Recyclable Fenton-like catalyst based on zeolite Y supported ultrafine,highly-dispersed Fe2O3 nanoparticles for removal of organics under mild conditions

The active Fenton-like catalyst, obtained by highly dispersed Fe₂O₃ nanoparticles in size of 5 nm on the surface of zeolite Y, shows the excellent degradation efficiency to phenol higher than 90% under the mild conditions of room temperature and neutral solution, and the catalyst can be easily recovered with stable catalytic activity for 8 cycles.     

Photo fenton like process Fe3+/(NH4)2S2O8/UV for the degradation of Di azo dye congo red using low iron concentration

Degradation of Congo Red (CR) a di azo dye in aqueous solution is investigated by a Photo Fenton like process using Fe³⁺ ions as the catalyst and peroxy disulfate as the oxidant. The influence of various reaction parameters like, concentration of Fe³⁺ ions, concentration of the dye, concentration of ammonium persulfate, pH of the solution and the presence of hydroxyl radical scavenger are studied and optimal conditions are reported. The degradation rate decreased at higher dye concentration and at higher pH. The rate constant (k), catalytic efficiency (k_c) and process efficiency (Φ) are evaluated for different concentration of Fe³⁺ ions. The degradation of CR by the photo Fenton like process leads to the formation of 4-Amino, 3-azo naphthalene sulphonic acid, dihydroxy substituted naphthalene, dihydroxy substituted biphenyl, phenol, quinol etc., as intermediates, based on which probable degradation mechanism is proposed. These results show that a photo Fenton like process could be useful technology for the mineralization of di azo dyes under lower concentration of iron in acidic conditions. The present process is advantageous as it lowers the sludge production resulting from the iron comple      

Recyclable CuMgAl hydrotalcite for oxidative esterification of aldehydes with alkylbenzenes

A series of hydrotalcite-like compounds with various Cu:Mg:Al molar ratios were prepared by the co-precipitation method. The catalytic performance for oxidative esterification of aldehydes was investigated. X-ray diffraction, N₂ adsorption–desorption (BET), hydrogen temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy, the scanning electron microscope (SEM), the transmission electron microscope and atomic absorption spectrometry were used to characterize the catalysts. The results showed that the benzyl benzoate product was obtained in good to excellent yield using tert-butyl peroxybenzoate as oxidant at 90°C under air atmosphere over Cu₂Mg₁Al₁-LDH catalyst. The catalyst can be recovered and used with 45% conversion after recycling five times. The oxidative esterification reaction in the heterogeneous system is environmentally friendly.

The Cu₂Mg₁Al₁-LDH catalyst prepared by co-precipitation method showed high catalytic activity for oxidative esterification of aldehydes. 81.0% yield of benzyl benzoate with benzaldehyde and toluene as reactants was obtained using tert-butyl peroxybenzoate as oxidant at 90°C under air atmosphere over Cu₂Mg₁Al₁-LDH catalyst. The catalyst can be recovered and used with 45% conversion after recycling five runs. The oxidative esterification reaction in the heterogeneous system is environmentally friendly.     

Highly Efficient FeIII-initiated Self-cycled Fenton System in Piezo-catalytic Process for Organic Pollutants Degradation

Piezo-catalytic self-Fenton (PSF) system has been emerging as a promising technique for wastewater treatment, while the competing O₂ reductive hydrogen peroxide (H₂O₂) production and Fe^III reduction seriously limited the reaction kinetics. Here, we develop a two-electron water oxidative H₂O₂ production (WOR−H₂O₂) coupled with Fe^III reduction over a Fe^III/BiOIO₃ piezo-catalyst for highly efficient PSF. It is found that the presence of Fe^III can simultaneously initiate the WOR−H₂O₂ and reduction of Fe^III to Fe^II, thereby enabling a rapid reaction kinetics towards subsequent Fenton reaction of H₂O₂/Fe^II. The Fe^III initiating PSF system offers exceptional self-recyclable degradation of pollutants with a degradation rate constant for sulfamethoxazole (SMZ) over 3.5 times as that of the classic Fe^II-PSF system. This study offers a new perspective for constructing efficient PSF systems and shatters the preconceived notion of Fe^III in the Fenton reaction.     

Mechanochemically sulfured FeS1.92 as stable and efficient heterogeneous Fenton catalyst

Fenton reaction is one of most promising approaches for efficient removal of various robust organic pollutants in wastewater, however it faces several intrinsic challenges such as acidic condition, sludge waste and sensitive to sulfide-containing compound. Here we reported a novel FeS_1.92 as an efficient and sulfide resistant heterogeneous Fenton catalyst under mild condition. This novel FeS_1.92 was facilely prepared through a mechanochemical synthesis of mackinawite (FeS) with sulfur powder (S) by ball milling. The sulfured mackinawite (FeS_1.92) exhibits high performance in activating H₂O₂ to generate hydroxyle radicals for organic waste remediation. Furthermore, this FeS_1.92 based heterogeneous Fenton catalyst is highly sulfide resistant and shows improved performance for degrading sulfide-containing organic pollutants. This study provides an effective mechanochemical approach to fabricate heterogeneous Fenton catalysts for sulfide-containing wastewater treatment.     

α‐FeOOH−MoO3 Nanorod for Effective Photo‐Fenton Degradation of Dyes and Antibiotics at a Wide Range of pH

It's highly significant to develop a novel catalyst, which can be active at a wide range of pH, for an effective photo‐Fenton reaction. In this work, α‐FeOOH?MoO₃ nanorod was prepared by a one‐step hydrothermal method and applied in photo‐Fenton degradation of organic pollutants. Benefit from the electron migration mechanism of Z‐scheme and excellent photoelectric performance, the catalyst exhibited superior photo‐Fenton activity in degradation of organic pollutants. In addition, the catalyst holds good stability after 5 recycles. These results demonstrated that this catalyst has wide application prospect in organic wastewater treatment.     

Conversion of Chromium(III) Propionate to Chromate/dichromate(VI) by the Advanced Oxidation Process. Pretreatment of a Biomimetic Complex for Metal Analysis

The use of H₂O₂ and UV irradiation to remove organic ligands in a chromium(III) complex for the subsequent chromium analysis is reported. The Advanced Oxidation Process (AOP) using a 5.5-W UV lamp, H₂O₂ and Fe²⁺/Fe³⁺ as catalyst (photo Fenton process) was found to give complete and quantitative Cr(III) → Cr(VI) conversion and removal of ligands in chromium(III) propionate [Cr₃O(O₂CCH₂CH₃)₆(H₂O)₃]NO₃, a biomimetic chromium species, as subsequent chromium analyses by the 1,5-diphenylcarbazide method and atomic absorption revealed. The current process eliminates the need for mineralization and/or dissolution of the matrix in order to remove the organic ligand, the traditional pretreatments of a sample for metal analysis. Studies to optimize the conditions for the oxidation processes, including the use of Fe²⁺/Fe³⁺ catalyst, length of UV irradiation, H₂O₂ concentration, pH, power of UV lamp, and reactor size, are reported.     

THE ROLE OF HUMIC SUBSTANCES IN THE PHOTOCATALYTIC DEGRADATION OF WATER CONTAMINANTS

Abstract

Photocatalysis over irradiated Ti0₂ has been proved to efficiently abate more than 80% of the organic carbon pertaining to a commercial humic acid (HA). The presence of HA up to 50 mg L^?1 has been found to decrease the degradation rate of some model pollutants, namely phenol, 2,4-dichlorophenol and tetrachloromethane. However, the total organic carbon measurements and chloride evolution ensure that the disappearance of the initial pollutants is not due to binding to HA structure, but to an efficient mineralization process. HA' s are able to scavenge both the oxidative and the reductive active species as shown by the inhibiting effect on the rate of disappearance of phenol and 2,4-dichlorophenol (essentially oxidative), and of CCI4 (initially reductive).     

Investigation of photocatalytic mineralisation of Acridine Yellow G dye by BaCrO4 in the presence of eco-friendly LEDs irradiation

Degradation of toxic organic pollutants and dyes from industrial wastewater by photocatalysis is an environmentally friendly technique. The degradation of Acridine Yellow G (AYG) was investigated in aqueous solutions employing BaCrO₄ as a heterogeneous photocatalyst under eco-friendly LED irradiation. We studied the mineralisation kinetics of AYG by monitoring the dye concentration and chemical oxygen demand (COD) as a function of time. The impact of pH, concentrationdye, reactants, catalyst, Fenton reagent, salt effect, and temperature on the kinetics were investigated. The initial addition of optimal amounts of hydrogen peroxide and potassium persulfate increased the degradation rate, while NaCl and Na₂CO₃ retarded the reaction. The efficiency of visible light, LED (12 ?W) irradiation, compared with the traditional visible light source, the halogen lamp (500 ?W). At the optimum pH 10, the AYG degradation obeyed pseudo-first-order kinetics. With BaCrO₄ asa heterogeneous photocatalyst, complete mineralisation of AYG was achieved in 35 ?min. This process is green, eco-friendly, and the catalyst is easily recoverable and reusable five times without loss of catalytic efficiency.     

Cooperative coupling of photocatalytic production of H2O2 and oxidation of organic pollutants over gadolinium ion doped WO3 nanocomposite

This work reported the lanthanide ion (Gd³⁺) doped tungsten trioxide (Gd-WO₃) nanocrystal for remarkable promoted photocatalytic degradation of organic pollutants and simultaneous in-situ H₂O₂ production. With doped lanthanide ion (Gd³⁺), Gd-WO₃ showed a much broad and enhanced solar light absorption, which not only promoted the photocatalytic degradation efficiency of organic compounds, but also provided a suitable bandgap for direct reduction of oxygen to H₂O₂. Additionally, the isolated Gd³⁺ on WO₃ surface can efficiently weaken the *OOH binding energy, increasing the activity and selectivity of direct reduction of oxygen to H₂O₂, with a rate of 0.58 mmol L⁻¹ g⁻¹ h⁻¹. The in-situ generated H₂O₂ can be subsequently converted to ^•OH based on Fenton reaction, further contributed to the overall removal of organic pollutants. Our results demonstrate a cascade photocatalytic oxidation-Fenton reaction which can efficiently utilize photo-generated electrons and holes for organic pollutants treatment.     

CoFe2O4 with MoS2-xOy Nanosheets as a Co-catalyst for Enhanced Activation of Peroxydisulfate in Advanced Oxidation Processes

The application of advanced oxidation processes (AOPs) based on sulfate radicals for degrading persistent organic pollutants faces challenges due to the inefficient activation of peroxydisulfate (PDS) oxidant. Herein, a composite CoFe₂O₄/MoS_2-xO_y (CFM) catalyst consisting of CoFe₂O₄ nanoparticles uniformly dispersed on the nanosheets of oxygen-incorporated MoS₂ (MoS_2-xO_y) with flower-like morphology are fabricated through a facile two-step hydrothermal method, which results in the enhanced activation of PDS and a highly efficient degradation of phenolic pollutants. The oxygen-doping in MoS_2-xO_y leads to unsaturated sulfur and active sites on the surface of MoS₂ for accelerating the rate limiting step of Fe^III/Fe^II reduction cycle in PDS-CFM reaction. Aiming at the refractory organic pollutants in actual coking wastewater, CFM co-catalyst is introduced into a hydrogel made up of polyvinyl alcohol (PVA) and coal-tar pitch oxides (PO) to construct a multifunctional CFM@PO/PVA hydrogel. Upon hybrid CFM@PO/PVA, the coupling of the enhanced AOP with solar-driven interfacial vapor generation (SIVG) technology contributes to the degradation efficiency, the removal rate of phenol in solution and the total organic carbon in coking wastewater can reach 98 % and 91 %, respectively. The integration of heterogeneous AOPs with SIVG system provides a feasible strategy for the eco-friendly efficient purification of industrial wastewater.     

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

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

Oxidative degradation of phenols in sono-Fenton-like systems upon high-frequency ultrasound irradiation

The kinetics of oxidative degradation of phenol and chlorophenols upon acoustic cavitation in the megahertz range (1.7 MHz) is studied experimentally in model systems, and the involvement of in situ generated reactive oxygen species (ROSs) is demonstrated. The phenols subjected to high frequency ultrasound (HFUS) are ranked in terms of their rate of conversion: 2,4,6-trichlorophenol > 2,4-dichlorophenol ~ 2-chlorophenol > 4-chlorophenol ~ phenol. Oxidative degradation upon HFUS irradiation is most efficient at low concentrations of pollutants, due to the low steady-state concentrations of the in situ generated ROSs. A dramatic increase is observed in the efficiency of oxidation in several sonochemical oxidative systems (HFUS in combination with other chemical oxidative factors). The system with added Fe²⁺ (a sono-Fenton system) derives its efficiency from hydrogen peroxide generated in situ as a result of the recombination of OH radicals. The S₂O₈^2-/Fe²⁺/HFUS system has a synergetic effect on substrate oxidation that is attributed to a radical chain mechanism. In terms of the oxidation rates, degrees of conversion, and specific energy efficiencies of 4-chlorophenol oxidation based on the amount of oxidized substance per unit of expended energy the considered sonochemical oxidative systems form the series HFUS < S₂O₈^2-/HFUS < S₂O₈^2-/Fe²⁺/HFUS.     

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

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

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

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

Graphenes as Efficient Metal‐Free Fenton Catalysts

Reduced graphene oxide exhibits high activity as Fenton catalyst with HO^. radical generation efficiency over 82 % and turnover numbers of 4540 and 15023 for phenol degradation and H₂O₂ consumption, respectively. These values compare favorably with those achieved with transition metals, showing the potential of carbocatalysts for the Fenton reaction.     

Effect of simulated solar light on the autocatalytic degradation of nitrobenzene using Fe3+ and hydrogen peroxide

The effect of simulated solar light on nitrobenzene degradation in Fe³⁺/H₂O₂ solutions was investigated under different experimental conditions. Consumption profiles of NBE and H₂O₂ display an autocatalytic kinetic behavior for both dark and photo-assisted degradation experiments. The rates of the initial slow phase that precedes the catalytic phase are significantly enhanced by irradiation, although the effect of simulated solar light on the rates of the fast phase is negligible. The absolute rates of the slow phase increase with the concentrations of Fe³⁺ and H₂O₂, whereas the initial rate of the degree of conversion increase decreases with organic matter loading. The reaction progress was characterized by HPLC, GC–MS, IC, TOC (total organic carbon) and toxicity analyses. The main products detected were 4-nitrophenol, 3-nitrophenol, 2-nitrophenol, 1,3-dinitrobenzene, phenol, oxalic acid, formic acid, NO₂^? and NO₃^?. Product distribution profiles are discussed in connection with TOC and toxicity measurements. The results show that dark treatment is neither capable of lowering the organic content nor capable of reducing the effluent toxicity to acceptable levels. On the other hand, photo-assisted processes induced by simulated solar light can significantly enhance both mineralization and detoxification efficiencies.     

Designing 3D‐MoS2 Sponge as Excellent Cocatalysts in Advanced Oxidation Processes for Pollutant Control

3D‐MoS₂ can adsorb organic molecules and provide multidimensional electron transport pathways, implying a potential application for environment remediation. Here, we study the degradation of aromatic organics in advanced oxidation processes (AOPs) by a 3D‐MoS₂ sponge loaded with MoS₂ nanospheres and graphene oxide (GO). Exposed Mo⁴⁺ active sites on 3D‐MoS₂ can significantly improve the concentration and stability of Fe²⁺ in AOPs and keep the Fe³⁺/Fe²⁺ in a stable dynamic cycle, thus effectively promoting the activation of H₂O₂/peroxymonosulfate (PMS). The degradation rate of organic pollutants in the 3D‐MoS₂ system is about 50 times higher than without cocatalyst. After a 140 L pilot‐scale experiment, it still maintains high efficiency and stable AOPs activity. After 16 days of continuous reaction, the 3D‐MoS₂ achieves a degradation rate of 120 mg L^?1 antibiotic wastewater up to 97.87 %. The operating cost of treating a ton of wastewater is only US$ 0.33, suggesting huge industrial applications.     

Designing 3D-MoS2 Sponge as Excellent Cocatalysts in Advanced Oxidation Processes for Pollutant Control

3D-MoS₂ can adsorb organic molecules and provide multidimensional electron transport pathways, implying a potential application for environment remediation. Here, we study the degradation of aromatic organics in advanced oxidation processes (AOPs) by a 3D-MoS₂ sponge loaded with MoS₂ nanospheres and graphene oxide (GO). Exposed Mo⁴⁺ active sites on 3D-MoS₂ can significantly improve the concentration and stability of Fe²⁺ in AOPs and keep the Fe³⁺/Fe²⁺ in a stable dynamic cycle, thus effectively promoting the activation of H₂O₂/peroxymonosulfate (PMS). The degradation rate of organic pollutants in the 3D-MoS₂ system is about 50 times higher than without cocatalyst. After a 140 L pilot-scale experiment, it still maintains high efficiency and stable AOPs activity. After 16 days of continuous reaction, the 3D-MoS₂ achieves a degradation rate of 120 mg L⁻¹ antibiotic wastewater up to 97.87 %. The operating cost of treating a ton of wastewater is only US$ 0.33, suggesting huge industrial applications.     

Selective Lithium Adsorption of Silicon Oxide Coated Lithium Aluminum Layered Double Hydroxide Nanocrystals and Their Regeneration

Silicon oxide-coated lithium aluminum layered double hydroxide (Li_xAl₂-LDH@SiO₂) nanocrystals (NCs) are investigated to selectively separate lithium cations in aqueous lithium resources. We directly synthesized Li_xAl₂-LDH NC arrays by oxidation of aluminum foil substrate under a urea and lithium solution. Various lithium salts, including Cl⁻, CO₃²⁻, NO₃⁻, and SO₄²⁻, were applied in aqueous solution to confirm the anion effect on the captured and released lithium quantity of the Li_xAl₂-LDH NCs. In a 5% solution of sulfate ions mix with lithium chloride, the Li_xAl₂-LDH NCs separated a larger quantity of lithium than in other anion conditions. To enhance regeneration stability and lithium selectivity, thin layers of SiO₂ were coated onto the Li_xAl₂-LDH nanostructure arrays for inhibition of nanostructure destruction after desorption of lithium cations in hot water. The Li_xAl₂-LDH@SiO₂ nanostructures showed enhanced properties for lithium adsorption, including increase of stable regeneration cycles from three to five cycles, and they showed high lithium selectivity in the Mg²⁺, Na⁺, and K⁺ cation mixed aqueous resource. Our nanostructured LDH lithium adsorbents would provide a facile and efficient application for cost-efficient and large-scale lithium production.