Back Extraction Efficiency Research Articles

Extraction of lithium from salt lake brine with triisobutyl phosphate in ionic liquid and kerosene

Three ionic liquids(ILs), namely, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide with the triisobutyl phosphate(TIBP) and kerosene system were respectively used to extract lithium ion from salt lake brine with a high concentration ratio of magnesium and lithium experimentally. Results indicate that the highest extraction selectivity for lithium was obtained with IL 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)-sulfonyl]imide. The effects of solution pH and phase ratio R(O/A) on the extractive step and the influence of acid concentration of the stripping solution and R(O/A) on the back extraction step were also investigated systematically. The single-step extraction efficiency of lithium ion was 83.71% under the optimal extraction conditions, and the single-step back extraction efficiency was 85.61% with a 1.0 mol/L HCl in 1.0 mol/L NaCl medium as stripping agent at R(O/A)=2. The liquid-liquid extraction mechanism and the complex of the ligand with lithium were proposed.

Process optimization for reverse micellar extraction of stem bromelain with a focus on back extraction

In the current study, reverse micellar extraction (RME) for the purification of stem bromelain was successfully achieved using the sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane system. A maximum forward extraction efficiency of 58.0% was obtained at 100 mM AOT concentration, aqueous phase pH of 8.0 and 0.2 M NaCl. Back extraction studies on altering stripping phase pH and KCl concentration, addition of counter-ion and iso-propyl alcohol (IPA) and mechanical agitation with glass beads indicated that IPA addition and agitation with glass beads have significant effects on extraction efficiency. The protein extraction was higher (51.9%) in case of the IPA (10% v/v) added system during back extraction as compared to a cetyltrimethylammonium bromide (100 mM) added system (9.42%). The central composite design technique was used to optimize the back extraction conditions further. Concentration of IPA, amount of glass beads, mixing time, and agitation speed (in rpm) were the variables selected. IPA concentration of 8.5% (v/v), glass bead concentration of 0.6 (w/v), and mixing time of 45 min at 400 rpm resulted in higher back extraction efficiency of 45.6% and activity recovery of 88.8% with purification of 3.04-fold. The study indicated that mechanical agitation using glass beads could be used for destabilizing the reverse micelles and release of bromelain back into the fresh aqueous phase.

Steric hindrance effects in tripodal ligands for extraction and back-extraction of Ag+

A novel series of tripodal ligands with thiophenylether arms connected to an anchoring nitrogen has been investigated. Seven tripodal ligands were synthesized by combining methyl, isopropyl, and tert-butyl residue bearing thiophenylether sites as groups with different steric hindrance effects. The tripodal ligands allowed for the extraction of Ag+ ions from the aqueous phase into a chloroform phase by forming 1 : 1 complexes with Ag+. Back-extraction was performed with 1 M HNO3 aqueous solution. Each ligand showed different extraction and back-extraction efficiency for Ag+, affected by changes in steric hindrance caused by the various combinations of sidearms. These results are further supported by X-ray single crystal structural analysis.

Partition coefficients of ionizable solutes in aqueous micellar two-phase systems

The potential of micellar cloud point systems for extraction processes has been demonstrated for a broad range of different applications. The extraction is based on the phenomenon that aqueous non-ionic surfactant solutions split into two phases if the temperature is increased beyond a certain temperature, the so called cloud point temperature (CPT). Recently, aqueous micellar two-phase systems have been implemented in a counter current extraction. However, almost equally important for large scale applications is the recovery of the solute from micellar solutions, which remains a serious concern considering micellar cloud point systems as alternative to conventional solvents. In conventional solvent extraction processes the influence of the pH on the partitioning of ionizable solutes is an important parameter to control the extraction and back extraction efficiency. However, the partitioning of ionizable solutes such as organic acids and bases in micellar two-phase systems has not been studied so far. In this work the partitioning of various ionizable solutes including phenolic as well as pharmaceutical active compounds has been investigated. Lipophilicity profiles of all solutes were analyzed for the system TritonX-114/water in a pH range between 2 and 12. Further, the influence of temperature, solute concentration, as well as different salt concentrations on the partitioning of charged solutes was investigated. Experimental results are verified by means of predicted values using the thermodynamic model COSMO-RS. The results reveal that COSMO-RS can be applied to predict the partitioning of ionizable solutes in micellar biphasic systems, when the phase behavior of the pure surfactant is known.Based on these data optimal strategies for large scale micellar extraction processes are proposed and validated by means of a continuous pilot plant micellar extraction column.

Separation of Gallium and Aluminum from HCl Solution by Microemulsion

Gallium was separated from aluminum in hydrochloric acid medium by a steady microemulsion. In the cetyltrimethylammonium bromide (CTAB)/n-pentanol/n-heptane/HCl/tributyl phosphate (TBP) system, TBP was introduced as the modifier to avoid emulsification of the microemulsion. The extraction efficiency on gallium was also improved by adding TBP. The factors that influenced the separation efficiency were explored. The results of the experiments showed that the gallium and aluminum were effectively separated within a very short time, and the extraction efficiencies of gallium and aluminum were 92% and 5%, respectively. The maximum back-extraction efficiency of gallium was 92% in HCl solution (4 M).

Synthesis and evaluation of novel water-soluble ligands for the complexation of metals during the partitioning of actinides

Different types of water-soluble ligands were synthesized and their capability was evaluated by solvent extraction studies to complex trivalent actinides and suppress their extraction by a strong lipophilic ligand, such as TODGA. The back extraction efficiency of hydrophilic diglycolamide (DGA) derivatives with a varying number of ethylene glycol groups, or containing sodium acetate moieties on the amidic nitrogen shows a decrease in back-extraction efficiency with increasing number of ethylene glycol units on the amidic nitrogen at various pH values of the aqueous phase. Among the PS donating ligands only the ligand with a malonamide backbone exhibits a high reverse extraction efficiency, although, with no selectivity for americium. Within the water-soluble tripodal ligands, i.e. the amide derivatives of nitrilotriacid with N,N-dimethyl and N,N-bis(hydroxyethyl) moieties, the first one shows a pronounced selectivity for Am(III) over Eu(III), with a maximum separation factor of 11.1, while the latter one more efficiently complexes the radionuclides in the aqueous phase with a maximum separation factor of 5. Isothermal microcalorimetry experiments of the complexation of Eu(III) by a selected series of ligands confirm the observed trend in the back extraction properties.

Downstream processing of soy hull peroxidase employing reverse micellar extraction

Phase transfer studies were conducted to evaluate the solubilization of soy hull peroxidase (SHP) in reverse micelles formed in isooctane/butanol/hexanol using the cationic surfactant cetyltrimethylammonium bromide (CTAB). The effect of various parameters such as pH, ionic strength, surfactant concentration of the initial aqueous phase for forward extraction and buffer pH, type and concentration of salt, concentration of isopropyl alcohol and volume ratio for back extraction was studied to improve the efficiency of reverse micellar extraction. The active SHP was recovered after a complete cycle of forward and back extraction. A forward extraction efficiency of 100%, back extraction efficiency of 36%, overall activity recovery of 90% and purification fold of 4.72 were obtained under optimised conditions. Anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) did not yield good results under the conditions studied. The phase transfer of soy hull peroxidase was found to be controlled by electrostatic and hydrophobic interactions during forward and back extraction respectively.

Extraction of Bovine Serum Albumin Using Reverse Micelles Formed by Hexadecyl Trimethyl Ammonium Chloride

The extraction of bovine serum albumin (BSA) has been investigated using reverse micelles of hexadecyl trimethyl ammonium chloride/n-octanol/isooctane. Forward extraction process parameters such as the surfactant concentration, co-solvent concentration, pH, ionic strength, and species of the initial aqueous phase were important factors affecting the extraction performance. These parameters were varied to optimize the extraction efficiency. Under the optimized conditions, forward extraction efficiencies of BSA can reach practically 99.55%. The thermodynamic study revealed that the extraction of BSA is controlled by entropy changes. Maximum back-extraction efficiency of 85.16% can be obtained at low pH values and high salt concentrations. The structures of BSA during reverse micelle extraction did not change by comparing the circular dichroism spectra of BSA back-extracted to the aqueous phase with that of feed BSA.

A preliminary study of dihydroxyurea application in plutonium purification cycle

The back extraction of Pu from 30% TBP/kerosene with dihydroxyurea (DHU) was studied in relation to the contact time, nitric acid concentration, phase ratio, etc. The back-extraction efficiency can reach 87% at phase ratio (o/a) ≤4: 1, contacting time ≥1 min, niitric acid concentration ≤0.4 M, and reductant concentration ≥0.4 M at 15°C and Pu concentration in the organic phase of 12 g l−1. The back-extraction efficiency decreases with an increase in the Pu(IV) concentration in the organic phase or in the Pu(III) concentration in the aqueous phase. The application of DHU in Pu cycle was studied in a 12-step countercurrent cascade experiment. The results show that DHU can satisfy the technical requirements at 15°C and phase ratio (2BF: 2BX: 2BS) = 4: 1: 1. The Pu recovery efficiency is 99.96%.

Spectrophotometric determination of ultra trace uranium(VI) in seawater after extractive preconcentration with ionic liquid and dimethylphenylazosalicylfluorone

A simple and effective method is presented for extractive preconcentration of uranium(VI) in water, in which the ionic liquid, 1-octyl-3-methylimidazolium hexafluorophosphate, abbreviated as [C8mim][PF6], was used as novel medium for liquid/liquid extraction of uranium(VI) and new reagent, dimethylphenylazosalicylfluorone, abbreviated as DMPASF, was employed to form neutral uranium(VI)-DMPASF complex. DMPASF reacted with uranium(VI) rapidly to form a stable red complex, the complex was then extracted into [C8mim][PF6] phase, and the uranium(VI) in [C8mim][PF6] was back-extracted into aqueous phase again with 3.0 mol L−1 hydrochloric acid. The extraction efficiency, back-extraction efficiency and preconcentration factor were 98.9%, 96.5% and 200 times for 100 µg of standard uranium(VI) in 1000 mL of water samples, respectively. The preconcentration coupled with spectrophotometry with chlorophosphonazo III, abbreviated as CPAIII, was developed for determination of ultra trace uranium(VI) in natural water. The apparent molar absorptivity of the uranium(VI)-CPAIII complex and the detection limit which was calculated using three times the standard error of estimate of the calibration graph was found to be 3.17 × 106 l mol−1 cm−1 and 0.22 ng mL−1 of uranium(VI), respectively. The absorbance of the uranium(VI)-CPAIII complex at 670 nm increase linearly with the concentration of uranium(VI) up to 45 µg of uranium(VI) in 1000 mL of aqueous solution. The interference study show that the determination of uranium(VI) is free from interferences of almost all positive and negative ions found in water samples. The relative standard deviation (N = 10) was 1.3% for uranium for 10 replicate determinations in the solution containing 1.0 µg L−1 of uranium(VI). The proposed method has been successively applied to determination of ultra traces of uranium(VI) in seawater samples.

Reverse Micellar Extraction of β-Galactosidase from Barley (Hordeum vulgare)

The reverse micellar system of sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane was used for the extraction and primary purification of beta-galactosidase (EC 3.2.1.23) from the aqueous extract of barley (Hordeum vulgare) for the first time. The process parameters such as the concentration of the surfactant, the volume of the sample injected, and its protein concentration, pH, and ionic strength of the initial aqueous phase for forward extraction, buffer pH, and salt concentration for back extraction are varied to optimize the extraction efficiency. Studies carried out with both phase transfer and injection mode of reverse micellar extraction confirmed the injection mode to be more suitable for beta-galactosidase extraction. The extent of reverse micellar solubilization of proteins increased with an increase in protein concentration of the feed sample. However, back extraction efficiency remained almost constant (13-14.4%), which indicates the selectivity of AOT reverse micelles for a particular protein under given experimental conditions. beta-Galactosidase was extracted with an activity recovery of 98.74% and a degree of purification of 7.2-fold.

Selective extraction/isolation of hemoglobin with ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate (BtmsimPF 6)

Ionic liquid was for the first time employed for selective isolation of heme-protein species. Direct extraction of hemoglobin into ionic liquid without using any concomitant reagent or extractant was carried out. Hemoglobin at the level of 100 ng μL −1 could readily be quantitatively extracted into ionic liquid (IL) 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate (BtmsimPF 6) in the absence of any co-existing extractants/additives at pH 7, at the same time; however, the other protein species do not interfere and remain in the aqueous phase. A back extraction efficiency of ca. 80% for 20 ng μL −1 hemoglobin in ionic liquid phase was achieved with sodium dodecyl sulfate (SDS) solution as stripping reagent. 57Fe Mossbauer spectra and circular dichroism (CD) spectra indicated that the penta-coordinated ferrous atom in hemoglobin provide a vacant or free coordinating position, which could be occupied by the cationic Btmsim + moiety. The interaction/coordination reaction between the iron atom in the heme group of hemoglobin and the cationic ionic liquid moiety furnishes the driving force for facilitating fast transfer of hemoglobin into BtmsimPF 6. The present system was applied for selective isolation of heme-protein, i.e., hemoglobin from human whole blood without any pretreatment, giving rise to satisfactory results.

Use of reverse micellar systems for the extraction and purification of bromelain from pineapple wastes

Reverse micellar systems of CTAB/isooctane/hexanol/butanol and AOT/isooctane are used for the extraction and primary purification of bromelain from crude aqueous extract of pineapple wastes (core, peel, crown and extended stem). The effect of forward as well as back extraction process parameters on the extraction efficiency, activity recovery and purification fold is studied in detail for the pineapple core extract. The optimized conditions for the extraction from core resulted in forward and back extraction efficiencies of 45% and 62%, respectively, using reverse micellar system of cationic surfactant CTAB. A fairly good activity recovery (106%) and purification (5.2-fold) of bromelain is obtained under these conditions. Reverse micellar extraction from peel, extended stem and crown using CTAB system resulted in purification folds of 2.1, 3.5, and 1.7, respectively. Extraction from extended stem using anionic surfactant AOT in isooctane did not yield good results under the operating conditions employed.

Use of a Novel Medium, the Ionic Liquid 1-Butyl-3-Trimethylsilylimidazolium Hexafluorophosphate, for LiquidLiquid Extraction of Lead in Water and Its Determination by Graphite Furnace Atomic Absorption Spectrometry

The ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate, abbreviated as [C4tmsim][PF6], was developed as a novel medium for liquid-liquid extraction of lead(II) in water, in which dithizone was used as a metal chelator to form a neutral lead-dithizone complex. Under optimal conditions, the complex was extracted into the [C4tmsim][PF6] phase from aqueous solution and back-extracted with nitric acid solution into the aqueous phase that was used directly for the subsequent determination of Pb. The system using the ionic liquid demonstrated good extraction performance; the extraction and back-extraction efficiencies were 99.8 and 99.7%, respectively, for Pb(II) at 20 microg/L. The above procedure, including the extraction and back-extraction, was used to enrich trace levels of Pb(ll) in a relatively large volume of water samples (1000 mL water), and an enrichment factor of 400 was obtained. The enrichment coupled with graphite furnace atomic absorption spectrometry was successfully applied to the determination of Pb in water. The calibration graph was linear at levels near the detection limits up to > or = 100 ng/L Pb(II). The limits of quantitation and detection for lead in real water samples were 2.5 and 1.0 ng/L, respectively. Lead recoveries of 96.2-103.8% from spiked samples demonstrate the accuracy of the proposed method.

Ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate as a solvent for extraction of lead in environmental water samples with detection by graphite furnace atomic absorption spectrometry

A novel method is described for the preconcentration of ultratrace amounts of lead in water. Dithizone is employed as a chelator forming a neutral lead-dithizone complex to extract lead ions from aqueous solution into the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate. Under optimal conditions, the extraction efficiency in one step and back-extraction efficiency with 5 mL of 0.1 mol L−1 nitric acid were 99.9 and 99.8% for 20 µg of lead in 1 L of water solution, respectively. Preconcentration coupled with graphite furnace atomic absorption spectrometry was developed for the determination of lead in environmental water samples. The calibration graph was linear with a correlation coefficient of 0.998 at levels near the detection limits up to at least 0.1 µg L−1. The detection limit, calculated as three times the standard error of the estimated calibration graph, is 1.0 ng of lead per liter of water sample. The determination of lead was free from interference from almost all cations and anions, and from humic acid in water from plant rot. Lead recoveries between 97.8 and 100.8% for spiked samples prove the accuracy of the method.

A new room temperature ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate as a solvent for extraction and preconcentration of mercury with determination by cold vapor atomic absorption spectrometry

A new room temperature ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate abbreviated as [C 4tmsim][PF 6] was synthesized and developed as a novel medium for liquid/liquid extraction of inorganic mercury in this work. Under optimal condition, o-carboxyphenyldiazoamino- p-azobenzene abbreviated as CDAA reacted with inorganic mercury to form a neutral Hg–CDAA complex, the complex was rapidly extracted into ionic liquid phase. After back-extracting into aqueous phase with sulfide sodium solution, the mercury concentration was detected by cold vapor atomic absorption spectrometry. The extraction and back-extraction efficiencies were 99.9 and 100.1% for 5.0 μg L −1 standard mercury in 1000 mL of water solution, respectively. The detection limit, calculated using three times the standard error of estimate of the calibration graph, is 0.01 ng of mercury per milliliter water sample. The proposed method has been used to the determination of trace inorganic mercury in natural water with satisfactory results. Moreover, Zeta potential and surface tension of [C 4tmsim][PF 6] solution were measured and applied to explain the extraction mechanism of [C 4tmsim][PF 6] system.

The factors affecting the backward-transfer of Bovine Serum Albumin (BSA) from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micellar solutions

The factors affecting the back-extraction efficiency of Bovine Serum Albumin (BSA, 65kDa, pI 4.9) solubilized in an AOT reverse micellar solution, prepared by the injection method, to an excess aqueous phase were investigated. In particular, effects of pH, the type of salt and its concentration in the excess aqueous phase were examined. Furthermore, by comparing CD spectra of the back-extracted BSA with the feed BSA, the structural changes of the protein during the extraction process were determined. The addition of 1:1 salt such as KCl or NaCl to the aqueous phase resulted in a 100% recovery of the protein to the aqueous phase at a pH higher than its isoelectric point pI. This high efficiency of the back-extraction might be due to the change in the interactions between the protein and micellar aggregates driven by the added salt. For 1 : 2 salts like MgCl2 or CaCl2, BSA was back extracted with lower than 20% extraction efficiency. Maximum efficiencies were achieved at about pH=7 and pH=8 for monovalent and divalent salts, respectively. From the C D spectra of back-extracted BSA, it was observed that denaturation of BSA was not significant during the extraction process.