# Highly Selective and Efficient Transport of Au(III), Pt(IV), and Pd(II) from Hydrochloric Acid Across Polymer Inclusion Membranes Containing Ionic Liquid as Ion Carrier

## TL;DR

A new ionic liquid-based membrane efficiently and selectively transports gold ions from acidic solutions, outperforming other metals.

## Contribution

The first use of an ionic liquid as an ion carrier in membranes for selective transport of Au(III), Pt(IV), and Pd(II) from hydrochloric acid.

## Key findings

- High selectivity for Au(III) transport was achieved at HCl concentrations ≥0.5 M.
- Maximum Au(III) recovery of 93% was observed using a 0.010 M KI receiving phase.
- The selectivity order was Au(III) >> Pt(IV), Pd(II), with recovery factors of 94%, 8%, and 1% respectively after 6 hours.

## Abstract

Ionic liquid (IL) N-methyl-N′-1-(4-t-butylphenylphosphinyl)butylimidazolium bis(trifluoromethylsulphonyl) imide was used for the first time as an ion carrier in membrane systems to selectively transport Au(III), Pt(IV), and Pd(II) ions. Au(III), Pd(II), and Pt(IV) were transported from HCl solutions utilizing a polymer inclusion membrane (PIM) with cellulose triacetate as the support, o-nitrophenyl pentyl ether as the plasticizer, and ionic liquid as the mentioned ion carrier. The modifications of source and receiving aqueous phase compositions are examined. High selectivity for Au(III) using the ionic liquid in the membrane was achieved at elevated HCl concentrations (≥0.5 M). When a 0.010 M KI solution was used as the receiving phase and a membrane with the optimal composition was applied, the extraction of Au(III) ions reached a maximum recovery rate of 93%. Moreover, PIM studies showed that carrier molecules doped in the membrane creates complexes with the Au(III) ion with a molar ratio of 1:1. The extractability of Au(III) through PIMs exceeded that of other metal ions, with the selectivity of transported metal ions ranked as follows: Au(III) >> Pt(IV), Pd(II). The recovery factors for gold, platinum, and palladium ions after 6 h of transport were 94%, 8%, and 1%, respectively.