Magnetite/Fe-Al-montmorillonite as a Fenton catalyst with efficient degradation of phenol

Applying bottom ash as an alternative Fenton catalyst for effective removal of phenol from aqueous environment

In this study, coal bottom ash from a thermoelectric plant was tested as an alternative Fenton catalyst for phenol degradation in water. The effect of operating parameters such as initial pH, catalyst dosage and H2O2 concentration were evaluated. The characterization results indicated that the material has a mesoporous structure, with active species (Fe) well distributed on its surface. Under the optimal reaction conditions (6 mM H2O2, 1 g L-1 of catalyst and pH = 3), 98.7% phenol degradation efficiency was achieved in 60 min, as well as 71.6% TOC removal after 150 min. Hydroxyl radical was identified as the main oxidizing agent involved on the cleavage of the phenol molecule. After four consecutive reuse cycles, phenol degradation efficiency was around 80%, indicating good reusability and stability of the catalyst. Therefore, the obtained results demonstrated that the bottom ash presents remarkable activity for application in the Fenton reaction towards phenol degradation.

A comprehensive review on metal based active sites and their interaction with O3 during heterogeneous catalytic ozonation process: Types, regulation and authentication

Heterogeneous catalytic ozonation (HCO) was a promising water purification technology. Designing novel metal-based catalysts and exploring their structural-activity relationship continued to be a hot topic in HCO. Herein, we reviewed the recent development of metal-based catalysts (including monometallic and polymetallic catalysts) in HCO. Regulation of metal based active sites (surface hydroxyl groups, Lewis acid sites, metal redox cycle and surface defect) and their key roles in activating O₃ were explored. Advantage and disadvantage of conventional characterization techniques on monitoring metal active sites were claimed. In situ electrochemical characterization and DFT simulation were recommended as supplement to reveal the metal active species. Though the ambiguous interfacial behaviors of O₃ at these active sites, the existence of interfacial electron migration was beyond doubt. The reported metal-based catalysts mainly served as electron donator for O₃, which resulted in the accumulation of oxidized metal and reduced their activity. Design of polymetallic catalysts could accelerate the interfacial electron migration, but they still faced with the dilemma of sluggish Me^(n+m)+/Meⁿ⁺ redox cycle. Alternative strategies like coupling active metal species with mesoporous silicon materials, regulating surface hydrophobic/hydrophilic properties, polaring surface electron distribution, coupling HCO process with photocatalysis and H₂O₂ were proposed for future research.

Enhanced visible-light-driven photocatalysis of in-situ reduced of bismuth on BiOCl nanosheets and montmorillonite loading: Synergistic effect and mechanism insight

Various improvement strategies have been developed to enhance the visible light photocatalytic properties of materials. In these enhancement strategies, bismuth, a non-noble metal-based plasma metal, is deposited on the surface of the photocatalyst, which can improve the visible light response and photocatalytic performance of the photocatalyst. Herein, we constructed montmorillonite loaded BiOCl nanosheets with in situ reduced bismuth by one-step hydrothermal method. As for the results of TEM analysis, the in-situ reduced bismuth nanoparticles with diameters of 5-20 nm were evenly distributed on the surface of BiOCl nanosheets. Due to the surface plasmon resonance (SPR) effect of semi metallic bismuth nanoparticles on the BiOCl nanosheets, the light absorption range of the modified photocatalyst was expanded and its absorption band gap (E_g) was reduced from 3.16 eV (pure BiOCl) to 2.26 eV. Besides, the results of dark adsorption experiments confirmed that the montmorillonite supporter greatly enhanced the adsorption capacity of the modified photocatalyst for pollutants. Moreover, the radical species trapping tests revealed that •O₂^- and h⁺ were the pivotal active agents in the pollutant degradation process. The visible light driven photocatalytic degradation rate of TCs and RhB by the modified photocatalyst was 3 and 4 times higher than that of pure BiOCl because of the synergistic effect of montmorillonite supporter and bismuth nanoparticles. The present work provides an innovative strategy for the great feasibility of fabricating low-cost clay and effective bismuth nanoparticles as a substitute for noble metal in environmental pollutants degradation.

Production of biologically active hydroxytyrosol rich extract via catalytic conversion of tyrosol

An effective and economical process was established to produce hydroxytyrosol, a naturally occurring orthodiphenolic antioxidant molecule found in olive oil from its monophenolic precursor tyrosol. The approach proposed in the present work presents an environment-friendly method based on wet hydrogen peroxide catalytic oxidation with montmorillonite KSF as an inexpensive and environmentally benign solid acid at room temperature. The influence of the principal operating parameters including concentration of tyrosol, H₂O₂, and catalyst used were studied. The antioxidant activity was realized by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. High antioxidant activity was detected according to the high hydroxytyrosol production (IC₅₀ = 0.7 μg mL⁻¹). The bactericidal and fungicidal properties of hydroxytyrosol rich extract were investigated using the NCCLS broth dilution and EN 1276 standard methods. Positive bactericidal and fungicidal effects of concentrations ranging between 1–0.5 g L⁻¹ and 4–2 g L⁻¹ were obtained.

An effective and economical process was established to produce hydroxytyrosol, a natural antioxidant molecule.

Enhancement of Pentachlorophenol Removal in a Historically Contaminated Soil by Adding Ascorbic Acid to H2O2/Magnetite System

Development of new tools to improve the efficiency of iron minerals in promoting Fenton oxidation for environmental remediation is a highly promising field. Here, we examine for the first time the role of ascorbic acid (AA) in improving the magnetite (Fe3O4)-mediated Fenton oxidation to remove pentachlorophenol (PCP) in a historically contaminated soil. Experiments were performed in batch and flow-through conditions. In batch slurry experiments, the combination of Fe3O4/AA/H2O2 removed up to 95% of PCP as compared to the 43% removal by Fe3O4/H2O2. Dissolved Fe(II) measurements and Mössbauer spectroscopy highlight the role of AA in increasing the Fe(II) generation. Therefore, its presence enabled the Fe3O4 to maintain its structural Fe(II) content even after the oxidation reaction. Despite kinetic limitations in water-saturated columns, use of Fe3O4/AA/H2O2 removed about 70% of PCP contrary to the 20% PCP removal with Fe3O4/H2O2. This oxidation performance was affected by an injection flow rate or column residence time of AA and H2O2 in columns. Thus, the presence of AA significantly improved the ability of magnetite in promoting the Fenton reaction. Owing to the crucial role of AA in the Fe(II)/Fe(III) redox cycling, a mixed-valent character of magnetite makes it a potential catalyst for Fenton oxidation of organic pollutants.

Catalytic degradation of p-nitrophenol by magnetically recoverable Fe3O4 as a persulfate activator under microwave irradiation

In this study, Fe₃O₄ and microwave (MW) were combined to activate persulfate (PS) for the removal of organic matter, resulting in the enhanced degradation of p-nitrophenol (PNP) in solution. During the preparation of Fe₃O₄, the effect of sodium acetate was examined, and the results showed that the concentration of sodium acetate had little effect on the catalytic activity of the Fe₃O₄/PS/MW system but did have an effect on the Fe₃O₄ yield. In addition, with regards to the representative environmental factors, the degradation experiment showed that humic acid and the co-existing anions of chloride, sulfate, nitrate, and phosphate had little effects on p-nitrophenol removal; however, carbonate had a negative effect. In addition, the Fe₃O₄/PS/MW system performed well in the initial pH range of 3.0-9.0. According to the quenching experiment and electron paramagnetic resonance (EPR) detection, sulfate radicals and a minority of hydroxyl radicals play dominant roles in the degradation process. In addition, the role of Fe₃O₄ was confirmed to take part in the degradation process by X-ray photoelectron spectroscopy (XPS) analysis. Because of the good performance observed in the water matrices of tap water and the Songhua River, these results demonstrate the potential application of the Fe₃O₄/PS/MW system for wastewater treatment.

Use of an Environmental Pollutant From Hexavalent Chromium Removal as a Green Catalyst in The Fenton Process

The present study refers to the use of an environmental pollutant generated during the removal of hexavalent chromium from aqueous media. This pollutant is a material with catalytic properties suitable for application in the oxidative degradation of problematic organic compounds. The material, initially used as an adsorbent, is a composite prepared by modifying the crystalline phases of iron oxides together with the chitosan (CT-FeCr). Chemical and morphological characterizations of the materials were performed using SEM analysis coupled with EDS, XRD and DSC. The CT-FeCr beads were used in the degradation of methylene blue dye (MB) and showed excellent degradation potential (93.6%). The presence of Cr on the surface of the catalyst was responsible for the increase in catalytic activity compared to the CT-Fe and pure magnetite materials. The product of the effluent treatment and the presence of the catalyst itself in the environment do not pose toxic effects. In addition, the CT-FeCr beads showed catalytic stability for several consecutive reaction cycles with possible technical and economic viability. The concept of "industrial symbiosis" may be applied to this technology, with that term relating to the reuse of a byproduct generated in one particular industrial sector by another as a raw material.

A nanoscale "yarn ball"-like heteropoly blue catalyst for extremely efficient elimination of antibiotics and dyes

Fenton system is one of the most popular methods to eliminate antibiotics and dyes in aquatic environment. However, the existed Fenton system is limited by various factors such as potential second pollution and narrow pH range. In this study, we report that the bottlenecks for high strength antibiotics and dyes wastewater treatment at a wide pH range can be well tackled by the nanoscale "yarn ball"-like Mo/W-containing heteropoly blue (HPB) catalyst Mg₂Ti₆Mo₂₃O₁₁₉SiW₁₂ (1). This novel catalyst displayed extremely efficient elimination for several typical organic contaminants such as malachite green (MG), tetracycline (TC) and methyl orange (MO). Compared with other materials reported in previous papers, the catalytic performance of 1 in degradation of the organic contaminants of high concentrations increased several times. More than 90% of antibiotics and dyes are degraded within 60 min. Electron spin resonance (ESR) experiments and UV-vis spectra confirmed that the catalytic mechanisms of 1 could mainly ascribe to the 1/H₂O₂ process and the possible photocatalytic oxidation of adsorbed H₂O by holes (h⁺) in the valence band (VB) of 1 surface generated ·OH for extremely efficient degradation of organic contaminants. This work widens the optimal pH values up to neutral condition and it's significant for the expansion of the heterogeneous Fenton-like catalyst family and its application in the field of water treatment.

FeNiCeOx ternary catalyst prepared by ultrasonic impregnation method for diclofenac removal in Fenton-like system

FeNiCeO_x was firstly prepared by ultrasonic impregnation method and used to remove diclofenac in a Fenton-like system. The catalytic activity was improved successfully by doping Ni into FeCeO_x. The diclofenac removal efficiency reached 97.9% after 30 min reaction. The surface morphology and properties of FeNiCeO_x were characterized by Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Raman and X-ray photoelectron spectroscopy (XPS) analyses. FeNiCeO_x in this paper had larger specific surface area than those prepared by other methods, which was attributed to the cavitation effect and hot-spot effect during the ultrasonic synthesis process. Low crystallinity of Fe₂O₃ and NiO showed by characterization could lead to high interaction of Fe and Ni ions with support of CeO₂. They substituted Ce in CeO₂, caused lattice contraction and formed more oxygen vacancies, which favoured the catalytic reaction. Meanwhile, Fe and Ce ions both had redox cycles of Fe³⁺/Fe²⁺ and Ce⁴⁺/Ce³⁺, which facilitated the electron transfer in the reaction. The synergistic effect among Fe, Ni and Ce might lead to better catalytic performance of FeNiCeO_x than any binary metal oxides constituted from the above three elements. Finally, the potential mechanism of diclofenac removal in FeNiCeO_x-H₂O₂ system is proposed.

Heterogeneous Fenton-like oxidation of p-hydroxybenzoic acid using Fe/CeO2-TiO2 catalyst

This paper is built on the Fenton-like oxidation of p-hydroxybenzoic acid (p-HBZ) in the presence of H₂O₂ and 3%Fe supported on CeO₂-TiO₂ aerogels under mild conditions. These catalysts were deeply characterized by X-ray diffraction (XRD), hydrogen temperature programmed reduction (H₂-TPR), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The effect of thermal treatment, pH (2-3, 5, 7), H₂O₂/p-HBZ molar ratio (5, 15, 20, 25) and reaction temperature (25 °C, 40 °C and 60 °C) on the catalytic properties of supported Fe catalysts are studied. Our results highlight the role of CeO₂ and the calcination of the catalyst to obtain the highest catalytic properties after 10 min: 73% of p-HBZ conversion and 52% of total organic carbon (TOC) abatement.

Efficient phenol removal from petrochemical wastewater using biochar-La/ultrasonic/persulphate system: characteristics, reusability, and kinetic study

This research has analysed the physiochemical properties of a catalyst that has been developed - biochar-La, including BJH, BET, EDX, SEM, FTIR, pHpzc, and iodine number. The catalyst consisted of effective functional groups, including C=S, C-O, C=C, -COOH and O-H, with a specific surface area of 31.2 m²/g. The catalyst was used in the biochar-La/ultrasonic/persulphate system to remove phenol from wastewater. The kinetics, mechanism, and reusability of the catalyst for the phenol removal from synthetic wastewater were determined. The results suggested that phenol removal kinetics follows pseudo-first-order model (k = 0.0386 1/min), and the catalyst can be reused three times. The potential of operation of the biochar-La/ultrasonic/persulphate system - with the effective removal of phenol and other organic compounds from real petrochemical wastewater - was tested. The results indicated that the removal of phenol from the petrochemical wastewater with a relatively high total dissolved solid is >99%. The gas chromatography-mass spectrometry (GC-mass) test revealed that the complete decomposition of some contaminants in the petrochemical wastewater had occurred, as H₂O and CO₂ were detected. The contribution of a heterogeneous mechanism for phenol oxidation by biochar-La/ultrasonic/persulphate was calculated to be 60%. Overall, the results showed that the biochar-La/ultrasonic/persulphate system is very effective and promising for the removal of phenol from the petrochemical wastewater.

Preparation of new adsorbent-supported Fe/Ni particles for the removal of crystal violet and methylene blue by a heterogeneous Fenton-like reaction

Prepared material-supported Fe/Ni particles (PM-Fe/Ni) were produced and applied as an adsorbent, reductant and Fenton-like catalyst for removing methylene blue (MB) and crystal violet (CV) from aqueous solutions. Fe/Ni particles were prepared by reducing ferric chloride with sodium borohydride and supported on the produced porous material. Various techniques including X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy analysis (SEM) were employed to characterize the crystal phase, surface area, surface morphology and functional groups. Removal experiments were conducted to study the effects of different factors such as PM-Fe/Ni dosage, initial pH, H₂O₂ concentration, initial concentrations and temperature on MB and CV removal. The removal efficiency of CV and MB by PM-Fe/Ni/H₂O₂ were 91.86% and 61.41% under the conditions of dye concentration of 1000 mg L⁻¹, H₂O₂ concentration of 50 mM, PM-Fe/Ni dosage of 0.20 g and temperature of 293 K. The analysis of the degradation kinetics showed that the degradation of MB and CV followed well pseudo-first-order kinetics. A possible mechanism of removal of MB and CV was proposed, including the adsorption, reduction and dominating Fenton oxidation. The regeneration experiments of PM-Fe/Ni demonstrated that PM-Fe/Ni with H₂O₂ still showed a high removal efficiency after six reaction cycles.

Possible reaction mechanism for CV and MB removal by the PM-Fe/Ni with H₂O₂ system.

Adsorption Analyses of Phenol from Aqueous Solutions Using Magadiite Modified with Organo-Functional Groups: Kinetic and Equilibrium Studies

Organically-modified magadiite (MAG–CTAB–KH550) was synthesized via ion-exchange method and condensation reaction in the presence of pure magadiite (MAG), cetyltrimethylammonium bromide (CTAB) and γ-aminopropyltriethoxysilane (KH550) in aqueous solution in this research. This new adsorbent material was studied using scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and N₂ adsorption/desorption isotherms process. It was found that the MAG–CTAB–KH550 has high Brunaur-Emmet-Teller (BET) specific surface area and mesoporous pore size distribution which enhanced its ability to remove phenol in aqueous solution; and, the value of pH has a relatively large impact on the adsorption behavior of the sorbent. Finally, the adsorptive behavior of the mesoporous material on phenol was followed pseudo-second-order kinetic adsorption model. In contrast, the adsorption equilibrium isotherm was better performed Langmuir isotherm model than the Freundlich isotherm model; in addition, the results also showed that the MAG–CTAB–KH550 had a better adsorption capacity and removal efficiency than MAG.

A colorimetric sensor of H2O2 based on Co3O4–montmorillonite nanocomposites with peroxidase activity

Schematic of the colorimetric detection of H₂O₂ catalyzed using Co₃O₄–MMT NPs.