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

Elzbieta Radzyminska-Lenarcik,Ilona Pyszka,Artur Kosciuszko

doi:10.3390/ma14164436

Elzbieta Radzyminska-Lenarcik, Ilona Pyszka + Show 1 more

Open Access

https://doi.org/10.3390/ma14164436

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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.

Highlights

Electrical and electronic equipment has become ubiquitous and the consumption of such goods is increasing every year
The growing demand is accompanied by the increase in the flow of electro-waste (e-waste), which is among the fastest-growing ones in the world [1,2]
The high price of platinum ($1203/oz), palladium ($2785/oz) and gold ($175/oz) on the market (BASF Catalysts—Metal Prices) [3] further encourages the search for new ways to recover these metals from industrial waste

Summary

Introduction

Electrical and electronic equipment has become ubiquitous and the consumption of such goods is increasing every year. The increasing demand for precious metals is driven by the growing development of advanced technology and electronics. Since platinum metals (e.g., Pd, Pt) are among the rarest elements in nature and because of the depleting resources of gold deposits, the process of producing pure precious metals is expensive and technologically difficult. It is, necessary to recover them both from industrial waste and used products. The high price of platinum ($1203/oz), palladium ($2785/oz) and gold ($175/oz) on the market (BASF Catalysts—Metal Prices) [3] further encourages the search for new ways to recover these metals from industrial waste (e.g., from galvanic and tailings effluents, mining waste heaps, as well as from electronic and electrical waste)

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