Aqueous Hydrochloric Acid Medium Research Articles

Selenium dioxide catalysed oxidation of acetic acid hydrazide by bromate in aqueous hydrochloric acid medium

Selenium dioxide catalysed acetic acid hydrazide oxidation by bromate was studied in hydrochloric acid medium. The order in oxidant concentration, substrate and catalyst were found to be unity. Increasing hydrogen ion concentration increases the rate of the reaction due to protonation equilibria of the oxidant. The mechanism of the reaction involves prior complex formation between the catalyst and substrate, hydrazide, followed by its oxidation by diprotonated bromate in a slow step. Acetic acid was found to be the oxidation product. Other kinetic data like effect of solvent polarity and ionic strength on the reaction support the proposed mechanism. Selenium dioxide catalysed acetic acid hydrazide oxidation by bromate was studied in hydrochloric acid medium. The mechanism of the reaction involves prior complex formation between the catalyst and hydrazide, followed by its oxidation by diprotonated bromate in a slow step.

Mechanism of Oxidation of the Antituberculosis Drug Isoniazid by Bromate in Aqueous Hydrochloric Acid Medium

The oxidation of isoniazid by bromate was investigated kinetically under pseudo-first-order conditions in acid medium. The reaction was accelerated by the hydrogen ion due to the various protonation equilibria of both the reactants. The mechanism involves diprotonated isoniazid as the active species which forms two complexes with the diprotonated and unprotonated oxidant. The complex formed between the diprotonated oxidant and the protonated −NH2 group of hydrazide moiety of isoniazid decomposes into isonicotinic acid. Formation of another stable ion pair complex decreases the rate of reaction. The UV–vis examination of the solutions support the formation of both protonated isoniazid and the complexes. A probable mechanism on the basis of kinetic results involving formation of an acyl diimide of the isoniazid was proposed.

Synthesis and characterization of N‐ and O‐alkylated poly[aniline‐co‐N‐(2‐hydroxyethyl) aniline

AbstractPoly[aniline‐co‐N‐(2‐hydroxyethyl) aniline] was synthesized in an aqueous hydrochloric acid medium with a determined feed ratio by chemical oxidative polymerization. This polymer was used as a functional conducting polymer intermediate because of its side‐group reactivity. To synthesize the alkyl‐substituted copolymer, the initial copolymer was reacted with NaH to obtain the N‐ and O‐anionic copolymer after the reaction with octadecyl bromide to prepare the octadecyl‐substituted polymer. The microstructure of the obtained polymers was characterized by Fourier transform infrared spectroscopy, 1H‐NMR, and X‐ray diffraction. The thermal behavior of the polymers was investigated by thermogravimetric analysis and differential scanning calorimetry. The morphology of obtained copolymers was studied by scanning electron microscopy. The cyclic voltammetry investigation showed the electroactivity of poly [aniline‐co‐N‐(2‐hydroxyethyl) aniline] and N and O‐alkylated poly[aniline‐co‐N‐(2‐hydroxyethyl) aniline]. The conductivities of the polymers were 5 × 10−5 S/cm for poly[aniline‐co‐N‐(2‐hydroxyethyl) aniline] and 5 ×10−7 S/cm for the octadecyl‐substituted copolymer. The conductivity measurements were performed with a four‐point probe method. The solubility of the initial copolymer in common organic solvents such as N‐methyl‐2‐pyrrolidone and dimethylformamide was greater than polyaniline. The alkylated copolymer was mainly soluble in nonpolar solvents such as n‐hexane and cyclohexane. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

염산용액(鹽酸溶液)에서 TBP 및 Cyanex923을 이용(利用)한 루테늄(III)의 유출(抽出).분리(分離)에 관한 연구(硏究)

염화루테늄 용액에서 루테늄의 분리 및 회수를 위한 기초 연구로 TBP 및 Cyanex923을 이용하여 루테늄의 용매추출 거동을 조사하였다. 루테늄의 추출율에 영향을 미칠 수 있는 수용액상의 염산농도 및 염소이온 농도, 유기상의 추출제 농도, 온도 등에 대해서 고찰하였고, 유기상으로 추출원 루테늄의 탈거거동에 대해서도 조사하였다. 또한 백금, 비스무스, 납, 구리, 철, 주석 등과의 혼합용액에서 염산농도에 따라 각 성분들의 추출거동을 조사하였다. 실험결과 루테늄의 추출을 위해서는 Cyanex923이 효과적이었다. 그러나 TBP를 사용할 경우 루테늄의 추출율은 낮으나 백금, 비스무스, 주석 등의 불순물을 제거하는 데는 효과적이었다. Solvent extraction experiments were carried out to recover and separate Ru(III) from aqueous hydrochloric acid media using TBP and Cyanex923. The efficiency of the extraction was studied under various experimental conditions, such as concentration of HCl and NaCl, concentration of extractant in the organic phase and temperature. The extraction behavior of metal impurities, such as Pt, Bi, Sn, Fe, Pb and Cu in mixed solutions was examined. From the experimental studies, it was found that the Cyanex923 resulted in higher extraction percentage of Ru than TBP. However TBP was more effective for the separation of Ru and Pt, Bi, Sn in mixed solutions than Cyanex923.

Electrical properties of polyaniline-manganese chloride composites

Electrical and morphological properties of Polyaniline (PANI) filled with various mass fractions of manganese chloride (MnCl2) synthesized in aqueous hydrochloric acid (HCl) medium using ammonium persulphate as an oxidant were investigated. The sample morphology was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Significant changes were observed in the morphology of the samples depending on the filler level. The direct current (dc) and alternating current (ac) electrical properties were investigated as a function of temperature. The dc conductivity decreased 72% with 10% filler level whereas ac conductivity has shown a 120% increase with 6% filler level at room temperature. It is shown that the alternating charge transport mechanism of the unfilled and filled polyaniline samples is consistent with correlated barrier hopping (CBH) model. Imaginary (M″) parts of electric modulus exhibited temperature-dependent dielectric relaxation behavior for both filled and unfilled PANI samples. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.

Synthesis and characterisations of poly(aniline-co- o / m -toluidine)/Sb 2 O 3 nanocomposites

This study is focused on the preparation and characterisation of conducting poly(aniline-co-o/m-toluidine)/Sb2O3 nanocomposites. These nanocomposites were synthesised by the oxidative chemical polymerisation with peroxydisulphate as an oxidant in aqueous hydrochloric acid (HCl) medium and Sb2O3 as a nanomaterial under different experimental conditions. The nanocomposites were characterised by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis, high-resolution transmission electron microscopy and conductivity measurements. FTIR-based kinetics was proposed based on the relative intensities of FTIR peaks.

Unusual Behaviour During the Route of a Japp-Klingemann Reaction

Performing a standard Japp-Klingemann synthesis that involved diazotation of 2,6-dinitroaniline and reaction with pentane-2,4-dione in aqueous hydrochloric acid medium surprisingly yielded a mixture of the expected 2,6-dinitro- and the unexpected 2-chloro-6-nitro-substituted hydrazones. This mixture was isolated as solid-solution crystals containing the components in an approximate ratio of 1 to 2. Based on both, selected compounds of comparison that show the aromatic ring substituents changed in position and intermediate diazonium salts, potential causal connections of the unusual behaviour during the route of the particular Japp-Klingemann reaction were studied. X-Ray crystal structures of the relevant compounds have been determined to support the discussion.

Kinetics of the reduction of tetrakis (2,2′-bipyridine)-μ-oxo-di-iron(III) by 1,3-benzenediol in aqueous acidic medium

The stoichiometry and kinetics of the reduction of Fe2(III)(bpy)4OCl4 by 1,3-benzenediol have been investigated in aqueous hydrochloric acid medium. The reaction is first order in [oxidant] but zero order in [reductant]. There is no evidence for the formation of an intermediate complex of significant stability. The presence of NO3− or ClO4− had no effect on the rate of the reaction. Also, the reaction rate is not affected by the changes in the ionic strength and dielectric constant of the reaction media. A plausible mechanism involving an outer-sphere complex formed via an ion pair is proposed for the reaction.

Recovery of Gold from Hydrochloric Acid by using Lemon Peel Gel

Recovery of Au(III) in aqueous hydrochloric acid medium using lemon peel was studied. The adsorption gel prepared from lemon peel was found to adsorb Au(III) highly selectively showing negligible affinity for other precious metals and some base metal ions studied so far. The adsorption isotherm study gives the maximum loading capacity of the gel as 6.5 mol per kg dry weight of gel. XRD analysis and the digital micrograph of the gel taken after adsorption reveal the formation of gold particles during the adsorption process which is associated with the high selectivity and capacity of the gel for Au(III). Kinetic and electrochemical studies were performed at various temperatures. An endothermic adsorption process following pseudo-first order kinetics was established.

Chemical synthesis and characterization of aniline and o-anthranilic acid copolymer

The chemical co-polymerization of aniline with o-anthranilic acid (AA) to form copolymer films has been made in aqueous hydrochloric acid medium. The copolymer films were monitored by using the quartz crystal microbalance (QCM) technique. The effect of AA and its concentrations on the film formation was investigated. The results were justified by measuring the UV–Vis absorption spectra for the in situ copolymer films grown onto glass slides immersed into the polymerization media and the in situ UV–Vis absorption spectra for the copolymer in the bulk during the co-polymerization. The conductivity for the copolymer films and powder pellets at different molar ratios of aniline/AA were measured. Also, the IR spectra, X-ray diffraction and the thermal gravimetric analysis for the copolymer powder formed in the bulk in the absence and presence of AA were measured and discussed. It is found that the presence of AA affects the yield, induction period, depletion time and growth rate of the film formation. It also affects the crystallinity, and conductivity as well as the solubility of the polymer. Finally, the dopant weight fraction ( w) associated with the copolymer was determined. It is almost half the value determined for the polymer in absence of AA.

Preparation and characterization of polyaniline films in the presence of N-phenyl-1,4-phenylenediamine

The chemical oxidation of aniline to form polyaniline (PANI) films was made in the presence of N-phenyl-1,4-phenylenediamine (PPDA) in aqueous hydrochloric acid medium. The PANI films were monitored by using the quartz crystal microbalance (QCM) technique. The effect of PPDA and its concentration on the film formation was investigated. It was found that PPDA decreases the yield of the PANI film, the induction period and the depletion time of the polymerization. However, the growth rate of the film formation was found to increase by increasing PPDA concentration. These results were justified by measuring the UV–VIS absorption spectra for the in situ PANI films and the in situ UV–VIS absorption spectra for the polymer in the bulk during the polymerization. The conductivity for the PANI films at different concentrations of PPDA was measured. Also, the IR spectra, X-ray and the thermal gravimetric analysis for the PANI powder formed in the bulk in the presence of PPDA were measured and discussed.

Extraction and Separation of Precious Metals by a Column Packed with Divinylbenzene Homopolymeric Microcapsule Containing Tri‐n‐octylamine

The separation of palladium, platinum, and gold was investigated using a column packed with divinylbenzene homopolymeric microcapsules containing tri‐n‐octylamine (TOA). The extraction of precious metals except platinum using the microcapsules progresses by means of the same reaction proposed in a solvent extraction system. The microcapsules also effectively extracted precious metals from an aqueous hydrochloric acid medium in the column operation. The breakthrough point is delayed in the following order: platinum, palladium, and gold. Almost all TOA molecules enclosed in the microcapsules can act on the extraction reaction with precious metals, which was confirmed by the calculation of the concentration of precious metals extracted into the microcapsules based on the breakthrough curve of each precious metal. By selecting the appropriate eluent, palladium, gold, and platinum were successfully eluted from the column using an 8.0 mol/dm3 aqueous HCI solution, a 0.1 mol/dm3 thiourea in 0.1 mol/dm3 aqueous HCI solution, and a 0.5 mol/dm3 ethylenediamine in 0.1 mol/dm3 aqueous NaOH solution, respectively. By feeding the eluent stepwise into the column in this order, the mutual separation of precious metals can be successfully achieved.

Ion-pair extraction of cadmium complex anions from hydrochloric acid media using oxonium ion-dicyclohexyl-18-crown-6 complex

Solvent extraction of cadmium from aqueous hydrochloric acid media (1–11 mol dm −3) into dichloromethane solution of 18-crown-6, dibenzo-18-crown-6 and dicyclohexyl-18-crown-6 (DC18C6) has been studied at 25 °C. The highest extraction abilities have been found by DC18C6 in the range of 6–7 mol dm −3 hydrochloric acid. The conventional log–log plot analysis of the extraction equilibrium data at 3 and 8 mol dm −3 of the acid revealed that the cadmium ions were extracted as ion-pairs [ H L + ] [ CdC l 3 − ] and [ H L + ] 2 [ CdC l 4 2 − ] (L = DC18C6), respectively. The effect of diluent has been investigated using chloroform, dichloromethane, 1,2-dichloroethane, carbon tetrachloride and toluene. The extraction of the cadmium increased with diluent polarity. The ability of DC18C6 to separate cadmium from binary mixtures of Cd and M (M = Ni, Mn, Co, Zn, Pb and Fe) has been evaluated. The efficiency and selectivity of the method allow to propose it for the recovery of cadmium from consumed Ni–Cd rechargeable batteries.

Synergistic extraction of cobalt (II) by beta hydroxy naphthaldoxime and neutral donors.

Liquid - liquid extraction of Cobalt (II) from aqueous hydrochloric acid medium by the use of oxime derivative of beta-hydroxy naphthaldehyde in o-xylene medium is being reported. The ligand was synthesized and characterized in our laboratory. The typical pH range of extraction of Co (II) by the ligand - donor combination was seen to be between 8 - 9. The effect of different donors like dimethyl sulphoxide (DMSO), trioctyl phosphine oxide (TOPO) and bis(2-ethylhexyl) phosphonate and the effect of various diluents on the extraction of Co(II) by the present method were studied in detail. The binary adduct formation constant (log kex) in the organic phase was found to be 3.182. The overall equilibrium constant (log K) for the ternary species [Co(A)(DMSO)(Cl)], [Co(A)(TOPO)(Cl)] and [Co(A)(phosphonate)(Cl)] were estimated to be 6.42, 6.22 and 6.25 respectively. The trend in equilibrium constants were in accordance with their basic character, i.e., (DMSO > or = TOPO approximately/= phosphonate). The results were extrapolated in the determination of Cobalt in pharmaceutical drugs and cobalt bearing ore samples.

Separation of Te(IV) and Se(IV) by Extraction with Cyanex 925

Liquid–liquid extraction of tellurium(IV) and selenium(IV) with Cyanex 925 in toluene from aqueous hydrochloric acid media was studied separately, under the influence of variables such as: hydrochloric acid concentration, reagent concentration, equilibration time, diverse ions, stripping agents, and temperature. The difference in extractability of these metal ions in hydrochloric acid media toward Cyanex 925 facilitates their separation. The temperature dependence of extraction equilibriums were examined by the temperature variation method to estimate apparent thermodynamic function, ΔH. From the temperature study, the extraction reaction for Te(IV) was found to be exothermic in nature, while that of Se(IV) endothermic.

Kinetics and mechanism of oxidation of antimony(III) by keggin‐type 12‐tungstocobaltate(III) in aqueous hydrochloric acid medium

AbstractThe reaction between Sb(III) and [CoIIIW12O40]5− proceeds with two, one‐electron steps; formation of unstable Sb(IV) is the slow first step followed by its reaction with another oxidant in a fast step. The reaction rate is unaffected by the [H+] as there are no protonation equlibria involved with both the reactants, whereas the accelerating effect of chloride ion is due to the formation of an active chlorocomplex of the reductant, SbCl63−. Increase in the ionic strength and decrease in the relative permittivity of the medium increases the rate of the reaction, which is attributed to the formation of an outer‐sphere complex between the reactants. The activation parameters were also determined and these values support the proposed mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 9–14, 2003

Extraction separation of Ir(III) and Rh(III) with Cyanex 923 from chloride media: a possible recovery from spent autocatalysts

AbstractLiquid–liquid extraction of Ir(III) and Rh(III) with Cyanex 923 from aqueous hydrochloric acid media has been studied. Quantitative extraction of Ir(III) was observed in the range of 5.0–8.0 mol dm−3 HCl with 0.1 mol dm−3 Cyanex 923, while Rh(III) was extracted quantitatively in the range of 1.0–2.0 mol dm−3 HCl with 0.05 mol dm−3 Cyanex 923 in toluene along with 0.2 mol dm−3 SnCl2. The Ir(III) was back extracted with 4.0 mol dm−3 HNO3 quantitatively from the organic phase while Rh(III) was stripped with 3.0 mol dm−3 HNO3. The extraction of Rh(III) with Cyanex 923 was not quantitative without use of SnCl2. However in the extraction of Ir(III) a negative trend was observed in the presence of SnCl2. Varying the temperature of extraction showed that the extraction reactions of both the metal ions are exothermic in nature, and the stoichiometric ratio of Ir(III)/Rh(III) to Cyanex 923 in organic phase was found to be 1:3. The methods developed were applied to the recovery of these metal ions from a synthetic solution of similar composition to that from leaching of spent autocatalysts in 6.0 mol dm−3 HCl.© 2002 Society of Chemical Industry

Synthesis and characterization of conducting poly(aniline‐co‐o‐aminophenethyl alcohol)s

AbstractPoly(o‐aminophenethyl alcohol) and its copolymers containing the aniline unit were synthesized in aqueous hydrochloric acid medium by chemical oxidative polymerization. The chemical composition of these novel polymers was determined spectroscopically, and their viscosities were measured. These polymers exhibit good solubility in organic solvents that is attributed mainly to the polar hydroxyethyl side groups. Their structures (chain conformation and morphological structure) and properties (conductivity, electrochemical characteristics, glass transition, and degradation behavior) were characterized and then interpreted on the basis of the chemical composition along with the electronic and steric hindrance effects associated with the hydroxyethyl side group. Overall, the side group has a significant effect on the polymerization and influences the structure, chain conformation, and properties of the resultant polymer. The poly(aniline‐co‐o‐aminophenethyl alcohol)s containing 20–40 mol % o‐aminophenethyl alcohol units are potential conducting materials for microelectronic and electromagnetic shielding applications because they are easier to process than polyaniline but retain its beneficial properties. These polymers can also be used as a functional conducting polymer intermediate owing to the reactivity of the side group. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 983–994, 2002

Extraction separation studies of Os, Ru and Ir using Cyanex 921 in toluene

Extraction of osmium, ruthenium and iridium with Cyanex 921 from aqueous hydrochloric acid media has been examined in the absence and in the presence of tin(II) chloride. In order to facilitate the separation of these individual metal ions, the extraction of each metal ion was studied separately under the influence of variables such as: hydrochloric acid concentration, reagent concentration, tin(II)chloride concentration, equilibration time, diverse ions and stripping agents. The method developed was applied to the recovery of these metal ions from some catalyst samples.

Extraction separation studies of Rh, Pt and Pd using Cyanex 921 in toluene—a possible application to recovery from spent catalysts

Liquid–liquid extraction of rhodium, platinum and palladium with Cyanex 921 from aqueous hydrochloric acid media has been examined in the absence and in the presence of tin(II) chloride. In order to facilitate the separation of these individual metal ions from their mixtures, the extraction of each metal ion was studied separately, under the influence of variables such as: hydrochloric acid concentration, tin(II) chloride concentration, reagent concentration, equilibration time and stripping agents. Thereafter, the method developed was applied to the recovery of these metal ions from a synthetic solution similar in composition to that expected from the leaching of spent catalysts in 6.0 M hydrochloric acid.