Hongmin Cui

Extraction Mechanism of Rare Earths with Bifuncional Ionic Liquids (Bif-ILs) [A336][CA-12]/[A336][CA-100] in Nitrate Medium

Abstract In this study, solvent extraction of rare earths with bifuncional ionic liquids (Bif-ILs) [A336][CA-12]/[A336][CA-100] was systematically investigated in nitate medium. The extraction abilities for rare earths were compared with those of organic carboxylic acids CA-12/CA-100 and neutral organophosphorus extractants TBP/P350, and they are in the descending order: [A336][CA-12]/[A336][CA-100]>CA-12/CA-100>P350>TBP. The slope analysis method was used to determine the extraction stoichiometry. The study of extraction mechanisms of rare earths by Bif-ILs [A336][CA-12]/[A336][CA-100] showed that the mechanism is in accord with complexing mechanism. By studying the effect of extraction equilibration time and temperature on the extraction efficiencies, we found that the extraction process of rare earths by Bif-ILs [A336][CA-12]/[A336][CA-100] is a fast equilibrium and an exothermic reaction. The recycling and stripping experiments indicated Bif-ILs [A336][CA-12]/[A336][CA-100] with high stability and easy stripping characteristics are suitable for extracting rare earths.

Solvent Extraction of Yttrium by Task-specific Ionic Liquids Bearing Carboxylic Group

Abstract A new kind of hydrophobic ionic liquids [1-alkyl-3-(1-carboxylpropyl)im][PF 6 ] has been synthesized, and their extraction properties for Y(III) in the nitric acid medium was also investigated. The effects of extractant concentration, equilibrium pH of aqueous phase, salt concentration, temperature etc . were discussed. The results show that this kind of Task-Specific Ionic Liquid (TSIL) needs to be saponified before being used for the Y(III) extraction, and the extraction is acid dependent, and the extraction efficiency increases with the aqueous phase acidity decreasing. Furthermore, the loaded organic phase is easy to be stripped; more than 95% Y(III) could be stripped from the loaded organic phase when the stripping acidity is higher than 0.07 mol·L −1 . The slope analysis technique is used to investigate the extraction mechanism, and a possible cation-exchange extraction mechanism is proposed in the present extraction system.

Extraction mechanism of rare earths from chloride acidic solution with ammonium-bifunctionalized ionic liquid extractants

A series of ammonium-bifunctionalized ionic liquid extractants (ammonium-Bif-ILEs) combined with a number of anions, including carboxylic acids and 1,3-diketonates, have been prepared and studied in this report. Their extraction behavior and properties toward rare earth ions (REs(III)) are systematically investigated in chloride media as a function of important parameters such as aqueous phase pH, salting-out agent concentrations, and extraction temperature. The separation performance of ammonium-Bif-ILEs toward REs(III) are systematically discussed. The results demonstrate that ammonium-Bif-ILEs have a synergistic effect between the cation and anions in separation of REs(III). The influences of different anions on separation factor (β) values are further studied. By comparison, ammonium-Bif-ILEs containing 1,3-diketonates have more potential applications in La(III)/RE(III) separation than those containing carboxylic acids.

Kinetics of Cerium(IV) and Fluoride Extraction from Sulfuric Solutions Using Bifunctional Ionic Liquid Extractant (Bif-ILE) [A336][P204]

Abstract The extraction kinetics of Ce(IV) and Ce(IV)-F − mixture systems from sulfuric solutions to n -heptane solution containing Bif-ILE [A336][P204] ([trialkylmethylammonium][di-2-ethylhewanxylphosphinate]) with a constant interfacial area cell with laminar flow were studied, just to elucidate the extraction mechanism and the mass transfer models. The data were analyzed in terms of pseudo-first-order constants. The effects of stirring speed, specific interfacial area and temperature on the extraction rate in both systems were discussed, suggesting that the extractions were mixed bulk phases-interfacial control process. Supported by the experimental data, the corresponding rate equations for Ce(IV) extraction system and Ce(IV)–F − mixture extraction system were obtained. The experimental results indicated the rate-controlling step. The kinetics model was deduced from the rate-controlling step and consistent with the rate equation.

Application of Ionic Liquid Extractants on Rare Earth Green Separation

A green solvent extraction process for the separation of rare earth elements (REEs) in different media (such as hydrochloric acid media, nitric acid media, and sulfuric media) was developed using bifunctional ionic liquid extractants (Bif-ILEs) especially containing quaternary ammonium and phosphonium-based ILs. The characteristics of the Bif-ILEs are simple synthesis, high extraction ability and selectivity, low extraction acid and base consumption, and easy stripping. Bif-ILEs could be synthesized by acid/base neutralization, and this reaction process was under mild condition with easier purification. The extraction thermodynamics showed that the separation factor (β) values for REEs were changed with the different Bif-ILEs or reaction media. The inner synergistic effect between cations and anions in Bif-ILEs has greatly facilitated the β values of REEs and also avoided the production of ammonia nitrogen caused by the acidity extractant saponification. The kinetic experimental data on the separation of REEs by Bif-ILEs, with a constant interfacial area cell with laminar flow, showed that there exist real possibilities for increasing the efficiency of the separation by the use of kinetic factors. The kinetics model could be deduced from the rate-controlling step. Serving as extractants, additives, and templating materials, ILs were used in the preparation of separation materials, including silica-supported ionic liquids (S-SILs), membrane-supported ionic liquids (M-SILs), and polymer-supported ionic liquids (P-SILs). ILs were usually attached or doped into the solid support and offered high extraction efficiency and excellent stability for REEs separation. Using such separation materials may indeed enable us to substantially reduce the steps for the separation of REEs and thus decrease both the separation time and waste production.

Adsorption and Separation of As(V) with N-Methylimidazolium Functionalized Anion Exchange Resin

The adsorption behavior of As(V) with N-methylimidazolium functionalized strongly basic anion exchange resin in Cl- form (RCl) was systematically investigated. The RCl had high thermal stability and good chemical stability under the experimental conditions, and it could be used in the wide pH range from 1 to 12. So RCl was very suitable for removing As(V) from water at a low concentration level. The adsorption mechanism was in accord with anion exchange mechanism. The adsorption equilibrium was attained at 60 min. To make sure true equilibrium was established, all the subsequent adsorption experiments were carried out for 2 h. The adsorption data for RCl was consistent with the Langmuir isotherm equation, and the maximum adsorption capacity of As(V) was 67.2 mg/g. The adsorption percentage increased slightly with increasing temperature, which showed that the reaction was endothermic. RCl was easily regenerated by 0.1 mol/L HCl, and the desorption percentage was up to 99.46%.