Photocatalytic removal of methyl orange in an aqueous solution by a WO3/TiO2 composite film

WO₃/TiO₂ composite film was prepared by microarc oxidation technique and characterized by SEM, XRD, UV-vis spectra and Zeta-potential. The photocatalytic activity of WO₃/TiO₂ composite film was evaluated by examining the degradation of methyl orange. The influence of solution pH and inorganic anions on removal ratio of methyl orange was investigated. Removal ratio of methyl orange decreased with an increase of pH value in acidic solution, while it increased with the pH value in alkaline solution. The influence of added anions on the removal ratio is divided into two aspects. Addition of Cl^? and SO ₄ ^2? resulted in a decrease in photocatalytic removal ratio of methyl orange, while it was facilitated by PO ₄ ^3? , HCO ₃ ^? and NO ₃ ^? .     

Effect of supplying a carbon extracting solution on denitrification in horizontal subsurface flow constructed wetlands

Denitrification strongly depends on the availability of carbon source in constructed wetlands (CWs). In this study, several relevant carbon source extracting solutions made from hydrolyzate of selected wetland litters were added to CWs for nitrogen removal enhancement. The feasibility of supplying a carbon extracting solution to improve potential denitrification rate in horizontal subsurface flow constructed wetland was deeply investigated. Combinations of different hydraulic retention time (HRT, especially for 2-day and 4-day) with different influent COD/N ratios were designed to prove the enhancement on denitrification by carbon source supplement. In addition, specific denitrification rate (SDNR) was calculated for the comparison of the nitrogen removal at different COD/N ratios. The sequential operation results on total nitrogen (TN) and nitrate (NO ₃ ^? -N) removal efficiencies were obtained in CW system with an influent COD/N ratio of 4.0. The accumulation of nitrite (NO ₂ ^? -N) was found to be closely related to the removal of NO ₃ ^? -N. Meanwhile, no obvious accumulation of NO ₂ ^? -N was found when the removal of NO ₃ ^? -N was relatively high.     

Optimizing photocatalytic degradation of phenol by TiO2/GAC using response surface methodology

TiO₂ deposited on granular activated carbon (TiO₂/GAC) was used for photocatalytic degradation of phenol. The effects of photocatalyst loading, initial substrate concentration and addition of an oxidizing agent as H₂O₂ were investigated using a one-factor-at-a-time experiment. Central composite design, an experimental design for response surface methodology (RSM), was used for the modelling and optimization of the phenol degradation. Analysis of variance (ANOVA) indicated that the proposed quadratic model was in agreement with the experimental case with R² and R _adj ² correlation coefficients of 0.9760 and 0.9544, respectively. Accordingly, the optimum conditions for phenol degradation were a photocatalyst loading of two layers, initial phenol concentration of 34.44 mg L^?1 and H₂O₂ concentration of 326.90 mg L^?1. The TiO₂/GAC was used for five cycles with phenol degradation efficiency still higher than 90%. Finally, the phenol that remained adsorbed on GAC was able to migrate to TiO₂ and then photocatalytically be degraded.     

Electrochemical study of aluminium ion reduction in acidic AlCl3-n-butyl-pyridinium chloride melts

Electrochemical reduction of AlCl₃ dissolved in acidic AlCl₃-n-butyl-pyridinium chloride melt was studied by linear sweep voltammetry and chronopotentiometry at tungsten and platinum electrodes, in the Al₂Cl ₇ ^? concentration range 0.3 to 0.5 M between 30 and 60°C. Al₂Cl ₇ ^? bulk reduction was preceded by a nucleation (tungsten) or alloy formation phenomenon (platinum). The overall results agree rather well with the mechanism: $$\begin{gathered} 2AlCl_4^ - \rightleftarrows Al_2 Cl_7^ - + Cl^ - \hfill \\ 4Al_2 Cl_7^ - + 3e \rightleftarrows Al + 7AlCl_4^ - \hfill \\ \end{gathered} $$ The electrochemical reaction appeared quasi-reversible. Calculated values of the product of the transfer coefficient by the number of the electron exchanged in the rate determining step were in the range 0.45 to 0.7. Diffusion coefficients for Al₂Cl ₇ ^? were calculated.     

Kinetic modeling and dynamic simulation for the catalytic wet air oxidation of aqueous ammonia to molecular nitrogen

A kinetic model for the catalytic wet air oxidation of aqueous ammonia over Ru/TiO₂ catalyst was developed considering the consecutive reaction steps as follows: (i) formation of active oxygen sites O* by the dissociative adsorption of aqueous O₂ on the catalyst, (ii) oxidation of aqueous NH₃ by the reaction with three O* sites to produce HNO₂, (iii) aqueous phase dissociation of HNO₂ into H⁺ and NO ₂ ^? , (iv) formation of NH ₄ ⁺ by the association of NH₃ with the HNO₂-dissociated H⁺, (v) formation of N₂ by the aqueous phase reaction between NO ₂ ^? and NH ₄ ⁺ , (vi) formation of NO₃ by the reaction of NO ₂ ^? with an O* site. For each reaction step, a rate equation was derived and its kinetic parameters were optimized by experimental data fitting. Activation energies for the reactions (ii), (v), and (vi) were 123.1, 76.7, and 54.5 kJ/mol, respectively, suggesting that the oxidation reaction of aqueous NH₃ to HNO₂ was a ratedetermining step. From the simulation using the kinetic parameters determined, the initial pH adjustment of the ammonia solution proved to be critical for determining the oxidation product selectivity between desirable N₂ and undesirable NO ₃ ^? as well as the degree of oxidation conversion of ammonia.     

Influence of inorganic and organic additives on the composition of the precipitate of synthetic hydroxylapatite and calcium oxalate monohydrate

Synthetic hydroxylapatites are prepared with additives, such as Mg²⁺, CO ₃ ^2? , and C₂O ₄ ^2? . An increase in the concentration of magnesium leads to the formation of struvite. In the Ca(NO₃)₂-(NH₄)HPO₄-Na₂CO₃-NH₄OH-H₂O system, an excess of carbonate ions leads to the formation of calcite. When the synthesis is performed using oxalate ions as additives, calcium oxalate does not form the inherent phase. Calcium oxalate monohydrate is synthesized with additives, such as CO ₃ ^2? , HPO ₄ ^2? , and SO ₄ ^2? ions and urea, glycine, and glutamic acid. X-ray powder diffraction analysis has revealed that the composition of the CaC₂O₄ · H₂O precipitate remains unchanged under these conditions and in the presence of the aforementioned additives.     

Thermodynamic diagrams of the copper/ molten potassium nitrate system

Thermodynamic diagrams for the copper/molten potassium nitrate system have been calculated and expressed either as potential/pO^2?, potential/pO ₂ ^? or potential/pO ₂ ^2? diagrams. They exhibit the corresponding immunity, active dissolution, passivity and transpassivity regions.     

Synthesis and Properties in Solution of Gaussian Homo Asymmetric Polysiloxanes with a Bulky Side Group

Ring opening polymerization (ROP) of 1,3,5-tri-n-hexyl,1,3,5-trimethylcyclotrisiloxane (D ₃ ^Hexa ) and 1,3,5-tri-n-heptyl,1,3,5-trimethylcyclotrisiloxane (D ₃ ^Hepta ) was promoted by acid-treated synthetic silica–alumina to obtain Gaussian homo asymmetric polysiloxanes. M_w was above 70?kg/mol, meaning that homo asymmetric bulky side-group polysiloxane chains with high molecular weight were obtained. The material was treated in an acidic medium to improve the contents of acid sites and successfully tested as an inorganic acidic catalyst for ROP of D ₃ ^Hexa and D ₃ ^Hepta cyclosiloxanes. The samples of poly(methylhexylsiloxane) (PMHS) and poly(methylheptylsiloxane) (PMHepS) obtained were structurally characterized mainly by ²⁹Si NMR. All the experimental values including the refractive index increment (dn/dc), the second virial coefficient (A₂), the square root of the mean square radius of gyration ( $ \langle {{\text{RMS}}_{\text{radius}}}^{ 2} \rangle^{ 1/ 2} $ ), the average molecular weight (M_w), the average molecular numeral (M_n), and the weight polydispersity (M_w/M_n) were obtained using a gel permeation chromatography/light scattering (GPC/LS) coupled system. The A₂ experimental value for the two polymers (between 4 and 6.5?×?10^?4?mol/mL?g²) indicated that toluene was a good solvent. In addition, PMHS and PMHepS $ \langle {{\text{RMS}}_{\text{radius}}}^{ 2} \rangle^{ 1/ 2} $ were greater than 30?nm, indicating that larger chains of high molecular weight were obtained.     

Unexpected Photocatalytic Activity of Simple and Platinum Modified Tubular SiO2 for the Oxidation of Oxalic Acid to CO2

The photocatalytic mineralization of oxalic acid over SiO₂-based materials was investigated in the 200–800 nm range. The photocatalytic activity was found to be strongly related to the morphology of SiO₂ materials. The simple as well as the Pt-modified SiO₂ particles having a predominant spherical shape exhibited null photocatalytic activity. In contrast, the tubular shaped SiO₂ particles revealed an interesting photocatalytic activity, the rate of CO₂ evolvement being 45 µmol g _cat ^?1  h^?1. The initial activity was significantly enhanced (428 µmol CO₂ g _cat ^?1  h^?1) by platinum photodeposition on the outer and inner surface of tubular SiO₂. The catalytic materials were characterized by TEM, UV–VIS and XPS to obtain rational explanations for the phocatalytic activity that was noticed. The experiments revealed that SiO₂ tubes behave as efficient photooxidation microreactors. The morphology-dependent photocatalysis can be an efficient tool in future for the abatement of pollutants in liquid phase.     

Preparation of titanium dioxide/tungsten disulfide composite photocatalysts with enhanced photocatalytic activity under visible light

Titanium dioxide/tungsten disulfide (TiO₂/WS₂) composite photocatalysts were fabricated via a one-step hydrothermal synthesis process, using TiCl₄ as titanium source and bulk WS₂ as sensitizer. The morphology, structure, specific surface area and optical absorption properties of the composite photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), specific surface area analyzer and ultraviolet-visible diffuse reflection spectrum (UV-vis DRS), respectively. The photocatalytic activity of as-prepared photocatalysts was evaluated by the degradation of methyl orange (MO) under illumination of 500W Xenon lamp. The results indicated that TiO₂/WS₂ composite photocatalysts possessed excellent photocatalytic activity, and ～95% of the degradation rate for MO was reached when molar ratio of WS₂ to TiO₂ was 0.004 and the irradiation time was 60 min. Moreover, the carrier trapping experiment and fluorescence spectra showed that ·O ₂ ^? was the key component in the photocatalytic degradation process and O₂ was reduced to be ·O ₂ ^? by the electrons from the conduction band of TiO₂ and WS₂ for the degradation of MO.     

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.     

Mass spectrometry study of glasses based on sulfur, phosphorus, and arsenic

The mass spectrometry study of chalcogenide glasses in the P-S binary system and P-As-S ternary system is used to demonstrate that the composition of the gas phase in binary samples is characterized by the conventional spectra of ions, such as PS ₂ ⁺ , P₂S ₇ ⁺ , P₂S ₇ ⁺ and P₄S ₁₀ ⁺ . The introduction of As to the binary glass systems first demonstrated the presence of ions AsPS⁺, AsPS ₄ ⁺ , AS_{2 5} ⁺ and As₂PS₅ ⁺ in the gas phase of the ternary chalcogenide system, which correspond to the ternary compositions AsPS₄ and As₂P₂S₇ in the solid phase.     

Characterization and Evaluation of Methylcyclopentane and Cyclohexane Ring Opening over Ir/ZrO2–MoO3 Catalysts

Methyl bromide was synthesized by reacting methane with oxygen and hydrogen bromide over Rh/SiO₂ catalyst. The reaction started from the oxidation of HBr to form active bromine species (Br^? radicals and Br* surface species), which in turn reacted with CH₄ to form CH ₃ ^? radicals and $\hbox{CH}_{3}^{\ast}$ surface species. These CH ₃ ^? and $\hbox{CH}_{3}^{\ast}$ species reacted with the active bromine species to form CH₃Br and CH₂Br₂. The presence of HBr inhibited the deep oxidation and the steam reformation of CH₄ and therefore, guaranteed the high selectivity of CH₃Br. In the presence of HBr, CO was formed from the oxidation and steam reformation of CH₃Br, while CO₂ was formed from the oxidation and steam reformation of CO over Rh/SiO₂ at reaction temperature higher than 560 °C.     

Dependence of the electrocatalytic performance of platinized counter electrodes on the redox mediator employed in dye-sensitized solar cells

The electrocatalytic properties of platinized counter electrodes (Pt CEs) prepared by various coating methods were investigated with respect to the redox mediator, including the widely used iodide/tri-iodide (I^?/I ₃ ^? ) and the more recently introduced cobalt(II/III)tris(2,2′-bipyridine) (Co(bpy) ₃ ^2+/3+ ), for application in dye-sensitized solar cells (DSCs). The coating methods controlled Pt loading and the surface morphology of the Pt CEs. For a high-performance DSC with a fill factor >0.7, the charge-transfer resistance at the Pt CE/electrolyte interface should be <4.5 Ω cm² for both redox mediators. The I^?/I ₃ ^? -mediated DSCs were insensitive to Pt loading as low as 0.001 mg cm^?2, while the Co(bpy) ₃ ^2+/3+ -mediated DSCs required relatively large Pt loadings of > 0.005 mg cm^?2. Our results indicated that care should be taken in the preparation of Pt CEs with high transparency and low loading to obtain high-performance DSCs employing cobalt–ligand redox electrolyte.     

Synthesis and single-crystal structure of lead oxide nanoclusters in zeolite Y, |Pb 15.5 2+ (Pb4O4(Pb 16/19 2+ Pb 3/19 4+ )4)4.75|[Si117Al75O384]-FAU

A single crystal of excessively Pb²⁺-exchanged zeolite Y (|Pb _15.5 ²⁺ (Pb₄O₄(Pb _16/19 ²⁺ Pb _3/19 ⁴⁺ )₄)_4.75|[Si₁₁₇Al₇₅O₃₈₄]-FAU) was prepared by exchange of Na–Y (|Na₇₅|[Si₁₁₇Al₇₅O₃₈₄]-FAU, Si/Al = 1.56) with an aqueous stream 0.05 M Pb(C₂H₃O₂)₂ at 294 K, followed by vacuum dehydration at 1 × 10^?6 Torr and 693 K. Its structure was determined at 100 K, by X-ray diffraction techniques in the cubic space group Fd $ \overline{3} $ 3 ¯ m and was refined to the final error indices R ₁/wR ₂ = 0.0639/0.1323. About 53.5 Pbⁿ⁺ ions per unit cell occupy three different equipoints; 26 are at site I′, 19 are at site II, and the remaining 8.5 are at another site II. Three Pb⁴⁺ ions at some of the positions must have higher oxidation states due to elevated dehydration temperature; Pb(IIa) is supposed to coexist with Pb²⁺ and Pb⁴⁺ ions assuming the charge balance of the zeolite framework. A distorted Pb₄O₄ cube, alternating Pb²⁺ at Pb(I′) and O^2? at O(5), coordinates with four Pb²⁺ and/or Pb⁴⁺ ions through its oxygen atoms to give a [Pb ₄ ²⁺ O ₄ ^2? (Pb _16/19 ²⁺ Pb _3/19 ⁴⁺ )₄]^176/19+ cluster in 4.75 of eight sodalite cavities per unit cell in zeolite Y.     

Absorption of three slow-release nitrogen fertilizers by perennial ryegrass turf

The absorption of three new slow-release fertilizers (Coron, N-Sure and Nitrazine) by perennial ryegrass turf was compared to uptake of NO ₃ ^- and urea using a nutrient solution culture system. Each source of nitrogen was supplied to turf cultures at a rate equivalent to 21 kg N ha^?1 every five days during a twenty day experimental period. Nitrate and urea produced the most growth, while growth on Coron and N-Sure was reduced 30%. Growth on Nitrazine-N was further reduced to only 40% of that on NO ₃ ^- and urea. Coron and N-Sure were absorbed relatively rapidly during the first 24 hour period, with cumulative absorption over the five day period amounting to approximately 80% of the total supplied. Nitrazine-N was absorbed more slowly, with only 40% of the N absorbed after five days. Perennial ryegrass was apparently capable of metabolizing both Coron and N-Sure. The slow-release N component of Nitrazine (melamine) was inhibitory to photosynthesis, and at higher solution concentrations, was toxic to the turf.     

The novel [(dME)2(HIM)P]2Ti(IV) complex: synthesize, characterization, and its utility in ROP of d,l-lactide

The novel {2,4-bis(1,1-dimethylethyl)-6-{[(2-hydroxyethyl)imino]methyl}phenoxy}₂ titanium(IV) complex {[(dME)₂(HIM)P]₂Ti(IV)} had been synthesized and characterized by EA, XRF, IR, and NMR methods. The [(dME)₂(HIM)P]₂Ti(IV) complex was reactive and promoted ring-opening polymerization (ROP) of d,l-lactide in the presence of benzyl alcohol (BnOH). And the results showed that ROP of d,l-lactide were produced upon addition of an excess (1–8?equiv.) of external BnOH. The complex showed a living and controlled fashion (M _w/M _n?=?1.15–1.32) for ROP of d,l-lactide and could produce the poly(d,l-lactide) with average molecular weight (M _n) up to 8.87?×?10⁴?g?mol^?1. The mechanism study by ¹H NMR spectrum of poly(d,l-lactide) with terminal benzyl ester group and [(dME)₂(HIM)P]₂Ti(IV) complex revealed that the polymerization proceeded through the traditional activated monomer mechanism and the acyl-oxygen bond cleavage mode of monomer. And the ¹³C NMR spectra and TG/DSC analysis showed that poly(d,l-lactide) was essential atactic and thermal stable polymer.     

Simultaneous removal of SO2 and NO X with ammonia absorbent in a packed column

Catalytic oxidation of NO followed by simultaneous removal of SO₂ and NO _X with ammonia is a promising method for control of coal-fired flue gas pollutants. We investigated simultaneous absorption of SO₂ and NO _X in a packed column with ammonia, and found that SO₂ and NO _X could promote absorption with each other in the process of simultaneous removal SO₂ and NO _X . The removal efficiency of SO₂ and NO _X was, respectively, about 98% and 70.9% at pH 5.5, temperature 323.15 K, SO₂ concentration 1,800×10^?6, NO _X concentration 400×10^?6 and ${{m_{NO_2 } } \mathord{\left/ {\vphantom {{m_{NO_2 } } {m_{NO} }}} \right. \kern-0em} {m_{NO} }}$ in our experimental system. The experimental results also show that the formation of sulfite oxidized by reacting with dissolved NO₂ and the molar ratio of sulfite to total sulfur is more than 0.8 in the solution. Accordingly, the energy consumption for sulfite oxidation would be greatly reduced in the process of simultaneous desulfurization and denitrification with ammonia.     

Preparation, Crystal Structure and Magnetic Properties of Two 1,2-Di(4-pyridyl)ethylene-Bridged Manganese(II) Complexes

Two polymeric carboxylato-bridged manganese(II) complexes, $ {}_{\infty }^{1} $ ∞ 1 [Mn(bpe)(NBA)₂] (1) and $ {}_{\infty }^{1} $ ∞ 1 [Mn(bpe)(MBA)₂] (2) (bpe = 1,2-di(4-pyridyl)ethylene; HNBA = m-nitrobenzoic acid; HMBA = m-methyl-benzoic acid), were synthesized and characterized. Compounds 1 and 2 are isostructural. X-ray diffraction studies show that the title compounds possess a double chain structure. The chains in 1 and 2 are assembled into 2-D layers via C–H···O hydrogen bonds interactions. Furthermore, owing to the offset face-to-face π–π stacking interactions, the adjacent 2-D layers embed into each other to form a 3-D supramolecular framework. Variable-temperature (2–300 K) magnetic susceptibility measurements show the presence of weak antiferromagnetic interactions between the high-spin Mn(II) (S = 5/2) ions through a carboxylato bridge with the best fit parameters for 1 being J = ?0.13 cm^?1, zJ′ = ?0.098 cm^?1 and for 2, J = ?0.33 cm^?1, zJ′ = ?0.001 cm^?1.     

Changes in physicochemical properties and gaseous emissions of composting swine manure amended with alum and zeolite

Ammonia emissions from composted swine manure and the resulting physicochemical changes were monitored to determine the effectiveness of adding alum and zeolite during the composting process, as well as the most effective addition method. The two amendments reduced ammonia emissions 85?C92%, with the finished compost retaining three-fold more NH ₄ ⁺ -N than the unamended control. The addition of zeolite sequestered 44% of the retained NH ₄ ⁺ -N at zeolite exchange sites. The addition of amendments did not appear to significantly affect microbial activity, because the patterns of CO₂ emissions, total organic carbon (TOC) reduction, and the ratio of humic acid to TOC of amended and unamended composts were very similar. The final respiration rates and Solvita? maturity index indicated that the finished compost was well matured and aged. Alum has a high potential to reduce ammonia emissions and concomitantly enhance fertilizer N value. Zeolite further reduces ammonia emissions, and improves fertilizer quality, by serving as a slow-release N source.