Effect of Pretreatment of Sulfide Refractory Concentrate with Sodium Hypochlorite, Followed by Extraction of Gold by Pressure Cyanidation, on Gold Removal

Abstract

The majority of the refractory gold and silver occurs in occlusion in sulphides, then precious metal dissolution is possible by first oxidizing auriferous sulfide concentrate using sodium hypochlorite-sodium-hydroxide solution followed of pressure cyanidation of the oxidized concentrate, for the extraction of precious metals. This process was conducted and evaluated under cyanide and oxygen pressure. This versatile approach offers many advantages, including low temperatures, low pressure and less costly materials of construction than conventional pressure oxidation. In this study, the effect of oxygen pressure, concentration of sodium hypochlorite, temperature, and initial pH, in precious metals recovery and As removal were evaluated using a 2 4 factorial design. Characterization of the ores showed that pyrite and arsenopyrite were the main minerals present on the concentrate. The best results for gold extraction were obtained with oxygen pressure of 80 psi, 10% (w/w) sodium hypochlorite, temperature of 80˚C, at pH = 13, and a constant stirring speed of 600 rpm. These conditions allowed an approximated 60% of gold and 90% of silver extractions in 1 hr.

ZVI (Fe0) desalination: catalytic partial desalination of saline aquifers

“…11) dechlorides the water to produce two principal products Cl 2 (aq) and HO (Pourbaix 1974). The expected change in the Eh and pH (Hasab et al 2012;Valenzuela et al 2013) of the intra-particle porosity in the presence of NaCl (during desalination) is (i) a progressive drop in pH [relative to the situation without NaCl from 11 (e.g., Antia 2010, 2011a, b) to 4-5 (e.g., Antia 2015b, 2016a)], and (ii) an increase in Eh from < 0.6 (e.g., Antia 2015b, 2016a) to > 1.1 V (Pourbaix 1974).…”

Acidithiobacillus ferrooxidans Leaching of Silica-Sulfide Gold Ores from May-Hibey Deposits, Tigray, Ethiopia

“…Te processes of mining gold, one of the most valuable and economical metals, produce large amounts of waste that still contain large amounts of valuable substances and in some cases, the toxic chemicals cyanide and thiocyanide, often buried as landfll or waste near the mining areas [5]. It is important to develop better methods to avoid the use of these chemicals when extracting gold from its ores [6,7].…”

“…Bioleaching typically involves in the removal of sulfde minerals by the action of chemolithotrophic acidophilic bacteria and is an economically viable competitive and respectful environmentally friendly biotechnology [2,4,8]. Te environmental conditions of bioleaching are characterized by low pH values and high concentrations of reduced sulfur and iron compounds; in these ores, rocks and acid drainage waters from the mine represent prime places of iron-oxidizing Acidithiobacillus species [4,7,[9][10][11]. Bioleaching is a promising and revolutionary method that uses environmentally friendly technologies, which are useful for the mining industry as well as for environmental detoxifcation [1][2][3][4][5].…”

“…Acidophilic bacteria participate in the biooxidation of minerals and produce sulfuric acid or ferric ions that act as chemical lixiviants, and resilience to increasingly unfavorable environmental conditions that arise when minerals undergo biooxidation [3,12,15]. Te dissolution of minerals is obtained by these bacteria, which alter the local environmental conditions such as pH, metal concentrations, oxygen availability, and redox potential [2,4,7,15]. Tis bioleaching process is inhibited by the oxidation of Fe 2+ and the presence of heavy metal ions [13][14][15].…”

Gold recovery of refractory sulfide concentrates using direct cyanide leaching with nitrite as an oxidant

“…An aqueous oxidation based on the principle of hydrometallurgy process is one of the methods of pretreatment where the sulfur species tend to oxidize to the less harmful sulfate form. There are several aqueous oxidation techniques prior to cyanidation to treat refractory gold ores: chemical (chlorine, hypochlorite, chlorates, perchlorates, ozone, oxygen, and sulfuric acid) or electrochemical oxidation, pressure leaching, and bacterial leaching (Li et al, 2006;Hu, Wang and Wei, 2012;Valenzuela, Valenzuela and Parga, 2013).…”