Efficient degradation of tetrabromobisphenol A by heterostructured Ag/Bi5Nb3O15 material under the simulated sunlight irradiation

Atomically dispersed dual-atom catalysts: A new rising star in environmental remediation

Single-atom catalysts, characterized by individual metal atoms as active centers, have emerged as promising candidates owing to their remarkable catalytic efficiency, maximum atomic utilization efficiency, and robust stability. However, the limitation of single-atom catalysts lies in their inability to cater to multistep reactions using a solitary active site. Introducing an additional metal atom can amplify the number of active sites, modulate the electronic structure, bolster adsorption ability, and enable a gamut of core reactions, thus augmenting their catalytic prowess. As such, dual-atom catalysts have risen to prominence. However, a comprehensive review elucidating the realm of dual-atom catalysts in environmental remediation is currently lacking. This review endeavors to bridge this gap, starting with a discourse on immobilization techniques for dual-atom catalysts, which includes configurations such as adjacent atoms, bridged atoms, and co-facially separated atoms. The review then delves into the intrinsic activity mechanisms of these catalysts, elucidating aspects like adsorption dynamics, electronic regulation, and synergistic effects. Following this, a comprehensive summarization of dual-atom catalysts for environmental applications is provided, spanning electrocatalysis, photocatalysis, and Fenton-like reactions. Finally, the existing challenges and opportunities in the field of dual-atom catalysts are extensively discussed. This work aims to be a beacon, illuminating the path towards the evolution and adoption of dual-atom catalysts in environmental remediation.

Rapid debromination of tetrabromobisphenol A by Cu/Fe bimetallic nanoparticles in water, its mechanisms, and genotoxicity after treatments

Tetrabromobisphenol A (TBBPA), a widely used brominated flame retardants, has been detected in various environmental matrices and is known to cause various adverse effects on human bodies. This study examined the feasibility and effectiveness of remediating TBBPA using Cu/Fe bimetallic nanoparticles (Cu/Fe BNPs) at various environmental and operational conditions. In general, TBBPA removal rate and debromination efficiency increased with higher Cu doping, higher Cu/Fe BNPs loading, higher temperature, and lower pH. At optimal conditions, TBBPA was completed removed at a rate constant > 0.2 min^-1 where over 90% TBBPA was transformed to BPA within 30 min. The activation energy was found to be 35.6 kJ/mol, indicating that TBBPA was predominantly removed via surface-controlled reactions. Under pH 3-7 and ≥ 25 °C, debromination was the dominant removal mechanism compared to adsorption. The complete debromination pathway and the time-evolution of intermediates byproducts at different pHs were also presented. Cu/Fe BNPs can be reused for more than 6 times with performance constancy. Genotoxic tests showed that the treated solution did not find a significant hazardous potential. The byproducts can be further degraded by additional H₂O₂ through Fenton reaction. These results demonstrated the efficacy of Cu/Fe BNPs for treating TBBPA and its potential for degrading other halogenated organic compounds.

Copper doping and organic sensitization enhance photocatalytic activity of titanium dioxide: Efficient degradation of phenol and tetrabromobisphenol A

A novel photocatalyst (Cu-TiO₂@HQ) had been synthesized by combining Cu-doped TiO₂ nanoparticles with 8-Hydroxyquinoline (HQ) via hydrothermal method. The photocatalytic activities of Cu-TiO₂@HQ were investigated by using phenol and tetrabromobisphenol A (TBBPA) as target pollutants, respectively. The results indicated that the degradation efficiencies of phenol and TBBPA by Cu-TiO₂@HQ were 99.2% (in 30 min) and 99.4% (in 10 min) under visible light irradiation. Both of them were much better than that of pure TiO₂ (8.63% in 30 min) and Cu-TiO₂ (14.74% in 30 min). When phenol or TBBPA were degraded together with the reduction of Cr (VI), the reaction rate of each pollutant was significantly increased, and the cyclic stability of photocatalyst Cu-TiO₂@HQ was greatly improved. Based on the spectroscopic and photoelectric characteristic analysis we found that in the mixture of phenol-Cr (VI) or TBBPA-Cr (VI) both photo-generated electrons and holes can be consumed simultaneously, thus preventing their recombination. The possible degradation products of phenol and TBBPA including its degradation path way were also analyzed by high resolution liquid chromatography-mass spectrometry-mass spectrometry.

Transformation/degradation of tetrabromobisphenol A and its derivatives: A review of the metabolism and metabolites

Although the abiotic and biotic transformation/degradation (T/D) processes of tetrabromobisphenol A (TBBPA) have been widely investigated in model experiments, few reviews have focused on these processes along with their metabolites or degradation products. In this paper, we summarize the current knowledge on the T/D of TBBPA and its derivatives, including abiotic and biotic T/D strategies/conditions, mechanisms, metabolites and environmental occurrences. Various treatments, such as pyrolysis, photolysis, chemical reactions and biotransformation, have been employed to study the metabolic mechanism of TBBPA and its derivatives and to remediate associated contaminated environments. To date, more than 100 degradation products and metabolites have been identified, dominated by less brominated compounds such as bisphenol A, 2,6-dibromo-4-isopropylphenol, 2,6-dibromo-4-hydroxyl-phenol, 2,6-dibromophenol, isopropylene-2,6-dibromophenol, 4-(2-hydroxyisopropyl)-2,6-dibromophenol, etc. It can be concluded that the T/D of TBBPA mainly takes place through debromination and β-scission. In some environmental media and human and animal tissues, brominated metabolites, glucoside and sulfate derivatives are also important T/D products. Here, the T/D products of TBBPA and its derivatives have been most comprehensively presented from the literature in recent 20 years. This review will enhance the understanding of the environmental behaviors of TBBPA-associated brominated flame retardants along with their ecological and health risks.

Photocatalytic removal of tetrabromobisphenol A by magnetically separable flower-like BiOBr/BiOI/Fe3O4 hybrid nanocomposites under visible-light irradiation

A novel flower-like three-dimensional BiOBr/BiOI/Fe₃O₄ heterojunction photocatalyst was synthesized using a simple in situ co-precipitation method at room temperature. The hybrid composites were characterized by a couple of techniques including X-ray powder diffraction, scanning electron microscope, transmission electron microscopy, ultraviolet-visible diffuse reflection spectroscopy, Brunauer-Emmett-Teller, X-ray photo-electron spectroscopy, photoluminescence technique, and vibrating sample magnetometer. Fe₃O₄ nanoparticles were perfectly loaded on the surface of BiOBr/BiOI microspheres. The recyclable magnetic BiOBr/BiOI/Fe₃O₄ was employed to degrade TBBPA under visible light irradiation. The optimal removal efficiency of the ternary BiOBr/BiOI/Fe₃O₄ (2:2:0.5) nanocomposite reached up to 98.5% for TBBPA in aqueous solution. The superior photocatalytic activity of BiOBr/BiOI/Fe₃O₄ was mainly ascribed to large surface area and appropriate energy gaps, resulting in the effective adsorption and separation of electrons-hole pairs. The photogenerated reactive species determined by free radicals trapping experiments revealed that the excellent catalytic activity was primarily driven by O₂^- radical. The photocatalytic degradation kinetics and a detailed mechanism were also proposed. Result demonstrated that the BiOBr/BiOI/Fe₃O₄ can be magnetically recycled, and maintain high photocatalytic activity after reuse over five cycles. It suggested that the synthesized material had a potentially promising application for TBBPA removal by photocatalytic degradation from wastewater.

Ag/AgxH3-xPMo12O40 Nanowires with Enhanced Visible-Light-Driven Photocatalytic Performance

Photocatalysis, a promising technology platform to address the environmental problems, has been attracting considerable attention. In this paper, Ag/Ag_xH_3-xPMo₁₂O₄₀ (simplified as Ag/AgHPMo₁₂) nanowires have been synthesized by a facile solid reaction route and in situ photodeposited method. The results of SEM and TEM indicate that the diameters of AgHPMo₁₂ nanowires are about 45 ± 10 nm, and Ag nanoparticles with diameters in the range of 5-15 nm are uniformly anchored on the surface of AgHPMo₁₂ nanowires. The Ag content in the Ag/AgHPMo₁₂ composite was manipulated by the light irradiation time (Ag/AgHPMo₁₂-x; x stands for the irradiation time; x = 2, 4, 6, 8 h, respectively). With increasing irradiation time, the light absorption of as-synthesized samples in the visible region was gradually enhanced. The Ag/AgHPMo₁₂-4 exhibits the best photocatalytic performance for the degradation of methyl orange and reduction of Cr₂O₇^2- under visible-light (λ > 420 nm) irradiation. The study of the photocatalytic mechanism reveals that both Ag and AgHPMo₁₂ can be excited by visible light. The photoinduced electrons were transferred from AgHPMo₁₂ to metallic Ag, and combined with the Ag plasmonic holes. The Ag plasmonic electrons were trapped by O₂ to form ·O₂^-, or directly reduced Cr₂O₇^2- to Cr³⁺. Meanwhile, the ·O₂^- species and the photogenerated holes of AgHPMo₁₂ were used to oxidize MO or i-PrOH; thus, they showed highly efficient and recyclable photocatalytic performance for removing the organic and inorganic pollutants.

Morphology-controlled preparation and plasmon-enhanced photocatalytic activity of Pt-BiOBr heterostructures

Pt-BiOBr nanosheets, microflowers, microspheres and sphere-like microflowers are controllably fabricated via a hydro(solvo)thermal treatment-photodeposition route and adjusting Br sources and solvents in the preparation systems. The simulated sunlight and visible-light photocatalytic properties of various morphological Pt-BiOBr heterostructures are evaluated by the degradation of two aqueous light insensitive organic pollutants, p-nitrophenol (PNP) and tetrabromobisphenol-A (TBBPA), and the relationship between the morphological characteristics and photocatalytic properties of the Pt-BiOBr is revealed accordingly. The sphere-like Pt-BiOBr microflowers and microspheres show considerably higher photocatalytic activity with respect to their microflowers and nanosheets counterparts, and their activity outperforms P25 TiO2. This excellent photoactivity is explained in terms of unique performance of BiOBr and plasmonic metal nanoparticles as well as fascinating morphological characteristics. The Pt-BiOBr heterostructures can be reused four times without obvious activity loss.

Photochemical transformation of tetrabromobisphenol A under simulated sunlight irradiation: Kinetics, mechanism and influencing factors

A systematic study on photolysis of tetrabromobisphenol A (2,2',6,6'-tetrabromo-4,4'-isopropylidendiphenol, TBBPA) in water was investigated under simulated sunlight irradiation. The results showed that the photolysis of TBBPA followed apparent pseudo-first-order kinetics. The photolysis rate constants (k) changed from 2.80 × 10(-2) to 0.70 × 10(-2)min(-1) with the concentrations of TBBPA varying from 0.1 to 10 mg L(-1). Increasing humic acid (HA) concentration from 0-100 mg L(-1) led to the decrease of k from 2.53 × 10(-2) to 0.39 × 10(-2)min(-1), which was due to the competitive adsorption for photons between HA and TBBPA molecules. The photolysis rate was faster at near-neutral conditions (pH=6 and 7) than that in either acidic or basic conditions. Electron spin resonance (ESR) and reactive oxygen species (ROS) scavenging experiments indicated that TBBPA underwent self-sensitized photooxidation via ROS (i.e., OH, (1)O2 and O2(-)), and the process was mainly controlled by O2(-). After irradiation of 180 min, about 35.0% reduction of TOC occurred accompanied with approximate 99.1% of TBBPA removed. The detection of products (i.e., Br(-), bisphenol A, 2,6-dibromophenol, 2-bromophenol and phenol) revealed that the main photolytic pathways of TBBPA were debromination and breakage of C-C bond.

Fabrication of a Ag/Bi3TaO7 Plasmonic Photocatalyst with Enhanced Photocatalytic Activity for Degradation of Tetracycline

A novel Ag/Bi3TaO7 plasmonic photocatalyst has been prepared by a simple photoreduction process. The as-prepared Ag/Bi3TaO7 photocatalyst exhibited an enhanced photocatalytic activity for the degradation of tetracycline (TC) compared to that of a bare Bi3TaO7 catalyst. The 1 wt % Ag-loaded Bi3TaO7 sample showed the highest photocatalytic efficiency for TC degradation (85.42%) compared with those of the other samples. The enhanced photocatalytic activity could be ascribed to the synergistic effect of the surface plasmon resonance caused by Ag nanoparticles. Electrochemical impedance spectroscopy demonstrated that the incorporation of silver nanoparticles onto the Bi3TaO7 surface promoted the separation of photogenerated carriers. In addition, an electron spin resonance (ESR) and trapping experiment revealed that the photoinduced active species hydroxyl radical and superoxide radical were the main active species in the photocatalytic process of TC degradation. The photocatalytic reaction mechanism was discussed by active species trapping and ESR analysis.

Photolysis Kinetics, Mechanisms, and Pathways of Tetrabromobisphenol A in Water under Simulated Solar Light Irradiation

The photolysis of tetrabromobisphenol A (TBBPA) in aqueous solution under simulated solar light irradiation was studied under different conditions to find out mechanisms and pathways that control the transformation of TBBPA during photoreaction. Particular attention was paid to the identification of intermediates and elucidation of the photolysis mechanism of TBBPA by UPLC, LC/MS, FT-ICR-MS, NMR, ESR, and stable isotope techniques ((13)C and (18)O). The results showed that the photolysis of TBBPA could occur under simulated solar light irradiation in both aerated and deaerated conditions. A magnetic isotope effect (MIE)-hydrolysis transformation was proposed as the predominant pathway for TBBPA photolysis in both cases. 2,6-Dibromophenol and two isopropylphenol derivatives were identified as photooxidation products of TBBPA by singlet oxygen. Reductive debromination products tribromobisphenol A and dibromobisphenol A were also observed. This is the first report of a photolysis pathway involving the formation of hydroxyl-tribromobisphenol A.

Enhanced photocatalytic degradation activity for tetracycline under visible light irradiation of Ag/Bi3.84W0.16O6.24nanooctahedrons

In this work, a Ag/Bi_3.84W_0.16O_6.24nanooctahedron composite photocatalyst was successfully synthesizedviaa green method at room temperature using silver nitrate (AgNO₃) as the silver source.

Preparation and enhanced visible-light photocatalytic activity of graphitic carbon nitride/bismuth niobate heterojunctions

A series of graphitic carbon nitride/bismuth niobate (g-C3N4/Bi5Nb3O15) heterojunctions with g-C3N4 doping level of 10-90 wt% were prepared by a facile milling-heat treatment method. The phase and chemical structures, surface compositions, electronic and optical properties as well as morphologies of the prepared g-C3N4/Bi5Nb3O15 were well-characterized. Subsequently, the photocatalytic activity and stability of g-C3N4/Bi5Nb3O15 were evaluated by the degradation of aqueous methyl orange (MO) and 4-chlorophenol (4-CP) under the visible-light irradiation. At suitable g-C3N4 doping levels, g-C3N4/Bi5Nb3O15 exhibited enhanced visible-light photocatalytic activity compared with pure g-C3N4 or Bi5Nb3O15. This excellent photocatalytic activity was revealed in terms of the extension of visible-light response and efficient separation and transportation of the photogenerated electrons and holes due to coupling of g-C3N4 and Bi5Nb3O15. Additionally, the active species yielded in the pure g-C3N4- and g-C3N4/Bi5Nb3O15-catalyzed 4-CP photodegradation systems were investigated by the free radical and hole scavenging experiments.

Enhanced visible-light-driven photocatalytic inactivation of Escherichia coli by Bi2O2CO3/Bi3NbO7 composites

The Bi2O2CO3/Bi3NbO7 (BiCO/BiNbO) composite was successfully fabricated by a simple hydrothermal method and found to be an effective visible-light-driven photocatalyst for inactivation of Escherichia coli (E. coli). The BiCO/BiNbO composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectrum (UV-vis DRS), and Fourier transform infrared (FT-IR) spectroscopy. The BiCO/BiNbO composite exhibited largely enhanced photocatalytic inactivation of E. coli as compared to the pure Bi3NbO7 under visible light irradiation. The enhanced photocatalytic performance can be attributed to the improved separation efficiency of the photogenerated holes and electrons. In addition, the possible bactericidal mechanism of the BiCO/BiNbO composite under visible light irradiation was discussed.

Preparation and properties of visible light responsive Y3+ doped Bi5Nb3O15 photocatalysts for Ornidazole decomposition

Nanoparticle of Bi(5)Nb(3)O(15) doped with Y(3+) was prepared for the first time by the sol-gel method combined with impregnation. The degradation of Ornidazole reacting with Y(3+)-Bi(5)Nb(3)O(15) was investigated to explore the feasibility of using Y(3+)-Bi(5)Nb(3)O(15) to treat antibiotics in wastewater. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, UV-vis diffuse reflectance spectrum and X-ray photoelectron spectroscopy. The results showed that the Y(3+)-Bi(5)Nb(3)O(15) exhibited single-crystalline orthorhombic structure with small particle size (20-100 nm); additionally, its UV-vis absorbance edges significantly shift to the visible-light region. The as-prepared nanoparticles exhibited a high photocatalytic activity in the decomposition of Ornidazole and several possible pathways of degradation of Ornidazole were proposed according to the results of ultra-performance liquid chromatography tandem mass spectrometry.

Hierarchical nitrogen doped bismuth niobate architectures: controllable synthesis and excellent photocatalytic activity

Nitrogen doped bismuth niobate (N-Bi(3)NbO(7)) hierarchical architectures were synthesized via a facile two-step hydrothermal process. XRD patterns revealed that the defect fluorite-type crystal structure of Bi(3)NbO(7) remained intact upon nitrogen doping. Electron microscopy showed the N-Bi(3)NbO(7) architecture has a unique peony-like spherical superstructure composed of numerous nanosheets. UV-vis spectra indicated that nitrogen doping in the compound results in a red-shift of the absorption edge from 450nm to 470nm. XPS indicated that [Bi/Nb]N bonds were formed by inducing nitrogen to replace a small amount of oxygen in Bi(3)NbO(7-x)N(x), which is explained by electronic structure calculations including energy band and density of states. Based on observations of architectures formation, a possible growth mechanism was proposed to explain the transformation of polyhedral-like nanoparticles to peony-like microflowers via an Ostwald riping mechanism followed by self-assembly. The N-Bi(3)NbO(7) architectures due to the large specific surface area and nitrogen doping exhibited higher photocatalytic activities in the decomposition of organic pollutant under visible-light irradiation than Bi(3)NbO(7) nanoparticles. Furthermore, an enhanced photocatalytic performance was also observed for Ag/N-Bi(3)NbO(7) architectures, which can be attributed to the synergetic effects between noble metal and semiconductor component.