Liquid Extraction of Noble Metal Ions with an α-Amino Phosphonate

Abstract

The extraction of Au(III), Pt(IV), and Pd(II) ions from aqueous hydrochloric acid solutions with solutions of bis(2-ethylhexyl) N-butyl-N-octylaminomethylphosphonate in chloroform and xylene was studied. The recovery of the noble metal ions is the most efficient at low acidities of the aqueous solution, with a high selectivity of separation from the concomitant Fe(III), Cu(II), Ni(II), and Co(II) ions. a-Amino phosphonates show promise as extractants for recovery of Au(III) and Pd(II) from hydrochloric acid solutions [1, 2]. Palladium(II) is recovered most efficiently at an HCl concentration in the aqueous phase of 0.5 M; Au(III) ions are quantitatively extracted with a-amino phosphonate solutions in a wider range of acidity of the aqueous phase. By varying the acidity of the medium and the extractant concentration, it is possible to efficiently separate noble metal ions from the concomitant Fe(III) and Cu(II) ions.In this study we examined the extraction of Au, Pt, and Pd ions with a new extractant of the a-amino phosphonate series, allowing group extraction of noble metal ions and their highly selective separation from the concomitant metal ions. Previously we prepared a large series of a-amino phosphoryl compounds and studied their acid3base, extraction, and membrane-transport properties [335]. The results obtained served as a basis for choosing an a-amino phosphonate suitable for commercial applications. In particular, we determined the distribution constants in water3organic solvent systems of a-amino phosphonates containing various organic groups at the P, C, and N atoms of the aminomethylphosphonate moiety [6]. We observed linear correlations between the distribution constant and number of carbon atoms in the amino phosphonate molecule, irrespective of particular organic phase. The regression equations obtained [6] show that the logarithm of the distribution constant of amino phosphonates containing more than 20 carbon atoms exceeds 6, i.e., the extractant loss due to its transfer to the aqueous phase will be negligible.When choosing the particular extractant, we also took into account its chemical stability. As shown in [7], amino phosphonates containing a primary or secondary nitrogen atom tend to disproportionate when kept for a long time in a condensed phase. We also noted that the derivatives substituted at the a-C atom undergo partial tarring in storage. We believe that this is die to the decomposition by the reaction reverse to addition of hydrophosphoryl compounds to imines or enamines [8] which, apparently, readily polymerize. Therefore, we chose as extractant for noble metals bis(2-ethylhexyl) N-butyl-N-octylaminomethylphosphonate containing branched and fairly lipophilic hydrocarbon groups at the P atom, which suppress the surfactant properties, and alkyl groups at the N atom, providing the required hydrophilic-lipophilic balance.

Selective extraction of palladium(II) from hydrochloric acid solutions with phosphonium extractants

“…Traditionally, the hydrometallurgical recovery of PGMs is based on solvent extraction processes based on the fact that noble metal ions can easily form species which are extractable into the organic phase with various reagents [3,4]. Many different extractants have been studied and proposed, including dialkyl sulphides and sulphoxides [5][6][7][8], alkyl derivatives of 8-hydroxyquinoline [9], hydroxyoximes and ketoximes [10][11][12][13][14][15], hydrophobic amines and quaternary ammonium salts [16][17][18][19][20][21], organophosphorus extractants [22][23][24][25][26] and pyridinecarboxamides [27,28].…”

Extraction of palladium(II) from chloride solutions with Cyphos®IL 101/toluene mixtures as novel extractant

“…Various reagents have been studied and proposed, including hydroxyoximes and ketoximes [5][6][7][8][9][10], dialkyl sulphides and sulphoxides [11][12][13][14], alkyl derivatives of 8-hydroxyquinoline [15], hydrophobic amines and quaternary ammonium salts [16][17][18][19][20][21] pyridinecarboxamides [22,23], and organophosphorus extractants [24][25][26][27][28].…”

Reversed phase extraction chromatographic separation of gold(III) with high molecular mass liquid anion exchanger on silica gel

“…Solvent Extraction of Au(III), Pt(IV), and Pd(II) Ions with bis(2-ethylhexyl) Nbutyl-N-octylaminomethylphosphonate in chloroform and xylene was studied. The quantitative recovery found in hydrochloric acid solution and separation of associated Fe(III), Cu(II), Ni(II), and Co(II) ions carried out by this DOI: http://dx.doi.org/10.22192/ijcrcps.2017.04.07.005 method 3 . Liquid liquid extraction of gold by N-noctylaniline, using xylene as a diluents from aq.…”