liquid–liquid extraction of lactic acid with Alamine 336

The extraction of lactic acid (HL) from aqueous solutions by Alamine 336 (B) dissolved in toluene was studied. Experiments were performed in the temperature range of 25–60°C and for two amine concentrations of 20 and 40% (v/v) in toluene. The extent to which the organic phase (amine + toluene) may be loaded with lactic acid is expressed as a loading ratio, Z = C_HL /C_B. Z values are independent of the amine concentration and, hence, the extracted complex contains only one molecule of amine. Z decreases with increasing temperature. Experimental results indicate that the system presents overloading, i.e. Z > 1. The extraction equilibrium may be interpreted as a result of consecutive formation of three acid–amine species with stoichiometries of 1:1, 2:1 and 3:1.     

Molecular mechanism for liquid–liquid extraction: Two‐film theory revisited

We investigate here the molecular mechanism for liquid‐liquid extraction and revisit the classical two‐film theory. With equilibrium and non‐equilibrium molecular dynamics simulations, we illustrate the kinetics of solute crossing the interface and in particular the structure of the interface at which two stagnant liquid films adhere. Our simulation results show that beyond the two‐film theory, the interface is well structured and plays an essential role in solute transfer. We found that at the well‐developed interface region the overall density profile exhibits a dip, while the solute concentration shows a significant maximum. Free energy analysis demonstrates the interfacial enrichment of solute molecules serving as a potential well for solute adsorption. Thus, different from the assumption of the two‐film theory, our simulations show that there exists a resistance for solute molecules crossing the interface, which could be overcome only at high interface concentration of solute caused by interfacial enrichment. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2464–2470, 2017     

A new bubbling extraction tower: Toward liquid–liquid solvent extraction at large aqueous‐to‐oil phase ratios

Enrichment and recovery of valuable components in industrial waste waters by traditional liquid–liquid solvent extraction is not economic due to extremely low concentrations of those targets. Large‐phase‐ratio extraction exhibits potential advantages for recovery of small quantities of target components from large volume of aqueous solutions. A novel bubbling extraction tower is proposed toward performing solvent extraction at large aqueous‐to‐oil phase ratios in this work. Organic extractants were covered onto surface of gas bubbles to form a layer of organic liquid membrane and the dispersed organic phase in tower could be small enough. The target components are extracted from aqueous feed solution onto the surface of the bubbles, and the enrichment ratios could be extremely high. We develop a feasible methodology to calculate tower height and operation phase ratios of the bubbling extraction tower, which is essential for future industrial scale‐up. Experimental results in pilot test are highly consistent with calculations. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3889–3897, 2015     

酮类试剂萃取分离铼的研究

简述了碱性体系中酮类试剂对铼的萃取分离研究，研究了萃取率与萃取剂用量、体系碱性浓度以及金属离子浓度等之间的关键，并比较了含氧萃取剂及酮类试剂间对铼的萃分离的能力。丙酮对铼的萃取分离已用于岩石中痕量铼的实际分析测定。     

Production of ethanol by continuous fermentation and liquid–liquid extraction

A continuous pilot plant was constructed for fermentation production of ethanol, using liquid–liquid extraction to remove the product and with recycle of the fermented broth raffinate. The plant was operated for up to 18 days with feed glucose concentrations in the range 10·0–45·8% (w/w). The solvent was n-dodecanol and immobilised yeast was used to overcome the problem of emulsification. The concentration of by-products in the fermented broth had no adverse effect on the rate of ethanol production. A mathematical model to predict the time required for achievement of 99% of the steady-state by-products concentrations was shown to be in good agreement with the experimentally determined concentration of the main by-product, glycerol. At a feed glucose concentration of 45·8% (w/w), the aqueous purge was equivalent to 2·8 m³ of effluent per m³ of ethanol produced and represented a 78% reduction in the volume of the aqueous purge compared with using a feed containing 10% (w/w) glucose.     

Enantioseparation of chiral aromatic acids in process intensified liquid–liquid extraction columns

Enantioselective liquid–liquid extraction (ELLE) is a powerful alternative to common technologies for separation of racemic mixtures. The first application of ELLE for aromatic acids in liquid–liquid extraction columns is described. The ELLE is investigated experimentally and theoretically for phenylsuccinic acid (PSA) as a representative for aromatic acids. A racemic mixture of (R/S)‐PSA is separated with hydroxypropyl‐β‐cyclodextrin as selector molecule. The ELLE obtained the highest operative selectivity (α_op = 1.8–2) for low pH‐values and temperatures. Because of the low operative selectivity, a countercurrent process is necessary to separate both enantiomers completely. The countercurrent process is investigated in process intensified extraction columns (Ø_in = 15 mm) with a high number of equilibrium stages. The experiments demonstrate a good symmetric separation with an enantiomeric excess of 60% and yields of 80% for both enantiomers. Finally, the back extraction is investigated to recycle the selector molecule and increase the efficiency. © 2014 American Institute of Chemical Engineers AIChE J, 61: 266–276, 2015     

Chemical conversion and liquid–liquid extraction of 5‐hydroxymethylfurfural from fructose by slug flow microreactor

A dehydration of fructose in the water/methyl isobuthyl ketone (MIBK) biphasic system can yield 5‐hydroxymethylfurfural (HMF) to be successfully extracted into the organic MIBK phase. The HMF production and yield in MIBK phase was discussed by using a simplified model taking into consideration of the slug flow. The extraction resistance of HMF across the interface between water and MIBK depended on the line velocity and the flow rate ratio. It was likely that the velocity field generated in the slug flow contributed to an increase in the mass transfer of HMF. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2135–2143, 2016     

Adsorption and separation of rhenium(VII) using N‐methylimidazolium functionalized strong basic anion exchange resin

BACKGROUND: Rhenium is a rare and valuable metal coexisting with molybdenum in molybdenite and sulfide copper ores and is hard to separate. Methods such as solvent extraction, ion exchange, adsorption, precipitation, etc. have been used to separate and purify Re(VII), and resin ion exchange has been widely investigated and used owing to its convenient operation and relatively low‐cost. The main challenge comes from the preparation of resins having high performance and stability. In an earlier study, an N‐methylimidazolium functionalized strong basic anion exchange resin was successfully synthesized and used for Cr(IV) extraction. This paper, reports on further synthesis and application of this resin for adsorption and separation of Re(VII) and Mo(VI), especially from copper arsenic filter cake. RESULTS: At pH 6.25, Re(VII) and Mo(VI) can be effectively separated with the N‐methylimidazolium functionalized strong basic anion exchange resin, giving a Re(VII) recovery of up to 93.3%, but only 5.1% for Mo(VI). When using the copper arsenic filter cake sample 89.1% Re(VII) recovery was achieved. CONCLUSION: The N‐methylimidazolium functionalized strong basic anion exchange resin exhibited high selectivity and recovery for Re(VII) in a mixed system. © 2012 Society of Chemical Industry     

Mass transfer into/from nanofluid drops in a spray liquid‐liquid extraction column

The performance of a spray liquid‐liquid extraction column at two mass‐transfer directions was experimentally studied in the presence of silica nanoparticles. Toluene‐based nanofluid drops containing 0.0005–0.01 vol % silica nanoparticles were dispersed in aqueous phase and acetic acid (AA) transfer between phases was investigated. The experiments were performed at fixed volumetric flow rates of dispersed and continuous phases. Maximum enhancement of 47.4% and 107.5% in overall mass‐transfer coefficient, respectively, for mass‐transfer direction of dispersed to continuous phase and vice versa were achieved for drops with 0.001 vol % silica nanoparticles. These enhancements can be referred to Brownian motion of nanoparticles and induced microconvection. The results showed that nanoparticles are more effective in augmenting AA transfer from continuous to dispersed phase. Probable reason is that smaller diameter and lower internal turbulence of drops in this transfer direction increase dispersed phase resistance potential to be manipulated by Brownian motion of nanoparticles. © 2015 American Institute of Chemical Engineers AIChE J, 62: 852–860, 2016     

Effect of aqueous phase pH on liquid–liquid extraction with impinging-jets contacting technique

The influence of aqueous phase pH on the rate of liquid–liquid extraction was investigated using a two impinging-jets contacting device with a high velocity of jet flows. The recommended chemical system of toluene–acetone–water was employed. Applying pH values from its natural value of 5.6–8, a range in which most industrial waters are lain, for the jets colliding force within 70.3–214.6 mN, leads a reduction in extraction efficiency and overall volumetric mass transfer coefficient up to about 18.9% and 35.2% respectively. A significant high variation is observed when the aqueous phase pH exceeds the water neutral value toward alkali conditions. These variations can be attributed to the adsorption of hydroxyl ions and lowering interfacial tension. A comparison between the results in this work and those for drop dispersion extraction indicates a high sensitivity in the impinging technique. As expected, increasing jets force improves the performance of the contacting device; however, simultaneously, the retarding effect of pH would be intensified. The variation of interfacial tension with pH was obtained and with the aid of dimensionless numbers, an empirical correlation was developed for the prediction of overall volumetric mass transfer coefficient.     

Investigation of liquid–liquid phase equilibria for reactive extraction of lactic acid with organophosphorus solvents

BACKGROUND: Lactic acid is a versatile commodity chemical with a variety of applications. Synthesis of lactic acid either through fermentation of carbohydrates or through chemical synthesis is state of the art. Separation from dilute aqueous solution is complex and accounts for the major part of production costs. Reactive extraction based on reversible adduct formation is a promising alternative for the separation of lactic acid. RESULTS: Extraction was carried out with the organophosphorus solvents tri‐n‐butyl phosphate, tri‐n‐octylphosphine oxide and Cyanex 923. Shellsol T was used as diluent. Partition coefficients increase with increasing extractant content and decreasing temperature. Cyanex 923 has several advantages compared with tri‐n‐butyl phosphate and tri‐n‐octylphosphine oxide with respect to lactic acid distribution and hydrodynamic properties. Liquid‐liquid phase equilibria for lactic acid extraction with Cyanex 923 were modeled. Selectivity of lactic acid extraction with respect to glycolic acid and formic acid was discussed. CONCLUSION: The organophosphorus extractant Cyanex 923 was found to be an appropriate solvent for lactic acid extraction from aqueous solutions. Experimental data and model data based on the Law of Mass Action showed good agreement. Lactic acid extraction from multi‐acid solution showed good selectivity compared with glycolic acid. Lactic acid selectivity is low with respect to formic acid. © 2012 Society of Chemical Industry     

Enhancing separation of titanium and iron by three‐liquid‐phase extraction with 1,10‐phenanthroline as additive

BACKGROUND: A three‐liquid‐phase system (TLPS) composed of an organic solvent‐rich top phase, a polymer‐rich middle phase and a salt‐rich bottom phase is a newly emerging separation medium. Due to low affinity of the polymer‐rich phase for metals it is necessary and important to search for a suitable complexing agent that has a definite affinity for the polymer‐rich middle phase and a high selectivity for the metal ion of interest. RESULTS: Addition of 1,10‐phenanthroline (phen) is effective in enhancing the separation of titanium and iron from magnesium in the TLPS consisting of trialkylphosphine oxide (TRPO)‐PEG 2000‐(NH₄)₂SO₄. Hydrogen‐bonding interactions between PEG 2000 and phen molecules are the driving force for anchoring tri(phen)‐iron(II) sulfate complexes in the middle phase. Under the conditions (pH = 1.5, molar ratio of phen to iron(II) = 3.4:1), nearly 86% of titanium was extracted into the top phase while 100% of iron(II) was distributed in the middle phase, without any interference between the metal species. The separation factor of titanium and iron in the upper two phases was greater than 20 000. CONCLUSIONS: A single step of extraction and separation of titanium and iron from magnesium was realized in the TRPO‐PEG 2000‐(NH₄)₂SO₄ TLPS with phen as additive. It highlights the effectiveness of TLPS in dealing with multi‐metal solutions and suggests a potential use of TLPS in the separation of iron and other target metals. As iron is ubiquitous the separation of iron is often needed in both analytical processes and the hydrometallurgical industry. Copyright © 2012 Society of Chemical Industry     

Removal of arsenic(III) and arsenic(V) from sulfuric acid solution by liquid–liquid extraction

Extraction of arsenic(III) and arsenic(V) from sulfuric acid solution was studied. Cyanex^® 923, Cyanex^® 925, dialkyldithiophosphinic acids (Cyanex^® 301), hydrophobic glycol (2‐ethylhexane‐1,3‐diol), and hydroxamic acids were used as extractants. The efficiency of extraction depended on extractant, diluent, valency of arsenic, and sulfuric acid concentration. Acidic reagents extracted As(III) better than As(V), while the opposite order of extraction efficiency was observed for the solvating extractants. The use of an aromatic diluent (toluene) was preferred. Toluene was found to be a better diluent for the Cyanex^® 923 and Cyanex^® 925 than Exxsol D 220/230 and octane. In the case of neo‐decanohydroxamic acids, the type of diluent had no significant effect on extraction of arsenic. The extraction of both As(III) and As(V) increased when the concentration of the sulfuric acid in the feed increased. The co‐extraction of sulfuric acid was observed. The extraction with hydroxamic acids was significantly slower in comparison to the extraction with other reagents. Extractant: arsenic species: sulfuric acid molar ratios were determined and they confirmed the composition of extracted species. Copyright © 2003 Society of Chemical Industry     

Investigation on local and average static hold‐ups in liquid–liquid systems in a rotary disc contactor

A rotating disc contactor with inner diameter of 91 mm and 21 compartments was used to investigate local and average static hold‐ups in the column. Three chemical systems, including distilled water as stagnant continuous phase and toluene, kerosene, and butyl acetate as dispersed phase, in case of no mass transfer, were applied. Different parameters consisting of drop size and static hold‐up were measured experimentally under various operating conditions, and two dimensionless correlations for estimation of local static hold‐up as a function of average mother drop size, physical properties, rotor speed, and stage number were proposed in two cases: (1) immovable and (2) rotating rotor discs. Furthermore, two dimensionless correlations were presented to estimate average static hold‐up as a function of average mother drop size, physical properties, rotor speed, and number of stages in the column in the two aforementioned conditions.     

Characterization of extracted complexes in liquid–liquid extraction of rhodium with Kelex 100 in the presence of SnCl2

Mixed Rh? Sn complexes found in aqueous and organic solutions involved in the liquid–liquid extraction of Rh(III) from chloride solutions, also containing SnCl₂, with 7-(4-ethyl-1-methyloctyl)-8-hydroxyquinoline (Kelex 100) were characterized through ¹¹⁹Sn NMR and Raman spectroscopy. At Sn: Rh molar ratios of 3:1 and 12:1, it was found that [Rh^IIICl₃(SnCl₃)₃]^3? and [Rh^I(SnCl₃)₅]^4?, respectively, are the dominant complexes in both the aqueous and organic solutions. These complexes can be quantitatively extracted from the aqueous solutions in less than 1 min contact time via ion-pair formation with the protonated 7-substituted 8-hydroxyquinoline reagent such that for both Sn:Rh ratios, the same Rh? Sn complex is found in the aqueous feed and in the fully loaded organic. In addition, it was found that [Rh^I(SnCl₃)₅]^4? is preferentially extracted over excess free Sn(II). Preliminary characterization of the complex stripped from the 12:1 loaded organic using 1·7 M H₂SO₄ shows an Rh? Sn complex having a ratio of 5:1 Sn:Rh.     

Homogeneous liquid–liquid extraction using perfluorooctanesulfonic acid and calcium and its application to the separation and recovery of vitamin B12

A new phase separation phenomenon was observed in which the perfluorooctanesulfonate ion (PFOS⁻) and calcium ion form an ion‐pair associator and the sedimented liquid phase occurs from the homogeneous aqueous solution. This phenomenon was observed in the neutral pH region at room temperature (25 °C). The optimum concentration conditions for the reagents were [PFOS⁻]_T = 7 × 10⁻³ mol dm^‐3 and [Ca²⁺]_T = 1.1 mol dm^‐3. When these findings were applied to the homogeneous liquid–liquid extraction of vitamin B₁₂, the extraction percentage (E) was 83% and the concentration ratio (ie V_a/V_s, where V_a is the volume of the aqueous phase and V_s is the volume of the sedimented liquid phase) was a maximum of 149. The recovery of vitamin B₁₂ was achieved by adding the propanol–acetone (20 : 80 v/v%) mixed solvent to the sedimented liquid phase; the vitamin B₁₂ precipitated and was filtered. Both the PFOS⁻ and Ca²⁺ were removed by dissolution in the mixed solvent. The recovery percentage of vitamin B₁₂ was 78%. © 1999 Society of Chemical Industry     

Recovery of aconitic and lactic acids from simulated aqueous effluents of the sugar‐cane industry through liquid–liquid extraction

The recovery of aconitic and lactic acids from dilute aqueous effluents of the sugar‐cane industry by a solvent extraction technique has been investigated in order to reduce environmental pollution and in view of the possible uses of pure solutes in the field of foods and pharmaceuticals. Reactive extraction of carboxylic acids with tributylphosphate dissolved in dodecane was examined. Experiments were performed at 25 °C for three extractant concentrations of 50%, 60% and 70% (mass %) in dodecane. The decrease of specific gravity and viscosity of solvent resulting from the presence of an inert diluent was favourable to the phase settling and the mass transfer. The percentage of acids recovered in the organic phase for a volumetric solvent ratio varying from 0.5 to 5.0 was determined. Taking into account the difference between the partition coefficients for the carboxylic acids under consideration, the selectivity of solvent with regard to aconitic acid also was quantified. Moreover, owing to its water‐insolubility, its availability and its low cost, tributylphosphate can be considered as a promising extractant for large‐scale applications. © 2000 Society of Chemical Industry