Fast selective homogeneous extraction of UO22+ with carboxyl-functionalised task-specific ionic liquids.
ABSTRACT: The carboxyl-functionalised task-specific ionic liquid of 1-carboxymethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide ([HOOCmim][NTf2]) was used as solvent and extractant for UO22+ extraction from aqueous solution. A homogeneous phase of [HOOCmim][NTf2]-H2O system could be achieved at 75?°C, and 86.8?±?4.8% of UO22+ was separated from the aqueous solution after vibrating for only 1?min. Furthermore, nearly 97.3?±?2.9% of UO22+ was stripped from [HOOCmim][NTf2] phase by 1?M HNO3 solution. K+, Na+, Mg2+, Dy3+, La3+, and Eu3+ have little influence on the homogeneous extraction of UO22+, and the extraction efficiency of UO22+ still remained at ca. 80%. Experimental and theoretical study on the selectivity of [HOOCmim][NTf2]-H2O system were performed for the first time. Density functional theory calculation indicates that the solvent effect plays a significant role on the selectivity of [HOOCmim][NTf2]-H2O.
Project description:We develop a minimal model for the prediction of solvent extraction. We consider a rare earth extraction system for which the solvent phase is similar to water-poor microemulsions. All physical molecular quantities used in the calculation can be measured separately. The model takes into account competition complexation, mixing entropy of complexed species, differences of salt concentrations between the two phases, and the surfactant nature of extractant molecules. We consider the practical case where rare earths are extracted from iron nitrates in the presence of acids with a common neutral complexing extractant. The solvent wetting of the reverse aggregates is taken into account via the spontaneous packing. All the water-in-oil reverse aggregates are supposed to be spherical on average. The minimal model captures several features observed in practice: reverse aggregates with different water and extractant content coexist dynamically with monomeric extractant molecules at and above a critical aggregate concentration (CAC). The CAC decreases upon the addition of electrolytes in the aqueous phase. The free energy of transfer of an ion to the organic phase is lower than the driving complexation. The commonly observed log-log relation used to determine the apparent stoichiometry of complexation is valid as a guideline but should be used with care. The results point to the fact that stoichiometry, as well as the probabilities of a particular aggregate, is dependent on the composition of the entire system, namely the extractant and the target solutes' concentrations. Moreover, the experimentally observed dependence of the extraction efficiency on branching of the extractant chains in a given solvent can be quantified. The evolution of the distribution coefficient of particular rare earth, acid, or other different metallic cations can be studied as a function of initial extractant concentration through the whole region that is typically used by chemical engineers. For every chemical species involved in the calculation, the model is able to predict the exact equilibrium concentration in both the aqueous and the solvent phases at a given thermodynamic temperature.
Project description:We propose the statistical thermodynamic model for the prediction of the liquid-liquid extraction efficiency in the case of rare-earth metal cations using the common bis(2-ethyl-hexyl)phosphoric acid (HDEHP) extractant. In this soft matter-based approach, the solutes are modeled as colloids. The leading terms in free-energy representation account for: the complexation, the formation of a highly curved extractant film, lateral interactions between the different extractant head groups in the film, configurational entropy of ions and water molecules, the dimerization, and the acidity of the HDEHP extractant. We provided a full framework for the multicomponent study of extraction systems. By taking into account these different contributions, we are able to establish the relation between the extraction and general complexation at any pH in the system. This further allowed us to rationalize the well-defined optimum in the extraction engineering design. Calculations show that there are multiple extraction regimes even in the case of lanthanide/acid system only. Each of these regimes is controlled by the formation of different species in the solvent phase, ranging from multiple metal cation-filled aggregates (at the low acid concentrations in the aqueous phase), to the pure acid-filled aggregates (at the high acid concentrations in the aqueous phase). These results are contrary to a long-standing opinion that liquid-liquid extraction can be modeled with only a few species. Therefore, a traditional multiple equilibria approach is abandoned in favor of polydisperse spherical aggregate formations, which are in dynamic equilibrium.
Project description:A novel macrocyclic calixarene extractant having a long alkyl chain thioamide, 25,26,27,28-tetrakis(N-n-octylthiocarbamoyl)methoxy-5,11,17,23-tetra-tert-butylcalixarene (1), was synthesized from 25,26,27,28-tetrakis(N-n-octylcarbamoyl)methoxy-5,11,17,23-tetra-tert-butylcalixarene (2) using Lawesson's reagent. Extractant 1 was characterized using 1H NMR, 13C NMR, FT-IR spectroscopy, and elemental analysis. The Pd(II) extraction abilities of 1 and 2 were studied in high-boiling-point and environmentally friendly hydrocarbon diluents. Pd(II) extraction experiments were conducted using single-metal Pd(II) solutions, simulated mixed palladium group metal (PGM) solutions, and acid-leached automotive catalyst residue solutions. Different experimental conditions, including the shaking time, HCl/HNO3 concentration, Pd(II) concentration, extractant concentration, and the organic/aqueous phase ratio, were studied systematically. Extractant 1 showed very selective (> 99.9%) Pd(II) extraction from the mixed PGM/base metal solutions and the acid-leached automotive catalyst residue solution. Conversely, the Pd(II) extraction ability of extractant 2 was found to be negligible. Extractant 1 showed very fast extraction kinetics and a high extraction capacity as compared to those of the commercial extractant di-n-octyl sulfide. Effective stripping of Pd(II) from 1 was performed using HCI, HNO3, NH3, and HCl-thiourea solutions. Furthermore, 1 was successfully recycled over five extraction/stripping cycles. The Pd(II) extraction mechanism of 1 was studied using FT-IR spectroscopy. Extractant 1 exhibited very selective Pd(II) extraction and high acid stability, demonstrating its industrial applicability for the extraction of Pd(II) from leached automotive catalyst liquors containing PGMs and base metals.
Project description:Uranyl ion, the most soluble toxic uranium species, is recognized as an important index for monitoring nuclear wastewater quality. The United States Environmental Protection Agency (US EPA) and the World Health Organization (WHO) prescribed 30 ppb as the allowable concentration of uranyl ion in drinking water. This paper reports on a nanohybrid material that can detect uranyl ions spectroscopically and act as a uranyl ion absorbent in an aqueous system. Compound 1, possessing a salicyladazine core and four acetic acid groups, was synthesized and the spectroscopic properties of its UO22+ complex were studied. Compound 1 had a strong blue emission when irradiated with UV light in the absence of UO22+ that was quenched in the presence of UO22+. According to the Job's plot, Compound 1 formed a 1:2 complex with UO22+. When immobilized onto mesoporous silica, a small dose (0.3 wt %) of this hybrid material could remove 96% of UO22+ from 1 mL of a 100-ppb UO22+ aqueous solution.
Project description:Extractive fermentation with the removal of carboxylic acid requires low pH conditions because acids are better partitioned into the solvent phase at low pH values. However, this requirement conflicts with the optimal near-neutral pH conditions for microbial growth.CO2 pressurization was used, instead of the addition of chemicals, to decrease pH for the extraction of butyric acid, a fermentation product of Clostridium tyrobutyricum, and butyl butyrate was selected as an extractant. CO2 pressurization (50 bar) improved the extraction efficiency of butyric acid from a solution at pH 6, yielding a distribution coefficient (D) 0.42. In situ removal of butyric acid during fermentation increased the production of butyric acid by up to 4.10 g/L h, an almost twofold increase over control without the use of an extraction process.In situ extraction of butyric acid using temporal CO2 pressurization may be applied to an integrated downstream catalytic process for upgrading butyric acid to value-added chemicals in an organic solvent.
Project description:While phase separation of immiscible liquid-liquid systems has become increasingly significant in diverse areas, the irreversible nature limits their further application in controllable extraction-concentration or capture-release fields. There is a need for the development of simple, efficient and reversible methods for numerous research and industrial extraction and separation applications. We envisioned Boc-modified lipophilic acids as a simple model for such use based on the studies of the multi-phase transitions of Boc-modified supramolecular polymeric systems. Here, we demonstrate that in the presence of Boc-7-aminoheptanoic acid (Boc-7), phase separation occurs in mixtures of miscible organic solvent and water. The separation behavior was confirmed by differential colorimetric development in aqueous and organic phases using methyl orange staining assays. Component substitution experiments verified that the phase separation results from the subtle balance between the aggregation and the solvation forces of Boc-7, and is reversible by adjusting the solution pH. Owing to the intrinsic hydrophobic properties of the organic phase and the hydrogen bonding-forming ability of the carboxyl group of Boc-7, the phase separation system captures and releases Sudan Red, fluorescein, and streptavidin in a controllable manner. Consequently, a reversible and simple phase separation system can be designed as a multifunctional extractant.
Project description:A new type of supramolecular chemosensor based on the polyoxometalate (POM) Na9DyW10O36 (DyW10) and the block copolymer poly(ethylene oxide-b-N,N-dimethylaminoethyl methacrylate) (PEO114-b-PDMAEMA16) is reported. By taking advantage of the CO2 sensitivity of PDMAEMA blocks to protonate the neutral tertiary amino groups, CO2 can induce the electrostatic coassembly of anionic DyW10 with protonated PDMAEMA blocks, and consequently trigger the luminescence chromism of DyW10 due to the change in the microenvironment of Dy3+. The hybrid complex in dilute aqueous solution is very sensitive to CO2 content and shows rapid responsiveness in luminescence. The luminescence intensity of the DyW10/PEO-b-PDMAEMA complex increases linearly with an increasing amount of dissolved CO2, which permits the qualitative and quantitative detection of CO2. The complex solution also shows good selectivity for CO2, with good interference tolerance of CO, N2, HCl, H2O and SO2. The supramolecular chemosensor can be recycled through disassembly of the hybrid complex by simply purging with inert gases to remove CO2.
Project description:The catalytic reactivity of the high-spin Mn(II) pyridinophane complexes [(Py2NR2)Mn(H2O)2](2+) (R=H, Me, tBu) toward O2 formation is reported. With small macrocycle N-substituents (R=H, Me), the complexes catalytically disproportionate H2O2 in aqueous solution; with a bulky substituent (R=tBu), this catalytic reaction is shut down, but the complex becomes active for aqueous electrocatalytic H2O oxidation. Control experiments are in support of a homogeneous molecular catalyst and preliminary mechanistic studies suggest that the catalyst is mononuclear. This ligand-controlled switch in catalytic reactivity has implications for the design of new manganese-based water oxidation catalysts.
Project description:Reactive extraction is a significant technique employed for the removal of organic acids such as carboxylic acid which are usually present in low concentrations in aqueous solutions. This technique was explored by applying Response Surface Methodology (RSM) in process parameter optimization for malic acid recovery from aqueous streams using Trioctylamine as extractant and 1-decanol as organic diluent. Malic acid, a C4 dicarboxylic acid has a wide variety of applications in the polymer, food, chemical and pharmaceutical industries. The optimization of the response function: extraction efficiency was systematically carried out using three process parameters for reactive extraction: temperature, initial malic acid concentration and extractant (Trioctylamine) composition. Response Surface Methodology in combination with Box-Behnken design involving seventeen experimental runs was employed for malic acid reactive extraction in this study. A statistical second-order polynomial predicted an extraction efficiency of 97.53%. The optimum conditions of the process variables were found to be: temperature: 304.73?K, acid concentration: 0.25 kmol/m3, Trioctylamine composition: 23.54% (v/v). Under these optimum conditions, the experimental response of extraction efficiency of 93.25% was obtained. The experimental results obtained was in close conformity with the predicted values by numerical optimization using Response Surface Methodology. These findings can pave the way for the reactive separation process design for recovery of carboxylic acids from dilute aqueous waste streams as well as a fermentation broth.
Project description:The determination of trace rare-earth elements (REEs) can be used for the assessment of environmental pollution, and is of great significance to the study of toxicity and toxicology in animals and plants. N, N, N', N'-tetraoctyl diglycolamide (TODGA) is an environmental friendly extractant that is highly selective to REEs. In this study, an analytical method was developed for the simultaneous determination of 16 trace REEs in simulated water samples by inductively coupled plasma optical emission spectroscopy (ICP-OES). With this method, TODGA was used as the extractant to perform the liquid-liquid extraction (LLE) sample pretreatment procedure. All 16 REEs were extracted from a 3 M nitric acid medium into an organic phase by a 0.025 M TODGA petroleum ether solution. A 0.03 M ethylenediaminetetraacetic acid disodium salt (EDTA) solution was used for back-extraction to strip the REEs from the organic phase into the aqueous phase. The aqueous phase was concentrated using a vacuum rotary evaporator and the concentration of the 16 REEs was detected by ICP-OES. Under the optimum experimental conditions, the limits of detection (3?, n = 7) for the REEs ranged from 0.0405 ng mL-1 (Nd) to 0.5038 ng mL-1 (Ho). The relative standard deviations (c = 100 ng mL-1, n = 7) were from 0.5% (Eu) to 4.0% (Tm) with a linear range of 4-1000 ng mL-1 (R2 > 0.999). The recoveries of 16 REEs ranged from 95% to 106%. The LLE-ICP-OES method established in this study has the advantages of simple operation, low detection limits, fast analysis speed and the ability to simultaneously determine 16 REEs, thereby acting as a viable alternative for the simultaneous detection of trace amounts of REEs in water samples.