Aqueous Mineral Acid Solutions Research Articles

Extraction and sorption recovery of rhenium(VII) using oligodentate β-аminophosphoryl compounds

The interphase distribution of microquantities of ReO4– between aqueous solutions of mineral acids and solutions of oligodentate β-aminophosphoryl compounds in organic solvents was studied. The stoichiometry of the extracted complexes was determined, the influence of the concentration of HClO4, HNO3, HCl and H2SO4 in the aqueous phase, the structure of the extractant and the nature of the organic solvent on the efficiency of the transition of ReO4– ions into the organic phase was considered. The possibility of selective extraction and concentration of Re(VII) with a complexing sorbent obtained by non-covalent attachment of tris[bis(2-diphenylphosphorylethyl)aminoethyl]amine on the surface of the macroporous polymer Amberlite XAD7HP was demonstrated.

Image analysis data for the study of the reactivity of the phases in Nd-Fe-B magnets etched with HCl-saturated Cyphos IL 101.

Three phases can be distinguished in Nd‒Fe‒B permanent magnets: a Nd2Fe14B matrix grain phase, a Nd-rich grain boundary phase and a Nd-oxide phases. Common reaction models for leaching, such as the shrinking-particle model, cannot simply be applied to composite Nd‒Fe‒B permanent magnets because of the different chemical reactivities of the crystalline phases mentioned above. Etching the surface of a Nd‒Fe‒B magnet to expose its microstructure to electron microscopy is a necessary practice to correlate the microstructure itself to the specific properties of the magnets. Aqueous solutions of mineral acids are often used for etching purposes. However, these solutions are too low viscous to easily control the etching front and they show little selectivity in the etching process. In our work, the ionic liquid Cyphos IL 101 was used to etch bulk magnets instead of aqueous HCl solutions. The bulk Nd‒Fe‒B magnets were first polished, then exposed to a solution of 3 M HCl in Cyphos IL 101 for different times and at different temperatures. Afterwards, the etched Nd‒Fe‒B magnets were washed with ethanol and acetone. The results were examined via scanning-electron microscopy and image analysis. A commercial software, ImageJ®, was employed for image analysis. The latter technique was used to correlate the etched area (%area) or the grain and oxide size to the etching temperature or the etching time. The grain or the oxide size were calculated as Feret diameter. Image analysis revealed to be a necessary tool to support and correct the findings first suggested by the simple scanning-electron microscopy. The data presented in this article might be reused to corroborate a new reactivity order of the three Nd‒Fe‒B phases, different from that traditionally reported in literature, which is – from the most to the least reactive – grain boundary > oxides > the Nd2Fe14B grain phase.

Extraction and sorption preconcentration of rhenium with the use of 2-phosphorylphenoxyacetamides

Interfacial distribution of micro amount of ReO4 - between aqueous solutions of mineral acids and solutions of 2-phosphorylphenoxyacetamides in dichloroethane has been studied. Stoichiometry of extracted complexes has been determined; the effect of HNO3, HCl, and H2SO4 concentration in aqueous phase, extractant structure, and organic solvent nature on the efficiency of ReO4 - ions transfer into organic phase has been considered. It has been shown that Re(VII) can be selectively recovered and concentrated with complexing sorbent obtained by the noncovalent binding of 2-[2-(diphenylphosphoryl)-4-ethylphenoxy]-N,N-dioctylacetamide on the surface of macroporous polymer Amberlite XAD7HP.

Extractive and sorption preconcentration of rhenium(VII) with the use of phosphoryl-containing podands

Interphase distribution of micro amounts of ReO 4 − between aqueous solutions of mineral acids and solutions of phosphoryl-containing mono-, di-, and tripodands, derived from 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene in dichloroethane was studied. The stoichiometry of extracted complexes was determined, the effect of HNO3, HCl, and H2SO4 concentration in aqueous phase and the nature of organic solvent on the efficiency of transition of ions into organic phase was considered. The growth of the number of phosphoryl groups in podand molecule enhances its extraction ability toward Re(VII). The possibility of selective recovery and preconcentration of Re(VII) with complexing sorbent obtained by noncovalent binding of phosphoryl-containing podand on the surface of macroporous polymer Amberlite XAD7HP was shown.

Investigation of the acid-catalyzed hydrolysis and reaction mechanisms ofN,N′-diarylsulfamides using various criteria

The mechanism of acid-catalyzed hydrolysis of a series of p-substituted N,N′-diarylsulfamides was investigated in aqueous mineral acid solutions. Rate profiles, reaction activation parameters, catalytic order of strong acids, solvent isotope effects, and analysis of the kinetic data by the excess acidity method suggest a change in the mechanism from A2 to A1. While the hydrolysis proceeds with an A2 mechanism in low acidity regions, an A1 mechanism takes place in high acid concentrations. Copyright © 2013 John Wiley & Sons, Ltd.

Extractive and sorption preconcentration of rhenium(VII) ions with the use of bis(diphenylphosphoryl)-substituted aza podand

Interfacial distribution of trace amounts of ReO4− ions between aqueous solutions of mineral acids and solutions of diphosphoryl-substituted aza podand [Ph2P(O)CH2CH2OCH2CH2]2NBu (I) in dichloroethane was studied. The stoichiometry of extracted complexes was determined, the influence of HClO4, HNO3, HCl, and H2SO4 concentration in aqueous phase and the nature of organic solvent on the efficiency of transition of ReO4− ions into organic phase was considered. Aza podand I shows larger extraction ability toward Re(VII) than monophosphorylated amines. The possibility of selective extraction and preconcentration of ReO4− ions by a complex-forming sorbent obtained by the noncovalent binding of compound I on the surface of carbon nanotubes was shown.

Extraction of metal ions from aqueous solutions of mineral acids with crown ether-ionic liquid systems

The extraction of U(VI), Sr, and Cs from solutions of mineral acids (HNO3, HCl) with a crown ether, cis-syn-cis-dicyclohexyl-18-crown-6 (DCH18C6-A), dissolved in ionic liquids (ILs), 1-butyl-3-methyl-imidazolium derivatives (bmimPF6, bmimBF4, bmimTf2N), was studied. The best physicochemical characteristics (solubility in the aqueous phase, viscosity, hydrophobicity, etc.) are exhibited by a solution of DCH18C6-A in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (bmimTf2N). The metal distribution ratios (D M) in the extraction with a 0.01 M DCH18C6-A solution are 80 for CsNO3, 78 for CsCl, and 162 for Sr(NO3)2. With an increase in the HNO3 and HCl concentrations, D M decreases, and with 1 M acids it does not exceed 1. The U(VI) extraction from nitric acid solutions with a 1 M solution of DCH18C6-A in bmimTf2N initially increases with an increase in the aqueous phase acidity, with D U(VI) reaching 5.4 in 4 M HNO3, but then decreases in the interval 4–8 M HNO3, whereas in the extraction with a 1 M solution of tributyl phosphate (TBP) in bmimTf2N D U(VI) monotonically increases with an increase in the HNO3 concentration to 8 M. From hydrochloric acid solutions, U(VI) is extracted with solutions of DCH18C6-A in bmimTf2N with the D U(VI) values characteristic of solutions of DCH18C6-A in nonpolar organic diluents. On the whole, ILs as solvents exhibit unusual properties in the extraction of alkali and alkaline-earth elements from neutral solutions and of U(VI) with TBP from concentrated nitric acid solutions.

Investigation of scientific foundations and development of technology of complex processing of worked-out hydrofinishing catalysts

Physicochemical foundations of the complex processing of worked-out hydrofinishing catalysts are investigated experimentally. The kinetics and mechanism of dissolution of Mo(VI) oxide from the worked-out catalyst in aqueous solutions of mineral acids and sodium carbonate are investigated with the use of models of formal heterogeneous kinetics in order to select the reagent and leaching conditions. The behavior of the main components of the system during the sintering of alumina residue with sodium carbonate is determined, and the optimal conditions are determined based on a thermodynamic simulation of sintering with the use of the Astra software complex. A production flow chart of the industrial processing of worked-out hydrofinishing catalysts while obtaining ammonium paramolybdate, alumina, or coagulants is obtained.

Synthesis and Properties of 5‐Diazoimidazoles and Imidazolyl‐5‐diazonium Salts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Simple Synthesis of Pyridine Aminophosphinic Acids and Pyridine Aminophosphine Oxides. The Unusual Cleavage of Pyridylmethyl-( N -benzylamino)-phenylphosphinic Acids and Phosphine Oxides in Acidic Solutions

Pyridine aminophosphinic acids were synthesized in reaction of N-(benzyl)-pyridylmethylimines with ethyl phenylphosphinate, in the presence of bromotrimethylsilane. Pyridine aminophosphine oxides were obtained in excellent yields by treatment of the corresponding imines with diphenylphosphine oxide. Among these compounds, the 2-pyridyl and 4-pyridyl derivatives were subject to a simple cleavage in aqueous mineral acid solutions. Products of the cleavages were N-(pyridylmethyl)benzylamines and phenylphosphonic (or diphenylphosphinic) acid, respectively.

Synthesis and properties of 5-diazoimidazoles and imidazolyl-5-diazonium salts

Diazotization of 4-R-5-aminoimidazoles (R = CONHAr, CONHAlk, morpholinocarbonyl, or piperidinocarbonyl) with sodium nitrite in aqueous solutions of mineral acids afforded the corresponding 5-diazoimidazoles, whereas the reactions in concentrated tetrafluoroboric acid produced imidazolyl-5-diazonium salts. In the solid phase, diazonium salts are transformed into the corresponding diazo compounds.

17O and1H chemical shifts of water in solutions of some ammonium salts: evaluation of the anionic effect on the17O and1H chemical shifts of water in aqueous solutions of mineral acids

In this paper the 1H chemical shifts δ(1Hav) and the water 17O chemical shifts δ(17OH2) in aqueous solutions of NH4Cl, NH4Br, NH4I, NH4NO3, NH4ClO4, (NH4)2SO4, NH4H2HPO4 and (NH4)2HPO4 are presented and discussed. For δ(17OH2), values shift towards higher frequencies, relative to pure water δ(17OH2). NH4NO3 and NH4ClO4 change the water oxygen chemical shift value only slightly as compared with the other solutes. Both positive and negative δ(1Hav) values relative to pure water as an external reference were observed. The strong contribution of the conjugate base anion of the acids to the measured 17O and 1H chemical shift values of water was found. Using the ammonium ion as standard, the anionic effect on these parameters was estimated and subtracted from the measured δ(17OH2) and δ(1Hav) values for the aqueous solutions of these acids.

Pyrrolidine Carboxaldehyde Hydrohalide Catalyzed Halogenations of Aliphatic Aldehydes

Abstract Efficient methods for the direct chlorination or bromination of aliphatic aldehydes to their corresponding α,α-dihalo aldehydes in high yield and purity are unknown. Many approaches have suffered from one or more of the following, formation of byproducts, aldol condensations incomplete conversions and losses through tedious workup procedures. Early investigations have shown that the vapor phase chlorination of aliphatic ketones has produced good yields of 2-chloro ketones,(1) while the vapor phase chlorination of aliphatic aldehydes has resulted in the formation of acid chlorides.(2) One of the first successful acid catalyzed chlorinations of propionaldehyde was reported by Dick(3) who obtained 50–60% yields of 2,2-dichloropropionaldehyde accompanied by aldol condensations and polyhalogenated trioxanes. The reaction was carried out in standardized aqueous mineral acid solutions and the product was isolated by means of a laborious azeotropic distillation. The use of sulfuryl chloride in the presence of a catalytic amount of diphenyl sulfide for the chlorination of aldehydes was shown by Dalman(4) to give 60–70% yields of 2-chloro and 2,2-dichlorinated aldehydes. Clean separations i.e. products free of sulfuryl chloride could only be obtained by distillation with a spinning band column at high reflux ratios.

Extraction of molybdenum(VI) by 4-(5-nonyl)pyridine in benzene from aqueous mineral acid solutions containing thiocyanate ions

Extraction of Mo(VI) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiocyanate ions has been investigated at room temperature (23±2°C). From mineral acid (HCl, HNO3, and H2SO4) solutions alone Mo(VI) is not extracted quantitatively while the presence of small amounts of KSCN in the system augments the extraction by a large factor. Stoichiometric studies indicate that ion-pair type complexes (NPyH)2·[MoO2(SCN)4] are responsible for the extraction. Separation factors determined at fixed extraction conditions (0.1M Npy/C6H6−0.1M acid +0.2M KSCN) reveal that Ag(I), Cu(II), Co(II), Zn(II), Hg(II) and U(VI) are co-extracted while a clean separation from alkali metals, alkaline earths and some transition metals like Ln(III), Zr(IV), Hf(IV), Cr(III), Cr(VI) and Ir(III) is possible. Some of the complexing anions like oxalate, citrate, acetate, thiosulfate or ascorbate do not affect the degree of extraction of Mo(VI) allowing it to be recovered from diverse matrices.

Search for optimal conditions for the extraction of thiosulfate complexes of Cu(II) by 4-(5-nonyl)pyridine from aqueous mineral acid solutions

Solvent extraction of Cu(II) by 4-(5-nonyl)pyridine (NPy) in benzene from mineral acid solutions containing thiosulfate ions has been studied at room temperature (23±2°C). Mineral acid solutions alone constitute an aqueous phase from which Cu(II) is not extracted. Addition of small amounts of thiosulfate ions augments the extraction to an extent that quantitative recovery is possible. Stoichiometric studies reveal the involvement of ion-pair type complexes (NPy·H)2·Cu(S2O3)2 which are responsible for extraction. Stability constants lg Kex for this complex are 7.2±0.2; 9.1±0.2 and 9.5±0.2 for HCl, HNO3 and H2SO4, respectively. The presence of 0.01 mol/l of some complexing ions like ascorbate, acetate, citrate, oxalate, tartrate or iodide does not affect the extraction, thus allowing the recovery of the metal from diverse matrices. Under optimal conditions (0.1M NPy in benzene-0.1M HNO3 or H2SO4+0.01M S2O3−2 or 0.5M HCl+0.05 M S2O3−2) a clean separation from some elements, e.g. Cs(I). Co(II), Fe(III), Eu(III), Ce(III), Se(IV) and Cr(VI) can be achieved.

Vinyl ether hydrolysis. XV. Methyl β,β-di-tert-butylvinyl ether: buttressing steric effects

The highly congested molecule, methyl β,β-di-tert-butyl vinyl ether, undergoes reaction in dilute aqueous mineral acid solutions by a normal vinyl ether hydrolysis mechanism and gives an unrearranged aldehyde product. The tert-butyl groups retard the rate of hydrolysis, but the effect of cis and trans substituents is not cumulative; this is attributed to a repulsive nonbonded interaction, relieved in the course of reaction, between the ether oxygen atom and the cis-tert-butyl group buttressed by the trans-tert-butyl group.

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.

Mesoionic compounds. Part 7. Acid catalysed hydrolysis of ethyloxatriazole

The acid catalysed hydrolysis of ethyloxatriazole has been studied in aqueous solutions of mineral acids at 120 °C. Analyses of the data by Bunnett and Bunnett–Olsen criteria and entropies of activation are consistent with a gradual change-over from an A-2 mechanism at low acid concentration to a predominantly A-1 mechanism at high acidities. Values of the kinetic solvent isotope effect indicate the involvement of a modified A-2 mechanism in which a proton transfer is partially rate determining.

Mesoionic compounds. Part 6. Acid-catalysed hydrolysis of alkyloxatriazoles

The acid-catalysed hydrolyses of isopropyl- and methyloxatriazole have been studied in aqueous solutions of mineral acids at 120°C. Analyses of the data by Bunnett–Olsen criteria, solvent deuterium isotope effects and entropies of activation are consistent with an A-1 mechanism for the hydrolysis of isopropyloxatriazole. On the other hand the hydrolysis of methyloxatriazole involves a rate-determining proton-transfer mechanism.

PH-dependence of the fluorescence of acridone in aqueous mineral acid solutions

pH-dependence of the fluorescence of acridone in aqueous mineral acid solutions