Amine-based Extraction Research Articles

One-step recycling of mineral acid from concentrated gold mining wastewater by high-temperature liquid–liquid extraction

Liquid-liquid extraction (LLE) was investigated for mineral acid (H2SO4) recycling from membrane distillation (MD) concentrate treating gold mining wastewater. Five extractants (Alamine 336, Aliquat 336, Cyanex 923, TEHA, and Versatic Acid) were preferably diluted in kerosene or 1-decanol (30 vol%) in extraction experiments conducted at 60 °C. Cyanex 923 extracts the mineral acid mainly by solvation of the neutral species, whereas the mechanisms for amine-based extractants involve an ion-pair formation. An important outcome was the temperature contribution to extraction efficiency. The endothermic nature of extraction would be advantageous to acid recovery and the integration of MD with LLE considering that the MD concentrated is produced at ∼ 60 °C. If stripping is considered, Aliquat 336 (diluted in 1-decanol), Cyanex 923, and TEHA (diluted in 1-decanol) become the most appropriate organic phases for mineral acid recycling given the greater efficiency for acid recovery (>90%) after a single contact stage. The results for extraction efficiency, selectivity, stripping efficiency, and costs demonstrated that TEHA (30 vol% in 1-decanol) was the most cost-effective (US$ 0.57/kg) alternative for mineral acid recycling. It would be possible to recover 4.8 kg of mineral acid per cubic meter of MD concentrate as an acid solution (concentration: 25 mmol/L). Overall, LLE was a feasible alternative to enhance gold mining wastewater exploitation and MD concentrate management. From a broader perspective, acid recycling would imply environmental gains, economical savings given the lower requirements of neutralizing agents for mining wastewater treatment and residual sludge disposal, or additional incomes by its commercialization.

Effect of alkyl chain configuration of tertiary amines on uranium extraction and phase stability – Part I: Evaluation of phase stability, extraction, and aggregation properties

Amine-based extraction processes are broadly exploited for the selective extraction of uranium from sulfuric leaching liquors. The molecular forces (that is, the enthalpy associated with the multi-scale structuration of tertiary amines) are balanced by entropic effects that have not yet been identified. This first part in a series of reports describes the effects of the alkyl chain configuration on the phase stability and aggregation properties of tertiary amines. It is demonstrated that tertiary amines with longer or slightly branched alkyl chains provide better phase stability and enable constant extraction of uranium. In comparison, more branching of the alkyl chains hinders the formation of a highly curved interfacial layer, thus preventing efficient extraction. Combined small-angle scattering determination of the nanostructures in the organic phase and oil–water surface tension measurements revealed that the alkyl chains effects on the efficiency of the extraction process and phase stability are associated with reverse aggregates with smaller polar core volumes and less co-extracted water, suggesting that packing of the alkyl chains has a direct impact on the extraction efficiency of the solvent extraction system.

The separation of zirconium and hafnium from (NH4)3Zr(Hf)F7 using amine-based extractants

The separation of zirconium and hafnium from (NH4)3Zr(Hf)F7 using amine-based extractants

Separation of Zr and Hf from sulfuric acid solutions with amine-based extractants by solvent extraction

The extraction and separation behavior of Zr and Hf was investigated from sulfuric acid solutions by using amine-based extractants. In the sulfuric acid concentration range of 0.1–3M, zirconium was selectively extracted over hafnium by using amines. Among the tested amines (Aliquat 336, Alamine 300, Alamine 308, Alamine 336, and TEHA), Alamine 308 led to the highest separation factor of 12.4 at 0.5M H2SO4 solution. The extraction behavior of Zr and Hf in sulfate medium by amines was compared with that by acidic extractants in terms of solvent extraction reaction and complex formation. Quantitative stripping of both metals from the loaded Alamine 308 was achieved by using low concentration of Na2CO3 solution.

Separation of Zr from Hf in Hydrochloric Acid Solution Using Amine-Based Extractants

Liquid–liquid extraction studies have been performed to investigate the selective extraction of zirconium (Zr) and hafnium (Hf) in hydrochloric acid medium. For this purpose, several amine-based extractants were used at varying concentrations of extractants and HCl. Among the tested extractants, Alamine 336 showed good selectivity for Zr over Hf and led to the highest separation factor. A McCabe–Thiele diagram was constructed for the extraction of Zr with Alamine 336 in kerosene, and the tested batch simulation of counter-current extraction studies showed that the extractions of Zr and Hf impurities were 98.5% and 12.5%, respectively. The coextracted Hf was scrubbed with dilute H2SO4 solution, and complete stripping of Zr was successfully achieved from the loaded organic phase by simple contact with 1 M HCl solution.

Reactive Extraction of Propionic Acid Using Tri-n-octylamine

Propionic acid has been received increasing attention due to its various usages as an antifungal agent in food and a chemical in the production of several chemical products. In order to develop an alternative production process of propionic acid such as fermentation of glycerol, the cost effective recovery process of propionic acid from its fermentation broth is needed. Differently from conventional physical extraction, long chain amine (TOA)-based extraction is the separation process using reactions between amine and materials extracted. The equilibrium distribution of propionic acid increased with amine concentration and decreased with increase of n-heptane composition in mixed diluents. From the loading values with TOA concentrations, it was found that the stoichiometries of acid-amine-1-octanol complex were (1,1) and (1,1,1). From this study, amine-based extraction can be promising separation process for the recovery of propionic acid.

Purification of 1,3-Propanediol for Production of Polytrimethylene Terephthalate (PTT) from Biomass

1,3-Propanediol (1,3-PDO) has received increasing attention due to usage as the monomer of biopolymer-polytrimethylene terephthalate (PTT) which can be produced from bioresources. For the economic production of 1,3-PDO, the deveolpment of cost effective removal process of by-products such as carboxylic acids from its fermentation broth. Amien-based extraction is the separation process using reactions between amine and materials extracted. The extractabilities for carboxylic acid increased with amine concentration and decreased with pH values. It was also observed that the removal efficiency of carboxylic acids from 1,3-PDO solution was above 90% without any coextraction of 1,3-PDO. From this work, it was found that the amine-based extraction can be promising separation process for the production of pure 1,3-PDO.

Temperature Effect on the Extraction of Carboxylic Acids by Amine-Based Extractants

The extraction of carboxylic acids by extractants that contain lipophilic amines is dependent on temperature. That phenomenon is used in industry, where extraction is conducted at approximately ambient temperature and back-extraction occurs at an elevated temperature. In this work, stronger temperature effects are observed in cases where the alkyl amine is relatively weak (pHhn <5), the alkyl amine is highly substituted, the carboxylic acid is relatively weak (pKa >3), polycarboxylic acid is extracted, the concentration of the amine and/or the carboxylic acid in the organic phase is low, the amine and/or acid are bulky, and the diluent of the amine has low polarity. This shows that the temperature effect is strong in systems where the ion-pair interaction between the protonated amine and the acid's anion is relatively weak (weak acid and amine), where ion-pair stabilization is dependent on the aggregates' formation (hydrophilic acids, low-polarity amine, low concentration) and where the formation of those aggregates is hindered (bulky amines and acids).

Acids Extraction by Amine-Based Extractants: An Analysis of the Effect of Anion Concentration in the Aqueous Phase Using the Donnan Model

The concentration of an acid's anion in the aqueous phase affects that acid's extraction efficiency by amine-based extractants. The anion effect is explained by using the acid-dissociation equation in the case that the acid is mainly extracted though H-bonding or solvation. This explanation does not hold in the extraction of strong acids such as hydrochloric or dichloroacetic acid by a relatively strong base extractant (pKaB ≫ pKaA). To explain the anion effect in these systems, we reexamined our theory and modified it with the Gibbs−Donnan model. The modified theory shows that the proton activity in the organic phase could differ significantly from that in the aqueous phase, depending on the relative activities of the anions in those two phases. Thus, in turn, the relative activity of the anion affects the protonation of the amine in the organic phase, pKaB. Accordingly, the modified theory successfully explains the effect of the anion concentration on the extraction efficiency.

Extraction of Carboxylic Acids by Amine-Based Extractants: Apparent Extractant Basicity According to the pH of Half-Neutralization

This article analyzes the extraction of hydrochloric, trichloroacetic, propionic, lactic, and acetic acids by nine amine-based extractants, including Primene JMT, tris(2-ethylhexyl)amine (TEHA), an...

Effect of pH on Dicarboxylic Acids Extraction by Amine-Based Extractants

The work presented here studies the effect of pH on the extraction of malic, maleic, and glutaric acids by Primene JMT, tris(2-ethylhexyl)amine , and tri-n-octylamine and the IR and NMR spectra of the formed organic phases. Three categories were found: (1) In the first case, the extractant is a weaker base than both anions of the acid, i.e., pHhn < pKa1 < pKa2. The undissociated acid is the dominant species in the organic phase. Extraction is mainly due to H-bonding or solvation interactions and shows a drop-off at pH ≈ pKa1. (2) For systems in which pKa1 < pHhn < pKa2, at acid-to-amine molar ratios greater than 1, undissociated acid is above-stoichiometrically extracted, R3NH+···AH-···HAH, in addition to ion-paired acid. As the pH is increased, the undissociated acid is neutralized first. Thus, the extraction curve shows a drop-off at pH ≈ pKa1. At stoichiometric loading, the monovalent ion pair, R3NH+···AH-, becomes the dominant species. Upon further pH elevation, the protonated amine R3NH+ is the neut...

Competitive Complexation/Solvation Theory of Solvent Extraction. III. Influence of Active Solvents on Acid Solvent Extraction by Amine Based Extractants

Competitive complexation/solvation theory is used to interpret the influence of active solvents on solvent extraction of acids by amine-based extractants. This theory is based on the modified competitive preferential solvation theory, the concept of amphoteric properties of extractants, and the concept of changing aggregation structures when extractant loading increases. Active solvent concentration parameter is introduced to the quantitative consideration of the extraction systems. The paper discusses four possible stages of extraction behavior, interaction mechanisms, and aggregate structures formation, depending on solute–solvent affinity constant and concentration ratios. The influence of different types of active solvents in each stage is analyzed. Mathematical description is introduced for the quantification of results and process simulation. It gives a key for preliminary quantitative prediction of suitable extraction systems.

Application of reactive extraction to recovery of carboxylic acids

Carboxylic acids are examples of compounds with wide industrial applications and high potential. This article presents the principles of reactive extraction along with the characteristics of tertiary amine extractants, while is given on considering the effect of the amine class and chain length. As such a brief overview the current research on reactive extraction, including the recovery of citric acid, selective amine-based extraction, and extractive fermentation is given. When discussing extractive fermentation, strategies for reducing solvent toxicity are also suggested based on specific examples. Finally, solvent regeneration and stripping of extracted acid are explained.

Selective extraction of succinic acid from binary mixture of succinic acid and acetic acid

In production of succinic acid by fermentation, succinic acid and acetic acid are co-produced. To purify the succinic acid from binary-acid mixture of succinic acid and acetic acid, the tertiary amine-based extraction was used. In 1-octanol, the selectivity for succinic acid was proportional to the chain length of tertiary amine. But, the distribution of acids into organic phase was low in n-heptane. These results are due to the different degree of intramolecular hydrogen bonding of succinic acid and hydrophobicity of each acid.

Amine-Based Extraction Recovery of Cu(II) from Aqueous Solutions in the Presence of EDTA. Equilibrium Studies

The distribution ratios of Cu(II) between kerosene solutions of Aliquat 336 and water containing EDTA (ethylenediaminetetraacetic acid) are measured. Experiments were performed as a function of the pH, the concentration of Cu(II), the concentration ratio of EDTA to Cu(II), and the concentration of amine. It is shown that the distribution ratios first increase with pH and then decrease with a further increase in pH up to 7.0. The effect of temperature on the extraction was studied, and the enthalpy of the extraction reaction was determined. Finally, the nonideal behavior of the organic phase is discussed.

PH Dependence of Carboxylic and Mineral Acid Extraction by Amine-Based Extractants: Effects of pKa, Amine Basicity, and Diluent Properties

Extraction mechanism strongly depends on the acid-base properties of the extractant as well as on those of the extracted acid. For amines of basicity similar to that of the anion of the extracted acid, or higher, extraction is governed by ion-pair formation. H-bonding of undissociated acid becomes important only for extraction of weak acids by weak bases. Extraction mechanism determines the effect of various parameters. Thus the degree of extraction is most sensitive to pH at about the pK{sub a} of the amine for extraction through ion-pair formation. Extraction by H-bonding, however, is most sensitive at about the pK{sub a} of the acid. Polar and protic diluents enhance extraction through ion-pair formation, but may have no effect on H-bonding or even hinder it. Extraction through ion-pair formation prefers stronger acids at low pH while H-bonding extracts weaker acids more efficiently. Clarification of the extraction mechanism and its dependence on extracted acid properties and on the pH provide for designing extractants of high efficiency and selectivity.

RECOVERY AND CONCENTRATION OF STRONG MINERAL ACIDS FROM DILUTE SOLUTIONS THROUGH LLX. I: REVIEW OF PARAMETERS FOR ADJUSTING EXTRACTANT PROPERT AND ANALYSIS OF PROCESS OPTIONS

ABSTRACT Parameters affecting extraction power of amine-based extractants for mineral acids are reviewed. Means for adjusting extractant composition for reversible extraction of mineral acids from dilute solutions are discussed. The paper also analyses process options for recovery of the extracted acid at concentrations higher than those in the original solution. Introduction of the required energy as thermal energy without resorting to evaporation of the acid or to evaporation of water is highly attractive.