Acid In Aqueous Phase Research Articles

Magnetic Assisted Separation of Trivalent F- Elements from Dilute Nitric Acid Medium

The thio glycolamic acid functional groups were chemically anchored on magnetic iron oxide (Fe3O4) particles and it was characterized by TG-DTA, XRD, and scanning electron microscopy. The extraction behavior of hazardous Am(III) and Eu(III) from dilute nitric acid medium in the sorbent (abbreviated as Fe-SDGAH) was studied. The effect of various parameters such as the duration of equilibration, and concentrations of nitric acid and europium ion in aqueous phase on the distribution coefficient (Kd) of Am(III) and Eu(III) was studied. The studies indicated the possibility of using Fe-SDGAH particles for magnetic separation of Eu(III) and Am(III) with high decontamination factors.

Studies on the Extraction of Actinides Using a Solvent Containing D2EHiBA in Room Temperature Ionic Liquids: Unusual Extraction of the Tetravalent Ions

The extraction behavior of U(VI), Pu(IV), and Np(IV) from nitric acid medium has been studied using branched chain di(2-ethylhexyl)isobutyramide (D2EHiBA) dissolved in different room temperature ionic liquids (RTILs) [Cnmim][NTf2] (where n = 4, 6, or 8). Uranium extraction (DU) increased gradually with aqueous phase acidity for the three RTILs used in this study suggesting solvation mechanism. There was a reversal in the extraction behavior of Pu(IV) and Np(IV) from nitric acid medium using D2EHiBA dissolved in RTILs as solvents as compared to the behavior reported in the molecular diluent, n-dodecane, which shows negligible extraction of these metal ions. The extraction of Pu(IV) increased with aqueous phase acidity in different RTILs in the order: [C8mim][NTf2] > [C6mim][NTf2] > [C4mim][NTf2]. The distribution ratio values of these metal ions followed the order: DPu(IV) ≥ DNp(IV) > DU(VI) using D2EHiBA as extractant suggesting that RTILs can modify the extraction behavior of extractants.

A highly stable and efficient magnetically recoverable and reusable Pd nanocatalyst in aqueous media heterogeneously catalysed Suzuki C–C cross‐coupling reactions

Surface modification of Fe3O4 nanoparticles with triethoxyethylcyanide groups was used for the immobilization of palladium nanoparticles to produce Fe3O4/Ethyl‐CN/Pd. The catalyst was characterized using Fourier transform infrared, wavelength‐dispersive X‐ray, energy‐dispersive X‐ray and X‐ray photoelectron spectroscopies, field‐emission scanning electron and transmission electron microscopies, and X‐ray diffraction, vibrating sample magnetometry and inductively coupled plasma analyses. In this fabrication, cyano groups played an important role as a capping agent. The catalytic behaviour of Fe3O4/Ethyl‐CN/Pd nanoparticles was measured in the Suzuki cross‐coupling reaction of various aryl halides (ArI, ArBr, ArCl) with phenylboronic acid in aqueous phase at room temperature. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture by applying an external magnet device and recycled seven times without any significant loss in activity. Copyright © 2015 John Wiley & Sons, Ltd.

Solvent impregnated carbon nanotube embedded polymeric composite beads: An environment benign approach for the separation of rare earths

An environment benign process for the separation of rare earths has been delineated for the first time by developing polyethersulfone based composite beads through phase inversion method, where the use of hazardous organic diluents could be circumvented. The porosity and pore structure of these beads were controlled through different additives, of which, polyvinyl alcohol and multiwall carbon nanotubes proved to be the most efficacious. The extraction efficiency of rare earths was ameliorated by four fold with the application of the developed nanotube incorporated beads. The influence of various process parameters, namely, aqueous phase acidity, metal ion concentration, presence of other competitive ions and temperature on the separation of representative yttrium ion has been elaborated in the present investigation. The experimental results attribute to the excellent stability and reusability of the developed beads. The feasibility of employing this novel technology in large scale has been established by successful operation in continuous column mode. The developed assay exhibits profound application towards a greener approach due to the elimination of hazardous organic diluents and prevention of significant organic extractant loss during the process of recovery of rare earths from aqueous media.

Dysprosium sorption by polymeric composite bead: Robust parametric optimization using Taguchi method

Polyethersulfone-based beads encapsulating di-2-ethylhexyl phosphoric acid have been synthesized and evaluated for the recovery of rare earth values from the aqueous media. Percentage recovery and the sorption behavior of Dy(III) have been investigated under wide range of experimental parameters using these beads. Taguchi method utilizing L-18 orthogonal array has been adopted to identify the most influential process parameters responsible for higher degree of recovery with enhanced sorption of Dy(III) from chloride medium. Analysis of variance indicated that the feed concentration of Dy(III) is the most influential factor for equilibrium sorption capacity, whereas aqueous phase acidity influences the percentage recovery most. The presence of polyvinyl alcohol and multiwalled carbon nanotube modified the internal structure of the composite beads and resulted in uniform distribution of organic extractant inside polymeric matrix. The experiment performed under optimum process conditions as predicted by Taguchi method resulted in enhanced Dy(III) recovery and sorption capacity by polymeric beads with minimum standard deviation.

Synthesis and Evaluation of N,N′-dimethyl-N,N′-dicyclohexyl-Malonamide (DMDCMA) as an Extractant for Actinides

A malonamide based extractant, i.e., N,N′-dimethyl-N,N′-dicyclohexyl-malonamide (DMDCMA) was synthesized in a single step and tested for the extraction of several actinide ions such as Am(III), U(VI), Np(IV), Np(VI), Pu(IV), Pu(VI), etc., from nitric acid medium. The extractant was soluble in phenyltrifluoromethylsulphone (PTMS or FS-13) unless stated otherwise. The effect of various experimental parameters, such as the aqueous phase acidity (0.01–3 M HNO3), nature of the acid, oxidation states of the metal ions, ligand concentration, nature of the diluent and temperature on the extraction behavior of metal ions was studied. The extracted Am(III) species was determined from slope analysis method as [Am(NO3)3(DMDCMA)2]. The extraction of the metal ions was found to increase with the aqueous phase acidity. The temperature variation studies allowed the calculation of the heat of the two-phase extraction reaction as well as the corresponding extraction constants. These studies revealed that DMDCMA showed good extraction for all the actinide metal ions investigated, and have the advantage of single stage synthesis and easier purification protocol.

Highly Selective Solvent Extraction of Zn(II) and Cu(II) from Acidic Aqueous Chloride Solutions with Mixture of Cyanex 272 and Aliquat 336

Selective solvent extraction of zinc(II) and copper(II) from aqueous acidic chloride solutions by mixture of bis(2,2,4-trimethylpentyl)phosphinic acid (Cyanex 272) and trioctymethylammonium chloride (Aliquat 336) in kerosene has been investigated. Detailed studies have been conducted by varying pH, hydrochloric acid, and chloride concentrations in aqueous phase as well as extractants concentration in organic phase. A full and high selective solvent extraction of zinc(II) over copper(II) from acidic chloride solutions has been achieved by 0.1 M Cyanex 272 and 0.06 M Aliquat 336 in kerosene while efficient Zn(II) stripping has been performed by using 1 M sulphuric acid. The following selectivity coefficients of zinc(II) over Cu(II) (SZn/Cu) during their solvent extraction from 1 M NaCl at pH 0.5 by Cyanex 272, Aliquat 336, and their mixture were found to be equal to: 1.7, 62, and 3162, respectively.

Simultaneous determination of multi-mycotoxins in palm kernel cake (PKC) using liquid chromatography-tandem mass spectrometry (LC-MS/MS)

Palm kernel cake (PKC) is a useful source of protein and energy for livestock. Recently, it has been used as an ingredient in poultry feed. Mycotoxin contamination of PKC due to inappropriate handling during production and storage has increased public concern about economic losses and health risks for poultry and humans. This concern has accentuated the need for the evaluation of mycotoxins in PKC. Furthermore, a method for quantifying mycotoxins in PKC has so far not been established. The aims of this study were therefore (1) to develop a method for the simultaneous determination of mycotoxins in PKC and (2) to validate and verify the method. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using an electrospray ionisation interface (ESI) in both positive- and negative-ion modes was developed for the simultaneous determination of aflatoxins (AFB1, AFB2, AFG1 and AFG2), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), fumonisins (FB1 and FB2), T-2 and HT-2 toxin in PKC. An optimum method using a 0.2 ml min–1 flow rate, 0.2% formic acid in aqueous phase, 10% organic phase at the beginning and 90% organic phase at the end of the gradient was achieved. The extraction of mycotoxins was performed using a solvent mixture of acetonitrile–water–formic acid (79:20:1, v/v) without further clean-up. The mean recoveries of mycotoxins in spiked PKC samples ranged from 81% to 112%. Limits of detection (LODs) and limits of quantification (LOQs) for mycotoxin standards and PKC samples ranged from 0.02 to 17.5 μg kg−1 and from 0.06 to 58.0 μg kg−1, respectively. Finally, the newly developed method was successfully applied to PKC samples. The results illustrated the fact that the method is efficient and accurate for the simultaneous multi-mycotoxin determination in PKC, which can be ideal for routine analysis.

The potential risk assessment for different arsenic species in the aquatic environment

The different toxicity characteristics of arsenic species result in discrepant ecological risk. The predicted no-effect concentrations (PNECs) 43.65, 250.18, and 2.00×103μg/L were calculated for As(III), As(V), and dimethylarsinic acid in aqueous phase, respectively. With these PNECs, the ecological risk from arsenic species in Pearl River Delta in China and Kwabrafo stream in Ghana was evaluated. It was found that the risk from As(III) and As(V) in the samples from Pearl River Delta was low, while much high in Kwabrafo stream. This study implies that ecological risk of arsenic should be evaluated basing on its species.

Solvent extraction of thorium from nitrate medium by TBP, Cyanex272 and their mixture

The extraction behavior of thorium(IV) has been investigated with tri-butyl phosphate (TBP) and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex272) in kerosene from nitrate medium. The effect of operating variables including time, aqueous phase acidity (pH), extractant concentration and temperature were investigated. This study also examined the synergistic enhancement of the extraction of thorium(IV) from nitrate medium by mixtures of TBP and Cyanex272 for the first time. The optimum synergistic enhancement factor of 3.86 was obtained at a Cyanex272/TBP molar ratio of 1:4.

Magnetically palladium catalyst stabilized by diaminoglyoxime-functionalized magnetic Fe3O4 nanoparticles as active and reusable catalyst for Suzuki coupling reactions

A Pd supported on diaminoglyoxime (DAG)-functionalized Fe3O4 (Fe3O4/DAG/Pd) hybrid materials was fabricated for the first time. In this fabrication, DAG played an important role as a capping agent. The immobilized palladium catalyst was an efficient catalyst without added phosphine ligands for the Suzuki cross-coupling reaction of several aryl halides with phenylboronic acid in aqueous phase at room temperature. The yields of the products were in the range from 70% to 98%. The prepared heterogeneous nanocatalyst was characterized by XRD, XPS, EDS, FT-IR, ICP, FESEM, VSM and TEM. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture by applying an external magnet device and recycled eight times without any significant loss in activity.

A kinetic study on solvent extraction of samarium from nitrate solution with D2EHPA and Cyanex 301 by the single drop technique

The reactive extraction of Sm(III) from aqueous nitrate solution with D2EHPA and Cyanex 301 in kerosene was investigated by single drop column method. Various parameters affecting the extraction process including the column height, nozzle diameter and concentration of extractant, hydrogen ions and Sm(III) were studied. The rate equations for the extraction of Sm(III) with two reagents were obtained on the basis of the slope analysis data. The rate of samarium extraction was found to be directly proportional to the concentration of Sm(III), D2EHPA and Cyanex 301 and inversely proportional to aqueous phase acidity. The extraction of Sm(III) increases with the increase in rising drop diameter and indicate that the extraction is mainly controlled by diffusion mechanism.The extraction rate of samarium with Cyanex 301 was lower than that of D2EHPA, therefore D2EHPA extractant provided faster extraction rate and it would be useful in industrial continuous extraction process.

Diglycolamic acid modified silica gel for the separation of hazardous trivalent metal ions from aqueous solution

The surface of the silica gel was modified with diglycolamic acid moieties and the product (Si-DGAH) was characterized by elemental analysis, TG–DTA, 1H and 29Si NMR and scanning electron microscopy (SEM). The adsorption behavior of hazardous americium (III) and europium (III) in Si-DGAH was studied from aqueous nitric acid medium to examine the feasibility using the modified silica for the separation of Am(III) and Eu(III) from aqueous wastes. In this context, the effect of various parameters such as the duration of equilibration, and concentrations of europium, nitric acid, sodium nitrate and diethylenetriaminepentaacetic acid (DTPA) in aqueous phase, on the distribution coefficient (Kd) of Am(III) and Eu(III) was investigated. The distribution coefficient of ∼103mL/g (>99.9% extraction) was obtained for both Am(III) and Eu(III) at pH 3, and the Kd values decreased with increase in the concentration of nitric acid. Rapid kinetics of extraction in the initial stages of equilibration, followed by the establishment of equilibrium occurred within 30min. The extraction data were fitted into Langmuir adsorption model and the apparent europium extraction capacity was determined. Europium loading capacity of the sorbent was determined at various feed pH by column method. The study indicated the possibility of using diglycolamic acid-modified silica for the separation of Eu(III) and Am(III) from aqueous wastes.

Biphasic Enantioselective Partitioning of <i>R</i>,<i>S</i>-Omeprazole Enantiomers Using Chiral Extraction

Enantioselective partitioning of racemic omeprazole enantiomers was studied using a biphasic recognition chiral extraction system. Hydrophilic hydroxypropyl-ڂ-cyclodextrin in aqueous phase and hydrophobic D-tartaric acid hexyl ester in organic phase as chiral selectors which preferentially recognize (R)-omeprazole enantiomer and (S)-omeprazole enantiomer, respectively. Different experimental variable parameters could affect the chiral extraction efficiency. The largest distribution coefficientskS,kRand separation factorځwere obtained at concentrations o f 0.1 mol/L HP-ڂ-CD and 0.2 mol/L D-tartaric acid hexyl ester, which were 47.38, 58.65 and 1.24, respectively.kRis always larger thankSwhen using different kinds of tartaric acid derivatives as chiral selectors in organic phase. The present study also reveal the mechanism of biphasic recognition chiral extraction forR,S-omeprazole enantiomers.

Equilibria of the quaternary system including phosphoric acid, hydrochloric acid, water and tri-n-butyl phosphate at T = 303.2 K and atmosphere pressure

The equilibrium data of quaternary system {phosphoric acid+hydrochloric acid+water+tri-n-butyl phosphate (TBP)} was determined at T=303.2K and atmospheric pressure by the method of components analysis. It was investigated experimentally over the mass concentration range (1 to 11)% hydrochloric acid and (9 to 21)% phosphoric acid in the initial aqueous phase. With increasing concentration of phosphoric acid, the distribution coefficients of phosphoric acid changed gently, and with the increased content of hydrochloric acid, the distribution coefficients of phosphoric acid increased, while the separation factor of hydrochloric acid decreased with the increase of phosphoric acid concentration. The experimental tie-line results were correlated with the non-random two-liquid (NRTL) activity coefficient model, and the reliability of the experimental values was determined through the Hand and Othmer-Tobias plots. The Othmer-Tobias and NRTL models are suitable for the system.

Correlation of νOHSpectral Shifts of Phenol–Benzene O–H···π Hydrogen-Bonded Complexes with Donor’s Acidity: A Combined Matrix Isolation, Infrared Spectroscopy, and Quantum Chemistry Study

O-H stretching infrared fundamentals (νOH) of phenol and a series of fluorophenol monomers and their 1:1 complexes with benzene have been measured under a matrix isolation condition (8 K). Spectral analysis reveals that ring fluorine substitutions have little effect on phenolic νO-H as long as the molecules in the matrix are fully dispersed as monomers. The substitution effects are pronouncedly manifested only when the phenols are complexed with benzene, and the measured shift in phenolic νOH from the monomer value varies from ∼78 cm(-1) in phenol to ∼98 cm(-1) in 3,4,5-trifluorophenol. The spectral shifts are found to display a linear correlation with the aqueous phase acid dissociation constants (pKa) of the phenols. The spectral changes predicted by electronic structure calculations at several levels of theory are found to be consistent with the observations. Such correlations are also found to exist with respect to different energetic, geometric, and other electronic structure parameters of the complexes. Atoms in Molecules (AIM) analysis shows a distinct bond critical point due to accumulation of electron density at the hydrogen-bonding site. The variation of electron densities both on the hydrogen bond as well the donor O-H group is in accordance with the experimentally observed νO-H of the various fluorophenol-benzene complexes. Partitioning of binding energies into components following the Morokuma-Kitaura scheme shows that the π-hydrogen-bonded complexes are stabilized predominantly by dispersion interactions, although electrostatics, polarization, and charge-transfer terms have appreciable contribution to overall binding energies. NBO analysis reveals that hyperconjugative charge-transfers from the filled π-orbitals of the hydrogen bond acceptor (benzene) to the antibonding σ*(O-H) orbital of the donors (phenols) display correlations which are fully consistent with the observed variations of spectral shifts. The analysis also shows that the O-H bond dipole moments of all the phenolic species are nearly the same, implying that local electrostatics has only a little effect at the site of hydrogen bonding.

Extraction of U(VI) by a novel polyazamacrocycle extractant

The extraction of U(VI) from nitrate solution was investigated using a polyazamacrocycle-type C8-cyclen ligand as extractant. The effect of aqueous phase acidity, temperature, ligand concentration, nitrate concentration and irradiation dose on the distribution ratio of U(VI) was studied. The extraction of U(VI) was significantly affected by pH due to the protonation of C8-cyclen and the hydrolysis of U(VI). Uranyl nitrate was extracted via neutral complex reaction mechanism, forming a 1:1 complex with C8-cyclen. The extraction is an exothermic reaction with entropy reduction. U(VI) could be easily stripped from the loaded organic phase by sodium carbonate solution. C8-cyclen showed good stability toward γ-irradiation. No obvious decomposition was observed under the dose of 104 Gy. A small amount of C8-cyclen decomposed at the dose of 105 Gy and the distribution ratio of U(VI) increased to some extent.

Extraction of some Hexavalent Actinide Ions from Nitric Acid Medium using Several Substituted Diglycolamides

Several substituted diglycolamides, namely TPDGA, THDGA, TODGA, and TDDGA, were evaluated in a comparative study on the extraction of hexavalent actinide ions such as UO22+, NpO22+, and PuO22+ from nitric acid medium. The acid extraction constants (KH) for the diglycolamides were determined to be 3.8 ± 0.6, 1.6 ± 0.1, 4.1 ± 0.4, and 1.4 ± 0.2 for TPDGA, THDGA, TODGA, and TDDGA, respectively. Though metal ion extraction generally increased with increasing the feed acid concentration, the nature of the extracted species changed with aqueous-phase acidity. While complexes of the type MO2(NO3)2·nL (where L is the diglycolamide extractant and n is 1 and 2) were found to be extracted at 1 M HNO3, the average number of ligand molecules associated with the complex decreased to ˜1 when the nitric acid concentration increased to 3 M. These results have great significance from the actinide separation point of view, as the actinides ions can be made virtually inextractable by adjusting their oxidation state. The thermodynamic parameters were also calculated, which indicated spontaneous reactions with large exothermicities.

Application of reactive oily bubbles to bastnaesite flotation

Reactive oily bubble, defined as air bubbles covered with a thin layer of kerosene containing collectors, was used to float a major rare earth mineral, bastnaesite from rare earth ores. Both fatty acid and hydroxamic acid were used to generate reactive oily bubbles. The flotation of bastnaesite with reactive oily bubble was investigated by zeta potential, zeta potential distribution and induction time measurement and micro-flotation tests. The results showed a quicker attachment to bastnaesite and a stronger collecting power of reactive oily bubbles containing 100ppm fatty acid than conventional air bubbles, resulting in an enhanced bastnaesite recovery. The flotation recovery of bastnaesite by reactive oily bubbles containing hydroxamic acid is lower than that by conventional air bubble flotation where the bastnaesite was pre-conditioned by hydroxamic acid in aqueous phase. During induction time measurement, no attachment is observed between bastnaesite particles and reactive oily bubbles containing hydroxamic acid, illustrating the importance of collector type in reactive oily bubble flotation technology. These findings suggest the superior performance of reactive oily bubble technique than conventional bastnaesite flotation method only when proper collector is used to generate the reactive oily bubbles.

Theoretical calculations of the pK a values of 1-aryl-4-propylpiperazine drugs in aqueous solution

Theoretical calculations were carried out to predict the aqueous-phase acidities of a series of drug 1-phenyl-4-propylpiperazine and its derivatives. The performances of the density functional theory(DFT) methods B3LYP and B3P86, solvation models[the polarized continuum model(PCM) and the conductor-like polarized continuum model(CPCM)], and the basis set effect were tested. A comparison between the theoretical and experimental pK a values for para-substituted 1-phenyl-4-propylpiperazines reveals that the accuracy of B3LYP is better than that of B3P86, and the basis set 6-31++G(d,p) and the CPCM model are suitable for calculating pK a values of the substituted 1-phenyl-4-propylpiperazine. For the investigated compounds, a reasonable agreement between the experimental and calculated pK a values was also observed.