Galvanic coupling and its effect on origin potential flotation system of sulfide minerals

Emerging Trends of Computational Chemistry and Molecular Modeling in Froth Flotation: A Review

Froth flotation is the most versatile process in mineral beneficiation, extensively used to concentrate a wide range of minerals. This process comprises mixtures of more or less liberated minerals, water, air, and various chemical reagents, involving a series of intermingled multiphase physical and chemical phenomena in the aqueous environment. Today's main challenge facing the froth flotation process is to gain atomic-level insights into the properties of its inherent phenomena governing the process performance. While it is often challenging to determine these phenomena via trial-and-error experimentations, molecular modeling approaches not only elicit a deeper understanding of froth flotation but can also assist experimental studies in saving time and budget. Thanks to the rapid development of computer science and advances in high-performance computing (HPC) infrastructures, theoretical/computational chemistry has now matured enough to successfully and gainfully apply to tackle the challenges of complex systems. In mineral processing, however, advanced applications of computational chemistry are increasingly gaining ground and demonstrating merit in addressing these challenges. Accordingly, this contribution aims to encourage mineral scientists, especially those interested in rational reagent design, to become familiarized with the necessary concepts of molecular modeling and to apply similar strategies when studying and tailoring properties at the molecular level. This review also strives to deliver the state-of-the-art integration and application of molecular modeling in froth flotation studies to assist either active researchers in this field to disclose new directions for future research or newcomers to the field to initiate innovative works.

Galvanic effect of pyrite on arsenic release from arsenopyrite dissolution in oxygen-depleted and oxygen-saturated circumneutral solutions

Arsenopyrite (FeAsS), the most common arsenic-bearing mineral, is usually found associated with pyrite (FeS₂) in gold mining tailings. This work examined the galvanic effect of FeS₂ on As release from FeAsS oxidation in circumneutral media under oxygen-depleted and oxygen-saturated conditions. The oxidation experiments were conducted with a flow-through reactor in the absence of FeS₂ particles and in the presence of different contents of this sulfide. The results indicated that the permanent, physical contact between FeAsS and FeS₂ particles causes an increase in the accumulated As release, mainly under O₂-saturated conditions. At 30% wt. FeS₂, the increases relatively to FeS₂-free conditions were 82% and 117% in O₂-depleted and O₂-saturated solutions, respectively. At steady-state, the As release rates increased from (4.9 ± 0.5)× 10^-4 µmol m^-2 s^-1 (0% wt. FeS₂) to (1.1-1.9)× 10^-3 µmol m^-2 s^-1 (5-30% wt. FeS₂) under O₂-saturated conditions. Analysis of FeAsS samples after oxidation revealed oxidized particles partially or entirely covered by precipitates with different sizes, shapes and compositions (e.g., As-S-bearing ferrihydrite, elemental sulfur, and As-O phases). A fine (3-4 nm thick) amorphous layer of S-As-bearing ferric oxy-hydroxide was also identified on oxidized FeAsS, with Fe(III) and As(III) species.

The Combined Effects of Galvanic Interaction and Silicate Addition on the Oxidative Dissolution of Pyrite: Implications for Acid and Metalliferous Drainage Control

The aim of this study was to determine the combined effect of galvanic interaction and silicate addition on the dissolution of pyrite, the major contributor to acid and metalliferous drainage (AMD). Single (pyrite, sphalerite, and galena)- and bi-sulfide (pyrite-sphalerite and pyrite-galena) batch dissolution experiments were carried out with addition of 0.8 mM dissolved silicate for comparison to previously published data. The pyrite dissolution rate was reduced by 98% upon silicate addition at pH 7.4 with little effect at pH 3.0 and 5.0. The effect of galvanic interaction on reducing pyrite dissolution decreased with increasing pH and was greater in the presence of sphalerite than galena. In contrast, the effect of silicate addition increased with increasing pH and was greater in the presence of galena than sphalerite. The greatest combined effect was at pH 7.4, with <0.1% of pyrite leached in both bi-sulfide systems. Silicate addition also significantly reduced the dissolution of sphalerite or galena (by 10-44%, except at pH 3 for the pyrite-sphalerite system). These results suggest that silicate addition, for reducing both pyrite dissolution and metalliferous drainage, may be applicable at a broad pH in mixed sulfide systems.