Process Mechanism for Production of Green Lixiviant Thiosulfate at Atmospheric Pressure

Abstract

The serious environmental pollution and human health risks caused by highly toxic cyanide have necessitated the search for a nontoxic and alternative lixiviant. However, conventional chemical thiosulfate suffers from high consumption, which makes the commercialization of non-cyanide green extraction of precious metals difficult. Therefore, the development of green and low-energy technology for producing thiosulfate from sulfur-containing materials is of high academic and industrial interest. Herein, the process mechanism of producing thiosulfate at atmospheric pressure was first elucidated to facilitate the production of sufficient thiosulfate. By precisely regulating significant parameters, the concentration of thiosulfate can be increased to up to 0.32 M under optimal conditions. Furthermore, the conversion characteristics of sulfur and iron in this process are as follows:and Fe(II)−S 2 → Fe(II)−S → Fe(II)−O/S n → Fe(III)−O/OH and Fe(III)−SO 3 /SO 4 . Importantly, the sustainable existence of metastable thiosulfate is achieved under the oxidation system designed, preventing the peroxidation of S 2 O 3 2− into S 4 O 6 2− and S 3 O 6 2−. This fruitful research provides valuable scientific insights for promoting the commercial application of thiosulfate with lower cost and environmental impact in the precious metal extraction industry.

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

“…As previously stated, sufficient metastable thiosulfates have been successfully generated, and the oxidation to oxysulfide anions (S 4 O 6 2– , S 3 O 6 2– , SO 3 2– , and SO 4 2– ) has been prevented by regulating the process parameters. , Therefore, to further refine the theoretical framework of this groundbreaking technology, the still unclear theoretical basis of thermodynamics and kinetics must be urgently clarified. The relevant process thermodynamic analysis and kinetics calculations are illustrated in Figures and , respectively.…”

“…And the oxygen pressure system causes the metastable thiosulfate to overoxidize into oxysulfide anions (S 4 O 6 2– , S 3 O 6 2– , SO 3 2– and SO 4 2– ), inevitably increasing production costs and energy consumption. In our previous reports , we have achieved the self-generation of thiosulfate from sulfur in sulfur-containing minerals under atmospheric pressure using a clean, low-energy consumption innovative approach, while enabling the sustainable existence of metastable thiosulfate. At a deeper level, our ultimate objective is to apply this technology to in situ leaching of gold encapsulated within refractory sulfide ores (high-sulfur and high-arsenic) by using self-generated thiosulfate.…”