Leaching Behavior of Gold and Silver from Concentrated Sulfide Ore Using Ammonium Thiosulfate

Abstract

Ammonium thiosulfate is an alternative lixiviant for the hydrometallurgical treatment of sulfide gold ores. The present study is primarily focused on ammonium thiosulfate leaching of gold (Au) and silver (Ag) from the sulfide ore (Sunshin mine in Korea). The main chemical composition of the concentrate was Au (84 ppm), Ag (852 ppm), Fe (18.9%), Si (23.2%), and S (21.1%). The effects of various parameters on the process, such as leaching time (1–4 h), ammonium thiosulfate concentration (0.05–0.5 M), copper sulfate (CuSO4), concentration (0.05–0.25 M), solid to liquid ratio (0.2–0.5), and reaction temperature (40–60 °C) were systematically examined. Optimum Au leaching efficiency (>99%) was obtained under the following leaching conditions: 0.5 M ammonium thiosulfate with 0.05 M CuSO4 concentration, 0.2 S/L ratio at 60 °C for 2 h. The results indicate that the behavior of Ag was similar to that of Au. Almost complete dissolution of Ag occurred under following leaching conditions: 0.5 M ammonium thiosulfate with 0.05 M CuSO4 concentration at 60 °C for 4 h. This study would be useful in understanding the eco-friendly leaching systems of Au and Ag during the hydrometallurgical process of sulfide gold ore.

A Study on the Applicability of Agitated Cyanide Leaching and Thiosulphate Leaching for Gold Extraction in Artisanal and Small-Scale Gold Mining

“…It is important to note that the experiments on the Akeshi and Hishikari ores were run for only 5 h, and the study did not provide detailed mineralogy or an indication of whether or not some gangue minerals in the ore could have been consumers of the reagent. In this current study, the experiments were run for 24 h; however, the extractions achieved with the three ores after 5 h were already close to those achieved after 24 h. These findings are further supported by a study conducted by Bae et al [39] that also investigated the effect of (NH 4 ) 2 S 2 O 3 , NH 3 , and Cu(II) concentrations on the leaching of gold ores. This ore had a much higher Au and Cu content (84 g/t and 0.38 wt.%, respectively) compared to the three ores under study.…”

“…It was found that increasing the (NH 4 ) 2 S 2 O 3 concentration from 0.05 M to 0.5 M increased gold extraction, reaching an impressive 99% extraction at 0.5 M. This extraction was however much faster than what this study achieved. This must be attributed to the fact that the experiment conducted by Bae et al [39] was conducted at a much finer grind size (45.3 µm) and a much lower solids loading (20%), which significantly improved leaching.…”

Anodic oxidation of thiosulfate ions at a carbon-based electrode with deposited Au-particles

“…The high reducing activity of thiosulfates is used in a number of applications, among them: textile industry (removal of an excess bleach) [1], leather industry (treatment of hides) [2], water conditioning systems (dechlorination of a ballast water) [3], analytical chemistry [4]. As a complexing reagent, sodium and ammonium thiosulfates are considered as a possible replacement for highly toxic cyanides in the extraction of precious metals (gold, silver) from ores [5]:…”

Leaching of Copper Contained in Waste Printed Circuit Boards, Using the Thiosulfate—Oxygen System: A Kinetic Approach

“…In this work, the authors propose the use of thiosulfate as leaching reagent to recover the copper contained in PCBs, as an hydrometallurgical alternative to leaching in an alkaline medium, due to its complexation capacity [ 43 , 44 , 45 , 46 ] and degree of stability in the compound formed, which is the copper thiosulfate [ 47 ]. Generally the formation of this compound is reported as a problem in the leaching of precious metals (Au and Ag) due to the consumption and degradation of thiosulfate that occurs, but in this case the authors have taken the advantage of this tendency to recover the copper present in these types of wastes.…”