Heterogeneous Fenton-like Catalyst Research Articles

Engineering of a wafer-shaped titanium-based catalyst of TiO2/MIL-125(Ti)@Ti3C2 for enhanced Fenton-like degradation of Congo red: Optimization, mechanistic study, and reusability

A titanium-based Fenton-like heterogeneous catalyst was synthesized from titanium dioxide (TiO2), MIL-125(Ti), and Ti3C2 MXene for degrading the notorious Congo red (CR). The successful combination of the titanium components was assured by bountiful characterization apparatuses. Optimization of the finest conditions of the Fenton-like degradation of CR dye was performed by studying the impact of the pH and temperature of the catalytic system, the dosage of TiO2/MIL-125(Ti)@Ti3C2, the concentrations of hydrogen peroxide (H2O2) and CR, and the mass ratio between the catalyst’s components. A kinetic study was executed on the degradation of CR and H2O2 during a reaction time of 60 min using First-order and Second-order models. The degradation pathway of CR by TiO2/MIL-125(Ti)@Ti3C2 was investigated by the scavenging test. Additionally, Adsorption and catalytic degradation mechanisms were resumed using X-Ray Photoelectron Spectroscopy (XPS) analysis. The cycling test proceeded on TiO2/MIL-125(Ti)@Ti3C2 for five succeeding Fenton-like degradation runs of CR dye. Ultimately, the Ti-based heterogeneous catalyst exhibited superior adsorption and Fenton-like degradation performances toward the anionic dye with a good recyclability feature.

Anchoring highly dispersed FeCo/C nanoparticles within zeolite 13X to promote 1O2 generation in the degradation of tetracycline hydrochloride

This paper reports the preparation of a FeCo/C@13X catalyst derived from FeCo/ZIF using Na-13X molecular sieves as substrates through the ion-exchange method, followed by in situ FeCo/ZIF growth and a carbonization step. Compared with FeCo/ZIF@13X and Co/C@13X, FeCo/C@13X exhibited an improved peroxymonosulfate (PMS) activation effect owing to the well-dispersed FeCo sites embedded in the carbon@13X matrix, as confirmed by high-resolution transmission electron microscopy, Fourier transform infrared spectra and X-ray diffraction. The cobalt loading in the FeCo/C@13X catalysts was up to 15.32 wt% as determined by ICP-OES. FeCo/C@13X, prepared by the introduction of organic Fe and calcining FeCo/ZIF@13X, exhibited good reusability and stability, viz. 92 % degradation efficiency after five cycles compared to 84 % of Co/C@13X and 79 % of FeCo/ZIF@13X. The FeCo/C@13X/PMS system was highly stable over a wide pH range and showed excellent tolerance for background substances in aqueous environments because of non-radical-dominated degradation. Quenching experiments and electron paramagnetic resonance analysis demonstrated that singlet oxygen (1O2) primarily facilitated the tetracycline hydrochloride (TCH) removal during the FeCo/C@13X catalytic process. The electron transfer and free radicals (SO4∙−, ∙OH, and O2∙−) were engaged in the TCH degradation. Through electrochemical measurements and in situ Raman spectroscopy, electrons were rapidly transferred from FeCo/C@13X to PMS, consuming HSO5− to generate metastable active species (FeCo/C@13X-PMS* complexes), which can efficiently accelerate the cycling of Fe3+/Co3+ to Fe2+/Co2+ and enhance 1O2 production. This study provides a suitable method for designing heterogeneous Fenton-like catalysts with high and stable catalytic performances for the continuous production of 1O2.

Development of a γ-Al2O3-Based Heterogeneous Fenton-like Catalyst and Its Application in the Advanced Treatment of Maotai-Flavored Baijiu Wastewater

Heterogeneous Fenton technology was employed for the advanced treatment of Maotai-flavored Baijiu wastewater. Novel catalysts were prepared by loading different active ingredients (Mn, Fe, and Cu) on γ-Al2O3 using an impregnation method. The effects of active ingredient, reaction time, initial pH, H2O2 dosage, catalyst dosage, and other factors on the reaction were examined. The properties of the new catalysts were analyzed using BET analysis, XPS, and SEM. Moreover, the mechanisms of Fenton-like oxidation and its reaction kinetics were explored through experiments and analyses including GC–MS and intermediate active species scavenging by tertiary butyl alcohol (TBA) and/or para-benzoquinone. The results revealed that the most effective removal of organic matter was achieved with a Mn-Fe/Al (2:1 wt%) catalyst dosage of 30 g/100 g water, pH of 5.0, H2O2 dosage of 0.3 g/L, and reaction time of 60 min; the effluent COD value was 12 ± 1 mg/L, and the degradation rate was 65.7 ± 3%, approximately 14% higher than that of the conventional Fenton catalyst under similar conditions; moreover, the catalytic efficacy remained high after seven cycles. Kinetic analysis indicated that the heterogeneous Fenton oxidation reaction followed a third-order kinetics model, with R2 = 0.9923 and K = 0.0006 min−1.

Boosting the Ni(II)-EDTA decomplexation and Ni(II) immobilization in a heterogeneous Fenton-like system with L-cysteine functionalized zero-valent iron

The remarkable stability and detrimental environmental impacts of nickel(II)-ethylenediaminetetraacetic acid (Ni(II)-EDTA) complexes originated from electroplating effluents have sparked a growing curiosity about their efficient remediation. In this study, L-cysteine functionalized zero-valent iron (C-ZVIbm) was synthesized via a ball-milling method and employed as a heterogeneous Fenton-like catalyst to decomplex Ni(II)-EDTA and immobilize Ni(II) from wastewater. The results demonstrated that the pseudo-second-order kinetic rate constant (2.096 L·mol−1·min−1) for EDTA degradation in the C-ZVIbm/H2O2 system was 123.3 times that in the ZVIbm/H2O2 system (0.017 L·mol−1·min−1). The incorporation of L-cysteine onto the surface of ZVI significantly enhanced the H2O2 activation, reactive oxygen species (OH, O2−, and 1O2) generation, and the sequential Ni(II)-EDTA decomplexation and EDTA degradation. The results of capture experiments revealed that 1O2 played a crucial role in the degradation of EDTA in the C-ZVIbm/H2O2 system. The optimization of the experimental variables indicated that the degradation of EDTA and the reduction/adsorption of Ni(II) were antagonistic in the C-ZVIbm/H2O2 system, resulting in an efficient reduction/immobilization of Ni(II) and an inhibition of EDTA degradation at a higher dosage of C-ZVIbm. Our findings provide new insights into the promising heterogeneous Fenton-like process that enables the decomplexation of Ni(II)-EDTA, the degradation of EDTA, and the synchronous immobilization of Ni(II).

Higher efficiency of vanadate iron in heterogeneous Fenton-like systems to pretreat sugarcane bagasse and its enzymatic saccharification.

Pretreatment is crucial for effective enzymatic saccharification of lignocellulose such as sugarcane bagasse (SCB). In the present study, SCB was pretreated with five kinds of heterogeneous Fenton-like systems (HFSs), respectively, in which α-FeOOH, α-Fe2O3, Fe3O4, and FeS2 worked as four traditional heterogeneous Fenton-like catalysts (HFCs), while FeVO4 worked as a novel HFC. The enzymatic reducing sugar conversion rate was then compared among SCB after different heterogeneous Fenton-like pretreatments (HFPs), and the optimal HFS and pretreatment conditions were determined. The mechanism underlying the difference in saccharification efficiency was elucidated by analyzing the composition and morphology of SCB. Moreover, the ion dissolution characteristics, variation of pH and Eh values, H2O2 and hydroxyl radical (·OH) concentration of FeVO4 and α-Fe2O3 HFSs were compared. The results revealed that the sugar conversion rate of SCB pretreated with FeVO4 HFS reached up to 58.25%, which was obviously higher than that under other HFPs. In addition, the surface morphology and composition of the pretreated SCB with FeVO4 HFS were more conducive to enzymatic saccharification. Compared with α-Fe2O3, FeVO4 could utilize H2O2 more efficiently, since the dissolved Fe3+ and V5+ can both react with H2O2 to produce more ·OH, resulting in a higher hemicellulose and lignin removal rate and a higher enzymatic sugar conversion rate. It can be concluded that FeVO4 HFP is a promising approach for lignocellulose pretreatment.

Fabrication of N-doped graphitic carbon encapsulated Fe3C/Fe nanoparticles with dual-reaction centers for highly effective Fenton-like degradation of organic pollutants

The highly active and durable design of heterogeneous catalysts holds vital importance in the popularization of Fenton-like process for wastewater remediation. In this study, we successfully fabricated magnetic N-doped graphitic carbon (NC) encapsulated Fe3C/Fe nanoparticles, designated as Fe3C/Fe@NC-2.8, with a two-step pyrolysis method. We employed chitosan as a green precursor of NC, which is used as a heterogeneous Fenton-like catalyst to degrade refractory organic pollutants. Density functional theory (DFT) calculations revealed that the built-in electric field from the shell to core promoted electron transfer from NC to Fe3C/Fe, and thereby improved regeneration of Fe(II) and H2O2 activation. Because of the strong synergistic effects of the dual-reaction regions of Fe and Fe3C, as well as the core-shell structure advantages, the optimized Fe3C/Fe@NC rapidly degraded the typical refractory organic pollutants, and showed a much higher activity than the reference Fe2O3 and Fe3O4 samples. The total organic carbon removal efficiency of bisphenol A reached 70 % after reaction for 60 min. In addition, Fe3C/Fe@NC-2.8 possessed trace Fe leaching and satisfactory magnetically separable ability. This work provides mechanistic and practical perspectives for the development of advanced catalysts for recalcitrant pollutant treatment.

Performance and Mechanism of Cu-Ce/γ-Al2O3 as a Heterogeneous Fenton-Like Catalyst for Phenol Degradation

Performance and Mechanism of Cu-Ce/γ-Al2O3 as a Heterogeneous Fenton-Like Catalyst for Phenol Degradation

Heterostructure engineered membranes based on two-dimensional bimetallic MOF for enhanced remediation of dye contaminated wastewater

As a heterogeneous Fenton-like catalyst, two-dimensional (2D) bimetallic MOF can be readily engineered into lamellar membranes which integrate precise separation and Fenton-like degradation to enhance the elimination of organic contaminants from wastewater by rational design of interlayer spacing and constituent units. In this work, a 2D FeNi-MOF is assembled with ultrathin graphitic carbon nitride (g-C3N4) spacers into heterostructure membranes for enhanced remediation of dye contaminated wastewater by synergistic promotion of membrane separation and Fenton-like processes. For the establishment of heterostructure, FeNi-MOF and g-C3N4 nanosheets are alternately arranged by the coordination bonds between bimetallic nodes and pyridinic N to create orderly laminar nanochannels. On the one hand, the heterostructure provides abundant water passages and fixes the membrane interlayer distance to 1.0–1.2 nm with the permeation flux of 47.8–110.1 L·m2·h−1·bar−1. On the other hand, the heterostructure can act as the Fenton-like mediator to expedite the cycle efficiency of Fe(III)/Fe(II) and Ni(II)/Ni(III). The synergistic promotion mechanism of membrane separation and Fenton-like processes is elaborated by simulating the molecular transport peculiarity through membrane nanochannels and the electron transfer efficiency between dual active centers. The contaminant molecules are trapped within the membrane by specific or non-specific channel-guest interaction with heterostructure nanochannels while the steadily generated radicals attack and degrade the confined contaminants, reaching the dye removal rate of approximately 99.0%. Anchoring between adjacent layers and bimetallic cycle reaction in confined fluid confer the stability and recyclability to the heterostructure membrane under wide-range pH and pressures, which are promising for the sustainable treatment of dye contaminated wastewater.

Facile construction of a novel S-scheme Fe2TiO5/BiVO4 photocatalyst for efficient visible light-driven fenton-like degradation of ciprofloxacin

The rational design and fabrication of stable and efficient heterogeneous Fenton-like catalyst is of great significance for wastewater treatment, but is still fraught with obstacles. In this paper, a novel S-scheme Fe2TiO5/BiVO4 nano-heterojunction with high visible-light photocatalytic performance was synthesized by an in-situ growth method. The optimized Fe2TiO5 (20 wt%)/BiVO4 composite exhibited remarkable photocatalytic activity and rapid degradation ability towards CIP (50 mg/L) with the addition of H2O2 (20 mM), achieving a removal efficiency of 94.2 % within 90 mins. This performance is significantly superior to that of pure BiVO4 (43.8 %) or pure Fe2TiO5 (48.2 %). The S-scheme heterojunction formed between Fe2TiO5 and BiVO4 facilitates efficient charge separation, and preserves the powerful photogenerated electrons in CB of Fe2TiO5 and holes in the VB of BiVO4, contributing to the fast degradation of CIP. The synergistic effects of the S-scheme heterojunction and H2O2 activation account for the excellent performance of Fe2TiO5/BiVO4 photocatalyst. The prepared photocatalyst demonstrates remarkable efficiency, non-selectivity, exceptional stability, and adaptability to various environmental conditions. This study proposes a novel approach for designing and synthesizing photo-assisted Fenton-like S-scheme photocatalysts for efficient removal of organic pollutants in wastewater.

The correlation between electron exchange capacity of Fenton-like heterogeneous catalyst and catalytic activity

Electron transfer played key role in peroxymonosulfate (PMS) activation for heterogeneous Fenton-like catalysts (HFCs). However, the relationship between electron exchange capacity (EEC) and catalytic activity of HFCs has not been elucidated. Herein, thirteen HFCs reported in our previous studies were selected to measure their EEC via electrochemical methods and to investigate the correlation between EEC and catalytic activity for PMS. The results show that nitrogen-doped graphene oxide had much higher EEC (5.299 mM(e) g−1), followed by reduced graphene oxide (3.23 mM(e) g−1), nitrogen-doped biochar-700 (2.032 mM(e) g−1), graphene oxdie (1.789 mM(e) g−1), nitrogen-doped biochar-300 (1.15 mM(e) g−1), g-C3N4 (0.752 mM(e) g−1) and biochar (0.351 mM(e) g−1). For carbon materials, their catalytic activity was not determined by electron donor capacity (EDC), electron acceptor capacity (EAC) and EEC (EDC + EAC), but was linear correlation with |EDC-EAC| that can characterize the extent of HFCs reacting with PMS. The higher the |EDC-EAC| is, the higher the catalytic activity of HFCs is. For carbonaceous materials, their catalytic activity was not proportional to EAC, but had good linear correlation with EDC and |EDC-EAC|. The discrepancy between carbon materials and carbonaceous materials could be due to the different activation mechanisms. Further analysis found that there was no correlation between EEC and the reactive species derived from PMS, indicating that the produced reactive species was not only controlled by EEC. This study firstly elucidated the correlation between EEC and catalytic activity of HFCs, and |EDC-EAC| could be used as an index for evaluating the catalytic activity of HFCs.

Hydrothermal Synthesis and Catalytic Activity of a Nanosized Fe2V4O13 Material in Heterogeneous Fenton-like Reaction for Degradation of Organic Compounds

In this research, the nanosized Fe2V4O13 complex oxide material was synthesized by the hydrothermal method. Its structure, morphology characterization, and other properties were determined using X-ray, SEM, EDX, and DTA-TG methods. The catalytic activity of the material was evaluated in terms of the decolorization and the degradation of the Indigo carmine dye. The optimal condition for the degradation and the reusability of the catalyst were determined. The results showed that the heterogeneous Fenton-like catalyst is a promise for wastewater treatment.

Mechanochemical synthesis of sulfidated microscale zerovalent iron/graphene composite for enhanced degradation of tetracycline

This study introduces a novel ternary composite comprising sulfur (S), reduced graphene oxide (rGO), and microscale iron (mZVI) powder through a straightforward ball milling process. The composite was employed as an activator for H2O2 in the degradation of tetracycline (TC). Impressively, the S-mZVI/rGO composite exhibits significantly enhanced TC removal efficiency in the presence of H2O2 compared to bare mZVI and S-mZVI alone. In the S-mZVI/rGO/H2O2 system, 97.2 % of the TC can be removed within 60 min, with an apparent rate constant (kobs) of 0.054 min−1, which is 49.18 and 2.14 times than that in the mZVI/H2O2 (0.001 min−1) and S-mZVI/H2O2 system (0.025 min−1), respectively. Furthermore, the S-mZVI/rGO composite exhibits outstanding TC removal efficiency across a broad pH range (3 ∼ 9), consistently exceeding 90 % under optimal conditions. The much superior activity of S-mZVI/rGO/H2O2 process is attributed to both radical (OH) and non-radical pathways (1O2 and electron transfer), with the latter contributing more. The catalyst’s performance is also affected by the defective sites on the surface and the rapid cycle of Fe2+/Fe3+. Moreover, the degradation pathways of TC are proposed according to the intermediate products detected by UPLC-MS. Finally, the S-mZVI/rGO/H2O2 demonstrates high resistance to inorganic anions and natural organic matter in aquatic environments. Overall, S-mZVI/rGO is expected to be a cost-effective and highly efficient heterogeneous Fenton-like catalyst for the removal of organic contaminants from wastewater.

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.

An organic-inorganic hybrid based on bicapped Keggin polyoxometalate as a heterogeneous catalyst for MB removal via Fenton-like/photo-Fenton-like degradation or reduction

An organic-inorganic hybrid polyoxometalate (POM) [CuI(phen)2]4[PMoVI8VIV6O42{CuI(phen)}2]•H5O2 (CuPMoV) was explored as heterogeneous Fenton-like catalyst for methylene blue (MB) degradation in the absence/presence of visible light at neutral pH. CuPMoV was characterized by XRD, SEM, FT-IR and UV–vis DRS techniques. The effect of initial pH, the concentrations of H2O2 and dye, and CuPMoV dosage on the degradation was evaluated. The possible mechanism for the Fenton-like/photo-Fenton-like was proposed. Under the optimum conditions, the MB degradation rates were 85.3 % (Fenton-like reaction) and 95.2 % (photo-Fenton-like reaction) in 12 min, respectively. CuPMoV also exhibited excellent catalytic performance for MB reduction in the presence of NaBH4, with the reduction rate of 98.6 % in 90 s. The pseudo-first-order rate constant of the reduction was estimated as 0.0246 s−1. The high reusability and stability of CuPMoV enabled it to undergo five cycles of usage without significant loss of catalytic activity. The multi-metal composition of CuPMoV and the bicapped Keggin unit were the root of its excellent catalytic activities. CuPMoV may be a potential candidate for the practical treatment of MB contaminated wastewater via oxidation or reduction.

Regulating localized state electron and ordered electron transfer in Cu2Se using Indium element for efficient heterogeneous Fenton-like process

Local electron density at the reaction center atoms is closely related to the H2O2 activation performance of a heterogeneous Fenton-like catalyst. However, the random electron transfer often restricts the oriented electron delivery to the active center. In this study, we proposed that only efficient electrons and their ordered transfer were desirable to boost Cu(II)/Cu(I) cycle for H2O2 activation based on regulation of local electron density and electron transfer efficiency of Cu atoms in Cu2Se. Experimental results and density function theory (DFT) calculation proved that Indium atom can drive electrons to accumulate on Cu active center and provide an efficient electron transfer pathway in CuInSe2 (from Se → Cu to In → Se → Cu). Hence, compared with Cu2Se, more reductive electrons can participate in the H2O2 activation process for CuInSe2, which resulted in much more efficient ofloxacin (OFX) degradation with a TOC removal rate up to 71.5 %. The electron exchange capacity of CuInSe2 was further regulated by changing the atomic ratios of Cu and In elements including CuInSe2, Cu1.5In0.5Se2 and Cu1.75In0.25Se2. CuInSe2 had the lowest electron exchange capacity and exhibited the highest reaction activity with a radical transformation efficiency from H2O2 of 9.83 × 10-4, in contrast, the value for Cu1.75In0.25Se2 was 2.78 × 10-4. We provided a new insight for improving the heterogeneous Fenton catalytic performance.

Application of 3D hierarchical porous NiCo-spinel nanosheet array for enhancement of synergistic activation of peroxymonosulfate: Degradation, Intermediates, mechanism and degradation pathway of tetracycline

The rational design of the morphology and structure of bimetallic-based heterogeneous Fenton-like catalyst derived from metal-organic-frameworks (MOFs) for peroxymonosulfate (PMS) activation via a non-radical pathway is attractive but challenging. Herein, a spinel-type 3D hierarchical porous NiCo2O4 nanosheet array for the activation of PMS is rationally designed by surfactant-assisted interfacial engineering. The experimental results showed that the NiCo2O4/PMS system demonstrated remarkable oxidative degradation of tetracycline (TC) through 1O2 attack and electron transfer process. In literature, it was thought that the PMS activation process in above system is dominated by radical pathway. In this work, we employ surfactant modified-nanostructure engineering to design hierarchical mesoporous nanosheet array structures and combined them with intrinsic bimetallic synergy to enhance catalytic activity, and interestingly the strategy transformed the PMS activation pathway into a nonradical (1O2 and electron transfer)-dominated process. This is benefit from the favorable morphological and electronic structure of the designed catalysts to facilitate mass transfer and electron transfer processes. The system also possessed a broad spectrum for degrading other typical contaminants, and was effective in tolerating actual water matrix and pH changes, as well as resisting interference from anions and organic matter. Furthermore, the robust stability of the structure and catalytic activity make it promising for practical water treatment. It can be expected that this proposal will provide insights for the delicate structural design and the understanding of its PMS activation mechanism of bimetallic-based Fenton-like catalysts, as well as for the efficient degradation of emerging organic pollutants.

Fe-N-C heterogeneous Fenton-like catalyst for the degradation of tetracycline: Fe-N coordination and mechanism studies

Fe-N-C materials have received increasing attention, due to its distinctive catalytic activity. However, the Fe-N coordination number dependence of catalytic ability and mechanism for H2O2 activation remain elusive. Herein, a series of Fe-N-C heterogeneous Fenton-like catalysts with different Fe-N coordination number were prepared for tetracycline degradation. The results demonstrated that samples with Fe-N4 structure exhibited high activity. The excellent performance was mainly ascribed to the high adsorption capacity and the formation of superoxide radicals (•O2−) catalyzed by Fe linked to pyridinic nitrogen. The intermediates and degradation pathways of tetracycline degradation by Fe-N-C/H2O2 system were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Furthermore, we applied our Fe-N-C catalysts to treat simulated pharmaceutical wastewater with high tetracycline degradation capacity despite high concentrations of organic matter such as oxalic acid and various ionic interferences. Our work reveals the dependence of the activation H2O2 on the Fe-N coordination environment and the degradation mechanism of these catalysts. It provides insights into the prospects for tuning the catalyst in practical applications.

Preparation of a Novel Copper–Cobalt Composite Catalyst and Study on Performance Degradation of Methyl Orange

A novel Co–Cu composite heterogeneous Fenton-like catalyst was prepared by using a modified hydrothermal method for the degradation of methyl orange solution. The catalyst was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and a Fourier transform infrared spectrometer (FT-IR), which confirmed that the catalyst contained Co(OH)2, Cu2O, and an exhibition of a hexagonal crystalline structure with sizes within the range of 0.5–5 μm. The influential factors were researched with the use of univariate analysis and the results showed that: the catalyst has better catalytic properties in the pH range of 2–10 and there was an optimum value of the dosage of the catalyst; the greater the dosage of the catalyst, the faster the COD degradation rate achieves its maximum value; the COD degradation rate increases with a higher reaction temperature. When the pH is 7, the dosage of the catalyst is 0.3 g/L, the dosage of hydrogen peroxide is 50 mL/L, and the reaction temperature is 313 K. The COD degradation rate reached 94% after 50 min of treatment, which proved that the catalyst exhibited high catalysis in a Fenton-like process. Furthermore, reuse of the catalyst and the degradation mechanism of methyl orange were also researched.

Efficient removal of aromatic pollutants via catalytic wet peroxide oxidation over synthetic anisotropic ilmenite/carbon nanocomposites

As one of the most common ferrous (Fe2+)-containing oxide minerals in the Earth’s crust, ilmenite (FeTiO3) is a potential low-cost heterogeneous Fenton-like catalyst for organic wastewater treatment via catalytic wet peroxide oxidation (CWPO). However, it suffers from low activity and long induction time. Herein anisotropic FeTiO3/C nanocomposite with rich Fe2+ ions on large surface area of 159.0 m2 g−1 (surface Fe/Ti and Fe2+/Fe3+ ratios were respectively 2.1 and 2.0) was prepared via cetyltrimethylammonium (CTA+)-assisted sol-gel synthesis. CTA+ modulated the growth of FeTiO3 nanoparticles with more exposed metallic sites by preferential adsorption on its (104) plane via electrostatic attraction, provided the carbon source and facilitated the generation of more Fe2+ ions at the interface of FeTiO3/C via carbothermal reduction of FeTiO3. FeTiO3/C efficiently catalyzed CWPO removal of six aromatic pollutants with different charges (25 mg L−1 each) at 25 oC and pH 3.0 without an induction period owing to rich Fe2+ content on neutral surface (pHpzc ~3.3)—three dye solutions completely decolorized in 1 h and three antibiotics degraded by >90% in 3 h. Reusability of FeTiO3/C was demonstrated with cationic rhodamine B and anionic orange G dyes in five consecutive runs. Scavenging tests and spin-trapping EPR spectra confirmed the generation of dominant ·OH and minor O2•− species for organic degradation via catalytic decomposition of H2O2 on FeTiO3/C as a heterogeneous Fenton-like catalyst.

Insight into the role of heterogeneous Fenton-like catalyst FeCo-γ-Al2O3 with dual electron-rich centers for Ni-EDTA removal

To enhance the polarization distribution of electron cloud density on the catalyst surface, we have introduced a novel bimetallic-substituted dual-reaction center (DRC) catalyst (FeCo-γ-Al2O3) comprising iron (Fe) and cobalt (Co) for the decomplexation and mineralization of heavy metal complex Ni-EDTA in this study. Compared to the catalysts doped solely with Fe or Co, the bimetal-doped catalyst offered several advantages, including enhanced electron cloud polarization distribution, additional electron transfer pathway, and improved capacity of free radical generation. Through DFT calculations and EPR tests, we have elucidated the influences of the catalyst's adsorption toward Ni-EDTA and its decomplexation products on the electron transfer between the pollutant and the catalyst. The competition between the pollutants and H2O2 affects the generation of free radicals in both electron-rich Fe and Co centers as well as electron-deficient Al center. Building on these findings, we have proposed a plausible removal mechanism of Ni-EDTA using the heterogeneous Fenton-like catalyst FeCo-γ-Al2O3. This study sheds light on the potential of FeCo-γ-Al2O3 as a DRC catalyst and emphasizes the significance of pollutant characteristics in determining the catalyst's performance.