Trans. Nonferrous Met. Soc. China 25(2015) 3461−3466 Leaching kinetics of gold bearing pyrite in H2SO4−Fe2(SO4)3 system Shui-ping ZHONG1,2,3 1. …
leaching agent for gold, to achieve a much higher gold extraction (> 90%) under ambient leaching conditions and neutral solutions (pH 6-7) (35). A fundamental study on the use of iron(III)-oxalate-thiosulfate-thiourea for gold leaching has also been reported (36). Figures 1-6 clearly show the complex behaviour of
The process of dissolution of metallic gold leaching is carried out in a system containing a ligand and an oxidizer, where the solubility of gold is increased by the addition of aromatic compounds containing ring sulfur or nitrogen. The leaching of gold using less corrosive fluids without significant losses in the dissolution rate of the metal ...
sulphur. Standard cyanide leaching of the residue, using long retention times, 24-72 hours, at atmospheric conditions leads to cyanide consumption two orders of magnitude greater than the consumption typically experienced in conventional cyanide leaching of gold ores, i.e. 35-100 kg NaCN/tonne residue [3]. Alternative Gold Recovery Options Explored
Download scientific diagram | Equilibrium species Eh-pH Diagram for Sulfur and Alkaline Sulfide Gold (Anderson et al., 2005) from publication: Alkaline Sulfide Gold Leaching Kinetics | Recently ...
Main chemical reactions occurring in cyanide‑sulfur aqueous systems at 25 °C during gold and silver leaching are as follows. Sodium cyanide (NaCN), the major reagent used for gold and silver leaching, dissolves in water forming a metal cation and free cyanide ion (CN −) as presented in the following reaction (Deschenes et al., 2009).
Jeffrey and Breuer (2000) used gold containing 5% silver rather than high purity gold to investigate the effect of sulfur species and suggested that soluble sulfide hinders the rate of gold leaching by forming a protective layer of the type Au/S x. They showed that this was a monolayer of sulfur which forms at potentials negative of the bulk ...
Leaching gold in Calcine. The principal cyanides in the calcine are copper, ferrous iron, and smaller amounts of Mo, Co, Ni, Mn, etc. Most of the …
Gold leaching kinetics were measured using a rotating electrochemical quartz crystal microbalance (REQCM), which measures the leaching rates in-situ. When the mineral is electrically in contact with gold, the gold dissolution rate increases as a result of the extra surface area available for oxygen reduction.
The effect of bio-oxidation and neutral atmospheric oxidation pre-treatment of refractory gold concentrates on gold and silver extraction during cyanidation was investigated. A series of pre-treatment experiments was conducted on three high sulfur (> 9%) refractory concentrates with 0.92–1.25 g/t gold and 64–90 g/t silver. Cyanidation of the pre-treated …
An inefficient gold leaching in the cyanidation process from refractory gold. tailings . was caused by gold particle locked in specific minerals. The aim of this study was to harness the ability of a sulfur-oxidizing bacterium to oxidize iron and sulfur and its behaviour on ferrous sulfate heptahydrate (FeSO 4.7H 2 O) and pyrite (FeS 2
Previous investigations on gold leaching confirmed that a pH value of near 9.5 was optimal for gold extraction [1,2,11]; therefore, the effect of pH on gold adsorption was studied in this range. As can be seen from the results shown in Table 3, the pH variation did affect the gold adsorption, i.e., it was severely retarded at the lower and ...
Thiobacillus bacteria are acidophilic aerobic chemolithotrophs which grow most rapidly at a pH in the range of 2-3. T. ferrooxidans derive their energy by oxidizing ferrous iron, elemental sulfur and reduced sulfur compounds and …
These bacteria live from the "energy gap" between the incomplete chemical oxidation of the sulfur moiety of pyrite at neutral pH values and its complete oxidation to sulfuric acid. In addition, by acid production the pH is lowered, allowing acidophilic leaching bacteria, like T. ferrooxidans, to grow and to oxidize pyrite. 3.3.
The gold dissolution rate is dependent on the concentration of NaCN and the alkalinity of the solution, the optimum pH is around 10.5. For efficient leaching, the gold should occur as free, fine-size, clean particles in an ore.
For selected experiments a gold disk containing 20 wt% silver was used to investigate the leaching behavior of a common gold alloy. The Ag20Au-disks were produced at the IME and are identical in ...
The actual speciation of the reduced sulfur species in the circuits will primarily depend on the redox potential, pH, cyanide levels and existing sulfur species in recycled process water, as well as the presence of other reactive metal species.
solution also contains polysulfide, it is likely that this species is the oxidant for gold leaching. The potential of the sulfide / polysulfide system can be conveniently represented by an E-pH diagram. A metastable E-pH diagram for sulfur in alkaline solutions was generated using the StabCal thermochemistry package (Huang
During leaching with Ferric ion a critical balance between Fe 2 + and Fe 3 + ions in the leach solution is essential to maintain efficiency of leaching and subsequent electrolysis. The ferric ion is also very sensitive to pH changes, hydrolysis and precipitation of basic ferric salts starting at pH 3.5. 2. Chlorine water and hypochlorite:
oxidative leaching with ozone is relevant in copper-iron sulphide and gold- and silver- containing sulphides. Moreover, oxidative leaching of coal-containing iron sulphide might also have a positive impact on coal cleaning prior to its use in energy related applications. The hydrometallurgy of different sulphide minerals will be treated.
Sulphur leaching . Sulphur behaves similarly to nitrogen in the soil. Sulphate ions, as nitrate ions, are dissolved and very prone to leaching. fertiliser application should therefore be matched to plant growth in order to ensure rapid uptake. …
and capacity for gold, even at low pH values. Gold uptake by Spirulina was 7.0 g Au/kg biomass OW in 1-2 hr at pH 2.0, and about 3.0 g Au/~g OW in 15 min atpH 2 through 7 14. Metabolically acti ve fungal cells of Aspergillus fumigatus Fresen and A. niger Tiegh removed gold
Chemical leaching of the concentrate (slurry density at 200 g/L) by ferric sulfate biosolvent (initial concentration at 35.6 g/L), which was obtained by microbial oxidation of ferrous sulfate for 2 hours at 70°C at pH 1.4, was allowed to oxidize 20.4% ofarsenopyrite and 52.1% of sulfur.
effects. Diagnostic leaching was used to show that mineralogy was not an important factor in the enhanced gold extraction in the presence of activated carbon for the ores. Kinetic models were developed for the leaching of gold from the ore, adsorption onto activated carbon and preg-robbing at the ore surface. A variable order empirical
The solution pH had very little effect on gold recovery between 9.5 and 11.5. The ratio of glycine to perman-ganate concentration is significant, if potassium permanganate is in a molar excess, the recovery is greatly reduced due to oxidation of the glycine. The main products of this reaction, when lime was used as pH modifier,
For the high sulfur refractory gold concentrate with 41.82% sulfur and 15.12 g/t gold, of which 82.11% was wrapped in sulfide, a well-controlled stirring tank leaching was carried out to improve the bio-oxidation efficiency. Results show that bio-oxidation pretreatment can greatly improve the gold recovery rate of high-sulfur refractory gold concentrate, and at the optimum …
Microorganisms are important in metal recovery from ores, particularly sulfide ores. Copper, zinc, gold, etc. can be recovered from sulfide ores by microbial leaching. Mineral solubilization is achieved both by 'direct (contact) leaching' by bacteria and …
Thiosulfate offers a nontoxic alternative to cyanide for processing gold ores. The mechanism of leaching gold using ammoniacal thiosulfate solution is driven by the Cu(II)-Cu(I) redox couple and is complicated by competing ligands such as NH 3 and S 2 O 3 2−.It is shown that an understanding of the copper speciation and sulfur speciation is required to optimize …