Solvent Extraction Separation Research Articles

Poly (vinyl alcohol-co-ethylene) (EVOH) modified polymer inclusion membrane in heavy rare earths separation with advanced hydrophilicity and separation property

Efficient separation of adjacent rare earths is an interesting and challenging job for membrane separation scientists. In this article, a novel polymer inclusion membrane (PIM) incorporating the hydrophilic additive random copolymer poly (vinyl alcohol-co-ethylene) (EVOH) was synthesized. Due to the polarity of P = O and P-OH groups in Cyanex272 and hydrophilicity of –OH groups in EVOH, the membranes exhibited much smaller water contact angles than pure PVDF membranes. And FT-IR results indicated that the addition of EVOH made no difference on the coordination between P = O, P-OH in Cyanex272 and Lu3+. SEM and AFM results indicated that the addition of appropriate amount of EVOH could generate more and larger surface pores and internal channels. Optimum membrane compositions and permeation conditions were fixed via static adsorption and dynamics permeation experiments. Separation factor was calculated as high as 3.78, which was much higher than previous studies no matter in solvent extraction or membrane separation. It is worth noting that it’s the first time an obvious carrier’s leakage was observed via characterizations which implied Cyanex272 may be not a perfect carrier in terms of PIM’s stability. All these results proved that this novel PIM with EVOH serving as hydrophilic additive could be further testified in heavy rare earths separation and purification process.

Extraction of microplastic from marine sediments: A comparison between pressurized solvent extraction and density separation

Due to the ecotoxicological effects, microplastics are considered a threat for the marine environment. Recent reports indicate their presence not only in subsurface water and in coastal beach sediments, but also in the deep-sea. Notwithstanding, there is still not a scientific consensus about the analytical procedure to be applied for their determination. In this work we compared the performance of two extraction methods: pressurized solvent extraction (PSE) and density separation. Sea sand and seafloor sediments were spiked with known amounts of polystyrene (PS), polyethylene (PE) and polypropylene (PP) microplastics and submitted to both the extraction procedures. Results showed that the PSE ensured higher recoveries for the smaller size particle fractions (89,2 ± 1.1% in the 50–150 μm range) whereas the density separation enabled precise recoveries for the larger size particles (SD = 1,5%). No significant differences in terms of blanks control were highlighted.

Non-equilibrium solvent extraction in milliflow reactors: Precious and base metal separations with undiluted ionic liquids

Milliflow devices operating under slug flow (Taylor-flow) conditions provide an efficient mass transfer, a highly uniform droplet morphology and a narrow residence time distribution i.e. characteristics which are excellent for the performance of reactions under kinetic control. Milliflow devices have also been proposed in combination with ionic liquids, due to their ability to intensify the solvent use of these rather expensive and viscous liquids. In present research, the solvent extraction separation of a mixture of Au(III), Pd(II), Cu(II) and Fe(III) was studied using the chloride and bromide forms of the undiluted quaternary ammonium ionic liquid Aliquat 336 in a slug flow reactor channel with an internal diameter of 1.0 mm. The extraction of Au(III) and Pd(II) was found to be faster than that of Cu(II) and Fe(III), allowing the precious/base metal separation to be improved by modification of the contact time between both phases. An apparent correlation between the observed extraction rates and the equilibrium distribution ratio D was found. The most significant separation improvement was achieved at those conditions where the equilibrium separation was best i.e. low halide and metal concentrations and low organic-to-aqueous flow rate ratios. At a residence time of 25 s, quantitative Au(III) and Pd(II) recovery was achieved and decontamination factors increased by a factor up to 2, which corresponds to an increase in product purity of up to 14%. Upon substituting the chloride system for a bromide extraction medium, similar observations were made, except for a reversed Cu(II)/Fe(III) selectivity. Experiments were also conducted on the separation of Pt(IV), Pd(II) and Rh(III), where a reduced Rh(III) extraction rate was observed, allowing to suppress its co-extraction by up to 20%. A hydrodynamic analysis of the obtained flow regime of the ionic liquids revealed a stable and uniform slug flow characterized by a decreasing plug length and width with increasing flow rates. A comparison of the applied and observed phase ratio revealed a stagnant ionic liquid excess (i.e. hold-up) inside the reactor of up to 40% which effectively reduced the reactor diameter and consequently plug residence time.

Determination of trace uranium in thorium matrix by laser induced fluorimetry after separation of thorium by its fluoride precipitation using NH4HF2

Abstract Thorium, a major element in thorium matrix, quenches uranium fluorescence when it is present above the ratio (Th/U) of 2000 in conventional pellet fluorimetry determination of uranium. A single step ‘sample digestion cum thorium fluoride precipitation’ with NH4HF2 has been developed for separation of bulk thorium as hydrated thorium fluoride precipitates. Uranium in aqueous solution is extracted into ethyl acetate and stripped into pyrophosphate medium (pH ∼ 7), prior to its laser induced fluorimetry determination. Optimizations of certain parameters such as the effects of fluoride flux, mineral acid, temperature and time, stripping solution, diverse ions etc. are discussed in detail. The method has been validated by analyzing a set of synthetic mixtures and certified reference materials of rock samples such as SY-2, SY-3, GSP-2, NKT-1 and CG-2 doped with a large excess of thorium. This method has been applied for the determination of microgram to nanogram uranium in thorium rich rocks and synthetic nuclear grade ThO2 with high degree of accuracy and precision. This is the improvement of the existing method which involves two liquid-liquid solvent extraction separation of thorium and uranium using the chelating agent 2,3-dihydroxynaphthalene at the different pH, compared to one solvent extraction separation of uranium in the present method, because separation of thorium by precipitation as its fluoride has already been carried out during sample digestion step itself. The proposed method involving ammonium hydrogen fluoride in combination with laser induced fluorimetry is simple, rapid, cost effective and more eco-friendly.

Methods for separating microplastics from complex solid matrices: Comparative analysis

Microplastics (MPs) are widely found in complex solid matrices such as soil, sediments and sludge. The separation procedure is crucial for effective analysis of MPs, but existing methods varied among studies. Here, we systematically summarize and compare separation methods including density, oil, electrostatic, magnetic, and solvent extraction separation. Density separation is the most commonly used approach, but time-consuming and discharging hazardous materials dependent on extraction solutions. In contrast, oil, electrostatic, magnetic separation and solvent extraction separation are emerging approaches with advantages of low-cost, quick, or environmentally-friendly, but with high request of instruments. Despite variation among these approaches, the separation efficiency is closely related to characteristics of MPs including polymer types, sizes and shapes. The treatment of digestion and fluorescence staining can facilitate the detection of MPs. This analysis suggests that further optimization and improvement of existing approaches can facilitate the development of new separation technology for assaying MPs in complex environmental matrices.

Study on behavior of lithium ion in solvent extraction and isotope separation

Current research found that the extraction process of lithium ions by crown ether-ionic liquid system was a cation exchange process in which lithium ions are dehydrated. Obtained and predicted the structure of the composite product of crown ether and organolithium, and based on the weighing method, the formation of 1:1 complex [Li(B15C5)]+ was determined. and it was found that the extraction of lithium ion by the diluent was in accordance with the cavity effect of anion. The coextraction of diluent and ionic liquid, the percentage of competition of common metal cations in aqueous solution to the extraction of lithium ions by Benzo-15-crown 5-Ether(B15C5) were also discussed. Finally, the effect of different diluents on lithium isotope separation and the thermodynamics of lithium isotope exchange in the B15C5-[HMIm][NTf2]-anisole system were studied. The separation factor of lithium isotope was the largest when chloroform was used as the diluent (α = 1.034), and the exchange of lithium isotopes was a spontaneous reaction at low temperature (ΔH < 0, ΔS < 0).

Solvent Extraction Separation of Co(II) and Ni(II) from Weak Hydrochloric Acid Solution with Ionic Liquids Synthesized from Organophosphorus Acids

Solvent Extraction Separation of Co(II) and Ni(II) from Weak Hydrochloric Acid Solution with Ionic Liquids Synthesized from Organophosphorus Acids

Kinetics study on leaching of rare earth and aluminum from polishing powder waste using hydrochloric acid

In this study, a novel hydrometallurgical process consisting of hydrochloric acid three-stage countercurrent leaching and solvent extraction was proposed to recover rare earth oxide (REO) from the rare earth polishing powder waste (REPPW). The effects of HCl concentration, liquid–solid ratio (L/S ratio), temperature and time on the leaching yields of rare earths (in REO) and aluminum (in Al2O3) were studied. The result shows that the leaching yields of REO and Al2O3 are 90.96% and 43.89% respectively under the optimum leaching parameters of HCl concentration = 8.00 mol/L, L/S ratio = 4 mL/g, leaching temperature = 353 K and leaching time = 180 min. Meanwhile, the leaching kinetics of REO and Al2O3 were investigated in this study. The leaching behaviors of REO and Al2O3 follow a shrinking sphere/core model and the general leaching process is controlled by the surface chemical reaction. The leaching activation energies of REO and Al2O3 are 9.86 and 13.68 kJ/mol, respectively. The leaching yield of each substance in three-stage countercurrent leaching is improved substantially compared with single-stage leaching, with a change from 90.96% to 95.38% for REO and from 43.89% to 46.22% for Al2O3, respectively. Especially, the total concentration of REO in three-stage countercurrent leaching solution is greatly increased to above 300 g/L, and the acidity of which is decreased to ca. pH = 2, which is conducive to subsequent solvent extraction directly. High purity REO (99.92%) is obtained by solvent extraction separation, oxalate precipitation and calcination. The total recovery yield of REO is 85.13%.

Characterization of the ALSEP Process at Equilibrium: Speciation and Stoichiometry of the Extracted Complex.

We have determined the identity of the complexes extracted into the ALSEP process solvent from solutions of nitric acid. The ALSEP process is a new solvent extraction separation designed to separate americium and curium from trivalent lanthanides in irradiated nuclear fuel. ALSEP employs a mixture of two extractants, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and N,N,N′,N′-tetra(2-ethylhexyl)diglycolamide (TEHDGA) in n-dodecane, which makes it difficult to ascertain the nature of the extracted metal complexes. It is often asserted that the weak acid extractant HEH[EHP] does not participate in the extracted complex under ALSEP extraction conditions (2–4 M HNO3). However, the analysis of the Am extraction equilibria, Nd absorption spectra, and Eu fluorescence emission spectra of metal-loaded organic phases argues for the participation of HEH[EHP] in the extracted complex despite the high acidity of the aqueous phases. The extracted complex was determined to contain fully protonated molecules of HEH[EHP] with an overall stoichiometry of M(TEHDGA)2(HEH[EHP])2·3NO3. Computations also demonstrate that replacing one TEHDGA molecule with one (HEH[EHP])2 dimer is likely energetically favorable compared to Eu(TEHDGA)3·3NO3, whether the HEH[EHP] dimer is monodentate or bidentate.

Solvent Extraction Separation of La, Sm and Dy from Sulfate-Phosphate Medium by CYANEX 272 in Kerosene

Extraction and separation of La, Sm and Dy ions from acidic sulfate-phosphate solutions was investigated using a cation exchange extractant, bis(2,4,4-trimethylpentyl) phosphinic acid, CYANEX 272, in kerosene. The influence of shaking time, equilibrium pH, extractant, sulfate and phosphate ion concentrations, diluent type and temperature was studied. The extraction was found to be pH-dependent, and increasing the phosphate ion concentration inhibited the extraction which was found to be endothermic. The stoichiometry of the extracted metal species was found to be MOH.H2OHSO4H2A.A2. Aliphatic diluents were found to enhance the extraction compared to aromatic diluents. The results showed that there was a separation mode between the metal ions when varying the hydrogen ion and sulfate ion concentrations, under the used experimental conditions. The investigated process was used for the recovery of La, Sm and Dy from the acid solution resulting from the leaching of low-grade monazite.

Extractive separation of rare earth elements and their determination by inductively coupled plasma optical emission spectrometry in geological samples

A simple, rapid and effective solvent extraction separation of rare earth elements has been developed for their determination in geological samples such as rock, soil and core samples by inductively coupled plasma optical emission spectrometry.

Scaling up the Synthesis of a Hydroxyquinoline-Functionalized p-tert-Butylcalix[4]arene

The optimization for an upscaled technical production of a lower rim-functionalized p-tert-butylcalix[4]arene, furnished with N4O4-donor ligands for superior solvent extraction separation between h...

Antioxidant and antibacterial capabilities of phenolic compounds and organic acids from Camellia oleifera cake.

There is growing interest in the antioxidants and antibacterial activity from natural substances. The purpose of the research was to gain and distinguish phenolic substances and organic acids in the Camellia oleifera cake, and to study their antioxidant and antibacterial activities. The extraction and purification of them were achieved by solvent extraction and column separation, respectively. The conclusions displayed that purity of the phenolic substances was 94.1 ± 0.5%w/w and that of organic acid was 96.0 ± 0.3%w/w; Fifteen phenolic substances were certificated using HPLC-ESI-MS technology; oxalic, citric, acetic, malic, and succinic acids are discovered to be main organic acids. In addition, the phenolic substances and organic acids both have good antioxidant activity and obvious inhibition against six species of bacteria. These conclusions can be useful in the reuse of the waste of Camellia oleifera oil industry in the future.

Solvent extraction separation and spectrophotometric determination of ruthenium(III) with p-methylphenyl thiourea: sequential separation of ruthenium, osmium and iron

ABSTRACT A selective and sensitive solvent extraction and spectrophotometric study of the ruthenium(III)–p-methylphenyl thiourea (PMPT) system is presented. The optimum conditions were determined by a critical study of acid concentration, reagent concentration, equilibration period, heating time and effect of solvent on the equilibrium. Ruthenium(III) forms 1:1 complex with PMPT in 20% ethanol and extracted into chloroform. Conformity to Beer’s law at 600 nm was observed up to 40 µg mL–1 of ruthenium. Molar absorptivity and Sandell’s sensitivity were found to be 2.31 × 103 L mol−1cm−1 and 0.044 μg cm−2, respectively. The detection limits were 0.11 μg mL−1 of ruthenium. The method is free from interferences from large number of cations and anions. Proposed method was successfully applied to the separation and determination of ruthenium from synthetic alloys, catalyst and water samples. Sequential separation and determination method for ruthenium(III), osmium(VIII) and iron(II) has been developed.

Solvent Extraction Separation of Silver(I) and Zinc(II) from Nitrate Leach Solution of Spent Silver Oxide Batteries with D2EHPA

Solvent Extraction Separation of Silver(I) and Zinc(II) from Nitrate Leach Solution of Spent Silver Oxide Batteries with D2EHPA

A review of microplastics in sediments: Spatial and temporal occurrences, biological effects, and analytic methods

The persistence and prevalence of microplastics in the environment have raised concerns among scientists, the general public, and environmental regulatory agencies, and a large number of studies on microplastics in sediments have been published. We reviewed those studies and focused on understanding the spatial and temporal variations, biological effects, and analytic methods of microplastics in sediments. Microplastics are widely distributed in marine and freshwater sediments. The distribution of microplastics is mainly influenced by anthropogenic input and environmental processes that determine the transportation, transformation and accumulation. The appearance of microplastics in sedimentary records has been proposed as a stratigraphic marker for the onset of the Anthropocene Epoch. Our current understanding of biological effects of microplastics is based mainly on field research and laboratory-scale experiments using unrealistic concentration and limited forms of microplastics. Future studies should consider environmentally relevant concentration, the diverse composition and form of microplastics presenting in the natural environment. Density separation method for separation of microplastics in sediments is the most commonly used, and component identification by optical analysis (Fourier-transform infrared spectroscopy spectra, Raman spectra etc.) are important analytic methods. Yet the separation method remains to be standardized across laboratories. Other separation methods include electrostatics separation, organic solvent extraction and magnet separation. We recommend the combination of density separation, electrostatic separation and organic solvent separation to improve the separation efficiency of microplastics and to standardize the analytic process for sediment microplastics in future studies.

Influence of lactic acid on the solvent extraction separation of Sm(III) and Co(II) from chloride medium using DEHPA

ABSTRACTA novel process for the separation of Sm (III) and Co (II) from chloride medium using lactic acid in the aqueous feed employing Di-2-ethylhexyl phosphoric acid (DEHPA) in petrofin as organic phase solvent has been developed. Complete separation has been accomplished with 1 M HLac and 0.1 M DEHPA in the pH range 1–3 and using 2.2 M HLac at pH 3 with 0.2 M DEHPA. Sm (III) could be entirely stripped off the loaded organic solvent by means of 1.2 M HCl and HNO3. The extraction process is heat releasing for Sm (III) and heat absorbing for Co (II).

Review of Different Purification Techniques for Crude Glycerol from Biodiesel Production

The global glycerol market has experienced a surplus in recent decades due to an increase in biodiesel production and thus created a new form of challenge in terms of purification of the crude glycerol. Various techniques have been developed worldwide on purification of crude glycerol. These processes include chemical pre-treatment, methanol removal, vacuum distillation, ion exchange, adsorption, solvent extraction and membrane separation technology to mention a few.&#x0D; In Nigeria, domesticating these technologies or techniques to suit our peculiar situation and also be cost effective needs a critical evaluation of all the available options.&#x0D; This review, therefore, summarises the progress of crude glycerol purification technologies using various techniques as compared with the process technology developed by researchers at the Federal Institute of Industrial Research, Oshodi, Lagos Nigeria.

Analytical determination of bisphenol A (BPA) and bisphenol analogues in paper products by LC-MS/MS

ABSTRACTIn this study a sensitive analytical method based on liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) was developed for the simultaneous analysis of bisphenol A (BPA), bisphenol AF (BPAF), bisphenol B (BPB), bisphenol E (BPE), bisphenol F (BPF) and bisphenol S in different paper and board products, including virgin fibre samples and recycled samples. Analytes were extracted from the paper matrix using a simple solvent extraction and chromatographic separation was performed on a C18 core-shell (100 mm x 2.1 mm i.d.; 1.7 µm particle size) column. The developed method showed good linearity (R2 > 0.9921) for all analytes. Absolute recoveries ranged from 71 to 115% and precision in terms of reproducibility and repeatability (intra- and inter-day) yielded in relative standard deviations (RSDs) of less than 15.0% and 17.4%, respectively. The limit of detection (LOD) and limit of quantification (LOQ) for the different analytes ranged from 0.29 to 0.40 µg kg−1 paper and from 1.09 to 1.32 µg kg−1 paper, being in the same range for all analytes. Quantitation of the analytes was performed using the internal standard procedure, with concentrations of < LOQ to 9599 µg kg−1 for the different analytes. Furthermore, a calculation of the maximum migration, assuming the ‘worst case’ scenario of 100% migration was performed.

New insights into the separation of Nd from Pr in hydrochloric and sulfuric acid solutions

The solvent extraction separation of Nd from Pr with commercially available organic extractants has been studied using statistical design of experiments. In this regard, Taguchi’s L16 (44 × 21) orthogonal array was used to determine the optimum conditions for maximizing the separation factor between Nd and Pr (βNd/Pr). The effects of controllable operating experimental parameters including initial pH of the aqueous solutions (A: 2–5), concentration of rare earth element (B: 10–40 ppm), extractant type (C: DEHPA, PC88A, TOPO, and Cyanex 572), extractant concentration (D: 10–60 mM), and acid type (E: sulfuric and hydrochloric acid) on the separation performance were studied. Under selected experimental conditions Nd and Pr do not form any major chloride species, whereas both of the elements form cationic and anionic complexes in sulfate solutions (NdSO4+, PrSO4+, Nd(SO4)2−, and Pr(SO4)2−). The optimum operating conditions for maximizing the separation of Nd from Pr occurred at the experimental condition A4B3C1D3E2, where a maximum separation factor of 2.72 was achieved, which was higher than any values reported in the literature. Analysis of variance (ANOVA) showed that pH, extractant type, and acid type had the most influential effect on the separation of Nd and Pr. DEHPA and hydrochloric acid were found to be the best organic extractant and aqueous solution, respectively. The separation performance of organic extractants followed the order DEHPA > PC88A > Cyanex 572 > TOPO, indicating that the new acidic extractant Cyanex 572 does not perform well for the separation of Nd and Pr.