Effect of Pyrite on Thiosulfate Leaching of Gold and the Role of Ammonium Alcohol Polyvinyl Phosphate (AAPP)

Abstract

Abstract:The effect of pyrite and the role of ammonium alcohol polyvinyl phosphate (AAPP) during gold leaching in ammoniacal thiosulfate solutions were investigated using pure gold foils. The results showed that pyrite catalyzed the decomposition and also significantly increased the consumption of thiosulfate. This detrimental effect became more severe with increasing pyrite content. Further, the presence of pyrite also substantially slowed the gold leaching kinetics and reduced the overall gold dissolution. The reduction in gold dissolution was found to be caused primarily by the surface passivation of the gold. The negative effects of pyrite, however, can be alleviated by the addition of AAPP. Comparison of zeta potentials of pyrite with and without AAPP suggests that AAPP had adsorbed on the surface of the pyrite and weakened the catalytic effect of pyrite on the thiosulfate decomposition by blocking the contact between the pyrite and thiosulfate anions. AAPP also competed with thiosulfate anions to complex with the cupric ion at the axial coordinate sites, and thus abated the oxidation of thiosulfate by cupric ions. Moreover, the indiscriminate adsorption of AAPP on the surfaces of gold and passivation species prevented the passivation of the gold surface by surface charge and electrostatic repulsion. Therefore, AAPP effectively stabilized the thiosulfate in the solution and facilitated the gold leaching in the presence of pyrite.

Valuable Metal Recycling

“…They also suggested that ion-exchange resin adsorption may be beneficial for the recovery of aurothiosulphate because resins are often used in pulp or leach and can be easily regenerated. Liu et al [2] investigated the behavior of thiosulfate consumption with pyrite and ammonium alcohol polyvinyl phosphate (AAPP). It has been found that pyrite has detrimental effects on the thiosulfate consumption but AAPP reduces this consumption.…”

Role of Ag+ in the Bioleaching of Arsenopyrite by Acidithiobacillus ferrooxidans

“…In nature, significant amounts of gold are often found in arsenopyrite (FeAsS) [1][2][3]. However, most gold in the arsenopyrite is difficult to leach, mainly because the gold tends to be encapsulated in the mineral matrix [4,5].…”

A Thermodynamic Analysis on the Roasting of Pyrite

“…Pyrite (FeS 2 ) is one of the most common and widely distributed sulphide minerals [1]. In industry, pyrite is a chief raw material to produce sulphur, sulphur dioxide and sulphuric acid.…”