Efficient degradation of rhodamine B using Fe-based metallic glass catalyst by Fenton-like process

A Zn-Ca-Based Metallic Glass Composite Material for Rapid Degradation of Azo Dyes

The catalytic capabilities of metals in degrading azo dyes have garnered extensive interest; however, selecting highly efficient metals remains a significant challenge. We have developed a Zn-Ca-based metallic glass composite which shows outstanding degradation efficiency for Direct Blue 6. This alloy comprises a Zn2Ca crystalline phase and an amorphous matrix, allowing for the degradation of azo dyes within minutes in a wide temperature range of 0-60 °C. Kinetic calculations reveal an exceptionally low activation energy of 8.99 kJ/mol. The rapid degradation is attributed to the active element Ca and the unique amorphous structure of the matrix, which not only facilitates abundant redox conditions but also minimizes the hydrolysis of the active element. The newly developed metallic glass composite exhibits a notably higher azo dye degradation rate compared to those of general metallic glasses, offering a new avenue for the rapid degradation of azo dyes. This paper holds significant importance for the development of novel azo dye wastewater treatment agents.

Synthesis, magnetic properties, biotoxicity and potential mechanism of modified nano zero-valent iron for decolorization of dye wastewater

SiO2-coated nano zero-valent iron (nZVI) has emerged as a fine material for the treatment of dye wastewater due to its large specific surface area, high surface activity, and strong reducibility. However, the magnetic properties based on which SiO2-coated nZVI (SiO2-nZVI) could effectively separate and recover from treated wastewater, and the biotoxicity analysis of degradation products of the dye wastewater treated by SiO2-nZVI remain unclear. In this study, SiO2-nZVI was synthesized using a modified one-step synthesis method. The SiO2-nZVI nanoparticles were characterized using Transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, Fully automatic specific surface and porosity analyzer, Vibrating sample magnetometer, and Zeta potential analyzer. The removal rate of methyl orange (MO) by SiO2-nZVI composite reached 98.35% when the degradation performance of SiO2-nZVI treating MO was optimized. Since SiO2-nZVI analysed by magnetic hysteresis loops had large saturation magnetization and strong magnetic properties, SiO2-nZVI exhibited excellent ferromagnetic behaviour. The analysis of the degradation products showed that the MO treated by SiO2-nZVI was converted into a series of intermediates, resulting in reducing the toxicity of MO. The potential mechanism of MO degradated by SiO2-nZVI was speculated through degradation process and degradation kinetics analysis. Overall, the SiO2-nZVI composite may be regarded as a promising catalyst for decolorization of dye wastewater.

High-entropy-based nano-materials for sustainable environmental applications

High entropy materials (HEMs), epitomized by high entropy alloys (HEAs), have sparked immense interest for a range of clean energy and environmental applications due to their remarkable structural versatility and adjustable characteristics. In the face of environmental challenges, HEMs have emerged as valuable tools for addressing issues ranging from wastewater remediation to energy conversion and storage. This review provides a comprehensive exploration of HEMs, spotlighting their catalytic capabilities in diverse redox reactions, such as carbon dioxide reduction to value-added products, degradation of organic pollutants, oxygen reduction, hydrogen evolution, and ammonia decomposition using electrocatalytic and photocatalytic pathways. Additionally, the review highlights HEMs as novel electrode nanomaterials, with the potential to enhance the performance of batteries and supercapacitors. Their unique features, including high capacitance, electrical conductivity, and thermal stability, make them valuable components for meeting crucial energy demands. Furthermore, the review examines challenges and opportunities in advancing HEMs, emphasizing the importance of understanding the underlying mechanisms governing their catalytic and electrochemical behaviors. Essential considerations for optimizing the HEM performance in catalysis and energy storage are outlined to guide future research. Moreover, to provide a comprehensive understanding of the current research landscape, a meticulous bibliometric analysis is presented, offering insights into the trends, focal points, and emerging directions within the realm of HEMs, particularly in addressing environmental concerns.

Removal of nitrate by FeSiBC metallic glasses: high efficiency and superior reusability

The development of sustainable technologies for efficient nitrate removal has attracted increasing attention, because excessive nitrate emissions can result in serious environmental, economic, and health effects. Herein, we propose to utilize FeSiBC metallic glass (MG) powders as a potential solution for nitrate removal. In terms of removal efficiency and reusability, our results show that the MG powders, as special zero-valent iron carriers, are 2-3 orders of magnitude more efficient in nitrate removal than the previous studies, while maintaining more than 50% nitrate removal efficiency after 9 cycles of reaction. Moreover, the optimal FeSiBC MG dosage, pH value, and temperature for nitrate removal are determined. The mechanism of nitrate removal is also revealed. The present study offers a promising approach to remediate nitrate, one of the world's most widespread water pollutants.

Enhanced degradation performance of Fe75B12.5Si12.5 amorphous alloys on azo dye

The Fe₇₅B_12.5Si_12.5 and Fe₇₅B_12.5C_12.5 amorphous alloy ribbons were prepared by the melt spinning method. The decolorization performances of these ribbons were investigated in details. It is found that the Fe₇₅B_12.5C_12.5 amorphous ribbons and Fe₇₅B_12.5Si_12.5 annealed ribbons only adsorbed the azo dye molecules, with no chemical degradation process. However, the Fe₇₅B_12.5Si_12.5 amorphous ribbons can reduce -N = N- to -NH₂ because of their high reactivity and the local galvanic effect that occurred during the reaction to accelerate electron transfer. The reaction rate constant k_obs is 0.0872 min^-1, 0.0474 min^-1, and 0.0064 min^-1 for Fe₇₅B_12.5Si_12.5 amorphous ribbons, Fe₇₅B_12.5C_12.5 amorphous ribbons, and Fe₇₅B_12.5Si_12.5 annealed ribbons in the same condition, respectively. Fe₇₅B_12.5Si_12.5 amorphous ribbons can effectively degrade Acid Orange II (AO II) azo dyes and achieve decolorization by breaking azo bonds in the dye in a short time, indicating the prominent capacity of Fe₇₅B_12.5Si_12.5 ribbons on the degradation of AO II. Furthermore, the influence of chemical factors such as ribbons thickness, reaction temperature, initial pH, and AO II concentration of the solution on the reaction rate constant k_obs of Fe₇₅B_12.5Si_12.5 amorphous ribbons had also been studied. The k_obs can reach 0.177 min^-1 under optimal conditions. In addition, all the degradation processes in this work were fitted well with the pseudo-first-order kinetic model. The results are guidance for the practical applications, and they have important implications in developing Fe-based amorphous alloys for functional application materials in the field of wastewater treatment.

Cost-Effective H2 O2 -Regeneration of Powdered Activated Carbon by Isolated Fe Sites

The reuse of powdered activated carbon (PAC) vitally determines the economics and security of the PAC-based adsorption process, while state-of-the-art PAC regeneration technologies are usually unsatisfactory. Here, it is demonstrated that isolated Fe sites anchored on commercial PAC enable fast H₂ O₂ activation to produce Fe-based reactive oxygen species for highly efficient PAC regeneration at room temperature. Taking rhodamine B as a representative pollutant, PAC decorated with isolated Fe sites realize H₂ O₂ based regeneration with negligible adsorption capacity degradation for 10 cycles. Moreover, in terms of the PAC loss rate, this technology is greatly superior to traditional Fenton-based regeneration technology. Further operando experiments and theoretical calculations reveal that the high regeneration performance can be attributed to the isolated HOFeO motifs, which activate H₂ O₂ via a nonradical reaction pathway. These findings provide a very promising strategy toward reducing the cost of H₂ O₂ -based PAC regeneration technology.

Nanomaterials as a Sustainable Choice for Treating Wastewater: A Review

The removal of dyes from textile effluents utilizing advanced wastewater treatment methods with high efficiency and low cost has received substantial attention due to the rise in pollutants in water. The purpose of this work is to give a comprehensive analysis of the different treatments for removing chemical dyes from textile effluents. The capability and potential of conventional treatments for the degradation of dyeing compounds in aqueous media, as well as the influence of multiple parameters, such as the pH solution, initial dye concentration, and adsorbent dose, are presented in this study. This study is an overview of the scientific research literature on this topic, including nanoreductive and nanophotocatalyst processes, as well as nanoadsorbents and nanomembranes. For the purpose of treating sewage, the special properties of nanoparticles are currently being carefully researched. The ability of nanomaterials to remove organic matter, fungus, and viruses from wastewater is another benefit. Nanomaterials are employed in advanced oxidation techniques to clean wastewater. Additionally, because of their small dimensions, nanoparticles have a wide effective area of contact. Due to this, nanoparticles' adsorption and reactivity are powerful. The improvement of nanomaterial technology will be beneficial for the treatment of wastewater. This report also offers a thorough review of the distinctive properties of nanomaterials used in wastewater treatment, as well as their appropriate application and future possibilities. Since only a few types of nanomaterials have been produced, it is also important to focus on their technological feasibility in addition to their economic feasibility. According to this study, nanoparticles (NPs) have a significant adsorption area, efficient chemical reactions, and electrical conductivity that help treat wastewater effectively.

Fenton-like Remediation for Industrial Oily Wastewater Using Fe78Si9B13 Metallic Glasses

Metallic glasses (MGs) with a unique atomic structure have been widely used in the catalytic degradation of organic pollutants in the recent years. Fe78Si9B13 MGs exhibited excellent catalytic performance for the degradation of oily wastewater in a Fenton-like system for the first time. The oil removal and chemical oxygen demand (COD) removal from the oily wastewater were 72.67% and 70.18% within 60 min, respectively. Quenching experiments were performed to verify the production of active hydroxyl radicals (·OH) by activating hydrogen peroxide (H2O2). The formation of ·OH species can significantly contribute to the degradation reaction of oily wastewater. Fe78Si9B13 MG ribbons were highly efficient materials that exhibited superior reactivity towards H2O2 activation in oily wastewater treatment. The study revealed the catalytic capability of metallic glasses, presenting extensive prospects of their applications in oily wastewater treatment.

Preparation and application of a new Fenton-like catalyst from red mud for degradation of sulfamethoxazole

In this work, using molasses wastewater as a partial acidifying agent and bagasse pith as a pore-enlarging agent, a new low-cost Fenton-like catalyst (ACRM_bp) used for degradation of sulfamethoxazole was prepared through a simple process of acidification and calcination using red mud (RM) as the main material. The optimum preparation conditions of ACRM_bp were acquired, and the optimum preparation conditions of ACRM_bp were as follows: mass ratio of bagasse pith to RM (m_bp:m_RM) 0.033:1, particle size of bagasse pith 0.10-0.20 mm, calcination temperature 773 K, and calcination time 2 h. The ACRM_bp catalyst was characterized by XRD, SEM, EDS, and BET. According to the results of characterizations, it was found that the iron phase of ACRM_bp had completely transformed into α-Fe₂O₃ after the process of acidification and calcination, and the addition of bagasse pith significantly improved the surface area of the prepared ACRM_bp. Furthermore, under the reaction conditions of catalyst dosage of 2 g/L, initial pH 3 and reaction time 90 min, the ACRM_bp has showed the highest catalytic activity. ACRM_bp had significantly higher activity than red mud, and exhibited a remarkable settleability. Besides, ACRM_bp retained good recyclability and stability during use. Kinetic studies showed the degradation process could be described with the first-order model. Overall, the prepared ACRM_bp was an effective and excellent catalyst in the Fenton-like process.

Treatment of Olefin plant spent caustic by combination of Fenton-like and foam fractionation methods in a bench scale

Spent Merox caustic (SMC) is a hazardous waste that is produced during the Merox desulfurization process in the petroleum refinery industry and should be treated before discharging to environment. In the present study, treatment of SMC was investigated by three methods including Fenton-like process, foam fractionation, and a combination of both processes. Immobilized TiO₂/Fe⁰ on modified silica nanoparticles was used as a heterogeneous Fenton-like catalyst. The chemical and physical characteristics of the catalyst were determined using Fourier-transform infrared spectroscopy, X-ray diffraction, diffuse reflectance spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and transmission electron microscopy techniques. The treatment performance of the combined method was measured as a cost-effective method with chemical oxygen demand (COD) removal percentage. The effect of parameters including pH, gas flow rate, surfactant type and concentration of hydrogen peroxide, catalyst, and chelate were investigated. It is found that the prepared heterogeneous catalyst has high activity for the treatment of SMC. In addition, the results showed that the combined method achieved 97.6 ± 0.5% COD removal, while the measured values for Fenton or foam fractionation methods alone did not exceed 85.5 ± 1% and 47.2 ± 0.4%, respectively. The advantage of combination process over foam fractionation was the use of an advanced oxidation process in the separating column to eliminate or reduce the secondary phase contamination load. Besides, the role of the column in the effective contact of contaminants with the rising bubbles improved the degradation performance of the proposed process and reduced the consumption of hydrogen peroxide by 46% compared to the Fenton-like method.

Enhanced degradation of Rhodamine B dye by Fenton/peracetic acid and photo-Fenton/peracetic acid processes

In this research, the efficiency of advanced oxidation processes (AOPs) including Fenton−Peracetic Acid (PAA) and photo-Fenton− PAA in the removal of the Rodamine B (RhB) dye from aqueous solutions were studied. Investigating the effect of operating parameters such as pH (3–9), contact time (2–30 min), PAA concentration (10–80 mg/L), FeCl3.7H2O concentration (10–100 mg/L), and dye concentration (25–500 mg/L) on the performance of AOPs in removal of RhB was considered. The results showed that by decreasing pH and dye concentration, RhB removal efficiency increased. The optimal conditions for removal of RhB using Fenton− PAA process were determined to be as follows: dye concentration = 50 mg/L, pH = 3, PAA concentration = 50 mg/L, contact time = 10 min, and FeCl3 = 50 mg/L; in these conditions, removal efficiency of the RhB was 99.9%. In contrast, the photo-Fenton− PAA process was able to remove this amount of dye in just 5 min. The high performance of the system in a short time is attributed to the synergistic effect of the photo-Fenton− PAA process in the presence of UV. Finally, RhB dye was completely degraded by the photo-Fenton− PAA process and converted into CO2 and H2O products. In general, the photo-Fenton− PAA process compared to other methods can be used as a suitable and reliable method for the treatment of effluents of the dyeing industry and discharge them to the environment.

MoS2/FeS Nanocomposite Catalyst for Efficient Fenton Reaction

Nanocomposites containing FeS as catalyst and MoS2 as cocatalyst have been synthesized toward efficient heterogeneous Fenton reaction. The deposition of FeS nanoparticles in situ on the surface of MoS2 nanosheets creates strong contact between the two components and generates a large number of exposed Mo6+ sites and sulfur vacancies, which contribute to the enhanced degradation rate by accelerating Fe3+/Fe2+ cycling and ensuring rapid electron transfer. In addition, the MoS2/FeS nanocomposite catalysts exhibit the best performance at near-neutral conditions (pH 6.5), which solves the challenges in conventional Fenton reactions such as leaching of metal ions, the formation of iron slurry, and the need of adjusting solution pH. Further, the nanocomposite can maintain high efficiency after many recycling experiments. It is believed that the MoS2/FeS nanocomposite represents an efficient heterogeneous Fenton catalyst that can greatly promote the performance of advanced oxidation processes (AOPs) for solving practical environmental issues.

The catalytic performance of Cu46Zr47-xAl7Yx amorphous ribbons in the degradation of AO II dye wastewater

Metallic glasses (MGs) with unique disordered atomic stacking structures exhibit excellent catalytic performance in wastewater treatment. The catalytic degradation of Orange II (AO II) aqueous solutions by four CuZr-based MG ribbons under such processing parameters as pH values, the dosage of ribbons, and temperature was investigated in this paper. The catalytic performance of the MG ribbons was characterized by using the degradation efficiency of the dye wastewater. The phase constituent, surface morphology, and chemical valence state of elements on the surface of MG ribbons before and after use were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), respectively. The results indicate that the Cu₄₆Zr₄₂Al₇Y₅ MG ribbon has the best catalytic performance among the Cu₄₆Zr_47-xAl₇Y_x (x = 0, 1, 3, 5) MGs in the degradation process, and the dye in the wastewater can almost be completely decolorized within 60 min under the conditions of pH = 2, the dosage of ribbons being 1.8 g/L and water bath temperature of 313 K, with the degradation efficiency and chemical oxygen demand removal being 96.05% and 51.73%, respectively. Furthermore, the Cu₄₆Zr₄₂Al₇Y₅ MG ribbon still shows superior structural stability and degradation performance after repeated use, and the corrosion pits on the MG surface promote the physicochemical reaction between the wastewater and the ribbons.

Excellent dye degradation performance of FeSiBP amorphous alloys by Fenton-like process

Amorphous alloys are being newly applied in wastewater treatment because of their unique atomic packing structure. They possess excellent degradation efficiency, stability and reusability. In this work, Fe₈₀Si₁₀B₁₀ and Fe₈₃Si₅B₈P₄ amorphous ribbons exhibited advanced catalytic performance for the degradation of Methyl Blue (MB) and Rhodamine B (RhB) dyes, and the color removal reach nearly 100% within 11 min for both the dyes. Compared with the Fe₈₀Si₁₀B₁₀ amorphous ribbon, the Fe₈₃Si₅B₈P₄ ribbon showed higher degradation efficiency due to its lower reaction activation energy, higher electron transfer ability and higher Fe content, and the formation of the galvanic cell between the strong Fe-P bonds and the weak Fe-B bonds. It also exhibited high stability and reusability. The degradation efficiency was improved when the appropriate concentration of H₂O₂ is added. As regards the pH, high degradation efficiency was observed in acidic MB solution, but it decreased as the pH increased up to pH 7. The application of the electro-Fenton-like process is discussed, which can effectively improve the degradation performance in a nearly natural solution. This study presents a high efficiency low-cost catalyst for synthetic dye degradation and expands the functional applications of Fe-based amorphous alloys.

Redox cycling of copper mediated by hydrazine: efficient catalyst systems for oxidative degradation of rhodamine B

Catalytic processes based on Fenton-like reactions on the degradation of organic pollutants have been improved by accelerating the redox cycling of metal ions. This work presents, at first, the results obtained for the heterogeneous degradation of rhodamine B (RhB) by copper ferrite (CuFe₂O₄) in presence of hydrogen peroxide (H₂O₂) and hydrazine (N₂H₄) as redox cycle accelerator. Atomic absorption spectroscopy showed small amounts of Cu²⁺ are leached from ferrite highlighting the influence of the homogeneous catalysis in the whole process. The data obtained for the homogeneous process using Cu²⁺ in solution containing both N₂H₄ and H₂O₂ indicated such system is highly efficient mineralizing 73% of RhB within only 10 min of reaction and having H₂O and CO₂ as major products. Using tert-butyl alcohol as radical scavenger, it was confirmed hydroxyl radical (HO^•) is the active oxidant species regarding the RhB degradation. The homogeneous catalyst was applied to a real sample of textile effluent spiked with RhB and showed reasonable efficiency, although lower than that obtained for the standard solutions of RhB. This result was assigned to the interference of salts in the medium that react with HO^• thus acting as radical scavenger.

Reutilization of Fe-containing tailings ore enriched by iron(iii) chloride as a heterogeneous Fenton catalyst for decolorization of organic dyes

In this study, the Fe-containing tailings (Fe-TO) ore was reutilized and enriched with FeCl₃ as a heterogeneous catalyst for the Fenton process to degrade the organic dyes from aqueous solution. The determinants of the heterogeneous catalytic Fenton system which included iron modification ratio, solution pH, catalyst dosage, H₂O₂ dosage and initial concentration of organic dyes were systematically investigated. The modification ratio of 15% (w/w of iron), pH of 3, MFe-TO15 dosage of 0.5 g L⁻¹ and H₂O₂ dosage of 840 mg L⁻¹ were chosen as the best operational conditions for Fenton oxidation of organic dyes. The decolorization efficiency of both MB and RhB by MFe-TO15/H₂O₂ was higher than that of Fe-TO/H₂O₂ by about two times. The kinetic study showed the degradation of organic dyes well fitted the pseudo-first-order kinetic model with apparent constant rate values (K_d) following the same sequence as the degradation efficiency of organic dyes. The degradation mechanism of dyes could be attributed to adsorption due to the good-development in textural properties of the iron modified catalyst (MFe-TO) with an increase in BET surface area, pore volume and pore diameter of, respectively, 2, 5 and 5 times and leaching iron through homogeneous Fenton reaction. However, the oxidation process occurring on the MFe-TO15's surface by heterogeneous Fenton reaction which enhanced decomposition of H₂O₂ for continuous generation of hydroxyl radicals was the main mechanism. The key role of *OH radical in oxidation of organic dyes was further ascertained by the remarkable drop in the decolorization of both organic dyes when the various radical-scavengers, including tert-butanol and chloride were supplemented into Fenton systems. A good stability of the catalyst was obtained through leaching test with low leaching iron ratio. The applied modified catalyst remained stable through three consecutive runs. From these findings, it can be concluded that the modified material can be applied as a feasible, inexpensive and highly effective catalyst for removal of persistent organic compounds from wastewater.

In this study, the Fe-containing tailings (Fe-TO) ore was reutilized and enriched with FeCl₃ as a heterogeneous catalyst for the Fenton process to degrade the organic dyes from aqueous solution.

Investigation of the Structural Heterogeneity and Corrosion Performance of the Annealed Fe-Based Metallic Glasses

This study investigated the structural heterogeneity, mechanical property, electrochemical behavior, and passive film characteristics of Fe-Cr-Mo-W-C-B-Y metallic glasses (MGs), which were modified through annealing at different temperatures. Results showed that annealing MGs below the glass transition temperature enhanced corrosion resistance in HCl solution owing to a highly protective passive film formed, originating from the decreased free volume and the shrinkage of the first coordination shell, which was found by pair distribution function analysis. In contrast, the enlarged first coordination shell and nanoscale crystal-like clusters were identified for MGs annealed in the supercooled liquid region, which led to a destabilized passive film and thereby deteriorated corrosion resistance. This finding reveals the crucial role of structural heterogeneity in tuning the corrosion performance of MGs.

Nano-PAA-CuCl2 Composite as Fenton-Like Reusable Catalyst to Enhanced Degrade Organic Pollutant MB/MO

The treatment of organic dye contaminants in wastewaters has now becoming more imperative. Fenton-like degradation of methylene blue (MB) and methyl orange (MO) in aqueous solution was investigated by using a nanostructure that a layer of CuCl2 nanoflake film grown on the top surface of nanoporus anodic alumina substrate (nano-PAA-CuCl2) as catalyst. The new nano-PAA-CuCl2 composite was fabricated with self-assembly approach, that is, a network porous structure film composed of CuCl2 nanoflake grown on the upper surface of nanoporous anodic alumina substrate, and the physical and chemical properties are characterized systematically with the X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and high-resolution transmission electron microscopy (HRTEM), Energy Dispersive Spectrometer (EDS), X-ray photoelectron spectroscopy (XPS). The experimental results showed that the nano-PAA-CuCl2 catalyst presented excellent properties for the degradation of two typical organic pollutants such as MB and MO, which were almost completely degraded with 8 × 10−4mol/L nano-PAA-CuCl2 catalyst after 46 min and 60 min at reaction conditions of H2O2 18 mM and 23 mM, respectively. The effects of different reaction parameters such as initial pH, H2O2 concentration, catalyst morphology and temperature were attentively studied. And more, the stability and reusability of nano-PAA-CuCl2 were examined. Finally, the mechanism of MB and MO degradation by the nano-PAA-CuCl2/H2O2 system was proposed, based on the experimental data of the BCA and the temperature-programmed reduction (H2-TPR) and theoretical analysis, the reaction kinetics belonged to the pseudo-first-order equation. This new nanoporous composite material and preparation technology, as well as its application in Fenton-like reaction, provide an effective alternative method with practical application significance for wastewater treatment.

Green synthesized iron nanoparticles as highly efficient fenton-like catalyst for degradation of dyes

Iron nanoparticles (Fe NPs) were synthesized herein through a simple and eco-friendly method using FeCl₃ and aqueous plant extract (dimocarpus longan, DL). Compared with Fe NPs prepared via traditional chemical methods, this biogenetic DL-Fe NPs demonstrates higher catalytic activity in Fenton-like reaction to degrade methyl orange (MO) in a wide pH range. It's worth noting that the DL-Fe NPs manifest a superior stability even after storage for at least 28 days. Systematic characterizations indicate that the active biomolecules from plant extract significantly contribute to the superior performance of DL-Fe NPs, by facilitating the dye molecules to be adsorbed on the surfaces of DL-Fe NPs, and providing a stable acid environment for the Fenton-like catalytic reaction. The kinetics study demonstrates this removal process conforms to the pseudo first-order model with the reaction activation energy of 41.6 kJ/mol. Moreover, various typical dyes including congo red, malachite green, methylene blue, eosin-Y and rhodamine B can be dramatically degraded by this DL-Fe NPs with a satisfactory removal efficiency.

Continuous electrocoagulation degradation of oily wastewater with Fe78Si9B13 amorphous ribbons

The oily wastewater was treated by electrocoagulation with Fe₇₈Si₉B₁₃ amorphous ribbons as anode and graphite plates as cathode under such processing parameters as different pH values and current density, respectively. The degradation effect on the oily wastewater was characterized by chemical demand oxygen (COD), while the ribbons before and after using were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicate that under the conditions of pH = 3 and current density being 3.125 A/cm², the optimal COD removal efficiency was obtained to be 73.22%. Compared with the ordinary crystalline iron plate, the COD removal efficiency of resultant wastewater degraded by the amorphous ribbons is more than doubled. Simultaneously, the Fe₇₈Si₉B₁₃ amorphous ribbons exhibit good structural stability even after four cycles of using.

Efficiency and mechanisms of rhodamine B degradation in Fenton-like systems based on zero-valent iron

Based on the Fe0/H2O2 heterogeneous Fenton system, the degradation of rhodamine B (RhB, an organic dye pollutant) was researched in this paper. The effects of initial pH value, concentration of H2O2, dosage of zero-valent iron (ZVI), and initial RhB concentration on RhB degradation by Fe0/H2O2 were studied. The results showed that when the initial pH = 4, dosage of ZVI was 9 mM, and concentrations of H2O2 and RhB were 8 mM and 0.1 mM, respectively, the color of RhB could be completely faded within 30 min, and the total organic carbon (TOC) removal percentage was about 63% after 120 min. The dissolved oxygen (DO) content and oxidation-reduction potential (ORP) were monitored during the reaction. Quenching experiments with methanol confirmed that the degradation of the dye was mainly due to oxidation by the ˙OH radical. Besides, the results from UV-Vis spectroscopy showed that the degradation of RhB was mainly due to the destruction of the conjugated oxygen hetero-anthracene in the RhB molecule. The solid-phase characterization of the ZVI samples after reaction confirmed that the original regular and slippery ZVI samples finally were corroded into rough and irregular lepidocrocite and magnetite. Two possible competitive reaction pathways for the degradation of RhB by Fe0/H2O2 were proposed by GC-MS analysis, which were attributed to the dissociation of ethyl radicals and the degradation of chromophore radicals.

Three-Dimensional CuO/TiO2 Hybrid Nanorod Arrays Prepared by Electrodeposition in AAO Membranes as an Excellent Fenton-Like Photocatalyst for Dye Degradation

Three-dimensional (3D) CuO/TiO₂ hybrid heterostructure nanorod arrays (NRs) with noble-metal-free composition, fabricated by template-assisted low-cost processes, were used as the photo-Fenton-like catalyst for dye degradation. Here, CuO NRs were deposited into anodic aluminum oxide templates by electrodeposition method annealed at various temperatures, followed by deposition of TiO₂ thin films through E-gun evaporation, resulting in the formation of CuO/TiO₂ p-n heterojunction. The distribution of elements and compositions of the CuO/TiO₂ p-n heterojunction were analyzed by EDS mapping and EELS profiles, respectively. In the presence of H₂O₂, CuO/TiO₂ hybrid structure performed more efficiently than CuO NRs for Rhodamine B degradation under the irradiation of 500-W mercury-xenon arc lamp. This study demonstrated the effect of length of CuO NRs, on the photo-degradation performance of CuO NRs as well as CuO/TiO₂ heterostructure. The optimized CuO/TiO₂ hybrid NR array structure exhibited the highest photo-degradation activity, and the mechanism and role of photo-Fenton acting as the catalyst in photo-degradation of dye was also investigated.

Fe-Based Metallic Glasses and Dyes in Fenton-Like Processes: Understanding Their Intrinsic Correlation

Fe-based metallic glasses have been demonstrated as effective heterogeneous catalysts in Fenton-like processes for dye degradation. Yet, currently corresponding studies have limitations due to the limited study object (dyes) and the correlation between metallic glasses and dye pollutants in Fenton-like processes is still not comprehensively studied. Accordingly, this work intensively investigated the thermal catalytic behavior correlations between two Fe-based metallic glasses (Fe78Si9B13 and Fe73.5Si13.5B9Cu1Nb3) and eight different dyes. Results indicated a lower activation energy in the more active metallic glass and a dependence of the activation energy of Fe-based metallic glasses in dye solutions. In addition, a high H2O2 concentration led to a declined catalytic efficiency but a photo-enhanced Fenton-like process overcame this limitation at high concentration of H2O2 due to the decrease of pH and enhancement of irradiation. Furthermore, the average mineralization rates of Fe78Si9B13 and Fe73.5Si13.5B9Cu1Nb3 have been measured to be 42.7% and 12.6%, respectively, and the correlation between decolorization and mineralization revealed that a faster decolorization in a Fenton-like process contributed to a higher mineralization rate. This work provides an intrinsic viewpoint of the correlation between Fe-based metallic glasses and dyes in Fenton-like processes and holds the promise to further promote the industrial value of metallic glasses.

Effect of Ni Addition on Catalytic Performance of Fe87Si5B2P3Nb2Cu1 Amorphous Alloys for Degrading Methylene Blue Dyes

Fe-based amorphous alloys have shown great potential in degrading azo dyes and other organic pollutants. It has been widely investigated as a kind of environmentally friendly material for wastewater remediation. In this paper, we studied the effect of Ni addition on the catalytic performance of Fe87Si5B2P3Nb2Cu1 amorphous alloy for degradation of methylene blue dyes and analyzed the reaction mechanism. (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous powder with desirable performance was produced by specific ball milling durations. Characterization of the Fe87Si5B2P3Nb2Cu1 and (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous alloys prepared by ball milling was performed by XRD and SEM. Fe87Si5B2P3Nb2Cu1 and (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous alloys were used as catalysts to catalyze the degradation of methylene blue dyes, which were detected by UV-VIS near-infrared spectrophotometer. By a series of comparative experiments, it was found that a catalyst dosage of 0.2 g and a reaction temperature of 80 °C were conditions that produced the best catalytic effect. The degradation rate of (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous alloy to methylene blue dyes prepared by ball milling increased from 67.76% to 99.99% compared with the Fe87Si5B2P3Nb2Cu1 amorphous alloy under the same conditions.

Effect of Co addition on catalytic activity of FePCCu amorphous alloy for methylene blue degradation

A novel FeCoPCCu amorphous alloy as a highly efficient catalyst in Fenton-like reactions for methylene blue degradation.

Preparation of hollow iron/halloysite nanocomposites with enhanced electromagnetic performances

Nanostructures loaded on halloysite nanotubes (HNTs) have attracted global interest, because the nanotubular HNTs could extend the range of their potential applications. In this study, we fabricated a novel nanocomposite with hollow iron nanoparticles loaded on the surface of HNTs. The structure of the iron nanoparticles can be adjusted by ageing time. Owing to the increased remnant magnetization and coercivity values, the nanocomposites loaded with hollow iron nanoparticles showed better electromagnetic performance than that with solid iron nanoparticles. This study opens a new pathway to fabricate halloysite nanotubular nanocomposites that may gain applications in the catalytic degradation of organic pollutants and electromagnetic wave absorption.

Preparation of a new Fenton-like catalyst from red mud using molasses wastewater as partial acidifying agent

Using molasses wastewater as partial acidifying agent, a new Fenton-like catalyst (ACRM _sm ) was prepared through a simple process of acidification and calcination using red mud as main material. With molasses wastewater, both the free alkali and the chemically bonded alkali in red mud were effectively removed under the action of H₂SO₄ and molasses wastewater, and the prepared ACRM _sm was a near-neutral catalyst. The ACRM _sm preparation conditions were as follows: for 3 g of red mud, 9 mL of 0.7 mol/L H₂SO₄ plus 2 g of molasses wastewater as the acidifying agent, calcination temperature 573 K, and calcination time 1 h. Iron phase of ACRM _sm was mainly α-Fe₂O₃ and trace amount of carbon existed in ACRM _sm . The addition of molasses wastewater not only effectively reduced the consumption of H₂SO₄ in acidification of red mud but also resulted in the generation of carbon and significantly improved the distribution of macropore in prepared ACRM _sm . It was found that near-neutral pH of catalyst, generated carbon, and wide distribution of macropore were the main reasons for the high catalytic activity of ACRM _sm . The generated carbon and wide distribution of macropore were entirely due to the molasses wastewater added. In degradation of orange II, ACRM _sm retained most of its catalytic stability and activity after five recycling times, indicating ACRM _sm had an excellent long-term stability in the Fenton-like process. Furthermore, the performance test of settling showed ACRM _sm had an excellent settleability. ACRM_sm was a safe and green catalytic material used in Fenton-like oxidation for wastewater treatment.

Fe-based metallic glass catalyst with nanoporous surface for azo dye degradation

In this work, porous structures were introduced to the surface of Fe-based metallic glass ribbons for the first time by chemical treatment in order to increase the catalytic activity in the degradation of azo dyes. The results show that etching treatment in an HF solution with a volume concentration of 20% for 40 min leads to a porous structure on the FeSiBNb metallic glass with a dramatic increase in the specific surface area by 25 times. The much higher specific surface area of the porous ribbons greatly improves the catalytic activity in the degradation of Direct Blue 15 when compared with as-spun metallic ribbons.

Degradation of organic contaminants in effluents-synthetic and from the textile industry-by Fenton, photocatalysis, and H2O2 photolysis

In this study, the oxidation of the dye rhodamine B (RhB), present in a synthetic effluent, and the degradation of organic matter present in a textile effluent, were assessed by photolysis (H₂O₂, UV), homogeneous Fenton (Fe²⁺, H₂O₂), and photocatalysis (TiO₂, UV). The results showed that photolysis and Fenton had an efficiency of 100 % and photocatalysis, 96 %, to discoloration 10 mg L^-1 RhB, present in the synthetic effluent. The best experimental conditions determined for these reactions showed that the one performed with 51 mg L^-1 H₂O₂ and UV light had the best results, where 100 % of RhB was discolored in only 6 min of reaction. The optimum conditions determined in the first part of this study for the RhB oxidation did not show satisfactory results for the degradation of organic matter present in the textile effluent sample, and it was necessary to increase the amount of reagents in the three processes. After resizing the concentration of the reagents for the reactions with the textile effluent, the following reductions of color, total organic carbon (TOC), and total soluble solids (SS) were obtained: photocatalysis 29, 25, and 32 %; photolysis 85, 69, and 35 %; Fenton 98, 90, and 23 %; and biological (followed by physicochemical) treatment carried out by the textile industry 96, 48, and 9 %. It is observed that the Fenton reaction showed the best result, followed by photolysis reaction, a treatment carried out by industry and, at last, photocatalysis.

Controlled synthesis of Bi25FeO40 with different morphologies: growth mechanism and enhanced photo-Fenton catalytic properties

Bi₂₅FeO₄₀ microtetrahedra, microcubes and microspheres were synthesized via a simple hydrothermal method and the microcubes showed enhanced photo-Fenton catalytic activity.

Fabrication of nanoporous copper with tunable ligaments and promising sonocatalytic performance by dealloying Cu–Y metallic glasses

Nanoporous copper (NPC) with tunable ligaments was prepared by dealloying new Cu–Y binary metallic glasses. The sono-Fenton-like process of NPC with desired microstructure shows great potential in degrading organic dyes.

Ultra-sustainable Fe78Si9B13 metallic glass as a catalyst for activation of persulfate on methylene blue degradation under UV-Vis light

Stability and reusability are important characteristics of advanced catalysts for wastewater treatment. In this work, for the first time, sulfate radicals (SO4∙-) with a high oxidative potential (Eo = 2.5-3.1 V) were successfully activated from persulfate by a Fe78Si9B13 metallic glass. This alloy exhibited a superior surface stability and reusability while activating persulfate as indicated by it being used for 30 times while maintaining an acceptable methylene blue (MB) degradation rate. The produced SiO2 layer on the ribbon surface expanded strongly from the fresh use to the 20th use, providing stable protection of the buried Fe. MB degradation and kinetic study revealed 100% of the dye degradation with a kinetic rate k = 0.640 within 20 min under rational parameter control. The dominant reactive species for dye molecule decomposition in the first 10 min of the reaction was hydroxyl radicals (∙OH, Eo = 2.7 V) and in the last 10 min was sulfate radicals (SO4∙-), respectively. Empirical operating variables for dye degradation in this work were under catalyst dosage 0.5 g/L, light irradiation 7.7 μW/cm2, and persulfate concentration 1.0 mmol/L. The amorphous Fe78Si9B13 alloy in this work will open a new gate for wastewater remediation.

Effective degradation of rhodamine B by electro-Fenton process, using ferromagnetic nanoparticles loaded on modified graphite felt electrode as reusable catalyst: in neutral pH condition and without external aeration

Polytetrafluoroethylene/ferromagnetic nanoparticle/carbon black (PTFE/MNP/CB)-modified graphite felt (GF) was successfully applied as cathode for the mineralization of rhodamine B (RhB) in electro-Fenton (EF) process. The modified cathode showed high decolorization efficiency for RhB solution even in neutral pH condition and without external aeration, achieving nearly complete decolorization and 89.52 % total organic carbon (TOC) removal after 270-min oxidation with the MNP load 1.2 g at 50 A/m(2). Moreover, the operational parameters (current density, MNP load, initial pH, and airflow rate) were optimized. After that, adsorption isotherm was also conducted to compare the absorption quantity of CB and carbon nanotube (CNT). Then, the surface morphologies of MNPs were characterized by transmission electron microscope (TEM), energy-dispersive X-ray detector (EDX), and Fourier transform infrared spectroscopy (FTIR); and the modified cathode was characterized by SEM and contact angle. Finally, the stability and reusability of modified cathode were tested. Result uncovered that the PTFE/MNP/CB-modified cathode has the potential for industrial application and the solution after treatment was easily biodegradable.

Efficient degradation of rhodamine B using modified graphite felt gas diffusion electrode by electro-Fenton process

The electro-Fenton (EF) process treatment of 0.1-M (rhodamine B) RhB solution was studied with different graphite cathode materials, and graphite felt (GF) was selected as a promising material in further investigation. Then, the degradation performances of gas diffusion electrode (GDE) and graphite felt (GF) were compared, and GDE was confirmed to be more efficient in RhB removal. The operational parameters such as Fe(2+) dosage and current density were optimized, and comparison among different modified methods-polytetrafluoroethylene-carbon black (PTFE-CB), polytetrafluoroethylene-carbon nanotube (PTFE-CNT), electrodeposition-CB, and electrodeposition-CNT-showed 98.49 % RhB removal by PTFE-CB-modified cathode in 0.05 M Na2SO4 at a current density of 50 A/m(2) and an air flow rate of 1 L/min after 20 min. Meanwhile, after cathode modified by PTFE-CB, the mineralization efficiency and mineralization current efficiency performed absolutely better than the pristine one. Cyclic voltammograms, SEM images, contact angles, and BET surface area were carried out to demonstrate stronger current responses and higher hydrophilicity of GF after modified. The value of biochemical oxygen demand/chemical oxygen demand (BOD5/COD) increased from 0.049 to 0.331 after 90-min treatment, suggesting the solution was biodegradable, and the modified cathode was confirmed to be stable after ten circle runs. Finally, a proposed degradation pathway of RhB was put forward.

Ultrasound and heat enhanced persulfate oxidation activated with Fe(0) aggregate for the decolorization of C.I. Direct Red 23

Effluents from the paper printing and textile industries are often heavily contaminated with azo dyes. Azo dyes are difficult to oxidize biologically. This work investigated the decolorization of an azo dye, C.I. Direct Red 23 (DR23), by persulfate (PS) activated with Fe(0) aggregates (PS/Fe(0)). Ultrasound (US) and heat were used as enhancement tools in the PS oxidation system. Neither US-activated PS nor thermally activated PS was effective in oxidizing DR23. However, the decolorization was significantly enhanced by PS/Fe(0) combined with US (PS/Fe(0)/US) or heat (PS/Fe(0)/55 °C). Approximately 95% decolorization of 1×10(-4) M DR23 was achieved within 15 min in the PS/Fe(0)/US system at an initial pH of 6.0, PS of 5×10(-3) M, Fe(0) of 0.5 g/L and US irradiation of 106 W/cm(2) (60 kHz). Complete decolorization was achieved within 10 min in the Fe(0)/PS/55 °C system. The rate of decolorization doubled when US was introduced in the PS/Fe(0) system during the treatment of different initial dye concentrations. The dependence of dye and true color (ADMI) depletion on PS concentration has been discussed. DR23 was completely degraded based on the disappearance of aromatic groups of UV-vis spectra and the variation of TOC mineralization. The observed pseudo-first-order decolorization rate was substantially enhanced by increasing temperature. The Arrhenius activation energy for the PS activated with Fe(0) was estimated as 8.98 kcal/mol, implying that higher temperature is beneficial for the DR23 decolorization. The addition of US into the PS/Fe(0) system did not incur a substantial increase in electricity, whereas the mineralization of DR23 occurred quickly. Thus, both PS/Fe(0)/US and heated PS/Fe(0) systems are practically feasible for the effective degradation of the direct azo dye in textile wastewater.

A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders

A new Fe-based metallic glass with composition Fe₇₆B₁₂Si₉Y₃ (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C₁₄H₁₄N₃SO₃) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294–328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment.

Visible light induced photocatalytic degradation of rhodamine B by magnetic bentonite

The photocatalytic activity of magnetic bentonite, Fe3O4 nanoparticles decorated Al-pillared bentonite (Fe3O4/Al-B), for the degradation of rhodamine B (RhB) in the presence of H2O2 under visible light (VL) was evaluated. The effects of different reaction parameters such as catalyst dose, dye concentration and externally added H2O2 were also investigated. The magnetic bentonite showed good photocatalytic activity, magnetic separability and stability for repeated use. More than 95% of 40 mg/L RhB was converted within 3 h under VL with a catalyst dose of 0.5 g/L. Suitable mechanisms have been proposed to account for the photocatalytic activities in the presence and absence of H2O2. The efficiency of H2O2 in VL process was much higher than that of the dark process. Results obtained in the current study may be useful to develop a suitable photocatalyst for photocatalytic remediation of different water contaminants including organic dyes.

Quantitative characterization of hydroxyl radical generation in a goethite-catalyzed Fenton-like reaction

In order to find out the truth of influence of solution chemistry on the oxidation efficiency of a goethite-catalyzed Fenton-like reaction, the amount of hydroxyl radicals (OH) was quantified by using coumarin as its trapping agent to produce the only fluorescent derivative 7-hydroxycoumarin (7-HC), because OH was the reactive species responsible for the oxidation activity of Fenton reactions. The concentration of OH achieved maximum at solution pH of 3 and decreased with an increase of solution pH value. However, considerable amount of OH can also generate at near neutral pH (i.e. pH 6 and 7). The concentration of OH was increased both with increasing of goethite and H2O2 dosages, but H2O2 could compete with coumarin to scavenge OH to reduce the formation of 7-HC when the concentration of H2O2 was too high. Anions inhibited OH generation followed an order of H2PO4(-)>SO4(2-)>Cl(-)>NO3(-)>ClO4(-). Higher concentrations of Cl(-) and SO4(2-) resulted in greater inhibition of OH generation. Results of this study demonstrated that the influence of solution chemistry on the oxidation efficiency of the goethite-catalyzed Fenton-like reaction was greatly attributed to the effect of solution chemistry on the amount of OH formed in the process of reaction.