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

Abstract

This study indicates that a new amine derivative of β-diketone (EDAB-acac) can be successfully used in an acidic medium (HCl) to separate a mixture containing Au(III), Pd(II), and Pt(IV) ions using solvent extraction. The study was conducted in single and ternary model solutions. The impact of acid concentration and the type of solvent (toluene, chloroform, methylene chloride, 2-ethylhexanol) on separation efficiency was discussed. It has been shown that increasing the HCl concentration in the aqueous phase does not favor extraction. In contrast, solvents with high donor numbers (methylene chloride, 2-ethylhexanol) increase both the extraction percentage of Pd and Au as well as the separation coefficients of Pd in relation to Au and Pt. The palladium(II) and gold(III) (which form 4-coordinated planar [MCl4]2− complexes) are extracted most efficiently, Pd(II) (87–93%) and Au(III) (56–62%). The stripping of Au(III), Pd(II), and Pt(IV) ions from the EDAB-acac-methylene chloride phase was also investigated using 0.5 M ammonia aq., mineral acid (5 M HCl, 5 M HNO3), 0.1 M thiourea in HCl and 0.5 M ammonium thiocyanate. A 3-step stripping process was proposed for the recovery of Pd(II), Au(III), and Pt(IV) from the Pd-Au-Pt mixture in the EDAB-acac-methylene chloride system. In the first stage, the aqueous phase is treated with 5 M HNO3 (Pt separation), followed by the application of 0.5 M ammonia (Pd separation) and, finally, 0.1 M thiourea in HCl (Au separation). The solvent extraction with EDAB-acac in acidic medium (HCl) can be used for separation of Pd(II) and Au(III) ions from e-waste leach solutions.

Advances in Hydrometallurgical Gold Recovery through Cementation, Adsorption, Ion Exchange and Solvent Extraction

“…Another study by Kubota et al (2019) [66] discussed SX mechanisms in a chloride medium and proposed similar mechanisms wherein, when a basic extractant is used, negatively charged metal complexes such as [AuCl 4 ] − form ion-pairs with the protonated extractant. This proposed mechanism is in line with findings from other studies [67,68].…”

From waste to wealth: chelating polymeric membranes for precious palladium recovery from wastewater

“…A straight line of Q t versus t 0.5 that passes through the origin suggests the applicability of intraparticle diffusion and that the internal diffusion is solely controlling the kinetics of the adsorption. The liquid lm diffusion (Boyd's external diffusion) equation is shown in eqn (6). A plot of ln(1 − F) versus t where the linear t passes through the origin would indicate that the adsorption was controlled solely by liquid lm diffusion.…”

“…Palladium is a valuable and scarce resource, with its extraction and purification being both challenging and expensive. 6 Consequently, the recovery of palladium from industrial wastewater has attracted considerable attention as an alternative and sustainable source. 7 Palladium-containing wastewater is primarily generated during the manufacturing of electronic devices and automobile catalysts.…”

Recovery of Homogeneous Platinoid Catalysts from Pharmaceutical Media: Review on the Existing Treatments and the Perspectives of Membrane Processes

“…For the pharmaceutical industry, this organic phase also usually contains the active ingredient which induces some constraint for preserving the stability of the molecule. The choice often made by industries for removing catalysts is to use chelating agents such as ethylenediamine (EDA) and its derivatives [ 78 ]. Chelating agents are polydentate ligands, meaning they bond several times on the metal center.…”