Spectrophotometric evaluation of the photocatalytic degradation of formaldehyde by Fe2O3–TiO2 nano hybrid

Photocatalytic capabilities of sol–gel synthesized Fe₂O₃–TiO₂ nano hybrid was investigated in degradation of formaldehyde in presence of ultra violet and visible irradiation. The reaction stream was evaluated by UV–vis spectrophotometry at 330–500 nm spectral region, using Fluoral-P (4-amino-3-penten-2-one) as a complexing agent. Obtained results confirmed the effective role of Fe₂O₃ phase in nano hybrid for degradation of formaldehyde according to Baeyer–Villiger reaction. On the other hand TiO₂ would play the role of photocatalyst in presence of UV ray. Nano hybrid assisted process was monitored by spectrophotometry, utilizing multivariate curve resolution chemometric technique.     

Fe2(SO4)3/K2S2O8催化合成丙酸正丁酯的研究

以 Fe2 (SO4 ) 3和 K2 S2 O8为复配催化剂 ,对丙酸和正丁醇为原料合成丙酸正丁酯的反应进行了研究。探讨了催化剂用量、醇酸化、反应时间等对酯产率的影响。结果表明 :在正丁醇用量为 0 .12 5 m ol的情况下 ,以苯为带水剂 ,Fe2 (SO4 ) 3和 K2 S2 O8为催化剂 ,催化剂用量为 1.4 g,醇酸摩尔比为 1∶ 2 ,反应时间为 1.5 h,常压下 ,收集14 0～ 14 5 .5℃的馏分 ,酯产率达 98.5 %     

Removal of tylosin from aqueous solution by UV/nano Ag/S2O 8 2− process : Influence of operational parameters and kinetic study

The present work deals with the photooxidative degradation of tylosin antibiotic (TYL) in the presence of potassium peroxydisulfate (K₂S₂O₈) irradiated by UV-C in the presence of immobilized nano silver. Effects of pH, temperature, peroxydisulfate concentration and immobilized nano silver dosage on the degradation efficiency of TYL were examined. Degradation efficiency was small when the oxidation was carried out in the absence of UV irradiation. Results showed that degradation of TYL increases with temperature, nano Ag and peroxydisulfate initial concentration and decreases with pH. Due to UV/nano Ag/S₂O ₈ ^2? processes, more than 90% of TYL can be degraded at room temperature in 35 min at an initial concentration of 50 mgl^?. Degradation reaction order of TYL by UV/nano Ag/S₂O ₈ ^2? process is 1.89. Meanwhile, the initial rates of degradation in UV/nano Ag/S₂O ₈ ^2? processes can be described well by the Langmuir-Hinshelwood kinetic model.     

A kinetic study of the isothermal degradation process of Lexan® using the conventional and Weibull kinetic analysis

The degradation process of commercial grade Lexan® was investigated by thermogravimetric technique under isothermal experimental conditions at four different operating temperatures: 375 °C, 387.5 °C, 400 °C and 425 °C. The kinetic triplet (E _a , A, f(α)) was determined using conventional and Weibull kinetic analysis. The applied kinetic procedure shows that the investigated degradation process can be described by two-parameter autocatalytic ?esták–Berggren (SB) reaction model. It was established that the degradation process of Lexan® can be described by the following kinetic triplet: E _a? =?158.3 kJ mol^?1, A?=?8.80?×?10⁹ min^?1 and f(α)?=?α ^0.33 (1???α)^1.62. It was established that the operating temperature has an influence on the values of SB reaction orders (m and n) (0.27?m?n??1, represent the composite value from a complex degradation reaction and can not compare with the dissociation energy of the weak bonds in bisphenol-A polycarbonate. Also, it was concluded that the Weibull shape parameter (β) shows that the considered process occurs under the same reaction mechanism, independently on operating temperature (T), i.e. the change of rate-limiting step does not occur (β?ddf) of apparent activation energies for considered degradation process. On the other hand, it was shown that the experimentally evaluated density distribution function of apparent activation energies represents the intermediate case between the calculated density distribution functions at 375 °C and 425 °C.     

Fe(Ⅲ)-EDTA吸收H2S反应动力学的实验研究

本文采用双搅拌无梯度气液反应器实验研究了Fe(III)-EDTA吸收H2S的反应动力学.建立并求解了H2S吸收数学模型,实验确定 Fe(III)-EDTA吸收H2S的化学反应速度常数为     

Oxidation of catechol catalyzed by β-cyclodextrin-Cu(Ⅱ) complexes and its reaction kinetics

以β-环糊精(β-CD)作为骨架,经磺酰化反应、卤代反应和与L-组氨酸的亲核取代反应,得到了两种β-环糊精-组氨酸衍生物配体,再将配体与Cu(Ⅱ)配位,合成了具有多酚氧化酶催化活性的β-环糊精-Cu(Ⅱ)配合物。采用元素分析、傅里叶变换红外光谱、核磁共振波谱和原子吸收光谱等方法对配体和配合物的结构进行了表征。以O₂为氧化剂,用分光光度法测定了它们催化邻苯二酚氧化反应的性能,并考察了反应温度、pH值等因素对催化反应速率的影响。结果表明：β-环糊精-Cu(Ⅱ)配合物具有良好的催化性能;C-2位修饰得到的环糊精类金属衍生物因为活性基团与反应中心之间相对位置适宜,表现出较大的加速效果;反应动力学表明组胺基配位Cu(Ⅱ) 、β- CD疏水空腔和碱催化作用是反应加速的3个因素。     

Citrate-Nitrate Synthesis and the Electrophysical Properties of Ceramics in the K2O–TiO2–Fe2O3 System

Glass Physics and Chemistry - This paper presents a study of the electrically conductive properties of ceramics based on phases crystallizing in the K2O–Fe2O3–TiO2 system, when using...     

Mechanism of the hydrodenitrogenation of o-toluidine and methylcyclohexylamine over NiMo/γ-Al2O3

The hydrodenitrogenation (HDN) of o-toluidine and its reaction intermediates was studied over a NiMo/γ-Al₂O₃ catalyst. The kinetics of the HDN of methylcyclohexylamine and of the hydrogenation of cyclohexene were also studied. Hydrogenation of o-toluidine alone produces methylcyclohexene and methylcyclohexane. When a sufficient quantity of cyclohexene is added during the HDN of toluidine, methylcyclohexylamine, the first intermediate in the hydrogenation of toluidine, becomes detectable. Because of its strong adsorption constant and high rate constant for reacting further to methylcyclohexene and methylcyclohexane, methylcyclohexylamine is not observed in the HDN of toluidine. Adding cyclohexene decreases the adsorption of methylcyclohexylamine, thus enabling its detection. The rate and adsorption constants of methylcyclohexylamine and cyclohexene in the HDN of methylcyclohexylamine were calculated by fitting the kinetic data to a Langmuir–Hinshelwood equation. A two-site model was used to describe the surface reactions, with one site for the methylcyclohexylamine reactions and the other for the cyclohexene reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

[Fe(SCN)2(bipy)2]·2(S8): A two-dimensional coordination polymer intercalating the S8 molecules

A new coordination polymer compound [Fe(SCN)₂(bipy)₂]·2(S₈) (1) (bipy = 4,4′-bipyridine) has been synthesized by the reaction of the bifunctional ligand bipy, Fe(SCN)₂ and sulfur powder under hydrothermal conditions. The compound has been characterized by single and powder X-ray diffraction analysis, infrared spectroscopy and elemental analysis. Compound 1 features a two-dimensional layered structure with neutral S₈ molecules confined in between layers. The magnetic property studies of 1 indicated antiferromagnetic interactions.     

Fabrication and Formation Mechanism of Hollow-Structure Supermagnetic α-Fe2O3/Fe3O4 Heterogeneous Nanospindles

Journal of Inorganic and Organometallic Polymers and Materials - A simple process for the fabrication of hollow-structure supermagnetic α-Fe2O3/Fe3O4 heterogeneous nanospindles was introduced...     

Evaluation of kinetic parameters for the crystallization and degradation process of synthesized strontium mercaptosuccinate functionalized poly(ε-caprolactone) by non-isothermal approach

Strontium (Sr) mercaptosuccinate (MS) functionalized poly(ε-caprolactone) (PCL) was prepared by ring opening polymerization technique in the presence of Sr-MS nanohybrid initiator and stannous octoate (SO) catalyst for 2 h at 160 °C under nitrogen atmosphere. FTIR, NMR, DSC, TGA, GPC, POM, TEM and AFM techniques were employed to characterize the Sr-MS functionalized polymer. The FTIR spectrum showed a small peak at 526 cm⁻¹ due to the Sr–O stretching. The particle size of the Sr-MS nanohybrid functionalized PCL matrix was determined as less than 30 nm. The crystallization rate and crystallinity percentage were estimated from the non-isothermal exothermic curves. The crystallization temperature (T_c) was found to be decreased with increasing the cooling rate whereas the degradation temperature (T_d) was increased with increasing the heating rate. Various kinetic models were applied to comprehend the degradation behaviour of Sr-MS functionalized PCL as well as its related kinetic parameters under non-isothermal condition. The activation energy (E_a) was calculated for both crystallization (138.5 kJ/mol) and degradation (187 kJ/mol) behaviours of Sr-MS functionalized PCL under non-isothermal condition.

     

Comparative Study of Reactive Dyes Oxidation by H2O2/UV,H2O2/UV/Fe2+ and H2O2/UV/Fe° Processes

The decolorization and mineralization of two reactive dyes C.I. Reactive Blue 4 (RB 4) and C.I. Reactive Blue 268 (RB 268) were studied using various advanced oxidation processes (AOPs) such as H₂O₂/UV, H₂O₂/UV/Fe²⁺, and the H₂O₂/UV/Fe°. All processes were performed within a laboratory-scale photo-reactor setup. The experimental results were assessed in terms of absorbance (A) and total organic carbon (TOC) reduction. The main degradation products were identified by high resolution gas chromatography/high resolution mass spectrometry analyses. The results of our study demonstrated that the additions of moderate concentrations of H₂O₂ and Fe catalyst during the AOPs evidently increased the decolorization efficiencies within the first few minutes of the processing time (5–10 min) for both tested dyes, and prolonged irradiation does not necessarily significantly improve decolorization. On contrary, TOC removal rate increased with the processing time and with the addition of the catalyst from 40–50% up to 70–80% at defined experimental conditions. All the tested AOPs were very successful methods for RB 268 decolorization, having very complex structure and much higher molecular weight compared to the dye RB 4. This is important from both economic and ecological points of view.     

Mechanism of the action of Ag and As on the anodic corrosion of lead and oxygen evolution at the Pb/PbO(2−x)/H2O/O2/H2SO4 electrode system

When a Pb electrode, immersed in H₂SO₄ solution, is polarized anodically in the PbO₂ potential range the Pb/PbO(_2−x)/H₂O/O₂/H₂SO₄ electrode system is established. Oxygen is evolved at the oxide—solution interface. The oxygen atoms formed as intermediates diffuse into the anodic layer and oxidize the metal. Through a solid-state reaction, the metal is oxidized first to tet-PbO and then to PbO₂. By studying the changes in the rate—potential relations of the above reactions, as well as the phase and chemical composition of the anodic layer, it was possible to elucidate the effect of Ag and As on these processes. The additives were introduced into the electrode system either by alloying with lead or by dissolving them in the H₂SO₄ solution. When added to the solution, both Ag and As lower the overvoltage of the oxygen evolution reaction. They have practically no effect on the corrosion reaction under galvanostatic polarization conditions. If alloyed in the metal, Ag reduces the oxidation rate of Pb significantly, while As enhances it. Both additives lower the stoichiometric number of the anodic oxide layer, ie they retard the oxidation of PbO to PbO₂. The results of these investigations were used to develop further the model of the mechanism of the reactions proceeding during the anodic oxidation of lead in H₂SO₄ solutions.     

Structure and properties of nanostructured Fe(AlCr)2O4–Cr–(AlCr)2O3–Fe composite coating prepared by plasma spraying

In-situ nanostructured Fe(AlCr)₂O₄-based composite coating (FACr_52.5 coating) was prepared by reactive plasma spraying with micro-sized Al–Fe₂O₃–Cr₂O₃ powders. The microstructure, toughness and Vickers hardness, and adhesive strength of the coating were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and mechanical tests. The results indicated that the interlamellar spacing of the FACr_52.5 coating is only 1 μm. The coating exhibited nanostructured microstructure. The in-situ Cr (20 nm) and Fe (50–200 nm) particles were uniformly distributed in an Fe(AlCr)₂O₄ matrix, while the grain size of the Fe(AlCr)₂O₄ matrix is about 60 nm. The FACr_52.5 composite nano-coating exhibited much higher hardness, better wear resistance, stronger adhesive strength and toughness as compared to those of the composite nano-coating sprayed with Fe₂O₃–Al powders. Excellent mechanical properties of the FACr_52.5 coating were attributed to the uniform distribution of the in-situ nano-sized Cr particles in the coating matrix.     

Catalytic degradation of dimethyl phthalate by photo-assisted Fe(Ⅲ) immobilized collagen fiber

将Fe(Ⅲ)负载在胶原纤维上制备负载型铁催化剂(FeCF),并研究了该催化剂对邻苯二甲酸二甲酯（DMP）的非均相Fenton催化降解性能。结果表明：与FeCF/H₂O₂/暗光体系、FeCF/UV体系和H₂O₂/UV体系相比,FeCF/H₂O₂/UV体系对DMP的降解率明显提高。H₂O₂相似文献   

Facile synthesis of morphology and size-controlled α-Fe2O3 and Fe3O4 nano-and microstructures by hydrothermal/solvothermal process: The roles of reaction medium and urea dose

This paper reports a systematic study of the influences on the synthesis of α-Fe₂O₃ and Fe₃O₄ via a hydro/solvothermal process at 200 °C. Both the reaction medium and urea dose have been investigated. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM). Results showed that the reaction mediums, such as water and ethylene glycol, played important roles in forming different types of iron oxides. Pure crystalline α-Fe₂O₃ was formed via the hydrothermal process, and Fe₃O₄ was obtained through a solvothermal route with ethylene glycol as reaction medium. Increasing urea dose tuned the particle sizes of α-Fe₂O₃ and Fe₃O₄ from a few hundreds to several tens of nanometers. With addition of urea, the morphology of α-Fe₂O₃ evolved from olive-like to rhomb-like, and Fe₃O₄ evolved from hollow sphere, to pinecone-like, and finally into cracked nanostructures. The variations of the surface area of products were mainly dependent on the microstructure and intrinsic features of the iron oxide particles. Results of the mechanistic studies indicated that the generation of CO₂ and NH₃ via in situ thermal decomposition of urea was crucial for the formation of α-Fe₂O₃ and Fe₃O₄ nano-and microstructures. The as-synthesized α-Fe₂O₃ and Fe₃O₄ were used as catalysts for methylene blue degradation in the presence of H₂O₂, and α-Fe₂O₃ showed a higher degradation efficiency. Our findings demonstrated a promising strategy for the developments of rationally designed iron oxides.     

Mechanism of the Formation of Ba2Ti9O20-Based Phases in the Course of Solid-Phase Interaction in the BaO–TiO2(ZrO2) and Cs2O–BaO–TiO2(ZrO2) Systems

The mechanism of solid-phase interaction in the BaO–TiO₂(ZrO₂) and Cs₂O–BaO–TiO₂(ZrO₂) systems is investigated. It is established that the formation of the Ba₂Ti₉O₂₀ compound and Ba₂Ti₉O₂₀-based solid solutions is a multistage process proceeding through the formation of intermediate phases. The solid-phase interaction in the BaO–TiO₂(ZrO₂) system occurs through the formation of the BaTi₄O₉ intermediate compound. The Ba₂Ti₉O₂₀ single-phase product is formed only in the presence of ZrO₂ (0.82 mol %) upon heat treatment at a temperature of 1250°C for 5 h. In the Cs₂O–BaO–TiO₂(ZrO₂) system, the BaTi₅O₁₁ metastable intermediate phase is formed at the first stage of the solid-phase interaction. The Cs _x Ba_{2 – x/2}Ti_{9 – y} Zr _y O₂₀ single-phase solid solutions are prepared upon heat treatment at 1100°C for 1 h. It is demonstrated that, in the Ba₂Ti₉O₂₀ structure, cesium can isomorphously substitute for barium with the formation of Cs _x Ba_{2 – x/2}Ti_{9 – y} Zr _y O₂₀ solid solutions (0 x 0.8, y = 0 and 0.09).     

Measurement of the hydroxyl radical formation from H2O2, NO3−, and Fe(III) using a continuous flow injection analysis

Production of hydroxyl radical (OH) is of significant concern in engineered and natural environment. A simple in situ method was developed to measure OH formation in UV/H₂O₂, UV/Fe(III), and UV/NO₃^? systems using trapping of OH by benzoic acid (BA) and measuring fluorescence signals from hydroxylated products of BA. Method development included characterization of OH trapping mechanism and measurement of quantum yields (Φ_OH) for OH. The distribution of OHBA isomers was in the order of o-OHBA > p-OHBA > m-OHBA, although it changed with the H₂O₂ concentration and light intensity. This supports that OH attacks dominantly on the benzene rings. The quantum yields for OH formation in the UV/H₂O₂ process were 1.02 and 0.59 at 254 and 313 nm, which were in good agreement with the literature values, confirming that the method is suitable for the measurement of OH production from UV/H₂O₂ processes. Using the continuous flow method developed, quantum yields for OH in UV/H₂O₂, UV/Fe(III), and UV/NO₃^? systems were measured varying the initial concentration of OH precursors. The Φ_OH values increased with increasing concentrations of H₂O₂, Fe(III), and NO₃^? and approached constant values as the concentration increased. The Φ_OH values were 0.009 for H₂O₂ at 365 nm, showing that OH production is not negligible at such high wavelength. The Φ_OH values during the photolysis of Fe(OH)²⁺ (pH 3.0) and Fe(OH)₂⁺ (pH 6.0) at 254 nm were 0.34 and 0.037, respectively. The Φ_OH values for NO₃^? approached a constant value of 0.045 at 254 nm at the initial concentration of 10 mM.