Resource utilization of medical waste incineration fly ash to activate peroxydisulfate for tetracycline degradation: Synergy between adsorption and PDS activation.

Medical waste incineration fly ash (MWI FA) is classified as a hazardous solid waste. Therefore, the development of recycling technologies to convert MWI FA into useful products is necessary and challenging. In this study, we developed a sustainable approach for preparing a catalyst through the pyrolysis of water-washed MWI FA (WW FA-x, where x corresponds to the pyrolysis temperature). Subsequently, it was applied as a potent peroxydisulfate (PDS) activator to remove tetracycline (TC) from water. The results showed that the WW FA-800 exhibited remarkable adsorption performance as well as highly efficient catalytic activation of PDS, with a 115 mg/g maximum TC adsorption capacity and 93.5% (reaction kinetic rate = 315 µmol/g/h) TC removal within 60 min. A synergistic effect was achieved by adsorption and PDS activation. TC degradation was primarily driven by non-radical (1O2 and electron transfer) processes. WW FA-800 possesses multiple active sites, including defects, π-π*, O-CO groups, Fe0, and Cu(I). Three possible pathways for TC decomposition have been proposed, with the majority of intermediates exhibiting less toxicity than TC. Furthermore, the WW FA/PDS system exhibited an excellent anti-interference ability, and universality in the degradation of various organic contaminants. Notably, energy consumption was minimal, approximately 2.80 kWh/(g·TC), and the leachability of heavy metals in the WW FA-800 was within acceptable limits. This study provides a MWI FA recycling route for the development of highly active catalysts.

Low-coordinated Mn-N2 sites in graphene oxide induce peroxydisulfate activation for tetracycline degradation: Process optimization and theoretical calculation.

Atom-dispersed low-coordinated transition metal-Nx catalysts exhibit excellent efficiency in activating peroxydisulfate (PDS) for environmental remediation. However, their catalytic performance is limited due to metal-N coordination number and single-atom loading amount. In this study, low-coordinated nitrogen-doped graphene oxide (GO) confined single-atom Mn catalyst (Mn-SA/NGO) was synthesized by molten salt-assisted pyrolysis and coupled to PDS for degradation of tetracycline (TC) in water. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and X-ray absorption fine structure spectroscopy (XAFS) analysis showed the successful doping of single-atom Mn (weight percentage 1.6%) onto GO and the formation of low-coordinated Mn-N2 sites. The optimized parameters obtained by Box-Behnken Design achieved 100% TC removal in both prediction and experimental results. The Mn-SA/NGO + PDS system had strong anti-interference ability for TC removal in the presence of anions. Besides, Mn-SA/NGO possessed good reusability and stability. O2•-, •OH, and 1O2 were the main active species for TC degradation, and the TC mineralization reached 85.1%. Density functional theory (DFT) calculations confirmed that the introduction of single atoms Mn could effectively enhance adsorption and activation of PDS. The findings provide a reference for the synthesis of high-performance single-atom catalysts for effective removal of antibiotics.

Sulfur vacancy-enhanced In2S3-x hollow microtubes for photocatalytic Cr (VI) and tetracycline removal.

Morphological regulation and defect engineering are efficient methods for photocatalytic technology by improving photon absorption and electron dissociation. Herein, In2S3-x hollow microtubes with S-vacancies (MIS) were fabricated via a simple solvothermal reaction using In-based metal-organic frameworks (In-MOFs) as a precursor. Experimental results demonstrate that the hollow structure and optimal S-vacancies can jointly accelerate the photocatalytic reaction, attributed to a larger specific surface area, more active sites, and faster electron transfer efficiency. The champion MIS(2) displayed significantly better photocatalytic activity for Cr(VI) reduction and tetracycline (TC) degradation. The Cr(VI) reduction rate by MIS(2) is 3.67 and 2.82 times higher than those of optimal In2S3 template-free (HIS(2)) and MIS(1) with poor S-vacancies, respectively. The removal efficiency of TC by MIS(2) is 1.37 and 1.15 times higher than those of HIS(2) and MIS(1). Further integration of MIS(2) with aerogel simplifies the recovery process significantly.

Architecture engineering of Fe/Fe2O3@MoS2 enables highly efficient tetracycline remediation via peroxymonosulfate activation: Critical roles of adsorption capacity and redox cycle regulation.

Design and synthesis of high-efficiency multicomponent nanostructure for activating peroxymonosulfate (PMS) to destruct emerging antibiotics remains a daunting challenge. We report herein the simplest one-step hydrothermal construction of hierarchical Fe/Fe2O3@MoS2 architecture composed of MoS2 nanosheets integrated commercial Fe2O3 nanoparticles. The fabricated Fe/Fe2O3@MoS2 architecture can be utilized as an efficient PMS activator to destruct tetracycline hydrochloride (TCH) with a removal efficiency of 90.3 % within 40 min, outperforming Fe2O3 nanoparticles, MoS2 nanosheets analogues and many MoS2-based materials. The Fe/Fe2O3@MoS2/PMS works well under various reaction conditions, and SO4•- and 1O2 are identified as major reactive oxygen species. Thirteen intermediates towards TCH destruction are detected via four pathways, and their acute/chronic toxicity and phytotoxicity are assessed. The origins of Fe/Fe2O3@MoS2/PMS system for efficient degrading TCH are ascribed to the synergy catalysis between Fe2O3 and MoS2, which originate from: (a) the exposed Mo4+ sites on catalyst surface facilitating high-speed electron transfer from MoS2 to Fe3+ and accelerating the Fe2+ regeneration; (b) the generated Fe0 serving as an excellent electron donor to jointly promote Fe3+/Fe2+ redox cycle. This study provides a simple way to establish architecture for synergistically promoting PMS-mediated degradation.

Activation of peroxymonosulfate by novel magnetically recyclable CoFe2O4/MXene quantum dots composites for rapid degradation of tetracycline: Synergistic performance and mechanisms.

Tetracycline (TC), a commonly used antibiotic in wastewater, poses environmental and health risks, thus demanding advanced catalysts for its effective removal. In this work, for the first time, we integrated cobalt ferrite (CoFe2O4) and MXene quantum dots (MQDs) to form magnetic heterojunctions for rapid degradation of TC in the presence of peroxymonosulfate (PMS). Anchoring MQDs on the CoFe2O4 nanoparticles remarkably promoted the overall degradation rate of TC to 98.2% within 20 min via both radical and non-radical pathways. The first-order kinetic constant was 0.170 min-1, 3.5 and 15.5 times higher than that of CoFe2O4 and MQDs alone, respectively. Quenching experiments revealed that the addition of p-benzoquinone (p-BQ) and furfuryl alcohol (FFA) reduced the degradation of TC within 20 min to 56.2% and 28.4%, respectively, indicating that the primary reactive oxygen species for TC degradation in the CoFe2O4/MQDs + PMS system are •O2- and 1O2. CoFe2O4/MQDs also exhibited superparamagnetic property, which enabled their effective recovery by external magnetic field. Their reusability was verified by retaining 81.4% of catalytic efficacy in the consecutive 8th cycle. The CoFe2O4/MQDs + PMS system also exhibited excellent practicability in natural water samples as the degradation rates in both tap water and lake water environments exceeded 90%. Three potential pathways for TC degradation were proposed based on the liquid chromatography-mass spectrometry (LC-MS) characterizations and TC progressively transformed into 13 intermediates. This work may contribute to the ongoing efforts to develop advanced catalysts and strategies for mitigating the environmental impact of antibiotic pollution, offering a pathway toward sustainable and efficient water treatment technologies.

Investigation into the Synergistic Effect of the Zinc Peroxide/Peroxymonosulfate Double-Oxidation System for the Efficient Degradation of Tetracycline.

The increasingly severe antibiotic pollution has become one of the most critical issues. In this study, a zinc peroxide/peroxymonosulfate (ZnO2/PMS) double-oxidation system was developed for tetracycline (TC) degradation. A small amount of ZnO2 (10 mg) and PMS (30 mg) could effectively degrade 82.8% of TC (100 mL, 50 mg/L), and the degradation process could be well described by the pseudo-second-order kinetic model. Meanwhile, the ZnO2/PMS double-oxidation system showed high adaptability in terms of reaction temperature (2-40 °C), initial pH value (4-12), common inorganic anions (Cl-, NO3-, SO42- and HCO3-), natural water source and organic pollutant type. The quenching experiment and electron paramagnetic resonance (EPR) characterization results confirmed that the main reactive oxygen species (ROS) was singlet oxygen (1O2). Moreover, three possible pathways of TC degradation were deduced according to the analyses of intermediates. On the basis of comparative characterization and experiment results, a synergistic activation mechanism was further proposed for the ZnO2/PMS double-oxidation system, accounting for the superior degradation performance. The released OH- and H2O2 from ZnO2 could activate PMS to produce major 1O2 and minor superoxide radicals (•O2-), respectively.

Nb, Se-codoped ZnIn2S4/NbSe2composites with enhanced catalytic activity and photodegradation performance towards tetracycline.

Low quantum efficiency and serious photogenerated carrier recombination have been urgent bottleneck problems for photocatalytic materials. Herein, we prepared Nb, Se-codoped ZnIn2S4/NbSe2composites through a facile solvothermal method. The synergetic effect of codoping and cocatalyst was investigated on the photodegradation performance towards tetracycline under visible-light irradiation. By adjusting the final composition, the comprehensive characterization revealed that the optimum degradation efficiency of NS/ZIS-1.6 catalyst arrived at 75% in 70 min, which was 5.8 times higher than that of pure ZnIn2S4. Deep analysis indicated that the enhanced photocatalytic performance could be attributed to higher light absorption, more efficient electron/hole separation, faster charge transport, and lower carrier recombination. This work may offer novel viewpoint for design of high-performance catalysts towards the visible-light-driven photodegradation system.

Optimization of Electron Transport Pathway: A Novel Strategy to Solve the Photocorrosion of Ag-Based Photocatalysts.

Although Ag-containing photocatalysts exhibit excellent photocatalytic ability, they present great challenges owing to their photocorrosion and ease of reduction. Herein, an electron acceptor platform of Ag2O/La(OH)3/polyacrylonitrile (PAN) fiber was constructed using a heterojunction strategy and electrospinning technology to develop a novel photocatalytic membrane with a redesigned electron transport pathway. Computational and experimental results demonstrate that the optimized electron transport pathway included intercrystal electron transfer induced by the La-O bond between Ag2O and La(OH)3 as well as electron transfer between the catalyst crystal and electrophilic PAN membrane interface. In addition, the photocatalytic performance of the Ag2O/La(OH)3 membrane for tetracycline (TC) removal was still above 97% after five photocatalytic reaction cycles. Furthermore, the carrier life was greatly extended. Mechanistic study revealed that photogenerated holes on the Ag2O/La(OH)3 membrane were the main reactive species in TC degradation. Overall, this study proposes a novel electron transport pathway strategy that effectively solves the problems of photocatalyst photocorrosion and structural instability.

Preparation of copper-based catalysts from electroplating sludge by ultrasound treatment and their antibiotic degradation performance.

The recovery of heavy metals from electroplating sludge is important for alleviating heavy metal pollution and recycling metal resources. However, the selective recovery of metal resources is limited by the complexity of electroplating sludge. Herein, CuFe bimetallic Fenton-like catalysts were successfully prepared from electroplating sludge by a facile room-temperature ultrasonic-assisted co-precipitation method. The prepared CuFe-S mainly consisted of nanorods with diameters of 20-30 nm and lengths of 100-200 nm and a small number of irregular particles. Subsequently, we performed tetracycline (TC) degradation experiments, and the results showed that the product CuFe-S had very good performance over a wide pH range (2-11). At an initial pH = 2, CuFe-S could degrade 91.9% of 50 mg L-1 TC aqueous solution within 30 min, which is better than that of a single metal catalyst. Free radical scavenging experiments and electron paramagnetic resonance (EPR) tests revealed that ·OH was the main active species for the degradation of TC by CuFe-S. In conclusion, a CuFe bimetallic Fenton-like catalyst was developed for the catalytic degradation of antibiotics, which provides a novel technical route for the resource utilization of electroplating sludge and shows an important practical application prospect.

Heterogeneous photo-Fenton catalyst α-Fe2O3@g-C3N4@NH2-MIL-101(Fe) with dual Z-Scheme heterojunction for degradation of tetracycline.

A novel photo-Fenton catalyst α-Fe2O3@g-C3N4@NH2-MIL-101(Fe) (FGN) with dual Z-scheme heterojunction was successfully prepared by hydrothermal method to degrade tetracycline (TC). The preparation conditions were optimized by orthogonal test, and the successful synthesis was confirmed by characterization analyses. The prepared FGN showed better light absorption performance, higher photoelectrons-holes separation efficiency, lower photoelectrons transfer resistance, and higher specific surface area and pore capacity compared with α-Fe2O3@g-C3N4 and α-Fe2O3. The effects of experimental conditions on the catalytic degradation of TC were investigated. The degradation rate of 10 mg/L TC could reach 98.33% within 2 h when the dosage of FGN was 200 mg/L, and the degradation rate could remain 92.27% after 5 times of reuse. Furthermore, the XRD spectra and XPS spectra of FGN before and after reuse were compared to explore the structural stability and catalytic active sites of FGN, respectively. According to the identification of oxidation intermediates, three degradation pathways of TC were proposed. Through H2O2 consumption experiment, radical-scavenging experiments, EPR results, the mechanism of the dual Z-scheme heterojunction was proved. The improved performance of FGN was attributed to the dual Z-Scheme heterojunction effectively promoting the separation of photogenerated electrons from the holes and accelerating the electrons transfer, and the increase of the specific surface area.

Efficient Photocatalytic Degradation of Tetracycline on the MnFe2O4/BGA Composite under Visible Light.

In this work, the MnFe2O4/BGA (boron-doped graphene aerogel) composite prepared via the solvothermal method is applied as a photocatalyst to the degradation of tetracycline in the presence of peroxymonosulfate. The composite's phase composition, morphology, valence state of elements, defect and pore structure were analyzed by XRD, SEM/TEM, XPS, Raman scattering and N2 adsorption-desorption isotherms, respectively. Under the radiation of visible light, the experimental parameters, including the ratio of BGA to MnFe2O4, the dosages of MnFe2O4/BGA and PMS, and the initial pH and tetracycline concentration were optimized in line with the degradation of tetracycline. Under the optimized conditions, the degradation rate of tetracycline reached 92.15% within 60 min, whereas the degradation rate constant on MnFe2O4/BGA remained 4.1 × 10-2 min-1, which was 1.93 and 1.56 times of those on BGA and MnFe2O4, respectively. The largely enhanced photocatalytic activity of the MnFe2O4/BGA composite over MnFe2O4 and BGA could be ascribed to the formation of type I heterojunction on the interfaces of BGA and MnFe2O4, which leads to the efficient transfer and separation of photogenerated charge carriers. Transient photocurrent response and electrochemical impedance spectroscopy tests offered solid support to this assumption. In line with the active species trapping experiments, SO4•- and O2•- radicals are confirmed to play crucial roles in the rapid and efficient degradation of tetracycline, and accordingly, a photodegradation mechanism for the degradation of tetracycline on MnFe2O4/BGA is proposed.

Highly Water-Stable Zinc Based Metal-Organic Framework: Antibacterial, Photocatalytic Degradation and Photoelectric Responses.

A reported water-stable Zn-MOF ([Zn(L)2(bpa)(H2O)2]·2H2O, H2L = 5-(2-cyanophenoxy) isophthalic acid has been prepared via a low-cost, general and efficient hydrothermal method. It is worth noting the structural features of Zn-MOF which exhibit the unsaturated metal site and the main non-covalent interactions including O⋯H, N⋯H and π-π stacking interactions, which lead to strong antibacterial and good tetracycline degradation ability. The average diameter of the Zn-MOF inhibition zone against Escherichia coli and Staphylococcus aureus was 12.22 mm and 10.10 mm, respectively. Further, the water-stable Zn-MOF can be employed as the effective photocatalyst for the photodegradation of tetracycline, achieving results of 67% within 50 min, and it has good cyclic stability. In addition, the photodegradation mechanism was studied using UV-vis diffuse reflection spectroscopy (UV-VIS DRS) and valence-band X-ray photoelectron spectroscopy (VB-XPS) combined with the ESR profile of Zn-MOF, which suggest that ·O2- is the main active species responsible for tetracycline photodegradation. Also, the photoelectric measurement results show that Zn-MOF has a good photocurrent generation performance under light. This provides us with a new perspective to investigate Zn-MOF materials as a suitable multifunctional platform for future environmental improvement applications.

Efficient photocatalysis of tetracycline hydrochloride (TC-HCl) from pharmaceutical wastewater using AgCl/ZnO/g-C3N4 composite under visible light: Process and mechanisms.

AgCl/ZnO/g-C3N4, a visible light activated ternary composite catalyst, was prepared by combining calcination, hydrothermal reaction and in-situ deposition processes to treat/photocatalyse tetracycline hydrochloride (TC-HCl) from pharmaceutical wastewater under visible light. The morphological, structural, electrical, and optical features of the novel photocatalyst were characterized using scanning electron microscopy (SEM), UV-visible light absorption spectrum (UV-Vis DRS), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and transient photocurrent techniques. All analyses confirmed that the formation of heterojunctions between AgCl/ZnO and g-C3N4 significantly increase electron-hole transfer and separation compared to pure ZnO and g-C3N4. Thus, AgCl/ZnO/g-C3N4 could exhibit superior photocatalytic activity during TC-HCl assays (over 90% removal) under visible light irradiation. The composite could maintain its photocatalytic stability even after four consecutive reaction cycles. Hydrogen peroxide (H2O2) and superoxide radical (·O2) contributed more than holes (h+) and hydroxyl radicals (·OH) to the degradation process as showed by trapping experiments. Liquid chromatograph-mass spectrometer (LC-MS) was used for the representation of the TC-HCl potential degradation pathway. The applicability and the treatment potential of AgCl/ZnO/g-C3N4 against actual pharmaceutical wastewater showed that the composite can achieve removal efficiencies of 81.7%, 71.4% and 69.0% for TC-HCl, chemical oxygen demand (COD) and total organic carbon (TOC) respectively. AgCl/ZnO/g-C3N4 can be a prospective key photocatalyst in the field of degradation of persistent, hardly-degradable pollutants, from industrial wastewater and not only.

Zeolitic imidazolate framework (ZIF-8)/polyacrylonitrile derived millimeter-sized hierarchical porous carbon beads for peroxymonosulfate catalysis.

Well dispersed nanocatalysts on porous substrate with macroscopic morphology are highly desired for the application of heterogeneous catalysis. Traditional fabrication process suffers from multiple steps for controlling the structure on nanocatalysts and matrix or both. Herein, we report a facile strategy for the synthesis of millimeter-sized hierarchical porous carbon beads (HPCBs) which containing well dispersed hollow-nano carbon boxes for peroxymonosulfate catalysis. Specially, the precursors of HPCBs were prepared by phase inversion method, which involving introduction of zeolitic imidazolate framework (ZIF-8) nanocubes into polyacrylonitrile (PAN) solutions followed by solidification of the mixture. After pyrolysis, nitrogen doped and hierarchical porous HPCBs with diameter of about 1.2 mm were obtained. The merits of our synthesis strategy lie in that synchronizes the hollow microstructure evolution with the shaping of ZIF-8 nanocubes into millimeter scale beads. Attribute to its special structure feature and the appropriate chemical composition, the resultant millimeter-sized HPCBs exhibit enhanced catalytic performance by activation of peroxymonosulfate (PMS) for tetracycline degradation. The degradation efficiency of TC is up to 85.1% within 120 min, which is 18% higher than that of ZIF8-Solid/PAN carbon bead (SPCBs). In addition, the possible decomposition pathways, main reactive oxygen species, and reasonable enhanced mechanism for the HPCBs/PMS system are systematically investigated by quenching experiments, electron paramagnetic resonance (EPR) and liquid chromatography-mass spectrometry (LC-MS). This work addresses the issue of easy aggregation and recycling of carbon materials in industrial productions and extends the prospects of carbon materials in engineering applications.

The integrated production of ultrathing-C3N4and membrane assisted by edible syrup for the sustained photocatalytic treatment of Cr(VI) and tetracycline.

The exfoliation of bulk raw graphitic carbon nitride (g-C3N4) by edible glucose syrup to produce ultrathing-C3N4nanosheets in concentrations of up to 0.2 mg ml-1was achieved. Detailed characterization through TEM, AFM, FT-IR, XRD, Raman and TGA confirmed the formation of ultrathin structure and improved properties. Compared to rawg-C3N4, the prepared thing-C3N4layers exhibited a 18-fold enhancement in Cr(VI) reduction and a 3-fold enhancement in tetracycline hydrochloride degradation, which is ascribed to their larger specific surface area and more exposed active sites. The layeredg-C3N4membrane was constructed via direct vacuum filtration. The layer-stackedg-C3N4nanosheet membrane exhibited an excellent and sustained photocatalytic performance as the prepared thing-C3N4layers could maintain a layered lamella after stacking in filtration process. The recyclable synthesis of ultrathing-C3N4layers and layer-stackedg-C3N4membrane by our method provides a sustainable strategy to pollution treatment by 2D materials.

Tetracycline degradation by dual-frequency ultrasound combined with peroxymonosulfate.

Tetracycline has received a great deal of interest for the harmful effects of substance abuse on ecosystems and humanity. The effects of different processes on the degradation of tetracycline were compared, with dual-frequency ultrasound (DFUS) in combination with peroxymonosulfate (PMS) being the most effective for the tetracycline degradation. Free radical scavenging experiments showed that O2∙-,SO4∙- and •OH were the main reactive radicals in the degradation of tetracycline. According to the major intermediates of tetracycline degradation identified, three possible degradation pathways were proposed, which are of significance for translational studies of tetracycline degradation. Notably, these intermediates were found to be significantly less toxicity. The number of active bubbles in the degradation vessel was calculated using a semi-empirical formula, and a higher value of 1.44 × 108 L-1s-1 of bubbles was obtained when using dual-frequency ultrasound at 20 kHz (210 W/L) and 80 kHz (85.4 W/L). Therefore, compared to 20 kHz, although the yield of strong oxidizing substances from individual active bubbles decreased slightly, a significant increment of the number of active bubbles still resulted in a higher synergistic effect, and the combination of DFUS and PMS should be effective in promoting the generation of reactive free radicals and mass transfer processes within the degradation vessel, which provides a method for efficient removal of tetracycline from wastewater.

Green approach for the fabrication of dual-functional S/N doped graphene tagged ZnO nanograins for in vitro bioimaging and water pollutant remediation.

Dual-functional S/N (sulfur and nitrogen) doped graphene-tagged zinc oxide nanograins were synthesized for bioimaging applications and light-dependent photocatalytic activity. Applying the green synthesis approach, graphene was synthesized from kimchi cabbage through a hydrothermal process followed by tagging it with synthesized zinc oxide nanoparticles (ZnO-NPs). The 2D/0D heterostructure prepared by combining both exhibited exceptional advantages. Comprehensive characterizations such as TEM, SEM, XRD, FTIR, XPS, and UV-Vis spectra have been performed to confirm the structures and explore the properties of the synthesized nanocomposite. The graphene/ZnO-NP composite produced exhibited more intense fluorescence, greater chemical stability and biocompatibility, lower cytotoxicity, and better durability than ZnO NPs conferring them with potential applications in cellular imaging. While tagging the ZnO NPs with carbon derived from a natural source containing hydroxyl, sulfur, and nitrogen-containing functional group, the S/N doped graphene/ZnO heterostructure evidences the high photocatalytic activity under UV and visible irradiation which is 3.2 and 3.8 times higher than the as-prepared ZnO-NPs. It also demonstrated significant antibacterial activity which confers its application in removing pathogenic contaminant bacteria in water bodies. In addition, the composite had better optical properties and biocompatibility, and lower toxicity than ZnO NPs. Our findings indicate that the synthesized nanocomposite will be suitable for various biomedical and pollutant remediation due to its bright light-emitting properties and stable fluorescence.

MXene-supported MIL-88A(Fe) as persulfate activator for removal of tetracycline.

The poor conductivity, poor stability, and agglomeration of iron-based metal organic framework MIL-88A(Fe) limit its application as persulfate (PS) activator in water purification. Herein, MXene-supported MIL-88A(Fe) composites (M88A/MX) were synthesized to enhance its adsorption and catalytic capability for tetracycline (TC) removal. Scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR), and X-ray photoelectron spectroscopy (XPS) were used to characterize prepared materials, confirming the successful attachment of MIL-88A(Fe) to the surface of MXene. M88A/MX-0.2 composites, prepared with 0.2 g MXene addition, exhibit optimal degradation efficiency, reaching 98% under conditions of 0.2 g/L M88A/MX-0.2, 1.0 mM PS, 20 ppm TC, and pH 5. The degradation rate constants of M88A/MX-0.2 were 0.03217 min-1, which was much higher than that of MIL-88A(Fe) (0.00159 min-1) and MXene (0.00626 min-1). The removal effects of reaction parameters, such as dosage of M88A/MX-0.2 and PS; initial solution pH; and the presence of the common co-existing constituents (humic acid and the inorganic anions) were investigated in detail. Additionally, the reuse of M88A/MX-0.2 showed that the composites had good cycling stability by recurrent experiments. The results of electron paramagnetic resonance (EPR) and quenching experiments indicated that ·OH, ·SO4-, and ·O2- were involved in the M88A/MX-0.2/PS system where persulfate oxidation process was activated with prepared M88A/MX-0.2. In addition, the intermediates of photocatalytic degradation were determined by HPLC-MS, and the possible degradation pathways of the target molecules were inferred. This study offered a new avenue for sulfate-based degradation of Fe-based metal organic framework.

A novel BiOBr/rGO photocatalysts for degradation of organic and antibiotic pollutants under visible light irradiation: Tetracycline degradation pathways, kinetics, and mechanism insight.

In this study, the BiOBr/rGO nanocomposite photocatalysts are fabricated by a facile solvothermal method. The BiOBr growth on reduced graphene oxide (rGO) sheet could improve BiOBr's photocatalytic activity by increasing its adsorption ability, surface area, and charge carriers' separation efficiency. The prepared nanocomposites were characterized by XRD, Raman, FESEM, EDS, XPS, and UV-visible DRS. The BiOBr/rGO (BRG) nanocomposites showed improved photocatalytic activity for the photodegradation of Rhodamine B (RhB) dye and Tetracycline (TC) under visible light irradiation. Rhodamine B and tetracycline degradation efficiency were about 96% and 73% within 120 min under visible light irradiation. The PL analysis indicates that BiOBr/rGO nanocomposite exhibited maximum separation efficiency of photoinduced charge carriers. The trapping test confirmed that O2- and h+ are significant active photodegradation species. The GC-MS spectra detected the two plausible transformation routes of tetracycline degradation. The current work presented a low-cost and facile approach for fabricating Bi-based composites.

Boosting tetracycline degradation of BaTiO3-based piezo-catalysts via modulating phase boundary and band structure.

Piezoelectric catalysis, which converts mechanical energy into chemical activity, has important applications in environmental remediation. However, the piezo-catalytic activity of various piezoelectric materials is limited by the weak piezoelectricity as well as the mismatched band-gap, leading to inefficient electron-hole pair generation and difficult carrier migration. Here, a simple strategy combining phase boundary and energy band structure modulation was innovatively proposed to enhance the piezo-catalytic activity of BaTiO3 ferroelectric by Ce ions selecting different doping sites. Thanks to the coexistence of tetragonal (P4mm) and orthorhombic (Amm2) phases effectively flattened the Gibbs free-energy and thus enhanced the piezoelectric activity, as well as suitable energy bandwidth facilitating the carrier migration were realized in the B-sites doped Ba(Ti0.95Ce0.05)O3. The degradation rate constant k of tetracycline (TC) was high to 30.56 × 10-3 min-1, which was 2.03 times higher than that of pure BaTiO3 and superior to most representative lead-free perovskite piezoelectric materials. Theoretical calculations validated that the charge density and high O2 and OH- adsorption energy on the Ba(Ti0.95Ce0.05)O3 surface promoted more efficient •O2- and •OH radicals conversion and bettered response to piezo-catalytic reaction. This work is important to design high-performance piezo-catalysts by synergistic regulation of phase boundary and energy band structure in perovskite materials for long-term antibiotic tetracycline removal.