Sonocatalytic activity of a heterostructured β-Bi2O3/Bi2O2CO3 nanoplate in degradation of bisphenol A

Ultrasonic treatment of dye chemicals in wastewater: A review

The existence of pollutants, such as toxic organic dye chemicals, in water and wastewater raises concerns as they are inadequately eliminated through conventional water and wastewater treatment methods, including physicochemical and biological processes. Ultrasonic treatment has emerged as an advanced treatment process that has been widely applied to the decomposition of recalcitrant organic contaminants. Ultrasonic treatment has several advantages, including easy operation, sustainability, non-secondary pollutant production, and saving energy. This review examines the elimination of dye chemicals and categorizes them into cationic and anionic dyes based on the existing literature. The objectives include (i) analyzing the primary factors (water quality and ultrasonic conditions) that influence the sonodegradation of dye chemicals and their byproducts during ultrasonication, (ii) assessing the impact of the different sonocatalysts and combined systems (with ozone and ultraviolet) on sonodegradation, and (iii) exploring the characteristics-based removal mechanisms of dyes. In addition, this review proposes areas for future research on ultrasonic treatment of dye chemicals in water and wastewater.

Synergistic effects of layered Ti3C2TX MXene/MIL-101(Cr) heterostructure as a sonocatalyst for efficient degradation of sulfadiazine and acetaminophen in water

In this work, different mass loadings of MXene-coupled MIL-101(Cr) (MXe/MIL-101(Cr)) nanocomposites were generated through a hydrothermal process in order to investigate the potential of this nanocomposite as a novel sonocatalyst for the elimination of sulfadiazine (SD) and acetaminophen (AAP) in aqueous media. The sonocatalytic activity of different MXe/MIL-101(Cr) compositions and surface functionalities was investigated. In addition, the sonocatalytic activities at various pH values, temperatures, pollutant concentrations, catalyst dosages, initial H2O2 concentrations, and organic matter contents were investigated. The experiments on the sonocatalytic elimination of SD and AAP revealed that MXe/MIL-101(Cr) exhibited a catalytic efficiency of ∼ 98% in 80 min when the MXene loading was 30 wt% in the nanocomposite. Under optimized reaction conditions, the degradation efficiency of MXe/MIL-101(Cr) reached 91.5% for SD and 90.6% for AAP in 60 min; these values were 1.2 and 1.8 times greater than those of MXene and MIL-101(Cr), respectively. The high surface area of the MXe/MIL-101(Cr) nanocomposite increased from 4.68 m2/g to 294.21 m2/g, and the band gap of the tagged MIL-101(Cr) on the MXene surface was minimized. The superior sonocatalytic activity of MXe/MIL-101(Cr) was attributed to the effective contact interface, the effective separation rate of e- - h+ pairs through the type II heterostructure interface, and the favorable high free •OH radical production rates that promoted the degradation of SD and AAP. The solid heterointerface between MIL-101(Cr) and MXene was confirmed through Raman and FTIR analysis and was found to promote accessible •OH radical production under sonication, thus maximizing the catalytic activity of nanocomposites. The present results present an effective strategy for the design of a highly efficient, low-cost, reliable sonocatalyst that can eradicate pharmaceutical pollutants in our environment.

Performance and mechanism of a novel S-scheme heterojunction sonocatalyst CuS/BaWO4 for degradation of bisphenol A by ultrasonic activation

A novel CuS/BaWO₄ heterojunction catalyst was prepared and characterized. Taking bisphenol A as the target pollutant for catalytic degradation, the sonocatalytic activity of CuS/BaWO₄ composite was evaluated, and the combination with persulfate improved the sonocatalytic degradation of bisphenol A. The results showed that CuS/BaWO₄ composite had good sonocatalytic degradation activity for bisphenol A, and the degradation rate was 70.99% ± 1.46%. After combined with persulfate, the degradation rate was further increased to 95.34% ± 0.10%, and the reaction time was relatively shortened. The results of the trapping experiment and calculated energy band positions showed that the formation of S-scheme heterojunction and the formation of hydroxyl radicals and holes were the key to the catalytic degradation of bisphenol A by CuS/BaWO₄ composite. In this study, a new CuS/BaWO₄ heterojunction sonocatalyst was synthesized. The catalyst can efficiently remove bisphenol A from the water environment and can be used as a potential solution for endocrine disruptor pollution in the water environment.

Degradation synergism between sonolysis and photocatalysis for organic pollutants with different hydrophobicity: A perspective of mechanism and application for high mineralization efficiency

Despite extensive studies, the fundamental understanding of synergistic mechanisms between sonolysis and photocatalysis for the abatement of persistent organic pollutants (POPs) remains uncertain. As different phases formed under ultrasound irradiation, hydrophilic POPs, sulfamethoxazole (SMX, K_ow: 0.89), predominantly resides in bulk liquid and is ineffectively degraded by sonolysis (k_US = 3.33 × 10^-3 min^-1) since <10% of hydroxyl radicals (·OH) formed at the gas-liquid interface of cavitation is diffused into the bulk, whereas the other fraction rapidly recombines into hydrogen peroxide (H₂O₂). This study provides a proof-of-concept for the mechanism by presenting various analytical results, endorsing the synergistic role of photoexcited electrons in splitting sonolysis-induced H₂O₂ into ·OH, particularly in the bulk phase. In a sonophotocatalytic system, the hydrophobic POPs such as bisphenol A (BPA) and atrazine (ATZ) were mainly degraded in gas-liquid interface indicated by the low synergistic values correlation compared to SMX [i.e., SMX has a higher synergistic factor, f_syn (3.26) than BPA (1.30) and ATZ (1.35)]. Also, f_syn was found linearly correlated with the contribution factor of photocatalysis to split H₂O₂. Three times of consecutive kinetics using an effluent of municipal (MP) wastewater spiked by POPs presented >98% POPs and >96% total organic carbon (TOC) removal.

In situ construction of a direct Z-scheme AgBr/α-Ag2WO4 heterojunction with promoted spatial charge migration and photocatalytic performance

A hierarchical AgBr/α-Ag₂WO₄ Z-scheme heterojunction was facially constructed for greatly improved photocatalytic activity towards pollutant elimination due to promoted spatial separation of carriers with high redox capacity.

Novel Z-scheme Ag3PO4/Fe3O4-activated biochar photocatalyst with enhanced visible-light catalytic performance toward degradation of bisphenol A

A novel solid-state Z-scheme heterostructure, Ag₃PO₄/Fe₃O₄ co-doped bamboo-derived activated biochar (Ag-Fe@BAB), was synthesized as an efficient photocatalyst via a co-precipitation method. Ag-Fe@BAB was used as a magnetically recoverable photocatalyst to generate free radical species with peroxydisulfate (PDS) activation under visible-LED-light illumination. The successful synthesis of Ag-Fe@BAB was confirmed by various characterization techniques. Bisphenol A (BPA) was used as a model pollutant to evaluate the photocatalytic activities of the Vis/Ag-Fe@BAB/PDS system. To confirm the photocatalytic performance of the Vis/Ag-Fe@BAB/PDS system, the effects of significant operating parameters such as the contact time, concentration of oxidant, photocatalyst dosage, and solution pH on the degradation of BPA were evaluated. We confirmed that 95.6% BPA was degraded within 60 min in the Vis/Ag-Fe@BAB/PDS system under 1.0 g/L photocatalyst, pH 6.5, and 0.5 mM PDS. The degradation mechanism of BPA in the Vis/Ag-Fe@BAB/PDS system was mainly attributed to O₂^‾ owing to its photocatalytic performances in the presence of p-benzoquinone as a scavenger. Furthermore, the radical species produced in the Vis/Ag-Fe@BAB/PDS system were identified by electron spin resonance. Finally, we demonstrated the recyclability of the Ag-Fe@BAB photocatalyst through its excellent magnetic property.

Degradation of Bisphenol A by CeCu Oxide Catalyst in Catalytic Wet Peroxide Oxidation: Efficiency, Stability, and Mechanism

The CeCu oxide catalyst CC450 was prepared by citric acid complex method and the catalytic wet peroxide oxidation (CWPO) reaction system was established with bisphenol A (BPA) as the target pollutant. By means of characterization, this research investigated the phase structure, surface morphology, reducibility, surface element composition, and valence of the catalyst before and after reuse. The effects of catalyst dosage and pH on the removal efficiency of BPA were also investigated. Five reuse experiments were carried out to investigate the reusability of the catalyst. In addition, this research delved into the changes of pH value, hydroxyl radical concentration, and ultraviolet-visible spectra of BPA in CWPO reaction system. The possible intermediate products were analyzed by gas chromatography-mass spectrometry (GC-MS). The catalytic mechanism and degradation pathway were also discussed. The results showed that after reaction of 65 min, the removal of BPA and total organic carbon (TOC) could reach 87.6% and 77.9%, respectively. The catalyst showed strong pH adaptability and had high removal efficiency of BPA in the range of pH 1.6-7.9. After five reuses, the removal of BPA remained above 86.7%, with the structure of the catalyst remaining stable to a large extent. With the reaction proceeding, the pH value of the reaction solution increased, the concentration of OH radicals decreased, and the ultraviolet-visible spectrum of BPA shifted to the short wavelength direction, that is, the blue shift direction. The catalysts degraded BPA rapidly in CWPO reaction system and the C-C bond or O-H bond in BPA could be destroyed in a very short time. Also, there may have been two main degradation paths of phenol and ketone.

Ultrasonic energy-assisted in-situ synthesis of Ru0/PANI/g-C3N4 nanocomposite: Application for picomolar-level electrochemical detection of endocrine disruptor (Bisphenol-A) in humans and animals

Bisphenol A (BPA) is an endocrine-disrupting chemical which resembles structurally the hormone estrogen. Even a trace amount of BPA can bind estrogen receptors resulting in the inducement of reproductive disorders, cancers and problems related to sexual growth such as manliness in female and womanliness in male. So the determination of BPA in human and animal bodies is very essential. For this purpose, a new nanocomposite composed of ruthenium nanoparticles, polyaniline and graphitic carbon nitride (Ru⁰/PANI/g-C₃N₄) has been synthesized ultrasonically (40 ± 3 kHz, 200 W). A modification on glassy carbon electrode (GCE) with the nanocomposite detects BPA in human and animal urine samples with wide linear range (0.01-1.1 µM) and the limit of detection is pico molar-level. The synthesized nanocomposite was characterized by Ultraviolet-Visible and Fourier Transform-Infra Red spectroscopies, thermo gravimetric analysis, transmission electron microscopy, X-ray diffraction study, energy dispersive X-ray analysis, and elemental mapping analysis. This sensing system is selective, stable and reusable, by which the detection of BPA in various physiological fluids is very much possible.

Heterogeneous sonocatalytic degradation of an anionic dye in aqueous solution using a magnetic lanthanum dioxide carbonate-doped zinc ferrite-reduced graphene oxide nanostructure

We report herein the sonochemical synthesis of a lanthanum dioxide carbonate (La₂O₂CO₃) and zinc ferrite (ZnFe₂O₄)-loaded reduced graphene oxide (LZF-rGO) nanoheterostructure for ultrasound (US)-assisted degradation of methyl orange (MO) from water. The MO was chosen as a model organic dye due to its toxicological and biodegradable-resistant properties. The LZF-rGO catalyst was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results of characterizations confirmed successful synthesis of sonocatalyst. Among different removal systems, US/LZF-rGO displayed outstanding sonodegradation performance for degradation of MO. The maximum removal efficiency of 75.9% was achieved using 0.2 g/L sonocatalyst, 20 mg/L MO, and 0.71 W/cm² US power intensity for 65 min. MO can be partially adsorbed on LZF-rGO but mostly sonodegraded by reactive radical species. The reaction conditions were optimized by investigating the effect of key operating parameters, including the sonocatalyst dosage, initial MO concentration, US power intensity, presence of inorganic salts, and use of an enhancer, on the decolorization of MO. The degradation intermediates produced from MO during the sonocatalytic process were identified by UPLC^®/MS-MS, and possible mechanism and pathway for the degradation of MO in the US/LZF-rGO system were also proposed. Reusability experiments with this sonocatalyst revealed a less than 10% drop in the degradation efficiency after four adsorption-desorption cycles.

Heterogeneous sonocatalytic degradation of Bisphenol-A and the influence of the reaction parameters and ultrasonic frequency

In the present study, the sonocatalytic oxidation of Bisphenol-A (BPA) was investigated in the presence of a LaFeO₃ perovskite catalyst. The effects of the reaction temperature, initial pH, catalyst loading, presence of inorganic anions and sonication source (power and frequency) on the removal of BPA using heterogeneous sonocatalytic process were investigated. Under the studied temperature range of 288-318 K, 308 K was selected as the optimum temperature and the highest BPA removal and total oxygen demand (TOC) reduction of, 95.8% and 30.4% were achieved at that temperature. The thermodynamic parameters were calculated in the studied temperature range of 288-308 K. It was seen that an acidic pH of 3.0 was favorable for the BPA oxidation with the highest BPA removal and TOC reduction of 95.4% and 31.5%, respectively. Doubling the catalyst amount from 0.25 g/L to 0.5 g/L increased the BPA removal degree from 81.6% to 90.8%. However, further increase in catalyst amount has no remarkable positive effect on the removal of BPA. The removal of BPA was described by the first order kinetics with an activation energy of 14.9 kJ/mol. The results obtained from this study showed that the LaFeO₃ perovskite catalyst was a good sonocatalyst giving high oxidation rates of BPA.