Catalytic Pathway Research Articles

Engineered nanozymes for speedy colorimetric biosensing and sensitive cascaded-catalytic determining of norfloxacin

Nanozymes based on default engineering have garnered considerable interest for their ability to effectively imitate natural enzyme catalysis settings for detection. With the widespread use of quinolone antibiotics, it is worth noting that the antibiotic drugs represented by norfloxacin (NOR) are concentration-dependent when used. Therefore, residual or dosage differences in the body can lead to some central toxicity hazards, so monitoring and detection are necessary. Herein, we reported Fe3O4@MIL-101@polypyrroles (PPys) nanozymes with default engineering, which possessed a porous core–shell structure with Fe3O4 as the core and MIL-101 and PPys as the shells in sequence. X-Ray photoelectron spectroscopy (XPS) analysis and density functional theory (DFT) calculation were to guide and analyze the catalytic pathway of peroxidase-like activity. Furthermore, a versatile intelligent colorimetric and sensing platform has been established to achieve sensitive cascaded-catalytic determining norfloxacin (NOR). In addition, NOR has a lower threshold of acceptability detection of 0.14 μM, which is better than the interpreted detection methods. We have firstly explored the detection mechanisms of ascorbate (H2A) and NOR and discovered that NOR could selectively oxidize Fe2+ and support Bi-Bi mechanisms in the process of H2O2 catalysis. Excellent guidelines for the design of multifunctional nanozyme catalysts were provided by the inquiry.

Cobalt single-atom catalyst tailored ceramic membrane for selective removal of emerging organic contaminants

Water reuse is an effective way to solve the issues of current wastewater increments and water resource scarcity. Ultrafiltration, a promising method for water reuse, has the characteristics of low energy consumption, easy operation, and high adaptability to coupling with other water treatment processes. However, emerging organic contaminants (EOCs) in municipal wastewater cannot be effectively intercepted by ultrafiltration, which poses significant challenges to the effluent quality and sustainability of ultrafiltration process. Here, we develop a cobalt single-atom catalyst-tailored ceramic membrane (Co1-NCNT-CM) in conjunction with an activated peroxymonosulfate (PMS) system, achieving excellent EOCs degradation and anti-fouling performance. An interfacial reaction mechanism effectively mitigates membrane fouling through a repulsive interaction with natural organic matter. The generation of singlet oxygen at the Co-N3-C active sites through a catalytic pathway (PMS→PMS∗→OH∗→O∗→OO∗→1O2) exhibits selective oxidation of phenols and sulfonamides, achieving >90% removal rates. Our findings elucidate a multi-layered functional architecture within the Co1-NCNT-CM/PMS system, responsible for its superior performance in organic decontamination and membrane maintenance during secondary effluent treatment. It highlights the power of integrating Co1-NCNT-CM/PMS systems in advanced wastewater treatment frameworks, specifically for targeted EOCs removal, heralding a new direction for sustainable water management.

Role of Iridium in n‐Pentane Isomerization, Cyclohexane Ring Opening, and Cumene Cracking Over Ir/Pt‐HZSM5

AbstractProducing aromatic compounds sustainably from renewable sources is essential to reduce reliance on fossil fuels. This study aims to elucidate the multifunctional behavior of Ir on Pt‐HZSM5, and their influence on the catalytic activity of n‐pentane isomerization, cyclohexane ring opening, and cumene cracking. The results showed that Ir created another active and Lewis's acid site, which increased the acid sites (H+), thus enhancing the catalytic performance of Pt‐HZSM5. Moreover, Ir inhibited the atomic hydrogen bonding interaction and hence improved the main reaction and suppressed the side reaction. Therefore, the mechanism of the main reaction over Ir/Pt‐HZSM5 can be described as the following steps: (i) Interaction of reactant with H+; (ii) Reaction of carbenium ion intermediate; and (iii) Interaction of a carbenium ion intermediate with H−, followed by desorption. This study provides a comprehensive understanding of the intricate catalytic pathways, offering insights into the design of efficient multifunctional catalysts for various petrochemical applications.

In silico identification of papaya genome-encoded microRNAs to target begomovirus genes in papaya leaf curl disease.

Papaya leaf curl disease (PaLCuD) is widespread and classified in the genus begomovirus (Geminiviridae), disseminated by the vector whitefly Bemisia tabaci. RNA interference (RNAi)-based antiviral innate immunity stands as a pivotal defense mechanism and biological process in limiting viral genomes to manage plant diseases. The current study aims to identify and analyze Carica Papaya locus-derived capa-microRNAs with predicted potential for targeting divergent begomovirus species-encoded mRNAs using a 'four integrative in silico algorithms' approach. This research aims to experimentally activate the RNAi catalytic pathway using in silico-predicted endogenous capa-miRNAs and create papaya varieties capable of assessing potential resistance against begomovirus species and monitoring antiviral capabilities. This study identified 48 predicted papaya locus-derived candidates from 23 miRNA families, which were further investigated for targeting begomovirus genes. Premised all the four algorithms combined, capa-miR5021 was the most anticipated miRNA followed by capa-miR482, capa-miR5658, capa-miR530b, capa-miR3441.2, and capa-miR414 'effective' papaya locus-derived candidate capa-miRNA and respected putative binding sites for targets at the consensus nucleotide position. It was predicted to bind and target mostly to AC1 gene of the complementary strand and the AV1 gene of the virion strand of different begomovirus isolates, which were associated with replication-associated protein and encapsidation, respectively, during PaLCuD. These miRNAs were also found targeting betaC1 gene of betasatellite which were associated with retardation in leaf growth and developmental abnormalities with severe symptoms during begomovirus infection. To validate target prediction accuracy, we created an integrated Circos plot for comprehensive visualization of host-virus interaction. In silico-predicted papaya genome-wide miRNA-mediated begomovirus target gene regulatory network corroborated interactions that permit in vivo analysis, which could provide biological material and valuable evidence, leading to the development of begomovirus-resistant papaya plants. The integrative nature of our research positions it at the forefront of efforts to ensure the sustainable cultivation of papaya, particularly in the face of evolving pathogenic threats. As we move forward, the knowledge gained from this study provides a solid foundation for continued exploration and innovation in the field of papaya virology, and to the best of our knowledge, this study represents a groundbreaking endeavor, undertaken for the first time in the context of PaLCuD research.

Inductive effect in amino functionalized ionic liquids modified TS-1 nanosheets for efficiently sunlight-driven CO2 reduction

Photocatalytic technology for converting CO2 into useful chemicals or clean energy is an effective strategy to solve today's energy and environmental problems. In this study, we present a direct photocatalytic pathway for the conversion of CO2-to-CO involving the formation and activation of carboxyl intermediates over amino-functionalized ionic liquid (3-aminopiperidine hydrochloride, [3APip]Cl)-modified titanium silicalite-1 (TS-1) molecular sieve nanosheets. Various in-situ characterizations reveal that the key to activating this pathway lies in the CO2 adsorption capacity and the efficiency of photoexcited charge migration induced by [3APip]Cl in the hybrid catalyst. In the above catalytic pathway, CO2 molecules are first adsorbed on the surface of the [3APip]Cl/TS-1 hybrid catalyst under the induction of amino groups in the ionic liquid. Then, these adsorbed CO2 are activated and transformed into carboxyl intermediate, which can be further converted into CO and CH4 through photoexcited electrons captured by [3APip]Cl. Based on the results of CO2 reduction performance, the optimized [3APip]Cl/TS-1 hybrid catalyst achieves a 6-fold increase, and the CO selectivity is 83.0%. This research provides new insights into the CO2 reduction pathway in mild conditions and emphasizes the importance of the adsorption–activation tandem process for enhancing photoactivity and selectivity.

Enantioselective [2π + 2σ] Cycloadditions of Bicyclo[1.1.0]butanes with Vinylazaarenes through Asymmetric Photoredox Catalysis.

Here we present a highly enantioselective [2π + 2σ] photocycloaddition of bicyclo[1.1.0]butanes (BCBs). The reaction uses a variety of vinylazaarenes as partners and is catalyzed by a polycyclic aromatic hydrocarbon (PAH)-containing chiral phosphoric acid as a bifunctional chiral photosensitizer. A wide array of pharmaceutically important bicyclo[2.1.1]hexane (BCH) derivatives have been synthesized with high yields, enantioselectivity, and diastereoselectivity. In addition to the diverse 1-ketocarbonyl-3-substituted BCBs, α/β-substituted vinylazaarenes are compatible with such an unprecedented photoredox catalytic pathway, resulting in the successful assembly of an all-carbon quaternary stereocenter or two adjacent tertiary stereocenters on the product.

An eco-friendly self-assembled catalyst preparation and study of tetracycline degradation: Performance, mechanism to application

Chloromethyl styrene resin can undergo specific chemical modifications and is an excellent adsorbent material for treating difficult-to-degrade substances in wastewater. In this study, chloromethyl styrene resin will be used as a carrier, and polystyrene chloromethyl resin (PS-Cl) was converted into PS-NH2 by amino modification. The self-assembly of cobalt-based metal–organic framework (CoMOF) was induced on the surface of PS-NH2 by using a novel preparation technique. The performance of the prepared PS-NH2@CoMOF self-assembled catalysts with core–shell-like structures in degrading the target pollutant, tetracycline (TC), was evaluated. The catalysts effectively induced rapid OH radical production from H2O2, had a degradation rate of as high as 88.3 % for 20 mg/L TC solution, and were highly stable and adaptable to aqueous environments. Free radicals and intermediates in the catalytic degradation process were detected by electron paramagnetic resonance and high-performance liquid chromatography mass spectrometry, and possible catalytic degradation pathways were analyzed. The catalytic dissociation behavior of H2O2 in the presence of different catalysts was studied in depth and compared with that of similar metal–organic framework materials through density-functional theory calculations. Results demonstrated the excellent performance of the PS-NH2@CoMOF catalysts. Finally, the catalysts' potential for use in practical engineering applications was evaluated with a flow column experimental model, and the results were more than satisfactory. Therefore, the use of the catalysts to degrade TC has great potential.

Critical review of the role of ash content and composition in biomass pyrolysis

In the face of environmental challenges (e.g., dramatically increasing greenhouse gas emissions and climate change), it is utmost of importance to sustainable energy systems. Biomass consisting of agricultural and forest waste, municipal solid waste, and aquatics, has been identified as alternative and promising fuel sources. Thermochemical conversion approaches like pyrolysis can turn various types of biomass into three valuable product streams, namely, bio-oil, biochar, and syngas. To date, past review articles have considered the major operating parameters of kinetics, chemistry, and the application of pyrolysis products. However, ash content is one of the key biomass components that lacks investigation on its influence during biomass pyrolysis with respect to products yield and properties. This review article examines: i) the ash content and composition in different types of biomass; ii) effects of ash content on catalytic pathway and biomass thermal degradation; iii) ash related problems in the thermal degradation of biomass; and iv) available deashing techniques for biomass. The review aims to provide new understandings and insights regarding the effects of ash content and composition on biomass pyrolysis.

A DFT investigation of hydrazine nitrate dissociation mechanism on MoN(0 0 1)

Hydrazine nitrate (HN) is an important additive for hydrazine-based monopropellant. In this work, density functional theory (DFT) was adopted to calculate the decomposition process of HN components on MoN (001) catalyst surface. Firstly, two stable adsorption configurations of hydrazine nitrate were identified and determined the catalytic decomposition pathway of the thermodynamically favorable configuration. Pathway analysis revealed that the nitric acid group preferentially decomposes in all pathways. Moreover, due to the high activation and desorption energies, H2O molecules are more likely to be generated in the gas phase rather than preferentially adsorbed on the surface. By calculating the activation energies of each elementary reaction, it can be concluded that the cleavage of the NO bond in NO3– with the barrier energy of 0.32 eV plays a decisive role in the decomposition of the HN molecule.

Theoretical calculation study on the reaction mechanism of methanol/dimethyl ether carbonylation catalyzed by the B/Al/Ga-MOR zeolites

The reaction mechanism of methanol/dimethyl ether (DME) carbonylation catalyzed by isomorphously substituted B-, Al-, and Ga-MOR zeolites (B/Al/Ga-MOR) was comparatively investigated by the density functional theory (DFT) calculations. The commonalities and differences between methanol and dimethyl ether as the reactant as well as among various MOR zeolites in the catalytic reaction pathways were disclosed, where one Si atom was substituted by B, Al or Ga at the 8-ring side pockets T3 sites or the 12-ring channels T4 sites of MOR. The results indicate that the insertion of CO into methoxy group to form acetyl groups follows the SN2 mechanism and is the rate-determining step in the carbonylation reactions. Under 473 K, either methanol or dimethyl ether is used as feedstock, the formed acetyl group prefers to interact with CH3O in methanol to form methyl acetate. The T3 sites show better carbonylation selectivity, whereas T4 sites display better trimethoxonium ions selectivity which favors the generation of aromatics and leads to the catalyst deactivation. Comparing with Al-MOR, the introduction of Ga and B at the T3 sites increases the free energy barriers of carbonylation, whereas the introduction of Ga and B in particular at the T4 sites can substantially increase the energy barriers of generating trimethyloxonium ions, which can effectively suppress the side reaction and improve the catalyst stability. This work contributes to the understanding of the catalytic roles of various acidic sites in different channels of the MOR zeolites and provides certain theoretical support for tailoring and designing efficient MOR zeolite catalysts for methanol/dimethyl ether carbonylation.

Microwave‐assisted Rhodium(I)‐Catalyzed C8‐Regioselective C−H Alkenylation and Arylation of 1,2,3,4‐Tetrahydroquinolines with Alkenyl and Aryl Carboxylic Acids

AbstractRh(I)‐catalyzed C8‐selective C−H alkenylation and arylation of 1,2,3,4‐tetrahydroquinolines with alkenyl and aryl carboxylic acids under microwave assistance have been realized. Using [Rh(CO)2(acac)] as the catalyst and Piv2O as the acid activator, 1,2,3,4‐tetrahydroquinolines undergo C8‐selective decarbonylative C−H alkenylation with a wide range of alkenyl and aryl carboxylic acids, affording the C8‐alkenylated or arylated 1,2,3,4‐tetrahydroquinolines. This method enables the synthesis of C8‐alkenylated 1,2,3,4‐tetrahydroquinolines that would otherwise be difficult to access by means of conventional C−H alkenylation protocols. Moreover, this catalytic system also works well in C8‐selective decarbonylative C−H arylation of 1,2,3,4‐tetrahydroquinolines with aryl carboxylic acids. The catalytic activity strongly depends on the choice of the N‐directing group, with the readily installable and removable N‐(2‐pyrimidyl) group being optimal. The catalytic pathway is elucidated by mechanistic experiments.

In Silico Identification of Sugarcane Genome-Encoded MicroRNAs Targeting Sugarcane Mosaic Virus

Sugarcane mosaic virus (SCMV) (genus, Potyvirus; family, Potyviridae) is widespread, deleterious, and the most damaging pathogen of sugarcane (Saccharum officinarum L. and Saccharum spp.) that causes a substantial barrier to producing high sugarcane earnings. Sugarcane mosaic disease (SCMD) is caused by a single or compound infection of SCMV disseminated by several aphid vectors in a non-persistent manner. SCMV has flexuous filamentous particle of 700–750 nm long, which encapsidated in a positive-sense, single-stranded RNA molecule of 9575 nucleotides. RNA interference (RNAi)-mediated antiviral innate immunity is an evolutionarily conserved key biological process in eukaryotes and has evolved as an antiviral defense system to interfere with viral genomes for controlling infections in plants. The current study aims to analyze sugarcane (Saccharum officinarum L. and Saccharum spp.) locus-derived microRNAs (sof-miRNAs/ssp-miRNAs) with predicted potential for targeting the SCMV +ssRNA-encoded mRNAs, using a predictive approach that involves five algorithms. The ultimate goal of this research is to mobilize the in silico- predicted endogenous sof-miRNAs/ssp-miRNAs to experimentally trigger the catalytic RNAi pathway and generate sugarcane cultivars to evaluate the potential antiviral resistance surveillance ability and capacity for SCMV. Experimentally validated mature sugarcane (S. officinarum, 2n = 8X = 80) and (S. spp., 2n = 100–120) sof-miRNA/ssp-miRNA sequences (n = 28) were downloaded from the miRBase database and aligned with the SCMV genome (KY548506). Among the 28 targeted mature locus-derived sof-miRNAs/ssp-miRNAs evaluated, one sugarcane miRNA homolog, sof-miR159c, was identified to have a predicted miRNA binding site, at nucleotide position 3847 of the SCMV genome targeting CI ORF. To verify the accuracy of the target prediction accuracy and to determine whether the sugarcane sof-miRNA/ssp-miRNA could bind the predicted SCMV mRNA target(s), we constructed an integrated Circos plot. A genome-wide in silico-predicted miRNA-mediated target gene regulatory network was implicated to validate interactions necessary to warrant in vivo analysis. The current work provides valuable computational evidence for the generation of SCMV-resistant sugarcane cultivars.

Molecular insight into the enhanced performance of CALB toward PBDF degradation

Poly(butylene diglycolate-co-furandicarboxylate) (PBDF) is a newly developed biodegradable copolyester. Candida antarctica lipase B (CALB) has been identified as an effective catalyst for PBDF degradation. The mechanism is elucidated using a combination of molecular dynamics simulations and quantum chemistry approaches. The findings unveil a four-step catalytic reaction pathway. Furthermore, bond analysis, charge and interaction analysis are conducted to gain a more comprehensive understanding of the PBDF degradation process. Additionally, through the introduction of single-point mutations to crucial residues in CALB's active sites, two mutants, T138I and D134I, are discovered to exhibit improved catalytic efficiency. These significant findings contribute to the advancement of our comprehension concerning the molecular mechanism of underlying copolyesters degradation, while also presenting a novel approach for expediting the degradation rate by the CALB enzyme modification.

Catalytic hydrogenation of olefins by a multifunctional molybdenum-sulfur complex

Exploration of molybdenum complexes as homogeneous hydrogenation catalysts has garnered significant attention, but hydrogenation of unactivated olefins under mild conditions are scarce. Here, we report the synthesis of a molybdenum complex, [Cp*Mo(Ph2PC6H4S−CH = CH2)(Py)]+ (2), which exhibits intriguing reactivity toward C2H2 and H2 under ambient pressure. This vinylthioether complex showcases efficient catalytic activity in the hydrogenation of various aromatic and aliphatic alkenes, demonstrating a broad substrate scope without the need for any additives. The catalytic pathway involves an uncommon oxidative addition of H2 to the cationic Mo(II) center, resulting in a Mo(IV) dihydride intermediate. Moreover, complex 2 also shows catalytic activity toward C2H2, leading to the production of polyacetylene and the extension of the vinylthioether ligand into a pendant triene chain.

Is Metal Stabilization of the Leaving Group Required or Can Lysine Facilitate Phosphodiester Bond Cleavage in Nucleic Acids? A Computational Study of EndoV.

Endonuclease V (EndoV) is a single-metal-dependent enzyme that repairs deaminated DNA nucleobases in cells by cleaving the phosphodiester bond, and this enzyme has proven to be a powerful tool in biotechnology and medicine. The catalytic mechanism used by EndoV must be understood to design new disease detection and therapeutic solutions and further exploit the enzyme in interdisciplinary applications. This study has used a mixed molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) approach to compare eight distinct catalytic pathways and provides the first proposed mechanism for bacterial EndoV. The calculations demonstrate that mechanisms involving either direct or indirect metal coordination to the leaving group of the substrate previously proposed for other nucleases are unlikely for EndoV, regardless of the general base (histidine, aspartate, and substrate phosphate moiety). Instead, distinct catalytic pathways are characterized for EndoV that involve K139 stabilizing the leaving group, a metal-coordinated water stabilizing the transition structure, and either H214 or a substrate phosphate group activating the water nucleophile. In silico K139A and H214A mutational results support the newly proposed roles of these residues. Although this is a previously unseen combination of general base, general acid, and metal-binding architecture for a one-metal-dependent endonuclease, our proposed catalytic mechanisms are fully consistent with experimental kinetic, structural, and mutational data. In addition to substantiating a growing body of literature, suggesting that one metal is enough to catalyze P-O bond cleavage in nucleic acids, this new fundamental understanding of the catalytic function will promote the exploration of new and improved applications of EndoV.

Cobalt phthalocyanine promoted copper catalysts toward enhanced electro reduction of CO2 to C2: Synergistic catalysis or tandem catalysis?

The activity and selectivity of electrocatalytic CO2 reduction reaction (CO2RR) to C2 products on metal catalysts can be regulated by molecular surfactants. However, the mechanism behind it remains elusive and debatable. Herein, copper nanowires (Cu NWs) were fabricated and decorated with cobalt phthalocyanine (CoPc). The electronic interaction between the Cu NWs, CoPc, CO2 and CO2RR intermediates were explored by density functional theory (DFT) calculations. It was found that the selectivity and activity of CO2RR towards C2 products on Cu NWs were considerably enhanced from 35.2% to 69.9% by surface decoration of CoPc. DFT calculations revealed that CO2RR can proceed in the interphase between Cu substrate and CoPc, and the CO2RR intermediates could synergistically bond with both Cu and Co metal centre in CuNWs-CoPc, which favours the adsorption of CO2, CO and CO2RR intermediates, thus reducing the free energy for CO-CO coupling towards C2 products. The synergistic interaction was further extended to phthalocyanine (Pc) and other metal phthalocyanine derivatives (MPc), where a relatively weaker synergistic interaction of CO intermediates with MPc and Cu substrate and only a slight enhancement of CO2RR towards C2 products were observed. This study demonstrates a synergistic catalysis pathway for CO2RR, a novel perspective in interpreting the role of CoPc in enhancing the activity and selectivity of CO2RR on Cu NWs, in contrast to the conventional tandem catalysis mechanism.

Ce-doped CuCoO2 delafossite with switchable PMS activation pathway for tetracycline degradation

Heterogeneous Fenton-like catalytic oxidation has exhibited great potential in eliminating recalcitrant organic pollutants. Nevertheless, a precise modulation of intrinsic catalytic pathways (radical or nonradical) remains challenging. Herein, Ce-doped CuCoO2 hexagonal nanosheets (CCCO-x) were designed via a facile coprecipitation method toward peroxymonosulfate activation. The doped Ce optimized the interaction between CCCO-x and PMS and enhanced the interfacial electron transfer ability, tunning the catalytic pathway from radical role (57.4%) to nonradical role (69.2%). More than 96% of tetracycline (TC) could be degraded after Ce doping, accompanied by a first-order kinetic constant that is 2.5 times higher than that of pristine CuCoO2. Meanwhile, the introduction of Ce(III) not only significantly enlarged the specific surface area of the catalyst, but also effectively enhanced the synergistic effect of Co(III) and Cu(I) sites, which further accelerated the PMS decomposition. Besides, synergy of radical-nonradical mixed pathways (SO4•−, •OH, 1O2, and electron transfer pathway) for TC removal was verified by electron paramagnetic resonance (EPR) spectra, quenching tests, and electrochemical measurements. The degradation intermediates and possible degradation pathway of TC were also proposed. This work provides new insights and routes to modulate catalytic pathway in Fenton-like oxidation, especially broadening the application potential of delafossite-based (ABO2) catalysts in water treatment.

Study on the zinc porphyrins as potential carbonic anhydrase mimics for promoting CO2 absorption in K2CO3 solution

Zinc porphyrins, boasting a coordination environment akin to that of natural carbonic anhydrase (CA), coupled with excellent structural stability, built-in hydrophobic pocket, and suitable charge of center Zn2+, were considered as potential CA-mimics for CO2 capture. To validate this assumption, three zinc porphyrin representatives, zinc porphin (ZnP), zinc protoporphyrin IX (ZnPP), and zinc meso-tetrakis(N-methylpyridinium-4-yl) porphyrin (ZnTMPyP), were prepared, and tested performance in enhancing CO2 absorption in water and K2CO3 solutions. The results from CO2 absorption experiments indicated that ZnTMPyP with the optimal dosage increased CO2 absorption rate by 44.25 % in water, and ZnPP with the optimal dosage increased the CO2 absorption rate by 63.67 % in 20 wt% of K2CO3 solution, which are respectively 1.53 and 2.07 times of CO2 absorption performance of zinc cyclen (ZnC), the most effective CA-mimic reported. Besides, the zinc porphyrins demonstrated excellent stability and reusability throughout five cycles of CO2 absorption and desorption, which are vital aspects for practical applications. Through the calorimetric method and density functional theory (DFT) calculations, it was confirmed that the prepared zinc porphyrins had similar enzymatic behavior and catalytic CO2 hydration pathway to natural CA. According to the results of characterization and DFT calculations, high dispersion, the lowest charge of the Zn2+ center, and the existence of additional CO2 adsorption sites (propionate ions), endow ZnPP with the highest catalytic activity in the K2CO3 solution.

FeCo2O4@CNT/PVDF catalytic spheres as peroxymonosulfate activator for levofloxacin decontamination: Catalytic mechanism, ecotoxicity evolution and degradation pathways

Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) for antibiotics removal in aqueous environments are now widely investigated, but the separation of the powdered catalysts from the water at the end of reaction is a major problem that hinders the large-scale application of PMS-based catalytic systems. In this work, based on the synthesis of FeCo2O4@CNT, the FeCo2O4@CNT/polyvinylidene fluoride (PVDF) catalytic spheres (CSs) with a diameter of 3 mm was further fabricated by phase transition method, which as peroxymonosulfate activator not only could remove 95.68 % of LVF (10 mg/L) within 60 min, but also could be easily separated from water. The various characterization results show that FeCo2O4@CNT is mainly distributed in the interior of CSs, LVF and PMS enter the interior through the surface pore structure of CSs and undergo oxidation reactions. The non-free radical pathway coupled with radical pathway contributed to the degradation of LVF where the 1O2 was the major ROS. Meanwhile, the possible degradation pathways of LVF were proposed based on the identification by LC-MS for intermediates and the Toxicity Estimation Software Tool (T. E. S. T) was adopted to evaluate their ecotoxicity evolution. The degradation efficiency of catalytic sphere system for LVF can still be maintained at about 80 % after 20 h of continuous reaction or 5 cycles batch experiments, demonstrating the stability and recoverability of CSs. In addition, simple aqueous cleaning and subsequent standing treatment could help CSs recover to the original catalytic level. Thus, this work provides a promising material for the future wastewater treatment.

Co(CO3)0.5(OH)•0.11H2O as superior peroxymonosulfate activator for ciprofloxacin degradation via co-acting mechanism of low & high-valent cobalt and oxygen vacancy

In this study, oxygen vacancies-rich (OVs-rich) Co(CO3)0.5(OH)•0.11H2O catalyst was prepared by a hydrothermal process, which was used to activate peroxymonosulfate (PMS) and degrade ciprofloxacin (CIP). Although its specific surface area was only 46.2 m2 g−1, the Co(CO3)0.5(OH)•0.11H2O catalyst exhibited high performance. Under its natural pH, 91.0% of CIP (50 ppm) was degraded and chemical oxygen demand removal reached 70% in 10 min. The rapid degradation reaction followed Behnajady-Modirshahla-Ghnbery kinetic model. The research on catalytic mechanism indicated that three coexisting catalytic pathways resulted in the efficient degradation of CIP. (1) The low-valent Co2+ in Co(CO3)0.5(OH)•0.11H2O activate PMS to generate four kinds reactive oxygen species such as SO4•−, •OH, O2•− and 1O2. (2) The dissolved oxygen was adsorbed on Co(CO3)0.5(OH)•0.11H2O surface and the abundant localized electrons of OVs made them easily endow electrons to O2, reducing O2 to O2•− and then to 1O2. (3) The reaction between the Co2+ and PMS resulted in the high-valent Co4+(O) species, which possessed outstanding oxidation ability for CIP degradation.