Gold leaching by copper(II) in ammoniacal thiosulphate solutions in the presence of additives. Part I: A review of the effect of hard–soft and Lewis acid-base properties and interactions of ions

A review of factors affecting gold leaching in non-ammoniacal thiosulfate solutions including degradation and in-situ generation of thiosulfate

Silver leaching with the thiosulfate–nitrite–sulfite–copper alternative system

Dissolution mechanisms of noble metals in aqueous solutions of sodium thiosulfate, sodium sulfite, and their mixture under standard conditions (without heating the medium) in alkali and acidic media are described. The conditions of intensifying the dissolution process are evaluated. The reaction rates are investigated. Based on the obtained data, it is concluded that it is rational to apply the sulfite-thiosulfate solvents of noble metals to recover them from concentrates under the usual conditions.

Mechanism and kinetics of sulfite-thiosulfate dissolution of gold

The natural formation of silver nanoparticles (AgNPs) via biotic and abiotic pathways in water and soil media contributes to the biogeochemical cycle of silver metal in the environment. However, the formation of AgNPs in the atmosphere has not been reported. Here, we describe a previously unreported source of AgNPs via the reduction of Ag(I) by SO2 in the atmosphere, especially in moist environments, using multipronged advanced analytical and surface techniques. The rapid reduction of Ag(I) in the atmospheric aqueous phase was mainly caused by the sulfite ions formed from the dissolution of SO2 in water, which contributed to the formation of AgNPs and was consistent with the Finke-Watzky model with a major contribution of the reduction-nucleation process. Sunlight irradiation excited SO2 to form triplet SO2, which reacted with water to form H2SO3 and greatly enhanced Ag(I) reduction and AgNP formation. Different pH values affected the speciation of Ag(I) and S(IV), which were jointly involved in the reduction of Ag(I). The formation of AgNPs was also observed in the atmospheric gas phase via direct reduction of Ag(I) by SO2(gas), which occurred even in 50 ppbv SO2(gas). The natural occurrence of AgNPs in the atmosphere may also be involved in silver corrosion, AgNP transformation and regeneration, detoxification of gaseous pollutants, and the sulfur cycle in the environment.

Reduction of Ionic Silver by Sulfur Dioxide as a Source of Silver Nanoparticles in the Environment.

The thermodynamic probability of dissolution of noble metals in aqueous solutions of sodium thiosulfate, sodium sulfite, and their mixture under standard conditions (without heating of the solution) is considered. The influence of impurities and catalysts (divalent copper, elemental sulfur, oxygen access into the solution, and ammonia) is evaluated. Theoretical calculations of reaction rates are performed. As a result of theoretical investigations, a conclusion about the usefulness of applying sulfite-thiosulfate solvents of noble metals from ores and concentrates is made.

Thermodynamics of interaction between sulfite-thiosulfate solutions and noble metals

The results of investigations into the completeness of the sulfite-thiosulfate dissolution of noble metals depending on the conditions of the autoclave opening (AO) of flotation concentrates under various leaching conditions (the reagent concentration and the influence of various additions) are described. The necessity of carrying out the AO process with the complete maximum recovery using cyanidation is shown allowing for the factors that increase the content of elemental sulfur in the AO cake.

G. G. Mineev

Papers

Mechanism and kinetics of sulfite-thiosulfate dissolution of gold

Thermodynamics of interaction between sulfite-thiosulfate solutions and noble metals

Evaluation of autoclave oxidation of sulfide concentrates as applied to the subsequent sulfite-thiosulfate leaching of noble metals