Reduction of hexavalent chromium and degradation of tetracycline using a novel indium-doped Mn2O3 nanorod photocatalyst

A self-cleaning photocatalytic membrane loaded with Bi2O2CO3/In(OH)3 S-scheme heterojunction composites for removing tetracycline from aqueous solutions

Bi2O2CO3/In(OH)3 (BON) photocatalysts were synthesized by a one-pot method and loaded onto polyvinylidene fluoride (PVDF) membranes to obtain a Bi2O2CO3/In(OH)3/PVDF (BON-M) catalytic membrane system. The catalytic membranes demonstrated complete degradation of tetracycline within 40 min under visible light. They demonstrated robust photocatalytic activity across a broad pH range (5-11) and in the presence of coexisting ions. The membranes demonstrated excellent self-cleaning performance. Following exposure to light, the irreversible contamination decreased from 27.1% to 4.7% and the membrane's permeability was almost completely restored. Moreover, the charge transfer mechanism at the S-scheme heterojunction interface of BON was demonstrated by Density functional theory and in-situ X-ray Photoelectron Spectroscopy characterisation, and the active sites involved in tetracycline's degradation were identified. Meanwhile, the mechanism of the "anemone effect" of BON-M was demonstrated in conjunction with Electron paramagnetic resonance, and the intrinsic Some factors enhancing the membranes' photocatalytic activity are specified.

Optimization of cerium-based metal-organic framework synthesis for maximal sonophotocatalytic tetracycline degradation

Wastewater treatment is inevitably required to alleviate the pollution of water resources by various contaminants such as antibiotics. MOFs are novel materials with photocatalytic activities. In this study, sonophotocatalytic degradation of tetracycline (TC) by the Cerium-based MOF (Ce-MOF) is optimized by modification of its synthesis route. Ce-MOF synthesis by room temperature (RT), hydrothermal (HT), and sonochemical synthesis (SC) are studied. TC degradation experiments revealed the superiority of SC synthesis. The interplay of main synthesis parameters, namely, initial ligand concentration, ultrasound (US) power and time on sonophotocatalytic activity of Ce-MOF, were investigated by response surface methodology model (RSM) utilizing the central composite experimental design (CCD). The optimum SC synthesis conditions are an initial ligand concentration of 8.4 mmol/L, a sonication power of 50 amplitude, and a US time of 60 min. The optimally synthesized Ce-MOF was characterized by infrared spectroscopy, FTIR, XRD, FE-SEM, TEM, zeta potential analysis, diffuse reflectance spectroscopy, particle size analysis, Mott-Schottky analysis, photocurrent analysis, electrochemical impedance spectra, and photoluminescence spectroscopy. The findings indicate that the removal efficiency of TC can reach up to 81.75% within 120 min in an aqueous solution containing an initial TC concentration of 120 ppm and 1 g/L Ce-MOF at pH of 7. Mineralization efficiency of the process is 71% according to COD measurements. The Ce-MOF catalyst retained its chemical stability and remained active upon TC degradation which makes it a promising candidate for wastewater treatment.

Construction of SU-102 for adsorption and photocatalytic synergistic removal of tetracycline

Tetracycline (TC) is a significant group of broad-spectrum antibiotics that are frequently employed in medical health and animal husbandry. However, the problem of TC residues has been increasing globally with the large-scale production and widespread use, posing a serious threat to the human health and ecological environment. In this paper, a green plant-based MOF SU-102 was prepared, and the adsorption characteristics of SU-102 on TC were investigated. SU-102 was columnar crystal with considerable specific surface area and pore structure, and it could adsorb TC quickly and effectively. And compared to SU-102-a, the adsorption rate of TC by SU-102-b has increased by nearly four times. The adsorption reaction was a spontaneous, entropy-gaining, heat-absorbing process. The adsorption mechanisms between SU-102 and TC were π-π interaction and hydrogen bonding. In addition, SU-102 also had considerable photocatalytic properties, and its application in adsorbent desorption treatment effectively solved the problem of secondary pollution.

Enhanced tetracycline degradation with TiO2/natural pyrite S-scheme photocatalyst

In this study, TiO2 nanoparticles were employed as a photocatalyst for the degradation of tetracycline (TC) under visible light irradiation. The TiO2 nanoparticles were decorated on natural pyrite (TiO2/NP) and characterized using XRD, FTIR, and SEM-EDX methods. This study evaluated the impacts of various operational parameters such as pH, catalyst dosage, initial TC concentration, and light intensity on TC removal. The findings revealed that under optimal conditions (pH 7, catalyst: 2 g/L, TC: 30 mg/L, and light intensity: 60 mW/cm2), 100% of TC and 84% of TOC were removed within 180 min. The kinetics of TC elimination followed a first-order model. The dominant oxidation species involved in the photocatalytic elimination of TC was found to be ·OH radicals in the TiO2/NP system. The reuse experiments showed the high capability of the catalyst after four consecutive cycles. This study confirmed that the TiO2/NP system has high performance in photocatalytic TC removal under optimized experimental conditions.

CS/CoFe2O4 nanocomposite as a high-effective and steady chainmail catalyst for tetracycline degradation with peroxymonosulfate activation: performance and mechanism

Tetracycline becomes a crucial measure for managing and treating communicable diseases in both human and animal sectors due to its beneficial antibacterial properties and cost-effectiveness. However, it is important not to trivialize the associated concerns of environmental contamination following the antibiotic's application. In this study, cobalt ferrate (CoFe2O4) nanoparticles were loaded into chitosan (CS), which can avoid the agglomeration problem caused by high surface energy and thus improve the catalytic performance of cobalt ferrate. And it can avoid the problem of secondary contamination caused by the massive leaching of metal ions. The resulting product was used as a catalyst to activate peroxymonosulfate (PMS) for the degradation of tetracycline (TC). To determine the potential effects on TC degradation, various factors such as PMS dosing, catalyst dosing, TC concentration, initial solution pH, temperature, and inorganic anions (Cl-, H2PO4- and HCO3-) were investigated. The CS/CoFe2O4/PMS system exhibited superior performance compared to the CoFe2O4-catalyzed PMS system alone, achieving a 92.75% TC removal within 120 min. The catalyst displayed high stability during the recycling process, with the efficiency observed after five uses remaining at a stable 73.1%, and only minor leaching of dissolved metal ions from the catalyst. This confirms the high stability of the catalyst. The activation mechanism study showed that there are free radical and non-free radical pathways in the reaction system to degrade TC together, and SO4•- and 1O2 are the primary reactive oxygen radicals involved in the reaction, allowing for effective treatment of contaminated water by TC.

Constructing a novel type-Ⅱ ZnO/BiOCOOH heterojunction microspheres for the degradation of tetracycline and bacterial inactivation

A novel ZnO/BiOCOOH microsphere photocatalyst with a type-Ⅱ mechanism was developed for the first time. This strategy was accomplished by immobilizing ZnO onto 3D BiOCOOH microspheres via a single-step hydrothermal synthesis method. The ability to degrade tetracycline (TC) in water under visible light and inactivate bacteria of as-catalyst were analyzed. Among the prepared samples, the ZnO/BiOCOOH composite, with a mass ratio of 40%(Zn/Bi), exhibited the highest photocatalytic activity, which was able to degrade 98.22% of TC in just 90 min and completely eradicated Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in 48 h, and had potential application in solving water resource environmental pollution. The photoelectric characteristics of the photocatalysts were examined by means of electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectroscopy. The findings indicated that the superior photocatalytic performance could be credited to the dissociation of electrons (e-) and holes (h+) in heterojunction composites. Finally, electron paramagnetic resonance (EPR) and capture experiments were conducted to confirm the photocatalytic mechanism of the type-Ⅱ heterojunction. This work provides a new Bi-base photocatalyst for aqueous environmental control.

Tetracycline hydrochloride degradation by activation of peroxymonosulfate with lanthanum copper Ruddlesden-Popper perovskite oxide: Performance and mechanism

ABO₃-type perovskite oxides have been regarded as a kind of potential catalyst for peroxymonosulfate (PMS) activation. But some limitations such as specific pH conditions and coexisting ion interference restrict its practical application. Herein, a lanthanum copper Ruddlesden-Popper perovskite oxide (La₂CuO₄) was successfully synthesized through the sol-gel process and applied in the activation of PMS. And for the first time the La₂CuO₄/PMS system was used for tetracycline hydrochloride (TC-HCl) degradation. Results showed that La₂CuO₄ was a potential PMS activation catalyst in the removal of antibiotics. At optimized condition (0.2 g/L catalysts, 1 mM PMS, pH₀ 6.9), 96.05% of TC-HCl was removed in 30 min. In experiments of debugging control conditions, over a wide pH range of 3-11, more than 90% of TC-HCl can be removed. In the natural water treatment process, TC-HCl removal rates of about 84.2% and 70.3% were obtained in tap water and River water, respectively. According to the reusability and stability tests and the results of FTIR and XPS analysis, La₂CuO₄ had high structural and chemical stability. Electron paramagnetic resonance (EPR) suggested that the active species including ·OH, SO₄^-· and ¹O₂ were detected in degradation reaction. Finally, reasonable reaction mechanisms and possible degradation pathways of TC-HCl were proposed. These results indicate that La₂CuO₄ can act as a potential catalyst for PMS activation to degrade TC-HCl in water.

Visible-light-induced photocatalytic response of easily recoverable Mn2O3/SiO2 monolith in centimeter-scale towards degradation of ofloxacin: Performance evaluation and product analysis

Monolithic-photocatalysts being easily recoverable are a suitable alternative to powdered materials for pollutant treatment. This study was conducted to prepare Mn₂O₃/SiO₂ monoliths by wet-impregnating Mn(NO₃)₂^․4H₂O in SiO₂ monoliths. The crystallinity of oxide was affirmed via XRD analyses, whereas EDS and elemental-mapping, and XPS studies revealed the constituent elements and their oxidation states. FESEM images confirmed porous morphology, while BET-analysis confirmed its mesoporous nature (∼8.44 nm) and enormous surface area (∼241 m²/g). The DRS and PL studies disclosed that Mn₂O₃/SiO₂ monoliths consisted of narrow band-gap of ∼2.14 eV and had suitable electron/hole separation. The photocatalytic effectiveness of the monolith had been checked by degrading model dye methylene blue (MB) and antibiotic ofloxacin (OF). The influence of various reaction parameters for degradation, i.e., monolith dose, solution-pH, illumination-area, scavengers, etc., was noted. At optimal reaction conditions, outstanding competence was achieved for MB (95.23%; 0.0225 min^-1) and decent results were obtained for OF-degradation (73.2%; 0.0096 min^-1). The recyclable nature of the catalyst (∼12.7%-reduction in effectiveness after 10 successive cycles) was vindicated by several characterization studies after reusability. The O₂^•-radicals participated majorly in the degradation reaction. The reaction intermediates plus products, generated after the degradation of had been identified via LC/MS study. The mineralization extent of the OF and MB was also gauged through TOC analyses. The photocatalytic treatment of raw textile wastewater manifested ∼57.8% COD and 53% TOC-removal. This study emphasizes the competence of Mn₂O₃/SiO₂ monoliths for the photocatalytic abatement of refractory organic contaminants.

Photocatalytic Reduction of Hexavalent Chromium Using Cu3.21Bi4.79S9/g-C3N4 Nanocomposite

The photocatalytic reduction of hexavalent chromium, Cr(VI), to the trivalent species, Cr(III), has continued to inspire the synthesis of novel photocatalysts that are capable of achieving the task of converting Cr(VI) to the less toxic and more useful species. In this study, a novel functionalized graphitic carbon nitride (Cu3.21Bi4.79S9/gC3N4) was synthesized and characterized by using X-ray diffraction (XRD), thermogravimetry analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and scanning electron microscope (SEM). The composite was used for the photocatalytic reduction of hexavalent chromium, Cr(VI), under visible light irradiation. A 92.77% efficiency of the reduction was achieved at pH 2, using about 10 mg of the photocatalyst and 10 mg/L of the Cr(VI) solution. A pseudo-first-order kinetic study indicated 0.0076 min−1, 0.0286 min−1, and 0.0393 min−1 rate constants for the nanoparticles, pristine gC3N4, and the nanocomposite, respectively. This indicated an enhancement in the rate of reduction by the functionalized gC3N4 by 1.37- and 5.17-fold compared to the pristine gC3N4 and Cu3.21Bi4.79S9, respectively. A study of how the presence of other contaminants including dye (bisphenol A) and heavy-metal ions (Ag(I) and Pb(II)) in the system affects the photocatalytic process showed a reduction in the rate from 0.0393 min−1 to 0.0019 min−1 and 0.0039 min−1, respectively. Finally, the radical scavenging experiments showed that the main active species for the photocatalytic reduction of Cr(VI) are electrons (e−), hydroxyl radicals (·OH−), and superoxide (·O2−). This study shows the potential of functionalized gC3N4 as sustainable materials in the removal of hexavalent Cr from an aqueous solution.

New insights into the efficient charge transfer by construction of adjustable dominant facet of BiOI/CdS heterojunction for antibiotics degradation and chromium Cr(VI) reduction under visible-light irradiation

The narrow light-response range and high electron/hole recombination rate greatly restrict the widespread use of photocatalytic technology. The integration of exposing dominant facet of semiconductor and Z-scheme heterostructures designing is expected to break those barriers. Herein，In this work, hydrothermal and ultrasonic stirring methods were used to selectively exposed the (001) and (110) facet of BiOI to construct the BiOI/CdS heterostructures. The obtained BiOI(001)/CdS material shown the maximum degradation for tetracycline-based antibiotics (Oxytetracycline, Tetracycline and Doxycycline), and excellent reduction of hexavalent chromium. Combining the electron spin resonance and scavenger experiments, the superior photocatalytic capacity was attributed to the generation of superoxide and hydroxyl radicals. DFT calculation results shown BiOI(001)/CdS performed high binding energy and adsorption energy for hexavalent chromium, and the different work function between BiOI(001) and CdS confirmed the building of internal electric field, thereby increased the charge separation. Finally, the Gaussian 09 and HPLC-MS program investigated the attack sites of free radicals and degradation pathways in the degradation of antibiotics. This study not only provides a potential photocatalyst, also gives an in-depth understanding of the photocatalytic properties of heterojunctions constructed by different exposed crystal facets.

Rapid degradation of Congo red wastewater by Rhodopseudomonas palustris intimately coupled carbon nanotube - Silver modified titanium dioxide photocatalytic composite with sodium alginate

With a large number of Congo red used in textiles, Congo red wastewater was not easily degraded, resulting in environmental and health-related problems. In order to improve the degradation efficiency of Congo red wastewater, A novel intimately coupled photocatalysis and biodegradation (ICPB) system was prepared by coupling Rhodopseudomonas palustris (R. Palustris), carbon nanotube - silver modified titanium dioxide photocatalytic composite (CNT-Ag -TiO₂, CAT) and sodium alginate (SA) (R. palustris/CAT@SA). Compared with immobilized CAT and R. palustris, the R. palustris/CAT@SA improved the degradation and removal rates of Congo red by 14.3% and 42.1%, and the COD removal rates by 76% and 44.6%, respectively. The mechanism of the degradation of Congo red by the new ICPB was that the Congo red on the surface of the support was degraded into long-chain alkanes by the superoxide and hydroxyl radicals of CAT product, and then the long-chain alkanes were completely mineralization by R. Palustris, which reduced the accumulation of intermediates in the photocatalysis. Most of the Congo red was adsorbed to the interior of the carrier was degraded into aromatic hydrocarbons by R. Palustris, and then oxidized and degraded by CAT, and a small part of the Congo red would be directly mineralized by R. Palustris. A novel technical solution of R. palustris/CAT@SA provided a potential application to the degradation of dye wastewater.

An outer membrane photosensitized Geobacter sulfurreducens-CdS biohybrid for redox transformation of Cr(VI) and tetracycline

Microbe-photocatalyst biohybrids, integrating the optimal attributes of whole-cell catalysts and nanometer photocatalysts, have emerged as a promising strategy for environment-associated applications. However, few such biohybrids have been tested for complex pollution systems. Herein, we constructed an outer membrane photosensitized Geobacter sulfurreducens (G. sulfurreducens)-CdS biohybrid, which enabled to generate stronger photocurrent in response to irradiation and meanwhile achieved an significant promotion for the redox transformation of Cr(VI) and tetracycline compared with that of bare G. sulfurreducens or CdS counterparts. Further analysis revealed that the outer membrane played a significant role in photoelectron transfer. Differential pulse voltammetry (DPV) tests demonstrated that CdS enhanced the catalytic activity of C-type cytochromes on the outer membrane under irradiation, resulting in the increase of electron-hole pairs separation efficiency. The possible degradation pathway of tetracycline was proposed based on determined intermediates, whose toxicities were well evaluated. Importantly, the toxicity of the final detected intermediates was apparently decreased. Overall, this work aims to explore the working mechanisms of the novel G. sulfurreducens-CdS biohybrid system and opens up a new avenue to purifying combined wastewater by microbe-photocatalyst biohybrids.

One-step fabrication of dual functional Tb3+ coordinated polymeric micro/nano-structures for Cr(VI) adsorption and detection

Hexavalent chromium Cr(VI) has been considered as one of the most hazardous heavy metals because of its strong and persistent toxicity to the ecosystem and human beings. Herein, we have synthesized a double hydrophilic block co-polyarylene ether nitriles (abbreviated as dhPEN) bearing aromatic backbone as well as pendent carboxyl and sulfonate groups. Afterward, the synthesized dhPEN has been co-assembled with the lanthanide Tb³⁺ via a one-step solvent exchange protocol, leading to generation of Tb³⁺ coordinated dhPEN (Tb-dhPEN) micro/nano-structures that exhibit good adsorption capacity and detection sensitivity towards Cr(VI). More specifically, the direct self-assembly of dhPEN and Tb³⁺ in mixed H₂O/DMF solvents resulted to Tb-dhPEN microparticles with lamellar structures, which exhibited a high Cr(VI) adsorption capacity approaching to 402 mg/g. The detailed characterization confirm that Cr(VI) is adsorbed and partially reduced to Cr(III) by the Tb-dhPEN microparticles via chemical interaction. Furthermore, the self-assembly of dhPEN with Tb³⁺ in the H₂O/DMF mixed solvents containing NaOH contributed to the generation of spherical nanoparticles showing green emission at 545 nm, which can be selectively quenched by the Cr(VI), leading to the specific detection of trace concentration of Cr(VI) down to 0.12 nM as well as reliable determination of Cr(VI) presented in real environmental samples.

New insights into FeS/persulfate system for tetracycline elimination: Iron valence, homogeneous-heterogeneous reactions and degradation pathways

In this study, complete tetracycline (TTC) and above 50% of total organic carbon (TOC) were removed by FeS/PS after 30 min under optimized conditions. Although free radicals and high-valent iron ions were identified to generate in the process, the apparent similarity between intermediate products of FeS/PS, Fe/PS, and UV/PS systems demonstrated that the degradation of TTC was due to sulfate radicals (SO₄^⋅-) and hydroxyl radicals (⋅OH). Based on the reaction between free radicals and organic matter, we speculated that TTC in the FeS/PS system was decomposed and mineralized by dehydration, dehydrogenation, hydroxyl addition, demethylation, substitution, E-transfer, and ring-opening. Furthermore, a new understanding of FeS-mediated PS activation based on stoichiometry and kinetic analysis showed that there were both homogeneous and heterogeneous reactions that occurred in the entire progress. However, due to the effect of pH on the dissolution of iron ions, the homogeneous reaction became the principal process with iron ions concentration exceeding 1.35 mg/L. This work provides a theoretical basis for the study of the degradation of TTC-containing wastewater by the iron-based advanced oxidation process.

Dual-functional Z-scheme CdSe/Se/BiOBr photocatalyst: Generation of hydrogen peroxide and efficient degradation of ciprofloxacin

The major challenges of clean energy and environmental pollution have resulted in the development of photocatalysis technologies for energy conversion and the degradation of refractory pollutants. Herein, a novel CdSe/Se/BiOBr hydrangea-like photocatalyst was used to produce hydrogen peroxide (H₂O₂) and degrade ciprofloxacin (CIP). The Z-scheme heterojunction structure of the photocatalyst and the doping of selenium (Se) led to the efficient separation of electron-hole pairs and charge transfer. The optimized sample of 2 wt% CdSe/Se/BiOBr produced 142.15 mg·L^-1 rate of H₂O₂, which was much higher than that produced by pure BiOBr (89.4 mg·L^-1) or CdSe/Se (10.9 mg·L^-1). Additionally, almost 100 % of CIP was degraded within 30 min, with a first order rate constant of nearly 5.35 times that of pure BiOBr and 81.44 times that of pure CdSe/Se. The excellent removal efficiency of CIP from natural water matrices confirmed that the composites are promising for the removal of contaminants from natural waterways. Based on trapping experiments, electron spin resonance spectra (ESR) spectroscopy, and density functional theory (DFT) calculations, the photocatalytic mechanisms of H₂O₂ and CIP degradation by the Z-scheme CdSe/Se/BiOBr composites were proposed. Overall, the dual-functional CdSe/Se/BiOBr composite could potentially be applied for photocatalytic production of H₂O₂ and treatment of organic pollutants in water.

Generation of singlet oxygen over CeO2/K, Na-codoped g-C3N4 for tetracycline hydrochloride degradation in a wide pH range

Singlet oxygen (1O2) were widely studied for catalytic oxidation and photo dynamic therapy (PDT) and so on due to its unique properties, such as its long lifetime, wide pH tolerance,...

The mineralization ability of a chloride-resistant γ-Cu2(OH)3Cl Fenton catalyst: effects of the cation type, salt concentration and organic pollutants

A chloride-resistant heterogeneous Fenton catalyst γ-Cu2(OH)3Cl is used to mineralize aromatic organics (phenol, bisphenol A, salicylic acid and aniline) in saline solutions with different salts (MgCl2, CaCl2, NaCl and KCl) and concentrations.

Polydopamine-Bi2WO6-Decorated Gauzes as Dual-Functional Membranes for Solar Steam Generation and Photocatalytic Degradation Applications

The dual-functional Bi2WO6/polydopamine (PDA)-modified gauze membrane has been developed for applications in photocatalytic degradation and solar steam generation. Two types of membrane were prepared by changing the growth sequence of Bi2WO6 nanomaterials and PDA on gauze substrates. The spatial distribution of Bi2WO6 and polydopamine has a great influence on light absorption, photocatalytic degradation, and solar steam generation performances. Bi2WO6 photocatalysts can absorb short-wavelength light for the photocatalytic decoloration of organic dyes. The photothermal polydopamine can convert light into heat for water evaporation. Besides, the gauze substrate provides water transport channels to facilitate water evaporation. The morphology, surface chemistry, and optical properties of Bi2WO6-PDA modified gauzes were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance spectra. The photothermal properties, wetting properties, and solar steam generation rates of the composite films were also studied. Degradation of 96% of indigo carmine was achieved after being irradiated for 120 min in the presence of G/PDA/BWNP. The water evaporation rates of the G/BWP/PDA sample under the irradiation of an Xe lamp (light intensity = 1000 W/m2) reached 1.94 kg·m-2·h-1.

Photocatalytic degradation of tetracycline by metal-organic frameworks modified with Bi2WO6 nanosheet under direct sunlight

Porous metal-organic frameworks (MOFs) with visible-light response have attracted much attention in the field of environmental purification and solar energy conversion. In this study, MIL-100(Fe) was modified with Bi₂WO₆ nanosheets by a facile hydrothermal method to fabricate a photocatalyst with direct Z-scheme heterojunction. When treating the tetracycline (TC) solution under natural sunlight, 12 wt%MIL-100(Fe)/Bi₂WO₆ obtained the highest apparent rate constant of (6.59 ± 0.52)✕10^-3 L mg^-1 min^-1, which was 16.1 and 3.9 times than that of pristine MIL-100(Fe) and Bi₂WO₆, respectively. In addition to explore the feasibility of sunlight-activated MIL-100(Fe)/Bi₂WO₆ to remove TC under various conditions, the degradation intermediates and their possible transformation pathway were provided with the aid of three-dimensional excitation-emission matrix spectra and liquid chromatography-mass spectrometry system. The results of Escherichia coli culture demonstrated that the biotoxicity variation of TC solution would first increase and then decrease with the photodegradation time. Ultimately, based on the results of bandgap calculation, radicals trapping and charge flow tracking experiments, the direct Z-scheme heterojunction between MIL-100(Fe) and Bi₂WO₆ nanosheets was confirmed and the photocatalytic mechanism for TC degradation was rationally proposed. This work enriched MOFs-based heterojunction photocatalysts and provided a promising method to eliminate hazardous TC from aqueous solution.

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.

Insights into the novel application of Fe-MOFs in ultrasound-assisted heterogeneous Fenton system: Efficiency, kinetics and mechanism

In this work, as a new strategy, ultrasound/H₂O₂/MOF system was firstly applied by environmental-benign Fe-MOFs (MIL-53, MIL-88B and MIL-101) for tetracycline hydrochloride removal. The syntheticFe-MOFs were characterized by XRD, FTIR, SEM, XPS, N₂ sorption-desorption isotherms and CO-FTIR. MIL-88B demonstrated the best catalytic performance because of its highest amount of Lewis acid sites. Influencing factors, contrast experiment, and corresponding dynamics were carried out to obtain the best experimental conditions and reaction system. Under optimal conditions ([Tetracyclinehydrochloride] = 10 mg/L, [MIL-88B] = 0.3 g/L, [H₂O₂] = 44 mM, [ultrasound power] = 60 W, and pH = 5.0), the-first-order kinetic rate constant k was calculated to be 0.226 min^-1, higher than the simple combination of the ultrasound system (0.004) and MIL-88B/H₂O₂ system (0.163), indicating the importance of synergistic effect between ultrasound and Fenton reaction. EPR test and quenching experiment proved that ·OH is mainly responsible for tetracycline hydrochloride removal. The major reaction path is the adsorption and decomposition of H₂O₂ by coordinative unsaturated iron sites on Fe-MOF, but it is not the only path. The direct decomposition of H₂O₂ and the cavitation effect caused by ultrasound also contribute to the generation of OH.