IR spectral and quantum-chemical studies of binary extractants

The composition and ionic character of formation of binary extractants based on quaternary ammonium bases and organic acids were confirmed using spectral and quantum-chemical methods, the structures of the binary extractants were obtained. The energy of bond between cation and anion in molecules of the binary extractants was determined, it is by an order of magnitude higher than the energy of H bond and close to the energy of chemical (ionic) bond.     

Closed-Loop Recycling Dual-Mode Counter-Current Chromatography with Specified Sample Loading Durations: Modeling of Preparative and Industrial-Scale Separations

We previously reported on a new counter-current chromatography (CCC) operating mode called closed-loop recycling dual-mode counter-current chromatography (CLR DM CCC), which incorporates the advantages of closed-loop recycling (CLR) and dual-mode (DM) counter-current chromatography and includes sequential separation of compounds in the closed-loop recycling mode with the mobile x-phase and in the inverted-phase counter-current mode with the mobile y-phase. The theoretical analysis of several implementations of this separation method was carried out under impulse sample injection conditions. This study is dedicated to the further development of CLR DM CCC theory applied to preparative and industrial separations, where high-throughput operation is required. Large sample volumes can be loaded via continuous loading within a specified time. To simulate CLR DM CCC separations with specified sample loading durations, equations are developed and presented in “Mathcad” software.     

Study of metal extraction in high-frequency vibration mini-columns

The prospects of high-frequency vibration mini-columns for use as models for studying the extraction recovery and separation of metals are demonstrated.     

A new extraction method for the preparation of zinc oxide nanoparticles in aqueous two-phase systems

An extraction method was suggested for the preparation of differently shaped nano- and micrometer- sized zinc oxide particles at the interface boundary of aqueous two-phase systems based on polyethylene glycol (polyethylene oxide) and sodium sulfate using NaOH and aqueous ammonia as precipitating agents.     

Iron Extraction with Di(2-Ethylhexyl)dithiophosphoric Acid and a Binary Extractant Based on It

Iron(III) extraction with trioctylmethylammonium di(2-ethylhexyl)dithiophosphate and di(2- ethylhexyl)dithiophosphoric acid was studied. It was shown that di(2-ethylhexyl)dithiophosphoric acid extracts iron in the form of the complex FeA₂, regardless of the oxidation state of iron in the initial aqueous solution. It was also shown that the iron(III) extraction with trioctylmethylammonium di(2-ethylhexyl)dithiophosphate over a wide acidity range occurs primarily to produce extractable substance (R₄N)FeCl₄; and at pH > 1, iron(II) dialkyldithiophosphate is also extracted into the organic phase. It was established that, in a system with a binary extractant, iron can be efficiently stripped from the organic phase with water or diluted solutions of mineral acids.     

Recovery of rare-earth elements from nitrate solutions using polyethylene glycol 1500

Russian Chemical Bulletin - A new extraction system based on polyethylene glycol 1500 and NaNO3 was proposed for the recovery of light rare-earth elements (Ce, La, Nd, Pr, and Sm) from aqueous...     

Extraction of rare earth metals from nitrate solutions with a binary extractant based on Cyanex 272

Mechanisms for the extraction of rare earth metals with a binary extracting agent based on bis(2,4,4-trimethylpentyl)phosphinic acid with the formation of various complexes in the organic phase were proposed. The compositions of the extracted compounds were determined, and the distribution of these compounds was adequately described by calculated curves.     

Support-free pulsed liquid–liquid chromatography

A simple technique of support-free liquid–liquid chromatography is suggested that operates without incorporation of a centrifuge. The pulsed chromatography apparatus consists of a stationary coiled tube and a pulsation device to produce reciprocating motion of liquid phases within each individual coil segment. This reciprocating motion generates a centrifugal force field varying in intensity and direction that leads to an improved mixing of the two liquid phases and retains the stationary phase in the coiled tubing. The intensity of the back and forth motion of liquid phases within each coil unit can be varied by varying the frequency and/or the amplitude of the pulsations generated by the pulsation device. As the magnitude of the stationary phase retention is of paramount importance for success of the technique, the retention of the stationary phase in the pulsed coil column was experimentally studied. A few experiments were conducted to test the chromatographic behavior of valeric (n-pentanoic) and caproic (n-hexanoic) acids. The results obtained demonstrate the potential of the new separation method for preparative purposes.     

Extraction of mineral acids with methyltrioctylammonium dinonylnaphthalenesulfonate

The interphase distribution of hydrogen halides (HF, HCl, HBr, and HI) and oxygen-containing acids (H₂SO₄ and HClO₄) in a system with the binary extracting agent methyltrioctylammonium dinonylnaphthalenesulfonate was studied. It was found in the extraction of mineral acids depending on the aqueous acidity, that the distribution ratios of mineral anions B ^m? decreased with pH in accordance of the laws of binary extraction. The extraction isotherms of mineral acids were obtained, and the apparent constants of extraction were calculated.     

Extraction of acetic acid by binary extractants

Interface distribution of acetic acid has been studied in systems with binary extractants, namely, trioctylmethylammonium di(2-ethylhexyl)phosphate, di(2-ethylhexyl)dithiophosphate, and dinonylnaphthalenesulfonate. It has been determined that, with the increase in the strength of the organic acid involved in a binary extractant, the extraction ability of a monocarboxylic acid decreases and addition reaction with the formation of extracted compound of R₄NA · HX_(o) composition becomes the dominant mechanism of extraction.