Removal of metsulfuron methyl by Fenton reagent

The removal of metsulfuron methyl (MeS)—a sulfonyl urea herbicide from contaminated water was investigated by advanced oxidation process (AOP) using Fenton method. The optimum dose of Fenton reagent (Fe²⁺/H₂O₂) was 10 mg/L Fe²⁺ and 60 mg/L H₂O₂ for an initial MeS concentration ([MeS]₀) range of 0–80 mg/L. The Fenton process was effective under pH 3. The degradation efficiency of MeS decreased by more than 70% at pH > 3 (pH 4.5 and 7). The initial Fe²⁺ concentration ([Fe²⁺]₀) in the Fenton reagent affected the degradation efficiency, rate and kinetics. The degradation of MeS at optimum dose of Fenton reagent was more than 95% for [MeS] ₀ of 0–40 mg/L and the degradation time was less than 30 min. The determination of residual MeS concentration after Fenton oxidation by UV spectrophotometry was affected by the interferences from Fenton reagent. The estimation of residual MeS concentration after Fenton oxidation by high pressure/performance liquid chromatograph (HPLC) was interference free and represented the actual concentration of MeS and does not include the by-products of Fenton oxidation. The degradation kinetics of MeS was modelled by second order reactions involving 8 rate constants. The two reaction constants directly involving MeS were fitted using the experimental data and the remaining constants were selected from previously reported values. The model fit for MeS and the subsequent prediction of H₂O₂ were found to be within experimental error tolerances.     

Optimization of Fenton process for refinery wastewater biodegradability augmentation

The Fenton process was used to increase the biodegradability of refinery wastewater. Initially, effects of reaction time, H₂O₂/COD and H₂O₂/Fe²⁺ molar ratios were investigated and biodegradability of wastewater was determined in terms of the BOD₅/COD ratio. Preliminary results showed that the Fenton process was able to improve wastewater biodegradability from 0.27 to 0.43. Subsequently, the process was optimized by using response surface methodology based on a five-level central composite design. Adequacy and significance of results were analyzed in analysis of variance. The quadratic model was found to be significant to give less than 0.05 probability of error. The model was fit with data based on insignificant of lack-of-fit test at values of 0.93. The high R² and Adj.R² (0.95 and 0.91) indicates satisfactory adjustment of quadratic model to experimental data. Based on optimized conditions, wastewater biodegradability improved to 0.44 via H₂O₂/COD and H₂O₂/Fe²⁺ molar ratios of 2.8 and 4 within 71 minutes reaction time.     

Preparation of new heteronuclear (NH4)RE[FeII(CN)6]·nH2O complexes (RE = La,Ce, Pr,Nd, Sm,Gd, Dy,Y, Er,Lu) and their low-temperature decomposition for perovskite-type oxide

New heteronuclear (NH₄)RE^III[Fe^II(CN)₆]·nH₂O complexes (RE = La, Ce, Pr, Nd, Sm, Gd, Dy, Y, Er, Lu) were synthesized and their thermal decomposition products were investigated. The crystal structure of (NH₄)RE[Fe^II(CN)₆]·nH₂O would be a hexagonal unit cell (space group: P6₃/m), which was the same as that of La[Fe^III(CN)₆]·5H₂O. The hydration number n = 4 was estimated by TG results for all the RE complexes. The lattice constants depended on the ionic radius of the RE³⁺ ion for the heteronuclear complexes. The single phase of the perovskite type materials was directly obtained by decomposition of the heteronuclear complexes for RE = La, Pr, Nd, Sm, and Gd. A mixture of CeO₂ and Fe₂O₃ was formed for RE = Ce because of its oxidation to Ce⁴⁺. In the case of RE = Dy, Y, Er, and Lu complexes, the perovskite type materials formed at higher temperature via. mixed oxides such as RE₂O₃ and RE₄Fe₅O₁₃ due to the small RE³⁺ ionic radius.     

Optimization of the operating parameters using RSM for the Fenton oxidation process and adsorption on vegetal carbon of MO solutions

This study focused on the application of RSM on the Fenton process and the adsorption of vegetal carbon (VC) to obtain the optimal conditions for the minimization of the colored synthetic wastewater. Methyl orange (MO) with an azo dye was used as the model organic compound. Fenton processes were investigated to establish the optimal conditions. The Fe²⁺/H₂O₂ ratio was studied to establish the major MO degradation when 100 and 200 mg/L of MO were treated. For the adsorption process, to determine the optimal conditions, the principal variables studied were the vegetal carbon mass dosage, degradation time and dye concentration.     

COD and color removal from synthetic textile wastewater by ultrasound assisted electro-Fenton oxidation process

Combination of electro-Fenton (EF) oxidation process with sonication for both the degradation of C.I. Reactive Black 5 (RB 5) and removal of chemical oxygen demand (COD) from synthetic textile wastewater was investigated under different operating conditions. Optimal conditions were found as the initial pH of 3, DC current of 0.25 A, H₂O₂ dosage of 800 mg/L and electrode distance of 2.5 cm for both EF and ultrasound assisted electro-Fenton (sono-EF) processes. However, the combination of EF with sonication was negligibly improved in terms of COD and color removals, compared to EF process.     

Promoting effect of Fe in oxidative dehydrogenation of ethylbenzene to styrene with CO2 (I) preparation and performance of Ce1 − xFexO2 catalyst

To improve the lattice structure of CeO₂ and the transmission capacity of oxygen, Ce_1 − xFe_xO₂(x ≤ 0.2)solid solutions were prepared by a hydrothermal method and used in oxidative dehydrogenation of ethylbenzene to styrene with CO₂. Ce_1 − xFe_xO₂ solid solutions were characterized by powder X-ray diffraction, Raman spectroscopy, N₂-adsorption, H₂ temperature-programmed reduction and H₂–O₂ titration. Results showed that approximately 20% of Fe^3 + could dissolve into the CeO₂ lattice while portions of Fe₂O₃ were highly dispersed on the surface of the Ce_1 − xFe_xO₂ solid solution. The formation of Ce–Fe solid solutions could create more oxygen vacancies to promote the absorption and activation of CO₂, which improves the activity of the catalyst and increased ethylbenzene conversion by as much as 13%.     

Modeling and operating conditions optimization of Fischer–Tropsch synthesis in a fixed-bed reactor

The effect of a range of operation variables such as pressure, low temperature and H₂/CO molar feed ration the catalytic performance of 80%Co/20%Ni/30 wt% La₂O₃/1 wt% Cs catalyst was investigated. It was found that the optimum operating conditions is a H₂/CO = 2/1 molar feed ratio at 260 °C temperature and 2 bar pressure. Reaction rate equations were derived on the basis of the Langmuir–Hinshelwood–Hougen–Watson (LHHW) type models for the Fischer–Tropsch reactions. The activation energy obtained was 59.69 kJ/mol for optimal kinetic model.     

Effect of Fe2O3 doping on sintering of yttria-stabilized zirconia

This paper reports the effect of Fe₂O₃ doping on the densification and grain growth in yttria-stabilized zirconia (YSZ) during sintering at 1150 °C for 2 h. Fe₂O₃ doped 3 mol% YSZ (3YSZ) and 8 mol% YSZ (8YSZ) coatings were produced using electrophoretic deposition (EPD). For 0.5 mol% Fe₂O₃ doping, both 3YSZ and 8YSZ coatings during sintering at 1150 °C has similar densification. However, a significant grain growth occurred in 8YSZ during sintering, whereas grain size remains almost constant in 3YSZ. XRD results suggest that Fe₂O₃ addition substitutionally and interstitially dissolved into the lattice of 3YSZ and 8YSZ. In addition, colour of 3YSZ and 8YSZ changes differently with doping of Fe₂O₃. A Fe³⁺ ion interstitial diffusion mechanism is proposed to explain the densification and grain growth behaviour in the Fe₂O₃ doped 3YSZ and 8YSZ. A retard grain growth observed in the Fe₂O₃ doped 3YSZ is attributed to Fe³⁺ segregation at grain boundary.     

Design,synthesis, structure and magnetic behavior of a high spin binuclear Fe(III) complex of N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl) amine

The Mannich reaction of 2-aminoethanol, 2-tert-butyl-4-methylphenol, and formaldehyde at the ratio sets of 1:2:2 provided a new ligand, N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L). In the presence of base, H₃L reacted with FeCl₃·6H₂O to form a dinuclear Fe(III) complex [Fe₂L₂] 1. The value of μ_eff at room temperature (5.95 μ_B), is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ ZS(S + 1)]^1/2], indicating there were strong interactions between Fe³⁺ ions. The effective magnetic moment (μ_eff) decreased abruptly with cooling to a minimum value of 0.1 μ_B at 2 K. It was worth noting that Fe³⁺ ions of 1 exhibited thermally induced quartet ? doublet spin transitions, and these transitions were abrupt. The magnetic behaviors of 1 denoted the occurrence of intramolecular anti-ferromagnetic interactions. J (? 13.58 cm^? 1) agrees with the result from Gorun–Lippard equation, ? J (cm^? 1) = Aexp(BP(Å) = 12.9).     

Influence of iron content on the color of the C3A–Fe2O3 system synthesized under different conditions of temperature,atmosphere and cooling

The 3CaO·Al₂O₃–Fe₂O₃ (C₃A–Fe₂O₃) system is important for the production of white clinker. In the present study this system was examined from the perspective of improving the sustainability of the production process. Microstructural evaluation was employed to explain the changes in color caused by variation of: iron content; temperature; type of atmosphere; and cooling conditions. It was found that color was more significantly affected by the iron content, temperature and type of atmosphere than by the type of cooling used. It was also observed that the utility of iron-rich raw materials could be maximized by understanding and enhancing the solubility of Fe₂O₃ in C₃A. It was found that a 2 wt.% Fe₂O₃ solid solution was stable only under kiln open to atmospheric conditions and remained clear at temperatures up to 1370 °C. However, the same 2 wt.% Fe₂O₃ solid solution suffered a significant change in color when the temperature rose to 1400 °C. Mössbauer spectroscopy showed that the oxidation state of Fe was Fe³⁺, which did not change between 1370 and 1400 °C; however, a structural change in the C₃A–Fe₂O₃ solid solution was detected as a result of the alteration of the thermal treatment. The distinction between the structures at these two temperatures was that at 1370 °C, all of the Fe³⁺ had a tetrahedral coordination, while at 1400 °C, 19 wt.% of the Fe³⁺ appeared in octahedral sites, a result that was corroborated by Rietveld analysis.     

Remarkable effect of Co and Mn on the activity of Fe3 − xMxO4 promoted oxidation of organic contaminants in aqueous medium with H2O2

In this work substituted magnetites Fe_3 − xMn_xO₄ (x=0.21, 0.26 and 0.53), Fe_3 − xCo_xO₄ (x=0;0.19;0.38;0.75) and Fe_3 − xNi_xO₄ (x=0;0.10;0.28;0.54) have been used to promote two different reactions involving H₂O₂: (i) the oxidation of organic molecules namely phenol, hydroquinone and methylene blue dye in aqueous medium and (ii) the peroxide decomposition to O₂. The presence of Co or Mn in the magnetite structure strongly increased the rate of H₂O₂ decomposition and the oxidation of the organic molecules whereas the presence of Ni inhibited both reactions. Kinetic data and CEMS Mössbauer spectroscopy suggest that the H₂O₂ decomposition and the organic oxidation are competitive reactions involving oxidizing species generated by surface M²⁺ (M=Fe, Co or Mn).     

Removal of p-nitrophenol using hydrodynamic cavitation and Fenton chemistry at pilot scale operation

In the current work removal of p-nitrophenol has been investigated using hydrodynamic cavitation, either operated individually or in combination with H₂O₂ and conventional Fenton process. In hydrodynamic cavitation, two different cavitating devices viz. orifice plate and venturi have been used. Effect of different operating parameters such as initial concentration (5 g/l and 10 g/l), inlet pressure (over a range 5.7–42.6 psi) and pH (over a range 2–8) on the extent of removal has been investigated. In conventional Fenton process two loadings of FeSO₄, 0.5 g/l and 1 g/l were investigated and three ratios of FeSO₄:H₂O₂ viz. 1:5, 1:7.5 and 1:10 were used. Removal observed with venturi was higher than with orifice plate in combination with Fenton chemistry. For 5 g/l initial concentration of p-nitrophenol, maximum removal of 63.2% was observed whereas for 10 g/l solution it was 56.2%.     

New LiNi0.5PrxFe2−xO4 nanocrystallites: Synthesis via low cost route for fabrication of smart advanced technological devices

Praseodymium substituted nano-crystalline Li-Ni spinel ferrites with different Pr³⁺ contents were synthesized by micro-emulsion method. X-ray diffraction (XRD), scanning electron spectroscopy (SEM) and vibrating sample magnetometery (VSM) techniques were employed to study the impact of substitution of the Pr³⁺ on the structure, surface morphology and magnetic parameters. XRD confirmed the formation of the single phase spinel ferrites of all compositions of LiNi_0.5Pr_xFe_2−xO₄ nanocrystallites. The crystallite size determined from XRD data by Scherrer formula was calculated in range from 40 nm to 70 nm. However the nanoparticles size estimated by SEM was found 35–115 nm. The room temperature VSM measurements were carried out in the applied field range from “−10,000 Oe” to “10000” Oe. Saturation magnetization (M_S) (41 emu/g) and coercivity (H_C) values (156.9 Oe) of LiNi_0.5Fe₂O₄ were improved by the addition of rare earth Pr³⁺ cations. The value of Hc is low, which is a strong indication of soft ferrites. The synthesized LiNi_0.5Pr_xFe_2−xO₄ ferrites may be utilized for low core losses on transformers.     

Michael reaction of β-ketoesters with vinyl ketones by iron(III)-exchanged fluorotetrasilicic mica: catalytic and spectroscopic studies

Michael reaction of β-ketoesters with vinylketones at room temperature under solvent-free condition is investigated with various Fe³⁺ catalysts, including FeCl₃ ⋅ 6H₂O supported on various supports (Fe–mica, Fe–mont, Fe–SiO₂, Fe–Al₂O₃, Fe–NaY) and homogeneous catalysts, FeCl₃ ⋅ 6H₂O and Fe(NO₃)₃ ⋅ 9H₂O. Fe³⁺-exchanged fluorotetrasilicic mica (Fe–mica) shows highest activity. Fe–mica exhibits almost quantitative yields of Michael adducts, high turnover numbers (TON = 1000), and a low level of Fe leaching. After simple work-up procedures, Fe–mica can be recycled without a loss in activity. The relationship between catalytic activity and the catalyst structure determined by XRD, UV–vis, and Fe K-edge XANES/EXAFS is discussed in terms of the effect of clay support on the structure and reactivity of Fe³⁺ species. The Fe³⁺ cation, highly dispersed in the interlayer of clay (mica or mont) or on SiO₂, is more active than the cluster-like Fe³⁺ oxide or hydroxide species in Fe–NaY and Fe–Al₂O₃. UV–vis and XAFS results for the catalysts treated with reactants suggest that, during the reaction, the FeCl₂(O)₄ octahedral species in FeCl₃ ⋅ 6H₂O or those on Fe–SiO₂ are converted to the β-diketonato complexes with two β-diketonato ligands, whereas in Fe–mica β-diketonato complexes with one β-diketonato ligand are formed. The formation of β-diketonato complexes results in a slight lowering of the Fe oxidation number from 3+, probably as a result of the electron donation from the β-diketonato ligand to Fe³⁺ as a Lewis acid site. The lower numbers of β-diketonato ligand coordinated with Fe³⁺ in Fe–mica should result in a larger coordination strength for β-diketonato ligand than that in Fe–SiO₂, which was confirmed by acetylacetone-TPD. Thus, the central carbon atom of the β-diketonato ligand in Fe–mica is more reactive toward nucleophilic attack by the coordinated enone, leading to higher activity for the Michael reaction.     

Synthesis,structure and magnetic properties of spinel ferrite (Ni,Cu, Co)Fe2O4 from low nickel matte

Spinel ferrite (Ni, Cu, Co)Fe₂O₄ was synthesized from the low nickel matte by using a co-precipitation-calcination method for the first time. The influences of the added amount of NiCl₂·6H₂O, calcination temperature and time on the structure and magnetic properties of the as-prepared ferrites were studied in detail by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy, and Vibrating sample magnetometer (VSM). It is indicated that pure (Ni, Cu, Co)Fe₂O₄ with cubic phase could be obtained under the experimental conditions (NiCl₂·6H₂O added amount of 3.0: 100 g mL⁻¹, calcination temperature from 800 to 1000 °C and calcination time from 1 to 3 h). With increasing calcination temperature and time, saturation magnetization (M_S) of the synthesized (Ni, Cu, Co)Fe₂O₄ increased and the coercivity (H_C) decreased. Under the optimum conditions (i.e. NiCl₂·6H₂O added amount of 3.0: 100 g mL⁻¹, 1000 °C, 3 h), the M_S and H_C values of the product were approximately 46.1 emu g⁻¹ and 51.0 Oe, respectively, which were competitive to those of other nickel ferrites synthesized from pure chemical reagents. This method explores a novel pathway for efficient and comprehensive utilization of the low nickel matte.     

Photoelectrochemical properties of Ni-doped Fe2O3 thin films prepared by electrodeposition

Ni-doped Fe₂O₃ thin films which were active photoanodes for water splitting were prepared by electrodeposition. By adjusting Ni molar ratios (Ni/(Ni + Fe)) in the electrolyte, Fe₂O₃ thin films with various compositions of Ni could be tuned. The films were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, atomic absorption spectrophotometer, and UV–vis spectroscopy. The highest photo-response obtained from Fe₂O₃ doped with 2.08 mol.% Ni is 1.5 mA/cm² at 0.65 V vs. Ag/AgCl in 1.0 M NaOH solution. The high performance is attributed to the improvement of charge transport properties and retardation of the charge recombination resulting from the dopants in the lattice. The optical absorption spectra of the films reveal that the bandgaps of the Ni-doped Fe₂O₃ films are approximately 1.9–2.2 eV for all samples regardless of their doping level. XPS shows that the concentration of Ni is much higher on the surface than that in bulk.     

Biohydrogen production from palm oil mill effluent using immobilized mixed culture

Cell immobilization techniques were adopted to bio-hydrogen production using immobilized anaerobic sludge as the seed culture. Palm oil mill effluent (POME) was used as the substrate carbon source. It was found that with a POME concentration of 20 g COD/l in the feed, the suspended-cell containing reactor was able to produce hydrogen at an optimal rate of 0.348 l H₂/(l POME h) at HRT 6 h. However, the immobilized-cell containing reactor exhibited a better hydrogen production rate of 0.589 l H₂/(l POME h), which occurred at HRT 2 h. When the immobilized-cell containing reactor was scaled up to 5 l, the hydrogen production rate was 0.500–0.588 l H₂/(l POME h) for HRT 2–10 h, but after a thermal treatment (60 °C, 1 h) the rate increase to 0.632 l H₂/(l POME h) at HRT 2 h. The main soluble metabolites were butyric acid and acetic acid, followed by propionic acid and ethanol.     

Effect of niobium valence on the mechanochemical activation of niobium oxides–hematite magnetic ceramic nanoparticles

Three types of nanostructured systems: xNbO·(1?x)α-Fe₂O₃, xNbO₂·(1?x)α-Fe₂O₃, and xNb₂O₅·(1?x)α-Fe₂O₃ were synthesized by ball milling at different molar concentrations (x=0.1, 0.3, 0.5, and 0.7). The effect of Nb valence and milling time on mechanochemical activation of these systems were studied by X-ray diffraction and the Mössbauer spectroscopy measurements. In general, Nb-substituted hematite was obtained at lower molar concentrations for all Nb oxides. For the NbO–Fe₂O₃ system the favorable substitution of Fe²⁺ for Nb²⁺ in the octahedral sites in the NbO lattice was observed after 12 h milling for x=0.7. In the case of the NbO₂–Fe₂O₃ and Nb₂O₅–Fe₂O₃ systems a formation of orthorhombic FeNbO₄ compound was observed, in which Fe³⁺ cations were detected. For the highest concentration of NbO₂ (x=0.7) iron was completely incorporated into the FeNbO₄ phase after 12 h milling. The molar concentrations of x=0.3 and 0.5 were the most favorable for the formation of ternary FeNbO₄ compound in the Nb₂O₅–Fe₂O₃ system. Influence of ball milling on thermal behavior of the powders was investigated by simultaneous DSC–TG measurements up to 800 °C.     

A banana-shaped iron(III)-substituted tungstogermanate containing two types of lacunary polyoxometalate units

A novel polyoxotungstate cluster (H₂en)_2.5H₉[Fe₆Ge₃W₂₄O₉₄(H₂O)₂] · 14H₂O (1) (en = ethylenediamine) has been hydrothermally synthesized and structurally characterized by IR, TGA and single-crystal X-ray diffraction. The polyoxoanion skeleton of 1 is composed of two tri-Fe^III substituted B-α-(Fe₃GeW₉O₄₀) Keggin units connected by an unique hexavacant GeW₆O₂₆ Keggin fragment, leading to the first Fe(III)-containing banana-shaped tungstogermanate. Magnetic measurements of 1 reveal that the exchange interactions within the trimetal clusters are antiferromagnetic.     

Effects of mechanical milling on preparation and properties of CuAl1−xFexO2 thermoelectric ceramics

CuAl_1?xFe_xO₂ (x = 0, 0.1, and 0.2) thermoelectric ceramics produced by a reaction-sintering process were investigated. Pure CuAlO₂ and CuAl_0.9Fe_0.1O₂ were obtained. Minor CuAl₂O₄ phase formed in CuAl_0.8Fe_0.2O₂. Addition of 10 mol% Fe lowered the sintering temperature obviously and enhanced the grain growth. At x = 0.1, electrical conductivity = 3.143 Ω^?1 cm^?1, Seebeck coefficient = 418 μV K^?1, and power factor = 5.49 × 10^?5 W m^?1 K^?2 at 600 °C were obtained. The reaction-sintering process is simple and effective in preparing CuAlO₂ and CuAl_0.9Fe_0.1O₂ thermoelectric ceramics for applications at high temperatures.