Kinetics of absorption of hydrogen sulfide into aqueous Fe(III) solutions

In our recent studies, absorption of H₂S into the aqueous Fe₂(SO₄)₃ and FeCl₃ solutions with various values of ionic strength and pH was investigated in an agitated vessel with a flat interface. The experimental results for both systems revealed that the species which reacts with H₂S is FeOH²⁺. The absorption rates were explained by the theory of gas absorption with an irreversible (l,l)-th order reaction between H₂S and FeOH₂₊. The reaction rate constants were independent of the ionic strength of the solution and correlated as a function of temperature. In this paper, kinetics and mechanism of these absorption reactions are reviewed and the identity for both systems is emphasized.     

Removal of chromium (III) and cadmium (II) from aqueous solutions

Chromium and cadmium are toxic heavy metals present in wastewaters from a variety of industries. A strong cationexchange resin, Amberlite IR 120, was used for the removal of chromium and cadmium. The resin was prepared in two different cationic forms, as Na⁺ and H⁺. The optimum conditions were concentration, pH, stirring time and resin amount. The concentration range was between 2–50 mg/L, pH range between 2–10, stirring time between 5–60 min, and the amount of resin was from 50–1000 mg. Exchange capacities, moisture content and optimum conditions of this resin were determined in a batch system. The stirring speed was 2000 rpm during all of the batch experiments. The initial and final chromium and cadmium amounts were determined by atomic absorption spectrophotometry. The optimum conditions were found to be a concentration of 20 mg/L, pH of 5.5, stirring time of 20 min and 100 mg of resin. The results obtained show that the Amberlite IR 120 strong cation-exchange resin performed well for the removal and recovery of chromium and cadmium.     

Removal of Cu(II) and Fe(III) from aqueous solutions by dead sulfate reducing bacteria

The biosorption properties of dead sulfate reducing bacteria (SRB) for the removal of Cu(II) and Fe(III) from aqueous solutions was studied. The effects of the biosorbent concentration, the initial pH value and the temperature on the biosorption of Cu(II) and Fe(III) by the SRB were investigated. FTIR analysis verified that the hydroxyl, carbonyl and amine functional groups of the SRB biosorbent were involved in the biosorption process. For both Cu(II) and Fe(III), an increase in the SRB biosorbent concentration resulted in an increase in the removal percentage but a decrease in the amount of specific metal biosorption. The maximum specific metal biosorption was 93.25 mg?g^–1 at pH 4.5 for Cu(II) and 88.29 mg?g^–1 at pH 3.5 for Fe(III). The temperature did not have a significant effect on biosorption. In a binary metal system, the specific biosorption capacity for the target metal decreased when another metal ion was added. For both the single metal and binary metal systems, the biosorption of Cu(II) and Fe(III) onto a SRB biosorbent was better represented by a Langmuir model than by a Freundlich model.     

Electrochemical synthesis of Cr(II) at carbon electrodes in acidic aqueous solutions

The electrochemical synthesis of Cr(II) has been investigated on a vitreous carbon rotating disc electrode and a graphite felt electrode using cyclic voltammetry, impedance spectroscopy and chronoamperometry. The results show that in 0.1 M Cr(III) + 0.5 M sulphuric acid and in 0.1 M Cr(III) + 1 M hydrochloric acid over an electrode potential range of –0.8 to 0.8 V vs SCE, the electrochemical reaction at carbon electrodes is essentially a surface process of proton adsorption and desorption, without significant hydrogen evolution and chromium(II) formation. At electrode potentials more negative than –0.8 V vs SCE, both hydrogen evolution and chromium(II) formation occurred simultaneously. At electrode potentials –0.8 to –1.2 V vs SCE, the electrochemical reduction of Cr(III) on carbon electrodes is controlled mainly by charge transfer rather than mass transport. Measurements on vitreous carbon and graphite felt electrodes in 1 M HCl, with and without 0.1 M CrCl₃, allowed the exchange current density and Tafel slope for hydrogen evolution, and for the reduction of Cr(III) to Cr(II), to be determined. The chromium(III) reduction on vitreous carbon and graphite electrodes can be predicted by the extended high field approximation of the Butler–Volmer equation, with a term reflecting the conversion rate of Cr(III) to Cr(II).     

Preparation and characterization of photocured thiol‐ene hydrogel: Adsorption of Au(III) ions from aqueous solutions

In this study, photocured a novel thiol‐ene hydrogels based on P(Penta3MP4/PEG‐DA/HEMA) were investigated for adsorption of Au(III) ions from aqueous solutions purposes. The photopolymerization kinetics of thiol‐ene‐based formulations was investigated by real‐time infrared spectroscopy. The chemical composition and surface morphology of hydrogels were also characterized. The effect of different parameters on Au(III) adsorption efficiency was examined in detail. Better adsorption behavior was achieved for Au(III) by P(Penta3MP4/PEG‐DA/HEMA) F1 hydrogels. The maximum uptake for Au(III) was at pH 0.5. Both Langmuir and Freundlich adsorption isotherm models were applied and the reusability of thiol‐ene hydrogels investigated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Bioaccumulation and biosorption of copper(II) and chromium(III) from aqueous solutions by Pichia stipitis yeast

BACKGROUND: Bioaccumulation and biosorption by Pichia stipitis yeast has not yet been explored. This paper evaluates, for the first time, the use of both viable and nonviable P. stipitis yeast to eliminate Cu(II) and Cr(III) from aqueous solutions. The effect of Cu(II) and Cr(III) ions on the growth and bioaccumulation properties of adapted and nonadapted biomass is investigated as a function of initial metal concentration. Binding capacity experiments using nonviable biomass are also performed as a function of temperature. RESULTS: The addition of Cu(II) and Cr(III) had a significant negative effect on the growth of yeast. Nonadapted cells could tolerate Cu(II) and Cr(III) ions up to a concentration of 75 ppm. The growth rate of nonadapted and adapted cells decreased with the increase in Cu(II) and Cr(III) concentration. Adapted P. stipitis biomass was capable of removing Cu(II) and Cr(III) with a maximum specific uptake capacity of 15.85 and 9.10 mg g⁻¹, respectively, at 100 ppm initial Cu(II) and Cr(III) concentration at pH 4.5. Adsorption data on nonviable cells were found to be well modeled by the Langmuir and Temkin isotherms. The maximum loading capacity of dry biomass predicted from Langmuir isotherm for Cu(II) and Cr(III) at 20 °C were 16.89 and 19.2 mg g⁻¹, respectively, at pH 4.5. Biosorptive capacities were dependent on temperature for Cu(II) and Cr(III) solutions. CONCLUSION: Cu(II)‐ and Cr(III)‐adapted cells grow and accumulate these ions at high ratios. On the other hand, nonviable P. stipitis was found to be an effective biosorbent for Cu(II) and Cr(III) biosorption. Copyright © 2008 Society of Chemical Industry     

非均相Mn(Ⅲ)-甲苯氧化反应的动力学

研究了非均相Mn(Ⅲ）－甲苯氧化反应的动力学.了Mn(Ⅲ）（指MnSO4^ )的歧化反应的因素并结合平行反应的原理，建立了反应动力学方程模型。通过测定不同温度，酸度下，歧化反应中[MnSO4^ ]的浓度变化和[PhCH3]在Mn(Ⅲ）－甲苯氧化反应中的浓度变化，发现Mn(Ⅲ）的歧化反应在此条件下为零级反应，数据经数学处理后，求得氧化反应的速率常数，反应级数，反应活化能以及动力学微分方,同时对该反应的机理作了相应的推导。结果显示，由平行反应模型所得的动力学数据与Arrhenius's定理完全一致。     

Electrochemical synthesis of poly(5-nitroindole) on 316L-stainless steel in LiClO4-acetonitrile solution and its corrosion performance

The preparation of poly(5-nitroindole) (P5NI) coating was achieved on 316L-stainless steel (SS). Poly(5-nitroindole) was deposited via anodic oxidation of the corresponding monomer in acetonitrile (ACN) solution containing LiClO₄. The influence of P5NI coating against SS corrosion was studied in 3.5% NaCl solution by electrochemical impedance spectroscopy (EIS), anodic polarization curves and the open circuit potential–time (E_ocp–t) diagrams. The results obtained suggest that P5NI coating forms a sacrificial layer but the efficiency against corrosion is limited with increasing time.     

Separation and concentration processes of solutions of Co(II), Ni(II), Cr(III), Fe(III) and Mn(II) by extraction with toluene-dissolved rosin

The extraction and stripping of Co(II), Ni(II), Cr(III) and Fe(III) from aqueous solutions by rosin dissolved in toluene has been investigated. Results obtained show that rosin is better extractant than abietic or n-lauric acids under comparable conditions. From these results, and the data of Mn(II) solvent extraction studied previously under the same conditions, a separation and concentration process for these five cations in aqueous solutions has been designed. Saturated solutions of Fe(III), Cr(III), Mn(II) and finally Co(II) and Ni(II) have been obtained successively by extraction and stripping, by addition of ammonium hydroxide to obtain the appropriate pH value, and by modifying adequately the organic phase/aqueous phase volume ratio.     

Removal of Arsenic(III), Chromium(III) and Iron(III) Traces from Hydrofluoric Acid Solutions by Specialty Anion Exchangers

The removal of As(III), Fe(III), and Cr(III) at trace levels from HF solutions by means of specialty ion exchange resins has been investigated. These impurities are usually found in technical‐grade HF, and they need to be removed to prepare metal‐free HF for the semiconductor industry. It was assumed that Fe(III) and As(III) species in dilute HF were present in anionic form, while Cr(III) was probably in neutral form, CrF₃. First, a selection of specialty ion exchangers was performed. Then, fixed‐bed experiments were carried out to check the ability of selected resins to reach the impurity levels required in SEMI C29 for 5 wt.% HF (5 ppb of As, and 10 ppb of Cr and Fe). The effect of the flow rate and the HF concentration on the metal removal was studied with Purolite D‐3777 and Fuji PEI‐CS‐07 resins respectively. Fuji PEI‐CS‐07 showed the best performance for Fe(III) removal, even at high HF concentration (25 wt.%). A strong decrease in the Cr(III) and As(III) removal capacity with increasing concentration of HF was observed.     

Effect of potassium hydrogen phthalate (C8H5KO4) on the one-step electrodeposition of single-phase CuInS2 thin films from acidic solution

The effect of potassium hydrogen phthalate (C₈H₅KO₄) as a special additive on the one-step electrodeposition of single-phase CuInS₂ thin films from acidic solution (pH 2.5) was investigated in detail. The XRD, SEM and UV-vis-NIR characterization confirms that the addition of an adequate concentration of C₈H₅KO₄ (23 mM) to the electrolytic bath containing 12.5 mM Cu²⁺, 10 mM In³⁺, 40 mM S₂O₃²⁻ and 100 mM LiCl can contribute greatly to the controllable growth of pure chalcopyrite CuInS₂ films with uniform surfaces and an ideal band gap of approximately 1.54 eV. Complexation studies of C₈H₅KO₄ with Cu²⁺ and In³⁺ in electrolytic solutions indicated that C₈H₅KO₄ can complex Cu²⁺ more strongly than In³⁺ and move the electrode potentials of Cu²⁺ and In³⁺ near each other as determined by polarization analysis. Furthermore, the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) analysis performed in a series of solution systems revealed a three-step reaction mechanism for CuInS₂ deposition and considerable adsorption of C₈H₅O₄⁻ and Cu(C₈H₅O₄)⁺ to the cathode surface. This deposition shows that the synergetic effects of complexation and adsorption originated from the additive on the Cu²⁺ electro-reduction, thus promoting the co-deposition of copper, indium and sulfur in the form of single-phase CuInS₂.     

Development and Demonstration of Americium (III)-Europium (III) Separation Using Diglycolamic Acid

The extraction behavior of Eu(III) and Am(III) in a solution of bis(2-ethylhexyl)diglycolamic acid (HDEHDGA) in n-dodecane (n-DD) from citric acid (CA) medium was studied as a function of various parameters. The extraction increased with increase of pH, reached a maximum at pH 2 followed by decrease. The stripping behavior of Eu(III) and Am(III) from the loaded organic phase was studied by using a solution of diethylenetriaminepentaacetic acid (DTPA) and CA. The conditions needed for the efficient separation of Am(III) from Eu(III) were optimized. Based on the optimized conditions, the feasibility of separating Am(III) from Eu(III) present in CA feed solution was investigated in a 20- stage mixer-settler. Quantitative extraction of Eu(III) and Am(III) in 0.1 M HDEHDGA/n-DD was achieved in 3–4 stages, whereas the selective back extraction of Am(III) was achieved in ～20 stages upon contacting the loaded organic phase with a stripping formulation composed of DTPA-CA at pH 1.5. The results confirmed the possibility of using diglycolamic acid for the separation of trivalent actinides from the chemically similar lanthanides, which is indeed necessary for transmutation of minor actinides present in high-level liquid waste (HLLW).     

Electrochemical characterization of kinked Pt(7 5 1) surface in acidic media

Kinked Pt(7 5 1) surface was prepared and its electrochemical behaviors under different pretreatment conditions in acidic media were investigated systematically by using cyclic voltammetry. The results demonstrated that the upper limit of potential scanning and cooling atmospheres after the Pt(7 5 1) having been flame-annealed significantly influence the voltammetric behavior of Pt(7 5 1) electrode. The electric charge of hydrogen adsorption-desorption slightly increases with increasing the upper limit of potential scanning. Different cooling atmospheres give rise impacts to the surface structure of Pt(7 5 1) electrode, but hardly change the amount of hydrogen adsorption-desorption sites on the electrode. In addition, the so-called third oxidation peak appears near −0.08 V in H₂SO₄ media and −0.05 V in HClO₄ solution because of the presence of (1 1 0) terrace sites on this surface, and a plausible mechanism for the formation of this current peak is discussed. The results are of importance in understanding the electroadsorption properties of the kinked Pt(7 5 1) surface, as well as in further exploration of this kinked electrode in electrocatalysis.     

Separation of rhodium(III) and iridium(IV) chlorido complexes using polymer microspheres functionalized with quaternary diammonium groups

Merrifield resin functionalized with different quaternary diammonium groups derived from ethylenediamine (EDA), tetramethylenediamine (TMDA), hexamethylenediamine (HMDA), 1,8-diaminooctane (OMDA), 1,10-diaminodecane (DMDA) and 1,12-diaminododecane (DDMDA) were investigated for the separation of [RhCl₅(H₂O)]^2? and [IrCl₆]^2?. Selective loading of [IrCl₆]^2? in 6 M HCl medium onto the column was achieved in the presence of [RhCl₅(H₂O)]^2? by the synthesized sorbents. The iridium loading capacities were 3.80, 6.49, 13.07, 19.29, 27.09 and 4.36 mg/g for EDA, TMDA, HMDA, OMDA, DMDA and DDMDA-functionalized microspheres, respectively. The materials showed great potential for application in separating rhodium and iridium from aqueous HCl solutions.     

Highly efficient and fast adsorption of Au(III) and Pd(II) by crosslinked polyethyleneimine-glutaraldehyde

An adsorbent (PEI-GA) is prepared by crosslinking polyethyleneimine with glutaraldehyde. PEI-GA shows outstanding adsorption performance towards Au(III) and Pd(II). PEI-GA presents large adsorption capacity towards Au(III) in a wide application pH range from 1 to 9. The adsorption capacities of PEI-GA for Au(III) and Pd(II) at 25°C reach 2575 and 497 mg/g, respectively. Au(III) and Pd(II) can be adsorbed completely within 10 min for 8.3 mg/L Au(III) and 20 min for 9.7 mg/L Pd(II). The adsorption equilibrium time required for 523.9 mg/L Au(III) and for 565.6 mg/L Pd(II) is 2 and 9 h, respectively. The Sips model is the most suitable to describe the adsorption isotherms which leads to more realistic adsorption capacities for both metals. PEI-GA also exhibits high selectivity and repeatability towards Au(III) and Pd(II). The adsorption mechanism involves redox, chelation coordination, and electrostatic interactions for Au(III), and coordination and electrostatic interactions for Pd(II).     

新型荧光试剂5-(4-溴苯偶氮)-8-(8-喹啉重氮氨基)喹啉的合成及其分析应用

将具有荧光特性的8-氨基喹啉结构与具有良好特性的三氮烯结构相结合,首次合成了标题化合物。其结构经过元素分析、红外光谱、核磁共振谱证实。研究表明,在碱性介质中,该试剂在λex/λem=416 nm/512 nm处产生强荧光,并且能被Cu2+荧光增强。基于此,建立了BPAQAQ测定Cu2+的新型荧光分析法。该方法的线性范围为1.4×10-8~1.0×10-5mol/L,检测限为1.1×10-8mol/L。将其应用于大米粉和小麦粉中Cu2+的测定,结果满意。     

Extraction of Lanthanides(III) and Am(III) by Mixtures of Malonamide and Dialkylphosphoric Acid

Abstract

N,N′‐dimethyl‐N,N′‐dioctylhexylethoxymalonamide, DMDOHEMA, and di‐n‐hexylphosphoric acid, HDHP, are the extractants of reference for the French DIAMEX–SANEX process for the separation of trivalent actinide ions from the lanthanide ions. In this work, the extraction of Eu³⁺ and Am³⁺ by the two extractants, alone or in mixtures, has been investigated under a variety of experimental conditions. The two cations are extracted by HDHP as the M(DHP · HDHP)₃ complexes with an Eu/Am separation factor of ～10. With DMDOHEMA, Eu³⁺ and Am³⁺ are extracted as the M(NO₃)₃(DMDOHEMA)₂ disolvate species with an Am/Eu separation factor of ～2. The metal distribution ratios measured with a mixture of the two reagents indicated that almost all lanthanides are extracted equally well. The extraction of Eu³⁺ and Am³⁺ by HDHP‐DMDOHEMA mixtures exhibits a change of extraction mechanism and a reversal of selectivity taking place at ～1 M HNO₃ in the aqueous phase. Below this aqueous acidity, HDHP dominates the metal extraction by the mixture, whereas DMDOHEMA is the predominant extractant at higher aqueous acidities. Some measurements indicated apparent modest antagonism between the two extractants in the extraction of Eu³⁺ and synergism in the extraction of Am³⁺. These data were interpreted as resulting from the formation in the organic phase of mixed HDHP‐DMDOHEMA species containing two HDHP and five DMDOHEMA molecules.     

Mechanistic studies of ruthenium(III)-catalyzed oxidation of DL-methionine by hexacyanoferrate(III) in an alkaline medium

The kinetics and mechanism of ruthenium(III) catalyzed oxidation of dl-methionine by alkaline hexacyanoferrate(III) (HCF(III)) in an alkaline medium were studied spectrophotometrically at 30±0.1°C. The reaction was first-order-dependent each on [HCF(III)] and [ruthenium(III)] and fractional-order-dependent on [alkali]. The rate of the reaction was found to be decreased with the increase in [methionine]. The main product of oxidation was methionine sulfone nitrile (3-(methylsulfonyl)propanenitrile) and it was identified and confirmed by FT-IR and mass spectral studies. Further, no effect of added reaction product was observed. A plausible mechanism was proposed involving complexation between methionine and ruthenium(III) species, [Ru(H₂O)₅OH]²⁺. Thermodynamic parameters for the reaction, E _a and Δ S ^#, were computed using linear least squares method and are found to be 65.83±1.03 kJ/mol and?249.58±3.35 J/K mol, respectively.