Tri-n-octylamine Research Articles

Utilizing environment-friendly eugenol as a diluent with trioctylamine for the reactive extraction of aqueous levulinic acid

This paper focuses on the reactive extraction of levulinic acid (LA) from aqueous solution by reactive extraction. This goal is achieved using eugenol, a green alternative in the industry, as a solvent in the liquid-liquid equilibrium (LLE) measurements for the ternary system of LA + Eugenol + H2O and quaternary systems of LA + Eugenol/ Methanol (MeOH) + H2O + Tri-n-octylamine (TOA) at T = 293.15 K. Additionally, the distribution coefficients (KD) were calculated for LA using the two diluents. Also, the ability of different diluents with TOA, in the extraction of LA were compared. The distribution coefficient of eugenol with TOA (KD = 9.44) is compared with other organic diluents which indicated that eugenol is a suitable option. MeOH, being the shortest chain alcohol, also turned out to be a diluent that could be utilized for extraction of LA with TOA. Furthermore, the Non-Random Two-Liquid (NRTL) excess Gibbs energy model was applied to correlate the measured phase equilibria. The obtained parameters were further validated using a decanter model.

Realization for rapid extraction of citric acid from aqueous solutions using deep eutectic solvents

Citric acid is highlighted as a valuable chemical in the pharmaceutical and food industries. We present an extraction technique using hydrophobic deep eutectic solvents (HDES), which has emerged as an efficient and sustainable alternative solvent for the purification and recovery of this important compound from the production environment. HDES systems were formed by combining DL-Menthol as the hydrogen bond donor (HBD) and Tributyl Phosphate (TBP) as the hydrogen bond acceptor (HBA). HDES exhibited excellent performance as a hydrophobic medium for both physical and reactive extraction of citric acid. To demonstrate the effect of HDES composition over-extraction ability, HDESs with various DL-Menthol mole fractions (Xm) were prepared and tested. TOA molar concentration, initial citric acid concentration (CA0), and effect of temperature were also investigated as other effective parameters. The optimized HDES demonstrated remarkable extraction efficiency (E%) of over 90% using tri-n-octylamine (TOA) as the extractant, while offering rapid extraction rates within minutes. Our findings highlight the promising potential of these environmentally conscious HDES for sustainable chemical separation processes.

Removal of Co(II) and various metal ions from the residue of the zinc plant through solvent extraction using both acid and neutral extractants

AbstractThe recovery of cobalt from secondary sources is a crucial issue in technology development, particularly for its numerous applications in various industries. Solvent extraction has proven an effective method for metallic ions separation from secondary sources. The main goal of this work was to study the separation of metals by solvent extraction technique from zinc plant leach waste. Initially, several extractants, including Cyanex 272, Cyanex 301, LIX 5640 H, Alamine 336, and tri‐n‐octylamine (TOA), were tested to treat the leach solution. It was discovered that the saponified extractant di‐(2‐ethylhexyl) phosphoric acid (D2EHPA) (10%) + tri‐n‐butyl phosphate (TBP) (10%) effectively eliminated interfering elements such as manganese, zinc, and iron, with extraction efficiencies of 95%, 98%, and 99.9%, respectively. To increase the concentration of cobalt in the purified solution, the cobalt recovery step was performed using various acids on the loaded organic phase. The best outcome was achieved using ammonium sulphate salt (1 M), which recovered about 50% of the cobalt present in the organic phase. The recovered cobalt was then subjected to the electrowinning process to produce cobalt metal of high purity. A cathodic current density of 100 A/m2 was determined to be the optimal current for the electrolyte solution. Lastly, scanning electron microscope (SEM) and X‐ray fluorescence (XRF) analyses were carried out to examine the structure and purity of the resulting metallic cobalt, which was found to have a purity of 99.5%.

Removal of acrylic acid from aqueous solution utilizing tri-n-octyl amine or tributyl-phosphate in edible oils through reactive extraction

The separation of acrylic acid from its aqueous solutions with edible oils by reactive extraction method was investigated. Walnut oil, hazelnut oil, sesame oil, and safflower oil were used to prepare a relatively environmentally friendly and low-toxic organic phase. Tributyl phosphate (TBP) and tri-n-octyl amine (TOA) were chosen as extractants. In addition, a modifier (octanol, decanol, octyl acetate, methyl isobutyl ketone, 2-octanone, dimethyl phthalate) was added to the organic phase, and its effect on the extraction was investigated. The temperature effect (25, 45, and 65 °C), one of the parameters affecting the extraction process, was investigated. The results were presented as distribution coefficient (D), extraction efficiency (E%), and loading factor (Z). In the physical extraction experiments performed with edible oils, the extraction efficiency ranged between 14 and 21%, while it reached around 70% with TBP and above 90% with TOA in the reactive extraction. It was observed that the highest efficiency among the oils was obtained with safflower oil (71.88% for TBP and 92.68 % for TOA) for both extractants used. Moreover, using octanol as a modifier in the organic phase had a positive effect on the removal of acrylic acid from aqueous media by reactive extraction.

Reactive extraction of pyridinedicarboxylic acid (PDCA) with tri-n-octylamine and Aliquat 336 in 1-octanol – A promising approach to access microbially produced PDCA

Pyridinedicarboxylic acids (PDCA) are analogues to terephthalic acid and promising molecules for the production of bio-based plastics. Previous work achieved the microbial production of PDCAs from the renewable resource lignin but an efficient and low cost method to recover PDCA from fermentation broth is still missing. Reactive extraction is commonly applied for the extraction of carboxylic acids from aqueous phase. In this study, we investigate reactive extraction of PDCA with the two extractants tri-n-octylamine (TOA) and Aliquat 336 in the diluent 1-octanol. The extraction and re-extraction were optimized with 2,5-PDCA in an aqueous solution leading to up to 98 % extraction for both extractants. Re-extraction by pH swing resulted in > 95 % re-extracted 2,5-PDCA. A scale-up in liquid–liquid centrifuges enabled continuous extraction and re-extraction in liter scale with a yield of 95 %. A concentration factor of 3.6 was achieved and the organic phase was recycled. The approach also showed transferability to the processing of complex fermentation solution. 2,4-PDCA, microbially produced in a bioprocess, could be recovered by 65 % in one single extraction and re-extraction step from biomass-free fermentation broth.

Selective and efficient separation of levulinic, acetic and formic acids from multi-acid solutions by adjusting process parameters

This investigation focuses on the recovery of levulinic- (LA), acetic- (AA) and formic acids (FA) from aqueous mixed-acid solutions by reactive extraction using tri-n-octylamine (TOA). Alcohols were found to be the most efficient solvents tested. Recoveries increased with shorter alcohol chain length and higher TOA concentrations. Yields decreased with pH and maximum efficiencies were obtained at the unadjusted pH (1.83) of the ternary-acid solutions for all acids; with LA, maximum selectivity occurred at pH 5. Higher TOA levels enhanced efficiency in mixtures but slightly reduced selectivity. For LA recovery, efficiency and selectivity using 0.5 M TOA in 1-hexanol were 92 % and 23.8 %, respectively. Co-extraction of AA ceased at consecutive extractions (from 2nd to 10th) and 93.6 % of LA was recovered with a selectivity of 98 % after ten subsequent steps. LA in the organic phase was stripped with an efficiency of ~91 % with aqueous 1.0 M NaNO3. Selective extraction of AA and FA from binary-acid solutions was achieved at pH 5. The selectivity and separation factor decreased at higher TOA concentrations; however, 94.2 % of the AA was recovered with a selectivity of 93 % after seven successive extractions, followed by ~93 % recovery by back extraction. The remaining FA (94.2 %) in the aqueous solution had a selectivity of ~95 %. The data show that multi-stage reactive extraction can selectively separate LA, AA and FA from ternary- and binary-acid solutions.

High-efficient removal of tungsten from hafnium by TOA/XAD-7 extraction resin from HCl-HF media

ABSTRACT For removal of the natural isobar 182W interference prior to ultra-trace 182Hf determination by accelerator mass spectrometry, an extraction chromatographic method for separation of Hf from W has been developed by using a newly synthesized tri-n-octylamine (TOA)/XAD-7 resin as the stationary phase and HCl-HF media as the mobile phase. Based on the TOA liquid-liquid extraction studies in HF and HCl-HF solutions at wide concentration range, a maximum separation factor of 8.6 × 103 for W/Hf was obtained in 8 M HCl-0.05 M HF solution. Subsequently, the macroporous organic polymer-based TOA/XAD-7 resin was prepared by vacuum impregnation technique and its morphology, chemical structure and composition were characterized by SEM, EDS, FT-IR, TG-DSC, and EA. The results showed the self-assembly TOA/XAD-7 resin uptakes about 50% of extractant and keeps intact binding characteristic for metal ions. Hence, this resin was employed to investigate the column chromatographic behavior of Hf and W with variable parameters of sample loading and column bed dimensions. As a result, a high yield of more than 99% for Hf and high decontamination factor of 3.2 × 105 for W were achieved under the optimal column condition. The strategy developed provides a simple and efficient alternative to sample preparation for 182Hf measurement.

Elimination of glufosinate ammonium from aqueous solution with hollow fiber supported liquid membrane and mathematical modeling

A hollow fiber supported liquid membrane (HFSLM) was used to extract and eliminate glufosinate ammonium from aqueous solution using TOA (tri-n-octylamine) in hexane and sodium hydroxide (NaOH) as carrier and stripping phase, respectively. Maximum extraction (∼76%) and stripping (∼75%) were achieved by feed solution at pH 1.0, temperature 60 °C, TOA concentration 6% (v/v) and NaOH concentration 1.0 M. The developed mathematical model exhibited high precision when predicting the concentration of glufosinate ammonium in raffinate solution and extraction percentage under different feed flow rates, with correlation coefficient (R 2) 0.9863.

Liquid–Liquid Equilibria of the System Nitric Acid + Phosphoric Acid + Calcium Nitrate + Water + Tri-n-Octylamine at 298.15 K

Liquid–liquid equilibrium (LLE) data of the system nitric acid + phosphoric acid + calcium nitrate + water + tri-n-octylamine (TOA) were measured at 298.15 K and atmospheric pressure. The distribution coefficients of nitric acid, phosphoric acid, calcium nitrate, and water and the separation factors of nitric acid against phosphoric acid, nitric acid against calcium nitrate, and nitric acid against the water were calculated. Based on these data, the capability and selectivity of TOA for extracting nitric acid in this system were evaluated. The experimental results were used to obtain binary interaction parameters and pair parameters as correlated by the electrolyte non-random two-liquid (eNRTL) model. The eNRTL model was shown to be suitable for predicting the LLE data of this system, with a root-mean-square deviation of just 1.17%.

Investigation of reactive extraction of monocarboxylic acids with menthol-based hydrophobic deep eutectic solvent by response surface methodology

ABSTRACT The growing demand for producing organic acids by fermentative techniques has increased the significance of separating carboxylic acids from their fermentation broth with the reactive extraction process. Considering the environmental impacts, deep eutectic solvents can be considered as a potential green alternative for the replacement of volatile organic solvents commonly used in the extraction process. In this study, a new type of green solvent named hydrophobic deep eutectic solvent (HDES) based on decanoic acid as a hydrogen bond acceptor and menthol as a hydrogen bond donor was utilized for the reactive extraction of formic, acetic, and propionic acids from their aqueous solutions. The effect of initial acid concentration, HDES molar ratio, and tri-n-octyl amine (TOA) concentration on extraction efficiency was investigated. Modeling of the reactive extraction process was performed via a response surface methodology with a central composite design. Herein, the effect of the parameters of TOA concentration, HDES molar ratio, and initial acid concentration on the distribution coefficient was investigated. According to the results, it was reported that the most effective parameter on the extraction efficiency (%E) was the amount of extractant. The results of the experimental studies showed that the highest separation efficiency was obtained for 5% initial concentrations of formic, acetic, and propionic acids by using a mixture of 0.5 HDES molar ratio solvent and 1.9 mol/L TOA. The extraction efficiencies of these acids were found to be 88.71, 92.52, and 95.90 with ±0.1 standard deviation, respectively.

Liquid–liquid extraction of levulinic acid from aqueous solutions using hydrophobic tri-n-octylamine/alcohol-based deep eutectic solvent

Levulinic acid (LA) is one of the top-12 most promising biomass-based platform chemicals, which has a wide range of applications in a variety of fields. However, separation and purification of LA from aqueous solution or actual hydrolysate continues to be a challenge. Among various downstream separation technologies, liquid–liquid extraction is a low-cost, effective, and simple process to separate LA. The key breakthrough lies in the development of extractants with high extraction efficiency, good hydrophobicity, and low cost. In this work, three hydrophobic deep eutectic solvents (DESs) based on tri- n -octylamine (TOA) as hydrogen bond acceptor (HBA) and alcohols (butanol, 2-octanol, and menthol) as hydrogen bond donors (HBDs) were developed to extract LA from aqueous solution. The molar ratios of HBD and HBA, extraction temperature, contact time, solution pH, and initial LA concentration, DES/water volume ratios were systematically investigated. Compared with 2-octanol–TOA and menthol–TOA DES, the butanol–TOA DES exhibited the superior extraction performance for LA, with a maximum extraction efficiency of 95.79±1.4%. Moreover, the solution pH had a great impact on the LA extraction efficiency of butanol–TOA (molar ratio=3:1). It is worth noting that the extraction equilibrium time was less than 0.5 h. More importantly, the butanol–TOA (3:1) DES possesses good extraction abilities for low, medium, and high concentrations of LA

Thymol-menthol-based deep eutectic solvent as a modifier in reactive liquid–liquid extraction of carboxylic acids from pretreated sweet sorghum silage press juice

Reactive liquid–liquid extraction has been widely investigated as a means of isolating carboxylic acids from fermentation broths. However, commonly applied fossil-based solvent phases should be replaced by green alternatives. In this work, we investigate a thymol-menthol-based deep eutectic solvent (tmDES) as a green alternative to the commonly applied modifier 1–octanol for the extraction of lactic acid, acetic acid, and oxalic acid from a model solution and pre-treated sweet sorghum silage press juice (pSPJ); tri–n–octylamine (TOA) was used as a reactive extractant. Additionally, NMR spectroscopy was used to detect interactions between menthol and thymol molecules, as well as among these and TOA and lactic acid. NMR measurements of tmDES revealed the existence of multiple intermolecular contacts between thymol and menthol. Furthermore, nuclear Overhauser effects (NOEs) between the tmDES, TOA, and lactic acid molecules were found. Extraction experiments showed that tmDES improves the extraction efficiency when using pSPJ as the feed phase. The maximum extraction efficiency for lactic acid increased from 35.0 ± 0.8 % to 48.7 ± 0.7 % and for acetic acid from 52.4 ± 0.2 % to 82.2 ± 0.6 % when using a tmDES instead of 1–octanol at 50 °C. Furthermore, the use of tmDES resulted in higher extraction efficiencies as compared to the use of 1–octanol at equilibrium pH values ranging from five to seven, which is a common pH range for fermentation. Besides having superior biocompatibility and extraction efficiency as compared to 1–octanol, tmDES allow carboxylic acid extraction processes to be carried out at higher pH levels.

Modeling of synergistic solvent extraction of Zr(IV) / HCl / TOA+Cyanex 921 system using statistical analysis and neural network

Multi-linear regression analysis (MLR), radial basis function (RBF) and multilayer perceptron (MLP) of artificial neural network (ANN) with five inputs (temperature, concentrations of HCl, TOA, Cyanex 921, Zr (IV) and percentage of extraction (%E)) as only output were employed for the construction of models. It was observed that ANN (RBF and MLP) performed better as compared to the MLR model. Based on the models proposed, the extraction of Zr(IV) could be predicted under variable experimental conditions of concentrations of HCl, TOA (Tri-n-octylamine), Cyanex 921 (Tri-n-octyl phosphineoxide), Zr(IV) and temperature. The nonlinear and complex relation between the percentage of extraction and operating variables have been determined using two and three layered feed forward neural network with back-propagation of error learning algorithm. Uncertainties in data have been determined in terms of statistical parameters such as root mean-squared error and R-squared values to check the efficiency of the model for prediction.

Reactive extraction of gallic acid using tri-n-octylamine in a biocompatible mixture of diluents

The present study is an approach to develop a biocompatible extraction system using tri-n-octylamine (TOA), with a modifier, 1-decanol and inert diluent, n-dodecane for the recovery of gallic acid (GA) from aqueous solution. The effects of GA concentration, modifier volume ratio, solvent polarity and pH of aqueous solution on reactive extraction of GA, are examined. With optimized extraction system of 20% TOA with 40% 1-decanol and 40% n-dodecane, further investigations are carried out for the determination of reaction stoichiometry ( m = 1.53 – 2.02), equilibrium constants (K E = 20.30 – 83.23) and thermodynamics (∆H o = -94,385.86 J.mol –1 , ∆S o = -267.51 J.mol –1 .K –1 and ∆G o = -14,627.83 to -6602.54 J.mol –1 .K –1 ) in the range of GA concentrations (0.00294 kmol.m –3 – 0.04703 kmol.m –3 ) at different temperature (298.15 K – 328.15 K) using a bio-inspired, population based genetic algorithm, differential evolution (DE). At the temperature 298.15 K, maximum distribution of GA in organic phase is found as 81%.

Liquid-liquid extraction of zirconium(IV) from sulphuric acid medium using a binary mixture of tri-n-octylamine and Cyanex923 in kerosene

The extraction behaviour of zirconium(IV) from sulfuric acid medium has been studied with a binary mixture of tri-n-octyl amine (TOA) and Cyanex923 (a mixture of four trialkyl phosphine oxides) in kerosene using a novel liquid-liquid extraction method. Quantitative extraction of zirconium(IV) with binary mixture of Cyanex923 and TOA in kerosene was studied by changing different parameters such as acid variation, extractant variation, effect of chloride ion concentration, effect of temperature, metal concentration variation, diluent effect, and pH effect. The percentage of extraction of zirconium(IV) decreased when the concentration of Cyanex923 and TOA increased. The percentage of zirconium(IV) was observed as 97.56% in a binary mixture of 0.007 M Cyanex923 and 0.06 M TOA. Kerosene was found to be an effective diluent for the extraction of zirconium(IV) with 97.56% extraction using a binary mixture of Cyanex923 and TOA. In addition, the stripping of the zirconium(IV) metal ion in the organic phase was also examined.

Monitoring and investigating reactive extraction of (di–)carboxylic acids using online FTIR – Part II: Reaction equilibria, reaction kinetics and competition within the complex formation between itaconic acid and several amine extractants

The downstream processing of biocatalytically produced (di–)carboxylic acids still is a challenging task. One innovative approach, demonstrating industrial applicability, applies an initial reactive extraction (RE) using hydrophobic amine extractants into an organic solvent, followed by a subsequent back-extraction (BE) using water soluble amine extractants into a (fresh) aqueous solution. Although showing promising results in terms of yield and selectivity, state-of-the-art amine extractant selection is only based on trial-and-error screening approaches. Thus, to enable an optimized process design and thereby optimized downstream processing, a deeper understanding of RE and BE on a molecular level is crucial.Within this work, we successfully applied an experimental setup incorporating online Fourier Transform Infrared (FTIR) spectroscopy to elucidate influencing factors on RE and BE as well as to provide a guideline for an optimized selection of amine extractants. Investigations on the kinetics of complex formation between itaconic acid (IA) and tri-n-octylamine (TNOA) in 1-decanol revealed the reaction order to be zero in TNOA, indicating that mass transfer is the rate limiting step in RE. Reaction equilibrium investigations revealed that for all IA - amine extractants combinations in 1-decanol reaction equilibrium was almost completely on the product (complex) side. The strength of the acid-extractant complexes was evaluated using FTIR experiments, providing a novel approach / methodology to efficiently select an optimal combination of amine extractants for RE and BE. Applying the novel online FTIR spectroscopy setup allowed to monitor a complete process sequence of RE and BE of IA with selected amine extractants, validating the proposed guidelines for an optimized selection of amine extractants. The results of this work will facilitate the definition of appropriate RE and BE systems for biocatalytically produced (di–)carboxylic acids.

Reactive extraction of caproic acid using tri n-octylamine + 2 octanol system

Recovery of dilute caproic acid from waste streams by reactive extraction using tri n-octyl amine (TOA) as an extractant and 2 octanol as a diluent is attempted in this work. 0.005–0.0572 mol/lit concentration of caproic acid found in aqueous streams of fermentation broth is left untreated or found too expensive to recover by conventional methods. Reactive extraction is an intensified technology implemented for maximum recovery of acid. An identical concentration range of caproic acid was used for batch experiments using toluene, benzyl alcohol, 2 octanol, and decanol as diluents in independent experimental runs. A comparative experimental study was made by adding TOA as an extractant. The results revealed 2 octanol to be the suitable diluent among selected diluents for extraction of very dilute acid concentrations of 0.005 mol/lit. Hence, 2 octanol was selected for further study of reactive extraction experiments. Nearly 54–87 % degree of extraction was observed in physical extraction when 2 octanol alone was used as a diluent. However, reactive extraction using TOA in 2 octanol exhibited a synergetic effect on the recovery of the acid. The degree of extraction enhanced nearly by 30% and is reported in the range 86 to 98.60 % whereas the distribution coefficient is in the range 6.5–67. Encouraging results were achieved in a continuous counter-current extraction experiment, extraction efficiency was found to be 91% for very dilute acid (0.005 mol/lit). The novelty of the work is in exploring the TOA + 2 octanol system for extraction of caproic acid in batch and continuous mode of operation. Experimental work on reactive extraction of carboxylic acid using counter-current packed column is rarely reported and hence we have explored this technology in a continuous mode of operation.

Development of N,N,N′,N′-tetra-2-ethylhexyl-thiodiglycolamide silica-based adsorbent to separate useful metals from simulated high-level liquid waste

A novel silica-based adsorbent was synthesized by impregnating macroporous silica polymer composite (SiO2-P) particles with a mixture of N,N,N',N'-tetra-2-ethylhexyl-thiodiglycolamide (TEHTDGA) and tri-n-octylamine (TOA). Then, the possibility of separating Pd(II) and other metal ions from simulated high-level liquid waste (HLLW) using the newly synthesized adsorbent (TEHTDGA+TOA)/SiO2-P was evaluated based on various adsorption characteristics obtained via batch-adsorption experiments, such as the HNO3 concentration, contact time, reaction temperature, adsorption isotherm, and chemical stability of the adsorbent. Furthermore, column separation experiments were performed based on the characteristics obtained from the batch-adsorption experiment, and the possibility of simultaneous separation of multiple metal ions was examined. The experimental results revealed that (TEHTDGA+TOA)/SiO2-P performs well in the separation of multiple metal ions from simulated HLLW.

Reactive separation of nicotinic acid from aqueous solution using tri-n-octylamine in biocompatible modifier diluent mixture: Influencing parameters exploration, mechanism insights, thermodynamics, regeneration of solvents and column design

In the current study, reactive extraction using tri-n-octylamine (TOA) with n-dodecane and lauryl alcohol (modifier) as biocompatible extraction system is investigated for intensification of recovery of nicotinic acid (NA), a pharmaceutical industrially important compound. The effect of important parameters such as initial NA concentration (0.014 - 0.083 mol.kg−1), TOA concentration (0.148–1.201 mol.kg−1), initial pH value (2.5–6) and temperature (298–328±1 K) are explored and optimized as NA concentration of 0.548 mol.kg−1, TOA concentration (0.706 mol.kg−1 or 20% w/w), pH (3.3) and Temp.298±1 K at 101.325±1 kPa for 92% of extraction degree. Equilibrium mechanism insights are determined as stoichiometry of reactions, overall equilibrium constant (KE) and individual equilibrium constant (K11 and K21) for 1:1 and 2:1 NA-TOA complexes. Theoretical reaction mechanisms are also supported by FT-IR data analysis. Evaluations of entropy (∆S0), enthalpy (∆H0) and Gibb's free energy (ΔG0) are carried out to find suitability of the process. A suitable column (RDC) design at optimized conditions is proposed and theoretical stages (NTS) are calculated which are found to be 5. Finally, solvent regeneration as 99% is achieved using 0.05 M NaOH solutions. This study is useful to intensify the process and design an economical industrial scale recovery of NA from dilute aqueous/fermentation broth.

Monitoring and investigating reactive extraction of (di–)carboxylic acids using online FTIR – Part I: Characterization of the complex formed between itaconic acid and tri-n-octylamine

Reactive extraction (RE) using amine extractants in an organic solvent has been proven a promising downstream strategy for (di–)carboxylic acids of biocatalytic origin. Available analytical techniques allow for observation of the acid depletion in the aqueous phase and thus an indirect link to the course of the RE as well as concentration of the complex.In order to further optimize RE performance in these systems, a direct information on the complex concentration as well as its stoichiometry (amine extractant to (di–)carboxylic acid ratio in the complex) in the organic phase is crucial.Within this work, we successfully applied Fourier Transform Infrared (FTIR) spectroscopy for the detection and quantification of the acid-extractant complex formed between itaconic acid (IA) and tri-n-octylamine (TNOA) in 1-decanol. A newly developed experimental setup incorporating FTIR spectroscopy and a systematic procedure for the characterization of the acid-extractant complex allow clarifying the structure of the acid-extractant complex. Our investigations revealed the complex formation between IA and TNOA to be based on the ion-pair mechanism whereas the stoichiometry was identified to be 2:1 (TNOA:IA) when TNOA is available in excess. Applying the experimental setup enables online monitoring of the IA concentration simultaneously in both phases during extraction of IA using 1-decanol as organic extraction phase. The mechanistic understanding of the complex formation on a molecular basis gained from the results of this study as well as the possibility to online monitor RE enables the optimization of RE as downstream strategy for (di–)carboxylic acids.