Aqueous Hydrochloric Acid Medium Research Articles

KINETICS AND MECHANISM OF THE OXIDATION OF TANNIC ACID BY POTASSIUM TRISOXALATOFERRATE (III) IN AQUEOUS HYDROCHLORIC ACID MEDIUM

The kinetics of the redox reaction between tannic acid (TA) and potassium trisoxalatoferrate (III) trihydrate, (K3[Fe(C2O4)3].3H2O) has been studied in aqueous hydrochloric acid medium. The stoichiometry of the reaction determined by the mole ratio method was observed to be 1:1. The kinetic results showed first order dependence with respect to complex and tannic acid concentrations. The experimental data for the reaction system are consistent with the following rate law:where a = 2.0 × 10-3 mol-1 dm3 s-1 and b = 2.1 × 10-3 mol-2 dm6 s-1 at 420 nm and 27.0 ± 1.0 ºC. The rate of reaction was found to increase with increase in [H+] in the acid range used, but decreased with increase in ionic strength of the reaction medium. While the rate of reaction was observed to decrease with increasing dielectric constant of the reaction medium, the addition of CH3COO-, HCOO-, Ni2+and K+ catalyzed the rate of the reaction. The Michaelis-Menten plot of 1/kobs versus 1/[oxidant] gave a straight line with an insignificant positive intercept. The addition of acrylamide to the partially oxidized reaction mixture did gave a gel in the presence of excess methanol. Based on the experimental data, a plausible mechanism involving outer sphere electron transfer has been proposed for the redox reaction between tannic acid and potassium trisoxalatoferrate (III) trihydrate.

Indium and thallium extraction into betainium bis(trifluoromethylsulfonyl)imide ionic liquid from aqueous hydrochloric acid media

Carrier-free In and Tl radionuclides were extracted into a protic ionic liquid [Hbet][Tf2N] from HCl media with and without the presence of zwitterionic betaine in the aqueous phase.

Hydrophobic amine-based binary mixtures of active pharmaceutical and food grade ingredients: characterization and application in indium extraction from aqueous hydrochloric acid media

Indium extraction into novel hydrophobic binary mixtures based on common pharmaceutical and food grade compounds.

The Kinetics of the Oxidation of Lysine by μ-Peroxo-Bridged Binuclear Cobalt (III) Complex of Succinimide in Aqueous Hydrochloric Acid Medium

Abstract Kinetics of oxidation of Lysine (Lys) and mechanisms by μ-peroxo bis[bis(ethylenediamine)succinimidato-dicobalt(III)]dinitratedihydrate; [LCo(μ-O2)CoL](NO3)2.2H2O (L = suc(en)2), hereafter the complex, was investigated at 420 nm wavelength of maximum absorption of the complex under the conditions hydrogen ions concentration = 1.8 × 10-2 mol dm-3, temperature = 24 ± 1 °C, [LCo(μ-O2)CoL2+] = 1.4 × 10-4 mol dm-3 and ionic strength = 0.5 mol dm-3. First order in [LCo(μ- O2)CoL2+] and [Lys] were obtained but inverse first order in [H+]. The proposed overall rate equation is as shown: Rate of the reaction decreases when hydrogen ions concentration increase and exhibited converse effect with increase in concentration of ionic strength from 0.1 - 1.3 mol dm-3. Added cations and anions affected the reaction rate and the Michaelis-Menten plot passed through the origin indicating no absence of intermediate complex in the electron transfer processes. Putting all the results obtained together, the most probable reaction mechanism is in favour of outer-sphere and an appropriate rate law is established using steady state approximation.

The Kinetics of the Oxidation of Lysine by μ-Peroxo-Bridged Binuclear Cobalt (III) Complex of Succinimide in Aqueous Hydrochloric Acid Medium

Abstract Kinetics of oxidation of Lysine (Lys) and mechanisms by μ-peroxo bis[bis(ethylenediamine)succinimidato-dicobalt(III)]dinitratedihydrate; [LCo(μ-O2)CoL](NO3)2.2H2O (L = suc(en)2), hereafter the complex, was investigated at 420 nm wavelength of maximum absorption of the complex under the conditions hydrogen ions concentration = 1.8 × 10−2 mol dm−3, temperature = 24 ± 1 °C, [LCo(μ-O2)CoL2+] = 1.4 × 10−4 mol dm−3 and ionic strength = 0.5 mol dm−3. First order in [LCo(μ-O2)CoL2+] and [Lys] were obtained but inverse first order in [H+]. The proposed overall rate equation is as shown: Rate = ( k 1 k 2 + K 1 k 3 k 4 1 [ H + ] ) [ LCo ( μ O 2 ) CoL 2 + ] [ Lys ] $$Rate = ({{k_1 } \over {k_2 }} + {{K_1 k_3 } \over {k_4 }}{1 \over {[H^ + ]}})[LCo(\mu O_2 )CoL^{2 + } ][Lys]$$ Rate of the reaction decreases when hydrogen ions concentration increase and exhibited converse effect with increase in concentration of ionic strength from 0.1 – 1.3 mol dm−3. Added cations and anions affected the reaction rate and the Michaelis-Menten plot passed through the origin indicating no absence of intermediate complex in the electron transfer processes. Putting all the results obtained together, the most probable reaction mechanism is in favour of outer-sphere and an appropriate rate law is established using steady state approximation.

Extraction and separation of multiple platinum group metals from hydrochloric acid solution with sole 1-hexyl-3-methylimidazole-2-thione using microextraction method

In this study, palladium (II), platinum (IV), rhodium (III) and iridium (IV) were sequentially separated with 1-hexyl-3-methylimidazole-2-thione (HMImT) from aqueous hydrochloric acid media by adjustment of hydrochloric acid concentration or in the presence of tin (II) chloride using environmental-friendly microextraction method. It is the first time to use sole extractant to selectively separate four platinum group metals from aqueous solution. Through condition optimization, HMImT shows outstanding extraction capacity (Pd 0.54mmol/g, Pt 0.14mmol/g, Rh 0.82mmol/g) and high extraction percentage to palladium (99.4%), platinum (99.8%), rhodium (99.6%) respectively. The separation coefficient exceeds 10,000 and obtained metals purity reaches 99%. Based on Job's method, FT-IR spectra, UV–vis spectra, 1H NMR spectra and theoretical natural population analysis (NPA), the anion exchange mechanism of HMImT on Pt (IV) extraction was confirmed. By precipitating-calcining method palladium (II), platinum (IV) and rhodium (III) could be recycled in the form of Rh2O3, Pd and Pt2O.

Synthesis and characterization of poly(2-aminothiophenol-co-2-methylaniline)/silver nanoparticles as antisulfate-reducing bacteria

ABSTRACTPoly(2-aminothiophenol) (P2ATH), poly(2-methylaniline) (P2MeANI), and poly(2ATH-co-2MeANI) are synthesized using ammonium persulfate as an oxidant in aqueous hydrochloric acid (HCl) medium at room temperature. The obtained polymeric samples are assembling on silver nanoparticles. The structures of prepared polymeric samples are characterized by ultraviolet–visible, infrared, proton nucleus magnetic resonance (1H NMR), X-ray diffraction, electron microscope, transmittance electron microscope, and thermogravimetric analysis. The antibacterial efficiency of the prepared polymeric and polymer/Ag nanoparticle samples is studied for the removal of sulfate-reducing bacteria. The results reveal that the assembling of both P2ATH and P2MeANI on Ag nanoparticles enhances the antisulfate-reducing bacteria’s efficiencies, but in a case of P2ATH-co-2MeANI the efficiency is more than its Ag nanoparticles.

Kinetics and Mechanism of the Redox Reaction of Naphthol Green B with Hydrazine Dihydrochloride in Aqueous Acidic Medium

The kinetics of the redox reaction between naphthol green B and hydrazine dihydrochloride has been studied in aqueous hydrochloric acid medium at an ionic strength, I = 0.50 mol dm-3(NaCl), [H+] = 1.0×10-4 moldm-3 (HCl) and T = 21±1°C. The redox reaction displayed a stoichiometry of 1:1 and obeys the rate law: -d[NGB3-]/dt=k2[NGB3-][N2H4.2HCl]. Change in hydrogen ion concentration of the reaction medium has no effect on the rate of the reaction. Added cations and anions inhibited the rate of the reaction. The redox reaction showed negative salt effect, with the rate decreasing with increase in ionic strength of the reaction medium. Results of the Michaelis–Menten’s plot show that an intermediate complex was not formed during the course of the reaction. The outersphere mechanism is proposed for this reaction.

Influence of structure of poly(o-phenylenediamine) on the doping ability and conducting property

Poly(o-phenylenediamine) with ladder-type structure was formed in aqueous hydrochloric acid medium below pH 1, while open ring-type amine derivative, i.e., −NH2 functional group substitution of polyaniline structure, was obtained in 1:1 aqueous sulfuric acid medium from the chemical synthesis of the monomer o-phenylenediamine. However, poly(o-phenylenediamine) having structure like polyaniline derivative with free =NH functional groups was obtained by chemical synthesis in dimethyl sulfoxide medium. The ladder-type polymer was almost insoluble but the other two types of synthesized polymers having polar functional group substitutions were well soluble in polar organic solvent like dimethyl sulfoxide, N,N-dimethyl formamide, and tetrahydrofuran. The freestanding films were cast from dimethyl sulfoxide solution of both the soluble functional polymers. The polymers having different structures were doped with inorganic acid by solution doping technique and the doped polymers were characterized by various standard characterizations. In order to explore the electronic uses of the polymers like sensor and actuators, the influences of their structure on the doping ability as well as ionic properties of the sulfuric acid-doped polymers were compared.

Kinetics and Mechanism of Redox Reaction of Neutral Red with Nitrite Ion in Aqueous Acidic Medium

The kinetics of redox reaction of neutral red, NR+, with nitrite ion, NO2-, was studied in aqueous hydrochloric acid medium under pseudo-first order conditions at 25 ± 1°C, [H+] = 2.0 × 10-3 mol dm-3, I = 0.1 mol dm-3 (NaCl) and λmax = 525 nm. The reaction was first order with respect to [NR+], [NO2-] and [H+]. The reaction displayed a negative Bronsted-Debye salt effect. There was no evidence of the formation of an intermediate complex of significant stability and free radicals are probably not present in the reaction. The observations above, coupled with the result of Michaelis-Menten plot suggests an outer sphere mechanism for the reaction. The reaction obeys the rate law: -d [NR+]/dt = (a + b [H+])[NR+][NO2-]. A plausible mechanism has been proposed for the reaction.

Kinetics and Mechanism of Redox Reaction of Neutral Red with Nitrite Ion in Aqueous Acidic Medium

The kinetics of redox reaction of neutral red, NR+, with nitrite ion, NO2-, was studied in aqueous hydrochloric acid medium under pseudo-first order conditions at 25 ± 1°C, [H+] = 2.0 × 10-3mol dm-3, I = 0.1 mol dm-3(NaCl) and λmax= 525 nm. The reaction was first order with respect to [NR+], [NO2-] and [H+]. The reaction displayed a negative Bronsted-Debye salt effect. There was no evidence of the formation of an intermediate complex of significant stability and free radicals are probably not present in the reaction. The observations above, coupled with the result of Michaelis-Menten plot suggests an outer sphere mechanism for the reaction. The reaction obeys the rate law: -d [NR+]/dt = (a + b [H+])[NR+][NO2-]. A plausible mechanism has been proposed for the reaction.

Separation and Spectrophotometric Determination of Osmium(IV) and Ruthenium(III) with O-methoxyphenyl Thiourea as Chromogenic Legand: Sequential Separation of Osmium(IV), Ruthenium(III), and Platinum(IV)

A precise and selective method has been developed for extraction spectrophotometric determination of osmium(IV) and ruthenium(III) using o-methoxyphenyl thiourea (OMePT) as a chromogenic ligand. The basis of the proposed methods are osmium(IV)-OMePT complex was formed in 0.8 mol L−1 at room temperature while ruthenium(III)-OMePT complex was formed in 3.4 mol L−1 aqueous hydrochloric acid media after 5.0 min heating in boiling water bath. The osmium(IV)-OMePT and ruthenium(III)-OMePT complex were measured at 518 and 640 nm against the reagent blank, respectively. Complexes were also extracted in 10 mL chloroform and showed comparable absorbance values. Beer’s law was obeyed up to 110.0 μg mL−1 for osmium(IV)-OMePT complex and up to 50.0 μg mL−1 for ruthenium(III)-OMePT complex. Molar absorptivity and Sandell’s sensitivity of osmium(IV)-OMePT and ruthenium(III)-OMePT complexes were 2.12 × 103 L mol−1 cm−1, 0.089 μg cm−2 and 2.34 × 103 L mol−1 cm−1, 0.043 μg cm−2, respectively. The stoichiometry of osmium(IV)-OMePT and ruthenium(III)-OMePT complex was 1:1 and 1:2, respectively. Stability of osmium(IV)-OMePT complex was > 8 days and that of ruthenium(III)-OMePT complex was > 48 h. The proposed method was successfully applied for determination of osmium(IV) and ruthenium(III) from synthetic mixtures corresponding to platinum-osmium alloy and fissium alloy, respectively. The method was successfully applied for sequential separation of osmium(IV), ruthenium(III), and platinum(IV).

Chemical synthesis of processable conducting polyaniline derivative with free amine functional groups

Processable conducting polyaniline derivative with free amine functional groups was successfully synthesized from the monomer o-phenylenediamine in aqueous hydrochloric acid medium using ammonium persulfate as an oxidative initiator. The synthesized poly(o-phenylenediamine) (PoPD) in critical condition was found to be completely soluble in common organic solvents like dimethyl sulfoxide, N,N-dimethyl formamide etc. From the intrinsic viscosity measurement, the optimum condition for the polymerization was established. The polymer was characterized by ultraviolet visible spectroscopy, Fourier transform infrared spectroscopy, proton magnetic resonance spectroscopy (<TEX>$^1HNMR$</TEX>) and thermogravimetric (TGA) analyses. The weight average molecular weights of the synthesized polymers were determined by the dynamic light scattering (DLS) method. From the spectroscopic analysis the structure was found to resemble that of polyaniline derivative with free amine functional groups attached to ortho/meta position in the phenyl ring. However, very little ladder unit was also present with in the polymer chain. The moderate thermal stability of the synthesized polymer could be found from the TGA analysis. The average DC conductivity of <TEX>$2.8{\times}10^{-4}S/cm$</TEX> was observed for the synthesized polymer pellet after doping with hydrochloric acid.

English

English

Preliminary Study on the Kinetics and Mechanism of the Oxidation of Naphthol Green B by Dichromate Ion in Aqueous Hydrochloric Acid Medium

Abstract - The kinetics of the oxidation of naphthol green B (NGB3-) by Cr2O7 2- has been studied in aqueous hydrochloric acid medium at an ionic strength, I = 0.50 mol dm-3 (NaCl), H+ =1.0  10-4 mol dm-3 (HCl) and T = 25  1C. The redox reaction displayed a stoichiometry of 1:1 and obeys the rate law: -dNGB3-/dt = k2NGB3-]Cr2O7 2- . The second order rate constant increases with increase in acid concentration and in the ionic strength of reaction medium. The rates of reaction displayed a positive salt effect. Addition of acrylonitrile to a partially reacted mixture in the presence of excess methanol did not lead to gel formation. Added cations and anions inhibited the naphthol green B - Cr2O7 2- reaction. Results of the Michaelis – Menten plot gave no evidence of intermediate complex formation during the course of the reaction. Based on the results obtained, the reaction is believed to proceed through the outersphere mechanistic pathway.Keywords: Intermediate; Redox; Pseudo-octahedral; Michaelis – Menton; Outersphere

Synthesis and Characterization of Some Conducting Polymers and Their Complexed Compounds

The chemical co-polymerization of aniline with o-anthranilic acid (AA) to form copolymer films has been made in aqueous hydrochloric acid medium. Poly vinylcarbazole (PVK) was prepared by free radical mechanism. The copolymer (AA) and polymer (PVK) were reacted with KI respectively, to produce a complex compounds. Also, the complex of copolymer (AA) with NaOEt was prepared. The conductivity, IR spectra and the thermal gravimetric analysis of these polymers and their complexes were measured and discussed. It was found that, the specific electrical conductivity (σ) of the copolymer (AA) in presence of NaOEt increases with increase in temperature, whereas decreases with complex of copolymer (AA) +KI. The electrical properties of the PVK were enhanced upon reacting it with KI.

Development of a reliable analytical method for extraction spectrophotometric determination of ruthenium(III) from catalyst and fissium alloy using o-methylphenyl thiourea as a chromogenic chelating ligand

A simple and selective method is developed for the extraction spectrophotometric determination of ruthenium(III) using o-methylphenyl thiourea (OMPT) as a chromogenic chelating ligand. The basis of the proposed method is ruthenium(III)–OMPT complex formation in aqueous hydrochloric acid media (3.0molL−1) after 5.0min heating on a boiling water bath and the complex formed is extracted into chloroform. The absorbance of green colored ruthenium(III)–OMPT complex is measured at 590nm against the reagent blank. Beer’s law was obeyed up to 42.5μgmL−1 of ruthenium(III) and the optimum concentration range is 7.56–39.81μgmL−1 of ruthenium(III) as evaluated by Ringbom’s plot. Molar absorptivity and Sandell’s sensitivity of ruthenium(III)–OMPT complex in chloroform are 2.34×103Lmol−1 cm−1 and 0.043μgcm−2 respectively. The composition of ruthenium(III):OMPT complex (1:2) was established from slope ratio method, mole ratio method and Job’s continuous variation method. Complex was stable for more than 48h. The interfering effect of various foreign ions was studied and suitable masking agents are used wherever necessary to enhance the selectivity of the method. Proposed method is successfully applied for determination of ruthenium(III) from binary and ternary synthetic mixtures, synthetic mixtures corresponding to fissium alloy and ruthenium catalyst. Repetition of the method was checked by finding relative standard deviation (R.S.D) for 10 determinations which was 0.23%. A scheme for sequential separation of palladium(II), ruthenium(III), rhodium(III) and platinum(IV) has been developed.

Effect of the Protonation and Chemical Doping of Poly(o-toludine) with Copper Sulfate on the Spectral and Electrical Properties of the Host Polymer

Poly(o-toluidine) (POT) and its samples doped with copper sulfate, a transition metal salt, were synthesized by a chemical oxidative polymerization technique using potassium dichromate as oxidant in aqueous hydrochloric acid medium and chemical doping with copper sulfate. The prepared polymeric samples were characterized by ultraviolet (UV)-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, and DC conductivity measurement techniques. The UV-visible spectra of doped polymer displayed peaks indicating the presence of charged particles/polarons and/or formation of conducting POT. The characteristic FTIR peaks of the doped polymer provided information regarding structural changes in the backbone of POT and were consistent with the interaction of the benzenoid groups of the polymer with metal ions. X-ray diffraction patterns of powdered doped polymer showed an amorphous nature, as exhibited by most conducting polymers. The DC conductivity of doped polymer was measured by a two-probe method in the temperature range of 300–400 K; a significant enhancement in DC conductivity was observed with an increase in temperature, showing the semiconductor nature of the synthesized doped polymer.

Kinetics and Mechanism of Oxidation of L-Ascorbic Acid by Pt(IV)(aq) in Aqueous Hydrochloric Acid Medium

Reduction of [PtCl6]2− by L-ascorbic acid (H2ASc) in 0.1 M aqueous acid medium has been investigated spectrophotometrically under pseudo-first order condition at [PtCl6]2− = 0.005–0.007 mol dm−3, 0.05 ≤ [H2ASc]/mol dm−3 ≤ 0.3, 298 K ≤ T ≤ 308 K, [H+] = 0.14 mol dm−3, I=0.5 mol dm−3. The redox reaction follows the rate law: d[Pt(IV)]/dt = k[H2ASc][Pt(IV)], where k is the second-order rate constant and [H2ASc] is the total concentration of ascorbic acid. Electron transfer from [H2ASc] to Pt(IV) center leading to the release of two halide ions and formation of the reaction products, square planner Pt(II) halide complex, and dehydrated ascorbic acid is suggested. This redox reaction follows an outersphere mechanism as Pt(IV) complex is substituted inert. Activation parameters were calculated corresponding to rate of electron transfer reaction k. Activation parameters favor the electron transfer reaction.

Spectroscopic and Electrical Studies of Ferrous Sulphate Doped Polyaniline

Polyaniline (PANI) has been synthesized by chemical oxidative polymerization technique with potassium dichromate oxidant in aqueous hydrochloric acid medium. After polymerization, the polymer so prepared is doped with ferrous sulphate, a transition metal salt, with tetrahydrofuran and water as solvents. The undoped/doped samples were characterized by various techniques such as UV-visible spectroscopy, FTIR spectroscopy, X-ray diffraction and dc conductivity measurements. UV-visible absorption studies revealed the presence of cation/polaron transitions and the presence of direct optical transitions. FTIR studies provide information regarding structural changes in the backbone of PANI with doping concentration. X-ray diffraction patterns of powdered polymer composites showed amorphous nature as mostly conducting polymers exhibit. The dc conductivity of PANI-ferrous sulphate composites were measured by two probe method in pellet form at room temperature (300 K) and found to increase with temperature showing the semiconductor behavior of synthesized polymer composites