Mineral Acid Media Research Articles

Poređenje teorijskog i eksperimentalnog ispitivanja procesa protonacije nekih tionova u kiselim medijima

PM3 semiempirical method was used for quantum chemical investigation in order to investigate the electronic properties and to determine the protonation centre in 1,2,4-triazoline-3-thione molecule. Confirmation of protonation center in acid media of investigated compounds was made using the values of atomic charges, as well as, proton affinity values. The results from semiempirical calculations indicated that the protonation center in the thione molecule was the sulphur atom. The behavior of thiones was investigated in mineral acid media using UV spectroscopy. The influence of the strength of the acid and its anion on the protonation process was discussed using three different mineral acids (perchloric, hydrochloric and phosphoric acid) for protonation. The protonation process in perchloric and hydrochloric acid took place in one step, while in phosphoric acid was not finished even when its concentration was to the highest degree. The dissociation constants of protonated forms (pKBH + ) and the solvation parameter m* values were calculated in accordance with "excess acidity" function method (Cox and Yates) using the absorbance data from the experimental and reconstructed spectra (Characteristic Vector Analysis (CVA)). The determined pKBH + values in hydrochloric acid had more negative value than those obtained in perchloric acid media. The pKBH + values were in agreement with the literature data for this class of compounds.

Investigation into the Chemical Stability of the TiB2–TiN Eutectic Alloy Fabricated in the Combustion Mode in a Mineral Acid Medium

The results of studying the corrosion resistance of the powder of the TiB2–TiN eutectic alloy in a medium of HCl and HNO3 mineral acids are presented. The experiments are performed for samples synthesized in the combustion mode and then powdered in an agate mortar. The particle morphology, size distribution, and specific surface are determined for fabricated powders. The concentrations of acids are varied in a range from 0.2 to 6.0 M and the process temperature is varied from 25 to 80°C in experiments on studying the corrosion resistance. The chemical analysis of studied products of the interaction with the aggressive medium are performed for determining the content of main elements (titanium, boron, and nitrogen) according to procedures developed for refractory compounds. It is shown that the samples possess the largest resistance when interacting with solutions of diluted acids at room temperature, while their resistance decreases with an increase in the acid concentration and/or process temperature. It is found that the interaction with acid is inherent both to the TiB2 phase and for the TiN phase in all cases considered in the work. Herewith, the reaction with the participation of the TiB2 phase was more rapid. For the first time, the depth characteristics of corrosion are determined at room temperature and concentration of acids of 1.0 M, and the alloy corrosion resistance in the HCl and HNO3 medium is evaluated. Based on these data, the alloy was attributed to the group of resistant materials. The corrosion resistance in HCl and HNO3 media was 4 and 5 points, respectively, according to the 10-point scale.

Investigation of TiB2–TiN eutectic alloy obtained by combustion synthesis for chemical resistance in mineral acid media

The article presents the results obtained in the corrosion resistance study of TiB2/TiN eutectic alloy powder in HCl and HNO3 mineral acids. Experiments were carried out on samples synthesized in the combustion mode and then ground in an agate vessel. The morphology, size distribution and specific surface area of particles were determined in the obtained powder samples. Corrosion resistance experiments were conducted with varying acid concentration from 0.2 to 6.0 M and process temperature from 25 to 80 °C. Chemical analysis of the studied products of interaction with an aggressive medium was carried out to determine the content of main elements in them (titanium, boron, nitrogen) using methods developed for refractory compounds. As a result of the work carried out, it was shown that samples have the greatest resistance when interacting with solutions of diluted acids at room temperature, and their resistance decreases as acid concentration and/or process temperature rises. It was found that interaction with the acid occurs with both TiB2 and TiN phases in all cases considered in the paper. At the same time, the reaction involving the TiB2 phase was faster. For the first time deep corrosion and corrosion resistance of the alloy in HCl and HNO3 media were measured at room temperature and 1.0 M acid concentration. Based on the obtained data, the investigated alloy was classified as a «resistant» material. Corrosion resistance by a ten-point scale in HCl and HNO3 media was «4» and «5», respectively.

L-Dopa as Corrosion Inhibitor for Mild Steel in Mineral Acid Medium

Corrosion inhibition of mild steel was studied using L-Dopa in aqueous hydrochloric acid and sulphuric acid so- lutions. The corrosion behaviours of the steel specimen in the presence of inhibitor weret studied by galvanostatic polari- zation and weight loss techniques. The measured electrochemical data indicated good inhibition of corrosion in both the corrosive medium in presence of L-DOPA. The corrosion inhibition may be explained on the basis of adsorption and for- mation of surface film of L-DOPA on the metal surface. The surface of the steel specimen subjected to electrochemical corrosion in the presence and absence of the inhibitor was studied using scanning electron microscopic images. In the present investigation, L-DOPA is used as corrosion inhibitor for mild steel in aqueous hydrochloric acid and sulphuric acid solutions. The corrosion inhibition efficiency of the compound is studied by potentiodynamic polarization and weight loss studies. The surface morphology of the metal surface before and after corrosion is studied by SEM images. 2. EXPERIMENTAL Analytical Reagent (AR) grade chemicals (sd. fine chemicals, Mumbai) were used for the study. The aqueous solution of sulphuric acid and hydrochloric acid was used as the corrosive media. L-dopa was used as received and the structure of the L-dopa was used as corrosion inhibitor is as shown in Fig. (1).

Proton Transfer of Phenanthridone in the Lowest Excited Singlet State in Moderately Concentrated Mineral Acid Solutions

A modified form of the steady state treatment for the determination of excited state proton transfer rate constants was successfully applied to a variety of oxygen and nitrogen center aromatic excited acids. These compounds shared the characteristic of being more acidic in the lowest excited singlet state (S1) than in the ground electronic state (S0) and of requiring a concentrated mineral acid medium for protonation. This treatment was extended to phenanthridone, the lactam of 6-hydroxyphenanthridine, which is a weak enough base in the ground and the excited states to require moderately concentrated mineral acids for protonation, and becomes a stronger base in the excited state than it is in the ground state. Phenanthridone exists as an α-lactam and is a weaker base in the ground and excited states than the α-lactams derived from 2-hydroxypyridine, 2-hydroxyquinoline, and 1-hydroxyisoquinoline. It is also a much weaker base than the vinylogous γ-lactams. The reasons for this are discussed here.

EXTRACTION AND SEPARATION OF SOME 3d TRANSITION METAL IONS USING CYANEX 923

The paper embodies details on the extraction of different 3d transition metal ions namely Ti(IV), V(IV), Cr(III), Fe(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) in a toluene solution of Cyanex 923 from different mineral acid media. Effect of some important parameters such as the concentration of extractant and metal ion and nature of the diluent on the partition of Ti(IV), V(IV), Fe(III), Cu(II) and Zn(II) is examined. The extracting species of these metal ions are proposed and the loading capacity of Cyanex 923 is checked. The hydrolytic stability of the extractant solution has been examined and a procedure developed for its recycling. The extraction behavior of a number of commonly associated elements like Ce(IV), Al(III), Ga(III), Mg(II), Cd(II) and Pb(II) encountered in some of the matrices has also been investigated. Based on the distribution data it has been possible to achieve various binary separations of analytical interest involving 3d transition metal ions.

The Kinetics and Mechanism of Interaction of Fe40Ni40B20 Amorphous Metallic Alloys with Mineral Acid Media

Abstract The paper emphasizes the importance of amorphous metallic alloys thin films for magnetic coatings as well as their characterisation with respect to the mineral acid medium in a more qualitative way. The kinetics and mechanism of the interaction of Fe–Ni–B amorphous alloys films with various concentrations of mineral acids (o-phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid,) were studied. On the basis of the weighing method used we deduced that the overall physically and chemically complicated process consists of simultaneous formation of oxides on the surface of the thin films, their dissolution and moreover dissolution of the metal (Fe, Ni) and metalloid (B) elements through a tendency of all of them to react with hydrogen ions. It should be stressed that dissolution of the two-dimensional amorphous metallic alloys-ribbons significantly differs from such dissolution of the metal bulk systems.

Lactams in sulfuric acid. The mechanism of amide hydrolysis in weak to moderately strong aqueous mineral acid media

Lactams in sulfuric acid. The mechanism of amide hydrolysis in weak to moderately strong aqueous mineral acid media

Extraction and separation of mercury(II) using triisobutyl phosphine sulfide (TIBPS/Cyanex) as an extractant and its application to industrial effluent

Studies have been carried out on the extraction of Hg(II) along with Cr(III), Fe(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II) and Ag(I), from mineral acid media using TIBPS. The effect of different variables influencing extraction of Hg(II), such as, mineral acid used, nature of diluent, concentration of metal ion and extractant has been investigated. Based on the partition data some binary separations from Hg(II) have been achieved. The potential of the extractant for decontaminating Hg from paper industry effluent has been assessed.

Liquid—liquid extraction and reversed phase chromatographic behaviour of some 3d metal ions using bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301)

Studies have been carried out on the extraction behavior of some metal ions of the first transition series using bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) from mineral acid media. The effect of various parameters influencing the extraction such as the nature of the diluent, concentration of the acid and the extractant on the distribution has been investigated. Based on the distribution data some binary separations have been proposed. A flow sheet of a scheme is given for the recovery of manganese free cobalt from a spent catalyst used in the manufacture of poly(ethyleneterepthalate).

Extraction and separation of some 3d transition elements using Cyanex 925: application to zinc ores

The extraction behaviour of some 3d transition metal ions, along with Cd(II) and Pb (II), from mineral acid media using Cyanex 925 as an extractant was investigated. The effect of variables such as the concentration of mineral acid, metal ion and Cyanex 925 and the nature of the diluent on extraction was investigated. Optimum conditions were developed for the separation of Fe(III) and Zn(II) from various other metal ions. A method is proposed for the recovery of iron-free zinc from zinc blende and calcine.

Anion-exchange separation of uranium (VI) from thorium, zirconium, titanium, lanthanides and other elements in malonic and ascorbic acid media

The anion-exchange behaviour of uranium (VI) has been studied extensively in various mineral acid media [1], but similar studies with organic acid solutions are lacking. Although the negatively charged complex of uranium in acetic acid was studied [2, 3], very small amounts of uranium could be separated and phosphate interfered. Such studies were further extended to non-aqueous media [4]. The anionic ascorbate complex of uranium and thorium were separated by selective elution with 1 mol dm−3 hydrochloric acid and 3 mol dm−3 sulphuric acid [5–7] respectively. Some attempts were also made to study complexes of uranium in formic and propionic acid [1] and it was separated from copper and thorium in oxalate media [4]. However systematic studies in malonate and to some extent in ascorbate media are lacking. This paper presents such studies.

A Spectrophotometric Study OE Zirconium Complexes of 4,5‐Dihydroxyfluorescein

AbstractZirconium (IV) ions form violet red complex with 4,5‐dihydroxyfluorescein in fairly strong mineral acid medium. The reagent has been successfully applied as a metal indicator in the direct EDTA titration of zirconium.The complex formed by 4,5‐dihydroxyfluorescein and zirconium ions has been studied spectrophotometrically in 0.1M HCl solution. It is found that when an excess of metal ion is present, a violet red colored complex with metal‐ligand ratio of 1:1, (MR) is formed and when an excess of 4,5‐dihydroxyfluorescein is present a 1:2 complex (MR2) may be predominant. The 1:1 complex has maximum absorption at 510 mμ and the 1:2 complex has very low solubility and tends to precipitate out from the solution. Job's method, log‐ratio method and gravimetric method were used to establish the composition of complexes. The apparent stability constant of the 1:1 complex is found to be log Kh = 4.46 or Kh = 2.9×101 at pH 1.2.

Polarographic Behavior of Plutonium

O wing to the relatively high redox potential of Pu(III)_??_Pu(IV) system (Eo=+0.97 volt vs. THE) and PU(IV)_??_Pu(VI) system (Eo=+1.04 volt vs. NHE), 1) polarographic study of plutonium with the dropping mercury electrode (D.M.E.) is fairly limited to the plutonium complex ions formed in strongly complexing agents. Therefore, most of studies have been made with the solid electrodes; Harvey and others'examined the electrolytic reduction of plutonium in 1 N sulfuric acid and 1 N hydrochloric acid at the platinum electrode, but they could not obtain good reporducible results and hence the reliable half-wave potentials. The reason was attributed to the easiness of the disproportionation and the hydrolysis of Pu(IV) to form polymers which would deposit on the surface of the platinum electrode. Similarly, Cook and others3) have investigated the polarographic oxidation of Pu(III) in 1 N hydrochloric acid and determined the half-wave potential as +0.66 volt vs. SCE. Koyama4) also examined Pu(III) in 2 N nitric acid and 1 N hydrochloric acid using square wave polarograph. D.C. polarographic studies with the D. M. E . were made by Nebel and Schwabe5) and Cook and others3) in acetate, citrate and oxalate solutions, and A. C, polarographic studies in citrate solution by Milner and Wood.6) The results are summarized in the Table 1. In the present study, the authors have investigated the polarographic behaviors of Pu(III) and Pu(IV) in mineral acid media at the rotating platinum electrode (R.-P.E.). Special attention was paid to the control of the oxidation state of plutonium throughout the experiments.

Oscillopolarographic and polarographic investigation of the electrode reaction of Pu and U ions in carbonate solutions

Electrode-kinetic parameters for the one-electron irreversible step of Pu(IV)reduction in 1 M Na2CO3 are obtained by an oscillopolarographic technique. Conventional polargraphic data (half-wave potentials and diffusion coefficients) are given for the Pu(IV)/Pu(III) system in carbonate medium. Suggestions are made regarding the analytical determination of plutonium valence states in mineral acid media using the carbonate ion as complexing agent.

A study of the properties of lead tetraacetate as oxidizing and oxidimetric agent in analytical chemistry: I. Absorption spectra in the ultraviolet

The ultraviolet absorption spectra of lead tetraacetate solutions have been studied in mineral acid media. It has been found that in a medium of perchloric acid, lead tetraacetate solutions have a spectrum similar to that of bivalent lead, from which they differ only by the width of the absorption band. The formation of Pb(IV) phosphate complexes may be judged from variations in the absorption maximum position of tetravalent lead in phosphoric acid medium in dependence on the tetravalent lead and phosphoric acid concentration; these complexes result in a greater stability of tetravalent lead solutions in aqueous H 3PO 4 solutions. A comparison of the hydrochloric acid solution spectra with literature data has proved that in a medium containing more than 0.7 M HCl, lead tetraacetate (in concentrations of 2 · 10 −4 M) converts immediately into the complex ion [PbCl 6] 2−, decomposing later to chlorine and the lead(II) salt.

Chronopotentiometry of plutonium in mineral acid media

The chronopotentiometric behavior of plutonium(III), plutonium(IV), and plutonium(VI) at a platinum electrode in various mineral acid media has been studied in order to determine the diffusion coefficients of the different plutonium species, the effects of surface oxidation of the platinum electrode, and the possible analytical usefulness of chronopotentiometry for the determination of plutonium. The reduction of plutonium(IV) to plutonium(III) at a platinum wire cathode in perchloric, sulfuric, nitric, and hydrochloric acid solutions has been investigated. The relatively small diffusion coefficient of plutonium(IV) in each of these media plus the spontaneous chemical oxidation of the platinum electrode by plutonium(IV) result in a significant positive error in chronopotentiometry with concentrations of plutonium(IV) below O–O1 M. Chronopotentiograms for the oxidation of plutonium(III) to plutonium(IV) in sulfuric acid show one wave due to oxidation of plutonium(III) followed by a second wave attributable to the formation of a platinum oxide film. Plutonium(III) in sulfuric acid medium, chemically reduces the oxide film. The electro-oxidation of plutonium(III) in perchloric acid medium gives a well-defined chronopotentiogram at either pro-reduced or pre-oxidized electrodes. The chronopotentiometric reduction of plutonium(VI) in a 1 F perchloric acid solition proceeds, in a step-wise fashion, first to plutonium (V) and then to plutonium(III). For the experimental conditions employed, there was no evidence to show that plutonium(V) undergoes significant disproportionation in the perchloric acid medium.

The reduction mechanism of permanganic ion in mineral acid media

The reduction of MnO 4 − in nitric, perchloric and sulphuric acids on a bubbling platinum electrode and the influence of the acid anion on the behaviour of the permanganic ion in the presence of Mn(II) were studied. The rôle of Mn(II) and Mn (III) in the permanganate reduction process was fully investigated. Evidence is given for the formation of an Mn(III)-acid complex in sulphuric and perchloric acids. The presence of a surface film of MnMnO 3 on the platinum electrode and its reduction were observed and studied.

Polarography of niobium : Reduction in mineral acid media

The formation and interconversion of the nitro-, chloro-, perchloro- and sulphato-complexes of niobium in mineral acid media and the reduction of the nitro-complex have been studied. Conditions for a linear proportionality between the limiting current and the concentration of niobium in the microgram range have been worked out.

Photometric determination of traces of antimony with rhodamine b after sulfide precipitation

A method is described for the colorimetric determination of as little as a few tenths of a part per million of antimony in samples composed primarily of elements of atomic numbers 1–28 ( e.g., geo materials). Antimony is isolated by sulfide precipitation in mineral acid medium after reduction of ferric iron with hydroxylamine hydrochloride, with final determination by rhodamine B-benzene extraction. The procedure provides for the presence of gallium, thallium, tungsten and gold.