Reactive solvent extraction of amino acids with cationic extractants

A mixture of amino acids (arginine, phenylalanine, alanine, glycine and aspartic acid) in solution was extracted by four acidic extractants (dinonylnaphthalenesulphonic acid (DNNSA), di(2-ethylhexyl)monothiophosphoric acid (D2EHPA(S)), di(2-ethylhexyl)phosphoric acid (D2EHPA) and Versatic 10) in toluene. The extractive capacity of the organic phase for the amino acids, using DNNSA, D2EHPA(S) and D2EHPA was found to decrease in the order arginine>phenylalanine>alanine>glycine>aspartic acid, although at low pH values phenylalanine>arginine occurred for D2EHPA(S) and D2EHPA. Separation factors derived for pairs of amino acids were in the range 2·0 (glycine–aspartic acid) to 20·1 (alanine–glycine). The extractive and loading capability of the extractants for the amino acids was found to decrease in the order DNNSA>D2EHPA(S)>D2EHPA>Versatic 10, which follows the reverse order of their respective acid dissociation constants. DNNSA was shown to be a promising extractant for the extraction and fractionation of amino acids. © 1998 SCI     

二(2-乙基己基)磷酸萃取L-苯丙氨酸

以二（2-乙基己基）磷酸（D2EHPA）-正辛烷萃取L-苯丙氨酸为对象,研究了D2EHPA浓度、L-苯丙氨酸初始浓度以及pH值对萃取平衡分配系数的影响。不同pH值下负载有机相的红外谱图分析表明,D2EHPA与L-苯丙氨酸形成的萃合物结构与pH值无关。提出了在萃取过程中同时存在着离子交换反应和质子转移反应的观点。1个氨基酸分子与2个二（2-乙基己基）磷酸二聚体相结合。本文建立的萃取平衡分配系数关联式,拟合精度令人满意。     

Extraction and recovery of rhodamine B,methyl violet and methylene blue from industrial wastewater using D2EHPA as an extractant

The extraction behavior of cationic dyes namely rhodamine B (RB), methyl violet (MV) and methylene blue (MB) from industrial wastewater has been investigated using di-(2-ethylhexyl) phosphoric acid (D2EHPA) in hexane as a carrier. The extraction of cationic dyes increases with decreasing feed phase pH and increasing D2EHPA concentration in organic phase. The stripping percentage of dyes using acetic acid as the stripping agent from loaded D2EHPA was found to increase with increasing acid concentration. 98% stripping efficiency of dyes was achieved with 8.5 mol/L acetic acid solution at an organic:aqueous phase ratio (O/A) of 2:1. Parameters examined include D2EHPA concentration, effect of diluents, effect of pH, effect of initial dye concentration, equilibration time, and various stripping agents, aqueous to organic phase ratio in extraction and organic to aqueous phase ratio in stripping.     

Synergistic extraction and separation of Fe(III) and Zn(II) using TBP and D2EHPA

Waste chloride pickle liquors from hot-dip galvanizing plants, steel plants and flue dust contain reasonable amounts of heavy metals such as Zn, Cr, Ni, etc. Iron is invariably associated with most of these materials and comes into solution during leaching. Thus, the synergistic extraction of zinc(II) and iron(III) from leach solutions in tri-n-butyl phosphate (TBP)–di(2-ethylhexyl) phosphoric acid (D2EHPA) system diluted in kerosene was investigated. The Zn and Fe concentrations in the leach liquor used in the present study were 2 g/L. Experiments were carried out in the pH range of 0.5–4.0, temperature of 25°C, using sole D2EHPA, sole TBP and D2EHPA–TBP mixtures at different ratios. Results showed that the co-extraction of zinc(II) and iron(III) increased with increasing equilibrium pH using D2EHPA. It is demonstrated that the mixtures of TBP and D2EHPA are more efficient and selective than D2EHPA alone. At low pH values, the separation factor is low when pure D2EHPA is used as an extractant; however, using TBP as a synergist, the separation factor increases and results in a better separation of zinc from iron. Increasing TBP to D2EHPA ratios in the organic phase caused a slight shift to the right in the extraction isotherm of iron and a marked shift to the right in the extraction isotherm of zinc, and the maximum separation factor of 13.3 × 10³ was achieved at a TBP to D2EHPA volume ratio of 4:1 (0.58 M TBP: 0.12 M D2EHPA). Furthermore, the effect of equilibrium pH, organic to aqueous phase ratio and Cl^? concentration on the selective extraction was investigated. Using two extraction stages at the O/A ratio of 2:1 and pH_e (equilibrium pH) of 3 and 1 for zinc and iron, respectively, 99% of zinc(II) and 96.25% of iron(III) were extracted.     

Preparation of copolymer of L‐aspartic acid and L‐glutamic acid

In this article, a new copolymer of L ‐aspartic acid and L ‐glutamic acid, which may be a biodegradable high molecular polymer and can be used more widely in many areas, was synthesized. The conditions of preparation, such as catalyst, reaction time, reaction temperature, the amount of catalyst, the times of adding catalyst, and the molar ratio of L ‐aspartic acid to L ‐glutamic acid, were optimized. The copolymer was characterized by ¹³C NMR, infrared spectroscopy, and X‐ray diffractometer. The molecular weight was determined by GPC. The result indicated that production yield, purity of product, and molecular weight of product increased with amount of catalyst and molar ratio of L ‐aspartic acid to L ‐glutamic acid increasing. The best condition of preparation was the following: reacting 2–4 h at the temperature of 180–200°C. The product yield with the molecular weight 13,000.00 reached 63.2% and the purity of product was 96.33% when the copolymerization was carried out at the temperature of 200°C under vacuum for 2 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3626–3633, 2006     

非离子表面活性剂TX114浊点萃取D2EHPA的规律

引言浊点萃取[1-2]是利用表面活性剂水溶液的增溶和分相行为实现溶质富集的分离技术。由于分相后表面活性剂的富集相(亦称凝聚相)与水相的体积比非常小(0.007～0.04)[3],所以,对于被增溶的物质能够提供非常高的富集倍数和萃取效率。目前浊点萃取技术主要广泛应用于痕量有害物质     

Separation of Zinc by a Non‐dispersion Solvent Extraction Process in a Hollow Fiber Contactor

Abstract

A process for recovery of zinc from acid solution with di(2‐ethyl hexyl phosphoric acid) (D2EHPA) dissolved in iso‐dodecane was carried out at 20°C in a countercurrent tubular membrane extractor using a hollow fiber as solid support. Experiments were performed at different aqueous metal concentrations (0.1–1.0 g/L), pH 0.1–2.1, and D2EHPA concentrations (2–8 v%). It was found that both the flux of metal and the extraction extent was highly influenced by the extractant concentration and the pH of the feed solution. Overall mass transfer coefficients were determined and related to the tube side, the membrane, and the shell side mass transfer by varying the aqueous flow rate (0.38–0.80 L/min) and organic flow rate (0.22–0.57 L/min) in countercurrent flow. The overall mass transfer coefficient for zinc extraction ranged from 6.2×10^?6 m/s to 25.3×10^?6 m/s. It was concluded that extraction kinetics were a major contributor to the overall resistance to mass transfer.     

Removal of amino acids from water by adsorption on polystyrene resins

The adsorption of eight amino acids, L ‐asparagine, D,L ‐threonine, L ‐lysine, L ‐leucine D,L ‐methionine, L ‐tyrosine, L ‐phenylalanine and D,L ‐tryptophan, on the non‐polar macroporous adsorbents Amberlite XAD‐2 and XAD‐4 (polystyrene–divinylbenzene copolymers) was studied. Equilibrium adsorption experiments were conducted to estimate the types of isotherm and their parameters. The effect the chemical composition and structure of the amino acids on the efficiency of adsorption was evaluated. The influence of pH and ionic strength was also studied. The data of adsorption isotherms of the examined amino acids seemed generally to approach the Freundlich isotherm model. Tryptophan isotherm adsorption data could match in some cases the Langmuir model. The majority of the adsorption isotherms were almost linear. In terms of adsorbed amino acid on both resin surfaces, the amino acids can be ranked thus: D,L ‐tryptophan > L ‐phenylalanine > D,L ‐methionine, L ‐tyrosine > L ‐leucine > L ‐lysine > D,L ‐threonine > L ‐asparagine. In low pH solution, adsorption was generally higher than that at intermediate and high pH values. Generally, as the ionic strength increases, the adsorption of the amino acids increases. © 2001 Society of Chemical Industry     

Liquid membrane transport and separation of Zn2+ and Cd2+ from sulfate media using organophosphorus acids as mobile carriers

The transport and separation of Zn²⁺ and Cd²⁺ from binary sulfate solutions in a supported liquid membrane using di(2‐ethylhexyl)phosphoric acid (D2EHPA) and 2‐ethylhexylphosphonic acid mono‐2‐ethylhexyl ester (PC88A) as mobile carriers was studied. Batch solvent extraction experiments were conducted to obtain the reaction stoichiometries. Experiments were performed at different metal concentrations (1.4–14.5 mol m^?3), metal concentration ratios (0.4–9.2), pH (2–5), and carrier concentrations (0.1–0.6 mol dm^?3). A mass transfer model was proposed that considers diffusion in the aqueous feed and strip stagnant layers, and within the membrane. The interfacial reactions were assumed to approach equilibrium instantaneously. It was shown that the proposed model was applicable for binary Zn²⁺/Cd²⁺ systems (standard deviation, 5%). The larger separation factors of Zn²⁺ over Cd²⁺ with PC88A than D2EHPA under equilibrium (batch solvent extraction) and non‐equilibrium (liquid membrane) conditions were also evaluated and discussed. Copyright © 2003 Society of Chemical Industry     

二（2-乙基己基）磷酸/磷酸三丁酯复合萃取剂协萃对氨基苯甲酸

为强化两性官能团化合物的萃取分离性能,以对氨基苯甲酸（PABA）为被分离溶质,二（2-乙基己基）磷酸（D2EHPA）/磷酸三丁酯（TBP）/正庚烷的混合物为萃取剂进行了萃取平衡特性的研究,考察了溶液的pH值、D2EHPA浓度、TBP浓度对于萃取平衡的影响,建立了复合萃取剂协同萃取PABA的萃取平衡分配系数的表达式.结果表明,D2EHPA/TBP/正庚烷复合萃取剂萃取PABA具有明显的协萃效应,协萃机理为D2EHPA及TBP分别与PABA的Lewis碱性官能团（—NH2）和Lewis酸性官能团（—COOH）缔合形成亲油性更强的萃合物,且D2EHPA与TBP的浓度差异越小,协萃效应越明显.根据萃取平衡分配系数表达式拟合求取了表观萃取平衡常数,复合萃取剂的值远大于D2EHPA、TBP单独作为萃取剂的值,进一步证明了本文提出的协萃机理.     

Synergistic Effect of D2EHPA and Cyanex 272 on Separation of Zinc and Manganese by Solvent Extraction

The effect of bis-2-ethylhexylphosphoric acid (D2EHPA), bis (2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272), and tri-butyl phosphate (TBP) and their mixtures in various proportions for the separation and extraction of zinc and manganese from sulfate solutions were investigated. Experiments were carried out in the pH range of 0.5–5.0 at 25, 40, and 60°C. It was shown that the extraction of zinc and manganese by D2EHPA and/or Cyanex 272 can be increased by the increase in pH and temperature. The synergistic extraction and separation of zinc and manganese with a mixture of D2EHPA and Cyanex 272 was studied and the results showed that mixing the two extractants improved the extraction capacity of the mixture. Increasing the D2EHPA to Cyanex 272 ratio in the organic phase, caused a right shifting of extraction isotherms of manganese and zinc; shifting the manganese curve was more than zinc. The manganese curve had considerable right shifting with 5% D2EHPA and 15% Cyanex 272. TBP did not affect the zinc (Zn) and manganese (Mn) extraction. The stoichiometric coefficients of Zn and Mn were determined with 20% and 5% D2EHPA and 15% Cyanex 272 by applying the slope analysis method. The organic phase was stripped by sulfuric acid.     

Distribution Behavior of Amino Acid by Extraction with Di(2-ethylhexyl) Phosphoric Acid

Abstract

The distribution equilibrium of l-tryptophan (l-Trp) by extraction with di(2-ethylhexyl) phosphoric acid (D2EHPA) dissolved in n-hexane was studied. The effects of L-Trp and D2EHPA concentrations, pH, and ionic strength, particularly of L-Trp loading in the organic phase, on extraction equilibrium were examined in detail. When the amino acid loading ratio (the molar concentration ratio of the equilibrium amino acid in the organic phase to the initial dimeric D2EHPA) was less than 3 × 10^?3, one L-Trp molecule was extracted by forming a complex with four monomeric D2EHPA molecules, and the extraction equilibrium constant (K _e) was determined to be 0.045 dm³/mol. Above this loading ratio the equilibrium formula did not hold, and the apparent equilibrium constant (K _a) increased significantly with increasing loading ratio. The phenomenon was explained by taking into account two parallel reactions in which fewer D2EHPA molecules, two and one respectively, were needed to extract one l-Trp molecule.     

Kinetics of dehydration–polymerization of aspartic acid and synthesis of polyaspartate catalyzed by potassium bisulfate

The dehydration–polymerization kinetics of DL ‐ and L ‐aspartic acid, either in the absence or presence of KHSO₄, from 323 to 573 K, was studied by thermogravimetric analysis (TGA), and the synthesis of polyaspartate through the polymerization of L ‐aspartic acid was investigated by a thin‐layer polymerization method. The TGA results revealed that the dehydration–polymerization of both type of aspartic acids proceeds in two steps: first, the loss of one water molecule through the reaction of an amino group of one aspartic acid molecule and a hydroxyl group of another aspartic acid molecule, forming amide bonds, and secondly, the loss of another water molecule through the amide hydrogen and another hydroxyl group, leading to the formation of a succinimide ring. The kinetic parameters of the extrapolated onset temperatures of dehydration—the first and the second maxima—were obtained by a method similar to that of Ozawa–Flynn–Wall. The kinetic results indicate that the dehydration of L ‐aspartic acid is slightly more difficult than for DL ‐aspartic acid, and that the presence of potassium bisulfate effectively catalyzes the dehydration–polymerization of aspartic acid. In the synthesis of polyaspartate, the product with a weight‐average molecular mass (M_w) of 5000 g mol^?1 was obtained in the absence of catalyst. However, in the presence of potassium bisulfate, the products obtained had M_ws of up to 7000 g mol^?1 Copyright © 2003 Society of Chemical Industry     

二(2-乙基己基)磷酸萃取L-色氨酸

以二 (2 -乙基己基 )磷酸 (D2EHPA) -正辛烷 (体系A)及D2EHPA -正辛醇 +正辛烷 (体系B)萃取L -色氨酸为对象 ,研究了D2EHPA浓度、L -色氨酸初始浓度、稀释剂组成以及pH值对萃取平衡分配系数的影响 .结果表明 ,在实验研究涉及的pH值 (1.0     

Investigating the Synergistic Effect of D2EHPA and Cyanex 302 on Zinc and Manganese Separation

The synergistic effect of Cyanex 302 on the extraction of zinc and manganese with D2EHPA in sulfate media was investigated. Experiments were carried out in the pH range of 1.0–5.0, temperature of 23, 40, and 60°C with sole D2EHPA and Cyanex 302 as extractant and D2EHPA to Cyanex 302 ratios of 1:3, 1:1, and 3:1. The experimental results showed that the co-extraction of zinc and manganese increased with increasing equilibrium pH and temperature. Increasing the D2EHPA to Cyanex 302 ratio in the organic phase, caused a left shifting of the extraction isotherm of zinc and a right shifting of the extraction isotherm of manganese. Thus, a better separation of zinc over manganese was achieved. At low pHs, the separation factor is low when pure D2EHPA is used as an extractant; however, using Cyanex 302 as a synergist, the separation factor increases and results in a better separation of zinc from manganese. Stoichiometric coefficient of zinc for single D2EHPA and Cyanex 302 and their mixture was calculated to be close to 6.     

Equilibrium studies on reactive extraction of lactic acid with an amine extractant

Equilibrium studies on the extraction of lactic acid from aqueous solutions with tri-n-octylamine (TOA) in xylene were made in the temperature range 293–323 K. The formulation of the extracted species in the organic phase and the corresponding equilibrium constants were numerically determined at different temperatures. Also, the apparent thermodynamic functions were calculated. Finally, the effect of a water-insoluble organic acid, di(2-ethylhexyl)phosphoric acid (D2EHPA), on this extraction was investigated. Synergistic and antagonistic effects were observed in the presence of D2EHPA, mainly depending on the concentration ratio of D2EHPA to TOA.     

Molecular‐imprinted nylon membranes for the permselective binding of phenylalanine as optical‐resolution membrane adsorbents

Nylon 6, nylon 6,6, and terephthalic phenylene polyamide (TPPP) were functionalized by phase‐inversion molecular imprinting to add L ‐phenylalanine recognition ability. Formic acid containing 20 wt % nylon and 8 wt % L ‐phenylalanine was used as the solvent for the cast solution of the imprinting process. The resultant porous membranes behaved as membrane adsorbents that separated the L /D mixture of the substrate. The imprinted nylon 6 and nylon 6,6 presented high selectivity to the L ‐form substrate with respect to the TPPP membranes, but the imprinted TPPP membranes showed higher binding capacity with 0.57 μmol/g for L ‐phenylalanine. The apparent partition coefficients of L ‐ and D ‐forms by the imprinted membranes were 6.8, 4.2, and 1.7 for nylon 6, nylon 6,6, and TPPP, respectively. The separation manner of the L ‐ and D ‐forms from the mixture was also confirmed by membrane filtration under 1.5 kgf/cm² of applied pressure. The imprinted nylon 6, nylon 6,6, and TPPP membranes had separation factors of L ‐ and D ‐phenylalanines of 1.1, 1.1, and 1.2, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 620–626, 2005     

非离子表面活性剂C12E10的浊点分相行为及其应用

引言 络合萃取技术对极性有机物稀溶液和金属离子的分离具有高效性和高选择性,已广泛应用于湿法冶金领域.由于萃取剂在萃残液中分子水平的溶解以及萃取塔器操作时水相对于萃取剂相细小液滴的夹带,造成了一定程度的萃取剂流失和环境污染,同时,由于萃取剂大都分子量较大,生物降解性能不佳[1],因此,开展从水溶液中回收萃取剂的研究是十分必要的.     

Efficacy of tri-n-octylamine,tri-n-butyl phosphate and di-(2-ethylhexyl) phosphoric acid for reactive separation of protocatechuic acid

ABSTRACT

Owing to its chemical and pharmacological significances, the efficacy of reactive separation of protocatechuic acid (0.001–0.01 kmol m^?3) from aqueous stream by means of tri-n-octylamine (TOA), di-2-ethylhexyl phosphoric acid (D2EHPA) as well as tri-n-butyl phosphate (TBP) in octanol has been investigated, in terms of extraction efficiency, loading ratio, equilibrium complexation constants, and distribution coefficients. Extraction ability was obtained in the order TOA (91.2%) > TBP (88.64%) > D2EHPA (86.43%). In all cases, 1:1 protocatechuic acid:extractant complex is obtained. Further, diffusion coefficients, number of stages for extraction systems, and relative basicity model were used for relating the efficacy.     

EXTRACTION OF METAL IONS WITH DZEHPA FROM MIXED AQUEOUS-ORGANIC MEDIA

Extraction of metal ions from the aqueous-organic solution containing dimethyl formamide(DMF), dimethyl sulfoxide(DMSO) and acetonitrile(AN) was investigated by using di-2-ethylhexyl-phosphoric acid(D2EHPA) as an extractant. The organic phase was a binary solution of D2EHPA and n-hexane, or D2EHPA and toluene, while the polar phase was a three component solution of metal salt, non-aqueous solvent and water. The extracted metal ions were Cr(III), Fe(III), Al, Cu, Ni, Co(II), Mg and Ag.

The extraction behaviors may be explained by the solvation ability of non-aqueous solvents, the decrease in distribution of the extractant and extract into the organic phase, and the interaction between the extractant and non-aqueous solvents due to the dissolution of non-aqueous solvents in the organic phase.