The structure of aminofunctional silane coupling agents: 1. γ-Aminopropyltriethoxysilane and its analogues

Gamma-aminopropyltriethoxysilane (γ-APS) and its analogues are studied as aqueous solutions as well as solids by Fourier transform infra-red spectroscopy (FT i.r.) and laser Raman spectroscopy. Emphasis was placed on a determination of the nature of the interaction between the amine groups and the residual silanol groups in partially cured solids. Comparison with γ-aminopropyltrisilanolate and partially cured solids obtained from γ-aminopropylmethyldiethoxysilane and γ-aminopropyldimethylethoxysilane lead us to conclude that the residual silanol groups are strongly hydrogen bonded to the amine groups as SiOH … NH₂ rather than SiO^? … ⁺NH₃. Hydrolysis of γ-APS at concentrations ranging 2–80% by weight showed that the solutions below 40% by weight have a few unhydrolysed alkoxy groups. The amine groups are mutually hydrogen bonded in unhydrolysed silane. However, in an aqueous solution and highly cured solids, the amine groups are either free or are interacting predominantly with water molecules.     

Solvent Extraction of Au(III) by the Chloride Salt of the Amine Alamine 304 and Its Application to a Solid Supported Liquid Membrane System

Abstract

The extraction of Au(III) by the chloride salt of the amine Alamine 304 (R₃NH⁺Cl^?) in xylene from hydrochloric acid solutions has been investigated. The analysis of metal distribution data by numerical calculations suggested the formation of the species R₃NH⁺AuCl₄ ^? in the organic phase with formation constant log K _ext = 5.44. The results obtained on Au(III) distribution have been implemented in a solid‐supported liquid membrane system, where in NaSCN solutions were found to be the most effective to strip the metal from the organic solution. Influence of membrane composition, metal concentration on gold transport, and the selectivity of the system have also been studied.     

The absorption rate of CO2/SO2/NO2 into a blended aqueous AMP/ammonia solution

The Inter-governmental Panel on Climate Change (IPCC) reported that human activities result in the production of greenhouse gases (CO₂, CH₄, N₂O and CFCs), which significantly contribute to global warming, one of the most serious environmental problems. Under these circumstances, most nations have shown a willingness to suffer economic burdens by signing the Kyoto Protocol, which took effect from February 2005. Therefore, an innovative technology for the simultaneously removal carbon dioxide (CO₂) and nitrogen dioxide (NO₂), which are discharged in great quantities from fossil fuel-fired power plants and incineration facilities, must be developed to reduce these economical burdens. In this study, a blend of AMP and NH₃ was used to achieve high absorption rates for CO₂, as suggested in several publications. The absorption rates of CO₂, SO₂ and NO₂ into aqueous AMP and blended AMP+NH₃ solutions were measured using a stirred-cell reactor at 293, 303 and 313 K. The reaction rate constants were determined from the measured absorption rates. The effect of adding NH₃ to enhance the absorption characteristics of AMP was also studied. The performance of the reactions was evaluated under various operating conditions. From the results, the reactions with SO₂ and NO₂ into aqueous AMP and AMP+NH₃ solutions were classified as instantaneous reactions. The absorption rates increased with increasing reaction temperature and NH₃ concentration. The reaction rates of 1, 3 and 5 wt% NH₃ blended with 30 wt% AMP solution with respect to CO₂/SO₂/NO₂ at 313 K were 6.05～8.49×10^?6, 7.16–10.41×10^?6 and 8.02～12.0×10^?6 kmol m^?2s^?1, respectively. These values were approximately 32.3–38.7% higher than with aqueous AMP solution alone. The rate of the simultaneous absorption of CO₂/SO₂/NO₂ into aqueous AMP+NH₃ solution was 3.83–4.87×10^?6 kmol m^?2s^?1 at 15 kPa, which was an increase of 15.0–16.9% compared to 30 wt% AMP solution alone. This may have been caused by the NH₃ solution acting as an alternative for CO₂/SO₂/NO₂ controls from flue gas due to its high absorption capacity and fast absorption rate.     

Effect of Processing Variables on the Solution Characteristics of γ-Glycidoxypropyltrimethoxysilane (γ-GPS)

The effects of the hydrolysis and condensation processes on the molecular structure of γ-glycidoxypropyltrimethoxysilane (γ-GPS) in aqueous solutions were investigated using Fourier-transform nuclear magnetic resonance (FT-NMR) spectroscopy and FT-Raman spectroscopy. Hydrolysis was characterized by monitoring the production of methanol and the decrease in concentration of SiOCH₃ groups in 1% solutions of deuterium oxide using proton NMR. The production of methanol and loss of methoxy groups in 25% solutions of γ-GPS in water was characterized using Raman spectroscopy. Hydrolysis was found to be a very rapid process, whose rate could be increased or decreased by altering the pH of the solution. NMR spectroscopy showed that hydrolysis was complete in a 1% γ-GPS solution in deuterium oxide after 34 minutes. Raman spectroscopy also showed hydrolysis to be rapid and complete in a 25% solution of γ-GPS in water after 1 hour. Condensation, on the other hand, took a relatively long time to occur. In the NMR spectra, condensation was observed by the broadening of peaks due to the protons on the carbon atom adjacent to the silicon atom. In the Raman spectra, condensation was characterized by the disappearance of the SiOH band near 725 cm^?1 and the development of an SiOSi band near 600 cm^?1. In addition to the proton NMR, Si-29 NMR was used to characterize the silane in 10% solutions of γ-GPS in water. The Si-29 NMR showed oligomer growth with respect to time. The oligomer growth was correlated with mechanical test results.     

Aerosol Acidity Measurement Using Colorimetry Coupled With a Reflectance UV-Visible Spectrometer

In this study, aerosol acidity was measured using colorimetry integrated with a Reflectance UV-Visible spectrometer (C-RUV). An inorganic aerosol comprising NH₄ ⁺?H⁺?SO₄ ^2??H₂O was generated using an atomizer and introduced into a 2-m³ indoor Teflon film chamber. The produced aerosol was collected on the Teflon-coated glass fiber filter dyed with metanil yellow (MY) as an indicator for measuring proton concentrations in aerosol. A calibration curve for measuring aerosol acidity using the C-RUV technique was obtained through the relationship between the absorbance of the UV-Visible spectrum of the filter sample vs. theoretically calculated proton concentrations using the E-AIM Model II. To develop the C-RUV method under various humidities, the aerosol filter sample was mounted inside a small optical flow chamber controlled for humidity in situ. The humidity effect on the equilibrium thermodynamics of the indicator was theoretically described by inclusion of excess acidity (X) into the calibration curve. The calibration curve obtained from relatively highly acidic aerosols (e.g., H₂SO₄, NH₄H₃(SO₄)₂, and (NH₄)₇H₁₃(SO₄)₁₀) was extrapolated to estimate proton concentrations for weakly acidic aerosols (e.g., NH₄HSO₄ and (NH₄)₃H(SO₄)₂), which is more relevant to the ambient aerosol acidity but has been poorly predicted with typical inorganic thermodynamic models due to the limited experimental data. The C-RUV technique of this study permits one to estimate aerosol acidity for a variety of compositions of the NH₄ ⁺?H⁺?SO₄ ^2??H₂O system including both ammonia-poor and ammonia-rich sulfate aerosols.

Copyright 2012 American Association for Aerosol Research     

Raman spectroscopic studies of the polyacrylonitrile-zinc complexes in aqueous solutions of zinc chloride and bromide

Raman spectroscopic studies of the dissolution of polyacrylonitrile (PAN) in aqueous zinc halides are reported. The dissociation constants of aqueous PAN-zinc chloride and PAN-zinc bromide containing 60-75% wt/wt and 65-80% wt/wt zinc in aqueous polyacrylonitrile solutions, respectively, have been measured by Raman spectroscopy. Intensity measurements allowed for a quantitative measurement of the amount of free and complexed CN groups to be made, utilising the 2259 and 2290cm^?1 v(CN) stretching Raman bands. The degree of complexation was found to be small in many of the solutions. The effect of the addition of salt on the structure of the v(OH) band at 3000-3800 cm^?1 was studied for the aqueous zinc salts and an aqueous sodium thiocyanate solution. The low wavenumber regions of the Raman spectra, Δv = 100-350cm^?1, for both zinc chloride and zinc bromide solutions of PAN have also been studied.     

SOLVENT EXTRACTION OF PALLADIUM(II) WITH A SCHIFF BASE AND SEPARATION OF PALLADIUM FROM Pd(II)-Pt(VI) MIXTURE

ABSTRACT

A new Schiff base extractant, N,N'-bis[l-phenyl-3-methyl-5-hydroxy-pyrazole-4-benzylidenyl]-l,3-propylene diamine (H₂A) was synthesized and characterized. The extraction mechanism of palladium(II) from HNO₃ or HClO₄ medium with H₂A in chloroform or toluene was investigated. The influences of the Schiff base concentration in the organic phase, the concentration of palladium, the pH and anions (Cl^?, S0₄ ^?, NO₃ ^?, ClO₄ ^?) in the aqueous phase and the temperature on the distribution ratio for palladium (II) have been examined. The extracted complex has been confirmed by chemical analysis, thermoanalyses and IR spectroscopy. It was found that palladium is extracted according to the following extraction reaction:

The extraction equilibrium constants of palladium(II) were 8·4 and 21·3 in chloroform and toluene diluents, respectively. The values for the enthalpy and standard free energy of extraction were also obtained. The separation of Pd(II) from the mixed solution of Pd(II)-Pt(IV) was achieved by adjusting the pH.     

Treatment of the refinery wastewater in a gas–liquid–solid three‐phase flow airlift loop bioreactor

Aerobic treatment of refinery wastewater was carried out in a 200 dm³ gas–liquid–solid three‐phase flow airlift loop bioreactor, in which a biological membrane replaced the activated sludge. The influences of temperature, pH, gas–liquid ratio and hydraulic residence time on the reductions in chemical oxygen demand (COD) and NH₄‐N were investigated and discussed. The optimum operation conditions were obtained as temperature of 25–35 °C, pH value of 7.0–8.0, gas–liquid ratio of 50 and hydraulic residence time of 4 h. The radial and axial positions had little influence on the local profiles of COD and NH₄‐N. Under the optimum operating conditions, the effluent COD and NH₄‐N were less than 100 mg dm^?3 and 15 mg dm^?3 respectively for more than 40 days, satisfying the national primary discharge standard of China (GB 8978‐1996). Copyright © 2005 Society of Chemical Industry     

Mass Transfer Studies in Stirred AirLift Reactor

In the present work, water and three phase compositions of Solka-Floc, a cellulose fiber for simulating the biomass in bacteria, yeast, and fungal fermentation were studied in a 1.4?m³ stirred airlift reactor. The fractional dispersed phase holdup and the overall volumetric mass transfer coefficients were measured. The dispersed phase riser gas holdup and overall volumetric mass transfer coefficients both increased with increasing riser superficial dispersed phase velocity (0.02–0.1?ms^?1) and agitator speed in the range of 0–5?rs^?1. An increase in the Solka-Floc concentration (1–3% w/v) was found to reduce ?_GR and K _L a _L . Empirical correlations have been developed for fractional dispersed phase gas holdup and overall volumetric mass transfer coefficients.     

Interfacial synthesis of polypyrrole/graphene composites and investigation of their optical,electrical and electrochemical properties

We report the development of a novel route for the synthesis of polypyrrole/graphene (PPy/GR) composites by liquid ? liquid interfacial polymerization, where GR and the initiator were dispersed in the aqueous phase and the monomer was dissolved in the organic phase. The synthesized samples were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, ultraviolet–visible spectroscopy, Raman spectroscopy, X‐ray diffraction, thermogravimetric analysis, electrochemical and electrical conductivity measurements. Structural analysis reveals a uniform dispersion of GR sheets in the PPy matrix. The composites showed noticeable improvement in thermal stability and electrical conductivity (8.45 S cm^?1) and excellent electrochemical reversibility in comparison with pure PPy. A specific capacitance of 260 F g^?1 at a current density of 100 mA g^?1 was achieved for the composite during the charge–discharge process. © 2013 Society of Chemical Industry     

A diamino based resin modified silica composite for the selective recovery of tungsten from wastewater

A new adsorbent was developed by synthesizing 1,8‐diaminonaphthalene formaldehyde resin (DANFR) and coating it over the surface of silica gels. The silica composite was then treated with HCl for the activation of binding sites (?NH₃⁺Cl^?) on its surface. The structure of DANFR and its coating over the silanols were thoroughly characterized. Further, the adsorbent was applied to remove tungsten (W) from printed circuit board recycling unit wastewater that contained various co‐metal ions such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Pb²⁺, NH₄⁺, Zn²⁺, Cu²⁺ and Mn²⁺. The selective removal was achieved due to the anion exchange mechanism of Cl^? with W(VI) while other cations get repelled from the surface (?NH₃⁺) of the DANFR‐silica composite. X‐ray photoelectron spectroscopy studies, Raman spectra and overlay chromatograms of ion chromatography demonstrated selective separation of WO₄^2? species from the wastewater. A removal capacity of 55.32 mg g^?1 for W(VI) was achieved from the wastewater within 45 min of reaction (pH ca 6.0). Simultaneous treatment with neat aqueous solution of W brings out 63.27 mg g^?1 of W(VI) removal. Finally, recovery of WO₄^2? ions and regeneration of the adsorbent were carried out by using alkaline solution which demonstrated successful desorption, as investigated by using ion chromatography. © 2016 Society of Chemical Industry     

Facile mechano-chemical synthesis and enhanced photocatalytic performance of Cu2ZnSnS4 nanopowder

In the present study, Cu₂ZnSnS₄ (CZTS) powder was synthesized by the mechano-chemical method from its elemental constituents. X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and diffusion reflectance spectroscopy (DRS) were used for characterization of structural, morphological and optical properties. XRD result confirmed that a highly crystalline CZTS phase corresponding to the kesterite structure was formed after 50 h ball milling. Raman analysis confirmed the existence of single phase CZTS without any other phases. FESEM and TEM images reveal the irregular CZTS nanoparticles with an average size of 90 nm. The elemental mapping of the CZTS nanopowder showed the uniform distribution in agreement with the stoichiometry. DRS result showed a band gap value of 1.53 eV. XPS result revealed the oxidation states as Cu⁺, Zn²⁺, Sn⁴⁺ and S²⁻. The photocatalytic activity of CZTS has been investigated through photodegradation of methylene blue (MB) and methyl orange (MO) dyes solution with different concentrations under visible light irradiation. Although the CZTS decomposed MO only 81% until 210 min, the MB solution was completely photodegraded after 100 min. A kinetic study by Langmuir-Hinshelwood (L-H) model indicated about 3.7 times faster degradation of MB than MO and also higher adsorption capacity for MB by CZTS. Furthermore, the prepared CZTS was reusable and can be repeatedly used for the removal of dyes from aqueous solutions.     

Extraction and recovery of gold from KAu(CN)2 using cetyltrimethylammonium bromide microemulsions

Extraction and stripping of KAu(CN)₂ from alkaline solution by a w/o microemulsion formed with cetyltrimethylammonium bromide (CTAB) using ¹⁹⁸Au(I) tracer has been investigated. Various parameters, such as the Au(I) concentration in aqueous phase, concentrations of halide ions, NH₄SCN and thiodiethylene glycol in stripping solution as well as the relationship between water and Au(I) concentration in the organic phase in the extraction and stripping of Au(I) were studied. The results show that almost all of the Au(I) in the aqueous phase was extracted into the organic phase. The water content decreased significantly with an increase in Au(I) concentration in the organic phase, contrary to the results of a system with tributyl phosphate (TBP) as cosolvent. Almost all of the extracted Au(I) (～98%) can be recovered with pure thiodiethylene glycol as the stripping agent, and ～93% of the Au(I) is stripped with high concentrations of NH₄SCN(>3.0 mol dm^?3) or KI (>2.0 mol dm^?3). © 2001 Society of Chemical Industry     

Characterization of extracted complexes in liquid–liquid extraction of rhodium with Kelex 100 in the presence of SnCl2

Mixed Rh? Sn complexes found in aqueous and organic solutions involved in the liquid–liquid extraction of Rh(III) from chloride solutions, also containing SnCl₂, with 7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline (Kelex 100) were characterized through ¹¹⁹Sn NMR and Raman spectroscopy. At Sn: Rh molar ratios of 3:1 and 12:1, it was found that [Rh^IIICl₃(SnCl₃)₃]^3? and [Rh^I(SnCl₃)₅]^4?, respectively, are the dominant complexes in both the aqueous and organic solutions. These complexes can be quantitatively extracted from the aqueous solutions in less than 1 min contact time via ion-pair formation with the protonated 7-substituted 8-hydroxyquinoline reagent such that for both Sn:Rh ratios, the same Rh? Sn complex is found in the aqueous feed and in the fully loaded organic. In addition, it was found that [Rh^I(SnCl₃)₅]^4? is preferentially extracted over excess free Sn(II). Preliminary characterization of the complex stripped from the 12:1 loaded organic using 1·7 M H₂SO₄ shows an Rh? Sn complex having a ratio of 5:1 Sn:Rh.     

Influence of pH on U(VI) Adsorption using a Thermally-Treated Mg-Al Hydrotalcite and a Natural Zeolite in a Batch System

The capacity of a calcined hydrotalcite and a natural zeolite to remove U(VI) chemical species from both acidic and basic aqueous systems has been investigated. The U(VI) uptake by the calcined hydrotalcite and the natural zeolite was determined to be from 5 to 200 µmolmL^?1 and from 2 to 10 µmolmL^?1, respectively. Uranium was measured using UV-Vis spectroscopy in the remaining solutions. The U(VI) adsorption of both materials was higher in the acidic aqueous system. Independent of the pH of the aqueous media, the [UO₂(CO₃)₃]^4? species play an important role in the regeneration of the original crystalline structure of the HT.     

Adsorption of γ-aminopropyltriethoxysilane onto bulk iron from aqueous solutions

The adsorption of γ-aminopropyltriethoxysilane (γ-APS) onto mechanically polished iron coupons from 1% aqueous solutions has been investigated using reflection–absorption infrared spectroscopy. Thick films were formed on the coupons during 1-hr exposures to the γ-APS solutions. The outermost portion of these films consisted of highly hydrolyzed polysiloxanes that were weakly bound and easily desorbed by cold water. This fraction of the films was characterized by an infrared band near 1575 cm^?1 that was tentatively assigned to the NH₂ deformation of acceptor amine groups in strong hydrogen bonds or to coordination of the amino nitrogen atoms to silicon atoms. Removal of the weakly bound outermost portion of the films with water revealed an incompletely hydrolyzed, strongly bound film approximately 60 Å in thickness characterized by a band near 1510 cm^?1 that was assigned to NH groups. Formation of NH₃⁺ groups indicated that γ-APS may have been adsorbed initially as cyclic, internal zwitterions.     

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 gas carrier on morphological and optical properties of nanostructured In2O3 grown by solid-vapour process

Nanostructured indium oxide (In₂O₃) thin film was prepared by solid-vapour deposition method under NH₃ and Ar atmosphere. The influence of gas nature on the growth of In₂O₃ thin film was investigated in terms of structure, morphology and optical properties. X-ray diffraction, Raman spectroscopy and photoluminescence analyses indicated the formation of pure In₂O₃ phase with strong preferred orientation along c-axis, from cubic- to needles-like morphologies. The as-fabricated nanostructured In₂O₃ thin films with tailored morphology, enhanced crystallinity and optical quality can be used for gas sensing, solar cells and other potential applications. In addition, the potential use of NH₃ as carrier gas for an efficient control of morphology/size and optical properties can be proposed for the fabrication of other nanostructured oxides.     

EFFECT OF ANIONS ON THERMODYNAMICS OF EXTRACTION OF Am(III) AND Eu(III) WITH OCTYL(PHENYL)-N,N-DIISOBUTYL-CARBAMOYLMETHYLPHOSPHINE OXIDE

The extraction of Am(III) and Eu(III) by octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in xylene from aqueous media containing 1.0 M NH₄NO₃, NH₄SCN, NH₄ClO₄ or a mixture of 0.3 M NH₄NO₃ + 0.7 M NH₄ClO₄ at pH 2.70 and at the temperatures of 15, 25, 35 and 45±0.1 °C has been studied. At all the temperatures, the species extracted were ML₃ · 3CMPO (M = Am(III) or Eu(III), L = NO₃ ^?, SCN^? or ClO₄ ^?) and M(NO₃)(ClO₄)₂ · 3CMPO. The thermodynamic parameters of the extraction reactions have been evaluated using the temperature coefficient method. The ?ΔG values follow the order SCN^? > NO₃ ^? + ClO₄ ^? > NO₃ ^? ≈ ClO₄ ^?, whereas the ?ΔH values an order NO₃ ^? + ClO₄ ^? > SCN^? > NO₃ ^? ≈ ClO₄ ^?. The effect of these anions on the thermodynamic parameters have been discussed employing compensation effects and also on the basis of the energy associated with the transfer of these anions from aqueous to the extractant phase.     

Development and application of a simultaneous measurement method for gaseous ammonia and particulate ammonium in ambient air

Ammonia gas is one of the precursors contributing to the formation of secondary particulate ammonium via reactions with atmospheric acids, such as sulfuric and/or nitric acids, which are present in ambient air. In this study, a new instrument that is suitable for measuring ammonia gas and fine particulate ammonium (PM_2.5 NH₄⁺) concentrations simultaneously under ambient conditions was developed. A wetted frit sampler was connected in the back of a counter-current flow tube (CCFT) sampler, and the NH₃ gas and PM_2.5 NH₄⁺ samples were collected by CCFT and wetted frit samplers, respectively. An air sample was drawn through the samplers at a flow rate of 1.0 dm³ min^?1 and an absorption water flow rate of 120 mm³ min^?1. Then, the ammonium that formed in the absorption solution was detected by the indophenol method using a continuous flow analysis system. The estimated detection limits were 43 and 49 ng m^?3 for ammonia gas and PM_2.5 NH₄⁺, respectively. Notably, the ammonia gas was collected on the CCFT sampler with a collection efficiency of 98.5%, but most of the PM_2.5 NH₄⁺ passed through it and was captured on the wetted frit sampler with a collection efficiency of approximately 100%. The present method was applied to measure NH₃ gas and PM_2.5 NH₄⁺ at two urban sites: Osaka, Japan and Ho Chi Minh City, Vietnam. It was found that the simultaneous measurement method performed very well and that the measured concentrations were comparable with those obtained with the annular denuder method.

Copyright © 2016 American Association for Aerosol Research