低频与高频超声，以及协同超声对化合物/色素降解的影响

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This work presents the degradation of ampicillin (a highly consumed β-lactam antibiotic) in aqueous media by sonochemical advanced oxidation processes. Initially, effects of frequency, power and operation mode (continuous vs. pulsed) on the antibiotic degradation by sonochemistry were analyzed. Then, under the suitable operational conditions, pollutant degradation and antimicrobial activity (AA) evolution were monitored. Afterwards, computational calculations were done to establish the possible attacks by the hydroxyl radical to the ampicillin structure. Additionally, the antibiotic degradation in synthetic hydrolyzed urine by ultrasound was performed. Finally, the combination of sonochemistry with Fenton (sono-Fenton) and photo-Fenton (sono-photo-Fenton) was evaluated. Our research showed that ampicillin removal was favored at low frequency, high power (i.e., 375 kHz, 24.4 W) and continuous mode (exhibiting an initial degradation rate of 0.78 μM min-1). Interestingly, ampicillin degradation in the hydrolyzed urine by sonochemistry alone was favored by matrix components (i.e., the pollutant showed a degradation rate in urine higher than in distilled water). The sonochemical process decreased the antimicrobial activity from the treated water (100% removal after 75 min of treatment), which was related to attacks of hydroxyl radical on active nucleus (the computational analysis showed high electron density on sulfur, oxygen and carbon atoms belonging to the penicillin core). Sono-photo-Fenton system achieved the fastest degradation and highest mineralization of the pollutant (40% of organic carbon removal at 180 min of treatment). All these aspects reveal the good possibility of sonochemical advanced oxidation technologies application for the treatment of antibiotics even in complex aqueous matrices such as hydrolyzed urine.

The ability of the ultrasound (US) combined with peroxymonosulfate (PMS), and a carbonaceous material (BC) was evaluated in the degradation of a model pollutant (acetaminophen, ACE). The US/BC/PMS system was compared with other possible systems (US, oxidation by PMS, BC adsorption, BC/PMS, US/PMS, and US/BC. The effect of the ultrasonic frequency (40, 375, and 1135 kHz) on the kinetics and synergy of the ACE removal was evaluated. In the US system, kinetics was favored at 375 kHz due to the increased production of hydroxyl radicals (HO•), but this did not improve in the US/PMS and US/BC systems. However, synergistic and antagonistic effects were observed at the low and high frequencies where the production of radicals is less efficient but there is an activation of PMS through mechanical effects. US/BC/PMS at 40 kHz was the most efficient system obtaining ∼95% ACE removal (40 μM) in the first 10 min of treatment, and high synergy (S = 10.30). This was promoted by disaggregation of the carbonaceous material, increasing the availability of catalytic sites where PMS is activated. The coexistence of free-radical and non-radical pathways was analyzed. Singlet oxygen (1O2) played the dominant role in degradation, while HO• and sulfate radicals (SO4•-), scarcely generated at low frequency, play a minimum role. Performance in hospital wastewater (HWW), urine, and seawater (SW) evidenced the competition of organic matter by BC active sites and reactive species and the removal enhancement when Cl- is present. Besides, toxicity decreased by ∼20% after treatment, being the system effective after three cycles of reuse.

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CoFe2O4/ZnO magnetic nanocatalysts were synthesized using a low-frequency ultrasound-assisted technique to enhance the optical, morphological, magnetic and catalytic properties of ZnO. The as-synthesized nanocatalysts were characterized by XRD, Raman, TEM, DR-UV-Vis and VSM analyses in order to confirm the expected modifications of the resulting nanocatalysts. The Raman spectral analysis revealed substitutional Zn2+ in the CoFe2O4/ZnO nanocatalyst. The as-synthesized material was tested for its catalytic activity in the degradation of Acid Blue (AB113), a known textile pollutant. The CoFe2O4 and CoFe2O4/ZnO nanocatalysts revealed the efficient catalytic degradation of AB113 in ambient conditions. The nanocatalyst dosage and the initial concentration of AB113 were varied by fixing one parameter as constant in order to determine the maximum catalytic efficiency with the minimum catalyst loading for AB113 degradation. The CoFe2O4/ZnO nanocatalyst demonstrated 10-fold enhanced mineralization of AB113 compared to the individual bare nanocatalysts, which could be achieved within 3 hours of catalytic degradation of AB113. The magnetic CoFe2O4/ZnO nanocatalyst was found to be stable for six consecutive recycles of AB113 degradation, which indicates that the catalytic efficiency of the nanocatalyst was retained after various numbers of cycles.

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In this research, pure and Cu(II)‐doped TiO2 nanoparticles (NPs) were synthesized via a simple and nontoxic approach to fabricate a nanocatalyst for the oxidative sonophotocatalytic degradation of phenol. TiO2 NPs were prepared using a solvothermal method and doped with Cu(II) by high‐energy planetary ball mill. The as‐synthesized NPs were identified and characterized by X‐ray diffraction, energy‐dispersive X‐ray, and transmission electron microscopy techniques. The doped NPs were used for the first time in pollutant decomposition using phenol as a model pollutant in low‐energy and low‐frequency ultrasound at room temperature and pH = 7 in the presence of visible light. The progress of the pollutant degradation was followed by UV–Vis spectrophotometry. After about 60 min of sonophotocatalytic process (dual irradiation [visible light + ultrasound] in the presence of doped NPs), around 75% of the phenol degraded, with a rate constant of about 0.024 min−1. The sonophotocatalytic process was compared with photocatalysis and sonocatalysis processes conducted in the same conditions. Importantly, the combination of visible light and ultrasound irradiation in a sonophotocatalytic decomposition reaction represented about 58% of the synergy effect, demonstrating a positive synergy between the photocatalytic and sonocatalytic processes. The optimum condition was used to degrade the commercial sample (amoxicillin) with excellent performance. The reusability test represented the excellent stability of doped catalysts within four consecutive runs with less fading in their sonophotocatalytic reaction. This feature proves the reusability potential of the doped catalyst to be used in the commercial and industrial directions. The performance of the doped catalyst was affected severely by the addition of different scavengers, and based on the results, the sonophotocatalytic mechanism was discussed.

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Cyanotoxins, such as microcystins (MC) and nodularins (NOD), are highly stable and resistant to conventional physical and chemical degradation, posing a significant risk to human health. In the present work, low frequency ultrasound was used as an advanced oxidation process to degrade cyanotoxins from a Colombian reservoir, evaluating the efficiency of the sonication process, using different powers (10, 30 and 50 W) and exposure times (5, 10, 20 and 30 min) under a frequency of 40 kHz. Ultrasonication proved to be ineffective for MC-LR concentrations up to 2595.42 μg/L, as no significant degradation was observed after 30 minutes of treatment. Additionally, a notable difference was evident in the concentrations of cyanotoxins in the water between sampling campaigns. Thus, risk assessment, implementation of monitoring programs and mitigation efforts in reservoirs deserve greater attention.

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Frequent cyanobacterial blooms pose a serious threat to the aquatic ecosystem and human health, so developing an efficient algae removal method is a long-term goal for bloom management. Current technologies for algal bloom control need urgent improvement in terms of algicide recovery, eco-friendliness and cost. Here we propose a contact-electro-catalytic method, using polytetrafluoroethylene (PTFE) film as a reusable catalyst. This contact-electro-catalytic approach involves the generation of reactive oxygen species (e.g., O2•-, HO•, 1O2 and H2O2) through water-PTFE contact electrification under the low-frequency ultrasonic waves, facilitating the inactivation of algae. The removal rate of the cyanobacterium Microcystis aeruginosa (M. aeruginosa) exposured to the water-PTFE contact-electro-catalytic system is almost five times greater than that of ultrasound alone after 5 h. A mechanistic investigation revealed that the contact-electro-catalytic system damaged the photosynthetic activity, antioxidant system and membrane integrity of the cells. Additionally, LC-MS metabolomic analysis indicated that this system caused substantial significant disruptions in the TCA cycle, amino acid metabolism, purine metabolism and phospholipid metabolism. Three-dimensional fluorescence spectroscopy suggested contact-electro-catalysis could further availably degrade the organic matter. We anticipate that this method can provide an eco-friendly, highly efficient and economic approach for effective control of harmful algal blooms.

Sonochemical oxidation was employed for the degradation of the drug dexamethasone (Dex). The oxidation at 20 kHz followed pseudo-first-order kinetics and increased with applied ultrasound power density. Acoustic cavitation at 71 W/L was able to eliminate 500 μg/L of dexamethasone from ultrapure water at inherent pH in less than 60 min. The oxidation was enhanced at pH 3 and decreased at increased Dex concentration. Scavenging experiments with tert-butanol showed that hydroxyl radicals play a crucial role in decomposition, where the reaction mainly occurs on the gas-liquid interface of the formed cavities. The addition of chloride did not affect Dex removal, while in the presence of 10 mg/L of humic acid or bicarbonate, the apparent kinetic constant decreased from 0.0423 ± 0.004 min-1 to about 0.03 ± 0.002 min-1. The rate in secondary effluent was 3.3 times lower than in ultrapure water due to the complexity of the actual matrix. Six transformation products were identified via high resolution LC-MS during the sonochemical oxidation of 3 mg/L Dex in ultrapure water. The presence of polyethylene or polystyrene microplastics slightly enhanced DEX sonodegradation. The effect of ultrasound irradiation at 71 W/L for 60 min on the microplastics surfaces was inconsiderable.

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Azithromycin (AZT) is a broad-spectrum antibiotic present in different aqueous matrices due to its incomplete removal using conventional water treatments. Ultrasound (US) is an advanced oxidation technology that has demonstrated its capacity to degrade different types of organic molecules due to the generation of cavitation bubbles or cavities that promote the generation of radicals. In this paper, data regarding the use of low-frequency US (40 kHz) in the removal of AZT are presented. Tests were carried out at lab scale for 60 min considering a reaction volume of 300 mL (pollutant initial concentration 1.0 mg L−1). The effect of operational parameters such as pH, ultrasound power, the presence of external agents like ferrous ions, hydrogen peroxide, and UV radiation were evaluated. In general, obtained data show that under the experimental reaction conditions, it is feasible to reach extents of AZT removal ∼50.0%, and that the presence of other species in the medium could inhibit the reaction, mainly due to scavenging effects. This information is relevant to future applications of US, at pilot or real scale, in the treatment of water with presence of AZT or similar organic pollutants.

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This study investigated the catalytic role of chlorine in ultrasonic degradation of refractory explosives (HMX, RDX, and TNT). The effects of pH, frequency, chlorine dosage, and contact time were optimized. The hybrid ultrasound/chlorine (US/Cl) process generated hydroxyl and hypochlorite radicals that markedly accelerated degradation, as confirmed by LC-MS/MS analysis. Maximum removal was achieved at pH 11 and a free chlorine concentration of 20 mg/L as Cl2 under low-frequency sonication (28 kHz), with RDX and TNT completely removed within 120 min. Supplementing 10 mg/L of free chlorine after 120 min enabled complete HMX degradation. Synergistic oxidation by hydroxyl and hypochlorite radicals enhanced removal efficiency over 130 % compared to individual systems, while transformation products were non-toxic. Overall, US/Cl treatment demonstrated high efficiency and cost-effectiveness for the degradation of explosive contaminants in water.

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.

Mid-high-frequency ultrasound (200–1000 kHz) eliminates organic pollutants and also generates H2O2. To take advantage of H2O2, iron species can be added, generating a hybrid sono-Fenton process (sF). This paper presents the possibilities and limitations of sF. Heterogeneous (a natural mineral) and homogeneous (Fe2+ and Fe3+ ions) iron sources were considered. Acetaminophen, ciprofloxacin, and methyl orange were the target organic pollutants. Ultrasound alone induced the pollutants degradation, and the dual competing role of the natural mineral (0.02–0.20 g L−1) meant that it had no significant effects on the elimination of pollutants. In contrast, both Fe2+ and Fe3+ ions enhanced the pollutants’ degradation, and the elimination using Fe2+ was better because of its higher reactivity toward H2O2. However, the enhancement decreased at high Fe2+ concentrations (e.g., 5 mg L−1) because of scavenger effects. The Fe2+ addition significantly accelerated the elimination of acetaminophen and methyl orange. For ciprofloxacin, at short treatment times, the degradation was enhanced, but the pollutant complexation with Fe3+ that came from the Fenton reaction caused degradation to stop. Additionally, sF did not decrease the antimicrobial activity associated with ciprofloxacin, whereas ultrasound alone did. Therefore, the chemical structure of the pollutant plays a crucial role in the feasibility of the sF process.

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The synergistic activation of persulfate by multiple factors could degrade pollutants more efficiently. However, the co-activation method based on metal ions has the risk of leakage. The non-metallic coupling method could achieve the same efficiency as the metal activation and meanwhile release environmental stress. In this study, the original biochar (BC) was prepared through using Chinese medicinal residue of Acanthopanax senticosus as the precursor. Compared with other biochar, the pore size structure was higher and toxicity risk was lower. The ultrasonic (US)/Acanthopanax senticosus biochar (ASBC)/persulfate oxidation system was established for Atrazine (ATZ). Results showed that 45KHz in middle and low frequency band cooperated with ASBC600 to degrade nearly 70 % of ATZ within 50 min, and US promoted the formation of SO4- and OH. Meanwhile, the synergy index of US and ASBC was calculated to be 1.18, which showed positive synergistic effect. Finally, the potential toxicity was examined by using Toxicity Characteristic Leaching Procedure (TCLP) and luminescent bacteria. This study provides a promising way for the activation of persulfate, which is expected to bring a new idea for the win-win situation of pollutant degradation and solid waste resource utilization.

The nonsteroidal anti-inflammatory drug sodium diclofenac (DC) is an emerging water pollutant which resists conventional wastewater treatments. Here the sonophotocatalytic degradation of DC was carried out using micrometric TiO2 (both pristine and Ag-decorated), UV-A irradiation and 20 kHz pulsed ultrasound. Sonophotocatalytic tests were compared with photolysis, sonolysis, sonophotolysis, sonocatalysis and photocatalysis data performed in the same conditions. A synergy index of over 2 was determined for tests with pristine TiO2, while values close to 1.3 were observed for Ag-TiO2. Reaction intermediates were studied by HPLC-MS, showing degradation mechanisms activated by hydroxyl radicals. Similar pathways were identified for photocatalytic and sonophotocatalytic tests, although the latter led to more oxidized compounds. Different reactor configurations (static and dynamic set ups) were studied. Sequential and simultaneous application of UV light and ultrasound led to similar performance. The role of water matrix was investigated using ultrapure and drinking water, showing marked detrimental effects of electrolytes on the DC degradation. Overall, the combined treatment proved more efficient than photocatalysis alone especially in demanding working conditions, like in drinking water matrices.

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Highlights • Three halogenated pharmaceuticals of different therapeutic groups were treated in urine.• Selectivity comparison for sono-treatment, UVC/H2O2 and electrochemical oxidation.• Kinetics depended on chemical properties of pollutants and degradation routes of processes.• Sono-treatment showed higher selectivity for pollutants degradation in urine.• Sono-treatment decreased biological activity associated with the pharmaceuticals.

Ultrasound (US) is being considered as a promising emerging advanced oxidation process to degrade persistent organic-pollutants. This paper investigated the effect of several operating parameters on the degradation of a recalcitrant pharmaceutical product, namely ibuprofen (IBP), using an ultrasound-assisted biological reactor. The tested operating parameters are the power density (960, 480) W/L, US frequency (1,142, 860, 578) kHz, working volume (500, 250) mL, initial IBP concentration (30, 60) mg/L, and pH (8.2, 4). It was observed that the IBP degradation was directly influenced by the power density, and the highest degradation efficiency (99%) was obtained at 960 w/L. However, the degradation of IBP at sonication time of 120 min was found to increase from 39% to 96% while decreasing the US frequency from 1,142 to 578 kHz. The working volume had no clear effect on the IBP degradation. The optimal pH was found to be 4, which resulted in 99.5% IBP degradation efficiency after 120 min of sonication time. The degradation of IBP followed the first order kinetics. Finally, the sonically-treated water was fed to a subsequent aerobic biological reactor. The results revealed that the remaining chemical oxygen demand (COD) after sonication was lowered in the biological reactor by a percentage of 47%.

Highlights • Methylene blue (MB) is one of the most common pollutants found in wastewater.• A catalyst-free dual-frequency ultrasound degradation approach for MB is reported.• Dual-frequency ultrasound consistently outperforms single-frequency modes.• Larger difference between the frequencies gives more effective degradation of MB.

The advanced oxidation process (AOP) through ultrasound-assisted photocatalytic degradation has attracted much attention in removing emerging contaminants. Herein, CoFe2O4-GO and CoFe2O4-g-C3N4 nanocomposites were synthesized using the ultrasound-assisted co-precipitation method. TEM, XRD, XPS, EDS, SEM, and FT-IR techniques characterized the structural, morphological, and chemical properties of the synthesized nanocomposites. The analyses showed that CoFe2O4 structure was nano-sized and distributed more homogeneously in graphene oxide (GO) layers with oxygenated functional groups than graphitic carbon nitride (g-C3N4). While the efficiency of composite catalysts, as photocatalysts, for degradation of bisphenol-A (BPA) was low in the visible region in the presence of persulfate, their catalytic efficacy was higher with sonolytic activation. The addition of persulfate as an oxidant remarkably enhanced the target pollutant degradation and TOC removal of BPA solution. Both composite catalysts showed 100 % BPA removal with the synergistic effect of visible region photocatalytic oxidation and sonocatalytic oxidation in the presence of persulfate at pH 6.8. In ultrasound-assisted photocatalytic oxidation of BPA, the highest mineralization efficiencies were obtained at 2 h treatment time, pH 6.8, 16 mM PS, catalyst dosages of 0.1 g/L CoFe2O4-GO, and 0.4 g/L CoFe2O4-g-C3N4 as 62 % and 55 %, respectively. An effective catalyst was obtained by reducing e-/h+ recombination and charge transfer resistance by decorating the GO layers with CoFe2O4.

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Low-frequency ultrasound (LFUS) irradiation induces morphological, optical and surface changes in the commercial nano-TiO(2)-based photocatalyst, Evonik-Degussa P-25. Low-temperature electron spin resonance (ESR) measurements performed on this material provided the first experimental evidence for the formation of oxygen vacancies (V(o)), which were also found responsible for the visible-light absorption. The V(o) surface defects might result from high-speed inter-particle collisions and shock waves generated by LFUS sonication impacting the TiO(2) particles. This is in contrast to a number of well-established technologies, where the formation of oxygen vacancies on the TiO(2) surface often requires harsh technological conditions and complicated procedures, such as annealing at high temperatures, radio-frequency-induced plasma or ion sputtering. Thus, this study reports for the first time the preparation of visible-light responsive TiO(2)-based photocatalysts by using a simple LFUS-based approach to induce oxygen vacancies at the nano-TiO(2) surface. These findings might open new avenues for synthesis of novel nano-TiO(2)-based photocatalysts capable of destroying water or airborne pollutants and microorganisms under visible light illumination.

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Sonochemistry has shown potential to facilitate chemical conversion in near-ambient conditions without any chemical additive or other external stimulus. With the help of catalytic cavitation agents, the generation of radicals...

Abstract Electrochemical water splitting is a crucial process for the efficient production of green hydrogen and oxygen, via the hydrogen and oxygen evolution reactions (HER and OER, respectively). The efficiency of such reactions depends heavily not only on the electrocatalytic activity and selectivity of the electrode surface, but also on mass transport efficiency [1], [2]. A promising strategy to partially overcome the physico-chemical limitations of HER and OER is to couple the electrochemical system with ultrasound (US). This coupling is studied in the field of Sono-Electrochemistry [3]. The irradiation of liquid solution induces the formation of micron-sized cavitation bubbles capable of splitting water vapor trapped in these bubbles into hydrogen and hydroxyl radicals. The radicals can in-turn recombine to form hydrogen and oxygenated species that can interact with electrode surfaces, either to improve or inhibit electrocatalytic reactions. In this work, by coupling a multi-functional ultrasound frequency reactor (584-1140 kHz) with electrodes, in-situ generated radical’s species concentrations can be tuned based on the ultrasound frequency and amplitude applied, with respect to the electrode surfaces. Using this synergistic approach, we investigate the reduction and oxidation sugars (for instance glucose to sorbitol, or glucose to formic acid or oxalic acid). References [1] D. Strmcnik, P. P. Lopes, B. Genorio, V. R. Stamenkovic, and N. M. Markovic, “Design principles for hydrogen evolution reaction catalyst materials,” Nano Energy, vol. 29, pp. 29–36, Nov. 2016, doi: 10.1016/j.nanoen.2016.04.017. [2] M. S. Burke, L. J. Enman, A. S. Batchellor, S. Zou, and S. W. Boettcher, “Oxygen Evolution Reaction Electrocatalysis on Transition Metal Oxides and (Oxy)hydroxides: Activity Trends and Design Principles,” Chem. Mater., vol. 27, no. 22, pp. 7549–7558, Nov. 2015, doi: 10.1021/acs.chemmater.5b03148. [3] F. Foroughi, C. Immanuel Bernäcker, L. Röntzsch, and B. G. Pollet, “Understanding the Effects of Ultrasound (408 kHz) on the Hydrogen Evolution Reaction (HER) and the Oxygen Evolution Reaction (OER) on Raney-Ni in Alkaline Media,” Ultrasonics Sonochemistry, vol. 84, p. 105979, Mar. 2022, doi: 10.1016/j.ultsonch.2022.105979. Acknowledgements. This work is part of the EU-ELOBIO project. The project ELOBIO received funding from the European Union’s Horizon Europe EIC-2021- PATHFINDERCHALLENGES-01-04, under grant agreement Nº 101070856.

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Activated carbon (AC) has been widely used in water treatment because of its rich pore structure, large specific surface area, simple production process, low preparation cost and wide source of raw materials. In this paper, the regeneration efficiency of low-frequency ultrasonic pretreatment (40 kHz, 115Μw/cm3) on biological activated carbon (BAC) is investigated, and its principle is discussed. The results show that the micro-jet and micro-liquid flow with high temperature and pressure produced by micro-bubble rupture during ultrasonic cavitation play an important role in the regeneration of activated carbon. And optimum ultrasonic treatment time is determined (5 min). In addition, the preparation of cu-loaded activated carbon by ultrasound-microwave method is investigated to pretreat wastewater produced in paracetamol production. The results show that Cu and Cu oxides can be loaded on activated carbon surface by ultrasonic-microwave pretreatment. Finally, the pretreatments of activated carbon by physical, chemical and physical-chemical method are investigated. The effects of the above different pretreatment methods on the structure and adsorption properties of activated carbon are compared and evaluated.

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Tartrazine degradation was investigated by electrochemical and sonochemical oxidation processes. Anodic oxidation was carried out using boron-doped diamond (BDD) electrodes. The influence of current density and dye initial concentration on the removal of tartrazine from water was analyzed. The experimental results indicate that total removal of tartrazine was obtained, and Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removals of up to 94.4% and 72.8% were achieved, respectively. To optimize the process, the pollutant removal percentage, the kinetic rate constant, and the TOC removal efficiency were chosen as target variables. Moreover, sonochemical oxidation experiments at a high-frequency range of cavitation (up to 1MHz) were performed to establish the influence of three different operating variables, namely ultrasound frequency (0.5-1.1 MHz), ultrasound power (2.0-26.6 W ⋅L-1), and pulse-stop ratio (5:1-1:1). The process was also analyzed in terms of kinetics and energy costs. The kinetics resulted to be three times faster for the electrochemical process. However, the calculated energy costs were very similar, at least at long treatment times. Finally, the influence of three aqueous matrices was investigated. According to the experimental results, the natural occurrence of chloride and/or nitrate ions in water strongly conditions the rate of the process, although at least 90% of tartrazine removal was achieved within the first 50 minutes of treatment.

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Carbapenems are potent antibiotics that reach sewage systems and then the environment, causing negative impacts. Thus, research on degrading processes to limit the carbapenem discharge in sewage systems is needed. Herein, fundamental aspects of high-frequency ultrasound alone and hybridized with the (photo)Fenton process to deal with a representative carbapenem antibiotic (meropenem, MERO) in water were considered. Initially, the action of ultrasound alone (at 578 kHz) on MERO in distilled water was tested for degradation, resulting in a partial removal (∼53 % after 120 min) and a moderate pseudo-first-order-kinetics (k: 6.3 × 10−3 min−1). Then, to enhance the MERO elimination ferrous ions were added to the ultrasound system, forming the sono-Fenton process. The increase in the ferrous ions concentration from 0 to 5 mg L−1 augmented the rate of MERO degradation (k changed from 6.3 to 15.7 × 10−3 min−1) and diminished the electric energy consumption from 1.22 to 0.49 kWh L−1. Afterward, the MERO treatment by the hybridized sono-photo-Fenton process (i.e., ultrasound combined with Fe2+ and UVA light) was evaluated, showing that the degradation efficiency was higher than by the sono-Fenton or photolysis (indeed, a synergistic index of 1.11 was obtained). Moreover, the sono-photo-Fenton process decreased the antimicrobial activity (against Staphylococcus aureus) after 30 min of treatment, indicating that the by-products did not have antimicrobial activity. The structures of primary by-products, at 50 % of MERO degradation, were elucidated through Fukui indices and LC-MS, finding that the pyrroline ring, β-lactam core, and thioether group on MERO were susceptible to the attacks of generated hydroxyl radicals (HO•) and the primary transformations occurred on such moieties of the antibiotic. Finally, the treatment of MERO in synthetic hospital wastewater by the action of the sono-photo-Fenton process was assessed, degrading 36 % of MERO at 60 min of treatment. The results from this research indicated that the hybridized processes could be an alternative to be used in niche applications for treating carbapenem antibiotics even in complex matrices, transforming them into less problematic compounds.

Here we report that cavitation bubbles, formed by the ultrasonic irradiation of a liquid at a high frequency, induces the catalyst-free N-dealkylation of aniline derivatives in water, thus opening an...

Antiepileptic drugs are considered contaminants of emerging concern in water and are resistant to conventional wastewater treatment processes. Therefore, their presence has been detected in surface waters, and their elimination/degradation requires effective treatment methods. In this research, ultrasound-based methods (e.g., sonolysis, sono-Fenton, and sono-photo-Fenton) were addressed in the degradation of antiepileptic drug primidone at laboratory scale. A high-frequency ultrasound (at 578 kHz and 20.4 W) was applied. Then, Fe2+ ions (5 mg l-1) and a UVA lamp (4 W) were added to the sonochemical reactor. After 75 min of treatment, the sono-photo-Fenton method showed better degradation efficiency (93 %) than the sono-Fenton (83 %) and sonolysis (62 %) methods. Finally, the effectiveness of the degradation method by sono-photo-Fenton was tested in simulated pharmaceutical wastewater, degrading 72 % of primidone at 75 min of treatment, indicating matrix effect plays a role in the degradation (which could be a potential application of ultrasound hybridized with the photo-Fenton process).• Three ultrasound-based treatment methods were applied to degrade primidone in water.• The sono-photo-Fenton method degraded 93 % of primidone during 75 min of treatment.• The matrix influence on primidone degradation by sono-photo-Fenton was evaluated.

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Hydrazine is a chemical of outmost importance in our society, either for organic synthesis or energy purpose. The direct conversion of NH 3 to hydrazine is highly appealing but it remains a very difficult task because the degradation of hydrazine is thermodynamically more feasible than the cleavage of the N-H bond of NH 3 . As a result, any catalyst capable of activating NH 3 will thus unavoidably decompose N 2 H 4 . Here we show that cavitation bubbles, created by ultrasonic irradiation of aqueous NH 3 at a high frequency, act as micro-reactors to activate and convert NH 3 to NH species, without assistance of any catalyst, yielding hydrazine at the bubble-liquid interface. The compartmentation of in situ produced hydrazine in the bulk solution, which is maintained close to 30°C, advantageously prevents its thermal degradation, a recurrent problem faced by previous technologies. This work also points towards a path to scavenge •OH radicals by adjusting the NH 3 concentration.

The depolymerization of cellulose to glucose is a challenging reaction and often constitutes a scientific obstacle in the synthesis of downstream bio-based products. Here, we show that cellulose can be selectively depolymerized to glucose by ultrasonic irradiation in water at a high frequency (525 kHz). The concept of this work is based on the generation of H˙ and ˙OH radicals, formed by homolytic dissociation of water inside the cavitation bubbles, which induce the cleavage of the glycosidic bonds. The transfer of radicals on the cellulose particle surfaces prevents the side degradation of released glucose into the bulk solution, allowing maintaining the selectivity to glucose close to 100%. This work is distinguished from previous technologies in that (i) no catalyst is needed, (ii) no external source of heating is required, and (iii) the complete depolymerization of cellulose is achieved in a selective fashion. The addition of specific radical scavengers coupled to different gaseous atmospheres and ˙OH radical dosimetry experiments suggested that H˙ radicals are more likely to be responsible for the depolymerisation of cellulose.

Ciprofloxacin (CIP), a persistent fluoroquinolone antibiotic, poses serious environmental concerns due to its low biodegradability and widespread presence in aquatic ecosystems. This study investigates the synergistic application of low-frequency ultrasonic cavitation and biological treatment to enhance CIP removal efficiency. Experiments have shown that under the optimal biological treatment conditions (6 g/L sludge concentration, pH 8), single biological treatment for 48 h can only remove 41.9% CIP and 24.9% total organic carbon (TOC). Ultrasonic pretreatment was conducted under varying frequencies and pH conditions to determine optimal cavitation parameters, while biodegradation performance was evaluated at different sludge concentrations and pH levels. Results indicated that in 10 mg/L CIP wastewater under alkaline conditions (pH 9.0), CIP and TOC removal efficiencies reached 58.9% and 35.2%, respectively, within 30 min using 15 kHz ultrasound irradiation. When ultrasonic pretreatment was followed by biological treatment, overall removal rates increased to 96.3% for CIP and 90.4% for TOC, significantly outperforming either method alone. LC-MS analysis identified several degradation intermediates during ultrasonic pretreatment, revealing key transformation pathways such as piperazine ring cleavage, hydroxylation, and defluorination. Furthermore, toxicity evaluation using the T.E.S.T. model confirmed a substantial reduction in ecological risk after ultrasonic treatment. Overall, the combined ultrasonic–biological process offers a cost-effective and environmentally sustainable strategy for the efficient removal of fluoroquinolone antibiotics from wastewater.

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Ultrasonic frequency is one of the most important parameters that decides the characteristics of acoustic cavitation. Low- (16-50 kHz) and high- (≥200 kHz) frequency ultrasounds present opposite physical and chemical behaviors and have been extensively studied, yet frequencies in between are poorly characterized. In this study, acoustic cavitation at the intermediate ultrasonic frequency of 100 kHz is compared with that at 20 kHz and at 362 kHz by different experimental investigations: sonochemical yield (H2O2), images of sonochemiluminescence and sonoluminescence, as well as sonoluminescence spectra in aqueous media saturated with Ar or Ar/(20 vol %)O2. The chemical activity (H2O2 yield) of cavitation bubbles at 100 kHz presents a transitional behavior between low and high frequencies. The active cavitation zone distributes in the whole sonicated volume, similarly to high-frequency ultrasound and much further than at 20 kHz. The spectral shape of 100 kHz spectra is similar to that at 20 kHz. On the contrary, 100 kHz ultrasound provides the dissociation of O2 and N2 molecules inside the bubble, which is more typical for high-frequency ultrasound. This faculty is explained by the more extreme conditions reached at collapse compared with 20 kHz. Rovibronic temperatures of OH (A2Σ+) excited radicals derived from spectroscopic simulations confirm this interpretation.

High-frequency ultrasound (sonolysis) has been shown as a practical approach for mineralizing PFAS in highly concentrated PFAS waste. However, a fluorine mass balance approach showing complete mineralization for ultrasound treatment has not been elucidated. The impact of ultrasonic power density (W/L) and the presence of co-occurring PFAS on the degradation of individual PFAS are not well understood. In this research, the performance of a 10L sonochemical reactor was assessed for treating synthetic high-concentration PFAS waste with carboxylic and sulfonic perfluoroalkyl surfactants ranging in chain length from four to eight carbons at three different initial concentrations: 6, 55, 183 μM. The mass balance for fluorine was performed using three analytical techniques: triple quadrupole liquid chromatography-mass spectrometry, a fluoride ion selective electrode, and 19F nuclear magnetic resonance. The test results showed near complete mineralization of PFAS in the waste without the formation of intermediate fluorinated by-products. The PFAS mineralization efficiency of the sonolysis treatment at two different power densities for similar initial concentrations were almost identical; the G value at 145 W/L was 9.7*10-3 g/kWh, whereas the G value at 90 W/L was 9.3*10-3 g/kWh. The results of this study highlight the implications for the scalability of the sonolytic process to treat high-concentration PFAS waste.

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High-frequency ultrasound was employed to enhance degradation of micropollutant Bisphenol A in a Fenton-like oxidative system involving persulfate as the oxidant and ferrous iron (Fe(II)) as the catalyst US/Fe2+/S2O82−. Experiments were carried out in a 400 ml glass reactor. The influence of the initial concentration of BPA, the ratio of “oxidizer-substrate”, the ratio of “catalyst-substrate”, temperature, on the efficiency of the oxidation of BPA was established. The reaction rates of micropollutant degradation increased in the order: {Fe2+/S2O82−}<{US}<{US/Fe2+/S2O82−}. It was shown that ultrasonic activated Fenton-like oxidative system leads to degradation of micropollutants. As a result, a method of deep degradation of toxic organic pollutants based on the ultrasonic activated – Fenton process US/Fe2+/S2O82− was suggested.

The article presents the results of experimental studies of the efficiency of purification of model and real wastewater from dyeing and finishing industries using pneumatic flotation using an ozone‐air mixture instead of air and a combination of ultrasonic treatment and ozonation. The influence of gas mixture consumption, dye concentration, and ozone concentration in the gas mixture on the cleaning efficiency was studied. The purification efficiency was assessed by optical density and COD. By using an ozone‐air mixture instead of air in the flotation process, an efficiency increase of up to 12 times was achieved. It has also been shown that wastewater treatment efficiency increases by up to 12% when combining ozone‐air flotation with ultrasonic treatment at 630 W and operating frequency 22% ± 10% kHz. This effect may be associated, first of all, with the dispersion of bubbles of the ozone‐air mixture, which leads to an increase in their total surface and, accordingly, to the rise in the kinetics of mass transfer—ozone dissolution.

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Many different environmental researches were done on the treatment of water, wastewater and air pollutants by different biological, physical and chemical processes. Pollution of water sources by dye pollutants from various industries such as textile, paper, rubber and plastic industries is a major environmental problem. Organic dyes cause irreparable damage to the environment due to the avoiding the light entry to water, disruption of photosynthesis, reduction of oxygen transfer to water, occurrence of eutrophication, interference with the ecology of the receiving waters, toxic effects as well as unpleasant appearance [1-18]. Different methods are used for the treatment of dye wastewater [19-25].

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This study investigated the efficient removal of Acid Orange 7 (AO7) dye in water by using Makgeolli lees, a popular by‐product obtained during the production of traditional Makgeolli beverages in Korea. By incorporating ultrasound, the effects of contact time, Makgeolli lees dosage, initial AO7 dye concentration, and initial pH of the dye solution were investigated and comprehensively compared with the same experiment using the stirring method. The results consistently showed ultrasound not only enhances the excellent adsorption ability of Makgeolli lees but also accelerates the process compared to the stirring method. The Langmuir isotherm model best described the adsorption process for both methods, suggesting monolayer adsorption on the surface of Makgeolli lees, with maximum capacities of 25.13 mg/g for ultrasound at 40 kHz and 20.41 mg/g for stirring methods. Furthermore, the study showed that optimal dye removal efficiency can be achieved with ultrasound conditions at 28 kHz frequency, 125 W/L power density, and 100% ultrasound intensity. This research promises that the integration of low‐cost biomass coupled with ultrasound could provide a potential solution for dye wastewater treatment.

Textile wastewater accounts for a significant proportion of industrial wastewater worldwide. In particular, dye wastewater accounts for a large proportion and consists of non-degradable dyes, which are substances resistant to biodegradation. Methylene blue is a representative example of such non-degradable dyes. It is not biologically degraded and exhibits toxicity. Various methods for their decomposition are currently being studied. Advanced oxidation processes (AOPs), which generate highly reactive hydroxyl radicals that oxidize and degrade pollutants, have been actively studied. Particularly, the photocatalytic degradation method using TiO2 nanoparticles is one of the most actively studied fields; however, there are still concerns regarding the toxicity of nanoparticles. Research is currently being conducted on AOPs using the cavitation phenomenon of ultrasonic waves. However, achieving high efficiency using existing ultrasonic equipment is difficult. Therefore, in this study, we evaluated a new water treatment technology through AOPs using a focused ultrasonic system with a cylindrical piezoelectric ceramic structure. After determining the optimal conditions for degradation, the degradation process was evaluated as a useful tool for mitigating the toxicity of methylene blue. We found that, under the optimal conditions of 100 W intensity at a frequency of 400 kHz, this system is a helpful instrument for degradation and a new water treatment technology suitable for removing ecotoxicity and genotoxicity.

This study investigates the piezophotocatalytic (PPhC) performance of electrospun nanofibrous membranes composed of polyvinylidene fluoride (PVDF) and magnetite (Fe3O4) nanoparticles. The composite membranes were synthesized via electrospinning, with optimized parameters to promote β-phase crystallinity and uniform fiber morphology. Structural and phase analyses by SEM, FTIR, Raman, and XPS confirmed the predominance of the electroactive β-phase (99.8%) in the composite, as well as strong interfacial interaction between Fe3O4 and the PVDF matrix. The composites exhibited significantly enhanced surface hydrophilicity and piezoelectric response compared to pristine PVDF. The piezoelectric potential generation was confirmed using a flexible piezoelectric nanogenerator (PENG), where a 3 × 1 cm membrane generated output voltages up to ∼2 V under periodic mechanical deformation at 4 Hz. Photocatalytic and piezophotocatalytic degradation of methylene blue (MB) was carried out under UV and visible light at varying ultrasonic frequencies. Maximum PPhC efficiency was achieved at 40 kHz, with 93% dye degradation in 60 min and a reaction rate constant exceeding the sum of photocatalysis and piezocatalysis by 13%, indicating a pronounced synergistic effect. Reactive oxygen species trapping and fluorescence spectroscopy confirmed •OH as the dominant oxidant. H2O2 productivity under PPhC reached 1700 μmol·g–1·h–1 in pure water, with a light-to-chemical energy conversion efficiency of 0.26%. Additionally, experiments conducted under an alternating magnetic field (0.3 T, 1.3 Hz) demonstrated 50% MB degradation within 240 min, revealing the contribution of magnetoelectric coupling as an alternative catalytic activation mechanism. The results suggest that PVDF/Fe3O4 nanocomposites are highly promising for multifunctional catalytic applications, combining piezoelectric, photo-, and magnetoelectric activation for efficient water purification and green oxidant production.

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ABSTRACT The removal of reactive black-WNN dye from aqueous solutions was optimized using Taguchi optimization (TA) and particle swarm optimization (PSO) modeling in a batch mode potentiometric sono-electro-coagulation (SOEC) process with the aid of aluminum plates. The optimization process was based on four influencing factors: pH, current density (CD), electrolysis time (ET), and ultrasonic power (UP). A Taguchi orthogonal array L25 design matrix was used to optimize these factors to maximize the dye removal efficiency. The analysis of variance showed that the percentage of contribution of ET, pH, CD, and UP was 67.64%, 12.83%, 5.03%, and 6.80%, respectively. PSO modeling was found to be a better tool for predicting dye removal efficiency than TA optimization, with a prediction error of 1.17% compared to -4.63%. Under the optimized conditions of pH-6.6, CD-66.66 mA/cm2, ET-25 minutes, and UP-100 W, the dye removal efficiency was found to be 98.30%, with a total energy consumption of 0.1188 kW h/L. The kinetic degradation study between ET and CD was found to follow a second-order kinetic model. Additionally, the synergistic effect was evaluated by combining ultrasonication and electrocoagulation. The results showed that the combined process (sono-electrocoagulation) was more effective than either ultrasonication or electrocoagulation alone, with a synergistic effect of 15%. Overall, the results suggest that TA optimization and PSO modeling can be effective tools for optimizing process parameters in the removal of Reactive black-WNN dye from aqueous solutions. The optimized conditions identified in this study, as well as the demonstration of the synergistic effect, can be used to design more efficient treatment systems for the removal of dyes from wastewater.

To obtain greater knowledge on the stability of phenolic acids for the application of FSFP ultrasound technique in the extraction, the sonochemical effects of ultrasonic factors were investigated. The kinetic model and mechanism of degradation reaction were developed and identified by FT-IR and HPLC-ESIMS. The results showed that caffeic and sinapic acids were degraded under FSFP ultrasound treatment. The ultrasonic temperature, frequency, sweep range, sweep cycle, and pulse ratio were proved to be important factors in affecting the degradation rates of caffeic and sinapic acids. Relatively high temperature, frequency away from the resonance frequency, narrow sweep range, moderate sweep cycle, and relatively low or high pulse ratio were recommended to maintain high stability of caffeic and sinapic acids. The degradation kinetics of these two phenolic acids under FSFP ultrasound treatment were conformed to zeroth-order reaction at 10-50°C. Moreover, FSFP ultrasound had a stronger sonochemical effect on sinapic acid than caffeic acid. The FT-IR and HPLC-ESIMS proved that decomposition and polymerization reactions occurred when caffeic and sinapic acids were subjected to FSFP ultrasound. Degradation products, such as the corresponding decarboxylation products and their dimers, were tentatively identified.

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Removing decolorizing acid blue 113 (AB113) dye from textile wastewater is challenging due to its high stability and resistance to removal. In this study, we used an artificial neural network (ANN) model to estimate the effect of five different variables on AB113 dye removal in the sonophotocatalytic process. The five variables considered were reaction time (5-25 min), pH (3-11), ZnO dosage (0.2-1.0 g/L), ultrasonic power (100-300 W/L), and persulphate dosage (0.2-3 mmol/L). The most effective model had a 5-7-1 architecture, with an average deviation of 0.44 and R2 of 0.99. A sensitivity analysis was used to analyze the impact of different process variables on removal efficiency and to identify the most effective variable settings for maximum dye removal. Then, an imaginary sonophotocatalytic system was created to measure the quantitative impact of other process parameters on AB113 dye removal. The optimum process parameters for maximum AB 113 removal were identified as 6.2 pH, 25 min reaction time, 300 W/L ultrasonic power, 1.0 g/L ZnO dosage, and 2.54 mmol/L persulfate dosage. The model created was able to identify trends in dye removal and can contribute to future experiments.

Zinc oxide (ZnO) and its ternary composite ZnO-Nb-V were synthesized successfully via a sonochemical route using an ultrasonic frequency of 20 Hz, power of 500 W, and a reaction time of 120 minutes. The resulting precipitates were subjected to drying at 80°C followed by calcination at 600°C to achieve phase purity and crystallinity. Comprehensive characterization was carried out using UV-Visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) techniques, confirming the formation and nanostructured nature of the synthesized materials. The composite exhibited a bandgap of 2.6 eV, attributing enhanced photocatalytic properties. Application studies for the degradation of Chloro-Sulpha (Cl-Sulpha) dye under UV light showed marked photocatalytic efficiency across varying pH levels (4, 7, and 9). The highest degradation efficiency was observed at pH 4, indicating the material's optimal performance under acidic conditions. These results demonstrate the potential of ZnO-Nb-V nanocomposites as efficient photocatalysts for wastewater treatment applications.

Recently, clean-up of resistant organic compounds has attracted growing attention. In this study, a novel heterogeneous ultrasound-enhanced sludge biochar catalyst/persulfate (BC/PS/US) process was firstly developed for the degradation of bisphenol A (BPA) in water. The results revealed that BC/PS/US process could successfully achieve a positively synergistic effect between sonochemistry and catalytic chemistry on the degradation of BPA compared to its corresponding comparative process. Nearly 98% of BPA could be degraded within 80 min at optimum reaction conditions. The coexisting substances including Cl-, SO42- and NO3- had no obvious inhibition on the BPA degradation, whereas HCO3- and humic acid (HA) had significant inhibition effects on that. PS decomposition of BC/PS/US process was superior to that of BC/PS or US/PS process. Both SO4- and HO participated in the degradation of BPA, but SO4- was predominant radical in the BC/PS/US process. A possible pathway of BPA degradation was proposed, and the BPA molecule was attacked by SO4- and degraded into five kinds of intermediate products through hydroxylation and demethylation processes. This study helps to comprehend the application of sludge biochar catalyst as a persulfate activator for the degradation of organic compounds under ultrasound irradiation, and provides a new strategy in wastewater treatment.

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Bisphenol A (BPA) an organic compound largely used in the plastic industry as a monomer. The micropollutant BPA (43.8 μM) was employed under conditions of high-frequency ultrasound (1.7 MHz, 25 W) and ultraviolet radiation (254 nm). To enhance degradation a Fenton-like oxidation system was used, including persulfate as an oxidizing agent and ferrous iron (Fe (II))) as a catalyst. Experiments were carried out in a flow sonophotoreactor, flow rate 0.5 l/min. The progress of the treatment of Bisphenol-A solution has been monitored in terms of reduction in the concentration (HPLC) and dissolved organic carbon (DOC). A large synergistic effect (2.4) was shown in the oxidation of Bisphenol-A from the combined effect of two directed at each other sources of ultrasound. The efficacy of combined approaches was generally higher than individual treatment methods of sonolysis (87%) and photolysis (15%) in 240 min of treatment. Complete oxidation of BPA is achieved in the {UV/US/Fe2+/S2O8 2-} system in 120 minutes, however, mineralization reaches (50%), possibly due to the lack of an oxidizing agent. The reaction rates of Bisphenol A degradation and mineralization increase in the order: {UV} <{US} <{Fe2+/S2O8 2-} <{US/Fe2+/S2O8 2-} <{UV/US/Fe2+/S2O82-}.

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In the present study, hybrid activation of sodium peroxydisulfate (PS) by hydrodynamic cavitation and ultraviolet radiation was investigated for Congo Red (CR) degradation. Experiments were conducted using the Box-Benken design on inlet pressure (2-6 bar), PS concentration (0-50 mg. L-1) and UV radiation power (0-32 W). According to the results, at the optimum point where the pressure, PS concentration and UV radiation power were equal to 4.5 bar, 30 mg. L-1 and 16 W respectively, 92.01% of decolorization was achieved. Among the investigated processes, HC/UV/PS was the best process with the rate constant and synergetic coefficient of 38.6 × 10-3 min-1 and 2.76, respectively. At the optimum conditions, increasing the pollutant concentration from 20 mg. L-1 to 80 mg. L-1 decrease degradation rate from 92.01 to 45.21. Presence of natural organic mater (NOM) in all concentrations inhibited the CR degradation. Quenching experiments revealed that in the HC/UV/PS hybrid AOP free radicals accounted for 63.4% of the CR degradation, while the contribution of sulfate (SRs) and hydroxyl radicals (HRs) was 53.1% and 46.9%, respectively.

A carbon material Cu-corn straw-sludge biochar (Cu-CSBC) was prepared by hydrothermally modifying sewage sludge and corn stover. The composite coupled to ultrasound can effectively catalyze the activation of PS for organic pollutants degradation, and the removal rate of 20 mg/L TC reached 89.15% in 5 min in the presence of 0.5 g/L Cu-CSBC and 3 mM PS. The synergistic effect between the factors in the system, the reaction mechanism, and the efficient removal of TC in the aqueous environment were explored in a Cu-CSBC/US/PS system established for that purpose. Quenching experiments and electron paramagnetic resonance analysis both demonstrated the Cu-CSBC/US/PS system generated •OH, SO4-•, 1O2, and O2- •, which involved in the reaction. The Cu, carboxyl, and hydroxyl groups on the Cu-CSBC surface promoted the generation of radicals and non-radicals for the degradation process, which was dominated by both radical and non-radical pathways. The degradation pathway is proposed by measuring the intermediate products with LC-MS. Finally, the stability of the Cu-CSBC/US/PS system was tested under various reaction conditions. This study not only prepared a novel biochar composite material for the active degradation of organic pollutants by PS but also provided an effective method for the resource utilization of solid waste and sludge treatment.

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Objectives : As the variety and quantity of recalcitrant pollutants such as pharmaceuticals, pesticides, endocrine disruptors, and cosmetic products discharged into water bodies steadily increase, the need for AOPs following biological wastewater treatment processes is growing. In this study, we compared the Total Organic Carbon (TOC) removal capabilities of conventional AOPs, ultrasound, hydrogen peroxide, and persulfate-based multiple AOPs on the final effluent of S wastewater treatment plant. The study also evaluated the feasibility of wastewater reuse by examining the optimal operating conditions of the applied AOPs.Methods : The removal characteristics of TOC were investigated based on reaction time, US frequency, and oxidant dosage for the following conditions: ultrasound (US) alone, individual treatments with hydrogen peroxide (H₂O₂) and persulfate (PS) as oxidants, combined US/H₂O₂ and US/PS dual AOPs, and a US/PS/H₂O₂ multi-AOPs system.Results and Discussion : Only US oxidation treatment at 80 kHz for 60 minutes resulted in a 14.4% TOC removal efficiency. Individual treatment with H₂O₂ at 174 mM showed 69.2% removal efficiency, while persulfate oxidation treatment at 43.5 mM showed 13.8%. The PS/H₂O₂ oxidation treatment showed 68.5% removal efficiency at 174 mM H₂O₂ and 0.52 mM PS, and an 85.3% removal efficiency at 2.08 mM PS and 350 mM H₂O₂ conditions. Under the same 80 kHz ultrasound conditions, the combined US and other oxidant treatment resulted in an increased TOC removal efficiency: 87.8% for US/H₂O₂ at 174 mM H₂O₂, and 81.9% for US/PS at 43.5 mM PS. Additionally, the multi-treatment with US, PS, and H₂O₂ showed a removal efficiency of 87.0% at 2.08 mM PS and 350 mM H₂O₂, and 91.1% at 174 mM H₂O₂ and 0.52 mM PS conditions.Conclusion : In this study, among the AOPs, the oxidation treatment with US/PS/H₂O₂ exhibited the highest TOC removal efficiency at 91.1%. The integration of chemical oxidants with US demonstrated significant improvement in TOC removal capabilities, with PS showing superior performance at the same concentration conditions among the utilized chemical oxidants in the multi-AOPs. Although H₂O₂ also displayed commendable TOC removal abilities, its oxidation efficiency was lower at low concentration injections, whereas higher concentrations of H₂O₂ injections proved to be more effective in oxidation.

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The study proposed the ultrasound-activated persulfate oxidation as a novel approach to enhance sludge dewaterability. The results demonstrated that the reduction of water content of dewatered sludge cake was 16.5% and the capillary suction time was reduced to 39.5 s at the optimal conditions of 1.0 mmol/g-TS S2O82- and ultrasound energy density of 2.0 kW L-1 within 15 min. The promotion of dewaterability was closely associated with the enlarged floc size, decreased viscosity, and near-neutral zeta potential. Meanwhile, the correlation analysis revealed that the protein in extracellular polymeric substances (EPS) governed sludge dewaterability, especially in loosely bound EPS. Three-dimensional excitation-emission matrix fluorescence spectroscopy, Fourier transform infrared spectroscopy and scanning electronic microscopy analysis revealed that ultrasound-activated persulfate oxidation treatment effectively degraded the gel-like EPS matrix and attacked cells, releasing the moisture which was trapped in EPS and cells. The aggregation of particles promoted the elimination of moisture. Furthermore, heavy metals in conditioned dewatered sludge cakes all satisfied the A level of agricultural land (GB4284-2018) requirements and the chemical speciation distribution of some heavy metals changed significantly.

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The sonochemical system is highly effective at degrading hydrophobic substances but has limitations when it comes to eliminating hydrophilic compounds. This study examines the impact of organic and inorganic additives on improving the sonochemical degradation of hydrophilic pollutants in water. The effects of adding an organic substance (CCl4) and two inorganic ions (Fe2+ and HCO3-) were tested. The treatment was focused on a representative hydrophilic antibiotic, cefadroxil (CDX). Initially, the sonodegradation of CDX without additives was assessed and compared with two reference pollutants more hydrophobic than CDX: dicloxacillin (DCX) and methyl orange (MO). The results highlighted the limitations of ultrasound alone in degrading CDX. Subsequently, the impact of the additives on enhancing the removal of this recalcitrant pollutant was evaluated at two frequencies (375 and 990 kHz). A significant improvement in the CDX degradation was observed with the presence of CCl4 and Fe2+ at both frequencies. Increasing CCl4 concentration led to greater CDX elimination, whereas a high Fe2+ concentration had detrimental effects. To identify the reactive sites on CDX towards the species generated with the additives, theoretical calculations (i.e. Fukui indices and HOMO-LUMO gaps) were performed. These analyses indicated that the β-lactam and dihydrothiazine rings on CDX are highly reactive towards oxidizing species. This research enhances our understanding of the relationship between the structural characteristics of contaminants and the sonochemical frequency in the action of additives having diverse nature.

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One of the primary technologies currently being deployed for the removal of per- and polyfluoroalkyl substances (PFAS) from water is ion exchange (IX). For regenerable IX resins, concentrated PFAS in the resulting spent brine and/or still bottoms requires further treatment. This research demonstrated that PFAS in spent brine and still bottoms can be effectively degraded sonochemically at 1000 kHz. Overall, PFAS degradation was negatively impacted by high total organic carbon (TOC) and residual methanol (MeOH) solvent (up to 50 g/kg; 5% w:w), but was enhanced by the high chloride. The addition of caustic (up to 1 N NaOH) partially mitigated the inhibition by TOC and MeOH. Sonochemical degradation of individual PFAS compounds resulted in significant mineralization to form inorganic fluoride, but small quantities of volatile organic fluorine species (VOF) were noted. This is believed to be the first report of sonochemical degradation of PFAS in ion exchange regeneration wastes, and indicates the possibility for the application of this technology as part of a complete PFAS capture and destruction treatment train.

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This paper deals with the sonochemical water treatment of polycyclic aromatic sulfur hydrocarbons (PASHs), one of the most common impurities found in waste water coming from petroleum industry. The best fit of the experimental data appears to be the kinetic parameters determined using the Michaelis-Mentonmodel in the concentrations range of the study. For the initial increase in the degradation rates, it is simply considered that the more the bulk concentration increases, the more the concentration in the interfacial region increases. This will be explained by Michaelis-Menton kinetics. The influence of organic compounds in the water matrix as a mixture with Benzothiophene (BT) was also evaluated. The results indicated that BT degradation is unaffected by the presence of bisphenol A (BPA). Finally, the results indicated that ultrasonic action is involved in oxidation rather than pyrolitic processing in the BT sonochemical degradation.

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The sonochemical (850 kHz) reduction of Cr(VI) (0.3 mM, pH 2, reactor open to air) was analyzed in the presence of different additives. The effects on Cr(VI) reduction efficiency of added formic acid (FA, 10 mM), citric acid (Cit, 2 mM), ethylenediaminetetraacetic acid (EDTA, 1 mM), methanol (MeOH, 0.1 M), ethanol (EtOH, 0.1 M), 2-propanol (2-PrOH, 0.1 M), tert-butanol (t-BuOH, 0.1 M), phenol (PhOH, 2 mM) and sodium lauryl sulfate (SLS, 1 mM) have been evaluated in comparison with the system in the absence of additives. Complete Cr(VI) reduction was obtained only when using EDTA (at 120 min) and Cit (at 180 min). Cr(III) complexes with these compounds or with their degradation products were detected as final products. For EDTA, Cit, t-BuOH, FA and SLS, the Cr(VI) decay could be adjusted to a zero-order kinetics; in the cases of MeOH, EtOH and 2-PrOH, there was a deviation from the zero-order kinetics. The Cr(VI) conversion increased in the order SLS (very low) < no additive ≅ MeOH ≅ EtOH ≅ 2-PrOH < FA < t-BuOH < PhOH < Cit < EDTA. The role of EDTA and Cit in stabilizing intermediate Cr(V) peroxo compounds and enhancing their direct transformation into different Cr(III) species is considered a major factor in the acceleration of Cr(VI) reduction processes. Mechanistic pathways are proposed.

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In this work, nanomaterials of the SrMoO4/g-C3N4 heterostructure were synthesized in a single step by the sonochemical method with controlled temperatures. Structural and morphological investigations indicate the formation of heterojunctions, revealing the presence of g-C3N4 (CN) in the heterostructures and an interface region between the phases. Optical analyzes show broadening of the wavelength absorption range and a decrease in the photoluminescence (PL) intensity of the heterojunctions compared to the CN emission spectrum, proving a decrease in the recombination of the photogenerated charges. The results of the photocatalytic tests indicate that the insertion of CN promoted photocatalytic degradation of the Methylene Blue (MB), Rhodamine B (RhB) and Crystal Violet (CV) organic contaminants, up to 99.58%, 100% and 98.65%, respectively. The mixture of dyes used and reuse cycles was performed to analyze the applicability of the compounds in a real situation.

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In this study, machine learning (ML) algorithms were employed to predict the pseudo-1st-order reaction rate constants for the sonochemical degradation of aqueous organic pollutants under various conditions. A total of 618 sets of data, including ultrasonic, solution, and pollutant characteristics, were collected from 89 previous studies. Considering the difference between the electrical power (Pele) and calorimetric power (Pcal), the collected data were divided into two groups: data with Pele and data with Pcal. Eight input variables, including frequency, power density, pH, temperature, initial concentration, solubility, vapor pressure, and octanol–water partition coefficient (Kow), and one target variable of the degradation rate constant, were selected for ML. Statistical analysis was conducted, and outliers were determined separately for the two groups. ML models, including random forest (RF), extreme gradient boosting (XGB), and light gradient boosting machine (LGB), were used to predict the pseudo-1st-order reaction rate constants for the removal of aqueous pollutants. The prediction performance of the ML models was evaluated using different metrics, including the root mean squared error (RMSE), mean absolute error (MAE), and R squared (R2). A significantly higher prediction performance was obtained using data without outliers and augmented data. Consequently, all the applied ML models could be used to predict the sonochemical degradation of aqueous pollutants, and the XGB model showed the highest accuracy in predicting the rate constants. In addition, the power density and frequency were the most influential factors among the eight input variables in prediction with the Shapley additive explanation (SHAP) values method. The degradation rate constants of the two pollutants over a wide frequency range (20–1,000 kHz) were predicted using the trained ML model (XGB) and the prediction results were analyzed.

Methylene blue pollutants can be treated by photocatalytic methods using metal oxide-based semiconductor materials and metal organic framework (MOF). These two materials are often coupled into a composite to improve their physicochemical properties and catalytic activity. This research focuses on the synthesis of composites based on Cr-PTC MOF, ZnO, and Fe3O4 by the sonochemical method. The obtained composites were characterized and tested for catalytic activity in methylene blue pollutant degradation in an aqueous system under acidic conditions (pH = 5). Our investigation shows that the Cr-PTC@Fe3O4 composite possesses the lowest band gap energy of 1.86 eV and achieves the highest photocatalytic activity in methylene blue degradation at solution pH = 5, with a percent degradation of 84.36%. The sonochemical incorporation of Fe3O4 and Cr-PTC MOF is able to fabricate materials in a short time with better photocatalytic activity in degrading methylene blue than the single materials. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

In recent years, water contamination has become a significant crisis, and it is crucial to find new materials that can efficiently eliminate these contaminants. The current work presents the Sm2CuO4 nanophotocatalyst for the decolorization of different water-soluble organic contaminants. The fabrication of Sm2CuO4 nanostructures was achieved using a simple and rapid sonochemical pathway, resulting in an optical bandgap of 1.62 eV as determined by diffuse reflectance spectroscopy. Several factors, including different organic contaminants, organic contaminant concentrations, Sm2CuO4 dosages, and the pH of the media, were scrutinized to achieve the best efficiency. The results manifested that Sm2CuO4 was highly effective in removing different organic contaminants from water. For example, when 30 mg of Sm2CuO4 was used with 20 mg L-1 methyl orange under visible irradiation for 100 min, 91.4% of the methyl orange was destroyed. Further investigation revealed that holes (h+) were primarily responsible for pollutant photodegradation when using Sm2CuO4 as a photocatalyst. This finding suggests that Sm2CuO4 could be an excellent candidate for developing new materials to effectively remove water contaminants.

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This study investigated - for the first time - the simultaneous degradation of benzene, toluene, ethylbenzene and o-xylene (BTEX) by persulfate (PS) and peroxymonosulfate (PMS) activated by asphaltenes (Asph) under ultrasound (US) irradiation. Advantageous properties such as high thermal stability, low production cost and extensive availability make asphaltenes as an appealing carbonaceous material for heterogeneous catalysis. The application of asphaltenes in PS/US increased the degradation of BTEXs from 31%, 34%, 35%, 32%-78%, 94%, 98% and 98%, while the removal of these compounds in PMS/US system was improved from 26%, 27%, 24%, 20%-76%, 91%, 97%, 97%, respectively. PS and PMS activation followed a typical sulfate-radical based advanced oxidation processes. In terms of activation of PS and PMS, the particles of asphaltenes intensified formation of reactive radicals by creating additional centers of cavitational events. Moreover, owing to π-π stacking interaction between asphaltenes and sp2-hybridized systems of BTEX, the contaminants undergo adsorption on the surface of asphaltenes and subsequent oxidation by formed radicals. The radical route of BTEX degradation in both PS/US/Asph and PMS/US/Asph systems was mainly contributed by sulfate (SO4•-) and hydroxyl radicals (HO•) and coexisting superoxide radical anions (O2•-) played a minor role.

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Piezocatalysis, a heterogeneous catalytic technique, leverages the periodic electric field changes generated by piezoelectric materials under external forces to drive carriers for the advanced oxidation of organic pollutants. Antibiotics, as emerging trace organic pollutants in water sources, pose a potential threat to animals and drinking water safety. Thus, piezoelectric catalysis can be used to degrade trace organic pollutants in water. In this work, BaTiO3 and La-doped BaTiO3 were synthesized using an improved sol–gel–hydrothermal method and used as piezocatalytic materials to degrade sulfadiazine (SDZ) with ultrasound activation. High-crystallinity products with nano cubic and spherical morphologies were successfully synthesized. An initial concentration of SDZ ranging from 1 to 10 mg/L, a catalysis dosage range from 1 to 2.5 mg/mL, pH, and the background ions in the water were considered as influencing factors and tested. The reaction rate constant was 0.0378 min−1 under the optimum working conditions, and the degradation efficiency achieved was 89.06% in 60 min. La-doped BaTiO3 had a better degradation efficiency, at 14.98% on average, compared to undoped BaTiO3. Further investigations into scavengers revealed a partially piezocatalytic process for the degradation of SDZ. In summary, our work provides an idea for green environmental protection in dealing with new types of environmental pollution.

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Molecular multiferroics have garnered significant attention for their exceptional responsiveness to external stimuli, demonstrating remarkable potential in multi‐state information storage and sensing technologies. However, their catalytic capabilities remain underexplored. Here, the first demonstration of molecular multiferroic, N‐ethyl‐N‐(fluoromethyl)‐N‐methylethanaminium tetrabromoferrate(III) (DEFM‐FeBr4) is presented, achieving efficient catalytic oxidation of alkanes through synergistic multifield activation. Under concurrent ultrasonic and light irradiation, DEFM‐FeBr4 exhibits outstanding catalytic performance in the oxidation of ethylmethylbenzene, achieving a turnover number (TON) of 1942—a 29‐fold enhancement in activity compared to the inorganic ferroelectric barium titanate (BaTiO3). The material demonstrates excellent recyclability and broad substrate compatibility across diverse alkanes, underscoring its practical advantages in heterogeneous catalysis. Mechanistic investigations via scanning kelvin probe microscopy (SKPM) and electron paramagnetic resonance (EPR) reveal that the intrinsic ferroelectric polarization facilitates the efficient separation of photogenerated charge carriers through built‐in electric field modulation, thereby significantly enhancing catalytic activity. This work not only establishes molecular multiferroics as a new paradigm in catalytic materials science but also provides fundamental insights for designing advanced multiferroic catalysts with optimized multifield‐responsive properties. This multiferroic catalysis strategy opens new avenues for developing smart catalytic systems with dynamically tunable reactivity.

Fluoroquinolones are a major issue in aquatic ecosystems due to their persistence, potential to induce antibiotic resistance, and inability to be effectively removed using conventional treatment methods. Several advanced oxidation processes have been studied for their degradation; however, there is still a lack of knowledge about their degradation mechanisms and the precise roles played by reactive species. In this context, the study investigated the heterogeneous activation of persulfate (PS) to degrade fluoroquinolones (FQs), such as moxifloxacin (MFX), in iron-rich soil (Cat) under ultrasound irradiation (US). The analysis of the soil catalyst revealed the presence of quartz (35%), iron oxides (33%), and alumina (26%) as the predominant constituents of the sample. The mineral phase analysis indicated the presence of magnetite, hematite, and alumina. Then, the outcomes of the specific surface area, micropore volume, and total pore volume were determined to be 19 m2 g−1, 6 m3 g−1 and 9.10 m3 g−1, respectively. The MFX/PS/US/Cat system demonstrated 89% degradation and 56% mineralization after 300 min. However, the optimized concentrations of i-PrOH, t-BuOH, and CHCl3 were 50, 100, and 50 mM, respectively, in order to trap the radicals SO4•−, OH•, and O2•−. The study examined the individual contributions of SO4•−, OH•, and O2•− radicals to the overall process of MFX degradation. The results indicated that SO4•− was the primary radical, with a contribution of 52%, followed by OH• with 43%, and O2•− with 5%. Finally, the investigation revealed that laterite exhibited both good catalytic activity and reusability over several cycles. The development of this new process could stimulate the creation of cost-effective technology for water remediation through the effective removal of fluoroquinolones.

Using the bulk g-C3N4 as a precursor, four g-C3N4 nanosheets were further prepared by ultrasonic, thermal, acid, and alkali exfoliation. The structures of these materials were characterized by various techniques such as X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The synergistical Fenton catalysis of these materials with Cu2+ was evaluated by using rhodamine B as a simulated organic pollutant. The results showed that there existed a significant synergistical Fenton catalysis between Cu2+ and g-C3N4. This synergistic effect can be observed even when the concentration of Cu2+ was as low as 0.064 mg L-1. The properties of g-C3N4 strongly influenced the catalytic activity of the Cu2+/g-C3N4 system. The coexistent of Cu2+ and the alkali exfoliated g-C3N4 showed the best catalytic activity. Hydroxyl radicals as oxidizing species were confirmed in the Cu2+/g-C3N4 system by electron paramagnetic resonance spectra. The synergistic catalysis may be attributed to the easier reduction of Cu2+ adsorbed on the g-C3N4. This study provided an excellent Fenton catalytic system, and partly solved the rapid deactivation of heterogeneous Fenton catalysts caused by the leaching of metal ions.

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The bubble type, generated by an ultrasonic field, was studied in a batch and flow reactor using a multibubble sonoluminescence (MBSL) quenching technique with propanol and acetone. The influence of frequency and transducer configuration was evaluated using the same piezoelectric element in both setups. Results show that the bubble type not only depends on the frequency, but also on the input power or transducer configuration. Additionally, the effect of flow on sonoluminescence yield and bubble type was studied in the continuous setup at various frequencies. As the flow becomes turbulent, the sonoluminescence signal reaches a plateau for three out of four frequencies, and a transition from transient to stable cavitation occurs for frequencies below 200 kHz.

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The partial oxidation of methane (POM) into value-added C1 chemicals (e.g., CH3OH, HCHO, and CO) offers a promising approach for natural gas utilization under mild conditions. However, existing POM systems often rely on complex catalyst designs and the addition of extra oxidants. Here, we developed a catalyst-free POM system by integrating mechanical stirring with a low-frequency ultrasonic field. A high production rate of C1 chemicals (129.26 µmol h−1) and methane conversion rate (22%) were achieved under ambient conditions (298 K, PCH4 = 0.1 bar, PO2 = 0.1 bar, PN2 = 0.8 bar). Mechanism studies revealed that the introduction of mechanical stirring amplified the ultrasonic cavitation effect, promoting the in-situ release of reactive oxygen species. Reaction pathway investigation confirmed that hydroxyl radicals facilitated the cleavage of methane C-H bonds and that oxygen participated in the generation of POM products. This strategy provides a sustainable avenue for the value-added conversion of methane. The partial oxidation of methane to value-added C₁ chemicals is a promising approach for natural gas utilization. Here the authors report a catalyst-free oxidation method via mechanical stirring and ultrasonic cavitation.

Cavitation, chemical effect, and mechanical effect thresholds were investigated in wide frequency ranges from 22 to 4880kHz. Each threshold was measured in terms of sound pressure at fundamental frequency. Broadband noise emitted from acoustic cavitation bubbles was detected by a hydrophone to determine the cavitation threshold. Potassium iodide oxidation caused by acoustic cavitation was used to quantify the chemical effect threshold. The ultrasonic erosion of aluminum foil was conducted to estimate the mechanical effect threshold. The cavitation, chemical effect, and mechanical effect thresholds increased with increasing frequency. The chemical effect threshold was close to the cavitation threshold for all frequencies. At low frequency below 98kHz, the mechanical effect threshold was nearly equal to the cavitation threshold. However, the mechanical effect threshold was greatly higher than the cavitation threshold at high frequency. In addition, the thresholds of the second harmonic and the first ultraharmonic signals were measured to detect bubble occurrence. The threshold of the second harmonic approximated to the cavitation threshold below 1000kHz. On the other hand, the threshold of the first ultraharmonic was higher than the cavitation threshold below 98kHz and near to the cavitation threshold at high frequency.

This study explores the sonocatalytic activity of gold nanoclusters (Au NCs) combined with titanium dioxide (TiO2) nanoparticles, forming Au NCs/TiO2 composites. The hybrid material significantly enhances hydroxyl radical (•OH) generation under ultrasonic conditions, attributed to high-energy cavitation bubbles formed during ultrasonication. The effects of frequency (200, 430, and 950 kHz) and power were systematically evaluated on Au144/TiO2 composites, identifying 430 kHz as optimal for •OH production due to its efficient cavitation energy. Au144 NCs function as electron traps, reducing electron–hole recombination in ultrasonically activated TiO2, thereby improving charge separation and enhancing •OH generation. Size-dependent effects were also studied, showing an efficiency trend of Au144 > Au25 > plasmonic Au nanoparticles > bare TiO2. These findings highlight the importance of ultrasonication frequency and Au NC size in optimizing sonocatalytic performance in the Au NCs/TiO2 composites, providing valuable insights for designing advanced sonocatalysts with applications in chemical synthesis, environmental remediation, and biomedical fields.

Nanobubble and ultrasonic cavitation were applied to support and prolong oxidation reactions of ozonation. Nanobubbles increased ozone dissolution by a factor of 16 due to low buoyancy, high surface area, and stability in water. Hydroxyl radicals generated by ultrasonic cavitation produced hydrogen peroxide rather than recombining due to additional oxygen atoms supplied by the nanobubbles. The generated hydrogen peroxide formed hydroperoxyl ions that reacted with ozone to generate hydroxyl radicals. The process achieved improvements in both the loss of emitted ozone and radical recombination. Rhodamine B decomposition was used to gauge the effectiveness of the process, with the highest rhodamine B decomposition evident at a high initial pH and power and a frequency of 132 kHz as revealed in ultrasonic experiments. The process achieved more than 99% of the rhodamine B decomposition in 20 min under the most efficient conditions. The generation of hydrogen peroxide exhibited tendencies similar to those of rhodamine B decomposition, supporting the proposed mechanism. An ozonation process combined with nanobubble and ultrasonic cavitation can therefore sustain oxidizing power using continuous dissolution by nanobubbles and successive radical generation caused by hydrogen peroxide generated by cavitation.

Highlights • Mapping of pilot scale US reactor (20 L) at a frequency of 33 kHz for various operating powers.• Establishment of cavitation intensity distribution at various horizontal planes inside US reactor.• Validation of the cavitation intensity distribution by comparing with RO4 dye degradation.• Cavitation intensity distribution is much better compared to conventional design.• Intensity suitable for specific application can be tuned based on the operating conditions.

The current study focuses on the degradation of Procion brilliant yellow H‐E6G, an azo dye, using ultrasonic and hydrodynamic cavitation (HC), evaluating the impact of various parameters on the extent of degradation. The use of only ultrasound showed less oxidation capacity as indicated by only 19.1% degradation at an optimized power of 140 W, pH of 2.5, temperature of 40°C, and initial dye concentration of 15 ppm. The effectiveness of hybrid approaches involving US + H2O2, US + Fenton, and US + H2O2 + potassium persulfate (KPS) was subsequently evaluated under optimized conditions. A notable enhancement in decolorization extent was observed for combined operations, including US + H2O2, US + Fenton, and US + H2O2 + KPS (dual oxidant scheme) with the actual decolorization extents as 80.6%, 85%, and 92.2% respectively. An optimized scheme of US + H2O2 + KPS was also utilized to decolorize the dye at a pilot scale using a US flow cell and also an HC reactor that yielded 91.8% and 88% reductions in initial concentration. The dye decolorization was elucidated to follow first‐order kinetics for all the individual and combination approaches. The obtained values of the rate constants were also utilized for the evaluation of the synergistic index. A toxicity analysis was also performed on the dye, both before and following treatment, utilizing two bacterial strains. A comparative analysis of various treatment approaches has been presented focusing on factors such as cavitational yield, operational expenses, and energy requirements. The study elucidated that the combination of US + H2O2 + KPS effectively removes Procion brilliant yellow H‐E6G giving 92.2% as the maximum degradation at an operating cost of 0.1862 $/L.

Tandem strategy for lignin utilization with photocatalytic preoxidation and ultrasonic cavitation depolymerization was proposed. Cornstalk residual lignin from industrial bioethanol process was first photocatalytically preoxidized under visible light by g-C3N4 and WO3/g-C3N4/h-BN (WCB) photocatalysts respectively, then obtained lignin samples were characterized to confirm the preoxidation with raw lignin as a blank. During photocatalytic preoxidation, benzyl hydroxyls in lignin was transformed to carbonyls, but a certain degree of lignin degradation and condensation was observed. In comparison, WCB-catalyzed photopreoxidation was more effective. Thereafter, lignin depolymerization was achieved by ultrasonic cavitation-assisted ethanololysis under optimal conditions. Compared with the mere ultrasonic cavitation depolymerization of pristine lignin, WCB-induced photocatalytic preoxidation improved the conversion rate by 14%, the light-oil yield by 26%, and the phenolic monomer yield by 35%. In general, the reported tandem method worked very well for the enhancement of lignin depolymerization and provided a new idea for the development of lignin valorization.

Ultrasound technologies are well-known for their ability to intensify the heat and mass transfer processes. Hence, ultrasonic treatment processes are widely applied for the separation of oil–water emulsions, optimization of oil pumping processes, cleaning the bottomhole zone, etc. However, the main phenomenon under the positive influence of ultrasonic waves on such processes is the cavitation bubbles implosion on the water–oil boundary. It is well-known that ultrasound energy contributes to the reversible viscosity reduction in heavy oil systems. However, it is possible to exhibit chemical destruction of the weakest carbon–heteroatom bonds in the structure of the asphaltenes. This study investigates the influences of controllable ultrasound waves with frequency ranges of 20–60 kHz under the exposure time of 60 s on the rheology of a heavy crude oil sample produced from the Ashalcha reservoir (Tatarstan Republic, Russia). The specific feature of this study is the application of multi-frequency ultrasonic exposure with a wide spectrum of side harmonics with the frequency up to 400 kHz. The results of the Saturates, Aromatics, Resins and Asphaltenes (SARA) analysis method support the chemical consequences of ultrasonication of crude oil. The content of resins under the irradiation of ultrasound waves altered from 32.5 wt.% to 29.4 wt.%, while the number of aromatics hydrocarbons raised from 24.3 wt.% to 34.1 wt.%. The Gas Chromatography—Mass Spectroscopy (GC-MS) analytical analysis method was applied to qualitatively compare the composition of saturated and aromatics fractions between the initial and upgraded heavy crude oil in order to show the chemical destruction of asphaltene bonds after the ultrasonic treatment. It was demonstrated that ultrasound waves allowed chemical conversion of asphaltene fragments that led to irreversible viscosity reduction. The viscosity of the heavy oil sample under the favorable ultrasonic irradiation conditions reduced from 661.2 mPa·s to 178.8 mPa·s. This advantage can be used to develop enhanced oil recovery methods and partial upgrading processes in downstream conditions.