The investigation of the solvent extraction of molybdenum from concentrated solution of sulphuric acid

The solvent extraction of molybdenum(VI) from sulphuric acid solutions with di-(2-ethylhexyl)-phosphoric acid (HDEHP) and monododecylphosphoric acid (HDDP) in n-heptane has been studied (a) as a function of the concentration of sulphuric acid, molybdenum and the extractant; (b) in the presence of copper and zinc in the aqueous phase and (c) in the presence of tri-n-butylphosphate (TBP) in the organic phase. The distribution of the sulphuric acid between aqueous and organic phase has also been studied.     

Synthetic ceramic clay material as stationary phase in packed column supercritical fluid chromatography

Summary A novel inorganic synthetic clay material (SC) has been evaluated as the stationary phase in packed-column, supercritical fluid chromatography (SFC). The molecular recognition capability of the SC stationary phase in SFC for polycyclic aromatic hydrocarbons has been evaluated using carbon dioxide and carbon dioxide modified with methanol as the mobile phase. This recognition derives from the layer structure of the SC material which acts as a slit to distinguish non-planar solutes from the molecular-molecular interaction between solute and stationary phase and leads to smaller retention for non-planar solutes. The recognition capability is also dependent on the SFC conditions such as column pressure and column temperature.     

Influence of preferential adsorption of mobile phase on retention behavior of amino acids on the teicoplanin chiral selector

The adsorption behavior of two amino acids, i.e., l,d-threonine and l,d-methionine has been investigated on the chiral stationary phase (CSP)column packed with teicoplanin bonded to a silica support. The study has been performed under non-linear conditions of adsorption isotherm for various types of organic modifiers (methanol, ethanol, propan-2-ol and acetonitrile) in the reversed-phase mode. A heterogeneous adsorption mechanism of amino acids has been identified that was strongly affected by the nature of organic modifier. Generally, isotherm non-linearity and retention decreased with decrease of the modifier content in the mobile phase exhibiting a minimum at water-rich mobile phases. These trends were suggested to result from a combined effect of the mobile as well as the adsorbed phase composition. To determine the composition of the adsorbed phase the excess adsorption of modifiers in aqueous solutions has been measured and their binary adsorption equilibria have been quantified and compared. Strongly non-ideal behavior of solvents in the mobile phase and the adsorbed phase has been accounted for by activity coefficients. The fraction of the modifiers in the adsorbed phase decreased in the sequence: methanol, ethanol, propan-2-ol and acetonitrile.     

Extraction of uranium(VI) and thorium(IV) from nitric acid solution by N-alkylcaprolactam

Extraction of uranium(VI), thorium(IV) from nitric acid has been studied with N-octylcaprolactam and N-(2-ethyl)hexylcaprolactam. Distribution coefficients of U(VI), Th(IV) and HNO₃ as a function of aqueous NHO₃ concentration, extractant concentration and temperature have been studied. The compositions of extracted species, thermodynamic parameters of extraction have been evaluated. Third phase formation in extraction of U(VI) has been studied. Back extraction behavior of U(VI) and Th(IV) from the organic phase has also been tested. The results obtained are compared with those obtained by using TBP under the same experimental conditions.     

Tri-n-octylphosphine sulfide: : A selective organic extractant

Tri-n-octylphosphine sulfide (TOPS) has been investigated as the stationary phase in reversed-phase partition paper Chromatographie separations using nitric or hydrochloric acids as the mobile phase. TOPS has also been studied as an extractant for metal ions. Silver, mercury (II), and palladium (II) were found to have RF values of zero when nitric acid was used as the mobile phase. These same ions were also selectively extracted from aqueous nitric acid solutions. Gold(III), mercury(II), palladium (II), and platinum (IV) were found to have RF values of zero when hydrochloric acid was used as the mobile phase. However, only gold(III) and mercury(II) were extracted from aqueous hydrochloric acid solutions in liquid-liquid extraction systems. Several separations were successfully performed from 1 M nitric acid.     

Molecular precursor route to bulk and silica-supported Nb2Mo3O14 using water-soluble oxo-oxalato complexes

The catalytically relevant Nb2Mo3O14 phase has been prepared in bulk and silica-supported forms via the so-called "multiple molecular precursors method" from water-soluble oxo-oxalato complexes of Nb and Mo, (NH4)3[NbO(ox)3].H2O, and (NH4)2[MoO3(ox)].H2O. Thermal treatment of the mixed Nb-Mo precursor has been optimized for the formation of the pure Nb2Mo3O14 phase, either as bulk oxide or a silica-supported phase with high specific surface area. A characterization of the bulk phase obtained via the conventional ceramic route has also been carried out and a comparison has been made with the precursors route. According to this route, the Nb2Mo3O14 phase is shown to be formed in a pure form at 700 degrees C (i.e., 100 degrees C below the lowest temperature reported so far for the formation of the phase by the ceramic method). The supported samples have appreciable specific surface areas of 60-70 m(2) g(-1), much larger than those reached in the previous attempts under vacuum in sealed vials. The SEM and EDX analyses reveal a high dispersion of the desired phase on the silica support.     

Molecular organization of the lipid-bound EDTA—chromium(III) complex

Ethylenediaminetetraacetic acid bound to a lipid (dioctadecyldimethylammonium bromide) has been used as an immobilized ligand system for extracting chromium(III) salts from an aqueous solution. The morphology and nature of the aggregation of the metal-ion-bound lipid—ligand complex has been studied by transmission electron microscopy and differential scanning calorimetry. A strong dependence of the vesicle size on the gel—crystalline phase transition has been observed and the results are rationalized in terms of higher-ordered packing of the large vesicles below the phase transition temperatures.     

Studies on transport mechanism of Cr(VI) extraction from an acidic solution using liquid surfactant membranes

A mathematical model for analysing the extraction of Cr(VI) from aqueous acidic solution by emulsion liquid membrane using Aliquat 336 as extractant and NaOH as stripping agent has been presented. The existing models developed so far do not account for the existence of different forms of Cr(VI) ions in the aqueous phase depending on pH conditions. Accordingly, in the present model, reaction equilibrium has been considered instead of distribution coefficient to represent realistically the transport mechanism for this type of system through liquid surfactant membrane. Unlike other models, liquid–liquid equilibrium of sodium hydroxide-chloride of Aliquat 336 has also been considered. The carrier thus exists in the membrane phase in hydroxide and chloride forms and extraction of hexavalent chromium from the external phase proceeds by the two carriers. The validity of the model has been checked from comparison of the simulated curves and experimental data using chemical reaction equilibrium constant and D_eff/R² as fitting parameters.     

Extension of the Wilson-NRF Gibbs Energy Model in Correlating Vapor-Liquid and Liquid-Liquid Phase Behavior of Polymer-Polymer Aqueous Two-Phase Systems

In this work, the proposed model by Pazuki et al. based on the Local Composition Concept (LCC), has been used in correlating the vapor-liquid phase behavior of polymer solutions and the liquid-liquid phase behavior of aqueous two-phase systems. The Flory-Huggins model has been used as the combinatorial part of the proposed model, as well as the model proposed by Pazuki et al. was considered as the residual term. The proposed model has been used in correlating the vapor-liquid phase behavior for a number of PEG-Water systems at constant temperature. The results obtained from the proposed model have been compared with those obtained from the Poly-NRTL and the Poly-Wilson models. The results showed that the proposed model can accurately correlate the VLE data for PEG-Water systems. Also, the proposed model has been used to obtain phase behavior of aqueous two-phase systems for PEG-DEX-Water systems. The results obtained from the proposed model have been compared with those obtained from the UNIQUAC and the UNIQUAC-NRF models. The results showed that the proposed model can accurately correlate liquid-liquid phase behavior of aqueous two-phase systems than the UNIQUAC and the UNIQUAC-NRF models.     

Semi-xylenol orange and its purification by high-pressure liquid chromatography

By Mannich condensation of o-Cresol Red, iminodiacetic acid and formaldehyde, Semi-Xylenol Orange (SXO) has been prepared in a 10-hr batch-procedure with a yield of about 30%. From the crude product SXO has been isolated by reversed-phase HPLC with perchloric acid-acetone mixtures as the mobile phase and C(18)-bonded silica as the stationary phase. The SXO fraction was freed from accompanying perchloric acid by a second separation on the same column, with water as eluent. After elution with acetone, the SXO was crystallized by evaporation.     

Extraction of Fe(III) by n-dodecanoic acid dissolved in toluene

The extraction of Fe(III) from a nitrate medium of ionic strength 1.0 mol dm⁻³ by n-dodecanoic acid (HA) dissolved in toluene has been studied by distribution measurements. Experimental data, treated by different graphical and numerical methods, have been explained assuming the extraction of the species (FeA₃)₃ into the organic phase as well as the formation of a Fe(III)-HA complex in the aqueous phase.     

Interactions between surfactant capped CdS nanocrystals and organic solvent

The dispersibility of organic capped nanocrystals (NCs) in diverse solvents is one of the key factor of the success of such a class of nanostructured materials. In this work the α-cyclodextrins, mediated phase transfer has been considered as an effective procedure to direct the NC transfer from the organic solvent to water. The effect of the original organic solvent, namely hexane and chloroform, and of the ligand molecule coordinating CdS nanocrystal surface has been investigated by optical (UV-Vis, Photoluminescence, FTIR, Dynamic Light Scattering) and calorimetric techniques. The calorimetric investigation has been carried out by performing dilution experiments and the correlation between thermal effects and dilution ratio has been evaluated using the McMillan approach. The obtained results have provided relevant insight on the parameters driving the phase transfer process and on the NC mutual interaction, thus resulting valuable on the effectiveness of the phase transfer procedure.     

Kinetic analysis of the estrogen receptor alpha using RIfS

The label-free time-resolved reflectometric interference spectroscopy has been used to study the interaction of the human estrogen receptor alpha (ERa) and different types of ligands. Different possible sensor surface coatings including various estrogen derivatives were evaluated for their suitability for detection of ERa. The determination of the kinetic and thermodynamic constants was carried out for the interaction in the heterogeneous phase as well as for the interaction in homogeneous phase. In addition, the affinity of 11 ligands ranging from natural hormones and pharmaceuticals to endocrine disrupting chemicals (EDCs) has been determined with this label-free assay format.     

Studies on the solvent extraction of technetium from thiocyanate solutions in mineral acids

Technetium-99m, separated from fission molybdenum-99, has been studied as a component of liquid-liquid phase distribution equilibria. 5-(4-Pyridyl)nonane in a carrier diluent, benzene, has been used to study the distribution of the nuclide from thermodynamically suitable aqueous phases of electrolytes with and without sterically receptive thiocyanate ions. Efficient extraction of the metal can be accomplished in a variety of aqueous phase compositions. The separation factors with respect to molybdenum, under certain experimental conditions, are fairly high. The data have been utilized to effect clean separations of technetium from molybdenum.     

Biodegradable PEO/cellulose‐based solid–solid phase change materials

A series of poly(ethylene oxide) (PEO) blends with cellulose (CEL) or cellulose derivatives—carboxymethyl cellulose (CMC), cellulose acetate (CAC), and cellulose ether (CET)—has been investigated as phase change materials for thermal energy storage. For PEO/CEL blends solid–solid phase transition has been observed in the whole concentration's range; for PEO/CMC and PEO/CET blends solid–solid phase transition has been found for PEO content 25 or 50 and 25 wt%, respectively. Otherwise, solid–liquid phase transition takes place. MTDSC investigations revealed that for PEO/CEL and PEO/CMC blends transition the strongest recrystallization effect (as evidenced by exothermic effect in reversing heat flow) as melting process occurred. FTIR analysis shows a shift of the stretching vibration bands of both the proton‐donor O? H groups from CEL and PEO due to intermolecular hydrogen interactions between the blends' components. Copyright © 2010 John Wiley & Sons, Ltd.     

Liquid crystal dimers derived from naturally occurring chiral moieties: synthesis and characterization

Naturally occurring cholesterol and α-chloroalkanoyl units derived from natural α-amino acids (l-valine, l-leucine, and l-isoleucine) have been utilized to prepare three different series of nonsymmetric liquid crystal dimers. Tolane (diphenylacetylene), which is known to possess several promising structural features, has been chosen as the other mesogenic segment to covalently tether with cholesterol through a flexible spacer. In each series, the terminal α-chloro ester group attached to the tolane unit is kept constant, while the length and parity of the spacer have been varied; specifically, three dimers comprising even-parity spacer of varying length, and one compound with an odd-parity spacer constituted a series. The phase behavior of these dimers has been ascertained mainly by polarizing microscopic and calorimetric studies. Except one, all the 11 dimers display enantiotropic mesomorphism. Within the series, clearing temperatures exhibit a dramatic odd-even effect wherein the even-parity dimers possess higher values. In general, the dimers comprising α-chloro ester group derived from l-valine and l-leucine stabilize chiral nematic and/or smectic phase/s, while the compounds with terminal group resulting from l-isoleucine show twist grain boundary phase additionally; this implies that the nature of the α-chloro ester group influences the phase behavior. Notably, an odd-parity dimer with an α-chloro ester group derived from l-valine exhibits a transition from an intercalated smectic A phase to a monolayer (unknown) smectic phase, as evidenced by optical, calorimetric, and X-ray diffraction studies. As representative case, a dimer has been screened for antimicrobial activity by disc diffusion method; a notable activity has been found against some microbes.     

Phase separation and extraction with acetonitrile for sample preparation in HPLC analysis

Summary Acetonitrile can be salted-out from aqueous solution by adding tetrabutylammonium perchlorate. This phase separation method has been used for the extraction of the Fe(III)-4,7-diphenylphenanthroline complex into acetonitrile followed by direct injection onto an ODS column. The Fe complex is separated by using 9:1 acetonitrile/water as a mobile phase. The proposed reversed-phase high-performance liquid chromatography has been applied to the determination of Fe in serum.     

Studies on the liquid-liquid extraction of iron(III) and titanium(IV) with 3-phenyl-4-benzoyl-5-isoxazolone

The extraction behaviour of iron(III) and titanium(IV) from acidic chloride solutions has been investigated using 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) in xylene as an extractant. The results demonstrate that these metal ions are extracted into xylene as Fe(PBI)(3) and TiO(PBI)(2). The equilibrium constants of the extracted complexes have been deduced by non-linear regression analysis by taking into account complexation of metal ion with inorganic ligands in the aqueous phase and all plausible complexes extracted into the organic phase. IR and proton NMR ((1)H NMR) spectra were used to further clarify the nature of complexes extracted into organic phase. The effect of the nature of the diluent on the extraction of iron(III) and titanium(IV) has been studied and correlated with dielectric constants. The extraction behaviour of titanium(IV) has also been compared with that of other metal ions, viz. magnesium(II), vanadium(V), chromium(VI), iron(III), manganese(II), zinc(II) and zirconium(IV), which are associated with the titanium in waste chloride liquors of the titanium-mineral-processing industry.     

Calcium carbonate phase transformations during the carbonation reaction of calcium heavy alkylbenzene sulfonate overbased nanodetergents preparation

The preparation and application of overbased nanodetergents with excess alkaline calcium carbonate is a good example of nanotechnology in practice. The phase transformation of calcium carbonate is of extensive concern since CaCO(3) serves both as an important industrial filling material and as the most abundant biomineral in nature. Industrially valuable overbased nanodetergents have been prepared based on calcium salts of heavy alkylbenzene sulfonate by a one-step process under ambient pressure, the carbonation reaction has been monitored by the instantaneous temperature changes and total base number (TBN). A number of analytical techniques such as TGA, DLS, SLS, TEM, FTIR, and XRD have been utilized to explore the carbonation reaction process and phase transformation mechanism of calcium carbonate. An enhanced understanding on the phase transformation of calcium carbonate involved in calcium sulfonate nanodetergents has been achieved and it has been unambiguously demonstrated that amorphous calcium carbonate (ACC) transforms into the vaterite polymorph rather than calcite, which would be of crucial importance for the preparation and quality control of lubricant additives and greases. Our results also show that a certain amount of residual Ca(OH)(2) prevents the phase transformation from ACC to crystalline polymorphs. Moreover, a vaterite nanodetergent has been prepared for the first time with low viscosity, high base number, and uniform particle size, nevertheless a notable improvement on its thermal stability is required for potential applications.     

Recovery of plutonium and americium from laboratory acidic waste solutions using tri-n-octylamine and octylphenyl-N-N- diisobutylcarbamoylmethylphosphine oxide

Plutonium from acidic waste solutions has been recovered quantitatively using tri-n-octylamine (TnOA) in xylene and americium using a mixture of octylphenyl-N-N- diisobutylcarbamoylmethylphosphine oxide (CMPO) and TBP in dodecane by extraction and extraction chromatographic methods. The Pu ( IV ) TnOA species extracted into the organic phase from higher nitric acid concentrations has been confirmed as (R(3)NH)(2)Pu(NO(3))(6) (where R(3)N = TnOA by employing slope analysis as well as spectrophotometric studies.