Recovery of Palladium(II) and Platinum(IV) in Novel Extraction Systems

Abstract

Recovery of platinum group metals (PGM) from complex aqueous solutions generated as a result of leaching of various spent materials (e.g., spent automotive converters) is a vital issue in the context of the circular economy. In this study pyridinium derivatives containing an imidoamide or imine moiety (i.e., 3-[1-(2-ethylhexyloxyimine)methane]-1-propylpyridinium chloride, 3-[1-(decyloxyimine)methane]-1-propylpyridinium chloride, 3-[1-(decyloxyimine)ethane]-1-propylpyridinium chloride and 4-[1-amine(2-ethylhexyloxyimine)]-1-propylpyridinium chloride) are proposed as novel extractants for recovery of palladium(II) and platinum(IV) from model chloride aqueous solutions. The results of liquid-liquid extraction from one-component solutions of palladium(II) or platinum(IV) showed that quaternary pyridinium salts can be used as effective extractants for platinum metal ions. Moreover, PGM extraction from a two-component mixture proved no evident selectivity in the transfer of one of the metal ions to the organic phase. As the best extractant among the investigated ones, D3EI-PrCl (with straight alkyl chain at substituent) can be pointed out, however, problems with effective stripping or phase disengagement after stripping should be indicated as a drawback of the organic phases used. Further investigation should focus on the improvement of the organic phase properties (e.g., increase in hydrophobicity of the extractants and addition of an organic phase modifier) towards stripping efficiency.

Separation and Recovery of Gold(III), Palladium(II) and Platinum(IV) by Solvent Extraction Using a New β-Diketone Derivative from Acidic Solutions

“…The process has been in use for many years but still has great potential for future applications [ 20 ]. Many different extractants have been studied for PGM extraction, including quaternary ammonium salts [ 21 , 22 , 23 , 24 , 25 ], tertiary amide extractant [ 26 ], piperidine-based extractants [ 27 ], pyridine derivatives [ 28 , 29 ], hydroxyoximes [ 30 ], trialkylphosphine oxides [ 31 ], crown ethers [ 32 ], and β-diketone derivatives [ 33 , 34 , 35 ]. The separation of metal ions via solvent extraction depends mainly on the type of complexing reagent (extractant) and the effective solvent.…”

2,6-Bis((benzoyl-R)amino)pyridine (R = H, 4-Me, and 4-NMe2) Derivatives for the Removal of Cu(II), Ni(II), Co(II), and Zn(II) Ions from Aqueous Solutions in Classic Solvent Extraction and a Membrane Extraction

“…used 1-(biphenyl)-2-hydroxyimino-2-(4-chloroanilino)-1-ethanone, 1-(biphenyl)-2-hydroxyimino-2-(4-methylanilino)-1-ethanone, and 1-(biphenyl)-2-hydroxyimino-2-(Npyrrolidino)-1-ethanone for the removal of transition metal ions such as Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cd(II), and Hg(II) through a solvent extraction process [14]. Recently, Wiecka and coworkers applied pyridinium derivatives containing an imidoamide or imine moiety as novel extractants for the recovery of palladium(II) and platinum(IV) from model chloride aqueous solutions [15], while Bhargava and Uma synthesized a new Schiff base called N-(4-hydroxy-3-methoxy benzylidene)-biphenyl-4-amine) and used it for the adsorption of copper(II) ions [16]. Another compound, (E)-4-(2-hydroxyethyl imino)pentan-2-one (AcEt), was utilized during solvent extraction in the separation of thorium(IV) metal ions from chloride media [17].…”