Efficient Heterogeneous Fenton Catalyst Research Articles

0D/2D dual Fenton α-Fe2O3/Fe-doped g-C3N4 photocatalyst and the synergistic photo-Fenton catalytic mechanism insight

A novel dual Photo-Fenton photocatalyst Fe2O3–Fe–CN with excellent Fe(III)/Fe(II) conversion efficiency and trace metal ion leaching rate has been fabricated by in-situ deposition of α-Fe2O3 quantum dots on ultrathin porous Fe-doped carbon nitride (Fe–CN) nanosheets. The iron species in Fe–CN and α-Fe2O3 QDs constitute a mutually reinforcing dual Photo-Fenton effect. The 4% Fe2O3–Fe–CN showed superior performance with kobs values 8.60 and 4.80 folders greater than pure CN and Fe–CN, respectively. The synergistic effect between α-Fe2O3 QDs and the ultrathin porous structure of Fe–CN is the primary reason for the outstanding catalytic performance exhibited by α-Fe2O3/Fe–CN. On one hand, the ultrathin porous structure of Fe–CN promotes the rapid transfer of photogenerated electrons. On the other hand, the efficient photogenerated charge separation at the α-Fe2O3/Fe–CN interface enables more photogenerated electrons to participate in the Fe3+/Fe2+ conversion and H2O2 activation. The trapping experiments demonstrate that •OH and •O2− are the primary active species in TC degradation. This work presents novel insights into the design of efficient heterogeneous Fenton catalysts for practical applications.

Carbon/iron co-product from clean hydrogen production as a tri-functional adsorbent and catalyst for efficient wastewater treatment

Clean hydrogen production via methane pyrolysis (CH4 → 2H2 + C) generates large quantities of solid carbon. Realizing their applications is a critical gap to enable its broader adoption. Here, we show that carbon nano onions encapsulated with iron cores (Fe@CNO) produced in CH4 pyrolysis using low-cost Fe ore catalysts can serve as a tri-functional adsorbent and catalyst for organic contaminant degradation. Fe@CNO has a high adsorption capacity and fast pseudo-second-order adsorption kinetics for antibiotics in wastewater. Surface oxidized Fe@CNO presents a high catalytic activity for in situ hydrogen peroxide production. Fe@CNO is also an efficient heterogeneous Fenton catalyst to degrade adsorbed antibiotics. Further, the Fe core is magnetic, enabling easy separation from solvents as reusable adsorbents and catalysts. We demonstrate that the adsorption and electro-Fenton process applies to various organic pollutants in different water matrices. This opens a new strategy for utilizing co-products from H2 production for sustainable environmental applications.

Multivalent iron-based magnetic porous biochar from peach gum polysaccharide as a heterogeneous Fenton catalyst for degradation of dye pollutants

Water contamination caused by organic dyes has become a significant concern, and catalytic degradation of dye pollutants is an effective solution. However, developing an affordable, easy-to-prepare, high-catalytic-activity, and renewable catalyst has proved challenging. The current study addresses this issue by introducing an efficient heterogeneous Fenton catalyst, known as multivalent iron-based magnetic porous biochar (mFe-MPB). This catalyst comprises multiple iron species, such as Fe3O4, γ-Fe2O3, zero-valent Fe (Fe0), and Fe3C. The mFe-MPB was easily prepared by utilizing a straightforward crosslinking-pyrolysis strategy with natural peach gum polysaccharide (PGP), which has a unique structure and composition that facilitates the creation of multivalent iron species. The mFe-MPB demonstrates high catalytic activity in the degradation of an array of dyes, including cationic dyes such as methylene blue (MB) and methyl violet (MV), as well as anionic new coccine (NC) dye. Its mass standardized rate constant value for catalytic degradation of MB can reach as high as 1.65 L min−1 g−1. Additionally, the catalyst can be easily recovered through magnetic separation and possesses remarkable structural stability, enabling several reuses without compromising its efficiency. Therefore, this study offers a viable strategy to fabricate low-cost, efficient and sustainable Fenton catalyst for removal of dye pollutants from water.

Hydrothermally treated peat/magnetite composites as highly efficient heterogeneous Fenton catalyst: Integrating multiple reaction mechanisms to enhance the catalytic reactivity for BPA removal

Although various strategies have been developed to boost the reactivity of heterogeneous Fenton catalysts, integrating multiple strategies in one catalyst to achieve high Fenton reactivity is still a challenge. To tackle this issue, the ball-milled peat and magnetite (Mag) composites were hydrothermally treated to synthesize novel heterogeneous Fenton catalyst (i.e., Mag-HTP) for bisphenol A (BPA) removal. The degradation efficiency of BPA (30 mg/L) by H2O2 (2 mmol/L) activated with 50 %Mag-HTP (0.2 g/L) was above 98% within 120 min at initial pH 3. The calculated degradation rate constant of Mag-HTP was 0.0873, which was 20.6 folds higher than that of Mag; moreover, it possessed high reactivity over a wide pH range (3–7) with low H2O2 dosage (0.5–2 mM), and high reaction stability (eight cycles with degradation rate over 95%). The multiple reactive mechanisms were validated: (1) NMR/XPS spectra, H2O2 decomposition, and HO production experiments proved the HTP as an electron donor could directly reduce Fe(III); (2) C-V curves proved the formed C-O-Fe bonds could lower the Fe(II)/Fe(III) redox potential; (3) Raman/EIS spectra, Tafel plot, and radical scavenging tests proved that HTP could serve as an electron shuttle for transferring electrons from H2O2 to Fe(III); (4) NMR spectra proved the formed C-O-C bonds on HTP could function as the dual-reaction-center in Fenton reaction. These multiple mechanisms collectively contributed to the high reactivity of Mag-HTP in the Fenton reaction. Therefore, Mag-HTP shows great potential for practical applications in wastewater treatment and soil remediation due to its cost-effectiveness, easy separation, and high Fenton reactivity.

Efficient degradation of organic contaminants via a novel iron-based poly(ionic liquid)/polydopamine composite as the heterogeneous Fenton catalyst

Iron-based poly(ionic liquid)/polydopamine composite shows excellent degradation performance for organic pollutants, providing a promising route for the design of efficient and stable heterogeneous Fenton catalysts.

Removal of water-soluble lignin model pollutants with graphene oxide loaded ironic sulfide as an efficient adsorbent and heterogeneous Fenton catalyst

Advanced oxidation processes (AOPs) have gained extensive attentions in organic decontamination in past decades. Iron-contained compound is an interesting material due to its adsorptive and catalytic performance, which has been applied widely in AOPs. Thus, graphene oxide (GO)-Fe3S4 composite was synthesized by a solvothermal process and assessed as an effective adsorptive and catalytic dual functional material in this work. The composite displayed prominent adsorptive and heterogeneous Fenton-like catalytic performance, which was affected by preparation condition and the reactive parameters in catalytic system. Under optimized reactive conditions, the GO-Fe3S4 composite yielded rapid degradation of vanillic acid, which the corresponding apparent rate constant was 1.81 × 10−1 min−1. Catalytic mechanism analysis revealed that the main oxygen species was hydroxyl radicals bounded on the surface of the composite. And the generation of •O2– was contributed to the conversion of H2O2 to •OH. The analysis of degradation intermediates of vanillic acid and p-hydroxybenzoic showed that these compounds could be mineralized to small molecules. The prominent enhanced heterogeneous Fenton-like catalytic performance of GO-Fe3S4 was due to a larger specific surface area, plenty of reductive active sites in the composite and a high mass transfer efficiency of oxidizing radicals in the reactive system.

Honeycomb-like biochar framework coupled with Fe3O4/FeS nanoparticles as efficient heterogeneous Fenton catalyst for phenol degradation

Achieving an efficient and stable heterogeneous Fenton reaction over a wide pH range is of great significance for wastewater treatment. Here, a pollen-derived biochar catalyst with a unique honeycomb-like structure, coupled with the dispersion of magnetic Fe3O4/FeS (Fe/S) nanoparticles, was synthesized by simple impregnation precursor, followed by pyrolysis. The prepared Fe/S-biochar catalyst demonstrated outstanding phenol degradation efficiency across a wide pH range, with 98% of which eliminated even under neutral conditions (pH 7.0). The high catalytic activity was due to the multilevel porous structure of pollen-derived biochar provided enough active sites and allowed for better electron transfer, then increases oxidation ability to promote the reaction. Moreover, the acid microenvironment formed by SO42− group from Fe/S composite extended the pH range for Fenton reaction, and S2− facilitated the conversion of Fe3+ to Fe2+, resulting in remarkable degradation efficiency. Further, biochar can effectively promote cycling stability by limiting Fe leaching. This work may provide a general strategy for designing 3D framework biochar-based Fe/S catalysts with excellent performance for heterogeneous Fenton reactions.

Fe@Fe2O3-loaded biochar as an efficient heterogeneous Fenton catalyst for organic pollutants removal.

With increased demand for various chemical raw materials, sudden pollution incidents are more prone to occur during their transportation and usage, threatening the environment and human health. In this study, discarded tea stalks were recycled into composite materials (FSC-X00: X represents the calcination temperature) by impregnating tea stalks in Fe2+ solution combined with subsequent calcination. X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) patterns verified the existence of Fe0 and Fe2O3, and Fe2O3 was gradually reduced to Fe0 when the calcination temperature was raised from 700 °C to 900 °C. FSC-X00 was adopted as a heterogeneous catalyst for activating H2O2 to quickly degrade phenol in the water system. The degradation experiments indicated that FSC-600 exhibited superior degradation performance for phenol (20 mg/L) within 5 min and 80% total organic carbon (TOC) removal rate at pH = 3 within 30 min. The effects of the calcination temperature, the pH value and the amount of H2O2 on the degradation efficiency were investigated. Competing experiments showed that fulvic acid (FA) and inorganic salts Na+ had little effect on the degradation performance. The FSC-600 catalyst can be reused by thermal reduction. In addition, it was found that FSC-600 has a good degradation effect on ciprofloxacin (CIP), norfloxacin (NOR) and enrofloxacin (ENR), indicating that FSC-600 catalysts are a promising candidate for quick degradation of organic pollutants by Fenton reaction. Electron paramagnetic resonance (EPR) spectra analysis indicated that •OH is the dominant reactive oxygen species (ROS) and part 1O2 from O2 also participated in the degradation. This study provides an example of creating catalysts from organic solid waste for use in emergency treatment for phenol.

Insight into enhanced Fenton-like degradation of antibiotics over CuFeO2 based nanocomposite: To improve the utilization efficiency of [rad]OH/O2[rad]- via minimizing its migration distance

In Fenton or Fenton-like processes, the key step is to catalyze H2O2 and produce highly reactive OH radicals. More efforts are then focus on designing efficient heterogeneous Fenton catalysts by activating H2O2 to generate OH at the highest possible steady state concentration. In this study, using the antibiotic ofloxacin as target organic pollutant, we firstly demonstrate a point of view for improving OH utilization efficiency by regulating surface chemical reactions to minimizing its migration distance to the target pollutant. C doped g-C3N4 incorporated CuFeO2 (CCN/CuFeO2) exhibited almost ten times higher ofloxacin degradation rate constant than our previously reported CuFeO2 {012} catalyst (0.1634 vs 0.0179 min−1). Since similar amount of OH was generated, the different inhibition effect of tert-butyl alcohol and nitrobenzene on the ofloxacin degradation confirmed that the much-enhanced ofloxacin degradation was attributed to the surface Fenton reaction process. According to XPS and EXAFS characterization, the C–O–Cu bond between g-C3N4 and CuFeO2 established a closed-circuit surface Fenton reaction mechanism. H2O2 was adsorbed and decomposed into OH/O2- over ≡Cu + site in CuFeO2. The successful construction of CCN/CuFeO2 creates a negative surface potential and benefits the enrichment of target antibiotics from water, which greatly reduces the migration distance of OH/O2•- to adjacent pollutant and then increases the OH/O2- utilization efficiency by avoiding the unwanted quenching. Hence, CCN/CuFeO2 possesses superior Fenton catalytic activity and long-term stability.

Magnetic sludge-based biochar derived from Fenton sludge as an efficient heterogeneous Fenton catalyst for degrading Methylene blue

Fenton sludge was converted into magnetic sludge-based biochar (SMBC) using a one-step pyrolysis process and employed as a novel heterogeneous catalyst to activate hydrogen peroxide (H2O2) for the oxidative removal of methylene blue (MB). The crystal structure and catalytic activity of SMBC are strongly affected by the pyrolysis temperature. X-ray powder diffraction, Mössbauer, and scanning electron microscope-energy dispersive spectrometer analyses were conducted to determine the crystal phase transfer of iron (Fe) oxides at different pyrolytic temperatures and retention times. The results revealed that the catalytic efficiency of SMBC was strongly related to the crystal phase of Fe oxides. The catalyst obtained at 800 °C for 1 h exhibited superior catalytic properties and degraded 98.56% of the MB (100 mg·L−1) in 3 min via the synergistic effect of Fe3O4, Fe0, and biochar. Free radical quenching experiments and electron paramagnetic resonance studies demonstrated that ·OH, O2·− and 1O2 participated in the H2O2 system, and·OH radicals were promptly generated owing to the catalysis of the SMBC. Aging tests were repeated for four cycles in three conditions to examine the stability of the material. The results showed that SMBC was relatively stable in non-aerated and aqueous conditions, but its activation performance was severely inhibited in an oxygen environment. Furthermore, the catalytic ability of SMBC was maintained at 88.13% after the 4th run. This study presents a cost-effective method of converting ferric sludge to an environmentally friendly catalyst that enables H2O2 activation for degrading refractory organic contaminants.

Magnetite–reduced graphene oxide nanocomposite as an efficient heterogeneous Fenton catalyst for the degradation of tetracycline antibiotics

Effective Fenton degradation of tetracycline over magnetite nanoclusters supported on reduced graphene oxide was observed.

The preparation of δ-FeOOH/γ-Al2O3 under mild conditions as an efficient heterogeneous Fenton catalyst for organic pollutants degradation

The δ-FeOOH/γ-Al2O3 composite were prepared under mild conditions by the activated alumina absorption of Fe2+ followed by rapid oxidation by H2O2. The δ-FeOOH growing on γ-Al2O3 was composed of nanoneedles, forming a 3D flower-like morphology with a diameter of ~10 nm to provide a large number of active sites. The effects of Fenton reaction conditions, such as catalyst dosage, H2O2 concentration, phenol concentration, initial pH value and temperature, on the catalytic activity of δ-FeOOH/γ-Al2O3 were investigated. Under the optimal conditions, about 97.4% of phenol and 81.6% of total organic carbon (TOC) were removed in 5 min and 2 h, respectively. In addition, with γ-Al2O3 as macroscopic size carrier (the diameter of 1–2 mm), the catalyst could be easily reused 10 runs with no significant reduction in catalytic activity. The possible mechanism was discussed, and it revealed that OH· was the main active species for degradation of phenol into intermediates and further into CO2 and H2O. The δ-FeOOH/γ-Al2O3 also showed high catalytic activity and reusability in the treatment of real industrial wastewater, making it a promising catalyst for industrial application.

Key Considerations When Assessing Novel Fenton Catalysts: Iron Oxychloride (FeOCl) as a Case Study.

Iron oxychloride (FeOCl) has been reported to be a highly efficient heterogeneous Fenton catalyst over a wide pH range. In order to determine the true catalytic performance of FeOCl, we simultaneously quantified the adsorptive and oxidative removal of formate, oxalate, and rhodamine-B (RhB) and the formation of RhB oxidation products at both pH 4.0 and 7.0. FeOCl was found to be a poor Fenton catalyst at either pH, as gauged by the oxidation of formate, oxalate, and rhodamine B and the decomposition of H2O2, in comparison with ferrihydrite (Fhy), one of the most common Fe-containing Fenton catalysts. The adsorption of target contaminants to FeOCl and homogeneous Fenton processes, induced by dissolved iron, resulted in overevaluation of the catalytic performance of FeOCl, especially for (i) the use of strongly adsorbing target compounds, without consideration of the role of adsorption in their removal and (ii) exceedingly high concentrations of H2O2 to remove trace quantities of target contaminants. Overall, this study highlights that the systematic quantification of H2O2 decomposition, target compound adsorption, and oxidation as well as the concentrations of oxidized products formed are prerequisites for unequivocal elucidation of the catalytic nature and reaction mechanism of solid Fenton catalysts.

Efficient removal of tetracycline by H2O2 activated with iron-doped biochar: Performance, mechanism, and degradation pathways

In this study, novel iron-doped biochar (Fe-BC) was produced using a simple method, and it was used as an H2O2 activator for tetracycline (TC) degradation. Generally, iron loading can improve the separation performance and reactivity of biochar (BC). In the Fe-BC/H2O2 system, 92% of the TC was removed within 30 min with the apparent rate constant (kobs) of 0.155 min−1, which was 23.85 times that in the case of the BC/H2O2 system (0.0065 min−1). The effects of the H2O2 and Fe-BC dosage, initial pH, and TC concentration on the TC removal were investigated. The radical quenching and electron paramagnetic resonance (EPR) measurements demonstrated that the removal of TC using the Fe-BC/H2O2 process involved both radical (•OH and O2−•) and non-radical pathways (1O2 and electron transfer). In addition, the performance of the catalyst was also affected by the persistent free radicals (PFRs) and defective sites on the catalyst. Moreover, the degradation pathways of TC were proposed according to the intermediate products detected by LC-MS and the ecotoxicity of intermediates was evaluated. Finally, the Fe-BC/H2O2 showed high resistance to inorganic anions and natural organic matter in aquatic environments. Overall, Fe-BC is expected to be an economic and highly efficient heterogeneous Fenton catalyst for removing the organic contaminants in wastewater.

MoS2/FeS Nanocomposite Catalyst for Efficient Fenton Reaction.

Nanocomposites containing FeS as catalyst and MoS2 as cocatalyst have been synthesized toward efficient heterogeneous Fenton reaction. The deposition of FeS nanoparticles in situ on the surface of MoS2 nanosheets creates strong contact between the two components and generates a large number of exposed Mo6+ sites and sulfur vacancies, which contribute to the enhanced degradation rate by accelerating Fe3+/Fe2+ cycling and ensuring rapid electron transfer. In addition, the MoS2/FeS nanocomposite catalysts exhibit the best performance at near-neutral conditions (pH 6.5), which solves the challenges in conventional Fenton reactions such as leaching of metal ions, the formation of iron slurry, and the need of adjusting solution pH. Further, the nanocomposite can maintain high efficiency after many recycling experiments. It is believed that the MoS2/FeS nanocomposite represents an efficient heterogeneous Fenton catalyst that can greatly promote the performance of advanced oxidation processes (AOPs) for solving practical environmental issues.

Green synthesis of magnetic mesoporous carbon from waste-lignin and its application as an efficient heterogeneous Fenton catalyst

Various pretreatment strategies have been widely employed for the removal of lignin and made great progress in the utilization of cellulose from lignocellulosic biomass. However, how to make full use of the lignin component is still a great challenge. In this work, a novel magnetic mesoporous carbon (MMC, Fe3O4@mesoporous carbon) was successfully fabricated using waste-lignin and FeCl3 as precursors. The chemical/physical properties of MMC samples were systematically characterized by various characterization techniques. The mesoporous structure of MMC with average pore size of 3.86 nm and specific surface area of 138 m2/g was further confirmed by Brunauer-Emmet-Teller (BET) analysis. The saturation magnetization values of MMC samples increased from 7.28 to 36.55 emu/g with the increase of FeCl3 dosage. MMC also showed superior reusability in recycling experiments. The catalytic mechanism was revealed through reactive oxygen species quenching experiments and the generation of hydroxyl radicals (•OH) was further identified by electron paramagnetic resonance spectroscopy. This work provides a green and sustainable strategy for the fabrication of high-performance heterogeneous Fenton catalyst as well as all-round utilization of waste lignin.

Adsorption and heterogeneous Fenton catalytic performance for magnetic Fe3O4/reduced graphene oxide aerogel

Heterogeneous Fenton system has been widely used in water treatment because of its effective degradability in a wide range of pH. A two-step hydrothermal method for the synthesis of Fe3O4/reduced graphene oxide (RGO) aerogel was designed as an efficient and recyclable heterogeneous Fenton catalyst for degradation of methylene blue (MB). Firstly, the Fe3O4 colloidal solution was synthesized by hydrothermal progress. Secondly, graphene oxide hydrogels were formed by the self-assembling and reduced to graphene during the hydrothermal reaction. Meanwhile, zero-dimensional Fe3O4 nanoparticles were anchored onto the graphene oxide through the colloidal coagulation effect. The obtained samples were characterized by XRD, SEM, TEM, BET, Zeta, XPS, Raman, TG, and VSM. Adsorption isotherm and kinetics of MB onto Fe3O4/RGO composites revealed that the maximum adsorption capacity was 163.83 mg/g, and the adsorption process confirmed to the pseudo-second-order model. The determinants of heterogeneous Fenton system including oxidant concentration, initial pH, and reaction mechanism were investigated. The studies indicated that MB degradation efficiencies increased with the initial pH increasing (pH 3–10), showing a complete degradation in alkaline condition within 60 min. It is due to that catalytic reaction mainly occurs on the solid–liquid interface, as pH values increase, the electrostatic attraction between the cationic MB molecules and the surface of Fe3O4/RGO increases, the enhancement of adsorptivity is helpful to improve catalytic activity. The catalyst can be easily recovered by an applied magnetic field and exhibited excellent stability after five degradation cycles.

Cobalt doped iron oxychloride as efficient heterogeneous Fenton catalyst for degradation of paracetamol and phenacetin

Cobalt doped iron oxychloride (Co-FeOCl) was synthesized and employed as catalyst in Fenton degradation of paracetamol (APAP) and phenacetin (PNCT) for the first time. The catalytic performance was evaluated by means of various parameters including catalyst load, hydrogen peroxide (H2O2) dose and pH value. The high removal of APAP (87.5%) and PNCT (76.0%) was obtained under conditions of 0.2 g/L Co-FeOCl and 0.5 mM H2O2 at pH 7.0, with calculated pseudo-first order kinetic constants of 0.031 min−1 for APAP and 0.023 min−1 for PNCT. Particularly, quenching tests and in situ electron spin resonance (ESR) tests were employed for the identification of the reactive oxygen species (ROS) in system. Hydroxyl radical (·OH) and superoxide radical (O2−·) were the primary ROS in Co-FeOCl/H2O2 system. A possible mechanism for H2O2 activation by Co-FeOCl catalyst was proposed as well. Finally, the formation of typical disinfection by-products (DBPs) decreased slightly in Co-FeOCl/H2O2 pre-oxidation. However, stability and reusability of Co-FeOCl were deactivated in the consecutive three cycles.

Modified Fe-Rich Palygorskite as an Efficient and Low-Cost Heterogeneous Fenton Catalyst for NOx and SO2 Removal

In this paper, the entire removal process was based on a cycle absorption system which primary-absorber was used to scrubbing SO2 by urea, then NO and SO2 residual could be oxidized by the vaporize...

Fe3O4@S-doped ZnO: A magnetic, recoverable, and reusable Fenton-like catalyst for efficient degradation of ofloxacin under alkaline conditions

In this study, an efficient and reusable heterogeneous Fenton catalyst Fe3O4@S-doped ZnO magnetic composite was synthesized for the degradation of ofloxacin (OFX) under alkaline conditions without external energy input. The Fe3O4@S-doped ZnO exhibited excellent catalytic activity toward ofloxacin degradation within 120 min. Using 0.25 g/L of catalyst and 5.0 mL/L of H2O2 under optimized conditions, the catalyst was effective in pH values ranging from 5.2 to 9.0. The catalytic performance at optimal conditions was in accordance with a pseudo-first-order kinetics model. The reaction constant of Fe3O4@S-doped ZnO (0.0354 min−1) was three times than that of Fe3O4@ZnO (0.0124 min−1) under alkaline conditions (pH 8.2). The reactive oxygen species were the ·OH and O2·-, with ·OH dominating in the degradation of OFX. It is proposed that the catalyst acts as a Lewis acid, creating an acidic microenvironment on the catalyst's surface and widening the pH range of the Fenton reaction to alkaline conditions. Additionally, the catalyst was stable and reusable after six cycles of use. The Fenton-like Fe3O4@S-doped ZnO catalyst overcomes the problem of the narrow pH of the reaction system, thus providing promising environmental applications.