Fenton-like Process Research Articles

Regulation of free or surface hydroxyl radicals in MILs(Al)-Fe catalyzed Fenton-like systems by free carboxyl group on catalysts

Iron based Fenton-like processes have been widely investigated, while how to regulate active species generation still is a problem of concern. In this study, MILs(Al) with various carboxyl group amounts were used as research tools, loading iron for Fenton-like oxidation, to investigate the effect of free carboxyl group on surface or free HO generation. Active species identification indicates that surface and free HO were main active species for carbamazepine removal. Moreover, it was concluded that contribution of free HO for the decontamination was positively correlated with carboxyl group amounts on MILs(Al). With free carboxyl group amounts increasing from 3.07 to 5.09 mmol/g on MILs(Al)-Fe, concentration of free HO for carbamazepine removal increased from 47.4% to 62.5%. The mechanisms of carboxyl group amounts impact the chemical state of HO was proposed as steric hindrance effect and charge density near iron sites. The destruction of carbamazepine was proposed in different systems by intermediates determination, and the results indicate that the existing form of HO mainly influenced the efficiency of pollutant degradation, rather than oxidation mechanisms of it. Various pollutants degradation in different MILs(Al)-Fe catalyzed Fenton-like systems were investigated as well, to understand the superiority of different HO for decontamination. MILs(Al)-Fe with various carboxyl group amounts catalyzed Fenton-like processes could remove 34.2%–73.0% carbamazepine, 56.7%–93.8% sulfamethoxazole, 36.4%–75.6% bisphenol S and 43.8–79.7% salicylic acid. This study understood the regulation of active species by carboxyl group in MILs(Al)-Fe/H2O2 systems, and sheds new light on active species precise regulation in Fenton-like systems.

Synthesis and Peroxide Activation Mechanism of Bimetallic MOF for Water Contaminant Degradation: A Review.

Metal-organic framework (MOF) materials possess a large specific surface area, high porosity, and atomically dispersed metal active sites, which confer excellent catalytic performance as peroxide (peroxodisulfate (PDS), peroxomonosulfate (PMS), and hydrogen peroxide (H2O2)) activation catalysts. However, the limited electron transfer characteristics and chemical stability of traditional monometallic MOFs restrict their catalytic performance and large-scale application in advanced oxidation reactions. Furthermore, the single-metal active site and uniform charge density distribution of monometallic MOFs result in a fixed activation reaction path of peroxide in the Fenton-like reaction process. To address these limitations, bimetallic MOFs have been developed to improve catalytic activity, stability, and reaction controllability in peroxide activation reactions. Compared with monometallic MOFs, bimetallic MOFs enhance the active site of the material, promote internal electron transfer, and even alter the activation path through the synergistic effect of bimetals. In this review, we systematically summarize the preparation methods of bimetallic MOFs and the mechanism of activating different peroxide systems. Moreover, we discuss the reaction factors that affect the process of peroxide activation. This report aims to expand the understanding of bimetallic MOF synthesis and their catalytic mechanisms in advanced oxidation processes.

Peroxymonosulfate activation by CuFe-prussian blue analogues for the degradation of bisphenol S: Effect, mechanism, and pathway

The fenton-like process based on peroxymonosulfate (PMS) activation is considered as a promising strategy for the removal of organic pollutants. However, the development of efficient photocatalysts for PMS activation remains challenging. Herein, copper–iron prussian blue analogue (CunFe1-PBA, n = 1, 2, 3, 4) nanomaterials were first fabricated through a simple combination of co-precipitation and calcination processes. The as-synthesized CunFe1-PBA composite catalyst was used to activate PMS for the degradation of endocrine disruptor bisphenol S (BPS). As the result, Cu3Fe1-PBA calcined at 300 °C (Cu3Fe1-PBA*300 °C) mainly composed of CuFe2O4 and CuO showed a higher catalytic activity for activating PMS for BPS degradation than those of CunFe1-PBA composite. Additionally, Cu3Fe1-PBA*300 °C/PMS system was suitable for degradation of BPS at 400 mg/L catalyst or PMS and wide pH ranges from 3 to 11 while coexisting inorganic anions (SO42−, NO3−, and HCO3−) and humic acid all inhibited the reaction. Radical trapping experiment, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) proved that Cu and Fe could regulate the charge balance through changes of valence state, and active PMS to produce free radicals effectively, especially the production of 1O2. Furthermore, the analysis of the BPS intermediates of degradation was carried out by ultra-performance liquid chromatography–mass spectrometry, and two degradation pathways of BPS were proposed. In summary, this work provides a facile avenue to design efficient catalysts to activate PMS for the degradation of emerging organic pollutants in water remediation.

Enhancing zerovalent iron-based Fenton-like chemistry by copper sulfide: Insight into the active sites for sustainable Fe(II) supply

Zerovalent iron (ZVI)-based Fenton-like processes have been widely applied in degrading organic contaminants. However, the surface oxyhydroxide passivation layer produced during the preparation and oxidation of ZVI hinders its dissolution and Fe(III)/Fe(II) cycling, and restricts the generation of reactive oxygen species (ROS). In this study, copper sulfide (CuS) was found to effectively enhance the degradation of diverse organic pollutants in the ZVI/H2O2 system. Moreover, the degradation performance for the actual industrial wastewater (i.e., dinitrodiazophenol wastewater) in the ZVI/H2O2 system was impressively improved by 41% with CuS addition, and the COD removal efficiency could reach 97% after 2 h of treatment. Mechanism investigation revealed that the introduction of CuS accelerated the sustainable supply of Fe(II) in the ZVI/H2O2 system. Specifically, Cu(I) and reductive sulfur species (i.e., S2–, S22–, Sn2– and H2S (aq)) from CuS directly induced efficient Fe(III)/Fe(II) cycling. The iron-copper synergistic effect between Cu(II) from CuS and ZVI expedited Fe(II) generation from ZVI dissolution and Fe(III) reduction by formed Cu(I). This study not only elucidates the promotion effects of CuS on ZVI dissolution and Fe(III)/Fe(II) cycling in ZVI-based Fenton-like processes, but also provides a sustainable and high-efficiency iron-based oxidation system for removal of organic contaminants.

Pilot scale degradation of Sulfamerazine using different venturi based hydrodynamic cavitation and ultrasound reactors in combination with oxidation processes

In the present investigation, a sulfonamide drug named Sulfamerazine was degraded using the 5 L pilot scale hydrodynamic cavitation equipped with three different venturis namely circular (HCCV), slit (HCSV), and dual-slit venturi (HCDSV) operating at 4 bar inlet pressure. The novel HCDSV was successfully designed and applied for the first time to improve the cavitational activities and a subsequent increased ˙OH radical generation. The SMZ degradation achieved using individual HCDSV was 41.54% in comparison to 27.69% and 21.54% for HCSV and HCCV respectively, clearly showing the benefits for intensification. The resistance coefficient (convergent and divergent sections of the venturi), number of passes, and cavitation number significantly influence the cavitational activities, and HCDSV was observed to be the most efficient design based on these parameters. A pilot scale US reactor (USR) was likewise used for the degradation of SMZ at a similar capacity. The combination of hydrodynamic and acoustic cavitation with H2O2, PS, PMS, Fenton and Fenton-like processes were successfully demonstrated on a pilot scale investigation. The combined approach of Fenton (Fe2+ at 0.75 mM and H2O2 at 0.7 mM) coupled with hydrodynamic or acoustic cavitation was the most proficient approach, with maximum SMZ degradation of 96.92% and 97.25% achieved for HCDSV/Fe2+/H2O2 and USR/Fe2+/H2O2 (at 22 +44 kHz), respectively. The estimated cost of treatment for HCDSV/Fe2+/H2O2 and USR/Fe2+/H2O2 (at 22 +44 kHz) approaches were 0.1780 and 0.4583 ₹/L respectively, establishing HCDSV/Fe2+/H2O2 as the most effective method in terms of SMZ degradation as well as cost of degradation.

Fenton-like degradation of diclofenac in water using iron-impregnated mussel shell biochar (Fe@MSBC)

Emerging pollutants such as diclofenac (DFC) are a cause of concern worldwide due to their persistence in the environment. Advanced oxidation processes (AOPs), such as Fenton-like processes, are among the emerging technologies for wastewater treatment due to their capability to completely degrade even recalcitrant pollutants. However, previously-investigated catalysts are expensive. Here, we report the performance of the synthesized iron-impregnated biochar derived from mussel shells (Fe@MSBC) as a catalyst for DFC degradation in water using sodium percarbonate (SPC) as an oxidant. SEM, EDX, FTIR, DSC, and TGA confirmed the successful synthesis of Fe@MSBC. A Box-Behnken design of experiments was used to investigate the effects of Fe@MSBC catalyst loading, initial DFC concentration, and SPC concentration on the removal of DFC. Here, we found that a reduced cubic model can adequately model these effects. Lower Fe@MSBC catalyst loadings, higher initial DFC concentrations, and SPC concentrations near 1.5 mmol L-1 SPC yielded higher DFC degradation. Maximum DFC removal can be achieved at 15.1831 mg L-1 Fe@MSBC catalyst loading, 60 mg L-1 initial DFC concentration, and 1.5228 mmol L-1 SPC concentration. 98.2872 % ± 0.0278 % DFC can be degraded under these conditions. These results show the exceptional degradation efficiency of Fe@MSBC in degrading DFC. These findings could help our search for novel materials to degrade emerging pollutants in wastewater, leading to a safer wastewater effluent to be released into the environment.

Applications of Transition Metal Oxides and Chalcogenides and their Composites in Water Treatment: a review

High population growth, industrialization, precipitous urban settlement, and poor government policies in some circles have increased resource consumption and various environmental activities that promote water pollution. Diverse materials such as nanomaterials, quantum dots, carbonaceous materials, and quaternary-metallic oxides have been very successful in removing benign pollutants from contaminated water bodies. Lately, transition metal oxides (TMOs) and transition metal chalcogenides (TMCs), and their composites have attracted favorable research interest in environmental applications due to their flexible elemental composition, manipulatable bandgaps, earth abundance, optoelectrical properties, visible light activity, and catalytic stability. This review explores the applications of these binary, ternary, quaternary, and heterostructure TMOs and TMCs for a broad range of biological, organic, and inorganic pollutants in water and wastewater treatment. The most popular water treatment strategies used include photocatalysis, adsorption, antimicrobial, persulfate/peroxymonosulfate activation, and the Fenton-like process. The mechanisms of catalysis for these processes were briefly highlighted. Lastly, the conclusion and prospects of the use of the TMOs and TMCs in water and wastewater treatment were discussed.

Preparation and Characterization of a Coordination Polymer Based on Iron (III)-Cyamelurate as a Superior Catalyst for Heterogeneous Fenton-Like Processes.

We report on a new iron (iii)-cyamelurate-based coordination polymer. The new material based on a heptazine derivative was prepared in aqueous medium and characterized by a variety of techniques including TGA, FTIR, XRD, HRTEM, and STEM. Due to the high structural stability of the complex in aqueous media, its heterogeneous Fenton-like catalytic activity was evaluated using a model molecule. The results obtained showed a high catalytic activity in both in basic and acid media. The pseudo-first-order rate constants normalized by iron(III) concentrations was approximately 1000 times higher than the result obtained for traditional heterogeneous catalysts based on iron(III) oxyhydroxides. The best observed catalytic activities were attributed to the increase in the binding sites of Fe3+ ions, in parallel with the increased exposure of the catalytic sites, leading to a higher atomic efficiency of the reaction.

Molybdenum disulfide co-catalysis boosting nanoscale zero-valent iron based Fenton-like process: Performance and mechanism

The conventional Fenton process has the drawbacks of low efficiency of Fe3+/Fe2+ conversion, low utilization of H2O2, and narrow range of pH. In this paper, molybdenum sulfide (MoS2) was used as a co-catalyst to boost the nanoscale zero-valent iron (nZVI) based heterogeneous Fenton-like process for the degradation of Rhodamine B (RhB). The catalytic performance, influences of parameters, degradation mechanism, and toxicity of intermediates were explored. Compared with the conventional like-Fenton process, the existence of MoS2 accelerated the decomposition of H2O2 and the RhB degradation rate constant of MoS2/nZVI/H2O2 reached more than six times that of nZVI/H2O2. In addition, the effective pH range of MoS2/nZVI/H2O2 was broadened to 9.0 with 84.9% of RhB being removed within 15 min. The co-catalytic system of MoS2 and nZVI was stable and had high reusability according to the results of four consecutive runs. Quenching tests and electron paramagnetic resonance (EPR) demonstrated that hydroxyl radical (·OH), superoxide anions (·O2−), and singlet oxygen (1O2) were all involved in MoS2/nZVI/H2O2. Compared with nZVI/H2O2 system, MoS2 not only increased the corrosion of nZVI but also accelerated the conversion of Fe3+/Fe2+. ECOSAR analysis suggested that the overall acute and chronic toxicity of the degradation products decreased after treatment. Hence, this MoS2 co-catalytic nZVI based Fenton-like process can be used as a promising alternative for the treatment of organic wastewater.

Gaseous toluene heterogeneous oxidative degradation by iron-based hypercrosslinked polymeric resin LXQ-10

Heterogeneous Fenton-like reaction for gaseous toluene removal was enhanced by loading an amount of iron elements onto the hypercrosslinked polymeric resin (LXQ-10) as a novel catalyst. Characterization and experiment results confirmed that Fe/LXQ-10 with great catalytic and stability performance were successfully synthesized. The effects of several key running parameters such as iron loading amount, initial toluene concentration, H2O2 concentration, and reaction temperature were investigated. Under the optimal conditions for a Fenton-like reaction (gaseous toluene concentration, 200 mg/m3; H2O2 concentration, 0.15 mol/L; reaction temperature, 303 K), 3-Fe/LXQ-10 was identified to produce OH radical and the toluene removal efficiency reached 93.56%. Gas chromatography-mass spectrometry (GC–MS) was employed to detect the byproducts in the toluene removal process, and the possible degradation pathway of toluene was explored. Radical quenching tests and EPR investigation were carried out to clarify the contribution of OH radical in the Fenton-like process. Physical adsorption and OH oxidation were the possible mechanisms of toluene removal. In addition, the catalyst maintained its activity after the six cycles. suggesting strong stability and reusability. All the results demonstrated that Fe/LXQ-10 showed high potential and economic feasibility to remove gaseous toluene through adsorption and Fenton-like oxidation. This research not only presents a promising alternative for the effective removal of gaseous VOCs but also provides a theoretical basis in the field of VOCs control.

Enhanced catalytic performance of CuFeS2 chalcogenides for activation of persulfate towards decolorization and disinfection of pollutant in water

This study focuses on the synthesis and properties of CuFeS2 chalcogenides, which were prepared using a heat precipitation method. The effect of synthetic temperature on the catalytic activity of CuFeS2 was also investigated. The study found that CuFeS2 prepared at 250 °C (CuFeS2–250) had higher crystallinity, a higher concentration of Fe2+ on its surface, and a higher catalytic activity in the decolorization of rhodamine B (RhB) using a Fenton-like oxidation process with Na2S2O8 (99.0% RhB decolorization efficiency within 7 min). The iron sites of CuFeS2 were found to be the catalytic active sites through density-functional theory calculations. The study also determined that •SO4− and •OH radicals were the reactive species responsible for the decolorization of RhB. In addition, the study demonstrated that CuFeS2–250 had the ability to decolorize different dyestuffs (methylene blue, methyl orange, and acridine orange) in environmental water samples (river and seawater). Furthermore, CuFeS2–250/Na2S2O8 possessed excellent antibacterial activity (>90.4% eradication rate within 120 min) against pathogen (Escherichia coli, Staphylococcus aureus, and methicillin-susceptible S. aureus). In conclusion, this study highlights the enhanced catalytic activity of CuFeS2–250 and its potential for industrial applications related to the decomposition of organics from wastewater.

Regulating the charge density of Cu(I) single sites enriched on the surface of N3c Vacancies-engineered g-C3N4 for efficient Fenton-like reactions

The construction of highly accessible copper active sites with enhanced charge density is essential for the performance of Cu-based Fenton catalysts. Herein, we report the preparation of a catalyst comprising Cu(I) atoms anchored on the surface of N3c vacancies-engineered g-C3N4 (Cu/Nv-CN) and its enhanced Fenton-like performance. The surface-enrichment of single Cu(I) atoms maximizes the exposure of active sites and reduces the mass transfer limitation for short-lived hydroxyl radicals. The N3c vacancies, meanwhile, facilitate electron donation from N2c to Cu sites, greatly increasing the number of single Cu(I) sites. These two strategies synergistically enhance the hydroxyl radical production rate in the Fenton-like process and endow Cu/Nv-CN with not only excellent performance in degrading various contaminants (such as phenolic compounds, endocrine disruptors, antibiotics, and dyes), both in purified and real water samples matrixes, but also superior bactericidal properties for Escherichia coli. Compared to bulk Cu-doped g-C3N4 without N3c vacancies (CO-Cu/CN), Cu/Nv-CN shows a more than 14-fold increase in phenol degradation and an enhancement of approximately 4 log10 CFU/mL in bacterial inactivation. Our strategy of increasing the number of Cu(I) single atoms through surface enrichment and enhanced electron donation opens up a new route for the design of efficient Fenton-like catalysts for environmental remediation.

Enhanced activation of H2O2 by bimetallic Cu2SnS3: A new insight for Cu (II)/Cu (I) redox cycle promotion

HypothesisDespite that the development of Cu2SnS3 (CTS) catalyst has attracted increasing interests, few study has reported to investigate its heterogeneous catalytic degradation of organic pollutants in a Fenton-like process. Furthermore, the influence of Sn components towards Cu (II)/Cu (I) redox cycling in CTS catalytic systems remains a fascinating research. ExperimentsIn this work, a series of CTS catalysts with controlled crystalline phases were prepared via a microwave-assisted pathway and applied in the H2O2 activation for phenol degradation. The efficiency of phenol degradation in CTS-1/H2O2 system (CTS-1: the molar ratio of Sn (copper acetate) and Cu (tin dichloride) is determined to be Sn:Cu = 1:1) was systematically investigated by controlling various reaction parameters including H2O2 dosage, initial pH and reaction temperature. We discovered that Cu2SnS3 exhibited superior catalytic activity to the contrast monometallic Cu or Sn sulfides and Cu (I) acted as the dominant active sites. The higher Cu (I) proportions conduce to the higher catalytic activities of CTS catalysts. Quenching experiments and electron paramagnetic resonance (EPR) further proved that the activation of H2O2 by CTS catalyst produces reactive oxygen species (ROS) and subsequently leads to degradation of the contaminants. A reasonable mechanism of enhanced H2O2 activation in Fenton-like reaction of CTS/H2O2 system was proposed for phenol degradation by investigating the roles of copper, tin and sulfur species. FindingsThe developed CTS acted as a promising catalyst in Fenton-like oxidation progress for phenol degradation. Importantly, the copper and tin species contribute to a synergetic effect for the promotion of Cu (II)/Cu (I) redox cycle, which thus enhanced the activation of H2O2. Our work may offer new insight on the facilitation of Cu (II)/Cu (I) redox cycle in Cu-based Fenton-like catalytic systems.

Effect of MgFe2O4 catalyst preparation method on its surface characteristics and Fenton-like oxidation of tartrazine: Statistical comparison and DFT-assisted predation of mechanism

In this study, MgFe2O4 nanoparticles fabricated by co-precipitation (MgF-Cop) and sol-gel auto-ignition (MgF-SG) methods were applied in a Fenton-like process for the degradation of Tartrazine (TA) dye. XRD, FTIR, SEM, and EDX techniques were used to characterize the nanoparticles. Our aim is to compare the relative characteristics of catalysts synthesized by two different methods and to investigate which combinations resulted in better catalytic activity. The interactions between three operating parameters, including catalyst dosage, hydrogen peroxide concentration, and initial TA concentration, were evaluated by employing the Box–Behnken design. The optimal TA removal efficiency D (%) conditions were as follows: catalyst dosage of 0.1 g/L, initial H2O2 dosage of 229 mg/L, and initial TA concentration of 30 mg/L. D (%) achieved on this condition were 79.9% and 98.0% within 60 min for MgF-Cop and MgF-SG, respectively. The co-precipitation method yields a slightly less active catalyst with a lower crystallinity than the sol-gel auto-ignition method. Molecular dynamic (MD) simulations and density functional theory were applied to study the adsorption mechanism and the possible degradation mechanism of TA dye, respectively. The positive total energy calculated indicates that TA has almost no adsorption on the MgFe2O4 nanoparticles. The quantum parameters show that the dye is more reactive and has many sites for HO• radical attack. The Theoretical results correlated with the experimental findings.

Feasibility of a Heterogeneous Nanoscale Zero-Valent Iron Fenton-like Process for the Removal of Glyphosate from Water

Glyphosate is a widely used herbicide, and it is an important environmental pollutant that can have adverse effects on human health. Therefore, remediation and reclamation of contaminated streams and aqueous environments polluted by glyphosate is currently a worldwide priority. Here, we show that the heterogeneous nZVI-Fenton process (nZVI + H2O2; nZVI: nanoscale zero-valent iron) can achieve the effective removal of glyphosate under different operational conditions. Removal of glyphosate can also take place in the presence of excess nZVI, without H2O2, but the high amount of nZVI needed to remove glyphosate from water matrices on its own would make the process very costly. Glyphosate removal via nZVI--Fenton was investigated in the pH range of 3-6, with different H2O2 concentrations and nZVI loadings. We observed significant removal of glyphosate at pH values of 3 and 4; however, due to a loss in efficiency of Fenton systems with increasing pH values, glyphosate removal was no longer effective at pH values of 5 or 6. Glyphosate removal also occurred at pH values of 3 and 4 in tap water, despite the occurrence of several potentially interfering inorganic ions. Relatively low reagent costs, a limited increase in water conductivity (mostly due to pH adjustments before and after treatment), and low iron leaching make nZVI-Fenton treatment at pH 4 a promising technique for eliminating glyphosate from environmental aqueous matrices.

Application of nickel foam supported Cu–MnO2 in microwave enhanced Fenton-like process for p-nitrophenol removal: Degradation, synergy and mechanism insight

Diatomic metals catalysts (DAMCs) have attracted researchers' attention in Fenton-like reactions for persistent organic pollutants elimination. A novel composite of Cu–MnO2 loaded on the nickel foam (Cu–MnO2/NF) was synthesized and creatively combined with a microwave (MW) enhanced Fenton-like system—promoting the p-nitrophenol (PNP) removal efficiency to 92.4% within 10 min. The synergistic effect (ξ) between Cu–MnO2/NF and power-control MW-Fenton-like process was up to 11.69 ≫ 0, and the non-thermal result significantly contributed. The participation of Cu–MnO2/NF significantly increased the system's energy efficiency from 3.58 mg·kWh−1 to 44.35 mg·kWh−1. Different from specific degradation, the system maintained high removal efficiency with various pollutants (methylene blue (MB), rhodamine B (RhB), bisphenol A (BPA), and diclofenac sodium (DCF)). The stability of CuMnO2/NF was verified via the recovery experiment, and the applicability of the MW-Fenton-like system has been confirmed. The PNP degradation mechanism was systematically discovered by electron paramagnetic resonance (EPR) detection and radical scavenging experiments. Multiple active species (HO•, e−, O2•-, h+, and 1O2) were generated on the Cu–MnO2/NF surface via electronic transfer and the selective absorption of microwaves. Overall, this study proposes a new possibility in the MW-Fenton-like technology investigation.

Enhanced degradation of sulfamethazine in FeCeOx Fenton-like system by tea polyphenols as reducing agents: Performance, mechanism and pathway

In this study, we constructed a Fenton-like system with FeCeOx nanocomposite, tea polyphenols (TP) and H2O2 for the degradation of sulfamethazine (SMT). Compared with other reducing agents (RAs), the addition of TP had a strong promoting effect on SMT degradation of FeCeOx/H2O2/RAs system, then FeCeOx/H2O2/TP system could realize the complete degradation of SMT within 90 min under optimized conditions of 150 mg·L−1 of catalyst dosage, 2.12 mmol·L−1 of H2O2 concentration, 115 mg·L−1 of TP dosage and 5.2 of initial pH. The main active species in FeCeOx/H2O2/TP system and their corresponding contributions to the SMT degradation were ranked as following: ∙OH (52.5%) > 1O2 (31.9%) > ∙O2- (15.6%). The reduction mechanism (heterogeneous catalysis) and chelation mechanism (homogeneous catalysis) of FeCeOx/H2O2/TP system were proposed. The addition of TP not only achieved the circulation of Fe/Ce species and the formation of oxygen vacancies on the catalyst surface, but also could accelerated the formation of various chelate structure in solution, which both contributed to the generation of active species. SMT was mineralized into CO2, H2O2 and some short chain carboxylic acids through five degradation pathways. Finally, FeCeOx/H2O2/TP system exhibited favorable degradation rate (>90%) towards SMT after six recycling times, and it could work effectively in different water sources. This study provided a new insight into Fenton-like process for improving pollutant degradation.

A regenerable Cu2O/BiOBr S-scheme heterojunction photocatalysts for efficient photocatalytic degradation of mixed organic pollutants

Semiconductor photocatalysis, a powerful technology for water treatment, has been restricted by high recombination rate of photogenerated carriers. Here, we construct a Fenton-like catalyst Cu2O/BiOBr with S-scheme heterojunction. The Cu2O/BiOBr exhibits efficient photocatalytic degradation under saline solution, even actual water quality for various organic contaminant (MB, RhB, CR, MV, TC, and the mixed contaminants). Remarkably, the glucose reduction recovers the photocatalytic degradation of Cu2O/BiOBr from 60.10 % (after 4 cycles) to 89.98 %. This significant restoration can be ascribed to that the Fenton-like process, Cu(Ⅰ)-e-→Cu(Ⅱ), plays an important role in photocatalytic degradation. The Cu(Ⅰ) can be regenerated by glucose, which can reduce Cu(Ⅱ) produced in Fenton-like process. This is considered as a widely used regeneration method for Fenton catalyst. Benefiting from the S-scheme heterojunction and Fenton-like process, the efficient and recyclable Cu2O/BiOBr photocatalyst shows an excellent potential for practical application. It provides a design guide for preparing a green and energy-saving catalyst.

Three-Dimensionally Printed Zero-Valent Copper with Hierarchically Porous Structures as an Efficient Fenton-like Catalyst for Enhanced Degradation of Tetracycline

Three-dimensionally printed materials show great performance and reliable stability in the removal of refractory organic pollutants in Fenton-like reactions. In this work, hierarchically porous zero-valent copper (3DHP-ZVC) was designed and fabricated via 3D printing and applied as a catalyst for the degradation of tetracycline (TC) through heterogeneous Fenton-like processes. It was found that the 3DHP-ZVC/H2O2 system could decompose over 93.2% of TC within 60 min, which is much superior to the homogeneous Cu2+/H2O2 system under similar conditions. The leaching concentration of Cu2+ ions in the 3DHP-ZVC/H2O2 system is 2.14 times lower than that in the Cu powder/H2O2 system in a neutral environment, which could be ascribed to the unique hierarchically porous structure of 3DHP-ZVC. Furthermore, 3DHP-ZVC exhibited compelling stability in 20 consecutive cycles. The effects of co-existing inorganic anions, adaptability, and pH resistance on the degradation of TC were also investigated. A series of experiments and characterizations revealed that Cu0 and superoxide radicals as reducing agents could facilitate the cycling of Cu(II)/Cu(I), thus enhancing the generation of hydroxyl radicals to degrade TC. This study provides new insights into employing promising 3D printing technology to develop high-reactivity, stable, and recycling-friendly components for wastewater treatment.

Chalcogen Elements in Regulating the Local Electron Density of Cu2X for an Efficient Heterogeneous Fenton-like Process.

In this work, a novel strategy for Fenton activity improvement of Cu2X was reported, in which the local electron density of Cu sites was regulated via manipulation of simple chalcogen elements (O, S, and Se). Among them, Cu2Se catalysts show excellent catalytic activity to activate H2O2 for the complete removal of ofloxacin (10 mg/L) at an initial pH of 6.5 within 120 min. Radical scavenger experiments and electron spin resonance spectroscopy confirm that •OH radicals are the primary oxygen reactive species to drive ofloxacin degradation. In addition, density functional theory calculations further proved that electrons would migrate from X and accumulate on Cu active sites in the order Se > S > O. Compared with Cu2O and Cu2S, the highly concentrated electron density of Cu atoms in Cu2Se not only decreased the activation energy of the Fenton-like reaction but also boosted the Cu2+/Cu+ cycle with the generation of more •OH radicals (18-66 μm) and the maintenance of high stability of catalysts, leading to excellent catalytic activity and application potential. We believe this work will lay the foundation for designing excellent Fenton catalysts for practical applications since developing a heterogeneous Fenton system with the highest oxidation efficiency has always been the long-term goal in this field.