# Water-mediated recycling of gold, palladium and platinum using semimetallic TiS2 and TaS2 nanosheets

## TL;DR

Scientists developed a method using TiS2 and TaS2 nanosheets to efficiently recover gold, palladium, and platinum from waste, even at low concentrations.

## Contribution

The study introduces a novel water-mediated electron donation mechanism using semimetallic nanosheets for high-capacity precious metal recycling.

## Key findings

- TiS2 achieved extraction capacities of ~8 g/g for Au, 2.3 g/g for Pd, and 1.15 g/g for Pt.
- Precious metal ions are reduced and deposited as nanoparticles on the nanosheets.
- The method successfully recovers Au, Pd, and Pt from real-world waste like electronics and catalysts.

## Abstract

The intensive and irreplaceable consumption of precious metals (PMs) including gold (Au), palladium (Pd) and platinum (Pt) in the electronic and catalysis industries, coupled with their scarcity in Earth’s crust, demand innovative recycling solutions for PM sustainability. However, efforts to recycle PMs from leachates of their waste are frustrated by an unsatisfactory extraction capacity at low concentrations and remain predominantly focused on gold, leaving other PMs largely unexplored. We report the ultrahigh reductive recycling of PM ions and their simultaneous aqueous-phase deposition on semimetallic transition-metal dichalcogenides of TiS2 and TaS2 nanosheets. Notably, TiS2 shows unprecedentedly high extraction capacities of ∼8, 2.3 and 1.15 g/g for Au, Pd and Pt ions, respectively, and the adsorbed PM ions are directly transformed into nanoparticles deposited on the nanosheets. Mechanistic studies reveal that water-mediated electron donation from the sulfur site of the semimetallic TiS2 and TaS2 nanosheets is responsible for the ultrahigh extraction capacity, with a single TiS2 molecule donating >13 electrons to gold ions. This electron transfer is mediated by the formation of sulfur-oxygen species during water dissociation. We further demonstrate the selective and complete recovery of Au, Pd and Pt from real-world waste streams including electronic waste, spent catalysts and automotive catalytic converters.

2D TiS2 and TaS2 nanosheets show ultrahigh adsorption capacities for low-concentration Au, Pd and Pt ions, allowing the efficient recovery of precious metals from their waste streams.