Recent trends in the applications of sonochemical reactors as an advanced oxidation process for the remediation of microbial hazards associated with water and wastewater: A critical review

Simultaneous extraction of caffeic acid and production of cellulose microfibrils from coffee grounds using hydrodynamic cavitation in a Venturi tube

Large quantities of spent coffee grounds (SCGs) are produced daily across the globe, accumulating as industrial waste in factories. Developing a process that both extracts high-value components and utilizes the bulk material would offer significant academic and industrial advantages. This study explores the use of hydrodynamic cavitation, which utilizes the chemical and physical effects produced by bubble collapse, for high-efficiency, continuous processing. The optimization of cavitation conditions was conducted by measuring the aggressive intensity of hydrodynamic cavitation within a Venturi tube. Then, unbrewed coffee grounds was processed by hydrodynamic cavitation to obtain stable results, as caffeic acid in SCGs varied depending on how the coffee was brewed. It was revealed that the hydrodynamic cavitation in the Venturi tube increased extraction rate of coffeic acid and simultaneously generates cellulose microfibrils. Note that the upstream pressure of the Venturi tube was 3.4 MPa, which was generated by a screw pump, and the aggressive intensity of the hydrodynamic cavitation was enhanced by optimizing the downstream pressure of the Venturi tube. The type of cavitation, closely linked to the aggressive intensity, was also analyzed through high-speed photography.

Treatment of high concentration phenol wastewater by low-frequency ultrasonic cavitation and long-term pilot scale study

Acoustic cavitation is an advanced, eco-friendly oxidation technology effective in removing organic pollutants from water. However, research on its use for degrading phenol, a common and challenging phenolic pollutant, is limited. This study explores the optimal conditions for phenol degradation using acoustic cavitation and assesses its practical application through extensive pilot tests. Results from batch tests show that low-frequency (15 kHz) ultrasonic cavitation effectively treats high concentrations of phenol (1000 mg L-1). Aeration and acidic pH enhance removal efficiency, while alkaline conditions inhibit degradation. Analysis of total organic carbon (TOC), degradation products, and volatile organic compounds (VOCs) reveals that the primary intermediates are substituted benzenes and alkanes. Long-term pilot tests demonstrated the device's effectiveness in phenol removal and its operational stability over 180 days. The study also establishes a relationship between removal efficiency, hydraulic retention time (HRT), and operating costs, highlighting the feasibility of low-frequency ultrasonic cavitation for treating high-concentration phenolic wastewater and its potential role in the pretreatment stage of biochemical processes.

Nanomaterial-Enhanced Hybrid Disinfection: A Solution to Combat Multidrug-Resistant Bacteria and Antibiotic Resistance Genes in Wastewater

This review explores the potential of nanomaterial-enhanced hybrid disinfection methods as effective strategies for addressing the growing challenge of multidrug-resistant (MDR) bacteria and antibiotic resistance genes (ARGs) in wastewater treatment. By integrating hybrid nanocomposites and nanomaterials, natural biocides such as terpenes, and ultrasonication, this approach significantly enhances disinfection efficiency compared to conventional methods. The review highlights the mechanisms through which hybrid nanocomposites and nanomaterials generate reactive oxygen species (ROS) under blue LED irradiation, effectively disrupting MDR bacteria while improving the efficacy of natural biocides through synergistic interactions. Additionally, the review examines critical operational parameters-such as light intensity, catalyst dosage, and ultrasonication power-that optimize treatment outcomes and ensure the reusability of hybrid nanocomposites and other nanomaterials without significant loss of photocatalytic activity. Furthermore, this hybrid method shows promise in degrading ARGs, thereby addressing both microbial and genetic pollution. Overall, this review underscores the need for innovative wastewater treatment solutions that are efficient, sustainable, and scalable, contributing to the global fight against antimicrobial resistance.

Comparative phytochemical profile and biological activity of three Terminalia species as alternative antimicrobial therapies

Ethnopharmacological relevance

Medicinal plants can help combat antibiotic resistance by providing novel, active molecules. Three plant species of the Terminalia genus are widely used in traditional medicine in the Mouhoun region for the treatment of cutaneous and respiratory diseases. Therefore, it is important to determine the ethnopharmacological potential of bark extracts from the trunks of these three Terminalia species.

Aim of the study

This study compared the phytochemical and biological activities of extracts from three Terminalia species to determine their ethnopharmacology.

Materials and methods

The medicinal properties of the extracts were assessed based on their ability to inhibit the growth of the following microorganisms: Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Candida albicans, Candida krusei, Candida glabrata, and Candida tropicalis. The significant interest in these medicinal plants among the local communities were elucidated by their antioxidant properties and phytochemical composition, along with the detection key bioactive compounds. Major phytochemical groups and phenolic compounds were determined using high-performance liquid chromatography with a diode array detector. These phytochemical findings were validated by evaluating the antioxidant capacity of the extracts using DPPH, FRAP, and ABTS assays.

Results

Hydroethanolic, ethanolic, and hexane extracts from the bark of three Terminalia species inhibited the growth of both bacteria and fungi, as evidenced by their minimum inhibitory concentrations (MICs).The findings showed that Terminalia species were most effective against various tested bacteria and fungi, with MICs ranging from 0.1 to 6.25 mg/mL. Terminalia avicennioides, Terminalia macroptera, and Terminalia laxiflora extracts demonstrated 50 % inhibition of DPPH at concentrations ranging from 0.04 to 0.6 mg/mL. Phytochemical analysis revealed the presence of several families of chemical compounds, such as total phenolics and flavonoids. Phenolic compounds identified by HPLC in ethanolic extracts of T. avicennioides, such as isorhamnetin, quercetin, and ferulic acid, are recognised for their antimicrobial and antioxidant properties.

Conclusion

These findings establish an ethnobotany for these three Terminalia species, with their chromatographic characteristics facilitating the identification of key molecules of interest. The ethanolic extract of T. avicennioides can be used in phytomedicinal formulations against bacterial (P. aeruginosa and S. aureus) and fungal (C. albicans and C. glabrata) infections, both of which are recurrently recorded in certain skin and respiratory tract diseases.

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.

Piezoceramic membrane with built-in ultrasound for reactive oxygen species generation and synergistic vibration anti-fouling

Piezoceramic membranes have emerged as a prominent solution for membrane fouling control. However, the prevalent use of toxic lead and limitations of vibration-based anti-fouling mechanism impede their wider adoption in water treatment. This study introduces a Mn/BaTiO3 piezoceramic membrane, demonstrating a promising in-situ anti-fouling efficacy and mechanism insights. When applied to an Alternating Current at a resonant frequency of 20 V, 265 kHz, the membrane achieves optimal vibration, effectively mitigating various foulants such as high-concentration oil (2500 ppm, including real industrial oil wastewater), bacteria and different charged inorganic colloidal particles, showing advantages over other reported piezoceramic membranes. Importantly, our findings suggest that the built-in ultrasonic vibration of piezoceramic membranes can generate reactive oxygen species. This offers profound insights into the distinct anti-fouling processes for organic and inorganic wastewater, supplementing and unifying the traditional singular vibrational anti-fouling mechanism of piezoceramic membranes, and potentially propelling the development of piezoelectric catalytic membranes.

Facile Synthesis of Carbon-Based Inks to Develop Metal-Free ORR Electrocatalysts for Electro-Fenton Removal of Amoxicillin

The electro-Fenton process is based on the generation of hydroxyl radicals (OH•) from hydroxide peroxide (H2O2) generated in situ by an oxygen reduction reaction (ORR). Catalysts based on carbon gels have aroused the interest of researchers as ORR catalysts due to their textural, chemical and even electrical properties. In this work, we synthesized metal-free electrocatalysts based on carbon gels doped with graphene oxide, which were conformed to a working electrode. The catalysts were prepared from organic-gel-based inks using painted (brush) and screen-printed methods free of binders. These new methods of electrode preparation were compared with the conventional pasted method on graphite supports using a binder. All these materials were tested for the electro-Fenton degradation of amoxicillin using a homemade magnetite coated with carbon (Fe3O4/C) as a Fenton catalyst. All catalysts showed very good behavior, but the one prepared by ink painting (brush) was the best one. The degradation of amoxicillin was close to 90% under optimal conditions ([Fe3O4/C] = 100 mg L-1, -0.55 V) with the catalyst prepared using the painted method with a brush, which had 14.59 mA cm-2 as JK and a H2O2 electrogeneration close to 100% at the optimal voltage. These results show that carbon-gel-based electrocatalysts are not only very good at this type of application but can be adhered to graphite free of binders, thus enhancing all their catalytic properties.

Effective application of citric acid treated Trapa natans and Citrullus lanatus lignocellulosic macromolecules for adsorptive remediation of acid Violet-7 dye

The peels of Trapa natans (TRA) and Citrullus lanatus (CIT), were modified with a variety of chemicals to boost their surface for the optimization of adsorption performance by providing a greater number of additional active binding sites. Citric acid-processed peels (TRAC and CITC) had shown more favorable adsorption performance to eradicate acid violet 7 dye (AVS). Extra and additional active sites generated after chemical processing, including hydroxyl (OH), carboxyl (COOH), amines NH2, carbonyl, and ester (-O-CO-) groups, as evidenced from FTIR and SEM characterizations, may boost the potential of physicochemical integration of adsorbent surface activity in order to promote and encourage the retention of hazardous and risky AVS molecules from the water. The Langmuir isotherm assessed the qmax for the adsorption of AVS on TRAC, CITC, TRA, and CIT to be 212.8, 294, 24.3, and 60.6 mg/g, respectively, whereas the correlation coefficients assessed for both TRAC and CITC were 0.98 and for TRA and CIT were 0.97, closer to unity reflecting monolayer physio-sorption. According to Temkin, the adsorption of AVS on TRAC, TRA, CITC, and CIT gives "BT" values of 1.275, 0.947, 1.085, and 1.211 mg/g, also suggesting physio-sorption. Therefore, chemically modified peels can be employed for detoxification of AVS.

Insights into isotherms, kinetics, and thermodynamics of adsorption of acid blue 113 from an aqueous solution of nutraceutical industrial fennel seed spent

Research studies have been carried out to accentuate Fennel Seed Spent, a by-product of the Nutraceutical Industry, as an inexpensive, recyclable and operational biosorbent for bioremediation of Acid Blue 113 (AB113) in simulated water-dye samples and textile industrial effluent (TIE). The physical process of adhesion of AB113 on the surface of the biosorbent depends on various parameters, such as the initial amount of the dye, amount and expanse of the biosorbent particles, pH of the solution and temperature of the medium. The data obtained was analyzed using three two-parameter and five three-parameter adsorption isotherm models to glean the adsorbent affinities and interaction mechanism of the adsorbate molecules and adsorbent surface. The adsorption feature study is conducted employing models of Weber-Morris, pseudo 1st and 2nd order, diffusion film model, Dumwald-Wagner and Avrami model. The study through 2nd order pseudo and Avrami models produced complementary results for the authentication of experimental data. The thermodynamic features, ΔG0, ΔH0, and ΔS0 of the adsorption process are acclaimed to be almost spontaneous, physical in nature and endothermic in their manifestation. Surface characterization was carried out using Scanner Electron Microscopy, and identification and determination of chemical species and molecular structure was performed using Infrared Spectroscopy (IR). Maximum adsorption evaluated using statistical optimization with different combinations of five independent variables to study the individual as well as combined effects by Fractional Factorial Experimental Design (FFED) was 236.18 mg g-1 under optimized conditions; pH of 2, adsorbent dosage of 0.500 g L-1, and an initial dye concentration of 209.47 mg L-1 for an adsorption time of 126.62 min with orbital shaking of 165 rpm at temperature 49.95 °C.

Joint effects of gas bubbles and solid particles on sonochemical inhibition in sonicated aqueous solutions

Wastewater is a multicomponent and multiphase mixture. Gas bubbles and solid particles in the dispersed phase influence sonochemical efficiency during ultrasonic treatment of wastewater, sometimes unfavorably; however, the influencing factors and mechanisms remain unclear. In this paper, the influence of argon gas bubbles (1.2 mm) and monodisperse silica particles (0.1 mm) on sonochemical effects in an aqueous system using a horn-type reactor (20 kHz) is reported. Triiodide formation decreased with an increase in the volume fraction of either or both phases. The two phases started inhibiting sonoreactions as the total volume fraction approached 3.0-4.0 vol% compared to pure water. The effect of the gas-to-solid ratio is also considered. We propose an acoustic attenuation model, which incorporates the scattering effect of solid particles and the thermal effect of gas bubbles. The agreement between the modeling and experimental results demonstrates that the two phases are jointly responsible for sonochemical inhibition by increasing ultrasound attenuation. This enhances the understanding of sonochemistry in gas-solid-liquid systems and helps regulate gases and solids in sonochemical reactors.

Revealing the origins of vortex cavitation in a Venturi tube by high speed X-ray imaging

Hydrodynamic cavitation is useful in many processing applications, for example, in chemical reactors, water treatment and biochemical engineering. An important type of hydrodynamic cavitation that occurs in a Venturi tube is vortex cavitation known to cause luminescence whose intensity is closely related to the size and number of cavitation events. However, the mechanistic origins of bubbles constituting vortex cavitation remains unclear, although it has been concluded that the pressure fields generated by the cavitation collapse strongly depends on the bubble geometry. The common view is that vortex cavitation consists of numerous small spherical bubbles. In the present paper, aspects of vortex cavitation arising in a Venturi tube were visualized using high-speed X-ray imaging at SPring-8 and European XFEL. It was discovered that vortex cavitation in a Venturi tube consisted of angulated rather than spherical bubbles. The tangential velocity of the surface of vortex cavitation was assessed considering the Rankine vortex model.