V. V. Belova

Extraction of platinum-group metals from chloride solutions by salts of quaternary ammonium bases and binary extractants

Literature data are given on the extraction of platinum-group metals from hydrochloric acid solutions by salts of quaternary ammonium bases, as well as the authors’ data on the binary extraction of platinum metals from chloride solutions. The possibility is shown of using binary extractants based on quaternary ammonium bases (QABs) for efficient extraction and separation of platinum-group metals, as well as for simple reextraction of these metals from organic phases by water, contrary to the initial anion-exchange systems with QAB chlorides.

Palladium extraction by a cyanex 301-based binary extractant from chloride solutions

We studied the extraction of chloropalladium complexes by solutions of trioctylmethylammonium di(2,4,4-trimethylpentyl)dithiophosphinate in toluene over a wide range of aqueous acidities. Distribution factors and spectroscopic studies of extraction products showed that (R4N)[Pd2Cl4A] complexes are formed in the organic phase during extraction under near-saturation conditions. As the concentration of the binary extractant or dialkyldithiophosphinic acid increases, palladium di(2,4,4-trimethylpentyl)dithiophosphinate is formed in the organic phase.

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 Bm− 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 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.

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.

Extraction of platinum and palladium from hydrochloric solutions by trioctymethylammonium dinonylnaphthalenesulfonate

We investigated the phase distribution of chloride complex platinum and palladium acids in the presence of the binary extracting agent trioctylmethylammonium dinonylnaphthalenesulfonate. During the extraction of H2PtCl6 and H2PdCl4, the distribution coefficients were found to decrease as long as the pH value was growing, in full accordance with the known general trend of binary extraction. In contrast to the extraction variant using quaternary ammonium bases with inorganic counterions, a binary system, which was based on dinonylnaphthalenesulfonic acid, could be used for the further aqueous reextraction of platinum metals from the organic phase because of the higher thermodynamic stability of the binary reagent in the two-phase system.

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 of uranyl nitrate with a binary extractant based on di(2,4,4-trimethylpentyl)phosphinic acid

The extraction of uranyl nitrate with methyltrioctylammomium di(2,4,4-trimethylpentyl)phosphinate is compared to uranyl nitrate extraction with constituent cation-and anion-exchange extracting agents at various compositions of aqueous and organic phases. In UO2(NO3)2 extraction with quaternary ammonium nitrate and dialkylphosphinic acid solutions in toluene, the compounds (R4N)2UO2(NO3)4 and UO2A2, respectively, are formed in the organic phase. The binary extraction of uranyl nitrate is characterized by larger distribution ratios than extraction with the initial quaternary ammonium nitrate. Under saturation conditions, the capacity of the binary extractant is two times higher than the capacity of the anion-exchange extractant at the same concentration. Uranyl nitrate extraction with a binary extractant can yield, in the organic phase, complexes in which the uranyl ion either forms a salt with the anion of the organic acid or is incorporated into an extractable complex anion, depending on its thermodynamic stability in the heterogeneous system.

Extraction of lactic acid from technological (concentrated) solutions

The extraction of lactic acid from technological solutions by different extracting agents and their mixtures was studied. It was established that the most effective extraction of lactic acid is reached in systems with mixtures of trioctylamine and tributyl phosphate. The reextraction of lactic acid from the organic phase is performed by water.

Extraction of lanthanide nitrates with trioctylmethylammonium di(2,4,4-trimethylpentyl)phosphinate

A binary extractant based on trioctylmethylammonium di(2,4,4-trimethylpentyl)phosphinate R4NA was prepared. The extraction of lanthanide (Gd-Lu) nitrates from aqueous solutions with 0.6 M toluene solutions of R4NA and trioctylmethylammonium nitrate was studied. The extraction isotherms of lanthanide nitrates with these extractants were obtained and physicochemical and mathematical models of extraction of lanthanides were developed. The extraction isotherms with the binary extractant were analyzed assuming that the Ln(III) extractable complexes LnA3, (R4N)2[Ln(NO3)5], (R4N)3[Ln(NO3)6], (R4N)2[Ln(NO3)3A2], and (R4N)[Ln(NO3)3A] [A is di(2,4,4-trimethylpentyl)phosphinate anion] are formed in the organic phase. The extraction constants were calculated.