Gold nanoparticles-modified MnFe2O4 with synergistic catalysis for photo-Fenton degradation of tetracycline under neutral pH

A facile smartphone-based digital image colorimetric sensor for the determination of tetracyclines in water using natural phenolic compounds induced to grow gold nanoparticles

A cost-effective smartphone-based digital image colorimetric sensor was developed to determine tetracyclines by inducing in situ growth of gold nanoparticles using naturally occurring phenolic compounds derived from para rubber tree bark waste. The green intensity of the purple-red product was measured using smartphone-based digital image analysis. Under optimal conditions, the calibration graph exhibited linearity within the range 0.05 to 0.50 μg mL-1, with a coefficient of determination (R 2) of 0.9940. The limits of detection (LOD) and limits of quantitation (LOQ) were 15 and 50 ng mL-1, respectively, with levels of precision for intraday and interday less than 3.91% and 4.59%, respectively. The proposed method was effectively validated to determine the spiked tetracycline antibiotics in water samples, achieving a high relative recovery rate ranging from 86.4% to 114.4%. Our method is facile, convenient, dependable, and verifiable as an alternate procedure for measuring tetracycline levels in water.

Poor/rich dual electron reaction centers promoting photo-Fenton synergistic removal of organic pollutants: Graphite carbon-modified copper ferrite

Controlling high recombination of photogenerated carriers and optimizing low cycling of metal valence states are the two key control steps in enhancing photo-Fenton oxidation. To achieve multiscale synergy of photo-Fenton degradation, graphite carbon-modified copper ferrite composites (C/CFO) with poor/rich dual electron reaction centers were synthesized through direct carbonization of Fe/Cu bimetallic organic frameworks. A novel photo-Fenton catalytic system was constructed by irradiating the Fenton reaction with visible light. The photo-Fenton degradation efficiency of C/CFO for tetracycline (100 mg‧L-1) was 93.69% ± 0.02%, and the degradation rate constant was 4.84 times higher than that of the control. Optimized preparation and catalytic conditions, ensured good cyclic stability and broad applicability of C/CFO. This excellent stability performance improvement can be attributed to the following main factors: (1) The introduction of graphite carbon not only increases the specific surface area of C/CFO, but also acts as a bridge between the dual electron reaction centers, facilitating the transfer of photogenerated electrons. (2) On the one hand, the electron-poor reaction centers Fe and Cu capture photogenerated electrons, accelerate the Fenton reaction, and realize the valence cycling of Fe and Cu. On the other hand, the electron-rich reaction centers (oxygen vacancies) act as active sites for H2O2 adsorption, which greatly accelerate the decomposition of H2O2. Overall, the synergy of dual electron reaction centers effectively promoted photo-Fenton oxidation.

Phycogenic nanoparticles efficiently catalyse pesticide degradation through a novel metabolic pathway utilizing solar light

Cypermethrin (Cy) is a widely used insecticide, leading to significant environmental contamination in homes and agricultural areas. Effective methods to minimize or eliminate insecticidal residues are essential. Seaweeds, traditionally used in agriculture as soil conditioners, offer a promising solution for remediating pesticide-contaminated soils through biogenic nanoparticle synthesis. In this study, we synthesized biogenic silver nanoparticles (UL-AgNPs) from the green seaweed Ulva lactuca Lin (Ulvaceae) to degrade Cypermethrin. The UL-AgNPs were characterized using UV-Visible spectroscopy, Scanning Electron Microscopy equipped with Energy dispersive X-ray spectroscopy, Fourier Transform Infra-red spectroscopy, X-ray diffraction, Dynamic light scattering and zeta potential analysis, confirming their presence, size (81.29 nm), structure and stability. Response surface methodology (RSM) was used to assess the catalytic concentration of photocatalyst for degradation of pesticide including variables, Cy concentration and destined exposure time duration. The degradation efficiency of UL-AgNPs was evaluated, with the highest degradation (91.2%) achieved at pH 7 after 12 h using 16.6 mg L-1 of UL-AgNPs, following pseudo-first order kinetics with a rate of 2.7 h-1. GC-MS and UV-Visible spectroscopy revealed a novel degradation pathway, where Cypermethrin was broken down into compounds like Tetradecane, Dodecane, and Tetracosanoic acid through ester cleavage and benzene ring breakdown. The study also demonstrated the reusability of UL-AgNPs for four cycles, highlighting their potential for sustainable environmental management by reducing the long-term hazards of Cypermethrin.

Recent trends in magnetic spinel ferrites and their composites as heterogeneous Fenton-like catalysts: A review

In recent years, there has been a growing interest in utilizing spinel ferrite and their nanocomposites as Fenton-like catalysts. The use of these materials offers numerous advantages, including ability to efficiently degrade pollutants and potential for long-term and repeated use facilitated by their magnetic properties that make them easily recoverable. The remarkable catalytic properties, stability, and reusability of these materials make them highly attractive for researchers. This paper encompasses a comprehensive review of various aspects related to the Fenton process and the utilization of spinel ferrite and their composites in catalytic applications. Firstly, it provides an overview of the background, principles, mechanisms, and key parameters governing the Fenton reaction, along with the role of physical field assistance in enhancing the process. Secondly, it delves into the advantages and mechanisms of H2O2 activation induced by different spinel ferrite and their composites for the removal of organic pollutants, shedding light on their efficacy in environmental remediation. Thirdly, the paper explores the application of these materials in various Fenton-like processes, including Fenon-like, photo-Fenton-like, sono-Fenton-like, and electro-Fenton-like, for the effective removal of different types of contaminants. Furthermore, it addresses important considerations such as the toxicity, recovery, and reuse of these materials. Finally, the paper presents the challenges associated with H2O2 activation by these materials, along with proposed directions for future improvements.

Green synthesis of manganese ferrite magnetic nanoparticle and its modification with metallic-organic frameworks for the tetracycline adsorption from aqueous solutions: A mathematical study of kinetics, isotherms, and thermodynamics

In the current investigation, MnFe2O4/ZIF-8 nanocomposite was generated as a magnetic nanoadsorber using the extract of Dracocephalum plant and characterized by XRD, FTIR, VSM, BET, FESEM, EDS-mapping, TEM, XPS, TPD-NH3, and TGA analyses. Also, to determine its efficiency in the adsorption process of tetracycline, the effect of pH (3-9), nanocomposite dose (0.025-2 g/L), initial pollutant concentration (5-100 mg/L), contact time (5-200 min), and temperature (5-50 °C) were studied. The results of the morphological properties of the magnetic nanocomposite confirmed the spherical shape of this nanoadsorber with an average size of 54 ± 31 nm. BET analysis showed that modification of MnFe2O4 material with ZIF-8 as a new nanoadsorber leads to excellent modification of SBET (143.8 m2/g) and VTotal (0.44 cm3/g). The highest removal efficiency of tetracycline in optimal conditions (pH = 7, contact time = 120 min, nanocomposite dose = 1.5 g/L, and temperature = 20 °C for a tetracycline concentration of 20 mg/L) was 90.11%. As the temperature increased, the removal efficiency increased from 40.46% to 95.06% during 120 min, which indicates that the adsorption reaction is endothermic. In addition, the data obtained from the isotherms of Langmuir (R2 = 0.958), Freundlich (R2 = 0.534), and Temkin (R2 = 0.747) showed that the tetracycline adsorption is monolayer and on the homogeneous surface of the synthesized magnetic nanoadsorber. The elimination process of tetracycline by nanoadsorber followed the pseudo-second order model (R2 = 0.998). Investigating the effect of interfering ions also confirmed the decrease in the adsorption efficiency. Also, the investigation of the reusability of the synthesized magnetic nanoadsorber in tetracycline adsorption indicates that after eight cycles, the efficiency decreases by %16.51. According to the results, the magnetic nanocomposite synthesized in this work can be a suitable and economical adsorber for the removal of tetracycline from aqueous environments.

Construction of self-cleaning g-C3N4/Bi2MoO6/PVDF membrane and coupling with photo-Fenton-like reaction for sustainable removal of antibiotics in wastewater

Constructing a photocatalytic membrane and photo-Fenton reaction coupling system is a novel strategy to enhance the photocatalytic activity of the membrane and eliminate the problem of membrane contamination. Herein, a g-C3N4/Bi2MoO6/PVDF photocatalytic membrane was prepared using a tannic acid-assisted in-situ deposition method. The membrane was characterized by three advantages of photocatalytic, self-cleaning, and antibacterial properties. Under the photo-Fenton-like conditions, the membrane had superior photodegradation efficiency of 90.7% for tetracycline, one of the main antibiotic contaminants in the China's aquatic system. Moreover, the membrane had excellent photo-Fenton self-cleaning ability, its flux recovery rate was up to 96%-98% after the self-cleaning process. Photoluminescence spectra, diffuse UV-visible spectrum, transient photocurrent responses, and electrochemical AC impedance spectrum results show that the heterojunction structure formed by g-C3N4 and Bi2MoO6 could improve the separation efficiency of photogenerated electrons-hole pairs. Electron spin resonance spectroscopy confirmed the photo-electrons facilitated the formation of hydroxyl radical (·OH) in the existence of H2O2, which enhanced tetracycline degradation. Moreover, the superior photo-Fenton self-cleaning performance, which mainly relied on the active free radicals produced by the photo-Fenton-like membrane to remove dirt on the membrane surface or in the membrane pore channel. Our results may shed new light on the development of promising photocatalytic membrane systems by coupling with photo-Fenton-like processes, and facilitate their applications for wastewater treatment.

Effect of EDTA and Citric Acid Additive on the Polymorph, Morphology, and Photocatalytic Activity of Iron Oxyhydroxide

Iron oxyhydroxide [FeO(OH)] is a promising photocatalyst owing to its simple synthesis at mild temperatures and narrow band gap, which allows for the efficient harvesting of visible light. The selective production of FeO(OH) polymorphs and the modulation of their morphology by changing the iron salts, salt concentration, and additives have been widely reported. This study focuses on overcoming fast charge-carrier recombination by developing FeO(OH)-based heterostructure materials. The role of a chelating ligand (EDTA and citrate) in determining the polymorph type, morphology, and photocatalytic activity of FeO(OH) was studied. The findings revealed the additive produced of nanosized α-FeO(OH)/EDTA and layered γ-FeO(OH)/citrate with superior catalytic activities.

Z-scheme Fe@Fe2O3/BiOBr heterojunction with efficient carrier separation for enhanced heterogeneous photo-Fenton activity of tetracycline degradation: Fe2+ regeneration, mechanism insight and toxicity evaluation

The recombination of photogenerated carrier leads to inefficient Fe2+ regeneration, which limits the extensive application of heterogeneous photo-Fenton. Here, a novel Fe@Fe2O3/BiOBr catalyst with Z-scheme heterojunction structure is designed, and the establishment of the Z-scheme heterojunction facilitates the separation and transfer of photogenerated carrier and maintains the superior redox capability of the system. As-prepared Fe@Fe2O3/BiOBr catalyst exhibits outstanding catalytic performance and stability, especially for the optimum composite FFB-3, its degradation efficiency of tetracycline (TC) achieves 98.22% and the mineralization degree reaches 59.48% within 90 min under natural pH. The preeminent catalytic efficiency benefited from the synergistic of heterogeneous photo-Fenton and Z-scheme carriers transfer mechanism, where Fe2+ regeneration was achieved by photogenerated electrons, and increased hydroxyl radicals were produced with the participation of H2O2 in-situ generated. The results of free-radical scavenging experiment and ESR illustrated that •OH, •O2-, 1O2 and h+ were active species participating in TC degradation. Furthermore, the TC degradation paths were proposed according to LC-MS, and the toxicity evaluation result showed that the toxicity of TC solutions was markedly decreased after degradation. This study provides an innovative strategy for heterogeneous photo-Fenton degradation of antibiotic contaminations by constructing Z-scheme heterojunctions.

Enhanced Photocatalytic Activities of Sodium Borohydride-Calcined Magnetic Manganese Ferrite Nanoparticles

The synthesis, enhancement, and maintenance of magnetite-based catalyst nanoparticles (NPs) are important for photocatalytic activity and recovery rates. We used a sodium borohydride (NaBH4) calcination method to modify MnFe2O4 nanoparticles to optimize their performance in the photocatalytic oxidation of 2,5-hydroxymethylfurfural. The results indicated a 94% increase in photocatalytic efficiency, while magnetic assessments performed using a vibrating sample magnetometer showed an 8.9% improvement in magnetic properties without degradation. These findings show the dual benefits of increased photocatalytic performance with strong magnetic properties, which are important for the application and reusability of photocatalysts. The recycling of these photocatalysts reduces secondary pollution and increases the process cost-effectiveness. These results contribute to the solution of problems with the use of photocatalytic materials.

Electron transfer mediated photo-Fenton-like synergistic catalysis of Fe,Cu-doped MIL-101 coupled with Ag3PO4: Quantitative evaluation and DFT calculations

Widespread use of tetracycline (TC) results in its persistent residue and bioaccumulation in aquatic environments, posing a high toxicity to non-target organisms. In this study, a bimetal-doped composite material Ag3PO4/MIL-101(Fe,Cu) has been designed for the treatment of TC in aqueous solutions. As the molar ratio of Fe/Cu in composite is 1:1, the obtained material AP/MFe1Cu1 is placed in an aqueous environment under visible light irradiation in the presence of 3 mM peroxydisulfate (PDS), which forms a photo-Fenton-like catalytic system that can completely degrade TC (10 mg/L) within 60 min. Further, the degradation rate constant (0.0668 min-1) is 5.66 and 7.34 times higher than that of AP/MFe and AP/MCu, respectively, demonstrating a significant advantage over single metal-doped catalysts. DFT calculations confirm the strong adsorption capacity and activation advantage of PDS on the composite surface. Therefore, the continuous photogenerated electrons (e-) accelerate the activation of PDS and the production of SO4•-, resulting in the stripping of abundant photogenerated h + for TC oxidation. Meanwhile, the internal circulation of FeⅢ/FeⅡ and CuⅡ/CuⅢ in composite also greatly enhances the photo-Fenton-like catalytic stability. According to the competitive dynamic experiments, SO4•- have the greatest contribution to TC degradation (58.93%), followed by 1O2 (23.80%). The degradation intermediates (products) identified by high-performance liquid chromatography-mass spectrometry (HPLC/MS) technique indicate the involvement of various processes in TC degradation, such as dehydroxylation, deamination, N-demethylation, and ring opening. Furthermore, as the reaction proceeds, the toxicity of the intermediates produced during TC degradation gradually decreases, which can ensure the safety of the aquatic ecosystem. Overall, this work reveals the synergy mechanism of PDS catalysis and photocatalysis, as well as provides technical support for removal of TC-contaminated wastewater.

Enhanced photo-Fenton degradation of contaminants in a wide pH range via synergistic interaction between 1T and 2H MoS2 and copolymer tea polyphenols/polypyrrole

In this study, we present the successful development of a unique photo-Fenton catalyst, 1T-2H MoS2@TP/PPy (MTP), achieved through the coating of a copolymer of tea polyphenol (TP) and polypyrrole (PPy) onto the surface of heterophase molybdenum disulfide (1T-2H MoS2). This innovative approach involves the integration of hydrothermal synthesis with copolymerization techniques. Our strategy utilizes nanoflower-like 1T-2H MoS2 as the foundational framework, which is then enveloped in TP and PPy copolymer. This innovative approach involves the integration of hydrothermal synthesis with copolymerization techniques. Our strategy utilizes nanoflower-like 1T-2H MoS2 as the foundational framework, which is then enveloped in TP and PPy copolymer. This distinctive architecture demonstrates exceptional catalytic performance owing to the hetero-phase entanglement of 1T-2H MoS2, which provides a diverse array of active sites. The coupled structure of TP and iron (TP-Fe2+/Fe3+) effectively overcome the limitation associated with the iron source. The incorporation of PPy not only reduces the recombination of photogenerated electron-hole pairs but also enhances the stability of 1T-2H MoS2. Remarkably, our experiments on the degradation of methylene blue (MB) and tetracycline (TC) degradation demonstrate that TP-Fe2+/Fe3+ significantly expands the pH applicability range of the MTP composite catalyst. Additionally, we examine several factors, including different catalysts, H2O2 addition, variations in light intensity, solution pH, temperature fluctuations, and the role of active species, to comprehensively understand their impact on the photo-Fenton degradation process. In conclusion, MTP composite exhibits robust catalytic stability and demonstrates a broad pH utilization range in the photo-Fenton oxidation process, highlighting its promising potential for a wide range of applications.

Revealing the synergistic effect between radical and non-radical species of sulfur-doped carbon nitride for ciprofloxacin removal: Based on density functional theory study

The distinct characteristics of active species produced during the photocatalytic reaction can result in alterations in the degradation routes of organic pollutants with diverse chemical structures. The relationship between the active species and degradation pathways of organic pollutants lacks a direct experimental or characterization method, so in-depth research is still needed to understand the details of their interactions. In this study, sulfur-doped bulk carbon nitride (SBCN) was prepared based on bulk carbon nitride (BCN), and the process of S-doping enhancing the production of O21 was revealed. Through the degradation experiment, the degradation rate of CIP by SBCN reached 91 %, which was higher than that of BCN (66 %). The increase of degradation rate was mainly attributed to the increase of O21. Through the density functional theory (DFT) calculation of CIP and its degradation intermediate, due to the preferential oxidation of CIP by O21, O21 changes the initial degradation direction of CIP, releasing more attack sites for ˙O2-, thereby achieving more efficient degradation of CIP through the synergy of O21 and ˙O2-. In this study, the attack preferences of the active species and their synergistic promotion provide important insights for the efficient photocatalytic degradation of organic pollutants.

Photocatalytic degradation of chlorinated organic pollutants by ZnS@ZIF-8 composite through hydrogen peroxide generation by activating dioxygen under simulated sunlight irradiation

Photocatalytic hydrogen peroxide (H2O2) production and its application in advanced oxidation processes (AOPs) are regarded as low-cost and environmentally friendly wastewater treatment processes. Herein, by modifying a small amount of sulphide on the zeolitic imidazolate framework-8 (ZIF-8), a ZnS@ZIF-8 composite and used for photocatalytic H2O2 production to degrade chlorinated organic pollutants under simulated sunlight (SSL). ZnS@ZIF-8 composite could enhance the separation of photo-induced charge carriers, promote electron transfer from zinc sulphide (ZnS) to ZIF-8, which exhibited good selectivity for the two-electron oxygen reduction reaction (2e--ORR) and two-electron water oxidation (2e--WOR) pathways. Based on oxygen (O2) activation, the developed ZnS@ZIF-8/O2/SSL system could achieve 6.43 mmol/L H2O2 production within 150 min, which was approximately 8.66 and 10.36 times higher than that of the ZnS/O2/SSL and ZIF-8/O2/SSL systems, respectively. In the ZnS@ZIF-8/O2/SSL system, the ORR, WOR and H2O2 photolysis led to the generation of hydroxyl radical (•OH), while the photochemical behavior of ZnS in ZnS@ZIF-8 composite resulted in the generation of active hydrogen (*H). Benefitting from the high concentration of H2O2 and the coexistence of redox species in the ZnS@ZIF-8/O2/SSL system, various chlorinated organic pollutants could be dechlorinated and mineralized. In addition, a possible mechanism for photocatalytic H2O2 production was also proposed. Importantly, the proposed process did not involve an additional sacrificial agent or Fenton-like catalysts. This work provides insights into the potential application of ZnS@ZIF-8 composite for H2O2 production and wastewater treatment.

Preparation of three-dimensional ordered macroporous Ag/LaFeO3 and heterogeneous photo-Fenton degradation of penicillin G potassium

3DOMLaFeO3 was prepared by template method combined with sol-gel method using monodisperse polystyrene (PS) microspheres as template, and Ag/3DOMLaFeO3 perovskite catalyst was prepared by impregnation method combined with sodium borohydride reduction method. The catalysts were characterised by means of TG, XRD, SEM, BET, XPS, UV-vis DRS, etc. The photo-Fenton catalytic performance, stability and catalytic reaction mechanism of Ag/3DOMLaFeO3 were studied with penicillin G potassium (PEN G) as the model pollutant. The results indicated that the as-prepared Ag/3DOMLaFeO3 exhibited a three-dimensional ordered macroporous (3DOM) structure, and the light capture and mass transfer were enhanced through abundant pores and large specific surface area. Based on the surface plasmon resonance effect (SPR), Ag loading enhanced the absorption of the material in the visible light region, and inhibited the recombination of photogenerated carriers, which improved the photocatalytic performance of 3DOMLaFeO3 under visible light. Under the conditions of hydrogen peroxide dosage of 1.5 mL·L-1, initial pH of 5, PEN G initial concentration of 100 mg·L-1, catalyst dosage of 300 mg·L-1, xenon lamp irradiation, the degration ratio of PEN G and the removal rate of TOC reached 99.99% and 85.45% within 120 min, respectively. In addition, it had a wide range of pH application, excellent stability and practical application value. The quenching experiment and ESR test showed that ·OH and ·O2- were the reasons for high catalytic degradation. The least square method was used to fit the experimental data, and the results displayed that the degradation of PEN G was approximately in line with the first-order kinetic reaction.

Photo-Fenton degradation of tetracycline antibiotic over MIL-101(Cr)/FeOOH nanocomposite as stable and efficient visible light responsive photocatalyst

Designing an inexpensive, easily synthesized, stable and efficient photocatalyst is a major challenge in photocatalysis area, especially when photo-reaction is performed in aquatic medium to degrade organic pollutants. To this aim, nano-sized MIL-101(Cr) (MIL = Materials Institute Lavoisier), as chemically tolerant metal-organic framework (MOF), was simply prepared via HF-free hydrothermal synthesis procedure. In order to decorate amorphous FeOOH quantum dots (QDs) on the surface of this MOF, various amounts of FeOOH QDs (i.e., 5, 10, 15 and 20 wt%) were synthesized in the presence of MIL-101(Cr) to prepare MIL-101(Cr)/FeOOH(x%) nanocomposites. Decoration of such iron oxide quantum dots on the surface of MIL-101(Cr) and investigation of its activity in photo-Fenton degradation of tetracycline (TC) antibiotic is reported here for the first time. Among the synthesized nanocomposites, MIL-101(Cr)/FeOOH(15%) demonstrated superior photo-Fenton activity in degradation of TC (80%) at short reaction time under optimum reaction condition using the energy-efficient white LED lamps as visible light source. It was observed that the synergy between any component of this photo-Fenton system such as nanocomposite, hydrogen peroxide and visible light is the main reason for enhancement of TC removal over time. Also, neither MIL-101(Cr) nor FeOOH QDs exhibited poor degradation efficiency, which implies the positive role of the coupling of these materials. Furthermore, the stability and recoverability of MIL-101(Cr)/FeOOH(15%) nanocomposite was investigated in four photo-Fenton cycles, which no significant decrease in TC degradation performance was observed.

Reclamation of real textile wastewater by sequential advanced oxidation and adsorption processes using corn-cob based materials

Wastewater management has become crucial for sustaining biological life in the near future. One of the key aspects is integration of treatment processes aiming reuse of treated water for many purposes instead of water discharge. This study focused on combining two different methods, photo-Fenton-like oxidation, and adsorption, for treatment of real textile wastewater to improve water quality to be reused for irrigation. The real textile wastewater was collected from a local plant and subjected to photo-Fenton-like oxidation and adsorption as hybrid process. The operational parameters were optimized for each step by assessing the water quality according to the domestic regulations for irrigation water. The photo-Fenton-like oxidation itself was not successful to achieve the targeted water quality for reuse whereas adsorption as an additional step made the treated water reusable in terms of organic content. But the treated water still contained a certain amount of salinity due to extreme salt usage in textile processing. It was concluded that the treated water at the end of hybrid process could be used for salinity resistant plants such as sugar beet, barley, and cotton which demonstrates a promising contribution to the circular economy for biomass.

Recycling waste iron-rich algal flocs as cost-effective biochar activator for heterogeneous Fenton-like reaction towards tetracycline degradation: Important role of iron species and moderately defective structures

Harvesting aquatic harmful algal blooms (HABs) and reusing them is a promising way for antibiotic degradation. Herein, a novel iron-rich biochar (Fe-ABC), derived from algal biomass harvested by magnetic coagulation, was successfully designed and fabricated as activator for heterogeneous Fenton-like reaction. The modification methods and pyrolysis temperatures (400-800 °C) were optimized to enhance the formation of rich iron species and moderately defective structure, yielding Fe-ABC-600 with enhanced electron transfer and H2O2 activation capability. Thus, Fe-ABC-600 exhibited superior removal efficiency (95.33%) on tetracycline (TC), where the presence of multiple iron species (Fe3+, Fe2+ and Fe4+) and moderately defective structure accelerating the Fenton-like oxidation. The concentration of leaching Fe after each reaction was all below 0.74 mg/L in five cycles, ensuring the sustained degradation. And •OH was proved to be the major radical contributing to the degradation of TC, as well as the direct electron transfer mechanism together, in which the CO acted as electron regulator and electron donor. Fe-ABC as a cost-effective catalyst has notable application potentials in TC removal from wastewater owing to its remarkable advantages of high resource utilization, enhanced catalytic property, high ecological safe, notable TC degradation efficiency, low cost and environmental-friendliness.

Floating metal phthalocyanine@polyacrylonitrile nanofibers for peroxymonosulfate activation: Synergistic photothermal effects and highly efficient flowing wastewater treatment

Highly efficient floating photocatalysis has potential applications in organic pollutant treatment but remains limited by low degradation efficiency in practical applications. By introducing the photothermal effect into a peroxymonosulfate (PMS) coupled photocatalysis system, tetracycline hydrochloride (TCH) degradation could be significantly enhanced using floating metal phthalocyanine@polyacrylonitrile (MPc@PAN) nanofiber mats. MPc@PAN nanofibers with different metal centers showed similar photothermal conversion performance but different activation energies for PMS activation, resulting in metal-center-dependent synergistic photothermal effects, i.e., light-enhanced dominated, thermal-enhanced dominated, and conjointly light-thermal dominated mechanisms. The porous structures and floating ability of the FePc@PAN nanofibers provided a fast mass transfer process, with higher solar energy utilization and superior photothermal conversion performance than the FePc nanopowders. Meanwhile, the FePc@PAN nanofibers showed excellent TCH removal stability within 10 cycles (>92%) and extremely low Fe ion leaching (<0.055 mg/L) in a dual-channel flowing wastewater treatment system. This work provides new insight into PMS activation via photothermal effects for environmental remediation.

Photo-assisted degradation of Rhodamine B by a heterogeneous Fenton-like process: performance and kinetics

This study presents the degradation of rhodamine B (RhB) by photo Fenton-like (PF-like) process under visible light irradiation (λ > 380 nm) using cobalt phosphate microparticles (CoP-MPs). The effects of the initial concentration of RhB, pH value, CoP-MPs dosage, hydrogen peroxide (H2O2) concentration, and salts found in textile wastewater (such as NaNO3, Na2SO4, and NaCl) were investigated in detail. It was found that CoP-MPs can maintain high catalytic activity with wide pH values varying from 4 to 8. This indicated that the use of CoP-MPs overcame the low efficiency of Fenton-like reaction at neutral and even weakly alkaline pH. The PF-like degradation of RhB followed pseudo-first order kinetics in various conditions. Moreover, a comparison of experimental results showed that the PF-like system has good degradation ability for RhB and methyl blue (MB) solution, but is poor for methyl orange (MO) solution. The repeat experiments indicated that the chemical structures of CoP-MPs were stable. Furthermore, the Co2+ ions leaching to the solutions were measured by an inductively coupled plasma mass spectrometer (ICP-MS). Analysis of UV-vis spectra suggested that RhB was degraded by the formation of a series of N-de-ethylated intermediates followed by cleavage of the whole conjugate chromophore structure.HighlightsRhB can be effectively degraded in the PF-like process under visible light irradiation by CoP-MPs.The PF-like process can maintain high catalytic activity at neutral and even weakly alkaline pH.Degradation kinetics exhibited pseudo-first-order kinetics and were influenced by the key parameters.The variation in the UV-vis spectra of RhB was analyzed in detail to infer a possible degradation pathway.

Efficient degradation of the refractory organic pollutant by underwater bubbling pulsed discharge plasma: performance, degradation pathway, and toxicity prediction

It is essential to develop an efficient technology for the elimination of refractory contaminants due to their high toxicity. In this study, a novel underwater bubbling pulsed discharge plasma (UBPDP) system was proposed for the degradation of Orange II (OII). The degradation performance experiments showed that by enhancing the peak voltage and pulse frequency, the degradation efficiency of OII increased gradually. The removal efficiencies under different air flow rates were close. Reducing OII concentration and solution conductivity could promote the elimination of OII. Compared with neutral and alkaline conditions, acidic condition was more beneficial to OII degradation. The active species including ·OH, ·O2-, 1O2, and hydrated electrons were all involved in OII degradation. The concentrations of O3 and H2O2 in OII solution were lower than those in deionized water. During discharge, the solution pH increased while conductivity decreased. The variation of UV-vis spectra with treatment time indicated the effective decomposition of OII. Possible degradation pathways were speculated based on LC-MS. The toxicity of intermediate products was predicted by the Toxicity Estimation Software Tool. Coexisting constituents including Cl-, SO42-, HCO3-, and humic acid had a negative effect on OII removal. Finally, the comparison with other technology depicted the advantage of the UBPDP system.

Novel Ag-bridged dual Z-scheme g-C3N4/BiOI/AgI plasmonic heterojunction: Exceptional photocatalytic activity towards tetracycline and the mechanism insight

Rational design and synthesis of highly efficient and robust photocatalysts with positive exciton splitting and interfacial charge transfer for environmental applications is critical. Herein, aiming at overcoming the common shortcomings of traditional photocatalysts such as weak photoresponsivity, rapid combination of photo-generated carriers and unstable structure, a novel Ag-bridged dual Z-scheme g-C₃N₄/BiOI/AgI plasmonic heterojunction was successfully synthesized using a facile method. Results showed that Ag-AgI nanoparticles and three-dimensional (3D) BiOI microspheres were decorated highly uniformly on the 3D porous g-C₃N₄ nanosheet, resulting in a higher specific surface area and abundant active sites. The optimized 3D porous dual Z-scheme g-C₃N₄/BiOI/Ag-AgI manifested exceptional photocatalytic degradation efficiency of tetracycline (TC) in water with approximately 91.8% degradation efficiency within 165 min, outperforming majority of the reported g-C₃N₄-based photocatalysts. Moreover, g-C₃N₄/BiOI/Ag-AgI exhibited good stability in terms of activity and structure. In-depth radical scavenging and electron paramagnetic resonance (EPR) analyses confirmed the relative contributions of various scavengers. Mechanism analysis indicated that the improved photocatalytic performance and stability were ascribed to the highly ordered 3D porous framework, fast electron transfer of dual Z-scheme heterojunction, desirable photocatalytic performance of BiOI/AgI and synergistic effect of Ag plasmas. Therefore, the 3D porous Z-scheme g-C₃N₄/BiOI/Ag-AgI heterojunction had a good prospect for applications in water remediation. The current work provides new insight and useful guidance for designing novel structural photocatalysts for environment-related applications.

TET-Yeasate: An engineered yeast whole-cell lysate-based approach for high performance tetracycline degradation

The widespread of tetracycline (TC) residues in anthropogenic and natural environments pose an immediate threat to public health. Herein, we established the TET-Yeasate, an approach based on whole-cell lysate of engineered yeast, to mitigate the TC contamination in environment. The TET-Yeasate is defined as the biological matrix of whole cell lysate from engineered yeast that containing TC-degradative components (Tet(X), NADPH, Mg2+) and protective macromolecules. The TET-Yeasate was able to efficiently eliminate TC residues in tap water (98.8%), lake water (77.6%), livestock sewage (87.3%) and pharmaceutical wastewater (35.3%) without necessity for exogenous addition of expensive cofactors. The TET-Yeasate was further developed into lyophilized form for ease of storage and delivery. The TET-Yeasate in lyophilized form efficiently removed up to 74.6% TC residue within 0.25 h. In addition, the lyophilization confers promising resilience to TET-Yeasate against adverse temperatures and pH by maintaining degradation efficacy of 85.69%-97.83%. The stability test demonstrated that the biomacromolecules in lysate served as natural protectants that exerted extensive protection on TET-Yeasate during the 14-day storage at various conditions. In addition, 5 potential degradation pathways were elaborated based on the intermediate products. Finally, the analysis indicated that TET-Yeasate enjoyed desirable bio- and eco-safety without introduction of hazardous intermediates and spread of resistance genes. To summary, the TET-Yeasate based on whole cell lysate of engineered yeast provides a cost-effective and safe alternative to efficiently remove TC residues in environment, highlighting the great potential of such whole-cell based methods in environmental decontamination.

Ultrahigh Performance H2 O2 Generation by Single-Atom Fe Catalysts with N/O Bidentate Ligand via Oxalic Acid and Oxygen Molecules Activation

Single-atom catalysts (SACs) for photocatalytic hydrogen peroxide (H2 O2 ) generation are researched but it is still challenging to obtain high H2 O2 yields. Herein, graphite carbon nitride (FeSA /CN) confined single Fe atoms with N/O coordination is prepared, and FeSA /CN shows high H2 O2 production via oxalic acid and O2 activation. Under visible light illumination, the concentration of H2 O2 generated by FeSA /CN can achieve 40.19 mM g-1 h-1 , which is 10.44 times higher than that of g-C3 N4 . The enhanced H2 O2 generation can be attributed to the formation of metal-organic complexes and rapid electron transfer. Moreover, the O2 activation of photocatalysts is revealed by 3,3',5,5'-tetramethylbenzidine oxidation. The results display that the O2 activation capacity of FeSA /CN is higher than that of g-C3 N4 , which facilitates the formation of H2 O2 . Finally, density functional theory calculation demonstrates that O2 is chemically adsorbed on Fe atomic sites. The adsorption energy of O2 is enhanced from -0.555 to -1.497 eV, and the bond length of OO is extended from 1.235 to 1.292 Å. These results exhibit that the confinement of single Fe atoms can promote O2 adsorption and activation. Finally, the photocatalytic mechanism is elaborated, which provides a deep understanding for SACs-catalyzed H2 O2 generation.

Insights into the Degradation Mechanisms of TCH by Magnetic Fe3S4/Cu2O Composite

Unique Fe₃S₄/Cu₂O composites were constructed with high Fenton-like photocatalytic activity through the impregnation coprecipitation method. The structure, morphology, optical, magnetic, and photocatalytic properties of the as-prepared composites were explored in detail. The findings suggest that small Cu₂O particles were grown on the surface of Fe₃S₄. The removal efficiency of TCH by Fe₃S₄/Cu₂O was 65.7, 4.75, and 3.67 times higher than that of pure Fe₃S₄, Cu₂O, and the Fe₃S₄ + Cu₂O mixture, respectively, when the mass ratio of Fe₃S₄ and Cu₂O was 1:1 at pH 7.2. The synergistic effect between Cu₂O and Fe₃S₄ was the main factor for TCH degradation. The Cu⁺ species from Cu₂O increased the Fe³⁺/Fe²⁺ cycle during the Fenton reaction. ^•O₂^- and h⁺ were the main active radicals; however, ^•OH and e^- played the second role in the photocatalytic degradation reaction. Moreover, the Fe₃S₄/Cu₂O composite retained good recyclability and versatility, and could be conveniently separated by a magnet.

Efficient degradation of tetracycline residues in pharmaceutical wastewater by Ni/Fe bimetallic atomic cluster composite catalysts with enhanced electron transfer pathway

Metal cluster catalysts have large atomic load, interaction between atomic sites, and wide application of catalysis. In this study, a Ni/Fe bimetallic cluster material was prepared by a simple hydrothermal method and used as an efficient catalyst to activate the degradation system of peroxymonosulfate (PMS), which showed nearly 100% tetracycline (TC) degradation performance over a wide pH range (pH = 3-11). The results of electron paramagnetic resonance test, quenching experiment and density functional theory (DFT) calculation show that the non-free radical pathway electron transfer efficiency of the catalytic system is effectively improved, and a large number of PMS are captured and activated by high density Ni atomic clusters in Ni/Fe bimetallic clusters. The degradation intermediates identified by LC/MS showed that TC was efficiently degraded into small molecules. In addition, the Ni/Fe bimetallic cluster/PMS system has excellent efficiency for degrading various organic pollutants and practical pharmaceutical wastewater. This work opens up a new way for metal atom cluster catalysts to efficiently catalyze the degradation of organic pollutants in PMS systems.

Photocatalytic O2 activation by metal-free carbon nitride nanotube for rapid reactive species generation and organic contaminants degradation

Advanced oxidation processes (AOPs) using oxygen (O₂) as an oxidant represent a low-cost and sustainable wastewater treatment process. Herein, a metal-free nanotubular carbon nitride photocatalyst (CN NT) was prepared to activate O₂ to degrade organic contaminants. The nanotube structure allowed for sufficient O₂ adsorption, while the optical and photoelectrochemical properties enabled photogenerated charge to be efficiently transferred to the adsorbed O₂ to trigger the activation process. The developed CN NT/Vis-O₂ system based on O₂ aeration degraded various organic contaminants and mineralized 40.7% of chloroquine phosphate within 100 min. In addition, the toxicity and environmental risk of treated contaminants were reduced. Mechanistic studies suggested that the enhanced O₂ adsorption capacity and fast charge transfer behavior on CN NT surface led to reactive·O₂^-, ¹O₂ and h⁺ generation, each of which played a distinct role in contaminants degradation. Importantly, the proposed process could overcome the interference from water matrices and outdoor sunlight, and the energy and chemical reagent savings reduced the operating cost to about 1.63 US$·m^-3. Altogether, this work provides insights into the potential application of metal-free photocatalysts and green O₂ activation for wastewater treatment.

The Enhancement of CO Oxidation Performance and Stability in SO2 and H2S Environment on Pd-Au/FeOX/Al2O3 Catalysts

Carbon monoxide (CO) is a colourless, odourless, and toxic gas. Long-term exposure to high concentrations of CO causes poisoning and even death; therefore, CO removal is particularly important. Current research has focused on the efficient and rapid removal of CO via low-temperature (ambient) catalytic oxidation. Gold nanoparticles are widely used catalysts for the high-efficiency removal of high concentrations of CO at ambient temperature. However, easy poisoning and inactivation due to the presence of SO₂ and H₂S affect its activity and practical application. In this study, a bimetallic catalyst, Pd-Au/FeO_x/Al₂O₃, with a Au:Pd ratio of 2:1 (wt%) was formed by adding Pd nanoparticles to a highly active Au/FeO_x/Al₂O₃ catalyst. Its analysis and characterisation proved that it has improved catalytic activity for CO oxidation and excellent stability. A total conversion of 2500 ppm of CO at -30 °C was achieved. Furthermore, at ambient temperature and a volume space velocity of 13,000 h^-1, 20,000 ppm CO was fully converted and maintained for 132 min. Density functional theory (DFT) calculations and in situ FTIR analysis revealed that Pd-Au/FeO_x/Al₂O₃ exhibited stronger resistance to SO₂ and H₂S adsorption than the Au/FeO_x/Al₂O₃ catalyst. This study provides a reference for the practical application of a CO catalyst with high performance and high environmental stability.

Tuning Band Gap in Fe-Doped g-C3N4 by Zn for Enhanced Fenton-Like Catalytic Performance

Multiple oxidation states of first-row transition-metal cations were always doped in g-C₃N₄ to enhance the catalytic activity by the synergistic action between the cations in the Fenton-like reaction. It remains a challenge for the synergistic mechanism when the stable electronic centrifugation (3d¹⁰) of Zn²⁺ was used. In this work, Zn²⁺ was facilely introduced in Fe-doped g-C₃N₄ (named xFe/yZn-CN). Compared with Fe-CN, the rate constant of the tetracycline hydrochloride (TC) degradation increased from 0.0505 to 0.0662 min^-1 for 4Fe/1Zn-CN. The catalytic performance was more outstanding than those of similar catalysts reported. The catalytic mechanism was proposed. With the introduction of Zn²⁺ in 4Fe/1Zn-CN, the atomic percent of Fe (Fe²⁺ and Fe³⁺) and the molar ratio of Fe²⁺ to Fe³⁺ at the catalyst's surface increased, where Fe²⁺ and Fe³⁺ were the active sites for adsorption and degradation. In addition, the band gap of 4Fe/1Zn-CN decreased, leading to enhanced electron transfer and conversion from Fe³⁺ to Fe²⁺. These changes resulted in the excellent catalytic performance of 4Fe/1Zn-CN. Radicals •OH, •O₂^-, and ¹O₂ formed in the reaction and took different actions under various pH values. 4Fe/1Zn-CN exhibited excellent stability after five cycles under the same conditions. These results may give a strategy for synthesizing Fenton-like catalysts.

Fabrication of layered In2S3/WS2 heterostructure for enhanced and efficient photocatalytic CO2 reduction and various paraben degradation in water

Because of the excessive use of fossil fuels, CO₂ emissions into the environment are increasing. An efficient method of converting CO₂ to useful carbonaceous products in the presence of light is one way to address the issues associated with energy and environmental remediation. In₂S₃/WS₂ heterostructure has been fabricated using the efficient hydrothermal method. The results of structural, morphological, optical, and photo/electrochemical characterization confirm the formation of a hierarchical, layered heterostructure of type-II. Enhanced photocatalytic activity is observed in InS/WS heterostructure compared to pristine In₂S₃ and WS₂. InS/WS heterostructure exhibit higher photocatalytic activity than pure In₂S₃ and WS₂. For 12 h, photocatalytic CO₂ reduction produces 213.4 and 188.6 μmol of CO and CH₄, respectively. Furthermore, the photocatalytic ability of the synthesized materials to degrade different parabens (Methyl: MPB, Ethyl: EPB, and Benzyl: BPB) under visible radiation was evaluated. Under optimized conditions, the InS/WS heterostructure degraded 88.6, 90.4, and 95.8% of EPB, BPB, and MPB, respectively, in 90 min. The mechanism of photocatalysis was discussed in detail. MCF-7 cell viability was assessed and found to exhibit low mortality in InS/WS treated MPB aqueous solution. InS/WS heterostructure could improve the fabrication of more sulphide-based layered materials to combat environmental pollution.

3D-crumpled graphitic carbon nitride achieving promoted visible-light-driven molecular oxygen activation for phenol degradation

Boosting optical absorption and charge transfer of g-C₃N₄ is of great importance but a challenging task for developing metal-free high-performance photocatalyst. Herein, 3D-crumpled g-C₃N₄ (DCN) is synthesized through a direct top-down thermal etching strategy. The thermal exfoliation of layered bulk g-C₃N₄ (BCN) in air atmosphere induces partial distortion of heptazine-based g-C₃N₄ nanosheet, which further self-assemble into 3D-crumpled network structure. Spectroscopic and photoelectrochemical characterization demonstrate that the unique DCN can not only remarkably extend the visible-light response region to 600 nm by awakening the n-π* electron transition, but also significantly promote O₂ activation for selective H₂O₂ generation owing to the intensified electron delocalization and charge transport ability. Thus, DCN catalyst realizes an excellent photocatalytic phenol degradation rate under visible light irradiation (0.690 h^-1), far (4.4-fold) out from the BCN counterparts. This work enables synergistic optimization of optical absorption, charge transport and surface-active sites by constructing a 3D-crumpled structure, which expands the engineering toolbox of metal-free skeleton photocatalyst for developing practical and economical catalysts for environmental remediation.

Unveiling the roles of dissolved organic matters derived from different biochar in biochar/persulfate system: Mechanism and toxicity

Biochar has been frequently used as a persulfate (PS) activator due to its attractive properties, but dissolved organic matter (DOM) derived from the non‑carbonized part of biochar has received less attention, not to mention its specific role and impact in biochar/PS systems. In this study, wheat straw, municipal sludge, and swine bone were selected as the representative feed stocks of biochar. Subsequently, these three types of biochar were adopted to explore the roles of DOM in biochar/PS systems. Although the composition and amount of DOM derived from different biochar were discrepant, they exhibited similar effect in biochar/PS systems. To be specific, the pore-clogging effect of DOM on biochar suppressed the adsorption capacity and catalytic performance of the three biochar. Furthermore, the removal of DOM decreased the environmental risk of these biochar/PS systems and enhanced the stability of the involved biochar. With respect to the variation in degradation mechanism, the removal of DOM increased the proportion of electron transfer pathway in unison, but the diminution in the roles of O₂^•¯ and ¹O₂ was more remarkable in bone-derived-biochar/PS systems. Additionally, the toxicity test illustrated that the leakage and accumulation of DOM were toxic to Chlorella sp., and the DOM from sludge-derived-biochar presented the highest toxicity. Overall, this study analyzes the roles of DOM derived from different biochar in biochar/PS systems and evaluates their environmental risk, which contributes to a comprehensive understanding of the fate of DOM derived from biochar.

Recent advances in application of heterogeneous electro-Fenton catalysts for degrading organic contaminants in water

Over the last decades, advanced oxidation processes (AOPs) have been widely used in surface and ground water pollution control. The heterogeneous electro-Fenton (EF) process has gained much attention due to its properties of high catalytic performance, no generation of iron sludge, and good recyclability of catalyst. As of October 2022, the cited papers and publications of EF are around 1.3 × 10^-5 and 3.4 × 10^-3 in web of science. Among the AOP techniques, the contaminant removal efficiencies by EF process are above 90% in most studies. Current reviews mainly focused on the mechanism of EF and few reviews comprehensively summarized heterogeneous catalysts and their applications in wastewater treatment. Thus, this review focuses on the current studies covering the period 2012-2022, and applications of heterogeneous catalysts in EF process. Two kinds of typical heterogeneous EF systems (the addition of solid catalysts and the functionalized cathode catalysts) and their applications for organic contaminants degradation in water are reviewed. In detail, solid catalysts, including iron minerals, iron oxide-based composites, and iron-free catalysts, are systematically described. Different functionalized cathode materials, containing Fe-based cathodes, carbonaceous-based cathodes, and heteroatom-doped cathodes, are also reviewed. Finally, emphasis and outlook are made on the future prospects and challenges of heterogeneous EF catalyst for wastewater treatments.

Visible-light-driven iron-based heterogeneous photo-Fenton catalysts for wastewater decontamination: A review of recent advances

Visible-light-driven heterogeneous photo-Fenton process has emerged as the most promising Fenton-derived technology for wastewater decontamination, owing to its prominent superiorities including the potential utilization of clean energy (solar light), and acceleration of ≡Fe(II)/≡Fe(III) dynamic cycle. As the core constituent, catalysts play a pivotal role in the photocatalytic activation of H₂O₂ to yield reactive oxidative species (ROS). To date, all types of iron-based heterogeneous photo-Fenton catalysts (Fe-HPFCs) have been extensively reported by the scientific community, and exhibited satisfactory catalytic performance towards pollutants decomposition, sometimes even exceeding the homogeneous counterparts (Fe(II)/H₂O₂). However, the relevant reviews on Fe-HPFCs, especially from the viewpoint of catalyst-self design are extremely limited. Therefore, this state-of-the-art review focuses on the available Fe-HPFCs in literatures, and gives their classification based on their self-characteristics and modification strategies for the first time. Two classes of representative Fe-HPFCs, conventional inorganic semiconductors of Fe-containing minerals and newly emerging Fe-based metal-organic frameworks (Fe-MOFs) are comprehensively summarized. Moreover, three universal strategies including (i) transition metal (TMs) doping, (ii) construction of heterojunctions with other semiconductors or plasmonic materials, and (iii) combination with supporters were proposed to tackle their inherent defects, viz., inferior light-harvesting capacity, fast recombination of photogenerated carriers, slow mass transfer and low exposure and uneven dispersion of active sites. Lastly, a critical emphasis was also made on the challenges and prospects of Fe-HPFCs in wastewater treatment, providing valuable guidance to researchers for the reasonable construction of high-performance Fe-HPFCs.

Enhanced Photo-Assisted Fenton Degradation of Antibiotics over Iron-Doped Bi-Rich Bismuth Oxybromide Photocatalyst

Herein, combining photocatalysis and Fenton oxidation, a photo-assisted Fenton system was conducted using Fe-doped Bi₄O₅Br₂ as a highly efficient photocatalyst to realize the complete degradation of Tetracycline antibiotics under visible light. It has been observed that the optimized photocatalyst 5%Fe-doped Bi₄O₅Br₂ exhibits a degradation efficiency of 100% for Tetracycline with H₂O₂ after 3 h visible-light irradiation, while a degradation percentage of 59.8% over the same photocatalyst and 46.6% over pure Bi₄O₅Br₂ were obtained without the addition of H₂O₂ (non-Fenton process). It is unambiguous that a boost photo-assisted Fenton system for the degradation of Tetracycline has been established. Based on structural analysis, it demonstrated that the Fe atoms in place of the Bi sites may result in the distortion of the local structure, which induced the occurrence of the spontaneous polarization and thus enhanced the built-in electric field. The charge separation efficiency is enhanced, and the recombination of electrons and holes is inhabited so that more charges are generated to reach the surface of the photocatalyst and therefore improve the photocatalytic degradation efficiency. Moreover, more Fe (II) sites formed on the 5%Fe-Bi₄O₅Br₂ photocatalyst and facilitated the activation of H₂O₂ to form oxidative species, which greatly enhanced the degradation efficiency of Tetracycline.

Efficient degradation of tetracycline under the conditions of high-salt and coexisting substances by magnetic CuFe2O4/g-C3N4 photo-Fenton process

For the effective degradation of tetracycline (TC), a facilely prepared magnetic CuFe₂O₄/g-C₃N₄ (CFO/g) photocatalyst was successfully constructed. The structure, morphology, composition, optical, and magnetic properties of CFO/g were characterized. CFO/g demonstrated excellent photo-Fenton performance of TC in the presence of high-Cl^-, NO₃^-, HCO₃^-, HPO₄^2-, SO₄^2- and humic acid. Ten cycles of experiments with the removal rate of TC only decreasing by 2.8% confirmed the stability and high activity of CFO/g. The dissolved concentrations of Fe and Cu ions were 0.013 and 0.009 mg L^-1, respectively. Its excellent magnetic properties made CFO/g easier to be recycled than traditional catalysts. ·OH and O₂·^- were proposed to be the main active species in the photo-Fenton system. The CFO/g heterojunction enhanced the separation of photogenerated electron-hole pairs and visible light absorption range. Furthermore, the identification of intermediates suggested that TC degradation was classified into two pathways, and the most critical and rapid degradation was achieved within the first 30 min. The TC and its intermediates did not significantly inhibit the growth activity of Escherichia coli. This research provided a promising application of magnetic photocatalysts in wastewater treatment of pharmaceuticals and personal care products.

Construction lamellar BaFe12O19/Bi3.64Mo0.36O6.55 photocatalyst for enhanced photocatalytic activity via a photo-Fenton-like Mo6+/Mo4+redox cycle

The novel BaFe₁₂O₁₉/Bi_3.64Mo_0.36O_6.55 composite materials were constructed as magnetically recyclable photo-Fenton-like degradation systems. The composite catalyst not only promoted the effective transfer of photo-generated electrons and improved the Mo⁶⁺/Mo⁴⁺ cycle consequent, but also activated hydrogen peroxide to generate oxidizing free radicals. BaFe₁₂O₁₉/Bi_3.64Mo_0.36O_6.55-0.25 exhibited an outstanding degradation performance for tetracycline hydrochloride it is 1.3 times to Bi_3.64Mo_0.36O_6.55. The thermal catalytic performance of the Bi_3.64Mo_0.36O_6.55 monomer is similar to that of the BaFe₁₂O₁₉/Bi_3.64Mo_0.36O_6.55 material without light. However, the removal rate of BaFe₁₂O₁₉/Bi_3.64Mo_0.36O_6.55 material reaches 84.5% after 60 min with light, far exceeding that of Bi_3.64Mo_0.36O_6.55 material. By way of the contrast experiment with light and without light, it is further demonstrated that interfacial interaction between BaFe₁₂O₁₉ and Bi_3.64Mo_0.36O_6.55 acted a key role in the photocatalytic reaction system. It is also a good advantage that pollutants can be efficiently degraded without adjusting the pH. The characterization of photocurrent and X-ray photoelectron spectroscopy (XPS) also further proved the synergy between the two materials, which is useful to the separation of electrons and holes. The synergy ultimately improves the degradation performance. Besides, BaFe₁₂O₁₉/Bi_3.64Mo_0.36O_6.55 can be easily separated by an external magnetic field after the photocatalytic activity reaction owing to BaFe₁₂O₁₉'s magnetic properties. It provides a new research idea for the construction and iron-based heterogeneous Fenton-like system for magnetic degradation of antibiotics.

Self-cleaning MnZn ferrite/biochar adsorbents for effective removal of tetracycline

A renewable tri-metallic spinel decorated biochar adsorbent (MZF-BC) was fabricated by a facile hydrothermal method and to remove tetracycline. The physicochemical properties of MZF-BC were well studied. MZF-BC with a hybrid pore structure of mesopores (~7.6 nm) and macropores (~50 nm) has the maximum tetracycline adsorption capacity reaching 142.4 mg g^-1. Through the study of adsorption kinetics, isotherms and key influencing factors, it was found that MZF-BC adsorption on tetracycline was primarily multi-layer effect with the initial adsorption behavior of pore filling associated with hydrogen bonding and π-π stacking. Furthermore, the MZF-BC performs excellent regeneration ability by driving Fenton-like catalysis as the self-cleaning process in the liquid phase. This study contributes to a new insight into the in-situ regeneration of biochar-based adsorbents after adsorbing organic pollutants in pharmaceutical wastewater treatment.

Adsorptive removal of Ag/Au quantum dots onto covalent organic frameworks@magnetic zeolite@arabic gum hydrogel and their catalytic microwave-Fenton oxidative degradation of Rifampicin antibiotic

Recent progress in nanotechnology via incorporation of small particle size as quantum dots (QDs) (1-10 nm) in many industrial activities and commercial products has led to significant undesired environmental impacts. Therefore, QDs removal from wastewater represents an interesting research topic with a lot of challenges for scientists and engineers nowadays. In this work, the coagulative removal of metal quantum dots as silver and gold from industrial water samples is explored. A novel biosorbent was assembled via binding of covalent organic frameworks (COFs) with magnetic zeolite and Arabic gum hydrogel (COFs@MagZ@AGH) as a promising removal material for Ag-QDs and Au-QDs. This was fully characterized by EDX, SEM, TEM, FT-IR, XPS, XRD and surface area and applied in coagulative removal of Au-QDs and Ag-QDs in presence of several experimental factors as pH, presence of other electrolytes, stirring time, initial QDs concentration, coagulant dosage, and temperature in order to optimize the removal processes. At optimum conditions, COFs@MagZ@AGH was able to recover 99.19% and 87.57% of Ag-QDs and Au-QDs QDs, respectively via chemical adsorption mechanism with perfect fitting to pseudo-second order model. Reuse of the recovered Ag/Au-QDs@COFs@MagZ@AGH as efficient catalysts in catalytic degradation of Rifampicin antibiotic (Rf) from water was additionally investigated and optimized via microwave-Fenton catalysts with excellent oxidative degradation efficiency (100%). Reusability and applicability of the biosorbent (COFs@MagZ@AGH) and catalysts (Ag/Au-QDs@COFs@MagZ@AGH) in real industrial water samples were also explored and successfully accomplished.

Solar light induced photocatalytic degradation of tetracycline in the presence of ZnO/NiFe2O4/Co3O4 as a new and highly efficient magnetically separable photocatalyst

In this study, a new solar light-driven magnetic heterogeneous photocatalyst, denoted as ZnO/NiFe₂O₄/Co₃O₄, is successfully prepared. FT-IR, XPS, XRD, VSM, DRS, FESEM, TEM, EDS, elemental mapping, and ICP analysis are accomplished for full characterization of this catalyst. FESEM and TEM analyses of the photocatalyt clearly affirm the formation of a hexagonal structure of ZnO (25–40 nm) and the cubic structure of NiFe₂O₄ and Co₃O₄ (10–25 nm). Furthermore, the HRTEM images of the photocatalyst verify some key lattice fringes related to the photocatalyt structure. These data are in very good agreement with XRD analysis results. According to the ICP analysis, the molar ratio of ZnO/NiFe₂O₄/Co₃O₄ composite is obtained to be 1:0.75:0.5. Moreover, magnetization measurements reveals that the ZnO/NiFe₂O₄/Co₃O₄ has a superparamagnetic behavior with saturation magnetization of 32.38 emu/g. UV-vis DRS analysis indicates that the photocatalyst has a boosted and strong light response. ZnO/NiFe₂O₄/Co₃O₄, with band gap energy of about 2.65 eV [estimated according to the Tauc plot of (αhν)²vs. hν], exhibits strong potential towards the efficacious degradation of tetracycline (TC) by natural solar light. It is supposed that the synergistic optical effects between ZnO, NiFe₂O₄, and Co₃O₄ species is responsible for the increased photocatalytic performance of this photocatalyst under the optimal conditions (photocatalyst dosage = 0.02 g L⁻¹, TC concentration = 30 mg L⁻¹, pH = 9, irradiation time = 20 min, and TC degradation efficiency = 98%). The kinetic study of this degradation process is evaluated and it is well-matched with the pseudo-first-order kinetics. Based on the radical quenching tests, it can be perceived that ^•O₂⁻ species and holes are the major contributors in such a process, whereas the ^•OH radicals identify to have no major participation. The application of this methodology is implemented in a facile and low-cost photocatalytic approach to easily degrade TC by using a very low amount of the photocatalyst under natural sunlight source in an air atmosphere. The convenient magnetic isolation and reuse of the photocatalyst, and almost complete mineralization of TC (based on TOC analysis), are surveyed too, which further highlights the operational application of the current method. Notably, this method has the preferred performance among the very few methods reported for the photocatalytic degradation of TC under natural sunlight. It is assumed that the achievements of this photocatalytic method have opened an avenue for sustainable environmental remediation of a broad range of contaminants.

Photo-degradation of sugar processing wastewater by copper doped bismuth oxyiodide: Assessment of treatment performance and kinetic studies

In this study, photo-Fenton-like oxidation method was evaluated for synthetic sugar industry wastewater using visible-light driven Cu-BiOI photocatalyst. Reaction conditions including initial pH, catalyst loading, initial hydrogen peroxide (H₂O₂) concentration, and temperature, were optimized. At these optimized conditions, the total saccharide concentration (TSC) and total organic carbon (TOC) removals were 56.20% and 30.67%, respectively whereas the maximum TSC and TOC removal reached up to 93.35% and 74.72% respectively by decreasing initial sucrose concentration. The kinetic study showed that the reaction order for sucrose and TOC oxidation was determined as 2 for pseudo-homogeneous power law models with respect to sucrose concentration and TOC, respectively.For heterogeneous models, Langmuir-Hinshelwood model based on the mechanism of adsorbed pollutant and oxidant on different catalytic sites was the best fit for oxidation of sucrose and other organic intermediates. According to the catalyst characterization studies, incorporation of copper was successful and Cu-BiOI possesses high photocatalytic activity accomplished by acid-assisted synthesis method.

Role of persistent free radicals and lewis acid sites in visible-light-driven wet peroxide activation by solid acid biochar catalysts - A mechanistic study

We report the synthesis of H₂SO₄-modified biochars (SBCs) as solid-acid catalysts to activate H₂O₂ at circumneutral pH under visible light radiation. Spent coffee grinds were pyrolyzed with TiO₂ at 300, 500 and 600 °C followed by steeping in 5 M H₂SO₄ and were used for the Fenton-like degradation of methyl orange (MO). The catalytic activity of SBC depended on the pyrolysis temperature and correlated well with the surface acidity and persistent free radical (PFR) concentration. Results showed that a complete MO removal and a TOC reduction of 70.2% can be achieved with SBC500 under photo-Fenton conditions. However, poisoning of the Lewis acid sites on SBC by PO₄^3- led to a dramatic decrease in the removal of MO with inhibition effects more pronounced than with radical scavengers, suggesting the key role played by acid-sites on the activation of H₂O₂. Finally, electron paramagnetic resonance (EPR) studies identified •OH as the key transient in the degradation followed by •O₂^- and ¹O₂. These findings suggest that H₂O₂ was likely adsorbed on the surface oxygenated functional groups before being decomposed by accepting electrons from the PFRs on the SBC surface.

Bimetallic FeMn@C derived from Prussian blue analogue as efficient nanozyme for glucose detection

In recent decades, nanomaterial-based artificial enzymes called nanozymes have received more and more attention and have been applied in biological, chemical, medical, and other fields. In this work, bimetallic FeMn@C was synthesized by calcination from the Prussian blue analogue. The synthesized bimetallic FeMn@C exhibits efficient peroxidase-like activity. The effect of Mn doping amount, catalytic kinetics, and mechanism of FeMn@C nanozyme was further studied in detail. The results show that the peroxidase-like activity of bimetallic FeMn@C is nearly 16 times higher than that of single-metal Fe@C. The peroxidase-like activity of FeMn@C originates from its production of radicals. Compared with natural enzymes, FeMn@C nanozyme has a better affinity for the substrates. Besides, FeMn@C nanozyme has better stability than natural enzymes. Because of its strong magnetism, FeMn@C nanozyme can be recycled easily and exhibits excellent recycling performance. Based on the good affinity of FeMn@C for H₂O₂, a rapid and selective colorimetric assay for glucose detection is constructed, with a wide linear range of 0.01-0.75 mM and low detection limit of 4.28 µM. This sensor has been successfully applied to the determination of glucose in fruit juice, showing good selectivity and accuracy. The synthesis of bimetallic FeMn@C provides a feasible way to design nanozymes with excellent catalytic activity, high stability, and easy separation.

Peroxydisulfate activation by sulfur-doped ordered mesoporous carbon: Insight into the intrinsic relationship between defects and 1O2 generation

The carbon-catalyzed persulfate-based advanced oxidation process (PS-AOP) has recently received much focus owing to the green, economical, and sustainable nature of carbon catalysts. In this study, sulfur-doped ordered mesoporous carbons (S-OMCs) were utilized to activate peroxydisulfate (PDS) for ciprofloxacin (CIP) removal. A synthesis temperature gradient was set to regulate the defect level of S-OMCs, since the thermal decomposition of oxygen- and sulfur-containing groups at different temperatures could release S and O and then create defects. In all S-OMCs/PDS systems, ¹O₂ dominated CIP degradation. Interestingly, a high linear correlation (R² = 0.9091) between defect level and ¹O₂ yield was found, confirming the structure-activity relationship between defects and ¹O₂ generation. Moreover, the impacts of several important reaction conditions and water matrix on S-OMC-1000/PDS activation system were surveyed. In the S-OMC-1000/PDS activation system, CIP removal could attain 85.84% under the condition of unadjusted pH (pH = 5.3) and small amount of S-OMC-1000 (50 mg/L). The S-OMC-1000/PDS activation system also exhibited relatively stable or even better performance in the presence of common inorganic anions and natural organic matter (NOM), manifesting its good potential for practical applications. In addition, the reusability of S-OMC-1000 was investigated. This study provides a practical and high-efficiency way for decontaminating antibiotic-polluted water, and gives an alternative approach for identifying the active site of catalysts.

Swift reduction of nitroaromatics by gold nanoparticles anchored on steam-activated carbon black via simple preparation

Gold (Au) nanoparticles supported on certain platforms display highly efficient activity on nitroaromatics reduction. In this study, steam-activated carbon black (SCB) was used as a platform to fabricate Au/SCB composites via a green and simple method for 4-nitrophenol (4-NP) reduction. The obtained Au/SCB composites exhibit efficient catalytic performance in reduction of 4-NP (rate constant k_app = 2.1925 min^-1). The effects of SCB activated under different steam temperature, Au loading amount, pH, and reaction temperature and NaBH₄ concentration were studied. The structural advantages of SCB as a platform were analyzed by various characterizations. Especially, the result of N₂ adsorption-desorption method showed that steam activating process could bring higher surface area (from 185.9689 to 249.0053 m²/g), larger pore volume (from 0.073268 to 0.165246 cm³/g), and more micropore for SCB when compared with initial CB, demonstrating the suitable of SCB for Au NP anchoring, thus promoting the catalytic activity. This work contributes to the fabrication of other supported metal nanoparticle catalysts for preparing different functional nanocomposites for different applications.

Polythionine-mediated AgNWs-AuNPs aggregation conductive network: Fabrication of molecularly imprinted electrochemiluminescence sensors for selective capture of kanamycin

A molecularly imprinted electrochemiluminescence (ECL) sensor was developed for the specific detection of kanamycin in food using silver nanowires-gold nanoparticles (AgNWs-AuNPs) as a luminophore. Polythionine (pThi), another key component of the luminescent layer, can be used as an accelerator of the coreactant and can promote the formation of the AgNWs-AuNPs conductive network. In addition, molecularly imprinted polymers (MIPs) were polymerized on the AgNWs-AuNPs/pThi conductive network, which laid the foundation for the specific capture of kanamycin. The preparation and testing conditions of the sensor were optimized, and the performance was characterized. Under optimal conditions, the ECL intensity of AgNWs-AuNPs/pThi/MIP/GCE showed a good linear relationship (R² = 0.9956) with kanamycin concentration (1 × 10^-10-1 × 10^-6 M) and a low detection limit (3.14 × 10^-11 M, S/N = 3), showing satisfactory selectivity and stability. As proof, AgNWs-AuNPs/pThi/MIP/GCE was successfully used to detect kanamycin in actual samples with satisfactory recovery (83.27-94.13%), which was in good agreement with the results of HPLC-MS/MS (82.26-95.82%). The successful preparation of AgNWs-AuNPs/pThi/MIP/GCE in this experiment provided a new pathway for designing ECL components and constructing an ultrasensitive sensing platform in the field of hazardous substance detection.

Synergistic Mechanism of Photocatalysis and Photo-Fenton by Manganese Ferrite and Graphene Nanocomposite Supported on Wood Ash with Real Sunlight Irradiation

The present research aimed to evaluate the photocatalytic activity of reduced graphene oxide and manganese ferrite nanocomposite supported on eucalyptus wood ash waste (WA) from industrial boilers, for the decolorization of methylene blue (MB) solutions, using sunlight as an irradiation source. For this, the photocatalyst named MnFe2O4-G@WA was synthesized by a solvothermal method and characterized by analyzes of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller and zeta potential. Firstly, the photocatalyst was evaluated for photocatalytic decolorization of MB under different reaction conditions. Then, the influence of pH, photocatalyst dose and H2O2 was evaluated. MnFe2O4-G@WA showed 94% of efficiency for photocatalytic decolorization of MB under operating conditions of solar irradiation, 0.25 g/L of catalyst, 300 mg/L of H2O2. The proposed degradation reaction mechanism suggested that the photodegradation of MB was through a synergistic mechanism of photocatalysis and photo-Fenton reactions, with the combined action of the three materials used. The data adjusted to the first order kinetics from the Langmuir–Hinshelwood model. In addition, MnFe2O4-G@WA showed high stability, maintaining its efficiency above 90% after 5 cycles. The results indicated that the nanophotocatalyst is a potential technology for the decolorization of MB solutions.