纳米Fe2O3/膨润土复合催化剂的制备及光催化活性

Using the surfactant（PVA）in the preparation process,the nano-iron oxide / Bentonites were prepared through a reaction between a solution of iron salt and a dispersion of Bentonite clay. The X-ray diffraction（XRD）results reveal that the catalysts mainly consist of α-Fe2O3 . The photo-catalytic activity of iron oxide / Bentonites was examined in the photo-assisted degradation of an organic azo-dye Orange Ⅱ. It is found that the photo-catalytic activity of the catalysts is much higher than that of α-Fe2O3 . The experimental results（using the different catalysts in which the quantities of Fe2O3 are equal）demonstrate that the photo-catalytic activity of catalysts is as follows:Fe-A > Fe-B > Fe-C > Fe-D. In addition,the research shows that Orange Ⅱ degradation ratio of heterogeneous photo-Fenton process is higher than that of homogeneous one.     

Quantum-dots containing Fe/SBA-15 silica as “green” catalysts for the selective photocatalytic oxidation of alcohol (methanol,under visible light)

Fe/SBA-15 catalysts containing iron oxide nanoparticles confined inside silica pores (replicated, internal, poorly crystalline) and grown outside silica grains (external, mainly crystalline hematite) in different proportions are prepared using a single silica support. Fe-species are deposited by the two-solvent technique with two iron salts precursors (Fe(NO₃)₃·9H₂O, FeCl₃·6H₂O) and two solvents (cyclohexane, hexane) for 11 wt% of iron. Calcination is performed in reproducible conditions (700 °C, 2 °C/min, thin bed, in air). SAXS measurements are used to show that the 2D hexagonal structure of the used silica is maintained after Fe-loading and calcination. Ar sorption measurements show that the pores are partially plugged. The oxidation of pure methanol is used as a test reaction to compare photocatalytic properties. H₂O₂ and visible light both activate the reaction. More active catalysts are formed with hexane associated with FeCl₃·6H₂O than with Fe(NO₃)₃·9H₂O. A reversed situation is observed with cyclohexane. Iron leaching (after 1 h 30 of test, up to 3 mg of Fe by mL) is important. These results are expected to be of interest in the exploration of size and shape “nanocatalysis” and to provide a further understanding for the reactions that take place when porous silicas are used as supports.     

Decolorization and mineralization of yellow 5 (E102) by UV/Fe2+/H2O2 process. Optimization of the operational conditions by response surface methodology

In this study, the optimization and implementation of a homogeneous photo-Fenton process for the decolorization and mineralization of a wastewater containing highly concentrated yellow 5 (E102) dye, resulting from an industry placed in the suburbs of Medellin (Colombia), is presented. Response surface methodology was applied as a tool for the optimization of operational conditions such as initial dyestuff concentration, H₂O₂ concentration, and UV-radiation power (number of lamps). The decolorization, degradation and mineralization efficiencies were used as response variables. The following conditions were found to be optimal for decolorization and mineralization of yellow 5: UV radiation of 365 nm (4 W, one lamp), dye concentration of 200 mg/L, Fe²⁺ concentration of 1.0 mM, H₂O₂ concentration of 1.75 mL/L, treatment time of 180 min, Fe²⁺ concentration of 1 mM and pH = 3. Under these conditions (180 min), the photo-Fenton process allowed us to reach ca. 100% of color dye degradation, 99% of COD degradation, and 85% of mineralization (TOC). The scavenging effect of the Cl^– anion on the photodegradation process was also confirmed.     

Photo-Fenton oxidation of phenol over a Cu-doped Fe-pillared clay

A Cu-doped Fe-pillared Tunisian clay (Cu/Fe–PILC) was synthesized and used as a catalyst in the heterogeneous photo-Fenton oxidation of phenol in aqueous solution. Textural, structural and chemical characterization pointed to successful pillaring and incorporation of the Cu active phase. Photo-Fenton experiments proved the high activity of the Cu/Fe–PILC catalyst, which was able to completely mineralize the phenol present in the treated solution after a reaction time of 40 min and in the presence of UV-C light. Moreover, the catalytic activity was not influenced by the pH of the initial phenol solution, over a wide range of pH from 3 to 7. An optimal dosage of H₂O₂ and of the catalyst was found. Phenol degradation was found to be slower in the presence of UV-A irradiation, needing longer reaction times. Negligible metal leaching and catalyst reutilization without noticeable loss of activity point to an excellent catalytic stability for this Cu/Fe–PILC catalyst.     

Solar photooxidation of azo dye over mixed (Al-Fe) pillared bentonite using hydrogen peroxide

Summary The mixed Al-Fe pillared bentonite (Al/Fe-B) was tested as a heterogeneous catalyst for the photo-Fenton discoloration of azo dye X-3B under solar light irradiation. The structural characteristics of the catalyst were examined by XRD, BET, and TEM. The results indicate that the heterogeneous photo-Fenton process employing the Al/Fe-B as catalyst exhibits higher photo-catalytic activity compared to its corresponding homogeneous photo-Fenton process. The amount of Fe ions in solution leaching from the Al/Fe-B is less than 0.26% of the total iron content in the catalyst.     

Spectroscopic studies on the interaction between Pr(III) complex of an ofloxacin derivative and bovine serum albumin or DNA

The binding properties on [PrL₂(NO₃)](NO₃)₂ (L = 9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperaziny)-7-oxo-7Hpyrido[1,2,3-de]-1,4-benzoxazine-6-carbaldehyde benzoyl hydrazone) to bovine serum albumin (BSA) have been studied for the first time using fluorescence spectroscopy in combination with UV–Vis absorbance spectroscopy. The results showed that [PrL₂(NO₃)](NO₃)₂ strongly quenched the intrinsic fluorescence of BSA through a static quenching procedure, and non-radiation energy transfer happened within molecules. The number of binding site was about 1, and the efficiency of Förster energy transfer provided a distance of 4.26 nm between tryptophan and [PrL₂(NO₃)](NO₃)₂ binding site. At 288, 298, 310 K, the quenching constants of BSA–[PrL₂(NO₃)](NO₃)₂ system were 5.11 × 10⁴, 4.33 × 10⁴ and 3.71 × 10⁴ l M^?1. ΔH, ΔS and ΔG were obtained based on the quenching constants and thermodynamic theory (ΔH < 0, ΔS > 0 and ΔG < 0). These results indicated that hydrophobic and electrostatic interactions are the mainly binding forces in the [PrL₂(NO₃)](NO₃)₂–BSA system. In addition, the CD spectra have proved that BSA secondary structure changed in the presence of [PrL₂(NO₃)](NO₃)₂ in aqueous solution. Moreover, the interaction between [PrL₂(NO₃)](NO₃)₂ and calf thymus DNA (CT DNA) was studied by spectroscopy and viscosity measurements, which showed that the binding mode of the [PrL₂(NO₃)](NO₃)₂ with DNA is intercalation. The DNA cleavage results show that in the absence of any reducing agent, the [PrL₂(NO₃)](NO₃)₂ can cleave plasmid pBR322 DNA and its hydrolytic mechanism was demonstrated with hydroxyl radical scavengers and singlet oxygen quenchers.     

Laser Raman and ac impedance spectroscopic studies of PVA: NH4NO3 polymer electrolyte

Ion conducting polymer electrolyte PVA:NH₄NO₃ has been prepared by solution casting technique and characterized using XRD, Raman and ac impedance spectroscopic analyses. The amorphous nature of the polymer films has been confirmed by XRD and Raman spectroscopy. An insight into the deconvoluted Raman peaks of υ₁ vibration of NO₃^? anion for the polymer electrolyte reveals the dominancy of ion aggregates at higher NH₄NO₃ concentration. From the ac impedance studies, the highest ion conductivity at 303 K has been found to be 7.5 × 10^?3 S cm^?1 for 80PVA:20NH₄NO₃. The conductivity of the polymer electrolytes has been found to depend on the degree of dissociation of the salt in the host polymer matrix. The combination of the above-mentioned analyses has proven worth while and in fact necessary in order to achieve better understanding of these complex systems.     

Heptanuclear high-spin complex compounds based on S-donors

The precursors [Fe(III)(^SYL)Cl] (^SYLH₂) = N,N′-bis(1-hydroxy-Y-2-benzyliden)-1,6-diamino-3-thiohexane, (Y = H, 3EtO, 5Me) are high-spin (S = 5/2) complexes. The precursors are combined with [Fe(II)(CN)₆]⁴⁻ and [Co(III)(CN)₆]³⁻ to yield star-shaped heptanuclear clusters, [Fe(II)(CN–Fe(III)^SYL)₆]Cl₂ and [Co(III)(CN–Fe(III)^SYL)₆]Cl₃. The star-shaped compounds are high-spin (HS) systems at room temperature. On cooling to 20 K some of the iron(III) centers perform some HS–HS transition.     

Cloud-point measurement for (sulphate salts + polyethylene glycol 15000 + water) systems by the particle counting method

The phase separation of (water + salt + polyethylene glycol 15000) systems was studied by cloud-point measurements using the particle counting method. The effect of three kinds of sulphate salt (Na₂SO₄, K₂SO₄, (NH₄)₂SO₄) concentration, polyethylene glycol 15000 concentration, mass ratio of polymer to salt on the cloud-point temperature of these systems have been investigated. The results obtained indicate that the cloud-point temperatures decrease linearly with increase in polyethylene glycol concentrations for different salts. Also, the cloud points decrease with an increase in mass ratio of salt to polymer.     

Catalytic wet peroxide oxidation of phenol over pillared clays containing iron or copper species

The catalytic wet oxidation of phenol by hydrogen peroxide in the presence of oxygen is catalysed, at room temperature, by copper or iron homogeneous species at pH 5 or 3.5, respectively. In such conditions phenol mild oxidation is mainly observed, the total phenol oxidation to CO₂ (TOC abatement) not exceeding 20 %. In similar experimental conditions, Fe, Al or Cu, Al pillared clays (FAZA or CAZA) are much more active, the phenol or the TOC conversion being directly related to the iron or copper content. Moreover, in the presence of iron containing pillared clay (FAZA), the TOC abatement can reach 80 % at 70 °C, with only a H₂O₂ stoichiometric excess equal to 1.5. The low iron leaching (less than 0.2 % of the total amount of iron in the catalyst) observed after a standard experiment (4 h) shows that the FAZA catalyst is highly stable in water media and could be used several consecutive times. These properties could result in the iron species stabilization in the interlamellar space of the pillared clays both by bonding with the Al pillars (60 % of the iron species) or as oxide clusters dispersed between the clay layers.     

Synthesis and properties of iron (II) quinoline-2-carboxylates,crystal structure of trans-diaquabis(quinoline-2-carboxylato)iron (II) bis(dichloromethane) solvate

Two mononuclear iron complexes with the quinoline-2-carboxylate ion (quin-2-c ion) have been obtained by the reaction of iron powder with quinoline-2-carboxylic acid in dichloromethane. The compounds [Fe(quin-2-c)₂] (1), [Fe(quin-2-c)₂(H₂O)₂] · 2CH₂Cl₂ (2) and [Fe(quin-2-c)₂(H₂O)₂] · 2EtOH · 2H₂O (3) have been investigated by IR and UV–Vis spectroscopy, magnetic susceptibility and field-dependent magnetization measurements. The structure of 2 has been characterised by X-ray diffraction. The 2D bilayered frameworks of 2 and 3 are constructed by extensive hydrogen bonding interactions between water and the organic ligand coordinated to iron (II). The magnetic properties of 2 and 3 were interpreted on the basis of a spin Hamiltonian that included axial and rhombic crystal field components. The weak antiferromagnetic (2) and ferromagnetic (3) interactions are evident in the low temperature data and possibly occur via strong hydrogen bonds.     

Determination of the concentration profile and homogeneity of antioxidants and degradation products in a cross-linked polyethylene type A (PEXa) pipe

A solvent extraction technique has been developed to determine the concentration profile of two antioxidants and five degradation products of antioxidants in cross-linked polyethylene (PEX) materials. Irganox^® 1076 and two degradation products in a PEX pipe type A (PEXa) were detected after extraction in chloroform. Fick's second law of diffusion was used to verify that 24 h of extraction at room temperature was sufficient to extract Irganox^® 1076 and the degradation products from PEX materials with a thickness of 5 μm. With the use of gas chromatography and mass spectrometry, the concentration profile was measured at four different places on a 100 m PEXa pipe. A two-way ANOVA analysis showed that the composition of Irganox^® 1076 was homogenous in the radial direction and heterogeneous in the longitudinal direction. Two degradation products of antioxidants were detected, 2,6-di-tert-butyl-p-benzoquinone and 2,4-di-tert-butyl phenol. The composition of 2,6-di-tert-butyl-p-benzoquinone was found to be homogeneous in the radial and longitudinal direction. 2,4-Di-tert-butyl phenol was homogeneous in the radial direction but heterogeneous in the longitudinal direction.     

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.     

The mixed-valence iron compound Na0.1Fe7(PO4)6: crystal structure and 57Fe Mössbauer spectroscopy between 80 and 295 K

The crystal structure of the synthetic iron phosphate Na_0.10(1)Fe_6.99(1)(P_1.00(1)O₄)₆ has been refined at 270 and 100 K from single-crystal X-ray diffraction data. The compound is triclinic, P−1, Z=1, lattice parameters: a=6.3944(9) Å, b=7.956(1) Å, c=9.364(1) Å, α=105.13(1)°, β=108.35(1)°, γ=101.64(1)° at 270 K and adopts the well-known howardevansite structure type. Iron, being both in the divalent and the trivalent valence state, is ordered on the four symmetry non-equivalent iron positions [Fe²⁺ on Fe(1) and Fe(3), Fe³⁺ on Fe(2) and Fe(4)]. Three of the four iron positions show octahedral oxygen atom coordination, the fourth one, which is occupied by Fe²⁺, is five-fold coordinated. The structure consists of crankshafts (buckled chains) of edge sharing Fe-oxygen polyhedra, passing through the unit cell in [101] direction. Structural investigation at 100 K shows no change of symmetry. The valence state and distribution of iron was determined by ⁵⁷Fe Mössbauer spectroscopy. The compound shows 4 subspectra in agreement with the four different Fe sites. The assignment of the Fe²⁺ doublets to the Fe(1) and Fe(3) sites is trivial due to the 2:1 stoichiometry, also found in the Mössbauer spectra. For the Fe³⁺ sites, the temperature-dependent variation of structural distortion parameters and the quadrupole splitting led to a clear doublet assignment.     

Characterisation of salt films on dissolving metal surfaces in artificial corrosion pits via in situ synchrotron X-ray diffraction

The salt films formed on metal surfaces dissolving inside artificial corrosion pits formed in 1 M HCl have been probed with synchrotron X-ray diffraction. NiCl₂ · 6H₂O is the main phase in the salt film on nickel, whereas salt films on both iron and 316 L stainless steel are predominantly FeCl₂ · 4H₂O. However, the salt film on iron has a very fine homogeneous crystallite size whereas that on stainless steel is much coarser. The potential-dependence of the film formed on iron has been determined.     

Photocatalytic degradation of EU priority substances: A comparison between TiO2 and Fenton plus photo-Fenton in a solar pilot plant

Titanium dioxide photocatalysis (200 mg/L) and photo-Fenton were applied to the treatment of several different pesticides considered priority substances (PS) by the European Commission dissolved in water at 50 mg/L or at maximum water solubility (alachlor, atrazine, chlorfenvinphos, diuron, isoproturon and pentachlorophenol) alone (20 mg/L of iron) and as a mixture (10 mg/L of iron). All tests were performed in new twin 75-L compound parabolic collector (CPC) pilot plants driven by solar energy. Total organic carbon (TOC) mineralisation, disappearance of the parent compound and inorganic ion release are discussed as a function of treatment time. Photo-Fenton treatment was found to be shorter than TiO₂ and more appropriate for these compounds and mixtures of them.     

Sorption of iron(II) and ruthenium(III)-triazine complexes on silica gel and its analytical applicability

2,4,6-Tri(2′-pyridyl)-s-triazine (TPTZ) complexes with iron(II) and ruthenium(III) were prepared. Their sorption and desorption features on silica gel have been investigated. Both complexes were strongly adsorbed. This has been utilized for separating and preconcentrating iron(II) and ruthenium(III) using TPTZ-impregnated silica gel. The chromatographic behavior of TPTZ on silica gel column was examined and found to be effective modifier for silica gel surface. The sorption capacity of silica gel for those metal-triazine complexes has been determined under static conditions and was found to be 5.28 × 10^–3 mM (Fe(TPTZ)₂²⁺) and 2.9 × 10^–3 mM (Ru(TPTZ)₂³⁺). Saturated methanolic solutions of KI or 25% NaClO₄ solutions desorbed both complexes quantitatively from the silica gel surface.     

Fe-doped SnO2 transparent semi-conducting thin films deposited by spray pyrolysis technique: Thermoelectric and p-type conductivity properties

In this paper, we report structural, electrical, optical, and especially thermoelectrical characterization of iron (Fe) doped tin oxide films, which have been deposited by spray pyrolysis technique. The doping level has changed from 0 to 10 wt% in solution ([Fe]/[Sn] = 0–40 at% in solution). The thermoelectric response versus temperature difference has exhibited a nonlinear behavior, and the Seebeck coefficient has been calculated from its slope in temperature range of 300–500 K. The Hall effect and thermoelectric measurements have shown p-type conductivity in SnO₂:Fe films with [Fe]/[Sn] ≥ 7.8 at%. In doping levels lower than 7.8 at%, SnO₂:Fe films have been n-type with a negative thermoelectric coefficient. The Seebeck coefficient for SnO₂:Fe films with 7.8 at% doping level has been obtained to be as high as +1850 μV/K. The analysis of as-deposited samples with thicknesses ～350 nm by X-ray diffraction (XRD) and scanning electron microscopy (SEM) has shown polycrystalline structure with clear characteristic peak of SnO₂ cassiterite phase in all films. The optical transparency (T%) of SnO₂:Fe films in visible spectra decreases from 90% to 75% and electrical resistivity (ρ) increases from 1.2 × 10^?2 to 3 × 10³ Ω cm for Fe-doping in the range 0–40 at%.     

Effect of inorganic anions on the titanium dioxide-based photocatalytic oxidation of aqueous ammonia and nitrite

In this study, we investigated the effects of four inorganic anions (Cl⁻, SO₄²⁻, H₂PO₄⁻/HPO₄²⁻, and HCO₃⁻/CO₃²⁻) on titanium dioxide (TiO₂)-based photocatalytic oxidation of aqueous ammonia (NH₄⁺/NH₃) at pH ∼ 9 and ∼10 and nitrite (NO₂⁻) over the pH range of 4–11. The initial rates of NH₄⁺/NH₃ and NO₂⁻ photocatalytic oxidation are dependent on both the pH and the anion species. Our results indicate that, except for CO₃²⁻, which decreased the homogeneous oxidation rate of NH₄⁺/NH₃ by UV-illuminated hydrogen peroxide, OH scavenging by anions and/or direct oxidation of NH₄⁺/NH₃ and NO₂⁻ by anion radicals did not affect rates of TiO₂ photocatalytic oxidation. While HPO₄²⁻ enhanced NH₄⁺/NH₃ photocatalytic oxidation at pH ∼ 9 and ∼10, H₂PO₄⁻/HPO₄²⁻ inhibited NO₂⁻ oxidation at low to neutral pH values. The presence of Cl⁻, SO₄²⁻, and HCO₃⁻ had no effect on NH₄⁺/NH₃ and NO₂⁻ photocatalytic oxidation at pH ∼ 9 and ∼10, whereas CO₃²⁻ slowed NH₄⁺/NH₃ but not NO₂⁻ photocatalytic oxidation at pH ∼ 11. Photocatalytic oxidation of NH₄⁺/NH₃ to NO₂⁻ is the rate-limiting step in the complete oxidation of NH₄⁺/NH₃ to NO₃⁻ in the presence of common wastewater anions. Therefore, in photocatalytic oxidation treatment, we should choose conditions such as alkaline pH that will maximize the NH₄⁺/NH₃ oxidation rate.     

Elucidation of interference mechanisms caused by iron on stibine electrochemical generation by differential pulse anodic stripping voltametry. A case study

The interference effect caused by the presence of iron – both (II) and (III) oxidation states – on the electrochemical generation of SbH₃ has been characterized. Interference from Fe(III) was more severe than for Fe(II). Total signal suppression was obtained for a Fe(III) : Sb(III) concentration ratio of 5 : 1, whereas a 40% suppression was obtained for Fe(II). A mechanism is proposed based on the results obtained by differential pulse anodic stripping voltametry. The standard conditions used for the hydride electrochemical generation were simulated in the differential pulse anodic stripping voltametry measurements in order to achieve valid conclusions. The reduction of Fe(II) onto the cathode surface prevents the formation of stibine avoiding the recombination of Sb⁰ with the hydrogen atoms adsorbed on the surface. The mechanism by which the Fe(III) interferes on the stibine formation is related to the co-deposition of the iron and antimony that also avoid the further recombination of the Sb⁰. The formation of a specie of stoichiometry not determined (probably 1 : 1) on the cathode surface may justify the larger interference effect observed for the Fe(III).