Search Results (19)

Water contamination has become a global concern, and the prevalence of complex substances known as emerging contaminants constitute a risk to human health and the environment. This work focused on an innovative approach of integrating sonolysis and photocatalysis to remove a standard textile dye efficiently. A highly photo-active, bismuth ferrite (BiFeO₃) nanocatalyst with single particle sizes between 86 and 265 nm was obtained by a novel one-pot combustion method using a deep eutectic solvent as a precursor. The said catalyst was thoroughly characterized and evaluated for photocatalytic and sono-photocatalytic degradation of rhodamine B (RhB). Photocatalytic experiments were conducted under visible light irradiation (450–600 nm). Sono-photocatalytic (SPC) experiments were conducted, focusing on the influence of operational parameters (frequency, power, and pH) on the degradation performance. High-frequency values of 578, 866, and 1138 kHz were explored to promote cavitation dynamics and reactive species generation, improving removal efficiency. Results demonstrated that when sonolysis and photocatalysis were performed separately, the degradation efficiency ranged between 85 and 87%. Remarkably, when the combined SPC degradation was carried out, the RhB removal reached about 99.9% after 70 min. It is discussed that this behavior is due to the increased generation of OH^• radicals as a product of the cavitation phenomena related to the ultrasound-assisted process. Moreover, it is argued that SPC significantly improves reaction kinetics and mass transfer rates, facilitating catalyst dispersion and contact with the RhB molecules. Finally, the stability of the catalyst was evaluated in five repeated RhB removal cycles, where the activity remained consistently strong. Full article

Nanoparticles of NiLa_xFe_2−xO₄ ferrite spinel incorporated in a SiO₂ matrix were synthesized via a sol-gel method, followed by annealing at 200, 500, and 800 °C. The resulting materials were characterized via XRD, AFM, and BET techniques and evaluated for photocatalytic activity. The XRD diffractograms validate the formation of a single-phase cubic spinel structure at all temperatures, without any evidence of secondary peaks. The size of crystallites exhibited a decrease from 37 to 26 nm with the substitution of Fe³⁺ with La³⁺ ions. The lattice parameters and crystallite sizes were found to increase with the rise in La³⁺ content and annealing temperature. Isotherms were employed to calculate the rate constants for the decomposition of malonate precursors to ferrites and the activation energy for each ferrite. All nanocomposites have pores within the mesoporous range, with a narrow dispersion of pore sizes. The impact of La content on sonophotocatalytic activity was evaluated by studying Rhodamine B degradation under visible light irradiation. The results indicate that the introduction of La enhances nanocomposite performance. The prepared Ni-La ferrites may have potential application for water decontamination. Full article

Organic dyes play vital roles in the textile industry, while the discharge of organic dye wastewater in the production and utilization of dyes has caused significant damage to the aquatic ecosystem. This review aims to summarize the mechanisms of photocatalysis, sonocatalysis, and sonophotocatalysis in the treatment of organic dye wastewater and the recent advances in catalyst development, with a focus on the synergistic effect of ultrasound and light in the catalytic degradation of organic dyes. The performance of TiO₂-based catalysts for organic dye degradation in photocatalytic, sonocatalytic, and sonophotocatalytic systems is compared. With significant synergistic effect of ultrasound and light, sonophotocatalysis generally performs much better than sonocatalysis or photocatalysis alone in pollutant degradation, yet it has a much higher energy requirement. Future research directions are proposed to expand the fundamental knowledge on the sonophotocatalysis process and to enhance its practical application in degrading organic dyes in wastewater. Full article

Here, the magnetic Fe₃O₄@SiO₂/PAEDTC@MIL-101 (Fe) with a new core-shell structure was synthesized, and its sonophotocatalytic properties were evaluated for acid red 14 (AR14) degradation. Particle characterizations were determined by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and vibrating-sample magnetometer (VSM), and the analysis results offered an excellent synthesis of mesoporous particles. Fe₃O₄@SiO₂/PAEDTC@MIL-101 (Fe)/UV/US showed high degradation kinetics rate (0.0327 min⁻¹) compared to sonocatalytic processes (0.0181 min⁻¹), photocatalytic (0218 min⁻¹), sonolysis (0.008 min⁻¹), and photolysis (0.005 min⁻¹). Maximum removal efficiencies of AR14 (100%) and total organic carbon (69.96%) were obtained at pH of 5, catalyst mass of 0.5 g/L, initial AR14 concentration of 50 mg/L, and ultrasound power of 36 W. Evaluation of BOD₅/COD ratio during dye treatment confirmed that the sonophotocatalysis process can be useful for converting major contaminant molecules into biodegradable compounds. After recycling eight times, the prepared composite still has sonophotocatalytic degradation stability above 90% for AR14. Scavenging tests confirmed that holes (h⁺) and hydroxyl (^•OH) were the pivotal agents in the decomposition system. Based on the results, the synthesized sample can be suggested as an excellent and promising sonophotocatalyst for the degradation of AR14 dye and its conversion into biodegradable compounds. Full article

The present work investigates the effect of ultrasounds in the performance of combined advanced oxidation processes (AOPs) on the degradation of formaldehyde (HCHO)-polluted aqueous solutions for potential application in wastewater treatment. Different heterogeneous nanostructured catalysts based on TiO₂ and FeSO₄ for photocatalysis and the Fenton process were employed after electrospray deposition on electrospun nanofibrous membranes. Such systems were tested, without the use of any added hydrogen peroxide, by varying the combinations among the selected AOPs in a batch reactor configuration. The results show that, in the absence of a Fenton reaction, ultrasounds provided a significantly increased formaldehyde photocatalytic abatement, probably by increasing the concentration of active species through a different set of reactions while providing a favorable mass transfer regime by the cavitational effect. Due to the faster kinetics of the photo–Fenton process, thanks to its partial homogeneous nature, such a beneficial effect is more limited for the sono–photo–Fenton configuration. On the other hand, the employment of a sono–photocatalytic–Fenton process revealed a synergic effect that provided the best results, reducing the formaldehyde concentration to less than 99% after 240 min. Further analysis showed that, due to a mutual influence, only a tailored TiO₂/FeSO₄ ratio on the membranes was able to display the best performance. Full article

In this work, a hematite/porous graphite carbon-nitride (α-Fe₂O₃/g-C₃N₄) catalyst was synthesized through the doping of hematite loaded onto porous graphite carbon-nitride using a heat treatment process. Then, the ability of catalyst was evaluated to degrade diazinon (DZN) for the first time, mainly via the sonophotocatalytic process. Among the samples, the greatest DZN degradation was observed in the sonophotocatalytic system, which separated 100% of DZN from the aqueous solution after 50 min, while the removal percentages for the sonocatalytic, photocatalytic, and adsorption systems were 72.9, 89.1, and 58.1%, respectively. The results of scavengers showed that both sulfate and hydroxyl radicals (^•OH) participated in removing DZN, although positive holes and negative ^•OH played a major role. Moreover, the removal efficiencies of the target pollutant using the sonophotocatalytic process were higher than those using the photocatalytic, sonocatalytic, and adsorption processes. The reaction profile followed pseudo-first-order kinetics, and the reaction rate coefficient for the sonophotocatalytic system was 2.2 times higher than that of the photocatalytic system and 2.64 times higher than that of the sonocatalytic system. The energy consumption of the sonophotocatalytic system after 60 min was 11.6 kWh/m³, while it was 31.1 kWh/m³ for the photocatalytic system. A DZN removal percentage of 100% was obtained after 50 min under the following conditions: UV intensity of 36 watts, ultrasound frequency of 36 kHz, DZN concentration of 50 mg/L at pH 5, and α-Fe₂O₃/g-C₃N₄ dosage of 0.4 g/L. The catalyst reusability was examined with only a 9.9% reduction in efficiency after eight consecutive cycles. The chemical oxygen demand (COD) and total organic compound (TOC) removal percentages were 95.6% and 88.6%, respectively, and the five-day biochemical oxygen demand (BOD₅)/COD ratio was 0.16 at the beginning of the degradation process and 0.69 at the end of the process. In addition, toxicological experiments showed that degradation of DZN by the sonophotocatalytic process exhibited low toxicity. All results confirmed that the sonophotocatalytic process using α-Fe₂O₃/g-C₃N₄ was a highly efficient process for DZN pollutant removal from liquid wastes. Full article

A new nanocomposite based on Cloisite 30B clay modified with ZnO and Ag₂O nanoparticles (Cloisite 30B/ZnO/Ag₂O) was synthesized as an effective catalyst in the sono-photocatalytic process of crystal violet (CV) and methylene blue (MB) dyes simultaneously. The characteristics and catalytic activity of Cloisite 30B/ZnO/Ag₂O nanocomposite were investigated under different conditions. The specific active surface for Cloisite 30B/ZnO/Ag₂O nanocomposite was 18.29 m²/g. Additionally, the catalytic activity showed that Cloisite 30B/ZnO/Ag₂O nanocomposite (CV: 99.21%, MB: 98.43%) compared to Cloisite 30B/Ag₂O (CV: 85.38%, MB: 83.62%) and Ag₂O (CV: 68.21%, MB: 66.41%) has more catalytic activity. The catalytic activity of Cloisite 30B/ZnO/Ag₂O using the sono-photocatalytic process had the maximum efficiency (CV: 99.21%, MB: 98.43%) at pH 8, time of 50 min, amount of 40 mM H₂O₂, catalyst dose of 0.5 g/L, and the concentration of ‘CV + MB’ of 5 mg/L. The catalyst can be reused in the sono-photocatalytic process for up to six steps. According to the results, •OH and h⁺ were effective in the degradation of the desired dyes using the desired method. Data followed the pseudo-first-order kinetic model. The method used in this research is an efficient and promising method to remove dyes from wastewater. Full article

Naturally occurring sono- and photoactive minerals, which are abundant on Earth, represent an attractive alternative to the synthesized sonophotocatalysts as cost-effective materials for water and wastewater treatment. This study focuses on characterizing and evaluating the sonophotocatalytic activity of natural sphalerite (NatS) from Dovatka deposit (Siberia) under high-frequency ultrasonic (US, 1.7 MHz) and ultraviolet light-emitting diodes (UVA LED, 365 nm) irradiation towards degradation of 4-chlorophenol as a model organic pollutant. Since raw natural sphalerite did not exhibit a measurable photocatalytic activity, it was calcined at 500, 900 and 1200 °C. The natural sphalerite after calcination at 900 °C (NatS*) was found to be the most effective for sonophotocatalytic degradation of 4-chlorophenol, attaining the highest efficiency (55%, 1 h exposure) in the following row: UV < US ≈ UV/US ≈ US/NatS* < UV/NatS* < UV/US/NatS*. Addition of 1 mM H₂O₂ increased the removal to 74% by UV/US/NatS*/H₂O₂ process. An additive effect between UV/NatS* and US/NatS* processes was observed in the sonophotocatalytic system as well as in the H₂O₂-assisted system. We assume that the sonophotocatalytic hybrid process, which is based on the simultaneous use of high-frequency ultrasound, UVA light, calcined natural sphalerite and H₂O₂, could provide a basis of an environmentally safe and cost-effective method of elimination of organic pollutants from aqueous media. Full article

Eu-doped Y₂O₃ coated diatomite nanostructures with variable Eu³⁺ contents were synthesized by a facile hydrothermal technique. The products were characterized by means of energy dispersive X-ray photoelectron spectroscopy (EDX), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Brunauer–Emmett–Teller (BET), UV-vis diffuse reflectance spectroscopy, and photoluminescence spectroscopy techniques. As claimed by PXRD, the particles were crystallized excellently and attributed to the cubic phase of Y₂O₃. The influence of substitution of Eu³⁺ ions into Y₂O₃ lattice caused a redshift in the absorbance and a decrease in the bandgap of as-prepared coated compounds. The pore volume and BET specific surface area of Eu-doped Y₂O₃-coated diatomite is greater than uncoated biosilica. The sonophotocata-lytic activities of as-synthesized specimens were evaluated for the degradation of Reactive Blue 19. The effect of various specifications such as ultrasonic power, catalyst amount, and primary dye concentration was explored. Full article

Due to modernization and the scarcity of fossil fuel resources, energy demand is continuously increasing. In this regard, it is essential and necessary to create a renewable energy source that can meet future energy demands. Recently, the production of H₂ by water splitting and removing pollutants from the water has been essential for issues of energy and environmental demands. Herein, g-C₃N₄ and Ag-g-C₃N₄ composite structures have been successfully fabricated by the ultrasonication method. The physio/photochemical properties of prepared g-C₃N₄ and Ag-g-C₃N₄ were examined with different analytical techniques such as FTIR, XRD, UV-DRS, SEM, TEM, PL, and XPS analyses. The silver quantum dots (QDS) anchored to g-C₃N₄ structures performed the profound photocatalytic activities of H₂ production, dye degradation, and antimicrobial activity under visible-light irradiation. The Ag/g-C₃N₄ composite with an Ag loading of 0.02 mole has an optimum photoactivity at 335.40 μmol g⁻¹ h⁻¹, which is superior to other Ag loading g-C₃N₄ composites. The synthesized Ag/g-C₃N₄ nanoparticles showed potential microbial inhibition activity during the preliminary screening, and the inhibition zones were comparable to the commercial antibiotic chloramphenicol. The loading of Ag into g-C₃N₄ paves the suppression, recombination and transfer of photo-generated electron-hole pairs, leading to the enhancement of hydrogen production, the diminishment of pollutants in water under visible light irradiation, and antimicrobial activity against multidrug-resistant pathogens. Full article

The Polyacrylonitrile (PAN)/g-C₃N₄/CdS nanofiber sono-photocatalysts were successfully synthesized by an ordinary electrospining-chemical deposition method. The PAN/g-C₃N₄/CdS heterojunction nanofibers constructed with the CdS nanoparticles deposited on the PAN/g-C₃N₄ nanofibers. The g-C₃N₄/CdS heterojunction increase of light absorption and the construction of heterojunction can depress recombination of charge carrier and PAN nanofibers improve the recyclability successfully. Finally, a highly effective photocatalytic activity was performed by degradation of Rhodamine B (RhB) in visible light irradiation. Furthermore, an ultrasonic method is introduced into the sono-photocatalytic system to enhance the degradation efficiency of RhB ascribed to the synergistic effect of ultrasound. Full article

This work investigates the degradation of the azo dye solochrome dark blue (SDB) by measurement of the photocatalytic, sonocatalytic and sonophotocatalytic activities, under low ultrasonic frequency (40 kHz) and UV-C (254 nm) light, using Mn-doped ZnS semiconductor quantum dots (Mn²⁺:ZnS Qds) as catalysts, prepared by a simple chemical precipitation procedure. In order to study the different morphological and optical crystal properties, various characterization techniques were used, such as high resolution transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, N₂ adsorption-desorption at −196 °C and ultraviolet-visible spectroscopy. The average particle size of the semiconductor Qds was in the range of 3–4 nm. The optimal parameters affecting dye degradation, such as the catalyst loading, solution pH, time of irradiation, initial concentration of dye, dopant concentration, ultrasonic power and frequency effect were evaluated. The synthesized catalytic material exhibited a high activity for sonophotocatalytic degradation of SDB (89%), larger than that observed for sonocatalysis (69.7%) or photocatalysis (55.2%) alone, which was due to the improved electron-holes separation, formation of more reactive radicals and enhancement of the active surface area. Qds showed good stability and reusability after five repeated cycles. Finally, the degradation products were identified by liquid chromatography-mass spectrometry (LC-MS). Full article

Crude oil can undergo biotic and abiotic transformation processes in the environment. This article deals with the fate of an Italian crude oil under simulated solar irradiation to understand (i) the modification induced on its composition by artificial ageing and (ii) the transformations arising from different advanced oxidation processes (AOPs) applied as oil-polluted water remediation methods. The AOPs adopted were photocatalysis, sonolysis and, simultaneously, photocatalysis and sonolysis (sonophotocatalysis). Crude oil and its water-soluble fractions underwent analysis using GC-MS, liquid-state ¹H-NMR, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), and fluorescence. The crude oil after light irradiation showed (i) significant modifications induced by the artificial ageing on its composition and (ii) the formation of potentially toxic substances. The treatment produced oil oxidation with a particular effect of double bonds oxygenation. Non-polar compounds present in the water-soluble oil fraction showed a strong presence of branched alkanes and a good amount of linear and aromatic alkanes. All remediation methods utilised generated an increase of C₅ class and a decrease of C₆–C₉ types of compounds. The analysis of polar molecules elucidated that oxygenated compounds underwent a slight reduction after photocatalysis and a sharp decline after sonophotocatalytic degradation. Significant modifications did not occur by sonolysis. Full article

The incessant release of pharmaceuticals into the aquatic environment continues to be a subject of increasing concern. This is because of the growing demand for potable water sources and the potential health hazards which these pollutants pose to aquatic animals and humans. The inability of conventional water treatment systems to remove these compounds creates the need for new treatment systems in order to deal with these class of compounds. This review focuses on advanced oxidation processes that employ graphene-based composites as catalysts for the degradation of pharmaceuticals. These composites have been identified to possess enhanced catalytic activity due to increased surface area and reduced charge carrier recombination. The techniques employed in synthesizing these composites have been explored and five different advanced oxidation processes—direct degradation process, chemical oxidation process, photocatalysis, electrocatalyis processes and sonocatalytic/sono-photocatalytic processes—have been studied in terms of their enhanced catalytic activity. Finally, a comparative analysis of the processes that employ graphene-based composites was done in terms of process efficiency, reaction rate, mineralization efficiency and time required to achieve 90% degradation. Full article

In this study, Tb-doped CdSe nanoparticles with variable Tb³⁺ content were synthesized by a simple sonochemical technique. The synthesized nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and powder X-ray diffraction (XRD). The sono-photocatalytic activities of the as-prepared specimens were assessed for the degradation of Reactive Black 5. The experimental results show that the sono-photocatalytic process (85.25%) produced a higher degradation percentage than the individual sono- (22%) and photocatalytic degradation (8%) processes for an initial dye concentration and Tb-doped CdSe dosage of 20 mg/L and 1 g/L, respectively. Response surface methodology (RSM) was utilized to assess model and optimize the impacts of the operational parameters, namely, the Tb³⁺ content, initial dye concentration, catalyst dosage, and time. The addition of benzoquinone results in remarkably inhibited degradation and the addition of ammonium oxalate reduced the removal percentage to 24%. Superoxide radicals and photogenerated holes were detected as the main oxidative species. Full article