Zeolite-encapsulated copper(II) complexes with NNO-tridentate Schiff base ligands: catalytic activity for methylene blue (MB) degradation under near neutral conditions

Three novel copper Schiff base complexes, L1Cu(OAc)-L3Cu(OAc), bearing NNO tridentate ligands were synthesized and successfully entrapped in zeolite. All free and encapsulated complexes were fully characterized through experiments combined with theoretical calculations, and were subsequently employed as catalysts to activate H2O2 for degradation of methylene blue (MB). The catalytic activity of free complexes was tunable by substitution effects. The complex L3Cu(OAc) displayed enhanced efficiency by adopting bulky and donor substitutions due to the lower oxidation states. However, the free complexes exhibited modified structural and catalytic properties upon encapsulation into the zeolite. The constraint from the zeolite holes and coordination geometry caused the alteration of electronic structures and subsequently modified the reactivity. This study revealed that upon encapsulation, the larger molecular dimension of L3Cu(OAc) resulted in additional distorted geometry, leading to higher catalytic efficiency for MB degradation with more blue shifts in the UV-Vis spectrum. There was high catalytic activity by LnCu(OAc)-Y compared to that of the free complex, and high recyclability under near neutral conditions. In addition, the catalytic efficiency of L3Cu(OAc)-Y was higher or equivalent compared to other catalysts. This work provides new complexes with NNO tridentate ligands encapsulated inside zeolite and explains the relationship between the modified structure and functionality.

Efficient Fenton-like degradation of tetracycline by stalactite-like CuCo-LDO/CN catalysts: The overlooked contribution of dissolved oxygen

In the Fenton-like processes, the resources that exist in the system itself (e.g., dissolved oxygen, electron-rich pollutants) are often overlooked. Herein, a novel CuCo-LDO/CN composite catalyst with a strong "metal-π" effect was fabricated by in situ calcination which could activate dissolved oxygen to generate active oxygen species and degrade the electron-rich pollutants directly. The CuCo-LDO/CN (1:10) with the largest specific surface aera, most C-O-M bonds and least oxygen vacancies exhibited the best catalytic performance for tetracycline (TC)degradation (TC removal efficiency 93.2% and mineralization efficiency 40%, respectively, after 40 min at neutral pH) compared to CuCo-LDO and other CuCo-LDO/CN composite catalysts. In the absence of H2O2, dissolved oxygen could be activated by the catalyst to generate O2·-and ·OH, which contributed to approximately 20.7% of TC degradation, providing a faster and cost-effective way for TC removal from wastewater. While in the presence of H2O2, it was activated by CuCo-LDO/CN to generate·OH as the dominant reactive oxygen species and meanwhile TC transferred electrons to H2O2 through C-O-M bonds, accelerating the Cu+/Cu2+ and Co2+/Co3+ redox cycles. The possible degradation pathways of TC were proposed, and the environmental hazard of TC is greatly mitigated according to toxicity prediction.

Electrodeposited Fe on Cu foam as advanced fenton reagent for catalytic mineralization of methyl orange

In many countries, the textile industry remains the major contributor to environmental pollution. Untreated textile dyes discharged into water negatively impact the performance of aquatic organisms and may cause a variety of serious problems to their predators. Effective wastewater treatment is a key to reducing environmental and human health risks. In this work, the Fe/Cu catalysts were used in heterogeneous Fenton’s reaction for the degradation of high concentrations of methyl orange (model azo dye) in aqueous solutions. For the first time, the catalysts were prepared onto commercial copper foams by potentiostatic electrodeposition of iron using an environmentally friendly electrolyte. The influence of electrodeposition conditions, H₂O₂ concentration, dye concentration and temperature on the model dye degradation was investigated. It was revealed that both the surface area and the catalyst loading play the major role in the effective dye degradation. The experimental results involving spectrophotometric measurements coupled with total carbon and nitrogen quantification suggest that a solution containing up to 100 mg/L of methyl orange can be successfully decolorized within 90 s at 50°C using porous Fe/Cu catalyst in the presence of hydrogen peroxide that largely surpasses the current state-of-the-art performance. Already within the first 10°min, ∼ 30% of total methyl orange concentration is fully mineralized. The described process represents a cost-efficient and environmentally friendly way to treat azo dyes in aqueous solutions.

Review: Clay-Modified Electrodes in Heterogeneous Electro-Fenton Process for Degradation of Organic Compounds: The Potential of Structural Fe(III) as Catalytic Sites

Advanced oxidation processes are considered as a promising technology for the removal of persistent organic pollutants from industrial wastewaters. In particular, the heterogeneous electro-Fenton (HEF) process has several advantages such as allowing the working pH to be circumneutral or alkaline, recovering and reusing the catalyst and avoiding the release of iron in the environment as a secondary pollutant. Among different iron-containing catalysts, studies using clay-modified electrodes in HEF process are the focus in this review. Fe(III)/Fe(II) within the lattice of clay minerals can possibly serve as catalytic sites in HEF process. The description of the preparation and application of clay-modified electrodes in the degradation of model pollutants in HEF process is detailed in the review. The absence of mediators responsible for transferring electrons to structural Fe(III) and regenerating catalytic Fe(II) was considered as a milestone in the field. A comprehensive review of studies investigating the use of electron transfer mediators as well as the mechanism behind electron transfer from and to the clay mineral structure was assembled in order to uncover other milestones to be addressed in this study area.

Visible-Light-Active CuO x -Loaded Mo-BiVO4 Photocatalyst for Inactivation of Harmful Bacteria (Escherichia coli and Staphylococcus aureus) and Degradation of Orange II Dye

In the present study, Mo-BiVO4-loaded and metal oxide (MO: Ag2Ox, CoOx, and CuOx)-loaded Mo-BiVO4 photocatalysts were synthesized using a wet impregnation method and applied for microbial inactivation (Escherichia coli and Staphylococcus aureus) and orange II dye degradation under visible-light (VL) conditions (λ ≥ 420 nm). The amount of MO cocatalysts loaded onto the surface of the Mo-BiVO4 photocatalysts was effectively controlled by varying their weight percentages (i.e., 1-3 wt %). Among the pure Mo-BiVO4, Ag2Ox-, CoOx-, and CuOx-loaded Mo-BiVO4 photocatalysts used in bacterial E. coli and S. aureus inactivation under VL irradiation, the 2 wt % CuOx-loaded Mo-BiVO4 photocatalyst showed the highest degradation efficiency of E. coli (97%) and S. aureus (99%). Additionally, the maximum orange II dye degradation efficiency (80.2%) was achieved over the CuOx (2 wt %)-loaded Mo-BiVO4 photocatalysts after 5 h of radiation. The bacterial inactivation results also suggested that the CuO x -loaded Mo-BiVO4 nanostructure has significantly improved antimicrobial ability as compared to CuOx/BiVO4. The enhancement of the inactivation performance of CuOx-loaded Mo-BiVO4 can be attributed to the synergistic effect of Mo doping and Cu2+ ions in CuOx, which further acted as an electron trap on the surface of Mo-BiVO4 and promoted fast transfer and separation of the photoelectron (e-)/hole (h+) pairs for growth of reactive oxygen species (ROS). Furthermore, during the bacterial inactivation process, the ROS can disrupt the plasma membrane and destroy metabolic pathways, leading to bacterial cell death. Therefore, we provide a novel idea for visible-light-activated photocatalytic antibacterial approach for future disinfection applications.

Peroxidase-mimetic activity of FeOCl nanosheets for the colorimetric determination of glutathione and cysteine

For the first time the enzyme mimic activity of iron oxychloride (FeOCl) nanosheets has been studied. The intrinsic peroxidase-mimetic activity of the nanosheets in the presence of H₂O₂ was approved by the efficient oxidation of tetramethylbenzidine (TMB). The Michaelis-Menten constant of the nanosheets toward TMB was about six times lower than that of natural horseradish peroxidase. The superiority of the nanosheets' catalytic property ascribes to their H₂O₂ activation ability. Based on the inhibition of the nanozymes' catalytic reaction, an assay was developed for the quantitative measurement of glutathione (GSH) and cysteine (Cys). The linear range for both biomolecules was over the range of 3-33 μM. The LOD values (3σ/slope) for GSH and Cys were 2.23 μM and 2.76 μM, respectively. Importantly, we succeeded in colorimetric discrimination of GSH and Cys kinetically. We achieved high selectivity toward GSH and Cys. This work extends the feasibility of using FeOCl as nanozymes to construct biosensors, colorimetric probes for medical diagnosis, and nanozyme-based cancer therapy.

A charcoal-shaped catalyst NiFe2O4/Fe2O3 in electro-Fenton: high activity, wide pH range and catalytic mechanism

A charcoal-shaped catalyst NiFe₂O₄/Fe₂O₃ in electro-Fenton (EF) was synthesized by a facile precipitation approach via sintering products of oxalate co-precipitation. This obtained NiFe₂O₄/Fe₂O₃ catalyst was easily separated via an external magnetic field and was used as a heterogeneous electro-Fenton catalyst for rhodamine B (RhB, a target pollutant) degradation. Characteristics of NiFe₂O₄/Fe₂O₃ catalyst were assessed using scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Barrett-Emmett-Teller (BET), respectively. SEM results revealed that the proposed NiFe₂O₄/Fe₂O₃ was charcoal-shaped with the size in the range of 0.5-5 μm. Experiment results show that the EF process with the proposed catalyst could work in a wide pH range from 3 to 9. Under optimized conditions, estimated 90% RhB degradation was achieved in 60 min under the following conditions: 0.6 g/L NiFe₂O₄/Fe₂O₃, pH 3. Radical scavengers and electron spin resonance (ESR) spectra results demonstrated that the main oxidant species involved was ⋅OH, accounting for RhB degradation in EF. Moreover, according to our research on interfacial reaction, ⋅OH was mainly generated from the homogenous Fenton reaction rather than the surface Fenton reaction, stimulating by the dissolved Fe²⁺, Fe³⁺ and Ni²⁺ from catalyst. The reusability of NiFe₂O₄/Fe₂O₃ catalyst was evaluated for recycling the same catalyst for 5 runs. In conclusion, the facile fabrication NiFe₂O₄/Fe₂O₃ catalyst shows great potential in wastewater treatment with promising activity.

Degradation Kinetics of Methyl Orange Dye in Water Using Trimetallic Fe/Cu/Ag Nanoparticles

The release of azo dye contaminants from textile industries into the environment is an issue of major concern. Nanoscale zerovalent iron (nZVI) has been extensively studied in the degradation of azo dye pollutants such as methyl orange (MO). In this study, iron was coupled with copper and silver to make trimetallic Fe/Cu/Ag nanoparticles, in order to enhance the degradation of MO and increase reactivity of the catalyst by delaying the rate of oxidation of iron. The synthesis of the trimetallic nanoparticles (Fe/Cu/Ag) was carried out using the sodium borohydride reduction method. The characterization of the particles was performed using XRD, XPS, EDX, and TEM. The analyses confirmed the successful synthesis of the nanoparticles; the TEM images also showed the desired structures and geometry of the nanoscale zerovalent iron particles. The assessment of the nanoparticles in the degradation of methyl orange showed a notable degradation within few minutes into the reaction. The effect of parameters such as nanoparticle dosage, initial MO concentration, and the solution pH on the degradation of MO using the nanoparticles was investigated. Methyl orange degradation efficiency reached 100% within 1 min into the reaction at a low pH, with lower initial MO concentration and higher nanoparticle dosage. The degradation rate of MO using the nanoparticles followed pseudo first-order kinetics and was greatly influenced by the studied parameters. Additionally, LC-MS technique confirmed the degradation of MO within 1 min and that the degradation occurs through the splitting of the azo bond. The Fe/Cu/Ag trimetallic nanoparticles have proven to be an appropriate and efficient alternative for the treatment of dye wastewater.

Synthesis and catalytic utilization of bimetallic systems for wastewater remediation: A review

The environment is affected by agricultural, domestic, and industrial activities that lead to drastic problems such as global warming and wastewater generation. Wastewater pollution is of public concern, making the treatment of persistent pollutants in water and wastewater highly imperative. Several conventional treatment technologies (physicochemical processes, biological degradation, and oxidative processes) have been applied to water and wastewater remediation, but each has numerous limitations. To address this issue, treatment using bimetallic systems has been extensively studied. This study reviews existing research on various synthesis methods for the preparation of bimetallic catalysts and their catalytic application to the treatment of organic (dyes, phenol and its derivatives, and chlorinated organic compounds) and inorganic pollutants (nitrate and hexavalent chromium) from water and wastewater. The reaction mechanisms, removal efficiencies, operating conditions, and research progress are also presented. The results reveal that Fe-based bimetallic catalysts are one of the most efficient heterogeneous catalysts for the treatment of organic and inorganic contamination. Furthermore, the roles and performances of bimetallic catalysts in the removal of these environmental contaminants are different.

MOFs derived Co/Cu bimetallic nanoparticles embedded in graphitized carbon nanocubes as efficient Fenton catalysts

In this work, Cu-Co bimetallic nanoparticles embedded carbon nanocubes (Cu_xCo_10-x/CNC) are synthesized by direct carbonization of Cu-Co bimetal ZIF. The ratio of Cu and Co nanoparticles in Cu_xCo_10-x/CNC as well as morphology, pore structure and graphitization degree of carbon substrates can be tuned by adjusting the molar ratio of Cu/Co (0:10, 1:9, 2:8, 3:7, 4:6 and 5:5) in ZIF precursors. The Fenton catalytic performances of Cu_xCo_10-x/CNC are further studied by degrading a typical azo dye, Acid Orange II (AOII). The results show the Cu_xCo_10-x/CNC with a Cu/Co ratio of 4/6 display the highest catalytic activity with faster dye degradation rate than other catalysts, which may be ascribed to the synergetic effects of optimized ratio of Cu/Co bimetals, high surface area and graphitized carbon framework. The stability and reusability of the catalyst has been investigated, showing a good performance after five consecutive runs. The catalysts prepared in this study can be used as an attractive alternative in heterogeneous Fenton chemistry and wastewater treatment.

Recent advances in Cu-Fenton systems for the treatment of industrial wastewaters: Role of Cu complexes and Cu composites

Cu-based Fenton systems have been recognized as a promising suite of technologies for the treatment of industrial wastewaters due to their high catalytic oxidation capacity. Rapid progress regarding Cu Fenton systems has been made not only in fundamental mechanistic aspects of these systems but also with regard to applications over the past decade. Based on available literature, this review synthesizes the recent advances regarding both the understanding and applications of Cu-based Fenton processes for industrial wastewater treatment. Cu-based catalysts that are essential to the effectiveness of use of Cu Fenton reactions for oxidation of target species are mainly classified into two types: (i) Cu complexes with organic or inorganic ligands, and (ii) Cu composites with inorganic materials. Performance of the Cu-based catalysts for the removal of organic pollutants in industrial wastewaters are reviewed, with the key operating parameters illustrated. Furthermore, the roles of Cu complexes and composites in both homogeneous and heterogeneous Cu-Fenton systems are critically examined with particular focus on the mechanisms involved. Perspectives and future efforts needed for Cu-based Fenton systems using Cu complexes and composites for industrial wastewater treatment are presented.

Synergistic Catalysis of Co(OH)2/CuO for the Degradation of Organic Pollutant Under Visible Light Irradiation

The exploration of advanced water treatment technologies e.g. heterogeneous photocatalysis is the most promising way to address organic pollution issues. Semiconductors based bimetallic photocatalysis with wide bandgap, have displayed splendid degradation performance in the UV light region, but their extension to the visible light/near infra-red region is still a matter of great concern. CuO, Co(OH)₂, CoO and Co(OH)₂/CuO nanocomposites were synthesized via simple co-precipitation method and further practiced for Rhodamine B (RhB) decomposition by introducing per-sulfate (PS) as a sacrificial agent. Results revealed that Co(OH)₂/CuO catalyst had shown robust catalytic activity for RhB photodegradation (degradation time 8 min, k = 0.864 min⁻¹) under light illumination, significantly less (12–60 times) than the other reported bimetallic catalysts. Catalyst also have verified excellent performance for a broader pH range (5–9) with excellent stability. Main reactive species responsible for the photocatalytic reaction were sulfate (SO₄^•−) and superoxide (O₂^•) radicals, duly verified by ESR and by using radical scavengers. With outstanding recycling abilities, this is probably the fewer successful attempt for RhB decolorization and can be highly favorable for effluent treatment by using the synergic effect of absorption and photodegradation.

In situ anodic induction of low-valence copper in electro-Fenton system for effective nitrobenzene degradation

To achieve superior advanced oxidation processes (AOPs), transitional state activators are of great significance for the production of active radicals by H₂O₂, while instability limits their activation efficiency. In this study, density functional theory calculation (DFT) results showed that Cu⁺ exhibits excellent H₂O₂ activation performance, with Gibbs free energy change (ΔG) of 33.66 kcal/mol, two times less than that of Cu²⁺ (77.83 kcal/mol). Meanwhile, an electro-Fenton system using Cu plate as an anode was proposed for in situ generation of Cu⁺. The released Cu with low-valence state can be well-confined on the surface of the exciting electrode, which was confirmed by X-ray photoelectron spectroscopy (XPS), Raman, and UV-vis spectroscopy. The hydroxyl radicals in this Cu-based electro-Fenton system were determined by the electron spin resonance (ESR). The nitrobenzene degradation ratio was greatly increased by 43.90% with the introduction of the proposed in situ electrochemical Cu⁺ generation process. Various characterization results indicated that the production of Cu⁺ was the key factor in the highly efficient Cu-based electro-Fenton reaction.

Novel flexible Fenton-like catalyst: Unique CuO nanowires arrays on copper mesh with high efficiency across a wide pH range

Free-standing and flexible Cu@CuO nanowires (NWs) mesh as an easily recycled Fenton-like catalyst is developed for the first time. Dense CuO nanowire arrays were uniformly grown on a copper mesh surface simply by wet etching accompanied with thermal dehydration. These dense CuO NWs provide a large specific area and therefore guarantee excellent catalytic performance toward the degradation of rhodamine B (RhB). With a k-value of 0.23 min^-1, such a Cu@CuO NWs mesh is able to degrade 100% RhB in only 16 min. This Fenton-like catalyst is also appropriate for degrading other organic dyes, including crystal violet, methylene blue, and rhodamine 6G. Unlike the conventional Fenton catalyst implemented at a pH value around 3, the Cu@CuO NWs mesh could adapt to a wide pH range from 2.1 to 12.0. More intriguingly, the Cu@CuO NWs mesh with excellent flexibility could be easily recycled after catalysis, which is a significant advance compared to the previously reported Fenton catalysts in the form of powders or nanoparticles. In addition, the recycling performance of this Cu@CuO NWs mesh was also assessed. On the basis of electron spin resonance (ESR) results, O^2- rather than OH is the main active species for the dye degradation by the Cu@CuO NWs mesh. With a marvelous combination of excellent flexibility, wide pH adaptation, and high efficiency, this easily recycled three dimensional Cu@CuO NWs architecture can afford new ideas for the Fenton chemistry.

Highly Crystalline Zinc Oxide/Mesoporous Hollow Silica Composites Synthesized at Low Temperature for the Photocatalytic Degradation of Sodium Dodecylbenzenesulfonate

Highly crystalline ZnO/mesoporous hollow silica sphere (MHSS) composites have been successfully synthesized through an impregnation method at 323K without applying calcination. Three composites of different Zn/Si molar ratios of 1:2, 1:1, and 2:1 were prepared. X-Ray diffraction patterns confirmed the presence of highly crystalline ZnO in the materials. A layer of ZnO was formed on the MHSS as evidenced by field emission scanning electron microscopy analysis. Transmission electron microscopy analysis verified the mesoporous structure in ZnO/MHSS composites. N2 adsorption–desorption analysis indicated a type IV isotherm for 1ZnO/2MHSS and 1ZnO/1MHSS samples, confirming the presence of mesopores in the ZnO layer. It has been demonstrated that all the ZnO/MHSS composites exhibit a high photocatalytic activity towards sodium dodecylbenzenesulfonate degradation compared with bare ZnO under UV irradiation. A kinetic study showed that the photodegradation followed a second order model. Among the prepared composites, 1ZnO/1MHSS recorded the highest reaction rate of 6.03×10−3mM−1min−1 which is attributed to a high crystallinity and the monodispersity of a high amount of ZnO on MHSS.

Enhanced heterogeneous Fenton-like systems based on highly dispersed Fe0-Fe2O3 nanoparticles embedded ordered mesoporous carbon composite catalyst

Acceleration of Fe³⁺/Fe²⁺ cycle and simultaneous reduction of particle size with enhanced stability is extremely important for iron-based heterogeneous Fenton catalysts. In this work, Fe⁰-Fe₂O₃ composite nanoparticles embedded ordered mesoporous carbon hybrid materials (Fe⁰-Fe₂O₃/OMC) were rationally designed as efficient heterogeneous Fenton catalysts. Because of the confinement and reduction of OMC, highly dispersed Fe⁰-Fe₂O₃ active species with diameter of ∼8 nm were generated by an optimized carbothermic reduction process. In addition, Fe⁰-Fe₂O₃/OMC possesses ordered mesoporous structure with uniform mesopore, high surface area and pore volume. For comparison, two other catalysts, including solely Fe⁰ nanoparticles supported on ordered mesoporous carbon (Fe⁰/OMC) and solely Fe₂O₃ nanoparticles supported on ordered mesoporous carbon (Fe₂O₃/OMC) were also prepared. The Fenton catalytic performance of synthesized catalysts was evaluated by using H₂O₂ as oxidizing agent to degrade Acid Orange II (AOII). The results show that almost 98.1% of 100 mg L^-1 AOII was removed by Fe⁰-Fe₂O₃/OMC in condition of neutral pH and nearly room temperature, which is much higher than those of compared catalysts. The enhanced catalytic activity of Fe⁰-Fe₂O₃/OMC for AOII removal is due to the efficient electron transfer between the Fe⁰ and iron oxide and the accelerated Fe³⁺/Fe²⁺ cycle. The stability and reusability of the catalyst was also investigated, which showed a good performance even after five consecutive runs. The as-synthesized catalyst is proved to be an attractive candidate in heterogeneous Fenton chemistry and practical application.

The first morphologically controlled synthesis of a nanocomposite of graphene oxide with cobalt tin oxide nanoparticles

In the present research, the degradation and decolorization of Reactive Black 5 synthetic dye at 30 ppm concentration under sun irradiation in the presence of a newly synthesized graphene based cobalt tin oxide nanocomposite were investigated. These nanoparticles were synthesized by a simple hydrothermal approach using precursor chloride salt i.e., stannous chloride and cobalt chloride and then adsorbed on the surface of RGO by a solvothermal process by changing the condition. The newly synthesized product was subjected to various instrumentation to study the morphology and other properties. X-ray powder diffraction analysis (XRD) explained the structural composition and various parameters of the product, which were further verified by Vesta software. The surface morphology of the product was analyzed by scanning electron microscopy (SEM) and it was observed that the size of each cube was approximately 5–10 μm from every face of the cube. Transmission electron microscopy (TEM) explained that the nanoparticles were within the range of 100–250 nm. These synthesized nanocubes were used in one more application, which was the investigation of the fuel efficiency in the presence of different concentrations of newly synthesized nanocomposites as a catalyst. The efficiency of kerosene oil was investigated by studying different parameters: the flash point, fire point, specific gravity, cloud point, pour point, and calorific value at increasing dosages of catalyst (0, 30, 60 and 90 ppm). It was observed that the values of these parameters changed significantly by changing the concentration of the catalyst dosage. The effect of the nanoparticles on the degradation of the RB 5 azo dye showed the highest removal percentage at the largest value of catalyst dosage, which was 0.70 mg ml⁻¹ with the highest value of 3 ml of hydrogen peroxide.

Tin cobalt hydroxide nanoparticles were synthesized by a simple hydrothermal technique. A graphene based cobalt tin oxide nanocomposite was synthesized by a solvothermal method.

Tailoring the properties of a zero-valent iron-based composite by mechanochemistry for nitrophenols degradation in wastewaters

Zero-valent iron (ZVI) is a valuable material for environmental remediation, because of its safeness, large availability, and inexpensiveness. Moreover, its reactivity can be improved by addition of (nano-) particles of other elements such as noble metals. However, common preparation methods for this kind of iron-based composites involve wet precipitation of noble metal salt precursors, so they are often expensive and not green. Mechanochemical procedures can provide a solvent-free alternative, even at a large scale. The present study demonstrates that it is possible to tailor functional properties of ZVI-based materials, utilizing high-energy ball milling. All main preparation parameters are investigated and discussed. Specifically, a copper-carbon-iron ternary composite was prepared for fast degradation of 4-nitrophenol (utilized as model pollutant) to 4-aminophenol and other phenolic compounds. Copper and carbon are purposely chosen to insert specific properties to the composite: Copper acts as efficient nano-cathode that enhances electron transfer from iron to 4-nitrophenol, while carbon protects the iron surface from fast oxidation in open air. In this way, the reactive material can rapidly reduce high concentration of nitrophenols in water, it does not require acid washing to be activated, and can be stored in open air for one week without any significant activity loss.

Efficient transformation in characteristics of cations supported-reduced graphene oxide nanocomposites for the destruction of trichloroethane

Experiments were conducted to investigate the use of graphene-oxide supported metallic nanocomposites for improving the degradation of trichloroethane (TCA) by sodium percarbonate (SPC). Two methods of production, chemical reduction (CR) and solvo-thermal (ST), were tested for preparation of single (Fe) and binary (Fe-Cu) nanocomposites supported by reduced graphene oxide (rGO). A variety of analytical techniques including N2 adsorption Brunauer-Emmett-Teller (BET), x-ray diffraction (XRD), fourier-transfrom infrared spectroscopy (FTIR), and transmisison electron microscopy (TEM) were applied to characterize the physicochemical and microstructural properties of the synthesized nanocomposites. The characterization indicated that the CR method produced nanocomposites that comprised only mesoporous structure. Conversely, both micro and mesoporous structures were present for samples produced with the ST method. The synthesized single and bimetallic composites produced from the ST method showed higher surface areas, i.e. 93.6 m²/g and 119.2 m²/g as compared to the ones synthesized via the CR method, i.e. 13.8 m²/g and 38.0 m²/g respectively. The results of FTIR and XRD analyses confirmed that the ST method produced highly crystalline nanocomposites. SEM and TEM analysis validated that metallic particles with definite morphology well distributed on the surface of rGO. X-ray photoelectron spectroscopy (XPS) analysis confirmed the homogeneity nanocomposites and occurrence of variation in copper oxidation states during degradation process. EDS mapping validate the homogeneous distribution of Cu and Fe at reduced graphene oxide surface. The Fe-Cu/rGO (ST) activated SPC system effectively degraded TCA (92%) in 2.5 h at low nanocomposite dose compared to the Fe-Cu/rGO (CR) and only Fe, for which the maximum degradation efficiencies achieved were 81% and 34%. In conclusion, excellent catalytic characteristics were observed for the ST-synthesized single and bimetallic (Fe/rGO, Fe-Cu/rGO) catalysts. These catalysts were successful in improving the degradation of TCA via activated SPC.

Nanoporous Fe-Based Alloy Prepared by Selective Dissolution: An Effective Fenton Catalyst for Water Remediation

A fully nanoporous Fe-rich alloy, prepared by selective dissolution of melt-spun Fe_43.5Cu_56.5 ribbons, exhibits outstanding properties as a heterogeneous Fenton catalyst toward the degradation of methyl orange (MO) in aqueous solution. In addition, the ferromagnetic characteristics of this material enable its wireless manipulation toward specific locations within polluted wastewater. The influence of selective dissolution on the microstructure, sample morphology (surface and cross-section), elemental composition, and magnetic properties of the resulting nanoporous alloy is investigated. The dealloying procedure enhances the saturation magnetization and drastically increases the catalytic performance (i.e., the time required for full degradation of MO from the medium is reduced by a factor of approximately 2 by subjecting the Fe_43.5Cu_56.5 ribbons to prior dealloying). Remarkably, the effectiveness of this nanoporous material surpasses the results obtained by the homogeneous Fenton reaction using an equivalent concentration of Fe cations leached into the media from the nanoporous alloy. The different factors that promote the high catalytic activity are discussed. The outstanding catalytic activity, together with the simplicity of the synthetic procedure, makes this material very appealing for water remediation using advanced Fenton processes.

In situ synthesis and immobilization of a Cu(ii)–pyridyl complex on silica microspheres as a novel Fenton-like catalyst for RhB degradation at near-neutral pH

A Cu(ii)–pyridyl complex was in situ synthesized and immobilized onto silica microspheres as a highly effective Fenton-like catalyst at near-neutral pH.

Noncontact Synergistic Effect between Au Nanoparticles and the Fe2O3 Spindle Inside a Mesoporous Silica Shell as Studied by the Fenton-like Reaction

An Au-Fe₂O₃@mesoporous SiO₂ nanoreactor with a multiyolks/shell structure was synthesized through a multistep method. In this nanoreactor, the spindle Fe₂O₃ and Au nanoparticles were inside the same mesoporous SiO₂ shell as the yolks but in a noncontact manner. The noncontact synergistic effect between Au nanoparticles and the Fe₂O₃ spindle was studied with a Fenton-like reaction. The catalytic activity of the Au-Fe₂O₃@mesoporous SiO₂ nanoreactor to the Fenton-like reaction for the degradation of organic dyes was dramatically enhanced by the noncontact synergistic effect.

Mesoporous silica coating on hierarchical flowerlike Fe2O3 with enhanced catalytic activity for Fenton-like reaction

The catalytic activity of hierarchical flowerlike Fe₂O₃ in the Fenton-like reaction was dramatically enhanced by the mesoporous silica coating.

Iron–copper bimetallic nanoparticles supported on hollow mesoporous silica spheres: the effect of Fe/Cu ratio on heterogeneous Fenton degradation of a dye

A series of iron–copper bimetallic nanoparticles supported on hollow mesoporous silica spheres with different Fe/Cu ratios were prepared using a simple post-impregnation and sodium borohydride reduction strategy.

Interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials: A review

The heterogeneous Fenton reaction can generate highly reactive hydroxyl radicals (OH) from reactions between recyclable solid catalysts and H2O2 at acidic or even circumneutral pH. Hence, it can effectively oxidize refractory organics in water or soils and has become a promising environmentally friendly treatment technology. Due to the complex reaction system, the mechanism behind heterogeneous Fenton reactions remains unresolved but fascinating, and is crucial for understanding Fenton chemistry and the development and application of efficient heterogeneous Fenton technologies. Iron-based materials usually possess high catalytic activity, low cost, negligible toxicity and easy recovery, and are a superior type of heterogeneous Fenton catalysts. Therefore, this article reviews the fundamental but important interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials. OH, hydroperoxyl radicals/superoxide anions (HO2/O2(-)) and high-valent iron are the three main types of reactive oxygen species (ROS), with different oxidation reactivity and selectivity. Based on the mechanisms of ROS generation, the interfacial mechanisms of heterogeneous Fenton systems can be classified as the homogeneous Fenton mechanism induced by surface-leached iron, the heterogeneous catalysis mechanism, and the heterogeneous reaction-induced homogeneous mechanism. Different heterogeneous Fenton systems catalyzed by characteristic iron-based materials are comprehensively reviewed. Finally, related future research directions are also suggested.

Evaluation of cobalt oxide, copper oxide and their solid solutions as heterogeneous catalysts for Fenton-degradation of dye pollutants

Co_0.5Cu_0.5O nanoparticles were synthesized via the calcination of corresponding oxalates and showed outstanding catalytic performance for the Fenton-degradation of Congo red.