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.     

Turning the Inert Element Zinc into an Active Single-Atom Catalyst for Efficient Fenton-Like Chemistry

Amongst various Fenton-like single-atom catalysts (SACs), the zinc (Zn)-related SACs have been barely reported due to the fully occupied 3d¹⁰ configuration of Zn²⁺ being inactive for the Fenton-like reaction. Herein, the inert element Zn is turned into an active single-atom catalyst (SA−Zn−NC) for Fenton-like chemistry by forming an atomic Zn−N₄ coordination structure. The SA−Zn−NC shows admirable Fenton-like activity in organic pollutant remediation, including self-oxidation and catalytic degradation by superoxide radical (O₂⋅⁻) and singlet oxygen (¹O₂). Experimental and theoretical results unveiled that the single-atomic Zn−N₄ site with electron acquisition can transfer electrons donated by electron-rich pollutants and low-concentration PMS toward dissolved oxygen (DO) to actuate DO reduction into O₂⋅⁻ and successive conversion into ¹O₂. This work inspires an exploration of efficient and stable Fenton-like SACs for sustainable and resource-saving environmental applications.     

Crystallinity engineering of Au nanoparticles on graphene for in situ SERS monitoring of Fenton-like reaction

Fabrication of multifunctional nanoplatform to in situ monitor Fenton reaction is of vital importance to probe the underlying reaction process and design high-performance catalyst.Herein,a hybrid catalyst comprising of single-crystalline Au nanoparticles（SC Au NPs） on reduced graphene oxide（RGO） sheet was prepared,which not only exhibited an excellent ¹ O₂ mediated Fenton-like catalytic activity in promoting rhodamine 6 G（R6 G） degradation by activating H₂ O_...     

A natural manganese ore as a heterogeneous catalyst to effectively activate peroxymonosulfate to oxidize organic pollutants

Heterogeneous transition metal catalysts are indispensable in improving environmental pollution. However, their fabrication is often costly and cumbersome, and they can easily pollute the environment. This study proposed using a natural Gabonese ore (GBO) containing Mn_xO_y and Fe_xO_y as catalysts to degrade orange II (OII) via peroxymonosulfate (PMS) activation. The GBO + PMS system exhibited extraordinarily high stability and catalytic activity towards OII elimination (92.2%, 0.0453 min^?1). The reactive oxygen species (ROS) generated in the system were identified using radical scavenging tests and electron spin-resonance (ESR) analysis. Singlet oxygen (¹O₂) represented the dominant reactive species for OII degradation, while the system presented a lower reaction energy barrier and was effective in a broad pH range (2–10). This work also proposed the activation mechanism for the GBO + PMS system and OII degradation pathways. This study revealed a new approach for exploring inexpensive, eco-friendly, efficient, and stable heterogeneous transition metal catalysts.     

Ferric ion-ascorbic acid complex catalyzed calcium peroxide for organic wastewater treatment: Optimized by response surface method

Hydrogen peroxide (H₂O₂) disproportionation, iron precipitation, and narrow pH range are the drawbacks of traditional Fenton process. To surmount these barriers, we proposed a ferric ion (Fe³⁺)-ascorbic acid (AA) complex catalyzed calcium peroxide (CaO₂) Fenton-like system to remove organic dyes in water. This collaborative Fe³⁺/AA/CaO₂ system presented an obvious improvement in the methyl orange (MO) decolorization, and also effectively eliminated other dyes. Response surface method was employed to optimize the running parameters for this coupling process. Under the optimized arguments (2.76 mmol/L Fe³⁺, 0.68 mmol/L AA, and 4 mmol/L CaO₂), the MO removal achieved 98.90% after 15 min at pH 6.50, which was close to the computed outcome of 99.30%. Furthermore, this Fenton-like system could perform well in a wide range of pH (3–11), and enhance the H₂O₂ decomposition and Fe ions recycle. The scavenger experiment result indicated that hydroxyl radical, superoxide anion free radical, and singlet oxygen were acted on the dye elimination. Moreover, electron spin resonance analysis corroborated that the existences of these active species in the Fe³⁺/AA/CaO₂ system. This study could advance the development of Fenton-like technique in organic effluent disposal.     

Highly efficient degradation of emerging contaminants by magnetic CuO@FexOy derived from natural mackinawite（FeS） in the presence of peroxymonosulfate

In this study,natural mackinawite （Fe S）,a chalcophilic mineral,was utilized to prepare iron/copper bimetallic oxides （Cu O@Fe_xO_y） by displacement plating and calcination process.Various characterization methods prove that Cu⁰is successfully coated on the surface of Fe S,which were further oxidized to Cu O,Fe₃O₄and/or Fe₂O₃during calcination process,respectively.Cu O@Fe_xO_yperformed highly efficient...     

Heterogeneous Fenton-like reactions with a novel hybrid Cu–Mn–O catalyst for the degradation of benzophenone-3 in aqueous media

This study focuses on the heterogeneous Fenton-like reaction performed over a novel hybrid Cu–Mn–O catalyst for the degradation of a model compound benzophenone-3 (BP-3) in aqueous media. The hybrid Cu–Mn–O catalysts with different Cu/Mn molar ratios were synthesized using co-precipitation and hydrothermal methods, and their composition and morphology were characterized using XRD and SEM analyses. Key parameters including the Cu/Mn ratio in the synthesis, pH and titration of H₂O₂ were shown to significantly influence the degradation of BP-3. A hybrid catalyst with a chemical composition of Cu_1.4Mn_1.6O₄, Mn₃O₄, and Mn₂O₃ exhibiting a morphology of nanofibers and nanoparticles demonstrated the highest catalytic activity in the degradation of BP-3. After 240 min of degradation, 81.5% of BP-3 was removed, which could be mostly related to the presence of hydroxyl radicals (˙OH). Unlike the conventional Fenton reaction that performs well under highly acidic conditions, BP-3 can be degraded in a wider pH range (2.6–7.1) in the Fenton-like reaction presented herein. Considering the mild conditions used for this Fenton-like system, this novel hybrid catalyst remains promising for wastewater treatment.     

Enhancement of electrochemical performance and thermal compatibility of GdBaCo2/3Fe2/3Cu2/3O5+δ cathode on Ce1.9Gd0.1O1.95 electrolyte for IT-SOFCs

Transition-metal doped double-perovskite structure oxides GdBaCo_2/3Fe_2/3Ni_2/3O_5+δ (FN-GBCO), GdBaCo_2/3Fe_2/3Cu_2/3O_5+δ (FC-GBCO), GdBaCoCuO_5+δ (C-GBCO) and pristine GdBaCo₂O_5+δ (GBCO) were synthesized via a citrate combustion method. The thermal-expansion coefficient (TEC) and electrochemical performance of the oxides were investigated as potential cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The TEC exhibited by the FC-GBCO cathode up to 900 °C is 14.6 × 10^?6 °C^?1, which is lower than the value of GBCO (19.9 × 10^?6 °C^?1). Area specific resistances (ASR) of 0.165 Ω cm² at 700 °C and 0.048 Ω cm² at 750 °C were achieved for the FC-GBCO cathode on a Ce_0.9Gd_0.1O_1.95 (CGO) electrolyte. An electrolyte supported (300 μm thick) single-cell configuration of FC-GBCO/CGO/Ni-CGO attained a maximum power density of 435 mW cm^?2 at 700 °C. The unique composition of GBCO co-doped with Fe and Cu ions in the Co sites exhibited reduced TEC and enhancement of electrochemical performance and good chemical compatibility with CGO, and this composition is proving to be a potential cathode for IT-SOFCs.     

Fast and Long-Lasting Iron(III) Reduction by Boron Toward Green and Accelerated Fenton Chemistry

Generation of hydroxyl radicals in the Fenton system (Fe^II/H₂O₂) is seriously limited by the sluggish kinetics of Fe^III reduction and fast Fe^III precipitation. Here, boron crystals (C-Boron) remarkably accelerate the Fe^III/Fe^II circulation in Fenton-like systems (C-Boron/Fe^III/H₂O₂) to produce a myriad of hydroxyl radicals with excellent efficiencies in oxidative degradation of various pollutants. The surface B−B bonds and interfacial suboxide boron in the surface B₁₂ icosahedra are the active sites to donate electrons to promote fast Fe^III reduction to Fe^II and further enhance hydroxyl radical production via Fenton chemistry. The C-Boron/Fe^III/H₂O₂ system outperforms the benchmark Fenton (Fe^II/H₂O₂) and Fe^III-based sulfate radical systems. The reactivity and stability of crystalline boron is much higher than the popular molecular reducing agents, nanocarbons, and other metal/metal-free nanomaterials.     

Highly dispersed Mn2O3−Co3O4 nanostructures on carbon matrix as heterogeneous Fenton-like catalyst

This work reports the synthesis of various carbon (Vulcan XC-72 R) supported metal oxide nanostructures, such as Mn₂O₃, Co₃O₄ and Mn₂O₃−Co₃O₄ as heterogeneous Fenton-like catalysts for the degradation of organic dye pollutants, namely Rhodamine B (RB) and Congo Red (CR) in wastewater. The activity results showed that the bimetallic Mn₂O₃−Co₃O₄/C catalyst exhibits much higher activity than the monometallic Mn₂O₃/C and Co₃O₄/C catalysts for the degradation of both RB and CR pollutants, due to the synergistic properties induced by the Mn−Co and/or Mn (Co)−support interactions. The degradation efficiency of RB and CR was considerably increased with an increase of reaction temperature from 25 to 45°C. Importantly, the bimetallic Mn₂O₃−Co₃O₄/C catalyst could maintain its catalytic activity up to five successive cycles, revealing its catalytic durability for wastewater purification. The structure–activity correlations demonstrated a probable mechanism for the degradation of organic dye pollutants in wastewater, involving •OH radical as well as Mn²⁺/Mn³⁺ or Co²⁺/Co³⁺ redox couple of the Mn₂O₃−Co₃O₄/C catalyst.     

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 H₂ O₂ activator for tetracycline（TC） degradation.Generally,iron loading can improve the separation performance and reactivity of biochar（BC）.In the Fe-BC/H₂ O₂ system,92% of the TC was removed within 30 min with the apparent rate constant(k_obs) of 0.155 min^-1,which was 23.85 times that in the case of the BC/H₂ O_2<...     

Constructing heterojunction interface of Co3O4/TiO2 for efficiently accelerating acetaminophen degradation via photocatalytic activation of sulfite

Achieving efficient degradation of organic pollutants via activation of sulfite is meaningful but challenging. Herein, we have constructed a heterogeneous catalyst system involving Co₃O₄ and TiO₂ nanoparticles to form the p-n heterojunction (Co₃O₄/TiO₂) to degrade acetaminophen (ACE) through photocatalytic activation of sulfite. Specifically, X-ray photoelectron spectroscopy analysis and theoretical calculations provide compelling evidence of electron transfer from Co₃O₄ to TiO₂ at the heterointerface. The interfacial electron redistribution of Co₃O₄/TiO₂ tunes the adsorption energy of HSO₃^?/SO₃^2? in sulfite activation process for enhanced the catalytic activity. Owing to its unique heterointerface, the degradation efficiency of ACE reached 96.78% within 10 min. The predominant active radicals were identified as ^?OH, h⁺, and SO_x^?? through radical quenching experiments and electron spin resonance capture. Besides, the possible degradation pathway was deduced by monitoring the generated intermediate products. Thereafter, the enhanced roles of well-engineered compositing interface in photocatalytic activation of sulfite for complete degradation of ACE were unveiled that it can improve light absorption ability, facilitate the generation of active species, and optimize reactive pathways. Considering that sulfite is a waste from flue gas desulfurization process, the photocatalytic activation of sulfite system will open up new avenues of beneficial use of air pollutants for the removal of pharmaceutical wastewater.     

Stability and regeneration of metal catalytic sites with different sizes in Fenton-like system

Metal-based catalysts with different site sizes (e.g., metal nanoparticles (NPs) and single atom catalysts (SACs)) demonstrated outstanding catalytic activities in versatile Fenton-like reactions. However, the surface/structural instability is a critical issue, which will result in rapid passivation in Fenton-like reaction and fail in long-term operation. The catalytic stability of the catalysts with different metal sizes considering versatile peroxides (H₂O₂, peroxymonosulfate (PMS), and peroxodisulfate (PDS)) should be analyzed. In addition, strategies for catalyst regeneration and recyclability improvement are also important to realize the metal-based catalysts for practical applications. In this review, catalytic stability of catalysts with different metal sizes in the backgrounds of versatile peroxides and water matrixes in Fenton-like reactions were first evaluated. Regeneration of metal catalytic sites with different methods were also reviewed. Finally, major challenges and development of methods concerning the stability and regeneration of metal catalytic sites with different sizes were discussed to understand the future researches of metal catalytic sites in Fenton-like reactions.     

Improved chemical water oxidation with Zn in the tetrahedral site of spinel-type ZnCo2O4 nanostructure

Spinel oxides with the composition of A^IIB^III₂O₄ (A and B are metal ions) represent an important class of anode material for water splitting to replace the currently used noble-metal catalysts. Although spinel electrocatalysts have widely been investigated for electrochemical water oxidation, the role of octahedral and tetrahedral sites influencing catalytic performance has been a topic of discussion for a long time and still under debate. Lately, this issue has been addressed by substituting redox-inert cation to the tetrahedral sites of cobalt spinels and comparing the electrochemical activity between them. However, rapid surface structural transformation of the catalysts under operating electrochemical conditions makes it difficult to infer the exact contribution of tetrahedral and octahedral sites for water oxidation. Herein, for the first time, we utilize the oxidant-driven water oxidation approach to reveal the responsible active sites using two spinel-type nanostructures, Zn^IICo₂^IIIO₄ and Co^IICo₂^IIIO₄ (Co₃O₄), synthesized by using a single-source precursor approach. Strikingly, a superior O₂ production rate (0.98 mmol_O2 mol_Co^?1 s^?1) following first-order reaction kinetics was achieved for ZnCo₂O₄ in the presence of Ce^IV as sacrificial electron acceptor compared to Co₃O₄ spinel (0.29 mmol_O2 mol_Co^?1 s^?1). The structural and morphological stability of the ZnCo₂O₄ and Co₃O₄ post water oxidation catalysis confirms that the catalytic activity is strictly controlled by the geometry and electronic structure of the active site of the spinel structure. The higher performance of ZnCo₂O₄ over Co₃O₄ further indicates that the presence of Co^II is not essential for catalytic water oxidation. The presence of redox inert Zn^II at the tetrahedral site of ZnCo₂O₄ can facilitate the stabilization of a high-valent Co^IV intermediate via oxidation of Co^III (situated at the octahedral site), and this intermediate can be regarded as the active species for water oxidation catalyst along with structural defects caused by surface Zn leaching.     

Enhanced Interfacial Electron Transfer by Asymmetric Cu-Ov-In Sites on In2O3 for Efficient Peroxymonosulfate Activation

Enhancing the peroxymonosulfate (PMS) activation efficiency to generate more radicals is vital to promote the Fenton-like reaction activity, however, how to promote the PMS adsorption and accelerate the interfacial electron transfer to boost its activation kinetics remains a great challenge. Herein, we prepared Cu-doped defect-rich In₂O₃ (Cu-In₂O₃/O_v) catalysts containing asymmetric Cu−O_v−In sites for PMS activation in water purification. The intrinsic catalytic activity is that the side-on adsorption configuration of the O−O bond (Cu−O−O−In) at the Cu-O_v-In sites significantly stretches the O−O bond length. Meanwhile, the Cu-O_v-In sites increase the electron density near the Fermi energy level, promoting more and faster electron transfer to the O−O bond for generating more SO₄⋅⁻ and ⋅OH. The degradation rate constant of tetracycline achieved by Cu-In₂O₃/O_v is 31.8 times faster than In₂O₃/O_v, and it shows the possibility of membrane reactor for practical wastewater treatment.     

Removal of multiple pollutants from water using noble Ag/Au/magnetite/graphene/H2O2 system under light and ultrasound irradiation

Ag/Au/Fe₃O₄/graphene composites prepared by a hydrothermal method demonstrated excellent activation of H₂O₂ and were used to degrade methylene blue (MB) in solution in the presence of organic acids and inorganic ions under light and ultrasound irradiation. The physicochemical properties of the obtained composites were characterized using various methods. The results showed that the composites exhibited excellent magnetic properties, crystallinity, and stability. The results of catalysis experiments revealed that the removal efficiency of MB increased when Ag and Au were both incorporated into the Fe₃O₄/graphene/H₂O₂ system compared with the removal efficiency achieved with separate Ag-Fe₃O₄/graphene/H₂O₂ and Au-Fe₃O₄/graphene/H₂O₂ systems, indicating a substantial synergistic interaction between the two metallic nanoparticles and the Fe₃O₄/graphene/H₂O₂ systems. The presence of an organic acid accelerated degradation of the MB/H₂O₂ system, whereas almost all of the investigated anions inhibited the degradation of MB; their inhibition effects followed the order CO₃^2? > NO₃^? > Cl^? > F^? > H₂PO₄^? > SO₄^2? > I^?. Cations of Na⁺, K⁺, Ca²⁺, and Mg²⁺ also suppressed MB degradation, likely because of the influence of Cl^? coexisting in the solutions.     

High active amorphous Co(OH)2 nanocages as peroxymonosulfate activator for boosting acetaminophen degradation and DFT calculation

Acetaminophen (ACE) is commonly used in analgesic and antipyretic drug, which is hardly removed by traditional wastewater treatment processes. Herein, amorphous Co(OH)₂ nanocages were explored as peroxymonosulfate (PMS) activator for efficient degradation of ACE. In the presence of amorphous Co(OH)₂ nanocages, 100% of ACE removal was reached within 2 min with a reaction rate constant k₁ = 3.68 min^?1 at optimum pH 5, which was much better than that of crystalline β-Co(OH)₂ and Co₃O₄. Amorphous materials (disorder atom arrangement) with hollow structures possess large specific surface area, more reactive sites, and abundant vacancies structures, which could efficiently facilitate the catalytic redox reactions. The radicals quenching experiment demonstrated that SO₄^? radicals dominated the ACE degradation rather than OH radicals. The mechanism of ACE degradation was elucidated by the analysis of degradation intermediates and theoretical calculation, indicating that the electrophilic SO₄^? and OH tend to attack the atoms of ACE with high Fukui index (f ^?). Our finding highlights the remarkable advantages of amorphous materials as heterogeneous catalysts in sulfate radicals-based AOPs and sheds new lights on water treatment for the degradation of emerging organic contaminants.     

Synthesis,design of experiments and optimization of heterogeneous Fenton-like degradation of tartrazine by MgFe2O4 nano-catalyst

In this work, magnesium ferrites nanoparticles (MgFe₂O₄ NPs) were successfully fabricated by sol-gel auto-combustion (SGAC) method and were used in heterogeneous Fenton-like degradation of tartrazine. The obtained products were characterized using XRD, FTIR, SEM and EDX. XRD studies confirmed that the synthesized MgFe₂O₄ NPs had a cubic spinel structure. The average crystallite size was evaluated using the Debyee Scherrer formula and found to be in the range 16.18–28.55 nm. In FTIR spectra, two primary absorption bands at 571 cm^?1 and 415 cm^?1 were observed. The spinel ferrites are characterized by these bands and the EDX confirms the presence of the desired elements Mg, Fe, and O. The influences of operating parameters were examined using the Box Behnken statistical design (BD), including magnesium ferrite dosage (0.04–0.12 g/L), tartrazine concentration (30–50 mg/L) and H₂O₂ concentration (3.53–7.06 mM). Using analysis of variance, a significant quadratic model was created. Optimum conditions were magnesium ferrite dosage of 0.092 g/L, tartrazine concentration of 30.21 mg/L and H₂O₂ concentration of 6.66 mM, respectively. The predicted degradation efficiency within the optimum conditions as established by the suggested model was 98.4%. Confirmatory tests were carried out and the degradation efficiency of 98.9% was observed, which was in good agreement with the model's prediction. After five recuperation and reapplications, the catalyst's degradation efficiency remains stable. These findings indicate that a heterogeneous Fenton-like process utilizing MgFe₂O₄ is effective in advanced wastewater treatment.     

Amplification effects of magnetic field on hydroxylamine-promoted ZVI/H2O2 near-neutral Fenton like system

This study has demonstrated an interesting amplification effect of magnetic field（MF） on the hydroxylamine（HA）-promoted zero valent iron（ZVI）/H2 O₂ Fenton-like system.Sulfamethoxazole（SMX） could be efficiently degraded at near neutral pH.Conditional parameters affecting the SMX degradation in the ZVI/H₂ O₂/HA/MF system,e.g.,pH and the dosages of ZVI,HA and H₂ O₂,were investigated.Unlike the acid-favorable ZVI/H₂ O₂ and ...     

Photo-Fenton-like catalytic activity of nano-lamellar Fe2V4O13 in the degradation of organic pollutants

A new photo-Fenton-like catalyst with high activity, Fe₂V₄O₁₃, has been found. It can be obtained by a simple wet chemical process. The catalyst has a nano-lamellar structure with a thinness of less than 100 nm, a BET surface of 52.26 m² g^?1, and a band-gap of 1.59 eV favorable to absorption of visible light. Experiments demonstrated that Fe₂V₄O₁₃ could effectively catalyze degradation of Acid Orange II (AOII) by H₂O₂ in visible light. The degradation was well fitted by a simple pseudo-first-order reaction with a rate constant of 0.0965 min^?1. Moreover, the photo-Fenton-like catalytic activity of Fe₂V₄O₁₃ was much higher than that of not only α-Fe₂O₃ and V₂O₅ but also their mixture (Fe₂O₃ + 2V₂O₅) with an identical atomic ratio of Fe and V, and that of both Fe₃O₄ and γ-FeOOH. The high catalytic activity of Fe₂V₄O₁₃ possibly involves a special two-way Fenton-like, semiconductor photo-catalytic mechanism and the synergistic activation of Fe(III) and V(V) in Fe₂V₄O₁₃ towards H₂O₂.