Organic Diluents Research Articles

The Effect of Organic Diluent on the Extraction of Eu(III) by HEH[EHP

ABSTRACTBecause there are fewer tools available to probe the interactions therein, the effect of the fundamental chemistry of the organic diluent on solvent extraction equilibria has been under-characterized relative to the aqueous. As a result, diluents for solvent extraction are often selected for an application not for their utility as a medium for reaction, but for other (often equally) important reasons (like low flammability). To begin to improve this imbalance in the science, twenty different diluents have been used in a study of the extraction of radiotracer 152/154Eu3+ from dilute nitric acid solutions using the extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]). To increase the utility of the study and to honor the memory of Professor Jan Rydberg, this investigation was conducted by a cadre of comparatively inexperienced separation scientists (who are as a result no longer inexperienced separation scientists) as a radioanalytical chemistry and solvent extraction educational exercise. Slope analysis was used to determine the apparent stoichiometry of the extracted metal complex. The results discussed in the following indicate that, while the pH dependence exhibits the expected three H+ exchanged per metal ion extracted, the extractant dependence suggests that the number of protonated extractant molecules in the extracted complex changes with the organic diluent. The experimentally observed “extractant dependency” ranges from 2.5 to 3.0 dimer equivalent molecules per extracted metal ion. Ironically, in the diluents exhibiting the highest apparent M:(HA)3 stoichiometry, HEH[EHP] extracts Eu3+ less efficiently. Europium luminescence spectroscopy was used to probe for changes in the first coordination sphere of the complex in different diluents. A model and conceptual framework for understanding these observations is described.

Selective extraction of copper from Cu-Zn sulfate media by new generation extractants

The selective recovery of copper(II) from Cu-Zn sulfate solutions using solvent extraction and N,N-dialkyl-N′-hydroxypyridine-2-carboximidamides as extractants was investigated. Three compounds were synthesized and their extractability toward copper(II) and zinc(II) was studied. The influence of process parameters such as the pH of aqueous phase, shaking time, diluent type and also extractant’s structure and concentration on efficiency of both metals ions extraction was presented. Results indicated that the equilibrium pH and type of the organic diluent had the biggest impact on the copper(II) extraction efficiency, its selectivity over zinc(II), and the stoichiometry of formed copper complex. Obtained experimental data were used to develop a method of copper(II) extraction from Zn-Cu sulfate solution composed of 40.9 g/L Zn(II) and 1.2 g/L Cu(II). A flowsheet was tested in laboratory-scale reactors and the conducted test confirmed the possibility to selective recover of Cu(II) over Zn(II), and the concentration of Cu(II).

CO2 solubility and mass transfer in water-lean solvents

Shifting from aqueous to water lean solvents has been evaluated as a mean for increasing the mass transfer rates in regular chemical solvents with amines. An array of amines (monoethanolamine, 2-methylpiperazine and N-methyl diethanolamine) and diluents (sulfolane, ethylene glycol, 1-methylimidazole, dimethyl sulfoxide, N-methyl-2-pyrrolidinone) has been analyzed. Addition of organic diluents seem to generally induce both a shift in chemical equilibrium and an increase in mass transfer rates for a fixed CO2 partial pressure, though not necessarily for a fixed CO2 loading. However, these relative advantages in terms of mass transfer rates decrease the more loaded the water lean solvent is. The equilibrium shift caused by organic diluents has been evaluated in terms of de-stabilization of the species in the solvent, which for monoethanolamine-based solvents can be easily related to a decrease in dielectric permittivity. However, this analysis indicates that such treatment is insufficient for other types of water-lean solvents, suggesting that different kinds of intermolecular interactions should also be considered in future studies.

Poly(ionic liquid) augmented membranes for π electron induced separation/fractionation of aromatics

Novel polyionic liquid augmented membranes were fabricated using pressure assisted self-assembly and employed for π- electron cloud mediated separation of aromatics from their aliphatic homologues, which are otherwise difficult to achieve by conventional size exclusion basedmembrane filtration. The electron withdrawing/electron donating substituents on aromatic ring, which can lead to an overall change in the π cloud density on aromatic ring, can be employed in fractionating such aromatics such as benzene, toluene, p-xylene, nitrobenzene. High π electron could density due to extended conjugation over more than one aromatic ring was also utilized in fractionation of benzene, naphthalene, anthracene and phenanthrene. The most interestingly, these PIL augmented membranes were demonstrated to have preferential separation of one stereoisomer over other. The preferential separation of trans-stilbene over cis-stilbene was attributed to stereo-chemical arrangement assisted deviating from planarity of aromatic moieties of the later resulting deterioration of overall extended conjugation and π electron cloud delocalization. These PIL membranes also exhibited the preferential separation of regioisomers of bipyridine. These PIL augmented membranes were found to stable in presence of mainly non-polar organic diluents due to the π- stacking interaction between the aromatic phenylic moieties of the polyimide support and aromatic pyridinium moieties of the poly (ionic liquid) polymers.

A fluoride-free liquid-liquid extraction process for the recovery and separation of niobium and tantalum from alkaline leach solutions

The production of high purity niobium (Nb) or tantalum (Ta) compounds still relies on processes that require highly acidic conditions and concentrated HF or NH4F solutions. Recent progress in the chemistry of group V elements, along with the evolution of the environmental concerns, call for the development of more sustainable industrial processes for these strategic elements. In sharp contrast with the historical fluoride approach chosen by the Nb and Ta refining industry, there has been a recent surge in the literature concerning the chemistry of these elements in diluted alkaline or oxalate media. We here propose an innovative liquid-liquid extraction process that is amenable to separate Nb and Ta from alkaline feed solutions, can be operated at low acidity and that does not require any fluoride-based chemical. The developed strategy is as follows: first, Nb and Ta are co-extracted from their alkaline solution (pH 12) using a quaternary ammonium salt (Aliquat® 336) dissolved in an organic diluent; then, Nb is selectively back-extracted in a mixture of diluted nitric and oxalic acids; and finally, Ta is stripped in a diluted nitric media. The process also affords purifying Nb from Ti, Fe and Na. Following an optimization at laboratory scale, the full process has been validated during continuous running tests (160 h at 1.4 L h−1) using industrial Nb-Ta caustic solutions coming from the development of the so-called Maboumine process. The developed process works at room temperature, low acidity ([H+] < 1 M), exhibits high recovery yields, and allows producing Nb2O5·nH2O with purity higher than 99.5%. The process also yields a tantalum product (Ta2O5·nH2O with >20 wt% Ta) even when starting from a diluted feed (39 ppm Ta). The proposed strategy paves the way for new Nb and Ta hydrometallurgical processes operating under mild chemical environments and represents a concrete alternative to the current fluoride-intensive industrial methods.

Efficient removal of Indigo dye from aqueous solution by an innovative method of emulsion liquid membrane

Extraction of Indigo dye from aqueous solution is studied in this research using Emulsion Liquid Membrane (ELM). Water/Oil (W/O) emulsion was prepared by mixing aqueous phase with organic phase at an elevated homogenizing speed. H2SO4 and Hexane were used as internal stripping agent and organic diluent respectively. Monooleate Sorbitan commonly known as Span-80 was used as surfactant in organic phase. This W/O emulsion was later mixed with external feed phase containing Indigo dye to make W/O/W double emulsion. Stability of the membrane was optimized by experimenting different operating parameters. The ELM prepared under the optimum conditions was finally used to remove Indigo dye from aqueous solution. The parametric study of the process parameters affecting the extraction efficiency was also performed. Under optimum conditions of parameters like volume ratio of emulsion/feed, dye concentration in feed, stirring speed and contact time of two phases, the extraction of Indigo dye was found to be 99%. Therefore, ELM was found to be an attractive and effective technique for the removal of dyes.

CO2 Solubility and Mass Transfer in Water Lean Solvents

Abstract Shifting from aqueous to water lean solvents has been evaluated as a mean for increasing the mass transfer rates in regular chemical solvents with amines. An array of amines (monoethanolamine, 2-methylpiperazine and N-methyl diethanolamine) and diluents (sulfolane, ethylene glycol, 1-methylimidazole, dimethyl sulfoxide, N-methyl-2-pyrrolidinone) has been analyzed. Addition of organic diluents seem to generally induce both a shift in chemical equilibrium and an increase in mass transfer rates for a fixed CO2 partial pressure, though not necessarily for a fixed CO2 loading. However, these relative advantages in terms of mass transfer rates decrease the more loaded the water lean solvent is. The equilibrium shift caused by organic diluents has been evaluated in terms of de-stabilization of the species in the solvent, which for monoethanolamine-based solvents can be easily related to a decrease in dielectric permittivity. However, this analysis indicates that such treatment is insufficient for other types of water-lean solvents, suggesting that different kinds of intermolecular interactions should also be considered in future studies.

Parametric optimization of green synergistic reactive extraction of lactic acid using trioctylamine, Aliquat336, and butan-2-ol in sunflower oil by response surface methodology

A novel green synergistic reactive extraction technique for the removal of lactic acid (LA) from aqueous solution was explored. Response surface methodology (RSM) was applied to optimize the process variables for LA synergistic reactive extraction using a mixture of trioctylamine and Aliquat336 as extractants. During this present investigation, 2-butanol and sunflower oil were used as organic and green diluent. Systematic investigation has been carried out to obtain the optimum process conditions viz. initial LA concentration, pH of aqueous solution, extractant ratio, extractant concentration, solvent ratio, phase ratio, temperature, stirring speed, and contact time for maximizing the LA distribution coefficient (KD) and extraction efficiency (%, η). The highest experimentally achievable LA distribution coefficient (KD) and extraction efficiency (%) at optimized process conditions were found to be in close agreement with those predicted by numerical optimization using RSM. Thus, the results of present finding have been shown a great ability of sunflower oil as an economic and environmentally friendly green solvent for LA extraction.

Isobaric vapor-liquid equilibrium for binary system related to the organophosphoric extractant of D2EHPA + n-dodecane and TBP + n-dodecane at 0.13, 2.40 and 6.67 kPa

Vacuum distillation is selected as a technique for recycling in order to separate the mixture of a hydrometallurgical organophosphoric extractant from an organic diluent because of their low volatility and high selectivity. The experimental isobaric vapor-liquid equilibrium (VLE) data for the binary systems of di-(2-ethylhexyl) phosphoric acid (D2EHPA) + n-dodecane and tri-butyl phosphate (TBP) + n-dodecane were measured at pressures of 0.13, 2.40 and 6.67 kPa, using a glass vapor-liquid equilibrium ebulliometer. VLE data were generated in the form of T−x−y diagrams and checked for thermodynamic consistency via Herington area test and Van Ness point test. Data for all mixtures met the criteria of thermodynamic consistency and were found suitable for process modeling. At each pressure point, no azeotropic phenomenon was observed. Reduction in pressure of the system can significantly enhance the relative volatility and separation efficiency of both mixtures. At all pressure points, D2EHPA was noted to be more separable than TBP. Additionally, the experimental VLE results for all systems were found to have a good correlation with Raoult's law, Wilson and nonrandom two-liquid (NRTL) models. The corresponding binary interaction parameters were obtained by minimizing the deviation between the experimental and the calculated vapor phase composition and total pressure.

Extraction of hexavalent chromium by environmentally benign green emulsion liquid membrane using tridodecyamine as an extractant

In this present investigation, the potentiality of rice bran oil (RBO) and tridodecylamine (TDDA) to be incorporated as the key constituents in the formulation of new environmentally benign green emulsion liquid membrane (GELM) to extract hexavalent chromium (Cr(VI)) from aqueous feed phase was explored. The pertinent constituents of GELM were RBO (70%, v/v) and hexane (30%, v/v) as green and organic diluent, respectively; TDDA (0.75 (%, v/v) of diluent solution) as carrier; emulsifying agent (span 80: 1.75 (%v/v) of diluent solution); and NaOH as internal reagent. The investigation of optimum process conditions for various parameters has resulted in 0.45pH of aqueous solution, 0.25 [M] internal phase concentration, 2:1 (v/v) treat ratio, 0.40 (v/v) phase ratio, 550 (rpm) agitation speed, 25 (min) extraction time, and 30±2 (°C) feed phase temperature. The highest achievable extraction efficiency (η, %) and dynamic stability (min) of GELM have been obtained as 97±2% and 150±2min, respectively under these optimum process conditions. The present finding has revealed that RBO as a green diluent has huge capability to be further utilized for the extraction of Cr (VI) from various industrial effluent streams.

Extraction behavior of cesium from nitric acid medium with calix[4]-bis[(4-tert-butyl-1,2-phenylene)-crown-6

Cesium, one of the heat-emitting fission elements contained in high active liquid waste, deserved separation. Calixbiscrown is a class of chemical compounds, promising in the cesium extraction. In this study, calix[4]-bis[(4-tert-butyl-1,2-phenylene)-crown-6] (CalixBBC for short) was synthesized by a multi-step scheme. The cesium extraction study was carried out using CalixBBC in two organic diluents such as chloroform and o-nitroanisole, which were used as electron-deficient and electron-rich surrogate dilutions, respectively. The effects of HNO3 concentration, mixing time, temperature were investigated using a batch technique. Comparing with chloroform, o-nitroanisole was in favor of cesium extraction. Both extractions strongly relied on HNO3 concentration in the range of 0.4–6.0 M. The pseudo-second-order model fitted the extractions well. Both extractions were spontaneous, exothermal processes. The foreigner metal ions showed little influence on the extraction. The stoichiometry of cesium and CalixBBC in the complex was 1:1.

Extraction of REE(III), U(VI), and Th(IV) from Nitric Acid Solutions with Carbamoylmethylphosphine Oxides in the Presence of Dinonylnaphthalenesulfonic Acid

The extraction of REE(III), U(VI), and Th(IV) from nitric acid solutions with solutions of carbamoylmethylphosphine oxides (CMPOs) considerably increases in the presence of dinonylnaphthalenesulfonic acid. The stoichiometry of the extractable complexes was determined, and the influence of the aqueous phase composition, kind of organic diluent, and CMPO structure on the efficiency of the extraction of the metal ions was analyzed.

2,6-Bis(1-alkyl-1H-1,2,3-triazol-4-yl)-pyridines: selective lipophilic chelating ligands for minor actinides

Starting from the promising minor actinides (MA) affinity showed by the water-soluble ligands (PyTri-polyols) with the 2,6-bis[1H-1,2,3-triazol-4-yl]-pyridine chelating unit, different attempts were made to functionalize the same N3-donor set with alkyl chains in the 1-position of triazole nuclei to obtain novel lipophilic extractants endowed with comparable MA selectivity. Solubility in organic diluents was found to be the main limitation to the development of efficient lipophilic ligands, thus resulting in less efficient extractants with respect to their hydrophilic analogues and sometimes impairing the selectivity evaluation. Interestingly, the ethyl hexyl derivative (PTEH) showed adequate extraction capability and a MA selectivity comparable to that of the hydrophilic PyTri family.

ENRICHMENT OF IN VIVO EFFICACY OF CATECHIN RICH EXTRACT WITH THE APPLICATION OF NANOTECHNOLOGY

Objective: The primary goal of this study was to convert a natural catechin-rich extract into nanoparticles by using a biodegradable and non-toxic polymer Eudragit L 100 to address the various biopharmaceutical problems of catechin.Methods: Nanoparticles were prepared by emulsion solvent evaporation technique using Eudragit L 100 in increasing concentration. Optimization of processing conditions like a selection of organic solvents, diluent and surfactant concentrations, drug and polymer ratio and method of drying to increase the biological efficiency were duly attempted. Parameters such as dynamic light scattering, zeta potential, SEM and energy-dispersive X-ray spectroscopy were assessed for the evaluation of nanoparticles.Results: The entrapment efficiency was found to be between 35-45 % with methanol compared to other organic solvents. The zeta potential values of all the formulations were in the range of±30 mV to±60 mV) which confirms moderate to good stability. A rapid or ‘burst’ effect of the drug release in pH 6.8 buffer showing 92 % in the first 30 min which gradually decreased to 52 % by the end of 180 min but in the pH 7.4, the release was found to be moderate. SEM and DLS indicated particles were of spherical shape lying in a nanometer range of 100 to 200 nm with a proportional influence of polymer on the particles size.Conclusion: Nanoformulations were found to be more stable and confirmed the presence of major elements such as carbon and oxygen. The findings collectively indicate that it may be worthwhile to apply nanotechnology for the design of an advanced oral dosage form for an enhanced bioavailability and biological efficacy.

Emulsion breakage behaviour on chromium (VI) removal using emulsion liquid membrane containing quaternary ammonium compounds

Environmental pollution caused by heavy metals such as chromium, nickel, and lead has become a serious worldwide issue due to their threats to humans, animals and plants as well as to the stability of the overall ecosystem. Its removal from effluents such as electroplating rinse wastewater and tannery effluents is of primordial importance. In this study, the emulsion liquid membrane (ELM) technology was employed as a remediation technique that capable of removing Cr (VI) efficiently from wastewater where extraction and stripping processes are performed in a single operation. The ELM is consists of trioctylmethylammonium chloride (Alamine 336) as an extractant, palm oil as an organic diluent, sodium hydroxide (NaOH) as a stripping solution and sorbitan monooleate (Span-80) as a surfactant to stabilize the emulsion phase. The effect of operational parameters such as the agitation speed, phase contact time, extractant concentration and stripping agent concentration were studied to optimize the conditions for emulsion stability and maximum removal of chromium. The best removal efficiency was obtained at 350 rpm of agitation speed and 3 minutes of phase contact time with 0.04 M Alamine 336 as extractant and 0.1 M NaOH as stripping agent. In this condition, the maximum removal efficiency of 100% was obtained with a minimum breakage rate of 5%.

Extraction of U(VI), Th(IV), and REE(III) from Nitric Acid Solutions with 2,6-Bis(diphenylphosphorylmethyl)pyridine N-Oxide

The extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO3 solutions in the form of complexes with 2,6-bis(diphenylphosphorylmethyl)pyridine N-oxide (I) was studied in relation to the kind of organic diluent and to the HNO3 concentration in the equilibrium aqueous phase. The stoichiometry of the extractable complexes was determined. With respect to the ability to extract Th(IV) and REE(III), compound I considerably surpasses tetraphenylmethylenediphosphine dioxide and tetraalkyl-substituted analogs of I.

Evaluation of the emulsion liquid membrane performance on the removal of gadolinium from acidic solutions

This work evaluates the performance of emulsion liquid membrane (ELM) for the extraction of gadolinium(III) from acidic solution. The ELM was made up of di-(2-ethylhexyl) phosphoric acid (D2EHPA) as carrier, Span 80 (sorbitol monooleate) as emulsifying agent, commercial kerosene as organic diluent and Nitric acid as stripping phase. Important physical and chemical variables affecting the ELM performance for the extraction of gadolinium(III) such as carrier concentration, mixing time, surfactant concentration, agitation speed, initial pH of the feed phase, internal phase concentration, treatment ratio, and feed phase concentration were systematically investigated. Results indicated that the highest gadolinium(III) extraction can be attained after 10 min of mixing by using 0.05 M D2EHPA, 1.5% (v/v) Span 80, 1.0 M nitric acid as stripping phase at feed phase pH of 2, agitation speed of 180 rpm, and treatment ratio of 1:10. At the optimum condition, simultaneous quantitative extraction (>99%) and stripping (>79%) of gadolinium were achieved. Furthermore, the overall mass transfer coefficient was calculated and the results revealed that the extraction was interfacially controlled.

Mechanistic study for the simultaneous determination of metformin and teneligliptin in human plasma using hydrophilic interaction liquid chromatography-MS/MS.

A simple, selective and sensitive hydrophilic interaction liquid chromatography-MS/MS method is developed for the simultaneous determination of metformin (MET) and teneligliptin (TEN) in human plasma using deuterated internal standards. The mechanism of retention of analytes was studied by varying the proportion of organic diluent, buffer strength, pH of the mobile phase and temperature. The results showed a mixed-mode mechanism comprising of hydrophilic (partition) and electrostatic interaction (ion exchange) for MET and essentially hydrophilic for TEN. The linear calibration curves were established in the concentration range of 1.0-1000ng/ml for MET and 0.50-750ng/ml for TEN. The method was applied to determine plasma concentration of MET and TEN in healthy subjects.

Ion-Pair Based Solvent Extraction of Rhodium (III) from Malonate Medium Using 4-heptylaminopyridine as an Extractant: Application to Alloys and Environmentally Relevant Matrices

The main task of this research article is the extraction and subsequent separation of rhodium(III) from malonate medium (0.02 M) at pH 7.5 by a newly synthesized chelating reagent, 4-heptylaminopyridine(4-HAP). The reagent has been used to build up novel analytical procedure its determination at trace level. During the optimization of the present method, the influence of a variety of parameters like pH of medium, 4-HAP concentration, weak organic acid concentration, organic diluents, shaking time and stripping agents on the extraction of rhodium(III) was studied. From the slope analysis the probable composition of extracted species was found to 1:2:1 (metal: malonate: extractant). The effect of different interfering ions is studied together with the suitable masking agents. The applicability of the method was checked by separating rhodium(III) from binary and ternary metal ion mixtures, alloys and some environmentally relevant matrices.

Extraction of REE(III), U(VI), and Th(IV) from Nitric Acid Solutions with Carbamoylmethylphosphine Oxides in the Presence of Bis[(trifluoromethyl)sulfonyl]imide Ions

Extraction of microamounts of REE(III), U(VI), and Th(IV) with solutions of carbamoylmethylphosphine oxides (CMPOs) in organic diluents from aqueous HNO3 solutions containing lithium bis[(trifluoromethyl) sulfonyl]imide (LiTf2N) was studied. The efficiency of the REE(III), U(VI), and Th(IV) extraction from nitric acid solutions with CMPO solutions considerably increases in the presence of Tf2N– ions in the aqueous phase. The stoichiometry of the extractable complexes was determined, and the influence of the structure of the CMPO molecule, kind of organic diluent, and aqueous phase composition on the efficiency of the U(VI), Th(IV), and REE(III) extraction into the organic phase was considered.