative cavitational reactor, which hybridizes HC with cold plasma, showed remarkable efficiency and achieved 97% degradation of RhB in just 5 min when treating a 5 L solution at an inlet pressure of 20 bar in a loop configuration. In addition, a degradation rate of 58% was observed in a flow-through configuration, emphasising the robustness and scalability of the HC/electrical discharge (ED) plasma technology. These results underline the potential of hybrid HC/ED plasma technology as an intensified and scalable process for the purification of water, as it offers a catalyst- and oxidant-free protocol. Full article

The current study aims to degrade Procion Golden Yellow H-R through ultrasound-induced cavitation coupled with various oxidants. A comprehensive investigation was conducted to examine the impact of parameters, specifically pH, power, and frequency, on the extent of degradation. The primary aim was to optimize degradation by solely utilizing a cavitation reactor where only 23.8% degradation was observed under the established optimum conditions of pH 2.5, frequency of 22 kHz, and power of 200 W. The investigation of the combined process of cavitation with H₂O₂, Fenton reagent (H₂O₂/Fe²⁺), NaOCl, and potassium persulphate (KPS) was subsequently conducted under optimized conditions. The combined operations greatly enhanced degradation with the use of H₂O₂ loading of 0.1 g/L leading to 53.3% degradation and the H₂O₂/Fe²⁺ ratio of 1:0.25 resulting in 94.6% degradation, while the NaOCl quantum of 0.075 g/L yielded 90% degradation and the KPS quantity of 2 g/L resulted in 97.5% degradation in the specific combinations. A toxicity test on two bacterial strains, Staphylococcus aureus and Escherichia coli, was carried out using the original dye solution and after treatment. The various individual and combination processes were compared using the parameters of cavitational yield and total treatment cost. The study elucidates that combining ultrasonic cavitation with KPS is an effective method for treating wastewater containing Procion Golden Yellow H-R dye, especially when implemented at a larger scale of operation. Full article

Boron neutron capture therapy (BNCT) is radiotherapy in which a nuclear reaction between boron-10 (¹⁰B) in tumor cells and neutrons produces alpha particles and recoiling ⁷Li nuclei with an extremely short range, leading to the destruction of the tumor cells. Although the neutron source has traditionally been a nuclear reactor, accelerators to generate neutron beams have been developed and commercialized. Therefore, this treatment will become more widespread. Recurrent head and neck cancer (HNC) close to the body surface is considered a candidate for BNCT using the boron compound boronophenylalanine (BPA) and has been found to be highly responsive to this treatment. However, some cases recur early after the completion of the treatment, which needs to be addressed. Ultrasound is a highly safe diagnostic method. Ultrasound with microbubbles is expected to promote the uptake of BPA into tumor cells. Ultrasound also has the ability to improve the sensitivity of tumor cells to radiotherapy. In addition, high-intensity focused ultrasound may improve the efficacy of BNCT via its thermal and mechanical effects. This review is not systematic but outlines the current status of BPA-based BNCT and proposes plans to reduce the recurrence rate of HNC after BNCT in combination with ultrasound. Full article

Large amounts of agri-food waste are generated and discarded annually, but they have the potential to become highly profitable sources of value-added compounds. Many of these are lignin-rich residues. Lignin, one of the most abundant biopolymers in nature, offers numerous possibilities as a raw material or renewable resource for the production of chemical products. This study aims to explore the potential revalorization of agricultural by-products through the extraction of lignin and subsequent depolymerization. Different residues were studied; river cane, rice husks, broccoli stems, wheat straw, and olive stone are investigated (all local wastes that are typically incinerated). Traditional soda extraction, enhanced by ultrasound, is applied, comparing two different sonication methods. The extraction yields from different residues were as follows: river cane (28.21%), rice husks (24.27%), broccoli (6.48%), wheat straw (17.66%), and olive stones (24.29%). Once lignin is extracted, depolymerization is performed by three different methods: high-pressure reactor, ultrasound-assisted solvent depolymerization, and microwave solvolysis. As a result, a new microwave depolymerization method has been developed and patented, using for the first time graphene nanoplatelets (GNPs) as new promising carbonaceous catalyst, achieving a 90.89% depolymerization rate of river cane lignin and yielding several building blocks, including guaiacol, vanillin, ferulic acid, or acetovanillone. Full article

Oak bark is a by-product known for its richness in polyphenols, with tanning substances being particularly interesting for their application in different fields. Vegetable tannins are mostly utilized in the leather sector, but are also widely used as adhesives, in cement plasticizers and for medical and agrochemical applications owing to their natural antimicrobial activity. This study aimed to develop a green and efficient pilot-scale technique for extracting polyphenols from oak bark by ultrasound-assisted extraction (UAE) using a modified Dual-Frequency Reactor (DFR). Different parameters, such as extraction time, temperature, and solvent type (water, sodium hydroxide or sodium sulfite and bisulfite solutions) were investigated for their influence on the total phenolic content (TPC) and the quantity of dry extract. Control experiments by conventional methods were also performed. UAE at 50 °C yielded the highest TPC and dry extract (confirmed by ANOVA analysis, p < 0.05) in just 10 min, suggesting that UAE can be considered an energy- and cost-effective alternative to conventional techniques. The most suitable solvent was found to be a 0.5% sodium hydroxide solution. The molecular profile of the extracts was assessed by FTIR-ATR spectroscopy, revealing typical signals of tannins in all extracts. Furthermore, antimicrobial activity tests demonstrated the complete absence of Gram-positive and Gram-negative bacteria in the extracts, ensuring the suitability of the product for different kinds of application. Full article

Measuring temperature inside chemical reactors is crucial to ensuring process control and safety. However, conventional methods face a number of limitations, such as the invasiveness and the restricted dynamic range. This paper presents a novel approach using ultrasound transducers to enable accurate temperature measurements. Our experiments, conducted within a temperature range of 28.8 to 83.8 °C, reveal a minimal temperature accuracy of 98.6% within the critical zone spanning between 70.5 and 75 °C, and an accuracy of over 99% outside this critical zone. The experiments focused on a homogeneous environment of distilled water within a stainless-steel tank. This approach will be extended in a future research in order to diversify the experimental media and non-uniform environments, while promising broader applications in chemical process monitoring and control. Full article

Anaerobic digestion of sewage sludge is limited at the hydrolysis stage of the process. The goal of this study was to assess the effects of sludge retention times and ultrasound pretreatment on the ammonium concentration and organic matter transformation in anaerobic digesters treating sewage sludge. To achieve this, two laboratory-scale semicontinuous anaerobic digesters were operated for a period of over 70 d, including a control reactor and another fed by pretreated sludge. Both anaerobic systems were fed with mixed sludge (50%/50% primary/secondary treatment) in mesophilic conditions (37 °C), with solid retention times (SRT) of 7.5 d (Phase I) and 3 d (Phase II). The performance of the anaerobic digestion process was assessed in terms of the methane yield and the total and soluble chemical organic demand, total solids, and volatile solids removal. The results showed that the ultrasound pretreatment caused an increase of around 22.2% in CODt removal for an SRT of 7.5 d. Meanwhile, an SRT of 3 d resulted in a decrease of up to 92.4% in CODt removal. The performance in terms of biogas production and organic matter removal was significantly affected by the SRT reduction to 3 d, showing that the process is not viable in these conditions. Full article

Ultrasound waves have been widely used in the field of organic wastewater treatment due to their mechanical, thermal, and chemical effects derived from their cavitation effect. Many researchers have combined ultrasound waves with other organic wastewater treatment methods because they have the potential to offset the disadvantages of other methods. In recent years, many authors within the literature have reviewed the application of ultrasound combined with a certain wastewater treatment method. In this review, we introduce the working mechanism of ultrasound in the treatment of organic wastewater and then examine the synergistic effects of ultrasound with other organic wastewater treatment methods based on various applications, indicating a strong synergistic effect between ultrasound and other wastewater treatment methods. Subsequently, we introduce typical ultrasound-enhanced organic wastewater treatment equipment and propose some possible developmental directions for ultrasound in the treatment of organic wastewater. Full article

Acid Red 88 (AR88) is an azo dye highly used in the textile industry. This industry generates high volumes of wastewater with recalcitrant properties that can persist in nature for many years. This work intends to use a statistical model to better predict and understand the influence of different operational conditions. A Box-Behnken response surface methodology (RSM) was used, in which variables (H₂O₂, Fe²⁺, and radiation intensity) were changed. At the same time, the RSM model allowed the assessment of several advanced oxidation processes (AOPs). The results exhibited the photo-Fenton process as the most efficient, and the best operational conditions ([AR88] = 0.125 mM, pH = 3.0, [H₂O₂] = 7.9 mM, [Fe²⁺] = 0.22 mM, time = 30 min) were used in four different reactors (UV-C, UV-A, ultrasound, and solar). US reactors achieved high AR88 removal (98.2%, 50 min), similar to UV-C and UV-A (97.8 and 98.2%, respectively, 60 min). A solar reactor is concluded to be the most feasible choice, with 98.4% AR88 removal after 25 min. Full article

Obtaining phytochemical-rich plant extracts from natural products where the active ingredients are present in comparatively low levels in the tissue matrix is the critical initial step of any chemical analysis or bioactivity testing. The plant C. asiatica is rich in various phytochemicals, the major constituents being triterpenes and flavonoids, as well as other polyphenols, leading to a number of bioactivities. In this study, an attempt was made to achieve several green technology principles, while optimizing the extraction method for the efficient extraction of bioactive compounds from C. asiatica. Soxhlet extraction (SE), ultrasound-assisted extraction (UAE) with low-frequency sonication, microwave-assisted extraction (MAE) using a closed-vessel microwave digestion system, and subcritical water extraction (SWE) in a high-pressure reactor were employed to extract the bioactive compounds. The solvent system, extraction time, and solid-to-solvent ratio were varied to optimize the extraction. UAE gave the best extraction yield, while MAE gave similar results, with a solid-to-liquid ratio of 1:25, a binary solvent system of 9:1 methanol to water (v/v), and a 20 min extraction time for the extraction of triterpenes, including madecassoside, asiaticoside, madicassic acid, and asiatic acid. Investigation of different solvent systems based on water and methanol also revealed information on the extraction behavior of total triterpene content (TTC), total polyphenolic content (TPC), total flavonoid content (TFC), and the variations in the antioxidant capacity of the extracts. In this study, it was evident that UAE and MAE offer more efficient and effective extraction of bioactive compounds in terms of extraction yield, time, and minimal solvent and energy use. Furthermore, the results showed that the different solvent ratios in the extraction mixture will affect the extraction of bioactive compounds, and a binary solvent system with a combination of methanol and water was the most efficient for the studied compounds in Centella asiatica. Full article

Background: The Chernobyl nuclear disaster is still considered the worst nuclear accident in history. The particles were dispersed over the former USSR and large parts of Western Europe, leading to radioactive exposure to more than 10 million people. Radioactivity is a risk factor for the development of basal cell carcinoma (BCC), since radiation-induced mutations in both Sonic hedgehog (Shh) signaling pathway genes and TP53 have been described. Methods: We present the case of a patient with a history of radiation exposure following the 1986 Chernobyl accident who presented to our outpatient clinic with recurrent basal cell carcinoma in the facial region. Case: The patient presented to our clinic with two facial lesions suspicious for BCC. Although there were no typical risk factors, 11 BCCs had previously been removed. The patient had been building shelters for the construction workers working on the sarcophagus around the destroyed reactor immediately after the 1986 accident. Staging using an 18F-FDG-PET/CT as well as ultrasound of the abdomen revealed no other tumor manifestations. Diagnostic excision of the two facial lesions was performed, and a histopathological workup revealed BCC at the right temporal region and acanthopapillomatosis with no sign of malignancy at the corner of the mouth. After presentation to the tumor board, complete resection of the BCC was initiated. Conclusions: This case demonstrates the value of early use of 18F-FDG-PET/CT in staging/restaging to visualize BCC location, local spread and potential metastases or secondary tumors and to aid in the decision for therapeutic management. Full article

The use of phytochemicals as natural food additives is a topic of interest for both academic and food industry communities. However, many of these substances are sensitive to environmental conditions. For this reason, encapsulation is usually performed prior to incorporation into food products. In this sense, ultrasound-assisted encapsulation is an emerging technique that has been gaining attention in this field, bringing important advantages for the production of functional food products. This review article covered applications published in the last five years (from 2019 to 2023) on the use of ultrasound to encapsulate phytochemicals for further incorporation into food. The ultrasound mechanisms for encapsulation, its parameters, such as reactor configuration, frequency, and power, and the use of ultrasound technology, along with conventional encapsulation techniques, were all discussed. Additionally, the main challenges of existing methods and future possibilities were discussed. In general, ultrasound-assisted encapsulation has been considered a great tool for the production of smaller capsules with a lower polydispersity index. Encapsulated materials also present a higher bioavailability. However, there is still room for further developments regarding process scale-up for industrial applications. Future studies should also focus on incorporating produced capsules in model food products to further assess their stability and sensory properties. Full article