Dispersed platinum and tin polyaniline film electrodes for the anodes of the direct methanol fuel cell

To develop better and cheaper electrocatalysts for the oxidation of methanol in direct methanol fuel cells, several combinations of a conductive polymer polyaniline (PANI) and dispersed metal particles such as Pt and Sn were examined. The anodic current for the methanol oxidation (i _MeOH) showing the electrocatalytic activity of Pt particles was remarkably enhanced when the particles were dispersed on PANI films that should provide higher surface areas for the dispersed particles. The activity strongly depended on the morphology and the electric conductivity of the PANI films electropolymerized in five different acid solutions: H₂SO₄, HNO₃, HClO₄, HBF₄, and HCl. The highest activity was achieved using the dispersed Pt particle on PANI film electropolymerized from H₂SO₄ polymerizing solution. In order to reduce the dispersed amount of the expensive Pt particles, other metal particles were pre-dispersed on the PANI film prepared from the H₂SO₄ polymerizing solution, and then Pt particles were dispersed on the film. Among the pre-dispersed metal particles attempted here (Sn, Cu, Cr, Ni, In, Co, Sb, Bi, Pb, and Mn), the highest activity was obtained with Sn particles. When the ratio of dispersed Pt to Sn particles ranges from 32:68 to 100:0, i _MeOH is higher than that measured with the dispersed Pt particle on PANI films without the Sn particles. This means that the dispersed amount of the Pt particles could be reduced by utilizing dispersed Sn particles.     

The effect of HCl on the polymerization of aniline with ferric chloride

The chemical oxidation of aniline with ferric chloride, FeCl₃ · 6H₂O in the HCl aqueous solutions to form polyaniline (PANI) powder and films has been investigated. The effect of acid concentration on the deposition of PANI film in situ was studied. The presence of an acid affects both the yield of the polymer and the growth rate of the film. This effect was corroborated by the UV-visible absorption studies of the films deposited on glass supports during the polymerization. The influence of the acid on the yield of the PANI powder formed in the bulk solution was also examined. We have found that the yield of the polymer formed either on the surface or in the bulk solution decreased with the increasing concentration of HCl. The effect of HCl concentration on the in situ UV-visible absorption at the early stages of aniline polymerization is also discussed. The text was submitted by the authors in English.     

Cyclic potential sweep electropolymerization of aniline: The role of anions in the polymerization mechanism

The cyclic potential sweep (CPS) method was applied to aniline electropolymerization in several strong acids (H₂SO₄, HNO₃, HCl, HBF₄, HClO₄ and CF₃COOH). It is mainly the type of anion that determines the morphology of polyaniline (PANI) deposits, promoting either a compact (BF⁻₄, ClO₄⁻ and CF₃COO⁻, class 1 anions) or an open structure (SO₄²⁻, NO₃⁻ and Cl⁻, class 2 anions), as suggested by the linear (class 1) or quadratic (class 2) dependence of deposition charges on number of cycles, scan rate and concentration of anilinium and anion, as well as by SEM analysis. From the potential dependence of deposition currents, PANI growth onto PANI is suggested to occur via adsorption of anilinium-anion ionic couples onto fully oxidized (pernigraniline) sites of PANI.     

胆酸盐在酸性介质中自聚集作用的共振瑞利散射光谱及其分析应用研究

研究了牛磺胆酸钠、甘牛胆酸钠、胆酸钠和脱氧胆酸钠等四种胆酸盐在酸性介质中的聚集作用对共振瑞利散射光谱的影响及其分析应用. 结果表明: 在一定浓度的HCl, H₂SO₄或HNO₃溶液中, 四种胆酸盐均能自聚集形成粒径增大的聚集体. 该聚集体能导致溶液RRS显著增强, 并产生了新的RRS光谱. 不同胆酸盐在同种介质中的反应产物具有相似的光谱特征, 最大RRS波长分别位于349 (HNO₃介质), 359 (H₂SO₄介质)和369 nm (HCl介质). 在一定范围内, 胆酸盐的浓度与散射强度(ΔI_RRS)成正比. 对于不同的体系其检出限在12.0～21.8 ng/mL之间. 方法灵敏度高, 选择性较好, 而且十分简便快速. 可用于市售蛇胆川贝液和血清样品中胆酸盐的测定.     

Study of Polymerization of Ammonium Salts of N,N-Dimethylaminoethyl Methacrylate by Differential Scanning Calorimetry

The kinetics of thermal polymerization of ammonium salts of N,N-dimethylaminoethyl methacrylate and mineral acids (HCl, HNO₃, H₂SO₄, and H₃PO₄) were studied by dynamic differential scanning calorimetry. The apparent rate constants, reaction orders, and thermal effect of polymerization of the salts were determined.     

Separation of thorium by anion-exchange chromatography in malic acid media

Summary Systematic studies on the anion-exchange behaviour of thorium in malic acid solution on Amberlite IRA-401 have been carried out. Acids such as HNO₃, HCl, H₂SO₄, HClO₄ and salts such as NH₄Cl, (NH₄)₂SO₄, NaClO₄, NaCl and NaNO₃ have been tested as eluants for thorium, their efficiency being evaluated in terms of their distribution coefficients. HNO₃ is the best eluent for thorium. Methods have been developed for the separation of thorium from several elements in malic acid media using selective adsorption or selective elution. The proposed method is applied to the analysis of thorium in monazite where HClO₄ is a better eluant than HNO₃. The method is simple and the accuracy about ±3%.     

Flocculation of Butadiene-Styrene Latex with Polymeric Ammonium Salts of N,N-Dimethylaminoethyl Methacrylate and Mineral Acids

The flocculation performance of cationic polyelectrolytes (polymeric ammonium salts of N,N-dimethylaminoethyl methacrylate) and mineral acids (HCl, HNO₃, H₂SO₄, H₃PO₄) in recovery of rubber from SKS-30 ARK butadiene-styrene latex was studied.     

Studies on the extraction behaviour of zirconium from mixed aqueous media with TBP

A systematic study is presented on the extraction of Zr(IV) by tri-n-butylphosphate from H₂SO₄, HNO₃, HCl and HBr solutions as well from binary mixtures of H₂SO₄ and halogen acids. It has been found that Zr(IV) extraction is appreciably increased by addition of halogen acid to sulphuric acid solutions. On the other hand, the presence of water-miscible alcohols and acetone was found to enhance Zr(IV) extraction from HCl and HNO₃ solutions. An investigation of extracted Zr complexes from pure acids and mixed aqueous media enabled an explanation of the observed enhancements. In the light of the obtained results, an extraction mechanism is suggested.     

The effect of supporting electrolyte on the electrochemical synthesis,morphology, and conductivity of polyaniline

Electrochemical synthesis of polyaniline (PANI) was carried out under cyclovoltammetric conditions using H₂SO₄, HCl, HNO₃, and HClO₄ as supporting electrolytes. The observed different rate of PANI deposit growth depending on the acid in the solution has been explained on the grounds of a different degree of specific adsorption for particular anion. It has been found that morphology of the deposit depends greatly upon the anion present in the solution. Thus, PANI synthesized from the solution of oxyacids results in a dense sponge-like structure while PANI from the hydrochloric acid solution results in a spaghetti-like structure. The structure of the deposit influences the conductivity, being higher for a dense deposit from oxyacid solutions and three orders of magnitude lower in case of a deposit from hydrochloric acid solution. © 1994 John Wiley & Sons, Inc.     

Determination of inorganic acids by ion chromatography with n-tetradecylphosphocholine (zwitterionic surfactant) as the stationary phase and pure water as the mobile phase

A new ion chromatographic (IC) system, in which n-tetradecylphosphocholine (TDPC, a phosphobetaine type of zwitterionic surfactant) was used as the stationary phase, pure water as the mobile phase, and conductivity as the method of detection, has been developed for the determination of inorganic acids. Five model acids, HCl, HNO₃, HClO₄, H₂SO₄, and H₃PO₄, were separated to baseline and eluted in the order H₃PO₄ > HCl > HNO₃ > H₂SO₄ > HClO₄. When peak areas were plotted against the concentrations of the acids in samples, linear calibration curves were obtained. Ultimate determination limits were approximately 1 mmol L^–1, but the discrimination of the method between solutions of different concentration was better than 10 μmol L^–1 for those model analytes. Salts of divalent cations could also be separated, but they were eluted faster than the acids. No separation was observed for the salts of monovalent cations. This newly proposed approach is applicable to the simultaneous determination of the inorganic acids (produced by reactions of NO_x, SO_x, and HCl with water) in aerosols.     

Determination of plutonium in environmental samples by controlled valence in aniion exchange

The title method was successfully used for collecting^239,249Pu from 200 litres of seawater by coprecipitation with 16 g FeSO₄·7H₂O under redcing conditions witout filtering. The plutonium is leached by concentrate HNO₃+HCl from the coprecipitate and the solid particles. The precipitate is heated at 400°C and digested in aqua regia. Na₂SO₃ and NaNO₂ have been applied to obtain the Pu⁴⁺ valence state in 0.5–1N HNO₃ for different samples. Plutonium and thorium are coadsorbed on anionic resin from 8N HNO₃. The column is eluted with 8N HNO₃ containing fresh NaNO₂ to keep the Pu⁴⁺ state for uranium decontaination. The system of the column is changed from 8N HNO₃ to concentrated HCl with 50 ml concentrated HCl containing a few milligrams of NaNO₂. Furtheer decontaimination of torium was achieved by elution with concentrated HCl instead of 9N HCl. The plutonium is successfully stripped by H₂O, NaOH, 2N HNO₃ and 0.5N HNO₃ containign 0.01M NaNO₃. The chemica yield of plutonium for a 2001 seawate sample is 60–80%. The resolution of the electroplated thin source is very good.     

Accurate and precise reference method for the determination of chromium in high-alloy steel

Methods for determining chromium in high-alloy steels based on potentiometric titration after oxidation of chromium(III) to chromium(VI) with peroxodisulphate were studied using different dissolution procedures, viz., dissolution in HClHNO₃ and fuming with H₂SO₄H₃PO₄, dissolution in HClHNO₃ and fuming with HClO₄, dissolution in HClHNO₃HF in a microwave oven, fusion in sodium peroxide in a zirconium crucible and dissolution in dilute H₂SO₄ and oxidation with H₂O₂. A back-titration was used with dichromate after addition of solid ammonium iron (II) sulphate.The dissolution procedures were tested on 24 certified reference materials (0.01–3.3% C, 10–325% Cr). All procedures except the second gave good results for samples with ? 0.8% C. For samples with ? 0.8% C, the third and fourth procedures gave significantly higher values and better precisions, and gave the best results for all samples. The relative standard deviations were, with few exceptions, below 0.2%.     

Critical comparison of wet and dry digestion procedures for trace metal analysis of meat and fish tissues

The efficiency of four methods of digestion was evaluated for trace metal analysis of pork meat and carp fish tissues. Two methods of dry and two methods of wet ashing were compared in terms of calculated variances. Mixtures of HCl+HNO₃ were applied for wet ashing of the samples at 100 °C, while dry ashing with or without H₂SO₄ at 450 °C were the alternative methods. The digests were subsequently analysed for Pb, Cd, Cu and Zn by graphite furnace atomic absorption spectrometry. Analysis of variance and Student's t-test were performed separately for meat and fish analytical results. Wet digestion with a (1+1) mixture of HCl+HNO₃ has given better recovery and repeatability for almost all metals than a (9+1) mixture of HCl+HNO₃. Also between the dry ashing methods, the use of H₂SO₄ has given better results than ashing of the tissues without H₂SO₄.     

Extraction of some elements of the groups IV b and VI b with 1-phenyl-3-methyl-4-caproyl-pyrazolone-5 (PMCP) from aqueous mineral acid solutions

Solvent extraction of Cr(VI), Mo(VI), W(VI) and Hf(IV) with 1-phenyl-3-methyl-4-caproyl-pyrazolone-5 (PMCP) in methyl isobutylketone (MIBK), xylene and chloroform (CHCl₃) from mineral acid solutions was studied. Chromium(VI) is not extracted from any of the acids studied (HCl, H₂SO₄ and HClO₄). Molybdenum(VI) is quantitatively extracted by the reagent in xylene and CHCl₃ from HClO₄ and HNO₃ solutions. It is also extracted quantitatively by the reagent in MIBK from HCl, HNO₃ and H₂SO₄ solutions but the participation of the diluent as extractant is considerable. Tungsten(VI) is quantitatively extracted in xylene from 9M HClO₄ solution. MIBK used as diluent also affects its extraction with PMCP. Hafnium(IV) is not extracted from H₂SO₄ solutions while it extracts more than 99% at 3M HNO₃ and above. The extracted species likely are: MoO₂(PMCP)₂, WO₂(PMCP)₂ and Hf(PMCP)₄, respectively.     

Electrochemical polymerization of polyaniline doped with Zn2+ as the electrode material for electrochemical supercapacitors

Polyaniline doped with Zn²⁺ (PANI/Zn²⁺) films was synthesized by cyclic voltammetric method on stainless steel mesh substrates in 0.2 mol L^?1 aniline and 0.5 mol L^?1 sulfuric acid electrolyte with various concentrations of zinc sulfate (ZnSO₄·7H₂O). The structure and morphology of PANI and PANI/Zn²⁺ films were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques, respectively. The electrochemical properties of PANI and PANI/Zn²⁺ films were investigated by cyclic voltammetry, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy in 0.5 mol L^?1 H₂SO₄ electrolyte in a three-electrode system. The results show that the surface morphology of PANI/Zn²⁺ is more rough than that of pure PANI. The specific capacitance of the PANI/Zn²⁺ film displays a larger specific capacitance of 738 F g^?1, lower resistance, and better stability as compared with the pure PANI film. Thus, good capacitive performance demonstrates its potential superiority for supercapacitors.     

Extraction of mercury from aqueous iodide solutions by trilaurylamine N-oxide and its subsequent determination by atomic absorption spectrometry

A solvent extraction technique using 0.01M solution of trilaurylamine N-oxide in benzene as extractant has been used to concentrate mercury efficiently from water solutions with or without the presence of 0.02M KI in weakly acidic media. In addition to unmodified aqueous solutions, mercury can be extracted quantitatively from aqueous iodide solutions that are up to 1M in HCl, H₂SO₄, and HNO₃ in a single equilibration. Distribution coefficients and separation factors of several elements relative to mercury(II) are reported for media that contain 0.1 M HCl and 0.02M KI. The reagent is superior to aliphatic amines and quaternary amines for the extraction of mercury from aqueous iodide solutions.     

Dissolution of Al-Fe materials and analysis by inductively coupled plasma – atomic emission spectrometry

A technique was developed for the dissolution of Al-Fe materials containing difficult to dissolve Al₂O₃. The developed procedure uses HCl and HNO₃ for initial sample attack followed by digestion with a mixture of H₃PO₄ and H₂SO₄ at 200?°C. This procedure was employe to dissolve Al-Fe material samples before the determination of Al and Fe. Minor and trace elements (B, Cr, Cu, Mo, Si, Zr) were determined after dissolution in HCl and HNO₃. Results of a round robin study verified the procedure accuracy. The developed methods have the required accuracy and precision to be used as a quality control procedure for Al-Fe materials analysis.     

Comparison of Sample Digestion Procedures for the Determination of Arsenic in Bottom Sediment Using Hydride Generation AAS

Certified reference materials (JMS-2 and JMS-1 – Marine sediment, LKSD-1 Lake Sediment, and STSD-1 Stream Sediment) and bottom sediment were analysed for arsenic by hydride generation atomic absorption spectrometry (HG-AAS) after digestion by different methods (microwave digestion, digestion in aluminium block, dry digestion) and different combinations of acids (HNO₃, HCl, HClO₄, H₂SO₄). The study revealed that both wet and dry digestion can be used to digest the reference materials and bottom sediment. Exceptionally satisfactory results were produced by the application of aqua regia, HNO₃ + HCl + HClO₄, and HNO₃ + HCl mixtures. Addition of Mg(NO₃)₂ during dry digestion caused an increase in arsenic recovery in the reference materials and improved the accuracy of arsenic determination in the bottom sediments.     

Liquid-liquid extraction of 233Pa(V) with Aliquat 336</p> </p>

Summary The extraction of protactinium with Aliquat 336 (methyl-tri-caprylyl ammonium chloride) in toluene, cyclohexane and chloroform from HCl, HNO₃, H₂SO₄, HClO₄, HF and mixed HCl-HF media was investigated by radioactive tracer technique. Distribution ratios of protactinium between the aqueous solution and the organic phase were determined as a function of shaking time, concentrations of acid in aqueous solution phase, extractant concentration and type of diluents in the organic phase. Aliquat 336 can almost quantitatively extract protactinium from strong HCl solution. At the same time, small amounts of HF in HCl solutions have a strong effect on Pa distribution.</p> </p>     

Size-controlled synthesis and formation mechanism of manganese oxide OMS-2 nanowires under reflux conditions with KMnO4 and inorganic acids

This study presents a simplified approach for size-controlled synthesis of manganese oxide octahedral molecular sieve (OMS-2) nanowires using potassium permanganate (KMnO₄) and different inorganic acids (HCl, HNO₃, and H₂SO₄) under reflux conditions. The morphology and nanostructure of the synthesized products are characterized by X-ray diffraction, Ar adsorption, and electron microscopy analysis, in order to elucidate the controlling effects of acid concentration and type as well as the formation mechanism of OMS-2 nanowires. The concentration of inorganic acid is a crucial factor controlling the phase of the synthesized products. OMS-2 nanowires are obtained with HCl at the concentration ≥0.96 mol/L or with HNO₃ and H₂SO₄ at the concentrations ≥0.72 mol/L. Differently, the type of inorganic acid effectively determines the particle size of OMS-2 nanowires. When the acid is changed from HCl to HNO₃ and H₂SO₄ in the reflux system, the average length of OMS-2 declines significantly by 60–70% (1104–442 and 339 nm), with minor decreased in the average width (43–39 and 34 nm). The formation of OMS-2 nanowires under reflux conditions with KMnO₄ and inorganic acids involves a two-step process, i.e., the initial formation of layered manganese oxides, and subsequent transformation to OMS-2 via a dissolution-recrystallization process under acidic conditions. The proposed reflux route provides an alternative approach for synthesizing OMS-2 nanowires as well as other porous nano-crystalline OMS materials.