photo-Fenton Degradation Research Articles

Partially oxidized mackinawite/biochar for photo-Fenton organic contaminant removal: Synergistically improve interfacial electron transfer and H2O2 activation

Immobilizing Fe-based nanoparticles on electron-rich biochar has becoming an attractive heterogeneous Fenton-like catalysts (Fe/BC) for wastewater decontamination. However, the insufficient graphitization of biochar causing low electron transfer and by slow H2O2 activation limited its application. Herein, we firstly constructed FeS/biochar composite through all-solid molten salt method (Fe/MSBCs), which can provide strong polarization force and liquid reaction environment to improve carbonization. As expected, the obtained Fe/MSBCs exhibits high surface area and fast interfacial electron transfer between FeS and biochar. More importantly, the partially oxidized FeS (001) facet facilitate H2O2 adsorption and thermodynamically easily decomposition into •OH. Such a synergistic effect endowed them excellent photo-Fenton degradation performance for methyl orange (MO) with large kinetic rate constants (0.079 min−1) and high H2O2 utilization efficiency (95.9%). This study first demonstrated the critical regulatory role of molten salt method in iron-based biochar composites, which provide an alternative for H2O2 activator in water pollutant control.

Enhanced photo-Fenton degradation of dyes under visible light with recyclable γ-Fe2O3/CQDs: Catalyst preparation, performance and mechanism insight

A low band gap and visible light-responsive heterogeneous Photo-Fenton catalyst of γ-Fe2O3/CQDs micron composite was prepared under the one-pot hydrothermal method. The Photo-Fenton degradation of γ-Fe2O3/CQDs towards dye solution of rhodamine B(RhB), methyl blue (MB), and methyl orange (MO) was studied comparatively with α-Fe2O3. The γ-Fe2O3/CQDs exhibited remarkable catalytic performance for various dyes and with a first-order rate (k) of 14 times higher than that of initial α-Fe2O3 with a low concentration of H2O2 of 0.049 mmol. L−1 and a wider pH range of 3.1–7.1. The microstructure of the compounds was observed by XRD, SEM, TEM, FT-IR, and XPS characterization results suggested that the γ-Fe2O3/CQDs nanocomposite was formed through the stable Fe–O–C bonds, thus, the band gap decreased, and it is more favorable for the distance of holes and electrons. The free radical trapping experiment and EPR analysis indicated that •OH and 1O2 were the major active species during the typical photo-Fenton reaction. What's more, the γ-Fe2O3/CQDs also exhibited good stability and magnetic properties. DFT conclusion shows that the mechanism of the potential determination step (PDS) on α-Fe2O3(220) is the cleavage of H2O2 with an energy barrier of only 0.08 eV, which is 0.54 eV lower than that of OH* on γ-Fe2O3(220). Thus it can be deemed that γ-Fe2O3/CQDs perform much higher catalytic activity for the dissociation of H2O2 than α-Fe2O3. This work gives a feasible and economical countermeasure of visible light Photo-Fenton dispose of dye wastewater with a recyclable magnetic γ-Fe2O3/CQDs micron catalyst.

Effect of different salt precursors on zinc ferrite synthesis and their photo-Fenton activity

Polycrystalline and mesocrystalline zinc ferrite were successfully fabricated via a solvo-thermal method using different salt precursors. This study found that when iron sulfate salt was used as a precursor, polycrystalline zinc ferrite was formed. Polycrystalline zinc ferrite is a well-dispersed 400-nm sphere solid particle. Primary nano-crystals have highly preferred orientations; however, defects exist among the particles. When iron chloride salt was used as a substitute as a prime material, mesocrystalline zinc ferrite was synthesised. The products are shaped as hollow-spheres with an average size of approximately 500 nm and are composed of nano-crystal sub-units aligned in a highly oriented crystallographic structure. Zinc ferrite mesocrystalline samples have many voids, and the inter-spaces of their structure indicate the high porosity hollow-sphere architecture of zinc ferrite. The experimental results show that specific adsorption of Cl− and SO42− ions on the surface plays a crucial role during the growth process of products with different morphologies and crystallographic structures. Cl− adsorption on the surface may promote the formation of mesocrystal hollow-sphere particles; whereas, SO42− gives rise to polycrystalline solid spheres. The use of the as-prepared products as catalysts for the photo-Fenton degradation of Rhodamine B (RhB) with an H2O2 oxidant under visible-light irradiation and the effects of reaction conditions, including pH, catalyst amount and H2O2 contratentation on the removal of RhB, were investigated. The reuse of the catalysts and a possible catalytic mechanism were also proposed. These results indicate that mesocrystalline hollow-sphere zinc ferrite is a favourable catalyst for dye degradation photo-Fenton processes.

Broad Spectral Response FeOOH/BiO2-x Photocatalyst with Efficient Charge Transfer for Enhanced Photo-Fenton Synergistic Catalytic Activity.

In this work, to promote the separation of photogenerated carriers, prevent the catalyst from photo-corrosion, and improve the photo-Fenton synergistic degradation of organic pollutants, the coating structure of FeOOH/BiO2-x rich in oxygen vacancies was successfully synthesized by a facile and environmentally friendly two-step process of hydrothermal and chemical deposition. Through a series of degradation activity tests of synthesized materials under different conditions, it was found that FeOOH/BiO2-x demonstrated outstanding organic pollutant degradation activity under visible and near-infrared light when hydrogen peroxide was added. After 90 min of reaction under photo-Fenton conditions, the degradation rate of Methylene Blue by FeOOH/BiO2-x was 87.4%, significantly higher than the degradation efficiency under photocatalysis (60.3%) and Fenton (49.0%) conditions. The apparent rate constants of FeOOH/BiO2-x under photo-Fenton conditions were 2.33 times and 3.32 times higher than photocatalysis and Fenton catalysis, respectively. The amorphous FeOOH was tightly coated on the layered BiO2-x, which significantly increased the specific surface area and the number of active sites of the composites, and facilitated the improvement of the separation efficiency of the photogenerated carriers and the prevention of photo-corrosion of BiO2-x. The analysis of the mechanism of photo-Fenton synergistic degradation clarified that ·OH, h+, and ·O2- are the main active substances involved in the degradation of pollutants. The optimal degradation conditions were the addition of the FeOOH/BiO2-x composite catalyst loaded with 20% Fe at a concentration of 0.5 g/L, the addition of hydrogen peroxide at a concentration of 8 mM, and an initial pH of 4. This outstanding catalytic system offers a fresh approach to the creation and processing of iron-based photo-Fenton catalysts by quickly and efficiently degrading various organic contaminants.

Synthesis of ferrihydrite/polyaniline composite using waste Fe(III)/EPS-cultures with polyaniline and its application for tetracycline photo-Fenton degradation

Antibiotics pollutants are arousing seriously environmental issues, so the highly efficient photo-Fenton catalysts have been developed in their treatments. In this work, according to the results of XRD, Raman, FTIR, and XPS, ferrihydrite/polyaniline (Fh/PANI) catalyst could be successfully prepared in waste iron-bacterial cultures (shorted as Fe(III)/EPS-solutions) with PANI conductor ((C6H7N)n, 200–300 nm). The Fh/PANI was an optimal photo-Fenton catalyst with good physical properties for tetracycline hydrochloride (TCH, C22H25ClN2O8) degradation. In photo-Fenton systems with 30 mmol/L H2O2, 40 mg/L TCH, 0.2 g/L catalyst, and pH 4.0 under the visible light irradiation, degradation efficiency was 94% for Fh/PANI (82% for Fh). Kinetics data of TCH degradation well followed to pseudo-first-order model (R2=0.974 for Fh/PANI, and R2=0.929 for Fh). The Fh/PANI catalyst had a good stability for TCH degradation, and the efficiencies ranged in 94%−77% within its five runs. The TCH could be efficiently mineralized into H2O and CO2 inorganic molecules, and the producing ∙O2− was the key action group. These results indicate Fh/PANI photo-Fenton catalyst will have a potential application in treating antibiotic polluted waters. It also can provide a good approach of preparing Fe-(oxyhydr)oxide/conductor composites in waste iron-bacterial cultures.

Fabrication of (H2PO4−, Ni2+) – α-Fe2O3/Bi2S3 heterojunction photocatalysts with improved visible-light catalytic activity

In this work, the (H2PO4−, Ni2+) – α-Fe2O3(PNF) with abundant oxygen vacancies (OVs) was synthesized, and PNF/Bi2S3 heterojunction photocatalysts were then prepared by hydrothermal process. The obtained PNF showed higher photo-Fenton degradation activity. In comparison with PNF and Bi2S3, the prepared PNF/Bi2S3 composites significantly improved the photocatalytic degradation of p-nitrophenol (p-NP) under visible-light illumination. The production of active species was accelerated in the composite system through the synergistic effect of OVs, heterojunction, and photo-Fenton, resulting in high p-NP degradation efficiency. The PNF/B-2 composite exhibited the highest photocatalytic-Fenton degradation activity, which could be used as a high-performance visible-light-driven photocatalyst for the degradation of difficult-to-degrade pollutants.

Bismuth-doped lanthanum ferrite perovskites: A promising approach for enhancing photo-Fenton degradation of organic dye pollutants

Fabrication of efficient perovskite photo-Fenton catalytic systems is recognized as an effective strategy for clean water production. However, modifying perovskite catalysts effectively remains a formidable challenge. In this study, we prepared Bi-doped LaFeO3 photo-Fenton catalysts using a facile microwave-assisted method. Various characterization techniques confirmed the successful formation of these Bi-doped LaFeO3 perovskite materials. The photo-Fenton activity of the Bi-doped LaFeO3 perovskite materials with varying Bi content was assessed by monitoring the degradation of methylene blue (MB) dye solution. Remarkably, the optimized Bi-doped LaFeO3 (referred to as LBFO3) catalyst achieved approximately 93.64% degradation of MB within 100 min of visible light exposure, demonstrating exceptional efficacy in treating wastewater containing organic dye pollutants. The enhanced photocatalytic activity of the LBFO3 perovskite materials arises from the incorporation of Bi, leading to an expanded optical absorption range, increased specific surface area, and enhanced separation and migration of photo-generated carriers. Importantly, the LBFO3 photo-Fenton system exhibited remarkable stability during four successive cycling treatments, indicating promising practical applications. Additionally, quenching experiments were conducted to elucidate electron transfer in the LBFO3 catalyst related to the photo-Fenton degradation mechanism of MB. This study might pave the way toward designing novel perovskite based photo-Fenton systems for highly efficient degradation of waterborne contaminants.

Simple synthesis of floating Fe2O3/Luffa catalysts for the photo-Fenton degradation of methyl orange at near neutral pH

Although widely used in the textile industry, methyl orange is considered one of the most toxic dyes, which have negative impacts on the aquatic environment and needs to be removed from water bodies. Hence, the present paper reports the synthesis of new floating photo-Fenton catalysts based on the immobilization of Fe2O3 nanoparticles on the surface of Luffa sponges for the oxalate-induced-degradation of methyl orange. The floating catalytic sponges were prepared through a simple precipitation method followed by a reflux heating process and then characterized by field emission scanning electron microscopy, X-ray diffraction, atomic absorption spectrometry, and nitrogen adsorption-desorption experiments. According to the experimental results, methyl orange was effectively degraded over our floating catalytic sponges underlight illumination at near neutral pH. The catalytic activity was also found to be enhanced with the increase in crystallinity of Fe2O3 nanoparticles, which can be achieved by the reflux heating. Besides, owing to the floating feature, these sponges are easily separated from the solution, thereby not forming a secondary source of pollution for water

Oxygen vacancies in Z-scheme r-MIL-88A/OV-BiOBr heterojunctions enhance photo-Fenton degradation of chloroquine phosphate: Mechanisms insight, DFT calculations, degradation pathways and toxicity assessment

A low cycle of Fe2+/Fe3+, additional H2O2 use, and low mineralization efficiency have limited the wide application of Fe-MOFs. Herein, a novel Z-scheme r-MIL-88A/OV-BiOBr composites (OV-BM) with oxygen vacancies (OV) were fabricated by polyvinylpyrrolidone/ethylene glycol solvothermal method. The optimal OV-BM-25 showed the highest degradation efficiency of 97.8 % for chloroquine phosphate (CQ) by initiating H2O2 under LED visible light irradiation within 60 min. The presence of oxygen vacancies enhanced the electron/hole separation in OV-BM composites and the electron transfer from OV-BiOBr to r-MIL-88A, driving Fe2+/Fe3+ cycling and in-situ H2O2 generation. Quenching experiments and EPR analysis demonstrated that O2–, 1O2, and e– were the main active species, inducing deamination, decarbonization, and cleavage of ring structures in CQ. The possible decomposition pathways of CQ and the ecotoxicity of intermediates were evaluated through UPLC-MS and QSAR analysis. This study provides a theoretical basis for developing Fe-MOFs-based heterojunctions photocatalysts in a Z-scheme photo-Fenton system to treat CQ-bearing organic wastewater.

Photo-Fenton efficient degradation of organic pollutants over S-scheme ZnO@NH2-MIL-88B heterojunction established for electron transfer channel

Combining photocatalysts with Fenton technology can improve the catalytic properties of materials and achieve efficient degradation of organic pollutants. However, preparing low-cost catalysts using simple methods remains a challenge. This paper selected a more environmentally friendly and cost-effective semiconductor material, zinc oxide, for the modification of NH2-MIL-88B and prepared a new S-scheme heterojunction photo-Fenton catalyst ZnO@NH2-MIL-88B (ZMFe-x) by a simple solvothermal method. Moreover, the Zn-O-Fe bonds that were formed between the interfaces enabled a fast channel for the photoelectron transport that was created by photoexcitation from the ZnO conduction band to the NH2-MIL-88B valence band. This allowed the ZMFe-x catalysts to have better removal performance for organic pollutants in the photo-Fenton reaction. The dominating role of hydroxyl radicals in the degradation procedure was determined by ESR analysis and free radical trapping experiments, and the degradation mechanisms and pathway of contaminants were predicted by intermediate analysis and DFT calculations. This study provides a stable and effective new strategy for preparing MOFs catalysts for removing various pollutants.

Facile introduction of coordinative Fe into oxygen-enriched graphite carbon nitride for efficient photo-Fenton degradation of tetracycline

Tetracycline (TC) antibiotics have been widely used over the past decades, and their massive discharge led to serious water pollution. Photo-Fenton process has gained ever-increasing attention for its excellent oxidizing ability and friendly solar energy utilization ability in TC polluted water treatment. This work introduced coordinative Fe into oxygen-enriched graphite carbon nitride (OCN) to form FeOCN composites for efficient photo-Fenton process. Hemin was chosen as the source to provide the source of coordinative Fe-Nx groups. The degradation efficiency of TC reached 82.1 % within 40 min of irradiation, and remained 76.9 % after five runs of reaction. The degradation intermediates of TC were detected and the possible degradation pathways were gained. It was found that h+, OH, and O2− played major roles in TC degradation. Notably, the photo-Fenton performance of FeOCN was stable in highly saline water or strong acid/base environment (pH 3.0–9.0). Besides, H2O2 can be generated in-situ in this photo-Fenton process, which is favorable for practical application. It can be anticipated that the coordinative FeOCN composites will promote the application of photo-Fenton oxidation process in TC polluted water treatment.

Exploiting a dosage model to enhance Photo‐Fenton process performance

The performance of Photo-Fenton treatments is reported to heavily rely on how hydrogen peroxide is supplied. Rigorously optimizing the dosage profile of hydrogen profile is a challenge that has been hardly addressed. Although some model-based approaches have been explored, solutions of practical significance have not been produced. However, model-based approaches can be used to explore new dosage schemes and identify practical sub-optimal improvements. This work addressed the photo-Fenton degradation of Paracetamol (PCT) in an annular photoreactor, and used a kinetic model including variable H2O2 dosage previously fit and reported for simulating new dosage schemes for unexplored operational conditions. Preliminary results allowed understanding trends and proposing new simulations, which in turn allowed identifying promising operation alternatives. Finally, experimental validation confirmed that significant reduction of TOC levels (20 percent points, beyond 80%) are possible. Furthermore, alternatives that could reach total mineralization were also identified for larger processing times (beyond 20 h). Thus, the work has once again demonstrated that model exploitation allows producing significant practical outcomes with a much-reduced experimental effort, and has produced unexplored hydrogen peroxide dosage schemes that increase the process performance reported previously and indicates the way to total mineralization.

A new perspective for Dissolved Organic Matter in water potabilization: Exploitation before removal

The Dissolved Organic matter (DOM) has been demonstrated to contribute to water self-cleaning and waste-derived substances similar to DOM have already been tested as Fe(III) complexants to degrade compounds of emerging concern (CECs) via photo-Fenton process at pH 5–6. On the other sideDOM has to be removed during natural water potabilization because it negatively affects taste and smell and yields toxic disinfection by-products. In the present work, the DOM exploitation before removal has been explored for the first time. In particular, DOM has been developed as an iron complexing agent for the photo-Fenton degradation of caffeine (taken as representative CEC) in water matrix. The effect of pH, DOM concentration and Fe(II) concentration on the process has been studied. The formation of DOM-Fe(III) complexes has been demonstrated through potentiometric and fluorescence measurements. Promising results for caffeine degradation have been obtained, also when applying the method to a riverine water sample.

Mechanistic insights and DFT analysis of bimetal doped styrofoam-like LaFeO3 perovskites with in-built dual redox couples for enhanced Photo-Fenton degradation of Tetracycline

The rising number of contaminants released into the environment and the inadequacies of traditional wastewater treatment techniques have led to the demand for enhanced oxidation technologies like photo-Fenton. In this study, bimetal co-doped lanthanum orthoferrite (BixLa1-xCuyFe1-yO3 (x = 0, 0.01, 0.05, 0.1; y = 0, 0.01, 0.05, 0.1, 0.15)) based photo-Fenton catalysts with the in-built redox couples Fe3+/Fe2+, Cu2+/Cu+ and oxygen vacancies have been successfully synthesised via a facile one-pot solution combustion route. Systematic studies show that the Bi0.05La0.95Cu0.1Fe0.9O3 (LFOBC) exhibits an optimal photo-Fenton degradation rate of 0.0497/min for Tetracycline (TC) removal, being ∼ 1.8 and ∼ 6.2 times greater than Bi0.05La0.95FeO3 (LFOB) and pristine LaFeO3 (LFO) respectively. DFT analysis confirmed the better adsorption and dissociation of H2O2 on a bimetal co-doped catalyst and identified the electron density difference in LFOBC, which can induce the H2O2 dissociation. A detailed investigation of various influencing reaction parameters is explored. The degradation pathway for the LFOBC catalyst with the toxicological characteristics of each intermediate is analysed. This study presents the Bi0.05La0.95Cu0.1Fe0.9O3 as a potential photocatalyst for enhanced photo-Fenton degradation with excellent efficiency observed for the degradation of various harmful pollutants for environmental remediation.

Additive manufacturing of hollow connected networks for solar photo-Fenton-like catalysis.

A 3D-printing approach is used to fabricate green bodies/precursor microarchitectures that, upon annealing, allow the fabrication of hierarchical 3D hollow microarchitectures (3DHMs). The 3DHMs are composed mainly of TiO2 and inorganic stabilizers that enable the production of inorganic cellular units upon thermal annealing at 650 °C. Morphological inspection reveals that the 3D architecture beams comprise TiO2 nanoparticles (NPs). The inner and outer diameters of the hollow beams are ∼80 μm and ∼150 μm, retained throughout the 3D hollow network. A proof-of-concept photo-Fenton reaction is assessed. The 3DHMs are impregnated with α-Fe2O3 NPs to evaluate solar photo-Fenton degradation of organic compounds, such as MB used as control and acetaminophen, an organic pollutant. The optical, structural, and chemical environment characteristics, alongside scavenger analysis, generate insights into the proposed solar photo-Fenton degradation reaction over TiO2 3DHMs loaded with α-Fe2O3. Our work demonstrates newly hollow printed microarchitecture with interconnected networks, which can help direct catalytic reactions.

Cobalt-doped LaFeO3 for photo-Fenton degradation of organic pollutants and visible-light-assisted water splitting

Cobalt-doped LaFeO3 for photo-Fenton degradation of organic pollutants and visible-light-assisted water splitting

Boosting the catalytic activity of nanostructured ZnFe2O4 spinels incorporating with Cu2+ for photo-Fenton degradation under visible light

Boosting the catalytic activity of nanostructured ZnFe2O4 spinels incorporating with Cu2+ for photo-Fenton degradation under visible light

In-situ production and activation of H2O2 over hydroxyapatite modified CuFeO2 for self-sufficient heterogeneous photo-Fenton degradation of doxycycline hydrochloride

The self-sufficient heterogeneous photo-Fenton (SH-PF) system was constructed for doxycycline hydrochloride (DOH) degradation with hydroxyapatite (Hap) modified CuFeO2 (Hap/CuFeO2) composites through H2O2 in-situ production. The modification of Hap could improve the specific surface area, visible-light response, light conversion efficiency, photoelectron lifetime and oxygen vacancies (OVs) of CuFeO2, which was conducive to H2O2 production and DOH degradation in SH-PF system. Notably, Hap/CuFeO2 fabricated with 0.5 g Hap (Hap/CuFeO2-0.5) displayed more superior performance for DOH degradation compared to other synthesized catalysts. The Hap/CuFeO2-0.5 load and initial solution pH for DOH degradation in SH-PF system were optimized, and the Hap/CuFeO2-0.5 had good reusability and stability. The •OH was the main active species for DOH degradation, and the facilitation effect of •O2– and photoelectrons on DOH degradation was associated with the H2O2 production in the present work. In addition, the capture of photogenerated holes suppressed the recombination of photogenerated carriers, elevating the production of photoelectrons and thereby enhancing H2O2 production and DOH degradation. The degradation pathways for DOH were proposed and the comprehensive toxicities of DOH were relieved after degradation in SH-PF system.

Synthesis of NFO-immobilized yeast nanobiocomposite for ultrasound-assisted photo-fenton degradation of methylene blue by using central composite design

In this study, we synthesized nano-NiFe2O4-immobilized Saccharomyces cerevisiae yeast composites (NFO-SC) and investigated their photo-deterioration efficiency for methylene blue (MB) using central composite design (CCD). The morphological features of NFO-SC were comprehensively characterized through scanning electron microscopy (SEM), UV–VIS spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Initial XRD analysis of pristine NFO indicated an average particle size of 20 nm. Subsequent XRD, FTIR, SEM, and UV–VIS analyses were performed before and after immobilization, confirming the surface modification of yeast cells by NFO. The XRD results for NFO-SC revealed a reduced average particle size of nickel nano-ferrite (NFO) to 14 nm. The NiFe2O4-SC composite exhibited an impressive 99% MB deterioration efficiency under optimized conditions: 0.020 g of NFO-SC dosage, pH 4.5, initial MB concentration of 20 mg/L, and a photo-irradiation time of 120 min. Photo-catalytic activity was evaluated through UV–VIS spectroscopy and FTIR analysis, demonstrating that the NiFe2O4-SC composite outperformed pristine yeast and pure NFO in MB degradation efficiency. This study highlights the potential of the NiFe2O4-SC composite as an photo-catalyst for dye degradation, showcasing its promise for applications in environmental remediation processes.

Highly dispersed Fe/SnS2/kaolinite composite for the enhanced photo-Fenton degradation of tetracycline hydrochloride

A novel Fe/SnS2/kaolinite (Fe/SK) composite photocatalyst was successfully prepared herein to degrade tetracycline hydrochloride (TCH) in a photo-Fenton system. 5%Fe/SK-20% achieved the best TCH degradation efficiency in the photo-Fenton system within 60 min (80.38%), which was considerably higher than that achieved using pure SnS2 (31.46%). The introduction of the kaolinite carrier increased the dispersion of SnS2 particles and exposed more reactive sites, while Fe doping improved the energy band structure of SnS2 and enhanced electron transfer. Furthermore, photogenerated e− promoted the Fe2+/Fe3+ redox cycle, which facilitated the continuous and efficient activation of H2O2. Liquid chromatography–mass spectrometry was employed to identify the intermediate products and propose the possible pathway for TCH degradation. Free-radical trapping experiment and electron paramagnetic resonance revealed that •OH was the primary active substance in the 5%Fe/SK-20%/visible (vis)/H2O2 system, while h+ and •O2− were the auxiliary substances. In addition to TCH, 5%Fe/SK-20% exhibited excellent degradation efficiency for various organic pollutants, such as oxytetracycline hydrochloride, chlortetracycline hydrochloride, rhodamine B, and methyl orange, in the vis/H2O2 system. This study provides new insights into the efficient decontamination of antibiotic wastewater by kaolinite-based photocatalysts in a photo-Fenton system.