Fabrication of a novel Z-scheme SrTiO3/Ag2S/CoWO4 composite and its application in sonocatalytic degradation of tetracyclines

Synthesis of magnetic layered double hydroxide (Fe3O4@CuCr-LDH) decorated with ZIF-8 for efficient sonocatalytic degradation of tetracycline

A series of Fe3O4@CuCr-LDH hybrids decorated with different amount of ZIF-8 (FLZ, 10-40 wt%) was prepared using simple methods and characterized with different techniques. The activity of the synthesized nanocomposites was investigated in the sonocatalytic degradation of tetracycline (TC) antibiotic from wastewater. When the content of ZIF-8 in the nanocomposite structure was 20 wt%, the FLZ-20 sonocatalyst exhibited the high performance in the sonocatalytic removal of TC. At optimum conditions (0.7 g/L catalyst dosage, pH of 7, 50 mg/L initial concentration of antibiotic, and 15 min sonication time) of the sonocatalytic removal of TC approached to 91.4% under ultrasonic irradiation (USI) using FLZ-20. This efficiency was much higher than those of obtained results by Fe3O4@CuCr-LDH and pristine ZIF-8. The formed ●OH and ●O2- exhibited the major roles in the sonocatalytic TC degradation process. The excellent performance of FLZ-20 can be attributed to the heterojunctions created between composite components, which could improve the electron transfer ability and effectively separate e-/h+ pairs. In addition, FLZ-20 showed the superior reusability and stability during three successive recycling. Moreover, the facile magnetically separation of the sonocatalyst from the aqueous solution was another outstanding feature, which prevents the formation of secondary pollutants. It can be concluded that the fabrication of heterojunctions is an efficient procedure to promote the sonocatalytic acting of the catalyst.

Efficient sonochemical catalytic degradation of tetracycline using TiO2 fractured nanoshells

Overexposure to antibiotics originating in wastewater has profound environmental and health implications. Conventional treatment methods are not fully effective in removing certain antibiotics, such as the commonly used antibiotic, tetracycline, leading to its accumulation in water catchments. Alternative antibiotic removal strategies are garnering attention, including sonocatalytic oxidative processes. In this work, we investigated the degradation of tetracycline using a combination of TiO2 fractured nanoshells (TFNs) and an advanced sonochemical reactor design. The study encompassed an examination of multiple process parameters to understand their effects on the degradation of tetracycline. These included tetracycline adsorption on TFNs, reaction time, initial tetracycline concentration, solvent pH, acoustic pressure amplitude, number of acoustic cycles, catalyst dosage, TFNs' reusability, and the impact of adjuvants such as light and H2O2. Though TFNs adsorbed tetracycline, the addition of ultrasound was able to degrade tetracycline completely (with 100% degradation) within six minutes. Under the optimal operating conditions, the proposed sonocatalytic system consumed 80% less energy compared to the values reported in recently published sonocatalytic research. It also had the lowest CO2 footprint when compared to the other sono-/photo-based technologies. This study suggests that optimizing the reaction system and operating the reaction under low power and at a lower duty cycle are effective in achieving efficient cavitation for sonocatalytic reactions.

Carbonaceous CoCr LDH nanocomposite as a light-responsive sonocatalyst for treatment of a plasticizer-containing water

The carbonous-based nanocomposites of CoCr layered double hydroxide (LDH) with graphene oxide (GO) and reduced graphene oxide (rGO) were prepared. The successful synthesis of the CoCr LDH in hydrotalcite crystalline structure was deduced from the pattern obtained from X-ray diffraction, and the chemical composition of its surface was checked by X-ray photoelectron spectroscopy. The prosperous decorating of LDH on the sheets of rGO and GO was authenticated by the energy dispersive X-ray spectroscopy analysis and micrographs of scanning electron and transmission electron microscopy. The photo-assisted sonocatalytic activity of the prepared nanocomposites was appraised for the decomposition of dimethyl phthalate (DMP) as a plasticizer. The highest decomposition efficiency of 100% was obtained in the existence of CoCr LDH/rGO nanocomposite (0.5 g/L) during 20 min of reaction time via photo-assisted sonocatalysis. The rGO improved the catalytic activity of the CoCr LDH by increasing the specific surface area from 1.2 m²/g to 4.5 m²/g and reducing the band gap from 1.7 eV to 1.3 eV. Moreover, the results of the colony-forming unit method endorsed antibacterial property improvement of the CoCr LDH via hybridizing with rGO. The results of this research provide an optimistic perspective for applying carbonous-based nanocomposites of CoCr LDH as a novel catalyst with antibacterial properties in photo-assisted sonocatalytic processes.

Sonophotocatalysis with Photoactive Nanomaterials for Wastewater Treatment and Bacteria Disinfection

Sonophotocatalysis is described as a combination of two individual processes of photocatalysis and sonocatalysis. It has proven to be highly promising in degrading dissolved contaminants in wastewaters as well as bacteria disinfection applications. It eliminates some of the main disadvantages observed in each individual technique such as high costs, sluggish activity, and prolonged reaction times. The review has accomplished a critical analysis of sonophotocatalytic reaction mechanisms and the effect of the nanostructured catalyst and process modification techniques on the sonophotocatalytic performance. The synergistic effect between the mentioned processes, reactor design, and the electrical energy consumption has been discussed due to their importance when implementing this novel technology in practical applications, such as real industrial or municipal wastewater treatment plants. The utilization of sonophotocatalysis in disinfection and inactivation of bacteria has also been reviewed. In addition, we further suggest improvements to promote this technology from the lab-scale to large-scale applications. We hope this up-to-date review will advance future research in this field and push this technology toward widespread adoption and commercialization.

Efficient sonocatalytic degradation of heavy metal and organic pollutants using CuS/MoS2 nanocomposites

Eco-friendly and highly effective catalysts are receiving considerable attention for the removal of heavy-metal ions and organic pollutants. In this study, we developed CuS/MoS₂ nanocomposite sonocatalysts to enhance the degradation rate of environmental contaminants by harnessing ultrasonic irradiation. The successful synthesis of nanocomposite sonocatalysts was confirmed by X-ray diffraction (XRD) analysis, and energy-dispersive X-ray spectroscopy. The incorporation of CuS into MoS₂ resulted in a flower-like structure with an increased surface area. Importantly, the sonocatalytic efficiency was enhanced by increasing CuS concentration in the nanocomposites, achieving maximum removal efficiencies of 99% and 88.52% for rhodamine B (RhB) and Cr(VI), respectively. In addition, they showed excellent stability and recyclability over five consecutive cycles, without noticeable changes in the nanocomposite structure. Reactive oxygen species (ROS) used for the degradation were identified using ROS scavengers. We believe that this strategy of exploiting nanocomposite sonocatalysts has a great potential in the field of environmental catalysis.

Preparation of Ag3PO4/CoWO4 S-scheme heterojunction and study on sonocatalytic degradation of tetracycline

In this study, 0.6Ag₃PO₄/CoWO₄ composites were synthesized by hydrothermal method. The prepared materials were systematically characterized by techniques of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), N₂ adsorption/desorption, and UV-vis diffuse reflectance spectrum (DRS). Furthermore, the sonocatalytic degradation performance of 0.6Ag₃PO₄/CoWO₄ composites towards tetracycline (TC) was investigated under ultrasonic radiation. The results showed that, combined with potassium persulfate (K₂S₂O₈), the 0.6Ag₃PO₄/CoWO₄ composites achieved a high sonocatalytic degradation efficiency of 97.89 % within 10 min, which was much better than bare Ag₃PO₄ or CoWO₄. By measuring the electrochemical properties, it was proposed that the degradation mechanism of 0.6Ag₃PO₄/CoWO₄ is the formation of S-scheme heterojunction, which increases the separation efficiency of electron-hole pairs (e^--h⁺) and generates more electrons and holes, thereby enhancing the degradation activity. The scavenger experiments confirmed that hole (h⁺) was the primary active substance in degrading TC, and free radicals (OH) and superoxide anion radical (O₂^-) were auxiliary active substances. The results indicated that 0.6Ag₃PO₄/CoWO₄ nanocomposites could be used as an efficient and reliable sonocatalyst for wastewater treatment.

Application of perovskite oxides and their composites for degrading organic pollutants from wastewater using advanced oxidation processes: Review of the recent progress

In the recent years, perovskite oxides are gaining an increasing amount of attention owing to their unique traits such as tunable electronic structures, flexible composition, and eco-friendly properties. In contrast, their catalytic performance is not satisfactory, which hinders real wastewater remediation. To overcome this shortcoming, various strategies are developed to design new perovskite oxide-based materials to enhance their catalytic activities in advanced oxidation process (AOPs). This review article is to provide overview of basic principle and different methods of AOPs, while the strategies to design novel perovskite oxide-based composites for enhancing the catalytic activities in AOPs have been highlighted. Moreover, the recent progress of their synthesis and applications in wastewater remediation (pertaining to the period 2016-2022) was described, and the related mechanisms were thoroughly discussed. This review article helps scientists to have a clear outlook on the selection and design of new effective perovskite oxide-based materials for the application of AOPs. At the end of the review, perspective on the challenges and future research directions are discussed.

Ba substituted SrTiO3 induced lattice deformation for enhanced piezocatalytic removal of carbamazepine from water

Removal of pharmaceuticals and personal care products (PPCPs) from water by mechanical energy-driven piezocatalysis is a promising technology for environmental remediation that highly depends on the design of efficient piezocatalyst. In this study, Ba-substituted SrTiO₃ piezoelectric materials were constructed and used for piezocatalytic degradation of carbamazepine (CBZ) from water. The Ba_0.5Sr_0.5TiO₃ (BSTO-2) achieved the optimal performance, exhibiting 94.5% removal efficiency for CBZ (10 mg/L) after 30 min in the presence of BSTO-2 (0.5 g/L) and ultrasonic vibration (40 kHz, 100 W) with the minimal energy consumption. The kinetic rate constant was up to 0.106 min^-1, which were 1.86 and 2.08 times as high as that of pure SrTiO₃ and BaTiO₃, respectively. The enhanced piezocatalytic activity was attributed to its distorted structure and modified conductivity, resulting in a higher piezoelectric response and faster interfacial charge transfer. The involved reactive species, the effects of operational condition (catalyst dosage, CBZ concentration, solution pH, anions, water matrices and different pollutants), and the possible degradation products and their toxicity were discussed in detail. The work is of great significance to develop highly efficient piezocatalysts and highlights the potential of piezocatalysis in water remediation.

Removal of Ciprofloxacin from Wastewater by Ultrasound/Electric Field/Sodium Persulfate (US/E/PS)

Ciprofloxacin (CIP), as a common antibiotic used in human clinical and livestock farming, is discharged into natural water bodies and its concentration has increased in the last years. Its stable chemical structure is difficult to remove by conventional techniques. Residual ciprofloxacin in the environment has become an emerging micropollutant that promotes the generation of resistance genes of bacteria and endangers ecosystem balance and human health. Removal of ciprofloxacin from water by the system of ultrasound/electric field/sodium persulfate (US/E/PS) was investigated. Firstly, CIP degradation affects by different oxidation methods, such as ultrasonic oxidation, electro-oxidation, and persulfate oxidation, and their four combined oxidation methods (ultrasound-activated persulfate oxidation, electro-activated persulfate oxidation, ultrasound-enhanced electro-oxidation, and ultrasound-enhanced electro-activated persulfate oxidation), on the target contaminants were compared. Secondly, the influences of parameters on the CIP degradation by an ultrasound-enhanced electro-activation-persulfate reaction system were investigated. Thirdly, the possible free radical species in the ultrasound-enhanced electro-activation-sulfate reaction system were identified and the dominant free radical species in the system were analyzed. Finally, the samples of CIP in the US/E/PS system were tested by liquid mass spectrometry, and the possible intermediate products and degradation path were speculated. The results indicate that the US/E/PS system is of great potential application value in the removal of organic pollution and environmental purification.

A review of advances in multifunctional XTiO3 perovskite-type oxides as piezo-photocatalysts for environmental remediation and energy production

Over more than three decades, the field of engineering of photocatalytic materials with unique properties and enhanced performance has received a huge attention. In this regard, different classes of materials were fabricated and used for different photocatalytic applications. Among these materials, recently multifunctional XTiO₃ perovskites have drawn outstanding interest towards environmental remediation and energy conversion thanks to their unique structural, optical, physiochemical, electrical and thermal characteristics. XTiO₃ perovskites are able to initiate different surface catalytic reactions. Under ultrasonic vibration or heating, XTiO₃ perovskites can induce piezo-catalytic reactions due to the titling of their conduction and valence bands, resulting in the formation of separated charge carriers in the medium. In addition, under light irradiation, XTiO₃ perovskites are considered as a new class of photocatalysts for environmental and energy related applications. Herein, we addressed the recent advances on variously synthesized, doped and formulated XTiO₃ perovskite-type oxides showing piezo- and/or photocatalytic exploitation in environmental remediation and energy conversion. The control of structural crystallite size and phase, conductivity, morphology, oxygen vacancy control, doping agents and ratio has a significant role on the photocatalytic and piezocatalytic activities. The different piezo or/and photocatalytic processes mechanistic pathways towards varying applications were discussed. The current challenges facing these materials and future trends were addressed at the end of the review.

Photoinduced electronic and ionic effects in strontium titanate

The interaction of light with solids has been of ever-growing interest for centuries, even more so since the quest for sustainable utilization and storage of solar energy became a major task for industry and research. With SrTiO₃ being a model material for an extensive exploration of the defect chemistry of mixed conducting perovskite oxides, it has also been a vanguard in advancing the understanding of the interaction between light and the electronic and ionic structure of solids. In the course of these efforts, many phenomena occurring during or subsequent to the illumination of SrTiO₃ have been investigated. Here, we give an overview of the numerous photoinduced effects in SrTiO₃ and their inherent connection to electronic structure and defect chemistry. In more detail, advances in the fields of photoconductivity, photoluminescence, photovoltages, photochromism and photocatalysis are summarized and their underlying elemental processes are discussed. In light of recent research, this review also emphasizes the fundamental differences between illuminating SrTiO₃ either at low temperatures (<RT) or at high temperatures (>200 °C), where in addition to electronic processes, also photoionic interactions become relevant. A survey of the multitude of different processes shows that a profound and comprehensive understanding of the defect chemistry and its alteration under illumination is both vital to optimizing devices and to pushing the boundaries of research and advancing the fundamental understanding of solids.

In situ construction of 0D CoWO4 modified 1D Mn0.47Cd0.53S for boosted visible-light photocatalytic H2 activity and photostability

To enhance the photocatalytic activity, loading proper semiconductor with high efficiency and low cost is one of the most valid approaches. Herein, various amounts of CoWO₄ as a novel metal-free material were loaded on Mn_0.47Cd_0.53S (MCS) nanorods for photocatalytic hydrogen production reaction. The CoWO₄/Mn_0.47Cd_0.53S-25 (CW/MCS-25) exhibits the highest hydrogen production rate of 41.53 mmol·h^-1·g^-1 in the Na₂S/Na₂SO₃ system, which is about 2.68 times higher than that of pristine MCS. The Mapping and HRTEM reveals the deposited of CoWO₄ on the MCS. The detailed analyses of XPS, EIS, TRPL spectra and transient photocurrent responses indicate that CoWO₄ and MCS interacted closely and the photogenerated electrons of CoWO₄ can be transferred into MCS. In particular, the introduction of CoWO₄ can further transfer the photogenerated holes of MCS, thereby inhibiting the photocorrosion of MCS and improving photocatalytic activity. This work provides a reference for the exploration of noble metal-free composite material and shows great potential in the photocatalytic application.

Efficient degradation of tetracycline hydrochloride by photocatalytic ozonation over Bi2WO6

Photocatalytic ozonation technique for wastewater treatment has received much attention for their efficient capability in the mineralization of persistent organic pollutants. In this study, nanostructured Bi₂WO₆ was prepared by hydrothermal method and applied in the photocatalytic ozonation process for tetracycline hydrochloride (TCH) degradation under simulated solar light irradiation. Bi₂WO₆ triggered an effective synergy between photocatalysis and ozonation, and it showed a good activity and adaptability in the degradation of organic compounds. Besides, the influence of experimental factors on the total organic carbon removal (including catalyst dosage, ozone concentration, initial pH, reaction temperature and coexisting ions) was also investigated comprehensively. Spin-trapping electron paramagnetic resonance measurements and quenching experiments demonstrated that O₂^-, OH, ¹O₂ and h⁺ contributed to TCH degradation. The possible degradation pathways of TCH were proposed by identifying the intermediates with liquid chromatography-mass spectroscopy.

Optimization of synergistic biosorption of oxytetracycline and cadmium from binary mixtures on reed-based beads: modeling study using Brouers-Sotolongo models

The first aim of this study was to synthesize and characterize reed-based-beads (BBR), an enhanced adsorbent from Tunisian reed. The second purpose was to evaluate and optimize the BBR efficiency for the simultaneous removal of oxytetracycline (OTC) and cadmium (Cd(II)), using central composite design under response surface methodology. The third goal was to elucidate the biosorption mechanisms taking place. It was shown that under optimum conditions (4.19 g L^-1 of BBR, 165.54 μmol L^-1 of OTC, 362.16 μmol L^-1 of Cd(II), pH of 6, and 25.14-h contact time) the highest adsorption percentages (63.66% for OTC and 99.99% for Cd(II)) were obtained. It was revealed that OTC adsorption mechanism was better described by Brouers-Sotolongo fractal equation, with regression coefficient (R²) of 0.99876, and a Person's chi-square (χ²) of 0.01132. The Weibull kinetic equation better explained Cd(II) biosorption (R² = 0.99959 and χ² = 0.00194). FTIR and isotherm studies confirmed that the BBR surface was heterogeneous, and that adsorption mechanisms were better described by the Freundlich/Jovanovich equation (R² = 0.99276 and χ² = 0.04864) for OTC adsorption, and by the Brouers-Sotolongo model (R² = 0.9851 and χ² = 0.77547) for Cd(II) biosorption. Overall results indicate that, at last, the BBR lignocellulosic biocomposite beads could be considered as cost-effective and efficient adsorbent, which could be of socioeconomic and environmental relevance. Graphical abstract.

Sonochemical processes for the degradation of antibiotics in aqueous solutions: A review

Antibiotic residues in water are general health and environmental risks due to the antibiotic-resistance phenomenon. Sonication has been included among the advanced oxidation processes (AOPs) used to remove recalcitrant contaminants in aquatic environments. Sonochemical processes have shown substantial advantages, including cleanliness, safety, energy savings and either negligible or no secondary pollution. This review provides a wide overview of the different protocols and degradation mechanisms for antibiotics that either use sonication alone or in hybrid processes, such as sonication with catalysts, Fenton and Fenton-like processes, photolysis, ozonation, etc.

Chlortetracycline hydrochloride removal by different biochar/Fe composites: A comparative study

In the last years, the synthesis and applications of biochar/Fe composites have been extensively studied, but only few papers have systematically evaluated their removal performances. Herein, we successfully synthesized and structurally characterized Fe⁰, Fe₃C, and Fe₃O₄-coated biochars (BCs) for the removal of chlortetracycline hydrochloride (CH). Evaluation of their removal rate and affinity revealed that Fe⁰@BC could achieve better and faster CH removal and degradation than Fe₃C@BC and Fe₃O₄@BC. The removal rate was controlled by the O-Fe content and solution pH after the reaction. The CH adsorption occurred on the O C groups of Fe⁰@BC and the OC and OFe groups of Fe₃C@BC and Fe₃O₄@BC. Electron paramagnetic resonance analysis and radical quenching experiments indicated that HO and ¹O₂/ O₂^- were mainly responsible for CH degradation by biochar/Fe composites. Additional parameters, such as effects of initial concentrations and coexisting anions, regeneration capacity, cost and actual wastewater treatment were also explored. Principal component analysis was applied for a comprehensive and quantitative assessment of the three materials, indicating Fe⁰@BC is the most beneficial functional material for CH removal.

Preparation of a novel Z-scheme KTaO3/FeVO4/Bi2O3 nanocomposite for efficient sonocatalytic degradation of ceftriaxone sodium

In this work, a novel Z-scheme sonocatalyst, KTaO₃/FeVO₄/Bi₂O₃, is prepared via ultrasonic-assisted isoelectric point method. The prepared samples are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The catalytic activity of Z-scheme KTaO₃/FeVO₄/Bi₂O₃ sonocatalyst is studied in degradation of ceftriaxone sodium under ultrasonic irradiation. In addition, the influences of ultrasonic irradiation time, scavengers and sonocatalyst used times on sonocatalytic degradation of ceftriaxone sodium are examined. Under the experimental conditions of 150 min ultrasonic irradiation time, 1.00 g/L KTaO₃/FeVO₄/Bi₂O₃ addition amount and 10.00 mg/L ceftriaxone sodium concentration, the sonocatalytic degradation ratio of ceftriaxone sodium achieves 81.30%. Finally, the possible sonocatalytic degradation mechanism of ceftriaxone sodium caused by Z-scheme KTaO₃/FeVO₄/Bi₂O₃ sonocatalyst is proposed. The enhanced sonocatalytic activity may be attributed to the fact that the FeVO₄ as a special conductive channel provides a strong driving force to transfer electrons through valence state changes of iron and vanadium, which accelerates electron transfer from conduction band (CB) of Bi₂O₃ to valence band (VB) of KTaO₃. Perhaps, the KTaO₃/FeVO₄/Bi₂O₃ composite is an excellent Z-scheme sonocatalyst which can be used to effectively degrade the organic pollutants in wastewater under ultrasonic irradiation.

Sonocatalytic removal of ampicillin by Zn(OH)F: Effect of operating parameters, toxicological evaluation and by-products identification

Zinc hydroxyfluoride (Zn(OH)F) sonocatalyst was prepared by using solvothermal method and was characterized by using various techniques. The sonocatalytic degradation of ampicillin (AMP) in water by sonolysis, bare ZnO and Zn(OH)F was investigated in terms of AMP removal, mineralization, detoxification of solution, and remaining by-products at the end of process. Results revealed that the sonocatalytic performance of Zn(OH)F was significantly greater than that of bare ZnO. Under the optimum conditions, the removal percentage of AMP by Zn(OH)F was ∼97% after 90 min reaction, while 51% and 36% COD and TOC removal were achieved after 120 min reaction, respectively. The study of Zn(OH)F stability revealed that the degradation efficiency of AMP was reduced by only 5% even after being reused for four experiments. The toxicity of initial and treated solutions was assessed by using agar-well diffusion method and ToxTrak^™ toxicity assay, and the results indicated a substantial reduction in the toxicity of solution after the treatment. The formation of some by-products during the sonolysis and sonocatalysis was evaluated by LC-HR-MS/MS method. LC-HR-MS/MS results showed that the concentration of most by-products, which were produced after 90 min treatment by US/Zn(OH)F process, was considerably lower than those obtained during sonolysis and US/ZnO processes.