Heterogeneous Fenton-like Catalyst Research Articles

Magnetic CuFe2O4 Prepared by Polymeric Precursor Method as a Reusable Heterogeneous Fenton-like Catalyst for the Efficient Removal of Methylene Blue

The heterogeneous Fenton-like catalysts based on CuFe2O4 were prepared by polymeric precursor method at several annealing temperatures. The obtained catalysts were respectively characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, point of zero charge measurement, and vibrating sample magnetometer. The Fenton-like catalytic activity was evaluated via the oxidation of methylene blue with H2O2. The results show that the CuFe2O4 phase content and the particle size increase with the annealing temperatures whereas the surface OH groups and the surface acidity decrease. The prepared powders possess typical ferromagnetic properties which allow them to be easily recovered and reused. These catalysts also present highly catalytic activities for the oxidation of methylene blue, which is principally attributed to the catalysis of the CuFe2O4 phase. When the annealing temperature increased, the catalytic performance was reduced, corresponding to the increase of particle size and the decrease of surface OH groups.

Iron encapsulated in boron and nitrogen codoped carbon nanotubes as synergistic catalysts for Fenton-like reaction

Iron nanoparticles (NPs) encapsulated in B, N-codoped carbon nanotubes (Fe@C-BN) as heterogeneous Fenton-like catalysts were obtained by a simple and scalable pyrolysis method, and their performances were examined in the oxidative degradation of various organics in the presence of the different oxidants. The results showed that organic dyes can be effectively degraded by Fe@C-BN in the presence of peroxymonosulfate. Calcination temperature and mass of iron salt significantly affected the structures and performances of the catalysts. The effects of several reaction conditions, such as initial dye concentration, oxidant type (peroxymonosulfate, peroxydisulfate, and H2O2) and dosage, initial pH, inorganic anions, reaction temperature and dye types on oxidation as well as the stability of the composite were extensively evaluated in view of the practical applications. Through the investigation of reaction processes, HO· and SO4·− radicals were identified using quenching experiments. Owing to the synergistic effects between the iron NPs and B, N-doped carbon, Fe@C-BN catalysts intrinsically display an excellent catalytic activity for Fenton-like reaction. This study gives new insights into the design and preparation of iron NPs encapsulated in B, N-codoped carbon nanotubes as an effective strategy to enhance the overall catalytic activity.

Precursor chain length dependence of polymeric precursor method for the preparation of magnetic Fenton-like CuFe2O4-based catalysts

Heterogeneous Fenton-like catalysts based on CuFe2O4 were prepared by polymeric precursor method, using various polyhydroxy alcohols as polymeric agents: ethylene glycol, diethylene glycol and triethylene glycol. These catalysts were, respectively, characterized by XRD, SEM, pHPZC and VSM measurements. All catalysts showed typical ferromagnetic properties and highly catalytic activities for the degradation of methylene blue. When the chain length of polyhydroxy alcohols increased, the pHPZC value and particle size of these catalysts were not significantly modified, whereas the percentage of CuFe2O4 tetragonal spinel phase decreased, leading to the decline of catalytic activity and the reduction in coercive field.

Ionothermal synthesis of Fe3O4 magnetic nanoparticles as efficient heterogeneous Fenton-like catalysts for degradation of organic pollutants with H2O2

Fe3O4 magnetic nanoparticles (MNPs) are attractive heterogeneous Fenton-like catalysts for oxidative degradation of organic pollutants with H2O2. Herein highly efficient and stable Fe3O4 MNPs (Fe3O4-op-DES, ca. 10nm) were successfully prepared via a novel oxidative precipitation-combined ionothermal synthesis, which comprised oxidative precipitation of FeSO4·7H2O in choline chloride:2urea deep eutectic solvent. Among five different Fe3O4 particles tested, Fe3O4-op-DES MNPs exhibited the highest catalytic activity with the activation energy of 47.6kJmol−1 for degradation of Rhodamine B (RhB) with H2O2 under the same conditions (Fe3O4 dosage of 0.50gL−1, H2O2 concentration of 40mmolL−1, pH 6.4, 55°C, 2h). Fe3O4-op-DES MNPs were magnetically recoverable, and had good catalytic stability and recyclability without the need of regeneration (>98% degradation efficiency of RhB in 2h and pseudo-first-order rate constant of 0.0376min−1 after having been continuously running for 12h). The superior catalytic performance of Fe3O4-op-DES MNPs was attributed to the combination of multiple technologically important features, including the nanometer size, high Fe2+ content, large surface area, high density of surface active sites and stable crystal structure (no phase transformation, negligible iron leaching and particle aggregation after reaction). The wide applicability of Fe3O4-op-DES MNPs was also demonstrated by the degradation of four other organic pollutants.

Fe3O4@β-CD nanocomposite as heterogeneous Fenton-like catalyst for enhanced degradation of 4-chlorophenol (4-CP)

The magnetic Fe3O4@β-cyclodextrin (β-CD) nanocomposites were fabricated via Fe ions and β-CD in one pot and characterized as a heterogeneous Fenton-like catalyst that may be used for the degradation of 4-chlorophenol (4-CP). The catalytic capacity of Fe3O4@β-CD was evaluated on the basis of various parameters, including pH, H2O2 concentration and catalyst loading, with regards to the pseudo-first-order kinetics of 4-CP degradation. In addition, iron leaching, the effect of radical scavengers and reusability of the Fe3O4@β-CD nanocomposite were also studied. The results showed that Fe3O4@β-CD exhibited a higher catalytic ability than that Fe3O4 toward 4-CP degradation, the observed rate constants (kobs) were 0.0373min−1 for Fe3O4@β-CD, and 0.0162min−1 for Fe3O4, which may be ascribed to the construction of a ternary complex (Fe2+–β-CD–pollutant) that allowed the produced hydroxyl radicals (·OH) to directly attack the contaminant and simultaneously enhanced the solubility of the organic pollutant. Fe3O4@β-CD also exhibited an enhancement effect for chlorobenzene (CB) degradation with the kobs of 0.0392min−1 (kobs=0.0099min−1 for Fe3O4), which may be due to a synergistic effect in the Fe3O4@β-CD composite. Furthermore, Fe3O4@β-CD has an excellent catalytic activity, stable mechanical strength and adequate reusability. A possible reaction pathway of 4-CP degradation dominated by ·OH was proposed according to analyses of the degradation intermediates and chloride ions. The host-guest interaction between β-CD and 4-CP were examined with density functional theory (DFT) calculations, expounding the unicity of degraded intermediate owing to the specific spatial selectivity of β-CD. The findings of this study provide a novel material used in the Fenton-like process for the degradation of contaminants.

A comparative study of a series of ferrite nanoparticles as heterogeneous catalysts for phenol removal at neutral pH

This study aimed at understanding and assessing the effect of structural specifications on catalytic properties of several ferrite nanoparticles as the heterogeneous Fenton-like catalysts. Thus, a number of synthetic M-ferrite (where M = Zn, Mn, Fe and Cu) catalysts were compared for efficiency against phenol removal in the presence of hydrogen peroxide. It was found that the copper ferrite is more active than the other studied ferrites for phenol elimination at neutral pH. The effect of pH was studied in pH values of 3, 6, and 10, while the highest phenol removal rate over the Cu-ferrite catalyst was observed at pH 6. Studying the effect of different parameters and catalyst properties on the reaction rate suggested that the hydroxyl radical generation is not the only factor to control the reaction rate, but the roles of surface adsorption of the pollutants and the catalyst specifications are also significant. Besides, in agreement with the previous reports, it was concluded that the number of surface active sites is related to the number of surface hydroxyl groups, which results in the higher surface adsorption and hydrogen peroxide activation.

Modeling and kinetics study of Bisphenol A (BPA) degradation over an FeOCl/SiO2 Fenton-like catalyst

A heterogeneous Fenton-like catalyst was used for the oxidation of Bisphenol A (BPA), which is a typical endocrine disruptor. A simple semi-empirical kinetic equation was developed to define the effects of experimental conditions (initial concentration of H2O2, initial concentration of BPA, temperature and the catalyst loading) on the reaction rate. The plausible pathway of the degradation process was proposed. A pseudo-first-order reaction rate expression with respect to BPA concentration was developed to fit all data for these experiments, and the equation of kobs (observed rate constant) was obtained with the apparent activation energy of 42.2kJ/mol. In order to reduce the operational cost, the values of parameters (temperature, initial concentration of H2O2 and pH) that optimize the catalytic performance were studied by means of a response surface methodology. Finally, a plausible mechanism was proposed on the basis of kinetics and optimization studies, which illustrates the reaction process and optimization in a microscopic view.

Yerba Mate Tea Extract: a Green Approach for the Synthesis of Silica Supported Iron Nanoparticles for Dye Degradation

This work describes a green approach to the synthesis of iron nanoparticles supported in silica using tea extract of the South American plant yerba mate (Ilex paraguariensis). Catalysts with different iron contents were obtained according to the reaction conditions employed. Characterization by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) revealed the amorphous nature of the nanoparticles, tentatively ascribed to iron(II)/iron(III) oxide composites, as Fourier transform infrared (FTIR) and thermogravimetric analyses confirmed their functionalization by the tea polyphenolic compounds. For the sake of comparison, crystalline zero-valent iron nanoparticles were prepared by the classical method using NaBH4. Both materials were tested in the degradation of methyl orange and led to complete decolourization; the green nanoparticles were very active as heterogeneous Fenton-like catalysts in presence of hydrogen peroxide, while the nanoparticles prepared with NaBH4 were efficient in the reductive degradation of the dye.

Heterogeneous Fenton-like discoloration of methyl orange using Fe3O4/MWCNTs as catalyst: process optimization by response surface methodology

Fe3O4/MWCNTs nanocomposites were prepared by chemical oxidation coprecipitation method and developed as highly efficient heterogeneous Fenton-like catalyst. XRD results revealed that Fe3O4 nanoparticles deposited onto MWCNTs surface remained the inverse spinel crystal structure of cubic Fe3O4 phase. The FTIR characteristic peaks of MWCNTs weakened or disappeared due to the anchor of Fe3O4 nanoparticles and Fe–O peak at 570 cm–1 was indicative of the formation of Fe3O4. TEM observation revealed that Fe3O4 nanoparticles were tightly anchored by MWCNTs. The Fenton-like catalytic activity of Fe3O4/MWCNTs nanocomposites for the discoloration of methyl orange (MO) was much higher than that of Fe3O4 nanoparticles. The process optimization of this heterogeneous Fenton-like system was implemented by response surface methodology (RSM). The optimum conditions for MO discoloration were determined to be of 12.3 mmol/L H2O2 concentration, 2.9 g/L catalyst dosage, solution pH 2.7 and 39.3 min reaction time, with the maximum predicted value for MO discoloration ratio of 101.85%. The corresponding experimental value under the identical conditions was obtained as 99.86%, which was very close to the predicted one with the absolute deviation of 1.99%.

Efficient removal of dye from an aqueous phase using activated carbon supported ferrihydrite as heterogeneous Fenton-like catalyst under assistance of microwave irradiation

Ferrihydrite (Fh) stabilized inside porous activated carbon (Fh/AC) was prepared and used as a heterogeneous Fenton-like catalyst for oxidative degradation of methyl orange (MO) in simulated dye wastewater. The prepared catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and N2 adsorption–desorption isotherm. It was found that ferrihydrite was highly dispersed on the surface of pretreated AC and the as-prepared Fh/AC exhibited catalytic activity for degradation of MO in the Fenton-like system consisting of solid catalyst, hydrogen peroxide (H2O2) and MO solution. With the assistance of microwave (MW) irradiation, the degradation efficiency of MO was significantly enhanced, indicating a synergetic effect of MW and Fenton-like system. The initial pH value of MO solution exerted notable influence on the reaction and acidic condition is more favorable to the degradation of MO. The recyclability of the catalyst was also evaluated by successive batch experiments under optimum conditions.

Iron-glutamate-silicotungstate ternary complex as highly active heterogeneous Fenton-like catalyst for 4-chlorophenol degradation

A novel iron-glutamate-silicotungstate ternary complex (FeIIIGluSiW) was synthesized from ferric chloride (FeIII), glutamic acid (Glu), and silicotungstic acid (SiW), and used as a heterogeneous Fenton-like catalyst for 4-chlorophenol (4-CP) degradation at neutral pH value. The prepared FeIIIGluSiW was characterized using inductively coupled plasma atomic emission spectroscopy, thermogravimetry, Fourier-transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, X-ray diffraction, and field-emission scanning electron microscopy. The results showed that FeIIIGluSiW has the formula [Fe(C5H8NO4)(H2O)]2SiW12O40·13H2O, with glutamate moiety and Keggin-structured SiW12O404– heteropolyanion. The catalyst showed high catalytic activity in 4-CP degradation in the dark and under irradiation. Under the conditions of 4-CP 100 mg/L, FeIIIGluSiW 1.0 g/L, H2O2 20 mmol/L, and pH = 6.5, 4-CP was completely decomposed in 40 min in the dark and in 15 min under irradiation. When the reaction time was prolonged to 2 h, the corresponding total organic carbon removals under dark and irradiated conditions were ca. 27% and 72%, respectively. The high catalytic activity of FeIIIGluSiW is resulted from hydrogen bonding of H2O2 on the FeIIIGluSiW surface. The enhanced degradation of 4-CP under irradiation arises from simultaneous oxidation of 4-CP through Fenton-like and photocatalytic processes respectively catalyzed by ferric iron and the SiW12O404– hetropolyanion in FeIIIGluSiW.

One-step solvothermal synthesis of magnetic Fe3O4–graphite composite for Fenton-like degradation of levofloxacin

ABSTRACTA novel Fe3O4–graphite composite was prepared, characterized, and investigated as a heterogeneous Fenton-like catalyst for the degradation of levofloxacin (LEV) in an aqueous solution. The results revealed that the Fe3O4–graphite composite exhibited excellent properties for the degradation and mineralization of LEV, achieving a nearly complete degradation of 50 mg L−1 LEV in 15 min and 48% of total organic carbon removal in 60 min under optimal conditions. A large electronic conjugation structure exists in graphite, which may lead to the fast production of •OH radical species because of the easy reduction of Fe(III) to Fe(II). In addition, we observed that the graphite can degrade LEV in the presence of H2O2. Therefore, the synergistic results of the graphite structure and Fe3O4 magnetic nanoparticles (MNPs) may contribute to the high catalytic activity of the Fe3O4–graphite composite. Compared with pure Fe3O4 MNPs, lesser iron leaching of the Fe3O4–graphite composite was observed during the degradation of LEV. The degradation efficiency of LEV remained approximately 80% at the fifth recycling run, which indicates that the Fe3O4–graphite composite has potential applications in water treatment for removing organic pollutants.

Effect of iron–manganese–sepiolite as heterogeneous Fenton-like catalyst on the performance and microbial community of anaerobic granular sludge treatment system

Both short-term and long-term exposure experiments have been carried out to investigate the influence of iron (Fe)–manganese (Mn)–sepiolite, as a heterogeneous Fenton-like catalyst, on the performance and microbial community of anaerobic granular sludge. During the short-term exposure experiments, chemical oxygen demand (COD) removal efficiency decreased from 73.1% to 64.1% with the presence of 100mg/L of catalyst. However, long-term exposure to the catalyst did not significantly affect the COD removal efficiency (81.8%) as compared to the control (83.5%). Meanwhile, the absorption peaks of coenzyme F420 in extracellular polymeric substances (EPS) of sludge samples were remarkable by excitation–emission matrix (EEM) fluorescence spectra. After long-term exposure, the presence of the catalyst increased secretions of EPS from 83.7mg/g VSS to 89.1mg/g VSS. Further investigations with high throughput sequencing indicated that the abundance of Methanosaeta increased from 57.7% to 70.4% after long-term exposure. In bacterial communities, Proteobacteria, Firmicutes, and Synergistetes were predominant.

Gaseous elemental mercury removal through heterogeneous Fenton-like processes using novel magnetically separable Cu0.3Fe2.7−xTixO4 catalysts

A series of novel magnetic Cu0.3Fe2.7−xTixO4 composites was synthesized and used as recyclable heterogeneous Fenton-like catalysts for gaseous elemental mercury (Hg0) removal from simulated flue gases. The technique of inductively coupled plasma-atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM), and X-ray photoelectron spectrometry (XPS) were used, and Brunauer Emmett Teller (BET) analysis was achieved to determine the chemical composition, pore structure, and surface chemistry of the catalysts. The performance of heterogeneous Fenton-like reactions for Hg0 removal was investigated in a bench-scale bubbling reactor under neutral condition. Some main parameters such as Cu/Ti ratio in the catalysts, H2O2 concentration, solution pH, and gas flow were systematically studied to establish optimal reaction conditions. The effects of SO2 and NO on Hg0 removal were also analyzed. Vibrating sample magnetometer (VSM) analysis suggested the Cu0.3Fe2.7−xTixO4 catalysts can be manipulated by an external magnetic field, and have potential advantages in terms of separation and recovery. Hg0 removal remained efficient after five repeated experiments with only a slight decrease. Electron spin resonance (ESR) was applied to confirm the active hydroxyl radical (OH) generated during heterogeneous Fenton-like reactions.

Degradation of nitrobenzene by Fenton-like reaction in a H2O2/schwertmannite system

In this study, schwertmannite was used as heterogeneous Fenton-like catalyst for nitrobenzene degradation in a closed batch system. The properties of catalyst samples were characterized by measuring the specific area (SBET), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The catalytic activity was evaluated in view of the effect of various conditions (initial pH value, catalyst dosage, H2O2 concentration). The results showed that the removal efficiency of nitrobenzene was significantly enhanced in the presence of schwertmannite and the catalyst retained almost its high catalytic activity after 5 consecutive runs. The optimum pH value in this study was found to be 3.0 and the optimal concentration of H2O2 was 500mg/l. The removal of the nitrobenzene could be achieved 92.5% in 30min at initial conditions. The mechanism of catalytic oxidation was radical mechanism via the catalysis of schwertmannite to form hydroxyl radicals by decomposing H2O2. In addition, nitrophenols were the main transformation products detected by liquid chromatography and mass spectrometric (LC/MS).

Fenton-Like Oxidation of 4-Chlorophenol: Homogeneous or Heterogeneous?

Heterogeneous Fenton-like catalysts have received considerable research attention because they could potentially be attractive for oxidative removal of organic contaminants from tertiary wastewater. However, process design is still hampered by insufficient understanding of the chemical pathways involved, and especially whether oxidation activity stems from heterogeneous surface chemistry or minute concentrations of dissolved metal ions in the homogeneous phase. Using inductively coupled plasma-optical emission spectroscopy (ICP-OES) in combination with pH monitoring and ultraviolet–visible spectroscopy (UV–vis) we have monitored the degradation of 4-chlorophenol (4-CP) over two Fenton-like heterogeneous systems, namely FeOx supported on TiO2 and CuFe2O4. We show conclusively that these systems proceed predominantly through a homogeneous route via dissolved metal ions from the solid phase catalysts. Control experiments with homogeneous Fe3+ or Cu2+ systems reveal that even minute concentrations (μM/subppm) of dissolved metal ions leached from the solid phases account for the observed 4-CP degradation rates in the heterogeneous systems. ICP-OES revealed that metal leaching was time-dependent and variable because of pH variations associated with changing acid release rates. Buffering solutions at pH 7.4 suppressed metal leaching (and hence 4-CP degradation) in the FeOx/TiO2 system, but not in others. For example, pH buffering did not entirely suppress metal leaching from CuFe2O4, for which 4-CP degradation was retained through small concentrations of Fe and Cu ions in solution. Our results highlight the importance of careful monitoring of metal content in the aqueous phase, certainly with analytical sensitivity below ppm concentrations of the dissolved metals, and also the crucial influence of time-dependent pH variations on the reaction process. Recyclability of catalysts, pH buffering of solutions or monitoring of metal content in the solid phase by less sensitive analytical methods, for example, chemical analysis, gravimetry, X-ray fluorescence, or energy dispersive X-ray analysis in electron microscopes, cannot exclude the homogeneous Fenton route in the presence of solid catalysts.

Capsule-Like Fe3O4 Nanoparticles and Triangle Fe3O4 Nanoplates: Facile Synthesis, Magnetic Properties and Catalytic Performance

In this work, Fe 3 O 4 with nanosized triangle plates and capsule-like nanoparticles were prepared by solvothermal approach ( Fe 3 O 4- S ) and hydrothermal approach ( Fe 3 O 4- H ), respectively and their catalytic performance as a heterogeneous Fenton-like catalyst are investigated. Excellent ferromagnetic properties are obtained in both Fe 3 O 4- S nanoplates and Fe 3 O 4- H nanoparticles. The Fe 3 O 4- S nanoplates exhibited better catalytic performance than Fe 3 O 4- H nanoparticles in the degradation of Rhodamine B ( RhB ) with hydrogen peroxide. The relatively high catalytic activity of Fe 3 O 4- S can be ascribed to its high specific surface area and high degree of crystallinity. Fe 3 O 4- S nanoplates also exhibit good catalytic stability and reusability and do not generate significant loss of catalytic activity after four cycles of degradation.

Fenton-like degradation of Methylene Blue using paper mill sludge-derived magnetically separable heterogeneous catalyst: Characterization and mechanism

For the paper industry, the disposal and management of the yielded sludge are a considerable challenge. In our work, the paper mill sludge-derived magnetically separable heterogeneous catalyst (PMS-Fe-380) was prepared easily through a facile synthesis method. The morphology and structure of PMS-Fe-380 were fully characterized by means of X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmet–Teller analysis. The catalytic activity of PMS-Fe-380 was evaluated by degradation of Methylene Blue (MB). The reusability and stability of PMS-Fe-380 were evaluated in five repeated runs, which suggested that PMS-Fe-380 manifested excellent stability of catalytic activity. Moreover, leaching tests indicated that the leached iron is negligible (<0.5mg/L). This study provides an alternative environmentally friendly reuse method for paper mill sludge and a novel catalyst PMS-Fe-380 that can be considered as a promising heterogeneous Fenton-like catalyst.

Degradation of 2,4,6-trichlorophenol using magnetic nanoscaled Fe3O4/CeO2 composite as a heterogeneous Fenton-like catalyst

The degradation of 2,4,6-trichlorophenol (TCP) was investigated by using magnetic nanoscaled Fe3O4/CeO2 composite as a heterogeneous Fenton-like catalyst. The individual and interactive effects of four process variables, i.e. solution pH, initial TCP concentration, Fe3O4/CeO2 dosage and H2O2 concentration, on TCP removal, mineralization and dechlorination were investigated by response surface methodology (RSM) using the central composite design (CCD). The optimal regions of degradative conditions were pH 2.0–2.1, TCP 20–100mg/L, Fe3O4/CeO2 1.5–2.5g/L, and H2O2 17–30mM. The removal efficiency, mineralization and dechlorination rate of TCP was 99%, 65% and 95% after 90min, respectively under the conditions of pH 2.0, TCP 100mg/L, Fe3O4/CeO2 2.5g/L and H2O2 30mM, which agreed well with the modeling prediction. Fe3O4/CeO2 showed a high catalytic ability for the removal of TCP in comparison with other processes. The recyclability of Fe3O4/CeO2 was also examined. According to the results of iron leaching, the effects of radical scavengers and intermediates determination, a possible pathway of TCP degradation was proposed based on OH mechanism (including free OH in the bulk liquid and surface-bounded OH).

Effectiveness and Mechanisms of Fenton-like Si-FeOOH/H2O2 in 2,4-Dichlorophenol Wastewater Treatment

This research measured the effectiveness of Si-FeOOH as a type of heterogeneous Fenton-like catalyst made from alkaline precipitation methods, in catalyzing the degradation of 2,4-dichlorophenol (2,4-DCP) wastewater. Factors including catalyst dosage, pH, and hydrogen peroxide dosage were investigated, showing: with an initial concentration of 2,4-dichlorophenol at 100 mg/L, a dosage of catalyst at 0.1 g/L, a dosage of H2O2 at 1.5 ml/L, pH at 5 and indoors temperature at 25 ± 1 °C, the degradation rate of 2,4-dichlorophenol, CODCr and TOC has reached 94.21%, 83.67%, and 76.11%, separately. Comparisons were made with FeOOH used as catalyst, showing that Fenton-like Si-FeOOH is a better catalyst than FeOOH.