Yu. A. Zakhodyaeva

Extraction of monocarboxylic acids with binary extracting agents based on amines and quaternary ammonium bases

The distribution of monocarboxylic acids is reported for extraction systems with binary extracting agents, namely, amine and quaternary ammonium base (QAB) salts of organic acids with widely varied acid dissociation constants (pKa 1.5–10). Monocarboxylic acid extractability orders have been obtained for systems with binary extracting agents based on trioctylmethylammonium and trioctylammonium (TOA). The best extractability is shown by acids with long hydrocarbon radicals (butyric and caproic acids). Lactic acid is the least extractable. Extractive power orders have been obtained for QAB- and TOA-based binary extracting agents. For monocarboxylic acid extraction with QAB salts, the extractive power order correlates with the acid dissociation constants of the parent organic acids: trioctylmethylammonium p-tert-butylphenolate ≫ caprylate > dialkylphosphinate > dialkylmonothiophosphinate > dialkylphosphate > dinonylnaphthalene sulfonate > dialkyldithiophosphinate. The extractive power of the QAB-based binary extracting agents is much higher than that of the TOA salts.

Analysis of the efficiency of liquid membranes in extraction processes

Calculations were made to study the processes of purification of substances in a series of extraction and stripping columns or in a battery of mixer-settlers using a combination of free and supported liquid membranes. It was found that the efficiency of recovery or separation of substances in processes using liquid membranes exceeds that in conventional processes even after breaking up a series of columns or a battery of mixer-settlers into as few as two extractant-circulation loops. Investigation of the dependence of the purification processes on various parameters showed that the maximal effect on the processes is exerted by the distribution coefficients of substances at the stripping stage.

Extraction and separation of metals using the combined method of liquid membrane techniques

Experimental and computational studies of metal extraction and separation are performed using lanthanides chlorides in cascade of mixer-settlers connected in the conventional variant and according to the scheme based on the combined techniques of liquid membranes. An increase in the extraction degree of lanthanides, as well as the separation of these metals is found when the combined liquid membrane procedurebased scheme is used with increasing number extractor cascade. The calculated data show that increasing the organic phase flow with respect to the phase flow rate of the raffinate and reextract significantly increase the rate of extraction and separation of lanthanides in the case of circuits based on the combined liquid membrane technology.

Columns for cyclic extraction-chromatographic device

Three constructions of the columns of extraction-chromatographic device operating in cyclic mode have been compared. Experiments have been conducted with = shots containing caffeine, coumarin, and salicylic and acetylsalicylic acids using hexane-isopropyl alcohol-water biphase solvent system at a 1 : 1 : 1 ratio, respectively. All columns have demonstrated fairly high effectiveness. The certain advantage of the column with stirrers is the possibility to control contact time of phases.

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.

Analysis of the process of the countercurrent cyclic chromatography

Cyclic countercurrent chromatography, a new method of liquid chromatography, has been considered. A mathematical model of a cyclic process has been developed. Each cycle consists of two half-periods, i.e., a half-period of the motion of a light phase (a heavy phase plays a role of an immobile phase) and a half-period of the motion of a heavy phase (a light phase plays a role of an immobile phase). Sampling is introduced in the form of a pulse into the average zone of a system of sequentially connected equilibrium steps into the half-period of the motion of the light phase of the initial process cycle. Analytical dependences for calculating the cyclic processes of the countercurrent chromatography have been derived. The experiment and the theory are correlated, and satisfactory agreement between the experimental results and computational investigations has been established.

Interphase distribution of weak acids in systems with binary extractants

General dependences of interphase distribution of weak acids in systems containing binary extractants were studied. Substantial differences in the extraction dependences of the composition of the organic and aqueous phases were shown for weak acids compared to systems that contain strong acids and binary extractants, as well as weak acids and neutral extractants. The influence of hydrogen bonding between two extracted compounds was observed when low-molecular monocarboxylic acids were extracted with agents based on quaternary ammonium bases and organic hydroxy acids.

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.

Extraction of monocarboxylic acids by trioctylmethylammonium di(2-ethylhexyl)phosphate

The laws of the interphase distribution of saturated monocarboxylic acids in the system with the binary extracanttrioctylmethylammonium di(2-ethylhexyl)phosphate were studied. The extraction isoherms of monocarboxylic acids by 0.2 M solution of trioctylmethylammonium di(2-ethylhexyl)phosphate in toluene were obtained, and it was shown that they are rectilinear. The extractibility of acids decreases in the following order: butyric > propionic > formic> acetic> lactic, which corresponds to the anion-exchange order for the initial salts of quaternary ammonium bases. The mechanisms of the distribution of monocarboxylic acids were proposed. The study of the extraction of acetic and propionic acids as a function of the acidity of the aqueous phase revealed that the acids are extracted most efficiently from acid solutions. A decrease in the distribution coefficients with an increasing pH of the aqueous phase is observed, which indicates the possibility of efficient reextraction of monocarboxylic acids from organic solutions.

Extraction separation of the components of leach liquors of batteries

Waste batteries contain toxic metals (Pb, Ni, Zn, Fe, etc.) in high concentrations. In order to prevent harmful effects on human health and environment, it is necessary to recycle them. In this paper, prospective applications of aqueous two-phase systems for isolating and separating the components of leach liquors of batteries have been considered. The extraction of metal cations in the systems based on poly(ethylene oxide) with molecular masses of 1500 and ammonium sulfate depending on the process conditions has been studied. A flow diagram of the separation of the components of leach liquors that uses a studied aqueous two-phase system in the presence of KSCN complexing agent has been suggested.