Selective extraction of Au(III) and Pd(II) using p-tert-butyl-thiacalix[4]arene tetrathioamide as extractant

Abstract

The recovery of precious metals in e-waste has become an urgent problem to be solved due to its serious waste of resources and environmental pollution. Herein, a p-tert-butyl-thiacalix[4]arene tetrathioamide (TBTAT) was synthesized for exploring selective extraction of Au(III) and Pd(II) from hydrochloric acid media. The influence of different parameters on the extraction method was investigated by liquid-liquid extraction experiments. As a result, TBTAT exhibited outstanding extraction performance for Au(III) and Pd(II) with 100% extractability from 0.1 M hydrochloric acid media for 1 h. The outcomes of Job's continuous variation means experiments showed that TBTAT was complexed with Au and Pd at a ratio of 1:3 during the extraction process. The TBTAT showed excellent selectivity for Au(III) (99.6%) and Pd(II) (99.9%) in the mixed system including coexisting competing ions such as Cu, Zn, Fe, K and Pb. The extraction efficiencies of other ions were less than 10%. At the same time, gold and palladium could be efficiently stripped from the loaded organic phase through thiourea. The extractabilities of Au(III) and Pd(II) remained 100% after being reused 5 times, indicating the excellent reusability of TBTAT for extraction of Au(III) and Pd(II) from HCl media.