# Study on adsorption of kaolinite and gold thiosulfate

## TL;DR

This study explores how kaolinite adsorbs gold thiosulfate ions, combining experiments and quantum calculations to understand the process and its impact on gold extraction.

## Contribution

The paper introduces a novel combination of experimental and quantum chemical methods to analyze gold thiosulfate adsorption on kaolinite.

## Key findings

- Gold thiosulfate ions showed a 7.44% adsorption rate on kaolinite under specific conditions.
- Quantum calculations revealed an adsorption energy of −438.01 kJ·mol−1 for gold thiosulfate on kaolinite.
- Kaolinite's adsorption of gold impacts the efficiency of gold leaching processes.

## Abstract

The adsorption behavior of gold thiosulfate ions on the surface of kaolinite was studied using a combination of experimental research and quantum chemical calculations. Under the condition of a stirring time of 30 min, a stirring speed of 500 r·min−1, and a mass ratio of 30% kaolinite in the slurry, when the initial gold concentration of 56.50 mg·L−1,the adsorption rate of gold-thiosulfate ions from a kaolinite-containing solution was 7.44%. The results of Fourier transform infrared spectroscopy (FTIR) and energy dispersive spectroscopy (EDS) showed that the physical and chemical adsorption of kaolinite and gold thiosulfate occurred in solution. Quantum chemical calculations were performed using the CASTEP module in Materials Studio. The adsorption energy of gold thiosulfate on the surface of kaolinite (001) was calculated as − 438.01 kJ·mol−1.The calculated H76–O289 distance was 1.615 Å. Mulliken Charge population analysis and bond population analysis showed that gold thiosulfate ions form relatively stable bonds on the kaolinite surface (001). In the process of thiosulfate immersion, part of gold is adsorbed by kaolinite, which affects the extraction of gold. These results indicate that during the leaching process of gold thiosulfate, kaolinite has the ability to "catch" gold, which affects the leaching efficiency.