Eco-friendly and low-energy innovative scheme of self-generated thiosulfate by atmospheric oxidation for green gold extraction

Process Mechanism for Production of Green Lixiviant Thiosulfate at Atmospheric Pressure

“…According to our previous study, the thermal activation of pyrite is the most important step for achieving thiosulfate production at atmospheric pressure. In addition, monoclinic magnetic pyrite with extremely high chemical reactivity and sufficient sulfur content was obtained at the specified thermal activation pretreatment conditions . Therefore, in this study, the raw materials for producing thiosulfate at atmospheric pressure were monoclinic pyrrhotite obtained by thermal activation (700 °C, 40 min).…”

“…In addition, monoclinic magnetic pyrite with extremely high chemical reactivity and sufficient sulfur content was obtained at the specified thermal activation pretreatment conditions. 13 Therefore, in this study, the raw materials for producing thiosulfate at atmospheric pressure were monoclinic pyrrhotite obtained by thermal activation (700 °C, 40 min). From Figure 1a,d, pyrite has a very low content of gangue minerals, an abundant source of sulfur element (total S content of 52.96%), and a dense surface microstructure.…”

“…However, the oxygen-pressure system led to the peroxidation of metastable thiosulfate to oxysulfide anions, which also posed a potential threat to the environment and disposal safety and inevitably increased production costs and the consumption of energy . Fortunately, a green and low-energy innovative technology was proposed in our previous report that made the production of thiosulfate at atmospheric pressure a reality . The atmospheric pressure oxidation is greater operational flexibility as well as low production cost, and the conversion process of thiosulfate can be monitored in real time, thus preventing thiosulfate from being peroxide.…”

“…7 Fortunately, a green and low-energy innovative technology was proposed in our previous report that made the production of thiosulfate at atmospheric pressure a reality. 13 The atmospheric pressure oxidation is greater operational flexibility as well as low production cost, and the conversion process of thiosulfate can be monitored in real time, thus preventing thiosulfate from being peroxide. In fact, one of the major challenges also is that the metastable thiosulfate has a narrow thermodynamic stability interval and is susceptible to being peroxidized into oxysulfide anions (S 4 O 6 2− , S 3 O 6 2− , SO 3 2− , and SO 4 2− ), especially in the continuous presence of oxidative environments.…”

Eco-Friendly and Low-Energy Innovative Scheme for Green Gold Extraction: Thermodynamics, Kinetics, and Application of Self-Generating Thiosulfate at Atmospheric Pressure

“…Notably, pyrrhotite is the thermally activated product of pyrite, and other information about the preparation process of pyrrhotite and its oxidation process at atmospheric pressure can be obtained from an earlier report. 21 Further, gold extraction from oxide gold ore using self-generated thiosulfate is characterized, as indicated in Figure 1b− d. The mineral composition of oxide gold ore is mainly quartz and small amounts of tremolite (silicate minerals and aluminosilicate minerals). Additionally, the microstructure of the oxide gold ore exhibits a compact block-like morphology with numerous irregular fine particles on the surface (Figure 1d).…”